Rebase

- Iris joins shared Volmit update checks and reports
- The iris.update permission controls update visibility
- general.updateNotifications defaults to enabled
- Accepted settings changes reconfigure update checks
- Shutdown removes the settings listener and closes update checks
- Tests cover persisted opt-outs and notifier lifecycle

.github/ISSUE_TEMPLATE/bug.yml

@@ -49,9 +49,11 @@ body:
     id: mcversion
     attributes:
       label: Minecraft Version
-      description: What version of Minecraft is the server on? Iris 4.x targets 26.2 only; older versions are not supported.
+      description: What version of Minecraft is the server on? Iris 4.x supports 26.1.2 to 26.3 on Bukkit-family servers and 26.3 on Fabric, Forge and NeoForge; older versions are not supported.
       options:
+        - '26.3'
         - '26.2'
+        - '26.1.2'
         - Other (unsupported)
     validations:
       required: true
@@ -59,7 +61,7 @@ body:
     id: loaderversion
     attributes:
       label: Platform / Loader Version
-      description: Exact server or loader build (see console). For example "Paper 26.2-60", "Fabric Loader 0.19.3", "NeoForge 26.2.0.12-beta".
+      description: Exact server or loader build (see console). For example "Paper 26.3-133", "Fabric Loader 0.19.5", "NeoForge 26.3.0.33-beta".
       placeholder: DO NOT SAY "LATEST"
     validations:
       required: true

.gitignore

@@ -76,3 +76,8 @@ BUILDS/
 .compatwt/
 
 .worktrees/
+
+/VolmLib/
+/docs/
+/.perf/
+/.codegraph/

README.md

@@ -4,7 +4,7 @@ Iris is a world generation engine for Minecraft servers and mod loaders. It gene
 biomes, caves, structures, objects, and entities from editable JSON packs, with a full in-game
 studio authoring workflow. The same engine runs as a Bukkit-family plugin and as a Fabric, Forge,
 or NeoForge server mod. Cross-platform generation targets deterministic parity for identical
-artifacts, pack bytes, seeds, and test areas. The master branch targets Minecraft 26.2.
+artifacts, pack bytes, seeds, and test areas. The master branch targets Minecraft 26.3.
 
 # [Support](https://discord.gg/3xxPTpT) **|** [Documentation](https://github.com/VolmitSoftware/docs/blob/master/iris/00-overview.md) **|** [Git](https://github.com/IrisDimensions)
 
@@ -20,12 +20,12 @@ Canonical English is defined in the typed Java catalogs under `core/src/main/jav
 
 | Platform | Artifact | Minecraft | Notes |
 |---|---|---|---|
-| Paper / Purpur / Leaf / Canvas | plugin jar | 26.1.2 - 26.2 | Full feature set |
-| Folia | plugin jar | 26.1.2 - 26.2 | Region-safe scheduling throughout |
-| Spigot / CraftBukkit | plugin jar | 26.1.2 - 26.2 | Managed `iris:*` creation and generation; exact vanilla-slot `/iris replace` is unavailable |
-| Fabric | mod jar | 26.2 | Server worldgen + client HUD; requires Fabric Loader 0.19.3+ |
-| Forge | mod jar | 26.2 | Server worldgen + client HUD; current target is Forge 26.2-65.1.1 |
-| NeoForge | mod jar | 26.2 | Server worldgen + client HUD; current target is NeoForge 26.2.0.59 |
+| Paper / Purpur / Leaf / Canvas | plugin jar | 26.1.2 - 26.3 | Full feature set |
+| Folia | plugin jar | 26.1.2 - 26.3 | Region-safe scheduling throughout |
+| Spigot / CraftBukkit | plugin jar | 26.1.2 - 26.3 | Managed `iris:*` creation and generation; exact vanilla-slot `/iris replace` is unavailable |
+| Fabric | mod jar | 26.3 | Server worldgen + client HUD; requires Fabric Loader 0.19.5+ |
+| Forge | mod jar | 26.3 | Server worldgen + client HUD; current target is Forge 26.3-66.0.8 |
+| NeoForge | mod jar | 26.3 | Server worldgen + client HUD; current target is NeoForge 26.3.0.33-beta |
 
 Java 25 is required on every platform.
 
@@ -271,6 +271,12 @@ when it exists, otherwise `build/consumers/` inside the repo. `-Plocation=/path/
 changes only the consumer directory. Both tasks copy all four verified platform jars into
 `../PluginOuts/`.
 
+VolmLib is built from source when a `VolmLib` checkout sits beside the repo or in a parent directory
+(`VOLMLIB_DIR` or `-PlocalVolmLibDirectory=<path>` pick another one). Without one, or with
+`-PuseLocalVolmLib=false`, the build uses VolmLib `master-SNAPSHOT` from JitPack. There is no VolmLib
+version to bump. The build logs which VolmLib it used, and every jar records it in
+`META-INF/volmit/volmlib.properties`.
+
 If you need help compiling as a developer or contributor, ask in the Discord.
 
 ## Adapters / modded development
@@ -298,9 +304,10 @@ properties:
 | `-PirisWorldCheck=<world>` | `iris.worldcheck` | Post-generation world integrity check |
 
 Fabric additionally takes `-PirisClientRunDir=<dir>` to relocate the `runClient` working directory.
-Shared code lives in `adapters/minecraft-common` (all adapters), `adapters/modded-common`
-(loaders + the shared test suite), and `adapters/client-common` (client HUD and world-type
-screens); every adapter adds those source directories, so one edit reaches all three loaders.
+Shared code lives in `adapters/modded-common` (loaders + the shared test suite) and
+`adapters/client-common` (client HUD and world-type screens); every adapter adds those source
+directories, so one edit reaches all three loaders. Shared Minecraft-native code lives in VolmLib
+(`native/minecraft-common`).
 
 For IDE import you can surface the three adapter builds in the root composite with
 `-PincludeModdedAdapters=true`. It is off by default: each adapter includes the root build back to

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/DatapackStructureStateFilter.java

