Add alpha.14 Lost City and nearby certified expansions

Record alpha.13.1 release and existing Prism update
Fix Windows expansion journal persistence in alpha.13.1
2026-09-09 14:00:20 +02:00 · 2026-09-09 12:40:27 +02:00 · 2026-09-09 12:37:36 +02:00 · 2026-09-09 11:15:51 +02:00 · 2026-09-09 11:13:24 +02:00 · 2026-09-09 08:57:40 +02:00
91 changed files with 9374 additions and 294 deletions
@@ -1,6 +1,75 @@
 # Changelog

-## 0.1.0-alpha.12.1 — 2026-09-09, correctif local
+## 0.1.0-alpha.14 — en préparation
+
+- Biome Lost City et quartiers procéduraux contemporains : poches sur l’île
+  initiale et profil `lost_city` pour les nouvelles expansions. Dix-sept types
+  de parcelles, dont quatre parcs, ponts, parkings souterrains conditionnels,
+  fouilles, piscines, casernes, halls, hôtels, bibliothèques et cuisines.
+- Palette dominée par la pierre, la pierre lisse et les briques de pierre,
+  intérieurs accessibles, ruines déterministes et coffres à butin vanilla
+  différé. Zombies vanilla par spawn naturel ; aucun spawner ni zombie spécial.
+- Nouveau codec public `sanctuary:island_v14` et journal propre de génération
+  14. Les générations 12/13 restent chargeables sans conversion. Les nouveautés
+  demandent un nouveau monde ; aucune sauvegarde personnelle n’est modifiée.
+- Expansions 64/128/256/512/1 024 ; `quick` sans taille tire selon les poids
+  40/30/18/9/3, avec résultat stable pour la graine et l’identifiant réservés.
+  Recherche proche dans le secteur demandé, séparation circulaire des emprises
+  de terrain et de décoration, sans réserver tout le voisinage de lecture.
+- Contrat de reprise différée du vide : uniquement les chunks FULL prouvés
+  vierges et vides d’un nouveau monde 14, certificat lié à un jeton immuable du
+  journal, puis réouverture et nouvelle vérification. Une présence de terrain,
+  d’entité, de POI, de ticks ou une preuve manquante arrête cette reprise.
+
+`check build assemblePack`, les huit tests moteur, la création et la réouverture
+de Lost City passent. La reprise du vide conserve 154 chunks FULL éclairés
+correctement et un bloc témoin après réouvertures. JAR, MRpack et amorçage Prism
+vérifiés ; publication et synchronisations encore à attester. Voir les
+[preuves et limites alpha.14](docs/testing-alpha14.md).
+
+## 0.1.0-alpha.13.1 — 2026-09-09
+
+- Corrige l’arrêt des expansions sous Windows : le journal ne tente plus
+  d’ouvrir son dossier comme un fichier pour le synchroniser. Cette opération
+  reste exigée sur les systèmes de fichiers utilisant le séparateur Unix.
+- Écriture du fichier synchronisée, remplacement atomique et relecture stricte
+  conservés. Les véritables erreurs de stockage arrêtent toujours les expansions.
+- Après mise à jour et réouverture du même monde, une réservation valide déjà
+  enregistrée avant l’erreur est reprise automatiquement. Aucun changement de
+  schéma du journal, de génération, de paramètres ou de chunks existants.
+
+Le smoke du journal passe sur macOS, avec politique Windows simulée, erreurs
+après remplacement et récupération au rechargement. Aucun essai Windows natif
+n’a encore été réalisé. Voir le [dépannage](docs/alpha13-worldgen.md#correctif-alpha131--expansions-sous-windows)
+et les [contrôles ciblés](docs/testing.md#correctif-alpha131--journal-dexpansion-sous-windows).
+
+## 0.1.0-alpha.13 — 2026-09-09
+
+- Un seul choix public **Sanctuary**, avec le bouton natif **Personnaliser** :
+  Petit (512 blocs), Moyen (724, par défaut), Grand (1 024). Le diamètre est
+  enregistré dans le générateur ; confirmer ou annuler agit sur le monde à créer.
+- Île initiale issue de la densité et de l’hydrologie complète de Population,
+  avec sa forêt de surface et les poches de biomes souterrains natives du
+  laboratoire. Les eaux et les ressources restent dépendantes du terrain.
+- Reprise des outils d’expansion alpha.12.1 dans ce même monde : parent,
+  direction, climat, taille, relief, distance facultative et recherche de sites
+  libres, sans remplacer les chunks existants. Le déblocage collectif reste futur.
+- Nouveau codec `sanctuary:island_v13`, racine de génération 13 et journal
+  `data/sanctuary-world-v13/expansions.json`. Les extensions restent de génération
+  12. Anciens codecs et presets conservés mais cachés de la création ; aucun
+  monde existant converti, agrandi ou régénéré.
+- La suite GameTest unifiée devient le défaut de `check` et `runGameTest` ; les
+  essais historiques demandent `-PsanctuaryUnifiedTests=false`.
+
+`check build assemblePack`, interface client, trois tailles et rechargement des
+expansions vérifiés. Moyen : 63,66 s pour créer puis charger 289 chunks FULL
+autour du spawn sur la graine 0, 7,82 s pour les 80 suivants ; mesure serveur,
+sans garantie de FPS ni charge multijoueur. Release, MRpack et canal packwiz
+publiés ; même instance Prism synchronisée deux fois, avec 601 fichiers
+personnels et réglages suivis conservés.
+Voir le [guide alpha.13](docs/alpha13-worldgen.md) et les [preuves](docs/testing.md).
+
+## 0.1.0-alpha.12.1 — 2026-09-09 (historique)

 - Corrige le blocage de toutes les directions lorsque du vide a déjà été
  généré : la recherche continue plus loin sur le même rayon, sans remplacer
@@ -15,9 +84,11 @@

 Les contrôles moteur de création et de rechargement passent sur la graine 42,
 avec huit premiers sites occupés et distance explicite. `check build assemblePack`
-passe, avec les douze tests historiques. Publication à consigner. Voir [WG-14](docs/backlog.md).
+passe, avec les douze tests historiques. Release, MRpack et canal publiés ;
+la même instance Prism est synchronisée deux fois et ses 466 fichiers personnels
+et réglages suivis sont conservés. Voir [WG-14](docs/backlog.md).

-## 0.1.0-alpha.12 — 2026-09-09
+## 0.1.0-alpha.12 — 2026-09-09 (historique)

 - Nouveau preset Sanctuary — Laboratoire, distinct de Petit/Grand. Outils
  opérateur `quick`, `create`, `preview`, `list`, `visit`, `resume` pour tester
@@ -15,8 +15,105 @@ 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) prépare les premiers
 tickets. Les systèmes d’économie, de progression collective et les dimensions
-décrits dans la vision ne sont pas encore implémentés. L’alpha.12 fournit des
-outils d’expansion réservés à un nouveau monde de laboratoire.
+décrits dans la vision ne sont pas encore implémentés. **L’alpha.14 est validée,
+sa publication est en préparation** : Lost City ajoute des quartiers en ruine au monde flottant.
+Le dernier correctif publié reste l’alpha.13.1 tant que la nouvelle livraison
+n’est pas consignée dans [Distribution](docs/packwiz.md).
+
+## Alpha.14 — Lost City, en préparation
+
+Lost City est un biome de quartiers contemporains abandonnés, composé par du
+code Sanctuary original. Des poches urbaines peuvent apparaître sur l’île de
+départ ; le profil d’expansion `lost_city` permet d’en rechercher dans les
+nouveaux continents. Le relief et ses fondations décident des emplacements :
+un quartier ou un type de bâtiment n’est pas garanti sur chaque île.
+
+Les 17 types comprennent rues, ponts, quatre parcs (boisé, jardin, aire de jeux,
+mémorial), places, marchés, parkings, excavations, piscines abandonnées,
+immeubles d’appartements, hôtels, bibliothèques, restaurants avec cuisine,
+casernes et halls. **Pierre, pierre lisse et briques de pierre** forment la
+palette principale, avec des variantes fissurées ou moussues, du verre et
+quelques détails de fer et de chêne noir. Les étages disposent d’escaliers et
+les pièces d’aménagements propres à leur usage.
+
+Les parkings souterrains, fouilles et piscines demandent une épaisseur de roche
+vérifiée sur toute leur emprise. Les piscines ont un fond, des parois continues
+et des marches ; les ponts enjambent de courtes failles entre deux berges
+supportées. Les monstres naturels du biome sont des zombies vanilla, soumis
+aux règles de lumière et de difficulté du jeu. Aucun spawner ou zombie spécial
+n’est ajouté ; les variantes de zombies et la progression restent pour la bêta.
+
+Créer un **nouveau monde Sanctuary** pour la génération 14. Le bouton natif
+**Personnaliser** conserve Petit 512, Moyen 724 par défaut et Grand 1 024.
+Les mondes 12/13 gardent leurs codecs, journaux, paramètres et chunks.
+
+Dans un nouveau monde de génération 14, les outils opérateur acceptent des
+expansions de 64, 128, 256, 512 ou 1 024 blocs. `quick` sans taille effectue un
+tirage reproductible favorisant les petites îles. Les emplacements suivent des
+secteurs directionnels autour du parent, avec séparation des emprises écrites.
+La reprise éventuelle de chunks de vide déjà explorés exige un certificat
+strict lié au journal et une réouverture du monde ; aucun terrain occupé n’est
+admis dans ce mécanisme.
+
+Le [contrat et protocole alpha.14](docs/testing-alpha14.md) précisent les
+commandes, la protection des sauvegardes et les vérifications réussies :
+`check build assemblePack`, création et réouverture des quartiers, reprise du
+vide certifié et validation des artefacts de distribution.
+La publication et la synchronisation Prism ne sont pas encore attestées.
+
+## Alpha.13.1 — correctif des expansions sous Windows
+
+Le journal d’expansion n’essaie plus d’ouvrir son dossier comme un fichier sous
+Windows, ce qui provoquait `AccessDeniedException` et bloquait les expansions.
+La synchronisation du fichier, son remplacement atomique et sa relecture restent
+obligatoires. Le format du journal et la génération alpha.13 restent identiques.
+
+Après installation du correctif, **rouvrir le même monde** : une réservation déjà
+enregistrée est reprise après vérification du journal. Il ne faut pas supprimer
+`sanctuary-world-v13` ni recréer le monde pour ce correctif. Voir le
+[dépannage Windows](docs/alpha13-worldgen.md) et la [validation](docs/testing.md).
+
+La [release alpha.13.1](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.13.1)
+et le canal packwiz sont publiés. Deux synchronisations isolées et deux
+synchronisations de l’instance Mac existante passent ; les 713 fichiers personnels
+et réglages suivis restent identiques. Aucun accès à l’instance Windows n’a eu lieu.
+
+## Alpha.13 — un seul monde Sanctuary
+
+À la création d’un **nouveau monde**, sélectionner **Sanctuary**, puis utiliser
+le bouton natif **Personnaliser** pour choisir la taille de l’île :
+
+| Taille | Diamètre nominal |
+| --- | --- |
+| Petit | 512 blocs |
+| Moyen, par défaut | 724 blocs |
+| Grand | 1 024 blocs |
+
+**Terminé** conserve le choix ; **Annuler** revient sans l’appliquer. La hauteur
+reste de 384 blocs. Ces tailles décrivent une emprise, sans promettre un nombre
+de joueurs, une aire constructible ou un stock de minerais.
+
+L’île reprend les forêts, le relief flottant et les plans d’eau complets du
+générateur précédent : bassins, rivière, terrasses et cascades restent liés
+aux possibilités naturelles du terrain. Les poches de cavités natives de Minecraft
+du laboratoire rejoignent cette île. Les commandes opérateur
+d’expansion, avec leur distance facultative et leur recherche d’emplacements
+libres, sont accessibles dans ce même nouveau monde. Les déblocages par la
+production et l’XP restent à construire.
+
+Les anciens choix Petit/Grand et Laboratoire sont cachés à la création, tout
+en restant chargeables avec leurs paramètres enregistrés. **Aucun monde
+existant n’est converti ni régénéré.** Le [guide alpha.13](docs/alpha13-worldgen.md)
+détaille la création, les expansions et la séparation des sauvegardes.
+
+`check build assemblePack`, les tests client, les trois tailles et les scénarios
+d’expansion/rechargement passent. Moyen atteint 63,66 secondes pour la création
+puis 289 chunks FULL dans le test serveur de référence. Les preuves et leurs
+limites sont dans [Validation](docs/testing.md).
+
+À la livraison alpha.13, le canal packwiz, le MRpack et la même instance Prism
+avaient été mis à jour, avec les 601 fichiers personnels et réglages alors suivis conservés.
+Voir [Distribution](docs/packwiz.md).

 ## Socle livré jusqu’à l’alpha.8

@@ -63,7 +160,7 @@ sur les trois graines de référence, avec 1 800 ticks de fluides. Ces résultat
 ne valident pas par avance l’incrément suivant. Les observations et leurs
 limites figurent dans [Validation](docs/testing.md).

-## Alpha.9 : cavités vivantes et terrasses d’eau
+## Alpha.9, historique : cavités vivantes et terrasses d’eau

 L’incrément ajoute des cavités luxuriantes et lumineuses sous l’île, des
 secteurs à spéléothèmes, des géodes d’améthyste et des poches de soufre moins
@@ -129,7 +226,7 @@ en jeu reste à construire. Voir [Expansion et ressources](docs/expansion.md).
 Les détails du terrain et de ses limites sont dans [Génération](docs/worldgen.md),
 et la provenance dans [Audit 26.2](docs/migration-26.2.md).

-## Alpha.11 : Petit, Grand et génération plus rapide
+## Alpha.11, historique : Petit, Grand et génération plus rapide

 Les anciens formats sont trop grands et éloignent les constructions. Le
 nouveau choix de départ se limite à **Petit** et **Grand**, avec **Grand par
@@ -160,7 +257,7 @@ de la même instance sont consignées dans [Distribution](docs/packwiz.md).
 L’alpha.11 est publiée ; la même instance Prism a été synchronisée deux fois,
 avec les 364 fichiers personnels et réglages suivis conservés.

-## Alpha.12 — laboratoire d’expansion
+## Alpha.12, historique — laboratoire d’expansion

 Un troisième preset **Sanctuary — Laboratoire** permet de tester les expansions
 dans un **nouveau monde**, sur la même version Minecraft. Les choix Petit et
@@ -199,7 +296,7 @@ passent. L’alpha.12, son MRpack et le canal packwiz sont publiés ; la même
 instance Prism a été synchronisée deux fois, avec les 466 fichiers personnels
 et réglages suivis conservés. Voir [Distribution](docs/packwiz.md).

-## Alpha.12.1 — distance et emplacements libres
+## Alpha.12.1, historique — distance et emplacements libres

 Le correctif ajoute une distance minimale facultative à la fin des commandes :

@@ -215,7 +312,8 @@ ni réécrire les chunks. Les mondes laboratoire alpha.12 peuvent être conserv
 le journal et la génération restent compatibles. Voir le [guide](docs/alpha12-laboratory.md).

 `check build assemblePack`, les scénarios moteur et les tests de distance passent.
-Publication de l’alpha.12.1 en cours.
+L’alpha.12.1 et son MRpack sont publiés ; la même instance Prism est synchronisée
+deux fois, avec 466 fichiers personnels et réglages suivis conservés.

 ## Versions et prérequis

@@ -231,7 +329,7 @@ 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.12.1, vérifiée localement |
+| Sanctuary / pack | 0.1.0-alpha.14, validation et livraison en cours |

 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
@@ -252,13 +350,15 @@ cd sanctuary-beta
 ```

 `check` inclut les tests de forme et le serveur de test automatisé de Fabric,
-qui charge le vrai preset Sanctuary dans un monde de développement neuf.
+qui charge par défaut le nouveau générateur unifié Sanctuary dans un monde
+de développement neuf. Les suites historiques utilisent explicitement
+`-PsanctuaryUnifiedTests=false`.
 Les scénarios couverts et les essais multijoueurs restant à effectuer sont
 décrits dans [Validation](docs/testing.md).

 Résultats :

- `mods/sanctuary/build/libs/sanctuary-0.1.0-alpha.12.1.jar` : mod à installer avec
+- `mods/sanctuary/build/libs/sanctuary-0.1.0-alpha.14.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).
@@ -276,7 +376,8 @@ Lancer le client de développement :
 ./gradlew :sanctuary:runClient
 ```

-Créer un **nouveau monde**, puis sélectionner le type de monde **Sanctuary**.
+Créer un **nouveau monde**, sélectionner le type **Sanctuary**, puis
+**Personnaliser** pour changer la taille Moyen retenue par défaut.
 L'installation du mod seule ne transforme pas un monde Minecraft ordinaire.

 Pour un serveur de développement, lancer `./gradlew :sanctuary:runServer`, puis
@@ -0,0 +1,212 @@
+# Alpha.13 — un monde Sanctuary unifié
+
+**Publiée et synchronisée dans la même instance Prism.** Cette version réunit l’île de départ complète et les outils
+d’expansion du laboratoire.
+[Validation](testing.md) décrit les preuves disponibles et
+[Distribution](packwiz.md) indique la version effectivement publiée.
+
+La cible reste **Minecraft 26.3-pre-2 / Fabric**. Ce guide concerne un nouveau
+monde alpha.13. Les anciens mondes conservent leur génération.
+
+## Créer son monde
+
+1. Créer un **nouveau monde**, puis sélectionner le type **Sanctuary**.
+2. Ouvrir le bouton natif **Personnaliser**.
+3. Choisir la taille, puis cliquer sur **Terminé** avant de créer le monde.
+
+| Taille | Diamètre nominal de l’île initiale |
+| --- | --- |
+| Petit | 512 blocs |
+| Moyen, choix par défaut | 724 blocs |
+| Grand | 1 024 blocs |
+
+**Annuler** revient sans appliquer le changement. La hauteur reste de 384 blocs,
+de `Y=0` à `Y=383`. Le diamètre est une référence pour la forme : trous, surplombs,
+fragments et contour irrégulier dépendent de la graine. Il ne mesure pas une
+surface entièrement constructible et ne fixe pas un nombre de joueurs.
+
+La liste des types de monde contient un seul choix Sanctuary ; les types
+Minecraft habituels restent disponibles. Petit, Moyen et Grand sont des
+réglages de ce même choix. L’ancien Grand alpha.11, de 724 blocs, correspond
+au diamètre nominal du nouveau Moyen.
+
+Sur un serveur neuf, le preset suivant crée un monde de taille Moyen :
+
+```properties
+level-type=sanctuary:sanctuary
+level-name=sanctuary-dev
+level-seed=42
+```
+
+Choisir un dossier de monde neuf pour un essai. Le bouton **Personnaliser**
+configure la création en solo ; il ne modifie pas les fichiers d’un serveur
+existant. Installer le mod ou changer `level-type` ne transforme pas une partie.
+
+## L’île de départ
+
+Le nouveau monde reprend le générateur complet de l’île initiale : forêts de
+chênes et de bouleaux, clairières, affleurements, strates rocheuses et corniches
+intérieures. Son relief flottant conserve les trous et les surplombs, sans
+ajouter de noyau cylindrique pour garantir un terrain à l’origine.
+
+Les plans hydrologiques de Population sont repris : étangs et lacs, recherche
+de rivière, bassins étagés et leurs débordements, sources et cascades, poche et
+coulées de lave. Le placement dépend des supports réellement présents dans la
+roche. Un plan qui ne trouve pas de site admissible reste absent ; aucune
+rivière, terrasse ou ressource n’est garantie sur chaque graine. Les eaux en
+terrasses permettent la nage verticale sans ajouter de culture de riz.
+
+Les poches souterraines natives du laboratoire rejoignent cette île : cavités
+luxuriantes, à spéléothèmes ou soufrées, avec leurs décorations Minecraft.
+Il s’agit toujours des profondeurs de l’Overworld, pas de la dimension des
+cavernes prévue dans la vision. L’île garde sa palette tempérée en surface ;
+Dappled Forest reste disponible dans les expansions au climat automnal.
+
+L’intégration protège les volumes déclarés par les plans d’eau et de lave
+contre les écritures de décoration suivantes. Cette protection concerne les
+plans de génération, sans mettre les blocs à l’abri des actions des joueurs.
+Les preuves moteur et leurs limites sont suivies dans [Validation](testing.md).
+
+## Ajouter une île
+
+Les commandes demandent les commandes autorisées en solo ou la permission
+opérateur sur le serveur. Elles reprennent les outils alpha.12.1 dans le nouveau
+monde Sanctuary. L’économie, les recherches et les contributions collectives
+ne conditionnent pas encore leur utilisation.
+
+```text
+/sanctuary expansion quick north autumn 128 peaks
+/sanctuary expansion list
+/sanctuary expansion visit island_1
+/sanctuary expansion create oasis island_1 east arid 64 natural 2048
+```
+
+`quick` ouvre une île depuis Sanctuary et lui attribue un identifiant `island_N`.
+L’exemple de visite suppose qu’il s’agit de la première réservation ; `list`
+indique l’identifiant et l’état réels. La visite attend que l’île soit prête.
+`create` choisit un nom et un parent déjà prêt pour prolonger une branche.
+La création ne téléporte personne implicitement.
+
+Les nouveaux continents choisissent leur propre direction, climat, diamètre
+**64/128/256/512** et relief **natural/peaks/canyon/volcano**. La direction ne
+contraint pas le climat. L’autocomplétion fournit les huit directions et les
+douze profils : `temperate`, `boreal`, `glacial`, `cold_humid`, `humid`, `tropical`,
+`warm`, `arid`, `dry`, `cold_dry`, `autumn`, `cherry`.
+
+Le dernier nombre facultatif est une **distance minimale entre les centres**
+du parent et de l’enfant, entre 0 et 100 000 blocs. Une valeur de 0 ou son
+omission laisse le placement automatique. Les marges et l’alignement sur les
+chunks peuvent éloigner le centre retenu.
+
+Si le premier site est occupé, la recherche continue plus loin dans la même
+direction : au plus 32 positions et 30 secondes de lecture au total. Même du
+vide déjà généré compte comme occupé. Une erreur disque arrête la demande ;
+elle n’autorise pas à remplacer les chunks concernés.
+
+```text
+/sanctuary expansion preview glacier sanctuary northeast glacial 256 canyon 2048
+/sanctuary expansion resume island_1
+```
+
+`preview` calcule une proposition géométrique sans activer l’île et sans vérifier
+l’occupation ou les fondations. `resume` reprend une réservation interrompue,
+avec sa graine et ses paramètres conservés. Le système ne fournit aucune commande
+de régénération des régions déjà créées.
+
+Les îles ajoutées gardent la génération d’expansion alpha.12 : leurs climats,
+reliefs, décorations et structures compatibles. Elles ne reçoivent pas
+systématiquement la grande rivière ou les terrasses de l’île initiale. Villages,
+temples, cabanes de marais et camps abandonnés dépendent du biome, du diamètre
+et des fondations ; aucune présence n’est garantie. Les règles de progression
+futures restent décrites dans [Expansion](expansion.md).
+
+## Correctif alpha.13.1 — expansions sous Windows
+
+L’erreur `AccessDeniedException` visant le **dossier**
+`data/sanctuary-world-v13`, depuis `ExpansionJournal.persist`, vient de la
+synchronisation du répertoire après l’écriture du journal. Java sous Windows
+ne permet pas cette ouverture avec `FileChannel` ; ce message ne signifie pas
+à lui seul que le joueur manque de droits sur sa sauvegarde.
+
+1. Fermer Minecraft pour arrêter la session dont les expansions sont bloquées.
+2. Mettre l’instance Prism existante à jour vers **0.1.0-alpha.13.1** via son
+   canal packwiz, puis relancer le jeu.
+3. Rouvrir **le même monde** et consulter `/sanctuary expansion list`.
+
+Si l’instance Windows a été importée depuis le MRpack sans auto-update, fermer
+Minecraft puis remplacer seulement `sanctuary-0.1.0-alpha.13.jar` par le JAR
+`sanctuary-0.1.0-alpha.13.1.jar` de la release dans son dossier `mods`.
+Conserver un seul JAR Sanctuary actif ; les autres mods et les sauvegardes
+restent dans la même instance. Le raccordement au canal stable est décrit dans
+[Distribution](packwiz.md#raccorder-linstance-prism-existante).
+
+Le remplacement du journal ayant précédé cette erreur, l’expansion demandée
+peut déjà être enregistrée comme `reserved`. Au chargement, les réservations
+valides reprennent automatiquement avec leur identifiant, leur graine et leur
+position. Il n’est pas nécessaire de recréer le monde ou de supprimer le dossier
+du journal. La commande `resume` seule ne débloque pas une session dont le
+journal a été déclaré indisponible : sa relecture exige de rouvrir le monde.
+
+Le correctif conserve le format et le contenu du journal existant ; il ne
+migre ni ne régénère les chunks. La [validation ciblée](testing.md#correctif-alpha131--journal-dexpansion-sous-windows)
+distingue les contrôles locaux de l’essai Windows natif restant à effectuer.
+
+## Paramètres et sauvegardes
+
+Le preset public `sanctuary:sanctuary` utilise le nouveau codec de générateur
+`sanctuary:island_v13`. Sa source de biomes est également enregistrée sous
+`sanctuary:island_v13`. Le générateur sérialise `initial_diameter`, limité à
+512, 724 ou 1 024 ; une valeur absente prend 724. Ce champ appartient à la
+sauvegarde créée, et ne suit pas les changements ultérieurs de défaut du pack.
+
+Pour l’île initiale, les réglages internes `sanctuary:unified_5`,
+`sanctuary:unified_10` et `sanctuary:unified_20` correspondent respectivement
+aux diamètres 512, 724 et 1 024. Les suffixes sont des références de calcul,
+pas des capacités affichées. Ils reprennent la densité Population et son
+hydrologie avec le générateur et le `RandomState` propres à l’origine.
+
+La source combine la palette Population de départ et le sélecteur de cavités
+natives du laboratoire, avec les mêmes conditions de sélection de ces poches.
+Les îles enfants conservent le sélecteur climatique du laboratoire. Les 34
+biomes natifs de cette palette et les dix biomes Population sont déclarés
+avant la première expansion ; TerraMix n’est pas une dépendance téléchargée.
+
+Le nouveau journal est enregistré dans le dossier du monde :
+
+```text
+data/sanctuary-world-v13/expansions.json
+```
+
+Son schéma reste **1**, avec une racine de **génération 13** et des extensions
+de **génération 12**. Les identifiants, parents, graines, paramètres, positions
+et états d’ouverture sont conservés côté serveur. La racine et le diamètre
+initial ne sont pas modifiables par une commande d’expansion.
+
+Les mondes du laboratoire alpha.12/12.1 gardent leur codec et leur journal
+`data/sanctuary-expansion-v1/expansions.json`. Les générations Population et
+les autres générations antérieures gardent leurs paramètres enregistrés.
+Les presets historiques sont conservés mais cachés dans la création publique.
+**Aucun monde n’est converti, agrandi, réduit ou régénéré par l’alpha.13.**
+Le [guide alpha.12](alpha12-laboratory.md) est une référence historique, pas une
+instruction de sélectionner à nouveau le laboratoire pour cette version.
+
+## Contrôles de développement
+
+`./gradlew check build assemblePack` et `:sanctuary:runGameTest` sélectionnent
+par défaut la suite unifiée. Son diamètre de test se choisit avec
+`-PsanctuaryTestDiameter=512`, `724` ou `1024` ; il ne change pas le défaut public.
+
+Les suites Population historiques demandent `-PsanctuaryUnifiedTests=false`,
+avec leur profil `-PsanctuaryTestPlayers=5`, `10`, `20` ou `100`. Les essais du
+laboratoire historique utilisent aussi ce drapeau, avec
+`-PsanctuaryExpansionTests=true`. Ces processus travaillent dans les dossiers
+de développement ignorés, jamais dans les sauvegardes personnelles.
+
+Les validations et mesures des alpha.11, .12 et .12.1 restent historiques.
+Elles ne prouvent ni les temps de chargement ni le rendu de cette intégration.
+Les trois tailles, l’interface native et les expansions/rechargements passent
+les contrôles alpha.13. Moyen atteint 63,66 s pour créer le monde puis charger
+289 chunks FULL sur la graine 0 ; voir [Validation](testing.md) pour le protocole
+et ses limites. La release, le MRpack et le canal packwiz sont publiés ; deux
+synchronisations dans la même instance Prism conservent les 601 fichiers
+personnels et réglages suivis. Voir [Distribution](packwiz.md).
@@ -479,7 +479,109 @@ plus loin, et ne propose aucun paramètre de distance.

 **État :** correction implémentée, smokes et scénarios moteur de création/rechargement
 réussis. `check build assemblePack` et douze tests historiques réussis.
-Publication en cours.
+Release, MRpack et canal packwiz publiés ; même instance Prism synchronisée
+deux fois, avec 466 fichiers personnels et réglages suivis conservés.
+
+### WG-15 — Unifier Sanctuary et ses options — alpha.13
+
+**Branche :** `codex/unified-worldgen`.
+
+- Un seul type public Sanctuary, bouton Personnaliser avec Petit (512), Moyen
+  (724, défaut), Grand (1 024). Choix enregistré dans le générateur ; Annuler
+  conserve les réglages. Les types vanilla restent disponibles.
+- Réunir le relief, les forêts, minerais, rivières, bassins, terrasses et lave
+  de Sanctuary avec les cavités vanilla luxuriantes, à spéléothèmes et soufrées
+  du laboratoire, en protégeant les volumes hydrologiques pendant la décoration.
+- Les outils d’expansion alpha.12.1 fonctionnent dans les nouveaux mondes unifiés.
+  Même contrat opérateur, réservation de zones nouvelles et refus du vide exploré.
+- Nouveau codec et origine génération 13 ; les anciens codecs et journaux restent
+  chargeables. Aucun monde personnel n’est ouvert ou converti, aucun chunk régénéré.
+- Vérifier les trois tailles, cavités réellement décorées et fluides après ticks,
+  persistance/rechargement, UI client, build et distribution dans la même instance.
+
+**État :** implémenté et vérifié : bouton natif, paramètres sur disque, huit tests
+moteur par taille sur la graine 42, eau après 1 800 ticks, trois cavités natives,
+compatibilité historique et rechargement des expansions. Moyen : 63,66 s pour
+création et 289 chunks FULL dans le protocole serveur de référence.
+`check build assemblePack` passe. Release, MRpack et canal packwiz publiés ;
+même instance Prism synchronisée deux fois, avec 601 fichiers personnels et
+réglages suivis conservés.
+Les limites, dont l’absence de preuve de camp dans l’origine unifiée des graines
+inspectées, sont documentées dans [Validation](testing.md).
+
+### WG-16 — Journal d’expansion sous Windows — alpha.13.1
+
+**Branche :** `codex/windows-expansion-journal`.
+
+**Problème :** après le remplacement atomique du journal, l’ouverture de son
+répertoire par `FileChannel` échoue sous Windows avec `AccessDeniedException`.
+La session arrête alors toute expansion, même si la réservation a déjà été écrite.
+
+- Écarter uniquement la synchronisation de répertoire non prise en charge par
+  le système de fichiers Windows ; conserver force du fichier, remplacement
+  atomique, relecture stricte et arrêt sur les véritables erreurs de stockage.
+- Conserver le schéma, les identifiants, la géométrie et les journaux existants.
+  Après mise à jour et rechargement, reprendre les réservations déjà enregistrées
+  avec le mécanisme existant, sans suppression ni reconstruction de l’historique.
+- Tester le chemin Windows par injection, une panne après remplacement et la
+  reprise, puis le build et les scénarios moteur dans le développement local.
+- Publier le correctif sur le canal stable. La machine Windows signalée n’est
+  pas accessible depuis cet environnement Mac : ne pas prétendre l’avoir testée.
+
+**État :** correctif et tests vérifiés en alpha.13.1. `check build assemblePack`
+passe, ainsi que le smoke du journal et les scénarios de création/rechargement
+dans deux processus Minecraft distincts. Validation Windows par injection sur
+macOS ; aucun essai Windows natif. Correctif publié depuis `b19e93d`, canal
+stable avancé et deux synchronisations isolées puis deux dans la même instance
+Prism Mac réussies, avec 713 fichiers personnels et réglages suivis conservés.
+Preuves dans [Validation](testing.md) et [Distribution](packwiz.md).
+
+### WG-17 — Lost City, territoires urbains en ruine — alpha.14
+
+**Branche :** `codex/lost-city-biome`.
+
+**Contrat :** créer un biome Lost City avec quartiers contemporains explorables,
+rues, ponts, parcs boisés, jardins, aires de jeux, mémoriaux, places, marchés,
+parkings, excavations, piscines et bâtiments variés : appartements, hôtels,
+bibliothèques, restaurants/cuisines, casernes et grands halls. Les
+palettes reposent sur la pierre, la pierre lisse et les briques de pierre avec
+leurs variantes usées. Les zombies vanilla occupent les lieux par les règles
+de spawn ; aucun spawner ni nouveau zombie spécial dans cette étape.
+
+- Des quartiers localisés peuvent apparaître sur l’île initiale ; conserver
+  une majorité de terrain naturel et les systèmes hydrologiques/cavités.
+- Profil d’expansion `lost_city` pour tester des territoires urbains plus vastes.
+  Bâtiments, circulations et ponts s’appuient sur le relief, sans remplir le vide.
+- Structures natives persistantes, génération déterministe par graine,
+  décoration bornée par chunk, intérieurs accessibles et butin limité.
+- Dix-sept types de parcelles aux aménagements distincts. Parkings souterrains,
+  piscines et fouilles conditionnés à une roche continue sur toute l’emprise ;
+  garage en surface ou parc de repli sinon. Parois et marches des piscines,
+  escaliers et barrières des fouilles, ponts sans remplissage du vide.
+- Expansions 64/128/256/512/1 024 dans les nouveaux mondes 14 ; `quick` sans
+  taille tire selon les poids 40/30/18/9/3, avec résultat reproductible par graine
+  et identifiant. Placement proche dans un secteur directionnel, séparation
+  des emprises circulaires écrites et garde aux coins de chunks.
+- Nouvelle génération **14**, codec `sanctuary:island_v14`, journal propre
+  `data/sanctuary-world-v14/expansions.json` de schéma 1. Ce contrat s’applique
+  uniquement aux nouveaux mondes et à leurs expansions autorisées par commande.
+  Les codecs 12/13, leurs journaux et les chunks existants gardent leur génération.
+  Aucun monde personnel n’est ouvert, modifié, converti ou régénéré.
+- Contrat particulier de reprise du vide, limité aux mondes 14 : certificat
+  explicite pour des chunks FULL entièrement vides et vierges, lié au jeton
+  immuable de la réservation. Réouverture obligatoire avant préparation et
+  recontrôle de la preuve ; aucune régénération de terrain occupé. L’absence
+  d’une preuve complète, des entités, POI, ticks ou événements bloc empêchent
+  l’admission. Le [contrat détaillé](testing-alpha14.md) fait partie du ticket.
+- Vérifier structures et biomes dans le moteur, persistance après redémarrage,
+  fondations, circulation, absence de spawners/villageois, héritage Windows,
+  build et pack. Livrer dans le canal stable et la même instance Prism.
+
+**État :** implémentation et vérifications terminées ; la publication alpha.14
+et les synchronisations Prism restent à attester. Les résultats sont suivis dans
+[Validation alpha.14](testing-alpha14.md). Les alpha.15/.16 poursuivront la validation de génération
+avant la bêta consacrée aux systèmes et à la progression. Les infectés, spitters,
+boomers, hunters, chargeurs et autres variantes restent réservés à la bêta.

 ## Réserve de thèmes futurs

@@ -0,0 +1,115 @@
+{
+  "version": "0.1.0-alpha.13.1",
+  "date": "2026-09-09",
+  "minecraft": "26.3-pre-2",
+  "java": 25,
+  "host_os": "macOS",
+  "windows_native_tested": false,
+  "windows_policy_tested_by_injection": true,
+  "journal_contracts": [
+    "Windows policy skips only directory channel",
+    "file force and atomic replacement and strict read-back remain required",
+    "supported directory AccessDenied propagates after replacement",
+    "failed session refuses further writes",
+    "verified reload recovers persisted reservation",
+    "post-replacement corruption fails closed"
+  ],
+  "jar_sha256": "b340dfc58f3d2d1a2a375dc527ac6721c61430600622046db26228e0da46061b",
+  "logs": {
+    "journal-smoke": {
+      "path": "build/alpha131-journal-smoke.log",
+      "sha256": "c02e94713cf3f9a3c76674700cc5c800aecd84b213b2be9ed53629f8eb9cd3d0",
+      "passed": true,
+      "required_game_tests": null
+    },
+    "check": {
+      "path": "build/alpha131-check.log",
+      "sha256": "68f6cb97e2f80669d39e37623076229e030a0d9826c13e9420f51f6ba23885bd",
+      "passed": true,
+      "required_game_tests": 8
+    },
+    "expansion-create": {
+      "path": "build/alpha131-expansion-create.log",
+      "sha256": "61fa4513aef71290a1419c3425a329047c8fe623a561544c6a8d916fe50e226c",
+      "passed": true,
+      "required_game_tests": 2
+    },
+    "expansion-reload": {
+      "path": "build/alpha131-expansion-reload.log",
+      "sha256": "44fafb4636ff90707a068f325a245dbf9820ccb1bdf785c912f7e636fe7cfa43",
+      "passed": true,
+      "required_game_tests": 2
+    }
+  },
+  "binary_comparison": {
+    "base_version": "0.1.0-alpha.13",
+    "version": "0.1.0-alpha.13.1",
+    "added": [
+      "fr/koka/sanctuary/expansion/ExpansionJournal$DirectorySync.class"
+    ],
+    "removed": [],
+    "changed": [
+      "fabric.mod.json",
+      "fr/koka/sanctuary/expansion/ExpansionJournal$1.class",
+      "fr/koka/sanctuary/expansion/ExpansionJournal.class"
+    ],
+    "synthetic_switch_instructions_identical": true,
+    "all_other_entries_identical": true
+  },
+  "expansion": {
+    "seed": 42,
+    "initial_diameter": 724,
+    "generation": 13,
+    "creation_process": 13148,
+    "reload_process": 13279,
+    "creation_passed": true,
+    "reload_passed": true,
+    "creation_islands": [
+      {
+        "landing_biome": "minecraft:jungle",
+        "landing": [
+          0,
+          202,
+          -1792
+        ],
+        "climate": "tropical",
+        "upper_biome": "minecraft:jungle",
+        "diameter": 64,
+        "centre": [
+          0,
+          -1792
+        ],
+        "id": "alpha",
+        "parent": "sanctuary"
+      },
+      {
+        "landing_biome": "minecraft:desert",
+        "landing": [
+          2048,
+          198,
+          -1792
+        ],
+        "climate": "arid",
+        "upper_biome": "minecraft:desert",
+        "diameter": 64,
+        "centre": [
+          2048,
+          -1792
+        ],
+        "id": "beta",
+        "parent": "alpha"
+      }
+    ],
+    "reloaded_regions": 3,
+    "saved_generator_codec_decoded": true,
+    "after_reload_expansion": [
+      0,
+      1792
+    ],
+    "final_regions": 4,
+    "native_structure_status": "not_observed_after_complete_scan",
+    "native_structure_witness_required": false,
+    "limitation": "Optional native camp witness absent after complete search on seed 42, as in alpha.13; no new structures claim."
+  },
+  "scope": "No generation or journal schema change. Test worlds only; no personal world opened or regenerated. Windows native runtime and power-loss durability not tested."
+}
@@ -1,24 +1,45 @@
 # Climats, expansion et ressources

-Ce document fixe les décisions de conception pour la suite de Sanctuary.
-L’alpha.12 fournit un laboratoire avec registre persistant et commandes opérateur,
-suivant le [contrat de laboratoire](alpha12-laboratory.md). Le déblocage par
-recherches et contributions reste à implémenter. Le relevé de ressources décrit plus bas
-est un outil de développement séparé, exécuté dans le monde jetable des GameTests.
+Ce document distingue les outils de génération et la progression collective
+encore à construire. L’alpha.13 réunit l’île de départ et
+les commandes d’expansion dans le choix public **Sanctuary**. Le
+[guide alpha.13](alpha13-worldgen.md) décrit leur utilisation. Les versions
+alpha.12/12.1 et leur [laboratoire](alpha12-laboratory.md) restent historiques.
+Le déblocage par recherches, XP et contributions n’est pas encore implémenté.

-## Taille de l’île initiale — alpha.11
+## Taille initiale et extensions — alpha.13

-Deux choix de départ sont proposés : **Petit** et **Grand**, Grand par défaut.
-Petit garde un diamètre nominal de 512 blocs ; Grand vise environ 724 blocs,
-soit deux fois l’aire nominale de Petit. La hauteur reste de 384 blocs. Les
-repères internes 5/10 servent au calcul de surface, sans nom de capacité affiché
-ni promesse sur le nombre de joueurs, les minerais ou l’aire constructible.
+Le bouton natif **Personnaliser** propose **Petit** (512 blocs de diamètre
+nominal), **Moyen** (724, par défaut) et **Grand** (1 024). La hauteur reste de
+384 blocs. Ce choix configure un nouveau monde ; il ne promet ni nombre de
+joueurs, ni quantité de ressources, ni aire entièrement constructible.

-Cette taille se choisit pour un nouveau monde et ne remplace pas le futur
-déblocage collectif de continents. Grand utilise `population_10` ; les anciennes
-sauvegardes 5/20/100 conservent leurs réglages et leurs dimensions. Les formats
-20/100 sont cachés de la création. Les mesures de l’alpha.10 conservées plus bas
-restent historiques ; les contrôles alpha.11 sont dans [Validation](testing.md).
+L’île initiale reprend le relief, les forêts et l’hydrologie de Population,
+avec les poches de cavités natives issues du laboratoire. Les îles ajoutées
+conservent les tailles **64/128/256/512**, les douze profils climatiques et les
+quatre reliefs d’expansion. Leur génération ne reprend pas automatiquement
+la grande rivière et les terrasses de l’île initiale.
+
+Les commandes opérateur `quick`, `create`, `preview`, `list`, `visit` et
+`resume` reprennent le fonctionnement alpha.12.1. Le paramètre final de distance
+est facultatif ; les sites occupés sont écartés en cherchant plus loin dans la
+même direction. Même un chunk de vide déjà généré est protégé. Les recherches
+collectives et les objets de déblocage ne sont pas nécessaires à ces outils.
+
+La racine alpha.13 est de génération 13 ; les extensions restent de génération
+12, dans le journal `data/sanctuary-world-v13/expansions.json` du nouveau monde.
+Les anciens mondes gardent leurs codecs, leurs paramètres et leur journal.
+Les choix séparés Petit/Grand et Laboratoire sont désormais cachés à la
+création. Aucun monde existant n’est converti ou redimensionné.
+
+## Tailles et mesures historiques
+
+L’alpha.11 proposait Petit (512) et Grand (724), avec Grand par défaut ; ses
+repères internes 5/10 ne correspondaient pas à une capacité multijoueur promise.
+Les références `population_5/10/20/100` restent celles des sauvegardes historiques.
+Les mesures alpha.3 à alpha.11 conservées ci-dessous décrivent uniquement les
+versions et les emprises observées à leur date. Les contrôles de l’alpha.13,
+les rechargements et le benchmark Moyen sont consignés dans [Validation](testing.md).

 ## Les huit directions et les branches climatiques

@@ -130,12 +151,15 @@ Une graine peut donc manquer d’une ressource ; la présence de tout le parcour
 Minecraft n’est pas garantie. Les structures donnant accès à l’End et leur lien
 avec l’expansion restent à concevoir.

-## Relevé de développement disponible
+## Relevé de développement — générateurs historiques

 `ResourceSurveyDiagnostics`, dans `src/gametest`, lit les chunks au statut
 `FULL`, après le terrain, les matériaux et les décorations. Il ne figure pas
 dans le JAR Sanctuary distribué et n'ajoute aucune commande joueur ou admin.
 La tâche repart d'un monde GameTest neuf, jamais d'une sauvegarde personnelle.
+Depuis l’alpha.13, `runGameTest` et `check` sélectionnent la suite unifiée par
+défaut. Les commandes ci-dessous demandent explicitement une suite historique ;
+elles ne constituent pas un relevé du nouveau monde unifié.

 Le relevé standard inspecte **neuf chunks**, soit un carré de 48×48 blocs autour
 du chunk du spawn naturel, sur toute la hauteur de la dimension. Il prépare
@@ -146,13 +170,13 @@ n'est inclus dans ces comptes de blocs.

 ```sh
 # Contrôle standard : neuf chunks inspectés, total local uniquement.
-./gradlew :sanctuary:runGameTest -PsanctuaryResourceSurvey=sample --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryUnifiedTests=false -PsanctuaryResourceSurvey=sample --console=plain

 # Relevé de toute l'enveloppe déclarée de Sanctuary, sur un monde jetable neuf.
-./gradlew :sanctuary:runGameTest -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=island --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryUnifiedTests=false -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=island --console=plain

 # Désactiver seulement le relevé pour un autre diagnostic.
-./gradlew :sanctuary:runGameTest -PsanctuaryResourceSurvey=off --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryUnifiedTests=false -PsanctuaryResourceSurvey=off --console=plain
 ```

 Les modes sont transmis à la propriété JVM de test
@@ -162,7 +186,7 @@ ce dernier par défaut ; `20` et `100` servent à la compatibilité historique.
 Le mode `island` calcule l’enveloppe du profil actif, avec 16 blocs de marge de
 décoration et un halo de préparation d’un chunk. Les valeurs ci-dessous sont
 les bornes calculées lors de l’alpha.10, pas des relevés exécutés ni un nombre
-de chunks déjà validé pour le nouveau Grand :
+de chunks déjà validé pour l’ancien Grand alpha.11 :

 | Profil | Chunks comptés par `island` | Chunks FULL préparés avec halo |
 | --- | --- | --- |
@@ -257,16 +281,16 @@ essai client concurrent pendant environ 23 secondes. Elle décrit une machine
 chargée et cette exécution, pas une performance garantie sur d'autres machines.
 Le temps de préparation est distinct du coût du comptage par palettes.

-## Contrat du prochain ticket d'expansion
+## Contrat de progression collective restant à construire

-Avant toute activation de continent, enregistrer côté serveur son identifiant,
-sa direction parmi les huit, son centre, son emprise, sa graine dérivée, sa
-version de génération, son profil climatique et son état de déblocage.
-Le relevé des ressources intervient après la génération effective de sa région,
-avec une complétude explicite, indépendamment des contributions qui l'ont ouverte.
+Le registre et la réservation des alpha.12/12.1 sont repris dans l’alpha.13 :
+identifiant, parent, direction, centre, emprise, graine, génération, climat et
+statut sont enregistrés côté serveur. Les chunks existants, y compris le vide,
+sont protégés pendant la recherche d’une nouvelle région.

-Les zones déjà explorées dans le vide peuvent contenir des chunks sauvegardés
-ou des constructions. L'activation exige donc un contrat de réservation ou de
-matérialisation qui les protège ; elle ne peut pas régénérer silencieusement
-les chunks existants. Les règles de contribution, distances, tailles,
-réservations, migrations et prix ne sont pas décidées par ce diagnostic.
+Le prochain travail de progression doit relier ces ouvertures aux recherches,
+aux contributions et à leurs coûts. Un éventuel relevé de ressources intervient
+après la génération réelle, avec une complétude explicite ; il ne choisit pas
+une graine pour remplir un stock attendu. Les prix, les objets de déblocage et
+les règles de contribution restent à concevoir. Aucun contrat de migration
+ou de régénération d’anciennes parties n’est fourni par ce diagnostic.
@@ -13,18 +13,105 @@ 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.

-## Correctif alpha.12.1 — préparation
+## Alpha.14 en préparation

-WG-14 corrige la recherche d’emplacements occupés et ajoute la distance minimale
-aux commandes. Les mondes laboratoire alpha.12 restent compatibles, sans
-conversion. Le correctif, son MRpack et sa publication sont en validation ;
-le canal et l’instance installée restent alpha.12 jusqu’à vérification de livraison.
+Les sources ciblent `0.1.0-alpha.14`. `check build assemblePack`, les scénarios
+moteur et la vérification du JAR, du MRpack et du ZIP Prism passent. La publication
+immuable, l’avancement du canal et les synchronisations restent à attester
+avant d’annoncer cette version publiée. Le dernier reçu de livraison
+ci-dessous reste celui de l’alpha.13.1. Voir le
+[contrat de génération et les preuves attendues](testing-alpha14.md).
+
+La livraison conserve la même instance et ses sauvegardes. Pour les nouveautés
+Lost City, créer ensuite un **nouveau monde Sanctuary** de génération 14 ;
+mettre à jour le pack ne convertit pas les mondes 12/13. Dans ce nouveau monde
+uniquement, une expansion réservée sur du vide certifié peut demander de fermer
+et rouvrir le monde avant sa préparation. Ce mécanisme ne fait pas partie de
+l’installateur packwiz et n’autorise pas à supprimer un monde ou son journal.
+
+## Correctif alpha.13.1 publié — 9 septembre 2026
+
+[Sanctuary 0.1.0-alpha.13.1](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.13.1)
+est publié depuis le commit source `b19e93d`. Le canal stable utilise cette
+version. Le JAR, le [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.13.1/Sanctuary-0.1.0-alpha.13.1.mrpack)
+et le ZIP d’amorçage ont été vérifiés par téléchargement public. SHA-256 du JAR :
+
+```text
+b340dfc58f3d2d1a2a375dc527ac6721c61430600622046db26228e0da46061b
+```
+
+Deux synchronisations isolées puis deux dans la même instance Prism Mac ont
+réussi. Le second passage conserve les fichiers gérés à l’identique ; un seul
+JAR Sanctuary alpha.13.1 est actif. Les **713 fichiers personnels et réglages
+suivis** conservent leurs hashes. Aucune sauvegarde personnelle n’a été ouverte,
+convertie ou régénérée. Dossier de l’instance conservé : `Sanctuary-0.1.0-alpha.1`.
+Sauvegarde ciblée : `sanctuary-backups/before-0.1.0-alpha.13.1/` ; reçus locaux
+`build/alpha131-isolated-validation.json` et `build/alpha131-prism-validation.json`.
+
+Le correctif évite la synchronisation de dossier non prise en charge sous
+Windows. **Aucun nouveau monde requis :** fermer Minecraft, mettre l’instance
+à jour puis rouvrir le même monde. Les réservations enregistrées reprennent
+après vérification. La machine Windows n’a pas été accessible pour installation
+ou essai natif : le [guide](alpha13-worldgen.md#correctif-alpha131--expansions-sous-windows)
+décrit aussi le remplacement du seul JAR Sanctuary pour une instance issue du
+MRpack sans auto-update. Voir les [preuves et limites](testing.md#correctif-alpha131--journal-dexpansion-sous-windows).
+
+## Alpha.13 publiée — 9 septembre 2026
+
+[Sanctuary 0.1.0-alpha.13](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.13)
+est publiée depuis le commit source `78b63be`. Le canal stable utilisait alors
+cette version. Le JAR, le [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.13/Sanctuary-0.1.0-alpha.13.mrpack)
+et le ZIP d’amorçage ont été vérifiés par téléchargement public. SHA-256 du JAR :
+
+```text
+53eb5d8eda54d322250784203824993bd675de1cb90467e74d67589b15769e76
+```
+
+Deux synchronisations isolées puis deux passages dans la même instance Prism
+ont réussi. Le second passage laisse les fichiers gérés identiques ; un seul
+JAR Sanctuary alpha.13 est actif. Les **601 fichiers personnels et réglages
+suivis** conservent leurs hashes, notamment les mondes et mods tiers. Aucune
+sauvegarde personnelle n’a été ouverte, convertie ou régénérée.
+
+L’instance conserve son dossier `Sanctuary-0.1.0-alpha.1`, sans réimportation.
+Sauvegarde ciblée : `sanctuary-backups/before-0.1.0-alpha.13/` dans cette instance.
+Reçus locaux : `build/alpha13-isolated-validation.json` et
+`build/alpha13-prism-validation.json`.
+
+Pour tester : créer un **nouveau monde**, choisir **Sanctuary**, puis le bouton
+natif **Personnaliser** : Petit 512, Moyen 724 par défaut, Grand 1 024.
+Le laboratoire n’est plus un choix public ; ses cavités et outils d’expansion
+rejoignent le nouveau monde. Les anciennes générations restent chargeables.
+Voir [le guide alpha.13](alpha13-worldgen.md) et [les preuves](testing.md).
+
+## Correctif alpha.12.1 publié — 9 septembre 2026
+
+[Sanctuary 0.1.0-alpha.12.1](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.12.1)
+est publiée depuis le commit source `332d60b`. Le canal packwiz utilisait cette
+version. Le JAR, le [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.12.1/Sanctuary-0.1.0-alpha.12.1.mrpack)
+et le ZIP d’amorçage ont été vérifiés par téléchargement public. SHA-256 du JAR :
+
+```text
+c9df4da956cfa54581b3fde21de006bf8ac3ec025b8dd0daa5d060bcb70aabd4
+```
+
+Deux synchronisations isolées puis deux passages dans la même instance Prism
+ont réussi ; le second laisse les fichiers gérés identiques. Un seul JAR
+Sanctuary alpha.12.1 est actif, avec **466 fichiers personnels et réglages suivis
+conservés**, y compris les mondes et les mods tiers. Aucun monde n’a été ouvert
+ou régénéré. La sauvegarde ciblée est dans
+`sanctuary-backups/before-0.1.0-alpha.12.1/` de l’instance existante ; reçus locaux
+`build/alpha121-isolated-validation.json` et `build/alpha121-prism-validation.json`.
+
+WG-14 ajoute la distance et le contournement automatique des zones occupées.
+Les mondes laboratoire alpha.12 restent utilisables sans conversion : le journal
+v1 et les descripteurs de génération 12 sont conservés. Voir le [guide](alpha12-laboratory.md).

