docs: record verified alpha20 release and Prism update

feat: add detailed architecture for Sanctuary alpha20
docs: record verified alpha19 release and Prism update
2026-09-10 01:21:33 +02:00 · 2026-09-10 01:18:31 +02:00 · 2026-09-09 22:49:20 +02:00 · 2026-09-09 22:42:32 +02:00 · 2026-09-09 20:03:42 +02:00
81 changed files with 11130 additions and 62 deletions
@@ -1,5 +1,57 @@
 # Changelog

+## 0.1.0-alpha.20 — 2026-09-10
+
+- Passe architecturale sur les six bâtiments urbains, les quatorze anciennes
+  infrastructures, les espaces publics et les réseaux souterrains. Palettes
+  propres aux usages : chêne, bouleau, granit, diorite, andésite et tuf ;
+  fondations maçonnées en briques de pierre conservées.
+- Angles coupés, baies en saillie, portiques, retraits, loggias, toitures
+  nervurées et verrières avec passage lumineux. Sols et plafonds détaillés,
+  corniches, encadrements, murets et blocs ciselés ; bordures de routes en
+  briques de tuf et accents ciselés.
+- Vitres, barreaux, clôtures, murs bas et angles d’escaliers raccordés depuis
+  la géométrie complète de chaque pièce avant son découpage entre chunks.
+- Nouveau codec `sanctuary:island_v20`, journal et pièces distincts. Les mondes
+  19 et antérieurs gardent leurs rendus et futurs chunks. Les plans de terrain,
+  d’hydrologie et d’implantation restent ceux de la génération précédente.
+  Personnaliser conserve les trois tailles et les structures expérimentales.
+
+`check build assemblePack` passe, avec huit GameTests généraux. Création et
+réouverture de la ville et des infrastructures passent ; les rapports 19 restent
+identiques aux témoins publiés. Option désactivée et Petit/graine42 passent.
+JAR, MRpack et ZIP Prism vérifiés ; release et canal packwiz publiés. Deux
+synchronisations isolées puis deux dans la même instance Prism passent, avec
+925 fichiers personnels et réglages suivis conservés.
+
+Voir le [catalogue illustré](docs/architecture-alpha20.md) et les
+[vérifications et limites](docs/testing-alpha20.md). Les fonctions de la bêta
+restent à construire ; aucun nouveau système économique n’est activé.
+
+## 0.1.0-alpha.19 — 2026-09-09
+
+- Quatorze nouvelles infrastructures abandonnées sur l’île initiale, avec pièces,
+  accès, mobilier, secrets et outils vanilla associés. La présence varie selon
+  la graine et le relief ; les quatorze types ont été rencontrés en tests natifs.
+- Voies de fret aux rails incomplets et chemins entre destinations réelles.
+  Le témoin Moyen, graine 0, contient treize lieux et sept liaisons, dont un
+  fret de 499 blocs entre dépôt et pompage. Tracés enregistrés par chunk.
+- Option FR/EN « Structures expérimentales » dans le bouton natif Personnaliser,
+  trois tailles conservées. Codec `sanctuary:island_v19` et journal 19 ; les
+  anciens mondes gardent leurs plans et futurs chunks. Un nouveau monde avec
+  l’option désactivée conserve le socle urbain sans les expériences 17/19.
+- Commande opérateur `/sanctuary structures` pour relever les entrées.
+  La ville et ses sous-sols sont conservés ; les systèmes de la bêta restent
+  à construire.
+
+`check build assemblePack` passe, dont les huit GameTests généraux. Les trois
+formats sont vérifiés nativement ; le témoin moyen se rouvre avec ses 112 pièces,
+13 coffres, 68 cibles accessibles et la modification témoin. Les identités 17
+restent identiques à la release publiée. JAR, MRpack et ZIP Prism vérifiés ;
+release et canal packwiz publiés. Deux synchronisations isolées puis deux dans
+la même instance Prism passent, avec 767 fichiers personnels et réglages suivis
+conservés. Voir [les preuves et limites](docs/testing-alpha19.md).
+
 ## 0.1.0-alpha.17 — 2026-09-09

 - Prototype de trois réseaux oubliés sur l’île initiale : mines et ateliers,
@@ -15,10 +15,44 @@ infrastructures qui permettront progressivement d'ouvrir de nouveaux continents.
 Ce dépôt démarre la nouvelle base Fabric. La [vision complète](docs/vision.md)
 conserve les intentions ; le [backlog](docs/backlog.md) suit les
 tickets. Les systèmes d’économie, de progression collective et les dimensions
-décrits dans la vision ne sont pas encore implémentés. **L’alpha.17 est publiée** :
-trois familles de réseaux oubliés expérimentaux rejoignent la ville et ses grands
-sous-sols sur les nouvelles îles de départ. Le canal packwiz et la même instance
-Prism sont à jour ; voir [Distribution](docs/packwiz.md).
+décrits dans la vision ne sont pas encore implémentés. **L’alpha.20 est publiée** : elle reprend
+l’architecture des bâtiments, leurs palettes, les blocs sculptés et les raccords
+des vitres. Les villes, infrastructures et réseaux gardent leurs implantations.
+Voir le [catalogue illustré](docs/architecture-alpha20.md) et l’état du canal
+packwiz dans [Distribution](docs/packwiz.md).
+
+## Alpha.20 — identité des bâtiments
+
+La passe reprend les six bâtiments de ville, les quatorze infrastructures,
+les parcs et les sous-sols. Bois de chêne et de bouleau, granit, diorite et tuf
+identifient les usages ; biseaux, baies, corniches, portiques et verrières
+donnent du relief aux volumes. Les routes reçoivent des bordures de briques
+de tuf et des blocs ciselés. Les vitres et grilles se raccordent entre chunks.
+
+Créer un **nouveau monde Sanctuary, Moyen, graine 0**, avec **Structures
+expérimentales** activées pour retrouver le témoin. Les anciens mondes gardent
+leur génération. Le bouton natif **Personnaliser** et ses trois tailles restent
+identiques. Voir le [catalogue illustré](docs/architecture-alpha20.md) et les
+[essais alpha.20](docs/testing-alpha20.md). `check build assemblePack`, les essais natifs et les artefacts sont vérifiés ;
+la [release](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.20)
+et le canal packwiz sont publiés. La même instance Prism est synchronisée
+deux fois, avec 925 fichiers personnels et réglages suivis conservés.
+
+## Alpha.19 — anciennes infrastructures
+
+Le chantier ajoute une première passe des quatorze lieux du
+[catalogue](docs/structures-audit.md), avec leurs accès, des petits butins vanilla
+et des voies de fret ou chemins abandonnés entre destinations réelles.
+L’option **Structures expérimentales** reste enregistrée à la création du monde.
+La nouvelle génération garde les anciennes sauvegardes intactes. Aucun système
+de progression, mailbox, caméra ou réacteur n’est activé.
+Les trois tailles sont vérifiées en génération native ; création et réouverture
+conservent les structures et les coffres. `check build assemblePack` passe.
+Pour voir le grand fret : **Moyen, graine 0**, option activée ;
+`/sanctuary structures` liste les entrées. Voir [les preuves et la carte](docs/testing-alpha19.md).
+La [release alpha.19](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.19)
+et le canal packwiz sont publiés. La même instance Prism est synchronisée deux
+fois, avec 767 fichiers personnels et réglages suivis conservés.

 ## Alpha.17 — prototype des réseaux oubliés

@@ -409,7 +443,7 @@ sera une mise à jour explicite, avec vérification des API et des sauvegardes.
 | Fabric API | 0.160.0+26.3 |
 | Fabric Loom | 1.17.20 |
 | Gradle Wrapper | 9.5.1, distribution vérifiée par SHA-256 |
-| Sanctuary / pack | 0.1.0-alpha.17 |
+| Sanctuary / pack | 0.1.0-alpha.19 |

 Java 25 et Python 3.11 ou plus récent sont nécessaires. Le script pack utilise
 uniquement la bibliothèque standard et repère aussi une installation Python
@@ -438,7 +472,7 @@ décrits dans [Validation](docs/testing.md).

 Résultats :

- `mods/sanctuary/build/libs/sanctuary-0.1.0-alpha.17.jar` : mod à installer avec
+- `mods/sanctuary/build/libs/sanctuary-0.1.0-alpha.19.jar` : mod à installer avec
  Fabric API sur la version Minecraft indiquée.
 - `build/packwiz/` : pack de développement complet, avec le mod construit et
  l'index vérifié. Voir [Installation packwiz](packwiz/README.md).
@@ -0,0 +1,115 @@
+# Architecture de l’alpha.20
+
+Cette passe donne une identité visuelle aux lieux déjà planifiés : volumes,
+façades, sols, plafonds et mobilier. Elle réutilise les emprises et les accès
+certifiés des générations précédentes. Les bâtiments de ville et les sites
+expérimentaux restent inscrits dans leurs parcelles de 17 × 17 blocs ; leurs
+corniches et leurs retraits restent à l’intérieur de cette limite.
+
+Les nouveaux rendus demandent un **nouveau monde de génération 20**. Les mondes
+19 et antérieurs conservent leurs bâtiments, y compris dans les futurs chunks.
+Le bouton **Personnaliser**, les trois tailles et l’option **Structures
+expérimentales** restent disponibles. Le catalogue n’impose pas que chaque lieu
+apparaisse sur chaque île.
+
+![Sélection d’architectures produites par les rendus de l’alpha.20](images/architecture20-overview.png)
+
+*Vues des blocs réellement émis par les générateurs, affichés avec les modèles
+Minecraft, sans terrain. Ce montage est une prévisualisation géométrique, pas
+une capture du client en jeu ; il montre une sélection du catalogue.*
+
+## Les six bâtiments de Lost City
+
+Les étages conservent leurs plans alternés, leurs pièces et leurs escaliers.
+Les sanitaires sont clos, les lits adossés à de vrais murs, et les lampes
+reposent sur des blocs complets. Les aménagements de toit décrits ci-dessous
+possèdent des points d’accès vérifiés par le smoke du renderer.
+
+| Fonction | Forme et façade | Espaces et détails construits |
+| --- | --- | --- |
+| Immeuble | Angles avant coupés, baies en saillie, montants de chêne écorcé et bandeaux de tuf. | Parquets alternant chêne et bouleau, logements avec cuisine et chambre ; jardinières, portique de bois et table sur le toit. |
+| Hôtel | Portique et travées encadrées de diorite polie, garde-corps et bandeaux en bouleau ; pavillon de toit en retrait. | Réception, chambres, salons, sanitaires et buanderie ; petit local de linge et bancs sur le toit. |
+| Bibliothèque | Grandes baies, angles coupés et lames verticales en bouleau écorcé ; lanterneau vitré avec ouverture à travers le toit et le plafond du dernier étage. | Rayonnages, archives, tables et lutrins ; sols délimitant les espaces de lecture et terrasse de lecture sur le toit. |
+| Restaurant | Encadrements de granit poli, vitrines et auvents associant chêne et bouleau. | Salles à manger et cuisines réparties par étage, garde-manger et sanitaires ; tables sur le toit et sorties d’extraction maçonnées. |
+| Caserne | Piles épaisses de briques de tuf, soubassements ciselés et fenêtres grillagées. | Dortoirs, bureau de service, réserves d’équipement et sanitaires ; cage d’escalier coiffée d’un pavillon accessible. |
+| Hall | Travées monumentales, piliers ciselés, corniches de diorite et fronton de toit en gradins. | Billetterie, bureaux, salle avec scène sur deux niveaux, galerie protégée, salles de réunion et archives. |
+
+## Les quatorze anciennes infrastructures
+
+Chaque site conserve ses seuils, son accès de service et son coffre de découverte.
+Les fonctions ci-dessous sont exprimées par les pièces et les blocs vanilla
+présents ; elles ne constituent pas de nouveaux systèmes de progression.
+
+| Lieu | Architecture et usage visibles |
+| --- | --- |
+| Gare de fret | Halle aux angles coupés, lanterneau vitré et long auvent de quai en chêne ; voie, salle d’attente et petit bureau de signalisation. |
+| Poste et centre de tri | Façade de granit, accents de diorite et toiture en retrait ; guichet, rangées de tonneaux, passage de tri et bureau. |
+| Dépôt communal | Grand entrepôt nervuré de pierre, toiture industrielle à trois travées vitrées en dents de scie ; rails, chargement, caisses et mezzanine d’inventaire. |
+| Cartothèque d’expédition | Corps en bouleau, petites ailes différenciées et balcon arrière abrité ; table de cartographie, lutrin, archives et réserve. |
+| Observatoire et météo | Tour à pans coupés, contreforts de diorite et couronne ouverte portée par des nervures ; deux volées d’escalier, salle d’instruments et plateforme d’observation. |
+| Atelier ferroviaire | Large couverture à nervures et vitrages, piles de granit ; deux voies, fosse d’entretien avec escalier, établi, fourneau, meule et petite réserve. |
+| Station de pompage et château d’eau | Bâtiment bas, conduites figurées par des grilles et murets, cuve haute sur quatre piles ciselées ; galerie d’entretien et réserve sèche. L’eau reste dans la cuve. |
+| Sous-station | Cour clôturée, supports et grilles autour des équipements, locaux bas à toiture nervurée ; commandes vanilla et tranchée d’entretien accessible. |
+| Serre et graineterie | Verrière haute rythmée par des nervures de bouleau ; cultures, deux points d’irrigation contenus, allée de tuf et remise de rempotage. |
+| Quai sur le vide | Platelage en chêne, garde-corps à piliers sculptés, abris bas et grue de bois à chaîne ; attente, débarcadère et réserve. |
+| Relais radio et maison du gardien | Petite maison de chêne avec toiture à deux matières et cheminée ; antenne haute à traverses, plateforme accessible et chambre du gardien. |
+| Club photo et chambre noire | Façade claire de diorite, corniche sculptée et toiture arrière en retrait ; salle du club, chambre noire, bacs et espace de séchage à chaînes. |
+| Vestiaires et salles étranges | Entrée basse et étroite suivie d’une salle haute à colonnes répétées ; casiers, sols carrelés, alcôve et petite pièce de service. |
+| Refuge de chantier | Cabane surélevée sur piles ciselées, toiture inclinée et ossature inachevée ; couchage, établi, escalier extérieur et trappe avec échelle vers la réserve inférieure. |
+
+Les voies de fret gardent leur ballast, leurs traverses, leurs courbes et leurs
+rails manquants. Les chemins reçoivent des bordures de briques de tuf et des
+accents ciselés ; leurs pentes et leurs destinations restent celles du plan
+sauvegardé.
+
+## Espaces publics et équipements extérieurs
+
+| Espace | Détails présents en génération 20 |
+| --- | --- |
+| Rues et ponts | Chaussée d’andésite polie, bordures de tuf poli, bandes de briques de tuf ponctuées de blocs ciselés ; marches sur les pentes, piles de garde-corps et grilles sur les ponts. Les tabliers n’ajoutent pas de colonnes vers le vide. |
+| Parc arboré | Allées en croix, bancs de chêne à accoudoirs minéraux, lampadaires et petite couronne de bouleau à côté des arbres existants. |
+| Jardin | Quatre parterres bordés de diorite, angles de tuf sculpté, portique de bois et promenade centrale. |
+| Aire de jeux | Bac à sable bordé de bouleau, portique de balançoire, plateforme de jeu avec marches et garde-corps, bancs et éclairage. |
+| Place | Sol organisé en couronnes de diorite, granit et tuf ; fontaine sèche à coupe basse et piédestal sculpté. |
+| Mémorial | Sol minéral à lignes de tuf, marches autour du socle, colonne mêlant tuf et briques de pierre sculptées. |
+| Marché | Croisement piéton, quatre étals avec pieds ciselés, poteaux de chêne et couvertures alternant dalles de chêne et de bouleau. |
+| Parking | Rampe et stationnements conservés ; piliers d’andésite, assises ciselées, bandeau en tuf, grilles de ventilation et lampes de plafond. Il reste enterré seulement lorsque le sol est certifié. |
+| Piscine extérieure | Bassin et marches immergées conservés, margelles de diorite, chaises longues et auvent de bouleau près des bacs de douche. |
+| Excavation | Escalier central vers la fosse, barrières, piles sculptées, poutre sur appuis, établi et meule ; le chantier reste limité à la roche certifiée. |
+
+## Sous la ville et réseaux oubliés
+
+| Ensemble | Traitement architectural |
+| --- | --- |
+| Grande piscine couverte | Bassin, escaliers et colonnade conservés ; parois de calcite, bandeaux de diorite, chapiteaux ciselés et nervures hautes répétées. |
+| Parkings souterrains | Plateformes et rampes conservées ; fondations maçonnées et bandeaux de tuf ponctués de motifs ciselés. |
+| Grande salle sèche | Boiseries de chêne, assises de tuf, murs clairs, corniches et bancs de chêne ; le socle central reste sans machine de progression. |
+| Égouts et sorties d’eau | Briques de tuf, motifs ciselés et corniches hautes ; les canaux, passerelles et écoulements existants sont conservés. |
+| Passages et accès | Liserés de granit ou de tuf, seuils et accès verticaux conservés. |
+| Mines, ateliers et réserves oubliés | Poutres de chêne, tuf, sols bordés de granit, établi et outillage vanilla ; rails, réserves et plateforme de travaux interrompus. |
+| Archives et salles étranges | Parquets de bouleau, boiseries, rayonnages ; ailleurs, carrelages de calcite et diorite, colonnes et niches répétées. |
+| Salles techniques oubliées | Nervures minérales, corniches et encadrements ciselés autour des seuils ; pompes figurées, grilles et postes de commande vanilla. |
+
+## Matériaux et raccords
+
+Les fondations des nouveaux bâtiments et chemins sont en **briques de pierre**.
+La stone et la smooth stone restent présentes ; l’andésite, la diorite et le
+granit différencient les sols et les usages. Le tuf existe brut, poli, en
+briques et sous ses deux formes ciselées. Les dalles, escaliers inversés,
+murets, grilles et trappes donnent de l’épaisseur aux corniches, aux appuis de
+fenêtre et aux équipements. Le chêne et le bouleau apparaissent comme poteaux,
+boiseries, parquets, charpentes et couvertures selon les lieux.
+
+Le rendu 20 calcule les raccords des vitres, barreaux, clôtures, murets et
+angles d’escaliers à partir de tous les blocs de la pièce, après sa rotation
+et avant son découpage entre chunks. Une fenêtre peut ainsi rejoindre son
+véritable encadrement, même lorsque le chargement découpe le bâtiment.
+
+Les smokes des bâtiments de ville et des espaces extérieurs passent, notamment
+pour les accès, les sanitaires, les lits, les lampes, les rampes et les bassins.
+Les essais natifs de création et de réouverture de la ville et des infrastructures
+passent ; leurs résultats et les contrôles de compatibilité sont suivis dans [les essais alpha.20](testing-alpha20.md).
+
+Aucune caméra, mailbox, machine d’expansion ou production électrique dédiée
+n’est ajoutée par cette passe. Les meubles utilisables restent les blocs
+vanilla, et les butins de découverte restent partagés et non renouvelés.
@@ -700,6 +700,85 @@ Retour arrière par branche/artefact et option désactivée
 pour un autre nouveau monde. Aucun retour binaire vers 16 dans une sauvegarde 17
 n’est déclaré compatible ; les mondes d’essai restent séparés.

+### WG-21 — Audit des structures et des anciennes circulations
+
+**Branche :** `codex/structures-audit`.
+
+**Demande :** avant de poursuivre l’implémentation, proposer des structures
+contemporaines, des axes abandonnés à l’échelle de l’île et leurs liens possibles
+avec l’expansion, la mailbox et les objets utiles cachés dans des lieux secrets.
+
+**État : audit documenté, propositions à discuter.** Le
+[catalogue et schéma de relations](structures-audit.md) distinguent les trois
+petits ensembles actuels des futurs tracés entre destinations, proposent des
+voies de fret dégradées et des usages pour les bâtiments. Les outils vanilla
+servent d’idées de butin ; la caméra et les systèmes restent pour la bêta.
+Aucune structure, règle de butin, version binaire ou instance Prism modifiée.
+La sélection des lieux et la réalisation des axes feront l’objet du chantier
+suivant ; ce catalogue n’est pas une liste d’ajouts tous validés.
+
+### WG-22 — Anciennes infrastructures et liaisons — alpha.19
+
+**Branche :** `codex/heritage-worldgen-alpha19`.
+
+**Demande validée :** première passe de toutes les nouvelles structures du
+catalogue WG-21 et de leurs liaisons avant la bêta, en conservant la possibilité
+de revenir à une génération sans ce chantier.
+
+- Ajouter les quatorze lieux avec architectures, entrées, pièces, mobilier et
+  petits butins vanilla associés à leur usage. Présence selon le terrain ;
+  relever les lieux réellement générés et donner les coordonnées des témoins.
+- Planifier des voies de fret et chemins entre destinations réelles, avec
+  sections abandonnées lisibles, appuis et passages vérifiés. Rechercher les
+  raccords aux anciennes installations dans un budget borné.
+- Garder une majorité naturelle à l’île ; conserver le terrain, l’hydrologie,
+  la ville et les réseaux existants comme base. Première île uniquement.
+- Nouveau codec 19, option expérimentale sauvegardée à la création du monde.
+  Option désactivée : socle urbain seul. Les mondes 17 et antérieurs gardent
+  leur génération, leurs pièces et leurs futurs chunks. Aucune conversion,
+  suppression de structures ou rétrogradation d’une sauvegarde 19.
+- Les bâtiments préparent les futurs services ; mailbox, deposit boxes,
+  caméra, réacteur, progression et récompenses personnelles restent pour la
+  bêta. Les coffres de cette passe sont partagés et utilisent du butin vanilla.
+- Vérifier créations/réouvertures, option désactivée, anciens mondes, supports,
+  circulations et vrais placements. `check build assemblePack`, artefacts,
+  publication packwiz et mise à jour de la même instance Prism.
+
+**État : livré en alpha.19 ; code, artefacts et synchronisation Prism vérifiés.** Voir
+[les essais natifs et la carte des lieux](testing-alpha19.md). Version 19 demandée
+explicitement ; aucune version 18 publiée
+dans ce dépôt à l’ouverture du chantier. Le catalogue est maintenant accepté
+pour une première passe, sans imposer sa présence exhaustive sur chaque graine.
+
+### WG-23 — Identité architecturale et blocs détaillés — alpha.20
+
+**Branche :** `codex/architecture-alpha20`.
+
+**Demande :** donner aux bâtiments une identité contemporaine lisible selon
+leur fonction, corriger les vitres isolées et détailler formes, façades et
+circulations. Employer du tuf, ses briques et variantes ciselées, du chêne,
+du bouleau, du granit, de la diorite et de l’andésite ; conserver les fondations
+en briques de pierre. Ajouter des blocs sculptés et du relief architectural.
+
+- Reprendre les quatorze lieux expérimentaux, les bâtiments de Lost City,
+  leurs espaces extérieurs et leurs sous-sols ; palettes par usage, volumes
+  en retrait, biseaux, baies, corniches, liserés et mobilier adapté.
+- Résoudre les connexions des vitres, grilles, clôtures et murs ainsi que les
+  angles d’escaliers depuis la géométrie complète, avant le découpage par chunk.
+- Dessiner les bordures de routes avec les briques de tuf et le tuf ciselé,
+  en conservant la circulation et les tracés sauvegardés.
+- Garder les plans de placement et les emprises certifiées ; génération 20
+  et types de pièces distincts. Les mondes 19 et antérieurs gardent leurs
+  rendus, y compris dans les futurs chunks. Aucune rénovation rétroactive.
+- Garder le bouton natif Personnaliser, les trois tailles et l’option des
+  structures expérimentales pour les nouveaux mondes.
+- Vérifier les états réels des blocs, les accès, les supports, les coffres,
+  la création/réouverture et la compatibilité avec la version 19 publiée.
+  Livrer le pack 20 par le canal stable et synchroniser la même instance Prism.
+
+**État : livré en alpha.20 ; code, artefacts et même instance Prism vérifiés.** Voir
+[le contrat et les essais alpha.20](testing-alpha20.md).
+
 ## Réserve de thèmes futurs

 Ces thèmes servent à retrouver la vision, pas à demander leur implémentation immédiate. On en extrait un ticket seulement lorsqu'il devient utile au prochain incrément jouable.
@@ -13,10 +13,100 @@ JAR Sanctuary sont des pièces jointes de releases Gitea. Aucun JAR de mod ou
 dépendance téléchargée n'entre dans l'historique Git. Le canal Beta est distinct
 de l'ancien pack 26.2.

+## Alpha.20 publiée — 10 septembre 2026
+
+[Sanctuary 0.1.0-alpha.20](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.20)
+est publiée depuis le commit source `0edac29`. Le canal stable utilise cette
+version au commit `4e0967d`. Le JAR, le
+[MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.20/Sanctuary-0.1.0-alpha.20.mrpack)
+et le ZIP d’amorçage Prism ont été vérifiés par téléchargement public.
+SHA-256 du JAR :
+
+```text
+9ea10576e641d83c13e1277960a375448a22d416a98a6b327c4d6d2a204c423a
+```
+
+Passe de détails sur six bâtiments de ville, quatorze infrastructures,
+espaces publics et réseaux souterrains : palettes propres aux usages,
+boiseries, tuf ciselé, corniches, biseaux, verrières et raccords des vitres.
+Voir le [catalogue illustré](architecture-alpha20.md).
+
+`check build assemblePack` passe, avec huit GameTests généraux. Les créations
+et réouvertures natives conservent les structures, accès, supports et coffres.
+Le bassin et les sorties d’égout restent fonctionnels. Les rapports de la
+version19 restent identiques à ceux de la release publiée. Le mode désactivé
+et une petite île passent ; les quatorze infrastructures sont rencontrées sur
+les deux témoins. Les limites des raccords au terrain sont détaillées dans
+[les preuves alpha.20](testing-alpha20.md).
+
+Deux synchronisations isolées puis deux dans la même instance Prism Mac
+réussissent. Un seul JAR Sanctuary alpha.20 est actif ; les **925 fichiers
+personnels et réglages suivis** conservent leurs hashes. Le dossier reste
+`Sanctuary-0.1.0-alpha.1`, affiché « Sanctuary Beta ». Le JAR19 et le suivi
+packwiz sont sauvegardés dans `sanctuary-backups/before-0.1.0-alpha.20/`.
+Reçus locaux : `build/alpha20-isolated-validation.json` et
+`build/alpha20-prism-validation.json`.
+
+Pour voir cette architecture, créer un **nouveau monde Sanctuary, Moyen,
+graine 0**, avec **Structures expérimentales** activées dans **Personnaliser**.
+`/sanctuary structures` liste les entrées. Petit, graine42, possède la
+cartothèque à `-101 251 -25`. L’option désactivée d’un autre nouveau monde
+conserve la ville sans les réseaux expérimentaux. Les anciens mondes gardent
+leur génération ; aucune sauvegarde personnelle n’a été ouverte, convertie ou
+régénérée. Une sauvegarde20 ne se rétrograde pas vers le binaire19.
+
+Les vues du catalogue viennent des modèles et ne sont pas des captures de
+partie. Aucun essai client visuel ni essai Windows natif n’a été effectué.
+Les nouvelles fonctions de la bêta restent à construire.
+
+## Alpha.19 publiée — 9 septembre 2026
+
+[Sanctuary 0.1.0-alpha.19](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.19)
+est publiée depuis le commit source `c23e72b`. Le canal stable utilisait alors
+cette version, au commit `ea883b7`. JAR, [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.19/Sanctuary-0.1.0-alpha.19.mrpack)
+et ZIP d’amorçage Prism ont été vérifiés par téléchargement public.
+SHA-256 du JAR :
+
+```text
+a159b00a2778020800e81381e0608495a4d7909f1f853f0b8812cd4017865b0b
+```
+
+Première passe de quatorze architectures et de leurs voies de fret ou chemins
+abandonnés sur l’île initiale. Les trois tailles sont vérifiées nativement ;
+les quatorze types ont chacun été rencontrés et parcourus sur ces témoins.
+Créer un **nouveau monde Sanctuary, Moyen, graine 0**, puis garder
+**Structures expérimentales** activées dans **Personnaliser** : ce témoin
+contient treize lieux et sept liaisons, dont un fret de 499 blocs.
+`/sanctuary structures` relève les entrées. La présence des bâtiments et les
+raccords dépendent du relief ; voir [les preuves et la carte](testing-alpha19.md).
+
+`check build assemblePack` et les huit GameTests généraux passent.
+Création et réouverture natives conservent 112 pièces et 13 coffres ; 68 cibles
+sont accessibles. Le mode désactivé passe. Les empreintes de la génération 17
+restent identiques aux preuves publiées, y compris après réouverture.
+
+Deux synchronisations isolées puis deux dans la même instance Prism Mac
+réussissent. Un seul JAR Sanctuary alpha.19 est actif ; les **767 fichiers
+personnels et réglages suivis** conservent leurs hashes. Aucune sauvegarde
+personnelle n’a été ouverte, convertie ou régénérée. Le dossier reste
+`Sanctuary-0.1.0-alpha.1`, affiché « Sanctuary Beta ».
+
+Le JAR 17 et le suivi packwiz sont sauvegardés dans
+`sanctuary-backups/before-0.1.0-alpha.19/`. Reçus locaux ignorés :
+`build/alpha19-isolated-validation.json` et `build/alpha19-prism-validation.json`.
+
+Pour comparer, créer un autre nouveau monde avec l’option désactivée : le socle
+urbain demeure, sans les expériences 17/19. Cette option ne supprime pas de
+structures dans une sauvegarde existante. Les anciens mondes conservent leur
+génération ; une sauvegarde 19 ne doit pas être ouverte avec l’ancien binaire 17.
+Les bâtiments préparent les futurs usages, mais mailbox, caméra, réacteur et
+progression restent pour la bêta. Aucun essai visuel dans le client ni essai
+Windows natif n’a été effectué.
+
 ## Alpha.17 publiée — 9 septembre 2026

 [Sanctuary 0.1.0-alpha.17](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.17)
-est publiée depuis le commit source `0969ed5`. Le canal stable utilise cette
+est publiée depuis le commit source `0969ed5`. Le canal stable utilisait alors cette
 version, au commit `6e0c297`. JAR, [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.17/Sanctuary-0.1.0-alpha.17.mrpack)
 et ZIP d’amorçage Prism ont été vérifiés par téléchargement public.
 SHA-256 du JAR :
@@ -0,0 +1,164 @@
+# Structures contemporaines et anciennes circulations de Sanctuary
+
+Audit de conception du 9 septembre 2026, après l’essai de l’alpha.17.
+Ticket WG-21 ; branche `codex/structures-audit`.
+**Propositions à discuter : aucune nouvelle génération ni règle de progression
+n’est implémentée par ce document.** Le pack reste en alpha.17.
+
+## Ce que produit actuellement le mod
+
+L’alpha.17 recherche au maximum trois petits ensembles, un par famille. Chaque
+ensemble rassemble trois à cinq pièces autour d’un accès de surface, avec des
+salles généralement de 9 × 9 blocs. Leur position est cherchée indépendamment.
+Les rails sont des tronçons intérieurs de la galerie minière. Les rues et ponts
+de Lost City desservent son quartier compact. Aucun itinéraire ne relie ces
+ensembles à l’échelle de l’île : le manque d’axes perçu en jeu correspond donc
+au fonctionnement actuel.
+
+Les ateliers possèdent des outils et équipements vanilla utilisables. Les
+coffres emploient les tables de maison des plaines et de cartographe ; le mod
+n’a pas encore de distribution de trésors conçue pour chaque lieu secret.
+La mailbox, les deposit boxes, la caméra, la machine d’expansion et les
+récompenses personnelles restent des systèmes futurs.
+
+Sources locales : [planificateur17](../mods/sanctuary/src/main/java/fr/koka/sanctuary/worldgen/ruins/RuinsPlanner17.java),
+[rendu17](../mods/sanctuary/src/main/java/fr/koka/sanctuary/worldgen/ruins/RuinsRenderer17.java),
+[preuves alpha.17](testing-alpha17.md), [vision](vision.md).
+
+## Faire comprendre les usages avant d’introduire leurs systèmes
+
+Chaque lieu devrait répondre à trois questions : pourquoi était-il construit
+ici, par où arrivaient ses occupants ou ses marchandises, et que peut en faire
+un joueur aujourd’hui ? Une plateforme de chargement, un vestiaire, des rayonnages
+et une sortie de service racontent davantage son usage qu’une pièce portant un nom.
+
+La chaîne proposée pour l’expansion est : **observer → préparer une expédition
+→ rassembler des ressources → ouvrir un continent → construire ses liaisons**.
+Les lieux rendent ces activités compréhensibles. Ils n’imposent pas encore une
+campagne, un coût ou un ordre obligatoire de déblocage.
+
+La poste rend lisible la différence entre recevoir personnellement un colis et
+contribuer à un stock collectif dans le dépôt. La salle d’expansion déjà présente
+peut devenir le point où ces efforts collectifs prennent sens. Une future
+mailbox ne doit pas être confondue avec un coffre ordinaire décoré en alpha.
+Ces bâtiments pourraient présenter les services en bêta sans obliger les joueurs
+à revenir au même guichet pour chaque action ; les règles d’usage restent ouvertes.
+
+## Catalogue proposé
+
+Les objets cités sont des **idées de butin**, pas des ajouts de cette livraison.
+Les variantes d’une même famille peuvent se remplacer selon la graine et le
+relief ; ce catalogue ne demande pas de tout placer sur chaque île.
+
+| Lieu | Forme, pièces et implantation | Découverte en alpha à concevoir | Lien possible avec la bêta |
+| --- | --- | --- | --- |
+| **Gare de marchandises** | Quai bas, petite halle, balance, guichet, poste d’aiguillage et voie de garage ; à la jonction ville/industrie. | Comprendre la ligne abandonnée, trouver un wagonnet et quelques rails dans la réserve. | Transport des productions vers le dépôt collectif ; réparations faites par les joueurs. |
+| **Centre postal et atelier de tri** | Hall public, comptoir, casiers individuels, salle de tri, quai arrière, bureau du facteur. | Suivre physiquement le passage d’un colis de l’entrée à son casier ; boussole dans le bureau fermé. | Découverte de la mailbox personnelle et de la livraison des achats. |
+| **Halle du dépôt communal** | Grande porte, travées numérotées, aire de déchargement, mezzanine d’inventaire et atelier annexe. | Stock modeste, outils de manutention suggérés par le décor, chantier de rayonnages interrompu. | Contributions via les deposit boxes, stocks collectifs et préparation d’expansions. |
+| **Bureau des expéditions et cartothèque** | Salle de préparation, table de cartographie, vestiaire, réserves de voyage, balcon orienté vers le vide. | Boussole, papier et cartes vierges ; comparer les directions depuis le balcon. | Relevés de ressources, choix de climat et préparation des départs. Les cartes préremplies restent un travail distinct. |
+| **Observatoire et station météo** | Petite tour sur une crête, plateforme dégagée, salle des instruments, bureau abrité. | Une longue-vue vanilla dans une armoire repérable ; observation du ciel et du relief. | Constellations, signatures climatiques et futur instrument d’observation éventuel. |
+| **Dépôt de maintenance ferroviaire** | Hangar court avec fosse d’entretien, établis, pièces détachées, vestiaire et établi personnel caché. | Réparer des tronçons, récupérer un outil utile ; retrouver le travail interrompu d’un ancien occupant. | Production, maintenance et futures machines. |
+| **Station de pompage et château d’eau** | Prise d’eau, bassin, galerie de vannes, passerelles, réservoir et exutoire ; implantation dictée par l’eau et les altitudes. | Traverser les bassins, rejoindre un local sec par une coursive ; seau ou canne à pêche. | Eau pour les ateliers et cultures. Aucun système de pompage actif n’est supposé déjà disponible. |
+| **Sous-station et galerie de maintenance** | Cour technique, salle de distribution, chemins de câbles, tranchée laissée ouverte et pièce de service. | Horloge dans le poste de garde, redstone modeste dans l’atelier ; repérer les départs de galeries. | Préparer visuellement les infrastructures à réactiver. Ni réacteur ni alimentation obligatoire de l’expansion décidés ici. |
+| **Serre municipale et graineterie** | Serre partiellement effondrée, tables de rempotage, irrigation, remise et chambre de conservation. | Graines vanilla adaptées au lieu, pot de fleurs, outils de culture. | Récoltes localisées et cuisine d’**It’s Alive !** ; pas de plantes futures distribuées en alpha. |
+| **Quai d’expédition au bord du vide** | Plateforme ancrée, hangar, rambarde, grue inachevée et petite salle d’attente. | Point de vue et lieu de départ évident ; accès depuis la ville ou le dépôt. | Bateaux volants, Happy Ghast, biplans, ziplines ou ponts construits par les joueurs. Aucune île future présumée en face. |
+| **Relais radio et cabane du gardien** | Antenne sobre sur un promontoire, escalier d’entretien, logement minuscule et réserve sous le plancher. | Repère visible de loin ; boussole ou horloge, passage discret vers un atelier. | Réseau de services et rendez-vous collectifs, si ce rôle est retenu. |
+| **Club photo et laboratoire caché** | Petite boutique ou salle associative, réserve, chambre noire et séchoir ; accès secondaire depuis une cour ou un hôtel. | Un atelier secret identifiable, avec une récompense vanilla provisoire. | Lieu naturel pour découvrir une **caméra en bêta** ; aucune caméra factice ou promesse de butin inexistant en alpha. |
+| **Vestiaires et salles de service impossibles** | Derrière les grandes piscines : vestiaires, laverie, couloir de livraison, puis vaste salle carrelée hors proportion. | Étrangeté progressive, passages secondaires, récompense au bout d’un détour lisible. | Donjons physiques et secrets ; distincts de la dimension Backrooms des objets perdus. |
+| **Refuge de chantier dans un ouvrage inachevé** | Cabane dans une pile de viaduc, atelier suspendu avec ancrages, escalier arrêté à une plateforme et réserves laissées sur place. | Un lit, un outil et une installation récupérable ; sentir qu’un autre joueur s’était établi ici. | Réappropriation par les joueurs, bases individuelles et chemins à terminer. |
+
+## Des axes à l’échelle de l’île
+
+Une **ancienne ligne de fret**, quelques embranchements et un chemin de service
+peuvent suffire à donner une organisation au territoire. Son tracé suit la pente,
+entre brièvement dans la roche et franchit les ravins avec des ouvrages ponctuels.
+La majorité de l’île reste naturelle. Une longue voie ne signifie pas une grande
+gare ni une grande ville supplémentaire.
+
+```mermaid
+flowchart LR
+    M[Mine] --- A[Atelier et maintenance]
+    A --- G[Gare de marchandises]
+    G --- D[Dépôt communal]
+    G --- P[Centre postal]
+    D --- Q[Quai d'expédition]
+    P --- C[Cartothèque]
+    C --- O[Observatoire]
+    D -. passage technique .- E[Salle d'expansion existante]
+    E -. galerie de service .- H[Pompage et égouts]
+    H -. accès secondaire .- S[Salles étranges]
+```
+
+Ce schéma décrit les relations proposées, pas un plan rigide à reproduire ni
+des liaisons toutes ferroviaires. Mine, atelier, gare et dépôt partagent la ligne
+de fret ; les autres raccords peuvent être des rues, sentiers, escaliers ou
+galeries. Les réseaux techniques et les lieux étranges gardent leurs itinéraires
+propres, avec seulement quelques intersections utiles.
+
+Pour une rupture crédible, il faut concevoir **le trajet complet entre deux
+destinations présentes**, puis son état d’abandon :
+
+- **Rails arrachés** : le ballast et les traverses montrent le chemin à réparer.
+- **Petit pont effondré** : les culées et une pile conservée indiquent la portée
+  manquante ; un détour permet de rejoindre l’autre côté.
+- **Tunnel éboulé** : les deux portails suivent le même axe ; une galerie de
+  maintenance donne un autre parcours lorsque le relief le permet.
+- **Travaux jamais terminés** : terrassement, échafaudage, matériaux et butoir
+  forment une fin intentionnelle. Un chantier peut réellement s’arrêter là.
+- **Voie envahie** : végétation et débris alternent avec des sections utilisables.
+
+Les coupures ne doivent pas reproduire l’aspect d’un raccord de chunks cassé.
+Les rails qui subsistent ont un support ; les tronçons réparables suivent des
+pentes et courbes praticables en wagonnet. Un souterrain conserve des appuis et
+un passage pour le joueur. Les raccords impossibles sont abandonnés proprement,
+sans publier une porte donnant dans la roche ni annoncer une gare inexistante.
+
+Une liaison vers un nouveau continent reste à construire après son ouverture.
+Le quai exprime la possibilité de partir ; il ne prédit pas un terrain encore
+absent, sa position exacte ou la route que choisiront les joueurs.
+
+## Récompenser la découverte d’un lieu secret
+
+Un secret devrait offrir **un objet principal cohérent avec son ancien usage** :
+longue-vue dans l’observatoire, boussole dans la cartothèque, horloge dans le poste
+d’aiguillage, outil dans l’atelier. Quelques fournitures accompagnent cet objet.
+Le plaisir vient de trouver un équipement utile tôt et de comprendre son origine ;
+un objet vanilla fabriquable ne devient pas artificiellement une relique unique.
+
+L’accès se lit dans le décor : fenêtre donnant sur une pièce sans porte visible,
+escalier derrière une étagère déplacée, trappe de maintenance, conduit débouchant
+sur un établi éclairé. La pièce peut être cachée sans exiger de casser tous les
+murs au hasard. Des variations portent sur le plan, l’accès et l’usage, pas
+seulement sur la couleur d’une salle identique.
+
+Le bâti est lui-même une récompense récupérable. Les rails, équipements d’atelier,
+blocs de fer et autres matériaux du décor doivent compter dans l’inventaire
+des ressources réellement générées ; une infrastructure trop généreuse pourrait
+remplacer tout le minage du début de partie. Cela se mesure après génération.
+
+Pour un premier essai de butin en alpha, les coffres pourraient rester des
+conteneurs vanilla partagés, sans renouvellement automatique. La coexistence
+des **reliques collectives uniques** et des **récompenses personnelles** nécessite
+le contrat de bêta. L’accès à la mailbox ou à l’expansion ne devrait pas dépendre
+d’un objet ordinaire que le premier explorateur peut emporter et perdre.
+
+## Ordre de travail proposé
+
+1. Relier une destination existante et une nouvelle destination avec un axe
+   visible à l’échelle de l’île : atelier/mines, gare et dépôt. Vérifier les
+   trajets, les supports et quelques ruptures réparables en jeu.
+2. Donner à la ville une poste et une cartothèque ; placer un observatoire dans
+   le relief, avec des accès logiques et un premier atelier secret.
+3. Raccorder ponctuellement les galeries techniques aux égouts, piscines et
+   salles étranges existantes. Garder des secteurs indépendants et des accès
+   secondaires plutôt que transformer tous les sous-sols en un unique donjon.
+4. Définir puis essayer les petites tables de butin par usage avant d’introduire
+   les objets et règles de la bêta.
+
+Avant d’écrire ce générateur, valider la place de la ligne de fret, les premiers
+lieux retenus et le rôle des ruptures : réparations libres, détours ou chantiers
+à prolonger. Les essais doivent distinguer un axe planifié, ses tronçons réellement
+générés, ceux qui sont praticables et ceux qui sont volontairement interrompus.
+La recherche des raccords doit rester bornée, sans explorer ou charger toute
+l’île pour chercher un passage. Les mondes publiés gardent leur génération ;
+aucune transformation d’une sauvegarde existante n’est autorisée par cet audit.
@@ -0,0 +1,173 @@
+# Alpha.19 — anciennes infrastructures de Sanctuary
+
+**État : alpha.19 publiée, même instance Prism synchronisée et vérifiée.** Ticket WG-22, branche
+`codex/heritage-worldgen-alpha19`. Minecraft 26.3-pre-2, mêmes dépendances que
+l’alpha.17. La numérotation 19 est demandée explicitement ; aucune 18 n’est
+intercalée dans ce dépôt.
+
+## Périmètre et réversibilité
+
+Première passe des quatorze lieux du [catalogue](structures-audit.md) : gare de
+marchandises, centre postal, dépôt communal, cartothèque, observatoire,
+maintenance ferroviaire, pompage, sous-station, serre, quai d’expédition,
+relais radio, club photo, vestiaires/salles étranges et refuge de chantier.
+Les plans recherchent des sites admissibles et des voies de fret ou chemins
+entre destinations réelles ; ils ne garantissent pas tous les lieux sur chaque
+graine. Les mesures et coordonnées des essais figurent ci-dessous.
+
+Créer un **nouveau monde Sanctuary** et utiliser **Personnaliser** :
+Petit 512, Moyen 724 par défaut ou Grand 1 024, avec **Structures expérimentales**.
+L’option est activée par défaut et enregistrée avec le générateur 19. La désactiver
+pour un autre nouveau monde conserve le socle urbain sans les réseaux
+expérimentaux 17 et les infrastructures 19. Elle ne retire aucun bloc ni ne change
+les règles d’une sauvegarde existante.
+
+Les mondes 17 et antérieurs gardent leurs codecs, plans, pièces et futurs chunks.
+Le preset 17 public est conservé octet par octet sous un identifiant historique
+caché à la création. Le générateur 19 et son journal sont distincts. Il n’existe
+aucune conversion ou rétrogradation de sauvegarde 19 vers un ancien binaire.
+L’ancienne release reste disponible pour ses propres mondes, et l’option d’un
+nouveau monde permet de comparer les deux configurations du nouveau binaire.
+
+Les nouveaux lieux sont réservés à l’île initiale. La ville et les anciens
+réseaux servent de base ; leurs protections et celles de l’hydrologie restent
+respectées. Les liaisons vers de futurs continents seront construites après
+leur apparition, sans présumer leurs emplacements dans cette génération.
+
+## Objets et systèmes
+
+Les bâtiments suggèrent leurs usages futurs par leurs pièces et aménagements.
+Mailbox, deposit boxes, caméra, réacteur, progression et récompenses
+personnelles ne sont pas activés. Chaque nouveau lieu dispose d’une table
+de coffre propre à la génération 19, avec un outil vanilla lié à son usage et
+quelques fournitures. Les coffres sont partagés et ne se renouvellent pas.
+
+La valeur des rails, équipements et blocs récupérables du décor s’ajoute au
+butin. Leur distribution doit être constatée sur les témoins, sans transformer
+cette première passe en une garantie d’équilibrage économique pour la bêta.
+
+## Vérifications effectuées
+
+- Placement des quatorze architectures, ouvertures, circulation, orientation
+  et appuis du mobilier ; accès réel au coffre et retour possible.
+- Plans bornés sur les trois tailles, terrain non occupé, supports, continuité
+  des tracés et distinction entre ballast praticable et rails retirés.
+- Pièces natives et références locales, y compris pour les longues voies ;
+  géométrie, orientation et rails sauvegardés dans un schéma strict.
+- Création et réouverture d’un monde 19 avec modification témoin ; conservation
+  des starts, butins différés, accès, routes et supports.
+- Option désactivée, paramètres sauvegardés, génération 17 comparée aux preuves
+  de la version publiée, refus des migrations implicites de journaux.
+- `./gradlew check build assemblePack`, artefacts et index, publication immuable
+  puis canal packwiz et deux synchronisations de la même instance Prism.
+
+Les smokes des quatorze architectures, de leurs quatre orientations, des
+plans sur les trois tailles et des pièces natives passent. Le mode désactivé
+est vérifié dans un monde 19 neuf : aucun site ni liaison expérimental.
+`./gradlew check build assemblePack` passe, avec les huit GameTests généraux,
+125 chunks FULL, 5 923 blocs d’eau conservés et 1 800 ticks de fluides.
+Le JAR, le MRpack, les hashes du pack et le ZIP Prism sont vérifiés.
+La release et le canal packwiz sont publiés. Deux synchronisations isolées puis
+deux dans la même instance Prism passent ; 767 fichiers personnels et réglages
+suivis conservent leurs hashes. Le JAR précédent et le suivi packwiz sont
+sauvegardés dans `sanctuary-backups/before-0.1.0-alpha.19/`.
+Voir [le reçu de distribution](packwiz.md#alpha19-publiée--9-septembre-2026).
+Aucun essai visuel dans le client ni essai Windows natif n’a été effectué.
+
+## Témoin natif Moyen, graine 0
+
+Créer un nouveau monde avec **Structures expérimentales activées**.
+`/sanctuary structures` liste les entrées prévues sans charger de chunks ;
+`/locate structure sanctuary:heritage_networks` retrouve l’entrée d’un site.
+Le relevé ci-dessous provient des placements et parcours vérifiés par le moteur.
+
+![Entrées et tracés du témoin alpha.19](images/heritage19-seed0.svg)
+
+Treize des quatorze lieux apparaissent. **La cartothèque est absente de cette
+graine** : la recherche n’a pas trouvé d’emplacement admissible. La ville et les
+trois réseaux souterrains 17 sont conservés. Les raccords recherchés vers la
+ville et l’ancienne mine ne sont pas admis sur ce témoin.
+
+Les sept liaisons comprennent un tracé de fret **dépôt → pompage de 499 blocs**,
+d’une étendue de 245 blocs sur X et 181 sur Z. Son ballast est praticable ;
+478 rails sont présents et 21 sont volontairement manquants. Les autres voies
+et chemins relient gare, dépôt, atelier, poste, club photo, serre et vestiaires.
+Le quai, l’observatoire, le relais, la sous-station et le refuge gardent leurs
+propres accès au terrain, même sans liaison avec ce réseau.
+
+La création et la réouverture dans deux JVM distinctes passent chacune les deux
+GameTests : **112 pièces natives, 111 chunks FULL, 80 487 blocs contrôlés,
+2 882 contrôles de portance, 13 coffres différés et 68 cibles accessibles**.
+Trois tirages de chacune des quatorze tables de butin sont vérifiés
+séparément, sans ouvrir les coffres persistants. Une modification témoin à
+`-204 / 255 / -13` est conservée à la réouverture.
+
+Empreinte stable du plan :
+`7f476c2ecca703a05bf88a550c61cc5cbeff2594024c43ccd9f3620bbc2ad3de`.
+JVM de création `36366`, de réouverture `36481`. Reçus locaux ignorés :
+`build/alpha19-evidence/heritage19-create.json` et `heritage19-reload.json`.
+
+La planification supplémentaire utilise 15 144 colonnes natives, dans un plafond
+de 16 000, en 20,7 s sur le Mac de développement. Ce temps concerne ce plan,
+pas le chargement total du jeu. Les routes sont découpées par chunk ; aucun
+start ne couvre toute leur longueur ni ne charge une destination lointaine.
+
+La prospection 19 consulte les plans hydrologiques de toute l’enveloppe de
+départ, avant de publier les sites. Le contrôle général utilise donc pour 19
+une limite géographique calculée : 5 régions possibles pour Petit, 9 pour
+Moyen/Grand, avec les budgets de colonnes et de sondes contrôlés séparément.
+Le témoin Moyen en consulte 5 ; les quatre régions périphériques représentent
+3,38 s de calcul hydrologique supplémentaire dans le relevé du build.
+Ces consultations ne matérialisent aucun chunk. Les générations historiques
+conservent le contrôle initial de 4 régions maximum autour du spawn.
+
+```sh
+./gradlew :sanctuary:runGameTest -PsanctuaryHeritage19Tests=true -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryHeritage19Tests=true -PsanctuaryExpansionReload=true -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+```
+
+## Autres tailles et couverture du catalogue
+
+Les deux GameTests natifs passent aussi sur Petit et Grand, graine 42.
+Les quatorze architectures ont ainsi chacune été rencontrées et parcourues
+sur le terrain réel, en complément des rotations vérifiées par les smokes.
+
+| Taille et graine | Lieux | Liaisons | Pièces natives | Chunks FULL |
+| --- | ---: | ---: | ---: | ---: |
+| Petit 512, 42 | 10 | 2 | 35 | 44 |
+| Moyen 724, 0 | 13 | 7 | 112 | 111 |
+| Grand 1 024, 42 | 13 | 4 | 47 | 61 |
+
+Pour visiter la cartothèque : **Petit, graine 42**, entrée
+`-101 / 251 / -25`, ou **Grand, graine 42**, entrée `-252 / 249 / 146`.
+Le Petit testé n’a ni poste, ni observatoire, ni atelier ferroviaire, ni quai.
+Le Grand testé n’a pas de quai. Aucun grand axe n’est admis sur ces deux témoins :
+les portées maximales de leurs liaisons sont respectivement de 32 et 55 blocs.
+Le témoin Moyen, graine 0, reste celui conseillé pour découvrir le grand fret.
+Ces résultats rendent explicite la variation de cette première passe ; ils ne
+constituent pas une garantie de présence ou de connectivité pour chaque graine.
+
+Reçus locaux ignorés : `build/alpha19-evidence/small42-create.json` (JVM 36591)
+et `large42-create.json` (JVM 36669).
+
+## Compatibilité 17 vérifiée
+
+Deux JVM de développement distinctes créent puis rouvrent le témoin 17
+**Moyen, graine 0**, avec le nouveau binaire. Les deux GameTests passent dans
+chaque exécution. Le codec, les starts natifs, les butins différés et les
+parcours restent identiques aux preuves de l’alpha.17 publiée. Le bloc d’or
+placé par le test est conservé à la réouverture.
+
+Empreinte du plan 17 :
+`7358ecd7841c03be1977a7f45f37c0c3ef83a32dc27e8d3ec4f0d85d6ee5d3ef`.
+Les trois starts restent ceux documentés dans [le témoin 17](testing-alpha17.md).
+Reçus locaux ignorés : `build/alpha19-evidence/legacy17-create.json` et
+`legacy17-reload.json`.
+
+```sh
+./gradlew :sanctuary:runGameTest -PsanctuaryRuins17Tests=true -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryRuins17Tests=true -PsanctuaryExpansionReload=true -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+```
+
+Ces commandes visent uniquement le monde de développement ignoré. La première
+le recrée ; la seconde conserve ce même monde et lit ses preuves précédentes.
@@ -0,0 +1,327 @@
+# Alpha.20 — identité architecturale
+
+**État : alpha.20 publiée, même instance Prism synchronisée et vérifiée.**
+Ticket WG-23, branche `codex/architecture-alpha20`.
+Minecraft 26.3-pre-2, dépendances identiques à la version 19 publiée.
+
+## Intention
+
+Chaque fonction reçoit une palette et une composition propre : bois clairs et
+grandes baies des lieux publics, pierre et tuf des installations techniques,
+loggias et retraits des logements. Les détails utilisent les blocs vanilla :
+tuf ciselé, briques de tuf ciselées, briques de pierre sculptées, bois et
+planches de chêne/bouleau, granit, diorite et andésite. Moulures, liserés,
+encadrements, murs bas et corniches utilisent escaliers, dalles et trappes.
+Les fondations restent en briques de pierre. Le [catalogue architectural](architecture-alpha20.md)
+décrit les formes et les matériaux effectivement construits pour chaque usage.
+
+La passe concerne les quatorze infrastructures, la ville et ses sous-sols,
+ainsi que les petits réseaux oubliés. Elle ne déplace pas les sites ni les
+routes pour obtenir ses silhouettes. Les plans 19/17/16 servent d’emprises
+certifiées aux nouveaux rendus 20.
+
+## Connexions des blocs
+
+La géométrie complète d’une pièce est assemblée avant le découpage par chunk.
+Les états des vitres, grilles, clôtures et murets sont calculés à partir des voisins
+réellement présents dans ce plan ; les escaliers reçoivent leurs angles.
+Cela évite d’écrire des vitres sans raccord malgré leur juxtaposition, ou de
+dépendre de l’ordre de chargement des chunks voisins. Aucun chunk extérieur
+n’est chargé pour compléter ces états.
+
+## Sauvegardes et réversibilité
+
+Créer un **nouveau monde Sanctuary** pour voir la génération 20. Le bouton
+natif **Personnaliser** garde Petit 512, Moyen 724 et Grand 1 024.
+**Structures expérimentales** reste activé par défaut, enregistré avec le
+monde ; le désactiver dans un autre nouveau monde garde la ville sans les
+réseaux expérimentaux. Les détails urbains de la version 20 restent présents.
+
+Le nouveau codec `sanctuary:island_v20`, son journal et ses types de pièces
+distinguent les nouveaux rendus des précédents. Les mondes 19 et antérieurs
+gardent leurs codecs, leurs pièces et leurs futurs chunks. Aucun monde
+personnel n’est ouvert ni rénové par la mise à jour. Une sauvegarde 20 ne se
+rétrograde pas vers un ancien binaire ; la release 19 reste disponible pour
+ses propres mondes.
+
+## Vérification avant livraison
+
+- Parcours des entrées, pièces et coffres, quatre orientations, marches,
+  supports et limites d’écriture pour chaque type.
+- Connexions des vitres et grilles, angles d’escaliers, comparaison du rendu
+  complet et du rendu découpé selon plusieurs ordres de chunks.
+- Création et réouverture natives, option désactivée, ancien témoin 19.
+- `check build assemblePack`, intégrité des artefacts, publication immuable,
+  deux synchronisations isolées puis deux dans la même instance Prism.
+
+## Reçus natifs : infrastructures et réseaux oubliés
+
+**Création et réouverture réussies**, dans deux JVM distinctes, pour un monde
+jetable **Moyen 724, graine 0**, structures et structures expérimentales activées,
+codec `sanctuary:island_v20`. Les rapports locaux conservés sont
+`build/alpha20-evidence/heritage20-create.json` (processus 39381) et
+`build/alpha20-evidence/heritage20-reload.json` (processus 39736).
+Les journaux correspondants sont `build/alpha20-heritage-create-2.log` et
+`build/alpha20-heritage-reload.log`. Ces fichiers de développement restent
+ignorés par Git ; les valeurs utiles sont transcrites ci-dessous.
+
+| Vérification | Création | Réouverture |
+| --- | --- | --- |
+| Sites expérimentaux naturels | 13 types présents sur 14 | Mêmes 13 sites |
+| Structures natives des sites et voies | 85 starts, 112 pièces | Mêmes empreintes NBT et références |
+| Positions de blocs contrôlées pour sites et voies | 80 487 | 80 487, hors modification témoin autorisée |
+| Chunks `FULL` contrôlés pour sites, voies et réseaux oubliés | 120 | 120 |
+| Contrôles de roche porteuse | 2 882 | 2 882 |
+| Coffres des sites | 13 butins différés, non ouverts | Tables et graines conservées |
+| Réseaux oubliés | 3 réseaux, 15 pièces, 7 639 positions contrôlées | Mêmes plans et structures natives |
+| Coffres des réseaux oubliés | 3 butins différés, non ouverts | Tables et graines conservées |
+| Parcours depuis les entrées | 68 cibles dans les sites et 49 dans les réseaux oubliés | Parcours revérifiés |
+| Modification témoin | Bloc d’or placé en `-203 255 -13` | Bloc d’or conservé |
+
+La cartothèque d’expédition (`EXPEDITION_OFFICE`) n’a pas trouvé d’emplacement
+sur cette graine. Elle fait partie du catalogue et de ses smokes, mais ce reçu
+ne constitue pas une preuve de sa génération naturelle. Les quatorze tables
+de butin sont échantillonnées séparément sans consommer les coffres sauvegardés.
+Les portes et trappes ouvertes pendant le parcours retrouvent leur état initial.
+Aucune expansion ni sauvegarde personnelle n’est ouverte dans ces essais.
+
+Le plan des infrastructures conserve l’empreinte
+`7f476c2ecca703a05bf88a550c61cc5cbeff2594024c43ccd9f3620bbc2ad3de`
+entre création et réouverture. Celui des réseaux oubliés conserve
+`7358ecd7841c03be1977a7f45f37c0c3ef83a32dc27e8d3ec4f0d85d6ee5d3ef`.
+Les pièces passent aussi un aller-retour NBT exact et refusent un numéro de
+schéma inconnu.
+
+### Portée des vérifications de connexion
+
+Les états complets de **594 blocs détaillés** des infrastructures sont comparés
+au rendu : 362 vitres ou barreaux, 49 clôtures, 18 murets et 165 escaliers.
+Sur ce total, **565** sont aussi confrontés aux règles natives de mise à jour
+des voisins (`updateShape`), avec les tags du serveur chargés. **Onze raccords
+de vitres ou barreaux traversent une frontière de chunk** et restent connectés.
+
+Les **29 autres blocs détaillés** ont un voisinage extérieur au plan : leur
+état sauvegardé est bien comparé au rendu, mais ils sont exclus de cet oracle
+natif. Le compteur `externalNeighbors=29` désigne ces 29 blocs contrôlés,
+non un nombre de voisins uniques ; aucune stabilité complète vis-à-vis de ce
+voisinage extérieur n’est revendiquée. Les réseaux oubliés passent pour leur
+part **211 comparaisons d’états et 211 vérifications natives** : 6 vitres ou
+barreaux, 1 clôture et 204 escaliers. Ces résultats sont identiques à la
+réouverture.
+
+### Coordonnées du monde témoin
+
+Créer un nouveau monde **Moyen, graine 0**, avec les deux options de structures
+activées. Les coordonnées indiquent les pieds à l’entrée, pas le centre d’un
+toit. `/sanctuary structures` liste les lieux ;
+`/locate structure sanctuary:heritage_networks`, recherché depuis `0 250 0`
+dans le test, désigne l’entrée du refuge de chantier.
+
+| Lieu | Entrée X Y Z |
+| --- | --- |
+| Gare de fret | `-110 252 -144` |
+| Dépôt communal | `-75 254 -184` |
+| Atelier ferroviaire | `-83 253 -83` |
+| Château d’eau | `164 252 -3` |
+| Serre | `173 252 -42` |
+| Observatoire | `51 251 210` |
+| Quai sur le vide | `184 181 218` |
+| Refuge de chantier | `-10 251 -15` |
+| Réseau minier oublié | `78 252 179` |
+| Salles étranges oubliées | `-194 254 -22` |
+| Réseau technique oublié | `116 253 -157` |
+
+Sept liaisons sont parcourues dans le monde natif. La voie dépôt–château d’eau
+compte **499 positions**, 478 rails présents et 21 rails volontairement absents,
+avec une emprise de 245 blocs en X et 181 en Z. Le test prouve un parcours à pied,
+le ballast et les formes de rails sauvegardées ; il ne prouve pas un trajet
+ininterrompu en wagonnet sur ces voies abandonnées.
+
+## Reçu natif : ville, expansion et grands sous-sols
+
+**Création réussie ; réouverture encore en cours.** Le rapport
+`build/alpha20-evidence/city20-create.json` (processus 40221), associé au journal
+`build/alpha20-city-create.log`, couvre deux villes de génération 20 dans un
+monde de développement jetable. L’île initiale est **Moyen 724, graine 0**.
+Après trois prospections en lecture seule, une expansion de diamètre **256**
+est effectivement préparée : `city16_0_2`, graine `9111000990819250332`, centre
+`2000 -608`, climat `lost_city`. Les deux premiers prospects sont restés sans
+ville et n’ont pas été activés. L’identifiant de test historique ne change pas
+la version 20 enregistrée dans cette expansion.
+
+| Mesure | Ville initiale | Ville d’expansion |
+| --- | --- | --- |
+| Pièces natives | 48 | 23 |
+| Chunks `FULL` inspectés autour des districts | 43 | 19 |
+| Bâtiments parcourus | Immeuble, hôtel, bibliothèque | Immeuble, hall |
+| Cibles intérieures et de toit atteintes | 65 | 46 |
+| Entrées reliées par les rues et les porches seuls | 5 | 2 |
+| Pièces de rue ou pont traversées | 33 | 17, dont un pont |
+| Appuis contrôlés | 71 | 3 |
+| Coffres gardant leur butin différé, non ouvert | 3 | 2 |
+| Témoins de biome urbain | 38 | 19 |
+
+Les **71 pièces** sont issues des plans naturels des deux îles. Le parcours
+urbain ne prend aucun raccourci par le terrain naturel, les intérieurs ou les
+toits : il confirme la continuité des entrées par les rues dessinées.
+La table native d’apparition des monstres est vérifiée comme limitée aux
+zombies vanilla ; cela ne mesure pas un nombre de zombies effectivement apparus.
+Le pont de l’expansion se traverse de `2000 226 -613` à `2000 224 -597`.
+Aucune pile de viaduc n’est présente dans ces deux districts.
+
+Vingt-quatre pièces de test supplémentaires couvrent la sauvegarde des six
+modèles de bâtiments dans quatre orientations. Ce sont des témoins de
+sérialisation, pas vingt-quatre bâtiments naturels. Restaurant et caserne,
+ainsi que la piscine extérieure, ne sont pas présents dans ces deux villes ;
+leurs smokes ne constituent pas une preuve d’apparition naturelle ici.
+
+### Grands équipements du témoin initial
+
+| Repère | Géométrie ou coordonnées constatées |
+| --- | --- |
+| Entrée de l’immeuble | `-30 252 21` |
+| Entrée de l’hôtel | `-8 252 21` |
+| Entrée de la bibliothèque | `-52 252 43` |
+| Trappe d’accès aux sous-sols, position du bloc | `-19 252 41` |
+| Grande piscine, emprise du bâtiment | De `-47 224 -26` à `9 236 4` |
+| Volume d’eau du bassin | 50 × 25 blocs, quatre couches ; de `-44 225 -23` à `5 228 1`, avec les marches dans cette emprise |
+| Grande salle sèche, emprise | De `-54 228 8` à `-30 237 32`, niveau d’entrée 229 |
+| Parking, emprise | De `-8 116 8` à `22 237 32` |
+| Huit planchers du parking, niveaux Y | `117, 133, 149, 165, 181, 197, 213, 229` |
+| Bouche de sortie de l’égout | `-50 117 20` |
+
+La piscine conserve ses 40 appuis, la grande salle 16, le parking 9 et la
+sortie d’égout 6. Ces présences sont constatées sur cette graine ; elles ne
+sont pas garanties sur toutes les îles.
+
+### Fluides et connexions en création
+
+L’essai observe **120 ticks du monde** après la mise en activité des chunks.
+Dix-neuf petits témoins temporaires fermés, placés dans le ciel, démontrent
+l’exécution réelle des fluides par une descente d’eau observée dans chaque
+chunk concerné. Ils sont retirés avant la sauvegarde et exclus des quantités
+d’eau des structures.
+
+Après cette simulation, le grand bassin garde **4 976 cellules d’eau** dans
+son enceinte, et chaque égout conserve ses cinq cellules contrôlées. Les deux
+bouches gardent leur source et produisent de l’eau à l’extérieur. Leur écoulement
+rencontre cependant du terrain : premier bloc solide sous les sorties aux
+niveaux **113** et **191**. Ce témoin prouve des sorties d’eau actives, pas une
+chute libre continue jusqu’au vide.
+
+Les chiffres de connexion suivants sont ceux de l’inspection initiale des
+pièces, avant la simulation des fluides. Le contrôle de réouverture ci-dessous complète ces premières mesures.
+
+| États détaillés | Ville initiale | Expansion | Total |
+| --- | --- | --- | --- |
+| Vitres ou barreaux | 1 457 | 577 | 2 034 |
+| Clôtures | 36 | 14 | 50 |
+| Escaliers | 1 451 | 699 | 2 150 |
+| Comparaisons complètes au rendu | 2 944 | 1 290 | 4 234 |
+| Vérifications supplémentaires par règles natives | 2 277 | 1 276 | 3 553 |
+| Blocs exclus de cet oracle pour voisinage extérieur | 667 | 14 | 681 |
+| Raccords de vitres/barreaux à travers des frontières de chunks | 82 | 22 | 104 |
+
+Les **681 exclusions** gardent leur comparaison d’état au rendu. Elles ne
+prouvent pas la stabilité de la connexion face au voisinage extérieur, comme
+pour les infrastructures. Aucun muret n’est représenté dans cette partie du
+contrôle urbain. Le bloc d’or témoin est placé en `-38 252 21` et le journal
+est sauvegardé avec l’empreinte
+`e776dcab879458b3268ad34f44a003cb53b8b03cfcb67378559d40732f8ce73f` ;
+ils sont conservés à la réouverture.
+
+### Réouverture de la ville et raccords avec le terrain
+
+La réouverture passe dans une seconde JVM (40687), avec **71 pièces natives**,
+**5 coffres différés**, **74 appuis**, **111 cibles accessibles**, le bloc d’or et
+le journal conservés. Reçu : `build/alpha20-evidence/city20-reload.json` ; journal
+`build/alpha20-city-reload-2.log`. La piscine et les sorties d’eau sont revérifiées.
+
+Le test confronte les raccords au voisinage réellement présent. Au coin du
+parking `-8 118 8`, les grilles touchent de la deepslate au nord et à l’ouest :
+Minecraft ajoute légitimement ces raccords après une mise à jour de blocs.
+Le contrôle refuse tout changement de matériau, orientation, demi-bloc ou
+waterlogging ; seules les propriétés de raccord peuvent suivre les règles
+natives. À l’intérieur d’une géométrie connue, l’état du rendu reste exigé.
+
+Sur les **4 234 blocs détaillés**, **4 178** sont alors des états stables selon
+l’oracle Minecraft ; **640** de ces états ont un voisinage extérieur ou un
+voisin ayant lui-même évolué. **56** autres gardent exactement leur état de
+plan et attendent une mise à jour native extérieure : ils sont comptés
+séparément, sans revendiquer leur stabilisation. Les **104 raccords entre
+chunks** restent présents. `externalNeighbors=696` compte les blocs dont le
+voisinage n’est plus entièrement identique au plan, dont les 640 + 56 cas ;
+ce compteur a donc une portée plus large que les 681 exclusions initiales.
+
+## Compatibilité avec la version 19 publiée
+
+Avec le binaire 20, les deux rapports natifs 19 sont **identiques intégralement**
+aux reçus publiés, en retirant seulement le PID et le chemin du monde de test.
+La comparaison porte sur plans, pièces, paramètres, parcours, supports, butins
+et modification témoin, à la création comme à la réouverture.
+
+- Création canonique SHA-256 : `3b055a3bc0fc2ddf4146aef035f5103bb7fe20d55a86fa1d4b87aeedc02f7879`.
+- Réouverture canonique SHA-256 : `aed0962f8dfbfbbf69da1b2153861801c58a3ea2376e6bbec2ef44b90d555d63`.
+- Référence source publiée : `c23e72b8e6fd8308855459f26c08082a68e81b61`.
+- Reçus : `build/alpha20-evidence/legacy19-create.json` et `legacy19-reload.json`.
+
+Les renderers, modèles et pièces historiques restent inchangés ; le preset 19
+caché est identique octet par octet au preset public de la version publiée.
+Les journaux refusent les chargements croisés 19/20 au lieu de convertir un monde.
+
+## Option désactivée et petite île
+
+Le scénario **Moyen, graine 0, option désactivée** passe : plan expérimental
+vide, aucun start natif expérimental et aucune entrée localisable. Le paramètre
+est enregistré. Reçu : `build/alpha20-evidence/experimental-off.json`.
+
+Le témoin **Petit 512, graine 42, option activée** passe avec dix types de lieux,
+35 pièces de sites/voies et 50 chunks `FULL` contrôlés, réseaux oubliés compris.
+La cartothèque est présente, entrée **`-101 251 -25`**, et ses cinq cibles sont
+accessibles. Les **436 états détaillés** des infrastructures passent l’oracle
+natif, dont un avec voisin extérieur ; vingt raccords traversent des frontières
+de chunks. Reçu : `build/alpha20-evidence/small42-create.json`.
+
+Les deux témoins 20 réunis rencontrent et parcourent les **quatorze types
+d’infrastructures**. Ils ne garantissent pas leur présence sur toutes les îles.
+La génération native 20 Grand n’est pas rejouée ici : ses réglages sont couverts
+par les contrôles de codec et les plans de placement conservés. Les six modèles
+urbains sont vérifiés dans les quatre orientations ; leur apparition naturelle
+est distinguée des fixtures ci-dessus.
+
+## Prévisualisation et état de livraison
+
+Le [montage du catalogue](architecture-alpha20.md) provient des exports de
+blocs des renderers et des modèles Minecraft. Il permet de comparer les
+silhouettes, matières, escaliers, vitres et corniches. Il ne montre ni le
+terrain final ni le rendu d’un client avec ses shaders ; ce n’est pas une
+capture de partie et il ne remplace pas les essais de circulation ou de lumière.
+
+| Étape | État de ce reçu |
+| --- | --- |
+| Infrastructures et petits réseaux : création/réouverture natives | Réussi, dans le périmètre détaillé ci-dessus |
+| Ville 20, espaces publics et grands sous-sols : essais natifs | Création et réouverture réussies, 71 pièces et 5 coffres conservés |
+| Compatibilité avec le témoin 19 publié | Rapports complets identiques à la création et à la réouverture |
+| Autres configurations | Petit 512/graine 42 et option désactivée passent ; Grand 20 non rejoué nativement |
+| `check build assemblePack` final et intégrité des artefacts | Réussi ; huit GameTests généraux, JAR/MRpack/ZIP et hashes vérifiés |
+| Publication, canal packwiz et synchronisations Prism | Réussi ; deux passages isolés puis deux dans la même instance, 925 fichiers personnels et réglages préservés |
+
+`./gradlew check build assemblePack --max-workers=1` passe en 4 min 39 s sur
+la machine de développement : 62 tâches, dont 55 exécutées, huit GameTests,
+125 chunks `FULL`, 5 923 blocs d’eau conservés et 1 800 ticks de fluides.
+Les tests des sept nouveaux composants 20 et des anciennes générations passent.
+Les réglages des trois tailles et leur sauvegarde passent également.
+Journal : `build/alpha20-check-build-pack.log`.
+
+Le JAR de production ne contient aucune classe de test. Son identité est
+vérifiée dans le MRpack et le pack local ; les index et le bootstrap officiel
+Prism sont contrôlés. SHA-256 du JAR :
+`9ea10576e641d83c13e1277960a375448a22d416a98a6b327c4d6d2a204c423a`.
+Reçu : `build/alpha20-artifact-validation.log`.
+
+Release immuable depuis `0edac29`, canal packwiz `4e0967d` et deux
+synchronisations isolées vérifiés. Les deux passages dans la même instance
+Prism conservent les hashes de 925 fichiers personnels et réglages. Un seul
+JAR20 est actif ; JAR19 et suivi packwiz sont sauvegardés avant remplacement.
+Voir le [reçu de distribution](packwiz.md#alpha20-publiée--10-septembre-2026).
+Aucun essai client visuel ni essai Windows natif n’a été effectué.
@@ -8,6 +8,6 @@ loader_version=0.19.5
 loom_version=1.17.20
 fabric_api_version=0.160.0+26.3