@@ -1,509 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.pack.datapack.DatapackStructureScopeIndex;
-import art.arcane.iris.structure.nativegen.NativeStructureFrequencyScale;
-import art.arcane.iris.structure.nativegen.IrisImportedStructureControl;
-import net.minecraft.core.Holder;
-import net.minecraft.core.HolderOwner;
-import net.minecraft.core.Vec3i;
-import net.minecraft.resources.ResourceKey;
-import net.minecraft.world.level.levelgen.structure.StructureSet;
-import net.minecraft.world.level.levelgen.structure.placement.ConcentricRingsStructurePlacement;
-import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadStructurePlacement;
-import net.minecraft.world.level.levelgen.structure.placement.StructurePlacement;
-
-import java.lang.reflect.Field;
-import java.lang.reflect.Modifier;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.IdentityHashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Optional;
-import java.util.Set;
-
-final class DatapackStructureStateFilter {
-    private DatapackStructureStateFilter() {
-    }
-
-    static Selection filter(
-            List<Holder<StructureSet>> structureSets,
-            DatapackStructureScopeIndex scopeIndex,
-            Set<String> declaredSources
-    ) {
-        return filter(structureSets, scopeIndex, declaredSources, new IrisImportedStructureControl());
-    }
-
-    static Selection filter(
-            List<Holder<StructureSet>> structureSets,
-            DatapackStructureScopeIndex scopeIndex,
-            Set<String> declaredSources,
-            IrisImportedStructureControl importedStructures
-    ) {
-        return filter(
-                structureSets,
-                scopeIndex,
-                declaredSources,
-                importedStructures,
-                keyIndex(structureSets));
-    }
-
-    static Selection filter(
-            List<Holder<StructureSet>> structureSets,
-            DatapackStructureScopeIndex scopeIndex,
-            Set<String> declaredSources,
-            IrisImportedStructureControl importedStructures,
-            StructureSetKeyIndex keyIndex
-    ) {
-        if (scopeIndex.isEmpty()) {
-            return new Selection(
-                    scaleFrequencyOverrides(structureSets, importedStructures, keyIndex),
-                    0,
-                    0);
-        }
-        Map<String, Holder<StructureSet>> holdersByKey = new HashMap<>();
-        for (Holder<StructureSet> holder : structureSets) {
-            String key = structureSetKey(holder, keyIndex);
-            if (key != null) {
-                holdersByKey.putIfAbsent(key, holder);
-            }
-        }
-        Map<Holder<StructureSet>, Holder<StructureSet>> scopedByIdentity = new IdentityHashMap<>();
-        Set<Holder<StructureSet>> visiting = Collections.newSetFromMap(new IdentityHashMap<>());
-        List<Holder<StructureSet>> filteredSets = new ArrayList<>(structureSets.size());
-        int retainedManagedSets = 0;
-        int excludedManagedSets = 0;
-        for (Holder<StructureSet> holder : structureSets) {
-            String setKey = structureSetKey(holder, keyIndex);
-            boolean managedSet = setKey != null && scopeIndex.isManagedStructureSet(setKey);
-            Holder<StructureSet> scopedHolder = scopeHolder(
-                    holder,
-                    scopeIndex,
-                    declaredSources,
-                    holdersByKey,
-                    scopedByIdentity,
-                    visiting,
-                    keyIndex);
-            if (scopedHolder == null) {
-                if (managedSet) {
-                    excludedManagedSets++;
-                }
-                continue;
-            }
-            if (managedSet) {
-                retainedManagedSets++;
-            }
-            filteredSets.add(scopedHolder);
-        }
-        return new Selection(
-                scaleFrequencyOverrides(
-                        List.copyOf(filteredSets), importedStructures, keyIndex),
-                retainedManagedSets,
-                excludedManagedSets);
-    }
-
-    static String structureSetKey(Holder<StructureSet> holder) {
-        return structureSetKey(holder, keyIndex(List.of(holder)));
-    }
-
-    static StructureSetKeyIndex keyIndex(
-            Iterable<? extends Holder<StructureSet>> registeredStructureSets
-    ) {
-        return StructureSetKeyIndex.create(registeredStructureSets);
-    }
-
-    private static String structureSetKey(
-            Holder<StructureSet> holder,
-            StructureSetKeyIndex keyIndex
-    ) {
-        return keyIndex.resolve(holder)
-                .map(key -> key.identifier().toString())
-                .orElse(null);
-    }
-
-    private static List<StructureSet.StructureSelectionEntry> filterEntries(
-            List<StructureSet.StructureSelectionEntry> entries,
-            DatapackStructureScopeIndex scopeIndex,
-            Set<String> declaredSources
-    ) {
-        List<StructureSet.StructureSelectionEntry> filtered = new ArrayList<>(entries.size());
-        for (StructureSet.StructureSelectionEntry entry : entries) {
-            String structureKey = entry.structure().unwrapKey()
-                    .map(key -> key.identifier().toString())
-                    .orElse(null);
-            if (structureKey == null || scopeIndex.allowsStructure(structureKey, declaredSources)) {
-                filtered.add(entry);
-            }
-        }
-        return filtered;
-    }
-
-    private static Holder<StructureSet> scopeHolder(
-            Holder<StructureSet> holder,
-            DatapackStructureScopeIndex scopeIndex,
-            Set<String> declaredSources,
-            Map<String, Holder<StructureSet>> holdersByKey,
-            Map<Holder<StructureSet>, Holder<StructureSet>> scopedByIdentity,
-            Set<Holder<StructureSet>> visiting,
-            StructureSetKeyIndex keyIndex
-    ) {
-        if (scopedByIdentity.containsKey(holder)) {
-            return scopedByIdentity.get(holder);
-        }
-        if (!visiting.add(holder)) {
-            return null;
-        }
-        try {
-            String setKey = structureSetKey(holder, keyIndex);
-            if (setKey != null && scopeIndex.isManagedStructureSet(setKey)
-                    && !scopeIndex.allowsStructureSet(setKey, declaredSources)) {
-                scopedByIdentity.put(holder, null);
-                return null;
-            }
-            StructureSet originalSet = holder.value();
-            List<StructureSet.StructureSelectionEntry> entries = filterEntries(
-                    originalSet.structures(), scopeIndex, declaredSources);
-            if (entries.isEmpty()) {
-                scopedByIdentity.put(holder, null);
-                return null;
-            }
-            StructurePlacement placement = scopePlacement(
-                    originalSet.placement(),
-                    scopeIndex,
-                    declaredSources,
-                    holdersByKey,
-                    scopedByIdentity,
-                    visiting,
-                    keyIndex);
-            if (entries.size() == originalSet.structures().size()
-                    && placement == originalSet.placement()) {
-                scopedByIdentity.put(holder, holder);
-                return holder;
-            }
-            Holder<StructureSet> scoped = replacementHolder(
-                    holder, new StructureSet(entries, placement), keyIndex);
-            scopedByIdentity.put(holder, scoped);
-            return scoped;
-        } finally {
-            visiting.remove(holder);
-        }
-    }
-
-    static Optional<StructurePlacement.ExclusionZone> exclusionZone(StructurePlacement placement) {
-        Object value = declaredFieldValue(StructurePlacement.class, placement, Optional.class);
-        if (value instanceof Optional<?> optional && (optional.isEmpty()
-                || optional.get() instanceof StructurePlacement.ExclusionZone)) {
-            @SuppressWarnings("unchecked")
-            Optional<StructurePlacement.ExclusionZone> resolved =
-                    (Optional<StructurePlacement.ExclusionZone>) optional;
-            return resolved;
-        }
-        throw new IllegalStateException("Could not read structure placement exclusion zone from "
-                + placement.getClass().getName());
-    }
-
-    private static StructurePlacement scopePlacement(
-            StructurePlacement placement,
-            DatapackStructureScopeIndex scopeIndex,
-            Set<String> declaredSources,
-            Map<String, Holder<StructureSet>> holdersByKey,
-            Map<Holder<StructureSet>, Holder<StructureSet>> scopedByIdentity,
-            Set<Holder<StructureSet>> visiting,
-            StructureSetKeyIndex keyIndex
-    ) {
-        Optional<StructurePlacement.ExclusionZone> currentZone = exclusionZone(placement);
-        if (currentZone.isEmpty()) {
-            return placement;
-        }
-
-        Holder<StructureSet> target = currentZone.get().otherSet();
-        String targetKey = structureSetKey(target, keyIndex);
-        if (targetKey != null) {
-            target = holdersByKey.getOrDefault(targetKey, target);
-        }
-        Holder<StructureSet> scopedTarget = scopeHolder(
-                target,
-                scopeIndex,
-                declaredSources,
-                holdersByKey,
-                scopedByIdentity,
-                visiting,
-                keyIndex);
-        Optional<StructurePlacement.ExclusionZone> scopedZone = Optional.empty();
-        if (scopedTarget != null) {
-            scopedZone = Optional.of(new StructurePlacement.ExclusionZone(
-                    scopedTarget,
-                    currentZone.get().chunkCount()));
-        }
-        if (scopedTarget == currentZone.get().otherSet()) {
-            return placement;
-        }
-        return copyPlacement(placement, scopedZone, 1D);
-    }
-
-    private static List<Holder<StructureSet>> scaleFrequencyOverrides(
-            List<Holder<StructureSet>> structureSets,
-            IrisImportedStructureControl importedStructures,
-            StructureSetKeyIndex keyIndex
-    ) {
-        if (!importedStructures.hasFrequencyOverrides()) {
-            return structureSets;
-        }
-        Map<String, Holder<StructureSet>> holdersByKey = new HashMap<>();
-        for (Holder<StructureSet> holder : structureSets) {
-            String key = structureSetKey(holder, keyIndex);
-            if (key != null) {
-                holdersByKey.putIfAbsent(key, holder);
-            }
-        }
-        Map<Holder<StructureSet>, Holder<StructureSet>> scaledByIdentity = new IdentityHashMap<>();
-        List<Holder<StructureSet>> scaledSets = new ArrayList<>(structureSets.size());
-        boolean changed = false;
-        for (Holder<StructureSet> holder : structureSets) {
-            Holder<StructureSet> scaled = scaleFrequencyHolder(
-                    holder,
-                    importedStructures,
-                    holdersByKey,
-                    scaledByIdentity,
-                    keyIndex);
-            scaledSets.add(scaled);
-            changed |= scaled != holder;
-        }
-        return changed ? List.copyOf(scaledSets) : structureSets;
-    }
-
-    private static Holder<StructureSet> scaleFrequencyHolder(
-            Holder<StructureSet> holder,
-            IrisImportedStructureControl importedStructures,
-            Map<String, Holder<StructureSet>> holdersByKey,
-            Map<Holder<StructureSet>, Holder<StructureSet>> scaledByIdentity,
-            StructureSetKeyIndex keyIndex
-    ) {
-        if (scaledByIdentity.containsKey(holder)) {
-            return scaledByIdentity.get(holder);
-        }
-        if (!dependsOnFrequencyOverride(
-                holder, importedStructures, holdersByKey, keyIndex)) {
-            scaledByIdentity.put(holder, holder);
-            return holder;
-        }
-
-        ResourceKey<StructureSet> holderKey = keyIndex.resolve(holder).orElseThrow(() ->
-                new IllegalStateException(
-                        "An affected native structure-set exclusion graph has an unkeyed holder"));
-        ReboundStructureSetHolder scaledHolder = new ReboundStructureSetHolder(holderKey);
-        scaledByIdentity.put(holder, scaledHolder);
-
-        StructureSet originalSet = holder.value();
-        StructurePlacement originalPlacement = originalSet.placement();
-        Optional<StructurePlacement.ExclusionZone> originalZone = exclusionZone(originalPlacement);
-        Optional<StructurePlacement.ExclusionZone> scaledZone = originalZone;
-        if (originalZone.isPresent()) {
-            Holder<StructureSet> target = canonicalHolder(
-                    originalZone.get().otherSet(), holdersByKey, keyIndex);
-            Holder<StructureSet> scaledTarget = scaleFrequencyHolder(
-                    target,
-                    importedStructures,
-                    holdersByKey,
-                    scaledByIdentity,
-                    keyIndex);
-            if (scaledTarget != originalZone.get().otherSet()) {
-                scaledZone = Optional.of(new StructurePlacement.ExclusionZone(
-                        scaledTarget, originalZone.get().chunkCount()));
-            }
-        }
-
-        double multiplier = importedStructures.frequencyMultiplier(
-                structureSetKey(holder, keyIndex));
-        StructurePlacement scaledPlacement = multiplier == 1D && scaledZone.equals(originalZone)
-                ? originalPlacement
-                : copyPlacement(originalPlacement, scaledZone, multiplier);
-        scaledHolder.bind(new StructureSet(originalSet.structures(), scaledPlacement));
-        return scaledHolder;
-    }
-
-    private static boolean dependsOnFrequencyOverride(
-            Holder<StructureSet> holder,
-            IrisImportedStructureControl importedStructures,
-            Map<String, Holder<StructureSet>> holdersByKey,
-            StructureSetKeyIndex keyIndex
-    ) {
-        Set<Holder<StructureSet>> visited = Collections.newSetFromMap(new IdentityHashMap<>());
-        Holder<StructureSet> current = holder;
-        while (visited.add(current)) {
-            if (importedStructures.frequencyMultiplier(
-                    structureSetKey(current, keyIndex)) != 1D) {
-                return true;
-            }
-            Optional<StructurePlacement.ExclusionZone> zone =
-                    exclusionZone(current.value().placement());
-            if (zone.isEmpty()) {
-                return false;
-            }
-            current = canonicalHolder(zone.get().otherSet(), holdersByKey, keyIndex);
-        }
-        return false;
-    }
-
-    private static Holder<StructureSet> canonicalHolder(
-            Holder<StructureSet> holder,
-            Map<String, Holder<StructureSet>> holdersByKey,
-            StructureSetKeyIndex keyIndex
-    ) {
-        String key = structureSetKey(holder, keyIndex);
-        return key == null ? holder : holdersByKey.getOrDefault(key, holder);
-    }
-
-    private static Holder<StructureSet> replacementHolder(
-            Holder<StructureSet> original,
-            StructureSet replacement,
-            StructureSetKeyIndex keyIndex
-    ) {
-        Optional<ResourceKey<StructureSet>> key = keyIndex.resolve(original);
-        if (key.isEmpty()) {
-            return Holder.direct(replacement);
-        }
-        ReboundStructureSetHolder holder = new ReboundStructureSetHolder(key.get());
-        holder.bind(replacement);
-        return holder;
-    }
-
-    private static StructurePlacement copyPlacement(
-            StructurePlacement placement,
-            Optional<StructurePlacement.ExclusionZone> exclusionZone,
-            double frequencyMultiplier
-    ) {
-        Vec3i locateOffset = (Vec3i) declaredFieldValue(
-                StructurePlacement.class, placement, Vec3i.class);
-        StructurePlacement.FrequencyReductionMethod frequencyReductionMethod =
-                (StructurePlacement.FrequencyReductionMethod) declaredFieldValue(
-                        StructurePlacement.class,
-                        placement,
-                        StructurePlacement.FrequencyReductionMethod.class);
-        float frequency = (float) declaredFieldValue(
-                StructurePlacement.class, placement, float.class);
-        int salt = (int) declaredFieldValue(
-                StructurePlacement.class, placement, int.class);
-
-        if (placement instanceof RandomSpreadStructurePlacement randomSpread) {
-            NativeStructureFrequencyScale scale = NativeStructureFrequencyScale.randomSpread(
-                    frequency, randomSpread.spacing(), randomSpread.separation(), frequencyMultiplier);
-            return new RandomSpreadStructurePlacement(
-                    locateOffset,
-                    frequencyReductionMethod,
-                    scale.frequency(),
-                    salt,
-                    exclusionZone,
-                    scale.spacing(),
-                    randomSpread.separation(),
-                    randomSpread.spreadType());
-        }
-        if (placement.getClass() == ConcentricRingsStructurePlacement.class) {
-            ConcentricRingsStructurePlacement rings =
-                    (ConcentricRingsStructurePlacement) placement;
-            float scaledFrequency = NativeStructureFrequencyScale.probability(
-                    frequency, frequencyMultiplier);
-            return new ConcentricRingsStructurePlacement(
-                    locateOffset,
-                    frequencyReductionMethod,
-                    scaledFrequency,
-                    salt,
-                    exclusionZone,
-                    rings.distance(),
-                    rings.spread(),
-                    rings.count(),
-                    rings.preferredBiomes());
-        }
-        throw new IllegalStateException("Unsupported native structure placement in an affected "
-                + "frequency-override or datapack-scope graph: "
-                + placement.getClass().getName());
-    }
-
-    private static Object declaredFieldValue(
-            Class<?> declaringType,
-            Object target,
-            Class<?> fieldType
-    ) {
-        Field match = null;
-        for (Field field : declaringType.getDeclaredFields()) {
-            if (Modifier.isStatic(field.getModifiers()) || field.getType() != fieldType) {
-                continue;
-            }
-            if (match != null) {
-                throw new IllegalStateException("Ambiguous " + fieldType.getName() + " field on "
-                        + declaringType.getName());
-            }
-            match = field;
-        }
-        if (match == null) {
-            throw new IllegalStateException("Missing " + fieldType.getName() + " field on "
-                    + declaringType.getName());
-        }
-        try {
-            match.setAccessible(true);
-            return match.get(target);
-        } catch (IllegalAccessException e) {
-            throw new IllegalStateException("Could not read " + fieldType.getName() + " field on "
-                    + declaringType.getName(), e);
-        }
-    }
-
-    static final class StructureSetKeyIndex {
-        private final Map<List<StructureSet.StructureSelectionEntry>, ResourceKey<StructureSet>>
-                keysByEntries;
-
-        private StructureSetKeyIndex(
-                Map<List<StructureSet.StructureSelectionEntry>, ResourceKey<StructureSet>>
-                        keysByEntries
-        ) {
-            this.keysByEntries = keysByEntries;
-        }
-
-        private static StructureSetKeyIndex create(
-                Iterable<? extends Holder<StructureSet>> registeredStructureSets
-        ) {
-            Map<List<StructureSet.StructureSelectionEntry>, ResourceKey<StructureSet>> keys =
-                    new IdentityHashMap<>();
-            for (Holder<StructureSet> holder : registeredStructureSets) {
-                Optional<ResourceKey<StructureSet>> key = holder.unwrapKey();
-                if (key.isEmpty()) {
-                    continue;
-                }
-                List<StructureSet.StructureSelectionEntry> entries = holder.value().structures();
-                ResourceKey<StructureSet> previous = keys.put(entries, key.get());
-                if (previous != null && !previous.equals(key.get())) {
-                    throw new IllegalStateException(
-                            "Multiple registered structure sets share the same entry list");
-                }
-            }
-            return new StructureSetKeyIndex(keys);
-        }
-
-        private Optional<ResourceKey<StructureSet>> resolve(Holder<StructureSet> holder) {
-            Optional<ResourceKey<StructureSet>> key = holder.unwrapKey();
-            if (key.isPresent()) {
-                return key;
-            }
-            return Optional.ofNullable(keysByEntries.get(holder.value().structures()));
-        }
-    }
-
-    record Selection(
-            List<Holder<StructureSet>> structureSets,
-            int retainedManagedSets,
-            int excludedManagedSets
-    ) {
-    }
-
-    private static final class ReboundStructureSetHolder extends Holder.Reference<StructureSet> {
-        private ReboundStructureSetHolder(ResourceKey<StructureSet> key) {
-            super(Type.STAND_ALONE, new HolderOwner<>() {
-            }, key, null);
-        }
-
-        private void bind(StructureSet structureSet) {
-            bindValue(structureSet);
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/ImportedFeatureStage.java