 ## Alpha.12 publiée — 9 septembre 2026

 [Sanctuary 0.1.0-alpha.12](https://git.botsu.net/koka/sanctuary-beta/releases/tag/v0.1.0-alpha.12)
-est publiée depuis le commit source `cdfbba0`. Le canal stable pointe sur cette
-version. Le JAR, le [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.12/Sanctuary-0.1.0-alpha.12.mrpack)
+est publiée depuis le commit source `cdfbba0`. Le canal stable utilisait alors
+cette version. Le JAR, le [MRpack](https://git.botsu.net/koka/sanctuary-beta/releases/download/v0.1.0-alpha.12/Sanctuary-0.1.0-alpha.12.mrpack)
 et le ZIP d’amorçage Prism ont été téléchargés publiquement et vérifiés contre
 les artefacts locaux. SHA-256 du JAR :

@@ -0,0 +1,359 @@
+# Alpha.14 — Lost City et expansions
+
+**État : code et artefacts vérifiés ; publication et installation en attente.**
+`check build assemblePack` passe sur les sources finales avec les **8 GameTests
+requis**, le 9 septembre 2026 à **13 h 57 min 48 s**. La création de quartiers,
+leur réouverture et la reprise différée du vide passent également dans leurs
+mondes de développement distincts. Le JAR, le MRpack et le ZIP Prism sont
+vérifiés ; le canal public et l’instance Prism ne sont pas encore attestés ici.
+Les résultats des alpha.12, 13 et 13.1 restent historiques. Ticket [WG-17](backlog.md).
+
+Les smokes des sources finales passent sous Gradle et Java 25 :
+`LostCityRendererSmoke` pour les 17 types, dont confinement
+et accès des piscines dans quatre orientations, parcs distincts et sous-sols ;
+`ExpansionJournalSmoke`, dont l’immuabilité du jeton de reprise du vide ; et
+le contrôle de placement spatial de génération 14. `LostCityPlannerSmoke`
+passe également. Ses
+32 graines sur terrain contrôlé couvrent tous les types de lots ; un témoin
+distinct de faille couvre le pont, soit les 17 types. Le test de pente ascendante
+et descendante protège la sélection des lots contre le rejet asymétrique des
+terrains montants. Sur l’ancien planificateur compilé, ce nouveau test échouait
+avec **0 contre 9 lots** ; le planificateur corrigé satisfait l’égalité des
+deux sens et le minimum de cinq lots demandé par le test. Cette comparaison
+provient de la sortie d’exécution ; aucun journal séparé n’a été conservé.
+
+`:sanctuary:expansionVoidCertificateSmoke` passe aussi sous Gradle :
+champs NBT natifs obligatoires, types stricts, refus des contenus, preuves de
+chunks absents et stabilité du certificat face aux seuls compteurs volatils.
+Ces contrôles unitaires sont complétés par les essais moteur consignés plus
+bas.
+
+## Périmètre et création d’un monde
+
+Minecraft **26.3-pre-2**, Fabric et Java **25**, selon les versions épinglées dans
+`gradle.properties`. La livraison cible `0.1.0-alpha.14` pour le mod et le pack.
+
+Créer un **nouveau monde**, type **Sanctuary**, puis le bouton natif
+**Personnaliser** : Petit 512, Moyen 724 par défaut ou Grand 1 024 blocs de
+diamètre nominal. La hauteur reste de 384 blocs. Le codec public est
+`sanctuary:island_v14` ; les racines et les extensions de ces mondes portent la
+génération **14**. Le journal est séparé :
+`data/sanctuary-world-v14/expansions.json`, schéma 1.
+
+Les mondes de générations 12 et 13 conservent leurs codecs, paramètres et
+journaux. Ils ne reçoivent pas Lost City par conversion et ne changent pas de
+générateur au chargement. Aucune sauvegarde personnelle ne doit être utilisée
+pour les essais ci-dessous.
+
+## Lost City
+
+Les quartiers sont composés par du code Sanctuary original. Une poche urbaine
+peut être retenue sur l’île initiale ; les extensions de profil `lost_city`
+recherchent également des emplacements. Le biome suit les parcelles acceptées
+en surface et laisse les biomes de cavités profonds. Une île peut ne fournir
+aucun site convenable : la ville et ses différents types ne sont pas garantis.
+
+| Type | Aménagement distinctif |
+| --- | --- |
+| Rue | Chaussée, bordures de pierre lisse et variations de hauteur accessibles |
+| Pont | Tablier et garde-corps au-dessus d’une courte faille, appuis naturels aux deux extrémités |
+| Parc boisé | Chemins croisés, arbres et bancs |
+| Jardin | Haies basses, parterres fleuris et allées |
+| Aire de jeux | Sable, portique de balançoire, plate-forme et petit toboggan |
+| Parc mémorial | Cour, monument de pierre et bancs |
+| Place | Pavage et fontaine sèche |
+| Marché | Étals, auvents sobres et réserves |
+| Parking | Places marquées, poteaux, garage souterrain si la roche le permet, sinon en surface |
+| Excavation | Fouille ouverte, fondations inachevées, barrières et escalier |
+| Piscine abandonnée | Bassin de trois couches d’eau, marches immergées et plage minérale |
+| Immeuble d’appartements | Étages, chambres, coin cuisine et escaliers |
+| Hôtel | Réception, couloir central et chambres séparées |
+| Bibliothèque | Rayonnages, tables de lecture et pupitre |
+| Restaurant | Cuisine équipée et tables, espace de service à l’étage |
+| Caserne | Dortoirs et réserves |
+| Hall | Grande salle, estrade, rangées de sièges et balcon |
+
+Pierre, pierre lisse et briques de pierre dominent ; briques fissurées ou
+moussues, andésite, vitres, détails de fer et intérieurs en chêne noir complètent
+la palette. L’usure est déterministe. Les accès et les escaliers restent
+distincts des brèches de façade et de toiture. Le butin des coffres utilise des
+tables vanilla différées ; aucune génération de spawner ou de villageois.
+
+Le spawn naturel de monstres du biome et des pièces de structure est limité aux
+zombies vanilla. Lumière, difficulté, limites de population et distance aux
+joueurs continuent de s’appliquer ; une ruine n’implique pas la présence immédiate
+d’un groupe de zombies. Les classes de zombies spécifiques restent pour la bêta.
+
+Le placement vérifie la roche sous toute l’emprise. Un sous-sol, une piscine ou
+une excavation exige une continuité jusqu’à huit blocs sous le plancher de
+référence. À défaut, le parking reste en surface et piscine ou excavation se
+replient en parc. Les piscines gardent un fond et des parois continus ; les
+ponts ne construisent pas de piliers jusqu’au vide. Les volumes protégés de
+l’hydrologie et les sites insuffisamment supportés sont écartés.
+
+## Commandes d’essai et placement des expansions
+
+Les commandes restent des outils opérateur, accessibles avec les permissions
+adéquates. Elles n’utilisent pas encore la progression ou les ressources.
+
+```text
+/sanctuary expansion quick east lost_city 256 natural
+/sanctuary expansion list
+/sanctuary expansion visit island_1
+/sanctuary expansion preview quartier sanctuary northeast lost_city 128 natural
+/sanctuary expansion create quartier sanctuary northeast lost_city 128 natural
+/locate structure sanctuary:lost_city
+```
+
+`island_1` est l’exemple du premier identifiant libre créé par `quick` ; utiliser
+l’identifiant réellement indiqué par la commande. `visit` attend une île prête.
+`preview` examine un emplacement sans l’activer. `resume <id>` sert à reprendre
+une réservation interrompue. `create` choisit aussi son parent explicitement.
+La recherche exacte `/locate structure sanctuary:lost_city` retrouve les
+quartiers Sanctuary admissibles ; elle peut échouer si aucun quartier ne se
+trouve dans sa portée de recherche. Un profil `lost_city` ne garantit pas un
+terrain suffisamment adapté pour accepter un quartier.
+
+Les diamètres d’expansion possibles dans les mondes 14 sont **64, 128, 256,
+512 et 1 024**. Avec `quick east` ou `quick east lost_city`, le diamètre est tiré
+de manière reproductible à partir de la graine et de l’identifiant :
+
+| Diamètre | Poids du tirage |
+| --- | --- |
+| 64 | 40 % |
+| 128 | 30 % |
+| 256 | 18 % |
+| 512 | 9 % |
+| 1 024 | 3 % |
+
+Ces poids décrivent la distribution du tirage, pas un quota de cinq îles à
+reproduire sur chaque serveur. Une taille explicite remplace le tirage. Les
+recherches d’emplacement ne changent ni cette taille ni la graine retenue.
+Les mondes historiques gardent leurs tailles et comportements antérieurs.
+
+La direction choisit un secteur de 45° autour du parent. La recherche essaie
+d’abord des positions proches, puis des couronnes plus éloignées, avec un
+nombre borné de candidats. Les centres restent alignés sur les chunks.
+Les emprises circulaires incluent le terrain, la marge de décoration et une
+garde empêchant deux îles de posséder le même chunk de coin. Le voisinage lu
+par les étapes de génération n’est pas intégralement réservé comme terrain.
+Une distance minimale entre centres reste possible comme dernier argument.
+
+## Contrat de reprise différée du vide
+
+Ce mécanisme concerne **uniquement les nouveaux mondes de génération 14** et
+une expansion explicitement demandée. Les générations 12/13 gardent leur refus
+des chunks déjà générés, même vides. Il ne permet pas la régénération générale
+d’une île, d’un terrain occupé ou d’une construction.
+
+1. Examiner toute l’emprise d’écriture et produire, pour chaque chunk existant,
+   une preuve stricte qu’il est FULL, entièrement vide et vierge. Les positions
+   encore absentes sont également certifiées, y compris leurs stockages
+   d’entités et de POI. La simple absence de bloc visible ne suffit pas : entités
+   persistées, chargées ou en attente, POI, ticks, événements de blocs et autres
+   indices de contenu font partie des refus.
+2. Lier le certificat à l’identité exacte de l’expansion et à un jeton immuable
+   dans le journal. Une preuve isolée sans réservation correspondante ne donne
+   aucune autorisation ; un changement de paramètres ou une preuve manquante
+   doit faire échouer la reprise.
+3. Enregistrer la réservation et demander de **fermer puis rouvrir le monde**.
+   L’expansion reste différée pendant la session ayant établi la preuve.
+4. Au chargement suivant, vérifier le journal, le certificat et les données
+   actuelles sur toute l’emprise avant toute préparation. Une divergence bloque
+   la reprise avant l’écriture des positions absentes. Seuls les chunks
+   explicitement certifiés peuvent être réutilisés par cette expansion.
+
+La preuve lit le format natif exact de Minecraft 26.3-pre-2 : l’état d’air sans
+propriétés s’écrit comme la chaîne `minecraft:air` dans la palette ; sa forme
+composée autorisée utilise le champ `id`. L’ancien champ `Name` ne suffit pas
+à certifier un chunk. Les types NBT, sections, palettes, heightmaps et données
+annexes restent contrôlés strictement ; une métadonnée inconnue provoque un
+refus. Seuls les compteurs temporels et caches de lumière valides sont exclus
+de l’empreinte sémantique du vide.
+
+Il ne faut supprimer ni certificat, ni journal, ni dossier de région pour
+débloquer une commande. L’absence de preuve est un refus, pas une invitation à
+reconstruire l’historique. Les sauvegardes personnelles ne sont pas ouvertes
+par les tests ou par la mise à jour packwiz.
+
+## Protocole et preuves attendues
+
+Un seul processus Gradle ou Minecraft de développement à la fois. Les suites
+de création repartent de mondes ignorés sous `mods/sanctuary/build/run/`.
+Un scénario de réouverture doit suivre sa création sans intercaler un test qui
+effacerait ce monde de développement.
+
+```sh
+./gradlew :sanctuary:lostCityPlannerSmoke :sanctuary:lostCityRendererSmoke --console=plain
+./gradlew check build assemblePack -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryLostCityTests=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryLostCityTests=true -PsanctuaryExpansionReload=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+```
+
+La suite de reprise du vide repart ensuite d’un **autre monde de développement
+neuf**. La commande de réouverture est exécutée deux fois de suite :
+
+```sh
+./gradlew :sanctuary:runGameTest -PsanctuaryVoidReuseTests=true -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryVoidReuseTests=true -PsanctuaryExpansionReload=true -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryVoidReuseTests=true -PsanctuaryExpansionReload=true -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+```
+
+### Résultats moteur — graine 0
+
+Le 9 septembre 2026, la création sur les sources finales passe à **13 h 55 min
+15 s** dans le processus **19155** (`build/alpha14-city-final-create.log`,
+deux tests requis réussis, commande terminée en **2 min 24 s**). La réouverture
+du même monde de développement passe à **13 h 55 min 58 s** dans un second
+processus, **19372** (`build/alpha14-city-final-reload.log`, deux tests requis
+réussis, **33 s**).
+Ces durées sont celles des commandes Gradle complètes, pas des mesures de
+chargement en jeu ou de performance multijoueur.
+
+Les rapports locaux ignorés sont
+`mods/sanctuary/build/run/gameTest/diagnostics/lost-city-alpha14-seed-0.json`
+et `lost-city-alpha14-reload-seed-0.json` dans le même dossier. Leurs copies
+sont conservées dans `build/alpha14-evidence/` avant le nettoyage du monde de
+développement. Le monde racine est de diamètre **724**, graine **0**, codec
+`sanctuary:island_v14`.
+
+Trois extensions de diamètre 256 ont été examinées en lecture seule :
+
+| Candidat | Graine de l’extension | Quartiers admissibles |
+| --- | --- | --- |
+| `city_test` | `7890860792428309400` | 0 |
+| `city_harbor` | `-1594320136210322067` | 0 |
+| `city_gardens` | `6666275329838981856` | 1 |
+
+Seule `city_gardens` a ensuite été activée, à l’est, centre **(2032, 624)**.
+Sa préparation a terminé **418 chunks FULL**. L’inspection urbaine ci-dessous
+couvre les chunks des quartiers, pas la totalité de cette préparation.
+
+| Site généré | Parcelles sauvegardées | Chunks FULL inspectés | Coffres non ouverts à butin différé |
+| --- | --- | --- | --- |
+| Île initiale | 26 : appartement, hôtel, bibliothèque, marché, parc boisé, mémorial et 20 rues | 26 | 4 |
+| `city_gardens` | 12 : appartement, parc boisé et 10 rues | 13 | 1 |
+
+Les deux quartiers possèdent leurs références de structure natives ; la
+recherche native retrouve respectivement **(-49, 253, 13)** et **(2012, 229,
+621)**. Les intérieurs traversables et les tables de spawn limitées aux zombies
+sont contrôlés. Cela ne garantit pas des zombies visibles de jour. La
+couverture des **17 types dans quatre orientations** provient de 68 rendus
+témoins indépendants ; elle ne signifie pas que cette graine contient tous les
+types dans ses quartiers naturels.
+
+L’inspection native des bâtiments contrôle également qu’aucun minerai ne
+remplace la maçonnerie dans leurs volumes à partir du plancher. Cette preuve
+concerne les bâtiments effectivement générés et inspectés ; les minerais du
+terrain sous les fondations restent possibles.
+
+Une piscine native isolée, indépendante du tirage des quartiers, conserve
+**189 cellules d’eau**, ses marches et son confinement après l’exécution d’un
+tick d’eau. La réouverture conserve les mêmes 189 cellules et les marches ;
+elle n’exécute pas un second tick témoin.
+
+Dans le second processus, les **38 pièces natives**, les **5 coffres non
+ouverts**, le bloc d’or témoin à **(-61, 250, 11)** et le journal sont conservés.
+L’empreinte du journal contrôlé est
+`38e4bc1b2e493628d1e5d1775250c0bc48821bf49d025df3c37159fcff5801ba`.
+Ces essais utilisent uniquement un monde de développement ignoré, sans ouvrir
+de sauvegarde personnelle.
+
+### Reprise du vide — création et deux réouvertures
+
+Les trois exécutions Minecraft, sur la graine **0**, génération **14**, passent
+le 9 septembre 2026 :
+
+| Étape | Journal local | Résultat et durée de la commande |
+| --- | --- | --- |
+| Preuves et réservations | `build/alpha14-void-create.log` | Deux tests requis réussis à 13 h 43 ; 41 s |
+| Première réouverture | `build/alpha14-void-reload.log` | Deux tests requis réussis à 13 h 45 ; 1 min |
+| Deuxième réouverture | `build/alpha14-void-second-reload.log` | Deux tests requis réussis à 13 h 46 ; 29 s |
+
+Les rapports sont `void-reuse-before-reload.json`,
+`void-reuse-after-reload.json` et `void-reuse-second-reload.json`, sous
+`mods/sanctuary/build/run/gameTest/world/`. Ce sont des preuves locales à
+conserver avant le nettoyage du monde de développement.
+
+La première expansion, `void_loaded`, couvre **77 chunks FULL vides déjà
+chargés**. La seconde, `void_saved`, couvre **un chunk FULL vide uniquement
+stocké et 76 positions absentes**. Ce dernier scénario emploie une copie NBT
+native de chunk vide, déplacée uniquement pour constituer le témoin dans ce
+monde jetable. Chaque réservation reçoit son jeton durable propre et reste
+différée, sans publication dans le générateur pendant la session initiale.
+
+Quatre témoins indépendants, chacun contrôlé vide avant modification, prouvent
+le refus d’un **bloc**, d’un **coffre avec son entité de bloc**, d’une **entité
+vivante enregistrée** et d’un **tick de bloc programmé**. Une métadonnée NBT
+étrangère ajoutée après certification fait également échouer la vérification
+globale : l’empreinte SHA-256 du fichier de région et le contenu NBT modifié
+restent identiques après ce refus. Le test restaure ensuite son témoin vide
+pour poursuivre le scénario positif.
+
+À la première réouverture, les deux expansions atteignent **154 chunks FULL**,
+chacun conservant le marqueur de son jeton exact, avec **128 sections non
+vides**. Un bloc d’or témoin est alors posé à **(6080, 376, 1264)**. À la
+deuxième réouverture, il est préservé : les **154 chunks FULL marqués** et
+**129 sections non vides** sont retrouvés. Ce passage contrôle donc aussi
+qu’une reprise terminée ne réinitialise pas les blocs ajoutés ensuite.
+
+Une réouverture supplémentaire passe à **13 h 48**, avec deux tests requis
+réussis en **37 s** (`build/alpha14-void-final-reload.log`). Elle contrôle
+explicitement la lumière native terminée (`isLightCorrect`) sur les **154
+chunks** et **32 échantillons de biomes hors `the_void`** à l’intérieur des
+extensions. Le bloc d’or et les 129 sections non vides sont toujours conservés.
+Ce dernier rapport est copié hors du monde de test dans
+`build/alpha14-evidence/void-reuse-second-reload.json` pour survivre à son
+nettoyage. Les 32 échantillons ne constituent pas un relevé exhaustif de tous
+les biomes des extensions.
+
+### Vérification finale du build et des artefacts
+
+`./gradlew check build assemblePack` passe en **1 min 34 s** : **40 tâches**, dont
+33 exécutées et 7 à jour. Le journal est `build/alpha14-check-build-pack.log`.
+Les huit tests moteur requis réussissent ; le témoin hydrologique de graine 0
+contrôle **125 chunks FULL**, **5 923 blocs d’eau conservés** et **1 800 ticks de
+fluides**. La même suite vérifie la sérialisation des tailles **512 / 724 /
+1 024**, le défaut Moyen et le codec historique de génération **13**.
+
+Le smoke du journal valide aussi la politique de synchronisation de dossier
+Windows par simulation, ainsi que les échecs de stockage après remplacement.
+Ce résultat ne constitue pas une exécution native sous Windows.
+
+`build/verify-alpha14-artifacts.py` valide les versions alignées, l’index packwiz,
+le JAR de production sans classes de test, son inclusion dans le MRpack et le
+ZIP d’amorçage Prism. Le SHA-256 du JAR `sanctuary-0.1.0-alpha.14.jar` est :
+
+```text
+1c517a13e1151501c6f4974d1bc00faedf67aaecd9bf58f34ac4a655d09dc6ef
+```
+
+Ces vérifications portent sur les artefacts locaux. La publication du canal,
+les installations packwiz isolées et la synchronisation de l’instance Prism
+restent à consigner.
+
+| Contrôle | Preuve attendue | État de livraison |
+| --- | --- | --- |
+| Géométrie et fondations | Déterminisme, budget de colonnes, sites protégés, certificat de roche et ponts | Smoke Gradle réussi sur les sources finales |
+| Rendu des 17 types | Quatre orientations, limites des pièces, parcours vers les étages, lits complets, accès aux sous-sols et piscine contenue | Smoke Gradle réussi sur les sources finales |
+| Placement des expansions | Cinq tailles, tirage stable, huit secteurs, séparation et garde aux coins | Smoke Gradle réussi sur les sources finales |
+| Structures dans Minecraft | Quartier initial et extension Lost City réellement générés, références natives et coffres à butin différé | Réussi, graine 0 : 38 pièces et 5 coffres |
+| Rechargement dans un second processus | Journal et structures identiques, butin non recréé, bloc témoin de joueur conservé | Réussi sur les sources finales, graine 0, processus 19372 |
+| Protection de la maçonnerie | Aucun minerai dans les volumes des bâtiments à partir de leur plancher | Réussi sur les quartiers natifs inspectés, graine 0 |
+| Eau après ticks moteur | Piscine retenue et accès après écoulement, sans fuite extérieure | Réussi sur piscine native isolée : 189 cellules et marches conservées après tick puis réouverture |
+| Certificat de vide | Schéma NBT strict, refus des contenus et preuves de chunks absents | Smoke Gradle réussi, complété par les témoins natifs de création |
+| Reprise du vide | Refus des contenus et preuves invalides ; reprise bornée après réouverture avec preuve intacte | Réussi après deux réouvertures : 154 chunks FULL marqués, bloc d’or conservé |
+| Lumière et biomes après reprise | Lumière native terminée et remplacement du biome vide à l’intérieur des extensions | Réussi à 13 h 48 : 154 chunks éclairés correctement, 32 échantillons hors `the_void`, bloc d’or conservé |
+| Sérialisation et stockage | Trois tailles, codec historique et erreurs de stockage bloquantes | Suite native réussie pour les trois tailles et le codec 13 ; politique Windows simulée réussie |
+| Hydrologie conservée | Eau retenue après écoulement moteur | Réussi : 125 chunks FULL, 5 923 blocs d’eau, 1 800 ticks de fluides |
+| Build et pack | `check build assemblePack` réussi avec versions alignées | Réussi à 13 h 57 min 48 s, huit GameTests requis, JAR/MRpack/ZIP Prism vérifiés |
+| Distribution | Artefacts immuables vérifiés, canal avancé, deux installations isolées et deux synchronisations de la même instance | À exécuter et consigner |
+
+Les reçus devront préciser commit source, graine, diamètre, commandes, journaux,
+résultats et SHA-256 des artefacts ; ne pas remplacer une absence de témoin par
+une affirmation de présence. Aucun essai Windows natif, mesure de FPS ou test
+de charge multijoueur n’est attesté par cette liste. Une validation de géométrie
+en mémoire ne remplace pas la génération, les ticks et la persistance du moteur.
+
+La publication suit [Distribution packwiz et Prism](packwiz.md). Elle conserve
+l’instance existante, ses sauvegardes, ses réglages et les mods tiers.
@@ -19,6 +19,198 @@ Pour générer de vrais chunks et vérifier le spawn sur d'autres graines :
 La propriété ne s'applique qu'au mod de test, jamais au mod distribué ni à une
 sauvegarde de joueur. Chaque commande repart d'un monde de développement neuf.

+## Correctif alpha.13.1 — journal d’expansion sous Windows
+
+Le 9 septembre 2026, le contrôle ciblé suivant passe sur macOS et Java 25 :
+
+```sh
+./gradlew :sanctuary:expansionJournalSmoke --console=plain
+```
+
+Le journal de cette exécution est `build/alpha131-journal-smoke.log` :
+`BUILD SUCCESSFUL`, en 7 secondes. Le test écrit et relit de vrais fichiers
+temporaires ; il n’ouvre aucune sauvegarde Minecraft personnelle.
+
+Les contrôles existants de persistance, de corruption, d’historique immuable
+et de compatibilité des racines restent actifs. Trois scénarios couvrent le
+correctif :
+
+- La politique Windows, sélectionnée par le séparateur `\`, permet la création
+  du journal, une réservation, sa finalisation et leurs rechargements. Le
+  callback de synchronisation du dossier, qui lèverait `AccessDeniedException`,
+  n’est jamais appelé. Les écritures, remplacements atomiques et relectures du
+  fichier ont réellement lieu sur le système de fichiers du Mac.
+- La politique Unix conserve une erreur `AccessDeniedException` injectée après
+  le remplacement atomique. La session devient indisponible, garde son ancien
+  état en mémoire et refuse toute nouvelle écriture. Le journal sur disque
+  contient la réservation ; une nouvelle instance la relit et peut la terminer.
+- Une corruption injectée après le remplacement mais avant la relecture
+  empêche la publication du nouveau plan et conserve le fichier endommagé.
+  Le rechargement refuse ce journal au lieu de créer un historique vide.
+
+**La branche Windows est simulée ; aucun processus Java ou Minecraft Windows
+natif n’a encore été exécuté pour cette validation.**
+
+`check build assemblePack` passe sur les sources alpha.13.1, en 1 min 27 s,
+avec les huit GameTests du monde Moyen de graine 0. Les scénarios d’expansion
+passent ensuite dans deux processus Minecraft distincts, sur la graine 42 et
+le diamètre 724 : création (1 min 32 s), puis réouverture et nouvelle expansion
+(26 s). Deux tests requis passent à chaque étape. Commandes de reproduction :
+
+```sh
+./gradlew check build assemblePack -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryExpansionTests=true -PsanctuaryOptionalStructureWitness=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+./gradlew :sanctuary:runGameTest -PsanctuaryExpansionTests=true -PsanctuaryExpansionReload=true -PsanctuaryOptionalStructureWitness=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false --console=plain
+```
+
+Lancer les deux scénarios d’expansion consécutivement ; le second réutilise
+uniquement leur monde de développement. Comme pour l’alpha.13, le témoin de
+camp naturel est facultatif et absent après recherche complète sur cette
+graine ; aucune nouvelle preuve de structure n’est revendiquée.
+Les [résultats alpha.13.1](benchmarks/alpha131-journal.json) conservent les
+hashes des journaux de test, les identifiants des deux processus et les régions.
+La comparaison des JAR confirme que seuls le journal, sa classe de stratégie
+et la version changent ; le switch synthétique ne change que ses numéros de
+lignes. Toutes les autres classes et ressources restent identiques.
+Les résultats des trois tailles et de l’interface ci-dessous restent ceux de
+la livraison alpha.13 ; ils n’ont pas été réexécutés pour ce correctif de stockage.
+
+La cause est établie par les sources de
+[WindowsChannelFactory dans OpenJDK 25](https://github.com/openjdk/jdk/blob/jdk-25-ga/src/java.base/windows/classes/sun/nio/fs/WindowsChannelFactory.java#L206-L272) :
+`FileChannel.open` n’ajoute pas le drapeau `FILE_FLAG_BACKUP_SEMANTICS`, exigé
+pour ouvrir un répertoire selon la
+[documentation Microsoft de CreateFile](https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilew#directories).
+Seule cette synchronisation du dossier est omise sous Windows ; les exceptions
+d’écriture, de remplacement ou de relecture restent bloquantes.
+
+Le fichier temporaire est toujours synchronisé par `force(true)`, puis remplacé
+atomiquement et vérifié. Cette séquence ne garantit pas sous Windows la même
+durabilité du renommage en cas de coupure secteur qu’une synchronisation du
+répertoire sous Unix :
+[OpenJDK utilise MoveFileEx sans WRITE_THROUGH](https://github.com/openjdk/jdk/blob/jdk-25-ga/src/java.base/windows/classes/sun/nio/fs/WindowsFileCopy.java#L279-L294),
+et le contrat de
+[FileChannel.force](https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/nio/channels/FileChannel.html#force(boolean))
+porte sur les modifications du fichier. Aucun changement de format, de graine,
+de générateur ou de réservation enregistrée n’est introduit.
+
+## Alpha.13 — génération unifiée
+
+`check build assemblePack` passe, y compris le monde Moyen de graine 0 et les
+smokes. Les preuves exportées, journaux, paramètres, mesures et hashes figurent
+dans [le rapport alpha.13](benchmarks/alpha13-worldgen.json).
+
+Le test courant charge `sanctuary:sanctuary`, puis règle son vrai générateur
+`sanctuary:island_v13` comme le fait la personnalisation. Les suites historiques
+restent accessibles avec `-PsanctuaryUnifiedTests=false`.
+
+Les trois tailles passent les huit tests moteur sur la graine **42**, avec
+1 800 ticks de fluides. Chaque inspection des cavités utilise au plus 27 chunks
+FULL, choisis sur des sols et plafonds naturels ; les contrôles d’hydrologie
+emploient un autre échantillon borné. Ces volumes ne sont pas un inventaire de
+l’île et ne mesurent pas le rendu du client.
+
+| Taille | Chunks FULL du diagnostic d’eau | Blocs d’eau retenus après 1 800 ticks | Pilier de spéléothèmes dans l’air naturel |
+| --- | ---: | ---: | ---: |
+| Petit, 512 | 116 | 4 722 | 25 blocs |
+| Moyen, 724 | 80 | 1 196 | 18 blocs |
+| Grand, 1 024 | 136 | 1 434 | 18 blocs |
+
+Les trois cavités natives sont réellement décorées dans chacun de ces mondes :
+mousse et lianes récoltables pour le luxuriant, pointes et piliers pour les
+spéléothèmes, roche soufrée et pointes pour le soufre. Musiques, brouillard et
+table du `sulfur_cube` restent ceux des biomes Minecraft. La graine 0 présente
+seulement du luxuriant dans le raster naturel inspecté ; elle ne justifie pas
+de forcer les deux autres biomes dans la roche. Une livraison exige les preuves
+cumulées des trois types, pas leur présence sur toute graine.
+
+Le garde-fou est exercé par une vraie écriture `WorldGenRegion` : eau, lit,
+parois naturelles, sources et sorties sont protégés. Quatre témoins de berge
+appartiennent à un chunk voisin de leur cellule d’eau. Une écriture hors volume
+reste possible. Le test utilise une vue modifiable de chunk dédiée, car les
+holders FULL exposent normalement une vue de génération en lecture seule.
+Les blocs témoins temporaires sont restaurés dans le monde de développement.
+
+L’essai client ouvre le bouton natif **Personnaliser**, parcourt les trois
+tailles et vérifie Terminé, Annuler, Échap, réouverture et rafraîchissement des
+réglages. L’écriture/relecture réelle des paramètres conserve la taille, la
+graine, les options, le Nether et l’End. Les anciens générateurs ne deviennent
+pas personnalisables par erreur ; l’éditeur Superflat vanilla reste disponible.
+Une capture confirme la lisibilité de l’écran. Cet essai ne constitue pas une
+visite graphique de l’île.
+
+```sh
+./gradlew :sanctuary:runGameTest -PsanctuaryTestDiameter=512 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryTestDiameter=1024 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runClientGameTest -PsanctuaryClientTests=true
+```
+
+Les diagnostics détaillés restent dans le dossier ignoré
+`mods/sanctuary/build/run/gameTest/diagnostics/unified-<diamètre>-seed-<graine>-*.json`.
+Les anciennes mesures alpha.11 ci-dessous ne sont pas des mesures alpha.13.
+
+### Mesure alpha.13 de Moyen
+
+Sur le Mac M1 à 8 Go, Java 25.0.3 et heap de 2 Gio, graine 0, un seul processus
+de jeu actif : la création initiale prend **17,65 s**, puis 289 chunks FULL autour
+du spawn **46,01 s**, soit **63,66 s** cumulées. Le couloir suivant de 80 chunks
+FULL prend **7,82 s**. Le maximum observé pour une requête de chunk est de 1,30 s
+autour du spawn et de 0,79 s dans ce couloir.
+
+Le protocole conserve les anneaux 17 × 17 et le couloir est de l’alpha.11.
+L’ancien Grand et le nouveau Moyen ont le même diamètre nominal de 724 blocs,
+mais la décoration et le spawn peuvent différer : ce n’est pas une mesure
+d’équivalence de génération. Le résultat de départ reste proche des 62,67 s
+mesurées pour l’alpha.11. Un seul passage par version, sans mesure du GPU,
+des FPS, du réseau, de la disponibilité des chunks pour les ticks ou d’une
+charge multijoueur. Grand n’a pas de benchmark complet 289 + 80 dans cette
+livraison ; ses tests moteur ci-dessus ont une autre charge de travail.
+
+```sh
+./gradlew :sanctuary:runGameTest -PsanctuaryBenchmark=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=0 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+```
+
+Rapport local : `diagnostics/generation-performance-unified-724-seed-0.json`,
+log `build/alpha13-benchmark-medium.log`.
+
+### Expansions et rechargement alpha.13
+
+Sur le monde unifié Moyen de graine 42, les deux processus réussissent :
+refus des huit premiers sites occupés, tropicale plus loin au nord, branche
+aride à au moins 2 048 blocs de son parent, relecture du journal et des blocs
+témoins, puis nouvelle expansion après redémarrage. Les colonnes de terrain
+et les biomes enregistrés restent identiques après décodage du générateur.
+Le framework reconstruit les paramètres actifs depuis le preset ; le test
+vérifie séparément le codec sauvegardé et les fichiers réellement rechargés.
+
+Aucun camp admissible n’a été observé sur l’origine unifiée des graines 42 et
+8 675 309 : les fondations naturelles ou la protection hydrologique écartent
+les candidats. Les essais stricts y échouent donc sur la preuve de structure.
+La paire unifiée validée utilise explicitement un témoin de structure
+facultatif, seulement après inspection complète des candidats. Ses rapports
+indiquent `native_structure_observed=false` et ne constituent aucune preuve
+positive de placement ou de butin dans l’origine alpha.13. Les critères de
+fondation et la génération ne sont pas assouplis pour faire passer un test.
+
+Exécuter les deux commandes sans lancer un autre GameTest entre elles :
+
+```sh
+./gradlew :sanctuary:runGameTest -PsanctuaryExpansionTests=true -PsanctuaryOptionalStructureWitness=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryExpansionTests=true -PsanctuaryExpansionReload=true -PsanctuaryOptionalStructureWitness=true -PsanctuaryTestDiameter=724 -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+```
+
+Sans ce drapeau explicite, le scénario exige toujours une vraie structure avec
+son conteneur et sa table de butin native. La réouverture vérifie toujours ces
+trois éléments lorsqu’ils ont été observés dans le premier processus.
+
+La paire historique, rejouée avec le binaire alpha.13, réussit sur la graine
+42 sans rendre le témoin facultatif : camp abandonné de forêt, bloc du
+conteneur et table de butin native retrouvés après redémarrage. Cela valide
+la chaîne génération 12 conservée ; ce résultat ne vaut pas comme preuve
+d’un camp dans l’origine unifiée. Le smoke du journal teste aussi une origine
+13 de diamètre 1 024 avec un enfant 12, le schéma 1 et le refus d’une lecture
+avec une autre génération ou taille, sans modifier les octets enregistrés.
+
 ## Correctif alpha.12.1 — tous les premiers emplacements occupés

 Le scénario laboratoire utilise les mêmes commandes Gradle ci-dessous. Il
@@ -52,8 +244,8 @@ Le laboratoire possède un scénario moteur distinct, à lancer puis à rouvrir
 **dans cet ordre**, sans autre GameTest entre les deux :

 ```sh
-./gradlew :sanctuary:runGameTest -PsanctuaryExpansionTests=true -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
-./gradlew :sanctuary:runGameTest -PsanctuaryExpansionTests=true -PsanctuaryExpansionReload=true -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryUnifiedTests=false -PsanctuaryExpansionTests=true -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
+./gradlew :sanctuary:runGameTest -PsanctuaryUnifiedTests=false -PsanctuaryExpansionTests=true -PsanctuaryExpansionReload=true -PsanctuaryTestSeed=42 -PsanctuaryResourceSurvey=off -PsanctuaryDensityMaps=false
 ```

 Le premier passage crée le monde jetable. Le second saute volontairement
@@ -28,6 +28,11 @@ Le premier incrément porte sur le socle Fabric et la génération du monde : re

 La progression, l'économie, les nouveaux monstres, les interfaces de pack et les autres dimensions restent des intentions futures. Ils ne constituent pas des dépendances du premier générateur. Le [backlog](backlog.md) précise les premiers tickets et leurs critères d'acceptation.

+L’alpha se poursuit vers les versions 15 ou 16 pour éprouver la génération et
+ses structures. La bêta véritable commencera ensuite les systèmes de Sanctuary,
+en particulier la progression. Ce cap décrit un ordre de travail : une version
+n’est pas considérée terminée avant ses essais et sa livraison.
+
 ## Mod, modpack et modules autonomes

 | Ensemble | Rôle souhaité |
@@ -50,19 +55,19 @@ Les intégrations communautaires envisagées comprennent Fabric API, Sodium, Iri

 L'île de Sanctuary est le point de départ commun. Elle flotte dans un vide qui ne doit pas être rempli par la génération habituelle du monde. Les continents suivants sont de vastes terres suspendues, créées progressivement selon une taille et une direction maîtrisées.

-Le choix de taille initiale se limite à **Petit** et **Grand**, avec Grand
-par défaut. Petit prend une référence de 512 blocs de diamètre ; Grand vise
-environ 724 blocs, soit deux fois son aire nominale, sur une hauteur de
-384 blocs. Les repères internes 5/10 ne constituent ni les noms affichés ni
-une promesse de capacité multijoueur. Ce resserrement des tailles doit limiter
-les distances entre constructions.
+Le monde doit se créer par un seul choix **Sanctuary**, avec le bouton natif
+**Personnaliser** pour régler sa taille : **Petit** (512 blocs de diamètre
+nominal), **Moyen** (724, par défaut) et **Grand** (1 024). La hauteur reste de
+384 blocs. Ces dimensions ne promettent ni une aire entièrement habitable,
+ni un stock de ressources, ni une capacité multijoueur.

-L’alpha.11 implémente ces deux choix et l’optimisation des chargements. Les
-anciens formats 20/100 sont masqués à la création mais restent chargeables
-avec leurs paramètres enregistrés ; aucune sauvegarde n’est réduite.
-Les mesures serveur et leurs limites sont consignées dans [Validation](testing.md).
-Ce dimensionnement ne remplace pas l’expansion collective ni ne garantit
-une aire habitable ou un stock de ressources par joueur.
+L’alpha.13 implémente cette interface et la réunion de l’île complète de Population,
+de ses forêts et de son hydrologie, avec les cavités natives du laboratoire.
+L’alpha.11 et ses anciens choix Petit/Grand restent historiques. Les anciens
+codecs et paramètres sauvegardés restent chargeables ; les choix précédents
+sont cachés à la création et aucune partie n’est convertie ou redimensionnée.
+L’état d’intégration est décrit dans le [guide alpha.13](alpha13-worldgen.md) ;
+les observations réelles et leurs limites restent dans [Validation](testing.md).

 L'île initiale doit être **tempérée et légèrement humide**, avec quelques zones
 plus sèches, notamment de larges plages et dépôts irréguliers de sable, gravier,
@@ -143,12 +148,14 @@ parent ; le serveur conserve ainsi l’histoire des découvertes de son univers.
 La recherche porte sur des climats et leurs distributions, sans imposer la même
 forme ni le même climat à une direction pour toutes les parties.

-L’alpha.12 sert de laboratoire à cette conception : commandes opérateur pour
-créer et visiter les continents, reliefs hauts aussi expérimentés sur Sanctuary
-Island et structures vanilla compatibles. Ces essais sont réservés à une nouvelle
-génération. Les recherches, mailboxes et deposit boxes viendront ensuite ; elles
-ne sont pas nécessaires aux commandes d’essai. Le passage en bêta interviendra
-après clarification du périmètre de la vision et de la progression à développer.
+Les alpha.12 et alpha.12.1 ont fourni un laboratoire à cette conception :
+commandes opérateur, climats et reliefs indépendants, structures vanilla
+compatibles et recherche d’emplacements libres. L’alpha.13 reprend ces mêmes
+outils dans le nouveau monde Sanctuary unifié. Son journal est séparé de celui
+des anciens laboratoires, sans conversion de leur génération.
+Les recherches, mailboxes et deposit boxes viendront ensuite ; elles ne sont
+pas nécessaires aux commandes d’essai. Le passage en bêta dépendra du périmètre
+de progression retenu et de sa validation, pas du seul changement de générateur.

 L'économie naturelle d'une île doit être connue **après sa génération** : nombre
 de blocs de pierre, bûches, minerais de charbon, de fer et autres ressources,
@@ -168,8 +175,28 @@ L'ambition est de reprendre puis d'étendre la centaine de biomes du catalogue T
  biome, leur emprise et leurs fondations conviennent au terrain flottant.
  L’autorisation ne garantit pas leur présence sur chaque île. Le laboratoire
  commence par les villages, temples, cabanes de marais et camps abandonnés.
- **Lost Cities** : des zones traitées comme des biomes, où des bâtiments en ruine remplacent la végétation dominante. Le nom exprime ici un type de territoire souhaité, sans décider encore s'il sera produit par une intégration ou par du code Sanctuary.
- **Structures contemporaines** : parcs, parkings et autres vestiges. Les parkings sont souterrains et peuvent s'étendre comme une infestation. Ils n'apparaissent pas dans la dimension des cavernes.
+- **Lost City** : des quartiers traités comme un biome, où les bâtiments
+  contemporains en ruine prennent la place principale. L’alpha.14 développe une
+  réalisation originale Sanctuary, inspirée du principe de ville abandonnée,
+  sans ajouter le mod The Lost Cities ni reprendre ses assets. Des poches sont
+  souhaitées sur l’île de départ et dans les continents d’expansion, en laissant
+  une majorité naturelle à l’île initiale. La pierre, la pierre lisse et les
+  briques de pierre, notamment fissurées et moussues, donnent une palette sobre.
+- **Vie urbaine passée** : routes, ponts, places, marchés, appartements,
+  bibliothèques, restaurants et cuisines abandonnées, hôtels et chambres,
+  casernes, halls, excavations et piscines. Les parcs comprennent boisements,
+  jardins à haies et fleurs, aires de jeux et mémoriaux. Chaque usage doit se
+  reconnaître dans les volumes et les aménagements, avec entrées et circulations.
+- **Parkings et sous-sols** : creuser seulement là où l’épaisseur de roche
+  permet un volume soutenu ; un garage en surface reste possible ailleurs.
+  Les excavations ouvertes et les piscines doivent aussi garder des fondations,
+  des accès et, pour l’eau, un bassin contenu. Les parkings ne font pas partie
+  de la future dimension des cavernes. À terme, ils pourront former des réseaux
+  souterrains étendus ; cette connexion entre parkings reste à construire.
+- **Occupants de Lost City** : des zombies plutôt que des villageois, sans
+  spawner. L’alpha utilise le spawn naturel des zombies vanilla ; les infectés,
+  spitters, boomers, hunters, chargeurs et autres classes arrivent avec les
+  systèmes de la bêta. La présence de zombies dépend des règles du jeu.
 - **Structures uniques et donjons** : d'abord sur Sanctuary Island, puis dans les continents. Ils peuvent contenir des clés de chunk et d'autres ressources rares.
 - **Secret rooms et challenge rooms** : des accès présents dans le monde mènent à des indoors aménagés, avec des équipements, des épreuves ou des gisements de fer, d'or, d'argent ou de titane.

@@ -1,74 +1,80 @@
 # Premier monde Sanctuary

-Le preset `sanctuary:sanctuary` crée l'île principale à l'origine de l'Overworld,
-entourée de vide sans répétition d'îles à grande distance. C'est une première
-tranche de génération pour Minecraft **26.3-pre-2 / Fabric**, pas encore le
-système d'expansion collective.
+## Alpha.13 — génération unifiée

-L’alpha.11 propose deux choix de création, **Petit** et **Grand**, avec Grand
-par défaut. Les anciennes tailles 20/100 restent chargeables dans les sauvegardes.
-Les observations de chaque version restent dans [Validation](testing.md).
+Le choix public **Sanctuary** (`sanctuary:sanctuary`) crée l’île principale à
+l’origine de l’Overworld, entourée de vide. Son bouton natif **Personnaliser**
+propose **Petit** (512 blocs de diamètre nominal), **Moyen** (724, par défaut)
+et **Grand** (1 024). Les types vanilla restent disponibles. La hauteur reste
+de 384 blocs ; les dimensions nominales ne donnent ni aire habitable garantie
+ni capacité multijoueur.

-## Laboratoire d’expansion — alpha.12
+L’île initiale reprend la densité, les forêts et l’hydrologie complète de la
+famille Population, avec les poches de biomes souterrains natives du laboratoire.
+Les extensions conservent leurs profils climatiques et leurs commandes
+alpha.12.1. Leurs règles de génération restent distinctes de celles de l’île
+initiale : la grande hydrologie de départ n’est pas automatiquement reproduite
+sur chaque continent ajouté.

-Un troisième choix, **Sanctuary — Laboratoire** (`sanctuary:expansion_lab`),
-crée une origine de 512 blocs avec un relief supérieur expérimental. Les commandes
-opérateur peuvent ensuite ouvrir des régions de 64/128/256/512 blocs, avec
-parent, direction, climat et relief indépendants. Chaque région enregistre sa
-graine et sa génération 12 dans un journal serveur propre au monde.
+Les trois tailles et les cavités passent les contrôles moteur. Le [guide alpha.13](alpha13-worldgen.md)
+décrit l’interface, les paramètres sauvegardés et les outils d’expansion ;
+[Validation](testing.md) conserve la portée des essais de chaque version.

-Ce générateur distinct utilise la densité flottante comme base et les biomes,
-matériaux, décorations et structures compatibles de Minecraft. Il ne reprend
-pas encore les grandes rivières et terrasses alpha.11. Petit, Grand et les
-sauvegardes historiques conservent leurs réglages. Créer un nouveau monde pour
-le laboratoire ; aucune migration ou commande de régénération n’est fournie.
-Le [guide alpha.12](alpha12-laboratory.md) décrit les outils, les limites et les
-observations réelles. Les sections historiques ci-dessous gardent leur portée.
+## Créer un nouveau monde

-## Petit et Grand — alpha.11
+En solo, choisir **Sanctuary**, ouvrir **Personnaliser**, puis confirmer la
+taille avec **Terminé**. **Annuler** conserve le réglage précédent. Cette
+interface configure le monde à créer ; elle ne redimensionne pas une partie.

-| Choix public | Diamètre nominal | Aire nominale relative | Preset | Réglage enregistré |
-| --- | --- | --- | --- | --- |
-| Petit | 512 blocs | 1 | `sanctuary:sanctuary_5` | `sanctuary:population_5` |
-| Grand, défaut | Environ 724 blocs | 2 | `sanctuary:sanctuary` | `sanctuary:population_10` |
-
-La hauteur reste de 384 blocs. Les repères internes 5/10 décrivent le calcul
-de surface ; ils ne sont ni des noms affichés ni une capacité promise.
-Le relief réel garde ses trous, ses surplombs et sa bordure sculptée.
-
-Le nouveau Grand reçoit sa propre clé `population_10`. Les anciens mondes
-`population_5`, `population_20` et `population_100` restent chargeables avec
-leurs paramètres ; les formats 20/100 sont cachés dans les choix publics.
-Changer la valeur du preset de création n’agrandit ni ne réduit une sauvegarde.
-Les générations antérieures restent distinctes, dont `sanctuary_cavern` et
-`sanctuary_rift`.
-
-L’optimisation réutilise les coins d’interpolation avec la même arithmétique
-et borne ce cache à 192 Kio par thread, sans retenir fortement un monde.
-Les plans prêts restent accessibles pendant le calcul d’une autre région ;
-le sampler compilé est réutilisé dans ce calcul. Les contrôles d’équivalence,
-de persistance et les mesures à géométrie identique sont dans [Validation](testing.md).
-Les règles de forme, d’hydrologie et les anciens réglages restent inchangés.
-
-## Créer un monde
-
-La création solo propose **Sanctuary (Petit)** et **Sanctuary (Grand)**,
-ce dernier étant le défaut Sanctuary.
-Les types de monde vanilla restent disponibles.
-
-Sur un nouveau serveur Fabric disposant de cette version et de Fabric API,
-le choix Grand utilise :
+Sur un nouveau serveur Fabric avec Fabric API, le preset public utilise la
+taille **Moyen**, 724 blocs :

 ```properties
 level-type=sanctuary:sanctuary
-level-name=sanctuary
+level-name=sanctuary-dev
 level-seed=0
 ```

-Pour Petit, utiliser `level-type=sanctuary:sanctuary_5`. Choisir un nouveau
-`level-name` pour tester l’autre taille. La seed est libre ; ces exemples ne
-convertissent aucun monde déjà enregistré et n’autorisent aucune régénération.
-Les fichiers de test et les sauvegardes personnelles restent distincts.
+La graine est libre. Utiliser un dossier neuf pour un essai ; modifier
+`level-type` ne convertit aucun monde enregistré. Aucune commande de migration
+ou de régénération des anciennes îles n’est fournie.
+
+## Compatibilité et versions historiques
+
+L’alpha.13 enregistre le générateur `sanctuary:island_v13`, son diamètre initial
+et une racine de génération 13. Les nouvelles expansions restent de génération
+12. Leur journal utilise le dossier propre au monde
+`data/sanctuary-world-v13/`. Les anciens codecs et presets sont conservés, mais
+cachés de la sélection publique. Les mondes déjà créés conservent leurs réglages
+et leur journal ; aucun chunk n’est remplacé par cette mise à jour.
+
+### Alpha.12 et alpha.12.1 — laboratoire historique
+
+Le preset distinct `sanctuary:expansion_lab` proposait une origine de 512 blocs
+et des commandes opérateur pour ajouter des îles de 64/128/256/512 blocs.
+Son relief expérimental et ses biomes natifs ne reprenaient pas les grandes
+rivières et terrasses de Population. L’alpha.12.1 ajoutait une distance
+facultative et la recherche d’un emplacement libre au-delà des chunks occupés.
+
+Ces mondes gardent leur génération 12 et leur dossier
+`data/sanctuary-expansion-v1/`. Le [guide du laboratoire](alpha12-laboratory.md)
+reste la référence historique de ces versions, avec leurs seules observations.
+
+### Alpha.11 — Petit et Grand historiques
+
+| Ancien choix public | Diamètre nominal | Ancien preset | Réglage enregistré |
+| --- | --- | --- | --- |
+| Petit | 512 blocs | `sanctuary:sanctuary_5` | `sanctuary:population_5` |
+| Grand, ancien défaut | Environ 724 blocs | `sanctuary:sanctuary` | `sanctuary:population_10` |
+
+L’ancien Grand correspond à la taille nominale du nouveau Moyen. Les mondes
+historiques `population_5`, `population_10`, `population_20` et `population_100`
+restent chargeables avec leurs dimensions. Le preset public est une recette
+de création ; sa nouvelle définition ne remplace pas leur générateur sauvegardé.
+
+L’optimisation alpha.11 conserve l’arithmétique de l’interpolation et les règles
+de terrain et d’hydrologie. Ses mesures et contrôles sont historiques, sans
+validation anticipée des ajouts de l’alpha.13.

 ## Socle de génération conservé

@@ -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.12.1
-pack_version=0.1.0-alpha.12.1
+mod_version=0.1.0-alpha.14
+pack_version=0.1.0-alpha.14
 maven_group=fr.koka.sanctuary
@@ -37,18 +37,30 @@ tasks.named('runGameTest') {
    systemProperty('sanctuary.test.players', providers.gradleProperty('sanctuaryTestPlayers').getOrElse('10'))
    systemProperty('sanctuary.test.resourceSurvey', providers.gradleProperty('sanctuaryResourceSurvey').getOrElse('sample'))
    systemProperty('sanctuary.test.densityMaps', providers.gradleProperty('sanctuaryDensityMaps').getOrElse('true'))
+    systemProperty('sanctuary.test.unified', providers.gradleProperty('sanctuaryUnifiedTests').getOrElse('true'))
+    systemProperty('sanctuary.test.diameter', providers.gradleProperty('sanctuaryTestDiameter').getOrElse('724'))
    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.voidReuse', providers.gradleProperty('sanctuaryVoidReuseTests').getOrElse('false'))
+    systemProperty('sanctuary.test.optionalStructureWitness', providers.gradleProperty('sanctuaryOptionalStructureWitness').getOrElse('false'))
 }

 tasks.named('processGametestResources') {
    def benchmark = providers.gradleProperty('sanctuaryBenchmark').map { it.toBoolean() }.getOrElse(false)
    inputs.property('benchmark', benchmark)
+    def unified = providers.gradleProperty('sanctuaryUnifiedTests').map { it.toBoolean() }.getOrElse(true)
+    inputs.property('unified', unified)
    def expansion = providers.gradleProperty('sanctuaryExpansionTests').map { it.toBoolean() }.getOrElse(false)
    inputs.property('expansion', expansion)
+    def lostCity = providers.gradleProperty('sanctuaryLostCityTests').map { it.toBoolean() }.getOrElse(false)
+    inputs.property('lostCity', lostCity)
+    def voidReuse = providers.gradleProperty('sanctuaryVoidReuseTests').map { it.toBoolean() }.getOrElse(false)
+    inputs.property('voidReuse', voidReuse)
    filesMatching('fabric.mod.json') {
-        expand(gametest_entrypoint: expansion ? 'fr.koka.sanctuary.gametest.ExpansionWorldGameTests' : benchmark
+        expand(gametest_entrypoint: voidReuse ? 'fr.koka.sanctuary.gametest.ExpansionVoidReuseGameTests' : 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')
    }
 }
@@ -268,3 +280,36 @@ tasks.register('expansionPlacementSmoke', JavaExec) {
    mainClass = 'fr.koka.sanctuary.expansion.ExpansionPlacementSmoke'
 }
 tasks.named('check') { dependsOn('expansionPlacementSmoke') }
+
+// Alpha.14 planner uses bounded natural support and never queries loaded chunks.
+tasks.register('lostCityPlannerSmoke', JavaExec) {
+    group = 'verification'
+    dependsOn('testClasses')
+    classpath = sourceSets.test.runtimeClasspath
+    mainClass = 'fr.koka.sanctuary.worldgen.city.LostCityPlannerSmoke'
+}
+tasks.named('check') { dependsOn('lostCityPlannerSmoke') }
+
+tasks.register('lostCityRendererSmoke', JavaExec) {
+    group = 'verification'
+    dependsOn('testClasses')
+    classpath = sourceSets.test.runtimeClasspath
+    mainClass = 'fr.koka.sanctuary.worldgen.city.LostCityRendererSmoke'
+}
+tasks.named('check') { dependsOn('lostCityRendererSmoke') }
+
+tasks.register('expansionSpatial14Smoke', JavaExec) {
+    group = 'verification'
+    dependsOn('testClasses')
+    classpath = sourceSets.test.runtimeClasspath
+    mainClass = 'fr.koka.sanctuary.expansion.ExpansionSpatialPlacement14Smoke'
+}
+tasks.named('check') { dependsOn('expansionSpatial14Smoke') }
+
+tasks.register('expansionVoidCertificateSmoke', JavaExec) {
+    group = 'verification'
+    dependsOn('testClasses')
+    classpath = sourceSets.test.runtimeClasspath
+    mainClass = 'fr.koka.sanctuary.expansion.ExpansionVoidCertificateSmoke'
+}
+tasks.named('check') { dependsOn('expansionVoidCertificateSmoke') }
@@ -16,6 +16,7 @@ public final class SanctuaryClientRenderTests implements FabricClientGameTest {
                    "net.minecraft.client.renderer.fog.FogRenderer", "sanctuary$openVoidFog");
            SanctuaryMod.LOGGER.info("Client render tests passed: Sanctuary sky and fog mixins applied.");
        });
+        SanctuaryWorldOptionsClientChecks.run(context);
    }

    private static void assertApplied(ClassLoader loader, String target, String hook) {
@@ -0,0 +1,179 @@
+package fr.koka.sanctuary.gametest;
+
+import com.google.gson.GsonBuilder;
+import com.mojang.blaze3d.platform.InputConstants;
+import com.mojang.serialization.JsonOps;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.client.SanctuaryWorldOptionsScreen;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import net.fabricmc.fabric.api.client.gametest.v1.context.ClientGameTestContext;
+import net.minecraft.client.gui.components.CycleButton;
+import net.minecraft.client.gui.components.tabs.TabNavigationBar;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.client.gui.screens.worldselection.CreateWorldScreen;
+import net.minecraft.client.gui.screens.worldselection.WorldCreationUiState;
+import net.minecraft.client.input.KeyEvent;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.WorldGenSettings;
+import net.minecraft.world.level.storage.LevelStorageSource;
+
+/** The real new-world button path and saved settings, without starting or opening a game world. */
+final class SanctuaryWorldOptionsClientChecks {
+    private static final KeyEvent PRESS = new KeyEvent(InputConstants.KEY_RETURN, 0, 0);
+
+    static void run(ClientGameTestContext context) {
+        Screen previous = context.computeOnClient(client -> client.gui.screen());
+        context.runOnClient(client -> CreateWorldScreen.openFresh(client, () -> client.gui.setScreen(previous)));
+        context.waitFor(client -> client.gui.screen() instanceof CreateWorldScreen, 1200);
+        CreateWorldScreen create = context.computeOnClient(client -> (CreateWorldScreen) client.gui.screen());
+        List<Map<String, Object>> savedSizes = new ArrayList<>();
+        try {
+            context.runOnClient(client -> {
+                TabNavigationBar tabs = create.children().stream().filter(TabNavigationBar.class::isInstance)
+                        .map(TabNavigationBar.class::cast).findFirst().orElseThrow();
+                tabs.selectTab(1, false); // The vanilla World tab owns the world type and Customize widgets.
+                var state = create.getUiState();
+                long sanctuaryChoices = state.getNormalPresetList().stream().filter(entry -> entry.preset() != null
+                        && entry.preset().getRegisteredName().startsWith("sanctuary:")).count();
+                require(sanctuaryChoices == 1, "Exactly one public Sanctuary choice must remain");
+                require(state.getAltPresetList().stream().filter(entry -> entry.preset() != null
+                                && entry.preset().getRegisteredName().startsWith("sanctuary:")).count() == 1,
+                        "The extended world-type cycle must not expose the old laboratory or sizes");
+                CycleButton<?> worldType = create.children().stream().filter(CycleButton.class::isInstance)
+                        .map(CycleButton.class::cast)
+                        .filter(button -> button.getValue() instanceof WorldCreationUiState.WorldTypeEntry)
+                        .findFirst().orElseThrow();
+                int attempts = state.getNormalPresetList().size();
+                while (!isSanctuary(state) && attempts-- > 0) worldType.onPress(PRESS);
+                require(isSanctuary(state), "The real world-type cycle must reach Sanctuary");
+                require(diameter(create) == 724, "Sanctuary defaults to Medium");
+                state.setSeed("42");
+                state.setGenerateStructures(false);
+                state.setBonusChest(true);
+            });
+
+            // Cancel and Escape both leave the pending generator untouched.
+            context.clickScreenButton("selectWorld.customizeType");
+            context.waitForScreen(SanctuaryWorldOptionsScreen.class);
+            context.runOnClient(client -> chooseSize(client.gui.screen(), "LARGE"));
+            context.clickScreenButton("gui.cancel");
+            context.runOnClient(client -> require(diameter(create) == 724, "Cancel must not apply Large"));
+            context.clickScreenButton("selectWorld.customizeType");
+            context.runOnClient(client -> {
+                chooseSize(client.gui.screen(), "SMALL");
+                client.gui.screen().keyPressed(new KeyEvent(InputConstants.KEY_ESCAPE, 0, 0));
+                require(client.gui.screen() == create && diameter(create) == 724,
+                        "Escape must return to creation without applying Small");
+            });
+
+            Path diagnostics = Path.of("diagnostics").toAbsolutePath();
+            Files.createDirectories(diagnostics);
+            Path testRoot = Files.createTempDirectory(diagnostics, "world-options-settings-");
+            var storage = LevelStorageSource.createDefault(testRoot);
+            for (var size : Map.of("SMALL", 512, "MEDIUM", 724, "LARGE", 1024).entrySet()) {
+                var before = context.computeOnClient(client -> create.getUiState().getSettings());
+                context.clickScreenButton("selectWorld.customizeType");
+                context.waitForScreen(SanctuaryWorldOptionsScreen.class);
+                context.runOnClient(client -> chooseSize(client.gui.screen(), size.getKey()));
+                context.clickScreenButton("gui.done");
+                context.runOnClient(client -> {
+                    require(client.gui.screen() == create && diameter(create) == size.getValue(),
+                            "Done must apply the chosen diameter and return to creation");
+                    var after = create.getUiState().getSettings();
+                    require(after.options().equals(before.options()), "Size must preserve seed, structures and bonus chest");
+                    for (var dimension : List.of(LevelStem.NETHER, LevelStem.END)) {
+                        require(after.selectedDimensions().get(dimension).equals(before.selectedDimensions().get(dimension)),
+                                "Size must preserve other dimensions");
+                    }
+                    require(isSanctuary(create.getUiState()), "Customization must keep the single Sanctuary world type");
+                    create.getUiState().setSettings(after.withOptions(options -> options));
+                    require(diameter(create) == size.getValue(),
+                            "Refreshing world settings must preserve the custom size instead of restoring the preset default");
+                    String name = size.getKey().toLowerCase(java.util.Locale.ROOT);
+                    var settings = new WorldGenSettings(after.options(), after.selectedDimensions());
+                    try (var save = storage.createAccess(name)) {
+                        LevelStorageSource.writeWorldGenSettings(after.worldgenLoadContext(), storage.getLevelPath(name), settings);
+                        var restored = LevelStorageSource.readExistingSavedData(save, after.worldgenLoadContext(),
+                                WorldGenSettings.TYPE).getOrThrow();
+                        require(restored.dimensions().overworld() instanceof SanctuaryChunkGenerator generator
+                                && generator.initialDiameter() == size.getValue(), "Selected size must survive actual settings storage");
+                        var ops = RegistryOps.create(JsonOps.INSTANCE, after.worldgenLoadContext());
+                        require(WorldGenSettings.CODEC.encodeStart(ops, restored).getOrThrow()
+                                        .equals(WorldGenSettings.CODEC.encodeStart(ops, settings).getOrThrow()),
+                                "Stored options and dimensions must remain unchanged");
+                        savedSizes.add(Map.of("size", name, "diameter", size.getValue(), "disk_round_trip", true));
+                    }
+                });
+                context.clickScreenButton("selectWorld.customizeType");
+                context.runOnClient(client -> require(sizeButton(client.gui.screen()).getValue().toString().equals(size.getKey()),
+                        "Reopening Customize must restore the saved selection"));
+                if (size.getKey().equals("MEDIUM")) context.takeScreenshot("sanctuary-world-options-medium");
+                context.clickScreenButton("gui.cancel");
+            }
+
+            context.runOnClient(client -> {
+                var state = create.getUiState();
+                var settings = state.getSettings();
+                var presets = settings.worldgenLoadContext().lookupOrThrow(Registries.WORLD_PRESET);
+                var legacy = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("sanctuary_5")))
+                        .value().createWorldDimensions().overworld();
+                state.updateDimensions((registries, dimensions) -> dimensions.replaceOverworldGenerator(registries, legacy));
+                require(state.getPresetEditor() == null,
+                        "A legacy generator under the public key must not gain an implicit conversion editor");
+                state.setSettings(settings);
+                var flat = presets.getOrThrow(net.minecraft.world.level.levelgen.presets.WorldPresets.FLAT);
+                state.setWorldType(new WorldCreationUiState.WorldTypeEntry(flat));
+                require(state.getPresetEditor() != null
+                        && !(state.getPresetEditor().createEditScreen(create, state.getSettings()) instanceof SanctuaryWorldOptionsScreen),
+                        "Vanilla flat-world customization must remain available");
+            });
+            Files.writeString(diagnostics.resolve("sanctuary-world-options-client.json"),
+                    new GsonBuilder().setPrettyPrinting().create().toJson(Map.of(
+                            "public_sanctuary_choices", 1, "default_diameter", 724,
+                            "saved_sizes", savedSizes, "cancel_and_escape_preserved", true,
+                            "settings_refresh_preserved", true,
+                            "legacy_editor_guard", true, "vanilla_editor_preserved", true,
+                            "test_settings_directory", testRoot.toString(), "passed", true)) + "\n");
+            SanctuaryMod.LOGGER.info("Sanctuary world options client tests passed: one world type, three saved sizes, Done/Cancel/Escape.");
+        } catch (IOException failure) {
+            throw new AssertionError("Unable to verify the selected world settings on disk", failure);
+        } finally {
+            context.runOnClient(client -> create.onClose());
+        }
+    }
+
+    private static boolean isSanctuary(WorldCreationUiState state) {
+        var preset = state.getWorldType().preset();
+        return preset != null && preset.getRegisteredName().equals("sanctuary:sanctuary");
+    }
+
+    private static int diameter(CreateWorldScreen create) {
+        return ((SanctuaryChunkGenerator) create.getUiState().getSettings().selectedDimensions().overworld()).initialDiameter();
+    }
+
+    private static CycleButton<?> sizeButton(Screen screen) {
+        require(screen instanceof SanctuaryWorldOptionsScreen, "Customize must open the Sanctuary screen");
+        return screen.children().stream().filter(CycleButton.class::isInstance).map(CycleButton.class::cast)
+                .findFirst().orElseThrow();
+    }
+
+    private static void chooseSize(Screen screen, String target) {
+        CycleButton<?> button = sizeButton(screen);
+        int attempts = 3;
+        while (!button.getValue().toString().equals(target) && attempts-- > 0) button.onPress(PRESS);
+        require(button.getValue().toString().equals(target), "Size cycle must expose " + target);
+    }
+
+    private static void require(boolean condition, String message) {
+        if (!condition) throw new AssertionError(message);
+    }
+}
@@ -117,10 +117,10 @@ public final class ExpansionCommandChecks {
            helper.assertTrue(session.islands().equals(before), "Rejecting an unsupported diameter must preserve the registry");