-mod_version=0.1.0-alpha.17
-pack_version=0.1.0-alpha.17
+mod_version=0.1.0-alpha.20
+pack_version=0.1.0-alpha.20
 maven_group=fr.koka.sanctuary
@@ -40,13 +40,16 @@ tasks.named('runGameTest') {
    systemProperty('sanctuary.test.unified', providers.gradleProperty('sanctuaryUnifiedTests').getOrElse('true'))
    systemProperty('sanctuary.test.diameter', providers.gradleProperty('sanctuaryTestDiameter').getOrElse('724'))
    systemProperty('sanctuary.test.generation', providers.gradleProperty('sanctuaryTestGeneration').getOrElse(
-        providers.gradleProperty('sanctuaryLostCityTests').map { it.toBoolean() }.getOrElse(false) ? '14' : providers.gradleProperty('sanctuaryLostCity15Tests').map { it.toBoolean() }.getOrElse(false) ? '15' : providers.gradleProperty('sanctuaryLostCity16Tests').map { it.toBoolean() }.getOrElse(false) ? '16' : '17'))
+        providers.gradleProperty('sanctuaryLostCityTests').map { it.toBoolean() }.getOrElse(false) ? '14' : providers.gradleProperty('sanctuaryLostCity15Tests').map { it.toBoolean() }.getOrElse(false) ? '15' : providers.gradleProperty('sanctuaryLostCity16Tests').map { it.toBoolean() }.getOrElse(false) ? '16' : providers.gradleProperty('sanctuaryRuins17Tests').map { it.toBoolean() }.getOrElse(false) ? '17' : providers.gradleProperty('sanctuaryHeritage19Tests').map { it.toBoolean() }.getOrElse(false) ? '19' : '20'))
    systemProperty('sanctuary.test.expansion', providers.gradleProperty('sanctuaryExpansionTests').getOrElse('false'))
    systemProperty('sanctuary.test.expansionReload', providers.gradleProperty('sanctuaryExpansionReload').getOrElse('false'))
    systemProperty('sanctuary.test.lostCity', providers.gradleProperty('sanctuaryLostCityTests').getOrElse('false'))
    systemProperty('sanctuary.test.lostCity15', providers.gradleProperty('sanctuaryLostCity15Tests').getOrElse('false'))
+    systemProperty('sanctuary.test.lostCity20', providers.gradleProperty('sanctuaryLostCity20Tests').getOrElse('false'))
    systemProperty('sanctuary.test.lostCity16', providers.gradleProperty('sanctuaryLostCity16Tests').getOrElse('false'))
    systemProperty('sanctuary.test.ruins17', providers.gradleProperty('sanctuaryRuins17Tests').getOrElse('false'))
+    systemProperty('sanctuary.test.heritage20', providers.gradleProperty('sanctuaryHeritage20Tests').getOrElse('false'))
+    systemProperty('sanctuary.test.heritage19', providers.gradleProperty('sanctuaryHeritage19Tests').getOrElse('false'))
    systemProperty('sanctuary.test.experimentalStructures', providers.gradleProperty('sanctuaryExperimentalStructures').getOrElse('true'))
    systemProperty('sanctuary.test.cityMatrix', providers.gradleProperty('sanctuaryCityMatrix').getOrElse('false'))
    systemProperty('sanctuary.test.cityMatrixOnly', providers.gradleProperty('sanctuaryCityMatrixOnly').getOrElse('false'))
@@ -69,10 +72,16 @@ tasks.named('processGametestResources') {
    inputs.property('lostCity16', lostCity16)
    def ruins17 = providers.gradleProperty('sanctuaryRuins17Tests').map { it.toBoolean() }.getOrElse(false)
    inputs.property('ruins17', ruins17)
+    def lostCity20 = providers.gradleProperty('sanctuaryLostCity20Tests').map { it.toBoolean() }.getOrElse(false)
+    inputs.property('lostCity20', lostCity20)
+    def heritage20 = providers.gradleProperty('sanctuaryHeritage20Tests').map { it.toBoolean() }.getOrElse(false)
+    inputs.property('heritage20', heritage20)
+    def heritage19 = providers.gradleProperty('sanctuaryHeritage19Tests').map { it.toBoolean() }.getOrElse(false)
+    inputs.property('heritage19', heritage19)
    def voidReuse = providers.gradleProperty('sanctuaryVoidReuseTests').map { it.toBoolean() }.getOrElse(false)
    inputs.property('voidReuse', voidReuse)
    filesMatching('fabric.mod.json') {
-        expand(gametest_entrypoint: ruins17 ? 'fr.koka.sanctuary.gametest.Ruins17WorldGameTests' : voidReuse ? 'fr.koka.sanctuary.gametest.ExpansionVoidReuseGameTests' : lostCity16 ? 'fr.koka.sanctuary.gametest.LostCity16WorldGameTests' : lostCity15 ? 'fr.koka.sanctuary.gametest.LostCity15WorldGameTests' : lostCity ? 'fr.koka.sanctuary.gametest.LostCityWorldGameTests' : expansion ? 'fr.koka.sanctuary.gametest.ExpansionWorldGameTests' : benchmark
+        expand(gametest_entrypoint: lostCity20 ? 'fr.koka.sanctuary.gametest.LostCity20WorldGameTests' : heritage20 ? 'fr.koka.sanctuary.gametest.Heritage20WorldGameTests' : heritage19 ? 'fr.koka.sanctuary.gametest.Heritage19WorldGameTests' : ruins17 ? 'fr.koka.sanctuary.gametest.Ruins17WorldGameTests' : voidReuse ? 'fr.koka.sanctuary.gametest.ExpansionVoidReuseGameTests' : lostCity16 ? 'fr.koka.sanctuary.gametest.LostCity16WorldGameTests' : lostCity15 ? 'fr.koka.sanctuary.gametest.LostCity15WorldGameTests' : lostCity ? 'fr.koka.sanctuary.gametest.LostCityWorldGameTests' : expansion ? 'fr.koka.sanctuary.gametest.ExpansionWorldGameTests' : benchmark
            ? 'fr.koka.sanctuary.gametest.WorldgenPerformanceGameTests'
            : unified ? 'fr.koka.sanctuary.gametest.UnifiedWorldGameTests'
            : 'fr.koka.sanctuary.gametest.SanctuaryWorldGameTests')
@@ -415,3 +424,47 @@ tasks.named('check') { dependsOn('lostCityFoundation16Smoke') }
    }
    tasks.named('check') { dependsOn(smoke) }
 }
+
+// Local native starts keep the long heritage routes bounded by Minecraft's reference range.
+['Planner', 'Renderer', 'Piece'].each { component ->
+    def smoke = tasks.register("heritage19${component}Smoke", JavaExec) {
+        group = 'verification'
+        dependsOn('testClasses')
+        classpath = sourceSets.test.runtimeClasspath
+        mainClass = "fr.koka.sanctuary.worldgen.heritage.Heritage${component}19Smoke"
+    }
+    tasks.named('check') { dependsOn(smoke) }
+}
+
+// Generation20 architecture retains the previous renderers and verifies connected block states.
+[
+    connectedBlocks20Smoke: 'detail.ConnectedBlocks20Smoke',
+    heritage20RendererSmoke: 'heritage.HeritageRenderer20Smoke',
+    heritage20PieceSmoke: 'heritage.HeritagePiece20Smoke',
+    ruins20RendererSmoke: 'ruins.RuinsRenderer20Smoke',
+    lostCityUnderground20Smoke: 'city.LostCityUnderground20Smoke',
+    lostCitySurface20Smoke: 'city.LostCitySurface20Smoke',
+    lostCityInteriors20Smoke: 'city.LostCityInteriors20Smoke'
+].each { name, harness ->
+    def smoke = tasks.register(name, JavaExec) {
+        group = 'verification'
+        dependsOn('testClasses')
+        classpath = sourceSets.test.runtimeClasspath
+        mainClass = "fr.koka.sanctuary.worldgen.${harness}"
+    }
+    tasks.named('check') { dependsOn(smoke) }
+}
+
+// Optional actual block-state exports for architectural review; never enabled in ordinary checks.
+tasks.named('heritage20RendererSmoke') {
+    if (providers.gradleProperty('sanctuaryArchitecturePreview').isPresent())
+        systemProperty('sanctuary.test.heritage20.export', rootProject.layout.buildDirectory.dir('alpha20-preview/heritage').get().asFile.absolutePath)
+}
+tasks.named('lostCityInteriors20Smoke') {
+    if (providers.gradleProperty('sanctuaryArchitecturePreview').isPresent())
+        systemProperty('sanctuary.city20.preview', rootProject.layout.buildDirectory.file('alpha20-preview/city.json').get().asFile.absolutePath)
+}
+tasks.named('lostCitySurface20Smoke') {
+    if (providers.gradleProperty('sanctuaryArchitecturePreview').isPresent())
+        systemProperty('sanctuary.city20.exteriorPreview', rootProject.layout.buildDirectory.file('alpha20-preview/exterior.json').get().asFile.absolutePath)
+}
@@ -0,0 +1,452 @@
+package fr.koka.sanctuary.gametest;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.mojang.serialization.JsonOps;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import fr.koka.sanctuary.worldgen.heritage.HeritagePiece19;
+import fr.koka.sanctuary.worldgen.heritage.HeritagePlan19;
+import fr.koka.sanctuary.worldgen.heritage.HeritageRenderer19;
+import fr.koka.sanctuary.worldgen.heritage.HeritageStructures19;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.HexFormat;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Predicate;
+import net.fabricmc.fabric.api.gametest.v1.GameTest;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.DoorBlock;
+import net.minecraft.world.level.block.TrapDoorBlock;
+import net.minecraft.world.level.block.entity.RandomizableContainerBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.LevelResource;
+import net.minecraft.world.level.storage.loot.LootParams;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.level.storage.loot.parameters.LootContextParams;
+import net.minecraft.world.level.storage.loot.parameters.LootContextParamSets;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.phys.Vec3;
+
+/** Native creation/reload proof confined to a disposable generation19 starter island. */
+public final class Heritage19WorldGameTests {
+    private static final Direction[] HORIZONTAL = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    @GameTest(maxTicks = 12000)
+    public void heritagePersistsWithRealDestinations(GameTestHelper helper) {
+        helper.assertTrue(helper.getLevel().getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator,
+            "The heritage proof requires a Sanctuary generator");
+        var generator = (SanctuaryChunkGenerator) helper.getLevel().getChunkSource().getGenerator();
+        helper.assertTrue(generator.rootGeneration() == 19, "Use a fresh generation19 test world; do not convert an old save");
+        new Scenario(helper, generator, Boolean.getBoolean("sanctuary.test.expansionReload")).advance();
+    }
+    private static final class Scenario {
+        final GameTestHelper helper;
+        final ServerLevel level;
+        final SanctuaryChunkGenerator generator;
+        final HeritagePlan19 plan;
+        final boolean reload;
+        final Map<String, Object> report = new LinkedHashMap<>();
+        final List<ChunkPos> chunks = new ArrayList<>();
+        final List<StructureStart> starts = new ArrayList<>();
+        JsonObject previous;
+        BlockPos gold;
+        int nextChunk;
+        boolean prepared;
+        Scenario(GameTestHelper helper, SanctuaryChunkGenerator generator, boolean reload) {
+            this.helper = helper; this.level = helper.getLevel(); this.generator = generator; this.reload = reload;
+            this.plan = generator.heritagePlan19();
+            report.put("seed", level.getSeed()); report.put("size", generator.initialDiameter());
+            report.put("process_id", ProcessHandle.current().pid()); report.put("world_directory", world(level).toString());
+            report.put("experimental_structures", generator.experimentalStructures());
+            report.put("structures_enabled", level.structureManager().shouldGenerateStructures());
+            report.put("scope", "Native local starts, saved sites and routes, player-sized entrances, supports and unopened chests on the starter island. "
+                + "All14 tool tables are sampled separately without consuming a saved chest. Door states are restored after traversal. "
+                + "No personal save or expansion is opened; one disposable outer-wall edit is checked in a second JVM. "
+                + "Missing rails are intentional; this proof checks walking and saved rail shapes, not an uninterrupted minecart journey.");
+        }
+        void advance() {
+            try {
+                if (!prepared) { report.put("stage", "prepare"); prepare(); prepared = true; if (plan.isEmpty()) { finishDisabled(); return; } }
+                if (nextChunk < chunks.size()) {
+                    report.put("stage", "load_full_chunks"); var pos = chunks.get(nextChunk++);
+                    helper.assertTrue(level.getChunk(pos.x(), pos.z(), ChunkStatus.FULL, true) instanceof LevelChunk,
+                        "Heritage footprint must reach native FULL: " + pos);
+                    if (nextChunk % 20 == 0) SanctuaryMod.LOGGER.info("Heritage19 loaded {}/{} footprint chunks", nextChunk, chunks.size());
+                    helper.runAtTickTime(helper.getTick() + 1, this::advance); return;
+                }
+                report.put("stage", "verify_native_geometry"); verifyPlaced(); report.put("passed", true);
+                if (!reload) {
+                    helper.assertTrue(gold != null && level.getBlockState(gold).isCollisionShapeFullBlock(level, gold), "Gold witness must replace a solid wall away from circulation");
+                    level.setBlock(gold, Blocks.GOLD_BLOCK.defaultBlockState(), 3); report.put("gold_witness", coords(gold));
+                    helper.assertTrue(level.getServer().saveEverything(true, true, true), "Flush native starts, unopened loot and the wall edit");
+                    report.put("world_flushed_before_shutdown", true);
+                } else {
+                    helper.assertTrue(level.getBlockState(gold).is(Blocks.GOLD_BLOCK), "Reload replaced the player's wall edit");
+                    report.put("gold_witness", coords(gold)); report.put("gold_witness_preserved", true);
+                }
+                write(level, report, reload); helper.succeed();
+            } catch (Exception failure) {
+                report.put("passed", false); report.put("failure", failure.toString());
+                try { write(level, report, reload); } catch (IOException ignored) { }
+                throw new IllegalStateException("Heritage19 native " + (reload ? "reload" : "creation") + " failed", failure);
+            }
+        }
+        void prepare() throws IOException {
+            var ops = RegistryOps.create(JsonOps.INSTANCE, level.registryAccess());
+            var encoded = ChunkGenerator.CODEC.encodeStart(ops, generator).getOrThrow();
+            var decoded = ChunkGenerator.CODEC.parse(ops, encoded).getOrThrow();
+            helper.assertTrue(decoded instanceof SanctuaryChunkGenerator copy && copy.rootGeneration() == 19
+                && copy.experimentalStructures() == generator.experimentalStructures(), "Generation19 codec lost its experimental switch");
+            report.put("generator_codec", encoded); report.put("plan_sha256", planHash(plan));
+            report.put("planned_sites", plan.sites().stream().map(site -> Map.of("id", site.id(), "kind", site.kind().name(),
+                "entry", coords(HeritagePiece19.locator(site)), "floor_y", site.floorY(), "foundation_depth", site.foundationDepth(), "footings", site.supports().size())).toList());
+            report.put("planned_links", plan.links().stream().map(link -> Map.of("id", link.id(), "from", link.fromId(), "to", link.toId(), "kind", link.kind().name(), "length", link.path().size(), "path", pathCoords(link))).toList());
+            report.put("planning_samples", plan.samples()); report.put("planning_columns", plan.columns()); report.put("planning_diagnostics", plan.diagnostics());
+            helper.assertTrue(plan.samples() <= HeritagePlan19.MAX_SAMPLES && plan.columns() <= HeritagePlan19.MAX_COLUMNS, "Heritage planning exceeded its budget");
+            verifyLootTables(helper, report);
+            if (reload) {
+                previous = JsonParser.parseString(Files.readString(proof(level))).getAsJsonObject();
+                helper.assertTrue(previous.get("passed").getAsBoolean() && previous.get("world_flushed_before_shutdown").getAsBoolean(), "Reload needs a successful flushed creation proof");
+                helper.assertTrue(previous.get("process_id").getAsLong() != ProcessHandle.current().pid(), "Reload must use a second JVM");
+                helper.assertTrue(previous.get("seed").getAsLong() == level.getSeed() && previous.get("size").getAsInt() == generator.initialDiameter()
+                    && previous.get("world_directory").getAsString().equals(world(level).toString()), "Reload selected another world");
+                helper.assertTrue(previous.get("generator_codec").equals(encoded) && previous.get("plan_sha256").getAsString().equals(planHash(plan)), "Saved settings or planned identities changed on reload");
+                if (previous.has("gold_witness")) gold = readPos(previous.getAsJsonArray("gold_witness"));
+            }
+            if (!generator.experimentalStructures() || !level.structureManager().shouldGenerateStructures()) {
+                helper.assertTrue(plan.isEmpty() && plan.segments().isEmpty() && plan.links().isEmpty(), "Disabled generation published heritage geometry"); return;
+            }
+            helper.assertTrue(!plan.isEmpty(), "Enabled reference island has no heritage site");
+            report.put("present_site_kinds", plan.sites().stream().map(s -> s.kind().name()).distinct().sorted().toList());
+            report.put("missing_site_kinds", java.util.Arrays.stream(HeritagePlan19.Kind.values()).filter(k -> plan.sites().stream().noneMatch(s -> s.kind() == k)).map(Enum::name).toList());
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(HeritageStructures19.KEY);
+            var origins = new HashSet<ChunkPos>(); var uniqueChunks = new HashSet<ChunkPos>();
+            plan.sites().forEach(s -> origins.add(new ChunkPos(s.startChunkX(), s.startChunkZ())));
+            plan.segments().forEach(s -> origins.add(new ChunkPos(s.startChunkX(), s.startChunkZ())));
+            for (var origin : origins.stream().sorted(Comparator.comparingInt(ChunkPos::x).thenComparingInt(ChunkPos::z)).toList()) {
+                var chunk = level.getChunk(origin.x(), origin.z(), ChunkStatus.STRUCTURE_STARTS, true);
+                var start = chunk.getStartForStructure(structure.value());
+                helper.assertTrue(start != null && start.isValid(), "Accepted site/route has no native start at " + origin); starts.add(start);
+                for (var piece : start.getPieces()) {
+                    helper.assertTrue(piece instanceof HeritagePiece19, "Heritage loaded a foreign piece type");
+                    var box = piece.getBoundingBox();
+                    helper.assertTrue(Math.abs((long) (box.minX() >> 4) - origin.x()) <= 7 && Math.abs((long) (box.maxX() >> 4) - origin.x()) <= 7
+                        && Math.abs((long) (box.minZ() >> 4) - origin.z()) <= 7 && Math.abs((long) (box.maxZ() >> 4) - origin.z()) <= 7, "Native start references a distant route endpoint");
+                    box.intersectingChunks().forEach(uniqueChunks::add);
+                }
+            }
+            for (var site : plan.sites()) uniqueChunks.add(ChunkPos.containing(HeritagePiece19.locator(site)));
+            for (var link : plan.links()) for (var point : link.path()) uniqueChunks.add(new ChunkPos(point.x() >> 4, point.z() >> 4));
+            helper.assertTrue(uniqueChunks.size() <= 1024, "Bounded proof footprint exceeds1024 chunks");
+            chunks.addAll(uniqueChunks.stream().sorted(Comparator.comparingInt(ChunkPos::x).thenComparingInt(ChunkPos::z)).toList());
+        }
+        void finishDisabled() throws IOException {
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(HeritageStructures19.KEY);
+            var start = level.getChunk(0, 0, ChunkStatus.STRUCTURE_STARTS, true).getStartForStructure(structure.value());
+            helper.assertTrue(start == null || !start.isValid(), "Disabled heritage emitted a native start");
+            helper.assertTrue(generator.findNearestMapStructure(level, HolderSet.direct(structure), new BlockPos(0, 250, 0), 100, false) == null, "Disabled heritage is locatable");
+            report.put("empty_plan_verified", true); report.put("passed", true);
+            if (!reload) { helper.assertTrue(level.getServer().saveEverything(true, true, true), "Save disabled experiment setting"); report.put("world_flushed_before_shutdown", true); }
+            write(level, report, reload); helper.succeed();
+        }
+        void verifyPlaced() {
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(HeritageStructures19.KEY);
+            var context = StructurePieceSerializationContext.fromLevel(level); var summaries = new ArrayList<Map<String, Object>>();
+            int blocks = 0, chests = 0, pieces = 0, supports = 0;
+            for (var start : starts) {
+                var origin = start.getChunkPos(); var saved = start.createTag(context, origin); String nativeHash = hash(saved.toString());
+                var copy = StructureStart.loadStaticStart(context, saved, level.getSeed());
+                helper.assertTrue(copy != null && copy.isValid() && copy.createTag(context, origin).equals(saved), "Native start failed an exact NBT roundtrip");
+                var expectedPayloads = new HashSet<net.minecraft.nbt.CompoundTag>();
+                plan.sites().stream().filter(s -> s.startChunkX() == origin.x() && s.startChunkZ() == origin.z()).forEach(s -> expectedPayloads.add(HeritagePiece19.encodeSite(s)));
+                plan.segments().stream().filter(s -> s.startChunkX() == origin.x() && s.startChunkZ() == origin.z()).forEach(s -> expectedPayloads.add(HeritagePiece19.encodeSegment(s)));
+                var actualPayloads = new HashSet<net.minecraft.nbt.CompoundTag>();
+                if (reload) {
+                    JsonObject prior = null;
+                    for (var value : previous.getAsJsonArray("starts")) { var item = value.getAsJsonObject(); var at = item.getAsJsonArray("start_chunk"); if (at.get(0).getAsInt() == origin.x() && at.get(1).getAsInt() == origin.z()) prior = item; }
+                    helper.assertTrue(prior != null && prior.get("native_start_sha256").getAsString().equals(nativeHash), "Reload changed saved geometry or native reference count");
+                }
+                var loot = new ArrayList<Map<String, Object>>();
+                for (var value : start.getPieces()) {
+                    var piece = (HeritagePiece19) value; pieces++;
+                    var tag = piece.createTag(context); var restored = new HeritagePiece19(context, tag);
+                    helper.assertTrue(restored.createTag(context).equals(tag), "Saved piece parameters changed on native load");
+                    actualPayloads.add(tag.getCompound("SanctuaryHeritage").orElseThrow());
+                    var corrupt = tag.copy(); corrupt.getCompound("SanctuaryHeritage").orElseThrow().putInt("Schema", 20);
+                    boolean rejected = false; try { new HeritagePiece19(context, corrupt); } catch (IllegalArgumentException expected) { rejected = true; }
+                    helper.assertTrue(rejected, "Unknown schema must fail closed");
+                    piece.getBoundingBox().intersectingChunks().forEach(at -> helper.assertTrue(level.getChunk(at.x(), at.z(), ChunkStatus.FULL, true)
+                        .getReferencesForStructure(structure.value()).contains(origin.pack()), "FULL chunk lost its native structure reference"));
+                    var expected = rendered(piece); blocks += expected.blocks().size();
+                    for (var entry : expected.blocks().entrySet()) {
+                        var at = entry.getKey(); var wanted = entry.getValue(); helper.assertTrue(piece.getBoundingBox().isInside(at), "Renderer escaped saved bounds");
+                        if (reload && at.equals(gold)) continue;
+                        helper.assertTrue(level.getBlockState(at).is(wanted.getBlock()), "Clipping or decoration changed heritage at " + at + ": expected " + wanted + " got " + level.getBlockState(at));
+                        helper.assertTrue(!wanted.is(Blocks.SPAWNER), "Heritage must not create spawners");
+                    }
+                    if (piece.isSite()) {
+                        supports += verifySiteBearing(helper, generator, plan, piece.site());
+                        if (!reload && gold == null) {
+                            gold = expected.blocks().entrySet().stream().filter(e -> isOuterWall(piece.site(), e.getKey()) && e.getValue().isCollisionShapeFullBlock(level, e.getKey()))
+                                .map(Map.Entry::getKey).sorted(Comparator.<BlockPos>comparingInt(p -> p.getY()).thenComparingInt(p -> p.getX()).thenComparingInt(p -> p.getZ())).findFirst().orElse(null);
+                        }
+                    } else for (var cell : piece.segment().cells()) { supports++; assertRock(helper, new BlockPos(cell.x(), cell.minY() - 1, cell.z())); }
+                    for (var chest : expected.chests()) {
+                        helper.assertTrue(level.getBlockEntity(chest.position()) instanceof RandomizableContainerBlockEntity, "Deferred chest is missing");
+                        var entity = (RandomizableContainerBlockEntity) level.getBlockEntity(chest.position());
+                        helper.assertTrue(entity.getLootTable() != null && entity.getLootTable().equals(chest.table()) && entity.getLootTableSeed() == chest.seed(), "Deferred loot table/seed was lost or consumed");
+                        if (piece.isSite()) helper.assertTrue(chest.table().equals(lootKey(piece.site().kind())), "Site uses another kind's tool table");
+                        loot.add(Map.of("position", coords(chest.position()), "table", chest.table().identifier().toString(), "seed", chest.seed())); chests++;
+                    }
+                }
+                helper.assertTrue(actualPayloads.equals(expectedPayloads) && start.getPieces().size() == expectedPayloads.size(), "Native start lost or duplicated planned pieces");
+                summaries.add(Map.of("start_chunk", List.of(origin.x(), origin.z()), "native_start_sha256", nativeHash, "pieces", start.getPieces().size(), "unopened_chests", loot));
+            }
+            report.put("starts", summaries); report.put("native_pieces", pieces); report.put("native_blocks_checked", blocks);
+            report.put("full_chunks_checked", chunks.size()); report.put("rock_supports_checked", supports); report.put("unopened_deferred_chests", chests);
+            report.put("stage", "verify_site_routes"); var sites = new ArrayList<Map<String, Object>>(); for (var site : plan.sites()) sites.add(verifyAccess(helper, site)); report.put("native_sites", sites);
+            report.put("stage", "verify_read_only_landings");
+            report.put("read_only_landmarks", verifyReadOnlyLandings(helper, generator, plan));
+            report.put("stage", "verify_island_routes"); report.put("native_links", verifyLinks(helper, plan));
+            int greatestSpan = plan.links().stream().mapToInt(Heritage19WorldGameTests::routeSpan).max().orElse(0);
+            report.put("greatest_single_route_span", greatestSpan);
+            if (level.getSeed() == 0 && generator.initialDiameter() == 724) {
+                int requiredSpan = generator.initialDiameter() / 4;
+                report.put("reference_minimum_route_span", requiredSpan);
+                helper.assertTrue(greatestSpan >= requiredSpan, "Seed0 Medium must demonstrate an island-scale route spanning at least "
+                    + requiredSpan + " blocks on X or Z; got " + greatestSpan);
+            }
+            var located = generator.findNearestMapStructure(level, HolderSet.direct(structure), new BlockPos(0, 250, 0), 100, false);
+            helper.assertTrue(located != null && located.getSecond().is(HeritageStructures19.KEY) && plan.sites().stream().anyMatch(s -> HeritagePiece19.locator(s).equals(located.getFirst())), "Locate must lead to a real exterior site entry");
+            report.put("locate", coords(located.getFirst()));
+        }
+    }
+    private record Chest(BlockPos position, ResourceKey<LootTable> table, long seed) {}
+    private record Rendered(Map<BlockPos, BlockState> blocks, List<Chest> chests) {}
+    private static Rendered rendered(HeritagePiece19 piece) {
+        var blocks = new HashMap<BlockPos, BlockState>(); var chests = new ArrayList<Chest>();
+        int x0 = piece.isSite() ? piece.site().minX() : piece.segment().minX();
+        int y0 = piece.isSite() ? piece.site().floorY() : piece.segment().minY();
+        int z0 = piece.isSite() ? piece.site().minZ() : piece.segment().minZ();
+        var writer = new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState state) { blocks.put(new BlockPos(x0 + x, y0 + y, z0 + z), state); }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+                var at = new BlockPos(x0 + x, y0 + y, z0 + z); blocks.put(at, Blocks.CHEST.defaultBlockState()); chests.add(new Chest(at, table, RandomSource.create(seed).nextLong()));
+            }
+        };
+        if (piece.isSite()) HeritageRenderer19.render(piece.site(), writer); else HeritageRenderer19.renderSegment(piece.segment(), writer);
+        return new Rendered(blocks, chests);
+    }
+    private static boolean isOuterWall(HeritagePlan19.Site site, BlockPos pos) {
+        return pos.getY() >= site.floorY() + 2 && pos.getY() <= site.floorY() + 3
+            && (pos.getX() == site.minX() + 2 || pos.getX() == site.maxX() - 2 || pos.getZ() == site.minZ() + 2 || pos.getZ() == site.maxZ() - 2)
+            && Math.abs(pos.getX() - site.entry().x()) + Math.abs(pos.getZ() - site.entry().z()) > 6;
+    }
+    private static Map<String, Object> verifyAccess(GameTestHelper helper, HeritagePlan19.Site site) {
+        var level = helper.getLevel(); var expected = rendered(new HeritagePiece19(site)); var doors = new HashMap<BlockPos, BlockState>();
+        expected.blocks().forEach((at, state) -> {
+            if ((state.getBlock() instanceof DoorBlock || state.getBlock() instanceof TrapDoorBlock) && state.hasProperty(BlockStateProperties.OPEN)) doors.put(at, level.getBlockState(at));
+        });
+        doors.forEach((at, state) -> level.setBlock(at, state.setValue(BlockStateProperties.OPEN, true), 2));
+        try {
+            var entry = HeritagePiece19.locator(site);
+            Predicate<BlockPos> inside = p -> p.equals(entry) || p.getX() >= site.minX() && p.getX() <= site.maxX()
+                && p.getZ() >= site.minZ() && p.getZ() <= site.maxZ() && p.getY() >= site.floorY() - 4 && p.getY() < site.maxY();
+            var reached = walk(helper, entry, inside); int targets = 0;
+            for (var target : HeritageRenderer19.targets(site)) {
+                var at = new BlockPos(site.minX() + target.x(), site.floorY() + target.y(), site.minZ() + target.z());
+                helper.assertTrue(reached.contains(at), "Site " + site.id() + " cannot reach " + target.name() + " at " + at); targets++;
+            }
+            return Map.of("id", site.id(), "kind", site.kind().name(), "entry", coords(entry), "standing_cells", reached.size(), "walkable_targets", targets);
+        } finally { doors.forEach((at, state) -> level.setBlock(at, state, 2)); }
+    }
+    private static List<Map<String, Object>> verifyLinks(GameTestHelper helper, HeritagePlan19 plan) {
+        helper.assertTrue(!plan.links().isEmpty(), "Reference island needs a real route between accepted destinations");
+        var entries = new HashMap<String, HeritagePlan19.Entry>(); plan.sites().forEach(s -> entries.put(s.id(), s.entry())); plan.landmarks().forEach(s -> entries.put(s.id(), s.entry()));
+        var cells = new HashMap<Long, HeritagePlan19.Cell>(); plan.segments().forEach(s -> s.cells().forEach(c -> cells.put(column(c.x(), c.z()), c)));
+        var result = new ArrayList<Map<String, Object>>();
+        for (var link : plan.links()) {
+            var from = entries.get(link.fromId()); var to = entries.get(link.toId());
+            helper.assertTrue(from != null && to != null, "Route points to an absent destination");
+            var first = link.path().getFirst(); var last = link.path().getLast();
+            helper.assertTrue(first.x() == from.x() && first.z() == from.z() && first.floorY() + 1 == from.y()
+                && last.x() == to.x() && last.z() == to.z() && last.floorY() + 1 == to.y(), "Route does not meet its real entrances");
+            int present = 0, missing = 0;
+            for (int i = 0; i < link.path().size(); i++) {
+                var point = link.path().get(i); var at = new BlockPos(point.x(), point.floorY() + 1, point.z());
+                helper.assertTrue(standable(helper.getLevel(), at), "Ballast route " + link.id() + " is blocked at " + at);
+                if (i > 0) { var prior = link.path().get(i - 1); if (point.floorY() > prior.floorY()) helper.assertTrue(clearBody(helper.getLevel(), new BlockPos(prior.x(), prior.floorY() + 2, prior.z())), "Route slope cannot be climbed by a player"); }
+                var cell = cells.get(column(point.x(), point.z()));
+                if (cell != null && cell.rail() != HeritagePlan19.Rail.NONE) {
+                    var actual = helper.getLevel().getBlockState(at);
+                    if (cell.railPresent()) {
+                        helper.assertTrue(actual.is(Blocks.RAIL), "Saved existing rail disappeared");
+                        helper.assertTrue(actual.getValue(BlockStateProperties.RAIL_SHAPE).name().equals(cell.rail().name()), "Native rail update changed the intended slope or curve at " + at); present++;
+                    } else { helper.assertTrue(!actual.is(Blocks.RAIL), "An intentionally missing rail regenerated"); missing++; }
+                }
+            }
+            int spanX = link.path().stream().mapToInt(HeritagePlan19.Point::x).max().orElseThrow() - link.path().stream().mapToInt(HeritagePlan19.Point::x).min().orElseThrow();
+            int spanZ = link.path().stream().mapToInt(HeritagePlan19.Point::z).max().orElseThrow() - link.path().stream().mapToInt(HeritagePlan19.Point::z).min().orElseThrow();
+            result.add(Map.of("id", link.id(), "from", link.fromId(), "to", link.toId(), "kind", link.kind().name(), "length", link.path().size(),
+                "span_x", spanX, "span_z", spanZ, "existing_rails", present, "deliberately_missing_rails", missing, "path", pathCoords(link)));
+        }
+        return result;
+    }
+    private static int routeSpan(HeritagePlan19.Link link) {
+        int spanX = link.path().stream().mapToInt(HeritagePlan19.Point::x).max().orElseThrow()
+            - link.path().stream().mapToInt(HeritagePlan19.Point::x).min().orElseThrow();
+        int spanZ = link.path().stream().mapToInt(HeritagePlan19.Point::z).max().orElseThrow()
+            - link.path().stream().mapToInt(HeritagePlan19.Point::z).min().orElseThrow();
+        return Math.max(spanX, spanZ);
+    }
+    private static List<List<Integer>> pathCoords(HeritagePlan19.Link link) {
+        return link.path().stream().map(point -> List.of(point.x(), point.floorY(), point.z())).toList();
+    }
+    private static int verifySiteBearing(GameTestHelper helper, SanctuaryChunkGenerator generator, HeritagePlan19 plan, HeritagePlan19.Site site) {
+        int checked = 0;
+        // The planner certifies a nine-point bearing grid, either directly below its slab or below a saved short footing.
+        for (int dx : new int[] {1, 8, 15}) for (int dz : new int[] {1, 8, 15}) {
+            int x = site.minX() + dx, z = site.minZ() + dz;
+            var support = site.supports().stream().filter(s -> s.x() == x && s.z() == z).findFirst();
+            int bottom = support.map(HeritagePlan19.Support::minY).orElse(site.minY());
+            for (int below = 1; below <= 2; below++) {
+                var at = new BlockPos(x, bottom - below, z); assertRock(helper, at);
+                helper.assertTrue(plan.protects(at.getX(), at.getY(), at.getZ()) && generator.protectsCityDecoration(at),
+                    "Site's certified bearing layer is not published in the decoration mask: " + site.id() + " at " + at);
+                helper.assertTrue(!plan.contains(at.getX(), at.getY(), at.getZ()), "Original bearing rock became a writable heritage volume: " + at);
+                checked++;
+            }
+        }
+        return checked;
+    }
+    private static List<Map<String, Object>> verifyReadOnlyLandings(GameTestHelper helper, SanctuaryChunkGenerator generator, HeritagePlan19 plan) {
+        var used = new HashSet<String>(); plan.links().forEach(link -> { used.add(link.fromId()); used.add(link.toId()); });
+        var result = new ArrayList<Map<String, Object>>();
+        for (var landmark : plan.landmarks()) if (used.contains(landmark.id())) {
+            var e = landmark.entry(); int checked = 0;
+            for (int side = -1; side <= 1; side++) {
+                int x = e.x() + ((e.facing() & 1) == 0 ? side : 0), z = e.z() + ((e.facing() & 1) == 1 ? side : 0);
+                for (int y = e.y() - 2; y <= e.y() + 2; y++) {
+                    var at = new BlockPos(x, y, z);
+                    helper.assertTrue(plan.protects(x, y, z) && generator.protectsCityDecoration(at), "Read-only arrival lost its decoration mask: " + landmark.id() + " at " + at);
+                    helper.assertTrue(!plan.contains(x, y, z), "Heritage gained write ownership of a historical arrival: " + landmark.id() + " at " + at);
+                    if (y == e.y() - 1) assertRock(helper, at);
+                    if (y >= e.y()) helper.assertTrue(helper.getLevel().getBlockState(at).isAir(), "Decoration obstructed a certified historical arrival: " + at);
+                    checked++;
+                }
+            }
+            result.add(Map.of("id", landmark.id(), "entry", List.of(e.x(), e.y(), e.z()), "read_only_cells", checked));
+        }
+        return result;
+    }
+    private static void assertRock(GameTestHelper helper, BlockPos at) {
+        helper.assertTrue(helper.getLevel().getBlockState(at).isSolid() && helper.getLevel().getFluidState(at).isEmpty(), "Lost original rock bearing at " + at);
+    }
+    private static void verifyLootTables(GameTestHelper helper, Map<String, Object> report) {
+        var result = new ArrayList<Map<String, Object>>(); var level = helper.getLevel();
+        var params = new LootParams.Builder(level).withParameter(LootContextParams.ORIGIN, new Vec3(0, 160, 0)).create(LootContextParamSets.CHEST);
+        for (var kind : HeritagePlan19.Kind.values()) {
+            var table = level.getServer().reloadableRegistries().getLootTable(lootKey(kind));
+            helper.assertTrue(table != LootTable.EMPTY, "Heritage tool table did not load: " + kind);
+            for (long seed : new long[] {0, 42, -1}) helper.assertTrue(table.getRandomItems(params, seed).stream().anyMatch(stack -> stack.is(tool(kind))), "Tool table is empty or lacks its expected primary tool: " + kind);
+            result.add(Map.of("kind", kind.name(), "table", lootKey(kind).identifier().toString(), "sampled_seeds", List.of(0, 42, -1)));
+        }
+        report.put("tool_tables_sampled_separately", result);
+    }
+    private static ResourceKey<LootTable> lootKey(HeritagePlan19.Kind kind) { return ResourceKey.create(Registries.LOOT_TABLE, SanctuaryMod.id("chests/heritage19/" + kind.name().toLowerCase(Locale.ROOT))); }
+    private static Item tool(HeritagePlan19.Kind kind) {
+        return switch (kind) {
+            case OBSERVATORY -> Items.SPYGLASS;
+            case POST_OFFICE, EXPEDITION_OFFICE, RADIO_RELAY -> Items.COMPASS;
+            case SUBSTATION, IMPOSSIBLE_SERVICE -> Items.CLOCK;
+            case FREIGHT_STATION -> Items.MINECART;
+            case COMMUNAL_DEPOT -> Items.IRON_AXE;
+            case RAIL_WORKSHOP -> Items.IRON_PICKAXE;
+            case PUMP_STATION -> Items.BUCKET;
+            case GREENHOUSE -> Items.IRON_HOE;
+            case VOID_DOCK -> Items.LEAD;
+            case PHOTO_CLUB -> Items.BOOK;
+            case CONSTRUCTION_REFUGE -> Items.IRON_SHOVEL;
+        };
+    }
+    private static Set<BlockPos> walk(GameTestHelper helper, BlockPos start, Predicate<BlockPos> inside) {
+        var level = helper.getLevel(); helper.assertTrue(inside.test(start) && standable(level, start), "Blocked or unsupported exterior entrance: " + start);
+        var seen = new HashSet<BlockPos>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var pos = queue.removeFirst();
+            for (var direction : HORIZONTAL) for (int dy = -1; dy <= 1; dy++) {
+                var next = pos.relative(direction).offset(0, dy, 0);
+                if (!inside.test(next) || dy > 0 && !clearBody(level, pos.above())) continue;
+                if (standable(level, next) && seen.add(next)) queue.add(next);
+            }
+            for (int dy : new int[] {-1, 1}) {
+                var next = pos.offset(0, dy, 0); if (!inside.test(next)) continue;
+                if ((level.getBlockState(pos).is(Blocks.LADDER) || level.getBlockState(next).is(Blocks.LADDER) || level.getBlockState(pos.below()).is(Blocks.LADDER))
+                        && standable(level, next) && seen.add(next)) queue.add(next);
+            }
+            helper.assertTrue(seen.size() <= 50_000, "Native site traversal escaped its bounds");
+        }
+        return seen;
+    }
+    private static boolean standable(ServerLevel level, BlockPos pos) {
+        if (!clearBody(level, pos)) return false;
+        if (level.getBlockState(pos).is(Blocks.LADDER) || level.getBlockState(pos.below()).is(Blocks.LADDER)) return true;
+        var below = pos.below(); return level.getBlockState(below).getCollisionShape(level, below).toAabbs().stream()
+            .anyMatch(b -> b.maxY >= .5 && b.minX <= .5 && b.maxX >= .5 && b.minZ <= .5 && b.maxZ >= .5);
+    }
+    private static boolean clearBody(ServerLevel level, BlockPos pos) {
+        var body = new AABB(pos.getX() + .2, pos.getY(), pos.getZ() + .2, pos.getX() + .8, pos.getY() + 1.8, pos.getZ() + .8);
+        for (var at : new BlockPos[] {pos, pos.above()}) {
+            if (!level.getFluidState(at).isEmpty()) return false;
+            for (var shape : level.getBlockState(at).getCollisionShape(level, at).toAabbs()) if (shape.move(at.getX(), at.getY(), at.getZ()).intersects(body)) return false;
+        }
+        return true;
+    }
+    private static long column(int x, int z) { return (long) x << 32 ^ z & 0xffffffffL; }
+    private static List<Integer> coords(BlockPos pos) { return List.of(pos.getX(), pos.getY(), pos.getZ()); }
+    private static BlockPos readPos(com.google.gson.JsonArray value) { return new BlockPos(value.get(0).getAsInt(), value.get(1).getAsInt(), value.get(2).getAsInt()); }
+    private static Path world(ServerLevel level) { return level.getServer().getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize(); }
+    private static Path proof(ServerLevel level) { return world(level).resolve("heritage19-create-proof.json"); }
+    private static String planHash(HeritagePlan19 plan) { return hash(plan.sites().toString() + plan.landmarks() + plan.links() + plan.segments()); }
+    private static void write(ServerLevel level, Map<String, Object> report, boolean reload) throws IOException {
+        var path = Path.of("diagnostics", "heritage19-" + (reload ? "reload" : "create") + ".json"); Files.createDirectories(path.getParent());
+        var value = new GsonBuilder().setPrettyPrinting().create().toJson(report) + "\n"; Files.writeString(path, value); if (!reload) Files.writeString(proof(level), value);
+    }
+    private static String hash(String value) {
+        try { return HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(value.getBytes(StandardCharsets.UTF_8))); }
+        catch (NoSuchAlgorithmException impossible) { throw new AssertionError(impossible); }
+    }
+}
@@ -0,0 +1,556 @@
+package fr.koka.sanctuary.gametest;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.mojang.serialization.JsonOps;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import fr.koka.sanctuary.worldgen.heritage.HeritagePiece20;
+import fr.koka.sanctuary.worldgen.heritage.HeritagePlan19;
+import fr.koka.sanctuary.worldgen.heritage.HeritageRenderer20;
+import fr.koka.sanctuary.worldgen.heritage.HeritageStructures19;
+import fr.koka.sanctuary.worldgen.ruins.RuinsPiece20;
+import fr.koka.sanctuary.worldgen.ruins.RuinsPlan17;
+import fr.koka.sanctuary.worldgen.ruins.RuinsRenderer20;
+import fr.koka.sanctuary.worldgen.ruins.RuinsStructures17;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.HexFormat;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Predicate;
+import net.fabricmc.fabric.api.gametest.v1.GameTest;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.DoorBlock;
+import net.minecraft.world.level.block.TrapDoorBlock;
+import net.minecraft.world.level.block.entity.RandomizableContainerBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.LevelResource;
+import net.minecraft.world.level.storage.loot.LootParams;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.level.storage.loot.parameters.LootContextParams;
+import net.minecraft.world.level.storage.loot.parameters.LootContextParamSets;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.phys.Vec3;
+
+/** Native creation/reload proof confined to a disposable generation20 starter island. */
+public final class Heritage20WorldGameTests {
+    private static final Direction[] HORIZONTAL = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    @GameTest(maxTicks = 12000)
+    public void heritagePersistsWithRealDestinations(GameTestHelper helper) {
+        helper.assertTrue(helper.getLevel().getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator,
+            "The heritage proof requires a Sanctuary generator");
+        var generator = (SanctuaryChunkGenerator) helper.getLevel().getChunkSource().getGenerator();
+        helper.assertTrue(generator.rootGeneration() == 20, "Use a fresh generation20 test world; do not convert an old save");
+        new Scenario(helper, generator, Boolean.getBoolean("sanctuary.test.expansionReload")).advance();
+    }
+    private static final class Scenario {
+        final GameTestHelper helper;
+        final ServerLevel level;
+        final SanctuaryChunkGenerator generator;
+        final HeritagePlan19 plan;
+        final boolean reload;
+        final Map<String, Object> report = new LinkedHashMap<>();
+        final List<ChunkPos> chunks = new ArrayList<>();
+        final List<StructureStart> starts = new ArrayList<>();
+        final List<StructureStart> ruinsStarts = new ArrayList<>();
+        JsonObject previous;
+        BlockPos gold;
+        int nextChunk;
+        boolean prepared;
+        Scenario(GameTestHelper helper, SanctuaryChunkGenerator generator, boolean reload) {
+            this.helper = helper; this.level = helper.getLevel(); this.generator = generator; this.reload = reload;
+            this.plan = generator.heritagePlan19();
+            report.put("seed", level.getSeed()); report.put("size", generator.initialDiameter());
+            report.put("process_id", ProcessHandle.current().pid()); report.put("world_directory", world(level).toString());
+            report.put("experimental_structures", generator.experimentalStructures());
+            report.put("structures_enabled", level.structureManager().shouldGenerateStructures());
+            report.put("scope", "Native local starts, saved sites and routes, player-sized entrances, supports and unopened chests on the starter island. "
+                + "All14 tool tables are sampled separately without consuming a saved chest. Door states are restored after traversal. "
+                + "No personal save or expansion is opened; one disposable outer-wall edit is checked in a second JVM. "
+                + "Missing rails are intentional; this proof checks walking and saved rail shapes, not an uninterrupted minecart journey.");
+        }
+        void advance() {
+            try {
+                if (!prepared) { report.put("stage", "prepare"); prepare(); prepared = true; if (plan.isEmpty()) { finishDisabled(); return; } }
+                if (nextChunk < chunks.size()) {
+                    report.put("stage", "load_full_chunks"); var pos = chunks.get(nextChunk++);
+                    helper.assertTrue(level.getChunk(pos.x(), pos.z(), ChunkStatus.FULL, true) instanceof LevelChunk,
+                        "Heritage footprint must reach native FULL: " + pos);
+                    if (nextChunk % 20 == 0) SanctuaryMod.LOGGER.info("Heritage20 loaded {}/{} footprint chunks", nextChunk, chunks.size());
+                    helper.runAtTickTime(helper.getTick() + 1, this::advance); return;
+                }
+                report.put("stage", "verify_native_geometry"); verifyPlaced(); report.put("passed", true);
+                if (!reload) {
+                    helper.assertTrue(gold != null && level.getBlockState(gold).isCollisionShapeFullBlock(level, gold), "Gold witness must replace a solid wall away from circulation");
+                    level.setBlock(gold, Blocks.GOLD_BLOCK.defaultBlockState(), 3); report.put("gold_witness", coords(gold));
+                    helper.assertTrue(level.getServer().saveEverything(true, true, true), "Flush native starts, unopened loot and the wall edit");
+                    report.put("world_flushed_before_shutdown", true);
+                } else {
+                    helper.assertTrue(level.getBlockState(gold).is(Blocks.GOLD_BLOCK), "Reload replaced the player's wall edit");
+                    report.put("gold_witness", coords(gold)); report.put("gold_witness_preserved", true);
+                }
+                write(level, report, reload); helper.succeed();
+            } catch (Exception failure) {
+                report.put("passed", false); report.put("failure", failure.toString());
+                try { write(level, report, reload); } catch (IOException ignored) { }
+                throw new IllegalStateException("Heritage20 native " + (reload ? "reload" : "creation") + " failed", failure);
+            }
+        }
+        void prepare() throws IOException {
+            var ops = RegistryOps.create(JsonOps.INSTANCE, level.registryAccess());
+            var encoded = ChunkGenerator.CODEC.encodeStart(ops, generator).getOrThrow();
+            var decoded = ChunkGenerator.CODEC.parse(ops, encoded).getOrThrow();
+            helper.assertTrue(decoded instanceof SanctuaryChunkGenerator copy && copy.rootGeneration() == 20
+                && copy.experimentalStructures() == generator.experimentalStructures(), "Generation20 codec lost its experimental switch");
+            report.put("generator_codec", encoded); report.put("plan_sha256", planHash(plan));
+            report.put("planned_sites", plan.sites().stream().map(site -> Map.of("id", site.id(), "kind", site.kind().name(),
+                "entry", coords(HeritagePiece20.locator(site)), "floor_y", site.floorY(), "foundation_depth", site.foundationDepth(), "footings", site.supports().size())).toList());
+            report.put("planned_links", plan.links().stream().map(link -> Map.of("id", link.id(), "from", link.fromId(), "to", link.toId(), "kind", link.kind().name(), "length", link.path().size(), "path", pathCoords(link))).toList());
+            report.put("planning_samples", plan.samples()); report.put("planning_columns", plan.columns()); report.put("planning_diagnostics", plan.diagnostics());
+            helper.assertTrue(plan.samples() <= HeritagePlan19.MAX_SAMPLES && plan.columns() <= HeritagePlan19.MAX_COLUMNS, "Heritage planning exceeded its budget");
+            verifyLootTables(helper, report);
+            if (reload) {
+                previous = JsonParser.parseString(Files.readString(proof(level))).getAsJsonObject();
+                helper.assertTrue(previous.get("passed").getAsBoolean() && previous.get("world_flushed_before_shutdown").getAsBoolean(), "Reload needs a successful flushed creation proof");
+                helper.assertTrue(previous.get("process_id").getAsLong() != ProcessHandle.current().pid(), "Reload must use a second JVM");
+                helper.assertTrue(previous.get("seed").getAsLong() == level.getSeed() && previous.get("size").getAsInt() == generator.initialDiameter()
+                    && previous.get("world_directory").getAsString().equals(world(level).toString()), "Reload selected another world");
+                helper.assertTrue(previous.get("generator_codec").equals(encoded) && previous.get("plan_sha256").getAsString().equals(planHash(plan)), "Saved settings or planned identities changed on reload");
+                if (previous.has("gold_witness")) gold = readPos(previous.getAsJsonArray("gold_witness"));
+            }
+            if (!generator.experimentalStructures() || !level.structureManager().shouldGenerateStructures()) {
+                helper.assertTrue(plan.isEmpty() && plan.segments().isEmpty() && plan.links().isEmpty(), "Disabled generation published heritage geometry"); return;
+            }
+            helper.assertTrue(!plan.isEmpty(), "Enabled reference island has no heritage site");
+            report.put("present_site_kinds", plan.sites().stream().map(s -> s.kind().name()).distinct().sorted().toList());
+            report.put("missing_site_kinds", java.util.Arrays.stream(HeritagePlan19.Kind.values()).filter(k -> plan.sites().stream().noneMatch(s -> s.kind() == k)).map(Enum::name).toList());
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(HeritageStructures19.KEY);
+            var origins = new HashSet<ChunkPos>(); var uniqueChunks = new HashSet<ChunkPos>();
+            plan.sites().forEach(s -> origins.add(new ChunkPos(s.startChunkX(), s.startChunkZ())));
+            plan.segments().forEach(s -> origins.add(new ChunkPos(s.startChunkX(), s.startChunkZ())));
+            for (var origin : origins.stream().sorted(Comparator.comparingInt(ChunkPos::x).thenComparingInt(ChunkPos::z)).toList()) {
+                var chunk = level.getChunk(origin.x(), origin.z(), ChunkStatus.STRUCTURE_STARTS, true);
+                var start = chunk.getStartForStructure(structure.value());
+                helper.assertTrue(start != null && start.isValid(), "Accepted site/route has no native start at " + origin); starts.add(start);
+                for (var piece : start.getPieces()) {
+                    helper.assertTrue(piece instanceof HeritagePiece20, "Heritage loaded a foreign piece type");
+                    var box = piece.getBoundingBox();
+                    helper.assertTrue(Math.abs((long) (box.minX() >> 4) - origin.x()) <= 7 && Math.abs((long) (box.maxX() >> 4) - origin.x()) <= 7
+                        && Math.abs((long) (box.minZ() >> 4) - origin.z()) <= 7 && Math.abs((long) (box.maxZ() >> 4) - origin.z()) <= 7, "Native start references a distant route endpoint");
+                    box.intersectingChunks().forEach(uniqueChunks::add);
+                }
+            }
+            for (var site : plan.sites()) uniqueChunks.add(ChunkPos.containing(HeritagePiece20.locator(site)));
+            for (var link : plan.links()) for (var point : link.path()) uniqueChunks.add(new ChunkPos(point.x() >> 4, point.z() >> 4));
+            helper.assertTrue(uniqueChunks.size() <= 1024, "Bounded proof footprint exceeds1024 chunks");
+            var ruins = generator.ruinsPlan17();
+            report.put("ruins_plan_sha256", hash(ruins.networks().toString()));
+            if (reload) helper.assertTrue(previous.get("ruins_plan_sha256").getAsString().equals(hash(ruins.networks().toString())), "Reload changed forgotten room planning");
+            helper.assertTrue(!ruins.isEmpty(), "Reference20 must demonstrate native experimental room architecture");
+            var ruinsType = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(RuinsStructures17.KEY);
+            var ruinsOrigins = new HashSet<ChunkPos>();
+            for (var network : ruins.networks()) {
+                var origin = new ChunkPos(network.startChunkX(), network.startChunkZ()); if (!ruinsOrigins.add(origin)) continue;
+                var nativeStart = level.getChunk(origin.x(), origin.z(), ChunkStatus.STRUCTURE_STARTS, true).getStartForStructure(ruinsType.value());
+                helper.assertTrue(nativeStart != null && nativeStart.isValid(), "Missing native20 forgotten network: " + network.id());
+                ruinsStarts.add(nativeStart);
+                for (var piece : nativeStart.getPieces()) {
+                    helper.assertTrue(piece instanceof RuinsPiece20, "Generation20 loaded a historical forgotten piece");
+                    piece.getBoundingBox().intersectingChunks().forEach(uniqueChunks::add);
+                }
+            }
+            chunks.addAll(uniqueChunks.stream().sorted(Comparator.comparingInt(ChunkPos::x).thenComparingInt(ChunkPos::z)).toList());
+        }
+        void finishDisabled() throws IOException {
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(HeritageStructures19.KEY);
+            var start = level.getChunk(0, 0, ChunkStatus.STRUCTURE_STARTS, true).getStartForStructure(structure.value());
+            helper.assertTrue(start == null || !start.isValid(), "Disabled heritage emitted a native start");
+            helper.assertTrue(generator.findNearestMapStructure(level, HolderSet.direct(structure), new BlockPos(0, 250, 0), 100, false) == null, "Disabled heritage is locatable");
+            report.put("empty_plan_verified", true); report.put("passed", true);
+            if (!reload) { helper.assertTrue(level.getServer().saveEverything(true, true, true), "Save disabled experiment setting"); report.put("world_flushed_before_shutdown", true); }
+            write(level, report, reload); helper.succeed();
+        }
+        void verifyPlaced() {
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(HeritageStructures19.KEY);
+            var context = StructurePieceSerializationContext.fromLevel(level); var summaries = new ArrayList<Map<String, Object>>();
+            int blocks = 0, chests = 0, pieces = 0, supports = 0;
+            var connections = NativeConnections20.Stats.empty();
+            for (var start : starts) {
+                var origin = start.getChunkPos(); var saved = start.createTag(context, origin); String nativeHash = hash(saved.toString());
+                var copy = StructureStart.loadStaticStart(context, saved, level.getSeed());
+                helper.assertTrue(copy != null && copy.isValid() && copy.createTag(context, origin).equals(saved), "Native start failed an exact NBT roundtrip");
+                var expectedPayloads = new HashSet<net.minecraft.nbt.CompoundTag>();
+                plan.sites().stream().filter(s -> s.startChunkX() == origin.x() && s.startChunkZ() == origin.z()).forEach(s -> expectedPayloads.add(HeritagePiece20.encodeSite(s)));
+                plan.segments().stream().filter(s -> s.startChunkX() == origin.x() && s.startChunkZ() == origin.z()).forEach(s -> expectedPayloads.add(HeritagePiece20.encodeSegment(s)));
+                var actualPayloads = new HashSet<net.minecraft.nbt.CompoundTag>();
+                if (reload) {
+                    JsonObject prior = null;
+                    for (var value : previous.getAsJsonArray("starts")) { var item = value.getAsJsonObject(); var at = item.getAsJsonArray("start_chunk"); if (at.get(0).getAsInt() == origin.x() && at.get(1).getAsInt() == origin.z()) prior = item; }
+                    helper.assertTrue(prior != null && prior.get("native_start_sha256").getAsString().equals(nativeHash), "Reload changed saved geometry or native reference count");
+                }
+                var loot = new ArrayList<Map<String, Object>>();
+                for (var value : start.getPieces()) {
+                    var piece = (HeritagePiece20) value; pieces++;
+                    var tag = piece.createTag(context); var restored = new HeritagePiece20(context, tag);
+                    helper.assertTrue(restored.createTag(context).equals(tag), "Saved piece parameters changed on native load");
+                    actualPayloads.add(tag.getCompound("SanctuaryHeritage").orElseThrow());
+                    var corrupt = tag.copy(); corrupt.getCompound("SanctuaryHeritage").orElseThrow().putInt("Schema", 21);
+                    boolean rejected = false; try { new HeritagePiece20(context, corrupt); } catch (IllegalArgumentException expected) { rejected = true; }
+                    helper.assertTrue(rejected, "Unknown schema must fail closed");
+                    piece.getBoundingBox().intersectingChunks().forEach(at -> helper.assertTrue(level.getChunk(at.x(), at.z(), ChunkStatus.FULL, true)
+                        .getReferencesForStructure(structure.value()).contains(origin.pack()), "FULL chunk lost its native structure reference"));
+                    var expected = rendered(piece); blocks += expected.blocks().size();
+                    for (var entry : expected.blocks().entrySet()) {
+                        var at = entry.getKey(); var wanted = entry.getValue(); helper.assertTrue(piece.getBoundingBox().isInside(at), "Renderer escaped saved bounds");
+                        if (reload && at.equals(gold)) continue;
+                        helper.assertTrue(level.getBlockState(at).is(wanted.getBlock()), "Clipping or decoration changed heritage at " + at + ": expected " + wanted + " got " + level.getBlockState(at));
+                        helper.assertTrue(!wanted.is(Blocks.SPAWNER), "Heritage must not create spawners");
+                    }
+                    connections = connections.add(NativeConnections20.verify(helper, expected.blocks(), reload ? Set.of(gold) : Set.of()));
+                    if (piece.isSite()) {
+                        supports += verifySiteBearing(helper, generator, plan, piece.site());
+                        if (!reload && gold == null) {
+                            gold = expected.blocks().entrySet().stream().filter(e -> isOuterWall(piece.site(), e.getKey()) && e.getValue().isCollisionShapeFullBlock(level, e.getKey()))
+                                .map(Map.Entry::getKey).sorted(Comparator.<BlockPos>comparingInt(p -> p.getY()).thenComparingInt(p -> p.getX()).thenComparingInt(p -> p.getZ())).findFirst().orElse(null);
+                        }
+                    } else for (var cell : piece.segment().cells()) { supports++; assertRock(helper, new BlockPos(cell.x(), cell.minY() - 1, cell.z())); }
+                    for (var chest : expected.chests()) {
+                        helper.assertTrue(level.getBlockEntity(chest.position()) instanceof RandomizableContainerBlockEntity, "Deferred chest is missing");
+                        var entity = (RandomizableContainerBlockEntity) level.getBlockEntity(chest.position());
+                        helper.assertTrue(entity.getLootTable() != null && entity.getLootTable().equals(chest.table()) && entity.getLootTableSeed() == chest.seed(), "Deferred loot table/seed was lost or consumed");
+                        if (piece.isSite()) helper.assertTrue(chest.table().equals(lootKey(piece.site().kind())), "Site uses another kind's tool table");
+                        loot.add(Map.of("position", coords(chest.position()), "table", chest.table().identifier().toString(), "seed", chest.seed())); chests++;
+                    }
+                }
+                helper.assertTrue(actualPayloads.equals(expectedPayloads) && start.getPieces().size() == expectedPayloads.size(), "Native start lost or duplicated planned pieces");
+                summaries.add(Map.of("start_chunk", List.of(origin.x(), origin.z()), "native_start_sha256", nativeHash, "pieces", start.getPieces().size(), "unopened_chests", loot));
+            }
+            report.put("connected_blocks", connections);
+            helper.assertTrue(connections.panes() > 0 && connections.stairs() > 0 && connections.nativeOracles() > 0,
+                "Reference20 needs real panes/stairs validated by vanilla neighbor rules");
+            if (level.getSeed() == 0 && generator.initialDiameter() == 724)
+                helper.assertTrue(connections.crossChunkPaneLinks() > 0, "Reference20 must demonstrate a real pane join across a chunk boundary");
+            verifyRuins();
+            report.put("starts", summaries); report.put("native_pieces", pieces); report.put("native_blocks_checked", blocks);
+            report.put("full_chunks_checked", chunks.size()); report.put("rock_supports_checked", supports); report.put("unopened_deferred_chests", chests);
+            report.put("stage", "verify_site_routes"); var sites = new ArrayList<Map<String, Object>>(); for (var site : plan.sites()) sites.add(verifyAccess(helper, site)); report.put("native_sites", sites);
+            report.put("stage", "verify_read_only_landings");
+            report.put("read_only_landmarks", verifyReadOnlyLandings(helper, generator, plan));
+            report.put("stage", "verify_island_routes"); report.put("native_links", verifyLinks(helper, plan));
+            int greatestSpan = plan.links().stream().mapToInt(Heritage20WorldGameTests::routeSpan).max().orElse(0);
+            report.put("greatest_single_route_span", greatestSpan);
+            if (level.getSeed() == 0 && generator.initialDiameter() == 724) {
+                int requiredSpan = generator.initialDiameter() / 4;
+                report.put("reference_minimum_route_span", requiredSpan);
+                helper.assertTrue(greatestSpan >= requiredSpan, "Seed0 Medium must demonstrate an island-scale route spanning at least "
+                    + requiredSpan + " blocks on X or Z; got " + greatestSpan);
+            }
+            var located = generator.findNearestMapStructure(level, HolderSet.direct(structure), new BlockPos(0, 250, 0), 100, false);
+            helper.assertTrue(located != null && located.getSecond().is(HeritageStructures19.KEY) && plan.sites().stream().anyMatch(s -> HeritagePiece20.locator(s).equals(located.getFirst())), "Locate must lead to a real exterior site entry");
+            report.put("locate", coords(located.getFirst()));
+        }
+        void verifyRuins() {
+            var context = StructurePieceSerializationContext.fromLevel(level);
+            var registry = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(RuinsStructures17.KEY);
+            var summaries = new ArrayList<Map<String, Object>>(); int count = 0, blockCount = 0, lootCount = 0;
+            var connections = NativeConnections20.Stats.empty();
+            for (var start : ruinsStarts) {
+                var origin = start.getChunkPos(); var saved = start.createTag(context, origin); var digest = hash(saved.toString());
+                var loaded = StructureStart.loadStaticStart(context, saved, level.getSeed());
+                helper.assertTrue(loaded != null && loaded.createTag(context, origin).equals(saved), "Forgotten20 native start NBT changed");
+                var expectedRooms = generator.ruinsPlan17().networks().stream().filter(n -> n.startChunkX() == origin.x() && n.startChunkZ() == origin.z()).flatMap(n -> n.rooms().stream()).toList();
+                var actualRooms = start.getPieces().stream().map(RuinsPiece20.class::cast).map(RuinsPiece20::room).toList();
+                helper.assertTrue(expectedRooms.size() == actualRooms.size() && new HashSet<>(expectedRooms).equals(new HashSet<>(actualRooms)), "Forgotten20 native rooms differ from plan");
+                if (reload) {
+                    JsonObject prior = null;
+                    for (var value : previous.getAsJsonArray("ruins_starts")) { var item = value.getAsJsonObject(); var at = item.getAsJsonArray("start_chunk"); if (at.get(0).getAsInt() == origin.x() && at.get(1).getAsInt() == origin.z()) prior = item; }
+                    helper.assertTrue(prior != null && prior.get("native_start_sha256").getAsString().equals(digest), "Forgotten20 native start changed on a second JVM load");
+                }
+                for (var raw : start.getPieces()) {
+                    var piece = (RuinsPiece20) raw; var room = piece.room(); count++;
+                    var tag = piece.createTag(context); var roundtrip = new RuinsPiece20(context, tag);
+                    helper.assertTrue(roundtrip.room().equals(room) && roundtrip.createTag(context).equals(tag), "Forgotten20 piece lost saved parameters");
+                    piece.getBoundingBox().intersectingChunks().forEach(at -> helper.assertTrue(level.getChunk(at.x(), at.z(), ChunkStatus.FULL, true).getReferencesForStructure(registry.value()).contains(origin.pack()), "Forgotten20 chunk lost native references"));
+                    var expected = rendered(room); blockCount += expected.blocks().size();
+                    for (var entry : expected.blocks().entrySet()) {
+                        helper.assertTrue(piece.getBoundingBox().isInside(entry.getKey()), "Forgotten20 renderer escaped saved bounds");
+                        helper.assertTrue(level.getBlockState(entry.getKey()).is(entry.getValue().getBlock()), "Forgotten20 native geometry changed at " + entry.getKey());
+                    }
+                    connections = connections.add(NativeConnections20.verify(helper, expected.blocks(), Set.of()));
+                    for (var support : room.supports()) assertRock(helper, new BlockPos(support.x(), support.minY() - 1, support.z()));
+                    for (var chest : expected.chests()) {
+                        helper.assertTrue(level.getBlockEntity(chest.position()) instanceof RandomizableContainerBlockEntity, "Forgotten20 missing deferred chest");
+                        var entity = (RandomizableContainerBlockEntity) level.getBlockEntity(chest.position());
+                        helper.assertTrue(chest.table().equals(entity.getLootTable()) && chest.seed() == entity.getLootTableSeed(), "Forgotten20 consumed/changed saved loot"); lootCount++;
+                    }
+                }
+                summaries.add(Map.of("start_chunk", List.of(origin.x(), origin.z()), "native_start_sha256", digest, "pieces", start.getPieces().size()));
+            }
+            report.put("ruins_starts", summaries); report.put("ruins_native_pieces", count); report.put("ruins_native_blocks_checked", blockCount);
+            report.put("ruins_unopened_deferred_chests", lootCount); report.put("ruins_connections", connections);
+            report.put("ruins_access", generator.ruinsPlan17().networks().stream().map(n -> verifyAccess(helper, n)).toList());
+        }
+    }
+    private record Chest(BlockPos position, ResourceKey<LootTable> table, long seed) {}
+    private record Rendered(Map<BlockPos, BlockState> blocks, List<Chest> chests) {}
+    private static Rendered rendered(HeritagePiece20 piece) {
+        var blocks = new HashMap<BlockPos, BlockState>(); var chests = new ArrayList<Chest>();
+        int x0 = piece.isSite() ? piece.site().minX() : piece.segment().minX();
+        int y0 = piece.isSite() ? piece.site().floorY() : piece.segment().minY();
+        int z0 = piece.isSite() ? piece.site().minZ() : piece.segment().minZ();
+        var writer = new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState state) { blocks.put(new BlockPos(x0 + x, y0 + y, z0 + z), state); }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+                var at = new BlockPos(x0 + x, y0 + y, z0 + z); blocks.put(at, Blocks.CHEST.defaultBlockState()); chests.add(new Chest(at, table, RandomSource.create(seed).nextLong()));
+            }
+        };
+        if (piece.isSite()) HeritageRenderer20.render(piece.site(), writer); else HeritageRenderer20.renderSegment(piece.segment(), writer);
+        return new Rendered(blocks, chests);
+    }
+    private static Rendered rendered(RuinsPlan17.Room room) {
+        var blocks = new HashMap<BlockPos, BlockState>(); var chests = new ArrayList<Chest>();
+        RuinsRenderer20.render(room, new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState state) { blocks.put(at(room, x, y, z), state); }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+                var position = at(room, x, y, z); blocks.put(position, Blocks.CHEST.defaultBlockState()); chests.add(new Chest(position, table, RandomSource.create(seed).nextLong()));
+            }
+        });
+        return new Rendered(blocks, chests);
+    }
+    private static Map<String, Object> verifyAccess(GameTestHelper helper, RuinsPlan17.Network network) {
+        var level = helper.getLevel(); var access = network.rooms().stream().filter(r -> r.kind() == RuinsPlan17.Kind.ACCESS).findFirst().orElseThrow();
+        var hatches = new HashMap<BlockPos, BlockState>();
+        rendered(access).blocks().forEach((at, state) -> { if (state.is(Blocks.DARK_OAK_TRAPDOOR)) hatches.put(at, level.getBlockState(at)); });
+        helper.assertTrue(hatches.size() == 1, "Each network must have one usable wooden surface hatch");
+        hatches.forEach((at, state) -> {
+            helper.assertTrue(state.is(Blocks.DARK_OAK_TRAPDOOR) && state.canSurvive(level, at), "Surface hatch is missing its native support");
+            level.setBlock(at, state.setValue(BlockStateProperties.OPEN, true), 2);
+        });
+        try {
+            Predicate<BlockPos> inside = pos -> network.rooms().stream().anyMatch(r -> r.contains(pos.getX(), pos.getY(), pos.getZ()));
+            var start = RuinsPiece20.locator(access); var reached = walk(helper, start, inside);
+            int targets = 0;
+            for (var room : network.rooms()) for (var target : RuinsRenderer20.targets(room)) {
+                var point = at(room, target.x(), target.y(), target.z());
+                helper.assertTrue(reached.contains(point), "Native network " + network.id() + " cannot reach " + room.kind() + "/" + target.name() + " at " + point);
+                targets++;
+            }
+            for (var hatch : hatches.keySet()) helper.assertTrue(reached.contains(hatch), "Surface approach cannot enter its ladder shaft");
+            return Map.of("id", network.id(), "family", network.family().name(), "rooms", network.rooms().size(),
+                "entrance", coords(start), "walkable_targets", targets, "standing_cells", reached.size());
+        } finally { hatches.forEach((at, state) -> level.setBlock(at, state, 2)); }
+    }
+    private static BlockPos at(RuinsPlan17.Room room, int x, int y, int z) { return new BlockPos(room.minX() + x, room.minY() + y, room.minZ() + z); }
+    private static boolean isOuterWall(HeritagePlan19.Site site, BlockPos pos) {
+        return pos.getY() >= site.floorY() + 2 && pos.getY() <= site.floorY() + 3
+            && (pos.getX() == site.minX() + 2 || pos.getX() == site.maxX() - 2 || pos.getZ() == site.minZ() + 2 || pos.getZ() == site.maxZ() - 2)
+            && Math.abs(pos.getX() - site.entry().x()) + Math.abs(pos.getZ() - site.entry().z()) > 6;
+    }
+    private static Map<String, Object> verifyAccess(GameTestHelper helper, HeritagePlan19.Site site) {
+        var level = helper.getLevel(); var expected = rendered(new HeritagePiece20(site)); var doors = new HashMap<BlockPos, BlockState>();
+        expected.blocks().forEach((at, state) -> {
+            if ((state.getBlock() instanceof DoorBlock || state.getBlock() instanceof TrapDoorBlock) && state.hasProperty(BlockStateProperties.OPEN)) doors.put(at, level.getBlockState(at));
+        });
+        doors.forEach((at, state) -> level.setBlock(at, state.setValue(BlockStateProperties.OPEN, true), 2));
+        try {
+            var entry = HeritagePiece20.locator(site);
+            Predicate<BlockPos> inside = p -> p.equals(entry) || p.getX() >= site.minX() && p.getX() <= site.maxX()
+                && p.getZ() >= site.minZ() && p.getZ() <= site.maxZ() && p.getY() >= site.floorY() - 4 && p.getY() < site.maxY();
+            var reached = walk(helper, entry, inside); int targets = 0;
+            for (var target : HeritageRenderer20.targets(site)) {
+                var at = new BlockPos(site.minX() + target.x(), site.floorY() + target.y(), site.minZ() + target.z());
+                helper.assertTrue(reached.contains(at), "Site " + site.id() + " cannot reach " + target.name() + " at " + at); targets++;
+            }
+            return Map.of("id", site.id(), "kind", site.kind().name(), "entry", coords(entry), "standing_cells", reached.size(), "walkable_targets", targets);
+        } finally { doors.forEach((at, state) -> level.setBlock(at, state, 2)); }
+    }
+    private static List<Map<String, Object>> verifyLinks(GameTestHelper helper, HeritagePlan19 plan) {
+        helper.assertTrue(!plan.links().isEmpty(), "Reference island needs a real route between accepted destinations");
+        var entries = new HashMap<String, HeritagePlan19.Entry>(); plan.sites().forEach(s -> entries.put(s.id(), s.entry())); plan.landmarks().forEach(s -> entries.put(s.id(), s.entry()));
+        var cells = new HashMap<Long, HeritagePlan19.Cell>(); plan.segments().forEach(s -> s.cells().forEach(c -> cells.put(column(c.x(), c.z()), c)));
+        var result = new ArrayList<Map<String, Object>>();
+        for (var link : plan.links()) {
+            var from = entries.get(link.fromId()); var to = entries.get(link.toId());
+            helper.assertTrue(from != null && to != null, "Route points to an absent destination");
+            var first = link.path().getFirst(); var last = link.path().getLast();
+            helper.assertTrue(first.x() == from.x() && first.z() == from.z() && first.floorY() + 1 == from.y()
+                && last.x() == to.x() && last.z() == to.z() && last.floorY() + 1 == to.y(), "Route does not meet its real entrances");
+            int present = 0, missing = 0;
+            for (int i = 0; i < link.path().size(); i++) {
+                var point = link.path().get(i); var at = new BlockPos(point.x(), point.floorY() + 1, point.z());
+                helper.assertTrue(standable(helper.getLevel(), at), "Ballast route " + link.id() + " is blocked at " + at);
+                if (i > 0) { var prior = link.path().get(i - 1); if (point.floorY() > prior.floorY()) helper.assertTrue(clearBody(helper.getLevel(), new BlockPos(prior.x(), prior.floorY() + 2, prior.z())), "Route slope cannot be climbed by a player"); }
+                var cell = cells.get(column(point.x(), point.z()));
+                if (cell != null && cell.rail() != HeritagePlan19.Rail.NONE) {
+                    var actual = helper.getLevel().getBlockState(at);
+                    if (cell.railPresent()) {
+                        helper.assertTrue(actual.is(Blocks.RAIL), "Saved existing rail disappeared");
+                        helper.assertTrue(actual.getValue(BlockStateProperties.RAIL_SHAPE).name().equals(cell.rail().name()), "Native rail update changed the intended slope or curve at " + at); present++;
+                    } else { helper.assertTrue(!actual.is(Blocks.RAIL), "An intentionally missing rail regenerated"); missing++; }
+                }
+            }
+            int spanX = link.path().stream().mapToInt(HeritagePlan19.Point::x).max().orElseThrow() - link.path().stream().mapToInt(HeritagePlan19.Point::x).min().orElseThrow();
+            int spanZ = link.path().stream().mapToInt(HeritagePlan19.Point::z).max().orElseThrow() - link.path().stream().mapToInt(HeritagePlan19.Point::z).min().orElseThrow();
+            result.add(Map.of("id", link.id(), "from", link.fromId(), "to", link.toId(), "kind", link.kind().name(), "length", link.path().size(),
+                "span_x", spanX, "span_z", spanZ, "existing_rails", present, "deliberately_missing_rails", missing, "path", pathCoords(link)));
+        }
+        return result;
+    }
+    private static int routeSpan(HeritagePlan19.Link link) {
+        int spanX = link.path().stream().mapToInt(HeritagePlan19.Point::x).max().orElseThrow()
+            - link.path().stream().mapToInt(HeritagePlan19.Point::x).min().orElseThrow();
+        int spanZ = link.path().stream().mapToInt(HeritagePlan19.Point::z).max().orElseThrow()
+            - link.path().stream().mapToInt(HeritagePlan19.Point::z).min().orElseThrow();
+        return Math.max(spanX, spanZ);
+    }
+    private static List<List<Integer>> pathCoords(HeritagePlan19.Link link) {
+        return link.path().stream().map(point -> List.of(point.x(), point.floorY(), point.z())).toList();
+    }
+    private static int verifySiteBearing(GameTestHelper helper, SanctuaryChunkGenerator generator, HeritagePlan19 plan, HeritagePlan19.Site site) {
+        int checked = 0;
+        // The planner certifies a nine-point bearing grid, either directly below its slab or below a saved short footing.
+        for (int dx : new int[] {1, 8, 15}) for (int dz : new int[] {1, 8, 15}) {
+            int x = site.minX() + dx, z = site.minZ() + dz;
+            var support = site.supports().stream().filter(s -> s.x() == x && s.z() == z).findFirst();
+            int bottom = support.map(HeritagePlan19.Support::minY).orElse(site.minY());
+            for (int below = 1; below <= 2; below++) {
+                var at = new BlockPos(x, bottom - below, z); assertRock(helper, at);
+                helper.assertTrue(plan.protects(at.getX(), at.getY(), at.getZ()) && generator.protectsCityDecoration(at),
+                    "Site's certified bearing layer is not published in the decoration mask: " + site.id() + " at " + at);
+                helper.assertTrue(!plan.contains(at.getX(), at.getY(), at.getZ()), "Original bearing rock became a writable heritage volume: " + at);
+                checked++;
+            }
+        }
+        return checked;
+    }
+    private static List<Map<String, Object>> verifyReadOnlyLandings(GameTestHelper helper, SanctuaryChunkGenerator generator, HeritagePlan19 plan) {
+        var used = new HashSet<String>(); plan.links().forEach(link -> { used.add(link.fromId()); used.add(link.toId()); });
+        var result = new ArrayList<Map<String, Object>>();
+        for (var landmark : plan.landmarks()) if (used.contains(landmark.id())) {
+            var e = landmark.entry(); int checked = 0;
+            for (int side = -1; side <= 1; side++) {
+                int x = e.x() + ((e.facing() & 1) == 0 ? side : 0), z = e.z() + ((e.facing() & 1) == 1 ? side : 0);
+                for (int y = e.y() - 2; y <= e.y() + 2; y++) {
+                    var at = new BlockPos(x, y, z);
+                    helper.assertTrue(plan.protects(x, y, z) && generator.protectsCityDecoration(at), "Read-only arrival lost its decoration mask: " + landmark.id() + " at " + at);
+                    helper.assertTrue(!plan.contains(x, y, z), "Heritage gained write ownership of a historical arrival: " + landmark.id() + " at " + at);
+                    if (y == e.y() - 1) assertRock(helper, at);
+                    if (y >= e.y()) helper.assertTrue(helper.getLevel().getBlockState(at).isAir(), "Decoration obstructed a certified historical arrival: " + at);
+                    checked++;
+                }
+            }
+            result.add(Map.of("id", landmark.id(), "entry", List.of(e.x(), e.y(), e.z()), "read_only_cells", checked));
+        }
+        return result;
+    }
+    private static void assertRock(GameTestHelper helper, BlockPos at) {
+        helper.assertTrue(helper.getLevel().getBlockState(at).isSolid() && helper.getLevel().getFluidState(at).isEmpty(), "Lost original rock bearing at " + at);
+    }
+    private static void verifyLootTables(GameTestHelper helper, Map<String, Object> report) {
+        var result = new ArrayList<Map<String, Object>>(); var level = helper.getLevel();
+        var params = new LootParams.Builder(level).withParameter(LootContextParams.ORIGIN, new Vec3(0, 160, 0)).create(LootContextParamSets.CHEST);
+        for (var kind : HeritagePlan19.Kind.values()) {
+            var table = level.getServer().reloadableRegistries().getLootTable(lootKey(kind));
+            helper.assertTrue(table != LootTable.EMPTY, "Heritage tool table did not load: " + kind);
+            for (long seed : new long[] {0, 42, -1}) helper.assertTrue(table.getRandomItems(params, seed).stream().anyMatch(stack -> stack.is(tool(kind))), "Tool table is empty or lacks its expected primary tool: " + kind);
+            result.add(Map.of("kind", kind.name(), "table", lootKey(kind).identifier().toString(), "sampled_seeds", List.of(0, 42, -1)));
+        }
+        report.put("tool_tables_sampled_separately", result);
+    }
+    private static ResourceKey<LootTable> lootKey(HeritagePlan19.Kind kind) { return ResourceKey.create(Registries.LOOT_TABLE, SanctuaryMod.id("chests/heritage19/" + kind.name().toLowerCase(Locale.ROOT))); }
+    private static Item tool(HeritagePlan19.Kind kind) {
+        return switch (kind) {
+            case OBSERVATORY -> Items.SPYGLASS;
+            case POST_OFFICE, EXPEDITION_OFFICE, RADIO_RELAY -> Items.COMPASS;
+            case SUBSTATION, IMPOSSIBLE_SERVICE -> Items.CLOCK;
+            case FREIGHT_STATION -> Items.MINECART;
+            case COMMUNAL_DEPOT -> Items.IRON_AXE;
+            case RAIL_WORKSHOP -> Items.IRON_PICKAXE;
+            case PUMP_STATION -> Items.BUCKET;
+            case GREENHOUSE -> Items.IRON_HOE;
+            case VOID_DOCK -> Items.LEAD;
+            case PHOTO_CLUB -> Items.BOOK;
+            case CONSTRUCTION_REFUGE -> Items.IRON_SHOVEL;
+        };
+    }
+    private static Set<BlockPos> walk(GameTestHelper helper, BlockPos start, Predicate<BlockPos> inside) {
+        var level = helper.getLevel(); helper.assertTrue(inside.test(start) && standable(level, start), "Blocked or unsupported exterior entrance: " + start);
+        var seen = new HashSet<BlockPos>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var pos = queue.removeFirst();
+            for (var direction : HORIZONTAL) for (int dy = -1; dy <= 1; dy++) {
+                var next = pos.relative(direction).offset(0, dy, 0);
+                if (!inside.test(next) || dy > 0 && !clearBody(level, pos.above())) continue;
+                if (standable(level, next) && seen.add(next)) queue.add(next);
+            }
+            for (int dy : new int[] {-1, 1}) {
+                var next = pos.offset(0, dy, 0); if (!inside.test(next)) continue;
+                if ((level.getBlockState(pos).is(Blocks.LADDER) || level.getBlockState(next).is(Blocks.LADDER) || level.getBlockState(pos.below()).is(Blocks.LADDER))
+                        && standable(level, next) && seen.add(next)) queue.add(next);
+            }
+            helper.assertTrue(seen.size() <= 50_000, "Native site traversal escaped its bounds");
+        }
+        return seen;
+    }
+    private static boolean standable(ServerLevel level, BlockPos pos) {
+        if (!clearBody(level, pos)) return false;
+        if (level.getBlockState(pos).is(Blocks.LADDER) || level.getBlockState(pos.below()).is(Blocks.LADDER)) return true;
+        var below = pos.below(); return level.getBlockState(below).getCollisionShape(level, below).toAabbs().stream()
+            .anyMatch(b -> b.maxY >= .5 && b.minX <= .5 && b.maxX >= .5 && b.minZ <= .5 && b.maxZ >= .5);
+    }
+    private static boolean clearBody(ServerLevel level, BlockPos pos) {
+        var body = new AABB(pos.getX() + .2, pos.getY(), pos.getZ() + .2, pos.getX() + .8, pos.getY() + 1.8, pos.getZ() + .8);
+        for (var at : new BlockPos[] {pos, pos.above()}) {
+            if (!level.getFluidState(at).isEmpty()) return false;
+            for (var shape : level.getBlockState(at).getCollisionShape(level, at).toAabbs()) if (shape.move(at.getX(), at.getY(), at.getZ()).intersects(body)) return false;
+        }
+        return true;
+    }
+    private static long column(int x, int z) { return (long) x << 32 ^ z & 0xffffffffL; }
+    private static List<Integer> coords(BlockPos pos) { return List.of(pos.getX(), pos.getY(), pos.getZ()); }
+    private static BlockPos readPos(com.google.gson.JsonArray value) { return new BlockPos(value.get(0).getAsInt(), value.get(1).getAsInt(), value.get(2).getAsInt()); }
+    private static Path world(ServerLevel level) { return level.getServer().getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize(); }
+    private static Path proof(ServerLevel level) { return world(level).resolve("heritage20-create-proof.json"); }
+    private static String planHash(HeritagePlan19 plan) { return hash(plan.sites().toString() + plan.landmarks() + plan.links() + plan.segments()); }
+    private static void write(ServerLevel level, Map<String, Object> report, boolean reload) throws IOException {
+        var path = Path.of("diagnostics", "heritage20-" + (reload ? "reload" : "create") + ".json"); Files.createDirectories(path.getParent());
+        var value = new GsonBuilder().setPrettyPrinting().create().toJson(report) + "\n"; Files.writeString(path, value); if (!reload) Files.writeString(proof(level), value);
+    }
+    private static String hash(String value) {
+        try { return HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(value.getBytes(StandardCharsets.UTF_8))); }
+        catch (NoSuchAlgorithmException impossible) { throw new AssertionError(impossible); }
+    }
+}
@@ -0,0 +1,93 @@
+package fr.koka.sanctuary.gametest;
+
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.block.FenceBlock;
+import net.minecraft.world.level.block.IronBarsBlock;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.WallBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+
+/** Independent oracle: actual native neighbor-update rules, with datapack tags loaded by the test server. */
+public final class NativeConnections20 {
+    private NativeConnections20() {}
+    public record Stats(int panes, int fences, int walls, int stairs, int nativeOracles, int externalNeighbors,
+                        int crossChunkPaneLinks, int settledExternalStates, int unsettledExternalStates) {
+        public Stats add(Stats other) { return new Stats(panes + other.panes, fences + other.fences, walls + other.walls,
+            stairs + other.stairs, nativeOracles + other.nativeOracles, externalNeighbors + other.externalNeighbors,
+            crossChunkPaneLinks + other.crossChunkPaneLinks, settledExternalStates + other.settledExternalStates,
+            unsettledExternalStates + other.unsettledExternalStates); }
+        public static Stats empty() { return new Stats(0, 0, 0, 0, 0, 0, 0, 0, 0); }
+    }
+    public static Stats verify(GameTestHelper helper, Map<BlockPos, BlockState> geometry, Set<BlockPos> edits) {
+        var level = helper.getLevel(); int panes = 0, fences = 0, walls = 0, stairs = 0, oracles = 0, exterior = 0, cross = 0, settled = 0, unsettled = 0;
+        for (var entry : geometry.entrySet()) {
+            var pos = entry.getKey(); var wanted = entry.getValue(); if (edits.contains(pos)) continue;
+            boolean pane = wanted.getBlock() instanceof IronBarsBlock, fence = wanted.getBlock() instanceof FenceBlock;
+            boolean wall = wanted.getBlock() instanceof WallBlock, stair = wanted.getBlock() instanceof StairBlock;
+            if (!pane && !fence && !wall && !stair) continue;
+            if (pane) panes++; if (fence) fences++; if (wall) walls++; if (stair) stairs++;
+            var actual = level.getBlockState(pos);
+            helper.assertTrue(sameNonConnectionState(actual, wanted),
+                "Material, orientation, half or waterlogging changed at " + pos + ": expected " + wanted + " got " + actual);
+            boolean knownNeighborhood = true;
+            for (var side : Direction.values()) {
+                var at = pos.relative(side); var expectedNeighbor = geometry.get(at); var actualNeighbor = level.getBlockState(at);
+                // A changed neighbor's shape can propagate a legitimate exterior connection, e.g. stacked walls.
+                if (edits.contains(at) || (expectedNeighbor == null ? !actualNeighbor.isAir()
+                    : !expectedNeighbor.equals(actualNeighbor))) knownNeighborhood = false;
+            }
+            var updated = actual;
+            for (var side : Direction.values()) {
+                var at = pos.relative(side);
+                updated = updated.updateShape(level, level, pos, side, at, level.getBlockState(at), RandomSource.create(20));
+            }
+            if (knownNeighborhood) {
+                helper.assertTrue(actual.equals(wanted), "Native detailed state differs inside known geometry at " + pos
+                    + ": expected " + wanted + " got " + actual);
+                helper.assertTrue(updated.equals(actual), "Vanilla neighbor rules disagree with generation20 connections at " + pos
+                    + ": saved " + actual + " native " + updated);
+                oracles++;
+            } else {
+                exterior++;
+                if (updated.equals(actual)) { settled++; oracles++; }
+                else {
+                    // A fresh structure has not necessarily received an update from untouched surrounding rock.
+                    // Permit only its exact planned state until that update; a partially/wrongly changed state fails.
+                    helper.assertTrue(actual.equals(wanted) && sameNonConnectionState(updated, wanted),
+                        "Exterior connection is neither the untouched plan nor a vanilla fixed point at " + pos
+                            + ": plan " + wanted + " saved " + actual + " native " + updated);
+                    unsettled++;
+                }
+            }
+            if (pane) for (var side : new Direction[] {Direction.EAST, Direction.SOUTH}) {
+                var at = pos.relative(side); var neighbor = level.getBlockState(at);
+                if (neighbor.getBlock() instanceof IronBarsBlock && (pos.getX() >> 4 != at.getX() >> 4 || pos.getZ() >> 4 != at.getZ() >> 4)) {
+                    var property = side == Direction.EAST ? BlockStateProperties.EAST : BlockStateProperties.SOUTH;
+                    helper.assertTrue(actual.getValue(property), "Pane connection disappeared exactly at a native chunk boundary: " + pos);
+                    cross++;
+                }
+            }
+        }
+        return new Stats(panes, fences, walls, stairs, oracles, exterior, cross, settled, unsettled);
+    }
+    /** Normalize only geometry-derived properties. Everything else, including fluids and facing, stays exact. */
+    private static boolean sameNonConnectionState(BlockState actual, BlockState wanted) {
+        if (!actual.is(wanted.getBlock())) return false;
+        if (wanted.getBlock() instanceof IronBarsBlock || wanted.getBlock() instanceof FenceBlock) {
+            for (var property : new net.minecraft.world.level.block.state.properties.BooleanProperty[] {
+                    BlockStateProperties.NORTH, BlockStateProperties.EAST, BlockStateProperties.SOUTH, BlockStateProperties.WEST})
+                actual = actual.setValue(property, wanted.getValue(property));
+        } else if (wanted.getBlock() instanceof WallBlock) {
+            for (var property : WallBlock.PROPERTY_BY_DIRECTION.values()) actual = actual.setValue(property, wanted.getValue(property));
+            actual = actual.setValue(WallBlock.UP, wanted.getValue(WallBlock.UP));
+        } else if (wanted.getBlock() instanceof StairBlock) actual = actual.setValue(StairBlock.SHAPE, wanted.getValue(StairBlock.SHAPE));
+        return actual.equals(wanted);
+    }
+
+}
@@ -210,8 +210,30 @@ public final class PopulationDiagnostics {
        }

        void prepare() throws IOException {
-            helper.assertTrue(regionsAtInitialSpawn > 0 && regionsAtInitialSpawn <= 4,
-                "Initial spawn must plan only nearby regions, not materialize the large island: " + regionsAtInitialSpawn);
+            boolean heritage = level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator sanctuary
+                && (sanctuary.rootGeneration() == 19 || sanctuary.rootGeneration() == 20) && sanctuary.experimentalStructures();
+            // Generation19 explicitly prospects destinations across the root island before publishing them.
+            // A consulted hydrology region is a bounded immutable plan, not a loaded/generated chunk.
+            // Historical generators retain their original near-spawn contract.
+            int regionLimit = 4;
+            if (heritage) {
+                int extent = capacity.terrainLimit();
+                var first = capacity.regionAt(-extent, -extent); var last = capacity.regionAt(extent, extent);
+                regionLimit = 0;
+                for (int x = first.x(); x <= last.x(); x++) for (int z = first.z(); z <= last.z(); z++) {
+                    var region = new IslandCapacity.Region(x, z);
+                    double nearestX = Math.max(0, Math.max(region.minX(), -region.maxX()));
+                    double nearestZ = Math.max(0, Math.max(region.minZ(), -region.maxZ()));
+                    if (Math.hypot(nearestX, nearestZ) < extent) regionLimit++;
+                }
+                helper.assertTrue(regionLimit <= 9, "Heritage starter hydrology must fit within nine local regions");
+                var plan = ((SanctuaryChunkGenerator) level.getChunkSource().getGenerator()).heritagePlan19();
+                helper.assertTrue(plan.columns() <= fr.koka.sanctuary.worldgen.heritage.HeritagePlan19.MAX_COLUMNS
+                    && plan.samples() <= fr.koka.sanctuary.worldgen.heritage.HeritagePlan19.MAX_SAMPLES,
+                    "Island-wide heritage prospecting exceeded its independent column/probe budget");
+            }
+            helper.assertTrue(regionsAtInitialSpawn > 0 && regionsAtInitialSpawn <= regionLimit,
+                "Initial hydrology exceeded its geographic planning scope (limit " + regionLimit + "): " + regionsAtInitialSpawn);
            List<IslandCapacity.Region> targets = new ArrayList<>();
            targets.add(new IslandCapacity.Region(0,0));
            if (capacity.players() == 20) targets.add(new IslandCapacity.Region(1,0));
@@ -45,8 +45,14 @@ final class UnifiedWorldSettingsDiagnostics {
        var historical16 = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("sanctuary_v16"))).value().createWorldDimensions();
        helper.assertTrue(historical16.overworld() instanceof SanctuaryChunkGenerator old && old.rootGeneration() == 16
                && old.source().generation() == 16 && !old.experimentalStructures(), "Historical16 never gains experimental structures");
+        var historical17 = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("sanctuary_v17"))).value().createWorldDimensions();
+        helper.assertTrue(historical17.overworld() instanceof SanctuaryChunkGenerator old && old.rootGeneration() == 17
+                && old.source().generation() == 17 && old.experimentalStructures(), "Historical17 keeps its original experimental generator");
+        var historical19 = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("sanctuary_v19"))).value().createWorldDimensions();
+        helper.assertTrue(historical19.overworld() instanceof SanctuaryChunkGenerator old && old.rootGeneration() == 19
+                && old.source().generation() == 19 && old.experimentalStructures(), "Historical19 keeps its original renderer and world settings");
        var generator = (SanctuaryChunkGenerator) standard.overworld();
-        helper.assertTrue(generator.rootGeneration() == 17 && generator.source().generation() == 17 && generator.experimentalStructures(), "The public preset uses generation17 with its new-world option");
+        helper.assertTrue(generator.rootGeneration() == 20 && generator.source().generation() == 20 && generator.experimentalStructures(), "The public preset uses generation20 with its new-world option");
        helper.assertTrue(generator.initialDiameter() == 724, "The public preset defaults to Medium / 724 blocks");
        for (var tag : List.of(WorldPresetTags.NORMAL, WorldPresetTags.EXTENDED)) {
            var visible = presets.getOrThrow(tag).stream().map(holder -> holder.getRegisteredName())
@@ -56,11 +62,11 @@ final class UnifiedWorldSettingsDiagnostics {
        }

        var ops = RegistryOps.create(JsonOps.INSTANCE, access);
-        var activeCodec = generator.rootGeneration() == 17 ? SanctuaryChunkGenerator.RUINS17_CODEC : generator.rootGeneration() == 16 ? SanctuaryChunkGenerator.CITY16_CODEC : generator.rootGeneration() == 15 ? SanctuaryChunkGenerator.CITY15_CODEC : generator.rootGeneration() == 14 ? SanctuaryChunkGenerator.CITY_CODEC : SanctuaryChunkGenerator.CODEC;
+        var activeCodec = generator.rootGeneration() == 20 ? SanctuaryChunkGenerator.ARCHITECTURE20_CODEC : generator.rootGeneration() == 19 ? SanctuaryChunkGenerator.HERITAGE19_CODEC : generator.rootGeneration() == 17 ? SanctuaryChunkGenerator.RUINS17_CODEC : generator.rootGeneration() == 16 ? SanctuaryChunkGenerator.CITY16_CODEC : generator.rootGeneration() == 15 ? SanctuaryChunkGenerator.CITY15_CODEC : generator.rootGeneration() == 14 ? SanctuaryChunkGenerator.CITY_CODEC : SanctuaryChunkGenerator.CODEC;
        var serialized = activeCodec.codec().encodeStart(ops, generator).getOrThrow().getAsJsonObject();
        serialized.remove("experimental_structures");
        helper.assertTrue(activeCodec.codec().parse(ops, serialized).getOrThrow().experimentalStructures(),
-            "Generation17 omitted experimental option defaults to enabled");
+            "Generation20 omitted experimental option defaults to enabled");
        helper.assertTrue(!((SanctuaryChunkGenerator) historical16.overworld()).withExperimentalStructures(true).experimentalStructures(),
            "The new-world switch cannot activate experimental generation in a historical16 generator");
        serialized.remove("initial_diameter");
@@ -21,7 +21,8 @@ public abstract class SanctuaryGameTestServerMixin {
    // generation test's deadline before its IO/workers can complete. This is test-only pacing.
    @Inject(method = "waitUntilNextTick", at = @At("RETURN"))
    private void sanctuary$paceExpansionWorkers(CallbackInfo ci) {
-        if (Boolean.getBoolean("sanctuary.test.ruins17") || Boolean.getBoolean("sanctuary.test.expansion") || Boolean.getBoolean("sanctuary.test.lostCity")
+        if (Boolean.getBoolean("sanctuary.test.heritage20") || Boolean.getBoolean("sanctuary.test.lostCity20")
+                || Boolean.getBoolean("sanctuary.test.heritage19") || Boolean.getBoolean("sanctuary.test.ruins17") || Boolean.getBoolean("sanctuary.test.expansion") || Boolean.getBoolean("sanctuary.test.lostCity")
                || Boolean.getBoolean("sanctuary.test.lostCity16") || Boolean.getBoolean("sanctuary.test.lostCity15") || Boolean.getBoolean("sanctuary.test.voidReuse")) {
            long until = System.nanoTime() + 20_000_000L;
            long remaining;
@@ -46,9 +47,9 @@ public abstract class SanctuaryGameTestServerMixin {
        "Lnet/minecraft/world/level/levelgen/presets/WorldPresets;FLAT_ALL_DIMENSIONS:Lnet/minecraft/resources/ResourceKey;"))
    private static ResourceKey<WorldPreset> sanctuary$selectActualPreset() {
        if (Boolean.getBoolean("sanctuary.test.unified")) {
-            int generation = Integer.getInteger("sanctuary.test.generation", 17);
-            if (generation != 13 && generation != 14 && generation != 15 && generation != 16 && generation != 17) throw new IllegalArgumentException("Unsupported test generation");
-            return ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id(generation == 17 ? "sanctuary" : "sanctuary_v" + generation));
+            int generation = Integer.getInteger("sanctuary.test.generation", 20);
+            if (generation != 13 && generation != 14 && generation != 15 && generation != 16 && generation != 17 && generation != 19 && generation != 20) throw new IllegalArgumentException("Unsupported test generation");
+            return ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id(generation == 20 ? "sanctuary" : "sanctuary_v" + generation));
        }
        if (Boolean.getBoolean("sanctuary.test.expansion")) return ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("expansion_lab"));
        int players = Integer.getInteger("sanctuary.test.players", 10);
@@ -48,6 +48,7 @@ public final class SanctuaryMod implements ModInitializer {
        Registry.register(BuiltInRegistries.DENSITY_FUNCTION_TYPE, id("expansion_island"), fr.koka.sanctuary.expansion.ExpansionDensity.CODEC);
        fr.koka.sanctuary.expansion.ExpansionRuntime.register();
        fr.koka.sanctuary.expansion.ExpansionCommands.register();
+        fr.koka.sanctuary.worldgen.heritage.HeritageCommands19.register();
        Registry.register(BuiltInRegistries.DENSITY_FUNCTION_TYPE, id("main_island"), MainIslandDensity.CODEC);
        Registry.register(BuiltInRegistries.CHUNK_GENERATOR, id("island_v13"), SanctuaryChunkGenerator.CODEC);
        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("island_v13"), SanctuaryBiomeSource.CODEC);
@@ -60,6 +61,11 @@ public final class SanctuaryMod implements ModInitializer {
        Registry.register(BuiltInRegistries.CHUNK_GENERATOR, id("island_v17"), SanctuaryChunkGenerator.RUINS17_CODEC);
        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("island_v17"), SanctuaryBiomeSource.RUINS17_CODEC);
        fr.koka.sanctuary.worldgen.city.LostCityStructures.register();
+        Registry.register(BuiltInRegistries.CHUNK_GENERATOR, id("island_v19"), SanctuaryChunkGenerator.HERITAGE19_CODEC);
+        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("island_v19"), SanctuaryBiomeSource.HERITAGE19_CODEC);
+        Registry.register(BuiltInRegistries.CHUNK_GENERATOR, id("island_v20"), SanctuaryChunkGenerator.ARCHITECTURE20_CODEC);
+        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("island_v20"), SanctuaryBiomeSource.ARCHITECTURE20_CODEC);
+        fr.koka.sanctuary.worldgen.heritage.HeritageStructures19.register();
        fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.register();
        Registry.register(BuiltInRegistries.DENSITY_FUNCTION_TYPE, id("population_island"), PopulationIslandDensity.CODEC);
        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("population_island"), PopulationIslandBiomeSource.CODEC);
@@ -51,11 +51,11 @@ public final class SanctuaryWorldOptionsScreen extends Screen {
        contents.addChild(sizeButton);
        diameterHint = contents.addChild(new MultiLineTextWidget(diameterHint(), font)
                .setMaxWidth(310).setCentered(true));
-        if (generator.rootGeneration() == 17) {
+        if (generator.rootGeneration() == 17 || generator.rootGeneration() == 19 || generator.rootGeneration() == 20) {
            contents.addChild(CycleButton.builder((Boolean enabled) -> enabled ? CommonComponents.OPTION_ON : CommonComponents.OPTION_OFF, experimental)
                .withValues(true, false).create(0, 0, 280, 20, Component.translatable("sanctuary.world_options.experimental"),
                    (button, value) -> experimental = value));
-            contents.addChild(new MultiLineTextWidget(Component.translatable("sanctuary.world_options.experimental_hint"), font)
+            contents.addChild(new MultiLineTextWidget(Component.translatable((generator.rootGeneration() == 19 || generator.rootGeneration() == 20) ? "sanctuary.world_options.heritage_hint" : "sanctuary.world_options.experimental_hint"), font)
                .setMaxWidth(310).setCentered(true));
        }
        layout.addToContents(contents);
@@ -122,6 +122,7 @@ public class ExpansionChunkGenerator extends ChunkGenerator {
            ChunkAccess chunk, StructureTemplateManager templates, ResourceKey<Level> dimension) {
        fr.koka.sanctuary.worldgen.city.LostCityStructures.generate(this, registries, state, structures, chunk, templates, dimension);
        fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.generate(this, registries, state, structures, chunk, templates, dimension);
+        fr.koka.sanctuary.worldgen.heritage.HeritageStructures19.generate(this, registries, state, structures, chunk, templates, dimension);
        ExpansionStructures.generate(this, registries, state, structures, chunk, templates, dimension);
    }
    @Override public void spawnOriginalMobs(WorldGenRegion region) {
@@ -41,7 +41,7 @@ public record ExpansionIsland(String id, String parent, String direction, String
        if (!((spatialGeneration(generation) ? DIAMETERS : LEGACY_DIAMETERS).contains(diameter) || (id.equals("sanctuary") && (diameter == 724 || (generation == 13 || spatialGeneration(generation)) && diameter == 1024)))) throw new IllegalArgumentException("Unsupported nominal diameter");
        if (Math.abs((long) centerX) > 100_000 || Math.abs((long) centerZ) > 100_000 || (centerX & 15) != 0 || (centerZ & 15) != 0) throw new IllegalArgumentException("Invalid island centre");
        if (!List.of("reserved", "ready").contains(status) || (generation != GENERATION && !spatialGeneration(generation) && !(generation == 13 && id.equals("sanctuary")))) throw new IllegalArgumentException("Unsupported island state or generation");
-        if (climate.equals("lost_city") && (!spatialGeneration(generation) || id.equals("sanctuary"))) throw new IllegalArgumentException("Lost City requires a generation 14, 15, 16 or 17 expansion");
+        if (climate.equals("lost_city") && (!spatialGeneration(generation) || id.equals("sanctuary"))) throw new IllegalArgumentException("Lost City requires a generation 14, 15, 16, 17, 19 or 20 expansion");
        if (reuseToken == null || !reuseToken.isEmpty() && (!spatialGeneration(generation) || id.equals("sanctuary") || !reuseToken.matches("[0-9a-f]{64}")))
            throw new IllegalArgumentException("Invalid void reuse certificate token");
    }
@@ -53,7 +53,7 @@ public record ExpansionIsland(String id, String parent, String direction, String
        return new ExpansionIsland("sanctuary", "sanctuary", "north", "temperate", diameter, 0, 0, seed, "natural", "ready", generation);
    }