@@ -1,440 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.generation.runtime.DimensionStackContext;
-import art.arcane.iris.generation.runtime.DimensionStackLayout;
-import art.arcane.iris.nativegen.NativeGenerationWriteGuard;
-import art.arcane.iris.generation.runtime.Engine;
-import art.arcane.iris.structure.nativegen.NativeFeatureGenerationPolicy;
-import art.arcane.iris.generation.biome.IrisBiome;
-import art.arcane.iris.generation.biome.IrisBiomeCustom;
-import art.arcane.iris.generation.decoration.IrisDecorationStep;
-import art.arcane.iris.generation.terrain.IrisDimension;
-import art.arcane.iris.structure.nativegen.IrisImportedFeatureControl;
-import art.arcane.iris.structure.object.IrisStaticObjectLayer;
-import art.arcane.iris.spi.IrisLogging;
-import it.unimi.dsi.fastutil.ints.IntArraySet;
-import it.unimi.dsi.fastutil.ints.IntSet;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
-import net.minecraft.core.HolderSet;
-import net.minecraft.core.Registry;
-import net.minecraft.core.SectionPos;
-import net.minecraft.core.registries.Registries;
-import net.minecraft.resources.Identifier;
-import net.minecraft.world.level.ChunkPos;
-import net.minecraft.world.level.WorldGenLevel;
-import net.minecraft.world.level.biome.Biome;
-import net.minecraft.world.level.biome.BiomeGenerationSettings;
-import net.minecraft.world.level.biome.FeatureSorter;
-import net.minecraft.world.level.chunk.ChunkAccess;
-import net.minecraft.world.level.chunk.LevelChunkSection;
-import net.minecraft.world.level.chunk.ChunkGenerator;
-import net.minecraft.world.level.levelgen.RandomSupport;
-import net.minecraft.world.level.levelgen.Heightmap;
-import net.minecraft.world.level.levelgen.WorldgenRandom;
-import net.minecraft.world.level.levelgen.XoroshiroRandomSource;
-import net.minecraft.world.level.levelgen.placement.PlacedFeature;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.HashMap;
-import java.util.LinkedHashSet;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.function.IntBinaryOperator;
-
-/**
- * Bukkit twin of the modded imported-feature stage. Same control, same semantics, same seeds: with
- * {@code importedFeatures.enabled} the vanilla placed-feature pass runs over Iris terrain, and with the
- * control off nothing here allocates or runs.
- *
- * <p>Iris does its own native structure pass and calls the delegate with {@code addVanillaDecorations=false},
- * so the vanilla feature half never runs on its own. This reproduces that half only - structures are never
- * placed twice.
- *
- * <p>Threading: called from {@code applyBiomeDecoration} on the worldgen thread that owns the chunk. The
- * FEATURES chunk step is not parallel-safe.
- */
-final class ImportedFeatureStage {
-    private static final String CYCLE_MARKER = "Feature order cycle found";
-
-    private final Engine engine;
-    private final ConcurrentHashMap<Integer, RuntimeFeatureState> runtimeStates = new ConcurrentHashMap<>();
-
-    ImportedFeatureStage(Engine engine) {
-        this.engine = engine;
-    }
-
-    /**
-     * Generation settings for one biome holder, mapping Iris custom biomes onto their vanilla derivative.
-     * Pass-through while the control is off, which is what keeps {@code BiomeFilter} behaving exactly as it
-     * does today.
-     */
-    BiomeGenerationSettings generationSettings(Holder<Biome> biome) {
-        RuntimeFeatureState state = currentState();
-        FeatureTable table = state == null ? null : state.featureTable();
-        if (table == null) {
-            return null;
-        }
-        Holder<Biome> mapped = table.derivatives().get(holderKey(biome));
-        return mapped == null ? null : mapped.value().getGenerationSettings();
-    }
-
-    /**
-     * Builds the table on the first decorated chunk, or leaves the stage inert. A feature-order cycle is
-     * reported once here and degrades to features-off; it never reaches chunk generation as a crash.
-     */
-    void prepare(WorldGenLevel level) {
-        IrisDimension dimension = engine.getDimension();
-        int runtimeId = engine.getCacheID();
-        if (settled(runtimeStates.get(runtimeId), dimension)) {
-            return;
-        }
-        synchronized (this) {
-            if (settled(runtimeStates.get(runtimeId), dimension)) {
-                return;
-            }
-            runtimeStates.put(runtimeId, build(level, dimension));
-        }
-    }
-
-    void evictRuntime(int runtimeId) {
-        runtimeStates.remove(runtimeId);
-    }
-
-    private RuntimeFeatureState currentState() {
-        IrisDimension dimension = engine.getDimension();
-        RuntimeFeatureState state = runtimeStates.get(engine.getCacheID());
-        return settled(state, dimension) ? state : null;
-    }
-
-    private static boolean settled(RuntimeFeatureState state, IrisDimension dimension) {
-        return state != null && state.dimension() == dimension;
-    }
-
-    private RuntimeFeatureState build(WorldGenLevel level, IrisDimension dimension) {
-        IrisImportedFeatureControl control;
-        try {
-            control = NativeFeatureGenerationPolicy.control(engine);
-        } catch (RuntimeException error) {
-            IrisLogging.error("Iris could not read importedFeatures for this dimension; features off: "
-                    + error);
-            return new RuntimeFeatureState(dimension, null);
-        }
-        if (!control.shouldGenerateFeatures()) {
-            return new RuntimeFeatureState(dimension, null);
-        }
-        FeatureTable built;
-        try {
-            built = buildTable(level, control, dimension);
-        } catch (Throwable error) {
-            IrisLogging.error("Iris importedFeatures is off for " + dimensionKey()
-                    + ": feature table construction failed: " + error);
-            return new RuntimeFeatureState(dimension, null);
-        }
-        if (built == null) {
-            return new RuntimeFeatureState(dimension, null);
-        }
-        IrisLogging.info("Iris importedFeatures on for " + dimensionKey() + ": " + built.biomes().size()
-                + " biomes, " + built.steps().size() + " steps, " + built.derivatives().size()
-                + " custom-biome derivative maps");
-        return new RuntimeFeatureState(dimension, built);
-    }
-
-    private FeatureTable buildTable(WorldGenLevel level, IrisImportedFeatureControl control,
-                                    IrisDimension dimension) {
-        Registry<Biome> registry = level.registryAccess().lookupOrThrow(Registries.BIOME);
-        Set<String> visibleKeys = visibleBiomeKeys();
-        // Registry-ordered walk, never a hash-ordered set: FeatureSorter's cycle detection walks this list and
-        // an unordered walk makes detection depend on JVM hash order.
-        List<Holder<Biome>> biomes = new ArrayList<>();
-        Map<String, Holder<Biome>> byKey = new HashMap<>();
-        registry.listElements().forEach((Holder.Reference<Biome> reference) -> {
-            String key = holderKey(reference);
-            if (key != null && visibleKeys.contains(key)) {
-                biomes.add(reference);
-                byKey.put(key, reference);
-            }
-        });
-        if (biomes.isEmpty()) {
-            IrisLogging.error("Iris importedFeatures is on but " + dimensionKey()
-                    + " exposes no registered biomes; features off");
-            return null;
-        }
-        Map<String, Holder<Biome>> derivatives = customBiomeDerivatives(registry, byKey);
-        List<FeatureSorter.StepFeatureData> steps;
-        try {
-            steps = FeatureSorter.buildFeaturesPerStep(biomes,
-                    (Holder<Biome> biome) -> settingsFor(biome, derivatives).features(), true);
-        } catch (IllegalStateException error) {
-            String message = error.getMessage();
-            if (message == null || !message.contains(CYCLE_MARKER)) {
-                throw error;
-            }
-            IrisLogging.error("Iris importedFeatures is off for " + dimensionKey()
-                    + ": the registered placed features cannot be ordered. " + message
-                    + ". Remove or reorder the conflicting content, or leave importedFeatures.enabled false.");
-            return null;
-        }
-        boolean filtered = control.getDisabled() != null && !control.getDisabled().isEmpty();
-        return new FeatureTable(dimension, control, List.copyOf(biomes), Set.copyOf(biomes),
-                Map.copyOf(byKey), steps, Map.copyOf(derivatives), filtered);
-    }
-
-    /**
-     * Every biome key Iris can write into a chunk section: the structure derivative, the raw derivative, every
-     * scatter entry, and every generated custom biome.
-     */
-    private Set<String> visibleBiomeKeys() {
-        Set<String> keys = new LinkedHashSet<>();
-        for (IrisBiome irisBiome : engine.getDimension().getReachableBiomes(engine)) {
-            addKey(keys, irisBiome.getStructureDerivativeKey());
-            addKey(keys, irisBiome.getDerivativeKey());
-            addKey(keys, irisBiome.getVanillaDerivativeKey());
-            for (String scatter : irisBiome.getBiomeScatter()) {
-                addKey(keys, scatter);
-            }
-            for (String scatter : irisBiome.getBiomeSkyScatter()) {
-                addKey(keys, scatter);
-            }
-            if (!irisBiome.isCustom()) {
-                continue;
-            }
-            for (IrisBiomeCustom customBiome : irisBiome.getCustomDerivitives()) {
-                addKey(keys, engine.getData().customBiomeResourceKey(engine.getDimension(), customBiome));
-            }
-        }
-        return keys;
-    }
-
-    /**
-     * Maps every generated Iris custom biome key onto the registry holder of its Iris biome's vanilla
-     * derivative. The custom biome's own datapack JSON carries no features by design.
-     */
-    private Map<String, Holder<Biome>> customBiomeDerivatives(Registry<Biome> registry,
-                                                              Map<String, Holder<Biome>> byKey) {
-        Map<String, Holder<Biome>> derivatives = new HashMap<>();
-        for (IrisBiome irisBiome : engine.getDimension().getReachableBiomes(engine)) {
-            if (!irisBiome.isCustom()) {
-                continue;
-            }
-            String derivativeKey = normalizeKey(irisBiome.getVanillaDerivativeKey());
-            // Resolve from the registry, not only from the visible biome set: a sea or shore biome's structure
-            // derivative is rewritten away from its vanilla derivative, so the derivative whose features we
-            // want is not always a biome Iris can emit.
-            Holder<Biome> derivative = byKey.get(derivativeKey);
-            if (derivative == null) {
-                derivative = resolveHolder(registry, derivativeKey);
-            }
-            if (derivative == null) {
-                IrisLogging.warn("Iris importedFeatures: vanilla derivative " + derivativeKey + " of biome "
-                        + irisBiome.getLoadKey()
-                        + " is not registered; its custom biomes generate no imported features");
-                continue;
-            }
-            for (IrisBiomeCustom customBiome : irisBiome.getCustomDerivitives()) {
-                derivatives.put(
-                        engine.getData().customBiomeResourceKey(engine.getDimension(), customBiome),
-                        derivative
-                );
-            }
-        }
-        return derivatives;
-    }
-
-    private static Holder<Biome> resolveHolder(Registry<Biome> registry, String key) {
-        if (registry == null || key == null || key.isBlank()) {
-            return null;
-        }
-        Identifier identifier = Identifier.tryParse(key);
-        if (identifier == null) {
-            return null;
-        }
-        return registry.get(identifier).<Holder<Biome>>map((Holder.Reference<Biome> reference) -> reference)
-                .orElse(null);
-    }
-
-    private static BiomeGenerationSettings settingsFor(Holder<Biome> biome,
-                                                       Map<String, Holder<Biome>> derivatives) {
-        Holder<Biome> mapped = derivatives.get(holderKey(biome));
-        return mapped == null
-                ? biome.value().getGenerationSettings()
-                : mapped.value().getGenerationSettings();
-    }
-
-    /**
-     * Runs the vanilla placed-feature pass for one chunk on the calling worldgen thread. A no-op while the
-     * control is disabled or the table degraded.
-     */
-    void run(WorldGenLevel level, ChunkAccess chunk, ChunkGenerator owner) {
-        RuntimeFeatureState state = currentState();
-        FeatureTable table = state == null ? null : state.featureTable();
-        if (table == null) {
-            return;
-        }
-        ChunkPos centerPos = chunk.getPos();
-        SectionPos sectionPos = SectionPos.of(centerPos, level.getMinSectionY());
-        BlockPos origin = sectionPos.origin();
-        Registry<PlacedFeature> featureRegistry = level.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE);
-        List<FeatureSorter.StepFeatureData> steps = table.steps();
-        WorldgenRandom random = new WorldgenRandom(new XoroshiroRandomSource(RandomSupport.generateUniqueSeed()));
-        long decorationSeed = random.setDecorationSeed(level.getSeed(), origin.getX(), origin.getZ());
-        IrisStaticObjectLayer staticObjects = engine.getDimension().getStaticObjectLayer(engine.getData());
-        int staticMinY = engine.getMinHeight();
-        DimensionStackContext stackContext = engine.getDimensionStackContext();
-        Set<Holder<Biome>> chunkBiomes = chunkBiomes(level, sectionPos, table, stackContext);
-        IntBinaryOperator surfaceFirstFreeY = stackContext == null
-                ? (x, z) -> level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z)
-                : (x, z) -> Engine.hostHeight(engine, x, z, false) + staticMinY + 1;
-        IntBinaryOperator floorFirstFreeY = stackContext == null
-                ? (x, z) -> level.getHeight(Heightmap.Types.OCEAN_FLOOR_WG, x, z)
-                : (x, z) -> Engine.hostHeight(engine, x, z, true) + staticMinY + 1;
-        WorldGenLevel placementLevel = staticObjects.isEmpty() && stackContext == null
-                ? level
-                : NativeStructureWorldgenAccess.create(
-                level, centerPos,
-                surfaceFirstFreeY,
-                floorFirstFreeY,
-                stackContext != null,
-                NativeGenerationWriteGuard.protectedPositions(staticObjects, stackContext, staticMinY));
-
-        try {
-            for (int stepIndex = 0; stepIndex < steps.size(); stepIndex++) {
-                if (!table.control().shouldGenerateStep(IrisDecorationStep.byOrdinal(stepIndex))) {
-                    continue;
-                }
-                placeStep(placementLevel, table, steps.get(stepIndex), featureRegistry, chunkBiomes, owner,
-                        random, decorationSeed, origin, stepIndex);
-            }
-        } catch (Throwable error) {
-            throw new IllegalStateException("Iris imported feature placement failed for chunk "
-                    + centerPos.x() + "," + centerPos.z(), error);
-        } finally {
-            level.setCurrentlyGenerating(null);
-        }
-    }
-
-    private void placeStep(WorldGenLevel level, FeatureTable table, FeatureSorter.StepFeatureData stepData,
-                           Registry<PlacedFeature> featureRegistry, Set<Holder<Biome>> chunkBiomes,
-                           ChunkGenerator owner, WorldgenRandom random, long decorationSeed,
-                           BlockPos origin, int stepIndex) {
-        IntSet stepFeatures = new IntArraySet();
-        for (Holder<Biome> biome : chunkBiomes) {
-            List<HolderSet<PlacedFeature>> biomeFeatures = settingsFor(biome, table.derivatives()).features();
-            if (stepIndex >= biomeFeatures.size()) {
-                continue;
-            }
-            for (Holder<PlacedFeature> feature : biomeFeatures.get(stepIndex)) {
-                stepFeatures.add(stepData.indexMapping().applyAsInt(feature.value()));
-            }
-        }
-        if (stepFeatures.isEmpty()) {
-            return;
-        }
-        // Sorted global indices: identical ordering to vanilla, and each feature's seed comes from its own
-        // global index, so denying one feature never shifts another.
-        int[] featureIndices = stepFeatures.toIntArray();
-        Arrays.sort(featureIndices);
-        for (int globalIndex : featureIndices) {
-            PlacedFeature feature = stepData.features().get(globalIndex);
-            if (table.filtered()) {
-                Identifier featureId = featureRegistry.getKey(feature);
-                if (featureId != null && !table.control().shouldGenerate(featureId.toString())) {
-                    continue;
-                }
-            }
-            random.setFeatureSeed(decorationSeed, globalIndex, stepIndex);
-            level.setCurrentlyGenerating(() -> describeFeature(featureRegistry, feature));
-            feature.placeWithBiomeCheck(level, owner, random, origin);
-        }
-    }
-
-    private static String describeFeature(Registry<PlacedFeature> registry, PlacedFeature feature) {
-        Identifier id = registry.getKey(feature);
-        return id == null ? feature.toString() : id.toString();
-    }
-
-    private Set<Holder<Biome>> chunkBiomes(
-            WorldGenLevel level,
-            SectionPos sectionPos,
-            FeatureTable table,
-            DimensionStackContext stackContext
-    ) {
-        List<Holder<Biome>> collected = new ArrayList<>();
-        ChunkPos.rangeClosed(sectionPos.chunk(), 1).forEach((ChunkPos chunkPos) -> {
-            ChunkAccess neighbour = level.getChunk(chunkPos.x(), chunkPos.z());
-            LevelChunkSection[] sections = neighbour.getSections();
-            for (int sectionIndex = 0; sectionIndex < sections.length; sectionIndex++) {
-                LevelChunkSection section = sections[sectionIndex];
-                if (stackContext == null) {
-                    section.getBiomes().getAll(collected::add);
-                    continue;
-                }
-                int sectionMinimumY = neighbour.getSectionYFromSectionIndex(sectionIndex) << 4;
-                for (int quartY = 0; quartY < 4; quartY++) {
-                    int internalY = sectionMinimumY + (quartY << 2) - level.getMinY();
-                    for (int quartX = 0; quartX < 4; quartX++) {
-                        int blockX = chunkPos.getMinBlockX() + (quartX << 2);
-                        for (int quartZ = 0; quartZ < 4; quartZ++) {
-                            int blockZ = chunkPos.getMinBlockZ() + (quartZ << 2);
-                            DimensionStackLayout.Layer layer = stackContext.getLayerAt(
-                                    blockX, internalY, blockZ);
-                            if (layer.terrainContext().isSelfReferencing()) {
-                                collected.add(section.getBiomes().get(quartX, quartY, quartZ));
-                            }
-                        }
-                    }
-                }
-            }
-        });
-        Set<Holder<Biome>> present = new LinkedHashSet<>();
-        for (Holder<Biome> biome : collected) {
-            if (table.biomeSet().contains(biome)) {
-                present.add(biome);
-                continue;
-            }
-            String key = holderKey(biome);
-            Holder<Biome> canonical = key == null ? null : table.byKey().get(key);
-            if (canonical != null) {
-                present.add(canonical);
-            }
-        }
-        return present;
-    }
-
-    private static void addKey(Set<String> keys, String key) {
-        String normalized = normalizeKey(key);
-        if (normalized != null) {
-            keys.add(normalized);
-        }
-    }
-
-    private String dimensionKey() {
-        IrisDimension dimension = engine.getDimension();
-        return dimension == null ? "<unbound>" : dimension.getLoadKey();
-    }
-
-    private static String holderKey(Holder<Biome> holder) {
-        return holder.unwrapKey()
-                .map(key -> key.identifier().toString().toLowerCase(Locale.ROOT))
-                .orElse(null);
-    }
-
-    private static String normalizeKey(String key) {
-        Identifier identifier = key == null ? null : Identifier.tryParse(key);
-        return identifier == null ? null : identifier.toString().toLowerCase(Locale.ROOT);
-    }
-
-    private record FeatureTable(IrisDimension dimension, IrisImportedFeatureControl control,
-                                List<Holder<Biome>> biomes, Set<Holder<Biome>> biomeSet,
-                                Map<String, Holder<Biome>> byKey,
-                                List<FeatureSorter.StepFeatureData> steps,
-                                Map<String, Holder<Biome>> derivatives, boolean filtered) {
-    }
-
-    private record RuntimeFeatureState(IrisDimension dimension, FeatureTable featureTable) {
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NativeStructurePoiUpdates.java