            boolean outsideRangeRejected = false;
-            try { dispatcher.execute("sanctuary expansion create command_out_of_range sanctuary east boreal 513 natural", console); }
+            try { dispatcher.execute("sanctuary expansion create command_out_of_range sanctuary east boreal 1025 natural", console); }
            catch (CommandSyntaxException expected) { outsideRangeRejected = true; }
            helper.assertTrue(outsideRangeRejected && session.islands().equals(before),
-                "The parser must reject a diameter above 512 before changing the registry");
+                "The parser must reject a diameter above 1024 before changing the registry");
        } catch (CommandSyntaxException exception) {
            throw new IOException("Registered expansion command checks failed", exception);
        }
@@ -0,0 +1,254 @@
+package fr.koka.sanctuary.gametest;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonParser;
+import fr.koka.sanctuary.expansion.ExpansionAdmission;
+import fr.koka.sanctuary.expansion.ExpansionIsland;
+import fr.koka.sanctuary.expansion.ExpansionRuntime;
+import fr.koka.sanctuary.expansion.ExpansionVoidReuse;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import net.fabricmc.fabric.api.gametest.v1.GameTest;
+import net.minecraft.core.BlockPos;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.EntitySpawnReason;
+import net.minecraft.world.entity.EntityTypes;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.storage.LevelResource;
+
+/** Opt-in, disposable-world proof. Run fresh, then twice with sanctuaryExpansionReload=true. */
+public final class ExpansionVoidReuseGameTests {
+    private static final String LOADED = "void_loaded", SAVED = "void_saved";
+    @GameTest(maxTicks = 6000)
+    public void certifiedVoidRestartsThroughNativeGeneration(GameTestHelper helper) {
+        helper.assertTrue(helper.getLevel().getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator,
+            "Void reuse proof needs the unified generator");
+        var generator = (SanctuaryChunkGenerator) helper.getLevel().getChunkSource().getGenerator();
+        helper.assertTrue(generator.rootGeneration() == 14, "Void reuse is restricted to generation 14");
+        new Scenario(helper, generator).advance();
+    }
+
+    private static final class Scenario {
+        final GameTestHelper helper;
+        final ServerLevel level;
+        final SanctuaryChunkGenerator generator;
+        final ExpansionRuntime.Session session;
+        final boolean reload = Boolean.getBoolean("sanctuary.test.expansionReload");
+        final Map<String, Object> report = new LinkedHashMap<>();
+        ExpansionIsland loaded, saved;
+        final List<ExpansionIsland> rejectionFixtures = new ArrayList<>();
+        int phase;
+        Scenario(GameTestHelper helper, SanctuaryChunkGenerator generator) {
+            this.helper = helper; this.level = helper.getLevel(); this.generator = generator;
+            this.session = ExpansionRuntime.session(level);
+            report.put("world_seed", level.getSeed()); report.put("generation", 14);
+        }
+        void advance() {
+            try {
+                if (reload) { resume(); return; }
+                if (phase == 0) {
+                    loaded = session.candidate(LOADED, "sanctuary", "east", "temperate", 64, "natural", 6144);
+                    for (var pos : positions(loaded)) {
+                        level.setChunkForced(pos.x(), pos.z(), true);
+                        level.getChunk(pos.x(), pos.z());
+                    }
+                    for (int i = 0; i < 4; i++) {
+                        var fixture = new ExpansionIsland("reject_" + i, "sanctuary", "north", "temperate", 64,
+                            0, -12288 - i * 4096, level.getSeed() + i, "natural", "reserved", 14);
+                        rejectionFixtures.add(fixture);
+                        for (var pos : positions(fixture)) {
+                            level.setChunkForced(pos.x(), pos.z(), true);
+                            level.getChunk(pos.x(), pos.z());
+                        }
+                    }
+                    phase = 1;
+                    helper.runAtTickTime(helper.getTick() + 40, this::advance);
+                    return;
+                }
+                if (phase == 1) {
+                    report.put("stage", "loaded_positive_baseline");
+                    var proof = ExpansionVoidReuse.inspect(level, loaded, ExpansionAdmission.searchDeadline());
+                    helper.assertTrue(proof.certificates().stream().noneMatch(c -> c.absent()), "Loaded fixture needs native FULL void throughout its write scope");
+                    report.put("loaded_positive_baseline_passed", true);
+                    report.put("stage", "independent_rejections");
+                    rejectionChecks(helper, rejectionFixtures);
+                    report.put("stage", "loaded_positive_reservation");
+                    var source = level.getChunk(loaded.centerX() >> 4, loaded.centerZ() >> 4);
+                    CompoundTag snapshot = SerializableChunkData.copyOf(level, source).write();
+                    var admitted = session.create(LOADED, "sanctuary", "east", "temperate", 64, "natural", 6144);
+                    helper.assertTrue(admitted.centerX() == loaded.centerX() && admitted.centerZ() == loaded.centerZ(), "Inspection must retain the requested candidate");
+                    helper.assertTrue(!admitted.reuseToken().isEmpty() && ExpansionVoidReuse.requiresReload(level, LOADED), "Loaded FULL void must be deferred with a durable journal token");
+                    helper.assertTrue(session.island(LOADED).status().equals("reserved"), "A live FULL reservation cannot become ready before reopening");
+                    helper.assertTrue(generator.source().islands().stream().noneMatch(i -> i.id().equals(LOADED)), "Deferred island must remain invisible to generation");
+                    loaded = admitted;
+
+                    report.put("stage", "saved_positive_baseline");
+                    saved = session.candidate(SAVED, "sanctuary", "west", "temperate", 64, "natural", 6144);
+                    var pos = new ChunkPos(saved.centerX() >> 4, saved.centerZ() >> 4);
+                    helper.assertTrue(level.getChunkSource().chunkMap.read(pos).get(30, TimeUnit.SECONDS).isEmpty(), "Saved-only fixture starts from absent storage");
+                    // One genuine native FULL-void snapshot, relocated only inside this disposable test fixture.
+                    snapshot.putInt("xPos", pos.x()); snapshot.putInt("zPos", pos.z());
+                    level.getChunkSource().chunkMap.write(pos, snapshot).get(30, TimeUnit.SECONDS);
+                    level.getChunkSource().chunkMap.synchronize(true).get(30, TimeUnit.SECONDS);
+                    var savedProof = ExpansionVoidReuse.inspect(level, saved, ExpansionAdmission.searchDeadline());
+                    helper.assertTrue(savedProof.certificates().stream().filter(c -> !c.absent()).count() == 1
+                        && savedProof.certificates().stream().anyMatch(c -> c.absent()), "Saved-only fixture needs both FULL and certified absent positions");
+                    report.put("stage", "external_mutation_preflight");
+                    verifyMutationBlocksWholePreflight(helper, generator, savedProof, snapshot, pos);
+                    report.put("stage", "saved_positive_reservation");
+                    saved = session.create(SAVED, "sanctuary", "west", "temperate", 64, "natural", 6144);
+                    helper.assertTrue(!saved.reuseToken().isEmpty() && ExpansionVoidReuse.requiresReload(level, SAVED), "Saved void also needs a reload transaction");
+                    for (var loadedPos : positions(loaded)) level.setChunkForced(loadedPos.x(), loadedPos.z(), false);
+                    helper.assertTrue(level.getServer().saveEverything(true, true, true), "Save native void and reservations before the first real restart");
+                    report.put("loaded_full_chunks", positions(loaded).size());
+                    report.put("saved_only_full_chunks", 1);
+                    report.put("saved_only_absent_chunks", savedProof.certificates().stream().filter(c -> c.absent()).count());
+                    report.put("loaded_token", loaded.reuseToken()); report.put("saved_token", saved.reuseToken());
+                    report.put("rejected_block_chest_entity_tick", true); report.put("foreign_mutation_preserved_region_bytes", true);
+                    report.put("passed", true); write(level, "void-reuse-before-reload.json", report);
+                    helper.succeed();
+                }
+            } catch (Exception error) {
+                report.put("passed", false); report.put("failure", error.toString());
+                try { write(level, "void-reuse-failure.json", report); } catch (IOException ignored) { }
+                throw new IllegalStateException("Native void reuse proof failed", error);
+            }
+        }
+        void resume() throws Exception {
+            loaded = session.island(LOADED); saved = session.island(SAVED);
+            helper.assertTrue(!ExpansionVoidReuse.requiresReload(level, LOADED) && !ExpansionVoidReuse.requiresReload(level, SAVED),
+                "A genuine restart must open durable transactions");
+            if (!loaded.status().equals("ready") || !saved.status().equals("ready")) {
+                helper.assertTrue(ExpansionVoidReuse.failure(level, LOADED) == null && ExpansionVoidReuse.failure(level, SAVED) == null,
+                    "Native load must not block either certified transaction");
+                helper.runAtTickTime(helper.getTick() + 20, this::advance);
+                return;
+            }
+            Path witnessFile = path(level, "void-reuse-after-reload.json");
+            boolean secondReload = Files.exists(witnessFile);
+            if (secondReload) {
+                var original = JsonParser.parseString(Files.readString(witnessFile)).getAsJsonObject();
+                var p = original.getAsJsonArray("gold_witness");
+                helper.assertTrue(level.getBlockState(new BlockPos(p.get(0).getAsInt(), p.get(1).getAsInt(), p.get(2).getAsInt())).is(Blocks.GOLD_BLOCK),
+                    "A native marked FULL chunk must preserve gameplay blocks on subsequent reloads");
+            }
+            int full = 0, nonAir = 0, rebuiltBiomeSamples = 0;
+            for (var island : List.of(loaded, saved)) for (var pos : positions(island)) {
+                var chunk = level.getChunk(pos.x(), pos.z());
+                helper.assertTrue(chunk.getPersistedStatus() == ChunkStatus.FULL && ExpansionVoidReuse.marker(chunk).equals(island.reuseToken()),
+                    "Every claimed position must complete the native pipeline and retain its exact marker: " + pos);
+                helper.assertTrue(chunk.isLightCorrect(), "Every reconstructed FULL chunk must finish native lighting: " + pos);
+                int midX = pos.x() * 16 + 8, midZ = pos.z() * 16 + 8;
+                if (island.contains(midX, midZ)) {
+                    helper.assertTrue(!chunk.getNoiseBiome(pos.x() * 4 + 2, 220 / 4, pos.z() * 4 + 2)
+                            .is(net.minecraft.world.level.biome.Biomes.THE_VOID),
+                        "Native BIOMES must replace the previous void biome inside the expansion: " + pos);
+                    rebuiltBiomeSamples++;
+                }
+                full++;
+                for (var section : chunk.getSections()) if (!section.hasOnlyAir()) nonAir++;
+            }
+            helper.assertTrue(nonAir > 0, "A reconstructed expansion must contain actual generated terrain");
+            var witness = new BlockPos(loaded.centerX(), 376, loaded.centerZ());
+            if (!secondReload) level.setBlock(witness, Blocks.GOLD_BLOCK.defaultBlockState(), 3);
+            helper.assertTrue(level.getServer().saveEverything(true, true, true), "Flush generated native chunks and trusted markers");
+            report.put("full_marked_chunks", full); report.put("nonempty_sections", nonAir);
+            report.put("light_correct_chunks", full); report.put("rebuilt_biome_samples", rebuiltBiomeSamples);
+            report.put("gold_witness", List.of(witness.getX(), witness.getY(), witness.getZ()));
+            report.put("second_reload_preserved_gameplay", secondReload); report.put("passed", true);
+            write(level, secondReload ? "void-reuse-second-reload.json" : "void-reuse-after-reload.json", report);
+            helper.succeed();
+        }
+    }
+
+    private static void rejectionChecks(GameTestHelper helper, List<ExpansionIsland> fixtures) throws Exception {
+        var level = helper.getLevel();
+        for (int i = 0; i < fixtures.size(); i++) {
+            var island = fixtures.get(i); var p = new BlockPos(island.centerX(), 200, island.centerZ());
+            // Each witness has its own untouched native palette. Never reuse a section edited by a prior witness.
+            var baseline = ExpansionVoidReuse.inspect(level, island, ExpansionAdmission.searchDeadline());
+            helper.assertTrue(baseline.certificates().stream().noneMatch(c -> c.absent()), "Every rejection first proves its own FULL-void baseline");
+            switch (i) {
+                case 0 -> {
+                    level.setBlock(p, Blocks.STONE.defaultBlockState(), 3);
+                    expectOccupied(helper, island, "block");
+                }
+                case 1 -> {
+                    level.setBlock(p, Blocks.CHEST.defaultBlockState(), 3);
+                    helper.assertTrue(level.getBlockEntity(p) != null, "Chest witness must contain its native block entity");
+                    expectOccupied(helper, island, "chest");
+                }
+                case 2 -> {
+                    var entity = EntityTypes.ZOMBIE.create(level, EntitySpawnReason.COMMAND);
+                    helper.assertTrue(entity != null, "Entity rejection needs a real entity");
+                    entity.setPos(p.getX() + .5, p.getY(), p.getZ() + .5);
+                    helper.assertTrue(level.addFreshEntity(entity), "Entity fixture must be registered with the native manager");
+                    expectOccupied(helper, island, "entity"); entity.discard();
+                }
+                case 3 -> {
+                    level.scheduleTick(p, Blocks.STONE, 1000);
+                    expectOccupied(helper, island, "tick");
+                    level.getBlockTicks().clearArea(new BoundingBox(p));
+                }
+                default -> throw new IllegalStateException("Unexpected rejection witness");
+            }
+            for (var pos : positions(island)) level.setChunkForced(pos.x(), pos.z(), false);
+        }
+    }
+    private static void expectOccupied(GameTestHelper helper, ExpansionIsland island, String kind) throws Exception {
+        boolean refused = false;
+        try { ExpansionVoidReuse.inspect(helper.getLevel(), island, ExpansionAdmission.searchDeadline()); }
+        catch (ExpansionAdmission.OccupiedException expected) { refused = true; }
+        helper.assertTrue(refused, "Admission must reject " + kind + " even in an otherwise empty void chunk");
+    }
+
+    private static void verifyMutationBlocksWholePreflight(GameTestHelper helper, SanctuaryChunkGenerator generator,
+            ExpansionVoidReuse.Inspection proof, CompoundTag original, ChunkPos pos) throws Exception {
+        var level = helper.getLevel(); var session = ExpansionRuntime.session(level);
+        String token = ExpansionVoidReuse.persist(proof);
+        var mutated = original.copy(); mutated.putString("foreign_mod_metadata", "must survive unchanged");
+        var storage = level.getChunkSource().chunkMap;
+        storage.write(pos, mutated).get(30, TimeUnit.SECONDS); storage.synchronize(true).get(30, TimeUnit.SECONDS);
+        Path region = net.minecraft.world.level.dimension.DimensionType.getStorageFolder(level.dimension(),
+            level.getServer().getWorldPath(LevelResource.ROOT)).resolve("region/r."
+            + Math.floorDiv(pos.x(), 32) + "." + Math.floorDiv(pos.z(), 32) + ".mca");
+        byte[] before = MessageDigest.getInstance("SHA-256").digest(Files.readAllBytes(region));
+        var islands = List.of(session.island("sanctuary"), proof.island().withReuseToken(token));
+        boolean refused = false;
+        try { ExpansionVoidReuse.open(level, generator, islands); } catch (IOException expected) { refused = true; }
+        helper.assertTrue(refused, "External mutation must block startup before any absent chunk is staged");
+        helper.assertTrue(java.util.Arrays.equals(before, MessageDigest.getInstance("SHA-256").digest(Files.readAllBytes(region))),
+            "A rejected preflight must preserve the original region file byte for byte");
+        helper.assertTrue(storage.read(pos).get(30, TimeUnit.SECONDS).orElseThrow().equals(mutated), "Foreign NBT must be preserved");
+        storage.write(pos, original).get(30, TimeUnit.SECONDS); storage.synchronize(true).get(30, TimeUnit.SECONDS);
+        // This deliberately simulates startup inside a running test; restore the runtime's deferred state afterward.
+        ExpansionVoidReuse.open(level, generator, List.of(session.island("sanctuary")));
+        for (var island : session.islands()) if (!island.reuseToken().isEmpty()) ExpansionVoidReuse.deferred(level, island);
+    }
+    private static List<ChunkPos> positions(ExpansionIsland island) {
+        var result = new ArrayList<ChunkPos>(); int radius = island.terrainRadius() + ExpansionIsland.DECORATION_MARGIN;
+        for (int z = (island.centerZ() - radius) >> 4; z <= (island.centerZ() + radius) >> 4; z++)
+            for (int x = (island.centerX() - radius) >> 4; x <= (island.centerX() + radius) >> 4; x++)
+                if (island.ownsChunk(x, z)) result.add(new ChunkPos(x, z));
+        return result;
+    }
+    private static Path path(ServerLevel level, String name) { return level.getServer().getWorldPath(LevelResource.ROOT).resolve(name); }
+    private static void write(ServerLevel level, String name, Map<String, Object> report) throws IOException {
+        Files.writeString(path(level, name), new GsonBuilder().setPrettyPrinting().create().toJson(report) + "\n");
+    }
+}
@@ -44,6 +44,8 @@ import net.minecraft.world.level.storage.LevelResource;

 /** Opt-in end-to-end exercise on a new laboratory world; never rewrites chunks or a personal world. */
 public final class ExpansionWorldGameTests {
+    private static final boolean OPTIONAL_STRUCTURE_WITNESS = Boolean.getBoolean("sanctuary.test.optionalStructureWitness");
+
    @GameTest(maxTicks = 6000)
    public void islandsBranchPersistAndProtectVisitedChunks(GameTestHelper helper) {
        helper.assertTrue(Boolean.getBoolean("sanctuary.test.expansion"), "Expansion GameTest must be explicitly enabled");
@@ -63,6 +65,7 @@ public final class ExpansionWorldGameTests {
        Map<String, Object> report = new LinkedHashMap<>();
        report.put("seed", level.getSeed());
        report.put("process_id", ProcessHandle.current().pid());
+        report.put("optional_native_structure_witness", OPTIONAL_STRUCTURE_WITNESS);
        report.put("scope", "A second Java process opens the same saved development chunks and expansion journal, and verifies a "
            + "gold block written and flushed before the first shutdown. GameTestServer reconstructs its world settings from the preset; "
            + "the prior generator codec is decoded separately here and its base columns are compared. This is not a normal-client "
@@ -122,20 +125,41 @@ public final class ExpansionWorldGameTests {
                    "Decoding the saved generator codec must reproduce its base column and climate: " + island.id());
                samples.add(current);
            }
-            JsonObject nativeStructure = previous.getAsJsonObject("native_structure");
-            BlockPos containerPos = position(nativeStructure.getAsJsonArray("container"));
-            full(helper, level, containerPos.getX() >> 4, containerPos.getZ() >> 4);
-            helper.assertTrue(level.getBlockEntity(containerPos) instanceof RandomizableContainerBlockEntity,
-                "The native structure's placed container must be loaded from the saved chunk");
-            var container = (RandomizableContainerBlockEntity) level.getBlockEntity(containerPos);
-            helper.assertTrue(container.getLootTable() != null && container.getLootTable().identifier().toString()
-                .equals(nativeStructure.get("loot_table").getAsString()), "The native structure loot table must survive restart unconsumed");
+            boolean hasNativeStructure = previous.has("native_structure") && !previous.get("native_structure").isJsonNull();
+            if (hasNativeStructure) {
+                helper.assertTrue(!previous.has("native_structure_observed") || previous.get("native_structure_observed").getAsBoolean(),
+                    "Stored native structure evidence must not contradict the observation result");
+                JsonObject nativeStructure = previous.getAsJsonObject("native_structure");
+                BlockPos containerPos = position(nativeStructure.getAsJsonArray("container"));
+                full(helper, level, containerPos.getX() >> 4, containerPos.getZ() >> 4);
+                helper.assertTrue(level.getBlockState(containerPos).toString().equals(nativeStructure.get("placed_block").getAsString()),
+                    "The native structure's placed block state must survive restart");
+                helper.assertTrue(level.getBlockEntity(containerPos) instanceof RandomizableContainerBlockEntity,
+                    "The native structure's placed container must be loaded from the saved chunk");
+                var container = (RandomizableContainerBlockEntity) level.getBlockEntity(containerPos);
+                helper.assertTrue(container.getLootTable() != null && container.getLootTable().identifier().toString()
+                    .equals(nativeStructure.get("loot_table").getAsString()), "The native structure loot table must survive restart unconsumed");
+                report.put("native_container", coordinates(containerPos));
+                report.put("native_structure_observed", true);
+                report.put("native_container_verified", true);
+                report.put("native_structure_status", "placed_block_and_unconsumed_loot_verified_after_restart");
+            } else {
+                helper.assertTrue(OPTIONAL_STRUCTURE_WITNESS
+                        && previous.has("optional_native_structure_witness") && previous.get("optional_native_structure_witness").getAsBoolean()
+                        && previous.has("native_structure_observed") && !previous.get("native_structure_observed").getAsBoolean()
+                        && previous.has("native_structure_search_complete") && previous.get("native_structure_search_complete").getAsBoolean(),
+                    "Missing native structure evidence is allowed only after an explicitly optional, completed first-process search");
+                report.put("native_structure_observed", false);
+                report.put("native_container_verified", false);
+                report.put("native_structure_status", "not_observed_after_complete_first_process_scan; no_native_structure_reload_proof");
+                report.put("native_structure_limitation", "No natural structure with placed vanilla loot was observed in the first process. "
+                    + "This reload verifies chunks, generator settings, the journal and expansion behavior, but supplies no positive structure proof.");
+            }
            report.put("previous_process_id", previous.get("process_id").getAsLong());
            report.put("world_directory", worldDirectory(level));
            report.put("gold_witness", coordinates(witness));
            report.put("samples", samples);
            report.put("regions", session.islands().size());
-            report.put("native_container", coordinates(containerPos));
            report.put("saved_generator_codec_decoded", true);
            var firstCandidate = session.candidate("after_reload", "sanctuary", "south", "boreal", 64, "natural");
            var opened = session.create("after_reload", "sanctuary", "south", "boreal", 64, "natural");
@@ -213,11 +237,18 @@ public final class ExpansionWorldGameTests {
            this.session = ExpansionRuntime.session(level);
            report.put("seed", level.getSeed());
            report.put("process_id", ProcessHandle.current().pid());
-            report.put("generator_version", ExpansionIsland.GENERATION);
+            report.put("generator_version", generator.rootGeneration());
+            report.put("initial_diameter", generator.initialDiameter());
            report.put("islands", observedIslands);
-            report.put("scope", "Fresh laboratory world; real FULL chunks and native structure loot, asynchronous activation, "
+            report.put("optional_native_structure_witness", OPTIONAL_STRUCTURE_WITNESS);
+            report.put("native_structure_observed", false);
+            report.put("native_structure_search_complete", false);
+            report.put("native_structure_status", "not_searched");
+            report.put("scope", "Fresh versioned Sanctuary development world; real FULL chunks, a natural native-structure search, asynchronous activation, "
                + "branching, journal re-read and loaded void admission refusal. Journal re-read is not a process restart. "
-                + "The parent block witness represents a player edit; no player teleport, multiplayer or client rendering is simulated.");
+                + "The parent block witness represents a player edit; no player teleport, multiplayer or client rendering is simulated. "
+                + (OPTIONAL_STRUCTURE_WITNESS ? "The native structure witness is explicitly optional; an absent witness is reported as missing evidence, never as a successful structures test."
+                    : "A naturally accepted structure with placed vanilla loot is required."));
        }

        void advance() {
@@ -348,8 +379,8 @@ public final class ExpansionWorldGameTests {
        }

        private void verifyJournal() throws IOException {
-            Path directory = level.getServer().getWorldPath(LevelResource.ROOT).resolve("data/sanctuary-expansion-v1");
-            var reloaded = new ExpansionJournal(directory, level.getSeed(), generator.initialDiameter());
+            Path directory = level.getServer().getWorldPath(LevelResource.ROOT).resolve("data/" + ((ExpansionChunkGenerator) level.getChunkSource().getGenerator()).journalDirectory());
+            var reloaded = new ExpansionJournal(directory, level.getSeed(), generator.initialDiameter(), generator.rootGeneration());
            helper.assertTrue(reloaded.islands().equals(session.islands()), "Re-reading the saved journal must preserve all region identities and states");
            report.put("journal_reloaded_regions", reloaded.islands().size());
        }
@@ -381,6 +412,8 @@ public final class ExpansionWorldGameTests {
            for (int ring = 0; ring <= limit; ring++) for (int x = -ring; x <= ring; x++) for (int z = -ring; z <= ring; z++) {
                if (Math.max(Math.abs(x), Math.abs(z)) == ring && root.contains(x * 16 + 8, z * 16 + 8)) structureSearch.add(new ChunkPos(x, z));
            }
+            report.put("structure_search_candidate_chunks", structureSearch.size());
+            report.put("native_structure_status", "search_in_progress");
        }

        private boolean observeNativeStructure() {
@@ -397,10 +430,23 @@ public final class ExpansionWorldGameTests {
                    Map<String, Object> evidence = materializeAndFindLoot(start, name);
                    if (!evidence.isEmpty()) {
                        report.put("native_structure", evidence);
+                        report.put("native_structure_observed", true);
+                        report.put("native_structure_status", "natural_start_with_placed_vanilla_loot_observed");
+                        report.put("native_structure_search_complete", structureIndex == structureSearch.size());
                        return true;
                    }
                }
            }
+            report.put("native_structure_starts_seen", validStarts);
+            report.put("structure_start_chunks_inspected", structureIndex);
+            if (structureIndex == structureSearch.size()) {
+                report.put("native_structure_search_complete", true);
+                report.put("native_structure_status", "not_observed_after_complete_scan");
+                report.put("native_structure_limitation", "No naturally accepted native structure with placed vanilla loot was observed after "
+                    + structureIndex + " root-island start chunks and " + validStarts + " valid starts. "
+                    + "This is missing engine evidence for structures, not a positive generation or loot result.");
+                if (OPTIONAL_STRUCTURE_WITNESS) return true;
+            }
            helper.assertTrue(structureIndex < structureSearch.size(), "No naturally accepted native structure with placed vanilla loot was observed; "
                + validStarts + " valid starts. This is a missing engine proof, not a successful structures test.");
            return false;
@@ -471,11 +517,11 @@ public final class ExpansionWorldGameTests {
    }

    private static Path journalFile(ServerLevel level) {
-        return level.getServer().getWorldPath(LevelResource.ROOT).resolve("data/sanctuary-expansion-v1").resolve(ExpansionJournal.FILE_NAME);
+        return level.getServer().getWorldPath(LevelResource.ROOT).resolve("data/" + ((ExpansionChunkGenerator) level.getChunkSource().getGenerator()).journalDirectory()).resolve(ExpansionJournal.FILE_NAME);
    }
    private static String worldDirectory(ServerLevel level) { return level.getServer().getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize().toString(); }
    private static Path diagnostic(ServerLevel level, boolean reload) {
-        return Path.of("diagnostics", "expansion-alpha12-1-" + (reload ? "reload-" : "") + "seed-" + level.getSeed() + ".json");
+        return Path.of("diagnostics", (Boolean.getBoolean("sanctuary.test.unified") ? "expansion-alpha13-" : "expansion-alpha12-1-") + (reload ? "reload-" : "") + "seed-" + level.getSeed() + ".json");
    }
    private static void writeDiagnostic(ServerLevel level, boolean reload, Map<String, Object> report) throws IOException {
        Path output = diagnostic(level, reload);
@@ -0,0 +1,409 @@
+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.expansion.ExpansionIsland;
+import fr.koka.sanctuary.expansion.ExpansionJournal;
+import fr.koka.sanctuary.expansion.ExpansionRuntime;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import fr.koka.sanctuary.worldgen.city.LostCityPiece;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan;
+import fr.koka.sanctuary.worldgen.city.LostCityRenderer;
+import fr.koka.sanctuary.worldgen.city.LostCityStructures;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayList;
+import java.util.HexFormat;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import net.fabricmc.fabric.api.gametest.v1.GameTest;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.BuiltInRegistries;
+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.world.entity.EntityTypes;
+import net.minecraft.world.entity.MobCategory;
+import net.minecraft.world.entity.npc.villager.Villager;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.entity.RandomizableContainerBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+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.LootTable;
+import net.minecraft.world.phys.AABB;
+
+/** Opt-in native engine proof on a development world, including a separate-process reload. */
+public final class LostCityWorldGameTests {
+    @GameTest(maxTicks = 6000)
+    public void cityDistrictsAreNativePersistentStructures(GameTestHelper helper) {
+        helper.assertTrue(helper.getLevel().getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator,
+            "Lost City checks require the unified generator");
+        var generator = (SanctuaryChunkGenerator) helper.getLevel().getChunkSource().getGenerator();
+        helper.assertTrue(generator.rootGeneration() == 14, "Lost City must use new generation 14");
+        if (Boolean.getBoolean("sanctuary.test.expansionReload")) {
+            reload(helper, generator);
+            return;
+        }
+        new Scenario(helper, generator).advance();
+    }
+
+    private static final class Scenario {
+        final GameTestHelper helper;
+        final ServerLevel level;
+        final SanctuaryChunkGenerator generator;
+        final ExpansionRuntime.Session session;
+        final Map<String, Object> report;
+        final List<Map<String, Object>> sites = new ArrayList<>();
+        int phase;
+        long poolPlacedTick;
+        String childId;
+
+        Scenario(GameTestHelper helper, SanctuaryChunkGenerator generator) {
+            this.helper = helper; this.level = helper.getLevel(); this.generator = generator;
+            session = ExpansionRuntime.session(level); report = report(level);
+        }
+
+        void advance() {
+            try {
+                if (phase == 0) {
+                    report.put("archetypes", verifySavedArchetypes(helper));
+                    verifyLegacyCodec(helper, generator);
+                    placePoolFixture(helper, generator);
+                    poolPlacedTick = helper.getTick();
+                    var root = session.island("sanctuary");
+                    helper.assertTrue(root.generation() == 14, "New root must keep generation 14 in its journal");
+                    sites.add(observe(helper, generator, root));
+                    var prospects = new ArrayList<Map<String, Object>>();
+                    report.put("city_prospects", prospects);
+                    for (String id : List.of("city_test", "city_harbor", "city_gardens", "city_heights", "city_works")) {
+                        var candidate = session.candidate(id, "sanctuary", "east", "lost_city", 256, "natural", 2048);
+                        try {
+                            var plan = generator.lostCityPlan(candidate);
+                            prospects.add(Map.of("id", id, "seed", candidate.seed(), "diameter", candidate.diameter(),
+                                "districts", plan.districts().size(), "read_only", true));
+                            if (!plan.isEmpty()) { childId = id; break; }
+                        } finally { generator.discardUnpublishedContext(candidate); }
+                    }
+                    helper.assertTrue(childId != null, "Five bounded read-only prospects must find a naturally supported city reference");
+                    var child = session.create(childId, "sanctuary", "east", "lost_city", 256, "natural", 2048);
+                    helper.assertTrue(child.generation() == 14 && child.climate().equals("lost_city"),
+                        "City expansion must have its own saved generation and climate");
+                    phase = 1;
+                }
+                if (phase == 1 && session.island(childId).status().equals("ready") && helper.getTick() - poolPlacedTick >= 60) {
+                    report.put("native_pool_fixture", verifyPoolFixture(helper, true));
+                    forcePoolFixture(level, false);
+                    sites.add(observe(helper, generator, session.island(childId)));
+                    report.put("sites", sites);
+                    var first = generator.lostCityPlan(session.island("sanctuary")).districts().getFirst().parcels().getFirst();
+                    var marker = new BlockPos(first.minX(), first.floorY() + 1, first.minZ());
+                    level.setBlock(marker, Blocks.GOLD_BLOCK.defaultBlockState(), 3);
+                    report.put("gold_witness", List.of(marker.getX(), marker.getY(), marker.getZ()));
+                    report.put("islands", ExpansionIsland.CODEC.listOf().encodeStart(JsonOps.INSTANCE, session.islands()).getOrThrow());
+                    report.put("generator_codec", ChunkGenerator.CODEC.encodeStart(
+                        RegistryOps.create(JsonOps.INSTANCE, level.registryAccess()), generator).getOrThrow());
+                    report.put("journal_sha256", hash(Files.readString(journal(level, generator))));
+                    helper.assertTrue(level.getServer().saveEverything(true, true, true), "Flush city chunks, deferred loot and marker before restart");
+                    report.put("world_flushed_before_shutdown", true);
+                    report.put("passed", true);
+                    write(level, report, false);
+                    helper.succeed();
+                    return;
+                }
+                if (helper.getTick() % 200 == 0) SanctuaryMod.LOGGER.info("Lost City integration phase {}: {}", phase, session.progress());
+                helper.runAtTickTime(helper.getTick() + 10, this::advance);
+            } catch (Exception exception) {
+                forcePoolFixture(level, false);
+                report.put("passed", false); report.put("failure", exception.toString()); report.put("sites", sites);
+                try { write(level, report, false); } catch (IOException ignored) { /* Keep the original test failure. */ }
+                throw new IllegalStateException("Lost City native integration failed", exception);
+            }
+        }
+    }
+
+    // Deliberately isolated in development void, apart from the two naturally planned city witnesses.
+    private static final int POOL_X = 6000, POOL_Z = 0, POOL_Y = 366;
+    private static void forcePoolFixture(ServerLevel level, boolean forced) {
+        for (int x = (POOL_X - 1) >> 4; x <= (POOL_X + 17) >> 4; x++)
+            for (int z = (POOL_Z - 1) >> 4; z <= (POOL_Z + 17) >> 4; z++) level.setChunkForced(x, z, forced);
+    }
+    private static void placePoolFixture(GameTestHelper helper, SanctuaryChunkGenerator generator) {
+        ServerLevel level = helper.getLevel();
+        forcePoolFixture(level, true);
+        var parcel = new LostCityPlan.Parcel(LostCityPlan.Kind.POOL, POOL_X, POOL_Z, 17, 17, POOL_Y, 0, 0, 42, 8, new int[0]);
+        var piece = new LostCityPiece(parcel);
+        piece.getBoundingBox().intersectingChunks().forEach(pos -> {
+            level.getChunk(pos.x(), pos.z());
+            var clip = new net.minecraft.world.level.levelgen.structure.BoundingBox(pos.x() * 16, 0, pos.z() * 16,
+                pos.x() * 16 + 15, 383, pos.z() * 16 + 15);
+            piece.postProcess(level, level.structureManager(), generator, net.minecraft.util.RandomSource.create(42), clip, pos, BlockPos.ZERO);
+        });
+        level.scheduleTick(new BlockPos(POOL_X + 8, POOL_Y - 1, POOL_Z + 10), net.minecraft.world.level.material.Fluids.WATER, 5);
+    }
+    private static Map<String, Object> verifyPoolFixture(GameTestHelper helper, boolean requireTicks) {
+        var level = helper.getLevel();
+        var witness = new BlockPos(POOL_X + 8, POOL_Y - 1, POOL_Z + 10);
+        if (requireTicks) {
+            helper.assertTrue(level.shouldTickBlocksAt(ChunkPos.containing(witness).pack()), "Pool fixture must actually tick in Minecraft");
+            helper.assertTrue(!level.getFluidTicks().hasScheduledTick(witness, net.minecraft.world.level.material.Fluids.WATER),
+                "The explicitly scheduled water tick must have executed");
+        }
+        int water = 0;
+        for (int x = -1; x <= 17; x++) for (int z = -1; z <= 17; z++) for (int y = -9; y <= 1; y++) {
+            var pos = new BlockPos(POOL_X + x, POOL_Y + y, POOL_Z + z);
+            if (!level.getFluidState(pos).isEmpty()) {
+                water++;
+                helper.assertTrue(x >= 4 && x <= 12 && z >= 5 && z <= 12 && y >= -3 && y <= -1,
+                    "Native pool water escaped its intended basin after ticks or reload: " + pos);
+            }
+        }
+        helper.assertTrue(water >= 180, "The native pool lost its retained water");
+        for (int step = 1; step <= 3; step++) helper.assertTrue(level.getBlockState(
+            new BlockPos(POOL_X + 8, POOL_Y - step, POOL_Z + step + 4)).is(net.minecraft.tags.BlockTags.STAIRS),
+            "Native submerged access steps must survive fluid ticks");
+        return Map.of("scope", "Isolated native piece fixture, separate from random city placement", "retained_water_cells", water,
+            "scheduled_water_tick_executed", requireTicks, "contained", true, "steps_preserved", true);
+    }
+
+    private static Map<String, Object> observe(GameTestHelper helper, SanctuaryChunkGenerator generator, ExpansionIsland island) {
+        ServerLevel level = helper.getLevel();
+        LostCityPlan plan = generator.lostCityPlan(island);
+        helper.assertTrue(!plan.isEmpty(), "This reference seed must demonstrate an accepted city district on " + island.id());
+        var district = plan.districts().getFirst();
+        var registry = level.registryAccess().lookupOrThrow(Registries.STRUCTURE);
+        var holder = registry.getOrThrow(LostCityStructures.KEY);
+        var startChunk = level.getChunkSource().getChunk(district.startChunkX(), district.startChunkZ(), ChunkStatus.STRUCTURE_STARTS, true);
+        StructureStart start = startChunk.getStartForStructure(holder.value());
+        helper.assertTrue(start != null && start.isValid(), "Accepted district must have a native StructureStart");
+        helper.assertTrue(start.getPieces().size() == district.parcels().size(), "Every accepted parcel must be saved as a native piece");
+        Map<Long, LevelChunk> chunks = new TreeMap<>();
+        for (var piece : start.getPieces()) piece.getBoundingBox().intersectingChunks().forEach(pos -> {
+            if (!chunks.containsKey(pos.pack())) {
+                var chunk = level.getChunkSource().getChunk(pos.x(), pos.z(), ChunkStatus.FULL, true);
+                helper.assertTrue(chunk instanceof LevelChunk, "City inspection requires FULL chunks");
+                chunks.put(pos.pack(), (LevelChunk) chunk);
+            }
+        });
+        helper.assertTrue(chunks.size() <= 81, "One district is bounded; the check must not generate an entire island");
+        for (var chunk : chunks.values()) helper.assertTrue(chunk.getReferencesForStructure(holder.value()).contains(start.getChunkPos().pack()),
+            "Every touched FULL chunk must retain the native structure reference");
+        var context = StructurePieceSerializationContext.fromLevel(level);
+        var tag = start.createTag(context, start.getChunkPos());
+        var decoded = StructureStart.loadStaticStart(context, tag, island.seed());
+        helper.assertTrue(decoded != null && decoded.isValid() && decoded.createTag(context, decoded.getChunkPos()).equals(tag),
+            "Native start and complete parcel parameters must round-trip through saved NBT");
+        Map<String, Long> blocks = new TreeMap<>();
+        Map<String, Integer> kinds = new TreeMap<>();
+        List<Map<String, Object>> chests = new ArrayList<>();
+        int biomeWitnesses = 0, interiorWitnesses = 0;
+        for (var piece : start.getPieces()) {
+            helper.assertTrue(piece instanceof LostCityPiece, "Lost City must load the registered native parcel type");
+            var parcel = ((LostCityPiece) piece).parcel();
+            kinds.merge(parcel.kind().name(), 1, Integer::sum);
+            var box = piece.getBoundingBox();
+            for (int x = box.minX(); x <= box.maxX(); x++) for (int z = box.minZ(); z <= box.maxZ(); z++)
+                for (int y = box.minY(); y <= box.maxY(); y++) {
+                    var pos = new BlockPos(x, y, z);
+                    var state = level.getBlockState(pos);
+                    if (!state.isAir()) blocks.merge(BuiltInRegistries.BLOCK.getKey(state.getBlock()).toString(), 1L, Long::sum);
+                    if (parcel.kind().building() && y >= parcel.floorY()) helper.assertTrue(
+                        !BuiltInRegistries.BLOCK.getKey(state.getBlock()).getPath().endsWith("_ore"),
+                        "Native ore features must not replace a city's masonry after structure placement");
+                    helper.assertTrue(!state.is(Blocks.SPAWNER), "City buildings contain no zombie spawner");
+                    if (state.is(Blocks.CHEST) && level.getBlockEntity(pos) instanceof RandomizableContainerBlockEntity chest
+                            && chest.getLootTable() != null) {
+                        chests.add(Map.of("position", List.of(x, y, z), "table", chest.getLootTable().identifier().toString(), "seed", chest.getLootTableSeed()));
+                    }
+                }
+            var centre = new BlockPos(parcel.minX() + parcel.width() / 2, parcel.floorY() + 1, parcel.minZ() + parcel.depth() / 2);
+            if (level.getBiome(centre).is(SanctuaryMod.id("lost_city"))) biomeWitnesses++;
+            var entrance = entrance(parcel);
+            if (parcel.kind().building() && level.getBlockState(entrance).isAir()
+                    && level.getBlockState(entrance.above()).isAir() && level.getBlockState(entrance.below()).isSolid()) interiorWitnesses++;
+            var monsters = generator.getMobsAt(level, level.structureManager(), MobCategory.MONSTER, centre).unwrap();
+            helper.assertTrue(!monsters.isEmpty() && monsters.stream().allMatch(entry -> entry.value().type() == EntityTypes.ZOMBIE),
+                "The effective native monster spawn list inside a city piece contains only vanilla zombies");
+        }
+        helper.assertTrue(biomeWitnesses > 0, "The city must exist as a real saved biome, not only as placed buildings");
+        helper.assertTrue(interiorWitnesses > 0, "At least one observed contemporary building has a two-block-high traversable interior");
+        helper.assertTrue(blocks.getOrDefault("minecraft:stone", 0L) > 0 && blocks.getOrDefault("minecraft:smooth_stone", 0L) > 0
+                && blocks.getOrDefault("minecraft:stone_bricks", 0L) > 0, "The actual city contains stone, smooth stone and restrained stone bricks");
+        helper.assertTrue(!chests.isEmpty(), "An observed building must contain unconsumed deferred native loot");
+        var bounds = start.getBoundingBox();
+        helper.assertTrue(level.getEntitiesOfClass(Villager.class, new AABB(bounds.minX(), bounds.minY(), bounds.minZ(),
+            bounds.maxX() + 1, bounds.maxY() + 1, bounds.maxZ() + 1)).isEmpty(), "The abandoned district contains no generated villagers");
+        var located = generator.findNearestMapStructure(level, HolderSet.direct(holder),
+            new BlockPos(district.startChunkX() * 16 + 8, 220, district.startChunkZ() * 16 + 8), 100, false);
+        helper.assertTrue(located != null && located.getSecond().is(LostCityStructures.KEY), "The native locate path finds Lost City");
+        helper.assertTrue(!LostCityStructures.isPlacing(), "The scoped decoration bypass must be cleared after placement");
+        var result = new LinkedHashMap<String, Object>();
+        result.put("island", island.id()); result.put("generation", island.generation());
+        result.put("planned_districts", plan.districts().size()); result.put("start_chunk", List.of(start.getChunkPos().x(), start.getChunkPos().z()));
+        result.put("full_chunks", chunks.size()); result.put("parcel_kinds", kinds); result.put("blocks", blocks);
+        result.put("native_start_sha256", hash(tag.toString())); result.put("unopened_chests", chests);
+        result.put("biome_witnesses", biomeWitnesses); result.put("traversable_interiors", interiorWitnesses);
+        result.put("native_zombie_only_monster_spawns", true); result.put("native_locate", List.of(located.getFirst().getX(), located.getFirst().getY(), located.getFirst().getZ()));
+        return result;
+    }
+
+    private static List<Map<String, Object>> verifySavedArchetypes(GameTestHelper helper) {
+        var context = StructurePieceSerializationContext.fromLevel(helper.getLevel());
+        List<Map<String, Object>> results = new ArrayList<>();
+        for (var kind : LostCityPlan.Kind.values()) for (int facing = 0; facing < 4; facing++) {
+            var parcel = new LostCityPlan.Parcel(kind, -32, 48, 17, 17, 220, kind.building() ? 3 : 1,
+                facing, 0xA14C17L + kind.ordinal(), 4, new int[0]);
+            var piece = new LostCityPiece(parcel);
+            var tag = piece.createTag(context);
+            var decoded = new LostCityPiece(context, tag);
+            helper.assertTrue(decoded.createTag(context).equals(tag), "Every archetype and orientation must persist without changing parcel fields");
+            var original = render(helper, parcel); var reloaded = render(helper, decoded.parcel());
+            helper.assertTrue(!original.isEmpty() && original.equals(reloaded), "Reloaded parcels render exactly the same blocks and deferred loot seeds");
+            results.add(Map.of("kind", kind.name(), "facing", facing, "positions", original.size(), "sha256", hash(original.toString())));
+        }
+        return results;
+    }
+
+    private static BlockPos entrance(LostCityPlan.Parcel parcel) {
+        int x = parcel.width() / 2, z = 1;
+        int rotatedX = switch (parcel.facing()) {
+            case 1 -> parcel.width() - 1 - z;
+            case 2 -> parcel.width() - 1 - x;
+            case 3 -> z;
+            default -> x;
+        };
+        int rotatedZ = switch (parcel.facing()) {
+            case 1 -> x;
+            case 2 -> parcel.depth() - 1 - z;
+            case 3 -> parcel.depth() - 1 - x;
+            default -> z;
+        };
+        return new BlockPos(parcel.minX() + rotatedX, parcel.floorY() + 1, parcel.minZ() + rotatedZ);
+    }
+
+    private static Map<String, String> render(GameTestHelper helper, LostCityPlan.Parcel parcel) {
+        Map<String, String> rendered = new TreeMap<>();
+        LostCityRenderer.render(parcel, new LostCityRenderer.BlockWriter() {
+            private void put(int x, int y, int z, String value) {
+                helper.assertTrue(x >= 0 && x < parcel.width() && z >= 0 && z < parcel.depth()
+                        && parcel.floorY() + y >= parcel.minY() && parcel.floorY() + y <= parcel.maxY(),
+                    "Every renderer write must fit the persisted parcel bounds: " + parcel.kind() + " at " + x + "," + y + "," + z);
+                rendered.put(x + "," + y + "," + z, value);
+            }
+            @Override public void set(int x, int y, int z, BlockState state) {
+                helper.assertTrue(!state.is(Blocks.SPAWNER), "No original archetype emits a spawner");
+                put(x, y, z, state.toString());
+            }
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long seed) {
+                put(x, y, z, "loot:" + table.identifier() + ":" + seed);
+            }
+        });
+        return rendered;
+    }
+
+    private static void verifyLegacyCodec(GameTestHelper helper, SanctuaryChunkGenerator generator) {
+        var ops = RegistryOps.create(JsonOps.INSTANCE, helper.getLevel().registryAccess());
+        JsonObject json = ChunkGenerator.CODEC.encodeStart(ops, generator).getOrThrow().getAsJsonObject();
+        json.addProperty("type", "sanctuary:island_v13");
+        json.getAsJsonObject("biome_source").addProperty("type", "sanctuary:island_v13");
+        var old = (SanctuaryChunkGenerator) ChunkGenerator.CODEC.parse(ops, json).getOrThrow();
+        helper.assertTrue(old.rootGeneration() == 13 && old.journalDirectory().equals("sanctuary-world-v13"),
+            "The registered generation-13 codec keeps its journal and never enables city generation");
+        helper.assertTrue(old.lostCityPlan(ExpansionIsland.origin(generator.initialDiameter(), helper.getLevel().getSeed(), 13)).isEmpty(),
+            "Existing generation-13 worlds never acquire a city plan");
+    }
+
+    private static void reload(GameTestHelper helper, SanctuaryChunkGenerator generator) {
+        var level = helper.getLevel(); var result = report(level);
+        try {
+            JsonObject previous = JsonParser.parseString(Files.readString(path(level, false))).getAsJsonObject();
+            helper.assertTrue(previous.get("passed").getAsBoolean() && previous.get("world_flushed_before_shutdown").getAsBoolean(), "Reload requires a completed first process");
+            helper.assertTrue(previous.get("process_id").getAsLong() != ProcessHandle.current().pid(), "Native city reload must run in a second JVM");
+            helper.assertTrue(previous.get("seed").getAsLong() == level.getSeed()
+                    && previous.get("world_directory").getAsString().equals(level.getServer().getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize().toString()),
+                "Reload must read the exact same saved development world and seed");
+            var session = ExpansionRuntime.session(level);
+            helper.assertTrue(previous.get("islands").equals(ExpansionIsland.CODEC.listOf().encodeStart(JsonOps.INSTANCE, session.islands()).getOrThrow()),
+                "The ready root and Lost City expansion identities must persist across process restart");
+            helper.assertTrue(hash(Files.readString(journal(level, generator))).equals(previous.get("journal_sha256").getAsString()),
+                "Reload must preserve the existing expansion journal bytes");
+            var witness = previous.getAsJsonArray("gold_witness");
+            var gold = new BlockPos(witness.get(0).getAsInt(), witness.get(1).getAsInt(), witness.get(2).getAsInt());
+            helper.assertTrue(level.getBlockState(gold).is(Blocks.GOLD_BLOCK), "A saved edit inside the city must survive without structure regeneration");
+            var context = StructurePieceSerializationContext.fromLevel(level);
+            var structure = level.registryAccess().lookupOrThrow(Registries.STRUCTURE).getOrThrow(LostCityStructures.KEY);
+            int savedPieces = 0, deferredChests = 0;
+            for (var element : previous.getAsJsonArray("sites")) {
+                var site = element.getAsJsonObject(); var pos = site.getAsJsonArray("start_chunk");
+                var chunk = level.getChunk(pos.get(0).getAsInt(), pos.get(1).getAsInt(), ChunkStatus.FULL, true);
+                var start = chunk.getStartForStructure(structure.value());
+                helper.assertTrue(start != null && start.isValid(), "Native start must load from the existing saved chunk");
+                helper.assertTrue(hash(start.createTag(context, start.getChunkPos()).toString()).equals(site.get("native_start_sha256").getAsString()),
+                    "Saved native structure pieces, layout and decoration seeds must remain byte-equivalent after restart");
+                savedPieces += start.getPieces().size();
+                for (var chestElement : site.getAsJsonArray("unopened_chests")) {
+                    var saved = chestElement.getAsJsonObject(); var at = saved.getAsJsonArray("position");
+                    var chestPos = new BlockPos(at.get(0).getAsInt(), at.get(1).getAsInt(), at.get(2).getAsInt());
+                    level.getChunk(chestPos);
+                    helper.assertTrue(level.getBlockEntity(chestPos) instanceof RandomizableContainerBlockEntity,
+                        "Deferred chest block entity must survive native region storage");
+                    var chest = (RandomizableContainerBlockEntity) level.getBlockEntity(chestPos);
+                    helper.assertTrue(chest.getLootTable() != null && chest.getLootTable().identifier().toString().equals(saved.get("table").getAsString())
+                            && chest.getLootTableSeed() == saved.get("seed").getAsLong(), "Unopened loot table and seed must remain unconsumed after restart");
+                    deferredChests++;
+                }
+            }
+            var readback = new ExpansionJournal(journal(level, generator).getParent(), level.getSeed(), generator.initialDiameter(), 14);
+            helper.assertTrue(readback.healthy() && readback.islands().equals(session.islands()), "The generation-14 journal reopens with its exact immutable identities");
+            result.put("saved_native_pieces", savedPieces); result.put("preserved_deferred_chests", deferredChests);
+            result.put("native_pool_fixture", verifyPoolFixture(helper, false));
+            result.put("gold_witness_preserved", true); result.put("journal_preserved", true); result.put("passed", true);
+            write(level, result, true); helper.succeed();
+        } catch (Exception exception) {
+            result.put("passed", false); result.put("failure", exception.toString());
+            try { write(level, result, true); } catch (IOException ignored) { /* Keep the original failure. */ }
+            throw new IllegalStateException("Lost City native reload failed", exception);
+        }
+    }
+
+    private static Map<String, Object> report(ServerLevel level) {
+        var report = new LinkedHashMap<String, Object>();
+        report.put("seed", level.getSeed()); report.put("process_id", ProcessHandle.current().pid());
+        report.put("world_directory", level.getServer().getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize().toString());
+        report.put("scope", "Actual native district generation on a fresh development root and one activated city expansion. "
+            + "Archetype coverage is a separate deterministic fixture; it does not claim every building occurs on every seed. "
+            + "Zombie checks inspect the effective spawn table, not a guaranteed daylight population. No personal world is opened.");
+        return report;
+    }
+
+    private static Path journal(ServerLevel level, SanctuaryChunkGenerator generator) {
+        return level.getServer().getWorldPath(LevelResource.ROOT).resolve("data").resolve(generator.journalDirectory()).resolve("expansions.json");
+    }
+    private static Path path(ServerLevel level, boolean reload) {
+        return Path.of("diagnostics", "lost-city-alpha14" + (reload ? "-reload" : "") + "-seed-" + level.getSeed() + ".json");
+    }
+    private static void write(ServerLevel level, Map<String, Object> report, boolean reload) throws IOException {
+        Path path = path(level, reload); Files.createDirectories(path.getParent());
+        Files.writeString(path, new GsonBuilder().setPrettyPrinting().create().toJson(report) + "\n");
+    }
+    private static String hash(String text) {
+        try { return HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(text.getBytes(java.nio.charset.StandardCharsets.UTF_8))); }
+        catch (NoSuchAlgorithmException impossible) { throw new AssertionError(impossible); }
+    }
+}
@@ -37,9 +37,11 @@ public final class PopulationDiagnostics {

    static void verifyLegacyIsolation(GameTestHelper helper) {
        var level = helper.getLevel();
-        var generator = (NoiseBasedChunkGenerator) level.getChunkSource().getGenerator();
+        var binding = binding(level);
+        var generator = binding.generator();
        var capacity = IslandCapacity.forGenerator(generator);
-        helper.assertTrue(capacity != null && capacity.players() == Integer.getInteger("sanctuary.test.players", 10),
+        helper.assertTrue(capacity != null && capacity.players() == (level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator unified
+                ? unified.capacity().players() : Integer.getInteger("sanctuary.test.players", 10)),
            "The engine must create the requested production world preset");
        helper.assertFalse(HydrologyRuntime.enabled(generator) || NaturalHydrologyRuntime.enabled(generator)
            || LayeredHydrologyRuntime.enabled(generator) || WoodlandHydrologyRuntime.enabled(generator)
@@ -56,24 +58,34 @@ public final class PopulationDiagnostics {
            helper.assertFalse(new PopulationDecorationsFeature().place(level, old, RandomSource.create(0), BlockPos.ZERO),
                "New cave decorations must refuse older saved worlds");
        }
-        helper.assertTrue(generator.getBiomeSource() instanceof PopulationIslandBiomeSource,
-            "The biome palette must use the new versioned resource family");
-        helper.assertTrue(generator.getBiomeSource().possibleBiomes().size() == 10
-                && generator.getBiomeSource().possibleBiomes().stream().allMatch(b -> b.getRegisteredName().startsWith("sanctuary:population_")),
-            "All ten layers of the ecology must remain available at each capacity");
+        if (level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator) {
+            helper.assertTrue(generator.getBiomeSource() instanceof SanctuaryBiomeSource
+                    && generator.getBiomeSource().possibleBiomes().size() == (((SanctuaryChunkGenerator) level.getChunkSource().getGenerator()).rootGeneration() == 14 ? 45 : 44)
+                    && generator.getBiomeSource().possibleBiomes().stream().map(b -> b.getRegisteredName()).collect(java.util.stream.Collectors.toSet()).containsAll(SanctuaryBiomeSource.REQUIRED_BIOMES),
+                "The unified generator retains all 44 historical biome holders, with Lost City added only in generation 14");
+            helper.assertTrue(binding.random() != level.getChunkSource().randomState(),
+                "The unified starter must use its real terrain state, never the expansion host fallback");
+        } else {
+            helper.assertTrue(generator.getBiomeSource() instanceof PopulationIslandBiomeSource,
+                "The biome palette must use the new versioned resource family");
+            helper.assertTrue(generator.getBiomeSource().possibleBiomes().size() == 10
+                    && generator.getBiomeSource().possibleBiomes().stream().allMatch(b -> b.getRegisteredName().startsWith("sanctuary:population_")),
+                "All ten layers of the ecology must remain available at each capacity");
+        }
    }

    static void verifyDensity(GameTestHelper helper) throws IOException {
        var level = helper.getLevel();
-        var generator = (NoiseBasedChunkGenerator) level.getChunkSource().getGenerator();
+        var binding = binding(level);
+        var generator = binding.generator();
        var capacity = IslandCapacity.forGenerator(generator);
        var density = level.registryAccess().lookupOrThrow(Registries.DENSITY_FUNCTION).getOrThrow(
            ResourceKey.create(Registries.DENSITY_FUNCTION, SanctuaryMod.id("population_" + capacity.players()))).value();
        helper.assertTrue(density instanceof PopulationIslandDensity, "Inspect the actual compiled population density");
        var island = (PopulationIslandDensity) density;
        helper.assertTrue(island.capacity() == capacity, "Noise settings and density must agree on saved capacity");
-        var random = level.getChunkSource().randomState();
-        var replay = RandomState.create(level.registryAccess().lookupOrThrow(Registries.NOISE), level.getSeed(), generator.generatorSettings().value());
+        var random = binding.random();
+        var replay = RandomState.create(level.registryAccess().lookupOrThrow(Registries.NOISE), random.seed(), generator.generatorSettings().value());
        int step = Math.max(8, (int) Math.ceil(capacity.terrainLimit() / 32.0));
        int extent = (int) Math.ceil(capacity.terrainLimit() / (double) step) * step;
        int solidColumns = 0, outerColumns = 0, emptyColumns = 0;
@@ -132,7 +144,7 @@ public final class PopulationDiagnostics {

    static void verifyExterior(GameTestHelper helper) {
        var level = helper.getLevel();
-        var capacity = IslandCapacity.forGenerator(level.getChunkSource().getGenerator());
+        var capacity = IslandCapacity.forGenerator(binding(level).generator());
        int edge = Math.floorDiv(capacity.terrainLimit() + 48, 16) + 1;
        for (int[] point : new int[][]{{edge,0},{-edge-1,0},{0,edge},{0,-edge-1},{256,0},{-257,0}}) {
            var chunk = full(helper, level, point[0], point[1]);
@@ -168,6 +180,7 @@ public final class PopulationDiagnostics {
        final GameTestHelper helper;
        final ServerLevel level;
        final NoiseBasedChunkGenerator generator;
+        final RandomState random;
        final IslandCapacity capacity;
        final List<PopulationHydrologyRuntime.RegionPlan> regions = new ArrayList<>();
        final Map<Long, LevelChunk> chunks = new TreeMap<>();
@@ -190,7 +203,9 @@ public final class PopulationDiagnostics {

        Context(GameTestHelper helper) {
            this.helper = helper; level = helper.getLevel();
-            generator = (NoiseBasedChunkGenerator) level.getChunkSource().getGenerator();
+            var binding = binding(level);
+            generator = binding.generator();
+            random = binding.random();
            capacity = IslandCapacity.forGenerator(generator);
        }

@@ -207,7 +222,7 @@ public final class PopulationDiagnostics {
            Set<Long> requested = new TreeSet<>();
            for (var target : targets) {
                SanctuaryMod.LOGGER.info("Capacity {}: inspecting hydrology in region {}", capacity.players(), target);
-                var region = PopulationHydrologyRuntime.regionPlan(generator, level.getChunkSource().randomState(), target);
+                var region = PopulationHydrologyRuntime.regionPlan(generator, random, target);
                regions.add(region);
                var plan = region.water();
                checkOwnership(region);
@@ -257,7 +272,7 @@ public final class PopulationDiagnostics {
                for (int dx = -144; dx <= 144; dx += 48) for (int dz = -144; dz <= 144; dz += 48) {
                    int x = ox+dx, z=oz+dz;
                    int top = generator.getBaseHeight(x,z,net.minecraft.world.level.levelgen.Heightmap.Types.WORLD_SURFACE,
-                        level,level.getChunkSource().randomState());
+                        level,random);
                    if (top > highest) { highest=top; bestX=x; bestZ=z; }
                }
                helper.assertTrue(highest > 48, "Every inspected region must contain real natural terrain");
@@ -294,7 +309,7 @@ public final class PopulationDiagnostics {
                    "Hydrology must never be truncated at or written across region ownership: "+cell);
                helper.assertTrue(ids.contains(cell.featureId()),"Each retained cell needs its complete owning feature");
                for(int y=cell.bedY()-cell.sedimentDepth()-1;y<=cell.bedY();y++)
-                    helper.assertTrue(level.getChunkSource().randomState().sampleBlockValueUncached(
+                    helper.assertTrue(random.sampleBlockValueUncached(
                        generator.generatorSettings().value().noiseRouter().finalDensity(),cell.x(),y,cell.z())>0,
                        "Regional translation must retain the real natural support below sediment: "+cell);
            }
@@ -388,7 +403,7 @@ public final class PopulationDiagnostics {
        }

        float natural(BlockPos p) {
-            return level.getChunkSource().randomState().sampleBlockValueUncached(
+            return random.sampleBlockValueUncached(
                generator.generatorSettings().value().noiseRouter().finalDensity(), p.getX(), p.getY(), p.getZ());
        }

@@ -428,7 +443,7 @@ public final class PopulationDiagnostics {
                    helper.assertTrue(natural(p) > 0 && actual.isCollisionShapeFullBlock(level, p),
                        "Every sediment layer and its two natural supports must remain full after generation and ticks: " + p + "=" + actual);
                    if (d >= cell.sedimentDepth()) continue;
-                    BlockState expected = PopulationMaterials.sedimentBlock(cell, level.getSeed(), d);
+                    BlockState expected = PopulationMaterials.sedimentBlock(cell, random.seed(), d);
                    boolean ore = actual.is(Blocks.COAL_ORE) || actual.is(Blocks.DEEPSLATE_COAL_ORE)
                        || actual.is(Blocks.IRON_ORE) || actual.is(Blocks.DEEPSLATE_IRON_ORE)
                        || actual.is(Blocks.COPPER_ORE) || actual.is(Blocks.DEEPSLATE_COPPER_ORE)
@@ -575,10 +590,15 @@ public final class PopulationDiagnostics {
            Files.createDirectories(output.getParent());
            var report=new LinkedHashMap<String,Object>();
            report.put("players",capacity.players());report.put("seed",level.getSeed());
+            report.put("terrain_seed", random.seed());
+            if (level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator unified) {
+                report.put("generation", 13); report.put("diameter", unified.initialDiameter());
+                report.put("rejected_decoration_writes", unified.rejectedDecorationWrites());
+            }
            report.put("mod_version",FabricLoader.getInstance().getModContainer("sanctuary").orElseThrow().getMetadata().getVersion().getFriendlyString());
            report.put("settings",generator.generatorSettings().getRegisteredName());
            report.put("regions_at_initial_spawn",regionsAtInitialSpawn);
-            report.put("regions_cached_after_inspection",PopulationHydrologyRuntime.cachedRegionCount(level.getChunkSource().randomState()));
+            report.put("regions_cached_after_inspection",PopulationHydrologyRuntime.cachedRegionCount(random));
            report.put("regions",regionReports);report.put("inspected_full_chunks",chunks.size());
            report.put("retained_water_blocks",expectedWater.size());report.put("tested_springs",springs.size());
            report.put("tested_spills",spills.size());report.put("fluid_ticks",elapsed);
@@ -597,6 +617,10 @@ public final class PopulationDiagnostics {
        }
    }