-    public static boolean spatialGeneration(int generation) { return generation == 14 || generation == 15 || generation == 16 || generation == 17; }
+    public static boolean spatialGeneration(int generation) { return generation == 14 || generation == 15 || generation == 16 || generation == 17 || generation == 19 || generation == 20; }
    public boolean origin() { return id.equals("sanctuary"); }
    public double referenceDiameter() { return origin() && diameter == 724 ? Math.sqrt(2) * 512 : 512; }
    public double horizontalScale() { return origin() ? 1.0 : diameter / referenceDiameter(); }
@@ -25,7 +25,8 @@ public abstract class UnifiedDecorationProtectionMixin {
        var destination = generator.islandForChunk(pos.getX() >> 4, pos.getZ() >> 4);
        if (owner == null || destination == null || !owner.id().equals(destination.id())
                || !fr.koka.sanctuary.worldgen.city.LostCityStructures.isPlacing()
-                    && !fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.isPlacing() && generator.protectsCityDecoration(pos))
+                    && !fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.isPlacing()
+                    && !fr.koka.sanctuary.worldgen.heritage.HeritageStructures19.isPlacing() && generator.protectsCityDecoration(pos))
            callback.setReturnValue(false);
    }

@@ -40,7 +41,7 @@ public abstract class UnifiedDecorationProtectionMixin {
        if (state.is(Blocks.SUGAR_CANE)) return;
        // Generation16 reserves its architectural volume before decoration. Only its own
        // native pieces may replace water there; published generations retain the old rule.
-        if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17)
+        if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17 || generator.rootGeneration() == 19 || generator.rootGeneration() == 20)
                && fr.koka.sanctuary.worldgen.city.LostCityStructures.isPlacing()
                && generator.protectsCityDecoration(pos)) return;
        if (generator.protectsDecoration(pos) && !region.getBlockState(pos).equals(state)) {
@@ -42,6 +42,14 @@ public final class SanctuaryBiomeSource extends ExpansionBiomeSource {
        Biome.CODEC.listOf().fieldOf("biomes").forGetter(source -> source.allBiomes)
    ).apply(i, biomes -> new SanctuaryBiomeSource(biomes, 17)));

+    public static final MapCodec<SanctuaryBiomeSource> HERITAGE19_CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        Biome.CODEC.listOf().fieldOf("biomes").forGetter(source -> source.allBiomes)
+    ).apply(i, biomes -> new SanctuaryBiomeSource(biomes, 19)));
+
+    public static final MapCodec<SanctuaryBiomeSource> ARCHITECTURE20_CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        Biome.CODEC.listOf().fieldOf("biomes").forGetter(source -> source.allBiomes)
+    ).apply(i, biomes -> new SanctuaryBiomeSource(biomes, 20)));
+
    private final List<Holder<Biome>> allBiomes;
    private final PopulationIslandBiomeSource population;
    private final boolean cities;
@@ -75,7 +83,7 @@ public final class SanctuaryBiomeSource extends ExpansionBiomeSource {
        cityPlans = java.util.Map.copyOf(plans);
    }

-    @Override protected MapCodec<SanctuaryBiomeSource> codec() { return generation == 17 ? RUINS17_CODEC : generation == 16 ? CITY16_CODEC : generation == 15 ? CITY15_CODEC : cities ? CITY_CODEC : CODEC; }
+    @Override protected MapCodec<SanctuaryBiomeSource> codec() { return generation == 20 ? ARCHITECTURE20_CODEC : generation == 19 ? HERITAGE19_CODEC : generation == 17 ? RUINS17_CODEC : generation == 16 ? CITY16_CODEC : generation == 15 ? CITY15_CODEC : cities ? CITY_CODEC : CODEC; }

    @Override public BiomeResolver createResolver(Climate.Sampler sampler) {
        BiomeResolver woodlands = population.createResolver(sampler);
@@ -45,9 +45,23 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        Codec.BOOL.optionalFieldOf("experimental_structures", true).forGetter(SanctuaryChunkGenerator::experimentalStructures)
    ).apply(i, (source, diameter, experimental) -> new SanctuaryChunkGenerator(source, diameter, 17, experimental)));