@@ -1,142 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import ca.spottedleaf.moonrise.common.util.TickThread;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
-import net.minecraft.core.SectionPos;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.entity.ai.village.poi.PoiManager;
-import net.minecraft.world.entity.ai.village.poi.PoiRecord;
-import net.minecraft.world.entity.ai.village.poi.PoiSection;
-import net.minecraft.world.entity.ai.village.poi.PoiType;
-import net.minecraft.world.entity.ai.village.poi.PoiTypes;
-import net.minecraft.world.level.WorldGenLevel;
-import net.minecraft.world.level.block.Block;
-import net.minecraft.world.level.block.state.BlockState;
-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.LevelChunkSection;
-import net.minecraft.world.level.chunk.ProtoChunk;
-import org.bukkit.NamespacedKey;
-import org.bukkit.persistence.PersistentDataType;
-
-import java.util.Arrays;
-import java.util.Optional;
-
-final class NativeStructurePoiUpdates {
-    private static final NamespacedKey DIRTY_SECTIONS = new NamespacedKey("iris", "native_poi_sections");
-
-    private final int skipPoiFlag;
-
-    NativeStructurePoiUpdates(int skipPoiFlag) {
-        this.skipPoiFlag = skipPoiFlag;
-    }
-
-    static NativeStructurePoiUpdates create() {
-        try {
-            return new NativeStructurePoiUpdates(Block.class.getField("UPDATE_SKIP_POI").getInt(null));
-        } catch (NoSuchFieldException e) {
-            return null;
-        } catch (IllegalAccessException e) {
-            throw new ExceptionInInitializerError(e);
-        }
-    }
-
-    boolean setBlock(WorldGenLevel world, BlockPos position, BlockState state, int flags, int limit) {
-        if ((flags & skipPoiFlag) != 0) {
-            return world.setBlock(position, state, flags, limit);
-        }
-        ChunkAccess chunk = world.getChunk(position);
-        if (!(chunk instanceof ProtoChunk)) {
-            return world.setBlock(position, state, flags, limit);
-        }
-        if (!(chunk instanceof ImposterProtoChunk)
-                && !PoiTypes.forState(chunk.getBlockState(position)).equals(PoiTypes.forState(state))) {
-            markSection(chunk, chunk.getSectionIndex(position.getY()));
-        }
-        return world.setBlock(position, state, flags | skipPoiFlag, limit);
-    }
-
-    static void reconcile(LevelChunk chunk) {
-        long[] sections = chunk.persistentDataContainer.get(DIRTY_SECTIONS, PersistentDataType.LONG_ARRAY);
-        if (sections == null) {
-            return;
-        }
-        validateSections(chunk, sections);
-        ServerLevel world = (ServerLevel) chunk.getLevel();
-        TickThread.ensureTickThread(world, chunk.getPos(), "Native structure POIs require the chunk owning thread");
-        PoiManager manager = world.getPoiManager();
-        for (int word = 0; word < sections.length; word++) {
-            long remaining = sections[word];
-            while (remaining != 0) {
-                int index = (word << 6) + Long.numberOfTrailingZeros(remaining);
-                reconcileSection(chunk, manager, index);
-                remaining &= remaining - 1;
-            }
-        }
-        chunk.persistentDataContainer.remove(DIRTY_SECTIONS);
-        chunk.markUnsaved();
-    }
-
-    private static void markSection(ChunkAccess chunk, int index) {
-        long[] sections = chunk.persistentDataContainer.get(DIRTY_SECTIONS, PersistentDataType.LONG_ARRAY);
-        int word = index >>> 6;
-        long bit = 1L << (index & 63);
-        if (sections == null) {
-            sections = new long[word + 1];
-        } else {
-            validateSections(chunk, sections);
-            if (word < sections.length && (sections[word] & bit) != 0) {
-                return;
-            }
-            if (word >= sections.length) {
-                sections = Arrays.copyOf(sections, word + 1);
-            }
-        }
-        sections[word] |= bit;
-        chunk.persistentDataContainer.set(DIRTY_SECTIONS, PersistentDataType.LONG_ARRAY, sections);
-    }
-
-    private static void validateSections(ChunkAccess chunk, long[] sections) {
-        int count = chunk.getSectionsCount();
-        int words = (count + 63) >>> 6;
-        if (sections.length > words
-                || sections.length == words && (count & 63) != 0
-                && (sections[words - 1] >>> (count & 63)) != 0) {
-            throw new IllegalArgumentException("Native POI repair sections exceed chunk height at " + chunk.getPos());
-        }
-    }
-
-    private static void reconcileSection(LevelChunk chunk, PoiManager manager, int index) {
-        SectionPos sectionPosition = SectionPos.of(chunk.getPos(), chunk.getSectionYFromSectionIndex(index));
-        Optional<PoiSection> existing = manager.getOrLoad(sectionPosition.asLong());
-        if (existing.isPresent()) {
-            for (PoiRecord record : existing.get().getRecords(type -> true, PoiManager.Occupancy.ANY).toList()) {
-                if (!PoiTypes.forState(chunk.getBlockState(record.getPos())).equals(Optional.of(record.getPoiType()))) {
-                    manager.remove(record.getPos());
-                }
-            }
-        }
-        LevelChunkSection section = chunk.getSection(index);
-        if (!section.maybeHas(PoiTypes::hasPoi)) {
-            return;
-        }
-        BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
-        for (int y = 0; y < 16; y++) {
-            for (int z = 0; z < 16; z++) {
-                for (int x = 0; x < 16; x++) {
-                    Optional<Holder<PoiType>> type = PoiTypes.forState(section.getBlockState(x, y, z));
-                    if (type.isEmpty()) {
-                        continue;
-                    }
-                    position.set(sectionPosition.minBlockX() + x, sectionPosition.minBlockY() + y,
-                            sectionPosition.minBlockZ() + z);
-                    if (!manager.getType(position).equals(type)) {
-                        manager.add(position.immutable(), type.get());
-                    }
-                }
-            }
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NativeStructureWorldgenAccess.java