+    private static PopulationGenerationContext.Binding binding(ServerLevel level) {
+        return Objects.requireNonNull(PopulationGenerationContext.of(level), "This diagnostic requires Population or unified Sanctuary generation");
+    }
+
    private static String json(Object value) {return new GsonBuilder().setPrettyPrinting().create().toJson(value)+"\n";}
    private static BlockPos pos(PopulationHydrology.Position p) {return new BlockPos(p.x(),p.y(),p.z());}
    private static BlockPos lavaPos(PopulationLavaDeposit.Position p) {return new BlockPos(p.x(),p.y(),p.z());}
@@ -34,12 +34,12 @@ final class PopulationPersistenceDiagnostics {
        var presets = access.lookupOrThrow(Registries.WORLD_PRESET);
        var standard = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET,
            SanctuaryMod.id("sanctuary"))).value();
-        helper.assertTrue(IslandCapacity.forGenerator(standard.createWorldDimensions().overworld()) == IslandCapacity.TEN,
-            "The public Sanctuary preset defaults to the new large geometry");
+        helper.assertTrue(standard.createWorldDimensions().overworld() instanceof fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator unified && unified.initialDiameter() == 724,
+            "The public Sanctuary preset defaults to the unified medium geometry");
        var visible = presets.getOrThrow(WorldPresetTags.NORMAL).stream().map(holder -> holder.getRegisteredName())
            .filter(name -> name.startsWith("sanctuary:")).collect(Collectors.toSet());
-        helper.assertTrue(visible.equals(Set.of("sanctuary:sanctuary", "sanctuary:sanctuary_5", "sanctuary:expansion_lab")),
-            "World creation must preserve small and large and add the separate expansion laboratory");
+        helper.assertTrue(visible.equals(Set.of("sanctuary:sanctuary")),
+            "Only Sanctuary is public; saved historical presets remain registered");
        helper.assertTrue(presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("expansion_lab")))
                .value().createWorldDimensions().overworld() instanceof fr.koka.sanctuary.expansion.ExpansionChunkGenerator,
            "The laboratory must use its own codec, without changing the existing presets");
@@ -55,7 +55,7 @@ final class PopulationPersistenceDiagnostics {
        Files.createDirectories(testRoot);
        LevelStorageSource storage = LevelStorageSource.createDefault(testRoot);
        for (int players : new int[]{5, 10, 20, 100}) {
-            String presetId = players == 10 ? "sanctuary" : "sanctuary_" + players;
+            String presetId = "sanctuary_" + players;
            WorldDimensions dimensions = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET,
                SanctuaryMod.id(presetId))).value().createWorldDimensions();
            helper.assertTrue(IslandCapacity.forGenerator(dimensions.overworld()) == IslandCapacity.fromPlayers(players),
@@ -0,0 +1,322 @@
+package fr.koka.sanctuary.gametest;
+
+import com.google.gson.GsonBuilder;
+import com.mojang.serialization.JsonOps;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.worldgen.*;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+import net.fabricmc.fabric.api.gametest.v1.GameTest;
+import net.fabricmc.loader.api.FabricLoader;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.gametest.framework.GameTestHelper;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.server.level.GenerationChunkHolder;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.util.StaticCache2D;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ImposterProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkPyramid;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+
+/** Alpha.13 engine checks use the real starter binding and never reconfigure saved worlds. */
+public final class UnifiedWorldGameTests {
+    private static final List<String> CAVES = List.of("minecraft:lush_caves", "minecraft:dripstone_caves", "minecraft:sulfur_caves");
+    private static final Direction[] SIDES = {Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST};
+
+    @GameTest(maxTicks = 3000)
+    public void retainedHydrologySurvivesNativeDecoration(GameTestHelper helper) throws IOException {
+        PopulationDiagnostics.start(helper);
+    }
+
+    @GameTest(maxTicks = 200)
+    public void sizeAndPublicChoiceSurviveDiskStorage(GameTestHelper helper) throws IOException {
+        UnifiedWorldSettingsDiagnostics.verify(helper);
+        helper.succeed();
+    }
+
+    @GameTest(maxTicks = 200)
+    public void legacyPipelinesRemainIsolated(GameTestHelper helper) {
+        PopulationDiagnostics.verifyLegacyIsolation(helper);
+        helper.succeed();
+    }
+
+    @GameTest(maxTicks = 200)
+    public void populationTerrainAndNaturalSpawnRemainPresent(GameTestHelper helper) throws IOException {
+        PopulationDiagnostics.verifyDensity(helper);
+        var level = helper.getLevel();
+        var binding = binding(level);
+        helper.assertTrue(level.getMinY() == 0 && level.getHeight() == 384, "Unification preserves the complete vertical world extent");
+        var spawn = SanctuaryWorldGameTests.initialSpawn;
+        helper.assertTrue(spawn != null, "Capture the original natural spawn before the GameTest fixtures move it");
+        var at = spawn.pos();
+        helper.assertTrue(level.getBlockState(at.below()).isCollisionShapeFullBlock(level, at.below())
+                && level.getBlockState(at).getCollisionShape(level, at).isEmpty()
+                && level.getBlockState(at.above()).getCollisionShape(level, at.above()).isEmpty(),
+            "The unmodified starter spawn must stand on real usable terrain");
+        helper.assertTrue(natural(binding, at.below()) > 0, "The starter spawn never requires an added platform");
+        helper.succeed();
+    }
+
+    @GameTest(maxTicks = 200)
+    public void exteriorAndLowerMarginRemainVoid(GameTestHelper helper) {
+        PopulationDiagnostics.verifyExterior(helper);
+        PopulationDiagnostics.verifyLowerMargin(helper);
+        helper.succeed();
+    }
+
+    @GameTest(maxTicks = 200)
+    public void nativeCaveFeaturesExistOnNaturalLayers(GameTestHelper helper) throws IOException {
+        ServerLevel level = helper.getLevel();
+        var binding = binding(level);
+        var generator = unified(level);
+        List<Site> sites = caveSites(binding);
+        Map<Long, LevelChunk> chunks = new TreeMap<>();
+        for (Site site : sites) {
+            int cx = site.x() >> 4, cz = site.z() >> 4;
+            for (int dx = -1; dx <= 1; dx++) for (int dz = -1; dz <= 1; dz++) {
+                long key = ChunkPos.pack(cx + dx, cz + dz);
+                if (!chunks.containsKey(key)) chunks.put(key, full(helper, level, cx + dx, cz + dz));
+            }
+        }
+        helper.assertTrue(chunks.size() <= 27, "Native cave inspection is at most three independent 3x3 FULL patches");
+        Map<String, Map<String, Long>> counts = new TreeMap<>();
+        CAVES.forEach(name -> counts.put(name, new TreeMap<>()));
+        Map<String, Long> allBlocks = new TreeMap<>();
+        Map<String, Long> surfaceBiomes = new TreeMap<>();
+        int largestDripstoneColumn = 0;
+        var density = binding.generator().generatorSettings().value().noiseRouter().finalDensity();
+        for (LevelChunk chunk : chunks.values()) {
+            for (var section : chunk.getSections()) section.getStates().count((state, count) -> {
+                if (!state.isAir()) allBlocks.merge(BuiltInRegistries.BLOCK.getKey(state.getBlock()).toString(), (long) count, Long::sum);
+            });
+            for (int dx = 0; dx < 16; dx++) for (int dz = 0; dz < 16; dz++) {
+                int x = chunk.getPos().getMinBlockX() + dx, z = chunk.getPos().getMinBlockZ() + dz;
+                int run = 0;
+                for (int y = 0; y < 256; y++) {
+                    var pos = new BlockPos(x, y, z);
+                    var state = chunk.getBlockState(pos);
+                    String biome = chunk.getNoiseBiome(x >> 2, y >> 2, z >> 2).getRegisteredName();
+                    var bucket = counts.get(biome);
+                    if (bucket != null && !state.isAir()) bucket.merge(BuiltInRegistries.BLOCK.getKey(state.getBlock()).toString(), 1L, Long::sum);
+                    // Large vanilla pillars add thick dripstone into original cave air. A painted
+                    // floor or the old hand-placed support block cannot satisfy this witness.
+                    if (state.is(Blocks.DRIPSTONE_BLOCK) && biome.equals("minecraft:dripstone_caves")
+                            && binding.random().sampleBlockValueUncached(density, x, y, z) <= 0) run++;
+                    else run = 0;
+                    largestDripstoneColumn = Math.max(largestDripstoneColumn, run);
+                }
+                int top = chunk.getHeight(net.minecraft.world.level.levelgen.Heightmap.Types.WORLD_SURFACE, dx, dz);
+                if (top > 190) surfaceBiomes.merge(chunk.getNoiseBiome(x >> 2, top >> 2, z >> 2).getRegisteredName(), 1L, Long::sum);
+            }
+        }
+        var report = report(level);
+        report.put("sites", sites); report.put("inspected_full_chunks", chunks.size());
+        report.put("native_cave_blocks", counts); report.put("all_observed_blocks", allBlocks);
+        report.put("surface_biomes", surfaceBiomes); report.put("largest_natural_air_dripstone_column", largestDripstoneColumn);
+        report.put("rejected_decoration_writes", generator.rejectedDecorationWrites());
+        Map<String, Object> atmospheres = new TreeMap<>();
+        var ops = RegistryOps.create(JsonOps.INSTANCE, level.registryAccess());
+        for (String name : CAVES) {
+            var biome = level.registryAccess().lookupOrThrow(Registries.BIOME)
+                .getValue(net.minecraft.resources.Identifier.parse(name));
+            var encoded = Biome.DIRECT_CODEC.encodeStart(ops, biome).getOrThrow().getAsJsonObject();
+            atmospheres.put(name, encoded.get("attributes"));
+            helper.assertTrue(encoded.get("attributes").toString().contains("music.overworld." + name.substring("minecraft:".length())),
+                "The native cave's music must remain present in its loaded biome attributes: " + name);
+            if (name.equals("minecraft:sulfur_caves")) helper.assertTrue(encoded.get("attributes").toString().contains("minecraft:visual/fog_color")
+                    && encoded.get("attributes").toString().contains("minecraft:sulfur_cube"),
+                "The sulfur cave retains its distinct fog and native creature table");
+        }
+        report.put("native_attributes", atmospheres);
+        report.put("scope", "Up to 27 FULL chunks selected from real cave density; counts are observed blocks, not island-wide resource estimates or client screenshots");
+        boolean passed = false;
+        Set<String> encountered = new TreeSet<>(); sites.forEach(site -> encountered.add(site.biome()));
+        Set<String> verified = new TreeSet<>();
+        try {
+            helper.assertTrue(!sites.isEmpty(), "The demonstration world must provide at least one real native cave site");
+            if (encountered.contains("minecraft:lush_caves")) {
+                helper.assertTrue(count(counts, "minecraft:lush_caves", "minecraft:moss_block") > 0
+                        && count(counts, "minecraft:lush_caves", "minecraft:cave_vines")
+                            + count(counts, "minecraft:lush_caves", "minecraft:cave_vines_plant") > 0,
+                    "Actual native lush caverns must have moss and harvestable hanging vines");
+                verified.add("minecraft:lush_caves");
+            }
+            if (encountered.contains("minecraft:dripstone_caves")) {
+                helper.assertTrue(count(counts, "minecraft:dripstone_caves", "minecraft:pointed_dripstone") > 0 && largestDripstoneColumn >= 5,
+                    "Actual native dripstone caverns must include points and a substantial pillar in natural cave air");
+                verified.add("minecraft:dripstone_caves");
+            }
+            if (encountered.contains("minecraft:sulfur_caves")) {
+                helper.assertTrue(count(counts, "minecraft:sulfur_caves", "minecraft:sulfur") > 0
+                        && count(counts, "minecraft:sulfur_caves", "minecraft:sulfur_spike") > 0,
+                    "Actual native sulfur caverns must include native rock and spikes");
+                verified.add("minecraft:sulfur_caves");
+            }
+            helper.assertTrue(surfaceBiomes.keySet().stream().anyMatch(name -> name.startsWith("sanctuary:population_")),
+                "The starter surface must retain its Population biome family above these lower cave patches");
+            passed = true; helper.succeed();
+        } finally {
+            report.put("encountered_native_types", encountered); report.put("verified_native_types", verified);
+            report.put("unverified_native_types", CAVES.stream().filter(name -> !verified.contains(name)).toList());
+            report.put("all_three_types_demonstrated_here", verified.containsAll(CAVES));
+            report.put("validation_contract", "Every encountered type must pass its full block evidence; the release also requires cumulative evidence for all three types across its fresh demonstration worlds");
+            report.put("passed", passed); write(level, "native-caves", report);
+        }
+    }
+
+    @GameTest(maxTicks = 200)
+    public void decorationGuardRejectsChangesToHydrology(GameTestHelper helper) throws IOException {
+        var level = helper.getLevel(); var binding = binding(level); var generator = unified(level);
+        var plan = PopulationHydrologyRuntime.regionPlan(binding.generator(), binding.random(), new IslandCapacity.Region(0, 0)).water();
+        LinkedHashSet<BlockPos> witnesses = new LinkedHashSet<>();
+        int shells = 0;
+        for (var cell : plan.cells()) {
+            if (!cell.hasWater()) continue;
+            witnesses.add(new BlockPos(cell.x(), cell.waterY(), cell.z()));
+            witnesses.add(new BlockPos(cell.x(), cell.bedY() - cell.sedimentDepth() - 1, cell.z()));
+            for (Direction side : SIDES) {
+                var wall = new BlockPos(cell.x(), cell.waterY(), cell.z()).relative(side);
+                var next = plan.cellAt(wall.getX(), wall.getY(), wall.getZ());
+                if ((next == null || !next.hasWater()) && natural(binding, wall) > 0) { witnesses.add(wall); shells++; }
+            }
+            if (shells >= 2 && witnesses.size() >= 12) break;
+        }
+        int boundaryWitnesses = 0;
+        for (var cell : plan.cells()) {
+            if (!cell.hasWater()) continue;
+            for (Direction side : SIDES) {
+                var water = new BlockPos(cell.x(), cell.waterY(), cell.z());
+                var wall = water.relative(side);
+                var next = plan.cellAt(wall.getX(), wall.getY(), wall.getZ());
+                if (ChunkPos.pack(water) != ChunkPos.pack(wall) && (next == null || !next.hasWater()) && natural(binding, wall) > 0) {
+                    witnesses.add(wall); boundaryWitnesses++;
+                }
+            }
+            if (boundaryWitnesses >= 4) break;
+        }
+        for (var spring : plan.springs()) { witnesses.add(position(spring.source())); witnesses.add(position(spring.outlet())); }
+        for (var spill : plan.spills()) { witnesses.add(position(spill.source())); witnesses.add(position(spill.outlet())); }
+        helper.assertTrue(!witnesses.isEmpty() && shells > 0, "Inspect real source, bed and natural wall witnesses");
+        Map<Long, SanctuaryDecorationProtection> masks = new HashMap<>();
+        int compared = 0;
+        for (var witness : witnesses) {
+            var mask = masks.computeIfAbsent(ChunkPos.pack(witness), ignored -> SanctuaryDecorationProtection.create(binding, witness.getX() >> 4, witness.getZ() >> 4));
+            helper.assertTrue(mask.protects(witness) && generator.protectsDecoration(witness), "The published decoration mask protects the complete water geometry: " + witness);
+            helper.assertTrue(PopulationHydrologyRuntime.protects(binding.generator(), binding.random(), witness, 1, 1, 1),
+                "The mask must agree with the hydrology protection oracle including one-block clearance at natural walls");
+            compared++;
+        }
+        var witness = witnesses.getFirst();
+        LevelChunk chunk = full(helper, level, witness.getX() >> 4, witness.getZ() >> 4);
+        // FULL holders deliberately expose a read-only ImposterProtoChunk to generation.
+        // Use a test-local writable view; leave the world's real holder and saved status alone.
+        var writable = new ImposterProtoChunk(chunk, true);
+        GenerationChunkHolder testHolder = new GenerationChunkHolder(chunk.getPos()) {
+            @Override protected void addSaveDependency(java.util.concurrent.CompletableFuture<?> dependency) {}
+            @Override public int getTicketLevel() { return 0; }
+            @Override public int getQueueLevel() { return 0; }
+            @Override public ChunkAccess getChunkIfPresentUnchecked(ChunkStatus status) { return writable; }
+        };
+        var holders = StaticCache2D.<GenerationChunkHolder>create(chunk.getPos().x(), chunk.getPos().z(), 0,
+            (x, z) -> testHolder);
+        var worldgen = new WorldGenRegion(level, holders, ChunkPyramid.GENERATION_PYRAMID.getStepTo(ChunkStatus.FEATURES), chunk);
+        var before = chunk.getBlockState(witness);
+        long rejected = generator.rejectedDecorationWrites();
+        try {
+            helper.assertFalse(worldgen.setBlock(witness, Blocks.DIAMOND_BLOCK.defaultBlockState(), 2, 0),
+                "A real WorldGenRegion write must be denied on protected retained water");
+            helper.assertTrue(chunk.getBlockState(witness).equals(before) && generator.rejectedDecorationWrites() == rejected + 1,
+                "The native write path must preserve the original block and record the rejection");
+        } finally { if (!chunk.getBlockState(witness).equals(before)) chunk.setBlockState(witness, before, 0); }
+        BlockPos free = new BlockPos(chunk.getPos().getMinBlockX() + 8, 383, chunk.getPos().getMinBlockZ() + 8);
+        var freeBefore = chunk.getBlockState(free);
+        helper.assertFalse(generator.protectsDecoration(free), "A distant air witness must be outside the hydrology mask");
+        try {
+            helper.assertTrue(worldgen.setBlock(free, Blocks.DIAMOND_BLOCK.defaultBlockState(), 2, 0)
+                    && chunk.getBlockState(free).is(Blocks.DIAMOND_BLOCK),
+                "Decoration outside protected volumes must remain writable");
+        } finally { chunk.setBlockState(free, freeBefore, 0); }
+        write(level, "decoration-guard", Map.of("generation", 13, "seed", level.getSeed(),
+            "diameter", generator.initialDiameter(), "compared_plan_points", compared,
+            "natural_wall_witnesses", shells, "walls_owned_by_adjacent_chunk", boundaryWitnesses, "actual_write_rejected", true, "unprotected_write_allowed", true, "passed", true));
+        helper.succeed();
+    }
+
+    private record Site(String biome, int x, int floorY, int roofY, int z, int score) {}
+
+    private static List<Site> caveSites(PopulationGenerationContext.Binding binding) {
+        var capacity = IslandCapacity.forGenerator(binding.generator());
+        var resolver = binding.generator().getBiomeSource().createUncachedResolver(binding.random());
+        var density = binding.generator().generatorSettings().value().noiseRouter().finalDensity();
+        Map<String, List<Site>> candidates = new TreeMap<>(); CAVES.forEach(name -> candidates.put(name, new ArrayList<>()));
+        int radius = (capacity.terrainLimit() + 15) / 16;
+        for (int cx = -radius; cx <= radius; cx++) for (int cz = -radius; cz <= radius; cz++) {
+            int x = cx * 16 + 8, z = cz * 16 + 8;
+            if (Math.hypot(x, z) >= capacity.radius() - 24) continue;
+            for (int y = 164; y >= 40; y--) {
+                String biome = resolver.getNoiseBiome(x >> 2, (y + 1) >> 2, z >> 2).getRegisteredName();
+                var bucket = candidates.get(biome); if (bucket == null) continue;
+                if (sample(binding, density, x, y, z) <= 0 || sample(binding, density, x, y + 1, z) > 0
+                        || sample(binding, density, x, y + 2, z) > 0 || sample(binding, density, x, y - 1, z) <= 0) continue;
+                int roof = y + 3;
+                while (roof < Math.min(256, y + 96) && sample(binding, density, x, roof, z) <= 0) roof++;
+                if (roof >= Math.min(256, y + 96) || roof - y < 10 || sample(binding, density, x, roof + 1, z) <= 0) continue;
+                int score = Math.min(48, roof - y);
+                for (int dx : new int[]{-4, 0, 4}) for (int dz : new int[]{-4, 0, 4})
+                    if (sample(binding, density, x + dx, y, z + dz) > 0 && sample(binding, density, x + dx, roof, z + dz) > 0) score += 8;
+                bucket.add(new Site(biome, x, y, roof, z, score));
+                break;
+            }
+        }
+        List<Site> sites = new ArrayList<>();
+        for (String cave : CAVES) {
+            var ordered = candidates.get(cave).stream().sorted(Comparator.comparingInt(Site::score).reversed()
+                .thenComparingDouble(s -> Math.hypot(s.x(), s.z())).thenComparingInt(Site::x).thenComparingInt(Site::z)).toList();
+            for (Site candidate : ordered.stream().limit(32).toList()) {
+                var base = new BlockPos(candidate.x(), candidate.floorY() + 1, candidate.z());
+                if (!PopulationHydrologyRuntime.protects(binding.generator(), binding.random(), base, 8,
+                        candidate.roofY() - candidate.floorY(), 3)) { sites.add(candidate); break; }
+            }
+        }
+        return List.copyOf(sites);
+    }
+
+    private static float sample(PopulationGenerationContext.Binding binding, DensityFunction density, int x, int y, int z) {
+        return binding.random().sampleBlockValueUncached(density, x, y, z);
+    }
+    private static float natural(PopulationGenerationContext.Binding binding, BlockPos pos) {
+        return sample(binding, binding.generator().generatorSettings().value().noiseRouter().finalDensity(), pos.getX(), pos.getY(), pos.getZ());
+    }
+    private static long count(Map<String, Map<String, Long>> counts, String biome, String block) { return counts.get(biome).getOrDefault(block, 0L); }
+    private static BlockPos position(PopulationHydrology.Position p) { return new BlockPos(p.x(), p.y(), p.z()); }
+    private static PopulationGenerationContext.Binding binding(ServerLevel level) { return Objects.requireNonNull(PopulationGenerationContext.of(level)); }
+    private static SanctuaryChunkGenerator unified(ServerLevel level) { return (SanctuaryChunkGenerator) level.getChunkSource().getGenerator(); }
+    private static LevelChunk full(GameTestHelper helper, ServerLevel level, int x, int z) {
+        var chunk = level.getChunkSource().getChunk(x, z, ChunkStatus.FULL, true);
+        helper.assertTrue(chunk instanceof LevelChunk, "Inspect only real fully generated chunks"); return (LevelChunk) chunk;
+    }
+    private static Map<String, Object> report(ServerLevel level) {
+        var report = new LinkedHashMap<String, Object>();
+        report.put("generation", 13); report.put("seed", level.getSeed()); report.put("diameter", unified(level).initialDiameter());
+        report.put("mod_version", FabricLoader.getInstance().getModContainer("sanctuary").orElseThrow().getMetadata().getVersion().getFriendlyString());
+        return report;
+    }
+    private static void write(ServerLevel level, String kind, Object report) throws IOException {
+        Path target = Path.of("diagnostics", "unified-" + unified(level).initialDiameter() + "-seed-" + level.getSeed() + "-" + kind + ".json");
+        Files.createDirectories(target.getParent());
+        Files.writeString(target, new GsonBuilder().setPrettyPrinting().create().toJson(report) + "\n");
+        SanctuaryMod.LOGGER.info("Unified {} seed {} wrote {}", unified(level).initialDiameter(), level.getSeed(), target);
+    }
+}
@@ -0,0 +1,91 @@
+package fr.koka.sanctuary.gametest;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonPrimitive;
+import com.mojang.serialization.JsonOps;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+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.tags.WorldPresetTags;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.WorldGenSettings;
+import net.minecraft.world.level.levelgen.WorldOptions;
+import net.minecraft.world.level.storage.LevelStorageSource;
+
+/** Storage contract shared by the public preset and its three client-selected sizes. */
+final class UnifiedWorldSettingsDiagnostics {
+    static void verify(GameTestHelper helper) throws IOException {
+        var access = helper.getLevel().registryAccess();
+        var presets = access.lookupOrThrow(Registries.WORLD_PRESET);
+        var publicPreset = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET,
+                SanctuaryMod.id("sanctuary"))).value();
+        var standard = publicPreset.createWorldDimensions();
+        helper.assertTrue(standard.overworld() instanceof SanctuaryChunkGenerator,
+                "The sole Sanctuary world type must use the unified generator");
+        var historical = presets.getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("sanctuary_v13"))).value().createWorldDimensions();
+        helper.assertTrue(historical.overworld() instanceof SanctuaryChunkGenerator old && old.rootGeneration() == 13 && !old.source().citiesEnabled(),
+                "Historical alpha.13 codec retains its original biome source and generation");
+        var generator = (SanctuaryChunkGenerator) standard.overworld();
+        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())
+                    .filter(name -> name.startsWith("sanctuary:")).collect(Collectors.toSet());
+            helper.assertTrue(visible.equals(Set.of("sanctuary:sanctuary")),
+                    "Only one Sanctuary choice is present in the normal and extended world-type lists");
+        }
+
+        var ops = RegistryOps.create(JsonOps.INSTANCE, access);
+        var activeCodec = generator.rootGeneration() == 14 ? SanctuaryChunkGenerator.CITY_CODEC : SanctuaryChunkGenerator.CODEC;
+        var serialized = activeCodec.codec().encodeStart(ops, generator).getOrThrow().getAsJsonObject();
+        serialized.remove("initial_diameter");
+        helper.assertTrue(activeCodec.codec().parse(ops, serialized).getOrThrow().initialDiameter() == 724,
+                "An omitted new-generation size defaults to Medium");
+        for (int rejected : new int[]{0, 511, 513, 723, 725, 768, 1023, 1025, 2048}) {
+            helper.assertTrue(SanctuaryChunkGenerator.DIAMETER_CODEC.parse(JsonOps.INSTANCE, new JsonPrimitive(rejected)).error().isPresent(),
+                    "Only the three supported initial diameters are accepted");
+        }
+
+        Path directory = Path.of("diagnostics", "unified-world-settings-seed-" + helper.getLevel().getSeed()).toAbsolutePath();
+        Files.createDirectories(directory);
+        var storage = LevelStorageSource.createDefault(directory);
+        List<Map<String, Object>> results = new ArrayList<>();
+        for (int diameter : new int[]{512, 724, 1024}) {
+            var chosen = generator.withInitialDiameter(diameter);
+            helper.assertTrue(generator.initialDiameter() == 724 && chosen.source() != generator.source(),
+                    "Customizing a new world must copy the generator and its mutable biome source");
+            var dimensions = standard.replaceOverworldGenerator(access, chosen);
+            for (var dimension : List.of(LevelStem.NETHER, LevelStem.END)) {
+                helper.assertTrue(dimensions.get(dimension).equals(standard.get(dimension)),
+                        "Customizing the island preserves the other dimensions");
+            }
+            var original = new WorldGenSettings(new WorldOptions(helper.getLevel().getSeed(), false, true), dimensions);
+            String name = "diameter-" + diameter;
+            try (var save = storage.createAccess(name)) {
+                LevelStorageSource.writeWorldGenSettings(access, storage.getLevelPath(name), original);
+                var restored = LevelStorageSource.readExistingSavedData(save, access, WorldGenSettings.TYPE).getOrThrow();
+                helper.assertTrue(restored.dimensions().overworld() instanceof SanctuaryChunkGenerator reloaded
+                                && reloaded.initialDiameter() == diameter && reloaded.rootGeneration() == generator.rootGeneration(),
+                        "The selected diameter must survive real world-settings storage");
+                helper.assertTrue(WorldGenSettings.CODEC.encodeStart(ops, restored).getOrThrow()
+                                .equals(WorldGenSettings.CODEC.encodeStart(ops, original).getOrThrow()),
+                        "Seed, generation options and all dimensions survive the disk round trip");
+                results.add(Map.of("diameter", diameter, "disk_round_trip", true));
+            }
+        }
+        Files.writeString(directory.resolve("round-trip.json"), new GsonBuilder().setPrettyPrinting().create().toJson(Map.of(
+                "seed", helper.getLevel().getSeed(), "default_diameter", 724,
+                "public_presets", List.of("sanctuary:sanctuary"), "sizes", results,
+                "invalid_diameters_rejected", true, "copied_biome_source", true, "passed", true)) + "\n");
+    }
+}
@@ -23,13 +23,20 @@ public final class WorldgenPerformanceGameTests {
    @GameTest(maxTicks = 3000)
    public void spawnAreaAndExploration(GameTestHelper helper) throws Exception {
        ServerLevel level = helper.getLevel();
-        var capacity = IslandCapacity.forGenerator(level.getChunkSource().getGenerator());
+        var binding = fr.koka.sanctuary.worldgen.PopulationGenerationContext.of(level);
+        var capacity = IslandCapacity.forGenerator(binding.generator());
        var spawn = SanctuaryWorldGameTests.initialSpawn.pos();
        int cx = spawn.getX() >> 4, cz = spawn.getZ() >> 4;
        var report = new LinkedHashMap<String, Object>();
        report.put("version", FabricLoader.getInstance().getModContainer("sanctuary").orElseThrow()
            .getMetadata().getVersion().getFriendlyString());
        report.put("players", capacity.players()); report.put("seed", level.getSeed());
+        var host = level.getChunkSource().getGenerator();
+        String profile = "players-" + capacity.players();
+        if (host instanceof fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator unified) {
+            report.put("generation", 13); report.put("initial_diameter", unified.initialDiameter());
+            profile = "unified-" + unified.initialDiameter();
+        }
        report.put("spawn", List.of(spawn.getX(), spawn.getY(), spawn.getZ()));
        report.put("java", System.getProperty("java.version"));
        report.put("processors", Runtime.getRuntime().availableProcessors());
@@ -78,13 +85,13 @@ public final class WorldgenPerformanceGameTests {
        report.put("exploration_ms", millis(System.nanoTime() - exploreStart));
        report.put("exploration_full_chunks", 80); report.put("exploration_steps", steps);
        report.put("exploration_chunk_latency_ms", latency(chunkTimes));
-        report.put("regions_cached", PopulationHydrologyRuntime.cachedRegionCount(level.getChunkSource().randomState()));
+        report.put("regions_cached", PopulationHydrologyRuntime.cachedRegionCount(binding.random()));
        report.put("scope", "Fresh development world; 289 FULL chunks around natural spawn, then 80 eastward FULL chunks. "
            + "Synchronous server requests include dependent generation up to FULL, not guaranteed ticking readiness, client GPU, network, FPS or player load. "
            + "World creation before the test is timed separately by Minecraft's startup log.");
        helper.assertTrue(count == 289 && land > 100, "The benchmark must generate actual playable terrain");
        report.put("passed", true);
-        Path output = Path.of("diagnostics", "generation-performance-players-" + capacity.players() + "-seed-" + level.getSeed() + ".json");
+        Path output = Path.of("diagnostics", "generation-performance-" + profile + "-seed-" + level.getSeed() + ".json");
        Files.createDirectories(output.getParent());
        Files.writeString(output, new GsonBuilder().setPrettyPrinting().create().toJson(report) + "\n");
        helper.succeed();
@@ -21,7 +21,7 @@ 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$paceExpansionWorkers(CallbackInfo ci) {
-        if (Boolean.getBoolean("sanctuary.test.expansion")) {
+        if (Boolean.getBoolean("sanctuary.test.expansion") || Boolean.getBoolean("sanctuary.test.lostCity") || Boolean.getBoolean("sanctuary.test.voidReuse")) {
            long until = System.nanoTime() + 20_000_000L;
            long remaining;
            // Worker completion unparks the server; keep the pacing deadline despite those signals.
@@ -44,11 +44,12 @@ public abstract class SanctuaryGameTestServerMixin {
    @Redirect(method = "lambda$create$1", at = @At(value = "FIELD", target =
        "Lnet/minecraft/world/level/levelgen/presets/WorldPresets;FLAT_ALL_DIMENSIONS:Lnet/minecraft/resources/ResourceKey;"))
    private static ResourceKey<WorldPreset> sanctuary$selectActualPreset() {
+        if (Boolean.getBoolean("sanctuary.test.unified")) return ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("sanctuary"));
        if (Boolean.getBoolean("sanctuary.test.expansion")) return ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id("expansion_lab"));
        int players = Integer.getInteger("sanctuary.test.players", 10);
        String preset = switch (players) {
            case 5 -> "sanctuary_5";
-            case 10 -> "sanctuary";
+            case 10 -> "sanctuary_10";
            case 20 -> "sanctuary_20";
            case 100 -> "sanctuary_100";
            default -> throw new IllegalArgumentException("Test geometry must be 5, 10, 20 or 100");
@@ -56,12 +57,26 @@ public abstract class SanctuaryGameTestServerMixin {
        return ResourceKey.create(Registries.WORLD_PRESET, SanctuaryMod.id(preset));
    }

+    @Redirect(method = "lambda$create$1", at = @At(value = "INVOKE", target =
+        "Lnet/minecraft/world/level/levelgen/presets/WorldPreset;createWorldDimensions()Lnet/minecraft/world/level/levelgen/WorldDimensions;"))
+    private static net.minecraft.world.level.levelgen.WorldDimensions sanctuary$customizeSize(WorldPreset preset,
+            net.minecraft.world.level.LevelSettings settings, net.minecraft.server.WorldLoader.DataLoadContext context) {
+        var dimensions = preset.createWorldDimensions();
+        if (Boolean.getBoolean("sanctuary.test.unified")) {
+            var generator = (fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator) dimensions.overworld();
+            return dimensions.replaceOverworldGenerator(context.datapackWorldRegistries(),
+                generator.withInitialDiameter(Integer.getInteger("sanctuary.test.diameter", 724)));
+        }
+        return dimensions;
+    }
+
    @Inject(method = "startTests", at = @At("HEAD"))
    private void sanctuary$captureInitialSpawn(ServerLevel level, CallbackInfo ci) {
        // The framework moves its own spawn to a random test grid after this point.
        SanctuaryWorldGameTests.initialSpawn = level.getRespawnData();
        if (Boolean.getBoolean("sanctuary.test.expansion")) return;
-        fr.koka.sanctuary.gametest.PopulationDiagnostics.regionsAtInitialSpawn =
-            fr.koka.sanctuary.worldgen.PopulationHydrologyRuntime.cachedRegionCount(level.getChunkSource().randomState());
+        var binding = fr.koka.sanctuary.worldgen.PopulationGenerationContext.of(level);
+        fr.koka.sanctuary.gametest.PopulationDiagnostics.regionsAtInitialSpawn = binding == null ? 0 :
+            fr.koka.sanctuary.worldgen.PopulationHydrologyRuntime.cachedRegionCount(binding.random());
    }
 }
@@ -1,5 +1,8 @@
 package fr.koka.sanctuary;

+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import fr.koka.sanctuary.worldgen.SanctuaryBiomeSource;
+
 import fr.koka.sanctuary.worldgen.CavernIslandBiomeSource;
 import fr.koka.sanctuary.worldgen.PopulationIslandDensity;
 import fr.koka.sanctuary.worldgen.PopulationIslandBiomeSource;
@@ -46,6 +49,11 @@ public final class SanctuaryMod implements ModInitializer {
        fr.koka.sanctuary.expansion.ExpansionRuntime.register();
        fr.koka.sanctuary.expansion.ExpansionCommands.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);
+        Registry.register(BuiltInRegistries.CHUNK_GENERATOR, id("island_v14"), SanctuaryChunkGenerator.CITY_CODEC);
+        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("island_v14"), SanctuaryBiomeSource.CITY_CODEC);
+        fr.koka.sanctuary.worldgen.city.LostCityStructures.register();
        Registry.register(BuiltInRegistries.DENSITY_FUNCTION_TYPE, id("population_island"), PopulationIslandDensity.CODEC);
        Registry.register(BuiltInRegistries.BIOME_SOURCE, id("population_island"), PopulationIslandBiomeSource.CODEC);
        Registry.register(BuiltInRegistries.FEATURE_TYPE, id("population_groves"), PopulationGrovesFeature.CODEC);
@@ -0,0 +1,104 @@
+package fr.koka.sanctuary.client;
+
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.CycleButton;
+import net.minecraft.client.gui.components.MultiLineTextWidget;
+import net.minecraft.client.gui.layouts.HeaderAndFooterLayout;
+import net.minecraft.client.gui.layouts.LinearLayout;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.client.gui.screens.worldselection.CreateWorldScreen;
+import net.minecraft.client.gui.screens.worldselection.WorldCreationContext;
+import net.minecraft.network.chat.CommonComponents;
+import net.minecraft.network.chat.Component;
+
+/** Edits only the pending new world's island size. Cancel never changes its dimensions. */
+public final class SanctuaryWorldOptionsScreen extends Screen {
+    private final CreateWorldScreen parent;
+    private final SanctuaryChunkGenerator generator;
+    private final HeaderAndFooterLayout layout = new HeaderAndFooterLayout(this);
+    private IslandSize selectedSize;
+    private MultiLineTextWidget diameterHint;
+
+    public SanctuaryWorldOptionsScreen(CreateWorldScreen parent, WorldCreationContext context) {
+        super(Component.translatable("sanctuary.world_options.title"));
+        this.parent = parent;
+        if (!(context.selectedDimensions().overworld() instanceof SanctuaryChunkGenerator sanctuary)) {
+            throw new IllegalArgumentException("Sanctuary options require the unified generator");
+        }
+        generator = sanctuary;
+        selectedSize = IslandSize.fromDiameter(generator.initialDiameter());
+    }
+
+    @Override
+    protected void init() {
+        layout.removeChildren();
+        layout.addTitleHeader(title, font);
+
+        LinearLayout contents = LinearLayout.vertical().spacing(12);
+        contents.defaultCellSetting().alignHorizontallyCenter();
+        contents.addChild(new MultiLineTextWidget(Component.translatable("sanctuary.world_options.description"), font)
+                .setMaxWidth(310).setCentered(true));
+        CycleButton<IslandSize> sizeButton = CycleButton.builder(IslandSize::label, selectedSize)
+                .withValues(IslandSize.values())
+                .create(0, 0, 240, 20, Component.translatable("sanctuary.world_options.size"), (button, size) -> {
+                    selectedSize = size;
+                    diameterHint.setMessage(diameterHint());
+                    layout.arrangeElements();
+                });
+        contents.addChild(sizeButton);
+        diameterHint = contents.addChild(new MultiLineTextWidget(diameterHint(), font)
+                .setMaxWidth(310).setCentered(true));
+        layout.addToContents(contents);
+
+        LinearLayout actions = LinearLayout.horizontal().spacing(8);
+        actions.addChild(Button.builder(CommonComponents.GUI_DONE, button -> applyAndClose()).width(150).build());
+        actions.addChild(Button.builder(CommonComponents.GUI_CANCEL, button -> onClose()).width(150).build());
+        layout.addToFooter(actions);
+        layout.visitWidgets(this::addRenderableWidget);
+        repositionElements();
+    }
+
+    private Component diameterHint() {
+        return Component.translatable("sanctuary.world_options.diameter", selectedSize.diameter);
+    }
+
+    private void applyAndClose() {
+        parent.getUiState().updateDimensions((registries, dimensions) -> dimensions.replaceOverworldGenerator(
+                registries, generator.withInitialDiameter(selectedSize.diameter)));
+        onClose();
+    }
+
+    @Override
+    protected void repositionElements() {
+        layout.arrangeElements();
+    }
+
+    @Override
+    public void onClose() {
+        minecraft.gui.setScreen(parent);
+    }
+
+    private enum IslandSize {
+        SMALL("small", 512), MEDIUM("medium", 724), LARGE("large", 1024);
+
+        private final String id;
+        private final int diameter;
+
+        IslandSize(String id, int diameter) {
+            this.id = id;
+            this.diameter = diameter;
+        }
+
+        Component label() {
+            return Component.translatable("sanctuary.world_options.size." + id);
+        }
+
+        static IslandSize fromDiameter(int diameter) {
+            for (IslandSize size : values()) {
+                if (size.diameter == diameter) return size;
+            }
+            throw new IllegalArgumentException("Unsupported Sanctuary island diameter: " + diameter);
+        }
+    }
+}
@@ -79,11 +79,13 @@ public final class ExpansionAdmission {
        int radius = island.reservedRadius();
        int minX = Math.floorDiv(island.centerX() - radius, 16), maxX = Math.floorDiv(island.centerX() + radius, 16);
        int minZ = Math.floorDiv(island.centerZ() - radius, 16), maxZ = Math.floorDiv(island.centerZ() + radius, 16);
-        if ((long) (maxX - minX + 1) * (maxZ - minZ + 1) > MAX_CHUNKS) throw new IOException("Expansion admission exceeds 4000 chunks");
+        int limit = island.generation() == 14 ? 8000 : MAX_CHUNKS;
+        if ((long) (maxX - minX + 1) * (maxZ - minZ + 1) > limit) throw new IOException("Expansion admission exceeds " + limit + " chunks");
        ChunkMap map = level.getChunkSource().chunkMap;
        if (!(map instanceof ExpansionChunkMapAccessor)) throw new IOException("Expansion chunk safety accessor is unavailable");
        List<ChunkPos> positions = new ArrayList<>();
-        for (int z = minZ; z <= maxZ; z++) for (int x = minX; x <= maxX; x++) positions.add(new ChunkPos(x, z));
+        for (int z = minZ; z <= maxZ; z++) for (int x = minX; x <= maxX; x++)
+            if (island.generation() != 14 || island.ownsChunk(x, z)) positions.add(new ChunkPos(x, z));
        return positions;
    }

@@ -14,7 +14,7 @@ import net.minecraft.world.level.biome.Climate;
 import org.jspecify.annotations.Nullable;

 /** All future holders are known up front; only the immutable region snapshot changes on activation. */
-public final class ExpansionBiomeSource extends BiomeSource {
+public class ExpansionBiomeSource extends BiomeSource {
    public static final List<String> REQUIRED_BIOMES = Stream.of(
        "the_void", "forest", "birch_forest", "flower_forest", "plains", "meadow",
        "taiga", "snowy_taiga", "snowy_plains", "grove", "ice_spikes", "frozen_peaks",
@@ -59,7 +59,7 @@ public final class ExpansionBiomeSource extends BiomeSource {
        return null;
    }

-    @Override protected MapCodec<ExpansionBiomeSource> codec() { return CODEC; }
+    @Override protected MapCodec<? extends ExpansionBiomeSource> codec() { return CODEC; }
    @Override protected Stream<Holder<Biome>> collectPossibleBiomes() { return biomes.stream(); }

    @Override
@@ -75,7 +75,7 @@ public final class ExpansionBiomeSource extends BiomeSource {
        return (quartX, quartY, quartZ) -> resolve(snapshot, quartX * 4, quartY * 4, quartZ * 4);
    }

-    private Holder<Biome> resolve(List<ExpansionIsland> snapshot, int x, int y, int z) {
+    protected Holder<Biome> resolve(List<ExpansionIsland> snapshot, int x, int y, int z) {
        ExpansionIsland island = islandAt(snapshot, x, z);
        if (island == null || y < 0 || y >= 384) return biome("the_void");
        double scale = Math.clamp(island.diameter() / 3.0, 24.0, 144.0);
@@ -93,7 +93,7 @@ public final class ExpansionBiomeSource extends BiomeSource {
        }

        String selected = switch (island.climate()) {
-            case "temperate" -> Math.abs(variation) < 0.13 ? "plains"
+            case "temperate", "lost_city" -> Math.abs(variation) < 0.13 ? "plains"
                : variation < -0.33 ? "birch_forest" : moisture > 0.44 ? "flower_forest" : "forest";
            case "boreal" -> elevation > 244 ? "snowy_taiga" : variation < -0.2 ? "grove" : "taiga";
            case "glacial" -> elevation > 246 ? "frozen_peaks" : variation > 0.35 ? "ice_spikes" : "snowy_plains";
@@ -39,26 +39,30 @@ import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemp

 /** Laboratory only. Each immutable island has its own vanilla noise generator and seeded RandomState.
 * The host ChunkMap's empty fallback RandomState is deliberately never used for terrain. */
-public final class ExpansionChunkGenerator extends ChunkGenerator {
+public class ExpansionChunkGenerator extends ChunkGenerator {
    public static final MapCodec<ExpansionChunkGenerator> CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
        ExpansionBiomeSource.CODEC.fieldOf("biome_source").forGetter(ExpansionChunkGenerator::source),
        Codec.intRange(512, 724).optionalFieldOf("initial_diameter", 512).forGetter(ExpansionChunkGenerator::initialDiameter)
    ).apply(i, ExpansionChunkGenerator::new));
    private final ExpansionBiomeSource source;
    private final int initialDiameter;
-    private volatile RegistryAccess registries;
+    protected volatile RegistryAccess registries;
    private final Map<ExpansionIsland, Context> contexts = new ConcurrentHashMap<>();
-    private record Context(NoiseBasedChunkGenerator generator, RandomState random) {}
+    protected record Context(NoiseBasedChunkGenerator generator, RandomState random) { public Context {} }

    public ExpansionChunkGenerator(ExpansionBiomeSource source, int initialDiameter) {
+        this(source, initialDiameter, false);
+    }
+    protected ExpansionChunkGenerator(ExpansionBiomeSource source, int initialDiameter, boolean unified) {
        super(source);
-        if (initialDiameter != 512 && initialDiameter != 724) throw new IllegalArgumentException("Laboratory diameter must be 512 or 724");
+        if (initialDiameter != 512 && initialDiameter != 724 && !(unified && initialDiameter == 1024))
+            throw new IllegalArgumentException("Unsupported Sanctuary diameter");
        this.source = source;
        this.initialDiameter = initialDiameter;
    }
    public ExpansionBiomeSource source() { return source; }
    public int initialDiameter() { return initialDiameter; }
-    @Override protected MapCodec<ExpansionChunkGenerator> codec() { return CODEC; }
+    @Override protected MapCodec<? extends ExpansionChunkGenerator> codec() { return CODEC; }
    public void initialize(ServerLevel level, List<ExpansionIsland> islands) {
        registries = level.registryAccess();
        source.setIslands(islands);
@@ -68,12 +72,13 @@ public final class ExpansionChunkGenerator extends ChunkGenerator {
        var key = island.ready();
        if (source.islands().stream().noneMatch(saved -> saved.ready().equals(key))) contexts.remove(key);
    }
+    public Holder<Biome> structureBiome(Holder<Biome> biome) { return biome; }
    public ExpansionIsland islandAt(int x, int z) { return source.islandAt(x, z); }
    public ExpansionIsland islandForChunk(int x, int z) {
        for (ExpansionIsland island : source.islands()) if (island.ownsChunk(x, z)) return island;
        return null;
    }
-    private Context context(ExpansionIsland island) {
+    protected Context context(ExpansionIsland island) {
        if (registries == null) throw new IllegalStateException("Expansion generator used before world attachment");
        return contexts.computeIfAbsent(island.ready(), ignored -> {
            String baseKey = island.origin() && island.diameter() == 724 ? "population_10" : "population_5";
@@ -92,6 +97,9 @@ public final class ExpansionChunkGenerator extends ChunkGenerator {
            return new Context(delegate, random);
        });
    }
+    protected void afterTerrain(ExpansionIsland island, ChunkAccess chunk) { ExpansionTerrain.apply(island, chunk); }
+    public String journalDirectory() { return "sanctuary-expansion-v1"; }
+    public int rootGeneration() { return ExpansionIsland.GENERATION; }
    public RandomState randomState(ExpansionIsland island) { return context(island).random(); }
    public NoiseBasedChunkGenerator delegate(ExpansionIsland island) { return context(island).generator(); }
    @Override public CompletableFuture<ChunkAccess> createBiomes(RandomState ignored, Blender blender, StructureManager structures, ChunkAccess chunk) {
@@ -106,12 +114,13 @@ public final class ExpansionChunkGenerator extends ChunkGenerator {
        if (island == null) return CompletableFuture.completedFuture(chunk);
        var context = context(island);
        return context.generator().buildTerrain(chunk, blender, context.random(), structures, manager, region, biomes).thenApply(generated -> {
-            ExpansionTerrain.apply(island, generated);
+            afterTerrain(island, generated);
            return generated;
        });
    }
    @Override public void createStructures(RegistryAccess registries, ChunkGeneratorStructureState state, StructureManager structures,
            ChunkAccess chunk, StructureTemplateManager templates, ResourceKey<Level> dimension) {
+        fr.koka.sanctuary.worldgen.city.LostCityStructures.generate(this, registries, state, structures, chunk, templates, dimension);
        ExpansionStructures.generate(this, registries, state, structures, chunk, templates, dimension);
    }
    @Override public void spawnOriginalMobs(WorldGenRegion region) {
@@ -141,6 +150,7 @@ public final class ExpansionChunkGenerator extends ChunkGenerator {
    }
    @Override public void addDebugScreenInfo(List<String> text, RandomState ignored, BlockPos pos, SamplerContext context) {
        var island = islandAt(pos.getX(), pos.getZ());
-        text.add(island == null ? "Sanctuary alpha.12: void" : "Sanctuary alpha.12: " + island.id() + " / " + island.climate() + " / " + island.relief());
+        String prefix = "Sanctuary gen " + rootGeneration() + ": ";
+        text.add(island == null ? prefix + "void" : prefix + island.id() + " / " + island.climate() + " / " + island.relief());
    }
 }
@@ -48,12 +48,12 @@ public final class ExpansionCommands {
                .then(createTree("create", false)).then(createTree("preview", true))
                .then(Commands.literal("quick").then(Commands.argument("direction", StringArgumentType.word())
                    .suggests((c, b) -> SharedSuggestionProvider.suggest(ExpansionIsland.DIRECTIONS, b))
-                    .executes(c -> quick(c, null, 128, "natural"))
+                    .executes(c -> quick(c, null, 0, "natural"))
                    .then(Commands.argument("climate", StringArgumentType.word())
                        .suggests((c, b) -> SharedSuggestionProvider.suggest(ExpansionIsland.CLIMATES, b))
-                        .executes(c -> quick(c, word(c, "climate"), 128, "natural"))
-                        .then(Commands.argument("diameter", IntegerArgumentType.integer(64, 512))
-                            .suggests((c, b) -> SharedSuggestionProvider.suggest(List.of("64", "128", "256", "512"), b))
+                        .executes(c -> quick(c, word(c, "climate"), 0, "natural"))
+                        .then(Commands.argument("diameter", IntegerArgumentType.integer(64, 1024))
+                            .suggests((c, b) -> SharedSuggestionProvider.suggest(List.of("64", "128", "256", "512", "1024"), b))
                            .executes(c -> quick(c, word(c, "climate"), IntegerArgumentType.getInteger(c, "diameter"), "natural"))
                            .then(Commands.argument("relief", StringArgumentType.word())
                                .suggests((c, b) -> SharedSuggestionProvider.suggest(ExpansionIsland.RELIEFS, b))
@@ -78,8 +78,8 @@ public final class ExpansionCommands {
                })
                .then(Commands.argument("direction", StringArgumentType.word()).suggests((c, b) -> SharedSuggestionProvider.suggest(ExpansionIsland.DIRECTIONS, b))
                    .then(Commands.argument("climate", StringArgumentType.word()).suggests((c, b) -> SharedSuggestionProvider.suggest(ExpansionIsland.CLIMATES, b))
-                        .then(Commands.argument("diameter", IntegerArgumentType.integer(64, 512))
-                            .suggests((c, b) -> SharedSuggestionProvider.suggest(List.of("64", "128", "256", "512"), b))
+                        .then(Commands.argument("diameter", IntegerArgumentType.integer(64, 1024))
+                            .suggests((c, b) -> SharedSuggestionProvider.suggest(List.of("64", "128", "256", "512", "1024"), b))
                            .then(Commands.argument("relief", StringArgumentType.word()).suggests((c, b) -> SharedSuggestionProvider.suggest(ExpansionIsland.RELIEFS, b))
                                .executes(c -> create(c, preview, 0))
                                .then(distanceArgument().executes(c -> create(c, preview, IntegerArgumentType.getInteger(c, "distance"))))))))));
@@ -113,8 +113,11 @@ public final class ExpansionCommands {
            }
            String direction = word(c, "direction");
            if (!ExpansionIsland.DIRECTIONS.contains(direction)) throw new IllegalArgumentException("invalid_direction");
-            var island = session.create("island_" + next, "sanctuary", direction,
-                climate == null ? ExpansionIsland.directionalClimate(direction) : climate, diameter, relief, minimumDistance);
+            String id = "island_" + next;
+            int chosenDiameter = diameter != 0 ? diameter : session.islands().getFirst().generation() == 14
+                ? ExpansionRandomSize.choose(c.getSource().getLevel().getSeed(), id) : 128;
+            var island = session.create(id, "sanctuary", direction,
+                climate == null ? ExpansionIsland.directionalClimate(direction) : climate, chosenDiameter, relief, minimumDistance);
            describe(c, island, false);
            return Command.SINGLE_SUCCESS;
        });
@@ -122,6 +125,8 @@ public final class ExpansionCommands {
    private static void describe(CommandContext<CommandSourceStack> c, ExpansionIsland island, boolean preview) {
        c.getSource().sendSuccess(() -> Component.translatable(PREFIX + (preview ? "preview" : "created"),
            island.id(), island.centerX(), island.centerZ(), label("climate", island.climate()), island.diameter(), label("relief", island.relief())), false);
+        if (!preview && ExpansionVoidReuse.requiresReload(c.getSource().getLevel(), island.id()))
+            c.getSource().sendSuccess(() -> Component.translatable(PREFIX + "reuse_reload", island.id()), false);
    }
    private static int help(CommandContext<CommandSourceStack> context) {
        context.getSource().sendSuccess(() -> Component.translatable(PREFIX + "help"), false);
@@ -6,12 +6,13 @@ import java.util.List;

 /** Immutable alpha.12 region contract. Directions place islands; climate remains an explicit choice. */
 public record ExpansionIsland(String id, String parent, String direction, String climate,
-        int diameter, int centerX, int centerZ, long seed, String relief, String status, int generation) {
+        int diameter, int centerX, int centerZ, long seed, String relief, String status, int generation, String reuseToken) {
    public static final int GENERATION = 12;
    public static final List<String> DIRECTIONS = List.of("north", "northeast", "east", "southeast", "south", "southwest", "west", "northwest");
-    public static final List<String> CLIMATES = List.of("temperate", "boreal", "glacial", "cold_humid", "humid", "tropical", "warm", "arid", "dry", "cold_dry", "autumn", "cherry");
+    public static final List<String> CLIMATES = List.of("temperate", "boreal", "glacial", "cold_humid", "humid", "tropical", "warm", "arid", "dry", "cold_dry", "autumn", "cherry", "lost_city");
    public static final List<String> RELIEFS = List.of("natural", "peaks", "canyon", "volcano");
-    public static final List<Integer> DIAMETERS = List.of(64, 128, 256, 512);
+    public static final List<Integer> LEGACY_DIAMETERS = List.of(64, 128, 256, 512);
+    public static final List<Integer> DIAMETERS = List.of(64, 128, 256, 512, 1024);
    public static final int DECORATION_MARGIN = 32;
    public static final int GENERATION_HALO = 176;
    public static final Codec<ExpansionIsland> CODEC = RecordCodecBuilder.create(i -> i.group(
@@ -25,27 +26,39 @@ public record ExpansionIsland(String id, String parent, String direction, String
        Codec.LONG.fieldOf("seed").forGetter(ExpansionIsland::seed),
        Codec.STRING.fieldOf("relief").forGetter(ExpansionIsland::relief),
        Codec.STRING.fieldOf("status").forGetter(ExpansionIsland::status),
-        Codec.INT.fieldOf("generation").forGetter(ExpansionIsland::generation)
+        Codec.INT.fieldOf("generation").forGetter(ExpansionIsland::generation),
+        Codec.STRING.optionalFieldOf("reuse_token", "").forGetter(ExpansionIsland::reuseToken)
    ).apply(i, ExpansionIsland::new));

+    public ExpansionIsland(String id, String parent, String direction, String climate, int diameter,
+            int centerX, int centerZ, long seed, String relief, String status, int generation) {
+        this(id, parent, direction, climate, diameter, centerX, centerZ, seed, relief, status, generation, "");
+    }
+
    public ExpansionIsland {
        if (!id.matches("[a-z][a-z0-9_]{0,31}") || !parent.matches("[a-z][a-z0-9_]{0,31}")) throw new IllegalArgumentException("Invalid island identifier");
        if (!DIRECTIONS.contains(direction) || !CLIMATES.contains(climate) || !RELIEFS.contains(relief)) throw new IllegalArgumentException("Unknown island profile");
-        if (!(DIAMETERS.contains(diameter) || (id.equals("sanctuary") && diameter == 724))) throw new IllegalArgumentException("Unsupported nominal diameter");
+        if (!((generation == 14 ? DIAMETERS : LEGACY_DIAMETERS).contains(diameter) || (id.equals("sanctuary") && (diameter == 724 || (generation == 13 || generation == 14) && 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) throw new IllegalArgumentException("Unsupported island state or generation");
+        if (!List.of("reserved", "ready").contains(status) || (generation != GENERATION && generation != 14 && !(generation == 13 && id.equals("sanctuary")))) throw new IllegalArgumentException("Unsupported island state or generation");
+        if (climate.equals("lost_city") && (generation != 14 || id.equals("sanctuary"))) throw new IllegalArgumentException("Lost City requires a generation 14 expansion");
+        if (reuseToken == null || !reuseToken.isEmpty() && (generation != 14 || id.equals("sanctuary") || !reuseToken.matches("[0-9a-f]{64}")))
+            throw new IllegalArgumentException("Invalid void reuse certificate token");
    }

    public static ExpansionIsland origin(int diameter, long seed) {
-        return new ExpansionIsland("sanctuary", "sanctuary", "north", "temperate", diameter, 0, 0, seed, "natural", "ready", GENERATION);
+        return origin(diameter, seed, GENERATION);
+    }
+    public static ExpansionIsland origin(int diameter, long seed, int generation) {
+        return new ExpansionIsland("sanctuary", "sanctuary", "north", "temperate", diameter, 0, 0, seed, "natural", "ready", generation);
    }

    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(); }
    public double radius() { return diameter / 2.0; }
-    public int terrainRadius() { return origin() && diameter == 724 ? 395 : (int) Math.ceil(radius() * 1.125); }
-    public int reservedRadius() { return terrainRadius() + DECORATION_MARGIN + GENERATION_HALO; }
+    public int terrainRadius() { if ((generation == 13 || generation == 14) && origin()) return diameter == 724 ? 395 : diameter / 2 + 32; return origin() && diameter == 724 ? 395 : (int) Math.ceil(radius() * 1.125); }
+    public int reservedRadius() { return terrainRadius() + DECORATION_MARGIN + (generation == 14 ? 0 : GENERATION_HALO); }
    public boolean contains(int x, int z) { return Math.hypot((double) x - centerX, (double) z - centerZ) < terrainRadius(); }
    public boolean ownsChunk(int chunkX, int chunkZ) {
        int x = Math.clamp(centerX, chunkX * 16, chunkX * 16 + 15);
@@ -53,10 +66,12 @@ public record ExpansionIsland(String id, String parent, String direction, String
        return Math.hypot((double) x - centerX, (double) z - centerZ) <= terrainRadius() + DECORATION_MARGIN;
    }
    public boolean conflicts(ExpansionIsland other) {
+        if (generation == 14 && other.generation() == 14) return ExpansionSpatialPlacement14.conflicts(this, other);
        return Math.abs((long) centerX - other.centerX) <= reservedRadius() + other.reservedRadius()
            && Math.abs((long) centerZ - other.centerZ) <= reservedRadius() + other.reservedRadius();
    }
-    public ExpansionIsland ready() { return new ExpansionIsland(id, parent, direction, climate, diameter, centerX, centerZ, seed, relief, "ready", generation); }
+    public ExpansionIsland ready() { return new ExpansionIsland(id, parent, direction, climate, diameter, centerX, centerZ, seed, relief, "ready", generation, reuseToken); }
+    public ExpansionIsland withReuseToken(String token) { return new ExpansionIsland(id, parent, direction, climate, diameter, centerX, centerZ, seed, relief, status, generation, token); }
    public static String directionalClimate(String direction) {
        return switch (direction) {
            case "north" -> "boreal"; case "northeast" -> "cold_humid"; case "east" -> "humid";
@@ -39,11 +39,25 @@ public final class ExpansionJournal {
    private final Path file;
    private final long seed;
    private final int rootDiameter;
+    private final int rootGeneration;
+    private final DirectorySync directorySync;
    private List<ExpansionIsland> islands;
    private boolean failed;

    public ExpansionJournal(Path directory, long seed, int rootDiameter) throws IOException {
-        if (rootDiameter != 512 && rootDiameter != 724) throw new IOException("Unsupported expansion root diameter");
+        this(directory, seed, rootDiameter, ExpansionIsland.GENERATION);
+    }
+    public ExpansionJournal(Path directory, long seed, int rootDiameter, int rootGeneration) throws IOException {
+        this(directory, seed, rootDiameter, rootGeneration,
+            directorySyncFor(directory.getFileSystem().getSeparator(), ExpansionJournal::forceDirectory));
+    }
+
+    ExpansionJournal(Path directory, long seed, int rootDiameter, int rootGeneration, DirectorySync directorySync) throws IOException {
+        if (rootGeneration != 12 && rootGeneration != 13 && rootGeneration != 14) throw new IOException("Unsupported root generation");
+        if (rootDiameter != 512 && rootDiameter != 724 && !((rootGeneration == 13 || rootGeneration == 14) && rootDiameter == 1024))
+            throw new IOException("Unsupported expansion root diameter");
+        this.rootGeneration = rootGeneration;
+        this.directorySync = java.util.Objects.requireNonNull(directorySync);
        this.directory = directory.toAbsolutePath().normalize();
        this.file = this.directory.resolve(FILE_NAME);
        this.seed = seed;
@@ -55,7 +69,7 @@ public final class ExpansionJournal {
            // Creating the directory is the bootstrap marker. An interrupted bootstrap requires repair.
            Files.createDirectories(this.directory.getParent());
            Files.createDirectory(this.directory);
-            this.islands = List.of(ExpansionIsland.origin(rootDiameter, seed));
+            this.islands = List.of(ExpansionIsland.origin(rootDiameter, seed, rootGeneration));
            persist(this.islands);
        }
    }
@@ -103,7 +117,7 @@ public final class ExpansionJournal {
            // No fallback to a non-atomic replacement: failure must remain visible to the caller.
            Files.move(temporary, file, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
            temporary = null;
-            try (FileChannel parent = FileChannel.open(directory, StandardOpenOption.READ)) { parent.force(true); }
+            directorySync.force(directory);
            if (!read().equals(next)) throw new IOException("Expansion journal verification disagrees with the committed plan");
        } catch (IOException | RuntimeException e) {
            failed = true;
@@ -116,6 +130,19 @@ public final class ExpansionJournal {
        }
    }