+    public static final MapCodec<SanctuaryChunkGenerator> HERITAGE19_CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        SanctuaryBiomeSource.HERITAGE19_CODEC.fieldOf("biome_source").forGetter(SanctuaryChunkGenerator::source),
+        DIAMETER_CODEC.optionalFieldOf("initial_diameter", 724).forGetter(SanctuaryChunkGenerator::initialDiameter),
+        Codec.BOOL.optionalFieldOf("experimental_structures", true).forGetter(SanctuaryChunkGenerator::experimentalStructures)
+    ).apply(i, (source, diameter, experimental) -> new SanctuaryChunkGenerator(source, diameter, 19, experimental)));
+
+    public static final MapCodec<SanctuaryChunkGenerator> ARCHITECTURE20_CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        SanctuaryBiomeSource.ARCHITECTURE20_CODEC.fieldOf("biome_source").forGetter(SanctuaryChunkGenerator::source),
+        DIAMETER_CODEC.optionalFieldOf("initial_diameter", 724).forGetter(SanctuaryChunkGenerator::initialDiameter),
+        Codec.BOOL.optionalFieldOf("experimental_structures", true).forGetter(SanctuaryChunkGenerator::experimentalStructures)
+    ).apply(i, (source, diameter, experimental) -> new SanctuaryChunkGenerator(source, diameter, 20, experimental)));
+
    private final boolean experimentalStructures;
    private volatile fr.koka.sanctuary.worldgen.ruins.RuinsPlan17 ruinsPlan17 = fr.koka.sanctuary.worldgen.ruins.RuinsPlan17.EMPTY;
    private boolean ruinsPrepared;
+    private volatile fr.koka.sanctuary.worldgen.heritage.HeritagePlan19 heritagePlan19 = fr.koka.sanctuary.worldgen.heritage.HeritagePlan19.EMPTY;
+    private boolean heritagePrepared;
    private volatile Context originContext;
    private final int generation;
    private net.minecraft.world.level.LevelHeightAccessor heightAccessor;
@@ -83,12 +97,12 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
    }
    private SanctuaryChunkGenerator(SanctuaryBiomeSource source, int initialDiameter, int generation, boolean experimental) {
        super(source, initialDiameter, true);
-        this.experimentalStructures = generation == 17 && experimental;
+        this.experimentalStructures = (generation == 17 || generation == 19 || generation == 20) && experimental;
        this.generation = generation;
        if (generation != source.generation()) throw new IllegalArgumentException("Sanctuary generator and biome source versions must agree");
    }
    @Override public SanctuaryBiomeSource source() { return (SanctuaryBiomeSource) super.source(); }
-    @Override protected MapCodec<SanctuaryChunkGenerator> codec() { return generation == 17 ? RUINS17_CODEC : generation == 16 ? CITY16_CODEC : generation == 15 ? CITY15_CODEC : generation == 14 ? CITY_CODEC : CODEC; }
+    @Override protected MapCodec<SanctuaryChunkGenerator> codec() { return generation == 20 ? ARCHITECTURE20_CODEC : generation == 19 ? HERITAGE19_CODEC : generation == 17 ? RUINS17_CODEC : generation == 16 ? CITY16_CODEC : generation == 15 ? CITY15_CODEC : generation == 14 ? CITY_CODEC : CODEC; }
    public SanctuaryChunkGenerator withInitialDiameter(int diameter) {
        return new SanctuaryChunkGenerator(source().copy(), diameter, generation, experimentalStructures);
    }
@@ -97,8 +111,10 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        return new SanctuaryChunkGenerator(source().copy(), initialDiameter(), generation, enabled);
    }
    public fr.koka.sanctuary.worldgen.ruins.RuinsPlan17 ruinsPlan17() { return ruinsPlan17; }
+    public fr.koka.sanctuary.worldgen.heritage.HeritagePlan19 heritagePlan19() { return heritagePlan19; }
    public boolean intersectsExperimentalStructures(int minX, int minY, int minZ, int maxX, int maxY, int maxZ) {
-        return generation == 17 && ruinsPlan17.intersectsProtection(minX, minY, minZ, maxX, maxY, maxZ);
+        return (generation == 17 || generation == 19 || generation == 20) && ruinsPlan17.intersectsProtection(minX, minY, minZ, maxX, maxY, maxZ)
+            || (generation == 19 || generation == 20) && heritagePlan19.intersectsProtection(minX, minY, minZ, maxX, maxY, maxZ);
    }
    public IslandCapacity capacity() {
        return switch (initialDiameter()) {
@@ -134,11 +150,13 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        context(islands.getFirst());
        prepareCities(islands);
        prepareRuins(islands);
+        prepareHeritage(islands);
    }
    @Override public void setIslands(List<ExpansionIsland> islands) {
        // Complete and publish city geometry before workers can observe the new owner list.
        prepareCities(islands);
        prepareRuins(islands);
+        prepareHeritage(islands);
        super.setIslands(islands);
    }
    private void prepareCities(List<ExpansionIsland> islands) {
@@ -149,7 +167,7 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
            source().setCityPlans(java.util.Map.of());
            return;
        }
-        if ((generation == 16 || generation == 17) && !cityStructuresEnabled) {
+        if ((generation == 16 || generation == 17 || generation == 19 || generation == 20) && !cityStructuresEnabled) {
            cityProtection16 = fr.koka.sanctuary.worldgen.city.LostCityProtection16.EMPTY;
            activeCityPlans = java.util.Map.of();
            source().setCityPlans(java.util.Map.of());
@@ -165,7 +183,7 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
            }
            cityProtection15 = protection.build();
        }
-        if (generation == 16 || generation == 17) {
+        if (generation == 16 || generation == 17 || generation == 19 || generation == 20) {
            var protection = new fr.koka.sanctuary.worldgen.city.LostCityProtection16.Builder();
            for (var island : islands) {
                protection.add(published.get(island.id()), undergroundPlan16(island));
@@ -180,7 +198,7 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        source().setCityPlans(published);
    }
    private void prepareRuins(List<ExpansionIsland> islands) {
-        if (generation != 17 || !experimentalStructures || !cityStructuresEnabled || ruinsPrepared) return;
+        if ((generation != 17 && generation != 19 && generation != 20) || !experimentalStructures || !cityStructuresEnabled || ruinsPrepared) return;
        var root = islands.stream().filter(ExpansionIsland::origin).findFirst().orElseThrow();
        var terrain = context(root);
        var sampled = new fr.koka.sanctuary.worldgen.ruins.RuinsTerrain17(root, terrain.generator(), terrain.random(),
@@ -192,6 +210,22 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        SanctuaryMod.LOGGER.info("Experimental ruins17 seed {}: {} networks, {} probes, {} noise columns in {} ms",
            root.seed(), plan.networks().size(), plan.samples(), sampled.columnsUsed(), (System.nanoTime() - start) / 1_000_000);
    }
+    private void prepareHeritage(List<ExpansionIsland> islands) {
+        if ((generation != 19 && generation != 20) || !experimentalStructures || !cityStructuresEnabled || heritagePrepared) return;
+        var root = islands.stream().filter(ExpansionIsland::origin).findFirst().orElseThrow();
+        var terrain = context(root);
+        var sampled = new fr.koka.sanctuary.worldgen.heritage.HeritageTerrain19(root, terrain.generator(), terrain.random(),
+            heightAccessor, pos -> protectsDecoration(pos) || cityProtection16.contains(pos.getX(), pos.getY(), pos.getZ())
+                || ruinsPlan17.protects(pos.getX(), pos.getY(), pos.getZ()));
+        long start = System.nanoTime();
+        sampled.discoverLandmarks(lostCityPlan(root), ruinsPlan17);
+        var plan = fr.koka.sanctuary.worldgen.heritage.HeritagePlanner19.plan(root.seed(), root.centerX(), root.centerZ(), root.diameter(), sampled);
+        heritagePlan19 = plan;
+        heritagePrepared = true;
+        SanctuaryMod.LOGGER.info("Heritage19 seed {}: {} sites, {} routes, {} segments, {} probes, {} native columns in {} ms; {}",
+            root.seed(), plan.sites().size(), plan.links().size(), plan.segments().size(), plan.samples(), sampled.columnsUsed(),
+            (System.nanoTime() - start) / 1_000_000, plan.diagnostics());
+    }
    private static ExpansionIsland cityIdentity(ExpansionIsland island) {
        // State and receipt do not change the terrain geometry used by a cached plan.
        var ready = island.status().equals("ready") ? island : island.ready();
@@ -217,7 +251,7 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        return cityPlans.computeIfAbsent(cityIdentity(island), ignored -> {
            long start = System.nanoTime();
            var terrain = context(island);
-            if (generation == 16 || generation == 17) {
+            if (generation == 16 || generation == 17 || generation == 19 || generation == 20) {
                var sampled = new fr.koka.sanctuary.worldgen.city.LostCityTerrain16(island, terrain.generator(), terrain.random(),
                    heightAccessor, pos -> island.origin() && protectsDecoration(pos));
                var placement = LostCityPlanner16.plan(island.seed(), island.centerX(), island.centerZ(),
@@ -288,8 +322,9 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        });
    }
    public boolean protectsCityDecoration(net.minecraft.core.BlockPos pos) {
-        if (generation == 16 || generation == 17) return cityProtection16.contains(pos.getX(), pos.getY(), pos.getZ())
-            || generation == 17 && ruinsPlan17.protects(pos.getX(), pos.getY(), pos.getZ());
+        if (generation == 16 || generation == 17 || generation == 19 || generation == 20) return cityProtection16.contains(pos.getX(), pos.getY(), pos.getZ())
+            || (generation == 17 || generation == 19 || generation == 20) && ruinsPlan17.protects(pos.getX(), pos.getY(), pos.getZ())
+            || (generation == 19 || generation == 20) && heritagePlan19.protects(pos.getX(), pos.getY(), pos.getZ());
        if (generation == 15) return cityProtection15.contains(pos.getX(), pos.getY(), pos.getZ());
        if (generation != 14) return false;
        var island = islandAt(pos.getX(), pos.getZ());
@@ -311,20 +346,20 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
        return citySupports.getOrDefault(cityIdentity(island), List.of());
    }
    public boolean intersectsCityConstruction16(int minX, int minY, int minZ, int maxX, int maxY, int maxZ) {
-        return (generation == 16 || generation == 17) && cityProtection16.intersects(minX, minY, minZ, maxX, maxY, maxZ);
+        return (generation == 16 || generation == 17 || generation == 19 || generation == 20) && cityProtection16.intersects(minX, minY, minZ, maxX, maxY, maxZ);
    }
    public fr.koka.sanctuary.worldgen.city.LostCityUnderground16.Plan undergroundPlan16(ExpansionIsland island) {
-        if (generation != 16 && generation != 17) return new fr.koka.sanctuary.worldgen.city.LostCityUnderground16.Plan(List.of(), 0);
+        if (generation != 16 && generation != 17 && generation != 19 && generation != 20) return new fr.koka.sanctuary.worldgen.city.LostCityUnderground16.Plan(List.of(), 0);
        lostCityPlan(island);
        return undergroundPlans16.getOrDefault(cityIdentity(island), new fr.koka.sanctuary.worldgen.city.LostCityUnderground16.Plan(List.of(), 0));
    }
    public List<LostCityPlanner16.Support> citySupports16(ExpansionIsland island) {
-        if (generation != 16 && generation != 17) return List.of();
+        if (generation != 16 && generation != 17 && generation != 19 && generation != 20) return List.of();
        lostCityPlan(island);
        return citySupports16.getOrDefault(cityIdentity(island), List.of());
    }
    public LostCityPlanner16.Fallback cityReservation16(ExpansionIsland island) {
-        if (generation != 16 && generation != 17) return null;
+        if (generation != 16 && generation != 17 && generation != 19 && generation != 20) return null;
        lostCityPlan(island);
        return cityReservations16.get(cityIdentity(island));
    }
@@ -336,8 +371,10 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
            net.minecraft.core.BlockPos origin, int radius, boolean skipReferenced) {
        if (structures.size() == 1 && structures.get(0).is(fr.koka.sanctuary.worldgen.city.LostCityStructures.KEY))
            return fr.koka.sanctuary.worldgen.city.LostCityStructures.findNearest(level, structures, origin, radius, skipReferenced);
-        if (generation == 17 && structures.size() == 1 && structures.get(0).is(fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.KEY))
+        if ((generation == 17 || generation == 19 || generation == 20) && structures.size() == 1 && structures.get(0).is(fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.KEY))
            return fr.koka.sanctuary.worldgen.ruins.RuinsStructures17.findNearest(level, structures, origin, radius, skipReferenced);
+        if ((generation == 19 || generation == 20) && structures.size() == 1 && structures.get(0).is(fr.koka.sanctuary.worldgen.heritage.HeritageStructures19.KEY))
+            return fr.koka.sanctuary.worldgen.heritage.HeritageStructures19.findNearest(level, structures, origin, radius, skipReferenced);
        return super.findNearestMapStructure(level, structures, origin, radius, skipReferenced);
    }
    @Override protected Context context(ExpansionIsland island) {
@@ -365,7 +402,7 @@ public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
    @Override protected void afterTerrain(ExpansionIsland island, ChunkAccess chunk) {
        // Root water/lava are already applied by the Population hook on the named delegate.
        if (!island.origin()) super.afterTerrain(island, chunk);
-        if ((generation == 16 || generation == 17) && cityStructuresEnabled) {
+        if ((generation == 16 || generation == 17 || generation == 19 || generation == 20) && cityStructuresEnabled) {
            var reserved = cityReservations16.get(cityIdentity(island));
            if (reserved != null) {
                var mutable = new net.minecraft.core.BlockPos.MutableBlockPos();
@@ -0,0 +1,755 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Kind;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Parcel;
+import java.util.ArrayList;
+import fr.koka.sanctuary.worldgen.detail.ConnectedBlocks20;
+import java.util.List;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DoorHingeSide;
+import net.minecraft.world.level.block.state.properties.DoubleBlockHalf;
+import net.minecraft.world.level.block.state.properties.SlabType;
+import net.minecraft.world.level.storage.loot.BuiltInLootTables;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Complete generation-20 buildings. Published renderers deliberately never call this renderer.
+ * A north-facing plan is rotated once; all positions remain relative to the saved parcel. */
+public final class LostCityInteriors20 {
+    private static final BlockState AIR = Blocks.AIR.defaultBlockState();
+    private static final BlockState STONE = Blocks.STONE.defaultBlockState();
+    private static final BlockState SMOOTH = Blocks.SMOOTH_STONE.defaultBlockState();
+    private static final BlockState WOOD = Blocks.OAK_PLANKS.defaultBlockState();
+    private static final BlockState TILE = Blocks.POLISHED_ANDESITE.defaultBlockState();
+    private static final int STOREY = 5;
+
+    private LostCityInteriors20() {}
+
+    /** Reachable standing positions, in the same rotated local coordinates as BlockWriter. */
+    public record Room(String name, int x, int y, int z) {}
+
+    /** Local, already rotated enclosure including the floor, full ceiling, four walls and door. */
+    public record Bathroom(String name, int minX, int minY, int minZ, int maxX, int maxY, int maxZ,
+                           int doorX, int doorY, int doorZ) {}
+
+    private record Area(int left, int front, int right, int back) {}
+
+    /** Adjacent storeys always change plan; the saved parcel seed chooses which plan comes first. */
+    public static int layout(Parcel parcel, int floor) {
+        validate(parcel);
+        if (floor < 0 || floor >= parcel.floors()) throw new IllegalArgumentException("Invalid interior floor");
+        return (int) ((parcel.seed() ^ (parcel.seed() >>> 32)) & 1L) ^ (floor & 1);
+    }
+
+    private static Area rear(Parcel p, int floor, boolean east) {
+        boolean wide = layout(p, floor) == 1;
+        return east ? new Area(wide ? 10 : 11, wide ? 10 : 11, 14, 14)
+            : new Area(2, wide ? 10 : 11, wide ? 6 : 5, 14);
+    }
+
+    private static int frontWall(Parcel p, int floor) { return layout(p, floor) == 0 ? 7 : 8; }
+
+    private static String frontUse(Parcel p, int floor) {
+        int variant = layout(p, floor);
+        return switch (p.kind()) {
+            case APARTMENT -> variant == 0 ? "kitchen_dining" : "studio_bedroom";
+            case HOTEL -> floor == 0 ? "reception" : "guest_suite";
+            case LIBRARY -> variant == 0 ? "book_stacks" : "periodicals_reading";
+            case RESTAURANT -> variant == 0 ? "dining_room" : "kitchen";
+            case BARRACKS -> variant == 0 ? "dormitory" : "duty_office";
+            case HALL -> floor == 0 ? "ticket_office" : "administration";
+            default -> throw new IllegalArgumentException("Not an interior kind");
+        };
+    }
+
+    private static String rearUse(Parcel p, int floor, boolean east) {
+        int variant = layout(p, floor);
+        return switch (p.kind()) {
+            case APARTMENT -> east ? "bathroom" : variant == 0 ? "bedroom" : "kitchen_dining";
+            case HOTEL -> floor == 0 ? east ? "laundry" : "lounge"
+                : variant == 0 ? east ? "guest_room" : "bedroom" : east ? "bathroom" : "guest_lounge";
+            case LIBRARY -> variant == 0 ? east ? "archive" : "reading_room" : east ? "bathroom" : "catalogue_office";
+            case RESTAURANT -> variant == 0 ? east ? "kitchen" : "washrooms" : east ? "pantry" : "dining_room";
+            case BARRACKS -> east ? "equipment_store" : variant == 0 ? "washrooms" : "officer_bedroom";
+            case HALL -> variant == 0 ? east ? "bathroom" : "meeting_room" : east ? "meeting_room" : "archive";
+            default -> throw new IllegalArgumentException("Not an interior kind");
+        };
+    }
+
+    public static void render(Parcel parcel, LostCityRenderer.BlockWriter output) {
+        validate(parcel);
+        var connected = ConnectedBlocks20.buffer(output);
+        new Building(parcel, connected).render();
+        connected.flush();
+    }
+
+    /** These describe actual rooms and services, not decorative labels placed in the world. */
+    public static List<Room> rooms(Parcel parcel) {
+        validate(parcel);
+        List<Room> result = new ArrayList<>();
+        add(result, parcel, "street_entrance", 8, 1, 0);
+        add(result, parcel, "vestibule", 8, 1, 3);
+        for (int floor = 0; floor < parcel.floors(); floor++) {
+            int y = floor * STOREY + 1;
+            String prefix = "floor_" + floor + "/";
+            add(result, parcel, prefix + "corridor", 8, y, 8);
+            add(result, parcel, prefix + "stair_landing", 4, y, 8);
+            add(result, parcel, prefix + frontUse(parcel, floor), 11, y, 6);
+            if (parcel.kind() == Kind.HALL && floor < 2) {
+                if (floor == 0) {
+                    add(result, parcel, prefix + "auditorium", 8, y, 11);
+                    add(result, parcel, prefix + "stage", 9, y + 1, 13);
+                } else add(result, parcel, prefix + "gallery", 8, y, 10);
+            } else {
+                Area west = rear(parcel, floor, false), east = rear(parcel, floor, true);
+                add(result, parcel, prefix + rearUse(parcel, floor, false), west.right(), y, 11);
+                add(result, parcel, prefix + rearUse(parcel, floor, true), east.left(), y, 11);
+            }
+        }
+        for (var bath : bathroomPlans(parcel)) {
+            int targetZ = bath.southDoor() ? bath.z1() - 1 : bath.z0() + 1;
+            add(result, parcel, bath.name(), bath.doorX(), bath.floor() * STOREY + 1, targetZ);
+        }
+        add(result, parcel, "roof", 8, parcel.floors() * STOREY + 1, 8);
+        switch (parcel.kind()) {
+            case HOTEL -> add(result, parcel, "roof_laundry_pavilion", 10, parcel.floors() * STOREY + 1, 5);
+            case APARTMENT -> add(result, parcel, "roof_residents_terrace", 8, parcel.floors() * STOREY + 1, 10);
+            case LIBRARY -> add(result, parcel, "roof_reading_terrace", 11, parcel.floors() * STOREY + 1, 10);
+            case RESTAURANT -> add(result, parcel, "roof_dining_terrace", 11, parcel.floors() * STOREY + 1, 8);
+            case BARRACKS -> add(result, parcel, "roof_service_stair", 4, parcel.floors() * STOREY + 1, 8);
+            default -> { }
+        }
+        return List.copyOf(result);
+    }
+
+    private record BathPlan(String name, int floor, int x0, int z0, int x1, int z1, int doorX, boolean southDoor) {}
+
+    private static List<BathPlan> bathroomPlans(Parcel p) {
+        List<BathPlan> result = new ArrayList<>();
+        for (int floor = 0; floor < p.floors(); floor++) {
+            if (p.kind() == Kind.HOTEL && floor > 0)
+                result.add(new BathPlan("floor_" + floor + "/suite_bathroom", floor, 10, 1, 15, 4, 12, true));
+            if (p.kind() == Kind.HALL && floor < 2) continue;
+            for (boolean east : new boolean[]{false, true}) {
+                String use = rearUse(p, floor, east);
+                if (!use.equals("bathroom") && !use.equals("washrooms")) continue;
+                Area room = rear(p, floor, east);
+                result.add(new BathPlan("floor_" + floor + "/" + (east ? "east" : "west") + "_bathroom_interior",
+                    floor, room.left() - 1, 12, room.right() + 1, 15, east ? 12 : 4, false));
+            }
+        }
+        return List.copyOf(result);
+    }
+
+    public static List<Bathroom> bathrooms(Parcel p) {
+        validate(p);
+        List<Bathroom> result = new ArrayList<>();
+        for (var b : bathroomPlans(p)) {
+            int x0 = rx(b.x0(), b.z0(), p.facing()), z0 = rz(b.x0(), b.z0(), p.facing());
+            int x1 = rx(b.x1(), b.z1(), p.facing()), z1 = rz(b.x1(), b.z1(), p.facing());
+            int doorZ = b.southDoor() ? b.z1() : b.z0();
+            result.add(new Bathroom(b.name(), Math.min(x0, x1), b.floor() * STOREY, Math.min(z0, z1),
+                Math.max(x0, x1), b.floor() * STOREY + 4, Math.max(z0, z1), rx(b.doorX(), doorZ, p.facing()),
+                b.floor() * STOREY + 1, rz(b.doorX(), doorZ, p.facing())));
+        }
+        return List.copyOf(result);
+    }
+
+    private static void validate(Parcel p) {
+        if (!p.kind().building() || p.width() != 17 || p.depth() != 17 || p.floors() < 2)
+            throw new IllegalArgumentException("Generation-20 interiors require a 17x17 building with 2..5 floors");
+    }
+
+    private static void add(List<Room> result, Parcel p, String name, int x, int y, int z) {
+        result.add(new Room(name, rx(x, z, p.facing()), y, rz(x, z, p.facing())));
+    }
+    private static int rx(int x, int z, int facing) {
+        return switch (facing) { case 0 -> x; case 1 -> 16 - z; case 2 -> 16 - x; default -> z; };
+    }
+    private static int rz(int x, int z, int facing) {
+        return switch (facing) { case 0 -> z; case 1 -> x; case 2 -> 16 - z; default -> 16 - x; };
+    }
+
+    private static final class Building {
+        final Parcel p;
+        final LostCityRenderer.BlockWriter output;
+        final Rotation rotation;
+        Building(Parcel p, LostCityRenderer.BlockWriter output) {
+            this.p = p;
+            this.output = output;
+            rotation = switch (p.facing()) {
+                case 0 -> Rotation.NONE; case 1 -> Rotation.CLOCKWISE_90;
+                case 2 -> Rotation.CLOCKWISE_180; default -> Rotation.COUNTERCLOCKWISE_90;
+            };
+        }
+        void set(int x, int y, int z, BlockState state) {
+            output.set(rx(x, z, p.facing()), y, rz(x, z, p.facing()), state.rotate(rotation));
+        }
+        void set(int x, int y, int z, Block block) { set(x, y, z, block.defaultBlockState()); }
+        void box(int x0, int y0, int z0, int x1, int y1, int z1, BlockState state) {
+            for (int x = x0; x <= x1; x++) for (int z = z0; z <= z1; z++)
+                for (int y = y0; y <= y1; y++) set(x, y, z, state);
+        }
+        BlockState facing(Block block, Direction direction) {
+            return block.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, direction);
+        }
+        BlockState brick(int x, int y, int z) { return LostCityPalette.masonry(p.seed(), x, y, z); }
+        int roll(int x, int y, int z, int bound) { return LostCityPalette.roll(p.seed(), x, y, z, bound); }
+
+        void render() {
+            int roof = p.floors() * STOREY;
+            box(0, -p.foundationDepth(), 0, 16, -1, 16, Blocks.STONE_BRICKS.defaultBlockState());
+            box(0, 0, 0, 16, 0, 16, SMOOTH);
+            box(0, 1, 0, 16, roof + 4, 16, AIR);
+            shell(roof);
+            architecturalEnvelope(roof);
+            for (int floor = 0; floor < p.floors(); floor++) {
+                partitions(floor);
+                furnishings(floor);
+            }
+            stairs();
+            entrance();
+            roof(roof);
+            // Only one deferred loot table per building; empty furniture is not a resource vault.
+            int lootX = 6;
+            int lootZ = 6;
+            box(lootX, 2, lootZ, lootX, 3, lootZ, AIR);
+            ResourceKey<LootTable> table = switch (p.kind()) {
+                case LIBRARY, HALL -> BuiltInLootTables.VILLAGE_CARTOGRAPHER;
+                case RESTAURANT -> BuiltInLootTables.VILLAGE_BUTCHER;
+                case BARRACKS -> BuiltInLootTables.VILLAGE_FLETCHER;
+                default -> BuiltInLootTables.VILLAGE_PLAINS_HOUSE;
+            };
+            output.chest(rx(lootX, lootZ, p.facing()), 1, rz(lootX, lootZ, p.facing()), table,
+                p.seed() ^ 0x20c17a7eL ^ p.kind().ordinal());
+        }
+
+        void shell(int roof) {
+            for (int floor = 0; floor <= p.floors(); floor++) {
+                int base = floor * STOREY;
+                for (int x = 1; x <= 15; x++) for (int z = 1; z <= 15; z++)
+                    set(x, base, z, floor == p.floors() ? SMOOTH : floorMaterial(floor, x, z));
+                if (floor == p.floors()) continue;
+                // A pale ceiling and contrasting structural floor are separate layers.
+                box(2, base + 4, 2, 14, base + 4, 14,
+                    Blocks.SMOOTH_STONE_SLAB.defaultBlockState().setValue(BlockStateProperties.SLAB_TYPE, SlabType.TOP));
+                for (int y = 1; y <= 4; y++) for (int horizontal = 1; horizontal <= 15; horizontal++) {
+                    facade(horizontal, base + y, 1, horizontal, y, true);
+                    facade(horizontal, base + y, 15, horizontal, y, true);
+                    facade(1, base + y, horizontal, horizontal, y, false);
+                    facade(15, base + y, horizontal, horizontal, y, false);
+                }
+                // Floor bands remain intact even where windows have fallen out.
+                for (int n = 1; n <= 15; n++) {
+                    set(n, base, 1, SMOOTH); set(n, base, 15, SMOOTH);
+                    set(1, base, n, SMOOTH); set(15, base, n, SMOOTH);
+                }
+                if (p.kind() == Kind.HOTEL || p.kind() == Kind.LIBRARY) {
+                    for (int x : new int[]{3, 13}) for (int y = 0; y <= 4; y++) set(x, base + y, 0, SMOOTH);
+                }
+                if (p.kind() == Kind.APARTMENT) for (int x = 11; x <= 14; x++)
+                    set(x, base + 1, 0, Blocks.SMOOTH_STONE_SLAB);
+                if (p.kind() == Kind.RESTAURANT) box(10, base + 4, 0, 14, base + 4, 0,
+                    Blocks.DARK_OAK_SLAB.defaultBlockState());
+            }
+            if (p.kind() == Kind.HALL) {
+                // The auditorium spans two storeys; its upper level is a guarded gallery.
+                box(3, 4, 11, 13, 5, 14, AIR);
+                for (int x = 3; x <= 13; x++) set(x, 6, 11, rail(true));
+                for (int z = 12; z <= 14; z++) { set(3, 6, z, rail(false)); set(13, 6, z, rail(false)); }
+            }
+        }
+
+        BlockState floorMaterial(int floor, int x, int z) {
+            boolean border = x == 1 || z == 1 || x == 15 || z == 15;
+            if (border) return Blocks.TUFF_BRICKS.defaultBlockState();
+            return switch (p.kind()) {
+                case LIBRARY -> (x <= 5 || z >= 10 ? Blocks.OAK_PLANKS : Blocks.BIRCH_PLANKS).defaultBlockState();
+                case APARTMENT, HOTEL -> ((floor & 1) == 0 ? Blocks.OAK_PLANKS : Blocks.BIRCH_PLANKS).defaultBlockState();
+                case RESTAURANT -> ((x / 3 + z / 3) & 1) == 0 ? SMOOTH : Blocks.POLISHED_DIORITE.defaultBlockState();
+                case BARRACKS -> (x <= 5 ? Blocks.POLISHED_ANDESITE : Blocks.OAK_PLANKS).defaultBlockState();
+                default -> (x == 7 || x == 9 ? Blocks.POLISHED_GRANITE : Blocks.SMOOTH_STONE).defaultBlockState();
+            };
+        }
+
+        BlockState pier() {
+            return switch (p.kind()) {
+                case APARTMENT -> Blocks.STRIPPED_OAK_LOG.defaultBlockState();
+                case HOTEL -> Blocks.POLISHED_DIORITE.defaultBlockState();
+                case LIBRARY -> Blocks.STRIPPED_BIRCH_LOG.defaultBlockState();
+                case RESTAURANT -> Blocks.POLISHED_GRANITE.defaultBlockState();
+                case BARRACKS -> Blocks.TUFF_BRICKS.defaultBlockState();
+                default -> Blocks.CHISELED_TUFF_BRICKS.defaultBlockState();
+            };
+        }
+
+        void facade(int x, int y, int z, int horizontal, int withinFloor, boolean eastWest) {
+            boolean column = horizontal == 1 || horizontal == 6 || horizontal == 10 || horizontal == 15;
+            boolean window = !column && (withinFloor == 2 || withinFloor == 3
+                || withinFloor == 1 && (p.kind() == Kind.LIBRARY || p.kind() == Kind.RESTAURANT || p.kind() == Kind.HALL));
+            if (column) set(x, y, z, pier());
+            else if (window) {
+                if (roll(x, y / 5, z, 17) != 0) set(x, y, z,
+                    p.kind() == Kind.BARRACKS ? rail(eastWest) : pane(eastWest));
+            } else set(x, y, z, withinFloor == 4 ? Blocks.TUFF_BRICKS.defaultBlockState()
+                : p.kind() == Kind.APARTMENT || p.kind() == Kind.LIBRARY ? Blocks.BIRCH_PLANKS.defaultBlockState() : STONE);
+        }
+
+        /** Volume belongs to its use: projected bays, clipped corners and distinct roof profiles. */
+        void architecturalEnvelope(int roof) {
+            for (int floor = 0; floor < p.floors(); floor++) {
+                int y = floor * STOREY;
+                // Project the floor plates as a continuous, one-block cornice inside the parcel.
+                for (int n = 1; n <= 15; n++) {
+                    set(n, y, 0, stairTrim(Direction.NORTH)); set(n, y, 16, stairTrim(Direction.SOUTH));
+                    set(0, y, n, stairTrim(Direction.WEST)); set(16, y, n, stairTrim(Direction.EAST));
+                }
+                switch (p.kind()) {
+                    case APARTMENT -> {
+                        // Bay windows increase the living room rather than drawing flat stripes on it.
+                        for (int z : new int[]{4, 5, 6, 11, 12, 13}) {
+                            set(16, y, z, Blocks.BIRCH_PLANKS);
+                            set(16, y + 1, z, Blocks.OAK_PLANKS);
+                            set(16, y + 2, z, Blocks.GLASS_PANE);
+                            set(16, y + 3, z, Blocks.GLASS_PANE);
+                            set(16, y + 4, z, Blocks.BIRCH_SLAB.defaultBlockState().setValue(BlockStateProperties.SLAB_TYPE, SlabType.TOP));
+                        }
+                        for (int z : new int[]{3, 7, 10, 14}) box(16, y + 1, z, 16, y + 4, z, pier());
+                        // Original wall remains the sill, with an open bay above it; privacy walls restore themselves later.
+                        for (int z : new int[]{4, 5, 6, 11, 12, 13}) box(15, y + 2, z, 15, y + 3, z, AIR);
+                        bevelFront(y);
+                    }
+                    case HOTEL -> {
+                        for (int x : new int[]{2, 5, 11, 14}) box(x, y + 1, 0, x, y + 4, 0, pier());
+                        for (int x : new int[]{3, 4, 12, 13}) set(x, y + 1, 0, Blocks.BIRCH_FENCE);
+                        box(2, y + 4, 0, 5, y + 4, 0, Blocks.BIRCH_PLANKS.defaultBlockState());
+                        box(11, y + 4, 0, 14, y + 4, 0, Blocks.BIRCH_PLANKS.defaultBlockState());
+                    }
+                    case LIBRARY -> {
+                        // Tall fins frame broad glazing and project beyond the reading rooms.
+                        for (int x : new int[]{2, 5, 11, 14}) box(x, y + 1, 0, x, y + 4, 0, Blocks.STRIPPED_BIRCH_LOG.defaultBlockState());
+                        for (int x : new int[]{3, 4, 12, 13}) {
+                            set(x, y + 4, 0, Blocks.OAK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+                        }
+                        bevelFront(y);
+                    }
+                    case RESTAURANT -> {
+                        // Separate fascia and timber valance shelter the shop windows.
+                        for (int x = 10; x <= 14; x++) {
+                            set(x, y + 3, 0, Blocks.BIRCH_SLAB);
+                            set(x, y + 4, 0, ((x / 2) & 1) == 0 ? Blocks.OAK_PLANKS : Blocks.BIRCH_PLANKS);
+                        }
+                        for (int z : new int[]{3, 7, 11, 14}) set(16, y + 4, z, Blocks.POLISHED_GRANITE);
+                    }
+                    case BARRACKS -> {
+                        for (int z : new int[]{2, 7, 12, 15}) box(0, y + 1, z, 0, y + 4, z, pier());
+                        for (int x : new int[]{2, 5, 11, 14}) box(x, y + 1, 0, x, y + 4, 0, Blocks.TUFF_BRICKS.defaultBlockState());
+                        for (int x : new int[]{3, 4, 12, 13}) set(x, y + 1, 0, Blocks.CHISELED_TUFF_BRICKS);
+                    }
+                    case HALL -> {
+                        for (int x : new int[]{2, 5, 11, 14}) box(x, y + 1, 0, x, y + 4, 0, pier());
+                        for (int x = 2; x <= 14; x++) set(x, y + 4, 0,
+                            Blocks.POLISHED_DIORITE_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+                    }
+                    default -> throw new IllegalStateException();
+                }
+            }
+        }
+
+        BlockState stairTrim(Direction outward) {
+            Block block = p.kind() == Kind.RESTAURANT ? Blocks.POLISHED_GRANITE_STAIRS : Blocks.TUFF_BRICK_STAIRS;
+            return facing(block, outward.getOpposite()).setValue(BlockStateProperties.HALF,
+                net.minecraft.world.level.block.state.properties.Half.TOP);
+        }
+
+        void bevelFront(int y) {
+            // Remove two rectangular corners and close them with actual stepped returns.
+            for (int x : new int[]{1, 15}) {
+                box(x, y, 1, x, y + 4, 1, AIR);
+                int adjacent = x == 1 ? 2 : 14;
+                box(adjacent, y + 1, 1, adjacent, y + 4, 1, pier());
+                box(x, y + 1, 2, x, y + 4, 2, pier());
+            }
+        }
+
+        void partitions(int floor) {
+            int y = floor * STOREY;
+            int front = frontWall(p, floor);
+            // The west stairwell, central corridor and vestibule are independent of furniture.
+            box(5, y + 1, 2, 5, y + 4, 9, SMOOTH);
+            door(5, y + 1, 8, Direction.WEST, false);
+            box(10, y + 1, 2, 10, y + 4, front, SMOOTH);
+            box(10, y + 1, front, 15, y + 4, front, SMOOTH);
+            door(10, y + 1, 6, Direction.EAST, false);
+            if (floor == 0) {
+                box(6, 1, 4, 9, 4, 4, SMOOTH);
+                door(8, 1, 4, Direction.SOUTH, false);
+            }
+            if (p.kind() == Kind.HALL && floor < 2) {
+                if (floor == 0) {
+                    box(2, 1, 10, 14, 4, 10, SMOOTH);
+                    door(7, 1, 10, Direction.SOUTH, true);
+                    door(8, 1, 10, Direction.SOUTH, false);
+                }
+            } else {
+                Area west = rear(p, floor, false), east = rear(p, floor, true);
+                box(1, y + 1, west.front() - 1, west.right() + 1, y + 4, west.front() - 1, SMOOTH);
+                box(west.right() + 1, y + 1, west.front() - 1, west.right() + 1, y + 4, 15, SMOOTH);
+                box(east.left() - 1, y + 1, east.front() - 1, 15, y + 4, east.front() - 1, SMOOTH);
+                box(east.left() - 1, y + 1, east.front() - 1, east.left() - 1, y + 4, 15, SMOOTH);
+                door(west.right() + 1, y + 1, 11, Direction.WEST, false);
+                door(east.left() - 1, y + 1, 11, Direction.EAST, false);
+            }
+            // A hanging lantern touches a full ceiling block, never the recessed underside of a top slab.
+            set(8, y + 4, 8, SMOOTH);
+            set(8, y + 3, 8, Blocks.LANTERN.defaultBlockState().setValue(BlockStateProperties.HANGING, true));
+            // Weathering stays on facades and roofs: it must not replace a privacy partition.
+        }
+
+        void furnishings(int floor) {
+            int y = floor * STOREY;
+            int variant = layout(p, floor);
+            switch (p.kind()) {
+                case APARTMENT -> {
+                    if (variant == 0) { kitchenFront(y); bedroom(floor, false); }
+                    else { frontBedroom(floor); kitchenRear(floor, false); }
+                }
+                case HOTEL -> {
+                    if (floor == 0) { reception(y); lounge(floor, false); laundry(floor); }
+                    else {
+                        anchoredBed(14, y + 1, frontWall(p, floor) - 2, Direction.SOUTH);
+                        set(11, y + 1, 5, Blocks.BARREL); set(11, y + 2, 5, Blocks.FLOWER_POT);
+                        if (variant == 0) { bedroom(floor, false); bedroom(floor, true); }
+                        else lounge(floor, false);
+                    }
+                }
+                case LIBRARY -> {
+                    if (variant == 0) {
+                        box(14, y + 1, 2, 14, y + 3, 6, Blocks.BOOKSHELF.defaultBlockState());
+                        box(12, y + 1, 2, 12, y + 2, 3, Blocks.BOOKSHELF.defaultBlockState());
+                        desk(12, y, 5, Direction.SOUTH);
+                        readingRoom(floor, false); archive(floor, true);
+                    } else {
+                        readingFront(y); readingRoom(floor, false);
+                        set(2, y + 1, 14, Blocks.CARTOGRAPHY_TABLE);
+                    }
+                }
+                case RESTAURANT -> {
+                    if (variant == 0) {
+                        table(13, y, 3); table(13, y, 5);
+                        set(11, y + 1, 2, Blocks.POTTED_DEAD_BUSH);
+                        kitchenRear(floor, true);
+                    } else {
+                        kitchenFront(y); diningRear(floor, false); pantry(floor, true);
+                    }
+                }
+                case BARRACKS -> {
+                    if (variant == 0) {
+                        anchoredBed(12, y + 1, 3, Direction.NORTH); anchoredBed(14, y + 1, 3, Direction.NORTH);
+                        set(11, y + 1, 2, Blocks.BARREL); set(11, y + 2, 2, Blocks.BARREL);
+                        seat(13, y + 1, 6, Direction.NORTH);
+                    } else { reception(y); bedroom(floor, false); }
+                    box(12, y + 1, 14, 14, y + 2, 14, Blocks.BARREL.defaultBlockState());
+                    set(14, y + 1, 11, Blocks.FLETCHING_TABLE);
+                    set(12, y + 1, 11, Blocks.GRINDSTONE);
+                }
+                case HALL -> {
+                    if (floor == 0 || floor > 1 && variant == 0) reception(y); else readingFront(y);
+                    if (floor == 0) auditorium();
+                    else if (floor >= 2) {
+                        if (variant == 0) readingRoom(floor, false);
+                        else { archive(floor, false); readingRoom(floor, true); }
+                    }
+                }
+                default -> throw new IllegalArgumentException("Not an interior kind");
+            }
+            for (var bath : bathroomPlans(p)) if (bath.floor() == floor) bathroom(bath);
+        }
+
+        void kitchenFront(int y) {
+            kitchenLine(y, 11, 2, Direction.SOUTH);
+            table(13, y, 5);
+        }
+
+        void kitchenRear(int floor, boolean east) {
+            int y = floor * STOREY;
+            Area room = rear(p, floor, east);
+            kitchenLine(y, room.left(), 14, Direction.NORTH);
+            if (east) {
+                set(14, y + 1, 11, SMOOTH); set(14, y + 2, 11, Blocks.FLOWER_POT);
+                set(12, y + 1, 11, Blocks.CRAFTING_TABLE);
+            } else table(room.left() + 2, y, 11);
+        }
+
+        void kitchenLine(int y, int left, int z, Direction face) {
+            set(left, y + 1, z, facing(Blocks.FURNACE, face));
+            set(left + 1, y + 1, z, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 2));
+            set(left + 2, y + 1, z, facing(Blocks.SMOKER, face));
+            set(left + 3, y + 1, z, Blocks.BARREL);
+            box(left, y + 3, z, left + 3, y + 3, z, SMOOTH);
+            set(left + 2, y + 2, z, Blocks.IRON_TRAPDOOR);
+            for (int x = left; x <= left + 3; x++) set(x, y + 3, z, Blocks.POLISHED_DIORITE);
+            for (int x = left; x <= left + 3; x++) set(x, y, z, (x & 1) == 0 ? SMOOTH : TILE);
+        }
+
+        void bedroom(int floor, boolean east) {
+            int y = floor * STOREY;
+            Area room = rear(p, floor, east);
+            anchoredBed(east ? room.right() - 1 : room.left() + 1, y + 1, 13, east ? Direction.EAST : Direction.WEST);
+            set(east ? room.right() : room.left(), y + 1, 11, Blocks.BARREL);
+            desk(east ? room.left() + 1 : room.right() - 1, y, 11, Direction.SOUTH);
+            set(east ? room.left() : room.right(), y + 1, 14, Blocks.BOOKSHELF);
+        }
+
+        void frontBedroom(int floor) {
+            int y = floor * STOREY;
+            anchoredBed(14, y + 1, 3, Direction.NORTH);
+            set(11, y + 1, 2, Blocks.BARREL); set(11, y + 2, 2, Blocks.FLOWER_POT);
+            desk(12, y, 5, Direction.SOUTH);
+        }
+
+        void bathroom(BathPlan bath) {
+            int y = bath.floor() * STOREY;
+            for (int x = bath.x0(); x <= bath.x1(); x++) for (int z = bath.z0(); z <= bath.z1(); z++) {
+                set(x, y, z, ((x + z) & 1) == 0 ? SMOOTH : TILE);
+                set(x, y + 4, z, SMOOTH);
+                boolean wall = x == bath.x0() || x == bath.x1() || z == bath.z0() || z == bath.z1();
+                for (int up = 1; up <= 3; up++) set(x, y + up, z, wall ? SMOOTH : AIR);
+            }
+            int doorZ = bath.southDoor() ? bath.z1() : bath.z0();
+            door(bath.doorX(), y + 1, doorZ, bath.southDoor() ? Direction.NORTH : Direction.SOUTH, false);
+            int fixtureZ = bath.southDoor() ? bath.z0() + 1 : bath.z1() - 1;
+            int toiletX = bath.southDoor() ? bath.x1() - 2 : bath.x0() + 1;
+            Direction view = bath.southDoor() ? Direction.SOUTH : Direction.EAST;
+            set(toiletX, y + 1, fixtureZ, seating(Blocks.POLISHED_ANDESITE_STAIRS, view));
+            set(toiletX, y + 2, fixtureZ, Blocks.IRON_TRAPDOOR);
+            set(bath.x1() - 1, y + 1, fixtureZ, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 2));
+        }
+
+        void reception(int y) {
+            box(12, y + 1, 5, 14, y + 1, 5, Blocks.BIRCH_PLANKS.defaultBlockState());
+            set(13, y + 2, 5, Blocks.FLOWER_POT);
+            set(14, y + 1, 2, Blocks.BOOKSHELF); set(14, y + 2, 2, Blocks.BARREL);
+            desk(12, y, 3, Direction.SOUTH);
+            set(11, y + 1, 2, Blocks.POTTED_DEAD_BUSH);
+        }
+
+        void laundry(int floor) {
+            int y = floor * STOREY;
+            for (int z = 11; z <= 12; z++) set(14, y + 1, z, Blocks.WATER_CAULDRON.defaultBlockState()
+                .setValue(BlockStateProperties.LEVEL_CAULDRON, z == 11 ? 1 : 2));
+            box(12, y + 1, 14, 14, y + 1, 14, Blocks.BARREL.defaultBlockState());
+            box(12, y + 3, 14, 14, y + 3, 14, Blocks.DARK_OAK_SLAB.defaultBlockState());
+            set(12, y + 1, 11, Blocks.LOOM);
+        }
+
+        void lounge(int floor, boolean east) {
+            int y = floor * STOREY;
+            Area room = rear(p, floor, east);
+            box(room.left(), y + 1, 14, room.left() + 2, y + 1, 14, seating(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+            desk(room.left() + 1, y, 11, Direction.SOUTH);
+            set(room.left(), y + 1, 12, Blocks.BOOKSHELF);
+        }
+
+        void readingRoom(int floor, boolean east) {
+            int y = floor * STOREY;
+            Area room = rear(p, floor, east);
+            desk(east ? room.left() + 1 : room.right() - 1, y, 11, Direction.SOUTH);
+            box(room.left(), y + 1, 14, room.right(), y + 2, 14, Blocks.BOOKSHELF.defaultBlockState());
+            set(east ? room.right() : room.left(), y + 1, 11, facing(Blocks.LECTERN, Direction.NORTH));
+        }
+
+        void readingFront(int y) {
+            desk(12, y, 3, Direction.SOUTH);
+            box(14, y + 1, 2, 14, y + 2, 5, Blocks.BOOKSHELF.defaultBlockState());
+            set(11, y + 1, 2, facing(Blocks.LECTERN, Direction.SOUTH));
+        }
+
+        void archive(int floor, boolean east) {
+            int y = floor * STOREY;
+            Area room = rear(p, floor, east);
+            box(room.left(), y + 1, 14, room.right(), y + 3, 14, Blocks.BOOKSHELF.defaultBlockState());
+            box(east ? room.right() : room.left(), y + 1, 11, east ? room.right() : room.left(), y + 2, 12, Blocks.BARREL.defaultBlockState());
+            set(room.left() + 1, y + 1, 12, facing(Blocks.LECTERN, Direction.NORTH));
+        }
+
+        void pantry(int floor, boolean east) {
+            int y = floor * STOREY;
+            Area room = rear(p, floor, east);
+            box(room.left(), y + 1, 14, room.right(), y + 2, 14, Blocks.BARREL.defaultBlockState());
+            set(room.right(), y + 1, 11, Blocks.CRAFTING_TABLE);
+            set(room.right(), y + 2, 11, Blocks.FLOWER_POT);
+        }
+
+        void diningRear(int floor, boolean east) {
+            Area room = rear(p, floor, east);
+            int y = floor * STOREY;
+            table(room.left() + 2, y, 12);
+            box(room.left(), y + 1, 14, room.right(), y + 1, 14, seating(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+        }
+
+        void auditorium() {
+            for (int x : new int[]{3, 4, 5, 11, 12, 13}) seat(x, 1, 11, Direction.SOUTH);
+            box(3, 1, 13, 13, 1, 14, WOOD);
+            set(8, 1, 12, facing(Blocks.DARK_OAK_STAIRS, Direction.SOUTH));
+            set(8, 2, 14, facing(Blocks.LECTERN, Direction.NORTH));
+            for (int x : new int[]{3, 13}) {
+                box(x, 2, 14, x, 3, 14, WOOD);
+                set(x, 4, 14, Blocks.STONE_BRICK_SLAB);
+            }
+        }
+
+        void stairs() {
+            for (int floor = 0; floor < p.floors(); floor++) {
+                int base = floor * STOREY;
+                for (int step = 1; step <= STOREY; step++) {
+                    int z = step + 2;
+                    box(2, base + step, z, 3, base + step + 3, z, AIR);
+                    for (int x = 2; x <= 3; x++) set(x, base + step, z,
+                        facing(Blocks.STONE_BRICK_STAIRS, Direction.SOUTH));
+                }
+                box(2, base + STOREY, 8, 4, base + STOREY, 9, TILE);
+                box(2, base + STOREY + 1, 8, 4, base + STOREY + 3, 9, AIR);
+            }
+            // This full-height side aisle joins every lower stair approach to its landing door.
+            for (int floor = 0; floor <= p.floors(); floor++) {
+                int y = floor * STOREY;
+                box(4, y + 1, 2, 4, y + 3, 9, AIR);
+            }
+        }
+
+        void entrance() {
+            for (int x : new int[]{6, 9}) box(x, 1, 0, x, 3, 0, SMOOTH);
+            box(6, 4, 0, 9, 4, 1, Blocks.STONE_BRICK_SLAB.defaultBlockState());
+            box(7, 0, 0, 8, 0, 3, TILE);
+            // Native SOUTH/RIGHT opens against the west jamb; SOUTH/LEFT against the east jamb.
+            door(7, 1, 1, Direction.SOUTH, true);
+            door(8, 1, 1, Direction.SOUTH, false);
+            set(4, 1, 0, Blocks.POTTED_DEAD_BUSH);
+            set(12, 1, 16, Blocks.COMPOSTER);
+        }
+
+        void roof(int y) {
+            // Clipped parapets and a heavy coping keep each accessible roof legible from below.
+            for (int n = 2; n <= 14; n++) {
+                set(n, y + 1, 1, Blocks.TUFF_BRICKS); set(n, y + 1, 15, Blocks.TUFF_BRICKS);
+                set(1, y + 1, n, Blocks.TUFF_BRICKS); set(15, y + 1, n, Blocks.TUFF_BRICKS);
+                set(n, y + 2, 1, Blocks.TUFF_BRICK_SLAB); set(n, y + 2, 15, Blocks.TUFF_BRICK_SLAB);
+                set(1, y + 2, n, Blocks.TUFF_BRICK_SLAB); set(15, y + 2, n, Blocks.TUFF_BRICK_SLAB);
+            }
+            switch (p.kind()) {
+                case APARTMENT -> {
+                    // Two small roof gardens and a pergola leave the stair landing and central crossing free.
+                    roofPlanter(10, y, 4); roofPlanter(10, y, 12);
+                    for (int x : new int[]{6, 13}) box(x, y + 1, 14, x, y + 3, 14, Blocks.STRIPPED_OAK_LOG.defaultBlockState());
+                    box(6, y + 4, 14, 13, y + 4, 14, Blocks.BIRCH_SLAB.defaultBlockState());
+                    desk(8, y, 12, Direction.NORTH);
+                }
+                case HOTEL -> {
+                    roofRoom(y, 9, 3, 14, 7, Blocks.BIRCH_PLANKS);
+                    door(9, y + 1, 5, Direction.EAST, false);
+                    set(12, y + 1, 4, Blocks.BARREL); set(13, y + 1, 4, Blocks.LOOM);
+                    box(11, y + 1, 12, 13, y + 1, 12, seating(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+                }
+                case LIBRARY -> {
+                    // Clerestory above the stacks; its raised glass ridge is distinct from a flat roof.
+                    for (int x = 10; x <= 13; x++) for (int z = 3; z <= 7; z++) {
+                        set(x, y + 1, z, x == 10 || x == 13 || z == 3 || z == 7 ? Blocks.STRIPPED_BIRCH_LOG : Blocks.GLASS);
+                        if (x == 11 || x == 12) set(x, y + 2, z, Blocks.GLASS);
+                    }
+                    // Cut both the roof plate and the recessed ceiling beneath the glass.
+                    // The six-column light well stays enclosed by its complete timber frame;
+                    // the glass cap and the surrounding roof walkway remain intact.
+                    box(11, y - 1, 4, 12, y, 6, AIR);
+                    desk(11, y, 12, Direction.NORTH); set(14, y + 1, 12, Blocks.LECTERN);
+                }
+                case RESTAURANT -> {
+                    // A real dining terrace and rear kitchen extraction with full supporting columns.
+                    table(11, y, 6); table(11, y, 11);
+                    for (int z : new int[]{3, 14}) box(14, y + 1, z, 14, y + 3, z, Blocks.STRIPPED_OAK_LOG.defaultBlockState());
+                    box(14, y + 4, 3, 14, y + 4, 14, Blocks.BIRCH_PLANKS.defaultBlockState());
+                    box(6, y + 1, 14, 7, y + 3, 14, Blocks.TUFF_BRICKS.defaultBlockState());
+                    set(6, y + 4, 14, Blocks.IRON_BARS); set(7, y + 4, 14, Blocks.IRON_BARS);
+                }
+                case BARRACKS -> {
+                    // Enclosed stair head gives the barracks a service tower, without hiding its usable exit.
+                    // The whole last flight sits inside the stair head: a front wall at z=6
+                    // would cross the headroom over its penultimate step.
+                    roofRoom(y, 1, 2, 5, 10, Blocks.TUFF_BRICKS);
+                    door(5, y + 1, 8, Direction.EAST, false);
+                    box(10, y + 1, 12, 13, y + 1, 14, Blocks.POLISHED_ANDESITE.defaultBlockState());
+                    set(11, y + 2, 13, Blocks.IRON_TRAPDOOR);
+                }
+                case HALL -> {
+                    for (int step = 0; step < 3; step++) {
+                        int edge = 2 + step * 2;
+                        box(edge, y + 1 + step, 1, 16 - edge, y + 1 + step, 2, Blocks.TUFF_BRICKS.defaultBlockState());
+                    }
+                    for (int x : new int[]{4, 12}) set(x, y + 4, 2, Blocks.CHISELED_TUFF_BRICKS);
+                    desk(11, y, 12, Direction.NORTH);
+                }
+                default -> throw new IllegalStateException();
+            }
+        }
+
+        void roofRoom(int y, int x0, int z0, int x1, int z1, Block wall) {
+            for (int x = x0; x <= x1; x++) for (int z = z0; z <= z1; z++) {
+                boolean edge = x == x0 || x == x1 || z == z0 || z == z1;
+                for (int up = 1; up <= 3; up++) set(x, y + up, z, edge ? wall.defaultBlockState() : AIR);
+                set(x, y + 4, z, Blocks.TUFF_BRICK_SLAB.defaultBlockState().setValue(BlockStateProperties.SLAB_TYPE, SlabType.TOP));
+            }
+        }
+        void roofPlanter(int x, int y, int z) {
+            for (int dx = 0; dx <= 3; dx++) set(x + dx, y + 1, z, Blocks.TUFF_BRICKS);
+            set(x + 1, y + 1, z, Blocks.DIRT); set(x + 2, y + 1, z, Blocks.DIRT);
+            set(x + 1, y + 2, z, Blocks.OXEYE_DAISY); set(x + 2, y + 2, z, Blocks.CORNFLOWER);
+        }
+
+        void door(int x, int y, int z, Direction facing, boolean rightHinge) {
+            BlockState state = facing(Blocks.DARK_OAK_DOOR, facing)
+                .setValue(BlockStateProperties.DOOR_HINGE, rightHinge ? DoorHingeSide.RIGHT : DoorHingeSide.LEFT)
+                .setValue(BlockStateProperties.OPEN, false)
+                .setValue(BlockStateProperties.POWERED, false);
+            set(x, y, z, state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF, DoubleBlockHalf.LOWER));
+            set(x, y + 1, z, state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF, DoubleBlockHalf.UPPER));
+        }
+        void anchoredBed(int x, int y, int z, Direction facing) {
+            BlockState state = facing(Blocks.BED.white(), facing);
+            set(x, y, z, state.setValue(BlockStateProperties.BED_PART, BedPart.FOOT));
+            set(x + facing.getStepX(), y, z + facing.getStepZ(), state.setValue(BlockStateProperties.BED_PART, BedPart.HEAD));
+            int wallX = x + facing.getStepX() * 2, wallZ = z + facing.getStepZ() * 2;
+            Direction alongWall = facing.getClockWise();
+            for (int width = -1; width <= 1; width++) for (int up = 0; up <= 3; up++)
+                set(wallX + alongWall.getStepX() * width, y + up, wallZ + alongWall.getStepZ() * width, SMOOTH);
+        }
+        void table(int x, int y, int z) {
+            set(x, y + 1, z, Blocks.DARK_OAK_FENCE); set(x, y + 2, z, Blocks.DARK_OAK_PRESSURE_PLATE);
+            seat(x - 1, y + 1, z, Direction.EAST);
+            seat(x + 1, y + 1, z, Direction.WEST);
+        }
+        void desk(int x, int y, int z, Direction approachSide) {
+            set(x, y + 1, z, Blocks.DARK_OAK_FENCE); set(x, y + 2, z, Blocks.DARK_OAK_PRESSURE_PLATE);
+            seat(x + approachSide.getStepX(), y + 1, z + approachSide.getStepZ(), approachSide.getOpposite());
+        }
+        void seat(int x, int y, int z, Direction lookingToward) {
+            set(x, y, z, seating(Blocks.DARK_OAK_STAIRS, lookingToward));
+        }
+        BlockState seating(Block stair, Direction lookingToward) {
+            // Stair FACING points uphill, into its full-height back, opposite a seated player's view.
+            return facing(stair, lookingToward.getOpposite());
+        }
+        BlockState rail(boolean eastWest) { return connected(Blocks.IRON_BARS, eastWest); }
+        BlockState pane(boolean eastWest) { return connected(Blocks.GLASS_PANE, eastWest); }
+        BlockState connected(Block block, boolean eastWest) {
+            return block.defaultBlockState().setValue(BlockStateProperties.EAST, eastWest)
+                .setValue(BlockStateProperties.WEST, eastWest).setValue(BlockStateProperties.NORTH, !eastWest)
+                .setValue(BlockStateProperties.SOUTH, !eastWest);
+        }
+    }
+}
@@ -0,0 +1,92 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import java.util.Arrays;
+import net.minecraft.core.BlockPos;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Generation20 surface parcel. Its distinct native type preserves all published city renderers. */
+public final class LostCityPiece20 extends StructurePiece {
+    private static final int SCHEMA = 1;
+    private final LostCityPlan.Parcel parcel;
+
+    public LostCityPiece20(LostCityPlan.Parcel parcel) {
+        super(LostCityStructures.PIECE20, 0, bounds(parcel));
+        this.parcel = parcel;
+        setOrientation(null);
+    }
+
+    public LostCityPiece20(StructurePieceSerializationContext context, CompoundTag tag) {
+        super(LostCityStructures.PIECE20, tag);
+        if (tag.getInt("SanctuarySchema").orElseThrow() != SCHEMA)
+            throw new IllegalArgumentException("Unsupported Lost City piece schema");
+        parcel = new LostCityPlan.Parcel(LostCityPlan.Kind.valueOf(tag.getString("Kind").orElseThrow()),
+            tag.getInt("MinX").orElseThrow(), tag.getInt("MinZ").orElseThrow(),
+            tag.getInt("Width").orElseThrow(), tag.getInt("Depth").orElseThrow(),
+            tag.getInt("FloorY").orElseThrow(), tag.getInt("Floors").orElseThrow(),
+            tag.getInt("Facing").orElseThrow(), tag.getLong("ParcelSeed").orElseThrow(),
+            tag.getInt("FoundationDepth").orElseThrow(), tag.getIntArray("SurfaceHeights").orElseThrow());
+        if (!getBoundingBox().equals(bounds(parcel)))
+            throw new IllegalArgumentException("Lost City parcel disagrees with its saved native bounding box");
+        setOrientation(null);
+    }
+
+    public LostCityPlan.Parcel parcel() { return parcel; }
+
+    @Override public BlockPos getLocatorPosition() {
+        int x = parcel.width() / 2, z = parcel.depth() / 2;
+        return new BlockPos(parcel.minX() + x, parcel.surfaceY(x, z) + 1, parcel.minZ() + z);
+    }
+
+    @Override protected void addAdditionalSaveData(StructurePieceSerializationContext context, CompoundTag tag) {
+        tag.putInt("SanctuarySchema", SCHEMA);
+        tag.putString("Kind", parcel.kind().name());
+        tag.putInt("MinX", parcel.minX()); tag.putInt("MinZ", parcel.minZ());
+        tag.putInt("Width", parcel.width()); tag.putInt("Depth", parcel.depth());
+        tag.putInt("FloorY", parcel.floorY()); tag.putInt("Floors", parcel.floors());
+        tag.putInt("Facing", parcel.facing()); tag.putLong("ParcelSeed", parcel.seed());
+        tag.putInt("FoundationDepth", parcel.foundationDepth());
+        tag.putIntArray("SurfaceHeights", parcel.surfaceHeights());
+    }
+
+    @Override public void postProcess(WorldGenLevel level, StructureManager structures, ChunkGenerator generator,
+            RandomSource random, BoundingBox chunkClip, ChunkPos chunkPos, BlockPos pivot) {
+        LostCityStructures.placing(() -> render(parcel, new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState block) {
+                BlockPos pos = world(x, y, z);
+                if (getBoundingBox().isInside(pos) && chunkClip.isInside(pos))
+                    placeBlock(level, block, pos.getX(), pos.getY(), pos.getZ(), chunkClip);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> loot, long seed) {
+                BlockPos pos = world(x, y, z);
+                if (getBoundingBox().isInside(pos) && chunkClip.isInside(pos))
+                    createChest(level, chunkClip, RandomSource.create(seed), pos, loot, null);
+            }
+        }));
+    }
+
+    private static void render(LostCityPlan.Parcel parcel, LostCityRenderer.BlockWriter writer) {
+        LostCitySurface20.render(parcel, writer);
+    }
+
+    private BlockPos world(int x, int y, int z) {
+        return new BlockPos(parcel.minX() + x, parcel.floorY() + y, parcel.minZ() + z);
+    }
+
+    private static BoundingBox bounds(LostCityPlan.Parcel parcel) {
+        int low = Math.min(parcel.floorY(), Arrays.stream(parcel.surfaceHeights()).min().orElse(parcel.floorY()))
+            - parcel.foundationDepth();
+        int high = Math.max(parcel.maxY(), Arrays.stream(parcel.surfaceHeights()).max().orElse(parcel.floorY()) + 5);
+        return new BoundingBox(parcel.minX(), low, parcel.minZ(), parcel.maxX(), high, parcel.maxZ());
+    }
+}
@@ -29,17 +29,17 @@ public final class LostCityStructure extends Structure {
                    throw new IllegalStateException("Lost City district exceeds native structure reference range");
            }
            return Optional.of(new GenerationStub(LostCityStructures.locator(district), pieces -> {
-                if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17) && generator.cityReservation16(island) != null)
+                if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17 || generator.rootGeneration() == 19 || generator.rootGeneration() == 20) && generator.cityReservation16(island) != null)
                    pieces.addPiece(new LostCityFoundationPiece16(generator.cityReservation16(island), district.seed()));
                if (generator.rootGeneration() == 15) for (var support : generator.citySupports(island)) {
                    if (support.startChunkX() == district.startChunkX() && support.startChunkZ() == district.startChunkZ())
                        pieces.addPiece(new LostCitySupportPiece15(support));
                }
-                if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17)) for (var support : generator.citySupports16(island)) {
+                if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17 || generator.rootGeneration() == 19 || generator.rootGeneration() == 20)) for (var support : generator.citySupports16(island)) {
                    if (support.startChunkX() == district.startChunkX() && support.startChunkZ() == district.startChunkZ())
                        pieces.addPiece(new LostCitySupportPiece16(support));
                }
-                district.parcels().forEach(parcel -> pieces.addPiece((generator.rootGeneration() == 16 || generator.rootGeneration() == 17) ? new LostCityPiece16(parcel) : generator.rootGeneration() == 15
+                district.parcels().forEach(parcel -> pieces.addPiece(generator.rootGeneration() == 20 ? new LostCityPiece20(parcel) : (generator.rootGeneration() == 16 || generator.rootGeneration() == 17 || generator.rootGeneration() == 19 || generator.rootGeneration() == 20) ? new LostCityPiece16(parcel) : generator.rootGeneration() == 15
                    ? new LostCityPiece15(parcel) : new LostCityPiece(parcel)));
                if (generator.rootGeneration() == 15) for (var network : generator.undergroundPlan(island).networks()) {
                    if (network.startChunkX() != district.startChunkX() || network.startChunkZ() != district.startChunkZ()) continue;
@@ -49,13 +49,13 @@ public final class LostCityStructure extends Structure {
                    network.modules().stream().filter(m -> m.kind() == LostCityUnderground15.Kind.ACCESS)
                        .forEach(m -> pieces.addPiece(new LostCityUndergroundPiece15(m)));
                }
-                if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17)) for (var network : generator.undergroundPlan16(island).networks()) {
+                if ((generator.rootGeneration() == 16 || generator.rootGeneration() == 17 || generator.rootGeneration() == 19 || generator.rootGeneration() == 20)) for (var network : generator.undergroundPlan16(island).networks()) {
                    if (network.startChunkX() != district.startChunkX() || network.startChunkZ() != district.startChunkZ()) continue;
                    // Surface comes first, rooms/corridors next, shafts last so every entrance remains open.
                    network.modules().stream().filter(m -> m.kind() != LostCityUnderground16.Kind.ACCESS)
-                        .forEach(m -> pieces.addPiece(new LostCityUndergroundPiece16(m)));
+                        .forEach(m -> pieces.addPiece(generator.rootGeneration() == 20 ? new LostCityUndergroundPiece20(m) : new LostCityUndergroundPiece16(m)));
                    network.modules().stream().filter(m -> m.kind() == LostCityUnderground16.Kind.ACCESS)
-                        .forEach(m -> pieces.addPiece(new LostCityUndergroundPiece16(m)));
+                        .forEach(m -> pieces.addPiece(generator.rootGeneration() == 20 ? new LostCityUndergroundPiece20(m) : new LostCityUndergroundPiece16(m)));
                }
            }));
        }
@@ -40,8 +40,12 @@ public final class LostCityStructures {
        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_underground_v15"), LostCityUndergroundPiece15::new);
    public static final StructurePieceType SUPPORT15 = Registry.register(
        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_support_v15"), LostCitySupportPiece15::new);
+    public static final StructurePieceType PIECE20 = Registry.register(
+        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_parcel_v20"), LostCityPiece20::new);
    public static final StructurePieceType PIECE16 = Registry.register(
        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_parcel_v16"), LostCityPiece16::new);
+    public static final StructurePieceType UNDERGROUND20 = Registry.register(
+        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_underground_v20"), LostCityUndergroundPiece20::new);
    public static final StructurePieceType UNDERGROUND16 = Registry.register(
        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_underground_v16"), LostCityUndergroundPiece16::new);
    public static final StructurePieceType SUPPORT16 = Registry.register(
@@ -0,0 +1,248 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.detail.ConnectedBlocks20;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.block.state.properties.SlabType;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** New surface architecture on the saved generation16 footprints. Published renderers remain immutable. */
+public final class LostCitySurface20 {
+    private static final Direction[] HORIZONTAL = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    private LostCitySurface20() {}
+
+    public static void render(LostCityPlan.Parcel parcel, LostCityRenderer.BlockWriter output) {
+        if (parcel.kind().building()) { LostCityInteriors20.render(parcel, output); return; }
+        var connected = ConnectedBlocks20.buffer(output);
+        if (parcel.kind() == LostCityPlan.Kind.STREET || parcel.kind() == LostCityPlan.Kind.BRIDGE) {
+            road(parcel, connected);
+        } else {
+            new Exterior(parcel, connected).render();
+        }
+        connected.flush();
+    }
+
+    private static void road(LostCityPlan.Parcel p, LostCityRenderer.BlockWriter output) {
+        boolean alongX = p.width() > p.depth(), bridge = p.kind() == LostCityPlan.Kind.BRIDGE;
+        for (int z = 0; z < p.depth(); z++) for (int x = 0; x < p.width(); x++) {
+            int y = p.surfaceY(x, z) - p.floorY();
+            int across = alongX ? z : x, along = alongX ? x : z, breadth = alongX ? p.depth() : p.width();
+            boolean edge = across == 0 || across == breadth - 1;
+            // A legible curb and patterned shoulders, not per-block random pavement.
+            Block paving = edge ? Blocks.POLISHED_TUFF : across == 1 || across == breadth - 2
+                ? along % 4 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS
+                : Blocks.POLISHED_ANDESITE;
+            if (!bridge) for (int down = 1; down <= p.foundationDepth(); down++)
+                output.set(x, y - down, z, Blocks.STONE_BRICKS.defaultBlockState());
+            output.set(x, y, z, paving.defaultBlockState());
+            for (int up = 1; up <= 8; up++) output.set(x, y + up, z, Blocks.AIR.defaultBlockState());
+            if (bridge && edge) {
+                // Posts grow from the existing deck only; the certified natural bearings are untouched.
+                output.set(x, y + 1, z, (along % 5 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.IRON_BARS).defaultBlockState());
+                if (along % 5 == 0) output.set(x, y + 2, z, Blocks.TUFF_BRICK_SLAB.defaultBlockState());
+                continue;
+            }
+            for (var direction : HORIZONTAL) {
+                int nx = x + direction.getStepX(), nz = z + direction.getStepZ();
+                if (nx >= 0 && nx < p.width() && nz >= 0 && nz < p.depth()
+                        && p.surfaceY(nx, nz) == p.surfaceY(x, z) + 1) {
+                    output.set(x, y + 1, z, Blocks.TUFF_BRICK_STAIRS.defaultBlockState()
+                        .setValue(BlockStateProperties.HORIZONTAL_FACING, direction));
+                    break;
+                }
+            }
+        }
+    }
+
+    private static final class Exterior implements LostCityRenderer.BlockWriter {
+        final LostCityPlan.Parcel p;
+        final LostCityRenderer.BlockWriter output;
+        final Rotation turn;
+        Exterior(LostCityPlan.Parcel p, LostCityRenderer.BlockWriter output) {
+            this.p = p; this.output = output;
+            turn = switch (p.facing()) { case 1 -> Rotation.CLOCKWISE_90; case 2 -> Rotation.CLOCKWISE_180;
+                case 3 -> Rotation.COUNTERCLOCKWISE_90; default -> Rotation.NONE; };
+        }
+        int x(int x, int z) { return switch (p.facing()) { case 1 -> p.width() - 1 - z; case 2 -> p.width() - 1 - x; case 3 -> z; default -> x; }; }
+        int z(int x, int z) { return switch (p.facing()) { case 1 -> x; case 2 -> p.depth() - 1 - z; case 3 -> p.depth() - 1 - x; default -> z; }; }
+        @Override public void set(int x, int y, int z, BlockState state) { output.set(x(x, z), y, z(x, z), state.rotate(turn)); }
+        void set(int x, int y, int z, Block block) { set(x, y, z, block.defaultBlockState()); }
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+            output.chest(x(x, z), y, z(x, z), table, seed ^ 0x20c17a7eL);
+        }
+        void box(int x0, int y0, int z0, int x1, int y1, int z1, Block block) {
+            for (int x = x0; x <= x1; x++) for (int z = z0; z <= z1; z++) for (int y = y0; y <= y1; y++) set(x, y, z, block);
+        }
+        void render() {
+            if (p.width() != 17 || p.depth() != 17) throw new IllegalArgumentException("Generation20 amenities require the certified 17x17 footprint");
+            // Keep the proven pool containment, excavation steps and garage ramps. All new ornament is
+            // composed before connection resolution, so clipping cannot split a rail or window design.
+            var north = new LostCityPlan.Parcel(p.kind(), p.minX(), p.minZ(), 17, 17, p.floorY(), p.floors(), 0,
+                p.seed(), p.foundationDepth(), p.surfaceHeights());
+            LostCitySurface16.render(north, new LostCityRenderer.BlockWriter() {
+                @Override public void set(int x, int y, int z, BlockState state) {
+                    if (state.is(Blocks.STONE) && y < 0) state = Blocks.STONE_BRICKS.defaultBlockState();
+                    if (state.is(Blocks.DARK_OAK_PLANKS)) state = Blocks.OAK_PLANKS.defaultBlockState();
+                    if (state.is(Blocks.DARK_OAK_FENCE)) state = Blocks.OAK_FENCE.defaultBlockState();
+                    if (state.is(Blocks.DARK_OAK_STAIRS)) state = Blocks.OAK_STAIRS.defaultBlockState()
+                        .setValue(BlockStateProperties.HORIZONTAL_FACING, state.getValue(BlockStateProperties.HORIZONTAL_FACING));
+                    Exterior.this.set(x, y, z, state);
+                }
+                @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { Exterior.this.chest(x, y, z, table, seed); }
+            });
+            // The north threshold is a level promenade, shared by every admitted parcel.
+            for (int x = 0; x <= 16; x++) set(x, 0, 0, x % 4 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS);
+            switch (p.kind()) {
+                case PARK -> park();
+                case PARK_GARDEN -> garden();
+                case PARK_PLAYGROUND -> playground();
+                case PARK_MEMORIAL -> memorial();
+                case PLAZA -> plaza();
+                case MARKET -> market();
+                case PARKING -> garage();
+                case POOL -> { if (p.foundationDepth() >= 8) pool(); else park(); }
+                case EXCAVATION -> { if (p.foundationDepth() >= 8) excavation(); else park(); }
+                default -> throw new IllegalArgumentException("Not an exterior amenity");
+            }
+        }
+        void paths() {
+            for (int n = 1; n <= 16; n++) for (int across = 7; across <= 9; across++) {
+                set(across, 0, n, across == 8 ? Blocks.POLISHED_TUFF : Blocks.TUFF_BRICKS);
+                set(n, 0, across, across == 8 ? Blocks.POLISHED_TUFF : Blocks.TUFF_BRICKS);
+            }
+        }
+        void bench(int x, int y, int z, int length, Direction view) {
+            for (int dx = 0; dx < length; dx++) set(x + dx, y, z, Blocks.OAK_STAIRS.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, view.getOpposite()));
+            set(x - 1, y, z, Blocks.TUFF_BRICK_SLAB); set(x + length, y, z, Blocks.TUFF_BRICK_SLAB);
+        }
+        void lamp(int x, int z) {
+            set(x, 1, z, Blocks.CHISELED_TUFF_BRICKS); box(x, 2, z, x, 3, z, Blocks.BIRCH_FENCE);
+            set(x, 4, z, Blocks.BIRCH_PLANKS); set(x, 5, z, Blocks.LANTERN);
+        }
+        void park() {
+            paths(); bench(10, 1, 3, 3, Direction.SOUTH); bench(10, 1, 11, 3, Direction.NORTH);
+            lamp(5, 11); lamp(11, 5);
+            // A birch screen beside the existing oak trees changes the park's canopy and rhythm.
+            box(3, 1, 12, 3, 4, 12, Blocks.BIRCH_LOG);
+            for (int x = 2; x <= 4; x++) for (int z = 11; z <= 13; z++)
+                set(x, 5, z, Blocks.BIRCH_LEAVES.defaultBlockState().setValue(BlockStateProperties.PERSISTENT, true));
+            for (int z = 2; z <= 5; z++) set(6, 0, z, Blocks.POLISHED_GRANITE);
+        }
+        void garden() {
+            paths();
+            // Four parterres have low carved kerbs, soil beds and a shared central promenade.
+            for (int x0 : new int[]{2, 10}) for (int z0 : new int[]{2, 10}) {
+                for (int n = 0; n < 5; n++) {
+                    set(x0 + n, 0, z0, Blocks.POLISHED_DIORITE); set(x0 + n, 0, z0 + 4, Blocks.POLISHED_DIORITE);
+                    set(x0, 0, z0 + n, Blocks.POLISHED_DIORITE); set(x0 + 4, 0, z0 + n, Blocks.POLISHED_DIORITE);
+                }
+                set(x0, 1, z0, Blocks.CHISELED_TUFF); set(x0 + 4, 1, z0 + 4, Blocks.CHISELED_TUFF);
+            }
+            bench(7, 1, 15, 3, Direction.NORTH);
+            // Pergola along the west planting bed, not across a circulation route.
+            for (int z : new int[]{2, 6}) box(1, 1, z, 1, 3, z, Blocks.STRIPPED_OAK_LOG);
+            box(1, 4, 2, 1, 4, 6, Blocks.BIRCH_SLAB); lamp(15, 8);
+        }
+        void playground() {
+            paths();
+            for (int x = 1; x <= 7; x++) { set(x, 0, 1, Blocks.BIRCH_PLANKS); set(x, 0, 7, Blocks.BIRCH_PLANKS); }
+            for (int z = 1; z <= 7; z++) { set(1, 0, z, Blocks.BIRCH_PLANKS); set(7, 0, z, Blocks.BIRCH_PLANKS); }
+            // Braced climbing platform: low guards leave the three front steps open.
+            for (int x : new int[]{11, 13}) set(x, 4, 13, Blocks.BIRCH_FENCE);
+            set(12, 4, 13, Blocks.BIRCH_FENCE);
+            set(11, 4, 11, Blocks.BIRCH_FENCE); set(13, 4, 11, Blocks.BIRCH_FENCE);
+            bench(3, 1, 13, 3, Direction.NORTH); lamp(15, 3);
+        }
+        void plaza() {
+            for (int x = 1; x <= 15; x++) for (int z = 1; z <= 15; z++) {
+                int d = Math.max(Math.abs(x - 8), Math.abs(z - 8));
+                set(x, 0, z, d == 3 || d == 6 ? Blocks.POLISHED_GRANITE : d == 4 || d == 7 ? Blocks.TUFF_BRICKS : Blocks.POLISHED_DIORITE);
+            }
+            // Dry civic fountain: bevelled bowl, carved pedestal, projecting cap.
+            for (int x = 6; x <= 10; x++) for (int z = 6; z <= 10; z++) {
+                if (x != 6 && x != 10 && z != 6 && z != 10) continue;
+                boolean corner = (x == 6 || x == 10) && (z == 6 || z == 10);
+                set(x, 1, z, corner ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICK_SLAB);
+            }
+            set(8, 1, 8, Blocks.CHISELED_TUFF); set(8, 2, 8, Blocks.CHISELED_TUFF_BRICKS);
+            set(8, 3, 8, Blocks.POLISHED_TUFF_SLAB); lamp(2, 12); lamp(14, 4);
+        }
+        void memorial() {
+            // The memorial keeps its open central approach and gains stepped stone shoulders.
+            for (int x = 1; x <= 15; x++) for (int z = 1; z <= 15; z++)
+                set(x, 0, z, x == 5 || x == 11 || z == 5 || z == 11 ? Blocks.TUFF_BRICKS : Blocks.POLISHED_ANDESITE);
+            for (int x = 7; x <= 9; x++) {
+                set(x, 1, 7, Blocks.TUFF_BRICK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+                set(x, 1, 9, Blocks.TUFF_BRICK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            }
+            set(8, 2, 8, Blocks.CHISELED_TUFF); set(8, 3, 8, Blocks.CHISELED_TUFF_BRICKS);
+            set(8, 4, 8, Blocks.CHISELED_STONE_BRICKS); set(8, 5, 8, Blocks.POLISHED_DIORITE_SLAB);
+            lamp(3, 8); lamp(13, 8);
+        }
+        void market() {
+            for (int x = 1; x <= 15; x++) for (int z = 1; z <= 15; z++)
+                set(x, 0, z, x >= 7 && x <= 9 || z >= 7 && z <= 9 ? Blocks.TUFF_BRICKS : Blocks.POLISHED_GRANITE);
+            for (int x0 : new int[]{2, 11}) for (int z0 : new int[]{2, 11}) {
+                for (int x = x0; x <= x0 + 3; x++) for (int z = z0; z <= z0 + 2; z++)
+                    set(x, 4, z, (x - x0 & 1) == 0 ? Blocks.BIRCH_SLAB : Blocks.OAK_SLAB);
+                for (int x : new int[]{x0, x0 + 3}) {
+                    set(x, 1, z0, Blocks.CHISELED_TUFF_BRICKS);
+                    box(x, 2, z0, x, 3, z0, Blocks.STRIPPED_OAK_LOG);
+                }
+                set(x0 + 1, 5, z0 + 1, Blocks.BIRCH_SLAB);
+            }
+            lamp(1, 8); lamp(15, 8);
+        }
+        void pool() {
+            for (int x = 3; x <= 13; x++) for (int z = 4; z <= 13; z++) {
+                if (x == 3 || x == 13 || z == 4 || z == 13) set(x, 0, z, Blocks.POLISHED_DIORITE);
+            }
+            // Changing/showers canopy stands beside the deck; it never enters the sealed basin.
+            for (int x : new int[]{10, 15}) box(x, 1, 1, x, 3, 1, Blocks.STRIPPED_BIRCH_LOG);
+            box(10, 4, 1, 15, 4, 3, Blocks.BIRCH_SLAB);
+            for (int x = 11; x <= 14; x++) set(x, 1, 1, Blocks.WATER_CAULDRON.defaultBlockState()
+                .setValue(BlockStateProperties.LEVEL_CAULDRON, 2));
+            set(15, 4, 2, Blocks.BIRCH_PLANKS); set(15, 5, 2, Blocks.LANTERN);
+            for (int z : new int[]{5, 9}) set(15, 1, z, Blocks.OAK_STAIRS.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.EAST));
+            box(2, 0, 14, 14, 0, 15, Blocks.TUFF_BRICKS);
+        }
+        void excavation() {
+            // Reinforced temporary footings and timber trestles stay out of the central descent.
+            for (int x : new int[]{4, 12}) {
+                box(x, -4, 11, x, -1, 11, Blocks.CHISELED_STONE_BRICKS);
+                set(x, 0, 11, Blocks.OAK_PLANKS);
+            }
+            box(3, 3, 13, 13, 3, 13, Blocks.STRIPPED_OAK_LOG);
+            for (int x : new int[]{3, 13}) box(x, -4, 13, x, 2, 13, Blocks.STONE_BRICKS);
+            set(3, 4, 13, Blocks.LANTERN);
+            set(1, 1, 11, Blocks.GRINDSTONE); set(1, 1, 10, Blocks.CRAFTING_TABLE);
+        }
+        void garage() {
+            int base = p.foundationDepth() >= 8 ? -5 : 0;
+            for (int x : new int[]{3, 13}) for (int z : new int[]{3, 13}) {
+                box(x, base + 1, z, x, base + 4, z, Blocks.POLISHED_ANDESITE);
+                set(x, base + 1, z, Blocks.CHISELED_TUFF_BRICKS);
+            }
+            for (int z = 6; z <= 15; z++) for (int x = 1; x <= 15; x++)
+                if (x <= 5 || x >= 11) set(x, base, z, z % 4 == 0 ? Blocks.POLISHED_DIORITE : Blocks.POLISHED_ANDESITE);
+            // A ribbed structural fascia and ventilation blades make this an open modern garage.
+            for (int x = 0; x <= 16; x++) {
+                set(x, base + 5, 0, x % 4 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS);
+                if (x < 6 || x > 10) set(x, base + 3, 0, Blocks.IRON_TRAPDOOR.defaultBlockState()
+                    .setValue(BlockStateProperties.OPEN, true).setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            }
+            for (int x : new int[]{5, 11}) {
+                set(x, base + 4, 9, Blocks.SMOOTH_STONE);
+                set(x, base + 3, 9, Blocks.LANTERN.defaultBlockState().setValue(BlockStateProperties.HANGING, true));
+            }
+        }
+    }
+}
@@ -0,0 +1,88 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.detail.ConnectedBlocks20;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Architectural finish for the generation20 city undercroft. The certified generation16 geometry,
+ * stairs, wet tanks, outfalls and support positions are reused without changing their planning. */
+public final class LostCityUnderground20 {
+    private LostCityUnderground20() {}
+    public static void render(LostCityUnderground16.Module module, LostCityRenderer.BlockWriter output) {
+        var buffer = ConnectedBlocks20.buffer(output);
+        LostCityUnderground16.render(module, new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState state) {
+                buffer.set(x, y, z, material(module, x, y, z, state));
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> loot, long seed) {
+                buffer.chest(x, y, z, loot, seed);
+            }
+        });
+        if (module.kind() != LostCityUnderground16.Kind.ACCESS && module.kind() != LostCityUnderground16.Kind.GARAGE) {
+            int y = module.height() - 2;
+            Block molding = module.kind() == LostCityUnderground16.Kind.POOLROOM ? Blocks.POLISHED_DIORITE_STAIRS
+                : module.kind() == LostCityUnderground16.Kind.EXPANSION_HALL ? Blocks.OAK_STAIRS : Blocks.TUFF_BRICK_STAIRS;
+            // Coved edge beneath the high ceiling, with a complete external shell behind it.
+            // Doorway planes and floor circulation are left in their certified positions.
+            for (int x = 2; x < module.width() - 2; x++) {
+                buffer.set(x, y, 1, cove(molding, Direction.NORTH));
+                buffer.set(x, y, module.depth() - 2, cove(molding, Direction.SOUTH));
+            }
+            for (int z = 2; z < module.depth() - 2; z++) {
+                buffer.set(1, y, z, cove(molding, Direction.WEST));
+                buffer.set(module.width() - 2, y, z, cove(molding, Direction.EAST));
+            }
+            if (module.kind() == LostCityUnderground16.Kind.POOLROOM) {
+                for (int x : new int[] {8, 20, 34, 46}) {
+                    // Buttress capitals continue the existing pool colonnade, then span as
+                    // tall repeated ceiling ribs. The 50x25 pool and swimming volume remain open.
+                    for (int z = 1; z < module.depth() - 1; z++)
+                        buffer.set(x, y, z, (z == 1 || z == module.depth() - 2
+                            ? Blocks.CHISELED_TUFF_BRICKS : Blocks.POLISHED_DIORITE).defaultBlockState());
+                    for (int z : new int[] {1, module.depth() - 2}) {
+                        buffer.set(x - 1, y - 1, z, cove(Blocks.POLISHED_DIORITE_STAIRS, Direction.EAST));
+                        buffer.set(x + 1, y - 1, z, cove(Blocks.POLISHED_DIORITE_STAIRS, Direction.WEST));
+                    }
+                }
+            }
+        }
+        buffer.flush();
+    }
+    private static BlockState cove(Block block, Direction facing) {
+        return block.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, facing)
+            .setValue(BlockStateProperties.HALF, Half.TOP);
+    }
+    private static BlockState material(LostCityUnderground16.Module m, int x, int y, int z, BlockState state) {
+        if (state.is(Blocks.STONE) && (y <= 0 || m.kind() == LostCityUnderground16.Kind.GARAGE))
+            return Blocks.STONE_BRICKS.defaultBlockState();
+        boolean wall = x == 0 || z == 0 || x == m.width() - 1 || z == m.depth() - 1;
+        boolean masonry = state.is(Blocks.STONE_BRICKS) || state.is(Blocks.CRACKED_STONE_BRICKS)
+            || state.is(Blocks.MOSSY_STONE_BRICKS);
+        if (wall && masonry && y > 2 && y < m.height() - 1) {
+            int along = x == 0 || x == m.width() - 1 ? z : x;
+            return switch (m.kind()) {
+                case POOLROOM -> (y == 7 ? Blocks.POLISHED_DIORITE : y == 8 && along % 6 == 0
+                    ? Blocks.CHISELED_TUFF_BRICKS : Blocks.CALCITE).defaultBlockState();
+                case EXPANSION_HALL -> (along % 5 == 0 ? Blocks.STRIPPED_OAK_WOOD
+                    : y < 5 ? Blocks.TUFF_BRICKS : Blocks.SMOOTH_STONE).defaultBlockState();
+                case SEWER, SEWER_OUTLET -> (along % 6 == 0 ? Blocks.CHISELED_TUFF_BRICKS
+                    : Blocks.TUFF_BRICKS).defaultBlockState();
+                case PASSAGE -> (y == 3 ? Blocks.POLISHED_GRANITE : Blocks.TUFF).defaultBlockState();
+                default -> state;
+            };
+        }
+        if (m.kind() == LostCityUnderground16.Kind.GARAGE && state.is(Blocks.SMOOTH_STONE)
+                && y >= 1 && (y - 1) % 16 == 0 && (x <= 1 || z <= 1 || x >= m.width() - 2 || z >= m.depth() - 2))
+            return ((x + z) % 8 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS).defaultBlockState();
+        if (m.kind() == LostCityUnderground16.Kind.EXPANSION_HALL && state.is(Blocks.DARK_OAK_STAIRS))
+            return Blocks.OAK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING,
+                state.getValue(BlockStateProperties.HORIZONTAL_FACING));
+        return state;
+    }
+}
@@ -0,0 +1,88 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import java.util.ArrayList;
+import net.minecraft.core.BlockPos;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** A saved underground module includes its openings and certified supports, including their anchors. */
+public final class LostCityUndergroundPiece20 extends StructurePiece {
+    private final LostCityUnderground16.Module module;
+
+    public LostCityUndergroundPiece20(LostCityUnderground16.Module module) {
+        super(LostCityStructures.UNDERGROUND20, 0, bounds(module));
+        this.module = module;
+        setOrientation(null);
+    }
+
+    public LostCityUndergroundPiece20(StructurePieceSerializationContext context, CompoundTag tag) {
+        super(LostCityStructures.UNDERGROUND20, tag);
+        if (tag.getInt("SanctuarySchema").orElseThrow() != 1)
+            throw new IllegalArgumentException("Unsupported underground piece schema");
+        var supports = new ArrayList<LostCityUnderground16.Support>();
+        var saved = tag.getList("Supports").orElseThrow();
+        if (saved.size() > 128) throw new IllegalArgumentException("Too many underground supports");
+        for (var entry : saved) {
+            if (!(entry instanceof CompoundTag support)) throw new IllegalArgumentException("Invalid support");
+            supports.add(new LostCityUnderground16.Support(
+                LostCityUnderground16.Type.valueOf(support.getString("Type").orElseThrow()),
+                support.getInt("X").orElseThrow(), support.getInt("MinY").orElseThrow(),
+                support.getInt("Z").orElseThrow(), support.getInt("MaxY").orElseThrow()));
+        }
+        module = new LostCityUnderground16.Module(LostCityUnderground16.Kind.valueOf(tag.getString("Kind").orElseThrow()),
+            tag.getInt("MinX").orElseThrow(), tag.getInt("MinY").orElseThrow(), tag.getInt("MinZ").orElseThrow(),
+            tag.getInt("Width").orElseThrow(), tag.getInt("Height").orElseThrow(), tag.getInt("Depth").orElseThrow(),
+            tag.getInt("Openings").orElseThrow(), tag.getLong("ModuleSeed").orElseThrow(), supports);
+        if (!getBoundingBox().equals(bounds(module))) throw new IllegalArgumentException("Underground bounds disagree with saved geometry");
+        setOrientation(null);
+    }
+
+    public LostCityUnderground16.Module module() { return module; }
+
+    @Override protected void addAdditionalSaveData(StructurePieceSerializationContext context, CompoundTag tag) {
+        tag.putInt("SanctuarySchema", 1);
+        tag.putString("Kind", module.kind().name());
+        tag.putInt("MinX", module.minX()); tag.putInt("MinY", module.minY()); tag.putInt("MinZ", module.minZ());
+        tag.putInt("Width", module.width()); tag.putInt("Height", module.height()); tag.putInt("Depth", module.depth());
+        tag.putInt("Openings", module.openings()); tag.putLong("ModuleSeed", module.seed());
+        var supports = new ListTag();
+        for (var support : module.supports()) {
+            var value = new CompoundTag();
+            value.putString("Type", support.type().name()); value.putInt("X", support.x());
+            value.putInt("MinY", support.minY()); value.putInt("Z", support.z()); value.putInt("MaxY", support.maxY());
+            supports.add(value);
+        }
+        tag.put("Supports", supports);
+    }
+
+    @Override public void postProcess(WorldGenLevel level, StructureManager manager, ChunkGenerator generator,
+            RandomSource random, BoundingBox clip, ChunkPos chunk, BlockPos pivot) {
+        LostCityStructures.placing(() -> LostCityUnderground20.render(module, new LostCityRenderer.BlockWriter() {
+            private BlockPos world(int x, int y, int z) { return new BlockPos(module.minX() + x, module.minY() + y, module.minZ() + z); }
+            @Override public void set(int x, int y, int z, BlockState state) {
+                var pos = world(x, y, z);
+                if (getBoundingBox().isInside(pos) && clip.isInside(pos)) placeBlock(level, state, pos.getX(), pos.getY(), pos.getZ(), clip);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+                var pos = world(x, y, z);
+                if (getBoundingBox().isInside(pos) && clip.isInside(pos)) createChest(level, clip, RandomSource.create(seed), pos, table, null);
+            }
+        }));
+    }
+
+    public static BoundingBox bounds(LostCityUnderground16.Module module) {
+        return new BoundingBox(module.boundsMinX(), module.boundsMinY(), module.boundsMinZ(),
+            module.boundsMaxX(), module.boundsMaxY(), module.boundsMaxZ());
+    }
+}
@@ -0,0 +1,170 @@
+package fr.koka.sanctuary.worldgen.detail;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.Comparator;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.FenceBlock;
+import net.minecraft.world.level.block.FenceGateBlock;
+import net.minecraft.world.level.block.IronBarsBlock;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.WallBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.BooleanProperty;
+import net.minecraft.world.level.block.state.properties.StairsShape;
+import net.minecraft.world.level.block.state.properties.WallSide;
+import net.minecraft.world.level.material.FluidState;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.phys.shapes.BooleanOp;
+import net.minecraft.world.phys.shapes.Shapes;
+import net.minecraft.world.phys.shapes.VoxelShape;
+
+/** Generation20 only: resolve the complete, already-rotated geometry before a native writer clips chunks.
+ * Unwritten neighbors are air. This never reads loaded terrain, changes saved older renderers or creates loot early. */
+public final class ConnectedBlocks20 {
+    public static final int MAX_BLOCKS = 262_144;
+    private static final Direction[] SIDES = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    private static final VoxelShape POST_TEST = Block.column(2.0, 0.0, 16.0);
+    private static final Map<Direction, VoxelShape> WALL_TEST = Shapes.rotateHorizontal(Block.boxZ(2.0, 16.0, 0.0, 9.0));
+    private ConnectedBlocks20() {}
+    public static Buffer buffer(LostCityRenderer.BlockWriter destination) { return new Buffer(destination); }
+
+    public static final class Buffer implements LostCityRenderer.BlockWriter {
+        private final LostCityRenderer.BlockWriter destination;
+        private final Map<BlockPos, BlockState> blocks = new LinkedHashMap<>();
+        private final Map<BlockPos, Chest> chests = new LinkedHashMap<>();
+        private boolean flushed;
+        private Buffer(LostCityRenderer.BlockWriter destination) { this.destination = Objects.requireNonNull(destination); }
+        @Override public void set(int x, int y, int z, BlockState state) {
+            checkOpen(); var at = new BlockPos(x, y, z); admit(at);
+            blocks.put(at, Objects.requireNonNull(state)); chests.remove(at);
+        }
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+            checkOpen(); var at = new BlockPos(x, y, z); admit(at);
+            blocks.put(at, Blocks.CHEST.defaultBlockState()); chests.put(at, new Chest(Objects.requireNonNull(table), seed));
+        }
+        /** Final placement wins. Every connection sees all blocks even when the sink accepts only one chunk. */
+        public void flush() {
+            checkOpen(); flushed = true;
+            if (blocks.isEmpty()) return;
+            var view = new Geometry(blocks);
+            // Stair corners depend only on neighbors' facing and half, not on their previous corner shapes.
+            blocks.replaceAll((at, state) -> StairBlock.isStairs(state)
+                ? state.setValue(StairBlock.SHAPE, stairsShape(state, view, at)) : state);
+            // A pane/fence above a wall changes the underside used for LOW/TALL. Resolve it first.
+            // Their horizontal wall connection uses the wall tag, independent of wall arm heights.
+            blocks.replaceAll((at, state) -> connected(state, view, at));
+            // Walls depend on the final underside and post of the wall above, so visit from top to bottom.
+            blocks.keySet().stream().filter(at -> blocks.get(at).getBlock() instanceof WallBlock)
+                .sorted(Comparator.<BlockPos>comparingInt(at -> at.getY()).reversed()).toList()
+                .forEach(at -> blocks.put(at, wall(blocks.get(at), view, at)));
+            try {
+                for (var entry : blocks.entrySet()) {
+                    var at = entry.getKey(); var chest = chests.get(at);
+                    if (chest == null) destination.set(at.getX(), at.getY(), at.getZ(), entry.getValue());
+                    else destination.chest(at.getX(), at.getY(), at.getZ(), chest.table(), chest.seed());
+                }
+            } finally { blocks.clear(); chests.clear(); }
+        }
+        private void admit(BlockPos at) {
+            if (!blocks.containsKey(at) && blocks.size() >= MAX_BLOCKS)
+                throw new IllegalArgumentException("Generation20 connection buffer exceeded its per-piece block budget");
+        }
+        private void checkOpen() { if (flushed) throw new IllegalStateException("A generation20 geometry buffer can be flushed only once"); }
+    }
+    private record Chest(ResourceKey<LootTable> table, long seed) {}
+    private static BlockState connected(BlockState state, BlockGetter view, BlockPos at) {
+        if (!(state.getBlock() instanceof IronBarsBlock) && !(state.getBlock() instanceof FenceBlock)) return state;
+        for (var direction : SIDES) {
+            var neighborPos = at.relative(direction); var neighbor = view.getBlockState(neighborPos);
+            boolean sturdy = neighbor.isFaceSturdy(view, neighborPos, direction.getOpposite());
+            boolean connects = state.getBlock() instanceof IronBarsBlock pane ? pane.attachsTo(neighbor, sturdy)
+                : ((FenceBlock) state.getBlock()).connectsTo(neighbor, sturdy, direction.getOpposite());
+            state = state.setValue(property(direction), connects);
+        }
+        return state;
+    }
+    /** WallBlock's private MC26.3-pre-2 LOW/TALL/UP calculation, using the same native shapes. */
+    private static BlockState wall(BlockState state, BlockGetter view, BlockPos at) {
+        var abovePos = at.above(); var above = view.getBlockState(abovePos);
+        var support = above.getCollisionShape(view, abovePos).getFaceShape(Direction.DOWN);
+        for (var direction : SIDES) {
+            var neighborPos = at.relative(direction); var neighbor = view.getBlockState(neighborPos);
+            boolean sturdy = neighbor.isFaceSturdy(view, neighborPos, direction.getOpposite());
+            // Pane's predicate shares walls' solid/exception, pane and wall-tag rules; walls also accept gates.
+            boolean joins = ((IronBarsBlock) Blocks.IRON_BARS).attachsTo(neighbor, sturdy)
+                || neighbor.getBlock() instanceof FenceGateBlock
+                    && FenceGateBlock.connectsToDirection(neighbor, direction.getOpposite());