@@ -1,606 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.nativegen.WorldgenTerrainHeightmaps;
-import it.unimi.dsi.fastutil.longs.Long2LongOpenHashMap;
-import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Direction;
-import net.minecraft.core.Holder;
-import net.minecraft.core.QuartPos;
-import net.minecraft.core.RegistryAccess;
-import net.minecraft.core.particles.ParticleOptions;
-import net.minecraft.server.MinecraftServer;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.server.level.WorldGenRegion;
-import net.minecraft.sounds.SoundEvent;
-import net.minecraft.sounds.SoundSource;
-import net.minecraft.util.Mth;
-import net.minecraft.util.RandomSource;
-import net.minecraft.world.DifficultyInstance;
-import net.minecraft.world.attribute.EnvironmentAttributeReader;
-import net.minecraft.world.entity.Entity;
-import net.minecraft.world.entity.player.Player;
-import net.minecraft.world.flag.FeatureFlagSet;
-import net.minecraft.world.level.BlockGetter;
-import net.minecraft.world.level.ChunkPos;
-import net.minecraft.world.level.LightLayer;
-import net.minecraft.world.level.WorldGenLevel;
-import net.minecraft.world.level.biome.Biome;
-import net.minecraft.world.level.biome.BiomeManager;
-import net.minecraft.world.level.block.Block;
-import net.minecraft.world.level.block.Blocks;
-import net.minecraft.world.level.block.entity.BlockEntity;
-import net.minecraft.world.level.block.entity.BlockEntityType;
-import net.minecraft.world.level.block.state.BlockState;
-import net.minecraft.world.level.border.WorldBorder;
-import net.minecraft.world.level.chunk.ChunkAccess;
-import net.minecraft.world.level.chunk.ChunkSource;
-import net.minecraft.world.level.chunk.EmptyLevelChunk;
-import net.minecraft.world.level.chunk.status.ChunkStatus;
-import net.minecraft.world.level.dimension.DimensionType;
-import net.minecraft.world.level.entity.EntityTypeTest;
-import net.minecraft.world.level.gameevent.GameEvent;
-import net.minecraft.world.level.levelgen.Heightmap;
-import net.minecraft.world.level.lighting.LevelLightEngine;
-import net.minecraft.world.level.material.Fluid;
-import net.minecraft.world.level.material.FluidState;
-import net.minecraft.world.level.storage.LevelData;
-import net.minecraft.world.phys.AABB;
-import net.minecraft.world.phys.Vec3;
-import net.minecraft.world.ticks.LevelTickAccess;
-import net.minecraft.world.ticks.ScheduledTick;
-import org.bukkit.event.entity.CreatureSpawnEvent;
-
-import java.util.List;
-import java.util.Objects;
-import java.util.Optional;
-import java.util.function.IntBinaryOperator;
-import java.util.function.Predicate;
-import java.util.function.Supplier;
-
-final class NativeStructureWorldgenAccess implements WorldGenLevel {
-    private static final int WRITE_RADIUS = 1;
-    private static final NativeStructurePoiUpdates POI_UPDATES = NativeStructurePoiUpdates.create();
-
-    private final WorldGenLevel delegate;
-    private final ChunkPos generationCenter;
-    private final IntBinaryOperator surfaceFirstFreeY;
-    private final IntBinaryOperator floorFirstFreeY;
-    private final boolean virtualizeHeights;
-    private final Predicate<BlockPos> protectedPosition;
-    private final Holder<Biome> fallbackBiome;
-    private final BiomeManager biomeManager;
-    private final AABB generationBounds;
-    private final LevelTickAccess<Block> blockTicks;
-    private final LevelTickAccess<Fluid> fluidTicks;
-    private final Long2LongOpenHashMap terrainHeights;
-    private final Long2ObjectOpenHashMap<ChunkAccess> outsideChunks;
-
-    private NativeStructureWorldgenAccess(WorldGenLevel delegate, Boundary boundary) {
-        this.delegate = Objects.requireNonNull(delegate, "Native structure world access requires a delegate");
-        this.generationCenter = Objects.requireNonNull(
-                boundary.generationCenter(), "Native structure world access requires a generation center");
-        this.surfaceFirstFreeY = Objects.requireNonNull(
-                boundary.surfaceFirstFreeY(), "Native structure world access requires a surface resolver");
-        this.floorFirstFreeY = Objects.requireNonNull(
-                boundary.floorFirstFreeY(), "Native structure world access requires an ocean-floor resolver");
-        this.virtualizeHeights = boundary.virtualizeHeights();
-        this.protectedPosition = Objects.requireNonNull(
-                boundary.protectedPosition(), "World access requires a protected-position predicate");
-        BlockPos biomeSample = generationCenter.getMiddleBlockPosition(delegate.getSeaLevel());
-        this.fallbackBiome = delegate.getBiome(biomeSample);
-        this.biomeManager = delegate.getBiomeManager().withDifferentSource(this);
-        this.generationBounds = new AABB(
-                generationCenter.getMinBlockX() - 16,
-                delegate.getMinY(),
-                generationCenter.getMinBlockZ() - 16,
-                generationCenter.getMaxBlockX() + 17,
-                delegate.getMinY() + delegate.getHeight(),
-                generationCenter.getMaxBlockZ() + 17);
-        this.blockTicks = new BoundedTickAccess<>(delegate.getBlockTicks(), this::isWritable);
-        this.fluidTicks = new BoundedTickAccess<>(delegate.getFluidTicks(), this::isWritable);
-        this.terrainHeights = new Long2LongOpenHashMap();
-        this.terrainHeights.defaultReturnValue(Long.MIN_VALUE);
-        this.outsideChunks = new Long2ObjectOpenHashMap<>();
-    }
-
-    static NativeStructureWorldgenAccess create(WorldGenLevel delegate, ChunkPos generationCenter,
-                                                IntBinaryOperator surfaceFirstFreeY,
-                                                IntBinaryOperator floorFirstFreeY,
-                                                boolean virtualizeHeights,
-                                                Predicate<BlockPos> protectedPosition) {
-        return new NativeStructureWorldgenAccess(delegate, new Boundary(
-                generationCenter, surfaceFirstFreeY, floorFirstFreeY, virtualizeHeights, protectedPosition));
-    }
-
-    @Override
-    public long getSeed() {
-        return delegate.getSeed();
-    }
-
-    @Override
-    public boolean ensureCanWrite(BlockPos position) {
-        return isWritable(position) && delegate.ensureCanWrite(position);
-    }
-
-    @Override
-    public void setCurrentlyGenerating(Supplier<String> description) {
-        delegate.setCurrentlyGenerating(description);
-    }
-
-    @Override
-    public ServerLevel getLevel() {
-        return delegate.getLevel();
-    }
-
-    @Override
-    public DifficultyInstance getCurrentDifficultyAt(BlockPos position) {
-        if (isReadable(position)) {
-            return delegate.getCurrentDifficultyAt(position);
-        }
-        return delegate.getCurrentDifficultyAt(generationCenter.getMiddleBlockPosition(
-                Mth.clamp(position.getY(), getMinY(), getMaxY() - 1)));
-    }
-
-    @Override
-    public long nextSubTickCount() {
-        return delegate.nextSubTickCount();
-    }
-
-    @Override
-    public LevelTickAccess<Block> getBlockTicks() {
-        return blockTicks;
-    }
-
-    @Override
-    public LevelTickAccess<Fluid> getFluidTicks() {
-        return fluidTicks;
-    }
-
-    @Override
-    public LevelData getLevelData() {
-        return delegate.getLevelData();
-    }
-
-    @Override
-    public MinecraftServer getServer() {
-        return delegate.getServer();
-    }
-
-    @Override
-    public ChunkSource getChunkSource() {
-        return delegate.getChunkSource();
-    }
-
-    @Override
-    public RandomSource getRandom() {
-        return delegate.getRandom();
-    }
-
-    @Override
-    public void updateNeighborsAt(BlockPos position, Block block) {
-        if (isWritableNeighbourhood(position)) {
-            delegate.updateNeighborsAt(position, block);
-        }
-    }
-
-    @Override
-    public void neighborShapeChanged(Direction direction, BlockPos position,
-                                     BlockPos neighbourPosition, BlockState neighbourState,
-                                     int updateFlags, int updateLimit) {
-        if (isWritable(position) && isWritable(neighbourPosition)) {
-            delegate.neighborShapeChanged(
-                    direction, position, neighbourPosition, neighbourState, updateFlags, updateLimit);
-        }
-    }
-
-    @Override
-    public void playSound(Entity source, BlockPos position, SoundEvent sound,
-                          SoundSource soundSource, float volume, float pitch) {
-        if (isWritable(position)) {
-            delegate.playSound(source, position, sound, soundSource, volume, pitch);
-        }
-    }
-
-    @Override
-    public void addParticle(ParticleOptions particle, double x, double y, double z,
-                            double velocityX, double velocityY, double velocityZ) {
-        if (isWritable(BlockPos.containing(x, y, z))) {
-            delegate.addParticle(particle, x, y, z, velocityX, velocityY, velocityZ);
-        }
-    }
-
-    @Override
-    public void levelEvent(Entity source, int eventId, BlockPos position, int data) {
-        if (isWritable(position)) {
-            delegate.levelEvent(source, eventId, position, data);
-        }
-    }
-
-    @Override
-    public void gameEvent(Holder<GameEvent> event, Vec3 position, GameEvent.Context context) {
-        if (isWritable(BlockPos.containing(position))) {
-            delegate.gameEvent(event, position, context);
-        }
-    }
-
-    @Override
-    public ChunkAccess getChunk(int chunkX, int chunkZ) {
-        if (isInsideGenerationRegion(chunkX, chunkZ)) {
-            return delegate.getChunk(chunkX, chunkZ);
-        }
-        return outsideChunk(chunkX, chunkZ);
-    }
-
-    @Override
-    public ChunkAccess getChunk(int chunkX, int chunkZ, ChunkStatus status, boolean create) {
-        if (isInsideGenerationRegion(chunkX, chunkZ)) {
-            return delegate.getChunk(chunkX, chunkZ, status, create);
-        }
-        return create ? outsideChunk(chunkX, chunkZ) : null;
-    }
-
-    @Override
-    public ChunkAccess getChunkIfLoadedImmediately(int chunkX, int chunkZ) {
-        if (!isInsideGenerationRegion(chunkX, chunkZ)) {
-            return null;
-        }
-        return delegate.getChunkIfLoadedImmediately(chunkX, chunkZ);
-    }
-
-    @Override
-    public boolean hasChunk(int chunkX, int chunkZ) {
-        return isInsideGenerationRegion(chunkX, chunkZ) && delegate.hasChunk(chunkX, chunkZ);
-    }
-
-    @Override
-    public int getHeight(Heightmap.Types type, int x, int z) {
-        if (!virtualizeHeights && isInsideGenerationRegion(x >> 4, z >> 4)) {
-            return delegate.getHeight(type, x, z);
-        }
-        return height(type, x, z);
-    }
-
-    @Override
-    public int getSkyDarken() {
-        return delegate.getSkyDarken();
-    }
-
-    @Override
-    public BiomeManager getBiomeManager() {
-        return biomeManager;
-    }
-
-    @Override
-    public Holder<Biome> getNoiseBiome(int quartX, int quartY, int quartZ) {
-        return getUncachedNoiseBiome(quartX, quartY, quartZ);
-    }
-
-    @Override
-    public Holder<Biome> getUncachedNoiseBiome(int quartX, int quartY, int quartZ) {
-        if (isInsideGenerationRegion(QuartPos.toSection(quartX), QuartPos.toSection(quartZ))) {
-            return delegate.getUncachedNoiseBiome(quartX, quartY, quartZ);
-        }
-        return fallbackBiome;
-    }
-
-    @Override
-    public boolean isClientSide() {
-        return delegate.isClientSide();
-    }
-
-    @Override
-    public int getSeaLevel() {
-        return delegate.getSeaLevel();
-    }
-
-    @Override
-    public DimensionType dimensionType() {
-        return delegate.dimensionType();
-    }
-
-    @Override
-    public int getMinY() {
-        return delegate.getMinY();
-    }
-
-    @Override
-    public int getHeight() {
-        return delegate.getHeight();
-    }
-
-    @Override
-    public RegistryAccess registryAccess() {
-        return delegate.registryAccess();
-    }
-
-    @Override
-    public FeatureFlagSet enabledFeatures() {
-        return delegate.enabledFeatures();
-    }
-
-    @Override
-    public EnvironmentAttributeReader environmentAttributes() {
-        return delegate.environmentAttributes();
-    }
-
-    @Override
-    public LevelLightEngine getLightEngine() {
-        return delegate.getLightEngine();
-    }
-
-    @Override
-    public int getBrightness(LightLayer layer, BlockPos position) {
-        if (isReadable(position)) {
-            return delegate.getBrightness(layer, position);
-        }
-        return layer == LightLayer.SKY && canSeeSky(position) ? 15 : 0;
-    }
-
-    @Override
-    public int getRawBrightness(BlockPos position, int ambientDarkening) {
-        if (isReadable(position)) {
-            return delegate.getRawBrightness(position, ambientDarkening);
-        }
-        return Math.max(0, getBrightness(LightLayer.SKY, position) - ambientDarkening);
-    }
-
-    @Override
-    public boolean canSeeSky(BlockPos position) {
-        if (isReadable(position)) {
-            return delegate.canSeeSky(position);
-        }
-        return position.getY() >= height(Heightmap.Types.WORLD_SURFACE_WG, position.getX(), position.getZ());
-    }
-
-    @Override
-    public WorldBorder getWorldBorder() {
-        return delegate.getWorldBorder();
-    }
-
-    @Override
-    public BlockGetter getChunkForCollisions(int chunkX, int chunkZ) {
-        if (isInsideGenerationRegion(chunkX, chunkZ)) {
-            return delegate.getChunkForCollisions(chunkX, chunkZ);
-        }
-        return outsideChunk(chunkX, chunkZ);
-    }
-
-    @Override
-    public BlockEntity getBlockEntity(BlockPos position) {
-        return isWritable(position) ? delegate.getBlockEntity(position) : null;
-    }
-
-    @Override
-    public <T extends BlockEntity> Optional<T> getBlockEntity(
-            BlockPos position, BlockEntityType<T> type) {
-        return isWritable(position) ? delegate.getBlockEntity(position, type) : Optional.empty();
-    }
-
-    @Override
-    public BlockState getBlockState(BlockPos position) {
-        return isReadable(position) ? delegate.getBlockState(position) : terrainState(position);
-    }
-
-    @Override
-    public BlockState getBlockStateIfLoaded(BlockPos position) {
-        return isReadable(position) ? delegate.getBlockStateIfLoaded(position) : null;
-    }
-
-    @Override
-    public FluidState getFluidState(BlockPos position) {
-        return isReadable(position) ? delegate.getFluidState(position) : terrainState(position).getFluidState();
-    }
-
-    @Override
-    public FluidState getFluidIfLoaded(BlockPos position) {
-        return isReadable(position) ? delegate.getFluidIfLoaded(position) : null;
-    }
-
-    @Override
-    public List<Entity> getEntities(Entity source, AABB area, Predicate<? super Entity> predicate) {
-        AABB boundedArea = boundedArea(area);
-        return boundedArea == null ? List.of() : delegate.getEntities(source, boundedArea, predicate);
-    }
-
-    @Override
-    public <T extends Entity> List<T> getEntities(
-            EntityTypeTest<Entity, T> type,
-            AABB area, Predicate<? super T> predicate) {
-        AABB boundedArea = boundedArea(area);
-        return boundedArea == null ? List.of() : delegate.getEntities(type, boundedArea, predicate);
-    }
-
-    @Override
-    public List<? extends Player> players() {
-        return delegate.players();
-    }
-
-    @Override
-    public boolean isStateAtPosition(BlockPos position, Predicate<BlockState> predicate) {
-        return predicate.test(getBlockState(position));
-    }
-
-    @Override
-    public boolean isFluidAtPosition(BlockPos position, Predicate<FluidState> predicate) {
-        return predicate.test(getFluidState(position));
-    }
-
-    @Override
-    public BlockPos getHeightmapPos(Heightmap.Types type, BlockPos position) {
-        return position.atY(getHeight(type, position.getX(), position.getZ()));
-    }
-
-    @Override
-    public boolean setBlock(BlockPos position, BlockState state, int updateFlags, int updateLimit) {
-        return isWritable(position)
-                && (POI_UPDATES != null
-                ? POI_UPDATES.setBlock(delegate, position, state, updateFlags, updateLimit)
-                : delegate.setBlock(position, state, updateFlags, updateLimit));
-    }
-
-    @Override
-    public boolean removeBlock(BlockPos position, boolean move) {
-        if (!isWritable(position)) {
-            return false;
-        }
-        return POI_UPDATES != null && delegate instanceof WorldGenRegion
-                ? setBlock(position, Blocks.AIR.defaultBlockState(), Block.UPDATE_ALL, Block.UPDATE_LIMIT)
-                : delegate.removeBlock(position, move);
-    }
-
-    @Override
-    public boolean destroyBlock(BlockPos position, boolean drop, Entity source, int updateLimit) {
-        if (!isWritable(position)) {
-            return false;
-        }
-        return POI_UPDATES != null && delegate instanceof WorldGenRegion
-                ? !delegate.getBlockState(position).isAir()
-                && setBlock(position, Blocks.AIR.defaultBlockState(), Block.UPDATE_ALL, updateLimit)
-                : delegate.destroyBlock(position, drop, source, updateLimit);
-    }
-
-    @Override
-    public boolean addFreshEntity(Entity entity) {
-        return isWritable(entity.blockPosition()) && delegate.addFreshEntity(entity);
-    }
-
-    @Override
-    public boolean addFreshEntity(Entity entity, CreatureSpawnEvent.SpawnReason reason) {
-        return isWritable(entity.blockPosition()) && delegate.addFreshEntity(entity, reason);
-    }
-
-    private boolean isReadable(BlockPos position) {
-        return isInsideGenerationRegion(position.getX() >> 4, position.getZ() >> 4)
-                && !isOutsideBuildHeight(position);
-    }
-
-    private boolean isWritable(BlockPos position) {
-        return isReadable(position) && !protectedPosition.test(position);
-    }
-
-    private boolean isWritableNeighbourhood(BlockPos position) {
-        return isWritable(position)
-                && isWritable(position.north())
-                && isWritable(position.south())
-                && isWritable(position.east())
-                && isWritable(position.west())
-                && isWritable(position.above())
-                && isWritable(position.below());
-    }
-
-    private AABB boundedArea(AABB area) {
-        double minX = Math.max(area.minX, generationBounds.minX);
-        double minY = Math.max(area.minY, generationBounds.minY);
-        double minZ = Math.max(area.minZ, generationBounds.minZ);
-        double maxX = Math.min(area.maxX, generationBounds.maxX);
-        double maxY = Math.min(area.maxY, generationBounds.maxY);
-        double maxZ = Math.min(area.maxZ, generationBounds.maxZ);
-        if (minX >= maxX || minY >= maxY || minZ >= maxZ) {
-            return null;
-        }
-        if (minX == area.minX && minY == area.minY && minZ == area.minZ
-                && maxX == area.maxX && maxY == area.maxY && maxZ == area.maxZ) {
-            return area;
-        }
-        return new AABB(minX, minY, minZ, maxX, maxY, maxZ);
-    }
-
-    boolean isInsideGenerationRegion(int chunkX, int chunkZ) {
-        return Math.abs(chunkX - generationCenter.x()) <= WRITE_RADIUS
-                && Math.abs(chunkZ - generationCenter.z()) <= WRITE_RADIUS;
-    }
-
-    @Override
-    public boolean isOutsideBuildHeight(BlockPos position) {
-        return position.getY() < getMinY() || position.getY() >= getMaxY();
-    }
-
-    private BlockState terrainState(BlockPos position) {
-        if (isOutsideBuildHeight(position)) {
-            return Blocks.VOID_AIR.defaultBlockState();
-        }
-        long heights = heights(position.getX(), position.getZ());
-        int surface = (int) (heights >> 32);
-        int floor = (int) heights;
-        if (position.getY() < floor) {
-            return Blocks.STONE.defaultBlockState();
-        }
-        if (position.getY() < surface) {
-            return Blocks.WATER.defaultBlockState();
-        }
-        return Blocks.AIR.defaultBlockState();
-    }
-
-    private int height(Heightmap.Types type, int x, int z) {
-        long heights = heights(x, z);
-        if (type == Heightmap.Types.OCEAN_FLOOR || type == Heightmap.Types.OCEAN_FLOOR_WG) {
-            return (int) heights;
-        }
-        return (int) (heights >> 32);
-    }
-
-    private long heights(int x, int z) {
-        long key = ((long) x << 32) ^ (z & 0xffffffffL);
-        long cached = terrainHeights.get(key);
-        if (cached != Long.MIN_VALUE) {
-            return cached;
-        }
-        int floor = Mth.clamp(floorFirstFreeY.applyAsInt(x, z), getMinY(), getMaxY());
-        int surface = Mth.clamp(surfaceFirstFreeY.applyAsInt(x, z), floor, getMaxY());
-        long heights = ((long) surface << 32) | (floor & 0xffffffffL);
-        terrainHeights.put(key, heights);
-        return heights;
-    }
-
-    private ChunkAccess outsideChunk(int chunkX, int chunkZ) {
-        long key = ChunkPos.pack(chunkX, chunkZ);
-        ChunkAccess cached = outsideChunks.get(key);
-        if (cached != null) {
-            return cached;
-        }
-        EmptyLevelChunk chunk = new EmptyLevelChunk(getLevel(), new ChunkPos(chunkX, chunkZ), fallbackBiome);
-        WorldgenTerrainHeightmaps.primeTerrain(chunk, surfaceFirstFreeY, floorFirstFreeY);
-        outsideChunks.put(key, chunk);
-        return chunk;
-    }
-
-    private record Boundary(ChunkPos generationCenter,
-                            IntBinaryOperator surfaceFirstFreeY,
-                            IntBinaryOperator floorFirstFreeY,
-                            boolean virtualizeHeights,
-                            Predicate<BlockPos> protectedPosition) {
-    }
-
-    private static final class BoundedTickAccess<T> implements LevelTickAccess<T> {
-        private final LevelTickAccess<T> delegate;
-        private final Predicate<BlockPos> writable;
-
-        private BoundedTickAccess(LevelTickAccess<T> delegate, Predicate<BlockPos> writable) {
-            this.delegate = delegate;
-            this.writable = writable;
-        }
-
-        @Override
-        public void schedule(ScheduledTick<T> tick) {
-            if (writable.test(tick.pos())) {
-                delegate.schedule(tick);
-            }
-        }
-
-        @Override
-        public boolean hasScheduledTick(BlockPos position, T type) {
-            return writable.test(position) && delegate.hasScheduledTick(position, type);
-        }
-
-        @Override
-        public int count() {
-            return delegate.count();
-        }
-
-        @Override
-        public boolean willTickThisTick(BlockPos position, T type) {
-            return writable.test(position) && delegate.willTickThisTick(position, type);
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsGenerationHooks.java