+    @FunctionalInterface
+    interface DirectorySync { void force(Path directory) throws IOException; }
+
+    static DirectorySync directorySyncFor(String separator, DirectorySync supportedSync) {
+        // Windows FileChannel cannot open directory handles. Only this additional
+        // directory flush is omitted: file force, atomic replacement and read-back remain mandatory.
+        return "\\".equals(separator) ? directory -> {} : supportedSync;
+    }
+
+    private static void forceDirectory(Path directory) throws IOException {
+        try (FileChannel parent = FileChannel.open(directory, StandardOpenOption.READ)) { parent.force(true); }
+    }
+
    private List<ExpansionIsland> read() throws IOException {
        if (!Files.isRegularFile(file, LinkOption.NOFOLLOW_LINKS)) throw new IOException("Existing expansion directory has no regular journal file");
        if (Files.size(file) > MAX_BYTES) throw new IOException("Expansion journal exceeds its size limit");
@@ -131,10 +158,13 @@ public final class ExpansionJournal {
            List<ExpansionIsland> decoded = new ArrayList<>();
            for (JsonElement element : entries) {
                JsonObject entry = element.getAsJsonObject();
-                requireFields(entry, ISLAND_FIELDS);
+                var fields = new java.util.HashSet<>(ISLAND_FIELDS);
+                if (rootGeneration == 14 && entry.has("reuse_token")) fields.add("reuse_token");
+                requireFields(entry, fields);
                decoded.add(new ExpansionIsland(string(entry, "id"), string(entry, "parent"), string(entry, "direction"), string(entry, "climate"),
                    integer(entry, "diameter"), integer(entry, "center_x"), integer(entry, "center_z"), number(entry, "seed").longValueExact(),
-                    string(entry, "relief"), string(entry, "status"), integer(entry, "generation")));
+                    string(entry, "relief"), string(entry, "status"), integer(entry, "generation"),
+                    entry.has("reuse_token") ? string(entry, "reuse_token") : ""));
            }
            return validate(decoded);
        } catch (RuntimeException e) {
@@ -146,17 +176,18 @@ public final class ExpansionJournal {
        if (proposed == null || proposed.isEmpty() || proposed.size() > MAX_ISLANDS) throw new IOException("Expansion journal must contain 1 to 64 regions");
        List<ExpansionIsland> checked;
        try { checked = List.copyOf(proposed); } catch (RuntimeException e) { throw new IOException("Invalid expansion entries", e); }
-        if (!checked.getFirst().equals(ExpansionIsland.origin(rootDiameter, seed))) throw new IOException("Sanctuary root region is immutable");
+        if (!checked.getFirst().equals(ExpansionIsland.origin(rootDiameter, seed, rootGeneration))) throw new IOException("Sanctuary root region is immutable");
        Map<String, ExpansionIsland> previous = new HashMap<>();
        previous.put("sanctuary", checked.getFirst());
        for (int i = 1; i < checked.size(); i++) {
            ExpansionIsland island = checked.get(i);
+            if (island.generation() != (rootGeneration == 14 ? 14 : 12)) throw new IOException("Expansion generation does not match its world contract");
            if (previous.containsKey(island.id())) throw new IOException("Duplicate expansion identifier: " + island.id());
            ExpansionIsland parent = previous.get(island.parent());
            if (parent == null || !parent.status().equals("ready")) throw new IOException("Expansion parent must be an earlier ready region: " + island.parent());
            if (island.seed() != ExpansionIsland.deriveSeed(seed, island.id())) throw new IOException("Expansion seed differs from its saved identity: " + island.id());
            long dx = (long) island.centerX() - parent.centerX(), dz = (long) island.centerZ() - parent.centerZ();
-            if (!followsDirection(island.direction(), dx, dz)) throw new IOException("Expansion position does not follow its direction: " + island.id());
+            if (!(island.generation() == 14 ? ExpansionSpatialPlacement14.followsDirection(island.direction(), dx, dz) : followsDirection(island.direction(), dx, dz))) throw new IOException("Expansion position does not follow its direction: " + island.id());
            for (ExpansionIsland other : previous.values()) if (island.conflicts(other)) throw new IOException("Expansion reservations overlap: " + island.id() + " / " + other.id());
            previous.put(island.id(), island);
        }
@@ -187,7 +218,9 @@ public final class ExpansionJournal {
            entry.addProperty("direction", island.direction()); entry.addProperty("climate", island.climate());
            entry.addProperty("diameter", island.diameter()); entry.addProperty("center_x", island.centerX()); entry.addProperty("center_z", island.centerZ());
            entry.addProperty("seed", island.seed()); entry.addProperty("relief", island.relief()); entry.addProperty("status", island.status());
-            entry.addProperty("generation", island.generation()); array.add(entry);
+            entry.addProperty("generation", island.generation());
+            if (!island.reuseToken().isEmpty()) entry.addProperty("reuse_token", island.reuseToken());
+            array.add(entry);
        }
        root.add("islands", array);
        return root;
@@ -23,12 +23,15 @@ public final class ExpansionPlacement {
        if (!ExpansionIsland.DIAMETERS.contains(diameter)) throw new IllegalArgumentException("invalid_diameter");
        if (relief == null || !ExpansionIsland.RELIEFS.contains(relief)) throw new IllegalArgumentException("invalid_relief");
        validateDistance(minimumDistance);
+        int generation = islands.getFirst().generation() == 14 ? 14 : ExpansionIsland.GENERATION;
+        if ((climate.equals("lost_city") || diameter == 1024) && generation != 14) throw new IllegalArgumentException("city_generation_required");
        var parent = islands.stream().filter(i -> i.id().equals(parentId)).findFirst()
            .orElseThrow(() -> new IllegalArgumentException("unknown_island"));
        if (!parent.status().equals("ready")) throw new IllegalArgumentException("parent_not_ready");
        int ordinal = ExpansionIsland.DIRECTIONS.indexOf(direction);
        var sample = new ExpansionIsland(id, parentId, direction, climate, diameter, 0, 0,
-            ExpansionIsland.deriveSeed(worldSeed, id), relief, "reserved", ExpansionIsland.GENERATION);
+            ExpansionIsland.deriveSeed(worldSeed, id), relief, "reserved", generation);
+        if (generation == 14) return ExpansionSpatialPlacement14.candidates(islands, parent, sample, minimumDistance);
        int step = ((parent.reservedRadius() + sample.reservedRadius() + 63) / 16) * 16;
        boolean diagonal = DX[ordinal] != 0 && DZ[ordinal] != 0;
        int requestedComponent = (int) Math.ceil(minimumDistance / (diagonal ? Math.sqrt(2) : 1.0) / 16) * 16;
@@ -40,7 +43,7 @@ public final class ExpansionPlacement {
            long z = parent.centerZ() + DZ[ordinal] * component;
            if (Math.abs(x) > MAX_DISTANCE || Math.abs(z) > MAX_DISTANCE) break;
            var candidate = new ExpansionIsland(id, parentId, direction, climate, diameter, (int) x, (int) z,
-                sample.seed(), relief, "reserved", ExpansionIsland.GENERATION);
+                sample.seed(), relief, "reserved", generation);
            if (islands.stream().noneMatch(candidate::conflicts)) candidates.add(candidate);
        }
        return List.copyOf(candidates);
@@ -0,0 +1,15 @@
+package fr.koka.sanctuary.expansion;
+
+/** A quick request keeps its draw across placement retries; success records the size in the journal. */
+public final class ExpansionRandomSize {
+    private ExpansionRandomSize() {}
+
+    public static int choose(long worldSeed, String islandId) {
+        int draw = (int) Long.remainderUnsigned(ExpansionIsland.deriveSeed(worldSeed ^ 0xA14D1A6E7L, islandId), 100);
+        if (draw < 40) return 64;
+        if (draw < 70) return 128;
+        if (draw < 88) return 256;
+        if (draw < 97) return 512;
+        return 1024;
+    }
+}
@@ -0,0 +1,7 @@
+package fr.koka.sanctuary.expansion;
+
+/** Set only after an authorized certificate was consumed, or its native saved marker was verified. */
+public interface ExpansionReuseMarker {
+    String sanctuary$reuseMarker();
+    void sanctuary$reuseMarker(String token);
+}
@@ -0,0 +1,9 @@
+package fr.koka.sanctuary.expansion;
+
+import net.minecraft.nbt.CompoundTag;
+
+/** Transient serialization state; never inferred merely from a chunk's location. */
+public interface ExpansionReuseSerializedData {
+    void sanctuary$originalReuseNbt(CompoundTag tag);
+    void sanctuary$serializedReuseMarker(String token);
+}
@@ -22,7 +22,7 @@ import net.minecraft.world.level.Level;
 import net.minecraft.world.level.levelgen.Heightmap;
 import net.minecraft.world.level.storage.LevelResource;

-/** Server-owned append-only admission and bounded preparation queue. No existing chunk is regenerated. */
+/** Server-owned append-only admission and bounded preparation; certified void reuse starts on reload. */
 public final class ExpansionRuntime {
    private static final Map<ServerLevel, Session> SESSIONS = new HashMap<>();
    private static final TicketType PREPARATION = new TicketType(0L, 2 | 8);
@@ -33,11 +33,12 @@ public final class ExpansionRuntime {
            if (!(level.getChunkSource().getGenerator() instanceof ExpansionChunkGenerator generator)) return;
            if (level.dimension() != Level.OVERWORLD) throw new IllegalStateException("The expansion laboratory is Overworld only");
            try {
-                var directory = server.getWorldPath(LevelResource.ROOT).resolve("data/sanctuary-expansion-v1");
+                var directory = server.getWorldPath(LevelResource.ROOT).resolve("data/" + generator.journalDirectory());
                if (server.getWorldData().overworldData().isInitialized()
                        && !java.nio.file.Files.isDirectory(directory, java.nio.file.LinkOption.NOFOLLOW_LINKS))
                    throw new IOException("Initialized laboratory world is missing its expansion journal directory");
-                var journal = new ExpansionJournal(directory, level.getSeed(), generator.initialDiameter());
+                var journal = new ExpansionJournal(directory, level.getSeed(), generator.initialDiameter(), generator.rootGeneration());
+                ExpansionVoidReuse.open(level, generator, journal.islands());
                generator.initialize(level, journal.islands());
                var session = new Session(level, generator, journal);
                SESSIONS.put(level, session);
@@ -53,6 +54,7 @@ public final class ExpansionRuntime {
        ServerLevelEvents.UNLOAD.register((server, level) -> {
            Session session = SESSIONS.remove(level);
            if (session != null) session.releaseTicket();
+            ExpansionVoidReuse.close(level);
        });
        ServerLifecycleEvents.SERVER_STOPPED.register(server -> SESSIONS.clear());
    }
@@ -109,17 +111,20 @@ public final class ExpansionRuntime {
            for (var value : candidates) {
                ExpansionAdmission.checkDeadline(deadline);
                try {
-                    // Existing void is preserved: only proven occupation advances along the same ray.
-                    ExpansionAdmission.verify(level, value, deadline);
+                    var inspection = value.generation() == 14 ? ExpansionVoidReuse.inspect(level, value, deadline) : null;
+                    if (inspection == null) ExpansionAdmission.verify(level, value, deadline);
                    if (probe(value) == null) throw new IllegalArgumentException("no_ground");
+                    var admitted = inspection == null ? value : value.withReuseToken(ExpansionVoidReuse.persist(inspection));
                    var next = new ArrayList<>(islands());
-                    next.add(value);
-                    ExpansionAdmission.verifyHolders(level, value, deadline);
+                    next.add(admitted);
+                    if (inspection == null) ExpansionAdmission.verifyHolders(level, value, deadline);
                    commitJournal(next); // Durability and re-read come before worldgen sees the island.
-                    generator.setIslands(journal.islands());
+                    if (!admitted.reuseToken().isEmpty()) ExpansionVoidReuse.deferred(level, admitted);
+                    publishActiveIslands();
                    failure = "";
-                    enqueue(value);
-                    return value;
+                    if (ExpansionVoidReuse.requiresReload(level, admitted.id())) failure = admitted.id() + ": reload_required";
+                    else enqueue(admitted);
+                    return admitted;
                } catch (ExpansionAdmission.OccupiedException occupied) {
                    // IO failures, timeouts and unsuitable terrain stop this request without a new draw.
                } finally {
@@ -133,12 +138,19 @@ public final class ExpansionRuntime {
            requireHealthyJournal();
            var island = island(id);
            if (!island.status().equals("reserved")) return;
+            if (ExpansionVoidReuse.requiresReload(level, id)) throw new IllegalArgumentException("reload_required");
            failure = "";
            enqueue(island);
        }
        private void enqueue(ExpansionIsland island) {
+            String reuseFailure = ExpansionVoidReuse.failure(level, island.id());
+            if (reuseFailure != null) { failure = island.id() + ": " + reuseFailure; return; }
+            if (ExpansionVoidReuse.requiresReload(level, island.id())) return;
            if (jobs.stream().noneMatch(j -> j.island.id().equals(island.id()))) jobs.add(new Job(island));
        }
+        private void publishActiveIslands() {
+            generator.setIslands(journal.islands().stream().filter(i -> !ExpansionVoidReuse.requiresReload(level, i.id())).toList());
+        }
        private void requireHealthyJournal() {
            if (!journal.healthy()) {
                stopForJournalFailure(null);
@@ -213,6 +225,8 @@ public final class ExpansionRuntime {
            Job job = jobs.peek();
            if (job == null) return;
            try {
+                String reuseFailure = ExpansionVoidReuse.failure(level, job.island.id());
+                if (reuseFailure != null) throw new IllegalStateException(reuseFailure);
                if (job.pending != null) {
                    if (!job.pending.isDone()) return;
                    job.pending.join();
@@ -222,9 +236,10 @@ public final class ExpansionRuntime {
                    job.index++;
                }
                if (job.index == job.chunks.size()) {
+                    if (!ExpansionVoidReuse.complete(level, job.island)) throw new IllegalStateException("void_reuse_incomplete");
                    var next = islands().stream().map(i -> i.id().equals(job.island.id()) ? i.ready() : i).toList();
                    commitJournal(next);
-                    generator.setIslands(journal.islands());
+                    publishActiveIslands();
                    jobs.remove();
                    SanctuaryMod.LOGGER.info("Expansion {} ready: {} FULL chunks", job.island.id(), job.index);
                    for (var player : level.players()) if (player.permissions().hasPermission(net.minecraft.server.permissions.Permissions.COMMANDS_GAMEMASTER))
@@ -255,7 +270,8 @@ public final class ExpansionRuntime {
            this.island = island;
            int radius = island.terrainRadius() + ExpansionIsland.DECORATION_MARGIN;
            for (int x = (island.centerX() - radius) >> 4; x <= (island.centerX() + radius) >> 4; x++)
-                for (int z = (island.centerZ() - radius) >> 4; z <= (island.centerZ() + radius) >> 4; z++) chunks.add(new ChunkPos(x, z));
+                for (int z = (island.centerZ() - radius) >> 4; z <= (island.centerZ() + radius) >> 4; z++)
+                    if (island.generation() != 14 || island.ownsChunk(x, z)) chunks.add(new ChunkPos(x, z));
        }
    }
    public static boolean safeLanding(ServerLevel level, BlockPos feet) {
@@ -0,0 +1,97 @@
+package fr.koka.sanctuary.expansion;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** Generation 14 incremental Poisson-disc rejection with variable island radii.
+ * Accepted regions keep a minimum separation; candidate draws are reproducible and bounded.
+ * The requested direction selects a 45-degree sector, independently of biome and climate.
+ * Generation dependencies are read neighborhoods, not ownership reservations. */
+public final class ExpansionSpatialPlacement14 {
+    public static final int MAX_ATTEMPTS = 32;
+    // Distinct circular footprints must also avoid owning the same 16x16 corner chunk.
+    private static final int CHUNK_CORNER_GUARD = 24;
+    private static final int[] DX = {0, 1, 1, 1, 0, -1, -1, -1};
+    private static final int[] DZ = {-1, -1, 0, 1, 1, 1, 0, -1};
+    private static final double HALF_SECTOR_TANGENT = Math.tan(Math.PI / 8);
+
+    private ExpansionSpatialPlacement14() {}
+
+    /** The caller validates IDs/profile choices before constructing the prototype.
+     * Alternatives may overlap each other: only one is admitted, then added to islands.
+     * Subsequent calls reject its complete write footprint, including pending reservations. */
+    public static List<ExpansionIsland> candidates(List<ExpansionIsland> islands,
+            ExpansionIsland parent, ExpansionIsland prototype, int minimumDistance) {
+        if (parent.generation() != 14 || prototype.generation() != 14 || prototype.origin())
+            throw new IllegalArgumentException("Spatial placement requires generation 14 expansions");
+        if (!parent.status().equals("ready")) throw new IllegalArgumentException("parent_not_ready");
+        if (!prototype.parent().equals(parent.id())) throw new IllegalArgumentException("unknown_island");
+        ExpansionPlacement.validateDistance(minimumDistance);
+        int direction = ExpansionIsland.DIRECTIONS.indexOf(prototype.direction());
+        if (direction < 0) throw new IllegalArgumentException("invalid_direction");
+        double angle = Math.atan2(DZ[direction], DX[direction]);
+        double start = Math.max(minimumSeparation(parent, prototype), minimumDistance);
+        double annulus = Math.max(64, writeRadius(prototype) * .70);
+        long drawSeed = mix(prototype.seed() ^ parent.seed() ^ 0xA14D15C5EEDL);
+        List<ExpansionIsland> result = new ArrayList<>();
+        for (int attempt = 0; attempt < MAX_ATTEMPTS; attempt++) {
+            long draw = mix(drawSeed + attempt * 0x9E3779B97F4A7C15L);
+            // Eight nearby candidates are exhausted before moving to each farther annulus.
+            // Eighteen degrees leave snapping room inside the exact 22.5-degree sector.
+            double candidateAngle = angle + (unit(draw) * 2 - 1) * Math.PI / 10;
+            double distance = start + 24 + (attempt / 8 + unit(mix(draw ^ 0xD15C14L))) * annulus;
+            long x = Math.round((parent.centerX() + Math.cos(candidateAngle) * distance) / 16) * 16;
+            long z = Math.round((parent.centerZ() + Math.sin(candidateAngle) * distance) / 16) * 16;
+            if (Math.abs(x) > ExpansionPlacement.MAX_DISTANCE || Math.abs(z) > ExpansionPlacement.MAX_DISTANCE) continue;
+            if (!followsDirection(prototype.direction(), x - parent.centerX(), z - parent.centerZ())) continue;
+            if (Math.hypot(x - parent.centerX(), z - parent.centerZ()) < minimumDistance) continue;
+            ExpansionIsland candidate = new ExpansionIsland(prototype.id(), prototype.parent(), prototype.direction(),
+                prototype.climate(), prototype.diameter(), (int) x, (int) z, prototype.seed(), prototype.relief(), "reserved", 14);
+            if (islands.stream().noneMatch(saved -> conflicts(candidate, saved)) && !result.contains(candidate)) result.add(candidate);
+        }
+        return List.copyOf(result);
+    }
+
+    /** All coordinates writable by this island, including decoration spilling beyond its terrain. */
+    public static int writeRadius(ExpansionIsland island) {
+        return island.terrainRadius() + ExpansionIsland.DECORATION_MARGIN;
+    }
+
+    /** Vanilla neighboring stages may read this far, without claiming or changing those chunks. */
+    public static int readRadius(ExpansionIsland island) {
+        return writeRadius(island) + ExpansionIsland.GENERATION_HALO;
+    }
+
+    public static int minimumSeparation(ExpansionIsland a, ExpansionIsland b) {
+        int relevantSize = a.origin() ? b.diameter() : b.origin() ? a.diameter() : Math.max(a.diameter(), b.diameter());
+        return writeRadius(a) + writeRadius(b) + CHUNK_CORNER_GUARD + extraGap(relevantSize);
+    }
+
+    public static boolean conflicts(ExpansionIsland a, ExpansionIsland b) {
+        double dx = (double) a.centerX() - b.centerX(), dz = (double) a.centerZ() - b.centerZ();
+        return dx * dx + dz * dz < Math.pow(minimumSeparation(a, b), 2);
+    }
+
+    /** Direction validation for persisted v14 records; v12/v13 retain their exact-ray rule. */
+    public static boolean followsDirection(String direction, long dx, long dz) {
+        int ordinal = ExpansionIsland.DIRECTIONS.indexOf(direction);
+        if (ordinal < 0) return false;
+        double projection = (double) dx * DX[ordinal] + (double) dz * DZ[ordinal];
+        double cross = (double) dx * DZ[ordinal] - (double) dz * DX[ordinal];
+        return projection > 0 && Math.abs(cross) <= projection * HALF_SECTOR_TANGENT + 1.0e-9;
+    }
+
+    private static int extraGap(int diameter) {
+        if (diameter <= 64) return 0;
+        if (diameter <= 128) return 16;
+        if (diameter <= 256) return 48;
+        if (diameter <= 512) return 96;
+        return 160;
+    }
+    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);
+    }
+}
@@ -6,6 +6,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import net.minecraft.core.Holder;
+import net.minecraft.core.BlockPos;
 import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.Identifier;
@@ -57,7 +58,8 @@ public final class ExpansionStructures {
            return;
        }
        var sampler = randomState.createClimateSampler(SamplerContext.builder().enableCaches().build());
-        Holder<Biome> biome = generator.getBiomeSource().createResolver(sampler).getNoiseBiome(blockX >> 2, surfaceY >> 2, blockZ >> 2);
+        Holder<Biome> biome = generator.structureBiome(generator.getBiomeSource().createResolver(sampler)
+            .getNoiseBiome(blockX >> 2, surfaceY >> 2, blockZ >> 2));
        var registry = registries.lookupOrThrow(Registries.STRUCTURE);
        List<Holder<Structure>> villages = new ArrayList<>();
        // Villages remain optional and are never squeezed into the small formats.
@@ -85,7 +87,7 @@ public final class ExpansionStructures {
                String name = selected.unwrapKey().orElseThrow().identifier().toString();
                StructureStart start = structure.generate(selected, level, registries, generator, generator.getBiomeSource(),
                    sampler, randomState, templates, island.seed(), chunk.getPos(), previous == null ? 0 : previous.getReferences(),
-                    chunk, structure.biomes()::contains);
+                    chunk, candidateBiome -> structure.biomes().contains(generator.structureBiome(candidateBiome)));
                if (!start.isValid()) {
                    diagnostic(island, chunk, "native-rejected", name + " biome=" + biome.unwrapKey().orElseThrow().identifier() + " height=" + surfaceY);
                    continue;
@@ -121,6 +123,16 @@ public final class ExpansionStructures {
            RandomState randomState, StructureStart start, boolean temple) {
        // Native beard adaptation already expands this box by 12 blocks when applicable.
        BoundingBox total = start.getBoundingBox();
+        if (generator instanceof fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator city
+                && city.lostCityPlan(island).intersects(total.minX(), total.minZ(), total.maxX(), total.maxZ()))
+            return "occupied-city-district";
+        if (island.origin() && generator instanceof fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator unified) {
+            var binding = unified.starterContext();
+            int centreX = (total.minX() + total.maxX()) / 2, centreZ = (total.minZ() + total.maxZ()) / 2;
+            int radius = Math.max(total.getXSpan(), total.getZSpan()) / 2 + 3;
+            if (fr.koka.sanctuary.worldgen.PopulationHydrologyRuntime.protects(binding.generator(), binding.random(),
+                    new BlockPos(centreX, total.minY(), centreZ), radius, total.getYSpan() + 16, 26)) return "protected-hydrology";
+        }
        if (!inside(island, total.minX(), total.minZ(), 4) || !inside(island, total.maxX(), total.minZ(), 4)
                || !inside(island, total.minX(), total.maxZ(), 4) || !inside(island, total.maxX(), total.maxZ(), 4)) return "outside-island";
        if (total.minY() < chunk.getMinY() || total.maxY() > chunk.getMaxY() - 4) return "outside-height";
@@ -0,0 +1,169 @@
+package fr.koka.sanctuary.expansion;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.HashSet;
+import java.util.HexFormat;
+import java.util.Optional;
+import java.util.Set;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.Tag;
+import net.minecraft.world.level.ChunkPos;
+
+/** Strict read-only proof of generated, untouched Sanctuary void, including its independent stores.
+ * Fingerprints describe verified semantic emptiness; time counters and light caches may change on save. */
+public record ExpansionVoidCertificate(int x, int z, String terrain, String entities, String poi, boolean absent) {
+    private static final Set<String> CHUNK_KEYS = Set.of("DataVersion", "xPos", "yPos", "zPos", "Status", "LastUpdate",
+        "InhabitedTime", "isLightOn", "sections", "Heightmaps", "structures", "block_entities", "entities",
+        "block_ticks", "fluid_ticks", "PostProcessing", "UpgradeData");
+    private static final Set<String> HEIGHTMAPS = Set.of("WORLD_SURFACE_WG", "WORLD_SURFACE", "OCEAN_FLOOR_WG",
+        "OCEAN_FLOOR", "MOTION_BLOCKING", "MOTION_BLOCKING_NO_LEAVES");
+    private static final Set<String> FULL_HEIGHTMAPS = Set.of("WORLD_SURFACE", "OCEAN_FLOOR", "MOTION_BLOCKING", "MOTION_BLOCKING_NO_LEAVES");
+
+    public ChunkPos position() { return new ChunkPos(x, z); }
+
+    public static ExpansionVoidCertificate certify(ChunkPos pos, CompoundTag terrain, Optional<CompoundTag> entities,
+            Optional<CompoundTag> poi, int dataVersion) throws IOException {
+        return new ExpansionVoidCertificate(pos.x(), pos.z(), terrainFingerprint(pos, terrain, dataVersion),
+            entityFingerprint(pos, entities, dataVersion), poiFingerprint(pos, poi, dataVersion), false);
+    }
+
+    public static ExpansionVoidCertificate absent(ChunkPos pos, Optional<CompoundTag> entities,
+            Optional<CompoundTag> poi, int dataVersion) throws IOException {
+        return new ExpansionVoidCertificate(pos.x(), pos.z(), "absent", entityFingerprint(pos, entities, dataVersion),
+            poiFingerprint(pos, poi, dataVersion), true);
+    }
+
+    public static String terrainFingerprint(ChunkPos pos, CompoundTag tag, int dataVersion) throws IOException {
+        keys(tag, CHUNK_KEYS, "chunk");
+        for (String name : Set.of("DataVersion", "xPos", "yPos", "zPos")) type(tag, name, Tag.TAG_INT);
+        type(tag, "LastUpdate", Tag.TAG_LONG); type(tag, "InhabitedTime", Tag.TAG_LONG);
+        require(tag.getLong("LastUpdate").orElse(-1L) >= 0 && tag.getLong("InhabitedTime").orElse(-1L) >= 0,
+            "invalid chunk time counter");
+        if (tag.contains("isLightOn")) booleanByte(tag, "isLightOn");
+        require(tag.getInt("DataVersion").orElse(-1) == dataVersion, "different data version");
+        require(tag.getInt("xPos").orElse(Integer.MIN_VALUE) == pos.x()
+            && tag.getInt("zPos").orElse(Integer.MIN_VALUE) == pos.z() && tag.getInt("yPos").orElse(-1) == 0,
+            "unexpected chunk coordinates or vertical extent");
+        require(tag.getString("Status").orElse("").equals("minecraft:full"), "chunk is not FULL");
+        for (String name : Set.of("block_entities", "block_ticks", "fluid_ticks"))
+            require(list(tag, name).isEmpty(), "nonempty " + name);
+        emptyList(tag, "entities"); // Legacy in-chunk entities are optional for native FULL chunks.
+        if (tag.contains("UpgradeData")) require(compound(tag, "UpgradeData").isEmpty(), "pending upgrade data");
+        var structures = compound(tag, "structures");
+        keys(structures, Set.of("starts", "References"), "structures");
+        for (String name : Set.of("starts", "References")) require(compound(structures, name).isEmpty(), "structure start or reference");
+        var heightmaps = compound(tag, "Heightmaps");
+        keys(heightmaps, HEIGHTMAPS, "heightmaps");
+        require(heightmaps.keySet().containsAll(FULL_HEIGHTMAPS), "missing FULL heightmap");
+        for (String name : heightmaps.keySet()) {
+            var data = heightmaps.getLongArray(name).orElseThrow(() -> failure("invalid heightmap"));
+            // Native 384-block height maps use nine bits: seven columns per long, 37 longs for 16x16.
+            require(data.length == 37, "invalid heightmap length");
+            for (long value : data) require(value == 0L, "nonempty heightmap");
+        }
+        var postProcessing = list(tag, "PostProcessing");
+        require(postProcessing.size() == 24, "invalid post-processing section count");
+        for (var section : postProcessing)
+            require(section instanceof ListTag values && values.isEmpty(), "post-processing work");
+        Set<Integer> seen = new HashSet<>();
+        for (var entry : list(tag, "sections")) {
+            require(entry instanceof CompoundTag, "invalid section");
+            var section = (CompoundTag) entry;
+            keys(section, Set.of("Y", "block_states", "biomes", "BlockLight", "SkyLight"), "section");
+            type(section, "Y", Tag.TAG_BYTE);
+            int y = section.getByte("Y").map(Byte::intValue).orElse(Integer.MIN_VALUE);
+            require(y >= -1 && y <= 24 && seen.add(y), "duplicate or outside section");
+            for (String light : Set.of("BlockLight", "SkyLight")) if (section.contains(light))
+                require(section.getByteArray(light).map(bytes -> bytes.length == 2048).orElse(false), "invalid light cache");
+            if (y < 0 || y >= 24) {
+                require(!section.contains("block_states") && !section.contains("biomes"), "terrain outside 384-block world");
+                require(section.contains("BlockLight") || section.contains("SkyLight"), "empty non-native light halo");
+                continue;
+            }
+            var blocks = compound(section, "block_states");
+            keys(blocks, Set.of("palette", "data"), "block palette");
+            var palette = list(blocks, "palette");
+            require(palette.size() == 1, "non-pristine block palette");
+            // 26.3 encodes states without properties as strings; its full dispatch codec uses lowercase id.
+            if (palette.getFirst() instanceof CompoundTag only) {
+                keys(only, Set.of("id"), "block state");
+                require(only.getString("id").orElse("").equals("minecraft:air"), "block or fluid present");
+            } else require(palette.getString(0).orElse("").equals("minecraft:air"), "block or fluid present");
+            zeroData(blocks);
+            var biomes = compound(section, "biomes");
+            keys(biomes, Set.of("palette", "data"), "biome palette");
+            var biomePalette = list(biomes, "palette");
+            require(biomePalette.size() == 1 && biomePalette.getString(0).orElse("").equals("minecraft:the_void"),
+                "chunk is outside the pristine void biome");
+            zeroData(biomes);
+        }
+        for (int y = 0; y < 24; y++) require(seen.contains(y), "missing section; emptiness cannot be proved");
+        return digest("sanctuary-void-v1|" + dataVersion + "|" + pos.x() + "|" + pos.z() + "|384|air|the_void");
+    }
+
+    public static String entityFingerprint(ChunkPos pos, Optional<CompoundTag> raw, int dataVersion) throws IOException {
+        if (raw.isPresent()) {
+            var tag = raw.get(); keys(tag, Set.of("DataVersion", "Position", "Entities"), "entity storage");
+            type(tag, "DataVersion", Tag.TAG_INT);
+            require(tag.getInt("DataVersion").orElse(-1) == dataVersion, "different entity data version");
+            var coordinates = tag.getIntArray("Position").orElseThrow(() -> failure("missing entity position"));
+            require(coordinates.length == 2 && coordinates[0] == pos.x() && coordinates[1] == pos.z(), "misplaced entity storage");
+            require(list(tag, "Entities").isEmpty(), "saved entity present");
+        }
+        return digest("sanctuary-empty-entities-v1|" + pos.x() + "|" + pos.z());
+    }
+
+    public static String poiFingerprint(ChunkPos pos, Optional<CompoundTag> raw, int dataVersion) throws IOException {
+        if (raw.isPresent()) {
+            var tag = raw.get(); keys(tag, Set.of("DataVersion", "Sections"), "point-of-interest storage");
+            type(tag, "DataVersion", Tag.TAG_INT);
+            require(tag.getInt("DataVersion").orElse(-1) == dataVersion, "different point-of-interest data version");
+            var sections = compound(tag, "Sections");
+            for (String key : sections.keySet()) {
+                int y;
+                try { y = Integer.parseInt(key); } catch (NumberFormatException error) { throw failure("invalid point-of-interest section"); }
+                require(y >= 0 && y < 24 && key.equals(Integer.toString(y)), "outside or noncanonical point-of-interest section");
+                var section = compound(sections, key); keys(section, Set.of("Valid", "Records"), "point-of-interest section");
+                booleanByte(section, "Valid");
+                require(list(section, "Records").isEmpty(), "saved point of interest");
+            }
+        }
+        return digest("sanctuary-empty-poi-v1|" + pos.x() + "|" + pos.z());
+    }
+
+    private static void zeroData(CompoundTag tag) throws IOException {
+        // A native single-valued palette has no packed indices; nonempty arrays are not proof of pristine storage.
+        if (tag.contains("data")) require(tag.getLongArray("data")
+            .map(values -> values.length == 0).orElse(false), "unexpected single-valued palette data");
+    }
+    private static void type(CompoundTag tag, String key, byte expected) throws IOException {
+        require(tag.get(key) != null && tag.get(key).getId() == expected, "missing or invalid type for " + key);
+    }
+    private static void booleanByte(CompoundTag tag, String key) throws IOException {
+        type(tag, key, Tag.TAG_BYTE);
+        byte value = tag.getByte(key).orElse((byte) -1);
+        require(value == 0 || value == 1, "invalid boolean " + key);
+    }
+    private static void emptyList(CompoundTag tag, String key) throws IOException {
+        if (tag.contains(key)) require(list(tag, key).isEmpty(), "nonempty " + key);
+    }
+    private static ListTag list(CompoundTag tag, String key) throws IOException {
+        return tag.getList(key).orElseThrow(() -> failure("missing or invalid " + key));
+    }
+    private static CompoundTag compound(CompoundTag tag, String key) throws IOException {
+        return tag.getCompound(key).orElseThrow(() -> failure("missing or invalid " + key));
+    }
+    private static void keys(CompoundTag tag, Set<String> allowed, String where) throws IOException {
+        require(allowed.containsAll(tag.keySet()), "foreign or unsupported metadata in " + where);
+    }
+    private static void require(boolean condition, String reason) throws IOException { if (!condition) throw failure(reason); }
+    private static IOException failure(String reason) { return new IOException("void_not_pristine: " + reason); }
+    public static String digest(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 +1,510 @@
+package fr.koka.sanctuary.expansion;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.mojang.serialization.JsonOps;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.mixin.ExpansionChunkMapAccessor;
+import fr.koka.sanctuary.mixin.ExpansionVoidEntityManagerAccess;
+import fr.koka.sanctuary.mixin.ExpansionVoidEntityStorageAccess;
+import fr.koka.sanctuary.mixin.ExpansionVoidPoiStorageAccess;
+import fr.koka.sanctuary.mixin.ExpansionVoidServerLevelAccess;
+import fr.koka.sanctuary.mixin.ExpansionVoidTicksAccess;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.WeakHashMap;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.SectionPos;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.ai.village.poi.PoiManager;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ImposterProtoChunk;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+import net.minecraft.world.level.chunk.storage.SimpleRegionStorage;
+import net.minecraft.world.level.storage.LevelResource;
+import net.minecraft.world.ticks.LevelTicks;
+
+/** Generation-14-only transaction: certify untouched void, bind an immutable manifest in the journal,
+ * then let Minecraft rebuild certified chunks on the next world load. Never patches a live FULL chunk. */
+public final class ExpansionVoidReuse {
+    public static final String NBT_MARKER = "sanctuary:void_reuse";
+    private static final Gson JSON = new Gson();
+    private static final Map<ServerLevel, State> STATES = new WeakHashMap<>();
+    // Immutable snapshots are read by Minecraft's asynchronous NBT parser; mutable session state stays on the server thread.
+    private static volatile Map<ServerLevel, Set<Long>> CAPTURE = Map.of();
+    private static final int BATCH = 64;
+    private static final int MAX_CHUNKS = 8000;
+    private static final int MAX_MANIFEST_BYTES = 4_000_000;
+
+    private ExpansionVoidReuse() {}
+
+    public record Inspection(ServerLevel level, ExpansionIsland island, long deadline,
+                             List<ExpansionVoidCertificate> certificates) {
+        public Inspection { certificates = List.copyOf(certificates); }
+    }
+    private record Manifest(String token, ExpansionIsland island, List<ExpansionVoidCertificate> certificates) {}
+    private record Claim(Manifest manifest, ExpansionVoidCertificate certificate) {}
+    private static final class State {
+        final Map<String, Manifest> manifests = new HashMap<>();
+        final Map<Long, Claim> claims = new HashMap<>();
+        final Set<String> deferred = new HashSet<>();
+        final Set<Long> completed = new HashSet<>();
+        final Map<String, String> failures = new HashMap<>();
+    }
+    public record LoadDecision(ProtoChunk replacement, String trustedMarker) {
+        static final LoadDecision KEEP = new LoadDecision(null, "");
+    }
+
+    /** Every potential write chunk is inspected; existing halo neighbours are deliberately read-only. */
+    public static Inspection inspect(ServerLevel level, ExpansionIsland island, long deadline) throws IOException {
+        requireServerThread(level);
+        if (!(level.getChunkSource().getGenerator() instanceof ExpansionChunkGenerator generator)
+                || generator.rootGeneration() != 14 || island.generation() != 14 || island.origin())
+            throw new IOException("Void reuse is restricted to a new generation-14 expansion");
+        List<ChunkPos> positions = positions(island);
+        var entityStorage = entityRegion(level);
+        var poiStorage = ((ExpansionVoidPoiStorageAccess) level.getPoiManager()).sanctuary$simpleRegionStorage();
+        var certificates = new ArrayList<ExpansionVoidCertificate>();
+        var occupiedPoi = occupiedPoiChunks(level);
+        for (int offset = 0; offset < positions.size(); offset += BATCH) {
+            ExpansionAdmission.checkDeadline(deadline);
+            int end = Math.min(offset + BATCH, positions.size());
+            var reads = new ArrayList<Read>();
+            for (int i = offset; i < end; i++) {
+                ChunkPos pos = positions.get(i);
+                reads.add(new Read(pos, level.getChunkSource().chunkMap.read(pos), entityStorage.read(pos), poiStorage.read(pos)));
+            }
+            await(CompletableFuture.allOf(reads.stream().flatMap(read -> java.util.stream.Stream.of(
+                read.terrain(), read.entities(), read.poi())).toArray(CompletableFuture[]::new)), deadline);
+            IOException refusal = null;
+            for (Read read : reads) {
+                // Drain all submitted operations even if a preceding position is occupied.
+                var disk = await(read.terrain(), deadline);
+                var entities = await(read.entities(), deadline);
+                var poi = await(read.poi(), deadline);
+                try {
+                    verifyMemory(level, read.position(), false, occupiedPoi);
+                    ExpansionVoidCertificate.entityFingerprint(read.position(), entities, dataVersion());
+                    ExpansionVoidCertificate.poiFingerprint(read.position(), poi, dataVersion());
+                    ChunkAccess loaded = loaded(level, read.position());
+                    if (disk.isPresent()) ExpansionVoidCertificate.terrainFingerprint(read.position(), disk.get(), dataVersion());
+                    if (loaded != null) {
+                        // The holder is inspected as-is, never promoted, cancelled or reconfigured.
+                        if (!(unwrap(loaded) instanceof LevelChunk)) throw new IOException("void_reuse_retry: chunk generation is in progress at " + read.position());
+                        var snapshot = SerializableChunkData.copyOf(level, unwrap(loaded)).write();
+                        certificates.add(ExpansionVoidCertificate.certify(read.position(), snapshot, entities, poi, dataVersion()));
+                    } else if (disk.isPresent()) {
+                        certificates.add(ExpansionVoidCertificate.certify(read.position(), disk.get(), entities, poi, dataVersion()));
+                    } else {
+                        certificates.add(ExpansionVoidCertificate.absent(read.position(), entities, poi, dataVersion()));
+                    }
+                } catch (IOException error) { if (refusal == null) refusal = error; }
+            }
+            if (refusal != null) {
+                if (refusal.getMessage().startsWith("void_not_pristine"))
+                    throw new ExpansionAdmission.OccupiedException(refusal.getMessage());
+                throw refusal;
+            }
+        }
+        ExpansionAdmission.checkDeadline(deadline);
+        return new Inspection(level, island, deadline, certificates);
+    }
+
+    /** Must run immediately before committing the reservation, on the same server turn. */
+    public static String persist(Inspection inspection) throws IOException {
+        Inspection verified = inspect(inspection.level(), inspection.island(), inspection.deadline());
+        if (!verified.certificates().equals(inspection.certificates())) throw new IOException("void_reuse_retry: inspected chunks changed before commit");
+        if (verified.certificates().stream().allMatch(ExpansionVoidCertificate::absent)) return "";
+        var body = new JsonObject();
+        body.addProperty("schema", 1); body.addProperty("world_seed", inspection.level().getSeed());
+        body.addProperty("data_version", dataVersion());
+        body.add("island", ExpansionIsland.CODEC.encodeStart(JsonOps.INSTANCE, identity(inspection.island())).getOrThrow());
+        body.add("certificates", JSON.toJsonTree(inspection.certificates()));
+        String encoded = body + "\n";
+        String token = ExpansionVoidCertificate.digest(encoded);
+        Path file = manifestPath(inspection.level(), token);
+        Files.createDirectories(file.getParent());
+        if (Files.exists(file, LinkOption.NOFOLLOW_LINKS)) {
+            if (!readText(file).equals(encoded)) throw new IOException("Void certificate manifest changed on disk");
+            return token;
+        }
+        Path temporary = Files.createTempFile(file.getParent(), ".certificate-", ".tmp");
+        try {
+            try (FileChannel output = FileChannel.open(temporary, StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING)) {
+                ByteBuffer bytes = StandardCharsets.UTF_8.encode(encoded);
+                while (bytes.hasRemaining()) output.write(bytes);
+                output.force(true);
+            }
+            Files.move(temporary, file, StandardCopyOption.ATOMIC_MOVE);
+            if (!file.getFileSystem().getSeparator().equals("\\")) {
+                try (FileChannel parent = FileChannel.open(file.getParent(), StandardOpenOption.READ)) { parent.force(true); }
+            }
+            if (!readText(file).equals(encoded)) throw new IOException("Void certificate read-back failed");
+        } finally { Files.deleteIfExists(temporary); }
+        return token;
+    }
+
+    /** Run before publishing the journal islands to the generator at level startup. Missing authority aborts startup. */
+    public static void open(ServerLevel level, ExpansionChunkGenerator generator, List<ExpansionIsland> islands) throws IOException {
+        requireServerThread(level); close(level);
+        if (generator.rootGeneration() != 14) return;
+        var state = new State();
+        for (var island : islands) if (!island.reuseToken().isEmpty()) add(state, loadManifest(level, island));
+        // Validate every transaction before writing even an EMPTY placeholder or publishing any island.
+        // In particular, an originally absent position may have been explored during the deferred session.
+        var absent = new ArrayList<Claim>();
+        for (var manifest : state.manifests.values()) absent.addAll(preflight(level, manifest));
+        stageAbsent(level, absent);
+        STATES.put(level, state);
+        var captures = new HashMap<>(CAPTURE);
+        captures.put(level, Set.copyOf(state.claims.keySet()));
+        CAPTURE = Map.copyOf(captures);
+    }
+
+    public static void close(ServerLevel level) {
+        STATES.remove(level);
+        var captures = new HashMap<>(CAPTURE); captures.remove(level); CAPTURE = Map.copyOf(captures);
+    }
+
+    public static boolean needsOriginal(net.minecraft.world.level.LevelHeightAccessor height, CompoundTag raw) {
+        if (!(height instanceof ServerLevel level)) return false;
+        var claims = CAPTURE.get(level);
+        if (claims == null || claims.isEmpty()) return false;
+        var x = raw.getInt("xPos"); var z = raw.getInt("zPos");
+        return x.isPresent() && z.isPresent() && claims.contains(new ChunkPos(x.get(), z.get()).pack());
+    }
+
+    /** The just-committed reservation stays invisible until a real reload; a live FULL holder is never reset. */
+    public static void deferred(ServerLevel level, ExpansionIsland island) throws IOException {
+        requireServerThread(level);
+        if (island.reuseToken().isEmpty()) return;
+        State state = STATES.get(level);
+        if (state == null) throw new IOException("Void reuse session is unavailable");
+        state.deferred.add(island.id());
+        add(state, loadManifest(level, island));
+    }
+    public static boolean requiresReload(ServerLevel level, String island) {
+        State state = STATES.get(level); return state != null && state.deferred.contains(island);
+    }
+    public static String failure(ServerLevel level, String island) {
+        State state = STATES.get(level); return state == null ? null : state.failures.get(island);
+    }
+    public static boolean complete(ServerLevel level, ExpansionIsland island) {
+        if (island.reuseToken().isEmpty()) return true;
+        State state = STATES.get(level);
+        if (state == null || state.deferred.contains(island.id()) || state.failures.containsKey(island.id())) return false;
+        Manifest manifest = state.manifests.get(island.reuseToken());
+        return manifest != null && manifest.certificates().stream().allMatch(c -> state.completed.contains(c.position().pack()));
+    }
+
+    /** Called by SerializableChunkData.read on Minecraft's main-thread load executor. Refusal preserves the original data. */
+    public static LoadDecision read(ServerLevel level, ChunkPos position, CompoundTag raw) {
+        State state = STATES.get(level);
+        if (state == null) return LoadDecision.KEEP;
+        Claim claim = state.claims.get(position.pack());
+        if (claim == null) return LoadDecision.KEEP;
+        String island = claim.manifest().island().id();
+        if (raw == null && state.deferred.contains(island)) return LoadDecision.KEEP;
+        try {
+            requireServerThread(level);
+            if (raw == null) throw new IOException("Original chunk NBT is unavailable");
+            if (trustedMarker(level, position, raw, claim.manifest().token()))
+                return new LoadDecision(null, claim.manifest().token());
+            if (state.deferred.contains(island)) return LoadDecision.KEEP;
+            if (claim.certificate().absent()) throw new IOException("An originally absent chunk appeared without its transaction marker");
+            if (state.failures.containsKey(island)) return LoadDecision.KEEP;
+            long deadline = ExpansionAdmission.searchDeadline();
+            var entities = await(entityRegion(level).read(position), deadline);
+            var poi = await(((ExpansionVoidPoiStorageAccess) level.getPoiManager()).sanctuary$simpleRegionStorage().read(position), deadline);
+            verifyMemory(level, position, true);
+            if (loaded(level, position, true) != null) throw new IOException("A live chunk holder must not be replaced");
+            var freshProof = ExpansionVoidCertificate.certify(position, raw, entities, poi, dataVersion());
+            if (!freshProof.equals(claim.certificate())) throw new IOException("Void certificate no longer matches the saved chunk");
+            var replacement = new ProtoChunk(position, UpgradeData.EMPTY, level, level.palettedContainerFactory(), null);
+            marker(replacement, claim.manifest().token());
+            SanctuaryMod.LOGGER.debug("Rebuilding certified void {} for expansion {} through the native pipeline", position, island);
+            return new LoadDecision(replacement, claim.manifest().token());
+        } catch (Exception error) {
+            String failure = "void_reuse_blocked: " + position + ": " + error.getMessage();
+            state.failures.put(island, failure);
+            state.deferred.add(island);
+            if (level.getChunkSource().getGenerator() instanceof ExpansionChunkGenerator generator)
+                generator.setIslands(generator.source().islands().stream().filter(i -> !i.id().equals(island)).toList());
+            SanctuaryMod.LOGGER.error("Expansion {} stopped; the original chunk is preserved: {}", island, failure);
+            // ChunkMap treats an IOException from loading as permission to create EMPTY. Never throw one here.
+            return LoadDecision.KEEP;
+        }
+    }
+
+    public static String marker(ChunkAccess chunk) { return ((ExpansionReuseMarker) unwrap(chunk)).sanctuary$reuseMarker(); }
+    public static void marker(ChunkAccess chunk, String token) { ((ExpansionReuseMarker) unwrap(chunk)).sanctuary$reuseMarker(token); }
+    public static void loaded(ServerLevel level, ChunkAccess chunk, String token) {
+        if (token == null || token.isEmpty()) return;
+        marker(chunk, token);
+        State state = STATES.get(level);
+        Claim claim = state == null ? null : state.claims.get(chunk.getPos().pack());
+        if (claim != null && claim.manifest().token().equals(token) && unwrap(chunk) instanceof LevelChunk)
+            state.completed.add(chunk.getPos().pack());
+    }
+
+    /** Global startup gate. A native marked chunk may now contain gameplay data and is preserved whole. */
+    private static List<Claim> preflight(ServerLevel level, Manifest manifest) throws IOException {
+        var missing = new ArrayList<Claim>();
+        var occupiedPoi = occupiedPoiChunks(level);
+        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(120);
+        var entityStorage = entityRegion(level);
+        var poiStorage = ((ExpansionVoidPoiStorageAccess) level.getPoiManager()).sanctuary$simpleRegionStorage();
+        for (int offset = 0; offset < manifest.certificates().size(); offset += BATCH) {
+            var reads = new ArrayList<Read>();
+            int end = Math.min(offset + BATCH, manifest.certificates().size());
+            for (int i = offset; i < end; i++) {
+                ChunkPos pos = manifest.certificates().get(i).position();
+                reads.add(new Read(pos, level.getChunkSource().chunkMap.read(pos), entityStorage.read(pos), poiStorage.read(pos)));
+            }
+            await(CompletableFuture.allOf(reads.stream().flatMap(read -> java.util.stream.Stream.of(
+                read.terrain(), read.entities(), read.poi())).toArray(CompletableFuture[]::new)), deadline);
+            for (int i = 0; i < reads.size(); i++) {
+                var read = reads.get(i);
+                var certificate = manifest.certificates().get(offset + i);
+                var raw = await(read.terrain(), deadline);
+                var entities = await(read.entities(), deadline);
+                var poi = await(read.poi(), deadline);
+                if (raw.isPresent() && trustedMarker(level, read.position(), raw.get(), manifest.token())) continue;
+                verifyMemory(level, read.position(), false, occupiedPoi);
+                if (loaded(level, read.position()) != null) throw new IOException("Reload has a live uncertified holder at " + read.position());
+                ExpansionVoidCertificate proof;
+                if (raw.isEmpty()) {
+                    if (!certificate.absent()) throw new IOException("Certified saved void disappeared at " + read.position());
+                    proof = ExpansionVoidCertificate.absent(read.position(), entities, poi, dataVersion());
+                    missing.add(new Claim(manifest, certificate));
+                } else {
+                    if (certificate.absent()) throw new IOException("Unclaimed saved chunk appeared after reservation at " + read.position());
+                    proof = ExpansionVoidCertificate.certify(read.position(), raw.get(), entities, poi, dataVersion());
+                }
+                if (!proof.equals(certificate)) throw new IOException("Void reuse preflight changed at " + read.position());
+            }
+        }
+        return missing;
+    }
+
+    /** Durably starts the native pipeline in positions proven absent by the entire preflight.
+     * These EMPTY records contain no generated terrain. A crash leaves journal-authorized records
+     * which the next preflight recognizes, rather than an ambiguous partially activated footprint. */
+    private static void stageAbsent(ServerLevel level, List<Claim> claims) throws IOException {
+        if (claims.isEmpty()) return;
+        var storage = level.getChunkSource().chunkMap;
+        var occupiedPoi = occupiedPoiChunks(level);
+        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(120);
+        for (int offset = 0; offset < claims.size(); offset += BATCH) {
+            var writes = new ArrayList<CompletableFuture<Void>>();
+            int end = Math.min(offset + BATCH, claims.size());
+            for (int i = offset; i < end; i++) {
+                var claim = claims.get(i); ChunkPos pos = claim.certificate().position();
+                // This server turn cannot interleave gameplay. Re-read the owning IO worker to include queued writes.
+                if (await(storage.read(pos), deadline).isPresent() || loaded(level, pos) != null)
+                    throw new IOException("Previously absent chunk changed before staging at " + pos);
+                verifyMemory(level, pos, false, occupiedPoi);
+                var fresh = new ProtoChunk(pos, UpgradeData.EMPTY, level, level.palettedContainerFactory(), null);
+                marker(fresh, claim.manifest().token());
+                writes.add(storage.write(pos, SerializableChunkData.copyOf(level, fresh).write()));
+            }
+            await(CompletableFuture.allOf(writes.toArray(CompletableFuture[]::new)), deadline);
+        }
+        await(storage.synchronize(true), deadline);
+        for (var claim : claims) {
+            var pos = claim.certificate().position();
+            var raw = await(storage.read(pos), deadline).orElseThrow(() -> new IOException("Staged chunk was not saved at " + pos));
+            if (!trustedMarker(level, pos, raw, claim.manifest().token())
+                    || SerializableChunkData.getChunkStatusFromTag(raw) != ChunkStatus.EMPTY)
+                throw new IOException("Staged native EMPTY read-back failed at " + pos);
+        }
+    }
+
+    private static boolean trustedMarker(ServerLevel level, ChunkPos position, CompoundTag raw, String token) throws IOException {
+        if (!raw.contains(NBT_MARKER)) return false;
+        if (!raw.getString(NBT_MARKER).orElse("").equals(token)) throw new IOException("Chunk has a foreign reuse marker at " + position);
+        if (raw.getInt("DataVersion").orElse(-1) != dataVersion()
+                || raw.getInt("xPos").orElse(Integer.MIN_VALUE) != position.x()
+                || raw.getInt("zPos").orElse(Integer.MIN_VALUE) != position.z()
+                || raw.read("Status", ChunkStatus.CODEC).isEmpty()
+                || SerializableChunkData.parse(level, level.palettedContainerFactory(), raw) == null)
+            throw new IOException("Marked chunk cannot be read safely at " + position);
+        return true;
+    }
+
+    private static ChunkAccess unwrap(ChunkAccess chunk) { return chunk instanceof ImposterProtoChunk proxy ? proxy.getWrapped() : chunk; }
+    private static int dataVersion() { return SharedConstants.getCurrentVersion().dataVersion().version(); }
+    private static ExpansionIsland identity(ExpansionIsland island) { return island.withReuseToken("").ready(); }
+    private static Path manifestPath(ServerLevel level, String token) {
+        if (!token.matches("[a-f0-9]{64}")) throw new IllegalArgumentException("Invalid void reuse token");
+        return level.getServer().getWorldPath(LevelResource.ROOT).resolve("data/sanctuary-world-v14/void-reuse").resolve(token + ".json");
+    }
+    private static String readText(Path file) throws IOException {
+        if (!Files.isRegularFile(file, LinkOption.NOFOLLOW_LINKS) || Files.size(file) > MAX_MANIFEST_BYTES)
+            throw new IOException("Missing or invalid immutable void certificate: " + file.getFileName());
+        return Files.readString(file, StandardCharsets.UTF_8);
+    }
+    private static Manifest loadManifest(ServerLevel level, ExpansionIsland island) throws IOException {
+        try {
+            String encoded = readText(manifestPath(level, island.reuseToken()));
+            if (!ExpansionVoidCertificate.digest(encoded).equals(island.reuseToken())) throw new IOException("Void certificate checksum differs from the journal");
+            JsonObject body = JsonParser.parseString(encoded).getAsJsonObject();
+            if (!body.keySet().equals(Set.of("schema", "world_seed", "data_version", "island", "certificates"))
+                    || body.get("schema").getAsInt() != 1 || body.get("world_seed").getAsLong() != level.getSeed()
+                    || body.get("data_version").getAsInt() != dataVersion()) throw new IOException("Unsupported void certificate contract");
+            var identity = ExpansionIsland.CODEC.parse(JsonOps.INSTANCE, body.get("island")).getOrThrow();
+            if (!identity.equals(identity(island))) throw new IOException("Void certificate belongs to a different island");
+            var certificates = new ArrayList<ExpansionVoidCertificate>();
+            var positions = new HashSet<Long>();
+            for (var element : body.getAsJsonArray("certificates")) {
+                if (!element.getAsJsonObject().keySet().equals(Set.of("x", "z", "absent", "terrain", "entities", "poi"))) throw new IOException("Foreign void certificate fields");
+                var certificate = JSON.fromJson(element, ExpansionVoidCertificate.class);
+                if (!island.ownsChunk(certificate.x(), certificate.z()) || !positions.add(certificate.position().pack())
+                        || !(certificate.absent() ? certificate.terrain().equals("absent") : certificate.terrain().matches("[a-f0-9]{64}"))
+                        || !certificate.entities().matches("[a-f0-9]{64}")
+                        || !certificate.poi().matches("[a-f0-9]{64}")) throw new IOException("Invalid certified write scope");
+                certificates.add(certificate);
+            }
+            if (certificates.isEmpty() || certificates.size() > MAX_CHUNKS
+                    || certificates.stream().allMatch(ExpansionVoidCertificate::absent)
+                    || !positions.equals(positions(island).stream().map(ChunkPos::pack).collect(java.util.stream.Collectors.toSet())))
+                throw new IOException("Void certificate does not cover the complete write scope");
+            return new Manifest(island.reuseToken(), identity, List.copyOf(certificates));
+        } catch (RuntimeException error) { throw new IOException("Could not decode the journal's immutable void certificate", error); }
+    }
+    private static void add(State state, Manifest manifest) throws IOException {
+        Manifest old = state.manifests.get(manifest.token());
+        if (old != null) return;
+        for (var certificate : manifest.certificates()) {
+            Claim previous = state.claims.get(certificate.position().pack());
+            if (previous != null && !previous.manifest().token().equals(manifest.token()))
+                throw new IOException("Two void reuse transactions claim the same chunk");
+        }
+        state.manifests.put(manifest.token(), manifest);
+        for (var certificate : manifest.certificates()) state.claims.put(certificate.position().pack(), new Claim(manifest, certificate));
+    }
+    private static List<ChunkPos> positions(ExpansionIsland island) throws IOException {
+        int radius = island.terrainRadius() + ExpansionIsland.DECORATION_MARGIN;
+        var result = new ArrayList<ChunkPos>();
+        for (int z = Math.floorDiv(island.centerZ() - radius, 16); z <= Math.floorDiv(island.centerZ() + radius, 16); z++)
+            for (int x = Math.floorDiv(island.centerX() - radius, 16); x <= Math.floorDiv(island.centerX() + radius, 16); x++)
+                if (island.ownsChunk(x, z)) {
+                    result.add(new ChunkPos(x, z));
+                    if (result.size() > MAX_CHUNKS) throw new IOException("Expansion exceeds the bounded admission scope");
+                }
+        return result;
+    }
+    private static ChunkAccess loaded(ServerLevel level, ChunkPos pos) throws IOException {
+        return loaded(level, pos, false);
+    }
+    private static ChunkAccess loaded(ServerLevel level, ChunkPos pos, boolean currentLoad) throws IOException {
+        var map = level.getChunkSource().chunkMap;
+        if (((ExpansionChunkMapAccessor) map).sanctuary$pendingUnloads().containsKey(pos.pack()))
+            throw new IOException("void_reuse_retry: chunk is unloading at " + pos);
+        var holder = map.getUpdatingChunkIfPresent(pos.pack());
+        if (holder == null) return null;
+        var chunk = holder.getLatestChunk();
+        if (chunk == null && !currentLoad) throw new IOException("void_reuse_retry: chunk load is in progress at " + pos);
+        return chunk;
+    }
+    private static SimpleRegionStorage entityRegion(ServerLevel level) throws IOException {
+        var manager = ((ExpansionVoidServerLevelAccess) level).sanctuary$entityManager();
+        var storage = ((ExpansionVoidEntityManagerAccess) manager).sanctuary$permanentStorage();
+        if (!(storage instanceof ExpansionVoidEntityStorageAccess access)) throw new IOException("Entity storage cannot be verified");
+        return access.sanctuary$simpleRegionStorage();
+    }
+    private static void verifyMemory(ServerLevel level, ChunkPos pos) throws IOException {
+        verifyMemory(level, pos, false);
+    }
+    private static void verifyMemory(ServerLevel level, ChunkPos pos, boolean currentLoad) throws IOException {
+        verifyMemory(level, pos, currentLoad, null);
+    }
+    private static void verifyMemory(ServerLevel level, ChunkPos pos, boolean currentLoad, Set<Long> occupiedPoi) throws IOException {
+        requireServerThread(level);
+        var access = (ExpansionVoidServerLevelAccess) level;
+        var manager = (ExpansionVoidEntityManagerAccess) access.sanctuary$entityManager();
+        var entityStatus = manager.sanctuary$chunkLoadStatuses().get(pos.pack());
+        if (entityStatus != null && entityStatus.name().equals("PENDING"))
+            throw new IOException("void_reuse_retry: entity load is in progress at " + pos);
+        var poiAccess = (ExpansionVoidPoiStorageAccess) level.getPoiManager();
+        boolean prefetched = false;
+        synchronized (poiAccess.sanctuary$loadLock()) {
+            var pending = poiAccess.sanctuary$pendingLoads().get(pos.pack());
+            if (pending != null) {
+                // ChunkMap's own LOAD waits for this prefetch but native unpacking happens inside read.
+                if (!currentLoad || !pending.isDone() || pending.isCompletedExceptionally())
+                    throw new IOException("void_reuse_retry: point-of-interest load is in progress at " + pos);
+                prefetched = true;
+            }
+        }
+        if (prefetched && level.getPoiManager().getInChunk(holder -> true, pos, PoiManager.Occupancy.ANY).findAny().isPresent())
+            throw new IOException("void_not_pristine: prefetched point of interest at " + pos);
+        if (manager.sanctuary$sectionStorage().getExistingSectionsInChunk(pos.pack()).anyMatch(section -> !section.isEmpty())
+                || manager.sanctuary$loadingInbox().stream().anyMatch(chunk -> chunk.getPos().equals(pos) && !chunk.isEmpty()))
+            throw new IOException("void_not_pristine: loaded or loading entity at " + pos);
+        if ((occupiedPoi == null ? occupiedPoiChunks(level) : occupiedPoi).contains(pos.pack()))
+            throw new IOException("void_not_pristine: loaded point of interest at " + pos);
+        verifyTicks(level.getBlockTicks(), pos); verifyTicks(level.getFluidTicks(), pos);
+        if (access.sanctuary$blockEvents().stream().anyMatch(event -> ChunkPos.containing(event.pos()).equals(pos))
+                || access.sanctuary$blockEventsToReschedule().stream().anyMatch(event -> ChunkPos.containing(event.pos()).equals(pos)))
+            throw new IOException("void_not_pristine: pending block event at " + pos);
+    }
+    /** Snapshot once per admission/preflight turn; include every cached Y, even unsupported out-of-world sections.
+     * The server thread does not yield while inspecting, so loaded records cannot change between its chunk checks. */
+    private static Set<Long> occupiedPoiChunks(ServerLevel level) throws IOException {
+        requireServerThread(level);
+        var result = new HashSet<Long>();
+        var poi = ((ExpansionVoidPoiStorageAccess) level.getPoiManager()).sanctuary$storage();
+        for (var entry : poi.long2ObjectEntrySet()) if (entry.getValue().isPresent()
+                && entry.getValue().get().getRecords(holder -> true, PoiManager.Occupancy.ANY).findAny().isPresent())
+            result.add(new ChunkPos(SectionPos.x(entry.getLongKey()), SectionPos.z(entry.getLongKey())).pack());
+        return result;
+    }
+    private static void verifyTicks(LevelTicks<?> ticks, ChunkPos pos) throws IOException {
+        var access = (ExpansionVoidTicksAccess) ticks;
+        var container = access.sanctuary$allContainers().get(pos.pack());
+        if (container != null && container.count() != 0
+                || access.sanctuary$toRunThisTick().stream().anyMatch(tick -> ChunkPos.containing(tick.pos()).equals(pos))
+                || access.sanctuary$alreadyRunThisTick().stream().anyMatch(tick -> ChunkPos.containing(tick.pos()).equals(pos)))
+            throw new IOException("void_not_pristine: scheduled tick at " + pos);
+    }
+    private static void requireServerThread(ServerLevel level) throws IOException {
+        if (!level.getServer().isSameThread()) throw new IOException("Void inspection must run on the server thread");
+    }
+    private static <T> T await(CompletableFuture<T> future, long deadline) throws IOException {
+        try {
+            long remaining = deadline - System.nanoTime();
+            if (remaining <= 0) throw new TimeoutException();
+            return future.get(remaining, TimeUnit.NANOSECONDS);
+        } catch (InterruptedException error) { Thread.currentThread().interrupt(); throw new IOException("Void inspection interrupted", error); }
+        catch (ExecutionException error) { throw new IOException("Void storage read failed", error.getCause()); }
+        catch (TimeoutException error) { throw new IOException("search_timeout", error); }
+    }
+    private record Read(ChunkPos position, CompletableFuture<Optional<CompoundTag>> terrain,
+                        CompletableFuture<Optional<CompoundTag>> entities, CompletableFuture<Optional<CompoundTag>> poi) {}
+}
@@ -0,0 +1,14 @@
+package fr.koka.sanctuary.mixin;
+
+import fr.koka.sanctuary.expansion.ExpansionReuseMarker;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+
+/** Authority follows the actual chunk object; coordinates alone never confer permission to mark a chunk. */
+@Mixin(ChunkAccess.class)
+public abstract class ExpansionReuseChunkMarkerMixin implements ExpansionReuseMarker {
+    @Unique private String sanctuary$reuseMarker = "";
+    @Override public String sanctuary$reuseMarker() { return sanctuary$reuseMarker; }
+    @Override public void sanctuary$reuseMarker(String token) { sanctuary$reuseMarker = token; }
+}
@@ -0,0 +1,18 @@
+package fr.koka.sanctuary.mixin;
+
+import fr.koka.sanctuary.expansion.ExpansionVoidReuse;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(LevelChunk.class)
+public abstract class ExpansionReusePromotionMixin {
+    @Inject(method = "<init>(Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/world/level/chunk/ProtoChunk;Lnet/minecraft/world/level/chunk/LevelChunk$PostLoadProcessor;)V", at = @At("RETURN"))
+    private void sanctuary$promoteCertificate(ServerLevel level, ProtoChunk proto, LevelChunk.PostLoadProcessor processor, CallbackInfo ci) {
+        ExpansionVoidReuse.loaded(level, (LevelChunk) (Object) this, ExpansionVoidReuse.marker(proto));
+    }
+}
@@ -0,0 +1,60 @@
+package fr.koka.sanctuary.mixin;
+
+import fr.koka.sanctuary.expansion.ExpansionVoidReuse;
+import fr.koka.sanctuary.expansion.ExpansionReuseSerializedData;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.ai.village.poi.PoiManager;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+/** Retains the original NBT until the main-thread read boundary, before any native recovery can discard fields. */
+@Mixin(SerializableChunkData.class)
+public abstract class ExpansionReuseSerializationMixin implements ExpansionReuseSerializedData {
+    @Unique private CompoundTag sanctuary$originalNbt;
+    @Unique private String sanctuary$reuseMarker = "";
+    @Override public void sanctuary$originalReuseNbt(CompoundTag tag) { sanctuary$originalNbt = tag; }
+    @Override public void sanctuary$serializedReuseMarker(String token) { sanctuary$reuseMarker = token; }
+
+    @Inject(method = "parse", at = @At("RETURN"))
+    private static void sanctuary$captureOriginal(LevelHeightAccessor height, PalettedContainerFactory factory, CompoundTag raw,
+            CallbackInfoReturnable<SerializableChunkData> cir) {
+        if (cir.getReturnValue() != null && ExpansionVoidReuse.needsOriginal(height, raw))
+            ((ExpansionReuseSerializedData) (Object) cir.getReturnValue()).sanctuary$originalReuseNbt(raw.copy());
+    }
+
+    @Inject(method = "read", at = @At("HEAD"), cancellable = true)
+    private void sanctuary$restoreCertifiedVoid(ServerLevel level, PoiManager pois, RegionStorageInfo storage, ChunkPos position,
+            CallbackInfoReturnable<ProtoChunk> cir) {
+        var decision = ExpansionVoidReuse.read(level, position, sanctuary$originalNbt);
+        sanctuary$originalNbt = null;
+        sanctuary$reuseMarker = decision.trustedMarker();
+        if (decision.replacement() != null) cir.setReturnValue(decision.replacement());
+    }
+
+    @Inject(method = "read", at = @At("RETURN"))
+    private void sanctuary$restoreNativeMarker(ServerLevel level, PoiManager pois, RegionStorageInfo storage, ChunkPos position,
+            CallbackInfoReturnable<ProtoChunk> cir) {
+        if (cir.getReturnValue() != null) ExpansionVoidReuse.loaded(level, cir.getReturnValue(), sanctuary$reuseMarker);
+    }
+
+    @Inject(method = "copyOf", at = @At("RETURN"))
+    private static void sanctuary$captureNativeMarker(ServerLevel level, ChunkAccess chunk, CallbackInfoReturnable<SerializableChunkData> cir) {
+        ((ExpansionReuseSerializedData) (Object) cir.getReturnValue()).sanctuary$serializedReuseMarker(ExpansionVoidReuse.marker(chunk));
+    }
+
+    @Inject(method = "write", at = @At("RETURN"))
+    private void sanctuary$persistNativeMarker(CallbackInfoReturnable<CompoundTag> cir) {
+        if (!sanctuary$reuseMarker.isEmpty()) cir.getReturnValue().putString(ExpansionVoidReuse.NBT_MARKER, sanctuary$reuseMarker);
+    }
+}
@@ -0,0 +1,27 @@
+package fr.koka.sanctuary.mixin;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import java.util.Queue;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.entity.ChunkEntities;
+import net.minecraft.world.level.entity.EntityPersistentStorage;
+import net.minecraft.world.level.entity.EntitySectionStorage;
+import net.minecraft.world.level.entity.PersistentEntitySectionManager;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+/** Exposes both loaded and pending entity collections to the conservative admission check. */
+@Mixin(PersistentEntitySectionManager.class)
+public interface ExpansionVoidEntityManagerAccess {
+    @Accessor("permanentStorage")
+    EntityPersistentStorage<Entity> sanctuary$permanentStorage();
+
+    @Accessor("sectionStorage")
+    EntitySectionStorage<Entity> sanctuary$sectionStorage();
+
+    @Accessor("loadingInbox")
+    Queue<ChunkEntities<Entity>> sanctuary$loadingInbox();
+
+    @Accessor("chunkLoadStatuses")
+    Long2ObjectMap<? extends Enum<?>> sanctuary$chunkLoadStatuses();
+}
@@ -0,0 +1,13 @@
+package fr.koka.sanctuary.mixin;
+
+import net.minecraft.world.level.chunk.storage.EntityStorage;
+import net.minecraft.world.level.chunk.storage.SimpleRegionStorage;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+/** Lets admission inspect saved entities without pretending an unloaded chunk is empty. */
+@Mixin(EntityStorage.class)
+public interface ExpansionVoidEntityStorageAccess {
+    @Accessor("simpleRegionStorage")
+    SimpleRegionStorage sanctuary$simpleRegionStorage();
+}
@@ -0,0 +1,26 @@
+package fr.koka.sanctuary.mixin;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import net.minecraft.world.entity.ai.village.poi.PoiSection;
+import net.minecraft.world.level.chunk.storage.SectionStorage;
+import net.minecraft.world.level.chunk.storage.SimpleRegionStorage;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+/** Used only on the world's POI manager to inspect its persisted and already loaded records. */
+@Mixin(SectionStorage.class)
+public interface ExpansionVoidPoiStorageAccess {
+    @Accessor("simpleRegionStorage")
+    SimpleRegionStorage sanctuary$simpleRegionStorage();
+
+    @Accessor("storage")
+    Long2ObjectMap<Optional<PoiSection>> sanctuary$storage();
+
+    @Accessor("pendingLoads")
+    Long2ObjectMap<CompletableFuture<?>> sanctuary$pendingLoads();
+
+    @Accessor("loadLock")
+    Object sanctuary$loadLock();
+}
@@ -0,0 +1,23 @@
+package fr.koka.sanctuary.mixin;
+
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
+import java.util.List;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.BlockEventData;
+import net.minecraft.world.level.entity.PersistentEntitySectionManager;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+/** Read-only access for checking entity ownership before deferred void admission. */
+@Mixin(ServerLevel.class)
+public interface ExpansionVoidServerLevelAccess {
+    @Accessor("entityManager")
+    PersistentEntitySectionManager<Entity> sanctuary$entityManager();
+
+    @Accessor("blockEvents")
+    ObjectLinkedOpenHashSet<BlockEventData> sanctuary$blockEvents();
+
+    @Accessor("blockEventsToReschedule")
+    List<BlockEventData> sanctuary$blockEventsToReschedule();
+}
@@ -0,0 +1,23 @@
+package fr.koka.sanctuary.mixin;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import java.util.List;
+import java.util.Queue;
+import net.minecraft.world.ticks.LevelChunkTicks;
+import net.minecraft.world.ticks.LevelTicks;
+import net.minecraft.world.ticks.ScheduledTick;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+/** Admission checks scheduled, queued and currently executing ticks, not just chunk containers. */
+@Mixin(LevelTicks.class)
+public interface ExpansionVoidTicksAccess {
+    @Accessor("allContainers")
+    Long2ObjectMap<LevelChunkTicks<?>> sanctuary$allContainers();
+
+    @Accessor("toRunThisTick")
+    Queue<ScheduledTick<?>> sanctuary$toRunThisTick();
+
+    @Accessor("alreadyRunThisTick")
+    List<ScheduledTick<?>> sanctuary$alreadyRunThisTick();
+}
@@ -0,0 +1,45 @@
+package fr.koka.sanctuary.mixin;
+
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+/** Only new alpha.13 decoration writes are filtered, never player edits or saved chunk loading. */
+@Mixin(WorldGenRegion.class)
+public abstract class UnifiedDecorationProtectionMixin {
+    /** Some native features (notably ore veins) write directly to a chunk section after
+     * checking ensureCanWrite, so setBlock alone cannot enforce island ownership. */
+    @Inject(method = "ensureCanWrite", at = @At("HEAD"), cancellable = true)
+    private void sanctuary$keepIslandOwnership(BlockPos pos, CallbackInfoReturnable<Boolean> callback) {
+        var region = (WorldGenRegion) (Object) this;
+        if (!(region.getLevel().getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator generator)
+                || generator.rootGeneration() != 14) return;
+        var center = region.getCenter();
+        var owner = generator.islandForChunk(center.x(), center.z());
+        var destination = generator.islandForChunk(pos.getX() >> 4, pos.getZ() >> 4);
+        if (owner == null || destination == null || !owner.id().equals(destination.id())
+                || !fr.koka.sanctuary.worldgen.city.LostCityStructures.isPlacing() && generator.protectsCityDecoration(pos))
+            callback.setReturnValue(false);
+    }
+
+    @Inject(method = "setBlock", at = @At("HEAD"), cancellable = true)
+    private void sanctuary$keepHydrology(BlockPos pos, BlockState state, int flags, int recursion,
+            CallbackInfoReturnable<Boolean> callback) {
+        var region = (WorldGenRegion) (Object) this;
+        if (!(region.getLevel().getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator generator)) return;
+        // Vanilla rejects writes outside its region before reading the destination chunk.
+        if (!region.isWithinWriteZone(pos)) return;
+        // The dedicated shoreline feature still grows cane on its naturally valid dry banks.
+        if (state.is(Blocks.SUGAR_CANE)) return;
+        if (generator.protectsDecoration(pos) && !region.getBlockState(pos).equals(state)) {
+            generator.rejectedDecorationWrite();
+            callback.setReturnValue(false);
+        }
+    }
+}
@@ -0,0 +1,50 @@
+package fr.koka.sanctuary.mixin.client;
+
+import fr.koka.sanctuary.client.SanctuaryWorldOptionsScreen;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.util.Map;
+import java.util.Optional;
+import net.minecraft.client.gui.screens.worldselection.PresetEditor;
+import net.minecraft.client.gui.screens.worldselection.WorldCreationUiState;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.levelgen.presets.WorldPreset;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+/** Supplies the existing vanilla Customize button without replacing its editor registry. */
+@Mixin(WorldCreationUiState.class)
+public abstract class SanctuaryWorldOptionsMixin {
+    @Unique
+    private static final ResourceKey<WorldPreset> SANCTUARY_PRESET = ResourceKey.create(
+            Registries.WORLD_PRESET, Identifier.fromNamespaceAndPath("sanctuary", "sanctuary"));
+    @Unique
+    private static final PresetEditor SANCTUARY_EDITOR = SanctuaryWorldOptionsScreen::new;
+
+    @Inject(method = "getPresetEditor", at = @At("HEAD"), cancellable = true)
+    private void sanctuary$worldOptions(CallbackInfoReturnable<PresetEditor> callback) {
+        if (sanctuary$hasEditableGenerator()) callback.setReturnValue(SANCTUARY_EDITOR);
+    }
+
+    // Vanilla preserves custom dimensions on registry refresh only when this direct lookup finds an editor.
+    @Redirect(method = "updatePresetLists", at = @At(value = "INVOKE",
+            target = "Ljava/util/Map;get(Ljava/lang/Object;)Ljava/lang/Object;"))
+    private Object sanctuary$preserveCustomSize(Map<?, ?> editors, Object key) {
+        if (Optional.of(SANCTUARY_PRESET).equals(key) && sanctuary$hasEditableGenerator()) return SANCTUARY_EDITOR;
+        return editors.get(key);
+    }
+
+    @Unique
+    private boolean sanctuary$hasEditableGenerator() {
+        WorldCreationUiState state = (WorldCreationUiState) (Object) this;
+        var preset = state.getWorldType().preset();
+        // Recreating an older save may retain the same public preset key with a legacy generator.
+        return preset != null && preset.is(SANCTUARY_PRESET)
+                && state.getSettings().selectedDimensions().overworld() instanceof SanctuaryChunkGenerator;
+    }
+}
@@ -27,9 +27,9 @@ public enum IslandCapacity {
    public static IslandCapacity forGenerator(ChunkGenerator generator) {
        if (!(generator instanceof NoiseBasedChunkGenerator noise)) return null;
        var settings = noise.generatorSettings();
-        if (settings.is(SanctuarySpawn.POPULATION_5_SETTINGS)) return FIVE;
-        if (settings.is(SanctuarySpawn.POPULATION_10_SETTINGS)) return TEN;
-        if (settings.is(SanctuarySpawn.POPULATION_20_SETTINGS)) return TWENTY;
+        if (settings.is(SanctuarySpawn.POPULATION_5_SETTINGS) || settings.is(fr.koka.sanctuary.SanctuaryMod.id("unified_5"))) return FIVE;
+        if (settings.is(SanctuarySpawn.POPULATION_10_SETTINGS) || settings.is(fr.koka.sanctuary.SanctuaryMod.id("unified_10"))) return TEN;
+        if (settings.is(SanctuarySpawn.POPULATION_20_SETTINGS) || settings.is(fr.koka.sanctuary.SanctuaryMod.id("unified_20"))) return TWENTY;
        if (settings.is(SanctuarySpawn.POPULATION_100_SETTINGS)) return HUNDRED;
        return null;
    }
@@ -76,8 +76,10 @@ public final class PopulationDecorationsFeature implements Feature {
    }