+            state = state.setValue(WallBlock.PROPERTY_BY_DIRECTION.get(direction), !joins ? WallSide.NONE
+                : covered(support, WALL_TEST.get(direction)) ? WallSide.TALL : WallSide.LOW);
+        }
+        return state.setValue(WallBlock.UP, raisePost(state, above, support));
+    }
+    private static boolean raisePost(BlockState state, BlockState above, VoxelShape support) {
+        if (above.getBlock() instanceof WallBlock && above.getValue(WallBlock.UP)) return true;
+        var n = state.getValue(WallBlock.NORTH); var s = state.getValue(WallBlock.SOUTH);
+        var w = state.getValue(WallBlock.WEST); var e = state.getValue(WallBlock.EAST);
+        boolean noN = n == WallSide.NONE, noS = s == WallSide.NONE;
+        boolean noW = w == WallSide.NONE, noE = e == WallSide.NONE;
+        if (noN && noS && noW && noE || noN != noS || noW != noE) return true;
+        if (n == WallSide.TALL && s == WallSide.TALL || e == WallSide.TALL && w == WallSide.TALL) return false;
+        return above.is(BlockTags.WALL_POST_OVERRIDE) || covered(support, POST_TEST);
+    }
+    private static boolean covered(VoxelShape support, VoxelShape test) {
+        return !Shapes.joinIsNotEmpty(test, support, BooleanOp.ONLY_FIRST);
+    }
+    private static BooleanProperty property(Direction direction) {
+        return switch (direction) {
+            case NORTH -> BlockStateProperties.NORTH; case EAST -> BlockStateProperties.EAST;
+            case SOUTH -> BlockStateProperties.SOUTH; case WEST -> BlockStateProperties.WEST;
+            default -> throw new IllegalArgumentException("Connections are horizontal");
+        };
+    }
+    /** Matches MC26.3-pre-2 StairBlock's private shape selection, inspected in its native bytecode.
+     * Panes and fences call the native connection predicates directly, including tags and exceptions. */
+    private static StairsShape stairsShape(BlockState state, BlockGetter view, BlockPos at) {
+        var facing = state.getValue(StairBlock.FACING);
+        var front = view.getBlockState(at.relative(facing));
+        if (StairBlock.isStairs(front) && state.getValue(StairBlock.HALF) == front.getValue(StairBlock.HALF)) {
+            var other = front.getValue(StairBlock.FACING);
+            if (other.getAxis() != facing.getAxis() && canTakeShape(state, view, at, other.getOpposite()))
+                return other == facing.getCounterClockWise() ? StairsShape.OUTER_LEFT : StairsShape.OUTER_RIGHT;
+        }
+        var back = view.getBlockState(at.relative(facing.getOpposite()));
+        if (StairBlock.isStairs(back) && state.getValue(StairBlock.HALF) == back.getValue(StairBlock.HALF)) {
+            var other = back.getValue(StairBlock.FACING);
+            if (other.getAxis() != facing.getAxis() && canTakeShape(state, view, at, other))
+                return other == facing.getCounterClockWise() ? StairsShape.INNER_LEFT : StairsShape.INNER_RIGHT;
+        }
+        return StairsShape.STRAIGHT;
+    }
+    private static boolean canTakeShape(BlockState state, BlockGetter view, BlockPos at, Direction direction) {
+        var neighbor = view.getBlockState(at.relative(direction));
+        return !StairBlock.isStairs(neighbor) || neighbor.getValue(StairBlock.FACING) != state.getValue(StairBlock.FACING)
+            || neighbor.getValue(StairBlock.HALF) != state.getValue(StairBlock.HALF);
+    }
+    private static final class Geometry implements BlockGetter {
+        private final Map<BlockPos, BlockState> blocks;
+        private final int low, high;
+        Geometry(Map<BlockPos, BlockState> blocks) {
+            this.blocks = blocks;
+            low = blocks.keySet().stream().mapToInt(at -> at.getY()).min().orElse(0);
+            high = blocks.keySet().stream().mapToInt(at -> at.getY()).max().orElse(0);
+        }
+        @Override public BlockState getBlockState(BlockPos at) { return blocks.getOrDefault(at, Blocks.AIR.defaultBlockState()); }
+        @Override public FluidState getFluidState(BlockPos at) { return getBlockState(at).getFluidState(); }
+        @Override public BlockEntity getBlockEntity(BlockPos at) { return null; }
+        @Override public int getHeight() { return Math.addExact(Math.subtractExact(high, low), 1); }
+        @Override public int getMinY() { return low; }
+    }
+}
@@ -0,0 +1,34 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.util.Locale;
+import net.fabricmc.fabric.api.command.v2.CommandRegistrationCallback;
+import net.minecraft.commands.Commands;
+import net.minecraft.network.chat.Component;
+import net.minecraft.world.level.Level;
+
+/** Read-only operator catalogue. Inspecting a plan neither loads chunks nor activates an expansion. */
+public final class HeritageCommands19 {
+    private HeritageCommands19() {}
+    public static void register() {
+        CommandRegistrationCallback.EVENT.register((dispatcher, registries, environment) ->
+            dispatcher.register(Commands.literal("sanctuary")
+                .requires(Commands.hasPermission(Commands.LEVEL_GAMEMASTERS))
+                .then(Commands.literal("structures").executes(context -> {
+                    var source = context.getSource();
+                    var level = source.getLevel();
+                    if (!Level.OVERWORLD.equals(level.dimension())
+                            || !(level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator generator)
+                            || (generator.rootGeneration() != 19 && generator.rootGeneration() != 20) || !generator.experimentalStructures()) {
+                        source.sendFailure(Component.translatable("sanctuary.heritage.unavailable"));
+                        return 0;
+                    }
+                    var plan = generator.heritagePlan19();
+                    source.sendSuccess(() -> Component.translatable("sanctuary.heritage.header", plan.sites().size(), plan.links().size()), false);
+                    for (var site : plan.sites()) source.sendSuccess(() -> Component.translatable("sanctuary.heritage.entry",
+                        Component.translatable("sanctuary.heritage.kind." + site.kind().name().toLowerCase(Locale.ROOT)),
+                        site.entry().x(), site.entry().y(), site.entry().z()), false);
+                    return plan.sites().size();
+                }))));
+    }
+}
@@ -0,0 +1,185 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayList;
+import java.util.Set;
+import net.minecraft.core.BlockPos;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.Tag;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Self-contained schema19 geometry. Reload never needs the planner or a distant route destination. */
+public final class HeritagePiece19 extends StructurePiece {
+    private static final Set<String> SITE_KEYS = Set.of("Schema", "Type", "Id", "Kind", "MinX", "FloorY", "MinZ",
+        "Width", "Depth", "Height", "Facing", "Seed", "FoundationDepth", "Supports", "Entry");
+    private static final Set<String> ROUTE_KEYS = Set.of("Schema", "Type", "Id", "FromId", "ToId", "Kind",
+        "StartChunkX", "StartChunkZ", "Cells", "Seed");
+    private static final Set<String> SUPPORT_KEYS = Set.of("X", "MinY", "Z", "MaxY");
+    private static final Set<String> ENTRY_KEYS = Set.of("X", "Y", "Z", "Facing");
+    private static final Set<String> CELL_KEYS = Set.of("X", "FloorY", "Z", "FoundationDepth", "Rail", "RailPresent");
+    private final HeritagePlan19.Site site;
+    private final HeritagePlan19.Segment segment;
+
+    public HeritagePiece19(HeritagePlan19.Site site) {
+        super(HeritageStructures19.PIECE, 0, bounds(site));
+        this.site = site; this.segment = null; setOrientation(null);
+    }
+    public HeritagePiece19(HeritagePlan19.Segment segment) {
+        super(HeritageStructures19.PIECE, 0, bounds(segment));
+        this.site = null; this.segment = segment; setOrientation(null);
+    }
+    public HeritagePiece19(StructurePieceSerializationContext context, CompoundTag tag) {
+        super(HeritageStructures19.PIECE, tag);
+        var payload = tag.getCompound("SanctuaryHeritage").orElseThrow(() -> new IllegalArgumentException("Missing saved heritage geometry"));
+        String type = string(payload, "Type");
+        if (type.equals("SITE")) { site = decodeSite(payload); segment = null; }
+        else if (type.equals("ROUTE")) { site = null; segment = decodeSegment(payload); }
+        else throw new IllegalArgumentException("Unknown heritage piece type");
+        if (!getBoundingBox().equals(isSite() ? bounds(site) : bounds(segment)))
+            throw new IllegalArgumentException("Heritage geometry disagrees with its saved native bounds");
+        setOrientation(null);
+    }
+    public boolean isSite() { return site != null; }
+    public HeritagePlan19.Site site() { if (site == null) throw new IllegalStateException("This heritage piece is a route"); return site; }
+    public HeritagePlan19.Segment segment() { if (segment == null) throw new IllegalStateException("This heritage piece is a site"); return segment; }
+    @Override public BlockPos getLocatorPosition() {
+        if (isSite()) return locator(site);
+        var cell = segment.cells().getFirst(); return new BlockPos(cell.x(), cell.floorY() + 1, cell.z());
+    }
+    public static BlockPos locator(HeritagePlan19.Site site) { return new BlockPos(site.entry().x(), site.entry().y(), site.entry().z()); }
+    @Override protected void addAdditionalSaveData(StructurePieceSerializationContext context, CompoundTag tag) {
+        tag.put("SanctuaryHeritage", isSite() ? encodeSite(site) : encodeSegment(segment));
+    }
+    public static CompoundTag encodeSite(HeritagePlan19.Site site) {
+        var tag = header("SITE", site.id(), site.kind().name(), site.seed());
+        tag.putInt("MinX", site.minX()); tag.putInt("FloorY", site.floorY()); tag.putInt("MinZ", site.minZ());
+        tag.putInt("Width", site.width()); tag.putInt("Depth", site.depth()); tag.putInt("Height", site.height());
+        tag.putInt("Facing", site.facing()); tag.putInt("FoundationDepth", site.foundationDepth());
+        var entry = new CompoundTag(); entry.putInt("X", site.entry().x()); entry.putInt("Y", site.entry().y());
+        entry.putInt("Z", site.entry().z()); entry.putInt("Facing", site.entry().facing()); tag.put("Entry", entry);
+        var supports = new ListTag();
+        for (var support : site.supports()) {
+            var value = new CompoundTag(); value.putInt("X", support.x()); value.putInt("MinY", support.minY());
+            value.putInt("Z", support.z()); value.putInt("MaxY", support.maxY()); supports.add(value);
+        }
+        tag.put("Supports", supports); return tag;
+    }
+    public static CompoundTag encodeSegment(HeritagePlan19.Segment segment) {
+        var tag = header("ROUTE", segment.id(), segment.kind().name(), segment.seed());
+        tag.putString("FromId", segment.fromId()); tag.putString("ToId", segment.toId());
+        tag.putInt("StartChunkX", segment.startChunkX()); tag.putInt("StartChunkZ", segment.startChunkZ());
+        var cells = new ListTag();
+        for (var cell : segment.cells()) {
+            var value = new CompoundTag(); value.putInt("X", cell.x()); value.putInt("FloorY", cell.floorY());
+            value.putInt("Z", cell.z()); value.putInt("FoundationDepth", cell.foundationDepth());
+            value.putString("Rail", cell.rail().name()); value.putBoolean("RailPresent", cell.railPresent()); cells.add(value);
+        }
+        tag.put("Cells", cells); return tag;
+    }
+    public static HeritagePlan19.Site decodeSite(CompoundTag tag) {
+        schema(tag, "SITE", SITE_KEYS);
+        var entry = compound(tag, "Entry", ENTRY_KEYS);
+        var saved = list(tag, "Supports", 9); var supports = new ArrayList<HeritagePlan19.Support>();
+        for (var value : saved) {
+            var support = element(value, SUPPORT_KEYS);
+            supports.add(new HeritagePlan19.Support(coordinate(support, "X"), integer(support, "MinY"),
+                coordinate(support, "Z"), integer(support, "MaxY")));
+        }
+        return new HeritagePlan19.Site(id(tag, "Id"), HeritagePlan19.Kind.valueOf(string(tag, "Kind")),
+            coordinate(tag, "MinX"), integer(tag, "FloorY"), coordinate(tag, "MinZ"), integer(tag, "Width"),
+            integer(tag, "Depth"), integer(tag, "Height"), integer(tag, "Facing"), seed(tag), integer(tag, "FoundationDepth"),
+            supports, new HeritagePlan19.Entry(coordinate(entry, "X"), integer(entry, "Y"), coordinate(entry, "Z"), integer(entry, "Facing")));
+    }
+    public static HeritagePlan19.Segment decodeSegment(CompoundTag tag) {
+        schema(tag, "ROUTE", ROUTE_KEYS);
+        var saved = list(tag, "Cells", 256); var cells = new ArrayList<HeritagePlan19.Cell>();
+        for (var value : saved) {
+            var cell = element(value, CELL_KEYS);
+            type(cell, "RailPresent", Tag.TAG_BYTE);
+            byte present = cell.getByte("RailPresent").orElseThrow();
+            if (present != 0 && present != 1) throw new IllegalArgumentException("Invalid saved rail presence");
+            cells.add(new HeritagePlan19.Cell(coordinate(cell, "X"), integer(cell, "FloorY"), coordinate(cell, "Z"),
+                integer(cell, "FoundationDepth"), HeritagePlan19.Rail.valueOf(string(cell, "Rail")), present == 1));
+        }
+        String from = id(tag, "FromId"), to = id(tag, "ToId");
+        var kind = HeritagePlan19.RouteKind.valueOf(string(tag, "Kind"));
+        if (from.equals(to) && kind != HeritagePlan19.RouteKind.PATH)
+            throw new IllegalArgumentException("Only a local pedestrian landing may join a destination to itself");
+        return new HeritagePlan19.Segment(id(tag, "Id"), from, to, kind,
+            integer(tag, "StartChunkX"), integer(tag, "StartChunkZ"), cells, seed(tag));
+    }
+    private static CompoundTag header(String type, String id, String kind, long seed) {
+        var value = new CompoundTag(); value.putInt("Schema", 19); value.putString("Type", type);
+        value.putString("Id", id); value.putString("Kind", kind); value.putLong("Seed", seed); return value;
+    }
+    private static void schema(CompoundTag tag, String expected, Set<String> keys) {
+        if (!tag.keySet().equals(keys) || integer(tag, "Schema") != 19 || !string(tag, "Type").equals(expected))
+            throw new IllegalArgumentException("Unsupported or incomplete saved heritage schema");
+    }
+    private static CompoundTag compound(CompoundTag tag, String key, Set<String> keys) {
+        type(tag, key, Tag.TAG_COMPOUND); return element(tag.get(key), keys);
+    }
+    private static CompoundTag element(Tag tag, Set<String> keys) {
+        if (!(tag instanceof CompoundTag value) || !value.keySet().equals(keys))
+            throw new IllegalArgumentException("Unsupported or incomplete saved heritage element");
+        return value;
+    }
+    private static ListTag list(CompoundTag tag, String key, int maximum) {
+        type(tag, key, Tag.TAG_LIST); var value = tag.getList(key).orElseThrow();
+        if (value.size() > maximum) throw new IllegalArgumentException("Oversized saved heritage list"); return value;
+    }
+    private static long seed(CompoundTag tag) { type(tag, "Seed", Tag.TAG_LONG); return tag.getLong("Seed").orElseThrow(); }
+    private static String id(CompoundTag tag, String key) {
+        var value = string(tag, key);
+        if (value.isBlank() || value.length() > 128) throw new IllegalArgumentException("Invalid saved heritage identifier"); return value;
+    }
+    private static String string(CompoundTag tag, String key) { type(tag, key, Tag.TAG_STRING); return tag.getString(key).orElseThrow(); }
+    private static int coordinate(CompoundTag tag, String key) {
+        int value = integer(tag, key);
+        if (value < -30_000_000 || value > 30_000_000) throw new IllegalArgumentException("Heritage coordinate outside world bounds"); return value;
+    }
+    private static int integer(CompoundTag tag, String key) { type(tag, key, Tag.TAG_INT); return tag.getInt(key).orElseThrow(); }
+    private static void type(CompoundTag tag, String key, byte id) {
+        if (tag.get(key) == null || tag.get(key).getId() != id) throw new IllegalArgumentException("Invalid saved heritage field: " + key);
+    }
+    @Override public void postProcess(WorldGenLevel level, StructureManager manager, ChunkGenerator generator,
+            RandomSource random, BoundingBox clip, ChunkPos chunk, BlockPos pivot) {
+        final int x0 = isSite() ? site.minX() : segment.minX();
+        final int y0 = isSite() ? site.floorY() : segment.minY();
+        final int z0 = isSite() ? site.minZ() : segment.minZ();
+        var writer = new LostCityRenderer.BlockWriter() {
+            private BlockPos world(int x, int y, int z) { return new BlockPos(Math.addExact(x0, x), Math.addExact(y0, y), Math.addExact(z0, z)); }
+            @Override public void set(int x, int y, int z, BlockState block) {
+                var position = world(x, y, z);
+                if (getBoundingBox().isInside(position) && clip.isInside(position))
+                    placeBlock(level, block, position.getX(), position.getY(), position.getZ(), clip);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> loot, long seed) {
+                var position = world(x, y, z);
+                if (getBoundingBox().isInside(position) && clip.isInside(position))
+                    createChest(level, clip, RandomSource.create(seed), position, loot, null);
+            }
+        };
+        HeritageStructures19.placing(() -> {
+            if (isSite()) HeritageRenderer19.render(site, writer);
+            else HeritageRenderer19.renderSegment(segment, writer);
+        });
+    }
+    public static BoundingBox bounds(HeritagePlan19.Site site) {
+        return new BoundingBox(site.minX(), site.boundsMinY(), site.minZ(), site.maxX(), site.boundsMaxY(), site.maxZ());
+    }
+    public static BoundingBox bounds(HeritagePlan19.Segment segment) {
+        return new BoundingBox(segment.minX(), segment.boundsMinY(), segment.minZ(), segment.maxX(), segment.boundsMaxY(), segment.maxZ());
+    }
+}
@@ -0,0 +1,185 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayList;
+import java.util.Set;
+import net.minecraft.core.BlockPos;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.Tag;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Self-contained schema20 geometry. Reload never needs the planner or a distant route destination. */
+public final class HeritagePiece20 extends StructurePiece {
+    private static final Set<String> SITE_KEYS = Set.of("Schema", "Type", "Id", "Kind", "MinX", "FloorY", "MinZ",
+        "Width", "Depth", "Height", "Facing", "Seed", "FoundationDepth", "Supports", "Entry");
+    private static final Set<String> ROUTE_KEYS = Set.of("Schema", "Type", "Id", "FromId", "ToId", "Kind",
+        "StartChunkX", "StartChunkZ", "Cells", "Seed");
+    private static final Set<String> SUPPORT_KEYS = Set.of("X", "MinY", "Z", "MaxY");
+    private static final Set<String> ENTRY_KEYS = Set.of("X", "Y", "Z", "Facing");
+    private static final Set<String> CELL_KEYS = Set.of("X", "FloorY", "Z", "FoundationDepth", "Rail", "RailPresent");
+    private final HeritagePlan19.Site site;
+    private final HeritagePlan19.Segment segment;
+
+    public HeritagePiece20(HeritagePlan19.Site site) {
+        super(HeritageStructures19.PIECE20, 0, bounds(site));
+        this.site = site; this.segment = null; setOrientation(null);
+    }
+    public HeritagePiece20(HeritagePlan19.Segment segment) {
+        super(HeritageStructures19.PIECE20, 0, bounds(segment));
+        this.site = null; this.segment = segment; setOrientation(null);
+    }
+    public HeritagePiece20(StructurePieceSerializationContext context, CompoundTag tag) {
+        super(HeritageStructures19.PIECE20, tag);
+        var payload = tag.getCompound("SanctuaryHeritage").orElseThrow(() -> new IllegalArgumentException("Missing saved heritage geometry"));
+        String type = string(payload, "Type");
+        if (type.equals("SITE")) { site = decodeSite(payload); segment = null; }
+        else if (type.equals("ROUTE")) { site = null; segment = decodeSegment(payload); }
+        else throw new IllegalArgumentException("Unknown heritage piece type");
+        if (!getBoundingBox().equals(isSite() ? bounds(site) : bounds(segment)))
+            throw new IllegalArgumentException("Heritage geometry disagrees with its saved native bounds");
+        setOrientation(null);
+    }
+    public boolean isSite() { return site != null; }
+    public HeritagePlan19.Site site() { if (site == null) throw new IllegalStateException("This heritage piece is a route"); return site; }
+    public HeritagePlan19.Segment segment() { if (segment == null) throw new IllegalStateException("This heritage piece is a site"); return segment; }
+    @Override public BlockPos getLocatorPosition() {
+        if (isSite()) return locator(site);
+        var cell = segment.cells().getFirst(); return new BlockPos(cell.x(), cell.floorY() + 1, cell.z());
+    }
+    public static BlockPos locator(HeritagePlan19.Site site) { return new BlockPos(site.entry().x(), site.entry().y(), site.entry().z()); }
+    @Override protected void addAdditionalSaveData(StructurePieceSerializationContext context, CompoundTag tag) {
+        tag.put("SanctuaryHeritage", isSite() ? encodeSite(site) : encodeSegment(segment));
+    }
+    public static CompoundTag encodeSite(HeritagePlan19.Site site) {
+        var tag = header("SITE", site.id(), site.kind().name(), site.seed());
+        tag.putInt("MinX", site.minX()); tag.putInt("FloorY", site.floorY()); tag.putInt("MinZ", site.minZ());
+        tag.putInt("Width", site.width()); tag.putInt("Depth", site.depth()); tag.putInt("Height", site.height());
+        tag.putInt("Facing", site.facing()); tag.putInt("FoundationDepth", site.foundationDepth());
+        var entry = new CompoundTag(); entry.putInt("X", site.entry().x()); entry.putInt("Y", site.entry().y());
+        entry.putInt("Z", site.entry().z()); entry.putInt("Facing", site.entry().facing()); tag.put("Entry", entry);
+        var supports = new ListTag();
+        for (var support : site.supports()) {
+            var value = new CompoundTag(); value.putInt("X", support.x()); value.putInt("MinY", support.minY());
+            value.putInt("Z", support.z()); value.putInt("MaxY", support.maxY()); supports.add(value);
+        }
+        tag.put("Supports", supports); return tag;
+    }
+    public static CompoundTag encodeSegment(HeritagePlan19.Segment segment) {
+        var tag = header("ROUTE", segment.id(), segment.kind().name(), segment.seed());
+        tag.putString("FromId", segment.fromId()); tag.putString("ToId", segment.toId());
+        tag.putInt("StartChunkX", segment.startChunkX()); tag.putInt("StartChunkZ", segment.startChunkZ());
+        var cells = new ListTag();
+        for (var cell : segment.cells()) {
+            var value = new CompoundTag(); value.putInt("X", cell.x()); value.putInt("FloorY", cell.floorY());
+            value.putInt("Z", cell.z()); value.putInt("FoundationDepth", cell.foundationDepth());
+            value.putString("Rail", cell.rail().name()); value.putBoolean("RailPresent", cell.railPresent()); cells.add(value);
+        }
+        tag.put("Cells", cells); return tag;
+    }
+    public static HeritagePlan19.Site decodeSite(CompoundTag tag) {
+        schema(tag, "SITE", SITE_KEYS);
+        var entry = compound(tag, "Entry", ENTRY_KEYS);
+        var saved = list(tag, "Supports", 9); var supports = new ArrayList<HeritagePlan19.Support>();
+        for (var value : saved) {
+            var support = element(value, SUPPORT_KEYS);
+            supports.add(new HeritagePlan19.Support(coordinate(support, "X"), integer(support, "MinY"),
+                coordinate(support, "Z"), integer(support, "MaxY")));
+        }
+        return new HeritagePlan19.Site(id(tag, "Id"), HeritagePlan19.Kind.valueOf(string(tag, "Kind")),
+            coordinate(tag, "MinX"), integer(tag, "FloorY"), coordinate(tag, "MinZ"), integer(tag, "Width"),
+            integer(tag, "Depth"), integer(tag, "Height"), integer(tag, "Facing"), seed(tag), integer(tag, "FoundationDepth"),
+            supports, new HeritagePlan19.Entry(coordinate(entry, "X"), integer(entry, "Y"), coordinate(entry, "Z"), integer(entry, "Facing")));
+    }
+    public static HeritagePlan19.Segment decodeSegment(CompoundTag tag) {
+        schema(tag, "ROUTE", ROUTE_KEYS);
+        var saved = list(tag, "Cells", 256); var cells = new ArrayList<HeritagePlan19.Cell>();
+        for (var value : saved) {
+            var cell = element(value, CELL_KEYS);
+            type(cell, "RailPresent", Tag.TAG_BYTE);
+            byte present = cell.getByte("RailPresent").orElseThrow();
+            if (present != 0 && present != 1) throw new IllegalArgumentException("Invalid saved rail presence");
+            cells.add(new HeritagePlan19.Cell(coordinate(cell, "X"), integer(cell, "FloorY"), coordinate(cell, "Z"),
+                integer(cell, "FoundationDepth"), HeritagePlan19.Rail.valueOf(string(cell, "Rail")), present == 1));
+        }
+        String from = id(tag, "FromId"), to = id(tag, "ToId");
+        var kind = HeritagePlan19.RouteKind.valueOf(string(tag, "Kind"));
+        if (from.equals(to) && kind != HeritagePlan19.RouteKind.PATH)
+            throw new IllegalArgumentException("Only a local pedestrian landing may join a destination to itself");
+        return new HeritagePlan19.Segment(id(tag, "Id"), from, to, kind,
+            integer(tag, "StartChunkX"), integer(tag, "StartChunkZ"), cells, seed(tag));
+    }
+    private static CompoundTag header(String type, String id, String kind, long seed) {
+        var value = new CompoundTag(); value.putInt("Schema", 20); value.putString("Type", type);
+        value.putString("Id", id); value.putString("Kind", kind); value.putLong("Seed", seed); return value;
+    }
+    private static void schema(CompoundTag tag, String expected, Set<String> keys) {
+        if (!tag.keySet().equals(keys) || integer(tag, "Schema") != 20 || !string(tag, "Type").equals(expected))
+            throw new IllegalArgumentException("Unsupported or incomplete saved heritage schema");
+    }
+    private static CompoundTag compound(CompoundTag tag, String key, Set<String> keys) {
+        type(tag, key, Tag.TAG_COMPOUND); return element(tag.get(key), keys);
+    }
+    private static CompoundTag element(Tag tag, Set<String> keys) {
+        if (!(tag instanceof CompoundTag value) || !value.keySet().equals(keys))
+            throw new IllegalArgumentException("Unsupported or incomplete saved heritage element");
+        return value;
+    }
+    private static ListTag list(CompoundTag tag, String key, int maximum) {
+        type(tag, key, Tag.TAG_LIST); var value = tag.getList(key).orElseThrow();
+        if (value.size() > maximum) throw new IllegalArgumentException("Oversized saved heritage list"); return value;
+    }
+    private static long seed(CompoundTag tag) { type(tag, "Seed", Tag.TAG_LONG); return tag.getLong("Seed").orElseThrow(); }
+    private static String id(CompoundTag tag, String key) {
+        var value = string(tag, key);
+        if (value.isBlank() || value.length() > 128) throw new IllegalArgumentException("Invalid saved heritage identifier"); return value;
+    }
+    private static String string(CompoundTag tag, String key) { type(tag, key, Tag.TAG_STRING); return tag.getString(key).orElseThrow(); }
+    private static int coordinate(CompoundTag tag, String key) {
+        int value = integer(tag, key);
+        if (value < -30_000_000 || value > 30_000_000) throw new IllegalArgumentException("Heritage coordinate outside world bounds"); return value;
+    }
+    private static int integer(CompoundTag tag, String key) { type(tag, key, Tag.TAG_INT); return tag.getInt(key).orElseThrow(); }
+    private static void type(CompoundTag tag, String key, byte id) {
+        if (tag.get(key) == null || tag.get(key).getId() != id) throw new IllegalArgumentException("Invalid saved heritage field: " + key);
+    }
+    @Override public void postProcess(WorldGenLevel level, StructureManager manager, ChunkGenerator generator,
+            RandomSource random, BoundingBox clip, ChunkPos chunk, BlockPos pivot) {
+        final int x0 = isSite() ? site.minX() : segment.minX();
+        final int y0 = isSite() ? site.floorY() : segment.minY();
+        final int z0 = isSite() ? site.minZ() : segment.minZ();
+        var writer = new LostCityRenderer.BlockWriter() {
+            private BlockPos world(int x, int y, int z) { return new BlockPos(Math.addExact(x0, x), Math.addExact(y0, y), Math.addExact(z0, z)); }
+            @Override public void set(int x, int y, int z, BlockState block) {
+                var position = world(x, y, z);
+                if (getBoundingBox().isInside(position) && clip.isInside(position))
+                    placeBlock(level, block, position.getX(), position.getY(), position.getZ(), clip);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> loot, long seed) {
+                var position = world(x, y, z);
+                if (getBoundingBox().isInside(position) && clip.isInside(position))
+                    createChest(level, clip, RandomSource.create(seed), position, loot, null);
+            }
+        };
+        HeritageStructures19.placing(() -> {
+            if (isSite()) HeritageRenderer20.render(site, writer);
+            else HeritageRenderer20.renderSegment(segment, writer);
+        });
+    }
+    public static BoundingBox bounds(HeritagePlan19.Site site) {
+        return new BoundingBox(site.minX(), site.boundsMinY(), site.minZ(), site.maxX(), site.boundsMaxY(), site.maxZ());
+    }
+    public static BoundingBox bounds(HeritagePlan19.Segment segment) {
+        return new BoundingBox(segment.minX(), segment.boundsMinY(), segment.minZ(), segment.maxX(), segment.boundsMaxY(), segment.maxZ());
+    }
+}
@@ -0,0 +1,200 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import java.util.HashSet;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/** Immutable generation19 catalogue and real-destination routes. Pieces save geometry, not terrain queries. */
+public final class HeritagePlan19 {
+    private final List<Site> sites;
+    private final List<Landmark> landmarks;
+    private final List<Link> links;
+    private final List<Segment> segments;
+    private final int samples, columns;
+    private final Map<Kind, String> diagnostics;
+    private final Map<Long, List<Range>> protectedColumns;
+    private final Map<Long, List<Box>> protectedChunks;
+    public static final int MAX_COLUMNS = 16_000, MAX_SAMPLES = 800_000;
+    public static final HeritagePlan19 EMPTY = new HeritagePlan19(List.of(), List.of(), List.of(), List.of(), 0, 0, Map.of());
+    public enum Kind { FREIGHT_STATION, POST_OFFICE, COMMUNAL_DEPOT, EXPEDITION_OFFICE, OBSERVATORY,
+        RAIL_WORKSHOP, PUMP_STATION, SUBSTATION, GREENHOUSE, VOID_DOCK, RADIO_RELAY, PHOTO_CLUB,
+        IMPOSSIBLE_SERVICE, CONSTRUCTION_REFUGE }
+    public enum RouteKind { FREIGHT, PATH }
+    public enum LandmarkKind { CITY, MINE, UTILITY }
+    /** NONE is a side column or path; a missing rail retains its intended shape with railPresent=false. */
+    public enum Rail { NONE, NORTH_SOUTH, EAST_WEST, ASCENDING_EAST, ASCENDING_WEST, ASCENDING_NORTH,
+        ASCENDING_SOUTH, SOUTH_EAST, SOUTH_WEST, NORTH_WEST, NORTH_EAST }
+
+    /** Coordinates of the player's feet, immediately outside the facade. Facing0=N,1=E,2=S,3=W. */
+    public record Entry(int x, int y, int z, int facing) {
+        public Entry { if (!coordinate(x) || !coordinate(z) || y < 2 || y > 380 || facing < 0 || facing > 3) throw new IllegalArgumentException("Invalid heritage entry"); }
+    }
+    public record Support(int x, int minY, int z, int maxY) {
+        public Support { if (!coordinate(x) || !coordinate(z) || minY < 2 || maxY < minY || maxY - minY >= 12 || maxY > 370) throw new IllegalArgumentException("Invalid heritage support"); }
+    }
+    public record Site(String id, Kind kind, int minX, int floorY, int minZ, int width, int depth, int height,
+                       int facing, long seed, int foundationDepth, List<Support> supports, Entry entry) {
+        public Site {
+            supports = List.copyOf(supports);
+            if (!identifier(id) || !coordinate(minX) || !coordinate(minZ) || kind == null || width != 17 || depth != 17 || height < 7 || height > 24
+                    || floorY < 32 || floorY + height > 380 || facing < 0 || facing > 3
+                    || foundationDepth < 3 || foundationDepth > 8 || supports.size() > 9 || entry == null)
+                throw new IllegalArgumentException("Invalid heritage site");
+            int ex = facing == 1 ? minX + width : facing == 3 ? minX - 1 : minX + width / 2;
+            int ez = facing == 2 ? minZ + depth : facing == 0 ? minZ - 1 : minZ + depth / 2;
+            if (entry.x() != ex || entry.z() != ez || entry.y() != floorY + 1 || entry.facing() != facing)
+                throw new IllegalArgumentException("Heritage entry does not meet its rotated facade");
+            var positions = new HashSet<Long>();
+            for (var support : supports) if (support.x() < minX || support.x() >= minX + width
+                    || support.z() < minZ || support.z() >= minZ + depth || support.maxY() != floorY - foundationDepth - 1
+                    || !positions.add(key(support.x(), support.z()))) throw new IllegalArgumentException("Invalid site footing");
+        }
+        public int maxX() { return minX + width - 1; }
+        public int maxZ() { return minZ + depth - 1; }
+        public int minY() { return floorY - foundationDepth; }
+        public int maxY() { return floorY + height; }
+        public int boundsMinY() { return supports.stream().mapToInt(Support::minY).min().orElse(minY()); }
+        public int boundsMaxY() { return maxY(); }
+        public int centerX() { return minX + width / 2; }
+        public int centerZ() { return minZ + depth / 2; }
+        public int startChunkX() { return centerX() >> 4; }
+        public int startChunkZ() { return centerZ() >> 4; }
+    }
+    /** A pre-existing, read-only destination. Its coordinate is never granted a mask bypass. */
+    public record Landmark(String id, LandmarkKind kind, Entry entry) {
+        public Landmark { if (!identifier(id) || kind == null || entry == null) throw new IllegalArgumentException("Invalid heritage landmark"); }
+    }
+    /** Floor/block-support Y, not player feet. Endpoints may be read-only landmark coordinates. */
+    public record Point(int x, int floorY, int z) {
+        public Point { if (!coordinate(x) || !coordinate(z) || floorY < 2 || floorY > 370) throw new IllegalArgumentException("Invalid route point"); }
+    }
+    public record Link(String id, String fromId, String toId, RouteKind kind, List<Point> path) {
+        public Link {
+            path = List.copyOf(path);
+            if (!identifier(id) || !identifier(fromId) || !identifier(toId) || fromId.equals(toId)
+                    || kind == null || path.size() < 2 || path.size() > 1024) throw new IllegalArgumentException("Invalid heritage link");
+            for (int i = 1; i < path.size(); i++) {
+                var a = path.get(i - 1); var b = path.get(i);
+                if (Math.abs(a.x() - b.x()) + Math.abs(a.z() - b.z()) != 1 || Math.abs(a.floorY() - b.floorY()) > 1)
+                    throw new IllegalArgumentException("Heritage route has a discontinuous centerline");
+            }
+        }
+    }
+    /** Each written ground column belongs to exactly one Segment. Clear local y1..3 before rail placement. */
+    public record Cell(int x, int floorY, int z, int foundationDepth, Rail rail, boolean railPresent) {
+        public Cell {
+            if (!coordinate(x) || !coordinate(z) || floorY < 14 || floorY > 350 || foundationDepth < 1 || foundationDepth > 12 || rail == null
+                    || rail == Rail.NONE && railPresent) throw new IllegalArgumentException("Invalid heritage route cell");
+        }
+        public int minY() { return floorY - foundationDepth; }
+        public int maxY() { return floorY + 3; }
+    }
+    /** Chunk-local route piece: stable ownership prevents neighboring links painting a shared column twice. */
+    public record Segment(String id, String fromId, String toId, RouteKind kind, int startChunkX, int startChunkZ,
+                          List<Cell> cells, long seed) {
+        public Segment {
+            cells = List.copyOf(cells);
+            if (!identifier(id) || !identifier(fromId) || !identifier(toId) || fromId.equals(toId) && kind != RouteKind.PATH || kind == null || cells.isEmpty() || cells.size() > 256)
+                throw new IllegalArgumentException("Invalid heritage segment");
+            var positions = new HashSet<Long>();
+            for (var cell : cells) if ((cell.x() >> 4) != startChunkX || (cell.z() >> 4) != startChunkZ
+                    || !positions.add(key(cell.x(), cell.z()))) throw new IllegalArgumentException("Route cells escaped their owning chunk");
+        }
+        public int minX() { return cells.stream().mapToInt(Cell::x).min().orElseThrow(); }
+        public int maxX() { return cells.stream().mapToInt(Cell::x).max().orElseThrow(); }
+        public int minZ() { return cells.stream().mapToInt(Cell::z).min().orElseThrow(); }
+        public int maxZ() { return cells.stream().mapToInt(Cell::z).max().orElseThrow(); }
+        public int minY() { return cells.stream().mapToInt(Cell::minY).min().orElseThrow(); }
+        public int maxY() { return cells.stream().mapToInt(Cell::maxY).max().orElseThrow(); }
+        public int boundsMinY() { return minY(); }
+        public int boundsMaxY() { return maxY(); }
+    }
+
+    public HeritagePlan19(List<Site> sites, List<Landmark> landmarks, List<Link> links, List<Segment> segments,
+                         int samples, int columns, Map<Kind, String> diagnostics) {
+        sites = List.copyOf(sites); landmarks = List.copyOf(landmarks); links = List.copyOf(links); segments = List.copyOf(segments);
+        diagnostics = Map.copyOf(diagnostics);
+        if (sites.size() > 14 || landmarks.size() > 16 || links.size() > 24 || segments.size() > 512
+                || samples < 0 || samples > MAX_SAMPLES || columns < 0 || columns > MAX_COLUMNS)
+            throw new IllegalArgumentException("Invalid heritage plan budget");
+        var destinations = new HashSet<String>();
+        for (var site : sites) if (!destinations.add(site.id())) throw new IllegalArgumentException("Duplicate heritage destination");
+        for (var landmark : landmarks) if (!destinations.add(landmark.id())) throw new IllegalArgumentException("Duplicate heritage destination");
+        for (var link : links) if (!destinations.contains(link.fromId()) || !destinations.contains(link.toId()))
+            throw new IllegalArgumentException("A heritage route promises a nonexistent destination");
+        var occupied = new HashSet<Long>();
+        for (var segment : segments) {
+            if (!destinations.contains(segment.fromId()) || !destinations.contains(segment.toId()))
+                throw new IllegalArgumentException("A heritage segment promises a nonexistent destination");
+            for (var cell : segment.cells()) if (!occupied.add(key(cell.x(), cell.z())))
+                throw new IllegalArgumentException("Heritage segments write the same column");
+        }
+        this.sites = sites; this.landmarks = landmarks; this.links = links; this.segments = segments;
+        this.samples = samples; this.columns = columns; this.diagnostics = diagnostics;
+        var columnIndex = new HashMap<Long, List<Range>>(); var chunkIndex = new HashMap<Long, List<Box>>();
+        for (var site : sites) {
+            index(columnIndex, chunkIndex, new Box(site.minX(), site.minY() - 2, site.minZ(), site.maxX(), site.maxY(), site.maxZ()));
+            for (var support : site.supports()) index(columnIndex, chunkIndex,
+                new Box(support.x(), support.minY() - 2, support.z(), support.x(), support.maxY(), support.z()));
+        }
+        for (var segment : segments) for (var cell : segment.cells()) index(columnIndex, chunkIndex,
+            new Box(cell.x(), cell.minY() - 1, cell.z(), cell.x(), cell.maxY(), cell.z()));
+        var usedDestinations = new HashSet<String>();
+        for (var link : links) { usedDestinations.add(link.fromId()); usedDestinations.add(link.toId()); }
+        for (var landmark : landmarks) if (usedDestinations.contains(landmark.id())) {
+            Entry e = landmark.entry();
+            for (int side = -1; side <= 1; side++) {
+                int x = e.x() + ((e.facing() & 1) == 0 ? side : 0);
+                int z = e.z() + ((e.facing() & 1) == 1 ? side : 0);
+                // Read-only dependencies: these cells never enter contains() or any native writer.
+                index(columnIndex, chunkIndex, new Box(x, e.y() - 2, z, x, e.y() + 2, z));
+            }
+        }
+        columnIndex.replaceAll((key, values) -> List.copyOf(values)); chunkIndex.replaceAll((key, values) -> List.copyOf(values));
+        protectedColumns = Map.copyOf(columnIndex); protectedChunks = Map.copyOf(chunkIndex);
+    }
+    public List<Site> sites() { return sites; }
+    public List<Landmark> landmarks() { return landmarks; }
+    public List<Link> links() { return links; }
+    public List<Segment> segments() { return segments; }
+    public int samples() { return samples; }
+    public int columns() { return columns; }
+    public Map<Kind, String> diagnostics() { return diagnostics; }
+    public boolean isEmpty() { return sites.isEmpty(); }
+    public boolean contains(int x, int y, int z) {
+        for (var site : sites) {
+            if (x < site.minX() || x > site.maxX() || z < site.minZ() || z > site.maxZ()) continue;
+            if (y >= site.minY() && y <= site.maxY()) return true;
+            for (var support : site.supports()) if (x == support.x() && z == support.z() && y >= support.minY() && y <= support.maxY()) return true;
+        }
+        for (var segment : segments) if ((x >> 4) == segment.startChunkX() && (z >> 4) == segment.startChunkZ())
+            for (var cell : segment.cells()) if (cell.x() == x && cell.z() == z && y >= cell.minY() && y <= cell.maxY()) return true;
+        return false;
+    }
+    /** Protect the original rock below slabs as well as every written volume. */
+    public boolean protects(int x, int y, int z) {
+        for (var range : protectedColumns.getOrDefault(key(x, z), List.of())) if (y >= range.minY() && y <= range.maxY()) return true;
+        return false;
+    }
+    public boolean intersectsProtection(int x0, int y0, int z0, int x1, int y1, int z1) {
+        if (x0 > x1 || y0 > y1 || z0 > z1) throw new IllegalArgumentException("Reversed heritage query");
+        for (int cx = x0 >> 4; cx <= x1 >> 4; cx++) for (int cz = z0 >> 4; cz <= z1 >> 4; cz++)
+            for (var box : protectedChunks.getOrDefault(key(cx, cz), List.of()))
+                if (x0 <= box.maxX() && x1 >= box.minX() && z0 <= box.maxZ() && z1 >= box.minZ()
+                        && y0 <= box.maxY() && y1 >= box.minY()) return true;
+        return false;
+    }
+    private record Range(int minY, int maxY) {}
+    private record Box(int minX, int minY, int minZ, int maxX, int maxY, int maxZ) {}
+    private static void index(Map<Long, List<Range>> columns, Map<Long, List<Box>> chunks, Box box) {
+        for (int x = box.minX(); x <= box.maxX(); x++) for (int z = box.minZ(); z <= box.maxZ(); z++)
+            columns.computeIfAbsent(key(x, z), ignored -> new ArrayList<>()).add(new Range(box.minY(), box.maxY()));
+        for (int x = box.minX() >> 4; x <= box.maxX() >> 4; x++) for (int z = box.minZ() >> 4; z <= box.maxZ() >> 4; z++)
+            chunks.computeIfAbsent(key(x, z), ignored -> new ArrayList<>()).add(box);
+    }
+    private static boolean coordinate(int value) { return Math.abs((long) value) <= 29_999_000; }
+    private static boolean identifier(String value) { return value != null && !value.isBlank() && value.length() <= 128; }
+    private static long key(int x, int z) { return (long) x << 32 ^ z & 0xffffffffL; }
+}
@@ -0,0 +1,545 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.heritage.HeritagePlan19.*;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.EnumMap;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+
+/** Generation19 only. A finite catalogue is admitted before complete, repairable routes are published.
+ * Everything samples native columns; no chunk, player object or future continent is requested. */
+public final class HeritagePlanner19 {
+    public static final int MAX_COLUMNS = HeritagePlan19.MAX_COLUMNS, MAX_SAMPLES = HeritagePlan19.MAX_SAMPLES;
+    public static final int MAX_SITE_CUT = 6, MAX_ROUTE_CUT = 3;
+    private static final int SITE_COLUMNS = 11_000, SITE_SAMPLES = 540_000;
+    private static final int INVALID = Integer.MIN_VALUE;
+    private static final int[] DX = {0, 1, 0, -1}, DZ = {-1, 0, 1, 0};
+    private HeritagePlanner19() {}
+    public interface Terrain {
+        boolean owns(int x, int z);
+        int surfaceY(int x, int z);
+        boolean solid(int x, int y, int z);
+        boolean protectedAt(int x, int y, int z);
+        default List<Landmark> landmarks() { return List.of(); }
+    }
+
+    public static HeritagePlan19 plan(long seed, int cx, int cz, int diameter, Terrain terrain) {
+        if (!List.of(512, 724, 1024).contains(diameter)) throw new IllegalArgumentException("Heritage19 requires a starter size");
+        var probe = new Probe(terrain, cx, cz, diameter);
+        List<Landmark> landmarks = List.copyOf(terrain.landmarks()).stream().limit(16).toList();
+        var sites = new ArrayList<Site>(); var cells = new LinkedHashMap<Long, OwnedCell>(); var diagnostics = new EnumMap<Kind, String>(Kind.class);
+        for (var kind : Kind.values()) {
+            int remaining = Kind.values().length - kind.ordinal() - 1;
+            probe.columnLimit = SITE_COLUMNS - remaining * (SITE_COLUMNS / 14);
+            probe.sampleLimit = SITE_SAMPLES - remaining * (SITE_SAMPLES / 14);
+            SiteDraft admitted = null; int attempts = 0;
+            var reasons = new java.util.TreeMap<String, Integer>(); probe.reasons = reasons;
+            try {
+                for (var candidate : candidates(seed, kind, cx, cz, diameter, sites, landmarks, probe)) {
+                    attempts++;
+                    admitted = site(seed, kind, candidate, sites, landmarks, cells, probe);
+                    if (admitted != null) break;
+                }
+            } catch (BudgetExceeded exhausted) { reasons.merge(exhausted.columns ? "column-budget" : "probe-budget", 1, Integer::sum); }
+            if (admitted != null) {
+                sites.add(admitted.site());
+                Request landing = new Request(admitted.site().id() + "_landing", admitted.site().id(), admitted.site().id(), RouteKind.PATH);
+                for (var cell : admitted.landings()) cells.put(key(cell.x(), cell.z()), new OwnedCell(landing, cell));
+            }
+            diagnostics.put(kind, (admitted == null ? "not admitted" : "admitted") + "; candidates=" + attempts + "; " + reasons);
+        }
+        probe.columnLimit = MAX_COLUMNS; probe.sampleLimit = MAX_SAMPLES;
+        var links = new ArrayList<Link>();
+        var routeResults = new LinkedHashMap<String, String>();
+        var routeReasons = new java.util.TreeMap<String, Integer>(); probe.reasons = routeReasons;
+        Map<String, Endpoint> endpoints = new LinkedHashMap<>();
+        for (var site : sites) endpoints.put(site.id(), new Endpoint(site.id(), site.entry(), false));
+        for (var landmark : landmarks) if (!endpoints.containsKey(landmark.id()))
+            endpoints.put(landmark.id(), new Endpoint(landmark.id(), landmark.entry(), true));
+        List<Request> requests = requests(sites, landmarks).stream()
+            .filter(r -> endpoints.containsKey(r.from()) && endpoints.containsKey(r.to())).toList();
+        requests = new ArrayList<>(requests);
+        requests.sort(Comparator.comparingInt((Request r) -> r.kind() == RouteKind.FREIGHT ? 0
+            : span(endpoints.get(r.from()).entry(), endpoints.get(r.to()).entry()) >= diameter / 4 ? 1 : 2)
+            .thenComparingInt(r -> span(endpoints.get(r.from()).entry(), endpoints.get(r.to()).entry())));
+        int adaptiveLong = 0;
+        for (int requestIndex = 0; requestIndex < requests.size(); requestIndex++) {
+            var request = requests.get(requestIndex);
+            int remaining = requests.size() - requestIndex - 1;
+            // Failed alignments must not starve every later destination. Unused allowances carry forward.
+            boolean longAxis = span(endpoints.get(request.from()).entry(), endpoints.get(request.to()).entry()) >= diameter / 4;
+            int allowance = longAxis && adaptiveLong++ < 2 ? 4_500 : 1_400;
+            probe.columnLimit = Math.min(MAX_COLUMNS - remaining * 120, probe.columns.size() + allowance);
+            probe.sampleLimit = Math.min(MAX_SAMPLES - remaining * 4_000, probe.samples + (longAxis ? 150_000 : 75_000));
+            Endpoint from = endpoints.get(request.from()), to = endpoints.get(request.to());
+            if (from == null || to == null) continue;
+            int beforeRouteColumns = probe.columns.size();
+            try {
+                RouteDraft route = route(seed, request, from, to, sites, landmarks, cells, probe);
+                if (route == null) { probe.reject("no-complete-route"); routeResults.put(request.id(), "refused; columns=" + (probe.columns.size() - beforeRouteColumns)); continue; }
+                links.add(new Link(request.id(), request.from(), request.to(), request.kind(), route.path()));
+                routeResults.put(request.id(), "admitted; span=" + span(from.entry(), to.entry()) + "; length=" + route.path().size() + "; columns=" + (probe.columns.size() - beforeRouteColumns));
+                for (var cell : route.cells().values()) {
+                    long key = key(cell.x(), cell.z());
+                    OwnedCell old = cells.get(key);
+                    if (old == null) cells.put(key, new OwnedCell(request, cell));
+                    else if (cell.rail() != Rail.NONE && old.cell().rail() == Rail.NONE)
+                        cells.put(key, new OwnedCell(old.request(), cell));
+                    else if (cell.rail() != Rail.NONE && old.cell().rail() != Rail.NONE && cell.rail() != old.cell().rail()) {
+                        // A missing switch is intentional; never emit a rail with contradictory connections.
+                        var c = old.cell(); cells.put(key, new OwnedCell(old.request(),
+                            new Cell(c.x(), c.floorY(), c.z(), c.foundationDepth(), c.rail(), false)));
+                    }
+                }
+            } catch (BudgetExceeded exhausted) { probe.reject(exhausted.columns ? "route-column-budget" : "route-probe-budget"); routeResults.put(request.id(), "budget; columns=" + (probe.columns.size() - beforeRouteColumns)); }
+        }
+        var segments = segments(seed, cells);
+        if (Boolean.getBoolean("sanctuary.test.heritage19") || Boolean.getBoolean("sanctuary.heritage.plannerDiagnostics"))
+            System.getLogger(HeritagePlanner19.class.getName()).log(System.Logger.Level.INFO,
+                "Heritage19 seed=" + seed + " diameter=" + diameter + " sites=" + sites.stream().map(Site::kind).toList()
+                + " links=" + links.size() + " segments=" + segments.size() + " columns=" + probe.columns.size()
+                + " samples=" + probe.samples + " catalogue=" + diagnostics + " routes=" + routeReasons + " routeResults=" + routeResults);
+        return new HeritagePlan19(sites, landmarks, links, segments, probe.samples, probe.columns.size(), diagnostics);
+    }
+
+    private static List<Candidate> candidates(long seed, Kind kind, int cx, int cz, int diameter,
+            List<Site> sites, List<Landmark> landmarks, Probe probe) {
+        double angle = unit(mix(seed ^ 0x19ACEL)) * Math.PI * 2 + kind.ordinal() * 2.399963229728653;
+        double radius = diameter * (kind == Kind.VOID_DOCK ? .40 : kind == Kind.OBSERVATORY || kind == Kind.RADIO_RELAY ? .31 : .22);
+        int x = cx + (int) Math.round(Math.cos(angle) * radius), z = cz + (int) Math.round(Math.sin(angle) * radius);
+        Kind parent = switch (kind) {
+            case POST_OFFICE, COMMUNAL_DEPOT, RAIL_WORKSHOP -> Kind.FREIGHT_STATION;
+            case EXPEDITION_OFFICE, PHOTO_CLUB -> Kind.POST_OFFICE;
+            case SUBSTATION, CONSTRUCTION_REFUGE -> Kind.RAIL_WORKSHOP;
+            case GREENHOUSE, IMPOSSIBLE_SERVICE -> Kind.PUMP_STATION;
+            default -> null;
+        };
+        Site neighbor = parent == null ? null : find(sites, parent);
+        if (neighbor != null) {
+            double local = unit(mix(seed ^ kind.ordinal() * 179L)) * Math.PI * 2;
+            int distance = kind == Kind.RAIL_WORKSHOP ? 65 : 40;
+            x = neighbor.centerX() + (int) Math.round(Math.cos(local) * distance);
+            z = neighbor.centerZ() + (int) Math.round(Math.sin(local) * distance);
+        }
+        var candidates = new ArrayList<Candidate>();
+        for (int i = 0; i < 16; i++) {
+            double turn = angle + i * Math.PI / 3;
+            int offset = i == 0 ? 0 : i < 5 ? 24 : i < 8 ? 48 : i < 12 ? 72 : 96;
+            int px = x + (int) Math.round(Math.cos(turn) * offset), pz = z + (int) Math.round(Math.sin(turn) * offset);
+            if (Math.hypot((double) px - cx, (double) pz - cz) > diameter / 2.0 - 18) continue;
+            if (overlapsSites(px - 15, pz - 15, px + 15, pz + 15, sites)) continue;
+            int low = 384, high = -1; boolean dry = true;
+            for (int dz : new int[] {-8, 0, 8}) for (int dx : new int[] {-8, 0, 8}) {
+                int top = probe.surface(px + dx, pz + dz);
+                if (top < 48 || top > 330 || !probe.solid(px + dx, top, pz + dz)
+                        || probe.protectedAt(px + dx, top, pz + dz)) { dry = false; break; }
+                low = Math.min(low, top); high = Math.max(high, top);
+            }
+            if (!dry || high - low > 13) { probe.reject("coarse-terrain"); continue; }
+            int facing = direction(px, pz, neighbor == null ? cx : neighbor.centerX(), neighbor == null ? cz : neighbor.centerZ());
+            if (kind == Kind.VOID_DOCK) facing = (direction(px, pz, cx, cz) + 2) & 3;
+            int score = (i >= 8 ? 1_000 : 0) + high - low + (kind == Kind.OBSERVATORY || kind == Kind.RADIO_RELAY ? (300 - high) / 4 : 0);
+            candidates.add(new Candidate(px - 8, pz - 8, facing, score, mix(seed ^ kind.ordinal() * 463L ^ i)));
+        }
+        candidates.sort(Comparator.comparingInt(Candidate::score).thenComparingLong(Candidate::seed));
+        return candidates;
+    }
+
+    private static SiteDraft site(long seed, Kind kind, Candidate candidate, List<Site> previous,
+            List<Landmark> landmarks, Map<Long, OwnedCell> existing, Probe probe) {
+        int x = candidate.x(), z = candidate.z(), low = 384, high = -1;
+        for (var landmark : landmarks) if (landmark.entry().x() >= x - 2 && landmark.entry().x() <= x + 18
+                && landmark.entry().z() >= z - 2 && landmark.entry().z() <= z + 18) { probe.reject("existing-entry"); return null; }
+        var heights = new ArrayList<Integer>();
+        for (int dz = 0; dz < 17; dz++) for (int dx = 0; dx < 17; dx++) {
+            int top = probe.surface(x + dx, z + dz);
+            if (top < 48 || top > 330 || !probe.solid(x + dx, top, z + dz)) { probe.reject("dry-footprint"); return null; }
+            heights.add(top); low = Math.min(low, top); high = Math.max(high, top);
+        }
+        int minimum = Math.max(48, high - MAX_SITE_CUT), maximum = Math.min(330, low + 7);
+        if (minimum > maximum) { probe.reject("site-slope"); return null; }
+        heights.sort(Integer::compareTo);
+        int floor = Math.clamp(heights.get(heights.size() / 2), minimum, maximum);
+        int foundation = Math.max(3, floor - low + 1), height = height(kind);
+        int base = floor - foundation;
+        for (int dz = 0; dz < 17; dz++) for (int dx = 0; dx < 17; dx++)
+            for (int y = base; y <= floor + height; y++) if (probe.protectedAt(x + dx, y, z + dz)) {
+                probe.reject("site-protected-volume"); return null;
+            }
+        var supports = new ArrayList<Support>();
+        for (int dz : new int[] {1, 8, 15}) for (int dx : new int[] {1, 8, 15}) {
+            int bottom = base - 1, rock = bottom;
+            while (rock >= Math.max(2, base - 13) && (!probe.solid(x + dx, rock, z + dz)
+                    || !probe.solid(x + dx, rock - 1, z + dz))) rock--;
+            if (rock < Math.max(2, base - 13)) { probe.reject("site-no-bearing"); return null; }
+            for (int y = rock - 1; y <= bottom; y++) if (probe.protectedAt(x + dx, y, z + dz)) { probe.reject("support-protected"); return null; }
+            if (rock < bottom) supports.add(new Support(x + dx, rock + 1, z + dz, bottom));
+        }
+        int ex = candidate.facing() == 1 ? x + 17 : candidate.facing() == 3 ? x - 1 : x + 8;
+        int ez = candidate.facing() == 2 ? z + 17 : candidate.facing() == 0 ? z - 1 : z + 8;
+        Entry entry = new Entry(ex, floor + 1, ez, candidate.facing());
+        Site result = new Site(id(kind), kind, x, floor, z, 17, 17, height, candidate.facing(),
+            mix(seed ^ candidate.seed()), foundation, supports, entry);
+        var landings = landing(result.entry(), previous, probe);
+        if (landings == null) { probe.reject("entry-landing"); return null; }
+        for (var cell : landings) {
+            OwnedCell old = existing.get(key(cell.x(), cell.z()));
+            if (old != null && old.cell().floorY() != cell.floorY()) { probe.reject("landing-collision"); return null; }
+        }
+        return new SiteDraft(result, landings);
+    }
+
+    private static int height(Kind kind) {
+        return switch (kind) {
+            case FREIGHT_STATION, POST_OFFICE, RAIL_WORKSHOP, SUBSTATION, GREENHOUSE, PHOTO_CLUB -> 10;
+            case EXPEDITION_OFFICE, IMPOSSIBLE_SERVICE -> 12;
+            case COMMUNAL_DEPOT, VOID_DOCK, CONSTRUCTION_REFUGE -> 14;
+            case PUMP_STATION -> 18; case OBSERVATORY -> 20; case RADIO_RELAY -> 22;
+        };
+    }
+    private static List<Request> requests(List<Site> sites, List<Landmark> landmarks) {
+        var result = new ArrayList<Request>();
+        request(result, Kind.FREIGHT_STATION, Kind.COMMUNAL_DEPOT, RouteKind.FREIGHT);
+        request(result, Kind.FREIGHT_STATION, Kind.RAIL_WORKSHOP, RouteKind.FREIGHT);
+        request(result, Kind.COMMUNAL_DEPOT, Kind.PUMP_STATION, RouteKind.FREIGHT);
+        Site workshop = find(sites, Kind.RAIL_WORKSHOP);
+        for (var landmark : landmarks) if (landmark.kind() == LandmarkKind.MINE && workshop != null)
+            result.add(new Request("mine_freight", landmark.id(), workshop.id(), RouteKind.FREIGHT));
+        request(result, Kind.FREIGHT_STATION, Kind.POST_OFFICE, RouteKind.PATH);
+        request(result, Kind.POST_OFFICE, Kind.EXPEDITION_OFFICE, RouteKind.PATH);
+        request(result, Kind.EXPEDITION_OFFICE, Kind.OBSERVATORY, RouteKind.PATH);
+        request(result, Kind.COMMUNAL_DEPOT, Kind.VOID_DOCK, RouteKind.PATH);
+        request(result, Kind.RAIL_WORKSHOP, Kind.SUBSTATION, RouteKind.PATH);
+        request(result, Kind.SUBSTATION, Kind.PUMP_STATION, RouteKind.PATH);
+        request(result, Kind.PUMP_STATION, Kind.GREENHOUSE, RouteKind.PATH);
+        request(result, Kind.POST_OFFICE, Kind.PHOTO_CLUB, RouteKind.PATH);
+        request(result, Kind.PUMP_STATION, Kind.IMPOSSIBLE_SERVICE, RouteKind.PATH);
+        request(result, Kind.OBSERVATORY, Kind.RADIO_RELAY, RouteKind.PATH);
+        request(result, Kind.RAIL_WORKSHOP, Kind.CONSTRUCTION_REFUGE, RouteKind.PATH);
+        Site post = find(sites, Kind.POST_OFFICE);
+        for (var landmark : landmarks) if (landmark.kind() == LandmarkKind.CITY && post != null) {
+            result.add(new Request("city_post_" + result.size(), landmark.id(), post.id(), RouteKind.PATH)); break;
+        }
+        return result;
+    }
+    private static void request(List<Request> requests, Kind from, Kind to, RouteKind kind) {
+        requests.add(new Request(id(from) + "_" + id(to), id(from), id(to), kind));
+    }
+
+    /** Always persisted, including for an isolated destination: five steps return to natural terrain. */
+    private static List<Cell> landing(Entry entry, List<Site> sites, Probe probe) {
+        int facing = entry.facing(), floor = entry.y() - 1;
+        int endX = entry.x() + DX[facing] * 4, endZ = entry.z() + DZ[facing] * 4;
+        int target = probe.surface(endX, endZ);
+        if (target < 14 || target > 350 || Math.abs(target - floor) > 3) return null;
+        var result = new ArrayList<Cell>();
+        for (int step = 0; step < 5; step++) {
+            // Keep the first two rows flat for the facade and the first rail turn.
+            int y = floor + (int) Math.round((target - floor) * Math.max(0, step - 1) / 3.0);
+            for (int cross = -1; cross <= 1; cross++) {
+                int x = entry.x() + DX[facing] * step + DZ[facing] * cross;
+                int z = entry.z() + DZ[facing] * step - DX[facing] * cross;
+                if (overlapsSites(x, z, x, z, sites)) return null;
+                Cell cell = routeCell(x, y, z, Rail.NONE, false, probe);
+                if (cell == null) return null;
+                result.add(cell);
+                if (step == 4) {
+                    int beyond = probe.surface(x + DX[facing], z + DZ[facing]);
+                    if (Math.abs(beyond - y) > 1 || !probe.solid(x + DX[facing], beyond, z + DZ[facing])) return null;
+                }
+            }
+        }
+        return List.copyOf(result);
+    }
+
+    private static RouteDraft route(long seed, Request request, Endpoint from, Endpoint to, List<Site> sites,
+            List<Landmark> landmarks, Map<Long, OwnedCell> existing, Probe probe) {
+        Entry a = from.entry(), b = to.entry();
+        XZ start = new XZ(a.x(), a.z()), end = new XZ(b.x(), b.z());
+        XZ outA = start.move(a.facing(), 6), outB = end.move(b.facing(), 6);
+        int middleX = (outA.x() + outB.x()) / 2, middleZ = (outA.z() + outB.z()) / 2;
+        var alternatives = List.of(
+            List.of(outA, new XZ(outB.x(), outA.z()), outB),
+            List.of(outA, new XZ(outA.x(), outB.z()), outB),
+            List.of(outA, new XZ(middleX, outA.z()), new XZ(middleX, outB.z()), outB),
+            List.of(outA, new XZ(outA.x(), middleZ), new XZ(outB.x(), middleZ), outB),
+            List.of(outA, new XZ(outA.x(), middleZ - 16), new XZ(outB.x(), middleZ - 16), outB),
+            List.of(outA, new XZ(middleX + 16, outA.z()), new XZ(middleX + 16, outB.z()), outB));
+        for (var waypoints : alternatives) {
+            var points = new ArrayList<XZ>(); points.add(start);
+            boolean okay = true;
+            for (var waypoint : waypoints) if (!line(points, waypoint)) { okay = false; break; }
+            if (!okay || !line(points, end) || points.size() > 1024 || new HashSet<>(points).size() != points.size()) continue;
+            RouteDraft result = profile(seed, request, from, to, points, sites, landmarks, existing, probe);
+            if (result != null) return result;
+        }
+        return adaptive(seed, request, from, to, start, end, outA, outB, sites, landmarks, existing, probe);
+    }
+
+    /** Adaptive fallback. The coarse graph only proposes an alignment; it grants no writing permission. */
+    private static RouteDraft adaptive(long seed, Request request, Endpoint from, Endpoint to, XZ start, XZ end,
+            XZ outA, XZ outB, List<Site> sites, List<Landmark> landmarks, Map<Long, OwnedCell> existing, Probe probe) {
+        int stepSize = span(from.entry(), to.entry()) >= 160 ? 8 : 4;
+        int certificateReserve = Math.min(2_200, distance(outA, outB) * 3 + 80);
+        var excluded = new HashSet<XZ>();
+        for (int attempt = 0; attempt < 3; attempt++) {
+            var open = new java.util.PriorityQueue<SearchNode>(Comparator.comparingDouble(SearchNode::priority)
+                .thenComparingDouble(SearchNode::cost).thenComparingInt(n -> n.position().x()).thenComparingInt(n -> n.position().z()));
+            var best = new HashMap<XZ, Double>(); var parents = new HashMap<XZ, XZ>(); var closed = new HashSet<XZ>();
+            var terrainHeights = new HashMap<XZ, Integer>();
+            int begin = coarseRoute(outA, sites, terrainHeights, probe);
+            if (begin == INVALID) return null;
+            open.add(new SearchNode(outA, 0, distance(outA, outB))); best.put(outA, 0.0);
+            List<XZ> found = null;
+            int searchColumns = Math.max(probe.columns.size() + 150, probe.columnLimit - certificateReserve);
+            while (!open.isEmpty() && closed.size() < 500 && probe.columns.size() < searchColumns) {
+                var current = open.remove(); XZ p = current.position();
+                if (!closed.add(p) || current.cost() > best.getOrDefault(p, Double.POSITIVE_INFINITY)) continue;
+                if (distance(p, outB) <= stepSize * 2) {
+                    var reversed = new ArrayList<XZ>(); XZ ancestor = p;
+                    while (ancestor != null) { reversed.add(ancestor); ancestor = parents.get(ancestor); }
+                    java.util.Collections.reverse(reversed);
+                    for (int order = 0; order < 2 && found == null; order++) {
+                        var candidate = new ArrayList<XZ>(); candidate.add(start); boolean valid = true;
+                        for (XZ step : reversed) if (!line(candidate, step)) { valid = false; break; }
+                        XZ turn = order == 0 ? new XZ(outB.x(), p.z()) : new XZ(p.x(), outB.z());
+                        if (valid && line(candidate, turn) && line(candidate, outB) && line(candidate, end)
+                                && new HashSet<>(candidate).size() == candidate.size()) found = candidate;
+                    }
+                    if (found != null) break;
+                }
+                int top = terrainHeights.get(p); XZ parent = parents.get(p);
+                for (int d = 0; d < 4; d++) {
+                    if (parent == null && d == ((from.entry().facing() + 2) & 3)) continue;
+                    XZ next = p.move(d, stepSize);
+                    if (closed.contains(next) || excluded.contains(next)
+                            || Math.min(distance(next, outA), distance(next, outB)) > distance(outA, outB) + 64) continue;
+                    int height = coarseRoute(next, sites, terrainHeights, probe);
+                    if (height == INVALID || Math.abs(height - top) > stepSize + 3) continue;
+                    double turnCost = parent == null || parent.x() == next.x() || parent.z() == next.z() ? 0 : 1.5;
+                    double cost = current.cost() + stepSize + Math.abs(height - top) * 1.1 + turnCost;
+                    if (cost >= best.getOrDefault(next, Double.POSITIVE_INFINITY)) continue;
+                    best.put(next, cost); parents.put(next, p);
+                    open.add(new SearchNode(next, cost, cost + distance(next, outB) * 1.6));
+                }
+            }
+            if (found == null) { probe.reject("adaptive-no-alignment"); return null; }
+            RouteDraft certified = profile(seed, request, from, to, found, sites, landmarks, existing, probe);
+            if (certified != null) { probe.reject("adaptive-admitted"); return certified; }
+            if (probe.routeBlock == null) return null;
+            // A failed exact corridor removes only nearby coarse nodes on the next proposal.
+            XZ bad = probe.routeBlock;
+            int gx = outA.x() + (int) Math.round((bad.x() - outA.x()) / (double) stepSize) * stepSize;
+            int gz = outA.z() + (int) Math.round((bad.z() - outA.z()) / (double) stepSize) * stepSize;
+            excluded.add(new XZ(gx, gz));
+            for (int d = 0; d < 4; d++) excluded.add(new XZ(gx, gz).move(d, stepSize));
+        }
+        return null;
+    }
+    private record SearchNode(XZ position, double cost, double priority) {}
+    private static int distance(XZ a, XZ b) { return Math.abs(a.x() - b.x()) + Math.abs(a.z() - b.z()); }
+    private static int coarseRoute(XZ p, List<Site> sites, Map<XZ, Integer> cache, Probe probe) {
+        Integer old = cache.get(p); if (old != null) return old;
+        if (overlapsSites(p.x() - 2, p.z() - 2, p.x() + 2, p.z() + 2, sites)) { cache.put(p, INVALID); return INVALID; }
+        int top = probe.surface(p.x(), p.z());
+        if (top < 14 || top > 350 || !probe.solid(p.x(), top, p.z()) || probe.protectedAt(p.x(), top, p.z())) {
+            cache.put(p, INVALID); return INVALID;
+        }
+        for (int d = 0; d < 4; d++) {
+            XZ side = p.move(d, 1); int sideTop = probe.surface(side.x(), side.z());
+            if (sideTop < 14 || sideTop > 350 || Math.abs(sideTop - top) > 4 || probe.protectedAt(side.x(), sideTop, side.z())) {
+                cache.put(p, INVALID); return INVALID;
+            }
+        }
+        cache.put(p, top); return top;
+    }
+
+    /** Finite orthogonal alignments, each certified at full block resolution before publication. */
+    private static boolean line(List<XZ> points, XZ destination) {
+        XZ p = points.getLast();
+        if (p.x() != destination.x() && p.z() != destination.z()) return false;
+        int dx = Integer.signum(destination.x() - p.x()), dz = Integer.signum(destination.z() - p.z());
+        while (!p.equals(destination)) {
+            p = new XZ(p.x() + dx, p.z() + dz); points.add(p);
+            if (points.size() > 1024) return false;
+        }
+        return true;
+    }
+
+    private static RouteDraft profile(long seed, Request request, Endpoint from, Endpoint to, List<XZ> points,
+            List<Site> sites, List<Landmark> landmarks, Map<Long, OwnedCell> existing, Probe probe) {
+        int size = points.size(); probe.routeBlock = null;
+        int[] lo = new int[size], hi = new int[size], desired = new int[size], group = new int[size];
+        boolean[] flat = new boolean[size - 1];
+        for (int i = 1; i < size - 1; i++) if (turn(points, i)) { flat[i - 1] = true; flat[i] = true; }
+        for (int i = 0; i < size; i++) {
+            XZ point = points.get(i); probe.routeBlock = point; lo[i] = 14; hi[i] = 350;
+            desired[i] = probe.surface(point.x(), point.z());
+            boolean readOnly = i == 0 && from.readOnly() || i == size - 1 && to.readOnly();
+            for (XZ column : strip(points, i)) {
+                if (overlapsSites(column.x(), column.z(), column.x(), column.z(), sites)) { probe.reject("route-building"); return null; }
+                int top = probe.surface(column.x(), column.z());
+                if (top < 14 || top > 350 || !probe.solid(column.x(), top, column.z())) { probe.reject("route-dry-ground"); return null; }
+                lo[i] = Math.max(lo[i], top - MAX_ROUTE_CUT); hi[i] = Math.min(hi[i], top + 4);
+                OwnedCell old = existing.get(key(column.x(), column.z()));
+                if (old != null) { lo[i] = Math.max(lo[i], old.cell().floorY()); hi[i] = Math.min(hi[i], old.cell().floorY()); }
+                if (readOnly && top != (i == 0 ? from.entry().y() : to.entry().y()) - 1) return null;
+            }
+            if (i == 0 || i == size - 1) {
+                int exact = (i == 0 ? from.entry().y() : to.entry().y()) - 1;
+                lo[i] = Math.max(lo[i], exact); hi[i] = Math.min(hi[i], exact);
+            }
+            if (lo[i] > hi[i]) { probe.reject("route-grade-interval"); return null; }
+        }
+        // Curves and both adjacent rails share one elevation; a Minecraft curved rail cannot slope.
+        int groups = 1;
+        for (int i = 1; i < size; i++) { if (!flat[i - 1]) groups++; group[i] = groups - 1; }
+        int[] gl = new int[groups], gh = new int[groups], gd = new int[groups], y = new int[groups];
+        java.util.Arrays.fill(gl, 14); java.util.Arrays.fill(gh, 350);
+        for (int i = 0; i < size; i++) { int g = group[i]; gl[g] = Math.max(gl[g], lo[i]); gh[g] = Math.min(gh[g], hi[i]); gd[g] = desired[i]; }
+        for (int g = 1; g < groups; g++) { gl[g] = Math.max(gl[g], gl[g - 1] - 1); gh[g] = Math.min(gh[g], gh[g - 1] + 1); }
+        for (int g = groups - 2; g >= 0; g--) { gl[g] = Math.max(gl[g], gl[g + 1] - 1); gh[g] = Math.min(gh[g], gh[g + 1] + 1); }
+        for (int g = 0; g < groups; g++) {
+            if (gl[g] > gh[g]) { probe.reject("route-grade"); return null; }
+            int lower = g == 0 ? gl[g] : Math.max(gl[g], y[g - 1] - 1), upper = g == 0 ? gh[g] : Math.min(gh[g], y[g - 1] + 1);
+            y[g] = Math.clamp(gd[g], lower, upper);
+        }
+        var path = new ArrayList<Point>(); var floors = new LinkedHashMap<Long, Integer>();
+        for (int i = 0; i < size; i++) {
+            XZ point = points.get(i); int floor = y[group[i]]; path.add(new Point(point.x(), floor, point.z()));
+            if (i == 0 && from.readOnly() || i == size - 1 && to.readOnly()) continue;
+            for (XZ column : strip(points, i)) {
+                long key = key(column.x(), column.z()); Integer old = floors.putIfAbsent(key, floor);
+                if (old != null && old != floor) { probe.reject("route-self-grade"); return null; }
+                // Historical endpoints and their lateral landing are read-only, even at another nearby turn.
+                for (var landmark : landmarks) if (landingColumn(landmark.entry(), column)) {
+                    boolean actualEnd = from.readOnly() && landmark.id().equals(from.id())
+                        || to.readOnly() && landmark.id().equals(to.id());
+                    if (!actualEnd || floor != landmark.entry().y() - 1) { probe.reject("route-historical-entry"); return null; }
+                    floors.remove(key); break;
+                }
+            }
+        }
+        var cells = new LinkedHashMap<Long, Cell>();
+        for (var entry : floors.entrySet()) {
+            int x = (int) (entry.getKey() >> 32), z = (int) (long) entry.getKey();
+            probe.routeBlock = new XZ(x, z);
+            Cell cell = routeCell(x, entry.getValue(), z, Rail.NONE, false, probe);
+            if (cell == null) { probe.reject("route-column-certificate"); return null; }
+            cells.put(entry.getKey(), cell);
+        }
+        if (request.kind() == RouteKind.FREIGHT) for (int i = 0; i < path.size(); i++) {
+            Point point = path.get(i); long key = key(point.x(), point.z()); Cell cell = cells.get(key);
+            if (cell == null) continue;
+            Rail rail = rail(path, i);
+            // A one-block valley cannot carry two ascending slopes on the same rail. Keep a repairable rail gap.
+            boolean intact = rail != Rail.NONE && Math.floorMod(mix(seed ^ key ^ request.id().hashCode()), 19) != 0;
+            if (rail == Rail.NONE) rail = points.get(Math.max(0, i - 1)).x() == points.get(Math.min(size - 1, i + 1)).x() ? Rail.NORTH_SOUTH : Rail.EAST_WEST;
+            cells.put(key, new Cell(cell.x(), cell.floorY(), cell.z(), cell.foundationDepth(), rail, intact));
+        }
+        return new RouteDraft(List.copyOf(path), cells);
+    }
+
+    private static boolean landingColumn(Entry entry, XZ column) {
+        int dx = column.x() - entry.x(), dz = column.z() - entry.z();
+        return DX[entry.facing()] * dx + DZ[entry.facing()] * dz == 0 && Math.abs(dx) + Math.abs(dz) <= 1;
+    }
+    private static List<XZ> strip(List<XZ> points, int i) {
+        XZ p = points.get(i); var result = new ArrayList<XZ>();
+        if (turn(points, i)) {
+            for (int dx = -1; dx <= 1; dx++) for (int dz = -1; dz <= 1; dz++) result.add(new XZ(p.x() + dx, p.z() + dz));
+        } else {
+            XZ other = points.get(i == points.size() - 1 ? i - 1 : i + 1);
+            int dx = Integer.signum(other.x() - p.x()), dz = Integer.signum(other.z() - p.z());
+            for (int cross = -1; cross <= 1; cross++) result.add(new XZ(p.x() + dz * cross, p.z() - dx * cross));
+        }
+        return result;
+    }
+    private static boolean turn(List<XZ> points, int i) {
+        if (i == 0 || i == points.size() - 1) return false;
+        XZ a = points.get(i - 1), b = points.get(i + 1);
+        return a.x() != b.x() && a.z() != b.z();
+    }
+    private static Rail rail(List<Point> path, int i) {
+        Point p = path.get(i), a = path.get(Math.max(0, i - 1)), b = path.get(Math.min(path.size() - 1, i + 1));
+        if (a.floorY() > p.floorY() && b.floorY() > p.floorY()) return Rail.NONE;
+        Point high = a.floorY() > p.floorY() ? a : b.floorY() > p.floorY() ? b : null;
+        if (high != null) return switch (direction(p.x(), p.z(), high.x(), high.z())) {
+            case 0 -> Rail.ASCENDING_NORTH; case 1 -> Rail.ASCENDING_EAST; case 2 -> Rail.ASCENDING_SOUTH; default -> Rail.ASCENDING_WEST;
+        };
+        if (a.x() == b.x()) return Rail.NORTH_SOUTH;
+        if (a.z() == b.z()) return Rail.EAST_WEST;
+        boolean n = a.z() < p.z() || b.z() < p.z(), s = a.z() > p.z() || b.z() > p.z();
+        boolean e = a.x() > p.x() || b.x() > p.x();
+        return n ? e ? Rail.NORTH_EAST : Rail.NORTH_WEST : s && e ? Rail.SOUTH_EAST : Rail.SOUTH_WEST;
+    }
+    private static Cell routeCell(int x, int floor, int z, Rail rail, boolean present, Probe probe) {
+        int top = probe.surface(x, z);
+        if (floor < 14 || floor > 350 || top < floor - 4 || top > floor + MAX_ROUTE_CUT) return null;
+        int foundation = Math.max(1, floor - top + 1), base = floor - foundation;
+        if (!probe.solid(x, base - 1, z) || !probe.solid(x, base, z)) return null;
+        for (int y = base - 1; y <= floor + 3; y++) if (probe.protectedAt(x, y, z)) return null;
+        return new Cell(x, floor, z, foundation, rail, present);
+    }
+    private record XZ(int x, int z) { XZ move(int facing, int distance) { return new XZ(x + DX[facing] * distance, z + DZ[facing] * distance); } }
+    private record SegmentKey(Request request, int cx, int cz) {}
+    private static List<Segment> segments(long seed, Map<Long, OwnedCell> cells) {
+        var groups = new LinkedHashMap<SegmentKey, List<Cell>>();
+        for (var owned : cells.values()) {
+            Cell c = owned.cell(); var key = new SegmentKey(owned.request(), c.x() >> 4, c.z() >> 4);
+            groups.computeIfAbsent(key, ignored -> new ArrayList<>()).add(c);
+        }
+        var result = new ArrayList<Segment>();
+        for (var entry : groups.entrySet()) {
+            var k = entry.getKey(); var r = k.request();
+            // IDs are stable, bounded and independent of native generation order.
+            String id = "piece_" + r.id() + "_" + k.cx() + "_" + k.cz();
+            result.add(new Segment(id, r.from(), r.to(), r.kind(), k.cx(), k.cz(), entry.getValue(), mix(seed ^ key(k.cx(), k.cz()) ^ r.id().hashCode())));
+        }
+        return List.copyOf(result);
+    }
+
+
+    private static int span(Entry a, Entry b) { return Math.max(Math.abs(a.x() - b.x()), Math.abs(a.z() - b.z())); }
+    private static Site find(List<Site> sites, Kind kind) { return sites.stream().filter(site -> site.kind() == kind).findFirst().orElse(null); }
+    private static String id(Kind kind) { return kind.name().toLowerCase(Locale.ROOT); }
+    private static int direction(int x, int z, int tx, int tz) { return Math.abs(tx - x) >= Math.abs(tz - z) ? tx > x ? 1 : 3 : tz > z ? 2 : 0; }
+    private static boolean overlapsSites(int x0, int z0, int x1, int z1, List<Site> sites) {
+        for (var site : sites) if (x0 <= site.maxX() && x1 >= site.minX() && z0 <= site.maxZ() && z1 >= site.minZ()) return true;
+        return false;
+    }
+    private record SiteDraft(Site site, List<Cell> landings) {}
+    private record Candidate(int x, int z, int facing, int score, long seed) {}
+    private record Endpoint(String id, Entry entry, boolean readOnly) {}
+    private record Request(String id, String from, String to, RouteKind kind) {}
+    private record OwnedCell(Request request, Cell cell) {}
+    private record RouteDraft(List<Point> path, Map<Long, Cell> cells) {}
+    private static final class BudgetExceeded extends RuntimeException {
+        final boolean columns; BudgetExceeded(boolean columns) { this.columns = columns; }
+    }
+    private static final class Probe {
+        final Terrain terrain; final int cx, cz; final double radius;
+        final Map<Long, Integer> columns = new HashMap<>();
+        XZ routeBlock; Map<String, Integer> reasons = new HashMap<>(); int samples, columnLimit, sampleLimit;
+        Probe(Terrain terrain, int cx, int cz, int diameter) { this.terrain = java.util.Objects.requireNonNull(terrain); this.cx = cx; this.cz = cz; radius = diameter / 2.0 - 2; }
+        int surface(int x, int z) {
+            if (Math.hypot((double) x - cx, (double) z - cz) > radius || !terrain.owns(x, z)) return INVALID;
+            long key = key(x, z); var cached = columns.get(key); if (cached != null) return cached;
+            if (columns.size() >= columnLimit) throw new BudgetExceeded(true);
+            count(); int top = terrain.surfaceY(x, z); columns.put(key, top); return top;
+        }
+        boolean solid(int x, int y, int z) { if (y < 1 || y > 383 || surface(x, z) == INVALID) return false; count(); return terrain.solid(x, y, z); }
+        boolean protectedAt(int x, int y, int z) { if (y < 1 || y > 383 || surface(x, z) == INVALID) return true; count(); return terrain.protectedAt(x, y, z); }
+        void count() { if (samples >= sampleLimit) throw new BudgetExceeded(false); samples++; }
+        void reject(String reason) { reasons.merge(reason, 1, Integer::sum); }
+    }
+    private static long key(int x, int z) { return (long) x << 32 ^ z & 0xffffffffL; }
+    private static double unit(long value) { return (value >>> 11) * 0x1.0p-53; }
+    private static long mix(long value) { value = (value ^ value >>> 30) * 0xbf58476d1ce4e5b9L; value = (value ^ value >>> 27) * 0x94d049bb133111ebL; return value ^ value >>> 31; }
+}
@@ -0,0 +1,361 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.worldgen.city.LostCityPalette;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.AttachFace;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DoorHingeSide;
+import net.minecraft.world.level.block.state.properties.DoubleBlockHalf;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.block.state.properties.RailShape;
+
+/** Fourteen original, physical generation19 places. The saved site controls all geometry and loot.
+ * Site writes are local to minX/floorY/minZ; route writes are local to the segment's minimum bounds. */
+public final class HeritageRenderer19 {
+    private HeritageRenderer19() {}
+    public record Target(String name, int x, int y, int z) {}
+
+    /** These are already rotated local standing positions, not world coordinates. */
+    public static List<Target> targets(HeritagePlan19.Site site) {
+        var b = new Builder(site, null); b.layout(); return List.copyOf(b.targets);
+    }
+    public static void render(HeritagePlan19.Site site, LostCityRenderer.BlockWriter writer) {
+        var b = new Builder(site, writer); b.ground(); b.layout();
+        // Footings have absolute saved coordinates and must not undergo a second facade rotation.
+        for (var support : site.supports()) for (int y = support.minY(); y <= support.maxY(); y++)
+            writer.set(support.x() - site.minX(), y - site.floorY(), support.z() - site.minZ(),
+                y == support.minY() ? Blocks.SMOOTH_STONE.defaultBlockState() : Blocks.STONE_BRICKS.defaultBlockState());
+    }
+    public static void renderSegment(HeritagePlan19.Segment segment, LostCityRenderer.BlockWriter writer) {
+        int x0 = segment.minX(), y0 = segment.minY(), z0 = segment.minZ();
+        for (var cell : segment.cells()) {
+            int x = cell.x() - x0, z = cell.z() - z0, floor = cell.floorY() - y0;
+            for (int y = cell.minY() - y0; y <= floor; y++) {
+                Block material = Blocks.STONE;
+                if (y == floor) material = segment.kind() == HeritagePlan19.RouteKind.FREIGHT
+                    ? cell.rail() != HeritagePlan19.Rail.NONE && Math.floorMod(cell.x() + cell.z(), 3) == 0
+                        ? Blocks.DARK_OAK_PLANKS : Blocks.GRAVEL
+                    : LostCityPalette.roll(segment.seed(), cell.x(), y, cell.z(), 4) == 0 ? Blocks.ANDESITE : Blocks.STONE;
+                writer.set(x, y, z, material.defaultBlockState());
+            }
+            for (int y = floor + 1; y <= floor + 3; y++) writer.set(x, y, z, Blocks.AIR.defaultBlockState());
+            if (cell.railPresent()) writer.set(x, floor + 1, z, Blocks.RAIL.defaultBlockState()
+                .setValue(BlockStateProperties.RAIL_SHAPE, RailShape.valueOf(cell.rail().name())));
+        }
+    }
+
+    private static final class Builder {
+        final HeritagePlan19.Site s;
+        final LostCityRenderer.BlockWriter out;
+        final List<Target> targets = new ArrayList<>();
+        final Rotation rotation;
+        Builder(HeritagePlan19.Site s, LostCityRenderer.BlockWriter out) {
+            this.s = s; this.out = out;
+            rotation = switch (s.facing()) { case 1 -> Rotation.CLOCKWISE_90; case 2 -> Rotation.CLOCKWISE_180;
+                case 3 -> Rotation.COUNTERCLOCKWISE_90; default -> Rotation.NONE; };
+        }
+        int rx(int x, int z) { return switch (s.facing()) { case 1 -> 16 - z; case 2 -> 16 - x; case 3 -> z; default -> x; }; }
+        int rz(int x, int z) { return switch (s.facing()) { case 1 -> x; case 2 -> 16 - z; case 3 -> 16 - x; default -> z; }; }
+        void set(int x, int y, int z, BlockState state) {
+            if (x < 0 || x > 16 || z < 0 || z > 16 || y < -s.foundationDepth() || y > s.height())
+                throw new IllegalArgumentException("Heritage " + s.kind() + " renderer escaped saved site: " + x + "/" + y + "/" + z);
+            if (out != null) out.set(rx(x, z), y, rz(x, z), state.rotate(rotation));
+        }
+        void set(int x, int y, int z, Block b) { set(x, y, z, b.defaultBlockState()); }
+        void box(int x0, int y0, int z0, int x1, int y1, int z1, Block b) {
+            for (int y = y0; y <= y1; y++) for (int z = z0; z <= z1; z++) for (int x = x0; x <= x1; x++) set(x, y, z, b);
+        }
+        void target(String name, int x, int y, int z) { targets.add(new Target(name, rx(x, z), y, rz(x, z))); }
+        void ground() {
+            for (int y = -s.foundationDepth(); y <= s.height(); y++) for (int z = 0; z <= 16; z++) for (int x = 0; x <= 16; x++)
+                set(x, y, z, y < 0 ? Blocks.STONE.defaultBlockState() : y == 0
+                    ? LostCityPalette.pavement(s.seed(), x, z) : Blocks.AIR.defaultBlockState());
+        }
+        void layout() {
+            target("main_entry", 8, 1, 0);
+            switch (s.kind()) {
+                case FREIGHT_STATION -> station();
+                case POST_OFFICE -> post();
+                case COMMUNAL_DEPOT -> depot();
+                case EXPEDITION_OFFICE -> expedition();
+                case OBSERVATORY -> observatory();
+                case RAIL_WORKSHOP -> railway();
+                case PUMP_STATION -> pumping();
+                case SUBSTATION -> substation();
+                case GREENHOUSE -> greenhouse();
+                case VOID_DOCK -> dock();
+                case RADIO_RELAY -> radio();
+                case PHOTO_CLUB -> photo();
+                case IMPOSSIBLE_SERVICE -> impossible();
+                case CONSTRUCTION_REFUGE -> refuge();
+            }
+        }
+        void shell(int x0, int floor, int z0, int x1, int ceiling, int z1) {
+            for (int y = floor; y <= ceiling; y++) for (int z = z0; z <= z1; z++) for (int x = x0; x <= x1; x++) {
+                boolean wall = x == x0 || x == x1 || z == z0 || z == z1;
+                set(x, y, z, y == floor || y == ceiling ? Blocks.SMOOTH_STONE.defaultBlockState()
+                    : wall ? LostCityPalette.masonry(s.seed(), x, y, z) : Blocks.AIR.defaultBlockState());
+            }
+        }
+        void gable(int x0, int z0, int x1, int z1, int y) {
+            int rise = Math.min(3, (x1 - x0) / 2);
+            for (int step = 0; step <= rise; step++)
+                box(x0 + step, y + step, z0, x1 - step, y + step, z1, step == rise ? Blocks.STONE_BRICK_SLAB : Blocks.STONE_BRICKS);
+        }
+        void door(int x, int y, int z, Direction facing) { door(x, y, z, facing, false); }
+        void door(int x, int y, int z, Direction facing, boolean right) {
+            BlockState state = Blocks.DARK_OAK_DOOR.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, facing)
+                .setValue(BlockStateProperties.DOOR_HINGE, right ? DoorHingeSide.RIGHT : DoorHingeSide.LEFT)
+                .setValue(BlockStateProperties.OPEN, false).setValue(BlockStateProperties.POWERED, false);
+            set(x, y, z, state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF, DoubleBlockHalf.LOWER));
+            set(x, y + 1, z, state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF, DoubleBlockHalf.UPPER));
+        }
+        void doubleDoor(int x, int y, int z) { door(x, y, z, Direction.SOUTH, true); door(x + 1, y, z, Direction.SOUTH, false); }
+        void northWindows(int x0, int x1, int z, int y) { box(x0, y, z, x1, y + 1, z, Blocks.GLASS_PANE); }
+        void hang(int x, int ceiling, int z) { set(x, ceiling - 1, z, Blocks.LANTERN.defaultBlockState().setValue(BlockStateProperties.HANGING, true)); }
+        void seat(int x, int y, int z, Direction view) {
+            set(x, y, z, Blocks.DARK_OAK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, view.getOpposite()));
+        }
+        void lever(int x, int y, int z, Direction facing) {
+            set(x, y, z, Blocks.LEVER.defaultBlockState().setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR)
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, facing));
+        }
+        void rail(int x, int z, RailShape shape) { set(x, 1, z, Blocks.RAIL.defaultBlockState().setValue(BlockStateProperties.RAIL_SHAPE, shape)); }
+        void loot(int x, int y, int z, int approachX, int approachZ) {
+            target("loot_approach", approachX, y, approachZ);
+            if (out != null) out.chest(rx(x, z), y, rz(x, z), ResourceKey.create(Registries.LOOT_TABLE,
+                SanctuaryMod.id("chests/heritage19/" + s.kind().name().toLowerCase(Locale.ROOT))), s.seed() ^ 0x19CA7A10L);
+        }
+        void stairs(int x, int z, int base, int rise) {
+            for (int step = 1; step <= rise; step++) for (int xx = x; xx <= x + 1; xx++) {
+                box(xx, base + step + 1, z + step - 1, xx, base + step + 3, z + step - 1, Blocks.AIR);
+                set(xx, base + step - 1, z + step - 1, Blocks.STONE_BRICKS);
+                set(xx, base + step, z + step - 1, Blocks.STONE_BRICK_STAIRS.defaultBlockState()
+                    .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            }
+        }
+        void bed(int x, int y, int z, Direction facing) {
+            BlockState state = Blocks.BED.white().defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, facing);
+            set(x, y, z, state.setValue(BlockStateProperties.BED_PART, BedPart.FOOT));
+            set(x + facing.getStepX(), y, z + facing.getStepZ(), state.setValue(BlockStateProperties.BED_PART, BedPart.HEAD));
+            int wx = x + facing.getStepX() * 2, wz = z + facing.getStepZ() * 2;
+            Direction along = facing.getClockWise();
+            for (int side = -1; side <= 1; side++) for (int up = 0; up <= 2; up++)
+                set(wx + along.getStepX() * side, y + up, wz + along.getStepZ() * side, Blocks.SMOOTH_STONE);
+        }
+
+        void station() {
+            shell(4, 0, 3, 12, 6, 11); gable(4, 3, 12, 11, 6);
+            door(8, 1, 3, Direction.SOUTH); northWindows(5, 6, 3, 2); northWindows(10, 11, 3, 2);
+            box(5, 1, 5, 6, 1, 5, Blocks.SMOOTH_STONE); set(5, 1, 8, Blocks.BARREL); seat(10, 1, 5, Direction.WEST);
+            for (int z = 2; z <= 14; z++) rail(2, z, RailShape.NORTH_SOUTH);
+            set(2, 1, 15, Blocks.DARK_OAK_FENCE);
+            rail(8, 0, RailShape.NORTH_SOUTH); rail(8, 1, RailShape.NORTH_WEST);
+            for (int x = 3; x <= 7; x++) rail(x, 1, RailShape.EAST_WEST);
+            rail(2, 1, RailShape.SOUTH_EAST);
+            box(0, 5, 5, 3, 5, 11, Blocks.DARK_OAK_PLANKS);
+            for (int z : new int[] {5, 11}) box(1, 1, z, 1, 4, z, Blocks.STRIPPED_OAK_LOG);
+            shell(9, 0, 11, 15, 4, 15); door(10, 1, 11, Direction.SOUTH); door(12, 1, 15, Direction.NORTH);
+            set(10, 1, 13, Blocks.SMOOTH_STONE); lever(10, 2, 13, Direction.EAST);
+            northWindows(13, 14, 15, 2); hang(8, 6, 7); hang(12, 4, 12);
+            target("ticket_counter", 8, 1, 5); target("freight_platform", 3, 1, 9); target("signal_office", 12, 1, 12);
+            target("secondary_entry", 12, 1, 16); loot(14, 1, 14, 13, 14);
+        }
+        void post() {
+            shell(2, 0, 2, 14, 6, 14); door(8, 1, 2, Direction.SOUTH);
+            northWindows(3, 6, 2, 2); northWindows(10, 13, 2, 2);
+            box(3, 1, 7, 13, 5, 7, Blocks.SMOOTH_STONE); door(8, 1, 7, Direction.SOUTH);
+            box(4, 1, 6, 6, 1, 6, Blocks.DARK_OAK_PLANKS);
+            for (int z = 9; z <= 11; z++) { set(3, 1, z, Blocks.BARREL); set(3, 2, z, Blocks.BARREL); }
+            set(6, 1, 10, Blocks.CRAFTING_TABLE); set(8, 1, 12, Blocks.BARREL);
+            shell(10, 0, 10, 14, 6, 14); door(10, 1, 12, Direction.EAST); door(14, 1, 12, Direction.WEST);
+            set(11, 1, 11, Blocks.CARTOGRAPHY_TABLE); hang(8, 6, 4); hang(7, 6, 10); hang(12, 6, 12);
+            target("public_hall", 8, 1, 4); target("sorting_aisle", 7, 1, 10); target("factor_office", 12, 1, 12);
+            target("secondary_entry", 15, 1, 12); loot(13, 1, 13, 12, 13);
+        }
+        void depot() {
+            shell(1, 0, 2, 15, 9, 14); gable(1, 2, 15, 14, 9);
+            box(7, 1, 2, 9, 3, 2, Blocks.AIR); door(4, 1, 2, Direction.SOUTH);
+            for (int z : new int[] {5, 8}) {
+                box(4, 1, z, 5, 1, z + 1, Blocks.DARK_OAK_PLANKS); set(4, 2, z, Blocks.BARREL);
+                box(11, 1, z, 13, 1, z + 1, Blocks.DARK_OAK_PLANKS); set(13, 2, z + 1, Blocks.BARREL);
+            }
+            box(2, 5, 10, 14, 5, 13, Blocks.SMOOTH_STONE);
+            for (int x = 5; x <= 14; x++) set(x, 6, 10, Blocks.IRON_BARS);
+            shell(10, 5, 10, 14, 9, 14); door(10, 6, 12, Direction.EAST);
+            set(11, 6, 11, Blocks.LECTERN.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            stairs(2, 5, 0, 5); door(15, 1, 12, Direction.WEST); hang(8, 9, 6); hang(12, 9, 12);
+            for (int z = 0; z <= 8; z++) rail(8, z, RailShape.NORTH_SOUTH);
+            set(8, 1, 9, Blocks.DARK_OAK_FENCE);
+            target("unloading_bay", 8, 1, 5); target("inventory_mezzanine", 5, 6, 12);
+            target("secondary_entry", 16, 1, 12); loot(13, 6, 13, 12, 13);
+        }
+        void expedition() {
+            shell(2, 0, 2, 12, 6, 12); door(8, 1, 2, Direction.SOUTH);
+            northWindows(3, 5, 2, 2); northWindows(10, 11, 2, 2);
+            set(4, 1, 4, Blocks.CARTOGRAPHY_TABLE); set(5, 1, 4, Blocks.LECTERN.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH)); set(3, 1, 6, Blocks.BARREL);
+            shell(2, 0, 8, 6, 6, 12); door(6, 1, 10, Direction.WEST); set(3, 1, 9, Blocks.BOOKSHELF);
+            box(3, 0, 13, 14, 0, 15, Blocks.DARK_OAK_PLANKS);
+            box(3, 1, 15, 14, 1, 15, Blocks.DARK_OAK_FENCE); door(10, 1, 12, Direction.NORTH);
+            seat(6, 1, 13, Direction.SOUTH); hang(8, 6, 5); hang(4, 6, 10);
+            target("expedition_table", 5, 1, 5); target("balcony", 10, 1, 14);
+            target("secondary_entry", 10, 1, 13); loot(3, 1, 11, 4, 11);
+        }
+        boolean tower(int x, int z) { return x >= 3 && x <= 13 && z >= 3 && z <= 13 && Math.abs(x - 8) + Math.abs(z - 8) <= 8; }
+        void observatory() {
+            for (int y = 0; y <= 12; y++) for (int z = 3; z <= 13; z++) for (int x = 3; x <= 13; x++) if (tower(x, z)) {
+                boolean wall = !tower(x - 1, z) || !tower(x + 1, z) || !tower(x, z - 1) || !tower(x, z + 1);
+                set(x, y, z, y == 0 || y == 6 || y == 12 ? Blocks.SMOOTH_STONE.defaultBlockState()
+                    : wall ? LostCityPalette.masonry(s.seed(), x, y, z) : Blocks.AIR.defaultBlockState());
+                if (y == 12 && wall) set(x, 13, z, Blocks.IRON_BARS);
+            }
+            door(8, 1, 3, Direction.SOUTH); door(8, 1, 13, Direction.NORTH);
+            northWindows(7, 9, 3, 8); box(13, 8, 7, 13, 9, 9, Blocks.GLASS_PANE);
+            shell(9, 0, 9, 12, 4, 12); door(9, 1, 10, Direction.EAST); set(10, 1, 11, Blocks.BARREL);
+            set(10, 7, 5, Blocks.CARTOGRAPHY_TABLE); set(11, 7, 8, Blocks.SMOOTH_STONE); lever(11, 8, 8, Direction.WEST);
+            stairs(4, 5, 0, 6); stairs(4, 5, 6, 6);
+            box(4, 12, 11, 6, 12, 11, Blocks.SMOOTH_STONE); box(4, 13, 11, 6, 15, 11, Blocks.AIR);