@@ -1,61 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.platform.agent.Agent;
-import it.unimi.dsi.fastutil.shorts.ShortList;
-import net.bytebuddy.ByteBuddy;
-import net.bytebuddy.asm.Advice;
-import net.bytebuddy.matcher.ElementMatchers;
-import net.minecraft.world.level.chunk.ChunkAccess;
-import net.minecraft.world.level.chunk.ChunkGenerator;
-import net.minecraft.server.level.WorldGenRegion;
-import net.minecraft.core.BlockPos;
-import net.minecraft.world.level.ChunkPos;
-import java.util.function.LongPredicate;
-import net.minecraft.world.level.chunk.ProtoChunk;
-import net.minecraft.world.level.chunk.status.ChunkStatus;
-
-import java.util.List;
-
-final class NmsGenerationHooks {
-    private NmsGenerationHooks() {
-    }
-
-    static void install() {
-        ByteBuddy buddy = new ByteBuddy();
-        for (Class<?> clazz : List.of(ChunkAccess.class, ProtoChunk.class)) {
-            buddy.redefine(clazz)
-                    .visit(Advice.to(ChunkAccessAdvice.class).on(ElementMatchers.isMethod().and(ElementMatchers.takesArguments(ShortList.class, int.class))))
-                    .make()
-                    .load(clazz.getClassLoader(), Agent.installed());
-        }
-        buddy.redefine(WorldGenRegion.class)
-                .visit(Advice.to(WorldGenerationWriteAdvice.class).on(ElementMatchers.named("ensureCanWrite")
-                        .and(ElementMatchers.takesArguments(BlockPos.class))))
-                .make()
-                .load(WorldGenRegion.class.getClassLoader(), Agent.installed());
-    }
-
-    private static class WorldGenerationWriteAdvice {
-        @Advice.OnMethodExit
-        static void exit(@Advice.This WorldGenRegion region, @Advice.Argument(0) BlockPos position,
-                         @Advice.Return(readOnly = false) boolean allowed) {
-            if (!allowed) {
-                return;
-            }
-            ChunkGenerator generator = region.getLevel().getChunkSource().getGenerator();
-            if (generator instanceof LongPredicate predicate
-                    && generator.getClass().getName().equals("art.arcane.iris.platform.bukkit.nms.v26_2_R1.IrisChunkGenerator")
-                    && region.getChunk(position.getX() >> 4, position.getZ() >> 4)
-                    .getPersistedStatus().isOrAfter(ChunkStatus.FULL)) {
-                allowed = predicate.test(ChunkPos.pack(position.getX() >> 4, position.getZ() >> 4));
-            }
-        }
-    }
-
-    private static class ChunkAccessAdvice {
-        @Advice.OnMethodEnter(skipOn = Advice.OnNonDefaultValue.class)
-        static boolean enter(@Advice.This ChunkAccess access, @Advice.Argument(1) int index) {
-            return index >= access.getPostProcessing().length;
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsGenerationRegistry.java