    @Override public boolean place(WorldGenLevel level, ChunkGenerator generator, RandomSource ignored, BlockPos origin) {
-        if (!(generator instanceof NoiseBasedChunkGenerator noise) || !PopulationHydrologyRuntime.enabled(noise)) return false;
-        var state = level.getLevel().getChunkSource().randomState();
+        var binding = PopulationGenerationContext.of(generator, level.getLevel());
+        if (binding == null) return false;
+        var noise = binding.generator();
+        var state = binding.random();
        var density = noise.generatorSettings().value().noiseRouter().finalDensity();
        WoodlandGroveGeometry.Sampler sampler = (x, y, z) -> state.sampleBlockValueUncached(density, x, y, z);
        int cx = origin.getX() >> 4, cz = origin.getZ() >> 4;
@@ -0,0 +1,22 @@
+package fr.koka.sanctuary.worldgen;
+
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.RandomState;
+import org.jspecify.annotations.Nullable;
+
+/** Resolves the actual starter noise state; an expansion host's fallback state has no terrain. */
+public final class PopulationGenerationContext {
+    public record Binding(NoiseBasedChunkGenerator generator, RandomState random) {}
+    private PopulationGenerationContext() {}
+    public static @Nullable Binding of(ServerLevel level) {
+        return of(level.getChunkSource().getGenerator(), level);
+    }
+    public static @Nullable Binding of(ChunkGenerator generator, ServerLevel level) {
+        if (generator instanceof SanctuaryChunkGenerator unified) return unified.starterContext();
+        if (generator instanceof NoiseBasedChunkGenerator noise && PopulationHydrologyRuntime.enabled(noise))
+            return new Binding(noise, level.getChunkSource().randomState());
+        return null;
+    }
+}
@@ -53,8 +53,8 @@ public final class PopulationGrovesFeature implements Feature {
    @Override public MapCodec<PopulationGrovesFeature> codec() { return CODEC; }

    public static Optional<RemarkableTree> remarkablePlan(ServerLevel level) {
-        if (!(level.getChunkSource().getGenerator() instanceof NoiseBasedChunkGenerator noise)) return Optional.empty();
-        return remarkablePlan(noise, level.getChunkSource().randomState());
+        var binding = PopulationGenerationContext.of(level);
+        return binding == null ? Optional.empty() : remarkablePlan(binding.generator(), binding.random());
    }

    public static Optional<RemarkableTree> remarkablePlan(NoiseBasedChunkGenerator noise, RandomState state) {
@@ -87,10 +87,12 @@ public final class PopulationGrovesFeature implements Feature {

    @Override
    public boolean place(WorldGenLevel level, ChunkGenerator generator, RandomSource ignored, BlockPos origin) {
-        if (!(generator instanceof NoiseBasedChunkGenerator noise) || !PopulationHydrologyRuntime.enabled(noise)) return false;
+        var binding = PopulationGenerationContext.of(generator, level.getLevel());
+        if (binding == null) return false;
+        var noise = binding.generator();
        int minX = (origin.getX() >> 4) * 16, minZ = (origin.getZ() >> 4) * 16;
        if (!PopulationHydrologyRuntime.capacity(noise).areaExists(minX >> 4, minZ >> 4)) return false;
-        var state = level.getLevel().getChunkSource().randomState();
+        var state = binding.random();
        var density = noise.generatorSettings().value().noiseRouter().finalDensity();
        WoodlandGroveGeometry.Sampler sampler = (x, y, z) -> state.sampleBlockValueUncached(density, x, y, z);
        Protection protection = (base, radius, height, rootDepth) ->
@@ -57,7 +57,8 @@ public final class PopulationHydrologyRuntime {
        });
    }
    public static RegionPlan regionPlan(ServerLevel level, IslandCapacity.Region region) {
-        return regionPlan((NoiseBasedChunkGenerator) level.getChunkSource().getGenerator(), level.getChunkSource().randomState(), region);
+        var binding = Objects.requireNonNull(PopulationGenerationContext.of(level), "Population world required");
+        return regionPlan(binding.generator(), binding.random(), region);
    }
    public static List<RegionPlan> plansIntersecting(NoiseBasedChunkGenerator generator, RandomState state,
                                                    int minX, int minZ, int maxX, int maxZ) {
@@ -20,8 +20,10 @@ public final class PopulationShoreSugarCaneFeature implements Feature {

    @Override
    public boolean place(WorldGenLevel level, ChunkGenerator generator, RandomSource random, BlockPos origin) {
-        if (!(generator instanceof NoiseBasedChunkGenerator noise) || !PopulationHydrologyRuntime.enabled(noise)) return false;
-        var state = level.getLevel().getChunkSource().randomState();
+        var binding = PopulationGenerationContext.of(generator, level.getLevel());
+        if (binding == null) return false;
+        var noise = binding.generator();
+        var state = binding.random();
        var cells = PopulationHydrologyRuntime.cellsInChunk(noise, state, origin.getX() >> 4, origin.getZ() >> 4);
        var cane = Blocks.SUGAR_CANE.defaultBlockState();
        boolean placed = false;
@@ -26,8 +26,9 @@ public final class PopulationSpringOutlets {

    /** Called before vanilla consumes the queue; a fully processed/reloaded chunk has no work. */
    public static Pending capturePending(ServerLevel level, LevelChunk chunk) {
-        if (!(level.getChunkSource().getGenerator() instanceof NoiseBasedChunkGenerator noise)
-                || !PopulationHydrologyRuntime.enabled(noise)) return Pending.EMPTY;
+        var binding = PopulationGenerationContext.of(level);
+        if (binding == null) return Pending.EMPTY;
+        var noise = binding.generator();
        if (!PopulationHydrologyRuntime.capacity(noise).areaExists(chunk.getPos().x(), chunk.getPos().z())) return Pending.EMPTY;
        boolean queued = false;
        for (var section : chunk.getPostProcessing()) if (section != null && !section.isEmpty()) {
@@ -35,7 +36,7 @@ public final class PopulationSpringOutlets {
            break;
        }
        if (!queued) return Pending.EMPTY;
-        var regional = PopulationHydrologyRuntime.regionPlan(noise, level.getChunkSource().randomState(),
+        var regional = PopulationHydrologyRuntime.regionPlan(noise, binding.random(),
            PopulationHydrologyRuntime.capacity(noise).regionAt(chunk.getPos().getMinBlockX(), chunk.getPos().getMinBlockZ()));
        var plan = regional.water();
        List<PopulationHydrology.Position> sources = new ArrayList<>(), outlets = new ArrayList<>();
@@ -58,9 +59,11 @@ public final class PopulationSpringOutlets {