+            box(10, 13, 9, 10, 18, 9, Blocks.DARK_OAK_FENCE); box(9, 18, 9, 11, 18, 9, Blocks.IRON_BARS);
+            hang(8, 6, 6); hang(10, 4, 11);
+            target("instruments", 9, 7, 8); target("sky_platform", 8, 13, 8);
+            target("secondary_entry", 8, 1, 14); loot(11, 1, 11, 11, 10);
+        }
+        void railway() {
+            shell(1, 0, 2, 15, 6, 14); gable(1, 2, 15, 14, 6); doubleDoor(7, 1, 2);
+            for (int z = 3; z <= 13; z++) for (int x : new int[] {5, 11}) set(x, 1, z, Blocks.RAIL);
+            box(4, 1, 2, 6, 3, 2, Blocks.AIR); rail(8, 0, RailShape.NORTH_SOUTH); rail(8, 1, RailShape.NORTH_WEST);
+            rail(7, 1, RailShape.EAST_WEST); rail(6, 1, RailShape.EAST_WEST); rail(5, 1, RailShape.SOUTH_EAST); rail(5, 2, RailShape.NORTH_SOUTH);
+            box(7, -2, 5, 9, -2, 11, Blocks.SMOOTH_STONE); box(7, -1, 5, 9, 0, 11, Blocks.AIR);
+            for (int step = 0; step <= 2; step++) set(8, -step, 4 + step, Blocks.STONE_BRICK_STAIRS.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            for (int z = 6; z <= 11; z++) { set(6, 1, z, Blocks.IRON_BARS); set(10, 1, z, Blocks.IRON_BARS); }
+            set(2, 1, 4, Blocks.CRAFTING_TABLE); set(3, 1, 4, Blocks.FURNACE.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            set(2, 1, 6, Blocks.GRINDSTONE.defaultBlockState().setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR));
+            shell(1, 0, 10, 5, 5, 14); door(5, 1, 12, Direction.WEST); door(8, 1, 14, Direction.NORTH);
+            set(5, 1, 9, Blocks.DARK_OAK_FENCE);
+            set(2, 1, 11, Blocks.ANVIL); hang(8, 6, 8); hang(3, 5, 12);
+            target("maintenance_pit", 8, -1, 9); target("workbench", 3, 1, 5);
+            target("secondary_entry", 8, 1, 15); loot(2, 1, 13, 3, 13);
+        }
+        void pumping() {
+            shell(2, 0, 3, 9, 6, 12); door(8, 1, 3, Direction.SOUTH);
+            set(3, 1, 5, Blocks.DISPENSER.defaultBlockState().setValue(BlockStateProperties.FACING, Direction.EAST));
+            set(4, 1, 5, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 3));
+            set(3, 2, 5, Blocks.POLISHED_ANDESITE); box(3, 3, 5, 3, 5, 8, Blocks.IRON_BARS);
+            for (int x : new int[] {10, 15}) for (int z : new int[] {5, 11}) box(x, 1, z, x, 7, z, Blocks.POLISHED_ANDESITE);
+            shell(10, 8, 5, 15, 13, 11); box(11, 9, 6, 14, 11, 10, Blocks.WATER);
+            box(10, 3, 6, 14, 3, 13, Blocks.SMOOTH_STONE); stairs(10, 3, 0, 3);
+            shell(2, 0, 10, 6, 5, 15); door(5, 1, 10, Direction.SOUTH); door(5, 1, 15, Direction.NORTH);
+            set(3, 1, 11, Blocks.BARREL); hang(7, 6, 7); hang(4, 5, 12);
+            target("pump_room", 6, 1, 6); target("reservoir_walkway", 13, 4, 12);
+            target("secondary_entry", 5, 1, 16); loot(3, 1, 14, 4, 14);
+        }
+        void substation() {
+            for (int z = 2; z <= 14; z++) { set(1, 1, z, Blocks.IRON_BARS); set(15, 1, z, Blocks.IRON_BARS); }
+            for (int x = 1; x <= 15; x++) if (x < 7 || x > 9) set(x, 1, 2, Blocks.IRON_BARS);
+            for (int z : new int[] {5, 8}) {
+                box(3, 1, z, 4, 2, z + 1, Blocks.POLISHED_ANDESITE); box(3, 3, z, 4, 3, z, Blocks.IRON_BARS);
+            }
+            shell(10, 0, 4, 15, 5, 10); door(10, 1, 6, Direction.EAST); northWindows(12, 14, 4, 2);
+            set(12, 1, 5, Blocks.SMOOTH_STONE); lever(12, 2, 5, Direction.SOUTH); set(14, 1, 5, Blocks.CRAFTING_TABLE);
+            shell(10, 0, 10, 15, 5, 15); door(12, 1, 10, Direction.SOUTH); door(15, 1, 13, Direction.WEST);
+            box(6, -2, 10, 7, -2, 13, Blocks.SMOOTH_STONE); box(6, -1, 10, 7, 0, 13, Blocks.AIR);
+            for (int step = 0; step <= 2; step++) set(6, -step, 9 + step, Blocks.STONE_BRICK_STAIRS.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            hang(13, 5, 7); hang(12, 5, 13); target("distribution_yard", 8, 1, 6); target("cable_trench", 6, -1, 12);
+            target("secondary_entry", 16, 1, 13); loot(14, 1, 14, 13, 14);
+        }
+        void greenhouse() {
+            shell(1, 0, 2, 11, 6, 14);
+            for (int y = 2; y <= 5; y++) for (int z = 3; z <= 13; z++) { set(1, y, z, Blocks.GLASS); set(11, y, z, Blocks.GLASS); }
+            northWindows(2, 5, 2, 2); northWindows(7, 10, 2, 2); door(6, 1, 2, Direction.SOUTH);
+            for (int x = 2; x <= 10; x++) for (int z = 3; z <= 13; z++) set(x, 6, z, x == 6 ? Blocks.SMOOTH_STONE : Blocks.GLASS);
+            for (int x : new int[] {2, 3, 4, 8, 9, 10}) for (int z = 4; z <= 10; z++) {
+                set(x, 0, z, Blocks.FARMLAND.defaultBlockState().setValue(BlockStateProperties.MOISTURE, 7));
+                set(x, 1, z, Blocks.WHEAT.defaultBlockState().setValue(BlockStateProperties.AGE_7,
+                    2 + LostCityPalette.roll(s.seed(), x, 1, z, 6)));
+            }
+            set(3, 0, 6, Blocks.WATER); set(9, 0, 6, Blocks.WATER);
+            set(3, 1, 6, Blocks.AIR); set(9, 1, 6, Blocks.AIR);
+            shell(11, 0, 9, 15, 5, 15); door(11, 1, 12, Direction.EAST); door(13, 1, 15, Direction.NORTH);
+            set(12, 1, 10, Blocks.CRAFTING_TABLE); set(13, 1, 10, Blocks.FLOWER_POT); set(9, 1, 12, Blocks.COMPOSTER);
+            hang(6, 6, 5); hang(13, 5, 12); target("glasshouse_aisle", 6, 1, 7); target("potting_shed", 13, 1, 12);
+            target("secondary_entry", 13, 1, 16); loot(14, 1, 14, 13, 14);
+        }
+        void dock() {
+            box(0, 0, 0, 16, 0, 16, Blocks.DARK_OAK_PLANKS); box(0, 1, 16, 16, 1, 16, Blocks.DARK_OAK_FENCE);
+            box(0, 1, 1, 0, 1, 15, Blocks.DARK_OAK_FENCE); box(16, 1, 1, 16, 1, 15, Blocks.DARK_OAK_FENCE);
+            shell(2, 0, 3, 7, 5, 10); door(7, 1, 6, Direction.WEST); seat(3, 1, 5, Direction.EAST);
+            shell(2, 0, 10, 7, 5, 15); door(5, 1, 10, Direction.SOUTH); door(7, 1, 13, Direction.WEST);
+            box(12, 1, 5, 12, 11, 5, Blocks.STRIPPED_OAK_LOG); box(8, 11, 5, 14, 11, 5, Blocks.STRIPPED_OAK_LOG);
+            box(14, 7, 5, 14, 10, 5, Blocks.IRON_CHAIN); hang(10, 11, 5); hang(5, 5, 6); hang(5, 5, 12);
+            target("departure_deck", 8, 1, 14); target("waiting_room", 5, 1, 6); target("secondary_entry", 8, 1, 13);
+            loot(3, 1, 14, 4, 14);
+        }
+        void radio() {
+            shell(2, 0, 3, 10, 6, 12); door(8, 1, 3, Direction.SOUTH); northWindows(3, 5, 3, 2);
+            bed(4, 1, 5, Direction.NORTH); set(8, 1, 5, Blocks.CARTOGRAPHY_TABLE);
+            shell(2, 0, 8, 6, 6, 12); door(6, 1, 10, Direction.WEST); door(2, 1, 10, Direction.EAST);
+            box(11, 5, 6, 15, 5, 10, Blocks.SMOOTH_STONE);
+            for (int x : new int[] {11, 15}) for (int z : new int[] {6, 10}) box(x, 1, z, x, 4, z, Blocks.POLISHED_ANDESITE);
+            box(13, 1, 8, 13, 18, 8, Blocks.POLISHED_ANDESITE); box(11, 17, 8, 15, 17, 8, Blocks.IRON_BARS);
+            box(13, 19, 8, 13, 21, 8, Blocks.IRON_BARS); stairs(11, 1, 0, 5);
+            hang(7, 6, 6); hang(4, 6, 10);
+            target("caretaker_room", 7, 1, 6); target("antenna_platform", 12, 6, 9); target("secondary_entry", 1, 1, 10);
+            loot(3, 1, 11, 4, 11);
+        }
+        void photo() {
+            shell(2, 0, 2, 14, 6, 14); door(8, 1, 2, Direction.SOUTH); northWindows(3, 6, 2, 2); northWindows(10, 13, 2, 2);
+            box(3, 1, 8, 13, 5, 8, Blocks.SMOOTH_STONE); door(4, 1, 8, Direction.SOUTH);
+            box(8, 1, 9, 8, 5, 13, Blocks.SMOOTH_STONE); door(8, 1, 11, Direction.EAST);
+            box(10, 1, 5, 12, 1, 5, Blocks.DARK_OAK_PLANKS); set(3, 1, 4, Blocks.BOOKSHELF);
+            for (int z : new int[] {10, 12}) set(3, 1, z, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 3));
+            box(11, 4, 10, 11, 5, 12, Blocks.IRON_CHAIN); set(12, 1, 10, Blocks.CRAFTING_TABLE);
+            door(12, 1, 14, Direction.NORTH); hang(8, 6, 4); hang(5, 6, 11); hang(12, 6, 12);
+            target("club_room", 8, 1, 4); target("darkroom", 5, 1, 11); target("drying_room", 10, 1, 11);
+            target("secondary_entry", 12, 1, 15); loot(13, 1, 13, 12, 13);
+        }
+        void impossible() {
+            shell(3, 0, 2, 11, 4, 7); door(8, 1, 2, Direction.SOUTH);
+            for (int z = 3; z <= 5; z++) { set(4, 1, z, Blocks.BARREL); set(4, 2, z, Blocks.BARREL); }
+            seat(10, 1, 4, Direction.WEST);
+            shell(1, 0, 7, 15, 10, 15); door(8, 1, 7, Direction.SOUTH);
+            for (int x = 2; x <= 14; x++) for (int z = 8; z <= 14; z++) set(x, 0, z,
+                ((x + z) & 1) == 0 ? Blocks.CALCITE : Blocks.POLISHED_ANDESITE);
+            for (int x : new int[] {3, 6, 10, 13}) box(x, 1, 11, x, 9, 11, Blocks.CALCITE);
+            shell(1, 0, 12, 5, 5, 15); door(5, 1, 13, Direction.WEST); door(3, 1, 15, Direction.NORTH);
+            set(2, 2, 12, Blocks.GLASS); set(2, 1, 13, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 2));
+            hang(8, 4, 4); hang(8, 10, 11); hang(3, 5, 13);
+            target("lockers", 8, 1, 4); target("oversized_tiled_hall", 8, 1, 11);
+            target("secondary_entry", 3, 1, 16); loot(2, 1, 14, 3, 14);
+        }
+        void refuge() {
+            box(3, 4, 5, 14, 4, 15, Blocks.DARK_OAK_PLANKS);
+            for (int x : new int[] {3, 14}) for (int z : new int[] {5, 15}) box(x, 1, z, x, 3, z, Blocks.STONE_BRICKS);
+            shell(5, 4, 6, 13, 10, 14); gable(5, 6, 13, 14, 10); door(8, 5, 6, Direction.SOUTH);
+            bed(6, 5, 8, Direction.NORTH); set(12, 5, 8, Blocks.CRAFTING_TABLE);
+            shell(6, 0, 9, 11, 4, 14); door(6, 1, 11, Direction.EAST);
+            // Carry the ladder through the floor so opening the hatch leaves a climbable lip.
+            for (int y = 1; y <= 4; y++) set(10, y, 11, Blocks.LADDER.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST));
+            set(10, 5, 11, Blocks.DARK_OAK_TRAPDOOR.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST)
+                .setValue(BlockStateProperties.HALF, Half.BOTTOM));
+            stairs(7, 1, 0, 4); box(2, 1, 3, 3, 11, 4, Blocks.STONE_BRICKS); box(2, 11, 3, 14, 11, 4, Blocks.STRIPPED_OAK_LOG);
+            hang(10, 10, 8); hang(8, 4, 12);
+            target("suspended_hut", 9, 5, 8); target("hidden_floor_hatch", 10, 5, 11); target("secondary_entry", 5, 1, 11);
+            loot(7, 1, 13, 8, 13);
+        }
+    }
+}
@@ -0,0 +1,643 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.worldgen.city.LostCityPalette;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import fr.koka.sanctuary.worldgen.detail.ConnectedBlocks20;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.AttachFace;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DoorHingeSide;
+import net.minecraft.world.level.block.state.properties.DoubleBlockHalf;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.block.state.properties.RailShape;
+
+/** Generation20 architectural rendition of the immutable generation19 site geometry. The saved site controls all geometry and loot.
+ * Site writes are local to minX/floorY/minZ; route writes are local to the segment's minimum bounds. */
+public final class HeritageRenderer20 {
+    private HeritageRenderer20() {}
+    public record Target(String name, int x, int y, int z) {}
+
+    /** These are already rotated local standing positions, not world coordinates. */
+    public static List<Target> targets(HeritagePlan19.Site site) {
+        var b = new Builder(site, null); b.layout(); return List.copyOf(b.targets);
+    }
+    public static void render(HeritagePlan19.Site site, LostCityRenderer.BlockWriter writer) {
+        var buffer = ConnectedBlocks20.buffer(writer);
+        var b = new Builder(site, buffer); b.ground(); b.layout();
+        // Footings have absolute saved coordinates and must not undergo a second facade rotation.
+        for (var support : site.supports()) for (int y = support.minY(); y <= support.maxY(); y++)
+            buffer.set(support.x() - site.minX(), y - site.floorY(), support.z() - site.minZ(),
+                y == support.minY() ? Blocks.CHISELED_TUFF_BRICKS.defaultBlockState() : Blocks.STONE_BRICKS.defaultBlockState());
+        buffer.flush();
+    }
+    public static void renderSegment(HeritagePlan19.Segment segment, LostCityRenderer.BlockWriter writer) {
+        var buffer = ConnectedBlocks20.buffer(writer);
+        var occupied = new java.util.HashSet<Long>();
+        for (var cell : segment.cells()) occupied.add(columnKey(cell.x(), cell.z()));
+        int x0 = segment.minX(), y0 = segment.minY(), z0 = segment.minZ();
+        for (var cell : segment.cells()) {
+            int x = cell.x() - x0, z = cell.z() - z0, floor = cell.floorY() - y0;
+            for (int y = cell.minY() - y0; y <= floor; y++) {
+                Block material = Blocks.STONE_BRICKS;
+                if (y == floor) {
+                    boolean edge = false;
+                    for (Direction d : new Direction[] {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST}) {
+                        int nx = cell.x() + d.getStepX(), nz = cell.z() + d.getStepZ();
+                        // Unknown neighboring chunks are continuations, not artificial crosswise curbs.
+                        if ((nx >> 4) == segment.startChunkX() && (nz >> 4) == segment.startChunkZ()
+                                && !occupied.contains(columnKey(nx, nz))) edge = true;
+                    }
+                    if (cell.rail() != HeritagePlan19.Rail.NONE) material = Math.floorMod(cell.x() + cell.z(), 3) == 0 ? Blocks.OAK_PLANKS : Blocks.GRAVEL;
+                    else if (edge) material = Math.floorMod(cell.x() + cell.z(), 8) == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS;
+                    else material = LostCityPalette.roll(segment.seed(), cell.x(), 0, cell.z(), 5) == 0 ? Blocks.TUFF : Blocks.POLISHED_TUFF;
+                }
+                buffer.set(x, y, z, material.defaultBlockState());
+            }
+            for (int y = floor + 1; y <= floor + 3; y++) buffer.set(x, y, z, Blocks.AIR.defaultBlockState());
+            if (cell.railPresent()) buffer.set(x, floor + 1, z, Blocks.RAIL.defaultBlockState()
+                .setValue(BlockStateProperties.RAIL_SHAPE, RailShape.valueOf(cell.rail().name())));
+        }
+        buffer.flush();
+    }
+    private static long columnKey(int x, int z) { return (long) x << 32 ^ z & 0xffffffffL; }
+
+    private static final class Builder {
+        final HeritagePlan19.Site s;
+        final LostCityRenderer.BlockWriter out;
+        final List<Target> targets = new ArrayList<>();
+        final Rotation rotation;
+        Builder(HeritagePlan19.Site s, LostCityRenderer.BlockWriter out) {
+            this.s = s; this.out = out;
+            rotation = switch (s.facing()) { case 1 -> Rotation.CLOCKWISE_90; case 2 -> Rotation.CLOCKWISE_180;
+                case 3 -> Rotation.COUNTERCLOCKWISE_90; default -> Rotation.NONE; };
+        }
+        int rx(int x, int z) { return switch (s.facing()) { case 1 -> 16 - z; case 2 -> 16 - x; case 3 -> z; default -> x; }; }
+        int rz(int x, int z) { return switch (s.facing()) { case 1 -> x; case 2 -> 16 - z; case 3 -> 16 - x; default -> z; }; }
+        void set(int x, int y, int z, BlockState state) {
+            if (x < 0 || x > 16 || z < 0 || z > 16 || y < -s.foundationDepth() || y > s.height())
+                throw new IllegalArgumentException("Heritage " + s.kind() + " renderer escaped saved site: " + x + "/" + y + "/" + z);
+            if (out != null) out.set(rx(x, z), y, rz(x, z), state.rotate(rotation));
+        }
+        void set(int x, int y, int z, Block b) { set(x, y, z, b.defaultBlockState()); }
+        void box(int x0, int y0, int z0, int x1, int y1, int z1, Block b) {
+            for (int y = y0; y <= y1; y++) for (int z = z0; z <= z1; z++) for (int x = x0; x <= x1; x++) set(x, y, z, b);
+        }
+        void target(String name, int x, int y, int z) { targets.add(new Target(name, rx(x, z), y, rz(x, z))); }
+        void ground() {
+            for (int y = -s.foundationDepth(); y <= s.height(); y++) for (int z = 0; z <= 16; z++) for (int x = 0; x <= 16; x++)
+                set(x, y, z, y < 0 ? Blocks.STONE_BRICKS.defaultBlockState() : y == 0
+                    ? (x == 0 || z == 0 || x == 16 || z == 16 ? Blocks.TUFF_BRICKS
+                        : x >= 7 && x <= 9 ? Blocks.POLISHED_TUFF
+                        : LostCityPalette.roll(s.seed(), x, 0, z, 7) == 0 ? Blocks.TUFF : Blocks.ANDESITE).defaultBlockState()
+                    : Blocks.AIR.defaultBlockState());
+        }
+        void layout() {
+            target("main_entry", 8, 1, 0);
+            switch (s.kind()) {
+                case FREIGHT_STATION -> station();
+                case POST_OFFICE -> post();
+                case COMMUNAL_DEPOT -> depot();
+                case EXPEDITION_OFFICE -> expedition();
+                case OBSERVATORY -> observatory();
+                case RAIL_WORKSHOP -> railway();
+                case PUMP_STATION -> pumping();
+                case SUBSTATION -> substation();
+                case GREENHOUSE -> greenhouse();
+                case VOID_DOCK -> dock();
+                case RADIO_RELAY -> radio();
+                case PHOTO_CLUB -> photo();
+                case IMPOSSIBLE_SERVICE -> impossible();
+                case CONSTRUCTION_REFUGE -> refuge();
+            }
+            architecture();
+        }
+        void shell(int x0, int floor, int z0, int x1, int ceiling, int z1) {
+            for (int y = floor; y <= ceiling; y++) for (int z = z0; z <= z1; z++) for (int x = x0; x <= x1; x++) {
+                boolean wall = x == x0 || x == x1 || z == z0 || z == z1;
+                set(x, y, z, y == floor ? floorMaterial().defaultBlockState() : y == ceiling ? Blocks.TUFF_BRICKS.defaultBlockState()
+                    : wall ? wallMaterial(y - floor, ceiling - floor).defaultBlockState() : Blocks.AIR.defaultBlockState());
+            }
+        }
+        Block floorMaterial() {
+            return switch (s.kind()) {
+                case POST_OFFICE, EXPEDITION_OFFICE, RADIO_RELAY, CONSTRUCTION_REFUGE -> Blocks.OAK_PLANKS;
+                case PHOTO_CLUB, GREENHOUSE -> Blocks.BIRCH_PLANKS;
+                case IMPOSSIBLE_SERVICE -> Blocks.POLISHED_DIORITE;
+                default -> Blocks.POLISHED_ANDESITE;
+            };
+        }
+        Block wallMaterial(int y, int height) {
+            if (y == 1) return Blocks.STONE_BRICKS;
+            if (y == height - 1) return Blocks.CHISELED_TUFF_BRICKS;
+            return switch (s.kind()) {
+                case POST_OFFICE -> Blocks.POLISHED_GRANITE;
+                case FREIGHT_STATION, OBSERVATORY, PHOTO_CLUB -> Blocks.POLISHED_DIORITE;
+                case EXPEDITION_OFFICE, GREENHOUSE -> Blocks.BIRCH_PLANKS;
+                case RADIO_RELAY, VOID_DOCK, CONSTRUCTION_REFUGE -> Blocks.OAK_PLANKS;
+                case PUMP_STATION, SUBSTATION -> Blocks.ANDESITE;
+                case COMMUNAL_DEPOT, RAIL_WORKSHOP, IMPOSSIBLE_SERVICE -> Blocks.TUFF_BRICKS;
+            };
+        }
+        // These additions compose each use separately; all thresholds and maintenance passages stay in the saved footprint.
+        void architecture() {
+            switch (s.kind()) {
+                case FREIGHT_STATION -> stationArchitecture();
+                case POST_OFFICE -> postArchitecture();
+                case COMMUNAL_DEPOT -> depotArchitecture();
+                case EXPEDITION_OFFICE -> expeditionArchitecture();
+                case OBSERVATORY -> observatoryArchitecture();
+                case RAIL_WORKSHOP -> railwayArchitecture();
+                case PUMP_STATION -> pumpingArchitecture();
+                case SUBSTATION -> substationArchitecture();
+                case GREENHOUSE -> greenhouseArchitecture();
+                case VOID_DOCK -> dockArchitecture();
+                case RADIO_RELAY -> radioArchitecture();
+                case PHOTO_CLUB -> photoArchitecture();
+                case IMPOSSIBLE_SERVICE -> impossibleArchitecture();
+                case CONSTRUCTION_REFUGE -> refugeArchitecture();
+            }
+        }
+        void slab(int x, int y, int z, Block block) { set(x, y, z, block.defaultBlockState().setValue(BlockStateProperties.SLAB_TYPE, net.minecraft.world.level.block.state.properties.SlabType.BOTTOM)); }
+        void stair(int x, int y, int z, Block block, Direction direction, Half half) {
+            set(x, y, z, block.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, direction).setValue(BlockStateProperties.HALF, half));
+        }
+        /** Cut only the four exterior corner cells; the two adjacent wall faces keep the interior sealed. */
+        void bevel(int x0, int z0, int x1, int z1, int low, int high) {
+            for (int x : new int[] {x0, x1}) for (int z : new int[] {z0, z1}) {
+                box(x, low, z, x, high, z, Blocks.AIR);
+                set(x, low - 1, z, Blocks.CHISELED_STONE_BRICKS);
+            }
+        }
+        void rim(int x0, int z0, int x1, int z1, int y, Block material) {
+            for (int x = x0; x <= x1; x++) { slab(x, y, z0, material); slab(x, y, z1, material); }
+            for (int z = z0 + 1; z < z1; z++) { slab(x0, y, z, material); slab(x1, y, z, material); }
+        }
+        void screen(int x0, int z, int x1, int y) {
+            for (int x = x0; x <= x1; x++) set(x, y, z, Blocks.BIRCH_TRAPDOOR.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH).setValue(BlockStateProperties.OPEN, true));
+        }
+        void stationArchitecture() {
+            bevel(4, 3, 12, 11, 1, 6);
+            box(4, 7, 3, 12, 10, 11, Blocks.AIR);
+            rim(3, 2, 13, 12, 6, Blocks.TUFF_BRICK_SLAB);
+            for (int z = 5; z <= 9; z++) for (int x = 5; x <= 11; x++) {
+                if (x == 5 || x == 11 || z == 5 || z == 9) box(x, 7, z, x, 8, z, Blocks.GLASS_PANE);
+                slab(x, 9, z, Blocks.POLISHED_DIORITE_SLAB);
+            }
+            // Open the former ceiling beneath the sealed roof glazing. The middle beam
+            // still supports the existing hanging lantern and joins the two hall walls.
+            for (int z = 6; z <= 8; z++) for (int x = 6; x <= 10; x++) {
+                if (z != 7) set(x, 6, z, Blocks.AIR);
+                set(x, 9, z, Blocks.GLASS);
+            }
+            // The long cantilever reads as a train platform, distinct from the glazed passenger hall.
+            box(0, 5, 4, 3, 5, 12, Blocks.OAK_PLANKS);
+            for (int z : new int[] {4, 8, 12}) stair(0, 4, z, Blocks.TUFF_BRICK_STAIRS, Direction.EAST, Half.TOP);
+            for (int z : new int[] {5, 11}) box(1, 1, z, 1, 4, z, Blocks.OAK_WOOD);
+            for (int x : new int[] {4, 12}) box(x, 2, 4, x, 4, 4, Blocks.CHISELED_TUFF_BRICKS);
+            screen(5, 4, 6, 3); box(5, 0, 4, 11, 0, 10, Blocks.POLISHED_DIORITE);
+            box(7, 0, 3, 9, 0, 10, Blocks.BIRCH_PLANKS);
+            rim(9, 11, 15, 15, 4, Blocks.TUFF_BRICK_SLAB);
+        }
+        void postArchitecture() {
+            bevel(2, 2, 14, 14, 1, 6); rim(1, 1, 15, 15, 6, Blocks.POLISHED_GRANITE_SLAB);
+            box(4, 7, 4, 12, 7, 12, Blocks.TUFF_BRICKS);
+            rim(4, 4, 12, 12, 8, Blocks.TUFF_BRICK_SLAB);
+            for (int x : new int[] {2, 7, 9, 14}) {
+                box(x, 3, 1, x, 4, 1, Blocks.POLISHED_DIORITE);
+                stair(x, 5, 1, Blocks.TUFF_BRICK_STAIRS, Direction.SOUTH, Half.TOP);
+            }
+            box(5, 4, 1, 11, 4, 1, Blocks.CHISELED_TUFF_BRICKS);
+            box(4, 1, 6, 6, 1, 6, Blocks.BIRCH_PLANKS); screen(4, 6, 6, 3);
+            for (int z = 9; z <= 12; z++) { set(3, 3, z, Blocks.OAK_TRAPDOOR.defaultBlockState().setValue(BlockStateProperties.HALF, Half.TOP)); }
+            for (int x = 4; x <= 12; x++) set(x, 0, 5, x % 2 == 0 ? Blocks.POLISHED_GRANITE : Blocks.OAK_PLANKS);
+            box(10, 0, 8, 13, 0, 9, Blocks.DIORITE);
+        }
+        void depotArchitecture() {
+            bevel(1, 2, 15, 14, 1, 9); box(1, 10, 2, 15, 14, 14, Blocks.AIR);
+            // Three industrial north-light roof bays, not another pitched house roof.
+            for (int z : new int[] {3, 7, 11}) {
+                box(2, 10, z, 14, 11, z, Blocks.GLASS_PANE);
+                for (int x = 2; x <= 14; x++) {
+                    slab(x, 12, z, Blocks.TUFF_BRICK_SLAB);
+                    stair(x, 11, z + 1, Blocks.TUFF_BRICK_STAIRS, Direction.NORTH, Half.BOTTOM);
+                    stair(x, 10, z + 2, Blocks.TUFF_BRICK_STAIRS, Direction.NORTH, Half.BOTTOM);
+                    if (x > 2 && x < 14) {
+                        // Both transparent faces close the north-light well, while the
+                        // retained roof outside these bands keeps the warehouse sealed.
+                        set(x, 9, z, Blocks.GLASS);
+                        set(x, 12, z, Blocks.GLASS);
+                    }
+                }
+            }
+            for (int z : new int[] {3, 7, 11}) for (int x : new int[] {1, 15}) box(x, 1, z, x, 9, z, Blocks.POLISHED_ANDESITE);
+            for (int x : new int[] {6, 10}) { box(x, 1, 1, x, 3, 1, Blocks.CHISELED_TUFF); stair(x, 4, 1, Blocks.TUFF_BRICK_STAIRS, Direction.SOUTH, Half.TOP); }
+            box(6, 4, 1, 10, 4, 1, Blocks.TUFF_BRICKS);
+            for (int z : new int[] {5, 8}) for (int x : new int[] {4, 12}) { set(x, 3, z, Blocks.OAK_TRAPDOOR.defaultBlockState().setValue(BlockStateProperties.HALF, Half.TOP)); }
+            for (int z = 3; z <= 9; z++) { set(6, 0, z, Blocks.TUFF_BRICKS); set(10, 0, z, Blocks.TUFF_BRICKS); }
+            box(2, 5, 11, 9, 5, 13, Blocks.BIRCH_PLANKS);
+        }
+        void expeditionArchitecture() {
+            bevel(2, 2, 12, 12, 1, 6); rim(1, 1, 13, 13, 6, Blocks.TUFF_BRICK_SLAB);
+            box(3, 7, 3, 6, 9, 7, Blocks.BIRCH_WOOD); rim(3, 3, 6, 7, 10, Blocks.TUFF_BRICK_SLAB);
+            box(4, 8, 3, 5, 8, 3, Blocks.GLASS_PANE);
+            // Sheltered map table, archive wing and broad shaded rear balcony.
+            box(7, 4, 1, 9, 4, 1, Blocks.CHISELED_TUFF_BRICKS);
+            for (int x : new int[] {2, 12}) box(x, 2, 3, x, 5, 3, Blocks.OAK_WOOD);
+            screen(3, 4, 5, 3); box(3, 3, 9, 5, 3, 9, Blocks.OAK_PLANKS);
+            for (int x = 3; x <= 14; x++) for (int z = 13; z <= 15; z++) set(x, 0, z, x % 3 == 0 ? Blocks.OAK_WOOD : Blocks.OAK_PLANKS);
+            for (int x = 3; x <= 14; x++) slab(x, 5, 14, Blocks.BIRCH_SLAB);
+            box(3, 1, 14, 3, 4, 14, Blocks.BIRCH_FENCE); box(14, 1, 14, 14, 4, 14, Blocks.BIRCH_FENCE);
+        }
+        void observatoryArchitecture() {
+            // Eight faceted buttresses below a broken observatory dome with an open central viewing slot.
+            for (int[] p : new int[][] {{3, 8}, {5, 4}, {11, 4}, {13, 8}, {11, 12}, {5, 12}}) {
+                box(p[0], 1, p[1], p[0], 11, p[1], Blocks.DIORITE);
+                set(p[0], 5, p[1], Blocks.CHISELED_TUFF_BRICKS);
+                stair(p[0], 12, p[1], Blocks.TUFF_BRICK_STAIRS, p[0] < 8 ? Direction.EAST : Direction.WEST, Half.BOTTOM);
+            }
+            for (int z = 4; z <= 12; z++) for (int x = 4; x <= 12; x++) {
+                int distance = Math.max(Math.abs(x - 8), Math.abs(z - 8));
+                if (distance == 4) set(x, 15, z, Blocks.GLASS_PANE);
+                if (distance == 3 && x != 8) slab(x, 17, z, Blocks.TUFF_BRICK_SLAB);
+            }
+            for (int x : new int[] {4, 12}) for (int z : new int[] {5, 11}) box(x, 13, z, x, 14, z, Blocks.CHISELED_TUFF_BRICKS);
+            // Four short ribs visibly carry the inset crown; the central viewing slot stays open.
+            for (int x : new int[] {4, 12}) for (int z : new int[] {5, 11}) {
+                box(x, 15, z, x, 16, z, Blocks.CHISELED_TUFF_BRICKS);
+                stair(x < 8 ? x + 1 : x - 1, 16, z, Blocks.TUFF_BRICK_STAIRS,
+                    x < 8 ? Direction.EAST : Direction.WEST, Half.BOTTOM);
+            }
+            box(7, 0, 5, 9, 0, 11, Blocks.BIRCH_PLANKS);
+            box(7, 6, 5, 9, 6, 10, Blocks.POLISHED_DIORITE);
+        }
+        void railwayArchitecture() {
+            bevel(1, 2, 15, 14, 1, 6); box(1, 7, 2, 15, 10, 14, Blocks.AIR);
+            // Broad barrel-vault ribs sit above the two inspection tracks.
+            for (int z = 2; z <= 14; z++) for (int x = 1; x <= 15; x++) {
+                int rise = Math.min(3, Math.min(x - 1, 15 - x));
+                if (z % 4 == 2) set(x, 6 + rise, z, Blocks.TUFF_BRICKS);
+                else if (x >= 6 && x <= 10) set(x, 6 + rise, z, Blocks.GLASS);
+                else slab(x, 6 + rise, z, Blocks.TUFF_BRICK_SLAB);
+            }
+            for (int z : new int[] {3, 7, 11}) for (int x : new int[] {1, 15}) box(x, 2, z, x, 5, z, Blocks.GRANITE);
+            box(7, -2, 5, 9, -2, 11, Blocks.POLISHED_ANDESITE);
+            for (int z = 6; z <= 11; z++) { set(7, -1, z, Blocks.CHISELED_TUFF_BRICKS); set(9, -1, z, Blocks.CHISELED_TUFF_BRICKS); }
+            // Side ledges leave the one-block maintenance aisle and its stairs clear.
+            screen(2, 3, 3, 3); box(2, 3, 11, 4, 3, 11, Blocks.OAK_PLANKS);
+        }
+        void pumpingArchitecture() {
+            bevel(2, 3, 9, 12, 1, 6); rim(1, 2, 9, 13, 6, Blocks.TUFF_BRICK_SLAB);
+            for (int x : new int[] {10, 15}) for (int z : new int[] {5, 11}) {
+                box(x, 1, z, x, 7, z, Blocks.CHISELED_TUFF_BRICKS);
+                set(x, 8, z, Blocks.POLISHED_ANDESITE);
+            }
+            rim(9, 4, 16, 12, 13, Blocks.TUFF_BRICK_SLAB);
+            for (int x = 10; x <= 15; x++) for (int z = 5; z <= 11; z++) slab(x, 14, z, Blocks.POLISHED_ANDESITE_SLAB);
+            box(3, 7, 5, 3, 12, 5, Blocks.TUFF_BRICK_WALL);
+            box(3, 3, 6, 3, 5, 8, Blocks.IRON_BARS);
+            box(3, 0, 4, 8, 0, 9, Blocks.ANDESITE); box(5, 0, 4, 7, 0, 10, Blocks.POLISHED_DIORITE);
+            screen(3, 11, 4, 3);
+        }
+        void substationArchitecture() {
+            bevel(10, 4, 15, 10, 1, 5); rim(9, 3, 16, 15, 5, Blocks.TUFF_BRICK_SLAB);
+            for (int z : new int[] {2, 6, 10, 14}) for (int x : new int[] {1, 15}) {
+                set(x, 0, z, Blocks.STONE_BRICKS); set(x, 1, z, Blocks.CHISELED_TUFF_BRICKS);
+            }
+            box(2, 4, 5, 5, 4, 5, Blocks.IRON_BARS); box(2, 4, 8, 5, 4, 8, Blocks.IRON_BARS);
+            for (int x : new int[] {2, 5}) for (int z : new int[] {5, 8}) box(x, 1, z, x, 3, z, Blocks.TUFF_BRICK_WALL);
+            box(11, 6, 5, 14, 6, 9, Blocks.POLISHED_TUFF);
+            for (int z = 5; z <= 9; z += 2) screen(11, z, 14, 7);
+            for (int z = 3; z <= 8; z++) set(7, 0, z, Blocks.GRANITE);
+            box(6, -2, 10, 7, -2, 13, Blocks.CHISELED_TUFF_BRICKS);
+        }
+        void greenhouseArchitecture() {
+            // Tall birch ribs and a steep glass ridge give the glasshouse an agricultural silhouette.
+            for (int z = 2; z <= 14; z++) for (int x = 1; x <= 11; x++) {
+                int rise = Math.min(3, Math.min(x - 1, 11 - x));
+                if (z == 2 || z == 8 || z == 14 || x == 6) set(x, 6 + rise, z, Blocks.BIRCH_WOOD);
+                else set(x, 6 + rise, z, Blocks.GLASS);
+            }
+            for (int z : new int[] {3, 7, 11}) { box(1, 1, z, 1, 5, z, Blocks.BIRCH_WOOD); box(11, 1, z, 11, 5, z, Blocks.BIRCH_WOOD); }
+            rim(11, 9, 15, 15, 5, Blocks.TUFF_BRICK_SLAB);
+            box(12, 3, 10, 14, 3, 10, Blocks.OAK_PLANKS); screen(12, 10, 14, 4);
+            for (int z = 3; z <= 13; z++) set(6, 0, z, z % 3 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.POLISHED_TUFF);
+        }
+        void dockArchitecture() {
+            for (int x = 1; x <= 15; x++) for (int z = 0; z <= 15; z++) set(x, 0, z, x % 4 == 0 ? Blocks.OAK_WOOD : Blocks.OAK_PLANKS);
+            bevel(2, 3, 7, 10, 1, 5); rim(1, 2, 8, 15, 5, Blocks.BIRCH_SLAB);
+            for (int z : new int[] {2, 8, 14}) {
+                box(0, 1, z, 0, 2, z, Blocks.CHISELED_TUFF_BRICKS);
+                box(16, 1, z, 16, 2, z, Blocks.CHISELED_TUFF_BRICKS);
+                slab(0, 3, z, Blocks.TUFF_BRICK_SLAB); slab(16, 3, z, Blocks.TUFF_BRICK_SLAB);
+            }
+            // Brackets and a separated customs roof leave the departure platform open to the void.
+            for (int x = 2; x <= 7; x++) for (int z = 3; z <= 15; z++) if (z % 4 == 0) slab(x, 6, z, Blocks.BIRCH_SLAB);
+            stair(11, 9, 5, Blocks.OAK_STAIRS, Direction.EAST, Half.TOP);
+            stair(13, 9, 5, Blocks.OAK_STAIRS, Direction.WEST, Half.TOP);
+            screen(3, 4, 6, 3);
+        }
+        void radioArchitecture() {
+            bevel(2, 3, 10, 12, 1, 6); rim(1, 2, 10, 13, 6, Blocks.TUFF_BRICK_SLAB);
+            for (int x = 2; x <= 10; x++) for (int z = 3; z <= 12; z++) {
+                int roofY = 7 + Math.min(2, Math.min(x - 2, 10 - x));
+                slab(x, roofY, z, x <= 5 ? Blocks.BIRCH_SLAB : Blocks.TUFF_BRICK_SLAB);
+            }
+            box(9, 7, 4, 9, 11, 4, Blocks.CHISELED_TUFF_BRICKS);
+            for (int y : new int[] {10, 14, 18}) { box(12, y, 8, 14, y, 8, Blocks.IRON_BARS); box(13, y, 7, 13, y, 9, Blocks.IRON_BARS); }
+            box(3, 0, 8, 5, 0, 11, Blocks.BIRCH_PLANKS); screen(7, 4, 9, 3);
+        }
+        void photoArchitecture() {
+            bevel(2, 2, 14, 14, 1, 6); rim(1, 1, 15, 15, 6, Blocks.POLISHED_DIORITE_SLAB);
+            box(3, 7, 9, 13, 7, 13, Blocks.TUFF_BRICKS); rim(3, 9, 13, 13, 8, Blocks.TUFF_BRICK_SLAB);
+            for (int x : new int[] {2, 6, 10, 14}) stair(x, 4, 1, Blocks.TUFF_BRICK_STAIRS, Direction.SOUTH, Half.TOP);
+            box(3, 5, 1, 13, 5, 1, Blocks.CHISELED_TUFF_BRICKS);
+            for (int x = 4; x <= 12; x++) set(x, 0, 4, x % 2 == 0 ? Blocks.POLISHED_GRANITE : Blocks.BIRCH_PLANKS);
+            box(3, 0, 9, 7, 0, 13, Blocks.POLISHED_ANDESITE);
+            screen(10, 5, 12, 3); box(3, 3, 10, 3, 3, 12, Blocks.OAK_PLANKS);
+        }
+        void impossibleArchitecture() {
+            bevel(1, 7, 15, 15, 1, 10); rim(0, 6, 16, 16, 10, Blocks.TUFF_BRICK_SLAB);
+            box(4, 11, 9, 12, 11, 13, Blocks.TUFF_BRICKS);
+            for (int x : new int[] {4, 12}) for (int z : new int[] {9, 13}) set(x, 12, z, Blocks.CHISELED_TUFF);
+            // A cramped civil facade gives way to an over-scaled, deliberately ceremonial service hall.
+            for (int x : new int[] {3, 11}) box(x, 1, 1, x, 4, 1, Blocks.CHISELED_TUFF_BRICKS);
+            box(3, 5, 1, 11, 5, 1, Blocks.TUFF_BRICKS);
+            for (int x : new int[] {3, 6, 10, 13}) { set(x, 1, 11, Blocks.CHISELED_TUFF_BRICKS); set(x, 8, 11, Blocks.CHISELED_TUFF_BRICKS); }
+            screen(4, 3, 4, 3); box(12, 3, 14, 14, 3, 14, Blocks.BIRCH_PLANKS);
+        }
+        void refugeArchitecture() {
+            bevel(5, 6, 13, 14, 5, 10);
+            box(5, 11, 6, 13, 14, 14, Blocks.AIR);
+            for (int z = 6; z <= 14; z++) for (int x = 5; x <= 13; x++) {
+                int rise = Math.min(3, (x - 5) / 2);
+                slab(x, 11 + rise, z, (z & 1) == 0 ? Blocks.BIRCH_SLAB : Blocks.TUFF_BRICK_SLAB);
+            }
+            for (int x : new int[] {3, 14}) for (int z : new int[] {5, 15}) { box(x, 1, z, x, 3, z, Blocks.CHISELED_TUFF_BRICKS); set(x, 4, z, Blocks.OAK_WOOD); }
+            for (int z = 6; z <= 14; z += 4) box(4, 1, z, 4, 7, z, Blocks.IRON_BARS);
+            box(2, 1, 3, 3, 10, 4, Blocks.TUFF_BRICKS); box(2, 11, 3, 14, 11, 4, Blocks.OAK_WOOD);
+            // Upper lockers and a birch sleeping corner avoid the saved hatch and its complete ladder shaft.
+            screen(11, 7, 12, 7); box(7, 4, 7, 11, 4, 9, Blocks.BIRCH_PLANKS);
+        }
+
+        void gable(int x0, int z0, int x1, int z1, int y) {
+            int rise = Math.min(3, (x1 - x0) / 2);
+            for (int step = 0; step <= rise; step++)
+                box(x0 + step, y + step, z0, x1 - step, y + step, z1, step == rise ? Blocks.STONE_BRICK_SLAB : Blocks.STONE_BRICKS);
+        }
+        void door(int x, int y, int z, Direction facing) { door(x, y, z, facing, false); }
+        void door(int x, int y, int z, Direction facing, boolean right) {
+            BlockState state = Blocks.DARK_OAK_DOOR.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, facing)
+                .setValue(BlockStateProperties.DOOR_HINGE, right ? DoorHingeSide.RIGHT : DoorHingeSide.LEFT)
+                .setValue(BlockStateProperties.OPEN, false).setValue(BlockStateProperties.POWERED, false);
+            set(x, y, z, state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF, DoubleBlockHalf.LOWER));
+            set(x, y + 1, z, state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF, DoubleBlockHalf.UPPER));
+        }
+        void doubleDoor(int x, int y, int z) { door(x, y, z, Direction.SOUTH, true); door(x + 1, y, z, Direction.SOUTH, false); }
+        void northWindows(int x0, int x1, int z, int y) { box(x0, y, z, x1, y + 1, z, Blocks.GLASS_PANE); }
+        void hang(int x, int ceiling, int z) { set(x, ceiling - 1, z, Blocks.LANTERN.defaultBlockState().setValue(BlockStateProperties.HANGING, true)); }
+        void seat(int x, int y, int z, Direction view) {
+            set(x, y, z, Blocks.DARK_OAK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, view.getOpposite()));
+        }
+        void lever(int x, int y, int z, Direction facing) {
+            set(x, y, z, Blocks.LEVER.defaultBlockState().setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR)
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, facing));
+        }
+        void rail(int x, int z, RailShape shape) { set(x, 1, z, Blocks.RAIL.defaultBlockState().setValue(BlockStateProperties.RAIL_SHAPE, shape)); }
+        void loot(int x, int y, int z, int approachX, int approachZ) {
+            target("loot_approach", approachX, y, approachZ);
+            if (out != null) out.chest(rx(x, z), y, rz(x, z), ResourceKey.create(Registries.LOOT_TABLE,
+                SanctuaryMod.id("chests/heritage19/" + s.kind().name().toLowerCase(Locale.ROOT))), s.seed() ^ 0x19CA7A10L);
+        }
+        void stairs(int x, int z, int base, int rise) {
+            for (int step = 1; step <= rise; step++) for (int xx = x; xx <= x + 1; xx++) {
+                box(xx, base + step + 1, z + step - 1, xx, base + step + 3, z + step - 1, Blocks.AIR);
+                set(xx, base + step - 1, z + step - 1, Blocks.STONE_BRICKS);
+                set(xx, base + step, z + step - 1, Blocks.STONE_BRICK_STAIRS.defaultBlockState()
+                    .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            }
+        }
+        void bed(int x, int y, int z, Direction facing) {
+            BlockState state = Blocks.BED.white().defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, facing);
+            set(x, y, z, state.setValue(BlockStateProperties.BED_PART, BedPart.FOOT));
+            set(x + facing.getStepX(), y, z + facing.getStepZ(), state.setValue(BlockStateProperties.BED_PART, BedPart.HEAD));
+            int wx = x + facing.getStepX() * 2, wz = z + facing.getStepZ() * 2;
+            Direction along = facing.getClockWise();
+            for (int side = -1; side <= 1; side++) for (int up = 0; up <= 2; up++)
+                set(wx + along.getStepX() * side, y + up, wz + along.getStepZ() * side, Blocks.SMOOTH_STONE);
+        }
+
+        void station() {
+            shell(4, 0, 3, 12, 6, 11); gable(4, 3, 12, 11, 6);
+            door(8, 1, 3, Direction.SOUTH); northWindows(5, 6, 3, 2); northWindows(10, 11, 3, 2);
+            box(5, 1, 5, 6, 1, 5, Blocks.SMOOTH_STONE); set(5, 1, 8, Blocks.BARREL); seat(10, 1, 5, Direction.WEST);
+            for (int z = 2; z <= 14; z++) rail(2, z, RailShape.NORTH_SOUTH);
+            set(2, 1, 15, Blocks.DARK_OAK_FENCE);
+            rail(8, 0, RailShape.NORTH_SOUTH); rail(8, 1, RailShape.NORTH_WEST);
+            for (int x = 3; x <= 7; x++) rail(x, 1, RailShape.EAST_WEST);
+            rail(2, 1, RailShape.SOUTH_EAST);
+            box(0, 5, 5, 3, 5, 11, Blocks.DARK_OAK_PLANKS);
+            for (int z : new int[] {5, 11}) box(1, 1, z, 1, 4, z, Blocks.STRIPPED_OAK_LOG);
+            shell(9, 0, 11, 15, 4, 15); door(10, 1, 11, Direction.SOUTH); door(12, 1, 15, Direction.NORTH);
+            set(10, 1, 13, Blocks.SMOOTH_STONE); lever(10, 2, 13, Direction.EAST);
+            northWindows(13, 14, 15, 2); hang(8, 6, 7); hang(12, 4, 12);
+            target("ticket_counter", 8, 1, 5); target("freight_platform", 3, 1, 9); target("signal_office", 12, 1, 12);
+            target("secondary_entry", 12, 1, 16); loot(14, 1, 14, 13, 14);
+        }
+        void post() {
+            shell(2, 0, 2, 14, 6, 14); door(8, 1, 2, Direction.SOUTH);
+            northWindows(3, 6, 2, 2); northWindows(10, 13, 2, 2);
+            box(3, 1, 7, 13, 5, 7, Blocks.SMOOTH_STONE); door(8, 1, 7, Direction.SOUTH);
+            box(4, 1, 6, 6, 1, 6, Blocks.DARK_OAK_PLANKS);
+            for (int z = 9; z <= 11; z++) { set(3, 1, z, Blocks.BARREL); set(3, 2, z, Blocks.BARREL); }
+            set(6, 1, 10, Blocks.CRAFTING_TABLE); set(8, 1, 12, Blocks.BARREL);
+            shell(10, 0, 10, 14, 6, 14); door(10, 1, 12, Direction.EAST); door(14, 1, 12, Direction.WEST);
+            set(11, 1, 11, Blocks.CARTOGRAPHY_TABLE); hang(8, 6, 4); hang(7, 6, 10); hang(12, 6, 12);
+            target("public_hall", 8, 1, 4); target("sorting_aisle", 7, 1, 10); target("factor_office", 12, 1, 12);
+            target("secondary_entry", 15, 1, 12); loot(13, 1, 13, 12, 13);
+        }
+        void depot() {
+            shell(1, 0, 2, 15, 9, 14); gable(1, 2, 15, 14, 9);
+            box(7, 1, 2, 9, 3, 2, Blocks.AIR); door(4, 1, 2, Direction.SOUTH);
+            for (int z : new int[] {5, 8}) {
+                box(4, 1, z, 5, 1, z + 1, Blocks.DARK_OAK_PLANKS); set(4, 2, z, Blocks.BARREL);
+                box(11, 1, z, 13, 1, z + 1, Blocks.DARK_OAK_PLANKS); set(13, 2, z + 1, Blocks.BARREL);
+            }
+            box(2, 5, 10, 14, 5, 13, Blocks.SMOOTH_STONE);
+            for (int x = 5; x <= 14; x++) set(x, 6, 10, Blocks.IRON_BARS);
+            shell(10, 5, 10, 14, 9, 14); door(10, 6, 12, Direction.EAST);
+            set(11, 6, 11, Blocks.LECTERN.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            stairs(2, 5, 0, 5); door(15, 1, 12, Direction.WEST); hang(8, 9, 6); hang(12, 9, 12);
+            for (int z = 0; z <= 8; z++) rail(8, z, RailShape.NORTH_SOUTH);
+            set(8, 1, 9, Blocks.DARK_OAK_FENCE);
+            target("unloading_bay", 8, 1, 5); target("inventory_mezzanine", 5, 6, 12);
+            target("secondary_entry", 16, 1, 12); loot(13, 6, 13, 12, 13);
+        }
+        void expedition() {
+            shell(2, 0, 2, 12, 6, 12); door(8, 1, 2, Direction.SOUTH);
+            northWindows(3, 5, 2, 2); northWindows(10, 11, 2, 2);
+            set(4, 1, 4, Blocks.CARTOGRAPHY_TABLE); set(5, 1, 4, Blocks.LECTERN.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH)); set(3, 1, 6, Blocks.BARREL);
+            shell(2, 0, 8, 6, 6, 12); door(6, 1, 10, Direction.WEST); set(3, 1, 9, Blocks.BOOKSHELF);
+            box(3, 0, 13, 14, 0, 15, Blocks.DARK_OAK_PLANKS);
+            box(3, 1, 15, 14, 1, 15, Blocks.DARK_OAK_FENCE); door(10, 1, 12, Direction.NORTH);
+            seat(6, 1, 13, Direction.SOUTH); hang(8, 6, 5); hang(4, 6, 10);
+            target("expedition_table", 5, 1, 5); target("balcony", 10, 1, 14);
+            target("secondary_entry", 10, 1, 13); loot(3, 1, 11, 4, 11);
+        }
+        boolean tower(int x, int z) { return x >= 3 && x <= 13 && z >= 3 && z <= 13 && Math.abs(x - 8) + Math.abs(z - 8) <= 8; }
+        void observatory() {
+            for (int y = 0; y <= 12; y++) for (int z = 3; z <= 13; z++) for (int x = 3; x <= 13; x++) if (tower(x, z)) {
+                boolean wall = !tower(x - 1, z) || !tower(x + 1, z) || !tower(x, z - 1) || !tower(x, z + 1);
+                set(x, y, z, y == 0 || y == 6 || y == 12 ? Blocks.SMOOTH_STONE.defaultBlockState()
+                    : wall ? LostCityPalette.masonry(s.seed(), x, y, z) : Blocks.AIR.defaultBlockState());
+                if (y == 12 && wall) set(x, 13, z, Blocks.IRON_BARS);
+            }
+            door(8, 1, 3, Direction.SOUTH); door(8, 1, 13, Direction.NORTH);
+            northWindows(7, 9, 3, 8); box(13, 8, 7, 13, 9, 9, Blocks.GLASS_PANE);
+            shell(9, 0, 9, 12, 4, 12); door(9, 1, 10, Direction.EAST); set(10, 1, 11, Blocks.BARREL);
+            set(10, 7, 5, Blocks.CARTOGRAPHY_TABLE); set(11, 7, 8, Blocks.SMOOTH_STONE); lever(11, 8, 8, Direction.WEST);
+            stairs(4, 5, 0, 6); stairs(4, 5, 6, 6);
+            box(4, 12, 11, 6, 12, 11, Blocks.SMOOTH_STONE); box(4, 13, 11, 6, 15, 11, Blocks.AIR);
+            box(10, 13, 9, 10, 18, 9, Blocks.DARK_OAK_FENCE); box(9, 18, 9, 11, 18, 9, Blocks.IRON_BARS);
+            hang(8, 6, 6); hang(10, 4, 11);
+            target("instruments", 9, 7, 8); target("sky_platform", 8, 13, 8);
+            target("secondary_entry", 8, 1, 14); loot(11, 1, 11, 11, 10);
+        }
+        void railway() {
+            shell(1, 0, 2, 15, 6, 14); gable(1, 2, 15, 14, 6); doubleDoor(7, 1, 2);
+            for (int z = 3; z <= 13; z++) for (int x : new int[] {5, 11}) set(x, 1, z, Blocks.RAIL);
+            box(4, 1, 2, 6, 3, 2, Blocks.AIR); rail(8, 0, RailShape.NORTH_SOUTH); rail(8, 1, RailShape.NORTH_WEST);
+            rail(7, 1, RailShape.EAST_WEST); rail(6, 1, RailShape.EAST_WEST); rail(5, 1, RailShape.SOUTH_EAST); rail(5, 2, RailShape.NORTH_SOUTH);
+            box(7, -2, 5, 9, -2, 11, Blocks.SMOOTH_STONE); box(7, -1, 5, 9, 0, 11, Blocks.AIR);
+            for (int step = 0; step <= 2; step++) set(8, -step, 4 + step, Blocks.STONE_BRICK_STAIRS.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            for (int z = 6; z <= 11; z++) { set(6, 1, z, Blocks.IRON_BARS); set(10, 1, z, Blocks.IRON_BARS); }
+            set(2, 1, 4, Blocks.CRAFTING_TABLE); set(3, 1, 4, Blocks.FURNACE.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            set(2, 1, 6, Blocks.GRINDSTONE.defaultBlockState().setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR));
+            shell(1, 0, 10, 5, 5, 14); door(5, 1, 12, Direction.WEST); door(8, 1, 14, Direction.NORTH);
+            set(5, 1, 9, Blocks.DARK_OAK_FENCE);
+            set(2, 1, 11, Blocks.ANVIL); hang(8, 6, 8); hang(3, 5, 12);
+            target("maintenance_pit", 8, -1, 9); target("workbench", 3, 1, 5);
+            target("secondary_entry", 8, 1, 15); loot(2, 1, 13, 3, 13);
+        }
+        void pumping() {
+            shell(2, 0, 3, 9, 6, 12); door(8, 1, 3, Direction.SOUTH);
+            set(3, 1, 5, Blocks.DISPENSER.defaultBlockState().setValue(BlockStateProperties.FACING, Direction.EAST));
+            set(4, 1, 5, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 3));
+            set(3, 2, 5, Blocks.POLISHED_ANDESITE); box(3, 3, 5, 3, 5, 8, Blocks.IRON_BARS);
+            for (int x : new int[] {10, 15}) for (int z : new int[] {5, 11}) box(x, 1, z, x, 7, z, Blocks.POLISHED_ANDESITE);
+            shell(10, 8, 5, 15, 13, 11); box(11, 9, 6, 14, 11, 10, Blocks.WATER);
+            box(10, 3, 6, 14, 3, 13, Blocks.SMOOTH_STONE); stairs(10, 3, 0, 3);
+            shell(2, 0, 10, 6, 5, 15); door(5, 1, 10, Direction.SOUTH); door(5, 1, 15, Direction.NORTH);
+            set(3, 1, 11, Blocks.BARREL); hang(7, 6, 7); hang(4, 5, 12);
+            target("pump_room", 6, 1, 6); target("reservoir_walkway", 13, 4, 12);
+            target("secondary_entry", 5, 1, 16); loot(3, 1, 14, 4, 14);
+        }
+        void substation() {
+            for (int z = 2; z <= 14; z++) { set(1, 1, z, Blocks.IRON_BARS); set(15, 1, z, Blocks.IRON_BARS); }
+            for (int x = 1; x <= 15; x++) if (x < 7 || x > 9) set(x, 1, 2, Blocks.IRON_BARS);
+            for (int z : new int[] {5, 8}) {
+                box(3, 1, z, 4, 2, z + 1, Blocks.POLISHED_ANDESITE); box(3, 3, z, 4, 3, z, Blocks.IRON_BARS);
+            }
+            shell(10, 0, 4, 15, 5, 10); door(10, 1, 6, Direction.EAST); northWindows(12, 14, 4, 2);
+            set(12, 1, 5, Blocks.SMOOTH_STONE); lever(12, 2, 5, Direction.SOUTH); set(14, 1, 5, Blocks.CRAFTING_TABLE);
+            shell(10, 0, 10, 15, 5, 15); door(12, 1, 10, Direction.SOUTH); door(15, 1, 13, Direction.WEST);
+            box(6, -2, 10, 7, -2, 13, Blocks.SMOOTH_STONE); box(6, -1, 10, 7, 0, 13, Blocks.AIR);
+            for (int step = 0; step <= 2; step++) set(6, -step, 9 + step, Blocks.STONE_BRICK_STAIRS.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            hang(13, 5, 7); hang(12, 5, 13); target("distribution_yard", 8, 1, 6); target("cable_trench", 6, -1, 12);
+            target("secondary_entry", 16, 1, 13); loot(14, 1, 14, 13, 14);
+        }
+        void greenhouse() {
+            shell(1, 0, 2, 11, 6, 14);
+            for (int y = 2; y <= 5; y++) for (int z = 3; z <= 13; z++) { set(1, y, z, Blocks.GLASS); set(11, y, z, Blocks.GLASS); }
+            northWindows(2, 5, 2, 2); northWindows(7, 10, 2, 2); door(6, 1, 2, Direction.SOUTH);
+            for (int x = 2; x <= 10; x++) for (int z = 3; z <= 13; z++) set(x, 6, z, x == 6 ? Blocks.SMOOTH_STONE : Blocks.GLASS);
+            for (int x : new int[] {2, 3, 4, 8, 9, 10}) for (int z = 4; z <= 10; z++) {
+                set(x, 0, z, Blocks.FARMLAND.defaultBlockState().setValue(BlockStateProperties.MOISTURE, 7));
+                set(x, 1, z, Blocks.WHEAT.defaultBlockState().setValue(BlockStateProperties.AGE_7,
+                    2 + LostCityPalette.roll(s.seed(), x, 1, z, 6)));
+            }
+            set(3, 0, 6, Blocks.WATER); set(9, 0, 6, Blocks.WATER);
+            set(3, 1, 6, Blocks.AIR); set(9, 1, 6, Blocks.AIR);
+            shell(11, 0, 9, 15, 5, 15); door(11, 1, 12, Direction.EAST); door(13, 1, 15, Direction.NORTH);
+            set(12, 1, 10, Blocks.CRAFTING_TABLE); set(13, 1, 10, Blocks.FLOWER_POT); set(9, 1, 12, Blocks.COMPOSTER);
+            hang(6, 6, 5); hang(13, 5, 12); target("glasshouse_aisle", 6, 1, 7); target("potting_shed", 13, 1, 12);
+            target("secondary_entry", 13, 1, 16); loot(14, 1, 14, 13, 14);
+        }
+        void dock() {
+            box(0, 0, 0, 16, 0, 16, Blocks.DARK_OAK_PLANKS); box(0, 1, 16, 16, 1, 16, Blocks.DARK_OAK_FENCE);
+            box(0, 1, 1, 0, 1, 15, Blocks.DARK_OAK_FENCE); box(16, 1, 1, 16, 1, 15, Blocks.DARK_OAK_FENCE);
+            shell(2, 0, 3, 7, 5, 10); door(7, 1, 6, Direction.WEST); seat(3, 1, 5, Direction.EAST);
+            shell(2, 0, 10, 7, 5, 15); door(5, 1, 10, Direction.SOUTH); door(7, 1, 13, Direction.WEST);
+            box(12, 1, 5, 12, 11, 5, Blocks.STRIPPED_OAK_LOG); box(8, 11, 5, 14, 11, 5, Blocks.STRIPPED_OAK_LOG);
+            box(14, 7, 5, 14, 10, 5, Blocks.IRON_CHAIN); hang(10, 11, 5); hang(5, 5, 6); hang(5, 5, 12);
+            target("departure_deck", 8, 1, 14); target("waiting_room", 5, 1, 6); target("secondary_entry", 8, 1, 13);
+            loot(3, 1, 14, 4, 14);
+        }
+        void radio() {
+            shell(2, 0, 3, 10, 6, 12); door(8, 1, 3, Direction.SOUTH); northWindows(3, 5, 3, 2);
+            bed(4, 1, 5, Direction.NORTH); set(8, 1, 5, Blocks.CARTOGRAPHY_TABLE);
+            shell(2, 0, 8, 6, 6, 12); door(6, 1, 10, Direction.WEST); door(2, 1, 10, Direction.EAST);
+            box(11, 5, 6, 15, 5, 10, Blocks.SMOOTH_STONE);
+            for (int x : new int[] {11, 15}) for (int z : new int[] {6, 10}) box(x, 1, z, x, 4, z, Blocks.POLISHED_ANDESITE);
+            box(13, 1, 8, 13, 18, 8, Blocks.POLISHED_ANDESITE); box(11, 17, 8, 15, 17, 8, Blocks.IRON_BARS);
+            box(13, 19, 8, 13, 21, 8, Blocks.IRON_BARS); stairs(11, 1, 0, 5);
+            hang(7, 6, 6); hang(4, 6, 10);
+            target("caretaker_room", 7, 1, 6); target("antenna_platform", 12, 6, 9); target("secondary_entry", 1, 1, 10);
+            loot(3, 1, 11, 4, 11);
+        }
+        void photo() {
+            shell(2, 0, 2, 14, 6, 14); door(8, 1, 2, Direction.SOUTH); northWindows(3, 6, 2, 2); northWindows(10, 13, 2, 2);
+            box(3, 1, 8, 13, 5, 8, Blocks.SMOOTH_STONE); door(4, 1, 8, Direction.SOUTH);
+            box(8, 1, 9, 8, 5, 13, Blocks.SMOOTH_STONE); door(8, 1, 11, Direction.EAST);
+            box(10, 1, 5, 12, 1, 5, Blocks.DARK_OAK_PLANKS); set(3, 1, 4, Blocks.BOOKSHELF);
+            for (int z : new int[] {10, 12}) set(3, 1, z, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 3));
+            box(11, 4, 10, 11, 5, 12, Blocks.IRON_CHAIN); set(12, 1, 10, Blocks.CRAFTING_TABLE);
+            door(12, 1, 14, Direction.NORTH); hang(8, 6, 4); hang(5, 6, 11); hang(12, 6, 12);
+            target("club_room", 8, 1, 4); target("darkroom", 5, 1, 11); target("drying_room", 10, 1, 11);
+            target("secondary_entry", 12, 1, 15); loot(13, 1, 13, 12, 13);
+        }
+        void impossible() {
+            shell(3, 0, 2, 11, 4, 7); door(8, 1, 2, Direction.SOUTH);
+            for (int z = 3; z <= 5; z++) { set(4, 1, z, Blocks.BARREL); set(4, 2, z, Blocks.BARREL); }
+            seat(10, 1, 4, Direction.WEST);
+            shell(1, 0, 7, 15, 10, 15); door(8, 1, 7, Direction.SOUTH);
+            for (int x = 2; x <= 14; x++) for (int z = 8; z <= 14; z++) set(x, 0, z,
+                ((x + z) & 1) == 0 ? Blocks.CALCITE : Blocks.POLISHED_ANDESITE);
+            for (int x : new int[] {3, 6, 10, 13}) box(x, 1, 11, x, 9, 11, Blocks.CALCITE);
+            shell(1, 0, 12, 5, 5, 15); door(5, 1, 13, Direction.WEST); door(3, 1, 15, Direction.NORTH);
+            set(2, 2, 12, Blocks.GLASS); set(2, 1, 13, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 2));
+            hang(8, 4, 4); hang(8, 10, 11); hang(3, 5, 13);
+            target("lockers", 8, 1, 4); target("oversized_tiled_hall", 8, 1, 11);
+            target("secondary_entry", 3, 1, 16); loot(2, 1, 14, 3, 14);
+        }
+        void refuge() {
+            box(3, 4, 5, 14, 4, 15, Blocks.DARK_OAK_PLANKS);
+            for (int x : new int[] {3, 14}) for (int z : new int[] {5, 15}) box(x, 1, z, x, 3, z, Blocks.STONE_BRICKS);
+            shell(5, 4, 6, 13, 10, 14); gable(5, 6, 13, 14, 10); door(8, 5, 6, Direction.SOUTH);
+            bed(6, 5, 8, Direction.NORTH); set(12, 5, 8, Blocks.CRAFTING_TABLE);
+            shell(6, 0, 9, 11, 4, 14); door(6, 1, 11, Direction.EAST);
+            // Carry the ladder through the floor so opening the hatch leaves a climbable lip.
+            for (int y = 1; y <= 4; y++) set(10, y, 11, Blocks.LADDER.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST));
+            set(10, 5, 11, Blocks.DARK_OAK_TRAPDOOR.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST)
+                .setValue(BlockStateProperties.HALF, Half.BOTTOM));
+            stairs(7, 1, 0, 4); box(2, 1, 3, 3, 11, 4, Blocks.STONE_BRICKS); box(2, 11, 3, 14, 11, 4, Blocks.STRIPPED_OAK_LOG);
+            hang(10, 10, 8); hang(8, 4, 12);
+            target("suspended_hut", 9, 5, 8); target("hidden_floor_hatch", 10, 5, 11); target("secondary_entry", 5, 1, 11);
+            loot(7, 1, 13, 8, 13);
+        }
+    }
+}
@@ -0,0 +1,42 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import com.mojang.serialization.MapCodec;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.util.ArrayList;
+import java.util.Optional;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureType;
+
+/** Island-scale routes are split into small independent native starts before rendering. */
+public final class HeritageStructure19 extends Structure {
+    public static final MapCodec<HeritageStructure19> CODEC = simpleCodec(HeritageStructure19::new);
+    public HeritageStructure19(StructureSettings settings) { super(settings); }
+
+    @Override protected Optional<GenerationStub> findGenerationPoint(GenerationContext context) {
+        if (!(context.chunkGenerator() instanceof SanctuaryChunkGenerator generator)
+                || (generator.rootGeneration() != 19 && generator.rootGeneration() != 20) || !generator.experimentalStructures()) return Optional.empty();
+        var island = generator.islandForChunk(context.chunkPos().x(), context.chunkPos().z());
+        if (island == null || !island.origin() || (island.generation() != generator.rootGeneration())) return Optional.empty();
+        var plan = generator.heritagePlan19();
+        int x = context.chunkPos().x(), z = context.chunkPos().z();
+        var pieces = new ArrayList<net.minecraft.world.level.levelgen.structure.StructurePiece>();
+        // Local route segments render before buildings. No piece needs a distant link endpoint loaded.
+        for (var segment : plan.segments())
+            if (segment.startChunkX() == x && segment.startChunkZ() == z)
+                pieces.add(generator.rootGeneration() == 20 ? new HeritagePiece20(segment) : new HeritagePiece19(segment));
+        for (var site : plan.sites()) if (site.startChunkX() == x && site.startChunkZ() == z)
+            pieces.add(generator.rootGeneration() == 20 ? new HeritagePiece20(site) : new HeritagePiece19(site));
+        if (pieces.isEmpty()) return Optional.empty();
+        for (var piece : pieces) {
+            var box = piece.getBoundingBox();
+            if (Math.abs((long) Math.floorDiv(box.minX(), 16) - x) > 7
+                    || Math.abs((long) Math.floorDiv(box.maxX(), 16) - x) > 7
+                    || Math.abs((long) Math.floorDiv(box.minZ(), 16) - z) > 7
+                    || Math.abs((long) Math.floorDiv(box.maxZ(), 16) - z) > 7)
+                throw new IllegalStateException("Heritage piece exceeds its local native reference contract");
+        }
+        var locator = pieces.stream().filter(piece -> piece instanceof HeritagePiece19 old && old.isSite() || piece instanceof HeritagePiece20 detail && detail.isSite()).findFirst().orElse(pieces.getFirst()).getLocatorPosition();
+        return Optional.of(new GenerationStub(locator, builder -> pieces.forEach(builder::addPiece)));
+    }
+    @Override public StructureType<?> type() { return HeritageStructures19.TYPE; }
+}
@@ -0,0 +1,112 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import com.mojang.datafixers.util.Pair;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.expansion.ExpansionChunkGenerator;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashSet;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.StructureType;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceType;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+
+/** Experimental generation19 uses independent native starts, references and saved room pieces. */
+public final class HeritageStructures19 {
+    public static final ResourceKey<Structure> KEY = ResourceKey.create(Registries.STRUCTURE, SanctuaryMod.id("heritage_networks"));
+    public static final StructureType<HeritageStructure19> TYPE = Registry.register(BuiltInRegistries.STRUCTURE_TYPE,
+        SanctuaryMod.id("heritage_networks_v19"), () -> HeritageStructure19.CODEC);
+    public static final StructurePieceType PIECE = Registry.register(BuiltInRegistries.STRUCTURE_PIECE,
+        SanctuaryMod.id("heritage_piece_v19"), HeritagePiece19::new);
+    public static final StructurePieceType PIECE20 = Registry.register(BuiltInRegistries.STRUCTURE_PIECE,
+        SanctuaryMod.id("heritage_piece_v20"), HeritagePiece20::new);
+    private static final ThreadLocal<Integer> PLACEMENT_DEPTH = ThreadLocal.withInitial(() -> 0);
+
+    private HeritageStructures19() {}
+    public static void register() { /* Initialize serializers before the dynamic structure registry is read. */ }
+    public static boolean isPlacing() { return PLACEMENT_DEPTH.get() > 0; }
+    static void placing(Runnable renderer) {
+        int previous = PLACEMENT_DEPTH.get();
+        PLACEMENT_DEPTH.set(previous + 1);
+        try { renderer.run(); }
+        finally {
+            if (previous == 0) PLACEMENT_DEPTH.remove();
+            else PLACEMENT_DEPTH.set(previous);
+        }
+    }
+    public static void generate(ExpansionChunkGenerator generator, RegistryAccess registries,
+            ChunkGeneratorStructureState state, StructureManager manager, ChunkAccess chunk,
+            StructureTemplateManager templates, ResourceKey<Level> level) {
+        if (!Level.OVERWORLD.equals(level) || !manager.shouldGenerateStructures()
+                || !(generator instanceof SanctuaryChunkGenerator sanctuary) || (generator.rootGeneration() != 19 && generator.rootGeneration() != 20)
+                || !sanctuary.experimentalStructures()) return;
+        var island = generator.islandForChunk(chunk.getPos().x(), chunk.getPos().z());
+        if (island == null || !island.origin() || island.generation() != generator.rootGeneration()) return;
+        var plan = sanctuary.heritagePlan19();
+        if (!hasStart(plan, chunk.getPos().x(), chunk.getPos().z())) return;
+        Holder<Structure> holder = registries.lookupOrThrow(Registries.STRUCTURE).getOrThrow(KEY);
+        Structure structure = holder.value();
+        StructureStart previous = manager.getStartForStructure(structure, chunk);
+        if (previous != null && previous.isValid()) return;
+        var random = generator.randomState(island);
+        var sampler = random.createClimateSampler(SamplerContext.builder().enableCaches().build());
+        var start = structure.generate(holder, level, registries, generator, generator.getBiomeSource(), sampler,
+            random, templates, island.seed(), chunk.getPos(), previous == null ? 0 : previous.getReferences(),
+            chunk, structure.biomes()::contains);
+        if (start.isValid()) manager.setStartForStructure(structure, start, chunk);
+    }
+    /** Starts are loaded at STRUCTURE_STARTS; locating never creates an expansion or rebuilds an existing start. */
+    public static Pair<BlockPos, Holder<Structure>> findNearest(ServerLevel level, HolderSet<Structure> structures,
+            BlockPos origin, int radius, boolean skipReferenced) {
+        if (!Level.OVERWORLD.equals(level.dimension())
+                || !(level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator generator)
+                || (generator.rootGeneration() != 19 && generator.rootGeneration() != 20) || !generator.experimentalStructures()
+                || !level.structureManager().shouldGenerateStructures()) return null;
+        Holder<Structure> holder = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(KEY);
+        if (!structures.contains(holder)) return null;
+        var candidates = new ArrayList<HeritagePlan19.Site>();
+        int originChunkX = origin.getX() >> 4, originChunkZ = origin.getZ() >> 4;
+        for (var network : generator.heritagePlan19().sites()) {
+            var island = generator.islandForChunk(network.startChunkX(), network.startChunkZ());
+            if (island == null || !island.origin() || island.generation() != generator.rootGeneration() || !island.status().equals("ready")) continue;
+            if (Math.abs((long) network.startChunkX() - originChunkX) <= radius
+                    && Math.abs((long) network.startChunkZ() - originChunkZ) <= radius) candidates.add(network);
+        }
+        candidates.sort(Comparator.comparingDouble(n -> origin.distSqr(locator(n))));
+        var visited = new HashSet<Long>();
+        for (var network : candidates) {
+            long key = ((long) network.startChunkX() << 32) ^ (network.startChunkZ() & 0xffffffffL);
+            if (!visited.add(key)) continue;
+            var chunk = level.getChunk(network.startChunkX(), network.startChunkZ(), ChunkStatus.STRUCTURE_STARTS, true);
+            StructureStart start = level.structureManager().getStartForStructure(holder.value(), chunk);
+            if (start == null || !start.isValid() || skipReferenced && !start.canBeReferenced()) continue;
+            if (skipReferenced) level.structureManager().addReference(start);
+            var entrance = start.getPieces().stream().filter(p -> (p instanceof HeritagePiece19 site && site.isSite())
+                || (p instanceof HeritagePiece20 detail && detail.isSite())).findFirst().orElseThrow();
+            return Pair.of(entrance.getLocatorPosition(), holder);
+        }
+        return null;
+    }
+    static BlockPos locator(HeritagePlan19.Site site) { return HeritagePiece19.locator(site); }
+    static boolean hasStart(HeritagePlan19 plan, int x, int z) {
+        return plan.sites().stream().anyMatch(s -> s.startChunkX() == x && s.startChunkZ() == z)
+            || plan.segments().stream().anyMatch(s -> s.startChunkX() == x && s.startChunkZ() == z);
+    }
+}
@@ -0,0 +1,110 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.expansion.ExpansionIsland;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan;
+import fr.koka.sanctuary.worldgen.ruins.RuinsPlan17;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Predicate;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.RandomState;
+
+/** Read-only pre-decoration terrain. No loaded chunks or player-edited blocks enter a plan. */
+public final class HeritageTerrain19 implements HeritagePlanner19.Terrain {
+    private static final int[] DX = {0, 1, 0, -1}, DZ = {-1, 0, 1, 0};
+    private final ExpansionIsland island;
+    private final NoiseBasedChunkGenerator generator;
+    private final RandomState random;
+    private final LevelHeightAccessor height;
+    private final Predicate<BlockPos> protection;
+    private final Map<Long, NoiseColumn> columns = new HashMap<>();
+    private List<HeritagePlan19.Landmark> landmarks = List.of();
+
+    public HeritageTerrain19(ExpansionIsland island, NoiseBasedChunkGenerator generator, RandomState random,
+            LevelHeightAccessor height, Predicate<BlockPos> protection) {
+        this.island = island; this.generator = generator; this.random = random;
+        this.height = height; this.protection = protection;
+    }
+    private NoiseColumn column(int x, int z) {
+        if (!owns(x, z)) return null;
+        long key = ((long) x << 32) ^ (z & 0xffffffffL);
+        var previous = columns.get(key);
+        if (previous != null) return previous;
+        if (columns.size() >= HeritagePlan19.MAX_COLUMNS) return null;
+        var result = generator.getBaseColumn(x, z, height, random);
+        columns.put(key, result);
+        return result;
+    }
+    @Override public boolean owns(int x, int z) { return island.contains(x, z); }
+    @Override public boolean solid(int x, int y, int z) {
+        if (y < 0 || y >= 384) return false;
+        var column = column(x, z);
+        return column != null && column.getBlock(y).isSolid() && column.getBlock(y).getFluidState().isEmpty();
+    }
+    @Override public boolean protectedAt(int x, int y, int z) {
+        if (y < 0 || y >= 384) return true;
+        var column = column(x, z);
+        return column == null || !column.getBlock(y).getFluidState().isEmpty()
+            || protection.test(new BlockPos(x, y, z));
+    }
+    @Override public int surfaceY(int x, int z) {
+        var column = column(x, z);
+        if (column == null) return -1;
+        for (int y = 380; y >= 1; y--) {
+            var state = column.getBlock(y);
+            if (!state.isAir()) return state.isSolid() && state.getFluidState().isEmpty() ? y : -1;
+        }
+        return -1;
+    }
+    @Override public List<HeritagePlan19.Landmark> landmarks() { return landmarks; }
+    public int columnsUsed() { return columns.size(); }
+
+    /** Select actual dry ground abutting existing walkable platforms. Their protected blocks stay intact. */
+    public void discoverLandmarks(LostCityPlan city, RuinsPlan17 ruins) {
+        var result = new ArrayList<HeritagePlan19.Landmark>();
+        for (var network : ruins.networks()) {
+            var access = network.rooms().stream().filter(r -> r.kind() == RuinsPlan17.Kind.ACCESS).findFirst().orElse(null);
+            if (access == null) continue;
+            int deck = access.maxY() - 2;
+            for (int direction = 0; direction < 4; direction++) {
+                var entry = dryEntry(access.centerX() + DX[direction] * 3, access.centerZ() + DZ[direction] * 3, deck, direction);
+                if (entry == null) continue;
+                var kind = network.family() == RuinsPlan17.Family.MINE ? HeritagePlan19.LandmarkKind.MINE : HeritagePlan19.LandmarkKind.UTILITY;
+                result.add(new HeritagePlan19.Landmark("old_" + network.id(), kind, entry));
+                break;
+            }
+        }
+        int cityEntries = 0;
+        outer: for (var district : city.districts()) for (var parcel : district.parcels()) {
+            if (parcel.kind() != LostCityPlan.Kind.STREET) continue;
+            boolean eastWest = parcel.width() > parcel.depth();
+            for (int direction : eastWest ? new int[]{1, 3} : new int[]{0, 2}) {
+                int x = direction == 1 ? parcel.width() - 1 : direction == 3 ? 0 : parcel.width() / 2;
+                int z = direction == 2 ? parcel.depth() - 1 : direction == 0 ? 0 : parcel.depth() / 2;
+                var entry = dryEntry(parcel.minX() + x + DX[direction], parcel.minZ() + z + DZ[direction], parcel.surfaceY(x, z), direction);
+                if (entry == null) continue;
+                result.add(new HeritagePlan19.Landmark("old_city_" + cityEntries++, HeritagePlan19.LandmarkKind.CITY, entry));
+                if (cityEntries == 2) break outer;
+            }
+        }
+        landmarks = List.copyOf(result);
+    }
+    private HeritagePlan19.Entry dryEntry(int x, int z, int deck, int direction) {
+        int y = surfaceY(x, z);
+        if (y < 32 || y > 348 || Math.abs(y - deck) > 1) return null;
+        // A three-wide arrival can abut a platform without cutting its wall or footings.
+        for (int side = -1; side <= 1; side++) {
+            int px = x + DZ[direction] * side, pz = z + DX[direction] * side;
+            var column = column(px, pz);
+            if (column == null || surfaceY(px, pz) != y || !solid(px, y, pz)) return null;
+            for (int by = y - 1; by <= y + 3; by++) if (protectedAt(px, by, pz)) return null;
+            for (int by = y + 1; by <= y + 3; by++) if (!column.getBlock(by).isAir()) return null;
+        }
+        return new HeritagePlan19.Entry(x, y + 1, z, direction);
+    }
+}
@@ -0,0 +1,114 @@
+package fr.koka.sanctuary.worldgen.ruins;
+
+import java.util.ArrayList;
+import java.util.Set;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import net.minecraft.core.BlockPos;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.Tag;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Saved generation20 room geometry is rendered without replanning or reading neighboring chunks. */
+public final class RuinsPiece20 extends StructurePiece {
+    private static final Set<String> ROOM_KEYS = Set.of("Schema", "Kind", "MinX", "MinY", "MinZ", "Width",
+        "Height", "Depth", "Openings", "RoomSeed", "Supports");
+    private static final Set<String> SUPPORT_KEYS = Set.of("X", "MinY", "Z", "MaxY");
+    private final RuinsPlan17.Room room;
+
+    public RuinsPiece20(RuinsPlan17.Room room) {
+        super(RuinsStructures17.PIECE20, 0, bounds(room));
+        this.room = room;
+        setOrientation(null);
+    }
+    public RuinsPiece20(StructurePieceSerializationContext context, CompoundTag tag) {
+        super(RuinsStructures17.PIECE20, tag);
+        room = decodeRoom(tag.getCompound("SanctuaryRoom")
+            .orElseThrow(() -> new IllegalArgumentException("Missing saved forgotten room")));
+        if (!getBoundingBox().equals(bounds(room)))
+            throw new IllegalArgumentException("Forgotten room disagrees with its saved native bounding box");
+        setOrientation(null);
+    }
+    public RuinsPlan17.Room room() { return room; }
+    @Override public BlockPos getLocatorPosition() { return locator(room); }
+    public static BlockPos locator(RuinsPlan17.Room room) {
+        return new BlockPos(room.minX() + room.width() / 2,
+            room.kind() == RuinsPlan17.Kind.ACCESS ? room.minY() + room.height() - 2 : room.floorY() + 1,
+            room.minZ() + room.depth() / 2);
+    }
+    @Override protected void addAdditionalSaveData(StructurePieceSerializationContext context, CompoundTag tag) {
+        tag.put("SanctuaryRoom", encodeRoom(room));
+    }
+    public static CompoundTag encodeRoom(RuinsPlan17.Room room) {
+        var tag = new CompoundTag(); tag.putInt("Schema", 1); tag.putString("Kind", room.kind().name());
+        tag.putInt("MinX", room.minX()); tag.putInt("MinY", room.minY()); tag.putInt("MinZ", room.minZ());
+        tag.putInt("Width", room.width()); tag.putInt("Height", room.height()); tag.putInt("Depth", room.depth());
+        tag.putInt("Openings", room.openings()); tag.putLong("RoomSeed", room.seed());
+        var supports = new ListTag();
+        for (var support : room.supports()) {
+            var value = new CompoundTag(); value.putInt("X", support.x()); value.putInt("MinY", support.minY());
+            value.putInt("Z", support.z()); value.putInt("MaxY", support.maxY()); supports.add(value);
+        }
+        tag.put("Supports", supports);
+        return tag;
+    }
+    public static RuinsPlan17.Room decodeRoom(CompoundTag tag) {
+        if (!tag.keySet().equals(ROOM_KEYS)) throw new IllegalArgumentException("Incomplete or unknown forgotten room fields");
+        if (integer(tag, "Schema") != 1) throw new IllegalArgumentException("Unsupported forgotten room schema");
+        var kind = RuinsPlan17.Kind.valueOf(tag.getString("Kind").orElseThrow(() -> new IllegalArgumentException("Missing room kind")));
+        type(tag, "RoomSeed", Tag.TAG_LONG); type(tag, "Supports", Tag.TAG_LIST);
+        var saved = tag.getList("Supports").orElseThrow();
+        if (saved.size() > 64) throw new IllegalArgumentException("Too many saved forgotten room supports");
+        var supports = new ArrayList<RuinsPlan17.Support>();
+        for (var entry : saved) {
+            if (!(entry instanceof CompoundTag value) || !value.keySet().equals(SUPPORT_KEYS))
+                throw new IllegalArgumentException("Invalid forgotten room support fields");
+            supports.add(new RuinsPlan17.Support(integer(value, "X"), integer(value, "MinY"), integer(value, "Z"), integer(value, "MaxY")));
+        }
+        return new RuinsPlan17.Room(kind, integer(tag, "MinX"), integer(tag, "MinY"), integer(tag, "MinZ"),
+            integer(tag, "Width"), integer(tag, "Height"), integer(tag, "Depth"), integer(tag, "Openings"),
+            tag.getLong("RoomSeed").orElseThrow(), supports);
+    }
+    private static int integer(CompoundTag tag, String key) {
+        type(tag, key, Tag.TAG_INT);
+        return tag.getInt(key).orElseThrow();
+    }
+    private static void type(CompoundTag tag, String key, byte id) {
+        if (tag.get(key) == null || tag.get(key).getId() != id)
+            throw new IllegalArgumentException("Invalid saved forgotten room field: " + key);
+    }
+    @Override public void postProcess(WorldGenLevel level, StructureManager manager, ChunkGenerator generator,
+            RandomSource random, BoundingBox clip, ChunkPos chunk, BlockPos pivot) {
+        RuinsStructures17.placing(() -> RuinsRenderer20.render(room, new LostCityRenderer.BlockWriter() {
+            private BlockPos world(int x, int y, int z) { return new BlockPos(room.minX() + x, room.minY() + y, room.minZ() + z); }
+            @Override public void set(int x, int y, int z, BlockState block) {
+                var position = world(x, y, z);
+                if (getBoundingBox().isInside(position) && clip.isInside(position))
+                    placeBlock(level, block, position.getX(), position.getY(), position.getZ(), clip);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> loot, long seed) {
+                var position = world(x, y, z);
+                if (getBoundingBox().isInside(position) && clip.isInside(position))
+                    createChest(level, clip, RandomSource.create(seed), position, loot, null);
+            }
+        }));
+    }
+    public static BoundingBox bounds(RuinsPlan17.Room room) {
+        int minY = room.minY(), maxY = Math.addExact(room.minY(), room.height() - 1);
+        for (var support : room.supports()) {
+            minY = Math.min(minY, support.minY()); maxY = Math.max(maxY, support.maxY());
+        }
+        return new BoundingBox(room.minX(), minY, room.minZ(), Math.addExact(room.minX(), room.width() - 1),
+            maxY, Math.addExact(room.minZ(), room.depth() - 1));
+    }
+}
@@ -0,0 +1,347 @@
+package fr.koka.sanctuary.worldgen.ruins;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPalette;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayList;
+import java.util.List;
+import net.minecraft.core.Direction;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.AttachFace;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.storage.loot.BuiltInLootTables;
+
+/** Generation20 architectural details: original, physical rooms reconstructed solely from their saved inputs.
+ * Coordinates given to the writer are local to the saved room. There are no terrain reads, entities,
+ * active machines or free fluids. Openings are restored last so connected pieces share dry thresholds. */
+public final class RuinsRenderer20 {
+    private static final Direction[] DIRECTIONS = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    private RuinsRenderer20() {}
+
+    /** Local standing positions for native path checks, including approaches to useful fixtures. */
+    public record Target(String name, int x, int y, int z) {}
+
+    public static List<Target> targets(RuinsPlan17.Room room) {
+        var targets = new ArrayList<Target>();
+        if (room.kind() == RuinsPlan17.Kind.ACCESS) {
+            targets.add(new Target("surface_hatch_approach", room.width() / 2, room.height() - 2, room.depth() / 2));
+            targets.add(new Target("shaft_bottom", room.width() / 2, 2, room.depth() / 2));
+        } else {
+            targets.add(new Target("central_crossing", room.width() / 2, 2, room.depth() / 2));
+            switch (room.kind()) {
+                case WORKSHOP -> {
+                    targets.add(decorTarget(room, "workbench", 2, 2, 2));
+                    targets.add(decorTarget(room, "unfinished_work_platform", room.width() - 3, 4, room.depth() - 3));
+                }
+                case STORE -> targets.add(decorTarget(room, "supply_chest", room.width() - 3, 2, room.depth() - 2));
+                case ARCHIVE -> targets.add(decorTarget(room, "reading_desk", 2, 2, 2));
+                case PUMP_HALL, CONTROL_ROOM -> targets.add(decorTarget(room, "controls", 2, 2, 2));
+                default -> { }
+            }
+        }
+        for (int direction = 0; direction < 4; direction++) if ((room.openings() & 1 << direction) != 0) {
+            int x = direction == 1 ? room.width() - 1 : direction == 3 ? 0 : room.width() / 2;
+            int z = direction == 2 ? room.depth() - 1 : direction == 0 ? 0 : room.depth() / 2;
+            targets.add(new Target("opening_" + DIRECTIONS[direction].getName(), x, 2, z));
+        }
+        return List.copyOf(targets);
+    }
+
+    public static void render(RuinsPlan17.Room room, LostCityRenderer.BlockWriter output) {
+        var buffer = fr.koka.sanctuary.worldgen.detail.ConnectedBlocks20.buffer(output);
+        var b = new Builder(room, buffer);
+        b.shell();
+        switch (room.kind()) {
+            case ACCESS -> b.access();
+            case CORRIDOR -> b.corridor();
+            case MINE_GALLERY -> b.mine();
+            case WORKSHOP -> b.workshop();
+            case STORE -> b.store();
+            case TILED_HALL -> b.tiledHall();
+            case ARCHIVE -> b.archive();
+            case SERVICE_HALL -> b.service();
+            case PUMP_HALL -> b.pumps();
+            case CONTROL_ROOM -> b.controls();
+        }
+        if (room.kind() != RuinsPlan17.Kind.ACCESS) { b.architecture(); b.lights(); }
+        b.openings();
+        for (var support : room.supports()) for (int y = support.minY(); y <= support.maxY(); y++)
+            buffer.set(support.x() - room.minX(), y - room.minY(), support.z() - room.minZ(),
+                Blocks.STONE_BRICKS.defaultBlockState());
+        buffer.flush();
+    }
+
+    private static boolean turn(RuinsPlan17.Room room) { return (room.seed() & 1L) != 0; }
+    private static Target decorTarget(RuinsPlan17.Room room, String name, int x, int y, int z) {
+        return new Target(name, turn(room) ? room.width() - 1 - x : x, y, turn(room) ? room.depth() - 1 - z : z);
+    }
+
+    private static final class Builder {
+        final RuinsPlan17.Room room;
+        final LostCityRenderer.BlockWriter out;
+        final int w, h, d, cx, cz;
+        final boolean reverse;
+        Builder(RuinsPlan17.Room room, LostCityRenderer.BlockWriter out) {
+            this.room = room; this.out = out; w = room.width(); h = room.height(); d = room.depth();
+            cx = w / 2; cz = d / 2; reverse = turn(room);
+        }
+        void set(int x, int y, int z, BlockState state) { out.set(x, y, z, state); }
+        void set(int x, int y, int z, net.minecraft.world.level.block.Block block) { set(x, y, z, block.defaultBlockState()); }
+        void decor(int x, int y, int z, BlockState state) {
+            out.set(reverse ? w - 1 - x : x, y, reverse ? d - 1 - z : z,
+                reverse ? state.rotate(Rotation.CLOCKWISE_180) : state);
+        }
+        void decor(int x, int y, int z, net.minecraft.world.level.block.Block block) { decor(x, y, z, block.defaultBlockState()); }
+        boolean crossing(int x, int z) { return Math.abs(x - cx) <= 1 || Math.abs(z - cz) <= 1; }
+
+        void shell() {
+            for (int y = 0; y < h; y++) for (int z = 0; z < d; z++) for (int x = 0; x < w; x++) {
+                BlockState state;
+                boolean wall = x == 0 || x == w - 1 || z == 0 || z == d - 1;
+                if (y == 0) state = Blocks.STONE_BRICKS.defaultBlockState();
+                else if (y == 1) state = floor(x, z);
+                else if (wall || y == h - 1) state = wallMaterial(x, y, z);
+                else state = Blocks.AIR.defaultBlockState();
+                set(x, y, z, state);
+            }
+            // A continuous ceiling cornice and stone thresholds remain intact despite the weathering.
+            for (int x = 0; x < w; x++) for (int z = 0; z < d; z++) if (x == 0 || x == w - 1 || z == 0 || z == d - 1)
+                set(x, h - 2, z, trim());
+        }
+        net.minecraft.world.level.block.Block trim() {
+            return switch (room.kind()) {
+                case ARCHIVE -> Blocks.STRIPPED_OAK_WOOD;
+                case TILED_HALL, SERVICE_HALL -> Blocks.POLISHED_DIORITE;
+                case WORKSHOP, STORE -> Blocks.TUFF_BRICKS;
+                case MINE_GALLERY -> Blocks.STRIPPED_OAK_WOOD;
+                default -> Blocks.POLISHED_TUFF;
+            };
+        }
+        BlockState wallMaterial(int x, int y, int z) {
+            if (y <= 2) return Blocks.STONE_BRICKS.defaultBlockState();
+            if (y == h - 1) return (room.kind() == RuinsPlan17.Kind.ARCHIVE
+                ? Blocks.BIRCH_PLANKS : Blocks.SMOOTH_STONE).defaultBlockState();
+            int along = x == 0 || x == w - 1 ? z : x;
+            net.minecraft.world.level.block.Block wall = switch (room.kind()) {
+                case ARCHIVE -> along % 4 == 0 ? Blocks.STRIPPED_OAK_WOOD : Blocks.BIRCH_PLANKS;
+                case WORKSHOP -> along % 4 == 0 ? Blocks.POLISHED_ANDESITE : Blocks.TUFF_BRICKS;
+                case STORE -> along % 4 == 0 ? Blocks.STRIPPED_OAK_WOOD : Blocks.POLISHED_GRANITE;
+                case MINE_GALLERY -> along % 4 == 0 ? Blocks.STRIPPED_OAK_WOOD : Blocks.TUFF;
+                case TILED_HALL -> y == 3 ? Blocks.POLISHED_DIORITE : Blocks.CALCITE;
+                case SERVICE_HALL -> y == 3 ? Blocks.BIRCH_PLANKS : Blocks.SMOOTH_STONE;
+                case PUMP_HALL -> along % 4 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS;
+                case CONTROL_ROOM -> along % 4 == 0 ? Blocks.POLISHED_ANDESITE : Blocks.SMOOTH_STONE;
+                default -> along % 4 == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS;
+            };
+            return wall.defaultBlockState();
+        }
+        BlockState floor(int x, int z) {
+            boolean border = x == 1 || x == w - 2 || z == 1 || z == d - 2;
+            return switch (room.kind()) {
+                case MINE_GALLERY -> (x == cx ? Blocks.DARK_OAK_PLANKS : (x + z) % 5 == 0 ? Blocks.ANDESITE : Blocks.STONE).defaultBlockState();
+                case ARCHIVE -> (border ? Blocks.STRIPPED_OAK_WOOD : Blocks.BIRCH_PLANKS).defaultBlockState();
+                case WORKSHOP -> (border ? Blocks.POLISHED_GRANITE : Blocks.SMOOTH_STONE).defaultBlockState();
+                case STORE -> (border ? Blocks.TUFF_BRICKS : Blocks.OAK_PLANKS).defaultBlockState();
+                case TILED_HALL -> ((x / 2 + z / 2) % 2 == 0 ? Blocks.CALCITE : Blocks.POLISHED_DIORITE).defaultBlockState();
+                case SERVICE_HALL -> (border ? Blocks.POLISHED_DIORITE : Blocks.SMOOTH_STONE).defaultBlockState();
+                case PUMP_HALL, CONTROL_ROOM -> (x == cx || z == cz ? Blocks.POLISHED_ANDESITE : Blocks.SMOOTH_STONE).defaultBlockState();
+                default -> (border && Math.floorMod(x + z + room.seed(), 4) == 0 ? Blocks.CHISELED_TUFF_BRICKS
+                    : border ? Blocks.TUFF_BRICKS : Blocks.POLISHED_TUFF).defaultBlockState();
+            };
+        }
+
+        void architecture() {
+            // High inset cornices soften the square excavation without taking away the
+            // three-wide walking cross. The outer stone shell stays closed and watertight.
+            var stair = switch (room.kind()) {
+                case ARCHIVE -> Blocks.OAK_STAIRS;
+                case MINE_GALLERY, STORE -> Blocks.OAK_STAIRS;
+                case TILED_HALL, SERVICE_HALL -> Blocks.POLISHED_DIORITE_STAIRS;
+                default -> Blocks.TUFF_BRICK_STAIRS;
+            };
+            for (int x = 2; x < w - 2; x++) {
+                set(x, h - 2, 1, stair.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH)
+                    .setValue(BlockStateProperties.HALF, net.minecraft.world.level.block.state.properties.Half.TOP));
+                set(x, h - 2, d - 2, stair.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH)
+                    .setValue(BlockStateProperties.HALF, net.minecraft.world.level.block.state.properties.Half.TOP));
+            }
+            for (int z = 2; z < d - 2; z++) {
+                set(1, h - 2, z, stair.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST)
+                    .setValue(BlockStateProperties.HALF, net.minecraft.world.level.block.state.properties.Half.TOP));
+                set(w - 2, h - 2, z, stair.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.EAST)
+                    .setValue(BlockStateProperties.HALF, net.minecraft.world.level.block.state.properties.Half.TOP));
+            }
+            // Exposed joists read as timber construction in the archive and interrupted
+            // workshop; technical rooms use a repeated rib in their own mineral palette.
+            if (w >= 9 && d >= 9) for (int z = 3; z < d - 2; z += 4)
+                for (int x = 2; x < w - 2; x++) set(x, h - 2, z,
+                    (room.kind() == RuinsPlan17.Kind.ARCHIVE || room.kind() == RuinsPlan17.Kind.WORKSHOP
+                        ? Blocks.STRIPPED_OAK_WOOD : trim()).defaultBlockState()
+                        .trySetValue(BlockStateProperties.AXIS, Direction.Axis.X));
+            // Fitted thresholds and carved voussoirs distinguish doorways from random holes.
+            for (int direction = 0; direction < 4; direction++) if ((room.openings() & 1 << direction) != 0)
+                for (int side = -1; side <= 1; side++) {
+                    int x = direction == 1 ? w - 1 : direction == 3 ? 0 : cx + side;
+                    int z = direction == 2 ? d - 1 : direction == 0 ? 0 : cz + side;
+                    set(x, 5, z, side == 0 ? Blocks.CHISELED_TUFF_BRICKS : Blocks.TUFF_BRICKS);
+                }
+        }
+
+        void access() {
+            int exit = Integer.numberOfTrailingZeros(room.openings() == 0 ? 1 : room.openings());
+            int wall = (exit + 2) & 3;
+            int x = wall == 1 ? w - 2 : wall == 3 ? 1 : cx;
+            int z = wall == 2 ? d - 2 : wall == 0 ? 1 : cz;
+            Direction facing = DIRECTIONS[wall].getOpposite();
+            if ((room.openings() & 1 << wall) != 0) {
+                // A branching shaft cannot attach its lowest ladder to another open doorway.
+                // This corner post leaves all three doorway cells and the central crossing usable.
+                x = 1; z = 2; facing = Direction.SOUTH;
+                for (int y = 2; y <= h - 3; y++) set(1, y, 1, Blocks.STONE_BRICKS);
+            }
+            BlockState ladder = Blocks.LADDER.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, facing);
+            for (int y = 2; y <= h - 3; y++) set(x, y, z, ladder);
+            for (int zz = 0; zz < d; zz++) for (int xx = 0; xx < w; xx++) {
+                set(xx, h - 3, zz, xx == x && zz == z ? ladder : Blocks.SMOOTH_STONE.defaultBlockState());
+                set(xx, h - 2, zz, Blocks.AIR); set(xx, h - 1, zz, Blocks.AIR);
+            }
+            set(x, h - 2, z, Blocks.DARK_OAK_TRAPDOOR.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, facing));
+        }
+        void corridor() {
+            boolean alongX = w > d;
+            int length = alongX ? w : d;
+            for (int n = 2; n < length - 1; n += 4) {
+                if (alongX) {
+                    for (int y = 2; y <= h - 1; y++) { set(n, y, 0, Blocks.POLISHED_ANDESITE); set(n, y, d - 1, Blocks.POLISHED_ANDESITE); }
+                } else for (int y = 2; y <= h - 1; y++) { set(0, y, n, Blocks.POLISHED_ANDESITE); set(w - 1, y, n, Blocks.POLISHED_ANDESITE); }
+            }
+        }
+        void mine() {
+            for (int z : new int[] {2, d - 3}) {
+                for (int x : new int[] {2, w - 3}) for (int y = 2; y <= h - 2; y++) decor(x, y, z, Blocks.STRIPPED_OAK_LOG);
+                for (int x = 2; x <= w - 3; x++) decor(x, h - 2, z, Blocks.STRIPPED_OAK_LOG.defaultBlockState()
+                    .setValue(BlockStateProperties.AXIS, Direction.Axis.X));
+            }
+            for (int z = 1; z < d - 1; z++) set(cx, 2, z, Blocks.RAIL);
+            // A short second siding ends at a buffer; the main track and cross passage remain open.
+            if (w >= 13) {
+                for (int z = 3; z < d - 2; z++) decor(w - 5, 2, z, Blocks.RAIL);
+                decor(w - 5, 2, d - 2, Blocks.DARK_OAK_FENCE);
+            }
+            decor(1, 2, 1, Blocks.BARREL);
+            decor(w - 2, 2, d - 2, Blocks.ANDESITE);
+            if (LostCityPalette.roll(room.seed(), 1, 0, 0, 2) == 0) decor(w - 2, 3, d - 2, Blocks.COBBLESTONE);
+        }
+        void workshop() {
+            decor(1, 2, 1, Blocks.CRAFTING_TABLE);
+            decor(2, 2, 1, Blocks.FURNACE.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+            decor(1, 2, d - 3, Blocks.GRINDSTONE.defaultBlockState()
+                .setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR)
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.EAST));
+            decor(w - 2, 2, 1, Blocks.STONECUTTER.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST));
+            decor(1, 2, d - 2, Blocks.CAULDRON);
+            decor(2, 2, d - 2, Blocks.ANVIL);
+            // Two grounded posts and a small planked deck preserve the trace of unfinished repairs.
+            for (int x = w - 3; x <= w - 2; x++) {
+                decor(x, 2, d - 3, Blocks.STRIPPED_OAK_LOG);
+                for (int z = d - 3; z <= d - 2; z++) decor(x, 3, z, Blocks.DARK_OAK_PLANKS);
+            }
+            for (int y = 2; y <= 3; y++) decor(w - 3, y, d - 4, Blocks.LADDER.defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.NORTH));
+            decor(w - 2, 2, d - 2, Blocks.BARREL);
+        }
+        void store() {
+            for (int z = 1; z < d - 1; z++) if (!crossing(1, z)) {
+                decor(1, 2, z, Blocks.BARREL);
+                if ((z & 1) == 0) decor(1, 3, z, Blocks.BARREL);
+                decor(1, 4, z, Blocks.DARK_OAK_SLAB);
+            }
+            for (int x = cx + 2; x <= w - 2; x++) decor(x, 2, 1, Blocks.DARK_OAK_PLANKS);
+            decor(w - 2, 3, 1, Blocks.BARREL);
+            loot(w - 2, 2, d - 2, BuiltInLootTables.VILLAGE_PLAINS_HOUSE);
+        }
+        void tiledHall() {
+            // Repeated columns are interrupted by complete, centered cross passages.
+            for (int x : new int[] {2, w - 3}) for (int z : new int[] {2, d - 3})
+                for (int y = 2; y < h - 1; y++) decor(x, y, z, y == 2 || y == h - 2 ? Blocks.SMOOTH_STONE : Blocks.CALCITE);
+            if (w >= 13) for (int x : new int[] {3, w - 4}) for (int z = 1; z <= d - 2; z++)
+                if (Math.abs(z - cz) > 1) for (int y = 2; y < h - 1; y++)
+                    decor(x, y, z, y == h - 2 ? Blocks.POLISHED_ANDESITE : Blocks.SMOOTH_STONE);
+            for (int x = cx - 1; x <= cx + 1; x++) {
+                decor(x, h - 2, 1, Blocks.POLISHED_ANDESITE);
+                decor(x, h - 2, d - 2, Blocks.POLISHED_ANDESITE);
+            }
+            // Mismatched surviving benches give these physically reachable side niches a former use.
+            decor(1, 2, 1, seat(Direction.WEST));
+            decor(w - 2, 2, 1, seat(Direction.EAST));
+        }
+        void archive() {
+            for (int z = 1; z <= d - 2; z++) if (Math.abs(z - cz) > 1)
+                for (int y = 2; y <= 4; y++) decor(w - 2, y, z,
+                    y == 4 && (z & 1) == 0 ? Blocks.DARK_OAK_PLANKS : Blocks.BOOKSHELF);
+            decor(1, 2, 1, Blocks.BOOKSHELF);
+            decor(1, 2, 2, Blocks.LECTERN.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.EAST));
+            decor(1, 2, d - 2, Blocks.CARTOGRAPHY_TABLE);
+            decor(2, 2, d - 3, Blocks.BARREL);
+            loot(1, 2, d - 3, BuiltInLootTables.VILLAGE_CARTOGRAPHER);
+        }
+        void service() {
+            for (int z = 1; z < d - 1; z++) if (Math.abs(z - cz) > 1) {
+                decor(1, 2, z, Blocks.POLISHED_ANDESITE);
+                decor(1, 3, z, Blocks.IRON_BARS);
+            }
+            for (int z : new int[] {1, d - 2}) for (int x = 1; x < w - 1; x++)
+                decor(x, h - 2, z, Blocks.STRIPPED_OAK_LOG.defaultBlockState().setValue(BlockStateProperties.AXIS, Direction.Axis.X));
+            decor(w - 2, 2, 1, Blocks.BARREL);
+            decor(w - 2, 2, d - 2, Blocks.CRAFTING_TABLE);
+            decor(2, 2, d - 2, seat(Direction.SOUTH));
+        }
+        void pumps() {
+            for (int z : new int[] {1, d - 2}) {
+                decor(1, 2, z, Blocks.DISPENSER.defaultBlockState().setValue(BlockStateProperties.FACING, Direction.EAST));
+                decor(2, 2, z, Blocks.WATER_CAULDRON.defaultBlockState().setValue(BlockStateProperties.LEVEL_CAULDRON, 3));
+                decor(1, 3, z, Blocks.POLISHED_ANDESITE);
+                decor(1, 4, z, Blocks.IRON_BARS);
+                decor(w - 2, 2, z, Blocks.CAULDRON);
+            }
+            for (int z = 1; z <= d - 2; z++) decor(1, h - 2, z, Blocks.POLISHED_ANDESITE);
+            decor(w - 2, 2, 2, Blocks.SMOOTH_STONE);
+            decor(w - 2, 3, 2, Blocks.LEVER.defaultBlockState().setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR)
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.WEST));
+        }
+        void controls() {
+            for (int x = 1; x <= cx - 2; x++) {
+                decor(x, 2, 1, Blocks.SMOOTH_STONE);
+                decor(x, 3, 1, Blocks.LEVER.defaultBlockState().setValue(BlockStateProperties.ATTACH_FACE, AttachFace.FLOOR)
+                    .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH));
+                decor(x, 3, 0, Blocks.REDSTONE_LAMP);
+            }
+            decor(1, 2, 2, seat(Direction.WEST));
+            decor(w - 2, 2, 1, Blocks.CRAFTING_TABLE);
+            decor(w - 2, 2, d - 2, Blocks.BARREL);
+            // An inspection window remains backed by a complete wall: there is no opening into unverified rock or water.
+            for (int z = cz + 2; z < d - 1; z++) decor(0, 3, z, Blocks.GLASS);
+            decor(1, 2, d - 2, Blocks.CARTOGRAPHY_TABLE);
+        }
+        BlockState seat(Direction back) { return Blocks.DARK_OAK_STAIRS.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, back); }
+        void lights() {
+            // Every lantern hangs directly from the full masonry ceiling; never from a bottom slab.
+            for (int[] p : new int[][] {{1, 1}, {w - 2, d - 2}})
+                set(p[0], h - 2, p[1], Blocks.LANTERN.defaultBlockState().setValue(BlockStateProperties.HANGING, true));
+        }
+        void openings() {
+            for (int direction = 0; direction < 4; direction++) if ((room.openings() & 1 << direction) != 0)
+                for (int side = -1; side <= 1; side++) {
+                    int x = direction == 1 ? w - 1 : direction == 3 ? 0 : cx + side;
+                    int z = direction == 2 ? d - 1 : direction == 0 ? 0 : cz + side;
+                    set(x, 1, z, Blocks.SMOOTH_STONE);
+                    for (int y = 2; y <= 4; y++) set(x, y, z, Blocks.AIR);
+                }
+        }
+        void loot(int x, int y, int z, net.minecraft.resources.ResourceKey<net.minecraft.world.level.storage.loot.LootTable> table) {
+            out.chest(reverse ? w - 1 - x : x, y, reverse ? d - 1 - z : z, table, room.seed() ^ 0x17A6C41L);
+        }
+    }
+}
@@ -13,9 +13,9 @@ public final class RuinsStructure17 extends Structure {