@@ -1,182 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.spi.PlatformGenerationRegistry;
-import com.google.gson.JsonElement;
-import com.google.gson.JsonParser;
-import com.mojang.serialization.Codec;
-import com.mojang.serialization.JsonOps;
-import net.minecraft.core.Registry;
-import net.minecraft.core.RegistryAccess;
-import net.minecraft.core.registries.Registries;
-import net.minecraft.resources.Identifier;
-import net.minecraft.resources.RegistryOps;
-import net.minecraft.resources.ResourceKey;
-import net.minecraft.world.level.biome.Biome;
-import net.minecraft.world.level.dimension.DimensionType;
-
-import java.util.List;
-import java.util.Locale;
-import java.util.Objects;
-import java.util.function.Supplier;
-
-final class NmsGenerationRegistry implements PlatformGenerationRegistry {
-    private static final String BIOME_REGISTRY = "minecraft:worldgen/biome";
-    private static final String STRUCTURE_REGISTRY = "minecraft:worldgen/structure";
-    private static final String DIMENSION_TYPE_REGISTRY = "minecraft:dimension_type";
-    private static final String BLOCK_REGISTRY = "minecraft:block";
-    private static final String ENTITY_TYPE_REGISTRY = "minecraft:entity_type";
-
-    private final Supplier<RegistryAccess> registryAccess;
-    private final String runtimeIdentity;
-    private final String rendererIdentity;
-
-    NmsGenerationRegistry(
-            Supplier<RegistryAccess> registryAccess,
-            String runtimeIdentity,
-            String rendererIdentity
-    ) {
-        this.registryAccess = Objects.requireNonNull(registryAccess, "registryAccess");
-        this.runtimeIdentity = requireText(runtimeIdentity, "runtimeIdentity");
-        this.rendererIdentity = requireText(rendererIdentity, "rendererIdentity");
-    }
-
-    @Override
-    public String runtimeIdentity() {
-        return runtimeIdentity;
-    }
-
-    @Override
-    public String generatedDefinitionRendererIdentity() {
-        return rendererIdentity;
-    }
-
-    @Override
-    public String customBiomeResourceKey(String identitySha256) {
-        return PlatformGenerationRegistry.contentAddressedCustomBiomeResourceKey(identitySha256);
-    }
-
-    @Override
-    public List<String> legacyCustomBiomeResourceKeys(
-            String packName,
-            String dimensionKey,
-            String customBiomeId
-    ) {
-        return List.of(requireText(dimensionKey, "dimensionKey").toLowerCase(Locale.ROOT)
-                + ":" + requireText(customBiomeId, "customBiomeId").toLowerCase(Locale.ROOT));
-    }
-
-    @Override
-    public String dimensionTypeResourceKey(String packName, String dimensionKey, String dimensionTypeKey) {
-        return "iris:" + requireText(dimensionTypeKey, "dimensionTypeKey").toLowerCase(Locale.ROOT);
-    }
-
-    @Override
-    public Definition definition(String registryKey, String resourceKey) {
-        RegistryAccess access = Objects.requireNonNull(registryAccess.get(), "Minecraft registry access");
-        return switch (registryKey) {
-            case BIOME_REGISTRY -> presence(access, Registries.BIOME, registryKey, resourceKey);
-            case STRUCTURE_REGISTRY -> presence(access, Registries.STRUCTURE, registryKey, resourceKey);
-            case DIMENSION_TYPE_REGISTRY -> presence(
-                    access,
-                    Registries.DIMENSION_TYPE,
-                    registryKey,
-                    resourceKey
-            );
-            case BLOCK_REGISTRY -> presence(access, Registries.BLOCK, registryKey, resourceKey);
-            case ENTITY_TYPE_REGISTRY -> presence(access, Registries.ENTITY_TYPE, registryKey, resourceKey);
-            default -> throw new IllegalArgumentException("Unsupported generation registry: " + registryKey);
-        };
-    }
-
-    @Override
-    public Definition canonicalDefinition(String registryKey, String resourceKey, String sourceJson) {
-        RegistryAccess access = Objects.requireNonNull(registryAccess.get(), "Minecraft registry access");
-        return switch (registryKey) {
-            case BIOME_REGISTRY -> canonicalize(access, Biome.DIRECT_CODEC, sourceJson);
-            case DIMENSION_TYPE_REGISTRY -> canonicalize(access, DimensionType.DIRECT_CODEC, sourceJson);
-            default -> throw new IllegalArgumentException(
-                    "Registry does not accept generated JSON definitions: " + registryKey
-            );
-        };
-    }
-
-    @Override
-    public Definition generatedDefinition(String registryKey, String resourceKey) {
-        RegistryAccess access = Objects.requireNonNull(registryAccess.get(), "Minecraft registry access");
-        return switch (registryKey) {
-            case BIOME_REGISTRY -> exactRegistered(
-                    access,
-                    Registries.BIOME,
-                    Biome.DIRECT_CODEC,
-                    resourceKey
-            );
-            case DIMENSION_TYPE_REGISTRY -> exactRegistered(
-                    access,
-                    Registries.DIMENSION_TYPE,
-                    DimensionType.DIRECT_CODEC,
-                    resourceKey
-            );
-            default -> throw new IllegalArgumentException(
-                    "Registry does not contain Iris-generated definitions: " + registryKey
-            );
-        };
-    }
-
-    private static <T> Definition presence(
-            RegistryAccess access,
-            ResourceKey<? extends Registry<T>> registryKey,
-            String registryResourceKey,
-            String resourceKey
-    ) {
-        Registry<T> registry = access.lookupOrThrow(registryKey);
-        Identifier identifier = requireIdentifier(resourceKey);
-        T value = registry.getValue(identifier);
-        if (value == null) {
-            throw new IllegalStateException("Missing registry definition " + registryKey.identifier()
-                    + " / " + resourceKey + ".");
-        }
-        return Definition.resourceIdentity(registryResourceKey, resourceKey);
-    }
-
-    private static <T> Definition canonicalize(RegistryAccess access, Codec<T> codec, String sourceJson) {
-        RegistryOps<JsonElement> ops = RegistryOps.create(JsonOps.INSTANCE, access);
-        JsonElement source = JsonParser.parseString(Objects.requireNonNull(sourceJson, "sourceJson"));
-        T decoded = codec.parse(ops, source).getOrThrow(IllegalArgumentException::new);
-        JsonElement encoded = codec.encodeStart(ops, decoded).getOrThrow(IllegalStateException::new);
-        return Definition.exactJson(encoded.toString());
-    }
-
-    private static <T> Definition exactRegistered(
-            RegistryAccess access,
-            ResourceKey<? extends Registry<T>> registryKey,
-            Codec<T> codec,
-            String resourceKey
-    ) {
-        Registry<T> registry = access.lookupOrThrow(registryKey);
-        Identifier identifier = requireIdentifier(resourceKey);
-        T value = registry.getValue(identifier);
-        if (value == null) {
-            throw new IllegalStateException("Missing generated registry definition "
-                    + registryKey.identifier() + " / " + resourceKey + ".");
-        }
-        RegistryOps<JsonElement> ops = RegistryOps.create(JsonOps.INSTANCE, access);
-        JsonElement encoded = codec.encodeStart(ops, value).getOrThrow(IllegalStateException::new);
-        return Definition.exactJson(encoded.toString());
-    }
-
-    private static Identifier requireIdentifier(String resourceKey) {
-        Identifier identifier = Identifier.tryParse(resourceKey);
-        if (identifier == null) {
-            throw new IllegalArgumentException("Invalid registry resource key: " + resourceKey);
-        }
-        return identifier;
-    }
-
-    private static String requireText(String value, String label) {
-        String required = Objects.requireNonNull(value, label).trim();
-        if (required.isEmpty()) {
-            throw new IllegalArgumentException(label + " must not be blank.");
-        }
-        return required;
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsSavedTerrainCapture.java

@@ -1,266 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.world.history.NativeTerrainReceipt;
-import art.arcane.iris.world.history.SavedTerrainChunk;
-import art.arcane.iris.world.task.J;
-import ca.spottedleaf.concurrentutil.completable.Completable;
-import ca.spottedleaf.concurrentutil.executor.PrioritisedExecutor;
-import ca.spottedleaf.concurrentutil.util.Priority;
-import ca.spottedleaf.moonrise.common.PlatformHooks;
-import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
-import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
-import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.NewChunkHolder;
-import net.minecraft.core.registries.BuiltInRegistries;
-import net.minecraft.nbt.CompoundTag;
-import net.minecraft.nbt.NbtIo;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.level.ChunkPos;
-import net.minecraft.world.level.chunk.ChunkAccess;
-import net.minecraft.world.level.chunk.storage.SerializableChunkData;
-import org.bukkit.World;
-import org.bukkit.craftbukkit.CraftWorld;
-
-import java.io.ByteArrayOutputStream;
-import java.io.DataOutputStream;
-import java.io.IOException;
-import java.nio.file.Path;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.CompletionException;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
-import java.util.concurrent.locks.LockSupport;
-
-final class NmsSavedTerrainCapture {
-    private static final long WRITE_TIMEOUT_NANOS = TimeUnit.SECONDS.toNanos(30L);
-    private static final int SNAPSHOT_BATCH_SIZE = 64;
-
-    private NmsSavedTerrainCapture() {
-    }
-
-    static CompletableFuture<SavedTerrainChunk> capture(World world, int chunkX, int chunkZ, int minimumY, int height) {
-        ServerLevel level = ((CraftWorld) world).getHandle();
-        CompletableFuture<CapturedChunk> snapshot = new CompletableFuture<>();
-        J.runRegionFuture(world, chunkX, chunkZ, () -> {
-            try {
-                NewChunkHolder holder = level.moonrise$getChunkTaskScheduler().chunkHolderManager.getChunkHolder(chunkX, chunkZ);
-                ChunkAccess chunk = holder == null ? null : holder.getCurrentChunk();
-                if (chunk == null) {
-                    snapshot.complete(new CapturedChunk(new ChunkPos(chunkX, chunkZ), CompletableFuture.completedFuture(null)));
-                    return;
-                }
-                String status = BuiltInRegistries.CHUNK_STATUS.getKey(chunk.getPersistedStatus()).toString();
-                if (!SavedTerrainChunk.hasTerrain(status)) {
-                    throw new IOException("Native chunk " + chunkX + "," + chunkZ + " has no completed terrain at " + status);
-                }
-                snapshot.complete(scheduleSnapshot(level, chunk));
-            } catch (Throwable failure) {
-                snapshot.completeExceptionally(failure);
-            }
-        }).whenComplete((ignored, failure) -> {
-            if (failure != null) {
-                snapshot.completeExceptionally(failure);
-            }
-        });
-        return snapshot.thenApplyAsync(captured -> {
-            try {
-                long deadline = System.nanoTime() + WRITE_TIMEOUT_NANOS;
-                CompoundTag data = awaitSnapshot(level, captured, deadline);
-                Checkpoint checkpoint = checkpoint(chunkX, chunkZ, data);
-                awaitWrite(level, checkpoint.chunk(), deadline);
-                if (data == null) {
-                    return SavedTerrainChunk.read(world.getWorldFolder().toPath(), chunkX, chunkZ, minimumY, height);
-                }
-                verifyCheckpoint(world.getWorldFolder().toPath(), checkpoint);
-                ByteArrayOutputStream bytes = new ByteArrayOutputStream();
-                try (DataOutputStream output = new DataOutputStream(bytes)) {
-                    NbtIo.write(data, output);
-                }
-                return SavedTerrainChunk.readNbt(bytes.toByteArray(), chunkX, chunkZ, minimumY, height);
-            } catch (IOException failure) {
-                throw new CompletionException(failure);
-            }
-        });
-    }
-
-    static CompletableFuture<Void> flush(World world) {
-        ServerLevel level = ((CraftWorld) world).getHandle();
-        List<NewChunkHolder> holders = level.moonrise$getChunkTaskScheduler().chunkHolderManager.getChunkHolders();
-        return CompletableFuture.runAsync(() -> {
-            try {
-                flushSnapshots(world, level, holders);
-            } catch (IOException failure) {
-                throw new CompletionException(failure);
-            }
-        });
-    }
-
-    static void flushSnapshots(World world, ServerLevel level, List<NewChunkHolder> holders) throws IOException {
-        long deadline = System.nanoTime() + WRITE_TIMEOUT_NANOS;
-        List<Checkpoint> checkpoints = new ArrayList<>(holders.size());
-        for (int offset = 0; offset < holders.size(); offset += SNAPSHOT_BATCH_SIZE) {
-            int end = Math.min(holders.size(), offset + SNAPSHOT_BATCH_SIZE);
-            List<CompletableFuture<CapturedChunk>> snapshots = requestSnapshots(world, level, holders.subList(offset, end));
-            awaitSnapshots(snapshots, deadline);
-            for (CompletableFuture<CapturedChunk> future : snapshots) {
-                CapturedChunk captured = future.join();
-                CompoundTag data = awaitSnapshot(level, captured, deadline);
-                checkpoints.add(checkpoint(captured.chunk().x(), captured.chunk().z(), data));
-            }
-            for (int index = offset; index < end; index++) {
-                awaitWrite(level, checkpoints.get(index).chunk(), deadline);
-            }
-        }
-        finishCheckpoint(level, world.getWorldFolder().toPath(), checkpoints);
-    }
-
-    private static List<CompletableFuture<CapturedChunk>> requestSnapshots(
-            World world, ServerLevel level, List<NewChunkHolder> holders) {
-        List<CompletableFuture<CapturedChunk>> snapshots = new ArrayList<>(holders.size());
-        for (NewChunkHolder original : holders) {
-            ChunkPos position = new ChunkPos(original.chunkX, original.chunkZ);
-            CompletableFuture<CapturedChunk> snapshot = new CompletableFuture<>();
-            snapshots.add(snapshot);
-            J.runRegionFuture(world, position.x(), position.z(), () -> {
-                try {
-                    NewChunkHolder holder = level.moonrise$getChunkTaskScheduler().chunkHolderManager
-                            .getChunkHolder(position.x(), position.z());
-                    ChunkAccess chunk = holder == null ? null : holder.getCurrentChunk();
-                    snapshot.complete(chunk != null && chunk.isUnsaved() ? scheduleSnapshot(level, chunk)
-                            : new CapturedChunk(position, CompletableFuture.completedFuture(null)));
-                } catch (Throwable failure) {
-                    snapshot.completeExceptionally(failure);
-                }
-            }).whenComplete((ignored, failure) -> {
-                if (failure != null) {
-                    snapshot.completeExceptionally(failure);
-                }
-            });
-        }
-        return snapshots;
-    }
-
-    private static void awaitSnapshots(List<CompletableFuture<CapturedChunk>> snapshots, long deadlineNanos)
-            throws IOException {
-        try {
-            CompletableFuture.allOf(snapshots.toArray(CompletableFuture[]::new))
-                    .get(Math.max(0L, deadlineNanos - System.nanoTime()), TimeUnit.NANOSECONDS);
-        } catch (InterruptedException failure) {
-            Thread.currentThread().interrupt();
-            throw new IOException("Interrupted while copying terrain checkpoint chunks.", failure);
-        } catch (ExecutionException | TimeoutException failure) {
-            throw new IOException("Unable to copy terrain checkpoint chunks.", failure);
-        }
-    }
-
-    static void finishCheckpoint(ServerLevel level, Path worldFolder, List<Checkpoint> checkpoints) throws IOException {
-        long deadline = System.nanoTime() + WRITE_TIMEOUT_NANOS;
-        for (Checkpoint checkpoint : checkpoints) {
-            awaitWrite(level, checkpoint.chunk(), deadline);
-        }
-        MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA);
-        for (Checkpoint checkpoint : checkpoints) {
-            verifyCheckpoint(worldFolder, checkpoint);
-        }
-    }
-
-    static Checkpoint checkpoint(int chunkX, int chunkZ, CompoundTag data) {
-        if (data == null) {
-            return new Checkpoint(new ChunkPos(chunkX, chunkZ), null);
-        }
-        byte[] receipt = data.getCompound("ChunkBukkitValues")
-                .flatMap(values -> values.getByteArray(NativeTerrainReceipt.NBT_KEY)).orElse(null);
-        long structureActivation = data.getCompound("ChunkBukkitValues").map(values -> values.getLongOr(
-                NativeTerrainReceipt.STRUCTURE_ACTIVATION_KEY, 0)).orElse(0L);
-        return new Checkpoint(new ChunkPos(chunkX, chunkZ), new Verification(
-                data.getStringOr("Status", ""), receipt, structureActivation));
-    }
-
-    private static void verifyCheckpoint(Path worldFolder, Checkpoint checkpoint) throws IOException {
-        Verification expected = checkpoint.verification();
-        if (expected == null) {
-            return;
-        }
-        SavedTerrainChunk.verifyCheckpoint(worldFolder, checkpoint.chunk().x(), checkpoint.chunk().z(),
-                expected.status(), expected.receipt(), expected.structureActivation());
-    }
-
-    static void awaitWrite(ServerLevel level, ChunkPos chunk, long deadlineNanos) throws IOException {
-        ChunkTaskScheduler scheduler = level.moonrise$getChunkTaskScheduler();
-        while (true) {
-            checkWriteWait(chunk, deadlineNanos);
-            if (MoonriseRegionFileIO.getPriority(level, chunk.x(), chunk.z(),
-                    MoonriseRegionFileIO.RegionFileType.CHUNK_DATA) == Priority.COMPLETING) {
-                return;
-            }
-            helpSaveTasks(scheduler);
-        }
-    }
-
-    static CapturedChunk scheduleSnapshot(ServerLevel level, ChunkAccess chunk) {
-        SerializableChunkData snapshot = SerializableChunkData.copyOf(level, chunk);
-        PlatformHooks.get().chunkSyncSave(level, chunk, snapshot);
-        Completable<CompoundTag> nativeData = new Completable<>();
-        CompletableFuture<CompoundTag> data = new CompletableFuture<>();
-        PrioritisedExecutor.PrioritisedTask task = level.moonrise$getChunkTaskScheduler().saveExecutor
-                .createTask(() -> serializeSnapshot(snapshot, nativeData, data));
-        task.queue();
-        ChunkPos position = chunk.getPos();
-        MoonriseRegionFileIO.scheduleSave(level, position.x(), position.z(), nativeData, task,
-                MoonriseRegionFileIO.RegionFileType.CHUNK_DATA, Priority.NORMAL);
-        return new CapturedChunk(position, data);
-    }
-
-    static CompoundTag awaitSnapshot(ServerLevel level, CapturedChunk captured, long deadlineNanos) throws IOException {
-        ChunkTaskScheduler scheduler = level.moonrise$getChunkTaskScheduler();
-        while (!captured.data().isDone()) {
-            checkWriteWait(captured.chunk(), deadlineNanos);
-            helpSaveTasks(scheduler);
-        }
-        try {
-            return captured.data().join();
-        } catch (CompletionException failure) {
-            throw new IOException("Unable to serialize terrain checkpoint chunk " + captured.chunk(), failure.getCause());
-        }
-    }
-
-    private static void serializeSnapshot(SerializableChunkData snapshot, Completable<CompoundTag> nativeData,
-                                          CompletableFuture<CompoundTag> data) {
-        try {
-            CompoundTag serialized = snapshot.write();
-            nativeData.complete(serialized);
-            data.complete(serialized);
-        } catch (Throwable failure) {
-            nativeData.completeExceptionally(failure);
-            data.completeExceptionally(failure);
-        }
-    }
-
-    private static void checkWriteWait(ChunkPos chunk, long deadlineNanos) throws IOException {
-        if (Thread.currentThread().isInterrupted()) {
-            throw new IOException("Interrupted while saving terrain checkpoint chunk " + chunk);
-        }
-        if (System.nanoTime() - deadlineNanos >= 0L) {
-            throw new IOException("Timed out saving terrain checkpoint chunk " + chunk);
-        }
-    }
-
-    private static void helpSaveTasks(ChunkTaskScheduler scheduler) {
-        boolean helped = scheduler.saveExecutor.executeTask();
-        helped |= scheduler.compressionExecutor.executeTask();
-        if (!helped) {
-            LockSupport.parkNanos(1_000_000L);
-        }
-    }
-
-    record CapturedChunk(ChunkPos chunk, CompletableFuture<CompoundTag> data) {
-    }
-
-    record Checkpoint(ChunkPos chunk, Verification verification) {
-    }
-
-    record Verification(String status, byte[] receipt, long structureActivation) {
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsWorldLifecycle.java