    /** All neighbouring FEATURES have finished before a chunk reaches this stage. */
    public static void finish(ServerLevel level, LevelChunk chunk, Pending pending) {
-        if (pending.isEmpty() || !(level.getChunkSource().getGenerator() instanceof NoiseBasedChunkGenerator noise)
-                || !PopulationHydrologyRuntime.enabled(noise)) return;
-        var random = level.getChunkSource().randomState();
+        if (pending.isEmpty()) return;
+        var binding = PopulationGenerationContext.of(level);
+        if (binding == null) return;
+        var noise = binding.generator();
+        var random = binding.random();
        var density = noise.generatorSettings().value().noiseRouter().finalDensity();
        for (var outlet : pending.outlets()) {
            if (!owns(chunk, outlet)) throw new IllegalArgumentException("An outlet belongs to another chunk: " + outlet);
@@ -0,0 +1,101 @@
+package fr.koka.sanctuary.worldgen;
+
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import fr.koka.sanctuary.expansion.ExpansionBiomeSource;
+import fr.koka.sanctuary.expansion.ExpansionIsland;
+import java.util.List;
+import java.util.stream.Stream;
+import net.minecraft.core.Holder;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeResolver;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.biome.Climate;
+
+/** Alpha.13 keeps Population's origin woodlands and the laboratory's native cave pockets.
+ * Child islands retain the laboratory's complete climate palette. */
+public final class SanctuaryBiomeSource extends ExpansionBiomeSource {
+    public static final List<String> REQUIRED_BIOMES = Stream.concat(
+        ExpansionBiomeSource.REQUIRED_BIOMES.stream(), Stream.of(
+            PopulationIslandBiomeSource.OAK_FOREST, PopulationIslandBiomeSource.BIRCH_FOREST,
+            PopulationIslandBiomeSource.CLEARING, PopulationIslandBiomeSource.DRY_WOODLAND,
+            PopulationIslandBiomeSource.ROCKY_HEATH, PopulationIslandBiomeSource.DARK_GROVE,
+            PopulationIslandBiomeSource.BAMBOO_GROVE, PopulationIslandBiomeSource.SULFUR_DEPTHS,
+            PopulationIslandBiomeSource.LUSH_CAVES, PopulationIslandBiomeSource.DRIPSTONE_CAVES
+        ).map(key -> key.identifier().toString())).toList();
+
+    public static final MapCodec<SanctuaryBiomeSource> CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        Biome.CODEC.listOf().fieldOf("biomes").forGetter(source -> source.allBiomes)
+    ).apply(i, SanctuaryBiomeSource::new));
+    public static final MapCodec<SanctuaryBiomeSource> CITY_CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        Biome.CODEC.listOf().fieldOf("biomes").forGetter(source -> source.allBiomes)
+    ).apply(i, biomes -> new SanctuaryBiomeSource(biomes, true)));
+
+    private final List<Holder<Biome>> allBiomes;
+    private final PopulationIslandBiomeSource population;
+    private final boolean cities;
+    private final Holder<Biome> cityBiome;
+    private volatile java.util.Map<String, fr.koka.sanctuary.worldgen.city.LostCityPlan> cityPlans = java.util.Map.of();
+
+    public SanctuaryBiomeSource(List<Holder<Biome>> biomes) {
+        this(biomes, false);
+    }
+    private SanctuaryBiomeSource(List<Holder<Biome>> biomes, boolean cities) {
+        super(biomes);
+        this.cities = cities;
+        allBiomes = List.copyOf(biomes);
+        cityBiome = cities ? required(ResourceKey.create(net.minecraft.core.registries.Registries.BIOME,
+            fr.koka.sanctuary.SanctuaryMod.id("lost_city"))) : null;
+        population = new PopulationIslandBiomeSource(
+            required(PopulationIslandBiomeSource.OAK_FOREST), required(PopulationIslandBiomeSource.BIRCH_FOREST),
+            required(PopulationIslandBiomeSource.CLEARING), required(PopulationIslandBiomeSource.DRY_WOODLAND),
+            required(PopulationIslandBiomeSource.ROCKY_HEATH), required(PopulationIslandBiomeSource.DARK_GROVE),
+            required(PopulationIslandBiomeSource.BAMBOO_GROVE), required(PopulationIslandBiomeSource.SULFUR_DEPTHS),
+            required(PopulationIslandBiomeSource.LUSH_CAVES), required(PopulationIslandBiomeSource.DRIPSTONE_CAVES));
+    }
+
+    /** A world or delegate gets its own activation snapshot; registered holders remain immutable. */
+    public SanctuaryBiomeSource copy() { return new SanctuaryBiomeSource(allBiomes, cities); }
+    public boolean citiesEnabled() { return cities; }
+    public void setCityPlans(java.util.Map<String, fr.koka.sanctuary.worldgen.city.LostCityPlan> plans) {
+        cityPlans = java.util.Map.copyOf(plans);
+    }
+
+    @Override protected MapCodec<SanctuaryBiomeSource> codec() { return cities ? CITY_CODEC : CODEC; }
+
+    @Override public BiomeResolver createResolver(Climate.Sampler sampler) {
+        BiomeResolver woodlands = population.createResolver(sampler);
+        return (quartX, quartY, quartZ) -> resolveCombined(islands(), woodlands, quartX, quartY, quartZ);
+    }
+
+    @Override public BiomeResolver createResolverForChunk(Climate.Sampler sampler, int minQuartX, int minQuartY,
+            int minQuartZ, int quartSizeX, int quartSizeY, int quartSizeZ) {
+        List<ExpansionIsland> snapshot = islands();
+        BiomeResolver woodlands = population.createResolver(sampler);
+        return (quartX, quartY, quartZ) -> resolveCombined(snapshot, woodlands, quartX, quartY, quartZ);
+    }
+
+    private Holder<Biome> resolveCombined(List<ExpansionIsland> snapshot, BiomeResolver woodlands,
+                                          int quartX, int quartY, int quartZ) {
+        int x = quartX * 4, y = quartY * 4, z = quartZ * 4;
+        // Reuse the historical selector itself: its noise, thresholds, order and child
+        // climate choices stay exact rather than being approximated by another climate field.
+        Holder<Biome> laboratory = super.resolve(snapshot, x, y, z);
+        if (y < 0 || y >= 384 || laboratory.is(Biomes.LUSH_CAVES)
+                || laboratory.is(Biomes.DRIPSTONE_CAVES) || laboratory.is(Biomes.SULFUR_CAVES)) return laboratory;
+        for (ExpansionIsland island : snapshot) {
+            if (cities && island.generation() == 14 && island.contains(x, z)) {
+                var plan = cityPlans.get(island.id());
+                if (plan != null && plan.contains(x, y, z)) return cityBiome;
+            }
+            if (island.origin() && island.contains(x, z)) return woodlands.getNoiseBiome(quartX, quartY, quartZ);
+        }
+        return laboratory;
+    }
+
+    private Holder<Biome> required(ResourceKey<Biome> key) {
+        return allBiomes.stream().filter(holder -> holder.is(key)).findFirst()
+            .orElseThrow(() -> new IllegalArgumentException("Missing Sanctuary biome: " + key.identifier()));
+    }
+}
@@ -0,0 +1,192 @@
+package fr.koka.sanctuary.worldgen;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.DataResult;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import fr.koka.sanctuary.SanctuaryMod;
+import fr.koka.sanctuary.expansion.ExpansionChunkGenerator;
+import fr.koka.sanctuary.expansion.ExpansionIsland;
+import java.util.List;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.RandomState;
+
+/** Alpha.13 combines the complete starter island with the versioned expansion runtime.
+ * The historical laboratory codec keeps its original algorithm and journal. */
+public final class SanctuaryChunkGenerator extends ExpansionChunkGenerator {
+    public static final Codec<Integer> DIAMETER_CODEC = Codec.INT.validate(value ->
+        List.of(512, 724, 1024).contains(value) ? DataResult.success(value)
+            : DataResult.error(() -> "Sanctuary diameter must be 512, 724 or 1024"));
+    public static final MapCodec<SanctuaryChunkGenerator> CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        SanctuaryBiomeSource.CODEC.fieldOf("biome_source").forGetter(SanctuaryChunkGenerator::source),
+        DIAMETER_CODEC.optionalFieldOf("initial_diameter", 724).forGetter(SanctuaryChunkGenerator::initialDiameter)
+    ).apply(i, SanctuaryChunkGenerator::new));
+    public static final MapCodec<SanctuaryChunkGenerator> CITY_CODEC = RecordCodecBuilder.mapCodec(i -> i.group(
+        SanctuaryBiomeSource.CITY_CODEC.fieldOf("biome_source").forGetter(SanctuaryChunkGenerator::source),
+        DIAMETER_CODEC.optionalFieldOf("initial_diameter", 724).forGetter(SanctuaryChunkGenerator::initialDiameter)
+    ).apply(i, (source, diameter) -> new SanctuaryChunkGenerator(source, diameter, 14)));
+
+    private volatile Context originContext;
+    private final int generation;
+    private net.minecraft.world.level.LevelHeightAccessor heightAccessor;
+    // A prospect may reuse an ID at a different position after admission rejects a candidate.
+    // Terrain identity includes all descriptor fields except preparation state and reuse receipt.
+    private final java.util.Map<ExpansionIsland, fr.koka.sanctuary.worldgen.city.LostCityPlan> cityPlans = new java.util.concurrent.ConcurrentHashMap<>();
+    private volatile java.util.Map<String, fr.koka.sanctuary.worldgen.city.LostCityPlan> activeCityPlans = java.util.Map.of();
+    // Root extent is finite (at most 68x68 chunks); each immutable mask is at most 12 KiB.
+    private final java.util.concurrent.ConcurrentHashMap<Long, SanctuaryDecorationProtection> protections = new java.util.concurrent.ConcurrentHashMap<>();
+    private final java.util.concurrent.atomic.LongAdder rejectedWrites = new java.util.concurrent.atomic.LongAdder();
+    public boolean protectsDecoration(net.minecraft.core.BlockPos pos) {
+        if (pos.getY() < 0 || pos.getY() >= 384 || !capacity().areaExists(pos.getX() >> 4, pos.getZ() >> 4)) return false;
+        int cx = pos.getX() >> 4, cz = pos.getZ() >> 4;
+        long key = ((long) cx << 32) ^ (cz & 0xffffffffL);
+        return protections.computeIfAbsent(key, ignored -> SanctuaryDecorationProtection.create(starterContext(), cx, cz)).protects(pos);
+    }
+    public void rejectedDecorationWrite() { rejectedWrites.increment(); }
+    public long rejectedDecorationWrites() { return rejectedWrites.sum(); }
+
+    public SanctuaryChunkGenerator(SanctuaryBiomeSource source, int initialDiameter) {
+        this(source, initialDiameter, 13);
+    }
+    private SanctuaryChunkGenerator(SanctuaryBiomeSource source, int initialDiameter, int generation) {
+        super(source, initialDiameter, true);
+        this.generation = generation;
+        if ((generation == 14) != source.citiesEnabled()) 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 == 14 ? CITY_CODEC : CODEC; }
+    public SanctuaryChunkGenerator withInitialDiameter(int diameter) {
+        return new SanctuaryChunkGenerator(source().copy(), diameter, generation);
+    }
+    public IslandCapacity capacity() {
+        return switch (initialDiameter()) {
+            case 512 -> IslandCapacity.FIVE;
+            case 724 -> IslandCapacity.TEN;
+            case 1024 -> IslandCapacity.TWENTY;
+            default -> throw new IllegalStateException("Unvalidated Sanctuary size");
+        };
+    }
+    @Override public net.minecraft.core.Holder<net.minecraft.world.level.biome.Biome> structureBiome(
+            net.minecraft.core.Holder<net.minecraft.world.level.biome.Biome> biome) {
+        String name = biome.unwrapKey().orElseThrow().identifier().toString();
+        String equivalent = switch (name) {
+            case "sanctuary:population_oak_forest" -> "forest";
+            case "sanctuary:population_birch_forest" -> "birch_forest";
+            case "sanctuary:population_clearing" -> "plains";
+            case "sanctuary:population_dry_woodland" -> "forest";
+            case "sanctuary:population_rocky_heath" -> "meadow";
+            case "sanctuary:population_dark_grove" -> "dark_forest";
+            case "sanctuary:population_bamboo_grove" -> "bamboo_jungle";
+            default -> null;
+        };
+        return equivalent == null ? biome : registries.lookupOrThrow(Registries.BIOME).getOrThrow(
+            net.minecraft.resources.ResourceKey.create(Registries.BIOME, net.minecraft.resources.Identifier.withDefaultNamespace(equivalent)));
+    }
+    @Override public String journalDirectory() { return "sanctuary-world-v" + generation; }
+    @Override public int rootGeneration() { return generation; }
+    @Override public void initialize(ServerLevel level, List<ExpansionIsland> islands) {
+        heightAccessor = level;
+        super.initialize(level, islands);
+        // Publish one root context before any generation workers use it.
+        context(islands.getFirst());
+        prepareCities(islands);
+    }
+    @Override public void setIslands(List<ExpansionIsland> islands) {
+        // Complete and publish city geometry before workers can observe the new owner list.
+        prepareCities(islands);
+        super.setIslands(islands);
+    }
+    private void prepareCities(List<ExpansionIsland> islands) {
+        if (generation != 14) return;
+        var published = new java.util.LinkedHashMap<String, fr.koka.sanctuary.worldgen.city.LostCityPlan>();
+        for (var island : islands) published.put(island.id(), lostCityPlan(island));
+        // Rejected read-only prospects remain private and never enter the biome source.
+        activeCityPlans = java.util.Map.copyOf(published);
+        source().setCityPlans(published);
+    }
+    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();
+        return ready.reuseToken().isEmpty() ? ready : ready.withReuseToken("");
+    }
+    @Override public void discardUnpublishedContext(ExpansionIsland island) {
+        super.discardUnpublishedContext(island);
+        var key = cityIdentity(island);
+        if (source().islands().stream().noneMatch(saved -> cityIdentity(saved).equals(key))) {
+            cityPlans.remove(key);
+            // City prospecting may have prepared the receipt-free terrain context too.
+            super.discardUnpublishedContext(key);
+        }
+    }
+    public fr.koka.sanctuary.worldgen.city.LostCityPlan lostCityPlan(ExpansionIsland island) {
+        if (generation != 14 || island.generation() != 14 || (!island.origin() && !island.climate().equals("lost_city")))
+            return fr.koka.sanctuary.worldgen.city.LostCityPlan.EMPTY;
+        return cityPlans.computeIfAbsent(cityIdentity(island), ignored -> {
+            long start = System.nanoTime();
+            var terrain = context(island);
+            var plan = fr.koka.sanctuary.worldgen.city.LostCityPlanner.plan(island.seed(), island.centerX(), island.centerZ(),
+                island.diameter(), island.origin(), (x, z) -> {
+                    if (!island.contains(x, z)) return new fr.koka.sanctuary.worldgen.city.LostCityPlanner.Ground(0, 0, false, false);
+                    var column = terrain.generator().getBaseColumn(x, z, heightAccessor, terrain.random());
+                    int top = 383;
+                    while (top > 0 && column.getBlock(top).isAir()) top--;
+                    int bottom = top;
+                    while (bottom > 0 && top - bottom < 24 && column.getBlock(bottom).isSolid()
+                            && column.getBlock(bottom).getFluidState().isEmpty()) bottom--;
+                    boolean dry = column.getBlock(top).isSolid() && column.getBlock(top).getFluidState().isEmpty();
+                    boolean protectedWater = island.origin() && top >= 168 && dry && top - bottom >= 6
+                        && PopulationHydrologyRuntime.protects(terrain.generator(), terrain.random(), new net.minecraft.core.BlockPos(x, top, z), 1, 30, 12);
+                    return new fr.koka.sanctuary.worldgen.city.LostCityPlanner.Ground(top, top - bottom, dry, protectedWater);
+                });
+            SanctuaryMod.LOGGER.info("Lost City plan {} seed {}: {} districts in {} ms", island.id(), island.seed(),
+                plan.districts().size(), (System.nanoTime() - start) / 1_000_000);
+            return plan;
+        });
+    }
+    public boolean protectsCityDecoration(net.minecraft.core.BlockPos pos) {
+        if (generation != 14) return false;
+        var island = islandAt(pos.getX(), pos.getZ());
+        // Decoration is a per-block hot path, including while child islands are reserved.
+        var plan = island == null ? null : activeCityPlans.get(island.id());
+        return plan != null && plan.contains(pos.getX(), pos.getY(), pos.getZ());
+    }
+    /** Lost City handles exact, single-structure queries. Mixed sets retain the vanilla
+     * search unchanged: searching both engines with skipReferenced=true would consume
+     * two starts before choosing one result. Mixed-set city discovery is not added here. */
+    @Override public com.mojang.datafixers.util.Pair<net.minecraft.core.BlockPos, net.minecraft.core.Holder<net.minecraft.world.level.levelgen.structure.Structure>> findNearestMapStructure(
+            ServerLevel level, net.minecraft.core.HolderSet<net.minecraft.world.level.levelgen.structure.Structure> structures,
+            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);
+        return super.findNearestMapStructure(level, structures, origin, radius, skipReferenced);
+    }
+    @Override protected Context context(ExpansionIsland island) {
+        if (!island.origin()) return super.context(island);
+        Context current = originContext;
+        if (current != null) return current;
+        synchronized (this) {
+            if (originContext == null) {
+                if (registries == null) throw new IllegalStateException("Sanctuary used before world attachment");
+                var settings = registries.lookupOrThrow(Registries.NOISE_SETTINGS)
+                    .getOrThrow(net.minecraft.resources.ResourceKey.create(Registries.NOISE_SETTINGS,
+                        SanctuaryMod.id("unified_" + capacity().players())));
+                var delegate = new NoiseBasedChunkGenerator(source(), settings);
+                var random = RandomState.create(registries.lookupOrThrow(Registries.NOISE), island.seed(), settings.value());
+                originContext = new Context(delegate, random);
+            }
+            return originContext;
+        }
+    }
+    public PopulationGenerationContext.Binding starterContext() {
+        var current = originContext;
+        if (current == null) throw new IllegalStateException("Sanctuary used before world attachment");
+        return new PopulationGenerationContext.Binding(current.generator(), current.random());
+    }
+    @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);
+    }
+}
@@ -0,0 +1,60 @@
+package fr.koka.sanctuary.worldgen;
+
+import java.util.BitSet;
+import net.minecraft.core.BlockPos;
+
+/** Immutable per-chunk mask of the starter's water, beds, supports and flow passages.
+ * Native cave features may decorate freely outside these previously planned volumes. */
+public final class SanctuaryDecorationProtection {
+    private final int minX, minZ;
+    private final BitSet mask = new BitSet(16 * 16 * 384);
+    private SanctuaryDecorationProtection(int chunkX, int chunkZ) { minX = chunkX * 16; minZ = chunkZ * 16; }
+
+    public static SanctuaryDecorationProtection create(PopulationGenerationContext.Binding binding, int chunkX, int chunkZ) {
+        var result = new SanctuaryDecorationProtection(chunkX, chunkZ);
+        for (var region : PopulationHydrologyRuntime.plansIntersecting(binding.generator(), binding.random(),
+                result.minX - 1, result.minZ - 1, result.minX + 16, result.minZ + 16)) {
+            // A retaining wall can belong to the neighbouring chunk of its water cell.
+            for (int cx = chunkX - 1; cx <= chunkX + 1; cx++)
+                for (int cz = chunkZ - 1; cz <= chunkZ + 1; cz++)
+                    for (var cell : region.water().cellsInChunk(cx, cz)) {
+                        if (cell.x() < result.minX - 1 || cell.x() > result.minX + 16
+                                || cell.z() < result.minZ - 1 || cell.z() > result.minZ + 16) continue;
+                        result.box(cell.x() - 1, cell.bedY() - cell.sedimentDepth() - 2, cell.z() - 1,
+                            cell.x() + 1, cell.carveTop() + 1, cell.z() + 1);
+                    }
+            for (var spring : region.water().springs()) {
+                result.flow(spring.flowBounds(), 2);
+                var source = spring.source();
+                result.cube(source.x(), source.y(), source.z(), 3);
+            }
+            for (var spill : region.water().spills()) result.flow(spill.flowBounds(), 3);
+            for (var fall : region.lava().flowBounds()) result.flow(fall, 8);
+            for (var cell : region.lava().cells()) result.cube(cell.x(), cell.y(), cell.z(), 2);
+            for (var support : region.lava().supports()) result.cube(support.x(), support.y(), support.z(), 2);
+        }
+        return result;
+    }
+    public boolean protects(BlockPos pos) {
+        int x = pos.getX() - minX, z = pos.getZ() - minZ, y = pos.getY();
+        return x >= 0 && x < 16 && z >= 0 && z < 16 && y >= 0 && y < 384
+            && mask.get((x * 16 + z) * 384 + y);
+    }
+    public int protectedBlocks() { return mask.cardinality(); }
+    private void flow(PopulationHydrology.FlowBounds b, int pad) {
+        box(b.minX() - pad, b.minY() - pad, b.minZ() - pad,
+            b.maxX() + pad, b.maxY() + pad, b.maxZ() + pad);
+    }
+    private void cube(int x, int y, int z, int radius) {
+        box(x - radius, y - radius, z - radius, x + radius, y + radius, z + radius);
+    }
+    private void box(int x1, int y1, int z1, int x2, int y2, int z2) {
+        int lo = Math.max(0, y1), hi = Math.min(383, y2);
+        if (lo > hi) return;
+        for (int x = Math.max(minX, x1); x <= Math.min(minX + 15, x2); x++)
+            for (int z = Math.max(minZ, z1); z <= Math.min(minZ + 15, z2); z++) {
+                int column = ((x - minX) * 16 + z - minZ) * 384;
+                mask.set(column + lo, column + hi + 1);
+            }
+    }
+}
@@ -0,0 +1,37 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+
+/** Restrained masonry for the abandoned city; weathering never changes the structural palette. */
+public final class LostCityPalette {
+    public static final BlockState STONE = Blocks.STONE.defaultBlockState();
+    public static final BlockState SMOOTH = Blocks.SMOOTH_STONE.defaultBlockState();
+    public static final BlockState BRICK = Blocks.STONE_BRICKS.defaultBlockState();
+    public static final BlockState AIR = Blocks.AIR.defaultBlockState();
+
+    private LostCityPalette() {}
+
+    public static BlockState masonry(long seed, int x, int y, int z) {
+        int weather = roll(seed, x / 3, y / 2, z / 3, 29);
+        if (weather < 4) return Blocks.MOSSY_STONE_BRICKS.defaultBlockState();
+        if (weather < 8) return Blocks.CRACKED_STONE_BRICKS.defaultBlockState();
+        return BRICK;
+    }
+
+    public static BlockState pavement(long seed, int x, int z) {
+        int wear = roll(seed, x / 3, 0, z / 3, 31);
+        if (wear < 3) return Blocks.ANDESITE.defaultBlockState();
+        if (wear == 3) return Blocks.CRACKED_STONE_BRICKS.defaultBlockState();
+        return STONE;
+    }
+
+    public static int roll(long seed, int x, int y, int z, int bound) {
+        long value = seed ^ ((long) x * 0x9e3779b97f4a7c15L)
+            ^ ((long) y * 0xc2b2ae3d27d4eb4fL) ^ ((long) z * 0x165667b19e3779f9L);
+        value = (value ^ (value >>> 30)) * 0xbf58476d1ce4e5b9L;
+        value = (value ^ (value >>> 27)) * 0x94d049bb133111ebL;
+        value ^= value >>> 31;
+        return (int) Long.remainderUnsigned(value, bound);
+    }
+}
@@ -0,0 +1,88 @@
+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;
+
+/** A persisted parcel is sufficient to decorate a later chunk without recomputing the district. */
+public final class LostCityPiece extends StructurePiece {
+    private static final int SCHEMA = 1;
+    private final LostCityPlan.Parcel parcel;
+
+    public LostCityPiece(LostCityPlan.Parcel parcel) {
+        super(LostCityStructures.PIECE, 0, bounds(parcel));
+        this.parcel = parcel;
+        setOrientation(null);
+    }
+
+    public LostCityPiece(StructurePieceSerializationContext context, CompoundTag tag) {
+        super(LostCityStructures.PIECE, 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(() -> LostCityRenderer.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 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());
+    }
+}
@@ -0,0 +1,97 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import java.util.List;
+
+/** Immutable, bounded city geometry. Coordinates and block elevations are absolute.
+ * The plan uses only pre-decoration terrain, never loaded or player-edited chunks. */
+public final class LostCityPlan {
+    public static final LostCityPlan EMPTY = new LostCityPlan(List.of());
+    private final List<District> districts;
+
+    public LostCityPlan(List<District> districts) { this.districts = List.copyOf(districts); }
+    public List<District> districts() { return districts; }
+    public boolean isEmpty() { return districts.isEmpty(); }
+
+    /** City biomes follow accepted parcels, leaving underground cave biomes intact. */
+    public boolean contains(int x, int y, int z) {
+        for (District district : districts) for (Parcel parcel : district.parcels()) {
+            if (x >= parcel.minX() - 2 && x <= parcel.maxX() + 2
+                    && z >= parcel.minZ() - 2 && z <= parcel.maxZ() + 2
+                    && y >= parcel.floorY() - 8 && y <= 383) return true;
+        }
+        return false;
+    }
+
+    public boolean intersects(int minX, int minZ, int maxX, int maxZ) {
+        for (District district : districts) for (Parcel parcel : district.parcels()) {
+            if (minX <= parcel.maxX() + 2 && maxX >= parcel.minX() - 2
+                    && minZ <= parcel.maxZ() + 2 && maxZ >= parcel.minZ() - 2) return true;
+        }
+        return false;
+    }
+
+    public enum Kind {
+        STREET, BRIDGE, PARK, PLAZA, MARKET, PARKING,
+        APARTMENT, HOTEL, LIBRARY, RESTAURANT, BARRACKS, HALL,
+        EXCAVATION, POOL, PARK_GARDEN, PARK_PLAYGROUND, PARK_MEMORIAL;
+        public boolean building() {
+            return switch (this) {
+                case APARTMENT, HOTEL, LIBRARY, RESTAURANT, BARRACKS, HALL -> true;
+                default -> false;
+            };
+        }
+    }
+
+    public record District(int startChunkX, int startChunkZ, long seed, List<Parcel> parcels) {
+        public District {
+            parcels = List.copyOf(parcels);
+            if (parcels.isEmpty()) throw new IllegalArgumentException("Empty city district");
+            for (Parcel parcel : parcels) {
+                if (Math.abs(Math.floorDiv(parcel.minX(), 16) - startChunkX) > 7
+                        || Math.abs(Math.floorDiv(parcel.maxX(), 16) - startChunkX) > 7
+                        || Math.abs(Math.floorDiv(parcel.minZ(), 16) - startChunkZ) > 7
+                        || Math.abs(Math.floorDiv(parcel.maxZ(), 16) - startChunkZ) > 7)
+                    throw new IllegalArgumentException("City parcel exceeds native reference radius");
+            }
+        }
+        public int minX() { return parcels.stream().mapToInt(Parcel::minX).min().orElseThrow(); }
+        public int maxX() { return parcels.stream().mapToInt(Parcel::maxX).max().orElseThrow(); }
+        public int minZ() { return parcels.stream().mapToInt(Parcel::minZ).min().orElseThrow(); }
+        public int maxZ() { return parcels.stream().mapToInt(Parcel::maxZ).max().orElseThrow(); }
+    }
+
+    /** surfaceHeights is empty for a level parcel, or width*depth elevations for a street/ramp.
+     * Facing: 0 north, 1 east, 2 south, 3 west. Road coordinates are already world-aligned. */
+    public record Parcel(Kind kind, int minX, int minZ, int width, int depth,
+            int floorY, int floors, int facing, long seed, int foundationDepth, int[] surfaceHeights) {
+        public Parcel {
+            if (kind == null || width < 1 || depth < 1 || width > 25 || depth > 25
+                    || floors < 0 || floors > 5 || facing < 0 || facing > 3
+                    || foundationDepth < 0 || foundationDepth > 12
+                    || floorY < 48 || floorY + Math.max(8, floors * 5 + 5) > 382)
+                throw new IllegalArgumentException("Invalid city parcel dimensions");
+            surfaceHeights = surfaceHeights.clone();
+            if (surfaceHeights.length != 0 && surfaceHeights.length != width * depth)
+                throw new IllegalArgumentException("Invalid city road elevations");
+            for (int y : surfaceHeights) if (y < 48 || y > 370)
+                throw new IllegalArgumentException("Invalid road height");
+        }
+        @Override public int[] surfaceHeights() { return surfaceHeights.clone(); }
+        public int surfaceY(int localX, int localZ) {
+            return surfaceHeights.length == 0 ? floorY : surfaceHeights[localZ * width + localX];
+        }
+        public int maxX() { return minX + width - 1; }
+        public int maxZ() { return minZ + depth - 1; }
+        public int minY() {
+            int y = floorY;
+            for (int height : surfaceHeights) y = Math.min(y, height);
+            return y - foundationDepth;
+        }
+        public int maxY() {
+            int y = floorY;
+            for (int height : surfaceHeights) y = Math.max(y, height);
+            return y + Math.max(8, floors * 5 + 5);
+        }
+        public int maxRoofY() { return maxY(); }
+    }
+}
@@ -0,0 +1,316 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.District;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Kind;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Parcel;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/** A small connected, terraced street grid fitted to actual immutable noise columns.
+ * Planning never loads a chunk, edits terrain, or retries indefinitely to force a city.
+ * Unsupported parcels and protected hydrology remain natural, including on the starter island. */
+public final class LostCityPlanner {
+    private static final int CELL = 24;
+    private static final int LOT = 17;
+    private static final int MIN_FLOOR = 176;
+    private static final int MAX_COLUMNS = 16_000;
+    private static final Ground INVALID = new Ground(0, 0, false, true);
+    private static final Kind[] KINDS = {
+        Kind.APARTMENT, Kind.PARK, Kind.LIBRARY, Kind.RESTAURANT,
+        Kind.PLAZA, Kind.HOTEL, Kind.MARKET, Kind.BARRACKS,
+        Kind.PARKING, Kind.HALL, Kind.APARTMENT, Kind.PARK,
+        Kind.HOTEL, Kind.PLAZA, Kind.HALL, Kind.RESTAURANT,
+        Kind.EXCAVATION, Kind.POOL, Kind.PARK_GARDEN, Kind.PARK_PLAYGROUND, Kind.PARK_MEMORIAL
+    };
+
+    private LostCityPlanner() {}
+
+    public record Ground(int top, int solidDepth, boolean dry, boolean protectedTerrain) {}
+    @FunctionalInterface public interface GroundSampler { Ground sample(int x, int z); }
+
+    public static LostCityPlan plan(long seed, int centerX, int centerZ, int diameter,
+            boolean origin, GroundSampler sampler) {
+        if (diameter < 64 || diameter > 1024) throw new IllegalArgumentException("Unsupported city island size");
+        int cells = origin ? 3 : diameter >= 512 ? 4 : diameter >= 256 ? 3 : diameter >= 128 ? 2 : 1;
+        TerrainCache survey = new TerrainCache(centerX, centerZ, diameter, sampler);
+        List<Candidate> candidates = candidates(seed, centerX, centerZ, diameter, origin, cells, survey);
+        candidates.sort(Comparator.comparingInt(Candidate::score).reversed().thenComparingLong(Candidate::salt));
+        List<Parcel> best = List.of();
+        Candidate chosen = null;
+        List<Integer> acceptedPerAttempt = new ArrayList<>();
+        // A bounded fallback is useful when a coarse footprint concealed a fissure.
+        for (int i = 0; i < Math.min(3, candidates.size()); i++) {
+            Candidate candidate = candidates.get(i);
+            if (candidate.score() == 0 || survey.exhausted()) break;
+            List<Parcel> parcels = build(seed, candidate, cells, survey);
+            acceptedPerAttempt.add(lotCount(parcels));
+            if (lotCount(parcels) > lotCount(best)) { best = parcels; chosen = candidate; }
+            if (lotCount(best) >= (origin ? 5 : Math.min(6, cells * cells))) break;
+        }
+        if (chosen == null || lotCount(best) < (cells == 1 ? 1 : 2)
+                || best.stream().noneMatch(p -> p.kind().building())) {
+            if (Boolean.getBoolean("sanctuary.test.lostCity") || Boolean.getBoolean("sanctuary.city.plannerDiagnostics"))
+                System.getLogger(LostCityPlanner.class.getName()).log(System.Logger.Level.INFO,
+                    "Lost City rejected seed=" + seed + " diameter=" + diameter + " origin=" + origin
+                    + " coarse=" + candidates.stream().map(Candidate::score).toList()
+                    + " connected=" + acceptedPerAttempt + " " + survey.diagnostics());
+            return LostCityPlan.EMPTY;
+        }
+        return new LostCityPlan(List.of(new District(Math.floorDiv(chosen.x() + cells * CELL / 2, 16),
+            Math.floorDiv(chosen.z() + cells * CELL / 2, 16), mix(seed ^ chosen.salt()), best)));
+    }
+
+    private static int lotCount(List<Parcel> parcels) {
+        return (int) parcels.stream().filter(p -> p.kind() != Kind.STREET && p.kind() != Kind.BRIDGE).count();
+    }
+
+    private static List<Candidate> candidates(long seed, int cx, int cz, int diameter,
+            boolean origin, int cells, TerrainCache survey) {
+        List<Candidate> result = new ArrayList<>();
+        int attempts = origin ? 12 : 9;
+        double angle = unit(mix(seed ^ 0xC174A14L)) * Math.PI * 2;
+        for (int attempt = 0; attempt < attempts; attempt++) {
+            long salt = mix(seed ^ (attempt * 0x9E3779B97F4A7C15L) ^ 0xC17D157L);
+            double radius = origin ? Math.min(diameter * .20, 150) * (attempt < 8 ? 1 : .48)
+                : attempt == 0 ? 0 : diameter * .13;
+            double a = angle + attempt * Math.PI * 2 / 8;
+            int x = cx + (int) Math.round(Math.cos(a) * radius) - cells * CELL / 2;
+            int z = cz + (int) Math.round(Math.sin(a) * radius) - cells * CELL / 2;
+            int score = 0;
+            for (int row = 0; row < cells; row++) for (int col = 0; col < cells; col++) {
+                if (coarseLot(x + col * CELL + 4, z + row * CELL + 4, survey)) score++;
+            }
+            result.add(new Candidate(x, z, score, salt));
+        }
+        return result;
+    }
+
+    private static boolean coarseLot(int x, int z, TerrainCache survey) {
+        int low = Integer.MAX_VALUE, high = Integer.MIN_VALUE;
+        for (int[] point : new int[][] {{0, 0}, {16, 0}, {0, 16}, {16, 16}, {8, 8}, {8, 0}}) {
+            Ground g = survey.at(x + point[0], z + point[1]);
+            if (!supported(g)) { survey.reject("coarse-support"); return false; }
+            low = Math.min(low, g.top()); high = Math.max(high, g.top());
+        }
+        int floor = lotFloor(low, high);
+        if (low < floor - 10 || high > floor + 2) { survey.reject("coarse-slope"); return false; }
+        if (floor < MIN_FLOOR || floor > 350) { survey.reject("coarse-height"); return false; }
+        return true;
+    }
+
+    private static List<Parcel> build(long seed, Candidate site, int cells, TerrainCache survey) {
+        int[][] heights = new int[cells + 1][cells + 1];
+        for (int row = 0; row <= cells; row++) for (int col = 0; col <= cells; col++) {
+            Ground g = survey.at(site.x() + col * CELL, site.z() + row * CELL);
+            heights[row][col] = supported(g) && g.top() < 360 ? g.top() + 1 : -1;
+        }
+        List<Edge> edges = new ArrayList<>();
+        for (int row = 0; row < cells; row++) for (int col = 0; col < cells; col++) {
+            int x = site.x() + col * CELL, z = site.z() + row * CELL;
+            long parcelSeed = mix(seed ^ site.salt() ^ col * 0xD1342543DE82EF95L ^ row * 0xC6BC279692B5CC83L);
+            int kindOffset = (int) Long.remainderUnsigned(mix(seed ^ 0xC174CA7L), KINDS.length);
+            Kind kind = cells == 1 ? Kind.APARTMENT : KINDS[Math.floorMod(row * cells + col + kindOffset, KINDS.length)];
+            Parcel lot = lot(kind, x + 4, z + 4, parcelSeed, survey);
+            int middleY = lot == null ? survey.at(x + CELL / 2, z).top() + 1 : lot.floorY();
+            Parcel road = road(x, z, true, heights[row][col], middleY, heights[row][col + 1], parcelSeed ^ 31, survey);
+            if (road == null) continue;
+            Parcel entrance = lot == null ? null : entrance(lot, survey);
+            if (entrance == null) lot = null;
+            List<Parcel> pieces = new ArrayList<>();
+            pieces.add(road);
+            if (lot != null) { pieces.add(lot); pieces.add(entrance); }
+            edges.add(new Edge(node(col, row, cells), node(col + 1, row, cells), List.copyOf(pieces)));
+        }
+        // Cross streets join the rows; short unsupported runs can be bridge decks.
+        // Endpoints and the first/last two columns must have real, dry abutments.
+        for (int row = 0; row < cells - 1; row++) for (int col = 0; col <= cells; col++) {
+            int y0 = heights[row][col], y1 = heights[row + 1][col];
+            Parcel road = road(site.x() + col * CELL, site.z() + row * CELL, false,
+                y0, y0 < 0 || y1 < 0 ? -1 : (y0 + y1) / 2, y1,
+                mix(seed ^ site.salt() ^ row * 479L ^ col * 1861L), survey);
+            if (road != null) edges.add(new Edge(node(col, row, cells), node(col, row + 1, cells), List.of(road)));
+        }
+        return largestConnectedDistrict(edges);
+    }
+
+    private static Parcel lot(Kind kind, int x, int z, long seed, TerrainCache survey) {
+        if (!coarseLot(x, z, survey)) return null;
+        int low = Integer.MAX_VALUE, high = Integer.MIN_VALUE;
+        for (int dz = 0; dz < LOT; dz++) for (int dx = 0; dx < LOT; dx++) {
+            Ground g = survey.at(x + dx, z + dz);
+            if (!supported(g)) { survey.reject("lot-support"); return null; }
+            low = Math.min(low, g.top()); high = Math.max(high, g.top());
+        }
+        int floor = lotFloor(low, high);
+        if (low < floor - 10 || high > floor + 2) { survey.reject("lot-slope"); return null; }
+        if (floor < MIN_FLOOR || floor > 350) { survey.reject("lot-height"); return null; }
+        int floors = switch (kind) {
+            case APARTMENT, HOTEL -> 3 + (int) Long.remainderUnsigned(seed, 3);
+            case LIBRARY, RESTAURANT, BARRACKS, HALL -> 2;
+            case PARKING, MARKET -> 1;
+            default -> 0;
+        };
+        int foundation = Math.max(2, floor - low + 1);
+        if (kind == Kind.PARKING || kind == Kind.POOL || kind == Kind.EXCAVATION) {
+            // >=8 certifies a contained excavation, pool or optional underground garage.
+            // Every existing surface must cover the ceiling and solid rock must cover its floor.
+            if (low >= floor - 1 && solidTo(x, z, LOT, LOT, floor - 8, survey)) foundation = 8;
+            else if (kind != Kind.PARKING) kind = Kind.PARK;
+            else if (foundation >= 8) return null;
+        }
+        if (!solidTo(x, z, LOT, LOT, floor - foundation, survey)) { survey.reject("lot-foundation"); return null; }
+        // Every parcel faces its street to the north. Variety comes from the seed,
+        // facade details and building types, never from a door pointed into another building.
+        return new Parcel(kind, x, z, LOT, LOT, floor, floors, 0, seed,
+            foundation, new int[0]);
+    }
+
+    private static Parcel entrance(Parcel lot, TerrainCache survey) {
+        int x = lot.minX() + LOT / 2 - 1, z = lot.minZ() - 2, floor = lot.floorY(), foundation = 2;
+        for (int dz = 0; dz < 2; dz++) for (int dx = 0; dx < 3; dx++) {
+            Ground g = survey.at(x + dx, z + dz);
+            if (!supported(g) || g.top() < floor - 10 || g.top() > floor + 2) return null;
+            foundation = Math.max(foundation, floor - g.top() + 1);
+        }
+        if (!solidTo(x, z, 3, 2, floor - foundation, survey)) return null;
+        return new Parcel(Kind.STREET, x, z, 3, 2, floor, 0, 0, lot.seed() ^ 63, foundation, new int[0]);
+    }
+
+    private static Parcel road(int x, int z, boolean alongX, int startY, int middleY, int endY,
+            long seed, TerrainCache survey) {
+        if (startY < MIN_FLOOR || middleY < MIN_FLOOR || endY < MIN_FLOOR || startY > 360 || middleY > 360 || endY > 360
+                || Math.abs(startY - middleY) > CELL / 2 - 2 || Math.abs(endY - middleY) > CELL / 2 - 2) {
+            survey.reject("road-endpoint-height"); return null;
+        }
+        int width = alongX ? CELL + 1 : 5, depth = alongX ? 5 : CELL + 1;
+        int minX = alongX ? x : x - 2, minZ = alongX ? z - 2 : z;
+        int[] surface = new int[width * depth];
+        int foundation = 2, gapRun = 0;
+        boolean bridge = false;
+        for (int step = 0; step <= CELL; step++) {
+            // Flat 5x5 intersections agree in both directions; ramps start beyond them.
+            int y = step < 2 ? startY : step > CELL - 2 ? endY : step <= CELL / 2
+                ? lerp(startY, middleY, step - 2, CELL / 2 - 2)
+                : lerp(middleY, endY, step - CELL / 2, CELL / 2 - 2);
+            boolean gap = false;
+            for (int across = 0; across < 5; across++) {
+                int dx = alongX ? step : across, dz = alongX ? across : step;
+                Ground g = survey.at(minX + dx, minZ + dz);
+                // No deck cuts a protected river, spring or basin, even if an adjacent bank is solid.
+                if (g.protectedTerrain()) { survey.reject("road-protected"); return null; }
+                if (g.top() > y + 2) { survey.reject("road-cut"); return null; }
+                boolean support = supported(g) && g.top() >= y - 10;
+                if (!support) {
+                    if (g.top() >= y - 2) { survey.reject("road-weak-surface"); return null; }
+                    gap = true;
+                } else foundation = Math.max(foundation, y - g.top() + 1);
+                surface[dz * width + dx] = y;
+            }
+            if (gap) {
+                if (step < 2 || step > CELL - 2 || ++gapRun > 8) { survey.reject("road-bridge-support"); return null; }
+                bridge = true;
+            } else gapRun = 0;
+        }
+        if (!bridge) for (int dz = 0; dz < depth; dz++) for (int dx = 0; dx < width; dx++) {
+            Ground g = survey.at(minX + dx, minZ + dz);
+            if (g.top() - (surface[dz * width + dx] - foundation) + 1 > g.solidDepth()) {
+                survey.reject("road-foundation"); return null;
+            }
+        }
+        return new Parcel(bridge ? Kind.BRIDGE : Kind.STREET, minX, minZ, width, depth,
+            startY, 0, 0, seed, bridge ? 0 : foundation, surface);
+    }
+
+    private static List<Parcel> largestConnectedDistrict(List<Edge> edges) {
+        Map<Integer, List<Edge>> neighbors = new HashMap<>();
+        for (Edge edge : edges) {
+            neighbors.computeIfAbsent(edge.a(), ignored -> new ArrayList<>()).add(edge);
+            neighbors.computeIfAbsent(edge.b(), ignored -> new ArrayList<>()).add(edge);
+        }
+        Set<Integer> visited = new HashSet<>();
+        List<Parcel> best = List.of();
+        // Stable insertion order comes from edges, never HashMap iteration.
+        for (Edge start : edges) {
+            if (visited.contains(start.a())) continue;
+            Set<Edge> component = new HashSet<>();
+            ArrayDeque<Integer> queue = new ArrayDeque<>();
+            queue.add(start.a()); visited.add(start.a());
+            while (!queue.isEmpty()) {
+                int node = queue.removeFirst();
+                for (Edge edge : neighbors.getOrDefault(node, List.of())) {
+                    component.add(edge);
+                    int other = edge.a() == node ? edge.b() : edge.a();
+                    if (visited.add(other)) queue.addLast(other);
+                }
+            }
+            List<Parcel> parcels = new ArrayList<>();
+            for (Edge edge : edges) if (component.contains(edge)) parcels.addAll(edge.parcels());
+            if (lotCount(parcels) > lotCount(best)) best = List.copyOf(parcels);
+        }
+        return best;
+    }
+
+    private static boolean supported(Ground g) {
+        return g.dry() && !g.protectedTerrain() && g.solidDepth() >= 4 && g.top() >= MIN_FLOOR - 12;
+    }
+    /** A terrace follows the entire footprint rather than privileging its north entrance.
+     * Flat sites stay one block above their natural floor; modest uphill sites may cut at
+     * most two surface blocks. Foundation thickness and continuous rock are checked later. */
+    private static int lotFloor(int low, int high) {
+        return high + 1 - Math.min(2, (high - low) / 3);
+    }
+    private static boolean solidTo(int x, int z, int width, int depth, int bottomY, TerrainCache survey) {
+        for (int dz = 0; dz < depth; dz++) for (int dx = 0; dx < width; dx++) {
+            Ground g = survey.at(x + dx, z + dz);
+            if (g.top() < bottomY || g.top() - bottomY + 1 > g.solidDepth()) return false;
+        }
+        return true;
+    }
+    private static int lerp(int a, int b, int step, int length) { return a + Math.round((b - a) * (step / (float) length)); }
+    private static int node(int col, int row, int cells) { return row * (cells + 1) + col; }
+    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);
+    }
+    private record Candidate(int x, int z, int score, long salt) {}
+    private record Edge(int a, int b, List<Parcel> parcels) {}
+
+    private static final class TerrainCache {
+        private final int centerX, centerZ;
+        private final double radius;
+        private final GroundSampler sampler;
+        private final Map<Long, Ground> columns = new HashMap<>();
+        private final Map<String, Integer> rejections = new java.util.TreeMap<>();
+        TerrainCache(int centerX, int centerZ, int diameter, GroundSampler sampler) {
+            this.centerX = centerX; this.centerZ = centerZ; this.radius = diameter / 2.0 - 6;
+            this.sampler = java.util.Objects.requireNonNull(sampler);
+        }
+        boolean exhausted() { return columns.size() >= MAX_COLUMNS; }
+        void reject(String reason) { rejections.merge(reason, 1, Integer::sum); }
+        String diagnostics() {
+            return "columns=" + columns.size() + " heights=" + columns.values().stream().mapToInt(Ground::top).summaryStatistics()
+                + " dry=" + columns.values().stream().filter(Ground::dry).count()
+                + " solid4=" + columns.values().stream().filter(g -> g.solidDepth() >= 4).count()
+                + " protected=" + columns.values().stream().filter(Ground::protectedTerrain).count()
+                + " rejected=" + rejections;
+        }
+        Ground at(int x, int z) {
+            if (Math.hypot((double) x - centerX, (double) z - centerZ) > radius) return INVALID;
+            long key = ((long) x << 32) ^ (z & 0xffffffffL);
+            Ground cached = columns.get(key);
+            if (cached != null) return cached;
+            if (exhausted()) return INVALID;
+            Ground value = java.util.Objects.requireNonNull(sampler.sample(x, z));
+            columns.put(key, value);
+            return value;
+        }
+    }
+}
@@ -0,0 +1,633 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Kind;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Parcel;
+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.storage.loot.BuiltInLootTables;
+import net.minecraft.world.level.storage.loot.LootTable;
+
+/** Original, chunk-independent contemporary ruins. The saved parcel is the complete random input. */
+public final class LostCityRenderer {
+    private static final BlockState AIR = LostCityPalette.AIR;
+    private static final BlockState SMOOTH = LostCityPalette.SMOOTH;
+    private static final BlockState STONE = LostCityPalette.STONE;
+    private static final BlockState WOOD = Blocks.DARK_OAK_PLANKS.defaultBlockState();
+    private static final int FLOOR_HEIGHT = 5;
+
+    /** The structure piece owns world translation, clipping and deferred loot persistence. */
+    public interface BlockWriter {
+        void set(int x, int y, int z, BlockState state);
+        void chest(int x, int y, int z, ResourceKey<LootTable> table, long lootSeed);
+    }
+
+    private LostCityRenderer() {}
+
+    public static void render(Parcel parcel, BlockWriter output) {
+        boolean building = switch (parcel.kind()) {
+            case APARTMENT, HOTEL, LIBRARY, RESTAURANT, BARRACKS, HALL, PARKING,
+                EXCAVATION, POOL, PARK_GARDEN, PARK_PLAYGROUND, PARK_MEMORIAL -> true;
+            default -> false;
+        };
+        BlockWriter writer = building ? rotated(output, parcel) : output;
+        Painter paint = new Painter(parcel, writer);
+        switch (parcel.kind()) {
+            case STREET -> paint.street(false);
+            case BRIDGE -> paint.street(true);
+            case PARK -> paint.park();
+            case PARK_GARDEN -> paint.garden();
+            case PARK_PLAYGROUND -> paint.playground();
+            case PARK_MEMORIAL -> paint.memorial();
+            case PLAZA -> paint.plaza(false);
+            case MARKET -> paint.plaza(true);
+            case PARKING -> paint.parking();
+            case EXCAVATION -> paint.excavation();
+            case POOL -> paint.pool();
+            case APARTMENT, HOTEL, LIBRARY, RESTAURANT, BARRACKS, HALL -> paint.building();
+        }
+    }
+
+    private static BlockWriter rotated(BlockWriter output, Parcel parcel) {
+        if (parcel.facing() == 0) return output;
+        Rotation rotation = switch (parcel.facing()) {
+            case 1 -> Rotation.CLOCKWISE_90;
+            case 2 -> Rotation.CLOCKWISE_180;
+            case 3 -> Rotation.COUNTERCLOCKWISE_90;
+            default -> throw new IllegalArgumentException("Invalid Lost City facing");
+        };
+        return new BlockWriter() {
+            private int x(int x, int z) {
+                return switch (parcel.facing()) {
+                    case 1 -> parcel.width() - 1 - z;
+                    case 2 -> parcel.width() - 1 - x;
+                    default -> z;
+                };
+            }
+
+            private int z(int x, int z) {
+                return switch (parcel.facing()) {
+                    case 1 -> x;
+                    case 2 -> parcel.depth() - 1 - z;
+                    default -> parcel.depth() - 1 - x;
+                };
+            }
+
+            @Override public void set(int x, int y, int z, BlockState state) {
+                output.set(x(x, z), y, z(x, z), state.rotate(rotation));
+            }
+
+            @Override public void chest(int x, int y, int z, ResourceKey<LootTable> table, long lootSeed) {
+                output.chest(x(x, z), y, z(x, z), table, lootSeed);
+            }
+        };
+    }
+
+    private static final class Painter {
+        private final Parcel parcel;
+        private final BlockWriter writer;
+        private final int width;
+        private final int depth;
+        private final int middle;
+
+        Painter(Parcel parcel, BlockWriter writer) {
+            this.parcel = parcel;
+            this.writer = writer;
+            width = parcel.width();
+            depth = parcel.depth();
+            middle = width / 2;
+        }
+
+        private void set(int x, int y, int z, BlockState state) {
+            writer.set(x, y, z, state);
+        }
+
+        private void set(int x, int y, int z, Block block) {
+            set(x, y, z, block.defaultBlockState());
+        }
+
+        private void box(int x0, int y0, int z0, int x1, int y1, int z1, BlockState state) {
+            for (int z = z0; z <= z1; z++) {
+                for (int x = x0; x <= x1; x++) {
+                    for (int y = y0; y <= y1; y++) set(x, y, z, state);
+                }
+            }
+        }
+
+        private int roll(int x, int y, int z, int bound) {
+            return LostCityPalette.roll(parcel.seed(), x, y, z, bound);
+        }
+
+        private BlockState brick(int x, int y, int z) {
+            return LostCityPalette.masonry(parcel.seed(), x, y, z);
+        }
+
+        private void foundation() {
+            box(0, -parcel.foundationDepth(), 0, width - 1, -1, depth - 1, STONE);
+            box(0, 0, 0, width - 1, 0, depth - 1, SMOOTH);
+        }
+
+        private void street(boolean bridge) {
+            boolean eastWest = width > depth;
+            int length = eastWest ? width : depth;
+            int breadth = eastWest ? depth : width;
+            for (int along = 0; along < length; along++) {
+                for (int across = 0; across < breadth; across++) {
+                    int x = eastWest ? along : across;
+                    int z = eastWest ? across : along;
+                    int y = parcel.surfaceY(x, z) - parcel.floorY();
+                    if (!bridge) {
+                        for (int support = 1; support <= parcel.foundationDepth(); support++) set(x, y - support, z, STONE);
+                    }
+                    // Bridge banks are verified by the planner; the deck never grows support pillars.
+                    boolean edge = across == 0 || across == breadth - 1;
+                    set(x, y, z, edge ? SMOOTH : LostCityPalette.pavement(parcel.seed(), x, z));
+                    for (int air = 1; air <= 5; air++) set(x, y + air, z, AIR);
+                    if (bridge && edge) set(x, y + 1, z, bars(eastWest));
+                    if (!edge && along > 0 && along < length - 1 && across == breadth / 2
+                            && Math.floorMod(along, 7) < 3) set(x, y, z, SMOOTH);
+                }
+            }
+        }
+
+        private void building() {
+            foundation();
+            int floors = parcel.floors();
+            int roof = floors * FLOOR_HEIGHT;
+            box(0, 1, 0, width - 1, roof + 2, depth - 1, AIR);
+            for (int y = 1; y <= roof; y++) {
+                for (int z = 0; z < depth; z++) {
+                    for (int x = 0; x < width; x++) {
+                        boolean wall = x == 0 || x == width - 1 || z == 0 || z == depth - 1;
+                        boolean slab = y % FLOOR_HEIGHT == 0;
+                        boolean hallVoid = parcel.kind() == Kind.HALL && y < roof
+                            && x > 3 && x < width - 4 && z > 3 && z < depth - 4;
+                        if (slab && !hallVoid) {
+                            set(x, y, z, wall || y == roof ? SMOOTH : WOOD);
+                        } else if (wall) {
+                            boolean pillar = x % 4 == 0 && (z == 0 || z == depth - 1)
+                                || z % 4 == 0 && (x == 0 || x == width - 1);
+                            boolean window = !pillar && (y % FLOOR_HEIGHT == 2 || y % FLOOR_HEIGHT == 3);
+                            if (pillar) set(x, y, z, STONE);
+                            else if (window) {
+                                if (roll(x, y / 5, z, 7) != 0) set(x, y, z, panes(z == 0 || z == depth - 1));
+                            } else if (!damagedCorner(x, y, z, roof)) set(x, y, z, brick(x, y, z));
+                        }
+                    }
+                }
+            }
+            // Low parapets and rooftop ventilation distinguish flat-roofed modern buildings.
+            for (int x = 0; x < width; x++) {
+                if (!damagedCorner(x, roof, 0, roof)) set(x, roof + 1, 0, brick(x, roof, 0));
+                if (!damagedCorner(x, roof, depth - 1, roof)) set(x, roof + 1, depth - 1, brick(x, roof, depth - 1));
+            }
+            for (int z = 1; z < depth - 1; z++) {
+                set(0, roof + 1, z, brick(0, roof, z));
+                if (!damagedCorner(width - 1, roof, z, roof)) set(width - 1, roof + 1, z, brick(width - 1, roof, z));
+            }
+            box(width - 5, roof + 1, depth - 5, width - 3, roof + 1, depth - 3, SMOOTH);
+            set(width - 4, roof + 2, depth - 4, Blocks.IRON_TRAPDOOR);
+            for (int floor = 0; floor < floors; floor++) furnish(floor);
+            staircase(floors);
+            // Doorway, central lobby and stair approach are always restored after furnishings.
+            box(middle - 1, 1, 0, middle + 1, 3, 3, AIR);
+            box(1, 1, 1, middle + 1, 3, 1, AIR);
+            box(middle - 2, 4, 0, middle + 2, 4, 1, SMOOTH);
+            for (int y = 1; y <= 3; y++) {
+                set(middle - 2, y, 0, SMOOTH);
+                set(middle + 2, y, 0, SMOOTH);
+            }
+            for (int floor = 0; floor < floors; floor++) {
+                int y = floor * FLOOR_HEIGHT;
+                if (floor > 0 && parcel.kind() != Kind.HALL) {
+                    box(middle - 1, y + 1, 1, middle + 1, y + 3, depth - 2, AIR);
+                }
+                set(width - 2, y + 4, depth - 2, Blocks.COBWEB);
+            }
+            // A small breach on the far corner leaves stairs, doors and all floor plates intact.
+            if (roll(18, 0, 29, 3) == 0) {
+                box(width - 3, roof, depth - 3, width - 2, roof, depth - 2, AIR);
+                box(width - 2, roof - 3, depth - 2, width - 2, roof - 3, depth - 2, brick(width - 2, 0, depth - 2));
+            }
+        }
+
+        private boolean damagedCorner(int x, int y, int z, int roof) {
+            return x >= width - 4 && z >= depth - 4 && y > roof - 4
+                && roll(x / 2, y / 2, z / 2, 4) != 0;
+        }
+
+        private void staircase(int floors) {
+            for (int floor = 0; floor < floors; floor++) {
+                int base = floor * FLOOR_HEIGHT;
+                for (int step = 1; step <= FLOOR_HEIGHT; step++) {
+                    int z = step + 1;
+                    box(1, base + step, z, 2, base + step + 3, z, AIR);
+                    for (int x = 1; x <= 2; x++) set(x, base + step, z, stairs(Direction.SOUTH));
+                }
+                box(1, base + FLOOR_HEIGHT, 7, 3, base + FLOOR_HEIGHT, 8, WOOD);
+                box(1, base + FLOOR_HEIGHT + 1, 7, parcel.kind() == Kind.HALL ? 2 : 3,
+                    base + FLOOR_HEIGHT + 3, 8, AIR);
+                // West stairwell is accessible from every floor through the rear landing.
+                if (parcel.kind() != Kind.HALL || floor == 0) {
+                    box(3, base + 1, 7, middle - 1, base + 3, 8, AIR);
+                }
+            }
+        }
+
+        private void furnish(int floor) {
+            int y = floor * FLOOR_HEIGHT;
+            switch (parcel.kind()) {
+                case LIBRARY -> library(y);
+                case RESTAURANT -> restaurant(y, floor == 0);
+                case HOTEL -> hotel(y, floor == 0);
+                case BARRACKS -> barracks(y);
+                case HALL -> hall(y, floor == 0);
+                case APARTMENT -> apartment(y);
+                default -> throw new IllegalStateException("Not a building: " + parcel.kind());
+            }
+        }
+
+        private void library(int y) {
+            // Large wall shelves, reading tables and stacks with walkable aisles.
+            box(width - 2, y + 1, 2, width - 2, y + 3, depth - 3, Blocks.BOOKSHELF.defaultBlockState());
+            box(4, y + 1, depth - 2, width - 3, y + 3, depth - 2, Blocks.BOOKSHELF.defaultBlockState());
+            for (int z = 4; z < depth - 3; z += 5) {
+                box(4, y + 1, z, 5, y + 2, z, Blocks.BOOKSHELF.defaultBlockState());
+                table(width - 6, y + 1, z);
+            }
+            set(middle + 3, y + 1, 2, facing(Blocks.LECTERN, Direction.NORTH));
+            if (y == 0) loot(width - 3, 1, depth - 3, BuiltInLootTables.VILLAGE_CARTOGRAPHER);
+        }
+
+        private void restaurant(int y, boolean kitchen) {
+            if (kitchen) {
+                for (int x = 4; x < width - 2; x++) set(x, y + 1, depth - 3, SMOOTH);
+                set(4, y + 1, depth - 2, facing(Blocks.FURNACE, Direction.NORTH));
+                set(5, y + 1, depth - 2, facing(Blocks.SMOKER, Direction.NORTH));
+                set(6, y + 1, depth - 2, Blocks.CAULDRON);
+                set(width - 3, y + 1, depth - 2, Blocks.BARREL);
+                box(4, y + 3, depth - 2, 6, y + 3, depth - 2, SMOOTH);
+                loot(width - 4, y + 1, depth - 2, BuiltInLootTables.VILLAGE_BUTCHER);
+            }
+            for (int z = 4; z < depth - 5; z += 4) {
+                table(middle + 4, y + 1, z);
+                if (z > 7) table(4, y + 1, z);
+            }
+            if (!kitchen) {
+                box(4, y + 1, depth - 3, width - 3, y + 1, depth - 3, WOOD);
+                set(width - 3, y + 2, depth - 3, Blocks.FLOWER_POT);
+            }
+        }
+
+        private void hotel(int y, boolean reception) {
+            if (reception) {
+                box(middle + 3, y + 1, 3, width - 3, y + 1, 3, WOOD);
+                set(width - 3, y + 2, 3, Blocks.POTTED_DEAD_BUSH);
+                table(middle + 4, y + 1, 8);
+                loot(width - 3, y + 1, 2, BuiltInLootTables.VILLAGE_PLAINS_HOUSE);
+                bedroom(width - 5, y, depth - 6);
+                return;
+            }
+            // A central corridor, actual room partitions and doors into the bedrooms.
+            for (int x : new int[] { middle - 2, middle + 2 }) {
+                box(x, y + 1, 2, x, y + 4, depth - 2, WOOD);
+                box(x, y + 1, 4, x, y + 2, 5, AIR);
+                box(x, y + 1, 10, x, y + 2, 11, AIR);
+            }
+            box(middle + 3, y + 1, 8, width - 2, y + 4, 8, WOOD);
+            bedroom(width - 5, y, 3);
+            bedroom(width - 5, y, 10);
+            bedroom(3, y, 10);
+        }
+
+        private void apartment(int y) {
+            bedroom(width - 5, y, depth - 6);
+            box(middle + 2, y + 1, depth - 8, width - 2, y + 3, depth - 8, WOOD);
+            box(middle + 2, y + 1, depth - 7, middle + 2, y + 2, depth - 5, AIR);
+            table(middle + 4, y + 1, 4);
+            set(width - 3, y + 1, 2, facing(Blocks.FURNACE, Direction.SOUTH));
+            set(width - 4, y + 1, 2, SMOOTH);
+            set(width - 5, y + 1, 2, Blocks.CAULDRON);
+            box(4, y + 1, depth - 3, 5, y + 1, depth - 3, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+            if (y == 0) loot(width - 3, y + 1, depth - 3, BuiltInLootTables.VILLAGE_PLAINS_HOUSE);
+        }
+
+        private void barracks(int y) {
+            for (int z : new int[] { 3, 8, 12 }) {
+                bedroom(width - 5, y, z);
+                if (z > 8) bedroom(4, y, z);
+            }
+            box(4, y + 1, 2, 5, y + 1, 2, Blocks.BARREL.defaultBlockState());
+            box(4, y + 2, 2, 5, y + 2, 2, bars(true));
+            if (y == 0) loot(width - 3, y + 1, depth - 2, BuiltInLootTables.VILLAGE_FLETCHER);
+        }
+
+        private void hall(int y, boolean groundFloor) {
+            if (!groundFloor) {
+                for (int x = 4; x < width - 4; x++) {
+                    set(x, y + 1, 3, bars(true));
+                    set(x, y + 1, depth - 4, bars(true));
+                }
+                for (int z = 4; z < depth - 4; z++) {
+                    set(3, y + 1, z, bars(false));
+                    set(width - 4, y + 1, z, bars(false));
+                }
+                return;
+            }
+            // Double-height meeting hall: an aisle, rows of seats, a stage and lectern.
+            for (int z = 4; z < depth - 6; z += 3) {
+                for (int x = 4; x <= 5; x++) set(x, y + 1, z, facing(Blocks.DARK_OAK_STAIRS, Direction.SOUTH));
+                for (int x = width - 6; x < width - 3; x++) set(x, y + 1, z, facing(Blocks.DARK_OAK_STAIRS, Direction.SOUTH));
+            }
+            box(4, 1, depth - 5, width - 3, 1, depth - 2, WOOD);
+            set(middle, 2, depth - 3, facing(Blocks.LECTERN, Direction.NORTH));
+            set(middle + 3, 2, depth - 3, Blocks.POTTED_DEAD_BUSH);
+            loot(width - 3, 1, 2, BuiltInLootTables.VILLAGE_CARTOGRAPHER);
+        }
+
+        private void bedroom(int x, int y, int z) {
+            if (z + 1 >= depth - 1) return;
+            BlockState bed = Blocks.BED.white().defaultBlockState()
+                .setValue(BlockStateProperties.HORIZONTAL_FACING, Direction.SOUTH);
+            set(x, y + 1, z, bed.setValue(BlockStateProperties.BED_PART, BedPart.FOOT));
+            set(x, y + 1, z + 1, bed.setValue(BlockStateProperties.BED_PART, BedPart.HEAD));
+            set(x + 1, y + 1, z + 1, Blocks.BARREL);
+        }
+
+        private void table(int x, int y, int z) {
+            set(x, y, z, Blocks.DARK_OAK_FENCE);
+            set(x, y + 1, z, Blocks.DARK_OAK_PRESSURE_PLATE);
+            set(x - 1, y, z, facing(Blocks.DARK_OAK_STAIRS, Direction.EAST));
+            set(x + 1, y, z, facing(Blocks.DARK_OAK_STAIRS, Direction.WEST));
+        }
+
+        private void loot(int x, int y, int z, ResourceKey<LootTable> table) {
+            writer.chest(x, y, z, table, parcel.seed() ^ (x * 0x9e3779b9L) ^ (z * 0xc2b2ae35L));
+        }
+
+        private void park() {
+            parkGround();
+            for (int z : new int[] { 3, depth - 4 }) {
+                for (int x = middle + 3; x <= middle + 5; x++) set(x, 1, z, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+            }
+            tree(3, 3);
+            if (roll(0, 0, 0, 3) != 0) tree(width - 4, depth - 4);
+            set(3, 1, depth - 4, Blocks.COMPOSTER);
+        }
+
+        private void parkGround() {
+            foundation();
+            box(0, 1, 0, width - 1, 8, depth - 1, AIR);
+            for (int z = 0; z < depth; z++) {
+                for (int x = 0; x < width; x++) {
+                    if (Math.abs(x - middle) <= 1 || Math.abs(z - depth / 2) <= 1) {
+                        set(x, 0, z, LostCityPalette.pavement(parcel.seed(), x, z));
+                    } else {
+                        set(x, 0, z, Blocks.GRASS_BLOCK);
+                        if (roll(x, 0, z, 9) == 0) set(x, 1, z, Blocks.SHORT_GRASS);
+                    }
+                }
+            }
+        }
+
+        private void garden() {
+            parkGround();
+            BlockState hedge = Blocks.OAK_LEAVES.defaultBlockState().setValue(BlockStateProperties.PERSISTENT, true);
+            for (int z0 : new int[] { 2, depth - 7 }) {
+                for (int x0 : new int[] { 2, width - 7 }) {
+                    for (int z = z0; z <= z0 + 4; z++) {
+                        for (int x = x0; x <= x0 + 4; x++) {
+                            boolean edge = x == x0 || z == z0 || x == x0 + 4 || z == z0 + 4;
+                            set(x, 1, z, edge ? hedge : (roll(x, 0, z, 2) == 0 ? Blocks.POPPY : Blocks.OXEYE_DAISY).defaultBlockState());
+                        }
+                    }
+                }
+            }
+            for (int x = middle - 1; x <= middle + 1; x++) set(x, 1, depth - 2, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+            set(1, 1, depth - 2, Blocks.COMPOSTER);
+        }
+
+        private void playground() {
+            parkGround();
+            box(2, 0, 2, 6, 0, 6, Blocks.SAND.defaultBlockState());
+            box(2, 1, 2, 6, 5, 6, AIR);
+            // An abandoned swing frame, with a suspended wooden seat.
+            box(2, 1, 4, 2, 4, 4, Blocks.DARK_OAK_FENCE.defaultBlockState());
+            box(6, 1, 4, 6, 4, 4, Blocks.DARK_OAK_FENCE.defaultBlockState());
+            box(2, 5, 4, 6, 5, 4, WOOD);
+            box(4, 3, 4, 4, 4, 4, Blocks.IRON_CHAIN.defaultBlockState());
+            set(4, 2, 4, Blocks.DARK_OAK_SLAB);
+            // A small timber climbing platform and a stone slide, accessible by steps.
+            box(width - 6, 3, depth - 6, width - 4, 3, depth - 4, WOOD);
+            box(width - 6, 1, depth - 4, width - 6, 2, depth - 4, WOOD);
+            box(width - 4, 1, depth - 4, width - 4, 2, depth - 4, WOOD);
+            for (int step = 0; step < 3; step++) {
+                set(width - 5, step, depth - 9 + step, stairs(Direction.SOUTH));
+                box(width - 5, step + 1, depth - 9 + step, width - 5, step + 3, depth - 9 + step, AIR);
+            }
+            for (int x = 3; x <= 5; x++) set(x, 1, depth - 4, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+        }
+
+        private void memorial() {
+            plaza(false);
+            box(middle - 2, 1, depth / 2 - 2, middle + 2, 3, depth / 2 + 2, AIR);
+            box(middle - 1, 1, depth / 2 - 1, middle + 1, 1, depth / 2 + 1, SMOOTH);
+            set(middle, 2, depth / 2, Blocks.STONE_BRICKS);
+            set(middle, 3, depth / 2, Blocks.CHISELED_STONE_BRICKS);
+            set(middle, 4, depth / 2, Blocks.CHISELED_STONE_BRICKS);
+            set(middle, 5, depth / 2, Blocks.STONE_BRICK_SLAB);
+            for (int x : new int[] { middle - 3, middle + 3 }) {
+                set(x, 0, depth / 2, Blocks.GRASS_BLOCK);
+                set(x, 1, depth / 2, Blocks.OXEYE_DAISY);
+            }
+        }
+
+        private void excavation() {
+            if (parcel.foundationDepth() < 8) { park(); return; }
+            foundation();
+            box(0, 1, 0, width - 1, 7, depth - 1, AIR);
+            box(3, -4, 3, width - 4, 0, depth - 4, AIR);
+            for (int z = 3; z <= depth - 4; z++) {
+                for (int x = 3; x <= width - 4; x++) set(x, -5, z,
+                    roll(x / 2, 0, z / 2, 4) == 0 ? Blocks.GRAVEL.defaultBlockState() : STONE);
+            }
+            // Intact temporary barriers surround the pit; only the street-facing stair gate is open.
+            for (int x = 2; x < width - 2; x++) {
+                if (Math.abs(x - middle) > 1) set(x, 1, 2, bars(true));
+                set(x, 1, depth - 3, bars(true));
+            }
+            for (int z = 3; z < depth - 3; z++) {
+                set(2, 1, z, bars(false));
+                set(width - 3, 1, z, bars(false));
+            }
+            for (int step = 1; step <= 5; step++) {
+                for (int x = middle - 1; x <= middle + 1; x++) {
+                    box(x, -step + 1, step + 2, x, 2, step + 2, AIR);
+                    set(x, -step, step + 2, stairs(Direction.NORTH));
+                }
+            }
+            // Unfinished footings and construction supplies remain outside the stair route.
+            box(4, -4, depth - 6, 5, -3, depth - 5, SMOOTH);
+            box(width - 6, -4, depth - 6, width - 5, -2, depth - 5, brick(11, 0, 11));
+            set(1, 1, depth - 3, Blocks.BARREL);
+            set(1, 1, depth - 4, Blocks.CRAFTING_TABLE);
+        }
+
+        private void pool() {
+            if (parcel.foundationDepth() < 8) { park(); return; }
+            foundation();
+            box(0, 1, 0, width - 1, 7, depth - 1, AIR);
+            // Continuous floor and walls seal three layers of water. Weathering is above the waterline.
+            box(3, -4, 4, width - 4, 0, depth - 4, SMOOTH);
+            box(4, -3, 5, width - 5, -1, depth - 5, Blocks.WATER.defaultBlockState());
+            for (int z = 5; z < depth - 4; z++) {
+                for (int x = 4; x < width - 4; x++) {
+                    set(x, 0, z, AIR);
+                    if (roll(x, 0, z, 13) == 0) set(x, -4, z, Blocks.MOSS_BLOCK);
+                }
+            }
+            // Broad submerged steps connect the deck to the bottom without ladders or a jump trap.
+            for (int step = 1; step <= 3; step++) {
+                for (int x = middle - 1; x <= middle + 1; x++) {
+                    set(x, -step, step + 4, stairs(Direction.NORTH)
+                        .setValue(BlockStateProperties.WATERLOGGED, true));
+                    for (int y = -step + 1; y <= 0; y++) set(x, y, step + 4, AIR);
+                }
+            }
+            for (int z = 5; z < depth - 5; z += 4) {
+                set(1, 1, z, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+                set(1, 1, z + 1, Blocks.DARK_OAK_SLAB);
+                set(width - 2, 1, z, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+            }
+            set(width - 3, 1, 2, Blocks.CAULDRON);
+            set(width - 4, 1, 2, Blocks.BARREL);
+        }
+
+        private void tree(int x, int z) {
+            box(x, 1, z, x, 5, z, Blocks.OAK_LOG.defaultBlockState());
+            for (int y = 4; y <= 7; y++) {
+                int radius = y == 7 ? 1 : 2;
+                for (int dz = -radius; dz <= radius; dz++) {
+                    for (int dx = -radius; dx <= radius; dx++) {
+                        if (dx == 0 && dz == 0 && y <= 5) continue;
+                        if (Math.abs(dx) + Math.abs(dz) > radius + 1) continue;
+                        set(x + dx, y, z + dz, Blocks.OAK_LEAVES.defaultBlockState()
+                            .setValue(BlockStateProperties.PERSISTENT, true));
+                    }
+                }
+            }
+        }
+
+        private void plaza(boolean market) {
+            foundation();
+            box(0, 1, 0, width - 1, 7, depth - 1, AIR);
+            for (int z = 0; z < depth; z++) {
+                for (int x = 0; x < width; x++) set(x, 0, z,
+                    x % 4 == 0 || z % 4 == 0 ? SMOOTH : brick(x, 0, z));
+            }
+            if (market) {
+                stall(2, 2);
+                stall(width - 6, 2);
+                stall(2, depth - 6);
+                stall(width - 6, depth - 6);
+                loot(width - 4, 1, depth - 4, BuiltInLootTables.VILLAGE_PLAINS_HOUSE);
+            } else {
+                // A dry fountain avoids adding uncontrolled water to the hydrology.
+                for (int z = depth / 2 - 2; z <= depth / 2 + 2; z++) {
+                    for (int x = middle - 2; x <= middle + 2; x++) {
+                        set(x, 1, z, Math.abs(x - middle) == 2 || Math.abs(z - depth / 2) == 2 ? SMOOTH : AIR);
+                    }
+                }
+                set(middle, 1, depth / 2, Blocks.CHISELED_STONE_BRICKS);
+                set(middle, 2, depth / 2, Blocks.STONE_BRICK_WALL);
+                for (int x = 3; x <= 5; x++) {
+                    set(x, 1, 3, facing(Blocks.DARK_OAK_STAIRS, Direction.SOUTH));
+                    set(width - 1 - x, 1, depth - 4, facing(Blocks.DARK_OAK_STAIRS, Direction.NORTH));
+                }
+            }
+        }
+
+        private void stall(int x, int z) {
+            box(x, 1, z + 2, x + 3, 1, z + 2, WOOD);
+            for (int dx : new int[] { 0, 3 }) {
+                box(x + dx, 1, z, x + dx, 3, z, Blocks.DARK_OAK_FENCE.defaultBlockState());
+            }
+            for (int dx = 0; dx <= 3; dx++) {
+                for (int dz = 0; dz <= 2; dz++) {
+                    if (roll(x + dx, 4, z + dz, 8) != 0) set(x + dx, 4, z + dz,
+                        (dx & 1) == 0 ? Blocks.WOOL.lightGray() : Blocks.WOOL.green());
+                }
+            }
+            set(x + 1, 1, z, Blocks.BARREL);
+            set(x + 2, 2, z + 2, Blocks.FLOWER_POT);
+        }
+
+        private void parking() {
+            foundation();
+            // Depth >=8 is the planner's certificate of continuous rock under the whole garage.
+            boolean underground = parcel.foundationDepth() >= 8;
+            int base = underground ? -5 : 0;
+            box(0, base + 1, 0, width - 1, 6, depth - 1, AIR);
+            box(0, base, 0, width - 1, base, depth - 1, SMOOTH);
+            box(0, base + 5, 0, width - 1, base + 5, depth - 1, SMOOTH);
+            for (int z = 0; z < depth; z++) {
+                for (int x = 0; x < width; x++) {
+                    if (x == 0 || x == width - 1 || z == depth - 1) {
+                        for (int y = base + 1; y < base + 5; y++) {
+                            if (underground || y == base + 1 || x % 4 == 0 || z % 4 == 0) set(x, y, z, brick(x, y, z));
+                        }
+                    }
+                    if (Math.abs(x - middle) <= 2) set(x, base, z, STONE);
+                    else if (z % 4 == 0) set(x, base, z, Blocks.CALCITE);
+                }
+            }
+            for (int x : new int[] { 3, width - 4 }) {
+                for (int z : new int[] { 3, depth - 4 }) box(x, base + 1, z, x, base + 4, z, STONE);
+            }
+            box(0, base + 1, 0, middle - 3, base + 4, 0, SMOOTH);
+            box(middle + 3, base + 1, 0, width - 1, base + 4, 0, SMOOTH);
+            if (underground) {
+                for (int z = 0; z <= 5; z++) {
+                    int y = -z;
+                    box(middle - 2, y + 1, z, middle + 2, 3, z, AIR);
+                    for (int x = middle - 2; x <= middle + 2; x++) {
+                        set(x, y, z, z == 0 ? SMOOTH : stairs(Direction.NORTH));
+                    }
+                }
+            } else {
+                box(middle - 2, 1, 0, middle + 2, 3, 1, AIR);
+            }
+            set(width - 3, base + 1, depth - 3, Blocks.BARREL);
+            loot(width - 3, base + 1, depth - 2, BuiltInLootTables.VILLAGE_MASON);
+        }
+    }
+
+    private static BlockState facing(Block block, Direction direction) {
+        return block.defaultBlockState().setValue(BlockStateProperties.HORIZONTAL_FACING, direction);
+    }
+
+    private static BlockState stairs(Direction direction) {
+        return facing(Blocks.STONE_BRICK_STAIRS, direction);
+    }
+
+    private static BlockState panes(boolean eastWest) {
+        return Blocks.GLASS_PANE.defaultBlockState()
+            .setValue(BlockStateProperties.EAST, eastWest)
+            .setValue(BlockStateProperties.WEST, eastWest)
+            .setValue(BlockStateProperties.NORTH, !eastWest)
+            .setValue(BlockStateProperties.SOUTH, !eastWest);
+    }
+
+    private static BlockState bars(boolean eastWest) {
+        return Blocks.IRON_BARS.defaultBlockState()
+            .setValue(BlockStateProperties.EAST, eastWest)
+            .setValue(BlockStateProperties.WEST, eastWest)
+            .setValue(BlockStateProperties.NORTH, !eastWest)
+            .setValue(BlockStateProperties.SOUTH, !eastWest);
+    }
+}
@@ -0,0 +1,38 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import com.mojang.serialization.MapCodec;
+import fr.koka.sanctuary.worldgen.SanctuaryChunkGenerator;
+import java.util.Optional;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureType;
+
+/** A small native structure start per district, bounded by vanilla's eight-chunk reference reach. */
+public final class LostCityStructure extends Structure {
+    public static final MapCodec<LostCityStructure> CODEC = simpleCodec(LostCityStructure::new);
+
+    public LostCityStructure(StructureSettings settings) { super(settings); }
+
+    @Override protected Optional<GenerationStub> findGenerationPoint(GenerationContext context) {
+        if (!(context.chunkGenerator() instanceof SanctuaryChunkGenerator generator)
+                || generator.rootGeneration() != 14) return Optional.empty();
+        var island = generator.islandForChunk(context.chunkPos().x(), context.chunkPos().z());
+        if (island == null || island.generation() != 14) return Optional.empty();
+        for (var district : generator.lostCityPlan(island).districts()) {
+            if (district.startChunkX() != context.chunkPos().x() || district.startChunkZ() != context.chunkPos().z()) continue;
+            if (district.parcels().isEmpty()) return Optional.empty();
+            for (var parcel : district.parcels()) {
+                // Never save a start that vanilla cannot reference in every touched chunk.
+                if (Math.abs((parcel.minX() >> 4) - district.startChunkX()) > 8
+                        || Math.abs((parcel.maxX() >> 4) - district.startChunkX()) > 8
+                        || Math.abs((parcel.minZ() >> 4) - district.startChunkZ()) > 8
+                        || Math.abs((parcel.maxZ() >> 4) - district.startChunkZ()) > 8)
+                    throw new IllegalStateException("Lost City district exceeds native structure reference range");
+            }
+            return Optional.of(new GenerationStub(LostCityStructures.locator(district), pieces ->
+                district.parcels().forEach(parcel -> pieces.addPiece(new LostCityPiece(parcel)))));
+        }
+        return Optional.empty();
+    }
+
+    @Override public StructureType<?> type() { return LostCityStructures.TYPE; }
+}
@@ -0,0 +1,108 @@
+package fr.koka.sanctuary.worldgen.city;
+
+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 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;
+
+/** Native starts, pieces, references and deferred loot; only the placement plan is Sanctuary-owned. */
+public final class LostCityStructures {
+    public static final ResourceKey<Structure> KEY = ResourceKey.create(Registries.STRUCTURE, SanctuaryMod.id("lost_city"));
+    public static final StructureType<LostCityStructure> TYPE = Registry.register(
+        BuiltInRegistries.STRUCTURE_TYPE, SanctuaryMod.id("lost_city"), () -> LostCityStructure.CODEC);
+    public static final StructurePieceType PIECE = Registry.register(
+        BuiltInRegistries.STRUCTURE_PIECE, SanctuaryMod.id("lost_city_parcel"), LostCityPiece::new);
+    private static final ThreadLocal<Integer> PLACEMENT_DEPTH = ThreadLocal.withInitial(() -> 0);
+
+    private LostCityStructures() {}
+
+    public static void register() { /* Load static serializers before dynamic registries. */ }
+    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 (!manager.shouldGenerateStructures() || !(generator instanceof SanctuaryChunkGenerator sanctuary)
+                || generator.rootGeneration() != 14) return;
+        var island = generator.islandForChunk(chunk.getPos().x(), chunk.getPos().z());
+        if (island == null || island.generation() != 14) return;
+        var plan = sanctuary.lostCityPlan(island);
+        if (plan.districts().stream().noneMatch(d -> d.startChunkX() == chunk.getPos().x()
+                && d.startChunkZ() == 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());
+        StructureStart 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);
+    }
+
+    /** Search only activated, ready islands. Native starts are loaded at STRUCTURE_STARTS, never regenerated. */
+    public static Pair<BlockPos, Holder<Structure>> findNearest(ServerLevel level, HolderSet<Structure> structures,
+            BlockPos origin, int radius, boolean skipReferenced) {
+        if (!(level.getChunkSource().getGenerator() instanceof SanctuaryChunkGenerator generator)
+                || generator.rootGeneration() != 14 || !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<LostCityPlan.District>();
+        int originChunkX = origin.getX() >> 4, originChunkZ = origin.getZ() >> 4;
+        for (var island : generator.source().islands()) {
+            if (island.generation() != 14 || !island.status().equals("ready")) continue;
+            for (var district : generator.lostCityPlan(island).districts()) {
+                if (Math.abs((long) district.startChunkX() - originChunkX) <= radius
+                        && Math.abs((long) district.startChunkZ() - originChunkZ) <= radius) candidates.add(district);
+            }
+        }
+        candidates.sort(Comparator.comparingDouble(d -> origin.distSqr(locator(d))));
+        for (var district : candidates) {
+            var chunk = level.getChunk(district.startChunkX(), district.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);
+            return Pair.of(start.getPieces().getFirst().getLocatorPosition(), holder);
+        }
+        return null;
+    }
+
+    static BlockPos locator(LostCityPlan.District district) {
+        var parcel = district.parcels().getFirst();
+        int x = parcel.width() / 2, z = parcel.depth() / 2;
+        return new BlockPos(parcel.minX() + x, parcel.surfaceY(x, z) + 1, parcel.minZ() + z);
+    }
+}
@@ -1,5 +1,6 @@
 {
-  "generator.sanctuary.sanctuary": "Sanctuary (Large)",
+  "generator.sanctuary.sanctuary": "Sanctuary",
+  "generator.sanctuary.sanctuary_10": "Sanctuary (Large — legacy)",
  "biome.sanctuary.starter_forest": "Sanctuary Forest",
  "biome.sanctuary.starter_forest_hydrology": "Sanctuary Forest and Shores",
  "biome.sanctuary.temperate_forest": "Sanctuary Temperate Forest",
@@ -51,8 +52,8 @@
  "biome.sanctuary.population_lush_caves": "Sanctuary Lush Caves",
  "biome.sanctuary.population_dripstone_caves": "Sanctuary Dripstone Caves",
  "generator.sanctuary.sanctuary_20": "Sanctuary (20 players — legacy size)",
-  "generator.sanctuary.expansion_lab": "Sanctuary — Laboratory",
-  "sanctuary.expansion.help": "Laboratory — /sanctuary expansion quick <direction> [climate] [diameter] [relief] [distance]; create or preview <id> <parent> <direction> <climate> <diameter> <relief> [distance]; list; visit <id>; resume <id>. Diameters: 64, 128, 256, 512. Minimum centre-to-centre distance in blocks (0 = automatic, maximum 100000). Fill in preceding arguments to specify distance. Example: quick north autumn 128 peaks 2048. Creation searches farther if needed, up to 32 locations and 30 seconds.",
+  "generator.sanctuary.expansion_lab": "Sanctuary (legacy laboratory)",
+  "sanctuary.expansion.help": "/sanctuary expansion quick <direction> [climate] [diameter] [relief] [distance]; create or preview <id> <parent> <direction> <climate> <diameter> <relief> [distance]; list; visit <id>; resume <id>. Diameters: 64, 128, 256, 512. Minimum centre-to-centre distance in blocks (0 = automatic, maximum 100000). Fill in preceding arguments to specify distance. Example: quick north autumn 128 peaks 2048. Creation searches farther if needed, up to 32 locations and 30 seconds.",
  "sanctuary.expansion.entry": "%s ← %s · %s · %s · Ø%s · %s · X%s Z%s · %s",
  "sanctuary.expansion.progress": "Preparation: %s",
  "sanctuary.expansion.state.ready": "Ready",
@@ -63,13 +64,13 @@
  "sanctuary.expansion.visited": "Arrived on %s.",
  "sanctuary.expansion.resumed": "Resume requested for %s.",
  "sanctuary.expansion.error": "Expansion refused: %s",
-  "sanctuary.expansion.error.laboratory_required": "Create a new Sanctuary — Laboratory world. Existing worlds are not converted.",
+  "sanctuary.expansion.error.laboratory_required": "Create a new Sanctuary world. Older generators are not converted.",
  "sanctuary.expansion.error.unknown_island": "Unknown island.",
  "sanctuary.expansion.error.reserved_id": "Reserved identifier.",
  "sanctuary.expansion.error.invalid_direction": "Unknown direction.",
  "sanctuary.expansion.error.no_space": "No available location in this direction.",
  "sanctuary.expansion.error.id_conflict": "This identifier already belongs to a different island.",
-  "sanctuary.expansion.error.island_limit": "Laboratory limit: 64 islands including the origin.",
+  "sanctuary.expansion.error.island_limit": "Limit: 64 islands including the origin.",
  "sanctuary.expansion.error.no_ground": "No ground found in the proposed terrain. Choose another identifier or profile.",
  "sanctuary.expansion.error.not_ready": "This island must finish preparing first.",
  "sanctuary.expansion.error.no_landing": "No safe landing found.",
@@ -105,9 +106,23 @@
  "sanctuary.expansion.error.journal_unavailable": "The expansion journal is unavailable. Preparation has stopped; fix storage and reload the world before resuming.",
  "sanctuary.expansion.error.invalid_id": "An identifier must start with a lowercase letter and contain at most 32 lowercase letters, digits or underscores.",
  "sanctuary.expansion.error.invalid_climate": "Unknown climate. Use autocomplete to choose a profile.",
-  "sanctuary.expansion.error.invalid_diameter": "Allowed diameters are 64, 128, 256 and 512 blocks.",
+  "sanctuary.expansion.error.invalid_diameter": "Supported diameters are 64, 128, 256, 512 and 1024 blocks (1024 requires generation 14).",
  "sanctuary.expansion.error.invalid_relief": "Unknown relief: natural, peaks, canyon or volcano.",
  "sanctuary.expansion.error.invalid_distance": "Distance must be between 0 and 100000 blocks. 0 uses automatic placement.",
  "sanctuary.expansion.error.no_free_space": "No free location found within the search limits. Try a greater distance or a different parent. No existing terrain was changed.",
-  "sanctuary.expansion.error.search_timeout": "The search reached its 30-second limit. Try a greater distance. No existing terrain was changed."
+  "sanctuary.expansion.error.search_timeout": "The search reached its 30-second limit. Try a greater distance. No existing terrain was changed.",
+  "sanctuary.world_options.title": "Sanctuary Island",
+  "sanctuary.world_options.description": "A floating island, its rivers and caverns, then continents to discover.",
+  "sanctuary.world_options.size": "Island size",
+  "sanctuary.world_options.size.small": "Small",
+  "sanctuary.world_options.size.medium": "Medium",
+  "sanctuary.world_options.size.large": "Large",
+  "sanctuary.world_options.diameter": "Nominal diameter: %s blocks. The terrain and seed shape the outline.",
+  "biome.sanctuary.lost_city": "Lost City",
+  "structure.sanctuary.lost_city": "Ruined district",
+  "sanctuary.expansion.climate.lost_city": "Lost City",
+  "sanctuary.expansion.error.city_generation_required": "This profile or size requires a new Sanctuary alpha.14 world. This save keeps its original generation.",
+  "sanctuary.expansion.reuse_reload": "Expansion %s reserved in previously generated void. Close and reopen the world to begin preparation.",
+  "sanctuary.expansion.error.reload_required": "This expansion is waiting for the world to reopen before reusing verified void chunks.",
+  "sanctuary.expansion.error.void_reuse_incomplete": "Void reuse is incomplete. The reservation is retained; check the server log."
 }
@@ -1,5 +1,6 @@
 {
-  "generator.sanctuary.sanctuary": "Sanctuary (Grand)",
+  "generator.sanctuary.sanctuary": "Sanctuary",
+  "generator.sanctuary.sanctuary_10": "Sanctuary (Grand — ancien format)",
  "biome.sanctuary.starter_forest": "Forêt de Sanctuary",
  "biome.sanctuary.starter_forest_hydrology": "Forêt et rives de Sanctuary",
  "biome.sanctuary.temperate_forest": "Forêt tempérée de Sanctuary",
@@ -51,8 +52,8 @@
  "biome.sanctuary.population_lush_caves": "Grottes luxuriantes de Sanctuary",
  "biome.sanctuary.population_dripstone_caves": "Grottes de spéléothèmes de Sanctuary",
  "generator.sanctuary.sanctuary_20": "Sanctuary (20 joueurs — ancien format)",
-  "generator.sanctuary.expansion_lab": "Sanctuary — Laboratoire",
-  "sanctuary.expansion.help": "Laboratoire — /sanctuary expansion quick <direction> [climat] [diamètre] [relief] [distance] ; create ou preview <id> <parent> <direction> <climat> <diamètre> <relief> [distance] ; list ; visit <id> ; resume <id>. Diamètres : 64, 128, 256, 512. Distance minimale entre les centres, en blocs (0 = automatique, maximum 100000). Remplir les arguments précédents pour préciser la distance. Exemple : quick north autumn 128 peaks 2048. La création cherche plus loin si nécessaire, dans la limite de 32 emplacements et 30 secondes.",
+  "generator.sanctuary.expansion_lab": "Sanctuary (ancien laboratoire)",
+  "sanctuary.expansion.help": "/sanctuary expansion quick <direction> [climat] [diamètre] [relief] [distance] ; create ou preview <id> <parent> <direction> <climat> <diamètre> <relief> [distance] ; list ; visit <id> ; resume <id>. Diamètres : 64, 128, 256, 512. Distance minimale entre les centres, en blocs (0 = automatique, maximum 100000). Remplir les arguments précédents pour préciser la distance. Exemple : quick north autumn 128 peaks 2048. La création cherche plus loin si nécessaire, dans la limite de 32 emplacements et 30 secondes.",
  "sanctuary.expansion.entry": "%s ← %s · %s · %s · Ø%s · %s · X%s Z%s · %s",
  "sanctuary.expansion.progress": "Préparation : %s",
  "sanctuary.expansion.state.ready": "Prêt",
@@ -63,13 +64,13 @@
  "sanctuary.expansion.visited": "Arrivée sur %s.",
  "sanctuary.expansion.resumed": "Reprise demandée pour %s.",
  "sanctuary.expansion.error": "Expansion refusée : %s",
-  "sanctuary.expansion.error.laboratory_required": "Créer un nouveau monde Sanctuary — Laboratoire. Les anciennes parties ne sont pas converties.",
+  "sanctuary.expansion.error.laboratory_required": "Créez un nouveau monde Sanctuary. Les anciennes générations ne sont pas converties.",
  "sanctuary.expansion.error.unknown_island": "Île inconnue.",
  "sanctuary.expansion.error.reserved_id": "Identifiant réservé.",
  "sanctuary.expansion.error.invalid_direction": "Direction inconnue.",
  "sanctuary.expansion.error.no_space": "Aucun emplacement libre dans cette direction.",
  "sanctuary.expansion.error.id_conflict": "Cet identifiant désigne déjà une autre île.",
-  "sanctuary.expansion.error.island_limit": "Limite du laboratoire : 64 îles, origine comprise.",
+  "sanctuary.expansion.error.island_limit": "Limite : 64 îles, origine comprise.",
  "sanctuary.expansion.error.no_ground": "Aucun sol trouvé dans le terrain proposé. Choisir un autre identifiant ou profil.",
  "sanctuary.expansion.error.not_ready": "La préparation de cette île doit être terminée.",
  "sanctuary.expansion.error.no_landing": "Aucun point d’arrivée sûr trouvé.",
@@ -105,9 +106,23 @@
  "sanctuary.expansion.error.journal_unavailable": "Le journal d’expansion est indisponible. La préparation est arrêtée ; corrigez le stockage puis rechargez le monde avant de reprendre.",
  "sanctuary.expansion.error.invalid_id": "L’identifiant doit commencer par une lettre minuscule et contenir au plus 32 lettres minuscules, chiffres ou tirets bas.",
  "sanctuary.expansion.error.invalid_climate": "Climat inconnu. Utiliser l’autocomplétion pour choisir un profil.",
-  "sanctuary.expansion.error.invalid_diameter": "Les diamètres autorisés sont 64, 128, 256 et 512 blocs.",
+  "sanctuary.expansion.error.invalid_diameter": "Les diamètres autorisés sont 64, 128, 256, 512 et 1024 blocs (1024 à partir de la génération 14).",
  "sanctuary.expansion.error.invalid_relief": "Relief inconnu : natural, peaks, canyon ou volcano.",
  "sanctuary.expansion.error.invalid_distance": "La distance doit être comprise entre 0 et 100000 blocs. 0 utilise le placement automatique.",
  "sanctuary.expansion.error.no_free_space": "Aucun emplacement libre trouvé dans les limites de recherche. Réessayer avec une distance plus grande ou un autre parent. Aucun terrain existant n’a été modifié.",
-  "sanctuary.expansion.error.search_timeout": "La recherche a atteint sa limite de 30 secondes. Réessayer avec une distance plus grande. Aucun terrain existant n’a été modifié."
+  "sanctuary.expansion.error.search_timeout": "La recherche a atteint sa limite de 30 secondes. Réessayer avec une distance plus grande. Aucun terrain existant n’a été modifié.",
+  "sanctuary.world_options.title": "Sanctuary Island",
+  "sanctuary.world_options.description": "Une île flottante, ses rivières et ses cavités, puis des continents à découvrir.",
+  "sanctuary.world_options.size": "Taille de l’île",
+  "sanctuary.world_options.size.small": "Petit",
+  "sanctuary.world_options.size.medium": "Moyen",
+  "sanctuary.world_options.size.large": "Grand",
+  "sanctuary.world_options.diameter": "Diamètre nominal : %s blocs. Le relief et la graine dessinent le contour.",
+  "biome.sanctuary.lost_city": "Lost City",
+  "structure.sanctuary.lost_city": "Quartier en ruine",
+  "sanctuary.expansion.climate.lost_city": "Lost City",
+  "sanctuary.expansion.error.city_generation_required": "Ce profil ou cette taille demande un nouveau monde Sanctuary alpha.14. Cette sauvegarde conserve sa génération.",
+  "sanctuary.expansion.reuse_reload": "Expansion %s réservée dans du vide déjà généré. Fermez puis rouvrez le monde pour démarrer sa préparation.",
+  "sanctuary.expansion.error.reload_required": "Cette expansion attend la réouverture du monde pour réutiliser les chunks de vide vérifiés.",
+  "sanctuary.expansion.error.void_reuse_incomplete": "La réutilisation du vide est incomplète. La réservation est conservée ; consultez le journal du serveur."
 }
@@ -1,8 +1,6 @@
 {
  "replace": false,
  "values": [
-    "sanctuary:sanctuary",
-    "sanctuary:sanctuary_5",
-    "sanctuary:expansion_lab"
+    "sanctuary:sanctuary"
  ]
 }
@@ -0,0 +1,84 @@
+{
+  "attributes": {
+    "minecraft:audio/background_music": {
+      "default": {
+        "max_delay": 24000,
+        "min_delay": 12000,
+        "sound": "minecraft:music.overworld.meadow"
+      }
+    },
+    "minecraft:gameplay/natural_mob_spawns": {
+      "argument": {
+        "spawn_costs": {},
+        "spawns_by_category": {
+          "monster": [
+            {
+              "type": "minecraft:zombie",
+              "weight": 100,
+              "count": {
+                "type": "minecraft:uniform",
+                "min_inclusive": 2,
+                "max_inclusive": 4
+              }
+            }
+          ],
+          "ambient": [
+            {
+              "type": "minecraft:bat",
+              "weight": 10,
+              "count": 4
+            }
+          ],
+          "creature": [],
+          "axolotls": [],
+          "misc": [],
+          "water_ambient": [],
+          "water_creature": [],
+          "underground_water_creature": []
+        }
+      },
+      "modifier": "overlay"
+    },
+    "minecraft:visual/sky_color": "#79a6ff"
+  },
+  "carvers": [],
+  "downfall": 0.75,
+  "effects": {
+    "water_color": "#3f76e4",
+    "grass_color": "#81936b",
+    "foliage_color": "#768663",
+    "dry_foliage_color": "#b9a766"
+  },
+  "features": [
+    [],
+    [],
+    [],
+    [],
+    [],
+    [],
+    [
+      "sanctuary:rift_ore_coal",
+      "sanctuary:rift_ore_iron",
+      "sanctuary:rift_ore_copper",
+      "sanctuary:rift_ore_gold",
+      "sanctuary:rift_ore_redstone",
+      "sanctuary:rift_ore_lapis",
+      "sanctuary:rift_ore_diamond",
+      "sanctuary:rift_ore_emerald",
+      "sanctuary:rift_ore_coal_surface",
+      "sanctuary:rift_ore_iron_surface",
+      "sanctuary:rift_ore_copper_surface",
+      "sanctuary:rift_ore_coal_ledges",
+      "sanctuary:rift_ore_iron_ledges",
+      "sanctuary:rift_ore_copper_ledges"
+    ],
+    [],
+    [],
+    [],
+    [
+      "minecraft:freeze_top_layer"
+    ]
+  ],
+  "has_precipitation": true,
+  "temperature": 0.7
+}
@@ -0,0 +1,27 @@
+{
+  "type": "minecraft:sequence",
+  "sequence": [
+    {
+      "type": "minecraft:condition",
+      "if_true": {
+        "type": "minecraft:biome",
+        "biome_is": [
+          "minecraft:lush_caves",
+          "minecraft:dripstone_caves",
+          "minecraft:sulfur_caves"
+        ]
+      },
+      "then_run": {
+        "type": "minecraft:sequence",
+        "sequence": [
+          "minecraft:overworld",
+          {
+            "type": "minecraft:block",
+            "result_state": "minecraft:stone"
+          }
+        ]
+      }
+    },
+    "sanctuary:population_island"
+  ]
+}
@@ -0,0 +1,23 @@
+{
+  "default_block": "minecraft:stone",
+  "default_fluid": "minecraft:air",
+  "disable_mob_generation": false,
+  "legacy_random_source": true,
+  "material_rule": "sanctuary:unified_island",
+  "noise": {
+    "height": 384,
+    "min_y": 0
+  },
+  "noise_router": {
+    "chunk_surface_level": 0.0,
+    "continents": 0.0,
+    "depth": 0.0,
+    "erosion": 0.0,
+    "final_density": "sanctuary:population_10",
+    "ridges": 0.0,
+    "temperature": "sanctuary:temperate_variation",
+    "vegetation": "sanctuary:temperate_moisture"
+  },
+  "sea_level": -64,
+  "spawn_target": []
+}
@@ -0,0 +1,23 @@
+{
+  "default_block": "minecraft:stone",
+  "default_fluid": "minecraft:air",
+  "disable_mob_generation": false,
+  "legacy_random_source": true,
+  "material_rule": "sanctuary:unified_island",
+  "noise": {
+    "height": 384,
+    "min_y": 0
+  },
+  "noise_router": {
+    "chunk_surface_level": 0.0,
+    "continents": 0.0,
+    "depth": 0.0,
+    "erosion": 0.0,
+    "final_density": "sanctuary:population_20",
+    "ridges": 0.0,
+    "temperature": "sanctuary:temperate_variation",
+    "vegetation": "sanctuary:temperate_moisture"
+  },
+  "sea_level": -64,
+  "spawn_target": []
+}
@@ -0,0 +1,23 @@
+{
+  "default_block": "minecraft:stone",
+  "default_fluid": "minecraft:air",
+  "disable_mob_generation": false,
+  "legacy_random_source": true,
+  "material_rule": "sanctuary:unified_island",
+  "noise": {
+    "height": 384,
+    "min_y": 0
+  },
+  "noise_router": {
+    "chunk_surface_level": 0.0,
+    "continents": 0.0,
+    "depth": 0.0,
+    "erosion": 0.0,
+    "final_density": "sanctuary:population_5",
+    "ridges": 0.0,
+    "temperature": "sanctuary:temperate_variation",
+    "vegetation": "sanctuary:temperate_moisture"
+  },
+  "sea_level": -64,
+  "spawn_target": []
+}
@@ -0,0 +1,22 @@
+{
+  "type": "sanctuary:lost_city",
+  "biomes": "sanctuary:lost_city",
+  "step": "surface_structures",
+  "terrain_adaptation": "none",
+  "spawn_overrides": {
+    "monster": {
+      "bounding_box": "piece",
+      "spawns": [
+        {
+          "type": "minecraft:zombie",
+          "weight": 100,
+          "count": {
+            "type": "minecraft:uniform",
+            "min_inclusive": 2,
+            "max_inclusive": 4
+          }
+        }
+      ]
+    }
+  }
+}
@@ -3,21 +3,57 @@
    "minecraft:overworld": {
      "type": "sanctuary:sanctuary_384",
      "generator": {
-        "type": "minecraft:noise",
+        "type": "sanctuary:island_v14",
        "biome_source": {
-          "type": "sanctuary:population_island",
-          "oak_forest": "sanctuary:population_oak_forest",
-          "birch_forest": "sanctuary:population_birch_forest",
-          "clearing": "sanctuary:population_clearing",
-          "dry_woodland": "sanctuary:population_dry_woodland",
-          "dark_grove": "sanctuary:population_dark_grove",
-          "bamboo_grove": "sanctuary:population_bamboo_grove",
-          "sulfur_depths": "sanctuary:population_sulfur_depths",
-          "rocky_heath": "sanctuary:population_rocky_heath",
-          "lush_caves": "sanctuary:population_lush_caves",
-          "dripstone_caves": "sanctuary:population_dripstone_caves"
+          "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"
+          ]
        },
-        "settings": "sanctuary:population_10"
+        "initial_diameter": 724
      }
    },
    "minecraft:the_end": {
@@ -0,0 +1,45 @@
+{
+  "dimensions": {
+    "minecraft:overworld": {
+      "type": "sanctuary:sanctuary_384",
+      "generator": {
+        "type": "minecraft:noise",
+        "biome_source": {
+          "type": "sanctuary:population_island",
+          "oak_forest": "sanctuary:population_oak_forest",
+          "birch_forest": "sanctuary:population_birch_forest",
+          "clearing": "sanctuary:population_clearing",
+          "dry_woodland": "sanctuary:population_dry_woodland",
+          "dark_grove": "sanctuary:population_dark_grove",
+          "bamboo_grove": "sanctuary:population_bamboo_grove",
+          "sulfur_depths": "sanctuary:population_sulfur_depths",
+          "rocky_heath": "sanctuary:population_rocky_heath",
+          "lush_caves": "sanctuary:population_lush_caves",
+          "dripstone_caves": "sanctuary:population_dripstone_caves"
+        },
+        "settings": "sanctuary:population_10"
+      }
+    },
+    "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 +1,80 @@
+{
+  "dimensions": {
+    "minecraft:overworld": {
+      "type": "sanctuary:sanctuary_384",
+      "generator": {
+        "type": "sanctuary:island_v13",
+        "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"
+          ]
+        },
+        "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"
+      }
+    }
+  }
+}
@@ -10,11 +10,21 @@
    "LayeredSpringOutletMixin",
    "WoodlandSpringOutletMixin",
    "RiftSpringOutletMixin",
-    "CavernSpringOutletMixin"
+    "CavernSpringOutletMixin",
+    "UnifiedDecorationProtectionMixin",
+    "ExpansionVoidServerLevelAccess",
+    "ExpansionVoidEntityManagerAccess",
+    "ExpansionVoidEntityStorageAccess",
+    "ExpansionVoidPoiStorageAccess",
+    "ExpansionVoidTicksAccess",
+    "ExpansionReuseChunkMarkerMixin",
+    "ExpansionReusePromotionMixin",
+    "ExpansionReuseSerializationMixin"
  ],
  "client": [
    "client.SanctuarySkyMixin",
-    "client.SanctuaryFogMixin"
+    "client.SanctuaryFogMixin",
+    "client.SanctuaryWorldOptionsMixin"
  ],
  "injectors": {
    "defaultRequire": 1
@@ -2,12 +2,14 @@ package fr.koka.sanctuary.expansion;