    @Override protected Optional<GenerationStub> findGenerationPoint(GenerationContext context) {
        if (!(context.chunkGenerator() instanceof SanctuaryChunkGenerator generator)
-                || generator.rootGeneration() != 17 || !generator.experimentalStructures()) return Optional.empty();
+                || (generator.rootGeneration() != 17 && generator.rootGeneration() != 19 && generator.rootGeneration() != 20) || !generator.experimentalStructures()) return Optional.empty();
        var island = generator.islandForChunk(context.chunkPos().x(), context.chunkPos().z());
-        if (island == null || !island.origin() || island.generation() != 17) return Optional.empty();
+        if (island == null || !island.origin() || island.generation() != generator.rootGeneration()) return Optional.empty();
        var networks = generator.ruinsPlan17().networks().stream()
            .filter(n -> n.startChunkX() == context.chunkPos().x() && n.startChunkZ() == context.chunkPos().z()).toList();
        if (networks.isEmpty()) return Optional.empty();
@@ -30,9 +30,9 @@ public final class RuinsStructure17 extends Structure {
        return Optional.of(new GenerationStub(RuinsStructures17.locator(networks.getFirst()), pieces -> {
            // Shafts come last so their surface hatches cannot be filled by a connected room.
            networks.forEach(n -> n.rooms().stream().filter(r -> r.kind() != RuinsPlan17.Kind.ACCESS)
-                .forEach(r -> pieces.addPiece(new RuinsPiece17(r))));
+                .forEach(r -> pieces.addPiece(generator.rootGeneration() == 20 ? new RuinsPiece20(r) : new RuinsPiece17(r))));
            networks.forEach(n -> n.rooms().stream().filter(r -> r.kind() == RuinsPlan17.Kind.ACCESS)
-                .forEach(r -> pieces.addPiece(new RuinsPiece17(r))));
+                .forEach(r -> pieces.addPiece(generator.rootGeneration() == 20 ? new RuinsPiece20(r) : new RuinsPiece17(r))));
        }));
    }
    @Override public StructureType<?> type() { return RuinsStructures17.TYPE; }
@@ -35,6 +35,8 @@ public final class RuinsStructures17 {
        SanctuaryMod.id("forgotten_networks_v17"), () -> RuinsStructure17.CODEC);
    public static final StructurePieceType PIECE = Registry.register(BuiltInRegistries.STRUCTURE_PIECE,
        SanctuaryMod.id("forgotten_room_v17"), RuinsPiece17::new);
+    public static final StructurePieceType PIECE20 = Registry.register(BuiltInRegistries.STRUCTURE_PIECE,
+        SanctuaryMod.id("forgotten_room_v20"), RuinsPiece20::new);
    private static final ThreadLocal<Integer> PLACEMENT_DEPTH = ThreadLocal.withInitial(() -> 0);