 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.AccessDeniedException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;

 /** Persistence failures must never turn saved continents into a new empty history. No game world is opened. */
 public final class ExpansionJournalSmoke {
@@ -45,6 +47,77 @@ public final class ExpansionJournalSmoke {
            require(larger.islands().getFirst().equals(ExpansionIsland.origin(724, SEED)), "Large origin must reload exactly");
            reject(() -> new ExpansionJournal(scratch.resolve("unsupported"), SEED, 256), "Unsupported origin size");

+            // The new root shares schema 1, while its generation and diameter remain immutable.
+            Path unifiedDirectory = scratch.resolve("unified-large");
+            var unified = new ExpansionJournal(unifiedDirectory, SEED, 1024, 13);
+            var unifiedRoot = ExpansionIsland.origin(1024, SEED, 13);
+            require(unified.islands().equals(List.of(unifiedRoot)), "Unified large journal must contain the exact generation-13 root");
+            unified.commit(List.of(unifiedRoot, north));
+            Path unifiedState = unifiedDirectory.resolve(ExpansionJournal.FILE_NAME);
+            byte[] unifiedBytes = Files.readAllBytes(unifiedState);
+            require(com.google.gson.JsonParser.parseString(Files.readString(unifiedState)).getAsJsonObject()
+                    .get("schema").getAsInt() == 1, "Unified origins must keep journal schema 1");
+            require(new ExpansionJournal(unifiedDirectory, SEED, 1024, 13).islands().equals(List.of(unifiedRoot, north)),
+                    "Unified root and its generation-12 child reservation must reload identically");
+            reject(() -> new ExpansionJournal(unifiedDirectory, SEED, 1024, 12), "Unified large journal read as generation 12");
+            reject(() -> new ExpansionJournal(unifiedDirectory, SEED, 512, 13), "Unified large journal read with Small diameter");
+            reject(() -> new ExpansionJournal(unifiedDirectory, SEED, 724, 13), "Unified large journal read with Medium diameter");
+            require(Arrays.equals(unifiedBytes, Files.readAllBytes(unifiedState)), "Rejected unified journal reads changed its bytes");
+
+            // 724 is valid in both generations: this reaches the persisted root check, not the size guard.
+            Path unifiedMediumDirectory = scratch.resolve("unified-medium");
+            new ExpansionJournal(unifiedMediumDirectory, SEED, 724, 13);
+            byte[] unifiedMediumBytes = Files.readAllBytes(unifiedMediumDirectory.resolve(ExpansionJournal.FILE_NAME));
+            reject(() -> new ExpansionJournal(unifiedMediumDirectory, SEED, 724, 12), "Same-size unified journal read as generation 12");
+            require(Arrays.equals(unifiedMediumBytes, Files.readAllBytes(unifiedMediumDirectory.resolve(ExpansionJournal.FILE_NAME))),
+                    "Rejected cross-generation read changed its journal");
+
+            Path cityDirectory = scratch.resolve("city-generation");
+            var cityRoot = ExpansionIsland.origin(724, SEED, 14);
+            var city = new ExpansionJournal(cityDirectory, SEED, 724, 14,
+                ExpansionJournal.directorySyncFor("\\", ignored -> { throw new AssertionError("Windows must not open the directory"); }));
+            var district = ExpansionPlacement.candidates(SEED, List.of(cityRoot), "city", "sanctuary", "east", "lost_city", 256, "natural", 0).getFirst();
+            require(district.generation() == 14, "New city expansion retains generation 14");
+            city.commit(List.of(cityRoot, district));
+            require(new ExpansionJournal(cityDirectory, SEED, 724, 14).islands().equals(List.of(cityRoot, district)),
+                "Generation 14 root and reserved city survive journal reload");
+            byte[] cityBytes = Files.readAllBytes(cityDirectory.resolve(ExpansionJournal.FILE_NAME));
+            reject(() -> new ExpansionJournal(cityDirectory, SEED, 724, 13), "Reading a city journal as alpha.13");
+            reject(() -> new ExpansionJournal(unifiedMediumDirectory, SEED, 724, 14), "Reading alpha.13 as a city journal");
+            require(Arrays.equals(cityBytes, Files.readAllBytes(cityDirectory.resolve(ExpansionJournal.FILE_NAME)))
+                && Arrays.equals(unifiedMediumBytes, Files.readAllBytes(unifiedMediumDirectory.resolve(ExpansionJournal.FILE_NAME))),
+                "Cross-generation journal reads preserve both histories");
+            reject(() -> city.commit(List.of(cityRoot, district, north)), "Legacy expansion in generation 14 history");
+            var reuseDirectory = scratch.resolve("city-reuse");
+            var reuseJournal = new ExpansionJournal(reuseDirectory, SEED, 724, 14);
+            var certified = district.withReuseToken("a".repeat(64));
+            reuseJournal.commit(List.of(cityRoot, certified));
+            require(new ExpansionJournal(reuseDirectory, SEED, 724, 14).islands().get(1).equals(certified),
+                "Void certificate binding survives reservation reload");
+            byte[] reuseBytes = Files.readAllBytes(reuseDirectory.resolve(ExpansionJournal.FILE_NAME));
+            reject(() -> reuseJournal.commit(List.of(cityRoot, district)), "Removing a persisted certificate token");
+            reject(() -> reuseJournal.commit(List.of(cityRoot, district.withReuseToken("b".repeat(64)))), "Replacing a persisted certificate token");
+            require(Arrays.equals(reuseBytes, Files.readAllBytes(reuseDirectory.resolve(ExpansionJournal.FILE_NAME))),
+                "Rejected certificate changes preserve journal bytes");
+            reuseJournal.commit(List.of(cityRoot, certified.ready()));
+            require(new ExpansionJournal(reuseDirectory, SEED, 724, 14).islands().get(1).equals(certified.ready()),
+                "Completed island retains its immutable certificate binding");
+            for (var unsupported : List.of("../certificate", "A".repeat(64), "a".repeat(63))) {
+                try { district.withReuseToken(unsupported); throw new AssertionError("Invalid token was accepted"); }
+                catch (IllegalArgumentException expected) { }
+            }
+            for (var unsupported : List.of(cityRoot, north)) {
+                try { unsupported.withReuseToken("a".repeat(64)); throw new AssertionError("Root or legacy reuse was accepted"); }
+                catch (IllegalArgumentException expected) { }
+            }
+            require(!Files.readString(unifiedState).contains("reuse_token"), "Legacy journal encoding stays unchanged");
+            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");
+            } catch (IllegalArgumentException expected) {
+                require(expected.getMessage().equals("city_generation_required"), "Explain the legacy world contract");
+            }
+
            Path missing = scratch.resolve("missing"); Files.createDirectory(missing);
            reject(() -> new ExpansionJournal(missing, SEED, 512), "Existing directory with no state");
            Files.writeString(missing.resolve(".expansions-interrupted.tmp"), "partial");
@@ -95,10 +168,14 @@ public final class ExpansionJournalSmoke {
            afterCrash.commit(List.of(root, north.ready(), onward));
            require(new ExpansionJournal(resumeDirectory, SEED, 512).islands().size() == 3, "Resumed region lost its descendant");

+            windowsDirectoryPolicy(scratch.resolve("windows-policy"));
+            directoryFailureAfterReplacement(scratch.resolve("directory-failure"));
+            readbackFailureAfterReplacement(scratch.resolve("readback-failure"));
+
            var tooMany = new ArrayList<ExpansionIsland>(); tooMany.add(root);
            for (int i = 0; i < 64; i++) tooMany.add(island("overflow_" + i, "sanctuary", "north", 0, -(i + 1) * 1024));
            reject(() -> afterCrash.commit(tooMany), "Region count limit");
-            System.out.println("Expansion journal smoke passed: atomic persistence, restart, immutable history, corruption and interrupted reservation");
+            System.out.println("Expansion journal smoke passed: atomic persistence, restart, immutable history, corruption, interrupted reservation, unified root identity, Windows directory policy and post-replacement failures");
        } finally {
            try (var paths = Files.walk(scratch)) {
                for (Path path : paths.sorted(Comparator.reverseOrder()).toList()) Files.delete(path);
@@ -106,6 +183,77 @@ public final class ExpansionJournalSmoke {
        }
    }

+    private static void windowsDirectoryPolicy(Path directory) throws Exception {
+        var directoryAttempts = new AtomicInteger();
+        var windowsSync = ExpansionJournal.directorySyncFor("\\", path -> {
+            directoryAttempts.incrementAndGet();
+            throw new AccessDeniedException(path.toString());
+        });
+        var root = ExpansionIsland.origin(724, SEED, 13);
+        var north = island("windows_north", "sanctuary", "north", 0, -1024);
+        var journal = new ExpansionJournal(directory, SEED, 724, 13, windowsSync);
+        require(journal.healthy() && journal.islands().equals(List.of(root)),
+                "Windows policy must bootstrap a verified journal without opening the directory as a file");
+        journal.commit(List.of(root, north));
+        var reserved = new ExpansionJournal(directory, SEED, 724, 13, windowsSync);
+        require(reserved.healthy() && reserved.islands().equals(List.of(root, north)),
+                "Windows policy must persist and reload the exact reservation");
+        reserved.commit(List.of(root, north.ready()));
+        var ready = new ExpansionJournal(directory, SEED, 724, 13, windowsSync);
+        require(ready.healthy() && ready.islands().equals(List.of(root, north.ready())),
+                "Windows policy must complete and reload the same reservation");
+        require(directoryAttempts.get() == 0,
+                "Windows policy must never attempt the unsupported directory channel, including bootstrap and completion");
+    }
+
+    private static void directoryFailureAfterReplacement(Path directory) throws Exception {
+        var root = ExpansionIsland.origin(724, SEED, 13);
+        var north = island("retained_north", "sanctuary", "north", 0, -1024);
+        new ExpansionJournal(directory, SEED, 724, 13);
+        Path state = directory.resolve(ExpansionJournal.FILE_NAME);
+        var attempts = new AtomicInteger();
+        var denied = new AccessDeniedException(directory.toString());
+        var requiredSync = ExpansionJournal.directorySyncFor("/", path -> {
+            attempts.incrementAndGet();
+            throw denied;
+        });
+        var failed = new ExpansionJournal(directory, SEED, 724, 13, requiredSync);
+        try {
+            failed.commit(List.of(root, north));
+            throw new AssertionError("A directory sync failure on a supported filesystem was ignored");
+        } catch (AccessDeniedException actual) {
+            require(actual == denied, "The original directory sync error must reach the caller unchanged");
+        }
+        require(attempts.get() == 1, "A supported filesystem must attempt directory synchronization");
+        require(!failed.healthy() && failed.islands().equals(List.of(root)),
+                "Uncertain persistence must fail closed without publishing the new reservation to world generation");
+        byte[] reservedBytes = Files.readAllBytes(state);
+        var recovered = new ExpansionJournal(directory, SEED, 724, 13);
+        require(recovered.healthy() && recovered.islands().equals(List.of(root, north)),
+                "A verified reload must recover the reservation already installed before directory sync failed");
+        reject(() -> failed.commit(List.of(root, north)), "Retrying a failed journal without reload");
+        require(attempts.get() == 1 && Arrays.equals(reservedBytes, Files.readAllBytes(state)),
+                "A failed session must neither retry storage operations nor overwrite its retained reservation");
+        recovered.commit(List.of(root, north.ready()));
+        require(new ExpansionJournal(directory, SEED, 724, 13).islands().equals(List.of(root, north.ready())),
+                "A recovered reservation must complete normally without changing its identity");
+    }
+
+    private static void readbackFailureAfterReplacement(Path directory) throws Exception {
+        var root = ExpansionIsland.origin(724, SEED, 13);
+        var north = island("readback_north", "sanctuary", "north", 0, -1024);
+        new ExpansionJournal(directory, SEED, 724, 13);
+        Path state = directory.resolve(ExpansionJournal.FILE_NAME);
+        var journal = new ExpansionJournal(directory, SEED, 724, 13,
+                path -> Files.writeString(state, "damaged after atomic replacement", StandardCharsets.UTF_8));
+        reject(() -> journal.commit(List.of(root, north)), "Corruption detected by post-replacement verification");
+        require(!journal.healthy() && journal.islands().equals(List.of(root)),
+                "Successful replacement alone must not publish an unverified reservation");
+        require(Files.readString(state).equals("damaged after atomic replacement"),
+                "A failed readback must preserve evidence instead of silently recreating the journal");
+        reject(() -> new ExpansionJournal(directory, SEED, 724, 13), "Reloading a journal damaged after replacement");
+    }
+
    private static ExpansionIsland island(String id, String parent, String direction, int x, int z) {
        return new ExpansionIsland(id, parent, direction, ExpansionIsland.directionalClimate(direction), 64, x, z,
            ExpansionIsland.deriveSeed(SEED, id), "natural", "reserved", ExpansionIsland.GENERATION);
@@ -23,7 +23,7 @@ public final class ExpansionPlacementSmoke {
            require(first.equals(candidates(saved, "new_island", root.id(), direction, 64, 1).getFirst()),
                "A short requested distance must still respect the existing reservation and generation halo");

-            for (int diameter : ExpansionIsland.DIAMETERS) {
+            for (int diameter : ExpansionIsland.LEGACY_DIAMETERS) {
                var distant = candidates(saved, "new_island", root.id(), direction, diameter, 2048);
                verifyCandidates(distant, saved, root, direction, diameter, 2048);
                require(distance(root, distant.getFirst()) < 2048 + Math.sqrt(2) * 16,
@@ -17,7 +17,7 @@ public final class ExpansionReliefSmoke {
                    }
                }
            }
-            for (int diameter : ExpansionIsland.DIAMETERS) for (String relief : ExpansionIsland.RELIEFS) {
+            for (int diameter : ExpansionIsland.LEGACY_DIAMETERS) for (String relief : ExpansionIsland.RELIEFS) {
                var island = island(seed, diameter, relief, 1024, -2048);
                require(ExpansionRelief.verticalScale(island) >= 0.4 && ExpansionRelief.verticalScale(island) <= 1.0,
                    "Small islands keep enough vertical space for two levels");
@@ -0,0 +1,162 @@
+package fr.koka.sanctuary.expansion;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+public final class ExpansionSpatialPlacement14Smoke {
+    public static void main(String[] args) throws Exception {
+        ExpansionIsland origin = ExpansionIsland.origin(724, 42, 14);
+        List<ExpansionIsland> saved = new ArrayList<>(List.of(origin));
+        for (String direction : ExpansionIsland.DIRECTIONS) {
+            String id = "satellite_" + direction;
+            var sample = new ExpansionIsland(id, origin.id(), direction, "temperate", 64,
+                0, 0, ExpansionIsland.deriveSeed(42, id), "natural", "reserved", 14);
+            var first = ExpansionSpatialPlacement14.candidates(saved, origin, sample, 0);
+            var again = ExpansionSpatialPlacement14.candidates(saved, origin, sample, 0);
+            require(!first.isEmpty(), "No nearby satellite in " + direction);
+            require(first.equals(again), "Candidate draw is not deterministic");
+            require(first.size() <= 32, "Unbounded draw");
+            var chosen = first.getFirst();
+            double distance = ExpansionPlacement.distanceFromParent(chosen, origin);
+            require(distance - origin.terrainRadius() - chosen.terrainRadius() < 210,
+                "Small satellite too far from Sanctuary's edge");
+            for (var candidate : first) {
+                require((candidate.centerX() & 15) == 0 && (candidate.centerZ() & 15) == 0, "Not chunk aligned");
+                require(ExpansionSpatialPlacement14.followsDirection(direction,
+                    candidate.centerX() - origin.centerX(), candidate.centerZ() - origin.centerZ()), "Wrong compass sector");
+                for (var previous : saved) require(!ExpansionSpatialPlacement14.conflicts(candidate, previous), "Poisson separation violated");
+            }
+            saved.add(chosen.ready());
+        }
+        for (int a = 0; a < saved.size(); a++) for (int b = a + 1; b < saved.size(); b++) {
+            var first = saved.get(a); var second = saved.get(b);
+            require(!ExpansionSpatialPlacement14.conflicts(first, second), "Accepted island conflict");
+            // The diagonal chunk guard prevents two islands from claiming one corner chunk.
+            int minX = Math.floorDiv(second.centerX() - ExpansionSpatialPlacement14.writeRadius(second), 16);
+            int maxX = Math.floorDiv(second.centerX() + ExpansionSpatialPlacement14.writeRadius(second), 16);
+            int minZ = Math.floorDiv(second.centerZ() - ExpansionSpatialPlacement14.writeRadius(second), 16);
+            int maxZ = Math.floorDiv(second.centerZ() + ExpansionSpatialPlacement14.writeRadius(second), 16);
+            for (int z = minZ; z <= maxZ; z++) for (int x = minX; x <= maxX; x++)
+                require(!(first.ownsChunk(x, z) && second.ownsChunk(x, z)), "Two islands own the same chunk");
+        }
+        var large = new ExpansionIsland("continent", "sanctuary", "north", "lost_city", 512,
+            0, 0, ExpansionIsland.deriveSeed(42, "continent"), "natural", "reserved", 14);
+        var far = ExpansionSpatialPlacement14.candidates(saved, origin, large, 4096);
+        require(!far.isEmpty(), "No distant continent candidate");
+        require(far.stream().allMatch(i -> ExpansionPlacement.distanceFromParent(i, origin) >= 4096), "Explicit distance ignored");
+        require(ExpansionSpatialPlacement14.minimumSeparation(origin, large)
+            > ExpansionSpatialPlacement14.minimumSeparation(origin, saved.get(1)), "Size does not affect distance");
+        require(ExpansionSpatialPlacement14.readRadius(large) - ExpansionSpatialPlacement14.writeRadius(large) == 176,
+            "Native generation dependency halo lost");
+        require(!ExpansionSpatialPlacement14.followsDirection("north", 100, 0), "East accepted as north");
+        require(!ExpansionSpatialPlacement14.followsDirection("north", 0, 0), "Zero displacement accepted");
+        require(!ExpansionSpatialPlacement14.followsDirection("north", 100, -10), "Outside sector accepted");
+        require(ExpansionSpatialPlacement14.followsDirection("northeast", 512, -400), "Diagonal sector rejected");
+        largeContinentsAndStableRetries(origin);
+        weightedQuickSizes();
+        journalGeometry();
+        System.out.println("ExpansionSpatialPlacement14Smoke passed: bounded Poisson draws, eight sectors, nearby satellites, 1024-block continents, weighted stable quick draws, restart-safe sector/disc journal geometry and no shared chunks");
+    }
+
+    private static void largeContinentsAndStableRetries(ExpansionIsland origin) {
+        double previousDistance = 0;
+        for (int diameter : ExpansionIsland.DIAMETERS) {
+            String id = "same_draw";
+            var candidates = ExpansionPlacement.candidates(42, List.of(origin), id, origin.id(),
+                "north", "temperate", diameter, "natural", 0);
+            require(!candidates.isEmpty(), "Missing generation-14 size " + diameter);
+            var selected = candidates.getFirst();
+            require(selected.generation() == 14 && selected.diameter() == diameter, "Placement changed the requested size");
+            double distance = ExpansionPlacement.distanceFromParent(selected, origin);
+            require(distance > previousDistance, "Larger size was placed closer for an identical random draw");
+            previousDistance = distance;
+            var obstacle = new ExpansionIsland("obstacle", origin.id(), selected.direction(), selected.climate(),
+                selected.diameter(), selected.centerX(), selected.centerZ(), ExpansionIsland.deriveSeed(42, "obstacle"),
+                selected.relief(), "ready", 14);
+            var alternatives = ExpansionPlacement.candidates(42, List.of(origin, obstacle), id, origin.id(),
+                "north", "temperate", diameter, "natural", 0);
+            require(alternatives.stream().allMatch(c -> candidates.contains(c) && c.diameter() == diameter),
+                "Occupancy retry rerolls geometry or size instead of rejecting occupied draws");
+            require(!alternatives.contains(selected), "Occupied first candidate survives retry");
+            require(candidates.equals(ExpansionPlacement.candidates(42, List.of(origin), id, origin.id(),
+                "north", "temperate", diameter, "natural", 0)), "Retry perturbs a later identical request");
+        }
+        try {
+            ExpansionPlacement.candidates(42, List.of(ExpansionIsland.origin(724, 42, 13)), "large", "sanctuary",
+                "north", "temperate", 1024, "natural", 0);
+            throw new AssertionError("1024-block expansion silently enters an alpha.13 world");
+        } catch (IllegalArgumentException expected) {
+            require(expected.getMessage().equals("city_generation_required"), "Wrong legacy-size rejection");
+        }
+    }
+
+    private static void weightedQuickSizes() {
+        int[] counts = new int[ExpansionIsland.DIAMETERS.size()];
+        int changedBySeed = 0;
+        for (int i = 0; i < 10_000; i++) {
+            long seed = i / 100;
+            String id = "island_" + i % 100;
+            int diameter = ExpansionRandomSize.choose(seed, id);
+            require(diameter == ExpansionRandomSize.choose(seed, id), "Repeated quick request changes its chosen size");
+            int index = ExpansionIsland.DIAMETERS.indexOf(diameter);
+            require(index >= 0, "Quick returned an unsupported size");
+            counts[index]++;
+            if (diameter != ExpansionRandomSize.choose(seed + 1, id)) changedBySeed++;
+        }
+        require(Arrays.stream(counts).allMatch(count -> count > 0), "Quick never selects one of its five sizes");
+        require(counts[0] > counts[1] && counts[1] > counts[2] && counts[2] > counts[3] && counts[3] > counts[4],
+            "Quick no longer favors progressively smaller islands: " + Arrays.toString(counts));
+        require(counts[0] + counts[1] >= 6_000 && counts[0] + counts[1] <= 8_000,
+            "Quick should usually select the two small island sizes");
+        require(changedBySeed > 5_000, "World seed barely affects quick size selection");
+    }
+
+    private static void journalGeometry() throws Exception {
+        Path scratch = Files.createTempDirectory("sanctuary-spatial14-journal-");
+        try {
+            var root = ExpansionIsland.origin(724, 42, 14);
+            var first = record("first", "north", 0, -640, 64, 14);
+            // Physical bounding squares overlap, but the discs plus corner safety remain separate.
+            var diagonal = record("diagonal", "north", 128, -752, 64, 14);
+            require(Math.abs(first.centerX() - diagonal.centerX()) < first.reservedRadius() + diagonal.reservedRadius()
+                && Math.abs(first.centerZ() - diagonal.centerZ()) < first.reservedRadius() + diagonal.reservedRadius(),
+                "Fixture no longer exercises overlapping bounding squares");
+            require(!first.conflicts(diagonal), "Separated generation-14 discs still collide as squares");
+            var journal = new ExpansionJournal(scratch.resolve("new"), 42, 724, 14);
+            journal.commit(List.of(root, first, diagonal));
+            journal.commit(List.of(root, first.ready(), diagonal.ready()));
+            require(new ExpansionJournal(scratch.resolve("new"), 42, 724, 14).islands()
+                .equals(List.of(root, first.ready(), diagonal.ready())), "Sector/disc geometry does not survive journal reload");
+            byte[] before = Files.readAllBytes(scratch.resolve("new").resolve(ExpansionJournal.FILE_NAME));
+            reject(() -> journal.commit(List.of(root, first.ready(), diagonal.ready(),
+                record("overlap", "north", 128, -752, 64, 14))), "Overlapping disc accepted");
+            reject(() -> journal.commit(List.of(root, first.ready(), diagonal.ready(),
+                record("wrong_sector", "east", 0, -4096, 64, 14))), "Wrong sector accepted");
+            require(Arrays.equals(before, Files.readAllBytes(scratch.resolve("new").resolve(ExpansionJournal.FILE_NAME))),
+                "Rejected geometry changed a valid journal");
+            var legacyRoot = ExpansionIsland.origin(724, 42, 13);
+            var legacy = new ExpansionJournal(scratch.resolve("legacy"), 42, 724, 13);
+            reject(() -> legacy.commit(List.of(legacyRoot, record("off_axis", "north", 128, -4096, 64, 12))),
+                "Legacy exact-ray rule changed");
+        } finally {
+            try (var paths = Files.walk(scratch)) {
+                for (Path path : paths.sorted(Comparator.reverseOrder()).toList()) Files.delete(path);
+            }
+        }
+    }
+
+    private static ExpansionIsland record(String id, String direction, int x, int z, int diameter, int generation) {
+        return new ExpansionIsland(id, "sanctuary", direction, "temperate", diameter, x, z,
+            ExpansionIsland.deriveSeed(42, id), "natural", "reserved", generation);
+    }
+    @FunctionalInterface private interface Checked { void run() throws IOException; }
+    private static void reject(Checked action, String message) throws IOException {
+        try { action.run(); throw new AssertionError(message); } catch (IOException expected) { }
+    }
+    private static void require(boolean condition, String message) { if (!condition) throw new AssertionError(message); }
+}
@@ -0,0 +1,141 @@
+package fr.koka.sanctuary.expansion;
+
+import java.io.IOException;
+import java.util.Optional;
+import java.util.Set;
+import java.util.function.Consumer;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.nbt.StringTag;
+import net.minecraft.world.level.ChunkPos;
+
+/** Native-shaped 26.3 NBT fixtures: unknown, missing and malformed data never become an empty proof. */
+public final class ExpansionVoidCertificateSmoke {
+    private static final int DATA_VERSION = 5018;
+    private static final ChunkPos POS = new ChunkPos(18, -7);
+
+    public static void main(String[] args) throws IOException {
+        CompoundTag original = terrain();
+        var proof = certify(original);
+        require(!proof.absent() && proof.terrain().matches("[a-f0-9]{64}"), "FULL void must have a terrain fingerprint");
+        CompoundTag dispatch = original.copy();
+        CompoundTag airDispatch = new CompoundTag(); airDispatch.putString("id", "minecraft:air");
+        ListTag dispatchPalette = new ListTag(); dispatchPalette.add(airDispatch); blocks(dispatch).put("palette", dispatchPalette);
+        require(proof.equals(certify(dispatch)), "Native constant-string and full id-dispatch air representations must agree");
+        CompoundTag volatileFields = original.copy();
+        volatileFields.putLong("LastUpdate", 1_000_000); volatileFields.putLong("InhabitedTime", 20_000);
+        volatileFields.putBoolean("isLightOn", false);
+        section(volatileFields).putByteArray("SkyLight", new byte[2048]);
+        CompoundTag halo = new CompoundTag(); halo.putByte("Y", (byte) 24); halo.putByteArray("SkyLight", new byte[2048]);
+        volatileFields.getList("sections").orElseThrow().add(halo);
+        require(proof.equals(certify(volatileFields)), "Valid counters and light caches must not invalidate semantic emptiness");
+        require(proof.equals(ExpansionVoidCertificate.certify(POS, original, Optional.of(entities()), Optional.of(poi()), DATA_VERSION)),
+            "Absent and explicitly empty independent stores must agree semantically");
+        var absent = ExpansionVoidCertificate.absent(POS, Optional.empty(), Optional.empty(), DATA_VERSION);
+        require(absent.absent() && absent.terrain().equals("absent") && !absent.equals(proof),
+            "An absent chunk must remain distinct from an existing FULL chunk");
+
+        for (String key : Set.of("DataVersion", "xPos", "yPos", "zPos", "Status", "LastUpdate", "InhabitedTime",
+                "sections", "block_entities", "block_ticks", "fluid_ticks", "PostProcessing", "Heightmaps", "structures")) {
+            reject(tag -> tag.remove(key), "missing mandatory FULL field " + key);
+        }
+        reject(tag -> tag.put("LastUpdate", new CompoundTag()), "foreign payload hidden in LastUpdate");
+        reject(tag -> tag.putString("InhabitedTime", "0"), "wrong inhabited-time type");
+        reject(tag -> tag.putLong("InhabitedTime", -1), "negative inhabited-time counter");
+        reject(tag -> tag.putLong("LastUpdate", -1), "negative last-update counter");
+        reject(tag -> tag.putLong("DataVersion", DATA_VERSION), "numeric coercion of DataVersion");
+        reject(tag -> tag.putDouble("xPos", POS.x()), "numeric coercion of position");
+        reject(tag -> tag.putInt("xPos", POS.x() + 1), "different chunk coordinates");
+        reject(tag -> tag.putInt("yPos", -4), "different vertical world range");
+        reject(tag -> tag.putInt("DataVersion", DATA_VERSION - 1), "different data version");
+        reject(tag -> tag.putInt("isLightOn", 1), "wrong light flag type");
+        reject(tag -> tag.putByte("isLightOn", (byte) 2), "non-boolean light flag");
+        reject(tag -> tag.putString("Status", "minecraft:features"), "unfinished chunk");
+        reject(tag -> tag.put("foreign:attachments", new CompoundTag()), "unknown mod metadata");
+        reject(tag -> tag.getCompound("structures").orElseThrow().remove("starts"), "missing structure-start record");
+        reject(tag -> tag.getCompound("structures").orElseThrow().getCompound("References").orElseThrow()
+            .putLongArray("sanctuary:lost_city", new long[] {1}), "structure references");
+        reject(tag -> tag.getCompound("Heightmaps").orElseThrow().remove("WORLD_SURFACE"), "missing FULL heightmap");
+        reject(tag -> tag.getCompound("Heightmaps").orElseThrow().putLongArray("WORLD_SURFACE", new long[36]), "wrong heightmap length");
+        reject(tag -> { long[] heights = new long[37]; heights[0] = 1; tag.getCompound("Heightmaps").orElseThrow().putLongArray("WORLD_SURFACE", heights); }, "nonempty heightmap");
+        reject(tag -> section(tag).putInt("Y", 0), "wrong section elevation type");
+        reject(tag -> section(tag).putByte("Y", (byte) 1), "duplicate or missing section");
+        reject(tag -> section(tag).putByteArray("BlockLight", new byte[2047]), "wrong light-cache size");
+        reject(tag -> { CompoundTag emptyHalo = new CompoundTag(); emptyHalo.putByte("Y", (byte) 24);
+            tag.getList("sections").orElseThrow().add(emptyHalo); }, "empty non-native light halo");
+        reject(tag -> blocks(tag).putLongArray("data", new long[1]), "non-native single-palette data length");
+        reject(tag -> blocks(tag).getList("palette").orElseThrow().set(0, StringTag.valueOf("minecraft:stone")), "solid block");
+        reject(tag -> blocks(tag).getList("palette").orElseThrow().set(0, StringTag.valueOf("minecraft:water")), "fluid block");
+        reject(tag -> { ListTag palette = new ListTag(); palette.add(StringTag.valueOf("minecraft:air")); palette.add(StringTag.valueOf("minecraft:stone")); blocks(tag).put("palette", palette); }, "unused nonair palette entry");
+        reject(tag -> { CompoundTag old = new CompoundTag(); old.putString("Name", "minecraft:air"); ListTag palette = new ListTag(); palette.add(old); blocks(tag).put("palette", palette); }, "unsupported legacy state key");
+        reject(tag -> { ListTag palette = new ListTag(); palette.add(StringTag.valueOf("minecraft:plains")); section(tag).getCompound("biomes").orElseThrow().put("palette", palette); }, "foreign biome");
+        reject(tag -> tag.put("PostProcessing", new ListTag()), "missing per-section post-processing arrays");
+        reject(tag -> tag.getList("block_ticks").orElseThrow().add(new CompoundTag()), "pending block tick");
+        reject(tag -> tag.getList("fluid_ticks").orElseThrow().add(new CompoundTag()), "pending fluid tick");
+        reject(tag -> tag.getList("block_entities").orElseThrow().add(new CompoundTag()), "saved block entity");
+
+        CompoundTag entity = entities();
+        entity.getList("Entities").orElseThrow().add(new CompoundTag());
+        fails(() -> ExpansionVoidCertificate.certify(POS, original, Optional.of(entity), Optional.empty(), DATA_VERSION), "saved entity");
+        fails(() -> ExpansionVoidCertificate.absent(POS, Optional.of(entity), Optional.empty(), DATA_VERSION), "entity sidecar of absent terrain");
+        CompoundTag wrongEntity = entities(); wrongEntity.putIntArray("Position", new int[] {POS.x(), POS.z() + 1});
+        fails(() -> ExpansionVoidCertificate.entityFingerprint(POS, Optional.of(wrongEntity), DATA_VERSION), "misplaced entity sidecar");
+        CompoundTag interest = poi();
+        interest.getCompound("Sections").orElseThrow().getCompound("0").orElseThrow().getList("Records").orElseThrow().add(new CompoundTag());
+        fails(() -> ExpansionVoidCertificate.certify(POS, original, Optional.empty(), Optional.of(interest), DATA_VERSION), "saved POI");
+        fails(() -> ExpansionVoidCertificate.absent(POS, Optional.empty(), Optional.of(interest), DATA_VERSION), "POI sidecar of absent terrain");
+        CompoundTag malformedPoi = poi();
+        malformedPoi.getCompound("Sections").orElseThrow().getCompound("0").orElseThrow().putString("Valid", "true");
+        fails(() -> ExpansionVoidCertificate.poiFingerprint(POS, Optional.of(malformedPoi), DATA_VERSION), "malformed POI validity flag");
+        System.out.println("ExpansionVoidCertificateSmoke: native FULL schema, malformed/missing/foreign metadata refusals, semantic volatile fields and absent-sidecar contracts passed.");
+    }
+
+    private static CompoundTag terrain() {
+        CompoundTag tag = new CompoundTag();
+        tag.putInt("DataVersion", DATA_VERSION); tag.putInt("xPos", POS.x()); tag.putInt("yPos", 0); tag.putInt("zPos", POS.z());
+        tag.putString("Status", "minecraft:full"); tag.putLong("LastUpdate", 0); tag.putLong("InhabitedTime", 0);
+        tag.putBoolean("isLightOn", true);
+        for (String key : Set.of("block_entities", "block_ticks", "fluid_ticks")) tag.put(key, new ListTag());
+        ListTag sections = new ListTag(); ListTag post = new ListTag();
+        for (int y = 0; y < 24; y++) {
+            CompoundTag section = new CompoundTag(); section.putByte("Y", (byte) y);
+            CompoundTag blocks = new CompoundTag();
+            ListTag palette = new ListTag(); palette.add(StringTag.valueOf("minecraft:air")); blocks.put("palette", palette); section.put("block_states", blocks);
+            CompoundTag biomes = new CompoundTag(); ListTag biomePalette = new ListTag(); biomePalette.add(StringTag.valueOf("minecraft:the_void"));
+            biomes.put("palette", biomePalette); section.put("biomes", biomes); sections.add(section); post.add(new ListTag());
+        }
+        tag.put("sections", sections); tag.put("PostProcessing", post);
+        CompoundTag heightmaps = new CompoundTag();
+        for (String key : Set.of("WORLD_SURFACE", "OCEAN_FLOOR", "MOTION_BLOCKING", "MOTION_BLOCKING_NO_LEAVES")) heightmaps.putLongArray(key, new long[37]);
+        tag.put("Heightmaps", heightmaps);
+        CompoundTag structures = new CompoundTag(); structures.put("starts", new CompoundTag()); structures.put("References", new CompoundTag());
+        tag.put("structures", structures);
+        return tag;
+    }
+
+    private static CompoundTag entities() {
+        CompoundTag tag = new CompoundTag(); tag.putInt("DataVersion", DATA_VERSION);
+        tag.putIntArray("Position", new int[] {POS.x(), POS.z()}); tag.put("Entities", new ListTag()); return tag;
+    }
+
+    private static CompoundTag poi() {
+        CompoundTag tag = new CompoundTag(); tag.putInt("DataVersion", DATA_VERSION);
+        CompoundTag section = new CompoundTag(); section.putBoolean("Valid", true); section.put("Records", new ListTag());
+        CompoundTag sections = new CompoundTag(); sections.put("0", section); tag.put("Sections", sections); return tag;
+    }
+
+    private static CompoundTag section(CompoundTag tag) { return tag.getList("sections").orElseThrow().getCompound(0).orElseThrow(); }
+    private static CompoundTag blocks(CompoundTag tag) { return section(tag).getCompound("block_states").orElseThrow(); }
+    private static ExpansionVoidCertificate certify(CompoundTag tag) throws IOException {
+        return ExpansionVoidCertificate.certify(POS, tag, Optional.empty(), Optional.empty(), DATA_VERSION);
+    }
+    private static void reject(Consumer<CompoundTag> change, String reason) {
+        CompoundTag tag = terrain(); change.accept(tag); fails(() -> certify(tag), reason);
+    }
+    @FunctionalInterface private interface Attempt { void run() throws IOException; }
+    private static void fails(Attempt attempt, String reason) {
+        try { attempt.run(); throw new AssertionError("Accepted " + reason); }
+        catch (IOException expected) { /* Refusal must preserve the input, never repair or replace it. */ }
+    }
+    private static void require(boolean condition, String message) { if (!condition) throw new AssertionError(message); }
+}
@@ -0,0 +1,181 @@
+package fr.koka.sanctuary.worldgen.city;
+
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Kind;
+import fr.koka.sanctuary.worldgen.city.LostCityPlan.Parcel;
+import fr.koka.sanctuary.worldgen.city.LostCityPlanner.Ground;
+import fr.koka.sanctuary.worldgen.city.LostCityPlanner.GroundSampler;
+import java.util.Arrays;
+import java.util.EnumSet;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/** Pure geometry contracts. Engine tests separately witness real noise and saved structures. */
+public final class LostCityPlannerSmoke {
+    public static void main(String[] args) {
+        GroundSampler flat = (x, z) -> new Ground(220, 24, true, false);
+        LostCityPlan a = LostCityPlanner.plan(42, 0, 0, 724, true, flat);
+        LostCityPlan b = LostCityPlanner.plan(42, 0, 0, 724, true, flat);
+        LostCityPlan c = LostCityPlanner.plan(8675309, 0, 0, 724, true, flat);
+        require(!a.isEmpty(), "Flat starter fixture needs a city");
+        require(fingerprint(a).equals(fingerprint(b)), "Same seed has different city geometry");
+        require(!fingerprint(a).equals(fingerprint(c)), "Different seed has identical city geometry");
+        var district = a.districts().getFirst();
+        require((district.maxX() - district.minX() + 1L) * (district.maxZ() - district.minZ() + 1L)
+            < 724L * 724L / 10, "Starter district consumes too much of the island");
+        require(district.parcels().stream().filter(p -> p.kind().building()).count() >= 3, "Not enough buildings");
+        require(district.parcels().stream().map(Parcel::kind).distinct().count() >= 6, "City lacks varied parcel uses");
+        require(!a.contains(district.minX(), 100, district.minZ()), "City biome overwrites deep caves");
+        checkGeometry(a, flat);
+        arrayImmutability(a);
+        int gridX = district.minX() + 2, gridZ = district.minZ() + 2;
+        GroundSampler shortFissure = (x, z) -> new Ground(
+            x >= gridX - 2 && x <= gridX + 2 && z >= gridZ + 8 && z <= gridZ + 13 ? 90 : 220,
+            24, true, false);
+        LostCityPlan bridged = LostCityPlanner.plan(42, 0, 0, 724, true, shortFissure);
+        require(bridged.districts().stream().flatMap(d -> d.parcels().stream()).anyMatch(p -> p.kind() == Kind.BRIDGE),
+            "Short street fissure lacks supported bridge");
+        checkGeometry(bridged, shortFissure);
+        allArchetypes(flat, bridged);
+
+        for (int diameter : new int[] {64, 128, 256, 512}) {
+            AtomicInteger calls = new AtomicInteger();
+            LostCityPlan plan = LostCityPlanner.plan(42, 1024, -1024, diameter, false,
+                (x, z) -> { calls.incrementAndGet(); return flat.sample(x, z); });
+            require(!plan.isEmpty(), "Flat expansion lacks city at diameter " + diameter);
+            require(calls.get() <= 16_000, "Planner exceeds column budget");
+            checkGeometry(plan, flat);
+        }
+        GroundSampler slope = (x, z) -> new Ground(220 + Math.floorDiv(x, 9) + Math.floorDiv(z, 13), 24, true, false);
+        LostCityPlan sloping = LostCityPlanner.plan(42, 0, 0, 512, true, slope);
+        require(!sloping.isEmpty(), "Gently sloping terrain cannot host a city");
+        checkGeometry(sloping, slope);
+        // Both grades have continuous support and the same four-block rise across a lot.
+        // Choosing the level from the north entrance used to reject the uphill direction.
+        GroundSampler ascending = (x, z) -> new Ground(220 + Math.floorDiv(z, 4), 24, true, false);
+        GroundSampler descending = (x, z) -> new Ground(220 - Math.floorDiv(z, 4), 24, true, false);
+        LostCityPlan uphill = LostCityPlanner.plan(42, 0, 0, 512, true, ascending);
+        LostCityPlan downhill = LostCityPlanner.plan(42, 0, 0, 512, true, descending);
+        long uphillLots = lots(uphill), downhillLots = lots(downhill);
+        require(uphillLots >= 5 && uphillLots == downhillLots,
+            "Safe north/south grades receive asymmetric parcel acceptance: " + uphillLots + "/" + downhillLots);
+        checkGeometry(uphill, ascending); checkGeometry(downhill, descending);
+
+        require(LostCityPlanner.plan(42, 0, 0, 724, true, (x, z) -> new Ground(220, 24, false, false)).isEmpty(), "Wet island accepted");
+        require(LostCityPlanner.plan(42, 0, 0, 724, true, (x, z) -> new Ground(220, 24, true, true)).isEmpty(), "Protected island accepted");
+        require(LostCityPlanner.plan(42, 0, 0, 724, true, (x, z) -> new Ground(220, 1, true, false)).isEmpty(), "Thin shell accepted");
+        require(LostCityPlanner.plan(42, 0, 0, 724, true, (x, z) -> new Ground(372, 24, true, false)).isEmpty(), "City exceeds world ceiling");
+
+        // A narrow fissure is discovered by full footprint validation rather than the coarse probes.
+        AtomicInteger probes = new AtomicInteger();
+        GroundSampler fractured = (x, z) -> {
+            probes.incrementAndGet();
+            return Math.floorMod(x, 17) == 6 ? new Ground(90, 24, true, false) : new Ground(220, 24, true, false);
+        };
+        LostCityPlan constrained = LostCityPlanner.plan(42, 0, 0, 1024, true, fractured);
+        require(probes.get() <= 16_000, "Failure fallback exceeds column budget");
+        checkGeometry(constrained, fractured);
+        System.out.println("LostCityPlannerSmoke passed: deterministic plans, bounded city coverage, terrain foundations, connected ramps, protected water/caves and column budget");
+    }
+
+    private static void allArchetypes(GroundSampler flat, LostCityPlan bridgeWitness) {
+        EnumSet<Kind> flatKinds = EnumSet.noneOf(Kind.class), undergroundKinds = EnumSet.noneOf(Kind.class);
+        EnumSet<Kind> expectedFlat = EnumSet.allOf(Kind.class); expectedFlat.remove(Kind.BRIDGE);
+        EnumSet<Kind> expectedUnderground = EnumSet.of(Kind.PARKING, Kind.POOL, Kind.EXCAVATION);
+        for (long seed = 0; seed < 32; seed++) {
+            LostCityPlan plan = LostCityPlanner.plan(seed, 0, 0, 724, true, flat);
+            require(!plan.isEmpty(), "Flat reference lacks city for seed " + seed);
+            for (var district : plan.districts()) for (Parcel parcel : district.parcels()) {
+                flatKinds.add(parcel.kind());
+                if (expectedUnderground.contains(parcel.kind()) && parcel.foundationDepth() >= 8) {
+                    undergroundKinds.add(parcel.kind());
+                    for (int z = 0; z < parcel.depth(); z++) for (int x = 0; x < parcel.width(); x++) {
+                        Ground ground = flat.sample(parcel.minX() + x, parcel.minZ() + z);
+                        require(ground.top() >= parcel.floorY() - 1
+                            && ground.top() - (parcel.floorY() - 8) + 1 <= ground.solidDepth(),
+                            "Selected deep archetype lacks actual continuous-rock support");
+                    }
+                }
+            }
+        }
+        require(flatKinds.equals(expectedFlat), "Some flat-ground archetypes are unreachable: " + flatKinds);
+        require(undergroundKinds.equals(expectedUnderground), "Deep parking, pool or excavation is never selected: " + undergroundKinds);
+        // A bridge requires a gap, so its coverage comes from the separate real planner fixture.
+        EnumSet<Kind> allKinds = EnumSet.copyOf(flatKinds);
+        bridgeWitness.districts().forEach(d -> d.parcels().forEach(p -> allKinds.add(p.kind())));
+        require(allKinds.equals(EnumSet.allOf(Kind.class)), "Not every declared city kind can be planned");
+    }
+
+    private static void checkGeometry(LostCityPlan plan, GroundSampler sampler) {
+        for (var district : plan.districts()) for (Parcel parcel : district.parcels()) {
+            require(parcel.minY() >= 0 && parcel.maxY() <= 383, "Piece outside world height");
+            require(Math.abs(Math.floorDiv(parcel.minX(), 16) - district.startChunkX()) <= 7
+                && Math.abs(Math.floorDiv(parcel.maxX(), 16) - district.startChunkX()) <= 7
+                && Math.abs(Math.floorDiv(parcel.minZ(), 16) - district.startChunkZ()) <= 7
+                && Math.abs(Math.floorDiv(parcel.maxZ(), 16) - district.startChunkZ()) <= 7, "Native reference extent exceeded");
+            if (parcel.kind() == Kind.BRIDGE) checkBridge(parcel, sampler);
+            for (int z = 0; z < parcel.depth(); z++) for (int x = 0; x < parcel.width(); x++) {
+                int floor = parcel.surfaceY(x, z);
+                Ground ground = sampler.sample(parcel.minX() + x, parcel.minZ() + z);
+                require(!ground.protectedTerrain(), "Parcel crosses protected water or spring");
+                if (parcel.kind() != Kind.BRIDGE) {
+                    require(ground.dry() && ground.solidDepth() >= 4, "Foundation on water or hollow shell");
+                    require(ground.top() <= floor + 2, "City terrace cuts more than two surface blocks");
+                    require(ground.top() >= floor - parcel.foundationDepth(), "Foundation misses natural ground");
+                    require(ground.top() - (floor - parcel.foundationDepth()) + 1 <= ground.solidDepth(), "Foundation intrudes into cave");
+                }
+                if (x > 0) require(Math.abs(floor - parcel.surfaceY(x - 1, z)) <= 1, "Street height jumps by more than a block");
+                if (z > 0) require(Math.abs(floor - parcel.surfaceY(x, z - 1)) <= 1, "Street height jumps by more than a block");
+                if (parcel.kind() == Kind.POOL || parcel.kind() == Kind.EXCAVATION
+                        || parcel.kind() == Kind.PARKING && parcel.foundationDepth() >= 8) {
+                    require(parcel.foundationDepth() >= 8 && ground.top() >= floor - 1
+                        && ground.top() - (floor - 8) + 1 <= ground.solidDepth(), "Excavation/pool/parking lacks rock certificate");
+                }
+            }
+        }
+    }
+
+    private static long lots(LostCityPlan plan) {
+        return plan.districts().stream().flatMap(d -> d.parcels().stream())
+            .filter(p -> p.kind() != Kind.STREET && p.kind() != Kind.BRIDGE).count();
+    }
+
+    private static void checkBridge(Parcel parcel, GroundSampler sampler) {
+        require(parcel.foundationDepth() == 0, "Bridge fills the ravine underneath");
+        boolean alongX = parcel.width() > parcel.depth();
+        int length = alongX ? parcel.width() : parcel.depth(), gapRun = 0;
+        for (int step = 0; step < length; step++) {
+            boolean unsupported = false;
+            for (int across = 0; across < 5; across++) {
+                int x = alongX ? step : across, z = alongX ? across : step;
+                Ground ground = sampler.sample(parcel.minX() + x, parcel.minZ() + z);
+                if (!ground.dry() || ground.solidDepth() < 4 || ground.top() < parcel.surfaceY(x, z) - 10) unsupported = true;
+            }
+            if (unsupported) {
+                require(step >= 2 && step <= length - 3, "Bridge has no solid abutment");
+                require(++gapRun <= 8, "Bridge unsupported run too long");
+            } else gapRun = 0;
+        }
+    }
+
+    private static void arrayImmutability(LostCityPlan plan) {
+        Parcel road = plan.districts().getFirst().parcels().stream().filter(p -> p.surfaceHeights().length > 0).findFirst().orElseThrow();
+        int original = road.surfaceY(0, 0);
+        int[] heights = road.surfaceHeights(); heights[0] = 17;
+        require(road.surfaceY(0, 0) == original, "Caller can mutate cached city road");
+        int[] source = {220};
+        Parcel test = new Parcel(Kind.STREET, 0, 0, 1, 1, 220, 0, 0, 42, 2, source);
+        source[0] = 180;
+        require(test.surfaceY(0, 0) == 220, "Caller retains mutable road input");
+    }
+
+    private static String fingerprint(LostCityPlan plan) {
+        StringBuilder result = new StringBuilder();
+        for (var district : plan.districts()) {
+            result.append(district.startChunkX()).append(':').append(district.startChunkZ()).append(':').append(district.seed());
+            for (Parcel p : district.parcels()) result.append('|').append(p.kind()).append(':').append(p.minX()).append(':').append(p.minZ())
+                .append(':').append(p.width()).append(':').append(p.depth()).append(':').append(p.floorY()).append(':').append(p.floors())
+                .append(':').append(p.facing()).append(':').append(p.seed()).append(':').append(p.foundationDepth()).append(':').append(Arrays.toString(p.surfaceHeights()));
+        }
+        return result.toString();
+    }
+    private static void require(boolean condition, String message) { if (!condition) throw new AssertionError(message); }
+}
@@ -0,0 +1,193 @@
+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 LostCityRendererSmoke {
+    public static void main(String[] args) {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        run();
+        System.out.println("LostCityRendererSmoke: bounded deterministic masonry, doors, stairs, bedrooms, basements, sealed pools, excavation access, park variants and suspended bridges passed.");
+    }
+
+    /** Also callable from an already bootstrapped native GameTest. */
+    public static void run() {
+        for (Kind kind : Kind.values()) {
+            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)), "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()) {
+                        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), "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), "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");
+        }
+        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), "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");
+        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 Capture render(Parcel parcel) {
+        Capture result = new Capture(parcel);
+        LostCityRenderer.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);
+    }
+}
@@ -1,6 +1,6 @@
 name = "Sanctuary"
 author = "KOKA99CAB"
-version = "0.1.0-alpha.12.1"
+version = "0.1.0-alpha.14"
 pack-format = "packwiz:1.1.0"

 [index]
Author	SHA1	Message	Date
koka	1c5c2c2c7e	Add alpha.14 Lost City and nearby certified expansions Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 14:00:20 +02:00
koka	3a6a895874	Record alpha.13.1 release and existing Prism update Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 12:40:27 +02:00
koka	b19e93dd21	Fix Windows expansion journal persistence in alpha.13.1 Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 12:37:36 +02:00
koka	3569cf1f5f	docs(release): record alpha.13 publication and Prism update Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 11:15:51 +02:00
koka	78b63be8e1	feat(worldgen): unify Sanctuary and native size options for alpha.13 Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 11:13:24 +02:00
koka	818c6753f9	docs: record alpha.12.1 release and preserved Prism update Build Sanctuary / build (push) Canceled after 0s Details	2026-09-09 08:57:40 +02:00