    private RuinsStructures17() {}
@@ -53,10 +55,10 @@ public final class RuinsStructures17 {
            ChunkGeneratorStructureState state, StructureManager manager, ChunkAccess chunk,
            StructureTemplateManager templates, ResourceKey<Level> level) {
        if (!Level.OVERWORLD.equals(level) || !manager.shouldGenerateStructures()
-                || !(generator instanceof SanctuaryChunkGenerator sanctuary) || generator.rootGeneration() != 17
+                || !(generator instanceof SanctuaryChunkGenerator sanctuary) || (generator.rootGeneration() != 17 && generator.rootGeneration() != 19 && generator.rootGeneration() != 20)
                || !sanctuary.experimentalStructures()) return;
        var island = generator.islandForChunk(chunk.getPos().x(), chunk.getPos().z());
-        if (island == null || !island.origin() || island.generation() != 17) return;
+        if (island == null || !island.origin() || island.generation() != generator.rootGeneration()) return;
        var plan = sanctuary.ruinsPlan17();
        if (plan.networks().stream().noneMatch(n -> n.startChunkX() == chunk.getPos().x()
                && n.startChunkZ() == chunk.getPos().z())) return;
@@ -76,7 +78,7 @@ public final class RuinsStructures17 {
            BlockPos origin, int radius, boolean skipReferenced) {
        if (!Level.OVERWORLD.equals(level.dimension())
                || !(level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator generator)
-                || generator.rootGeneration() != 17 || !generator.experimentalStructures()
+                || (generator.rootGeneration() != 17 && generator.rootGeneration() != 19 && generator.rootGeneration() != 20) || !generator.experimentalStructures()
                || !level.structureManager().shouldGenerateStructures()) return null;
        Holder<Structure> holder = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(KEY);
        if (!structures.contains(holder)) return null;
@@ -84,7 +86,7 @@ public final class RuinsStructures17 {
        int originChunkX = origin.getX() >> 4, originChunkZ = origin.getZ() >> 4;
        for (var network : generator.ruinsPlan17().networks()) {
            var island = generator.islandForChunk(network.startChunkX(), network.startChunkZ());
-            if (island == null || !island.origin() || island.generation() != 17 || !island.status().equals("ready")) continue;
+            if (island == null || !island.origin() || island.generation() != generator.rootGeneration() || !island.status().equals("ready")) continue;
            if (Math.abs((long) network.startChunkX() - originChunkX) <= radius
                    && Math.abs((long) network.startChunkZ() - originChunkZ) <= radius) candidates.add(network);
        }
@@ -97,8 +99,8 @@ public final class RuinsStructures17 {
            StructureStart start = level.structureManager().getStartForStructure(holder.value(), chunk);
            if (start == null || !start.isValid() || skipReferenced && !start.canBeReferenced()) continue;
            if (skipReferenced) level.structureManager().addReference(start);
-            var entrance = start.getPieces().stream().filter(p -> p instanceof RuinsPiece17 room
-                && room.room().kind() == RuinsPlan17.Kind.ACCESS).findFirst().orElse(start.getPieces().getFirst());
+            var entrance = start.getPieces().stream().filter(p -> (p instanceof RuinsPiece17 room && room.room().kind() == RuinsPlan17.Kind.ACCESS)
+                || (p instanceof RuinsPiece20 detail && detail.room().kind() == RuinsPlan17.Kind.ACCESS)).findFirst().orElse(start.getPieces().getFirst());
            return Pair.of(entrance.getLocatorPosition(), holder);
        }
        return null;
@@ -127,5 +127,24 @@
  "sanctuary.expansion.error.void_reuse_incomplete": "Void reuse is incomplete. The reservation is retained; check the server log.",
  "sanctuary.world_options.experimental": "Experimental structures",
  "sanctuary.world_options.experimental_hint": "Mines, strange rooms and abandoned facilities. This choice is saved with the new world.",
-  "structure.sanctuary.forgotten_networks": "Forgotten networks"
+  "structure.sanctuary.forgotten_networks": "Forgotten networks",
+  "sanctuary.world_options.heritage_hint": "Adds forgotten networks, buildings and abandoned routes to the new island. This choice is saved with the world.",
+  "structure.sanctuary.heritage_networks": "Abandoned infrastructure",
+  "sanctuary.heritage.kind.freight_station": "Freight station",
+  "sanctuary.heritage.kind.post_office": "Post office",
+  "sanctuary.heritage.kind.communal_depot": "Communal depot",
+  "sanctuary.heritage.kind.expedition_office": "Expedition office and map archive",
+  "sanctuary.heritage.kind.observatory": "Observatory and weather station",
+  "sanctuary.heritage.kind.rail_workshop": "Rail workshop",
+  "sanctuary.heritage.kind.pump_station": "Pump station",
+  "sanctuary.heritage.kind.substation": "Utility substation",
+  "sanctuary.heritage.kind.greenhouse": "Greenhouse and seed store",
+  "sanctuary.heritage.kind.void_dock": "Expedition dock",
+  "sanctuary.heritage.kind.radio_relay": "Radio relay",
+  "sanctuary.heritage.kind.photo_club": "Photography club",
+  "sanctuary.heritage.kind.impossible_service": "Changing rooms and strange service rooms",
+  "sanctuary.heritage.kind.construction_refuge": "Construction refuge",
+  "sanctuary.heritage.unavailable": "This survey requires a Sanctuary alpha.19 or alpha.20 world with experimental structures enabled.",
+  "sanctuary.heritage.header": "Abandoned infrastructure: %s planned sites and %s links. Entrance coordinates:",
+  "sanctuary.heritage.entry": "%s : %s / %s / %s"
 }
@@ -127,5 +127,24 @@
  "sanctuary.expansion.error.void_reuse_incomplete": "La réutilisation du vide est incomplète. La réservation est conservée ; consultez le journal du serveur.",
  "sanctuary.world_options.experimental": "Structures expérimentales",
  "sanctuary.world_options.experimental_hint": "Mines, salles étranges et installations abandonnées. Ce choix reste attaché au nouveau monde.",
-  "structure.sanctuary.forgotten_networks": "Réseaux oubliés"
+  "structure.sanctuary.forgotten_networks": "Réseaux oubliés",
+  "sanctuary.world_options.heritage_hint": "Ajoute les anciens réseaux, bâtiments et voies abandonnées sur la nouvelle île. Ce choix est enregistré avec le monde.",
+  "structure.sanctuary.heritage_networks": "Anciennes infrastructures",
+  "sanctuary.heritage.kind.freight_station": "Gare de marchandises",
+  "sanctuary.heritage.kind.post_office": "Centre postal",
+  "sanctuary.heritage.kind.communal_depot": "Dépôt communal",
+  "sanctuary.heritage.kind.expedition_office": "Bureau des expéditions et cartothèque",
+  "sanctuary.heritage.kind.observatory": "Observatoire et station météo",
+  "sanctuary.heritage.kind.rail_workshop": "Atelier ferroviaire",
+  "sanctuary.heritage.kind.pump_station": "Station de pompage",
+  "sanctuary.heritage.kind.substation": "Sous-station",
+  "sanctuary.heritage.kind.greenhouse": "Serre et graineterie",
+  "sanctuary.heritage.kind.void_dock": "Quai d’expédition",
+  "sanctuary.heritage.kind.radio_relay": "Relais radio",
+  "sanctuary.heritage.kind.photo_club": "Club photo",
+  "sanctuary.heritage.kind.impossible_service": "Vestiaires et salles étranges",
+  "sanctuary.heritage.kind.construction_refuge": "Refuge de chantier",
+  "sanctuary.heritage.unavailable": "Ce relevé nécessite un monde Sanctuary alpha.19 ou alpha.20 avec les structures expérimentales activées.",
+  "sanctuary.heritage.header": "Anciennes infrastructures : %s lieux et %s liaisons prévus. Coordonnées des entrées :",
+  "sanctuary.heritage.entry": "%s : %s / %s / %s"
 }
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:iron_axe"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:torch",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:bread",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:iron_shovel"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:bread",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:torch",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:compass"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:paper",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:map",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:minecart"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:rail",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:coal",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:iron_hoe"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:wheat_seeds",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:pumpkin_seeds",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:clock"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:torch",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:string",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:spyglass"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:paper",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:book",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:book"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:paper",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:glass_pane",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:compass"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:paper",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:string",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:bucket"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:string",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:torch",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:compass"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:redstone",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:paper",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:iron_pickaxe"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:rail",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:coal",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:clock"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:redstone",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:copper_ingot",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,51 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:lead"
+        }
+      ]
+    },
+    {
+      "rolls": {
+        "type": "minecraft:uniform",
+        "min": 1,
+        "max": 2
+      },
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:torch",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        },
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:bread",
+          "functions": [
+            {
+              "function": "minecraft:set_count",
+              "count": {
+                "type": "minecraft:uniform",
+                "min": 1,
+                "max": 3
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,55 @@
+{
+  "replace": false,
+  "values": [
+    "#minecraft:is_overworld",
+    "sanctuary:cavern_bamboo_grove",
+    "sanctuary:cavern_birch_forest",
+    "sanctuary:cavern_clearing",
+    "sanctuary:cavern_dark_grove",
+    "sanctuary:cavern_dripstone_caves",
+    "sanctuary:cavern_dry_woodland",
+    "sanctuary:cavern_lush_caves",
+    "sanctuary:cavern_oak_forest",
+    "sanctuary:cavern_rocky_heath",
+    "sanctuary:cavern_sulfur_depths",
+    "sanctuary:layered_flower_meadow",
+    "sanctuary:layered_lower_grove",
+    "sanctuary:layered_meadow",
+    "sanctuary:layered_mossy_terraces",
+    "sanctuary:layered_rocky_terraces",
+    "sanctuary:lost_city",
+    "sanctuary:population_bamboo_grove",
+    "sanctuary:population_birch_forest",
+    "sanctuary:population_clearing",
+    "sanctuary:population_dark_grove",
+    "sanctuary:population_dripstone_caves",
+    "sanctuary:population_dry_woodland",
+    "sanctuary:population_lush_caves",
+    "sanctuary:population_oak_forest",
+    "sanctuary:population_rocky_heath",
+    "sanctuary:population_sulfur_depths",
+    "sanctuary:rift_bamboo_grove",
+    "sanctuary:rift_birch_forest",
+    "sanctuary:rift_clearing",
+    "sanctuary:rift_dark_grove",
+    "sanctuary:rift_dry_woodland",
+    "sanctuary:rift_oak_forest",
+    "sanctuary:rift_rocky_heath",
+    "sanctuary:rift_sulfur_depths",
+    "sanctuary:starter_forest",
+    "sanctuary:starter_forest_hydrology",
+    "sanctuary:temperate_birch_forest",
+    "sanctuary:temperate_dappled_forest",
+    "sanctuary:temperate_flower_forest",
+    "sanctuary:temperate_forest",
+    "sanctuary:temperate_plains",
+    "sanctuary:woodland_bamboo_grove",
+    "sanctuary:woodland_birch_forest",
+    "sanctuary:woodland_clearing",
+    "sanctuary:woodland_dark_grove",
+    "sanctuary:woodland_dry_woodland",
+    "sanctuary:woodland_oak_forest",
+    "sanctuary:woodland_rocky_heath",
+    "sanctuary:woodland_sulfur_depths"
+  ]
+}
@@ -0,0 +1,7 @@
+{
+  "type": "sanctuary:heritage_networks_v19",
+  "biomes": "#sanctuary:has_structure/heritage_networks",
+  "step": "underground_structures",
+  "terrain_adaptation": "none",
+  "spawn_overrides": {}
+}
@@ -3,7 +3,7 @@
    "minecraft:overworld": {
      "type": "sanctuary:sanctuary_384",
      "generator": {
-        "type": "sanctuary:island_v17",
+        "type": "sanctuary:island_v20",
        "biome_source": {
          "biomes": [
            "minecraft:the_void",
@@ -0,0 +1,81 @@
+{
+  "dimensions": {
+    "minecraft:overworld": {
+      "type": "sanctuary:sanctuary_384",
+      "generator": {
+        "type": "sanctuary:island_v17",
+        "biome_source": {
+          "biomes": [
+            "minecraft:the_void",
+            "minecraft:forest",
+            "minecraft:birch_forest",
+            "minecraft:flower_forest",
+            "minecraft:plains",
+            "minecraft:meadow",
+            "minecraft:taiga",
+            "minecraft:snowy_taiga",
+            "minecraft:snowy_plains",
+            "minecraft:grove",
+            "minecraft:ice_spikes",
+            "minecraft:frozen_peaks",
+            "minecraft:old_growth_spruce_taiga",
+            "minecraft:dark_forest",
+            "minecraft:swamp",
+            "minecraft:pale_garden",
+            "minecraft:jungle",
+            "minecraft:sparse_jungle",
+            "minecraft:bamboo_jungle",
+            "minecraft:mangrove_swamp",
+            "minecraft:savanna",
+            "minecraft:savanna_plateau",
+            "minecraft:desert",
+            "minecraft:badlands",
+            "minecraft:eroded_badlands",
+            "minecraft:wooded_badlands",
+            "minecraft:windswept_hills",
+            "minecraft:windswept_gravelly_hills",
+            "minecraft:stony_peaks",
+            "minecraft:dappled_forest",
+            "minecraft:cherry_grove",
+            "minecraft:lush_caves",
+            "minecraft:dripstone_caves",
+            "minecraft:sulfur_caves",
+            "sanctuary:population_oak_forest",
+            "sanctuary:population_birch_forest",
+            "sanctuary:population_clearing",
+            "sanctuary:population_dry_woodland",
+            "sanctuary:population_rocky_heath",
+            "sanctuary:population_dark_grove",
+            "sanctuary:population_bamboo_grove",
+            "sanctuary:population_sulfur_depths",
+            "sanctuary:population_lush_caves",
+            "sanctuary:population_dripstone_caves",
+            "sanctuary:lost_city"
+          ]
+        },
+        "initial_diameter": 724
+      }
+    },
+    "minecraft:the_end": {
+      "type": "minecraft:the_end",
+      "generator": {
+        "type": "minecraft:noise",
+        "biome_source": {
+          "type": "minecraft:the_end"
+        },
+        "settings": "minecraft:end"
+      }
+    },
+    "minecraft:the_nether": {
+      "type": "minecraft:the_nether",
+      "generator": {
+        "type": "minecraft:noise",
+        "biome_source": {
+          "type": "minecraft:multi_noise",
+          "preset": "minecraft:nether"
+        },
+        "settings": "minecraft:nether"
+      }
+    }
+  }
+}
@@ -0,0 +1,81 @@
+{
+  "dimensions": {
+    "minecraft:overworld": {
+      "type": "sanctuary:sanctuary_384",
+      "generator": {
+        "type": "sanctuary:island_v19",
+        "biome_source": {
+          "biomes": [
+            "minecraft:the_void",
+            "minecraft:forest",
+            "minecraft:birch_forest",
+            "minecraft:flower_forest",
+            "minecraft:plains",
+            "minecraft:meadow",
+            "minecraft:taiga",
+            "minecraft:snowy_taiga",
+            "minecraft:snowy_plains",
+            "minecraft:grove",
+            "minecraft:ice_spikes",
+            "minecraft:frozen_peaks",
+            "minecraft:old_growth_spruce_taiga",
+            "minecraft:dark_forest",
+            "minecraft:swamp",
+            "minecraft:pale_garden",
+            "minecraft:jungle",
+            "minecraft:sparse_jungle",
+            "minecraft:bamboo_jungle",
+            "minecraft:mangrove_swamp",
+            "minecraft:savanna",
+            "minecraft:savanna_plateau",
+            "minecraft:desert",
+            "minecraft:badlands",
+            "minecraft:eroded_badlands",
+            "minecraft:wooded_badlands",
+            "minecraft:windswept_hills",
+            "minecraft:windswept_gravelly_hills",
+            "minecraft:stony_peaks",
+            "minecraft:dappled_forest",
+            "minecraft:cherry_grove",
+            "minecraft:lush_caves",
+            "minecraft:dripstone_caves",
+            "minecraft:sulfur_caves",
+            "sanctuary:population_oak_forest",
+            "sanctuary:population_birch_forest",
+            "sanctuary:population_clearing",
+            "sanctuary:population_dry_woodland",
+            "sanctuary:population_rocky_heath",
+            "sanctuary:population_dark_grove",
+            "sanctuary:population_bamboo_grove",
+            "sanctuary:population_sulfur_depths",
+            "sanctuary:population_lush_caves",
+            "sanctuary:population_dripstone_caves",
+            "sanctuary:lost_city"
+          ]
+        },
+        "initial_diameter": 724
+      }
+    },
+    "minecraft:the_end": {
+      "type": "minecraft:the_end",
+      "generator": {
+        "type": "minecraft:noise",
+        "biome_source": {
+          "type": "minecraft:the_end"
+        },
+        "settings": "minecraft:end"
+      }
+    },
+    "minecraft:the_nether": {
+      "type": "minecraft:the_nether",
+      "generator": {
+        "type": "minecraft:noise",
+        "biome_source": {
+          "type": "minecraft:multi_noise",
+          "preset": "minecraft:nether"
+        },
+        "settings": "minecraft:nether"
+      }
+    }
+  }
+}
@@ -158,6 +158,37 @@ public final class ExpansionJournalSmoke {
            require(Arrays.equals(experimentBytes, Files.readAllBytes(experimentDirectory.resolve(ExpansionJournal.FILE_NAME)))
                && Arrays.equals(ruinsBytes, Files.readAllBytes(ruinsDirectory.resolve(ExpansionJournal.FILE_NAME))),
                "Rejected cross-generation changes preserve experiment and published16 bytes");
+            var heritageRoot = ExpansionIsland.origin(724, SEED, 19);
+            var heritageDirectory = scratch.resolve("heritage-19");
+            var heritageJournal = new ExpansionJournal(heritageDirectory, SEED, 724, 19);
+            var heritageChild = ExpansionPlacement.candidates(SEED, List.of(heritageRoot), "heritage", "sanctuary", "east", "lost_city", 128, "natural", 0).getFirst()
+                .withReuseToken("f".repeat(64));
+            heritageJournal.commit(List.of(heritageRoot, heritageChild));
+            require(new ExpansionJournal(heritageDirectory, SEED, 724, 19).islands().equals(List.of(heritageRoot, heritageChild)),
+                "Generation19 preserves the new world and its expansions across journal reload");
+            byte[] heritageBytes = Files.readAllBytes(heritageDirectory.resolve(ExpansionJournal.FILE_NAME));
+            reject(() -> new ExpansionJournal(heritageDirectory, SEED, 724, 17), "No implicit downgrade from19 to17");
+            reject(() -> new ExpansionJournal(experimentDirectory, SEED, 724, 19), "No implicit upgrade from17 to19");
+            reject(() -> heritageJournal.commit(List.of(heritageRoot, experimentChild)), "No generation17 child in19");
+            require(Arrays.equals(heritageBytes, Files.readAllBytes(heritageDirectory.resolve(ExpansionJournal.FILE_NAME)))
+                && Arrays.equals(experimentBytes, Files.readAllBytes(experimentDirectory.resolve(ExpansionJournal.FILE_NAME))),
+                "Rejected migrations preserve both generation17 and19 journals");
+            var architectureRoot = ExpansionIsland.origin(724, SEED, 20);
+            var architectureDirectory = scratch.resolve("architecture-20");
+            var architectureJournal = new ExpansionJournal(architectureDirectory, SEED, 724, 20);
+            var architectureChild = ExpansionPlacement.candidates(SEED, List.of(architectureRoot), "architecture", "sanctuary", "east", "lost_city", 128, "natural", 0).getFirst()
+                .withReuseToken("a".repeat(64));
+            architectureJournal.commit(List.of(architectureRoot, architectureChild));
+            require(new ExpansionJournal(architectureDirectory, SEED, 724, 20).islands().equals(List.of(architectureRoot, architectureChild)),
+                "Generation20 and its expansions retain an independent journal on reload");
+            byte[] architectureBytes = Files.readAllBytes(architectureDirectory.resolve(ExpansionJournal.FILE_NAME));
+            reject(() -> new ExpansionJournal(architectureDirectory, SEED, 724, 19), "No implicit downgrade from20 to19");
+            reject(() -> new ExpansionJournal(heritageDirectory, SEED, 724, 20), "No implicit upgrade from19 to20");
+            reject(() -> architectureJournal.commit(List.of(architectureRoot, heritageChild)), "No generation19 child in20");
+            reject(() -> heritageJournal.commit(List.of(heritageRoot, architectureChild)), "No generation20 child in19");
+            require(Arrays.equals(architectureBytes, Files.readAllBytes(architectureDirectory.resolve(ExpansionJournal.FILE_NAME)))
+                && Arrays.equals(heritageBytes, Files.readAllBytes(heritageDirectory.resolve(ExpansionJournal.FILE_NAME))),
+                "Cross-generation rejection preserves published19 and new20 journals");
            try {
                ExpansionPlacement.candidates(SEED, List.of(ExpansionIsland.origin(724, SEED, 13)), "city", "sanctuary", "east", "lost_city", 256, "natural", 0);
                throw new AssertionError("Lost City must not silently activate in a saved alpha.13 world");
@@ -0,0 +1,451 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Kind;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Parcel;
+import java.util.ArrayDeque;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.EmptyBlockGetter;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.DoorBlock;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DoubleBlockHalf;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.phys.AABB;
+
+/** Exercises final block geometry rather than reconstructing the painter's room allocation. */
+public final class LostCityInteriors20Smoke {
+    private static final Kind[] KINDS = {Kind.APARTMENT, Kind.HOTEL, Kind.LIBRARY,
+        Kind.RESTAURANT, Kind.BARRACKS, Kind.HALL};
+    private static final Direction[] HORIZONTAL = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        run();
+        System.out.println("LostCityInteriors20Smoke: six building uses, alternating physical floor plans, four rotations, connected rooms, fully enclosed bathrooms, wall-backed beds with lateral access, native door/seat geometry, supported lanterns and deferred loot passed.");
+    }
+
+    /** Also usable after the engine has already bootstrapped its registries. */
+    public static void run() {
+        Set<Map<BlockPos, BlockState>> distinct = new HashSet<>();
+        Set<Set<BlockPos>> distinctVolumes = new HashSet<>();
+        var previews = new java.util.ArrayList<Object>();
+        for (Kind kind : KINDS) for (int floors : new int[]{2, 3, 5}) for (long seed : new long[]{0, 43}) {
+            Capture canonical = render(parcel(kind, floors, seed, 0));
+            if (floors == 2 && seed == 0) {
+                distinct.add(canonical.blocks);
+                Set<BlockPos> volume = new HashSet<>();
+                canonical.blocks.forEach((at, state) -> { if (!state.isAir() && at.getY() > 0
+                    && (at.getY() > 10 || at.getX() == 0 || at.getX() == 16 || at.getZ() == 0 || at.getZ() == 16)) volume.add(at); });
+                require(distinctVolumes.add(volume), kind + " only recolors an existing facade/roof volume");
+            }
+            if (floors == 3 && seed == 43 && System.getProperty("sanctuary.city20.preview") != null) {
+                var blocks = new java.util.ArrayList<Object>();
+                canonical.blocks.forEach((at, state) -> { if (!state.isAir()) blocks.add(java.util.List.of(at.getX(), at.getY(), at.getZ(), state.toString())); });
+                previews.add(Map.of("kind", kind.name(), "seed", seed, "floors", floors, "facing", 0, "blocks", blocks));
+            }
+            for (int facing = 0; facing < 4; facing++) {
+                Parcel parcel = parcel(kind, floors, seed, facing);
+                Capture result = facing == 0 ? canonical : render(parcel);
+                Capture repeated = render(parcel);
+                require(result.blocks.equals(repeated.blocks) && result.loot.equals(repeated.loot), "Saved parcel is not deterministic");
+                rotationMatches(canonical, result, facing);
+                require(result.blocks.values().stream().anyMatch(state -> state.is(Blocks.STONE_BRICKS)), "Missing stone-brick foundations");
+                require(result.blocks.values().stream().anyMatch(state -> state.is(Blocks.SMOOTH_STONE)), "Missing smooth stone");
+                require(result.blocks.values().stream().noneMatch(state -> state.is(Blocks.SPAWNER)
+                    || !state.getFluidState().isEmpty()), "Building introduced a spawner or free flowing fluid");
+                require(result.loot.size() == 1, "Building must keep one deferred loot chest");
+                var entrance = LostCityInteriors20.rooms(parcel).getFirst();
+                Set<BlockPos> reached = walk(result, position(entrance));
+                for (var room : LostCityInteriors20.rooms(parcel)) require(reached.contains(position(room)),
+                    label(parcel) + " cannot walk from its entrance to " + room.name() + " at " + position(room));
+                verifyDoors(result, reached);
+                verifyBeds(result, reached);
+                verifyBathrooms(result, reached);
+                verifyFurnitureDirections(result);
+                verifyLanternSupports(result);
+                for (BlockPos chest : result.loot.keySet()) require(adjacentReached(chest, reached),
+                    label(parcel) + " loot cannot be approached");
+                semantics(result);
+                if (facing == 0) verifyStoreyVariation(result);
+                verifyArchitecture(result);
+            }
+        }
+        require(distinct.size() == KINDS.length, "Building uses only labels to vary an identical interior");
+        boolean rejected = false;
+        try { LostCityInteriors20.rooms(new Parcel(Kind.PARK, 0, 0, 17, 17, 160, 2, 0, 0, 4, new int[0])); }
+        catch (IllegalArgumentException expected) { rejected = true; }
+        require(rejected, "Interior dispatch must reject non-building parcels");
+        String preview = System.getProperty("sanctuary.city20.preview");
+        if (preview != null) try {
+            var file = java.nio.file.Path.of(preview); if (file.getParent() != null) java.nio.file.Files.createDirectories(file.getParent());
+            java.nio.file.Files.writeString(file, new com.google.gson.Gson().toJson(previews));
+        } catch (java.io.IOException e) { throw new AssertionError("Cannot write requested architecture preview", e); }
+    }
+
+    private static Parcel parcel(Kind kind, int floors, long seed, int facing) {
+        return new Parcel(kind, -81, 119, 17, 17, 160, floors, facing, seed, 4, new int[0]);
+    }
+    private static Capture render(Parcel parcel) {
+        var result = new Capture(parcel);
+        LostCityInteriors20.render(parcel, result);
+        return result;
+    }
+    private static String label(Parcel p) { return p.kind() + " floors=" + p.floors() + " facing=" + p.facing() + " seed=" + p.seed(); }
+    private static BlockPos position(LostCityInteriors20.Room room) { return new BlockPos(room.x(), room.y(), room.z()); }
+
+    private static void rotationMatches(Capture canonical, Capture rotated, int facing) {
+        require(canonical.blocks.size() == rotated.blocks.size(), "Rotation changed the number of emitted positions");
+        Rotation rotation = switch (facing) {
+            case 0 -> Rotation.NONE; case 1 -> Rotation.CLOCKWISE_90;
+            case 2 -> Rotation.CLOCKWISE_180; default -> Rotation.COUNTERCLOCKWISE_90;
+        };
+        for (var entry : canonical.blocks.entrySet()) {
+            BlockPos target = rotate(entry.getKey(), facing);
+            // Native chest placement owns its final facing, so its loot position is checked separately.
+            if (canonical.loot.containsKey(entry.getKey())) continue;
+            require(rotated.block(target).equals(entry.getValue().rotate(rotation)), "Geometry or block-state rotation drifted at " + target);
+        }
+        for (var entry : canonical.loot.entrySet()) require(entry.getValue().equals(rotated.loot.get(rotate(entry.getKey(), facing))),
+            "Rotation changed deferred loot identity or position");
+    }
+
+    private static void verifyDoors(Capture result, Set<BlockPos> reached) {
+        long lowerDoors = 0, pairedLeaves = 0;
+        for (var entry : result.blocks.entrySet()) {
+            BlockState state = entry.getValue();
+            if (!(state.getBlock() instanceof DoorBlock)) continue;
+            require(state.is(Blocks.DARK_OAK_DOOR) && !state.getValue(BlockStateProperties.POWERED), "A room door cannot be opened by an ordinary player");
+            boolean lower = state.getValue(BlockStateProperties.DOUBLE_BLOCK_HALF) == DoubleBlockHalf.LOWER;
+            BlockPos partner = lower ? entry.getKey().above() : entry.getKey().below();
+            BlockState expected = state.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF,
+                lower ? DoubleBlockHalf.UPPER : DoubleBlockHalf.LOWER);
+            require(result.block(partner).equals(expected), label(result.parcel) + " has an incomplete/mismatched door at " + entry.getKey());
+            if (!lower) continue;
+            lowerDoors++;
+            require(result.block(entry.getKey().below()).isSolid(), "Door has no solid threshold");
+            Direction normal = state.getValue(BlockStateProperties.HORIZONTAL_FACING);
+            require(reached.contains(entry.getKey().relative(normal)) && reached.contains(entry.getKey().relative(normal.getOpposite())),
+                label(result.parcel) + " door does not connect two walkable sides at " + entry.getKey());
+            for (Direction side : new Direction[]{normal.getClockWise(), normal.getCounterClockWise()}) {
+                BlockState neighbor = result.block(entry.getKey().relative(side));
+                if (!neighbor.is(Blocks.DARK_OAK_DOOR)
+                        || neighbor.getValue(BlockStateProperties.DOUBLE_BLOCK_HALF) != DoubleBlockHalf.LOWER
+                        || neighbor.getValue(BlockStateProperties.HORIZONTAL_FACING) != normal) continue;
+                AABB opened = state.setValue(BlockStateProperties.OPEN, true)
+                    .getCollisionShape(EmptyBlockGetter.INSTANCE, entry.getKey()).bounds();
+                require(againstOppositeEdge(opened, side), label(result.parcel) + " double door opens into its partner at " + entry.getKey());
+                pairedLeaves++;
+            }
+        }
+        require(lowerDoors >= result.parcel.floors() * 3L + 2, "Missing actual doors between distinct rooms");
+        require(pairedLeaves >= 2, "Entrance must retain a double door with its hinges against the outside jambs");
+        for (var room : LostCityInteriors20.rooms(result.parcel)) if (room.name().endsWith("/stair_landing")) {
+            BlockPos landing = position(room);
+            boolean opensIntoStairwell = false;
+            for (Direction side : HORIZONTAL) {
+                BlockPos at = landing.relative(side);
+                BlockState state = result.block(at);
+                if (state.is(Blocks.DARK_OAK_DOOR)) opensIntoStairwell |=
+                    at.relative(state.getValue(BlockStateProperties.HORIZONTAL_FACING)).equals(landing);
+            }
+            require(opensIntoStairwell, "Stairwell door must open into its landing, away from the central corridor");
+        }
+    }
+
+    private static boolean againstOppositeEdge(AABB box, Direction towardPartner) {
+        return switch (towardPartner) {
+            case EAST -> box.maxX <= .25; case WEST -> box.minX >= .75;
+            case SOUTH -> box.maxZ <= .25; case NORTH -> box.minZ >= .75;
+            default -> throw new AssertionError("Door partner must be horizontal");
+        };
+    }
+
+    private static void verifyFurnitureDirections(Capture result) {
+        int tableSeats = 0;
+        for (var entry : result.blocks.entrySet()) {
+            if (!entry.getValue().is(Blocks.DARK_OAK_FENCE)
+                    || !result.block(entry.getKey().above()).is(Blocks.DARK_OAK_PRESSURE_PLATE)) continue;
+            int aroundThisTable = 0;
+            for (Direction side : HORIZONTAL) {
+                BlockPos chair = entry.getKey().relative(side);
+                if (!result.block(chair).is(Blocks.DARK_OAK_STAIRS)) continue;
+                seatLooksToward(result, chair, side.getOpposite());
+                aroundThisTable++; tableSeats++;
+            }
+            require(aroundThisTable > 0, "A desk/table lost every chair facing its surface");
+        }
+        if (result.parcel.kind() != Kind.BARRACKS)
+            require(tableSeats >= result.parcel.floors(), "Every furnished storey needs a usable table or desk seat");
+        if (result.parcel.kind() == Kind.HALL) for (int x : new int[]{3, 4, 5, 11, 12, 13})
+            seatLooksToward(result, rotate(new BlockPos(x, 1, 11), result.parcel.facing()), rotated(Direction.SOUTH, result.parcel.facing()));
+        if (result.parcel.kind() == Kind.HOTEL) for (int x = 2; x <= 4; x++)
+            seatLooksToward(result, rotate(new BlockPos(x, 1, 14), result.parcel.facing()), rotated(Direction.NORTH, result.parcel.facing()));
+        if (result.parcel.kind() == Kind.BARRACKS) for (int floor = 0; floor < result.parcel.floors(); floor++)
+            if (LostCityInteriors20.layout(result.parcel, floor) == 0)
+                seatLooksToward(result, rotate(new BlockPos(13, floor * 5 + 1, 6), result.parcel.facing()), rotated(Direction.NORTH, result.parcel.facing()));
+        for (var entry : result.blocks.entrySet()) if (entry.getValue().is(Blocks.POLISHED_ANDESITE_STAIRS)) {
+            Direction look = entry.getValue().getValue(BlockStateProperties.HORIZONTAL_FACING).getOpposite();
+            require(clear(result.block(entry.getKey().relative(look))), "Sanitary seat faces a wall instead of its cubicle");
+        }
+    }
+
+    private static void seatLooksToward(Capture result, BlockPos chair, Direction towardUse) {
+        BlockState state = result.block(chair);
+        require(state.is(Blocks.DARK_OAK_STAIRS), "Missing chair at " + chair);
+        var boxes = state.getCollisionShape(EmptyBlockGetter.INSTANCE, chair).toAabbs();
+        double frontX = .5 + towardUse.getStepX() * .25, frontZ = .5 + towardUse.getStepZ() * .25;
+        double backX = .5 - towardUse.getStepX() * .25, backZ = .5 - towardUse.getStepZ() * .25;
+        require(boxes.stream().noneMatch(box -> box.contains(frontX, .75, frontZ))
+            && boxes.stream().anyMatch(box -> box.contains(backX, .75, backZ)),
+            label(result.parcel) + " chair's native back faces its table/stage at " + chair);
+        require(result.block(chair.below()).isCollisionShapeFullBlock(EmptyBlockGetter.INSTANCE, chair.below()),
+            "Chair does not rest on a complete floor");
+    }
+
+    private static Direction rotated(Direction direction, int facing) {
+        for (int turn = 0; turn < facing; turn++) direction = direction.getClockWise();
+        return direction;
+    }
+
+    private static void verifyLanternSupports(Capture result) {
+        int lanterns = 0;
+        for (var entry : result.blocks.entrySet()) if (entry.getValue().is(Blocks.LANTERN)) {
+            BlockPos support = entry.getValue().getValue(BlockStateProperties.HANGING) ? entry.getKey().above() : entry.getKey().below();
+            require(result.block(support).isCollisionShapeFullBlock(EmptyBlockGetter.INSTANCE, support),
+                label(result.parcel) + " lantern floats against a slab or lacks a full support block at " + entry.getKey());
+            lanterns++;
+        }
+        require(lanterns == result.parcel.floors(), "A junction lost its supported lamp");
+    }
+
+    private static void verifyBeds(Capture result, Set<BlockPos> reached) {
+        for (var entry : result.blocks.entrySet()) {
+            BlockState state = entry.getValue();
+            if (!state.is(Blocks.BED.white())) continue;
+            Direction direction = state.getValue(BlockStateProperties.HORIZONTAL_FACING);
+            BedPart part = state.getValue(BlockStateProperties.BED_PART);
+            BlockPos partner = entry.getKey().relative(part == BedPart.FOOT ? direction : direction.getOpposite());
+            require(result.block(partner).equals(state.setValue(BlockStateProperties.BED_PART,
+                part == BedPart.FOOT ? BedPart.HEAD : BedPart.FOOT)), label(result.parcel) + " has a severed bed at " + entry.getKey());
+            require(result.block(entry.getKey().below()).isSolid(), "Bed does not sit on a floor");
+            require(adjacentReached(entry.getKey(), reached) || adjacentReached(partner, reached),
+                label(result.parcel) + " bed cannot be approached from its room");
+            if (part == BedPart.HEAD) {
+                var backing = entry.getKey().relative(direction);
+                for (int up = 0; up < 3; up++) require(result.block(backing.above(up))
+                    .isCollisionShapeFullBlock(EmptyBlockGetter.INSTANCE, backing.above(up)),
+                    label(result.parcel) + " bed head is not against a complete wall at " + entry.getKey());
+            } else {
+                boolean lateral = false;
+                for (Direction side : new Direction[]{direction.getClockWise(), direction.getCounterClockWise()})
+                    lateral |= reached.contains(entry.getKey().relative(side)) && reached.contains(partner.relative(side));
+                require(lateral, label(result.parcel) + " bed lacks a reachable side along its full length at " + entry.getKey());
+            }
+        }
+    }
+
+    private static void verifyBathrooms(Capture result, Set<BlockPos> reached) {
+        for (var bath : LostCityInteriors20.bathrooms(result.parcel)) {
+            BlockPos door = new BlockPos(bath.doorX(), bath.doorY(), bath.doorZ());
+            require(result.block(door).is(Blocks.DARK_OAK_DOOR), "Enclosed bathroom lost its actual door: " + bath.name());
+            Direction intoRoom = result.block(door).getValue(BlockStateProperties.HORIZONTAL_FACING);
+            require(reached.contains(door.relative(intoRoom)), "Bathroom cannot be entered through its door: " + bath.name());
+            require(bath.minX() == 1 || bath.minZ() == 1 || bath.maxX() == 15 || bath.maxZ() == 15,
+                "Bathroom enclosure is detached from the exterior room wall");
+            for (int x = bath.minX(); x <= bath.maxX(); x++) for (int z = bath.minZ(); z <= bath.maxZ(); z++)
+                for (int y = bath.minY(); y <= bath.maxY(); y++) {
+                    boolean shell = x == bath.minX() || x == bath.maxX() || z == bath.minZ() || z == bath.maxZ()
+                        || y == bath.minY() || y == bath.maxY();
+                    if (!shell) continue;
+                    BlockPos at = new BlockPos(x, y, z);
+                    if (at.equals(door) || at.equals(door.above())) continue;
+                    require(result.block(at).isCollisionShapeFullBlock(EmptyBlockGetter.INSTANCE, at),
+                        label(result.parcel) + " bathroom has an incomplete floor, ceiling or connected wall at " + at + " in " + bath.name());
+                }
+        }
+    }
+
+    private static void verifyStoreyVariation(Capture result) {
+        for (int floor = 1; floor < result.parcel.floors(); floor++) {
+            require(LostCityInteriors20.layout(result.parcel, floor - 1) != LostCityInteriors20.layout(result.parcel, floor),
+                "Adjacent storeys selected the same plan");
+            Set<BlockPos> before = rearPartitions(result, floor - 1), after = rearPartitions(result, floor);
+            require(!before.equals(after), label(result.parcel) + " only changed furniture or labels between storeys " + (floor - 1) + " and " + floor);
+            Map<BlockPos, BlockState> beforeFixtures = furnishings(result, floor - 1), afterFixtures = furnishings(result, floor);
+            require(!beforeFixtures.equals(afterFixtures), label(result.parcel)
+                + " copied the same furniture between storeys " + (floor - 1) + " and " + floor);
+        }
+    }
+
+    private static Set<BlockPos> rearPartitions(Capture result, int floor) {
+        Set<BlockPos> walls = new HashSet<>();
+        for (int x = 2; x <= 14; x++) for (int z = 9; z <= 14; z++) {
+            boolean continuous = true;
+            for (int y = 1; y <= 3; y++) continuous &= result.block(new BlockPos(x, floor * 5 + y, z)).is(Blocks.SMOOTH_STONE);
+            if (continuous) walls.add(new BlockPos(x, 0, z));
+        }
+        return walls;
+    }
+
+    private static Map<BlockPos, BlockState> furnishings(Capture result, int floor) {
+        Map<BlockPos, BlockState> objects = new HashMap<>();
+        for (int x = 2; x <= 14; x++) for (int z = 2; z <= 14; z++) for (int up = 1; up <= 3; up++) {
+            BlockState state = result.block(new BlockPos(x, floor * 5 + up, z));
+            if (state.is(Blocks.BED.white()) || state.is(Blocks.BARREL) || state.is(Blocks.FURNACE)
+                    || state.is(Blocks.BOOKSHELF) || state.is(Blocks.WATER_CAULDRON) || state.is(Blocks.DARK_OAK_FENCE)
+                    || state.is(Blocks.LECTERN) || state.is(Blocks.CRAFTING_TABLE) || state.is(Blocks.DARK_OAK_STAIRS)
+                    || state.is(Blocks.DARK_OAK_PLANKS) || state.is(Blocks.OAK_PLANKS) || state.is(Blocks.BIRCH_PLANKS)) objects.put(new BlockPos(x, up, z), state);
+        }
+        return objects;
+    }
+
+    private static void semantics(Capture result) {
+        Map<BlockState, Long> counts = new HashMap<>();
+        result.blocks.values().forEach(state -> counts.merge(state, 1L, Long::sum));
+        java.util.function.Predicate<net.minecraft.world.level.block.Block> has = block ->
+            counts.keySet().stream().anyMatch(state -> state.is(block));
+        switch (result.parcel.kind()) {
+            case APARTMENT -> require(has.test(Blocks.FURNACE) && has.test(Blocks.BED.white())
+                && has.test(Blocks.WATER_CAULDRON), "Apartment lacks cooking, sleeping or washing fixtures");
+            case HOTEL -> require(has.test(Blocks.LOOM) && has.test(Blocks.BED.white())
+                && has.test(Blocks.WATER_CAULDRON), "Hotel lacks guest rooms or laundry fixtures");
+            case LIBRARY -> require(result.blocks.values().stream().filter(state -> state.is(Blocks.BOOKSHELF)).count() >= result.parcel.floors() * 12L
+                && has.test(Blocks.LECTERN), "Library is missing usable stacks and reading fixtures");
+            case RESTAURANT -> require(has.test(Blocks.SMOKER) && has.test(Blocks.FURNACE)
+                && has.test(Blocks.CRAFTING_TABLE) && has.test(Blocks.WATER_CAULDRON), "Restaurant lacks kitchen and washroom services");
+            case BARRACKS -> require(has.test(Blocks.BED.white()) && has.test(Blocks.FLETCHING_TABLE)
+                && has.test(Blocks.GRINDSTONE), "Barracks lacks dormitory and equipment fixtures");
+            case HALL -> {
+                require(has.test(Blocks.LECTERN) && has.test(Blocks.IRON_BARS), "Hall lacks stage or gallery guards");
+                require(result.block(rotate(new BlockPos(8, 5, 12), result.parcel.facing())).isAir(), "Auditorium lost its double-height volume");
+            }
+            default -> throw new AssertionError("Unexpected building");
+        }
+    }
+
+    /** Player-sized path: two clear cells above support, one-block steps and manually openable doors. */
+    private static Set<BlockPos> walk(Capture result, BlockPos start) {
+        require(standable(result, start), label(result.parcel) + " has a blocked entrance");
+        Set<BlockPos> seen = new HashSet<>();
+        ArrayDeque<BlockPos> queue = new ArrayDeque<>();
+        seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            BlockPos current = queue.removeFirst();
+            for (Direction direction : HORIZONTAL) for (int dy = -1; dy <= 1; dy++) {
+                BlockPos next = current.relative(direction).offset(0, dy, 0);
+                if (dy > 0 && !clearBody(result, current.above())) continue;
+                if (standable(result, next) && seen.add(next)) queue.addLast(next);
+            }
+        }
+        return seen;
+    }
+    private static boolean standable(Capture result, BlockPos pos) {
+        if (pos.getX() < 0 || pos.getX() > 16 || pos.getZ() < 0 || pos.getZ() > 16
+            || pos.getY() < 1 || pos.getY() > result.parcel.floors() * 5 + 4) return false;
+        if (!clearBody(result, pos)) return false;
+        var below = pos.below();
+        return opened(result.block(below)).getCollisionShape(EmptyBlockGetter.INSTANCE, below).toAabbs().stream()
+            .anyMatch(b -> b.maxY >= .5 && b.minX <= .5 && b.maxX >= .5 && b.minZ <= .5 && b.maxZ >= .5);
+    }
+    private static BlockState opened(BlockState state) {
+        return state.getBlock() instanceof net.minecraft.world.level.block.DoorBlock
+            || state.getBlock() instanceof net.minecraft.world.level.block.TrapDoorBlock
+            ? state.setValue(BlockStateProperties.OPEN, true) : state;
+    }
+    private static boolean clearBody(Capture result, BlockPos pos) {
+        var body = new AABB(pos.getX() + .2, pos.getY(), pos.getZ() + .2, pos.getX() + .8, pos.getY() + 1.8, pos.getZ() + .8);
+        for (var at : new BlockPos[]{pos, pos.above()}) {
+            var state = opened(result.block(at));
+            if (!state.getFluidState().isEmpty()) return false;
+            for (var shape : state.getCollisionShape(EmptyBlockGetter.INSTANCE, at).toAabbs())
+                if (shape.move(at.getX(), at.getY(), at.getZ()).intersects(body)) return false;
+        }
+        return true;
+    }
+    private static boolean clear(BlockState state) { return state.isAir() || state.is(Blocks.DARK_OAK_DOOR); }
+    private static void verifyArchitecture(Capture c) {
+        for (int x = 0; x <= 16; x++) for (int z = 0; z <= 16; z++)
+            require(c.block(new BlockPos(x, -1, z)).is(Blocks.STONE_BRICKS), "Foundation is not dressed stone brick");
+        long outsideVolume = c.blocks.entrySet().stream().filter(e -> e.getKey().getY() > 0
+            && (e.getKey().getX() == 0 || e.getKey().getX() == 16 || e.getKey().getZ() == 0 || e.getKey().getZ() == 16)
+            && !e.getValue().isAir()).count();
+        require(outsideVolume >= 40, label(c.parcel) + " has no cornice, bay, fins or entrance projection");
+        require(c.blocks.values().stream().anyMatch(b -> b.is(Blocks.TUFF_BRICKS)), "Missing structural tuff courses");
+        if (c.parcel.kind() == Kind.APARTMENT || c.parcel.kind() == Kind.LIBRARY)
+            require(c.block(rotate(new BlockPos(1, 2, 1), c.parcel.facing())).isAir(), "Front corner was not physically cut back");
+        if (c.parcel.kind() == Kind.LIBRARY) {
+            int roof = c.parcel.floors() * 5;
+            for (int x = 11; x <= 12; x++) for (int z = 4; z <= 6; z++) {
+                for (int y = roof - 1; y <= roof; y++)
+                    require(c.block(rotate(new BlockPos(x, y, z), c.parcel.facing())).isAir(),
+                        label(c.parcel) + " skylight is blocked by the roof plate or last-storey ceiling");
+                for (int y = roof + 1; y <= roof + 2; y++)
+                    require(c.block(rotate(new BlockPos(x, y, z), c.parcel.facing())).is(Blocks.GLASS),
+                        label(c.parcel) + " skylight lost its continuous transparent cap");
+                for (int y = roof + 3; y <= roof + 4; y++)
+                    require(c.block(rotate(new BlockPos(x, y, z), c.parcel.facing())).isAir(),
+                        label(c.parcel) + " another roof feature shades the light well");
+            }
+            for (int x = 10; x <= 13; x++) for (int z = 3; z <= 7; z++) {
+                if (x > 10 && x < 13 && z > 3 && z < 7) continue;
+                var base = rotate(new BlockPos(x, roof, z), c.parcel.facing());
+                require(c.block(base).isCollisionShapeFullBlock(EmptyBlockGetter.INSTANCE, base)
+                        && c.block(base.above()).is(Blocks.STRIPPED_BIRCH_LOG),
+                    label(c.parcel) + " skylight cut through its supporting perimeter or timber frame");
+            }
+        }
+        // Resolve every glazing edge from final neighbors, not precomputed straight strips.
+        for (var e : c.blocks.entrySet()) if (e.getValue().is(Blocks.GLASS_PANE)) {
+            for (Direction d : HORIZONTAL) {
+                var neighbor = c.block(e.getKey().relative(d));
+                if (!neighbor.isCollisionShapeFullBlock(EmptyBlockGetter.INSTANCE, e.getKey().relative(d))) continue;
+                var property = switch(d) { case NORTH -> BlockStateProperties.NORTH; case EAST -> BlockStateProperties.EAST;
+                    case SOUTH -> BlockStateProperties.SOUTH; case WEST -> BlockStateProperties.WEST; default -> throw new AssertionError(); };
+                require(e.getValue().getValue(property), "Window does not meet its actual stone or timber jamb");
+            }
+        }
+    }
+    private static boolean adjacentReached(BlockPos pos, Set<BlockPos> reached) {
+        for (Direction direction : HORIZONTAL) if (reached.contains(pos.relative(direction))) return true;
+        return false;
+    }
+    private static BlockPos rotate(BlockPos pos, int facing) {
+        return switch (facing) {
+            case 0 -> pos; case 1 -> new BlockPos(16 - pos.getZ(), pos.getY(), pos.getX());
+            case 2 -> new BlockPos(16 - pos.getX(), pos.getY(), 16 - pos.getZ());
+            default -> new BlockPos(pos.getZ(), pos.getY(), 16 - pos.getX());
+        };
+    }
+
+    private record Loot(ResourceKey<LootTable> table, long seed) {}
+    private static final class Capture implements LostCityRenderer.BlockWriter {
+        final Parcel parcel;
+        final Map<BlockPos, BlockState> blocks = new HashMap<>();
+        final Map<BlockPos, Loot> loot = new HashMap<>();
+        Capture(Parcel parcel) { this.parcel = parcel; }
+        @Override public void set(int x, int y, int z, BlockState state) {
+            require(x >= 0 && x < 17 && z >= 0 && z < 17 && y >= parcel.minY() - parcel.floorY()
+                && y <= parcel.maxY() - parcel.floorY(), label(parcel) + " writes outside its saved bounds at " + x + "," + y + "," + z);
+            blocks.put(new BlockPos(x, y, z), state);
+        }
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+            set(x, y, z, Blocks.CHEST.defaultBlockState());
+            loot.put(new BlockPos(x, y, z), new Loot(table, seed));
+        }
+        BlockState block(BlockPos pos) { return blocks.getOrDefault(pos, Blocks.AIR.defaultBlockState()); }
+    }
+    private static void require(boolean condition, String message) { if (!condition) throw new AssertionError(message); }
+}
@@ -0,0 +1,229 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Kind;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Parcel;
+import java.util.ArrayDeque;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Real block-state geometry, without creating a world: clipping, rotations and walkable floors. */
+public final class LostCitySurface20Smoke {
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        run();
+        System.out.println("LostCitySurface20Smoke: all exterior amenities, supported lamps, basements, contained pools, excavation access, carved park variants and suspended tuff roads passed.");
+    }
+
+    /** Also callable from an already bootstrapped native GameTest. */
+    public static void run() {
+        for (Kind kind : Kind.values()) {
+            if (kind.building()) continue;
+            for (int facing = 0; facing < 4; facing++) {
+                for (long seed : new long[] {0, 42, -61872}) {
+                    int floors = kind == Kind.HALL ? 2 : 3;
+                    int foundation = kind == Kind.POOL || kind == Kind.EXCAVATION ? 8 : 4;
+                    Parcel parcel = new Parcel(kind, 0, 0, 17, 17, 170, floors, facing, seed, foundation, new int[0]);
+                    Capture result = render(parcel);
+                    require(result.blocks.equals(render(parcel).blocks), "Renderer changed for identical saved parcel");
+                    require(result.blocks.values().stream().noneMatch(state -> state.is(Blocks.SPAWNER)), "City introduced a spawner");
+                    if (kind.building()) {
+                        require(result.blocks.values().stream().anyMatch(state -> state.is(Blocks.STONE_BRICKS)), "Missing explicit stone palette");
+                        require(result.blocks.values().stream().anyMatch(state -> state.is(Blocks.SMOOTH_STONE)), "Missing smooth stone palette");
+                        Set<BlockPos> reached = walk(result, rotate(8, 1, 0, facing));
+                        for (int floor = 1; floor <= floors; floor++) {
+                            int elevation = floor * 5 + 1;
+                            require(reached.stream().anyMatch(pos -> pos.getY() == elevation),
+                                kind + " facing " + facing + " cannot reach floor/roof " + floor);
+                        }
+                        require(result.loot.size() == 1, kind + " must keep exactly one deferred, limited loot chest");
+                    }
+                    for (var entry : result.blocks.entrySet()) {
+                        if (entry.getValue().is(Blocks.LANTERN)) {
+                            var support = entry.getValue().getValue(BlockStateProperties.HANGING) ? entry.getKey().above() : entry.getKey().below();
+                            require(result.block(support).isCollisionShapeFullBlock(net.minecraft.world.level.EmptyBlockGetter.INSTANCE, support), kind + " lantern lacks full support at " + entry.getKey());
+                        }
+                        BlockState state = entry.getValue();
+                        if (state.is(Blocks.BED.white()) && state.getValue(BlockStateProperties.BED_PART) == BedPart.FOOT) {
+                            Direction direction = state.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                            BlockState head = result.block(entry.getKey().relative(direction));
+                            require(head.is(Blocks.BED.white()) && head.getValue(BlockStateProperties.BED_PART) == BedPart.HEAD,
+                                "Rotated bedroom has an incomplete bed");
+                        }
+                    }
+                }
+            }
+        }
+        for (int facing = 0; facing < 4; facing++) {
+            Parcel garage = new Parcel(Kind.PARKING, 0, 0, 17, 17, 170, 1, facing, 9, 8, new int[0]);
+            Capture result = render(garage);
+            Set<BlockPos> reached = walk(result, rotate(8, 1, 0, facing));
+            require(reached.contains(rotate(8, -4, 10, facing)), "Underground garage is not reachable from its street ramp");
+            require(result.block(rotate(8, -6, 10, facing)).is(Blocks.STONE_BRICKS), "Garage excavation removed the certified rock below its floor");
+            Parcel pit = new Parcel(Kind.EXCAVATION, 0, 0, 17, 17, 170, 0, facing, 9, 8, new int[0]);
+            Capture excavation = render(pit);
+            require(walk(excavation, rotate(8, 1, 0, facing)).contains(rotate(8, -4, 10, facing)),
+                "Excavation has no walkable stairs from the street");
+            require(excavation.block(rotate(8, -6, 10, facing)).is(Blocks.STONE_BRICKS), "Excavation removed its certified bottom support");
+            Parcel pool = new Parcel(Kind.POOL, 0, 0, 17, 17, 170, 0, facing, 9, 8, new int[0]);
+            Capture water = render(pool);
+            sealedPool(water, facing);
+            require(walk(water, rotate(8, 1, 0, facing)).contains(rotate(8, -2, 7, facing)),
+                "Pool submerged steps cannot be reached from the deck");
+        }
+        // Every public type keeps a usable north approach, and its furniture does not consume the street threshold.
+        for (Kind kind : Kind.values()) if (!kind.building() && kind != Kind.STREET && kind != Kind.BRIDGE)
+            for (int facing = 0; facing < 4; facing++) {
+                Capture c = render(new Parcel(kind, 0, 0, 17, 17, 170, 0, facing, 42, 8, new int[0]));
+                var reached = walk(c, rotate(8, 1, 0, facing));
+                require(reached.size() >= 100, kind + " lost its public circulation");
+                for (var chest : c.loot.keySet()) require(java.util.Arrays.stream(new Direction[]{Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST})
+                    .anyMatch(d -> reached.contains(chest.relative(d))), kind + " loot is not approachable");
+            }
+        exportPreviews();
+        Set<Map<BlockPos, BlockState>> parks = new HashSet<>();
+        for (Kind park : new Kind[] {Kind.PARK, Kind.PARK_GARDEN, Kind.PARK_PLAYGROUND, Kind.PARK_MEMORIAL}) {
+            parks.add(render(new Parcel(park, 0, 0, 17, 17, 170, 0, 0, 42, 4, new int[0])).blocks);
+        }
+        require(parks.size() == 4, "Park variants must have distinct geometry");
+        for (Kind kind : new Kind[] {Kind.POOL, Kind.EXCAVATION}) {
+            Capture fallback = render(new Parcel(kind, 0, 0, 17, 17, 170, 0, 0, 42, 4, new int[0]));
+            require(fallback.blocks.values().stream().noneMatch(state -> !state.getFluidState().isEmpty()),
+                "Uncertified ground produced a wet excavation");
+            require(fallback.block(new BlockPos(8, -1, 8)).is(Blocks.STONE_BRICKS), "Uncertified ground was excavated");
+        }
+        int[] heights = new int[17 * 5];
+        for (int z = 0; z < 17; z++) for (int x = 0; x < 5; x++) heights[z * 5 + x] = 170 + z / 4;
+        Parcel bridge = new Parcel(Kind.BRIDGE, 0, 0, 5, 17, 170, 0, 0, 33, 0, heights);
+        Capture result = render(bridge);
+        require(result.blocks.entrySet().stream().noneMatch(entry -> !entry.getValue().isAir()
+                && entry.getKey().getY() < bridge.surfaceY(entry.getKey().getX(), entry.getKey().getZ()) - bridge.floorY()),
+            "Bridge grew a column below its suspended deck");
+        for (var e : result.blocks.entrySet()) if (e.getValue().is(Blocks.TUFF_BRICK_STAIRS)) {
+            var face = e.getValue().getValue(BlockStateProperties.HORIZONTAL_FACING);
+            var high = e.getKey().relative(face);
+            require(bridge.surfaceY(high.getX(), high.getZ()) - bridge.floorY() == e.getKey().getY(),
+                "Bridge stair fails to meet the higher deck");
+        }
+        Set<BlockPos> reached = walk(result, new BlockPos(2, 1, 0));
+        require(reached.contains(new BlockPos(2, 5, 16)), "Stepped bridge cannot be crossed");
+    }
+
+    private static void exportPreviews() {
+        String path = System.getProperty("sanctuary.city20.exteriorPreview");
+        if (path == null) return;
+        var examples = new java.util.ArrayList<Object>();
+        for (Kind kind : Kind.values()) if (!kind.building() && kind != Kind.STREET && kind != Kind.BRIDGE) {
+            var p = new Parcel(kind, 0, 0, 17, 17, 170, 0, 0, 42, 8, new int[0]); var c = render(p);
+            var blocks = new java.util.ArrayList<Object>();
+            c.blocks.forEach((at, state) -> { if (!state.isAir()) blocks.add(java.util.List.of(at.getX(), at.getY(), at.getZ(), state.toString())); });
+            examples.add(Map.of("kind", kind.name(), "seed", p.seed(), "facing", 0, "blocks", blocks));
+        }
+        try { var output = java.nio.file.Path.of(path); if (output.getParent() != null) java.nio.file.Files.createDirectories(output.getParent());
+            java.nio.file.Files.writeString(output, new com.google.gson.Gson().toJson(examples)); }
+        catch (java.io.IOException e) { throw new AssertionError("Cannot write requested geometry preview", e); }
+    }
+
+    private static Capture render(Parcel parcel) {
+        Capture result = new Capture(parcel);
+        LostCitySurface20.render(parcel, result);
+        return result;
+    }
+
+    /** Flood the cells a source can reach horizontally/downward, without permitting water to rise. */
+    private static void sealedPool(Capture result, int facing) {
+        Set<BlockPos> flooded = new HashSet<>();
+        ArrayDeque<BlockPos> queue = new ArrayDeque<>();
+        result.blocks.forEach((pos, state) -> {
+            if (!state.getFluidState().isEmpty()) { flooded.add(pos); queue.add(pos); }
+        });
+        require(flooded.size() > 150, "Pool must contain a real basin of water");
+        while (!queue.isEmpty()) {
+            BlockPos pos = queue.removeFirst();
+            require(pos.getY() >= -3 && pos.getY() <= -1, "Pool leaks vertically through its floor or coping");
+            BlockPos canonical = rotate(pos.getX(), pos.getY(), pos.getZ(), (4 - facing) % 4);
+            require(canonical.getX() >= 4 && canonical.getX() <= 12 && canonical.getZ() >= 5 && canonical.getZ() <= 12,
+                "Pool leaks outside its continuous side walls");
+            for (Direction direction : new Direction[] {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST, Direction.DOWN}) {
+                BlockPos next = pos.relative(direction);
+                BlockState state = result.block(next);
+                if ((state.isAir() || !state.getFluidState().isEmpty()) && flooded.add(next)) queue.addLast(next);
+            }
+        }
+    }
+
+    /** Conservative full-block walking with one-block steps and two blocks of clear headroom. */
+    private static Set<BlockPos> walk(Capture result, BlockPos start) {
+        require(standable(result, start), "Entrance is blocked: " + start);
+        Set<BlockPos> seen = new HashSet<>();
+        ArrayDeque<BlockPos> queue = new ArrayDeque<>();
+        queue.add(start);
+        seen.add(start);
+        while (!queue.isEmpty()) {
+            BlockPos current = queue.removeFirst();
+            for (Direction direction : new Direction[] {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST}) {
+                for (int dy = -1; dy <= 1; dy++) {
+                    BlockPos next = current.relative(direction).offset(0, dy, 0);
+                    if (standable(result, next) && seen.add(next)) queue.addLast(next);
+                }
+            }
+        }
+        return seen;
+    }
+
+    private static boolean standable(Capture result, BlockPos pos) {
+        if (pos.getX() < 0 || pos.getZ() < 0 || pos.getX() >= result.parcel.width() || pos.getZ() >= result.parcel.depth()) return false;
+        BlockState support = result.block(pos.below());
+        return (support.isSolid() || support.getBlock() instanceof StairBlock)
+            && clear(result.block(pos)) && clear(result.block(pos.above()));
+    }
+
+    private static boolean clear(BlockState state) { return state.isAir() || state.is(Blocks.WATER); }
+
+    private static BlockPos rotate(int x, int y, int z, int facing) {
+        return switch (facing) {
+            case 0 -> new BlockPos(x, y, z);
+            case 1 -> new BlockPos(16 - z, y, x);
+            case 2 -> new BlockPos(16 - x, y, 16 - z);
+            default -> new BlockPos(z, y, 16 - x);
+        };
+    }
+
+    private static final class Capture implements LostCityRenderer.BlockWriter {
+        private final Parcel parcel;
+        private final Map<BlockPos, BlockState> blocks = new HashMap<>();
+        private final Map<BlockPos, ResourceKey<LootTable>> loot = new HashMap<>();
+        Capture(Parcel parcel) { this.parcel = parcel; }
+
+        @Override public void set(int x, int y, int z, BlockState state) {
+            require(x >= 0 && z >= 0 && x < parcel.width() && z < parcel.depth()
+                    && y >= parcel.minY() - parcel.floorY() && y <= parcel.maxY() - parcel.floorY(),
+                parcel.kind() + " emitted a block outside its saved bounds at " + x + "," + y + "," + z);
+            blocks.put(new BlockPos(x, y, z), state);
+        }
+
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long lootSeed) {
+            set(x, y, z, Blocks.CHEST.defaultBlockState());
+            loot.put(new BlockPos(x, y, z), table);
+        }
+
+        BlockState block(BlockPos pos) { return blocks.getOrDefault(pos, Blocks.AIR.defaultBlockState()); }
+    }
+
+    private static void require(boolean condition, String message) {
+        if (!condition) throw new AssertionError(message);
+    }
+}
@@ -0,0 +1,230 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import java.util.ArrayDeque;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Actual renderer topology on disposable, finite terrain fixtures. No Minecraft save is changed. */
+public final class LostCityUnderground20Smoke {
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("LostCityUnderground20Smoke: Olympic pool, deep connected parking, exterior discharge, dry hall, bounds, rock anchors and protected terrain passed.");
+    }
+    public static void run() {
+        var terrain = new RockTerrain(); var surface = surface();
+        for (long seed : new long[] {0, 42}) {
+            var plan = LostCityUnderground16.plan(seed, surface, terrain);
+            require(!plan.isEmpty(), "Finite rock island has no accessible utilities");
+            require(plan.equals(LostCityUnderground16.plan(seed, surface, terrain)), "Same input changed saved module parameters");
+            var network = plan.networks().getFirst(); var capture = render(plan, terrain);
+            require(capture.blocks.equals(render(plan, terrain).blocks), "Saved parameters do not reconstruct the same blocks");
+            for (int a = 0; a < network.modules().size(); a++) for (int b = a + 1; b < network.modules().size(); b++)
+                require(!LostCityUnderground16.supportConflict(network.modules().get(a), network.modules().get(b)),
+                    "One connected room destroys another room's bearing rock");
+            var access = module(network, LostCityUnderground16.Kind.ACCESS);
+            var hatch = capture.blocks.entrySet().stream().filter(e -> e.getValue().is(Blocks.DARK_OAK_TRAPDOOR)
+                && access.contains(e.getKey().getX(), e.getKey().getY(), e.getKey().getZ())).map(Map.Entry::getKey).findFirst().orElseThrow();
+            var reached = walk(capture, hatch.above());
+            for (var m : network.modules()) {
+                require(reached.stream().anyMatch(p -> p.getY() == m.floorY() + 1 && p.getX() > m.minX()
+                    && p.getX() < m.maxX() && p.getZ() > m.minZ() && p.getZ() < m.maxZ()), "No two-block-high route from the hatch to " + m.kind());
+                for (var support : m.supports()) {
+                    int anchor = support.type() == LostCityUnderground16.Type.PILLAR ? support.minY() : support.maxY();
+                    int neighbor = anchor + (support.type() == LostCityUnderground16.Type.PILLAR ? -1 : 1);
+                    require(support.maxY() - support.minY() < 8 && terrain.solid(support.x(), anchor, support.z())
+                        && terrain.solid(support.x(), neighbor, support.z()), "A support has no short real rock anchor");
+                    for (int y = support.minY(); y <= support.maxY(); y++)
+                        require(!capture.block(new BlockPos(support.x(), y, support.z())).isAir(), "Interrupted saved support");
+                }
+                verifyLights(m, capture);
+            }
+            verifyPool(module(network, LostCityUnderground16.Kind.POOLROOM), capture, reached);
+            verifyGarage(module(network, LostCityUnderground16.Kind.GARAGE), capture, reached);
+            verifyOutlet(module(network, LostCityUnderground16.Kind.SEWER_OUTLET), capture, terrain, reached);
+            var hall = module(network, LostCityUnderground16.Kind.EXPANSION_HALL);
+            require(reached.contains(new BlockPos(hall.centerX(), hall.floorY() + 2, hall.centerZ())), "Future expansion plinth is disconnected");
+            capture.blocks.forEach((p, state) -> {
+                if (hall.contains(p.getX(), p.getY(), p.getZ())) require(state.getFluidState().isEmpty(), "Architectural expansion hall is wet");
+            });
+            require(plan.samples() <= LostCityUnderground16.MAX_SAMPLES, "Terrain sampling exceeded its cap");
+        }
+        var unsupported = new RockTerrain() { @Override public boolean solid(int x, int y, int z) { return false; } };
+        require(LostCityUnderground16.plan(0, surface, unsupported).isEmpty(), "Unsupported void acquired an underground city");
+        var protectedTerrain = new RockTerrain() { @Override public boolean protectedAt(int x, int y, int z) { return true; } };
+        require(LostCityUnderground16.plan(0, surface, protectedTerrain).isEmpty(), "Protected natural hydrology was overwritten");
+        var foreign = new RockTerrain() { @Override public boolean owns(int x, int z) { return false; } };
+        require(LostCityUnderground16.plan(0, surface, foreign).isEmpty(), "A network escaped chunk ownership");
+        var caveOnly = new RockTerrain() { @Override public boolean exteriorAir(int x, int y, int z, int dx, int dz) { return false; } };
+        require(LostCityUnderground16.plan(0, surface, caveOnly).networks().stream().flatMap(n -> n.modules().stream())
+            .noneMatch(m -> m.kind() == LostCityUnderground16.Kind.SEWER_OUTLET), "A pocket cave was treated as the island exterior");
+        foundationDependencies();
+    }
+    private static LostCityPlan surface() {
+        var street = new LostCityPlan.Parcel(LostCityPlan.Kind.STREET, -2, -12, 5, 25, 220, 0, 0, 7, 3, new int[0]);
+        return new LostCityPlan(List.of(new LostCityPlan.District(0, 0, 3, List.of(street))));
+    }
+    private static LostCityUnderground16.Module module(LostCityUnderground16.Network n, LostCityUnderground16.Kind kind) {
+        return n.modules().stream().filter(m -> m.kind() == kind).findFirst()
+            .orElseThrow(() -> new AssertionError("Reference island never generated " + kind + "; kinds=" + n.modules().stream().map(LostCityUnderground16.Module::kind).toList()));
+    }
+    private static void verifyPool(LostCityUnderground16.Module pool, Capture c, Set<BlockPos> reached) {
+        var bounds = pool.poolWaterBounds();
+        require(bounds.maxX() - bounds.minX() + 1 == 50 && bounds.maxZ() - bounds.minZ() + 1 == 25
+            && bounds.maxY() - bounds.minY() + 1 == 4, "Pool lost its fifty-by-twenty-five four-deep tank");
+        int wet = 0, steps = 0;
+        for (int z = bounds.minZ(); z <= bounds.maxZ(); z++) for (int x = bounds.minX(); x <= bounds.maxX(); x++)
+            for (int y = bounds.minY(); y <= bounds.maxY(); y++) {
+                var p = new BlockPos(x, y, z); var state = c.block(p);
+                if (!state.getFluidState().isEmpty()) {
+                    wet++;
+                    for (var direction : new Direction[] {Direction.DOWN, Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST}) {
+                        var q = p.relative(direction); var next = c.block(q);
+                        require(!next.isAir(), "Pool water has an unsealed horizontal or downward neighbor: " + q);
+                    }
+                }
+                if (state.getBlock() instanceof StairBlock) {
+                    steps++;
+                    require(state.getValue(BlockStateProperties.WATERLOGGED)
+                        && state.getValue(BlockStateProperties.HORIZONTAL_FACING) == Direction.NORTH, "Pool access step cannot descend from its north promenade");
+                }
+            }
+        require(wet >= 4_950 && steps == 16, "Large pool was replaced by tiny basins or lost its submerged stairs: " + wet);
+        for (int[] point : new int[][] {{2, 2}, {2, 28}, {54, 2}, {54, 28}})
+            require(reached.contains(new BlockPos(pool.minX() + point[0], pool.floorY() + 1, pool.minZ() + point[1])),
+                "The dry promenade cannot be walked around the pool");
+    }
+    private static void verifyGarage(LostCityUnderground16.Module garage, Capture c, Set<BlockPos> reached) {
+        var decks = garage.parkingFloors();
+        require(decks.size() == 8 && decks.getLast() - decks.getFirst() == 112, "Garage did not descend through eight widely separated platforms");
+        require(garage.supports().size() == 9, "Open parking is missing its nine certified load-bearing columns");
+        for (int y : decks) {
+            require(reached.contains(new BlockPos(garage.centerX() + 3, y + 1, garage.centerZ())), "Garage deck is disconnected from the public stair: " + y);
+            require(c.block(new BlockPos(garage.minX(), y + 5, garage.centerZ())).isAir(), "Parking exterior was closed by a solid wall");
+        }
+        for (int lower : decks.subList(0, decks.size() - 1)) for (int step = 0; step < 16; step++)
+            for (int x = 1; x <= 2; x++) {
+                var p = new BlockPos(garage.minX() + x, lower + step + 1, garage.minZ() + 3 + step);
+                require(c.block(p).getBlock() instanceof StairBlock && c.block(p).getValue(BlockStateProperties.HORIZONTAL_FACING) == Direction.SOUTH,
+                    "Parking stair flight has a gap or faces downhill");
+                require(c.block(p.above()).isAir() && c.block(p.above(2)).isAir(), "Parking stair lacks player headroom");
+            }
+    }
+    private static void verifyOutlet(LostCityUnderground16.Module outlet, Capture c, RockTerrain terrain, Set<BlockPos> reached) {
+        int[] dx = {0, 1, 0, -1}, dz = {-1, 0, 1, 0}; int direction = outlet.outletDirection();
+        var mouth = outlet.outletMouth(); var beyond = mouth.offset(dx[direction], 0, dz[direction]);
+        require(terrain.exteriorAir(beyond.getX(), beyond.getY(), beyond.getZ(), dx[direction], dz[direction]), "Sewer terminates in a cave or rock face");
+        require(c.block(mouth).isAir() && c.block(beyond).isAir(), "Outlet water level has a closed terminal wall");
+        var source = mouth.offset(-dx[direction] * 3, 0, -dz[direction] * 3);
+        require(c.block(source).is(Blocks.WATER), "Outflow has no real water source");
+        for (int distance = 1; distance <= 4; distance++) {
+            var p = source.offset(dx[direction] * distance, 0, dz[direction] * distance);
+            require(c.block(p).isAir(), "Sewer source cannot flow along the trough to the exterior");
+        }
+        require(solid(c.block(source.offset(-dx[direction], 0, -dz[direction]))), "Outlet weir allows water to flood back into the public network");
+        int length = Math.max(outlet.width(), outlet.depth());
+        var rows = new java.util.TreeMap<Integer, Integer>();
+        for (var support : outlet.supports()) {
+            int distance = dx[direction] == 0 ? direction == 0 ? outlet.maxZ() - support.z() : support.z() - outlet.minZ()
+                : direction == 1 ? support.x() - outlet.minX() : outlet.maxX() - support.x();
+            rows.merge(distance, 1, Integer::sum);
+        }
+        int prior = 0;
+        for (var row : rows.entrySet()) {
+            require(row.getValue() == 2 && row.getKey() - prior <= 12, "Sewer has a bridge span without its two short rock anchors");
+            prior = row.getKey();
+        }
+        require(length - 1 - prior <= 8, "Sewer outlet lip exceeds its eight-block cantilever");
+        require(reached.stream().anyMatch(p -> Math.abs(p.getX() - mouth.getX()) + Math.abs(p.getZ() - mouth.getZ()) <= 2
+            && p.getY() == mouth.getY() + 1), "Dry sewer banks do not reach the outlet");
+    }
+    private static void verifyLights(LostCityUnderground16.Module m, Capture c) {
+        c.blocks.forEach((p, state) -> {
+            if (state.is(Blocks.LANTERN) && m.contains(p.getX(), p.getY(), p.getZ())) {
+                require(state.getValue(BlockStateProperties.HANGING), "Utility lantern has no suspension");
+                var above = p.above();
+                while (c.block(above).is(Blocks.IRON_CHAIN) && above.getY() < m.maxY()) above = above.above();
+                require(solid(c.block(above)), "A suspended lantern is not anchored to a full block");
+            }
+        });
+    }
+    private static void foundationDependencies() {
+        var pool = new LostCityUnderground16.Module(LostCityUnderground16.Kind.POOLROOM, 0, 150, 0, 57, 13, 31, 1, 42, List.of(new LostCityUnderground16.Support(LostCityUnderground16.Type.PILLAR, 8, 149, 8, 149)));
+        var below = new LostCityUnderground16.Module(LostCityUnderground16.Kind.PASSAGE, 8, 143, 8, 5, 6, 5, 5, 1, List.of());
+        require(LostCityUnderground16.supportConflict(pool, below), "Another tunnel can remove the pool support's rock-bearing neighbor");
+        var deeper = new LostCityUnderground16.Module(LostCityUnderground16.Kind.PASSAGE, 8, 142, 8, 5, 6, 5, 5, 1, List.of());
+        require(!LostCityUnderground16.supportConflict(pool, deeper), "Pool bearing protection escaped its certified depth");
+    }
+    /** Rock with a sloping roof, irregular deep caverns and a finite, exposed island edge. */
+    private static class RockTerrain implements LostCityUnderground16.Terrain {
+        @Override public boolean solid(int x, int y, int z) {
+            int top = 220 + (int) Math.floor(Math.sin(x / 37.0) * 3 * Math.min(1, Math.abs(x) / 8.0));
+            return Math.abs(x) <= 104 && Math.abs(z) <= 104 && y <= top && y >= 70
+                && !(y < 100 && Math.floorMod(x * x + z * z, 71) < 14);
+        }
+        @Override public boolean protectedAt(int x, int y, int z) { return false; }
+        @Override public boolean owns(int x, int z) { return true; }
+        @Override public boolean exteriorAir(int x, int y, int z, int dx, int dz) {
+            if (Math.abs(x) <= 104 && Math.abs(z) <= 104) return false;
+            for (int n = 0; n <= 32; n++) if (solid(x + dx * n, y, z + dz * n)) return false;
+            return true;
+        }
+    }
+    private static Capture render(LostCityUnderground16.Plan plan, LostCityUnderground16.Terrain terrain) {
+        var result = new Capture(terrain);
+        for (var network : plan.networks()) for (var m : network.modules()) LostCityUnderground20.render(m, new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState state) {
+                var p = new BlockPos(m.minX() + x, m.minY() + y, m.minZ() + z);
+                require(p.getX() >= m.boundsMinX() && p.getX() <= m.boundsMaxX() && p.getY() >= m.boundsMinY()
+                    && p.getY() <= m.boundsMaxY() && p.getZ() >= m.boundsMinZ() && p.getZ() <= m.boundsMaxZ(), "Renderer exceeded saved bounds");
+                require(plan.contains(p.getX(), p.getY(), p.getZ()), "An actual block write is missing from the 3D mask");
+                require(!terrain.protectedAt(p.getX(), p.getY(), p.getZ()) && terrain.owns(p.getX(), p.getZ()), "Renderer entered protected or foreign terrain");
+                result.blocks.put(p, state);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> loot, long seed) { throw new AssertionError("Unrequested dungeon loot"); }
+        });
+        return result;
+    }
+    private static Set<BlockPos> walk(Capture c, BlockPos start) {
+        var seen = new HashSet<BlockPos>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var p = queue.removeFirst();
+            for (Direction direction : Direction.Plane.HORIZONTAL) for (int dy : new int[] {0, 1, -1}) {
+                var q = p.relative(direction).offset(0, dy, 0);
+                if (Math.abs(q.getX() - start.getX()) > 120 || Math.abs(q.getZ() - start.getZ()) > 120 || Math.abs(q.getY() - start.getY()) > 160) continue;
+                if (stand(c, q) && seen.add(q)) queue.add(q);
+            }
+            for (int dy : new int[] {-1, 1}) {
+                var q = p.offset(0, dy, 0);
+                if (Math.abs(q.getY() - start.getY()) > 160) continue;
+                if ((climb(c.block(p)) || climb(c.block(q)) || climb(c.block(p.below()))) && stand(c, q) && seen.add(q)) queue.add(q);
+            }
+        }
+        return seen;
+    }
+    private static boolean stand(Capture c, BlockPos p) {
+        return passable(c.block(p)) && passable(c.block(p.above()))
+            && (solid(c.block(p.below())) || c.block(p.below()).getBlock() instanceof StairBlock || climb(c.block(p)) || climb(c.block(p.below())));
+    }
+    private static boolean climb(BlockState b) { return b.is(Blocks.LADDER) || b.is(Blocks.DARK_OAK_TRAPDOOR); }
+    private static boolean passable(BlockState b) { return b.isAir() || climb(b) || b.is(Blocks.REDSTONE_WALL_TORCH); }
+    private static boolean solid(BlockState b) { return b.canOcclude() && b.getFluidState().isEmpty(); }
+    private static final class Capture {
+        final Map<BlockPos, BlockState> blocks = new HashMap<>(); final LostCityUnderground16.Terrain terrain;
+        Capture(LostCityUnderground16.Terrain terrain) { this.terrain = terrain; }
+        BlockState block(BlockPos p) { return blocks.getOrDefault(p, terrain.solid(p.getX(), p.getY(), p.getZ()) ? Blocks.STONE.defaultBlockState() : Blocks.AIR.defaultBlockState()); }
+    }
+    private static void require(boolean condition, String message) { if (!condition) throw new AssertionError(message); }
+}
@@ -0,0 +1,95 @@
+package fr.koka.sanctuary.worldgen.detail;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.HashMap;
+import java.util.Map;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.WallBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.block.state.properties.StairsShape;
+import net.minecraft.world.level.block.state.properties.WallSide;
+import net.minecraft.world.level.storage.loot.BuiltInLootTables;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Geometry-only proof. Native world tests additionally exercise datapack-bound fence/wall tags. */
+public final class ConnectedBlocks20Smoke {
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("ConnectedBlocks20Smoke: final geometry, native solid faces, panes, walls, stair corners, chunk clips and deferred loot passed.");
+    }
+    public static void run() {
+        var full = new Capture(); var b = ConnectedBlocks20.buffer(full);
+        b.set(15, 3, 8, Blocks.GLASS_PANE.defaultBlockState());
+        b.set(16, 3, 8, Blocks.IRON_BARS.defaultBlockState());
+        b.set(14, 3, 8, Blocks.STONE.defaultBlockState());
+        b.set(15, 3, 7, Blocks.SMOOTH_STONE_SLAB.defaultBlockState());
+        b.set(15, 3, 9, Blocks.STONE.defaultBlockState()); b.set(15, 3, 9, Blocks.AIR.defaultBlockState());
+        b.flush();
+        var pane = full.at(15, 3, 8);
+        require(pane.getValue(BlockStateProperties.EAST) && pane.getValue(BlockStateProperties.WEST), "Pane missed full geometry across a chunk boundary");
+        require(!pane.getValue(BlockStateProperties.NORTH) && !pane.getValue(BlockStateProperties.SOUTH), "Pane attached to a half slab or overwritten block");
+        require(full.at(16, 3, 8).getValue(BlockStateProperties.WEST), "Mixed panes/bars lost reciprocal connection");
+        var clipped = new Capture(); var clip = ConnectedBlocks20.buffer(new LostCityRenderer.BlockWriter() {
+            public void set(int x, int y, int z, BlockState state) { if (x < 16) clipped.set(x, y, z, state); }
+            public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { throw new AssertionError(); }
+        });
+        full.blocks.forEach((at, state) -> clip.set(at.getX(), at.getY(), at.getZ(), state)); clip.flush();
+        require(clipped.at(15, 3, 8).equals(pane) && !clipped.blocks.containsKey(new BlockPos(16, 3, 8)), "Clipping changed precomputed cross-chunk connectivity");
+        for (var face : new Direction[] {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST}) {
+            for (var half : Half.values()) {
+                require(corner(face, half, true, true, false) == StairsShape.OUTER_LEFT, "Outer-left corner lost rotation/half");
+                require(corner(face, half, true, false, false) == StairsShape.OUTER_RIGHT, "Outer-right corner lost rotation/half");
+                require(corner(face, half, false, true, false) == StairsShape.INNER_LEFT, "Inner-left corner lost rotation/half");
+                require(corner(face, half, false, false, false) == StairsShape.INNER_RIGHT, "Inner-right corner lost rotation/half");
+                require(corner(face, half, true, true, true) == StairsShape.STRAIGHT, "Parallel stair failed to block corner");
+            }
+        }
+        var walls = new Capture(); var wb = ConnectedBlocks20.buffer(walls);
+        for (int x : new int[] {0, 4}) {
+            wb.set(x, 0, 0, Blocks.STONE_BRICK_WALL.defaultBlockState().setValue(WallBlock.WATERLOGGED, true));
+            wb.set(x - 1, 0, 0, Blocks.STONE.defaultBlockState()); wb.set(x + 1, 0, 0, Blocks.STONE.defaultBlockState());
+        }
+        wb.set(4, 1, 0, Blocks.SMOOTH_STONE.defaultBlockState()); wb.flush();
+        require(walls.at(0, 0, 0).getValue(WallBlock.EAST) == WallSide.LOW && !walls.at(0, 0, 0).getValue(WallBlock.UP), "Open straight wall should be low without a post");
+        require(walls.at(4, 0, 0).getValue(WallBlock.WEST) == WallSide.TALL && !walls.at(4, 0, 0).getValue(WallBlock.UP), "Full underside should raise both wall arms, not a redundant post");
+        require(walls.at(0, 0, 0).getValue(WallBlock.WATERLOGGED), "Connection resolution erased waterlogging");
+        var overhead = new Capture(); var ob = ConnectedBlocks20.buffer(overhead);
+        ob.set(0, 0, 0, Blocks.TUFF_BRICK_WALL.defaultBlockState());
+        ob.set(0, 0, 1, Blocks.IRON_BARS.defaultBlockState());
+        ob.set(0, 1, 0, Blocks.IRON_BARS.defaultBlockState());
+        ob.set(0, 1, 1, Blocks.IRON_BARS.defaultBlockState());
+        ob.flush();
+        require(overhead.at(0, 0, 0).getValue(WallBlock.SOUTH) == WallSide.TALL,
+            "Wall height used a stale unconnected underside of the bars above");
+        var loot = new Capture(); var lb = ConnectedBlocks20.buffer(loot);
+        lb.chest(0, 0, 0, BuiltInLootTables.VILLAGE_PLAINS_HOUSE, 42); lb.set(0, 0, 0, Blocks.AIR.defaultBlockState());
+        lb.set(1, 0, 0, Blocks.STONE.defaultBlockState()); lb.chest(1, 0, 0, BuiltInLootTables.VILLAGE_CARTOGRAPHER, Long.MIN_VALUE); lb.flush();
+        require(loot.chests.size() == 1 && loot.chests.get(new BlockPos(1, 0, 0)).equals("" + BuiltInLootTables.VILLAGE_CARTOGRAPHER + ":" + Long.MIN_VALUE), "Deferred chest metadata lost final-write semantics");
+        boolean rejected = false; try { lb.flush(); } catch (IllegalStateException expected) { rejected = true; }
+        require(rejected, "Repeated flush duplicated chest placement");
+    }
+    private static StairsShape corner(Direction facing, Half half, boolean front, boolean left, boolean blocker) {
+        var out = new Capture(); var b = ConnectedBlocks20.buffer(out); var origin = BlockPos.ZERO;
+        var own = Blocks.STONE_BRICK_STAIRS.defaultBlockState().setValue(StairBlock.FACING, facing).setValue(StairBlock.HALF, half);
+        var other = left ? facing.getCounterClockWise() : facing.getClockWise();
+        var neighbor = origin.relative(front ? facing : facing.getOpposite());
+        b.set(0, 0, 0, own); b.set(neighbor.getX(), 0, neighbor.getZ(), own.setValue(StairBlock.FACING, other));
+        if (blocker) { var at = origin.relative(front ? other.getOpposite() : other); b.set(at.getX(), 0, at.getZ(), own); }
+        b.flush(); return out.at(0, 0, 0).getValue(StairBlock.SHAPE);
+    }
+    private static final class Capture implements LostCityRenderer.BlockWriter {
+        final Map<BlockPos, BlockState> blocks = new HashMap<>(); final Map<BlockPos, String> chests = new HashMap<>();
+        public void set(int x, int y, int z, BlockState state) { blocks.put(new BlockPos(x, y, z), state); }
+        public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { chests.put(new BlockPos(x, y, z), "" + table + ":" + seed); }
+        BlockState at(int x, int y, int z) { return blocks.get(new BlockPos(x, y, z)); }
+    }
+    private static void require(boolean value, String message) { if (!value) throw new AssertionError(message); }
+}
@@ -0,0 +1,85 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.ListTag;
+
+/** Exact, bounded independent schema19 persistence for catalogue sites and chunk-local abandoned routes. */
+public final class HeritagePiece19Smoke {
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("HeritagePiece19Smoke: 14 kinds, 4 facades, every rail profile, missing rails, strict NBT and local native bounds passed.");
+    }
+    public static void run() {
+        for (var kind : HeritagePlan19.Kind.values()) for (int face = 0; face < 4; face++) {
+            int x = -32, z = 40, floor = 160;
+            var entry = new HeritagePlan19.Entry(face == 1 ? x + 17 : face == 3 ? x - 1 : x + 8,
+                floor + 1, face == 2 ? z + 17 : face == 0 ? z - 1 : z + 8, face);
+            var supportList = new ArrayList<HeritagePlan19.Support>();
+            supportList.add(new HeritagePlan19.Support(x + 1, 150, z + 1, 155));
+            var site = new HeritagePlan19.Site("site_" + kind.name(), kind, x, floor, z, 17, 17, 20, face,
+                Long.MIN_VALUE + kind.ordinal(), 4, supportList, entry);
+            supportList.clear();
+            var saved = HeritagePiece19.encodeSite(site);
+            require(HeritagePiece19.decodeSite(saved).equals(site) && HeritagePiece19.encodeSite(HeritagePiece19.decodeSite(saved)).equals(saved), "Site roundtrip changed geometry");
+            require(site.supports().size() == 1 && HeritagePiece19.bounds(site).minY() == 150, "Support input is mutable or excluded from native bounds");
+            require(HeritagePiece19.locator(site).getX() == entry.x() && HeritagePiece19.locator(site).getY() == entry.y()
+                && HeritagePiece19.locator(site).getZ() == entry.z(), "Locate lost the rotated facade entry");
+            badSite(saved, t -> t.remove("Facing")); badSite(saved, t -> t.putInt("Schema", 17));
+            badSite(saved, t -> t.putString("Type", "ROUTE")); badSite(saved, t -> t.putString("Kind", "FUTURE"));
+            badSite(saved, t -> t.putDouble("FloorY", 160)); badSite(saved, t -> t.putInt("Seed", 1));
+            badSite(saved, t -> t.putInt("Future", 1)); badSite(saved, t -> t.putInt("MinX", Integer.MAX_VALUE));
+            badSite(saved, t -> t.putInt("Width", 18)); badSite(saved, t -> t.putInt("Facing", 4));
+            badSite(saved, t -> t.putInt("FoundationDepth", 0)); badSite(saved, t -> t.putString("Id", "x".repeat(129)));
+            badSite(saved, t -> t.getCompound("Entry").orElseThrow().putInt("X", entry.x() + 1));
+            badSite(saved, t -> t.getCompound("Entry").orElseThrow().putLong("Y", entry.y()));
+            badSite(saved, t -> t.getList("Supports").orElseThrow().getCompound(0).orElseThrow().putInt("MinY", 130));
+            badSite(saved, t -> t.getList("Supports").orElseThrow().getCompound(0).orElseThrow().putInt("X", site.maxX() + 1));
+            badSite(saved, t -> {
+                var list = t.getList("Supports").orElseThrow(); list.add(list.getFirst().copy());
+            });
+        }
+        var cells = new ArrayList<HeritagePlan19.Cell>();
+        int index = 0;
+        for (var rail : HeritagePlan19.Rail.values()) {
+            cells.add(new HeritagePlan19.Cell(-32 + index, 150 + index % 3, 32, 2 + index % 4, rail, rail != HeritagePlan19.Rail.NONE && index % 2 == 0)); index++;
+        }
+        var segment = new HeritagePlan19.Segment("freight/part0", "station", "mine", HeritagePlan19.RouteKind.FREIGHT, -2, 2, cells, Long.MAX_VALUE);
+        cells.clear();
+        var landing = new HeritagePlan19.Segment("station/landing", "station", "station", HeritagePlan19.RouteKind.PATH,
+            -2, 2, List.of(new HeritagePlan19.Cell(-32, 150, 32, 2, HeritagePlan19.Rail.NONE, false)), 42);
+        require(HeritagePiece19.decodeSegment(HeritagePiece19.encodeSegment(landing)).equals(landing), "Standalone entry landing lost its site binding");
+        var saved = HeritagePiece19.encodeSegment(segment);
+        require(HeritagePiece19.decodeSegment(saved).equals(segment) && HeritagePiece19.encodeSegment(HeritagePiece19.decodeSegment(saved)).equals(saved), "Route roundtrip changed shapes, supports or deliberate rail gaps");
+        require(segment.cells().size() == HeritagePlan19.Rail.values().length, "External route list mutation changed its saved cells");
+        require(HeritagePiece19.bounds(segment).intersectingChunks().count() == 1, "Segment escaped its one-chunk native start");
+        badRoute(saved, t -> t.putInt("Schema", 20)); badRoute(saved, t -> t.putString("Type", "SITE"));
+        badRoute(saved, t -> t.remove("FromId")); badRoute(saved, t -> t.putString("ToId", "station"));
+        badRoute(saved, t -> t.putString("Id", " ")); badRoute(saved, t -> t.putInt("StartChunkX", -1));
+        badRoute(saved, t -> t.putDouble("Seed", 42)); badRoute(saved, t -> t.put("Cells", new ListTag()));
+        badRoute(saved, t -> cell(t).putInt("RailPresent", 1)); badRoute(saved, t -> cell(t).putByte("RailPresent", (byte) 2));
+        badRoute(saved, t -> cell(t).putString("Rail", "FUTURE")); badRoute(saved, t -> cell(t).putBoolean("RailPresent", true));
+        badRoute(saved, t -> cell(t).putInt("X", -16)); badRoute(saved, t -> cell(t).putInt("FoundationDepth", 13));
+        badRoute(saved, t -> cell(t).putInt("FloorY", 2)); badRoute(saved, t -> cell(t).putInt("Extra", 0));
+        badRoute(saved, t -> { var list = t.getList("Cells").orElseThrow(); list.add(list.getFirst().copy()); });
+        badRoute(saved, t -> { var list = new ListTag(); list.add(IntTag.valueOf(1)); t.put("Cells", list); });
+        badRoute(saved, t -> { var list = t.getList("Cells").orElseThrow(); while (list.size() <= 256) list.add(list.getFirst().copy()); });
+    }
+    private static CompoundTag cell(CompoundTag tag) { return tag.getList("Cells").orElseThrow().getCompound(0).orElseThrow(); }
+    private static void badSite(CompoundTag original, Consumer<CompoundTag> mutation) {
+        var value = original.copy(); mutation.accept(value);
+        try { HeritagePiece19.decodeSite(value); } catch (IllegalArgumentException expected) { return; }
+        throw new AssertionError("Malformed saved site accepted: " + value);
+    }
+    private static void badRoute(CompoundTag original, Consumer<CompoundTag> mutation) {
+        var value = original.copy(); mutation.accept(value);
+        try { HeritagePiece19.decodeSegment(value); } catch (IllegalArgumentException expected) { return; }
+        throw new AssertionError("Malformed saved route accepted: " + value);
+    }
+    private static void require(boolean value, String message) { if (!value) throw new AssertionError(message); }
+}
@@ -0,0 +1,85 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.ListTag;
+
+/** Exact, bounded independent schema20 persistence for catalogue sites and chunk-local abandoned routes. */
+public final class HeritagePiece20Smoke {
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("HeritagePiece20Smoke: 14 kinds, 4 facades, every rail profile, missing rails, strict NBT and local native bounds passed.");
+    }
+    public static void run() {
+        for (var kind : HeritagePlan19.Kind.values()) for (int face = 0; face < 4; face++) {
+            int x = -32, z = 40, floor = 160;
+            var entry = new HeritagePlan19.Entry(face == 1 ? x + 17 : face == 3 ? x - 1 : x + 8,
+                floor + 1, face == 2 ? z + 17 : face == 0 ? z - 1 : z + 8, face);
+            var supportList = new ArrayList<HeritagePlan19.Support>();
+            supportList.add(new HeritagePlan19.Support(x + 1, 150, z + 1, 155));
+            var site = new HeritagePlan19.Site("site_" + kind.name(), kind, x, floor, z, 17, 17, 20, face,
+                Long.MIN_VALUE + kind.ordinal(), 4, supportList, entry);
+            supportList.clear();
+            var saved = HeritagePiece20.encodeSite(site);
+            require(HeritagePiece20.decodeSite(saved).equals(site) && HeritagePiece20.encodeSite(HeritagePiece20.decodeSite(saved)).equals(saved), "Site roundtrip changed geometry");
+            require(site.supports().size() == 1 && HeritagePiece20.bounds(site).minY() == 150, "Support input is mutable or excluded from native bounds");
+            require(HeritagePiece20.locator(site).getX() == entry.x() && HeritagePiece20.locator(site).getY() == entry.y()
+                && HeritagePiece20.locator(site).getZ() == entry.z(), "Locate lost the rotated facade entry");
+            badSite(saved, t -> t.remove("Facing")); badSite(saved, t -> t.putInt("Schema", 17));
+            badSite(saved, t -> t.putString("Type", "ROUTE")); badSite(saved, t -> t.putString("Kind", "FUTURE"));
+            badSite(saved, t -> t.putDouble("FloorY", 160)); badSite(saved, t -> t.putInt("Seed", 1));
+            badSite(saved, t -> t.putInt("Future", 1)); badSite(saved, t -> t.putInt("MinX", Integer.MAX_VALUE));
+            badSite(saved, t -> t.putInt("Width", 18)); badSite(saved, t -> t.putInt("Facing", 4));
+            badSite(saved, t -> t.putInt("FoundationDepth", 0)); badSite(saved, t -> t.putString("Id", "x".repeat(129)));
+            badSite(saved, t -> t.getCompound("Entry").orElseThrow().putInt("X", entry.x() + 1));
+            badSite(saved, t -> t.getCompound("Entry").orElseThrow().putLong("Y", entry.y()));
+            badSite(saved, t -> t.getList("Supports").orElseThrow().getCompound(0).orElseThrow().putInt("MinY", 130));
+            badSite(saved, t -> t.getList("Supports").orElseThrow().getCompound(0).orElseThrow().putInt("X", site.maxX() + 1));
+            badSite(saved, t -> {
+                var list = t.getList("Supports").orElseThrow(); list.add(list.getFirst().copy());
+            });
+        }
+        var cells = new ArrayList<HeritagePlan19.Cell>();
+        int index = 0;
+        for (var rail : HeritagePlan19.Rail.values()) {
+            cells.add(new HeritagePlan19.Cell(-32 + index, 150 + index % 3, 32, 2 + index % 4, rail, rail != HeritagePlan19.Rail.NONE && index % 2 == 0)); index++;
+        }
+        var segment = new HeritagePlan19.Segment("freight/part0", "station", "mine", HeritagePlan19.RouteKind.FREIGHT, -2, 2, cells, Long.MAX_VALUE);
+        cells.clear();
+        var landing = new HeritagePlan19.Segment("station/landing", "station", "station", HeritagePlan19.RouteKind.PATH,
+            -2, 2, List.of(new HeritagePlan19.Cell(-32, 150, 32, 2, HeritagePlan19.Rail.NONE, false)), 42);
+        require(HeritagePiece20.decodeSegment(HeritagePiece20.encodeSegment(landing)).equals(landing), "Standalone entry landing lost its site binding");
+        var saved = HeritagePiece20.encodeSegment(segment);
+        require(HeritagePiece20.decodeSegment(saved).equals(segment) && HeritagePiece20.encodeSegment(HeritagePiece20.decodeSegment(saved)).equals(saved), "Route roundtrip changed shapes, supports or deliberate rail gaps");
+        require(segment.cells().size() == HeritagePlan19.Rail.values().length, "External route list mutation changed its saved cells");
+        require(HeritagePiece20.bounds(segment).intersectingChunks().count() == 1, "Segment escaped its one-chunk native start");
+        badRoute(saved, t -> t.putInt("Schema", 21)); badRoute(saved, t -> t.putString("Type", "SITE"));
+        badRoute(saved, t -> t.remove("FromId")); badRoute(saved, t -> t.putString("ToId", "station"));
+        badRoute(saved, t -> t.putString("Id", " ")); badRoute(saved, t -> t.putInt("StartChunkX", -1));
+        badRoute(saved, t -> t.putDouble("Seed", 42)); badRoute(saved, t -> t.put("Cells", new ListTag()));
+        badRoute(saved, t -> cell(t).putInt("RailPresent", 1)); badRoute(saved, t -> cell(t).putByte("RailPresent", (byte) 2));
+        badRoute(saved, t -> cell(t).putString("Rail", "FUTURE")); badRoute(saved, t -> cell(t).putBoolean("RailPresent", true));
+        badRoute(saved, t -> cell(t).putInt("X", -16)); badRoute(saved, t -> cell(t).putInt("FoundationDepth", 13));
+        badRoute(saved, t -> cell(t).putInt("FloorY", 2)); badRoute(saved, t -> cell(t).putInt("Extra", 0));
+        badRoute(saved, t -> { var list = t.getList("Cells").orElseThrow(); list.add(list.getFirst().copy()); });
+        badRoute(saved, t -> { var list = new ListTag(); list.add(IntTag.valueOf(1)); t.put("Cells", list); });
+        badRoute(saved, t -> { var list = t.getList("Cells").orElseThrow(); while (list.size() <= 256) list.add(list.getFirst().copy()); });
+    }
+    private static CompoundTag cell(CompoundTag tag) { return tag.getList("Cells").orElseThrow().getCompound(0).orElseThrow(); }
+    private static void badSite(CompoundTag original, Consumer<CompoundTag> mutation) {
+        var value = original.copy(); mutation.accept(value);
+        try { HeritagePiece20.decodeSite(value); } catch (IllegalArgumentException expected) { return; }
+        throw new AssertionError("Malformed saved site accepted: " + value);
+    }
+    private static void badRoute(CompoundTag original, Consumer<CompoundTag> mutation) {
+        var value = original.copy(); mutation.accept(value);
+        try { HeritagePiece20.decodeSegment(value); } catch (IllegalArgumentException expected) { return; }
+        throw new AssertionError("Malformed saved route accepted: " + value);
+    }
+    private static void require(boolean value, String message) { if (!value) throw new AssertionError(message); }
+}
@@ -0,0 +1,197 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.heritage.HeritagePlan19.*;
+import java.util.ArrayDeque;
+import java.util.EnumSet;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.IntBinaryOperator;
+
+/** Pure geography contract: full catalogue, actual destinations, independent entrances and supported axes. */
+public final class HeritagePlanner19Smoke {
+    private static final int[] DX = {0, 1, 0, -1}, DZ = {-1, 0, 1, 0};
+    public static void main(String[] args) {
+        var catalogue = EnumSet.noneOf(Kind.class);
+        int freight = 0, paths = 0, missingRails = 0, islandAxes = 0;
+        for (int diameter : new int[] {512, 724, 1024}) for (long seed : new long[] {0, 1, 42, -1}) {
+            Fixture terrain = new Fixture((x, z) -> 220);
+            var plan = HeritagePlanner19.plan(seed, 0, 0, diameter, terrain);
+            verify(plan, terrain);
+            require(plan.sites().size() >= 8, "Flat starter loses most of its small physical catalogue: " + plan.diagnostics());
+            require(plan.links().size() >= 2, "Flat starter has no useful inter-destination axes");
+            plan.sites().forEach(site -> catalogue.add(site.kind()));
+            freight += (int) plan.links().stream().filter(l -> l.kind() == RouteKind.FREIGHT).count();
+            islandAxes += (int) plan.links().stream().filter(l -> {
+                Point first = l.path().getFirst(), last = l.path().getLast();
+                return Math.max(Math.abs(first.x() - last.x()), Math.abs(first.z() - last.z())) >= diameter / 4;
+            }).count();
+            paths += (int) plan.links().stream().filter(l -> l.kind() == RouteKind.PATH).count();
+            missingRails += (int) plan.segments().stream().flatMap(s -> s.cells().stream())
+                .filter(c -> c.rail() != Rail.NONE && !c.railPresent()).count();
+            var repeat = HeritagePlanner19.plan(seed, 0, 0, diameter, new Fixture((x, z) -> 220));
+            require(plan.sites().equals(repeat.sites()) && plan.links().equals(repeat.links())
+                && plan.segments().equals(repeat.segments()) && plan.samples() == repeat.samples()
+                && plan.diagnostics().equals(repeat.diagnostics()), "Planning depends on generation order or mutable state");
+        }
+        require(catalogue.equals(EnumSet.allOf(Kind.class)), "A requested heritage family never appears: " + catalogue);
+        require(islandAxes > 0, "All published networks remain local; no axis reaches island scale");
+        require(freight > 0 && paths > 0 && missingRails > 0, "Both networks and repairable missing rails must be represented");
+        var flat = HeritagePlanner19.plan(0, 0, 0, 724, new Fixture((x, z) -> 220));
+        require(!flat.sites().equals(HeritagePlanner19.plan(1, 0, 0, 724, new Fixture((x, z) -> 220)).sites()), "Seed does not affect sites");
+
+        Fixture wet = new Fixture((x, z) -> 220); wet.protection = (x, y, z) -> true;
+        var blocked = HeritagePlanner19.plan(0, 0, 0, 724, wet); verify(blocked, wet);
+        require(blocked.isEmpty() && blocked.links().isEmpty(), "Protected water or earlier city is overwritten");
+        Fixture voidTerrain = new Fixture((x, z) -> -1);
+        var absent = HeritagePlanner19.plan(0, 0, 0, 724, voidTerrain); verify(absent, voidTerrain);
+        require(absent.isEmpty() && absent.segments().isEmpty(), "Void receives unsupported structures or fictional routes");
+        Fixture thin = new Fixture((x, z) -> 220); thin.rock = (x, y, z) -> y >= 219 && y <= 220;
+        var thinPlan = HeritagePlanner19.plan(0, 0, 0, 724, thin); verify(thinPlan, thin);
+        require(thinPlan.isEmpty(), "Thin shelves receive buildings without anchored footings");
+
+        // Every site keeps its local access even when a protected ring rejects every inter-site alignment.
+        Set<Long> allowed = new HashSet<>();
+        for (var site : flat.sites()) for (int x = site.minX(); x <= site.maxX(); x++) for (int z = site.minZ(); z <= site.maxZ(); z++) allowed.add(key(x, z));
+        for (var segment : flat.segments()) if (segment.fromId().equals(segment.toId())) for (var c : segment.cells()) allowed.add(key(c.x(), c.z()));
+        Fixture isolated = new Fixture((x, z) -> 220); isolated.protection = (x, y, z) -> !allowed.contains(key(x, z));
+        var islands = HeritagePlanner19.plan(0, 0, 0, 724, isolated); verify(islands, isolated);
+        require(!islands.sites().isEmpty(), "Independent access fixture has no retained site");
+        require(islands.sites().stream().anyMatch(site -> islands.links().stream().noneMatch(l -> l.fromId().equals(site.id()) || l.toId().equals(site.id()))),
+            "The isolated destination witness unexpectedly has every long route");
+
+        // Historical landmark feet are read-only and have no mask bypass, even when a route reaches them.
+        Site station = flat.sites().stream().filter(s -> s.kind() == Kind.FREIGHT_STATION).findFirst().orElseThrow();
+        Entry historical = new Entry(station.entry().x() + DX[station.facing()] * 30,
+            221, station.entry().z() + DZ[station.facing()] * 30, (station.facing() + 2) & 3);
+        Fixture landmark = new Fixture((x, z) -> 220);
+        landmark.landmarks = List.of(new Landmark("old_mine", LandmarkKind.MINE, historical));
+        landmark.protection = (x, y, z) -> x == historical.x() && z == historical.z();
+        var linked = HeritagePlanner19.plan(0, 0, 0, 724, landmark); verify(linked, landmark);
+        require(!linked.contains(historical.x(), historical.y(), historical.z()), "A historical endpoint receives route painting");
+
+        Landmark left = new Landmark("left", LandmarkKind.CITY, new Entry(0, 101, 0, 1));
+        Landmark right = new Landmark("right", LandmarkKind.MINE, new Entry(1, 101, 0, 3));
+        Landmark unused = new Landmark("unused", LandmarkKind.UTILITY, new Entry(30, 101, 0, 0));
+        var dependency = new HeritagePlan19(List.of(), List.of(left, right, unused),
+            List.of(new Link("existing_access", "left", "right", RouteKind.PATH, List.of(new Point(0, 100, 0), new Point(1, 100, 0)))),
+            List.of(), 0, 0, Map.of());
+        for (int z = -1; z <= 1; z++) for (int y = 99; y <= 103; y++) {
+            require(dependency.protects(0, y, z) && dependency.intersectsProtection(0, y, z, 0, y, z), "Used historical access lost its rock/headroom dependency");
+            require(!dependency.contains(0, y, z), "Read-only historical access received writing permission");
+        }
+        require(!dependency.protects(30, 101, 0), "Unused historical landmark reserves unrelated terrain");
+
+        // Smooth slopes exercise certified cut/fill and route grade without allowing an unsupported plateau.
+        Fixture sloped = new Fixture((x, z) -> 220 + Math.floorDiv(z, 12));
+        var slopes = HeritagePlanner19.plan(42, 0, 0, 724, sloped); verify(slopes, sloped);
+        require(slopes.sites().size() >= 5, "A modest slope makes the entire catalogue inadmissible");
+        Fixture shifted = new Fixture((x, z) -> 220);
+        var translated = HeritagePlanner19.plan(42, -1024, 512, 724, shifted); verify(translated, shifted);
+        require(!translated.isEmpty(), "Negative chunk coordinates prevent generation");
+        require(flat.diagnostics().size() == Kind.values().length && blocked.diagnostics().size() == Kind.values().length,
+            "Missing kinds have no explicit diagnostic");
+        expectInvalid(() -> new Link("self", "a", "a", RouteKind.PATH, List.of(new Point(0, 100, 0), new Point(1, 100, 0))));
+        expectInvalid(() -> new Segment("self", "a", "a", RouteKind.FREIGHT, 0, 0, List.of(new Cell(0, 100, 0, 1, Rail.NONE, false)), 0));
+        expectInvalid(() -> new Cell(0, 100, 0, 13, Rail.NONE, false));
+        System.out.println("HeritagePlanner19Smoke passed: fourteen families, deterministic placements, persisted isolated entrances, real route destinations, bounded slopes and supported rails, unique chunk-local cells, indexed protection and budgets");
+    }
+
+    private static void verify(HeritagePlan19 plan, Fixture terrain) {
+        require(plan.samples() == terrain.samples && plan.samples() <= HeritagePlan19.MAX_SAMPLES, "Probe accounting differs from native calls");
+        require(plan.columns() == terrain.columns.size() && plan.columns() <= HeritagePlan19.MAX_COLUMNS, "Column budget exceeded");
+        Map<Long, Cell> cells = new HashMap<>(); Map<String, Entry> destinations = new HashMap<>();
+        Set<Long> footprints = new HashSet<>();
+        for (var site : plan.sites()) {
+            destinations.put(site.id(), site.entry());
+            require(site.foundationDepth() <= 8 && site.maxY() <= 380, "Architecture exceeds its bounded envelope");
+            require(Math.abs((site.minX() >> 4) - site.startChunkX()) <= 7 && Math.abs((site.maxX() >> 4) - site.startChunkX()) <= 7
+                && Math.abs((site.minZ() >> 4) - site.startChunkZ()) <= 7 && Math.abs((site.maxZ() >> 4) - site.startChunkZ()) <= 7, "Site exceeds native reference radius");
+            for (int z = site.minZ(); z <= site.maxZ(); z++) for (int x = site.minX(); x <= site.maxX(); x++) {
+                require(footprints.add(key(x, z)), "Two buildings overlap");
+                require(terrain.height.applyAsInt(x, z) - site.floorY() <= HeritagePlanner19.MAX_SITE_CUT, "Site cuts an excessive mound");
+                for (int y = site.minY(); y <= site.maxY(); y++) require(!terrain.protection.test(x, y, z), "Architecture intersects protected water/old structure");
+                require(plan.contains(x, site.floorY(), z) && plan.protects(x, site.maxY(), z)
+                    && plan.intersectsProtection(x, site.maxY(), z, x, site.maxY(), z), "Site is absent from indexed protection");
+            }
+            for (int dx : new int[] {1, 8, 15}) for (int dz : new int[] {1, 8, 15}) {
+                int x = site.minX() + dx, z = site.minZ() + dz;
+                var support = site.supports().stream().filter(s -> s.x() == x && s.z() == z).findFirst();
+                int rock = support.isPresent() ? support.get().minY() - 1 : site.minY() - 1;
+                require(terrain.rock.test(x, rock, z) && terrain.rock.test(x, rock - 1, z), "Site has no two-block rock bearing");
+            }
+            for (var support : site.supports()) {
+                require(support.maxY() - support.minY() < 12 && support.maxY() == site.minY() - 1, "Unbounded/disconnected architectural pier");
+                require(plan.protects(support.x(), support.minY() - 2, support.z()), "Pier bearing exposed to decoration");
+                for (int y = support.minY(); y <= support.maxY(); y++) require(!terrain.protection.test(support.x(), y, support.z()), "Pier overwrites protected terrain");
+            }
+        }
+        plan.landmarks().forEach(l -> destinations.put(l.id(), l.entry()));
+        for (var segment : plan.segments()) {
+            require(destinations.containsKey(segment.fromId()) && destinations.containsKey(segment.toId()), "Segment has a fictional destination");
+            for (Cell cell : segment.cells()) {
+                require(cells.put(key(cell.x(), cell.z()), cell) == null, "Two segments write the same column");
+                require(!footprints.contains(key(cell.x(), cell.z())), "Route crosses a building envelope");
+                require((cell.x() >> 4) == segment.startChunkX() && (cell.z() >> 4) == segment.startChunkZ(), "Route piece is not chunk-local");
+                require(terrain.rock.test(cell.x(), cell.minY() - 1, cell.z()), "Route ballast floats without bearing");
+                require(terrain.height.applyAsInt(cell.x(), cell.z()) - cell.floorY() <= HeritagePlanner19.MAX_ROUTE_CUT, "Route makes excessive terrain cuts");
+                for (int y = cell.minY(); y <= cell.maxY(); y++) require(!terrain.protection.test(cell.x(), y, cell.z()), "Route overwrites protected water/old structure");
+                require(plan.contains(cell.x(), cell.floorY(), cell.z()) && plan.protects(cell.x(), cell.minY() - 1, cell.z())
+                    && plan.intersectsProtection(cell.x(), cell.minY() - 1, cell.z(), cell.x(), cell.minY() - 1, cell.z()), "Route/ballast missing from protection index");
+                require(!cell.railPresent() || cell.rail() != Rail.NONE, "Present rail has no saved geometry");
+            }
+        }
+        for (var site : plan.sites()) {
+            Entry e = site.entry();
+            for (int cross = -1; cross <= 1; cross++) {
+                Cell cell = cells.get(key(e.x() + DZ[e.facing()] * cross, e.z() - DX[e.facing()] * cross));
+                require(cell != null && cell.floorY() == e.y() - 1, "Unlinked entrance has no independently painted three-wide landing");
+            }
+            // A five-row access profile must meet natural terrain; never stop on an isolated retaining ledge.
+            var reached = new HashSet<Long>(); var queue = new ArrayDeque<Long>();
+            queue.add(key(e.x(), e.z())); reached.add(key(e.x(), e.z())); boolean meetsGround = false;
+            while (!queue.isEmpty()) {
+                long key = queue.remove(); Cell c = cells.get(key);
+                if (Math.abs(c.x() - e.x()) + Math.abs(c.z() - e.z()) >= 4
+                    && Math.abs(c.floorY() - terrain.height.applyAsInt(c.x(), c.z())) <= 1) meetsGround = true;
+                for (int d = 0; d < 4; d++) {
+                    long next = key(c.x() + DX[d], c.z() + DZ[d]); Cell n = cells.get(next);
+                    if (n != null && Math.abs(n.floorY() - c.floorY()) <= 1 && reached.add(next)) queue.add(next);
+                }
+            }
+            require(meetsGround, "An entrance platform has no traversable return to the sampled terrain");
+        }
+        for (var link : plan.links()) {
+            Entry from = destinations.get(link.fromId()), to = destinations.get(link.toId());
+            require(link.path().getFirst().equals(new Point(from.x(), from.y() - 1, from.z()))
+                && link.path().getLast().equals(new Point(to.x(), to.y() - 1, to.z())), "Route does not actually join its promised entrances");
+            for (int i = 0; i < link.path().size(); i++) {
+                Point p = link.path().get(i); Cell c = cells.get(key(p.x(), p.z()));
+                boolean historical = plan.landmarks().stream().anyMatch(l -> l.entry().x() == p.x() && l.entry().z() == p.z() && l.entry().y() == p.floorY() + 1);
+                require(c != null && c.floorY() == p.floorY() || historical, "A complete route contains an unpainted gap");
+                if (i > 0) {
+                    Point a = link.path().get(i - 1);
+                    require(Math.abs(a.x() - p.x()) + Math.abs(a.z() - p.z()) == 1 && Math.abs(a.floorY() - p.floorY()) <= 1, "Route has a jump or excessive grade");
+                }
+            }
+        }
+        require(!plan.protects(100_000, 200, 100_000) && !plan.intersectsProtection(100_000, 0, 100_000, 100_002, 383, 100_002), "Protection escaped accepted constructions");
+    }
+    @FunctionalInterface private interface Volume { boolean test(int x, int y, int z); }
+    private static final class Fixture implements HeritagePlanner19.Terrain {
+        final IntBinaryOperator height; final Set<Long> columns = new HashSet<>(); int samples;
+        Volume protection = (x, y, z) -> false;
+        Volume rock; List<Landmark> landmarks = List.of();
+        Fixture(IntBinaryOperator height) { this.height = height; rock = (x, y, z) -> y >= 8 && y <= height.applyAsInt(x, z); }
+        public boolean owns(int x, int z) { return true; }
+        public int surfaceY(int x, int z) { samples++; columns.add(key(x, z)); return height.applyAsInt(x, z); }
+        public boolean solid(int x, int y, int z) { samples++; return rock.test(x, y, z); }
+        public boolean protectedAt(int x, int y, int z) { samples++; return protection.test(x, y, z); }
+        public List<Landmark> landmarks() { return landmarks; }
+    }
+    private static void expectInvalid(Runnable action) { boolean rejected = false; try { action.run(); } catch (IllegalArgumentException expected) { rejected = true; } require(rejected, "Invalid saved geometry was accepted"); }
+    private static void require(boolean value, String message) { if (!value) throw new AssertionError(message); }
+    private static long key(int x, int z) { return (long) x << 32 ^ z & 0xffffffffL; }
+}
@@ -0,0 +1,328 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.EmptyBlockGetter;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.DoorBlock;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.TrapDoorBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DoubleBlockHalf;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.phys.AABB;
+
+/** Native shapes and final geometry: distinguish real rooms, reachable secrets and supported routes. */
+public final class HeritageRenderer19Smoke {
+    private HeritageRenderer19Smoke() {}
+    private static final Direction[] DIRECTIONS = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("HeritageRenderer19Smoke passed: fourteen distinct architectures, four rotations, actual doors/bed/seat/light supports, every target and secret reachable, contained water, immutable loot and shaped abandoned routes");
+    }
+    public static void run() {
+        Set<Set<BlockPos>> silhouettes = new HashSet<>();
+        for (var kind : HeritagePlan19.Kind.values()) for (long seed : new long[] {0, 43}) {
+            var canonical = render(site(kind, 0, seed));
+            if (seed == 0) {
+                Set<BlockPos> shape = new HashSet<>(); canonical.blocks.forEach((p, b) -> { if (p.getY() > 0 && !b.isAir()) shape.add(p); });
+                require(silhouettes.add(shape), kind + " only repaints another catalogue building");
+            }
+            for (int facing = 0; facing < 4; facing++) {
+                var c = facing == 0 ? canonical : render(site(kind, facing, seed));
+                var repeat = render(c.site);
+                require(c.blocks.equals(repeat.blocks) && c.loot.equals(repeat.loot), label(c) + " is not deterministic");
+                rotate(canonical, c);
+                var targets = HeritageRenderer19.targets(c.site);
+                var reached = walk(c, at(targets.getFirst()));
+                for (var target : targets) require(reached.contains(at(target)), label(c) + " cannot reach " + target.name() + " at " + at(target));
+                require(targets.stream().anyMatch(t -> t.name().equals("secondary_entry")), "Missing secondary physical approach");
+                var secondary = targets.stream().filter(t -> t.name().equals("secondary_entry")).findFirst().orElseThrow();
+                Set<BlockPos> returnPath = walk(c, at(secondary));
+                require(returnPath.contains(at(targets.getFirst())), label(c) + " service exit cannot return through the certified courtyard");
+                require(c.loot.size() == 1, label(c) + " must have one shared, deferred discovery chest");
+                var chest = c.loot.entrySet().iterator().next();
+                require(chest.getValue().table().identifier().toString().equals("sanctuary:chests/heritage19/" + kind.name().toLowerCase(java.util.Locale.ROOT)), "Loot table is not generation19-specific");
+                require(approachable(chest.getKey(), reached), label(c) + " hidden chest cannot be opened from a reachable standing cell");
+                for (var t : targets) if (t.name().equals("loot_approach")) require(at(t).distManhattan(chest.getKey()) == 1, "Secret witness is not next to the actual chest");
+                furnishings(c, reached);
+                refugeShaft(c, reached);
+                railConnection(c);
+                fluids(c);
+                require(c.blocks.values().stream().noneMatch(b -> b.is(Blocks.SPAWNER) || b.is(Blocks.LAVA)), "Heritage added an unrequested spawner or lava");
+                identity(c);
+            }
+        }
+        require(silhouettes.size() == 14, "Catalogue does not contain fourteen physical architectures");
+        routes(); chunkPartition();
+    }
+    private static HeritagePlan19.Site site(HeritagePlan19.Kind kind, int facing, long seed) {
+        int height = switch (kind) {
+            case COMMUNAL_DEPOT, VOID_DOCK, CONSTRUCTION_REFUGE -> 14;
+            case EXPEDITION_OFFICE, IMPOSSIBLE_SERVICE -> 12;
+            case OBSERVATORY -> 20; case PUMP_STATION -> 18; case RADIO_RELAY -> 22;
+            default -> 10;
+        };
+        int x = -43, y = 180, z = 59;
+        var entry = new HeritagePlan19.Entry(facing == 1 ? x + 17 : facing == 3 ? x - 1 : x + 8, y + 1,
+            facing == 2 ? z + 17 : facing == 0 ? z - 1 : z + 8, facing);
+        return new HeritagePlan19.Site("test", kind, x, y, z, 17, 17, height, facing, seed, 3,
+            List.of(new HeritagePlan19.Support(x, y - 7, z, y - 4)), entry);
+    }
+    private static String label(Capture c) { return c.site.kind() + " facing=" + c.site.facing() + " seed=" + c.site.seed(); }
+    private static Capture render(HeritagePlan19.Site site) { var c = new Capture(site); HeritageRenderer19.render(site, c); return c; }
+    private static BlockPos at(HeritageRenderer19.Target t) { return new BlockPos(t.x(), t.y(), t.z()); }
+    private static BlockPos rotate(BlockPos p, int facing) {
+        return switch (facing) { case 1 -> new BlockPos(16 - p.getZ(), p.getY(), p.getX());
+            case 2 -> new BlockPos(16 - p.getX(), p.getY(), 16 - p.getZ());
+            case 3 -> new BlockPos(p.getZ(), p.getY(), 16 - p.getX()); default -> p; };
+    }
+    private static void rotate(Capture base, Capture other) {
+        int facing = other.site.facing();
+        Rotation rotation = switch (facing) { case 1 -> Rotation.CLOCKWISE_90; case 2 -> Rotation.CLOCKWISE_180;
+            case 3 -> Rotation.COUNTERCLOCKWISE_90; default -> Rotation.NONE; };
+        for (var e : base.blocks.entrySet()) {
+            // Saved footings are already in world coordinates; they do not rotate with the facade.
+            if (e.getKey().getY() < -base.site.foundationDepth() || base.loot.containsKey(e.getKey())) continue;
+            require(other.block(rotate(e.getKey(), facing)).equals(e.getValue().rotate(rotation)), label(other) + " rotates shape and block state differently at " + e.getKey());
+        }
+        for (var e : base.loot.entrySet()) require(e.getValue().equals(other.loot.get(rotate(e.getKey(), facing))), "Rotating a site changes its deferred treasure");
+    }
+    private static void furnishings(Capture c, Set<BlockPos> reached) {
+        for (var e : c.blocks.entrySet()) {
+            var p = e.getKey(); var b = e.getValue();
+            if (b.getBlock() instanceof DoorBlock) {
+                var half = b.getValue(BlockStateProperties.DOUBLE_BLOCK_HALF);
+                var partner = half == DoubleBlockHalf.LOWER ? p.above() : p.below();
+                require(c.block(partner).equals(b.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF,
+                    half == DoubleBlockHalf.LOWER ? DoubleBlockHalf.UPPER : DoubleBlockHalf.LOWER)), label(c) + " has a truncated door at " + p);
+                if (half == DoubleBlockHalf.LOWER) {
+                    require(full(c.block(p.below()), p.below()), "Door has no full threshold");
+                    Direction normal = b.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                    require(reached.contains(p.relative(normal)) && reached.contains(p.relative(normal.getOpposite())),
+                        label(c) + " door does not connect two usable sides at " + p);
+                }
+            }
+            if (b.is(Blocks.LADDER)) require(full(c.block(p.relative(b.getValue(BlockStateProperties.HORIZONTAL_FACING).getOpposite())), p),
+                label(c) + " floating ladder at " + p);
+            if (b.is(Blocks.LANTERN)) require(b.getValue(BlockStateProperties.HANGING) && full(c.block(p.above()), p.above()),
+                label(c) + " lantern does not hang from a complete ceiling at " + p);
+            if (b.is(Blocks.LEVER) || b.is(Blocks.GRINDSTONE)) require(full(c.block(p.below()), p.below()), "Usable fixture has no full support");
+            if (b.is(Blocks.DARK_OAK_STAIRS)) {
+                var front = p.relative(b.getValue(BlockStateProperties.HORIZONTAL_FACING).getOpposite());
+                require(reached.contains(front), label(c) + " seat faces an obstruction at " + p);
+            }
+            if (b.hasProperty(BlockStateProperties.BED_PART)) {
+                Direction direction = b.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                boolean head = b.getValue(BlockStateProperties.BED_PART) == BedPart.HEAD;
+                var partner = p.relative(head ? direction.getOpposite() : direction);
+                require(c.block(partner).equals(b.setValue(BlockStateProperties.BED_PART, head ? BedPart.FOOT : BedPart.HEAD)), "Bed halves disagree");
+                if (head) {
+                    for (int y = 0; y < 3; y++) require(full(c.block(p.relative(direction).above(y)), p), "Bed head is not against its real wall");
+                    boolean side = false;
+                    for (Direction d : new Direction[] {direction.getClockWise(), direction.getCounterClockWise()})
+                        side |= reached.contains(p.relative(d)) && reached.contains(partner.relative(d));
+                    require(side, "Bed has no reachable full lateral approach");
+                }
+            }
+            if (b.is(Blocks.CRAFTING_TABLE) || b.is(Blocks.CARTOGRAPHY_TABLE) || b.is(Blocks.FURNACE)
+                    || b.is(Blocks.GRINDSTONE) || b.is(Blocks.LECTERN))
+                require(approachable(p, reached), label(c) + " functional furnishing cannot be approached at " + p);
+        }
+    }
+    private static boolean full(BlockState b, BlockPos p) {
+        return b.getFluidState().isEmpty() && b.getCollisionShape(EmptyBlockGetter.INSTANCE, p).toAabbs().stream()
+            .anyMatch(a -> a.minX == 0 && a.minY == 0 && a.minZ == 0 && a.maxX == 1 && a.maxY == 1 && a.maxZ == 1);
+    }
+    private static boolean approachable(BlockPos p, Set<BlockPos> reached) {
+        for (var d : DIRECTIONS) if (reached.contains(p.relative(d))) return true;
+        return false;
+    }
+    private static boolean clear(Capture c, BlockPos p) {
+        var body = new AABB(p.getX() + .2, p.getY(), p.getZ() + .2, p.getX() + .8, p.getY() + 1.8, p.getZ() + .8);
+        for (var at : new BlockPos[] {p, p.above()}) {
+            var b = opened(c.block(at)); if (!b.getFluidState().isEmpty()) return false;
+            for (var shape : b.getCollisionShape(EmptyBlockGetter.INSTANCE, at).toAabbs())
+                if (shape.move(at.getX(), at.getY(), at.getZ()).intersects(body)) return false;
+        }
+        return true;
+    }
+    private static boolean stand(Capture c, BlockPos p) {
+        if (p.getX() < 0 || p.getX() > 16 || p.getZ() < 0 || p.getZ() > 16
+                || p.getY() < -c.site.foundationDepth() + 1 || p.getY() >= c.site.height() || !clear(c, p)) return false;
+        if (climb(c.block(p)) || climb(c.block(p.below()))) return true;
+        return opened(c.block(p.below())).getCollisionShape(EmptyBlockGetter.INSTANCE, p.below()).toAabbs().stream()
+            .anyMatch(a -> a.maxY >= .5 && a.minX <= .5 && a.maxX >= .5 && a.minZ <= .5 && a.maxZ >= .5);
+    }
+    private static BlockState opened(BlockState state) {
+        return state.getBlock() instanceof DoorBlock || state.getBlock() instanceof TrapDoorBlock
+            ? state.setValue(BlockStateProperties.OPEN, true) : state;
+    }
+    private static void refugeShaft(Capture c, Set<BlockPos> reached) {
+        if (c.site.kind() != HeritagePlan19.Kind.CONSTRUCTION_REFUGE) return;
+        var hatch = rotate(new BlockPos(10, 5, 11), c.site.facing());
+        require(c.block(hatch).is(Blocks.DARK_OAK_TRAPDOOR)
+            && c.block(hatch).getValue(BlockStateProperties.HALF) == Half.BOTTOM,
+            label(c) + " hatch is not at the climbable upper lip");
+        var direction = c.block(hatch).getValue(BlockStateProperties.HORIZONTAL_FACING);
+        require(stand(c, hatch) && reached.contains(hatch), label(c) + " open hatch has no reachable climbable support");
+        for (int y = 1; y <= 4; y++) {
+            var rung = new BlockPos(hatch.getX(), y, hatch.getZ());
+            require(c.block(rung).is(Blocks.LADDER)
+                && c.block(rung).getValue(BlockStateProperties.HORIZONTAL_FACING) == direction,
+                label(c) + " hatch descent loses a matching ladder at " + rung);
+            require(stand(c, rung) && reached.contains(rung) && clear(c, rung.above()),
+                label(c) + " hatch descent cannot traverse vertically at " + rung);
+        }
+    }
+    private static boolean climb(BlockState b) { return b.is(Blocks.LADDER); }
+    private static Set<BlockPos> walk(Capture c, BlockPos start) {
+        require(stand(c, start), label(c) + " starts without a standing surface at " + start);
+        Set<BlockPos> seen = new HashSet<>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var p = queue.removeFirst();
+            for (var d : DIRECTIONS) for (int dy : new int[] {0, 1, -1}) {
+                var q = p.relative(d).offset(0, dy, 0);
+                if (dy > 0 && !clear(c, p.above())) continue;
+                if (stand(c, q) && seen.add(q)) queue.add(q);
+            }
+            for (int dy : new int[] {-1, 1}) {
+                var q = p.offset(0, dy, 0);
+                if ((climb(c.block(p)) || climb(c.block(q)) || climb(c.block(p.below()))) && stand(c, q) && seen.add(q)) queue.add(q);
+            }
+        }
+        return seen;
+    }
+    private static void fluids(Capture c) {
+        Set<BlockPos> water = new HashSet<>(); c.blocks.forEach((p, b) -> { if (!b.getFluidState().isEmpty()) water.add(p); });
+        int expected = c.site.kind() == HeritagePlan19.Kind.PUMP_STATION ? 60 : c.site.kind() == HeritagePlan19.Kind.GREENHOUSE ? 2 : 0;
+        require(water.size() == expected, label(c) + " has unexpected water quantity: " + water.size());
+        for (var p : water) {
+            require(c.block(p).is(Blocks.WATER), "Only explicitly contained water is allowed");
+            for (var d : new Direction[] {Direction.DOWN, Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST}) {
+                var q = p.relative(d);
+                require(water.contains(q) || !c.block(q).isAir(), label(c) + " lets tank/irrigation water escape into air at " + q);
+            }
+        }
+    }
+    private static void identity(Capture c) {
+        switch (c.site.kind()) {
+            case FREIGHT_STATION -> { has(c, Blocks.RAIL); has(c, Blocks.LEVER); }
+            case POST_OFFICE -> { has(c, Blocks.BARREL); has(c, Blocks.CARTOGRAPHY_TABLE); }
+            case COMMUNAL_DEPOT -> { has(c, Blocks.BARREL); has(c, Blocks.LECTERN); }
+            case EXPEDITION_OFFICE -> { has(c, Blocks.CARTOGRAPHY_TABLE); has(c, Blocks.BOOKSHELF); }
+            case OBSERVATORY -> { has(c, Blocks.CARTOGRAPHY_TABLE); has(c, Blocks.IRON_BARS); }
+            case RAIL_WORKSHOP -> { has(c, Blocks.GRINDSTONE); has(c, Blocks.RAIL); has(c, Blocks.FURNACE); }
+            case PUMP_STATION -> { has(c, Blocks.DISPENSER); has(c, Blocks.WATER); }
+            case SUBSTATION -> { has(c, Blocks.LEVER); has(c, Blocks.IRON_BARS); }
+            case GREENHOUSE -> { has(c, Blocks.WHEAT); has(c, Blocks.FARMLAND); has(c, Blocks.COMPOSTER); }
+            case VOID_DOCK -> { has(c, Blocks.IRON_CHAIN); has(c, Blocks.STRIPPED_OAK_LOG); }
+            case RADIO_RELAY -> { has(c, Blocks.BED.white()); has(c, Blocks.IRON_BARS); }
+            case PHOTO_CLUB -> { has(c, Blocks.WATER_CAULDRON); has(c, Blocks.IRON_CHAIN); }
+            case IMPOSSIBLE_SERVICE -> { has(c, Blocks.CALCITE); has(c, Blocks.WATER_CAULDRON); }
+            case CONSTRUCTION_REFUGE -> { has(c, Blocks.BED.white()); has(c, Blocks.LADDER); has(c, Blocks.DARK_OAK_TRAPDOOR); }
+        }
+    }
+    private static void has(Capture c, Block b) { require(c.blocks.values().stream().anyMatch(v -> v.is(b)), label(c) + " loses its " + b); }
+    private static void railConnection(Capture c) {
+        BlockPos destination = switch (c.site.kind()) {
+            case FREIGHT_STATION -> new BlockPos(2, 1, 8);
+            case RAIL_WORKSHOP -> new BlockPos(5, 1, 7);
+            case COMMUNAL_DEPOT -> new BlockPos(8, 1, 7);
+            default -> null;
+        };
+        if (destination == null) return;
+        var start = rotate(new BlockPos(8, 1, 0), c.site.facing());
+        destination = rotate(destination, c.site.facing());
+        Set<BlockPos> seen = new HashSet<>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var p = queue.removeFirst(); var b = c.block(p);
+            require(b.is(Blocks.RAIL), label(c) + " freight entry has no supported rail");
+            for (var d : railEnds(b)) {
+                var next = p.relative(d); var state = c.block(next);
+                if (state.is(Blocks.RAIL) && railEnds(state).contains(d.getOpposite()) && seen.add(next)) queue.add(next);
+            }
+        }
+        require(seen.contains(destination), label(c) + " interior rail does not connect to its real external freight entry");
+    }
+    private static List<Direction> railEnds(BlockState b) {
+        return switch (b.getValue(BlockStateProperties.RAIL_SHAPE)) {
+            case NORTH_SOUTH, ASCENDING_NORTH, ASCENDING_SOUTH -> List.of(Direction.NORTH, Direction.SOUTH);
+            case EAST_WEST, ASCENDING_EAST, ASCENDING_WEST -> List.of(Direction.EAST, Direction.WEST);
+            case SOUTH_EAST -> List.of(Direction.SOUTH, Direction.EAST);
+            case SOUTH_WEST -> List.of(Direction.SOUTH, Direction.WEST);
+            case NORTH_WEST -> List.of(Direction.NORTH, Direction.WEST);
+            case NORTH_EAST -> List.of(Direction.NORTH, Direction.EAST);
+        };
+    }
+    private static void routes() {
+        var cells = new ArrayList<HeritagePlan19.Cell>();
+        int x = -15;
+        for (var rail : HeritagePlan19.Rail.values()) {
+            cells.add(new HeritagePlan19.Cell(x++, 160, 2, 2, rail, rail != HeritagePlan19.Rail.NONE));
+        }
+        cells.add(new HeritagePlan19.Cell(-1, 161, 2, 3, HeritagePlan19.Rail.ASCENDING_EAST, false));
+        var segment = new HeritagePlan19.Segment("route", "a", "b", HeritagePlan19.RouteKind.FREIGHT, -1, 0, cells, 7);
+        Map<BlockPos, BlockState> result = new HashMap<>();
+        HeritageRenderer19.renderSegment(segment, new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState b) {
+                var p = new BlockPos(segment.minX() + x, segment.minY() + y, segment.minZ() + z);
+                var cell = cells.stream().filter(c -> c.x() == p.getX() && c.z() == p.getZ()).findFirst().orElseThrow();
+                require(p.getY() >= cell.minY() && p.getY() <= cell.maxY(), "Route escaped its saved column mask"); result.put(p, b);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { throw new AssertionError("A route generated treasure"); }
+        });
+        for (var c : cells) {
+            var p = new BlockPos(c.x(), c.floorY() + 1, c.z());
+            require(full(result.get(p.below()), p.below()), "Rail or missing-rail witness lost its ballast support");
+            if (c.railPresent()) require(result.get(p).is(Blocks.RAIL)
+                && result.get(p).getValue(BlockStateProperties.RAIL_SHAPE).name().equals(c.rail().name()), "Saved rail shape was replaced by a straight track");
+            else require(result.get(p).isAir(), "An intentional abandoned-track gap was repaired by rendering");
+        }
+    }
+    private static void chunkPartition() {
+        var s = site(HeritagePlan19.Kind.CONSTRUCTION_REFUGE, 3, 43); var expected = render(s); var parts = new Capture(s);
+        for (int cz = s.maxZ() >> 4; cz >= s.minZ() >> 4; cz--) for (int cx = s.maxX() >> 4; cx >= s.minX() >> 4; cx--) {
+            final int chunkX = cx, chunkZ = cz;
+            HeritageRenderer19.render(s, new LostCityRenderer.BlockWriter() {
+                boolean owns(int x, int z) { return ((s.minX() + x) >> 4) == chunkX && ((s.minZ() + z) >> 4) == chunkZ; }
+                @Override public void set(int x, int y, int z, BlockState state) { if (owns(x, z)) parts.set(x, y, z, state); }
+                @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { if (owns(x, z)) parts.chest(x, y, z, table, seed); }
+            });
+        }
+        require(parts.blocks.equals(expected.blocks) && parts.loot.equals(expected.loot), "Native chunk order changes a site");
+    }
+    private record Loot(ResourceKey<LootTable> table, long seed) {}
+    private static final class Capture implements LostCityRenderer.BlockWriter {
+        final HeritagePlan19.Site site;
+        final Map<BlockPos, BlockState> blocks = new HashMap<>();
+        final Map<BlockPos, Loot> loot = new HashMap<>();
+        Capture(HeritagePlan19.Site site) { this.site = site; }
+        @Override public void set(int x, int y, int z, BlockState state) {
+            int wy = y + site.floorY();
+            boolean main = x >= 0 && x <= 16 && z >= 0 && z <= 16 && wy >= site.minY() && wy <= site.maxY();
+            boolean footing = site.supports().stream().anyMatch(s -> s.x() == x + site.minX() && s.z() == z + site.minZ() && wy >= s.minY() && wy <= s.maxY());
+            require(main || footing, label(this) + " writes outside its exact body and footing mask"); blocks.put(new BlockPos(x, y, z), state);
+        }
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+            require(loot.put(new BlockPos(x, y, z), new Loot(table, seed)) == null, "Duplicate shared treasure"); set(x, y, z, Blocks.CHEST.defaultBlockState());
+        }
+        BlockState block(BlockPos p) { return blocks.getOrDefault(p, Blocks.AIR.defaultBlockState()); }
+    }
+    private static void require(boolean value, String message) { if (!value) throw new AssertionError(message); }
+}
@@ -0,0 +1,420 @@
+package fr.koka.sanctuary.worldgen.heritage;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.EmptyBlockGetter;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.DoorBlock;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.block.TrapDoorBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BedPart;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.DoubleBlockHalf;
+import net.minecraft.world.level.block.state.properties.Half;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.phys.AABB;
+
+/** Native shapes and final geometry: distinguish real rooms, reachable secrets and supported routes. */
+public final class HeritageRenderer20Smoke {
+    private HeritageRenderer20Smoke() {}
+    private static final Direction[] DIRECTIONS = {Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST};
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("HeritageRenderer20Smoke passed: fourteen composed generation20 identities, four rotations, bounded chamfers and roofs, supported furnishings, reachable original targets, retained loot and connected block details");
+    }
+    public static void run() {
+        Set<Set<BlockPos>> silhouettes = new HashSet<>();
+        for (var kind : HeritagePlan19.Kind.values()) for (long seed : new long[] {0, 43}) {
+            var canonical = render(site(kind, 0, seed));
+            if (seed == 0) {
+                export(canonical);
+                Set<BlockPos> shape = new HashSet<>(); canonical.blocks.forEach((p, b) -> { if (p.getY() > 0 && !b.isAir()) shape.add(p); });
+                require(silhouettes.add(shape), kind + " only repaints another catalogue building");
+            }
+            for (int facing = 0; facing < 4; facing++) {
+                var c = facing == 0 ? canonical : render(site(kind, facing, seed));
+                var repeat = render(c.site);
+                require(c.blocks.equals(repeat.blocks) && c.loot.equals(repeat.loot), label(c) + " is not deterministic");
+                rotate(canonical, c);
+                var targets = HeritageRenderer20.targets(c.site);
+                var reached = walk(c, at(targets.getFirst()));
+                for (var target : targets) require(reached.contains(at(target)), label(c) + " cannot reach " + target.name() + " at " + at(target));
+                require(targets.stream().anyMatch(t -> t.name().equals("secondary_entry")), "Missing secondary physical approach");
+                var secondary = targets.stream().filter(t -> t.name().equals("secondary_entry")).findFirst().orElseThrow();
+                Set<BlockPos> returnPath = walk(c, at(secondary));
+                require(returnPath.contains(at(targets.getFirst())), label(c) + " service exit cannot return through the certified courtyard");
+                require(c.loot.size() == 1, label(c) + " must have one shared, deferred discovery chest");
+                var chest = c.loot.entrySet().iterator().next();
+                require(chest.getValue().table().identifier().toString().equals("sanctuary:chests/heritage19/" + kind.name().toLowerCase(java.util.Locale.ROOT)), "Loot table is not generation19-specific");
+                require(approachable(chest.getKey(), reached), label(c) + " hidden chest cannot be opened from a reachable standing cell");
+                for (var t : targets) if (t.name().equals("loot_approach")) require(at(t).distManhattan(chest.getKey()) == 1, "Secret witness is not next to the actual chest");
+                furnishings(c, reached);
+                refugeShaft(c, reached);
+                railConnection(c);
+                fluids(c);
+                require(c.blocks.values().stream().noneMatch(b -> b.is(Blocks.SPAWNER) || b.is(Blocks.LAVA)), "Heritage added an unrequested spawner or lava");
+                identity(c);
+                architecture20(c);
+                daylightAndCrown20(c);
+            }
+        }
+        require(silhouettes.size() == 14, "Catalogue does not contain fourteen physical architectures");
+        routes(); chunkPartition(); materials20();
+    }
+    private static HeritagePlan19.Site site(HeritagePlan19.Kind kind, int facing, long seed) {
+        int height = switch (kind) {
+            case COMMUNAL_DEPOT, VOID_DOCK, CONSTRUCTION_REFUGE -> 14;
+            case EXPEDITION_OFFICE, IMPOSSIBLE_SERVICE -> 12;
+            case OBSERVATORY -> 20; case PUMP_STATION -> 18; case RADIO_RELAY -> 22;
+            default -> 10;
+        };
+        int x = -43, y = 180, z = 59;
+        var entry = new HeritagePlan19.Entry(facing == 1 ? x + 17 : facing == 3 ? x - 1 : x + 8, y + 1,
+            facing == 2 ? z + 17 : facing == 0 ? z - 1 : z + 8, facing);
+        return new HeritagePlan19.Site("test", kind, x, y, z, 17, 17, height, facing, seed, 3,
+            List.of(new HeritagePlan19.Support(x, y - 7, z, y - 4)), entry);
+    }
+    private static String label(Capture c) { return c.site.kind() + " facing=" + c.site.facing() + " seed=" + c.site.seed(); }
+    private static Capture render(HeritagePlan19.Site site) { var c = new Capture(site); HeritageRenderer20.render(site, c); return c; }
+    private static BlockPos at(HeritageRenderer20.Target t) { return new BlockPos(t.x(), t.y(), t.z()); }
+    private static BlockPos rotate(BlockPos p, int facing) {
+        return switch (facing) { case 1 -> new BlockPos(16 - p.getZ(), p.getY(), p.getX());
+            case 2 -> new BlockPos(16 - p.getX(), p.getY(), 16 - p.getZ());
+            case 3 -> new BlockPos(p.getZ(), p.getY(), 16 - p.getX()); default -> p; };
+    }
+    private static void rotate(Capture base, Capture other) {
+        int facing = other.site.facing();
+        Rotation rotation = switch (facing) { case 1 -> Rotation.CLOCKWISE_90; case 2 -> Rotation.CLOCKWISE_180;
+            case 3 -> Rotation.COUNTERCLOCKWISE_90; default -> Rotation.NONE; };
+        for (var e : base.blocks.entrySet()) {
+            // Saved footings are already in world coordinates; they do not rotate with the facade.
+            if (e.getKey().getY() < -base.site.foundationDepth() || base.loot.containsKey(e.getKey())) continue;
+            require(other.block(rotate(e.getKey(), facing)).equals(e.getValue().rotate(rotation)), label(other) + " rotates shape and block state differently at " + e.getKey());
+        }
+        for (var e : base.loot.entrySet()) require(e.getValue().equals(other.loot.get(rotate(e.getKey(), facing))), "Rotating a site changes its deferred treasure");
+    }
+    private static void furnishings(Capture c, Set<BlockPos> reached) {
+        for (var e : c.blocks.entrySet()) {
+            var p = e.getKey(); var b = e.getValue();
+            if (b.getBlock() instanceof DoorBlock) {
+                var half = b.getValue(BlockStateProperties.DOUBLE_BLOCK_HALF);
+                var partner = half == DoubleBlockHalf.LOWER ? p.above() : p.below();
+                require(c.block(partner).equals(b.setValue(BlockStateProperties.DOUBLE_BLOCK_HALF,
+                    half == DoubleBlockHalf.LOWER ? DoubleBlockHalf.UPPER : DoubleBlockHalf.LOWER)), label(c) + " has a truncated door at " + p);
+                if (half == DoubleBlockHalf.LOWER) {
+                    require(full(c.block(p.below()), p.below()), "Door has no full threshold");
+                    Direction normal = b.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                    require(reached.contains(p.relative(normal)) && reached.contains(p.relative(normal.getOpposite())),
+                        label(c) + " door does not connect two usable sides at " + p);
+                }
+            }
+            if (b.is(Blocks.LADDER)) require(full(c.block(p.relative(b.getValue(BlockStateProperties.HORIZONTAL_FACING).getOpposite())), p),
+                label(c) + " floating ladder at " + p);
+            if (b.is(Blocks.LANTERN)) require(b.getValue(BlockStateProperties.HANGING) && full(c.block(p.above()), p.above()),
+                label(c) + " lantern does not hang from a complete ceiling at " + p);
+            if (b.is(Blocks.LEVER) || b.is(Blocks.GRINDSTONE)) require(full(c.block(p.below()), p.below()), "Usable fixture has no full support");
+            if (b.is(Blocks.DARK_OAK_STAIRS)) {
+                var front = p.relative(b.getValue(BlockStateProperties.HORIZONTAL_FACING).getOpposite());
+                require(reached.contains(front), label(c) + " seat faces an obstruction at " + p);
+            }
+            if (b.hasProperty(BlockStateProperties.BED_PART)) {
+                Direction direction = b.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                boolean head = b.getValue(BlockStateProperties.BED_PART) == BedPart.HEAD;
+                var partner = p.relative(head ? direction.getOpposite() : direction);
+                require(c.block(partner).equals(b.setValue(BlockStateProperties.BED_PART, head ? BedPart.FOOT : BedPart.HEAD)), "Bed halves disagree");
+                if (head) {
+                    for (int y = 0; y < 3; y++) require(full(c.block(p.relative(direction).above(y)), p), "Bed head is not against its real wall");
+                    boolean side = false;
+                    for (Direction d : new Direction[] {direction.getClockWise(), direction.getCounterClockWise()})
+                        side |= reached.contains(p.relative(d)) && reached.contains(partner.relative(d));
+                    require(side, "Bed has no reachable full lateral approach");
+                }
+            }
+            if (b.is(Blocks.CRAFTING_TABLE) || b.is(Blocks.CARTOGRAPHY_TABLE) || b.is(Blocks.FURNACE)
+                    || b.is(Blocks.GRINDSTONE) || b.is(Blocks.LECTERN))
+                require(approachable(p, reached), label(c) + " functional furnishing cannot be approached at " + p);
+        }
+    }
+    private static boolean full(BlockState b, BlockPos p) {
+        return b.getFluidState().isEmpty() && b.getCollisionShape(EmptyBlockGetter.INSTANCE, p).toAabbs().stream()
+            .anyMatch(a -> a.minX == 0 && a.minY == 0 && a.minZ == 0 && a.maxX == 1 && a.maxY == 1 && a.maxZ == 1);
+    }
+    private static boolean approachable(BlockPos p, Set<BlockPos> reached) {
+        for (var d : DIRECTIONS) if (reached.contains(p.relative(d))) return true;
+        return false;
+    }
+    private static boolean clear(Capture c, BlockPos p) {
+        var body = new AABB(p.getX() + .2, p.getY(), p.getZ() + .2, p.getX() + .8, p.getY() + 1.8, p.getZ() + .8);
+        for (var at : new BlockPos[] {p, p.above()}) {
+            var b = opened(c.block(at)); if (!b.getFluidState().isEmpty()) return false;
+            for (var shape : b.getCollisionShape(EmptyBlockGetter.INSTANCE, at).toAabbs())
+                if (shape.move(at.getX(), at.getY(), at.getZ()).intersects(body)) return false;
+        }
+        return true;
+    }
+    private static boolean stand(Capture c, BlockPos p) {
+        if (p.getX() < 0 || p.getX() > 16 || p.getZ() < 0 || p.getZ() > 16
+                || p.getY() < -c.site.foundationDepth() + 1 || p.getY() >= c.site.height() || !clear(c, p)) return false;
+        if (climb(c.block(p)) || climb(c.block(p.below()))) return true;
+        return opened(c.block(p.below())).getCollisionShape(EmptyBlockGetter.INSTANCE, p.below()).toAabbs().stream()
+            .anyMatch(a -> a.maxY >= .5 && a.minX <= .5 && a.maxX >= .5 && a.minZ <= .5 && a.maxZ >= .5);
+    }
+    private static BlockState opened(BlockState state) {
+        return state.getBlock() instanceof DoorBlock || state.getBlock() instanceof TrapDoorBlock
+            ? state.setValue(BlockStateProperties.OPEN, true) : state;
+    }
+    private static void refugeShaft(Capture c, Set<BlockPos> reached) {
+        if (c.site.kind() != HeritagePlan19.Kind.CONSTRUCTION_REFUGE) return;
+        var hatch = rotate(new BlockPos(10, 5, 11), c.site.facing());
+        require(c.block(hatch).is(Blocks.DARK_OAK_TRAPDOOR)
+            && c.block(hatch).getValue(BlockStateProperties.HALF) == Half.BOTTOM,
+            label(c) + " hatch is not at the climbable upper lip");
+        var direction = c.block(hatch).getValue(BlockStateProperties.HORIZONTAL_FACING);
+        require(stand(c, hatch) && reached.contains(hatch), label(c) + " open hatch has no reachable climbable support");
+        for (int y = 1; y <= 4; y++) {
+            var rung = new BlockPos(hatch.getX(), y, hatch.getZ());
+            require(c.block(rung).is(Blocks.LADDER)
+                && c.block(rung).getValue(BlockStateProperties.HORIZONTAL_FACING) == direction,
+                label(c) + " hatch descent loses a matching ladder at " + rung);
+            require(stand(c, rung) && reached.contains(rung) && clear(c, rung.above()),
+                label(c) + " hatch descent cannot traverse vertically at " + rung);
+        }
+    }
+    private static boolean climb(BlockState b) { return b.is(Blocks.LADDER); }
+    private static Set<BlockPos> walk(Capture c, BlockPos start) {
+        require(stand(c, start), label(c) + " starts without a standing surface at " + start);
+        Set<BlockPos> seen = new HashSet<>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var p = queue.removeFirst();
+            for (var d : DIRECTIONS) for (int dy : new int[] {0, 1, -1}) {
+                var q = p.relative(d).offset(0, dy, 0);
+                if (dy > 0 && !clear(c, p.above())) continue;
+                if (stand(c, q) && seen.add(q)) queue.add(q);
+            }
+            for (int dy : new int[] {-1, 1}) {
+                var q = p.offset(0, dy, 0);
+                if ((climb(c.block(p)) || climb(c.block(q)) || climb(c.block(p.below()))) && stand(c, q) && seen.add(q)) queue.add(q);
+            }
+        }
+        return seen;
+    }
+    private static void fluids(Capture c) {
+        Set<BlockPos> water = new HashSet<>(); c.blocks.forEach((p, b) -> { if (!b.getFluidState().isEmpty()) water.add(p); });
+        int expected = c.site.kind() == HeritagePlan19.Kind.PUMP_STATION ? 60 : c.site.kind() == HeritagePlan19.Kind.GREENHOUSE ? 2 : 0;
+        require(water.size() == expected, label(c) + " has unexpected water quantity: " + water.size());
+        for (var p : water) {
+            require(c.block(p).is(Blocks.WATER), "Only explicitly contained water is allowed");
+            for (var d : new Direction[] {Direction.DOWN, Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.WEST}) {
+                var q = p.relative(d);
+                require(water.contains(q) || !c.block(q).isAir(), label(c) + " lets tank/irrigation water escape into air at " + q);
+            }
+        }
+    }
+    private static void identity(Capture c) {
+        switch (c.site.kind()) {
+            case FREIGHT_STATION -> { has(c, Blocks.RAIL); has(c, Blocks.LEVER); }
+            case POST_OFFICE -> { has(c, Blocks.BARREL); has(c, Blocks.CARTOGRAPHY_TABLE); }
+            case COMMUNAL_DEPOT -> { has(c, Blocks.BARREL); has(c, Blocks.LECTERN); }
+            case EXPEDITION_OFFICE -> { has(c, Blocks.CARTOGRAPHY_TABLE); has(c, Blocks.BOOKSHELF); }
+            case OBSERVATORY -> { has(c, Blocks.CARTOGRAPHY_TABLE); has(c, Blocks.IRON_BARS); }
+            case RAIL_WORKSHOP -> { has(c, Blocks.GRINDSTONE); has(c, Blocks.RAIL); has(c, Blocks.FURNACE); }
+            case PUMP_STATION -> { has(c, Blocks.DISPENSER); has(c, Blocks.WATER); }
+            case SUBSTATION -> { has(c, Blocks.LEVER); has(c, Blocks.IRON_BARS); }
+            case GREENHOUSE -> { has(c, Blocks.WHEAT); has(c, Blocks.FARMLAND); has(c, Blocks.COMPOSTER); }
+            case VOID_DOCK -> { has(c, Blocks.IRON_CHAIN); has(c, Blocks.STRIPPED_OAK_LOG); }
+            case RADIO_RELAY -> { has(c, Blocks.BED.white()); has(c, Blocks.IRON_BARS); }
+            case PHOTO_CLUB -> { has(c, Blocks.WATER_CAULDRON); has(c, Blocks.IRON_CHAIN); }
+            case IMPOSSIBLE_SERVICE -> { has(c, Blocks.CALCITE); has(c, Blocks.WATER_CAULDRON); }
+            case CONSTRUCTION_REFUGE -> { has(c, Blocks.BED.white()); has(c, Blocks.LADDER); has(c, Blocks.DARK_OAK_TRAPDOOR); }
+        }
+    }
+    private static void architecture20(Capture c) {
+        var old = new Capture(c.site); HeritageRenderer19.render(c.site, old);
+        long changedVolume = c.blocks.entrySet().stream().filter(e -> e.getKey().getY() > 0
+            && e.getValue().isAir() != old.block(e.getKey()).isAir()).count();
+        require(changedVolume >= 12, label(c) + " merely substitutes a palette instead of changing its architecture: " + changedVolume);
+        has(c, Blocks.TUFF_BRICKS); has(c, Blocks.CHISELED_TUFF_BRICKS); has(c, Blocks.STONE_BRICKS);
+        // The working destinations keep exactly their historical entrances and service witnesses.
+        var previous = HeritageRenderer19.targets(c.site).stream().map(t -> t.name() + ":" + t.x() + ":" + t.y() + ":" + t.z()).toList();
+        var current = HeritageRenderer20.targets(c.site).stream().map(t -> t.name() + ":" + t.x() + ":" + t.y() + ":" + t.z()).toList();
+        require(previous.equals(current), label(c) + " changes the saved functional access contract");
+        for (var e : c.blocks.entrySet()) if (e.getKey().getY() < 0 && e.getKey().getY() >= -c.site.foundationDepth()) {
+            // Workshop/trench cuts are deliberate; the exterior foundation always remains brick masonry.
+            int x = e.getKey().getX(), z = e.getKey().getZ();
+            if (x == 0 || x == 16 || z == 0 || z == 16) require(e.getValue().is(Blocks.STONE_BRICKS), "Visible foundations lost the stone-brick construction");
+        }
+    }
+    private static void daylightAndCrown20(Capture c) {
+        if (c.site.kind() == HeritagePlan19.Kind.FREIGHT_STATION) {
+            for (int x : new int[] {7, 9}) for (int z : new int[] {6, 8}) {
+                require(c.block(rotate(new BlockPos(x, 9, z), c.site.facing())).is(Blocks.GLASS),
+                    label(c) + " passenger skylight is open to the sky instead of glazed");
+                clearLightWell(c, x, z, 6, c.site.height());
+            }
+        }
+        if (c.site.kind() == HeritagePlan19.Kind.COMMUNAL_DEPOT) {
+            for (int x : new int[] {5, 11}) for (int z : new int[] {3, 7, 11}) {
+                require(c.block(rotate(new BlockPos(x, 12, z), c.site.facing())).is(Blocks.GLASS)
+                        && c.block(rotate(new BlockPos(x, 9, z), c.site.facing())).is(Blocks.GLASS),
+                    label(c) + " warehouse north-light well lost a sealed transparent face");
+                clearLightWell(c, x, z, 8, c.site.height());
+            }
+        }
+        if (c.site.kind() == HeritagePlan19.Kind.OBSERVATORY) {
+            // The inset crown must be joined through face-adjacent masonry to the tower roof.
+            // This detects a detached decorative ring even when every individual voxel is in bounds.
+            Set<BlockPos> connected = new HashSet<>(); var pending = new java.util.ArrayDeque<BlockPos>();
+            c.blocks.forEach((p, block) -> {
+                if (p.getY() == 12 && !block.isAir()) { connected.add(p); pending.add(p); }
+            });
+            while (!pending.isEmpty()) {
+                var p = pending.removeFirst();
+                for (Direction direction : Direction.values()) {
+                    var next = p.relative(direction);
+                    if (next.getX() < 0 || next.getX() > 16 || next.getZ() < 0 || next.getZ() > 16
+                            || next.getY() < 12 || next.getY() > 17 || c.block(next).isAir()) continue;
+                    if (connected.add(next)) pending.addLast(next);
+                }
+            }
+            c.blocks.forEach((p, block) -> {
+                if (p.getY() == 17 && block.is(Blocks.TUFF_BRICK_SLAB))
+                    require(connected.contains(p), label(c) + " observatory crown floats above its buttresses at " + p);
+            });
+            require(c.block(rotate(new BlockPos(8, 17, 8), c.site.facing())).isAir(),
+                label(c) + " crown connection closes the sky-viewing slot");
+        }
+    }
+    private static void clearLightWell(Capture c, int x, int z, int low, int high) {
+        for (int y = low; y <= high; y++) {
+            var p = rotate(new BlockPos(x, y, z), c.site.facing());
+            var block = c.block(p);
+            require(block.isAir() || block.is(Blocks.GLASS) || block.is(Blocks.GLASS_PANE),
+                label(c) + " skylight is blocked by an opaque roof or ceiling at " + p + ": " + block);
+        }
+    }
+    private static void export(Capture c) {
+        String directory = System.getProperty("sanctuary.test.heritage20.export");
+        if (directory == null || directory.isBlank()) return;
+        var blocks = c.blocks.entrySet().stream().filter(e -> !e.getValue().isAir())
+            .sorted(java.util.Comparator.<Map.Entry<BlockPos, BlockState>>comparingInt(e -> e.getKey().getY())
+                .thenComparingInt(e -> e.getKey().getZ()).thenComparingInt(e -> e.getKey().getX()))
+            .map(e -> List.of(e.getKey().getX(), e.getKey().getY(), e.getKey().getZ(), e.getValue().toString())).toList();
+        var targets = HeritageRenderer20.targets(c.site).stream().map(t -> List.of(t.name(), t.x(), t.y(), t.z())).toList();
+        var document = Map.of("kind", c.site.kind().name(), "facing", c.site.facing(), "seed", c.site.seed(),
+            "width", 17, "depth", 17, "height", c.site.height(), "floor_y", 0, "blocks", blocks, "targets", targets);
+        try {
+            var root = java.nio.file.Path.of(directory); java.nio.file.Files.createDirectories(root);
+            java.nio.file.Files.writeString(root.resolve(c.site.kind().name().toLowerCase(java.util.Locale.ROOT) + ".json"),
+                new com.google.gson.GsonBuilder().setPrettyPrinting().create().toJson(document));
+        } catch (java.io.IOException error) { throw new AssertionError("Cannot export the requested architecture capture", error); }
+    }
+    private static void materials20() {
+        Set<Block> used = new HashSet<>();
+        for (var kind : HeritagePlan19.Kind.values()) render(site(kind, 0, 0)).blocks.values().forEach(b -> used.add(b.getBlock()));
+        for (Block block : new Block[] {Blocks.TUFF, Blocks.TUFF_BRICKS, Blocks.CHISELED_TUFF, Blocks.CHISELED_TUFF_BRICKS,
+            Blocks.CHISELED_STONE_BRICKS, Blocks.TUFF_BRICK_STAIRS, Blocks.TUFF_BRICK_SLAB, Blocks.TUFF_BRICK_WALL,
+            Blocks.OAK_WOOD, Blocks.BIRCH_WOOD, Blocks.OAK_PLANKS, Blocks.BIRCH_PLANKS,
+            Blocks.GRANITE, Blocks.DIORITE, Blocks.ANDESITE, Blocks.BIRCH_TRAPDOOR})
+            require(used.contains(block), "The generation20 architectural vocabulary omits " + block);
+    }
+    private static void has(Capture c, Block b) { require(c.blocks.values().stream().anyMatch(v -> v.is(b)), label(c) + " loses its " + b); }
+    private static void railConnection(Capture c) {
+        BlockPos destination = switch (c.site.kind()) {
+            case FREIGHT_STATION -> new BlockPos(2, 1, 8);
+            case RAIL_WORKSHOP -> new BlockPos(5, 1, 7);
+            case COMMUNAL_DEPOT -> new BlockPos(8, 1, 7);
+            default -> null;
+        };
+        if (destination == null) return;
+        var start = rotate(new BlockPos(8, 1, 0), c.site.facing());
+        destination = rotate(destination, c.site.facing());
+        Set<BlockPos> seen = new HashSet<>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var p = queue.removeFirst(); var b = c.block(p);
+            require(b.is(Blocks.RAIL), label(c) + " freight entry has no supported rail");
+            for (var d : railEnds(b)) {
+                var next = p.relative(d); var state = c.block(next);
+                if (state.is(Blocks.RAIL) && railEnds(state).contains(d.getOpposite()) && seen.add(next)) queue.add(next);
+            }
+        }
+        require(seen.contains(destination), label(c) + " interior rail does not connect to its real external freight entry");
+    }
+    private static List<Direction> railEnds(BlockState b) {
+        return switch (b.getValue(BlockStateProperties.RAIL_SHAPE)) {
+            case NORTH_SOUTH, ASCENDING_NORTH, ASCENDING_SOUTH -> List.of(Direction.NORTH, Direction.SOUTH);
+            case EAST_WEST, ASCENDING_EAST, ASCENDING_WEST -> List.of(Direction.EAST, Direction.WEST);
+            case SOUTH_EAST -> List.of(Direction.SOUTH, Direction.EAST);
+            case SOUTH_WEST -> List.of(Direction.SOUTH, Direction.WEST);
+            case NORTH_WEST -> List.of(Direction.NORTH, Direction.WEST);
+            case NORTH_EAST -> List.of(Direction.NORTH, Direction.EAST);
+        };
+    }
+    private static void routes() {
+        var cells = new ArrayList<HeritagePlan19.Cell>();
+        int x = -15;
+        for (var rail : HeritagePlan19.Rail.values()) {
+            cells.add(new HeritagePlan19.Cell(x++, 160, 2, 2, rail, rail != HeritagePlan19.Rail.NONE));
+        }
+        cells.add(new HeritagePlan19.Cell(-1, 161, 2, 3, HeritagePlan19.Rail.ASCENDING_EAST, false));
+        var segment = new HeritagePlan19.Segment("route", "a", "b", HeritagePlan19.RouteKind.FREIGHT, -1, 0, cells, 7);
+        Map<BlockPos, BlockState> result = new HashMap<>();
+        HeritageRenderer20.renderSegment(segment, new LostCityRenderer.BlockWriter() {
+            @Override public void set(int x, int y, int z, BlockState b) {
+                var p = new BlockPos(segment.minX() + x, segment.minY() + y, segment.minZ() + z);
+                var cell = cells.stream().filter(c -> c.x() == p.getX() && c.z() == p.getZ()).findFirst().orElseThrow();
+                require(p.getY() >= cell.minY() && p.getY() <= cell.maxY(), "Route escaped its saved column mask"); result.put(p, b);
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { throw new AssertionError("A route generated treasure"); }
+        });
+        for (var c : cells) {
+            var p = new BlockPos(c.x(), c.floorY() + 1, c.z());
+            require(full(result.get(p.below()), p.below()), "Rail or missing-rail witness lost its ballast support");
+            if (c.railPresent()) require(result.get(p).is(Blocks.RAIL)
+                && result.get(p).getValue(BlockStateProperties.RAIL_SHAPE).name().equals(c.rail().name()), "Saved rail shape was replaced by a straight track");
+            else require(result.get(p).isAir(), "An intentional abandoned-track gap was repaired by rendering");
+        }
+    }
+    private static void chunkPartition() {
+        var s = site(HeritagePlan19.Kind.CONSTRUCTION_REFUGE, 3, 43); var expected = render(s); var parts = new Capture(s);
+        for (int cz = s.maxZ() >> 4; cz >= s.minZ() >> 4; cz--) for (int cx = s.maxX() >> 4; cx >= s.minX() >> 4; cx--) {
+            final int chunkX = cx, chunkZ = cz;
+            HeritageRenderer20.render(s, new LostCityRenderer.BlockWriter() {
+                boolean owns(int x, int z) { return ((s.minX() + x) >> 4) == chunkX && ((s.minZ() + z) >> 4) == chunkZ; }
+                @Override public void set(int x, int y, int z, BlockState state) { if (owns(x, z)) parts.set(x, y, z, state); }
+                @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { if (owns(x, z)) parts.chest(x, y, z, table, seed); }
+            });
+        }
+        require(parts.blocks.equals(expected.blocks) && parts.loot.equals(expected.loot), "Native chunk order changes a site");
+    }
+    private record Loot(ResourceKey<LootTable> table, long seed) {}
+    private static final class Capture implements LostCityRenderer.BlockWriter {
+        final HeritagePlan19.Site site;
+        final Map<BlockPos, BlockState> blocks = new HashMap<>();
+        final Map<BlockPos, Loot> loot = new HashMap<>();
+        Capture(HeritagePlan19.Site site) { this.site = site; }
+        @Override public void set(int x, int y, int z, BlockState state) {
+            int wy = y + site.floorY();
+            boolean main = x >= 0 && x <= 16 && z >= 0 && z <= 16 && wy >= site.minY() && wy <= site.maxY();
+            boolean footing = site.supports().stream().anyMatch(s -> s.x() == x + site.minX() && s.z() == z + site.minZ() && wy >= s.minY() && wy <= s.maxY());
+            require(main || footing, label(this) + " writes outside its exact body and footing mask"); blocks.put(new BlockPos(x, y, z), state);
+        }
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+            require(loot.put(new BlockPos(x, y, z), new Loot(table, seed)) == null, "Duplicate shared treasure"); set(x, y, z, Blocks.CHEST.defaultBlockState());
+        }
+        BlockState block(BlockPos p) { return blocks.getOrDefault(p, Blocks.AIR.defaultBlockState()); }
+    }
+    private static void require(boolean value, String message) { if (!value) throw new AssertionError(message); }
+}
@@ -0,0 +1,219 @@
+package fr.koka.sanctuary.worldgen.ruins;
+
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import java.util.ArrayDeque;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.RailBlock;
+import net.minecraft.world.level.block.StairBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Exercises the final native block states, saved bounds and meaningful circulation of all prototypes. */
+public final class RuinsRenderer20Smoke {
+    private RuinsRenderer20Smoke() {}
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion(); Bootstrap.bootStrap(); run();
+        System.out.println("RuinsRenderer20Smoke passed: ten physical room types, saved seed variation, dry connected openings, usable work platform, native fixture supports, deferred loot and chunk-order reconstruction");
+    }
+    public static void run() {
+        Set<Map<BlockPos, BlockState>> kinds = new HashSet<>();
+        for (var kind : RuinsPlan17.Kind.values()) {
+            for (int size = 0; size < 3; size++) for (int openings : new int[] {1, 2, 4, 8, 5, 10, 15})
+                for (long seed : new long[] {0, 1}) {
+                    var room = room(kind, size, openings, seed);
+                    var c = render(room); var repeated = render(room);
+                    require(c.blocks.equals(repeated.blocks) && c.loot.equals(repeated.loot), label(room) + " is not deterministic");
+                    if (size == 0 && openings == 15 && seed == 0) kinds.add(c.blocks);
+                    var start = RuinsRenderer20.targets(room).getFirst();
+                    Set<BlockPos> reached = walk(c, position(start));
+                    for (var target : RuinsRenderer20.targets(room)) require(reached.contains(position(target)),
+                        label(room) + " cannot reach " + target.name() + " at " + position(target));
+                    openings(c, reached);
+                    supports(c);
+                    fixtures(c, reached);
+                    identity(c);
+                    for (var chest : c.loot.keySet()) require(approachable(chest, reached), label(room) + " chest is inaccessible at " + chest);
+                    require(c.blocks.values().stream().noneMatch(b -> b.is(Blocks.SPAWNER) || !b.getFluidState().isEmpty()),
+                        label(room) + " introduced a spawner or uncontrolled fluid");
+                }
+            var a = render(room(kind, 1, 15, 0)); var b = render(room(kind, 1, 15, 1));
+            require(!a.blocks.equals(b.blocks), kind + " ignores its saved variation seed");
+            if (kind != RuinsPlan17.Kind.ACCESS && kind != RuinsPlan17.Kind.CORRIDOR)
+                require(!furniture(a).equals(furniture(b)), kind + " varies only stone weathering, not physical use or furniture placement");
+        }
+        require(kinds.size() == RuinsPlan17.Kind.values().length, "Room names disguise identical rendered interiors");
+        nativeChunkPartition();
+    }
+
+    private static RuinsPlan17.Room room(RuinsPlan17.Kind kind, int size, int openings, long seed) {
+        int width = size == 0 ? 9 : size == 1 ? 13 : 17;
+        int depth = size < 2 ? 9 : 13, height = size < 2 ? 7 : 9;
+        if (kind == RuinsPlan17.Kind.ACCESS) { width = depth = 5; height = new int[] {14, 27, 40}[size]; }
+        if (kind == RuinsPlan17.Kind.CORRIDOR) { width = size == 2 ? 17 : 5; depth = size == 1 ? 13 : 5; height = 6; }
+        int x = -43, y = 150, z = 59;
+        return new RuinsPlan17.Room(kind, x, y, z, width, height, depth, openings, seed,
+            List.of(new RuinsPlan17.Support(x, y - 5, z, y - 1),
+                new RuinsPlan17.Support(x + width - 1, y - 12, z + depth - 1, y - 1)));
+    }
+    private static String label(RuinsPlan17.Room r) {
+        return r.kind() + " " + r.width() + "x" + r.height() + "x" + r.depth() + " openings=" + r.openings() + " seed=" + r.seed();
+    }
+    private static BlockPos position(RuinsRenderer20.Target target) { return new BlockPos(target.x(), target.y(), target.z()); }
+    private static Capture render(RuinsPlan17.Room room) {
+        var result = new Capture(room); RuinsRenderer20.render(room, result); return result;
+    }
+    private static void openings(Capture c, Set<BlockPos> reached) {
+        var r = c.room;
+        for (int direction = 0; direction < 4; direction++) for (int side = -1; side <= 1; side++) {
+            int x = direction == 1 ? r.width() - 1 : direction == 3 ? 0 : r.width() / 2 + side;
+            int z = direction == 2 ? r.depth() - 1 : direction == 0 ? 0 : r.depth() / 2 + side;
+            var threshold = new BlockPos(x, 1, z);
+            require(solid(c.block(threshold)), label(r) + " has no dry threshold at " + threshold);
+            if ((r.openings() & 1 << direction) == 0) {
+                require(!c.block(threshold.above()).isAir(), label(r) + " opens an unconnected wall");
+                continue;
+            }
+            for (int y = 2; y <= 4; y++) require(c.block(new BlockPos(x, y, z)).isAir(),
+                label(r) + " obstructs its three-wide opening at " + x + "/" + z);
+            require(reached.contains(threshold.above()), label(r) + " opening edge is not connected to the room");
+        }
+    }
+    private static void supports(Capture c) {
+        var r = c.room;
+        for (var support : r.supports()) {
+            for (int y = support.minY(); y <= support.maxY(); y++) require(solid(c.block(new BlockPos(
+                support.x() - r.minX(), y - r.minY(), support.z() - r.minZ()))), label(r) + " interrupts its saved footing");
+            require(solid(c.block(new BlockPos(support.x() - r.minX(), 0, support.z() - r.minZ()))),
+                label(r) + " footing does not meet the structural floor");
+        }
+        for (int x = 0; x < r.width(); x++) for (int z = 0; z < r.depth(); z++)
+            require(solid(c.block(new BlockPos(x, 0, z))), label(r) + " has a perforated structural floor");
+    }
+    private static void fixtures(Capture c, Set<BlockPos> reached) {
+        for (var entry : c.blocks.entrySet()) {
+            var p = entry.getKey(); var block = entry.getValue();
+            if (block.is(Blocks.LANTERN)) {
+                require(block.getValue(BlockStateProperties.HANGING), "Lantern must hang from the ceiling");
+                require(solid(c.block(p.above())), label(c.room) + " floating lantern at " + p);
+            }
+            if (block.is(Blocks.LADDER)) {
+                Direction facing = block.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                require(solid(c.block(p.relative(facing.getOpposite()))), label(c.room) + " ladder lacks a back wall at " + p);
+            }
+            if (block.is(Blocks.LEVER) || block.is(Blocks.GRINDSTONE)) require(solid(c.block(p.below())),
+                label(c.room) + " unsupported usable fixture at " + p);
+            if (block.is(Blocks.DARK_OAK_STAIRS)) {
+                Direction back = block.getValue(BlockStateProperties.HORIZONTAL_FACING);
+                require(solid(c.block(p.below())), label(c.room) + " seat has no floor");
+                require(reached.contains(p.relative(back.getOpposite())), label(c.room) + " seat faces an obstruction at " + p);
+            }
+            if (block.is(Blocks.CRAFTING_TABLE) || block.is(Blocks.FURNACE) || block.is(Blocks.GRINDSTONE)
+                    || block.is(Blocks.STONECUTTER) || block.is(Blocks.CARTOGRAPHY_TABLE) || block.is(Blocks.LECTERN))
+                require(approachable(p, reached), label(c.room) + " useful furniture cannot be approached at " + p);
+        }
+    }
+    private static void identity(Capture c) {
+        int expectedLoot = c.room.kind() == RuinsPlan17.Kind.STORE || c.room.kind() == RuinsPlan17.Kind.ARCHIVE ? 1 : 0;
+        require(c.loot.size() == expectedLoot, label(c.room) + " has unbounded or missing deferred loot");
+        switch (c.room.kind()) {
+            case ACCESS -> { has(c, Blocks.LADDER); has(c, Blocks.DARK_OAK_TRAPDOOR); }
+            case CORRIDOR -> has(c, Blocks.TUFF_BRICKS);
+            case MINE_GALLERY -> { has(c, Blocks.RAIL); has(c, Blocks.STRIPPED_OAK_LOG); has(c, Blocks.BARREL); }
+            case WORKSHOP -> { has(c, Blocks.CRAFTING_TABLE); has(c, Blocks.FURNACE); has(c, Blocks.GRINDSTONE); has(c, Blocks.STONECUTTER); has(c, Blocks.ANVIL); has(c, Blocks.LADDER); }
+            case STORE -> { has(c, Blocks.BARREL); has(c, Blocks.DARK_OAK_SLAB); }
+            case TILED_HALL -> { has(c, Blocks.CALCITE); has(c, Blocks.POLISHED_DIORITE); has(c, Blocks.DARK_OAK_STAIRS); }
+            case ARCHIVE -> { has(c, Blocks.BOOKSHELF); has(c, Blocks.LECTERN); has(c, Blocks.CARTOGRAPHY_TABLE); }
+            case SERVICE_HALL -> { has(c, Blocks.IRON_BARS); has(c, Blocks.CRAFTING_TABLE); }
+            case PUMP_HALL -> { has(c, Blocks.WATER_CAULDRON); has(c, Blocks.DISPENSER); has(c, Blocks.LEVER); }
+            case CONTROL_ROOM -> { has(c, Blocks.LEVER); has(c, Blocks.REDSTONE_LAMP); has(c, Blocks.CARTOGRAPHY_TABLE); }
+        }
+    }
+    private static void has(Capture c, Block block) {
+        require(c.blocks.values().stream().anyMatch(b -> b.is(block)), label(c.room) + " lost its recognizable " + block);
+    }
+    private static Map<BlockPos, BlockState> furniture(Capture c) {
+        var result = new HashMap<BlockPos, BlockState>();
+        c.blocks.forEach((p, b) -> {
+            if (p.getY() >= 2 && p.getY() < c.room.height() - 2 && !b.isAir()
+                    && !b.is(Blocks.STONE_BRICKS) && !b.is(Blocks.CRACKED_STONE_BRICKS)
+                    && !b.is(Blocks.MOSSY_STONE_BRICKS) && !b.is(Blocks.SMOOTH_STONE)) result.put(p, b);
+        });
+        return result;
+    }
+    private static boolean approachable(BlockPos p, Set<BlockPos> reached) {
+        for (Direction d : Direction.Plane.HORIZONTAL) if (reached.contains(p.relative(d))) return true;
+        return false;
+    }
+    private static Set<BlockPos> walk(Capture c, BlockPos start) {
+        require(stand(c, start), label(c.room) + " starts without two-block standing space at " + start);
+        var seen = new HashSet<BlockPos>(); var queue = new ArrayDeque<BlockPos>(); seen.add(start); queue.add(start);
+        while (!queue.isEmpty()) {
+            var p = queue.removeFirst();
+            for (Direction direction : Direction.Plane.HORIZONTAL) for (int dy : new int[] {0, 1, -1}) {
+                var q = p.relative(direction).offset(0, dy, 0);
+                if (stand(c, q) && seen.add(q)) queue.add(q);
+            }
+            for (int dy : new int[] {-1, 1}) {
+                var q = p.offset(0, dy, 0);
+                if ((climb(c.block(p)) || climb(c.block(q)) || climb(c.block(p.below())))
+                        && stand(c, q) && seen.add(q)) queue.add(q);
+            }
+        }
+        return seen;
+    }
+    private static boolean stand(Capture c, BlockPos p) {
+        if (p.getX() < 0 || p.getX() >= c.room.width() || p.getZ() < 0 || p.getZ() >= c.room.depth()
+                || p.getY() < 2 || p.getY() >= c.room.height() - 1) return false;
+        return passable(c.block(p)) && passable(c.block(p.above()))
+            && (solid(c.block(p.below())) || c.block(p.below()).getBlock() instanceof StairBlock
+                || climb(c.block(p)) || climb(c.block(p.below())));
+    }
+    private static boolean climb(BlockState b) { return b.is(Blocks.LADDER) || b.is(Blocks.DARK_OAK_TRAPDOOR); }
+    private static boolean passable(BlockState b) { return b.isAir() || climb(b) || b.getBlock() instanceof RailBlock || b.is(Blocks.LEVER); }
+    private static boolean solid(BlockState b) { return b.canOcclude() && b.getFluidState().isEmpty(); }
+
+    private static void nativeChunkPartition() {
+        var r = room(RuinsPlan17.Kind.WORKSHOP, 2, 15, 1); var all = render(r); var chunks = new Capture(r);
+        for (int cz = r.maxZ() >> 4; cz >= r.minZ() >> 4; cz--) for (int cx = r.maxX() >> 4; cx >= r.minX() >> 4; cx--) {
+            final int chunkX = cx, chunkZ = cz;
+            RuinsRenderer20.render(r, new LostCityRenderer.BlockWriter() {
+                private boolean belongs(int x, int z) { return ((r.minX() + x) >> 4) == chunkX && ((r.minZ() + z) >> 4) == chunkZ; }
+                @Override public void set(int x, int y, int z, BlockState state) { if (belongs(x, z)) chunks.set(x, y, z, state); }
+                @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) { if (belongs(x, z)) chunks.chest(x, y, z, table, seed); }
+            });
+        }
+        require(chunks.blocks.equals(all.blocks) && chunks.loot.equals(all.loot), "Chunk order changes saved room rendering");
+    }
+    private record Loot(ResourceKey<LootTable> table, long seed) {}
+    private static final class Capture implements LostCityRenderer.BlockWriter {
+        final RuinsPlan17.Room room;
+        final Map<BlockPos, BlockState> blocks = new HashMap<>();
+        final Map<BlockPos, Loot> loot = new HashMap<>();
+        Capture(RuinsPlan17.Room room) { this.room = room; }
+        @Override public void set(int x, int y, int z, BlockState state) {
+            int wx = room.minX() + x, wy = room.minY() + y, wz = room.minZ() + z;
+            require(room.contains(wx, wy, wz), label(room) + " wrote outside its saved exact body/support mask: " + x + "/" + y + "/" + z);
+            require(wy >= room.boundsMinY() && wy <= room.boundsMaxY(), "Write escapes native vertical bounds");
+            blocks.put(new BlockPos(x, y, z), state);
+        }
+        @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+            var pos = new BlockPos(x, y, z);
+            require(loot.put(pos, new Loot(table, seed)) == null, "Duplicate deferred chest");
+            set(x, y, z, Blocks.CHEST.defaultBlockState());
+        }
+        BlockState block(BlockPos p) { return blocks.getOrDefault(p, Blocks.AIR.defaultBlockState()); }
+    }
+    private static void require(boolean test, String message) { if (!test) throw new AssertionError(message); }
+}
@@ -1,6 +1,6 @@
 name = "Sanctuary"
 author = "KOKA99CAB"
-version = "0.1.0-alpha.17"
+version = "0.1.0-alpha.20"
 pack-format = "packwiz:1.1.0"

 [index]
Author	SHA1	Message	Date
koka	ae4c6200db	docs: record verified alpha20 release and Prism update Build Sanctuary / build (push) Canceled after 0s Details	2026-09-10 01:21:33 +02:00
koka	0edac29dd8	feat: add detailed architecture for Sanctuary alpha20 Build Sanctuary / build (push) Canceled after 0s Details	2026-09-10 01:18:31 +02:00
koka	2facf6f722	docs: record verified alpha19 release and Prism update Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 22:49:20 +02:00
koka	c23e72b8e6	feat(worldgen): add reversible alpha19 heritage structures and routes Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 22:42:32 +02:00
koka	f2da922bad	Document structure ideas and abandoned island routes Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 20:03:42 +02:00