@@ -1,403 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.platform.bukkit.nms.ServerShutdownBoundary;
-import art.arcane.iris.spi.IrisLogging;
-import art.arcane.iris.localization.C;
-import art.arcane.iris.platform.agent.Agent;
-import net.bytebuddy.agent.builder.AgentBuilder;
-import net.bytebuddy.agent.builder.ResettableClassFileTransformer;
-import net.bytebuddy.asm.Advice;
-import net.bytebuddy.description.type.TypeDescription;
-import net.bytebuddy.dynamic.DynamicType;
-import net.bytebuddy.matcher.ElementMatchers;
-import net.bytebuddy.utility.JavaModule;
-import net.minecraft.core.registries.Registries;
-import net.minecraft.resources.Identifier;
-import net.minecraft.resources.ResourceKey;
-import net.minecraft.server.MinecraftServer;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.level.Level;
-import net.minecraft.world.level.dimension.LevelStem;
-import net.minecraft.world.level.storage.LevelStorageSource;
-import org.bukkit.Bukkit;
-import org.bukkit.craftbukkit.CraftServer;
-import org.bukkit.generator.ChunkGenerator;
-import org.bukkit.plugin.Plugin;
-
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-import java.nio.file.Path;
-import java.util.concurrent.atomic.AtomicBoolean;
-
-final class NmsWorldLifecycle {
-    private final AtomicBoolean injected = new AtomicBoolean();
-    private volatile ResettableClassFileTransformer levelStorageAccessTransformer;
-    private volatile ResettableClassFileTransformer serverLevelTransformer;
-    private volatile ResettableClassFileTransformer pluginClassLoaderTransformer;
-    private boolean pluginClassLoaderCloseDeferred;
-
-    public boolean injectBukkit() {
-        synchronized (injected) {
-            if (injected.get()) {
-                return true;
-            }
-            try {
-                IrisLogging.info("Injecting Bukkit");
-                Agent.requireClassLoaderCloseDeferral();
-                Class<?> loaderCloseType = getClass().getClassLoader().getClass()
-                        .getMethod("close").getDeclaringClass();
-                PluginClassLoaderInjectionListener loaderListener = new PluginClassLoaderInjectionListener();
-                pluginClassLoaderTransformer = new AgentBuilder.Default()
-                        .disableClassFormatChanges()
-                        .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
-                        .with(AgentBuilder.RedefinitionStrategy.Listener.ErrorEscalating.FAIL_FAST)
-                        .with(loaderListener)
-                        .type(ElementMatchers.is(loaderCloseType))
-                        .transform((builder, typeDescription, classLoader, module, protectionDomain) ->
-                                builder.visit(Advice.to(PluginClassLoaderCloseAdvice.class)
-                                        .on(ElementMatchers.named("close")
-                                                .and(ElementMatchers.takesArguments(0))
-                                                .and(ElementMatchers.returns(void.class)))))
-                        .installOn(Agent.getInstrumentation());
-                loaderListener.requireInstalled();
-                levelStorageAccessTransformer = new AgentBuilder.Default()
-                        .disableClassFormatChanges()
-                        .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
-                        .type(ElementMatchers.is(LevelStorageSource.LevelStorageAccess.class))
-                        .transform((builder, typeDescription, classLoader, module, protectionDomain) ->
-                                builder.visit(Advice.to(LevelStorageAccessAdvice.class).on(ElementMatchers.isConstructor()
-                                        .and(ElementMatchers.takesArguments(4))
-                                        .and(ElementMatchers.takesArgument(0, LevelStorageSource.class))
-                                        .and(ElementMatchers.takesArgument(1, String.class))
-                                        .and(ElementMatchers.takesArgument(2, Path.class))
-                                        .and(ElementMatchers.takesArgument(3, ResourceKey.class)))))
-                        .installOn(Agent.getInstrumentation());
-                serverLevelTransformer = new AgentBuilder.Default()
-                        .disableClassFormatChanges()
-                        .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
-                        .type(ElementMatchers.is(ServerLevel.class))
-                        .transform((builder, typeDescription, classLoader, module, protectionDomain) ->
-                                builder.visit(Advice.to(ServerLevelAdvice.class).on(ElementMatchers.isConstructor()
-                                        .and(ElementMatchers.takesArgument(0, MinecraftServer.class))
-                                        .and(ElementMatchers.takesArgument(5, LevelStem.class)))))
-                        .installOn(Agent.getInstrumentation());
-                NmsGenerationHooks.install();
-
-                injected.set(true);
-                return true;
-            } catch (Throwable e) {
-                IrisLogging.reportError(C.RED + "Failed to inject Bukkit", e);
-                ResettableClassFileTransformer partialServerLevel = serverLevelTransformer;
-                ResettableClassFileTransformer partialStorageAccess = levelStorageAccessTransformer;
-                ResettableClassFileTransformer partialPluginClassLoader = pluginClassLoaderTransformer;
-                serverLevelTransformer = null;
-                levelStorageAccessTransformer = null;
-                pluginClassLoaderTransformer = null;
-                for (ResettableClassFileTransformer partial : new ResettableClassFileTransformer[]{
-                        partialServerLevel,
-                        partialStorageAccess,
-                        partialPluginClassLoader
-                }) {
-                    if (partial == null) {
-                        continue;
-                    }
-                    try {
-                        partial.reset(Agent.getInstrumentation(), AgentBuilder.RedefinitionStrategy.RETRANSFORMATION);
-                    } catch (Throwable cleanupFailure) {
-                        IrisLogging.reportError("Failed to remove partial Bukkit lifecycle injection", cleanupFailure);
-                    }
-                }
-                return false;
-            }
-        }
-    }
-
-    public void ensureServerLevelInjection() {
-        if (!injected.get()) {
-            throw new IllegalStateException("Iris world lifecycle injection is unavailable. Fix the Java Agent or Code Injection startup failure and restart before creating worlds.");
-        }
-        try {
-            Agent.getInstrumentation().retransformClasses(
-                    LevelStorageSource.LevelStorageAccess.class,
-                    ServerLevel.class
-            );
-        } catch (Throwable e) {
-            throw new IllegalStateException("Failed to re-apply Bukkit world lifecycle injection. World creation was stopped before loading the world.", e);
-        }
-    }
-
-    public void uninjectBukkit() {
-        synchronized (injected) {
-            ResettableClassFileTransformer activeServerLevel = serverLevelTransformer;
-            ResettableClassFileTransformer activeStorageAccess = levelStorageAccessTransformer;
-            serverLevelTransformer = null;
-            levelStorageAccessTransformer = null;
-            injected.set(false);
-            for (ResettableClassFileTransformer transformer : new ResettableClassFileTransformer[]{
-                    activeServerLevel,
-                    activeStorageAccess
-            }) {
-                if (transformer == null) {
-                    continue;
-                }
-                try {
-                    transformer.reset(Agent.getInstrumentation(), AgentBuilder.RedefinitionStrategy.RETRANSFORMATION);
-                } catch (Throwable e) {
-                    IrisLogging.reportError(C.RED + "Failed to remove Bukkit world lifecycle injection", e);
-                }
-            }
-        }
-    }
-
-    public boolean isServerStopping() {
-        return ((CraftServer) Bukkit.getServer()).getServer().hasStopped();
-    }
-
-    public ServerShutdownBoundary createServerShutdownBoundary() {
-        MinecraftServer server = ((CraftServer) Bukkit.getServer()).getServer();
-        return new ServerShutdownBoundary(
-                () -> server.hasFullyShutdown,
-                server.getRunningThread()
-        );
-    }
-
-    public void deferPluginClassLoaderClose() {
-        synchronized (injected) {
-            if (pluginClassLoaderTransformer == null || pluginClassLoaderCloseDeferred) {
-                return;
-            }
-            Agent.retainClassLoader(getClass().getClassLoader());
-            pluginClassLoaderCloseDeferred = true;
-        }
-    }
-
-    public void releasePluginClassLoaderClose() {
-        ResettableClassFileTransformer transformer;
-        boolean releaseLoader;
-        synchronized (injected) {
-            transformer = pluginClassLoaderTransformer;
-            pluginClassLoaderTransformer = null;
-            releaseLoader = pluginClassLoaderCloseDeferred;
-            pluginClassLoaderCloseDeferred = false;
-        }
-        try {
-            if (transformer != null
-                    && !transformer.reset(Agent.getInstrumentation(), AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)) {
-                throw new IllegalStateException("Failed to remove Iris plugin class loader lifecycle injection");
-            }
-        } finally {
-            if (releaseLoader) {
-                Agent.releaseClassLoader(getClass().getClassLoader());
-            }
-        }
-    }
-
-    private static final class PluginClassLoaderInjectionListener extends AgentBuilder.Listener.Adapter {
-        private volatile boolean transformed;
-        private volatile Throwable failure;
-
-        @Override
-        public void onTransformation(TypeDescription type, ClassLoader loader, JavaModule module,
-                                     boolean loaded, DynamicType dynamicType) {
-            transformed = true;
-        }
-
-        @Override
-        public void onError(String typeName, ClassLoader loader, JavaModule module,
-                            boolean loaded, Throwable throwable) {
-            failure = throwable;
-        }
-
-        private void requireInstalled() {
-            if (!transformed || failure != null) {
-                throw new IllegalStateException("Iris plugin class loader lifecycle injection failed", failure);
-            }
-        }
-    }
-
-    private static class PluginClassLoaderCloseAdvice {
-        @Advice.OnMethodEnter(skipOn = Advice.OnNonDefaultValue.class)
-        static boolean enter(@Advice.This ClassLoader loader) throws ReflectiveOperationException {
-            Class<?> installer = Class.forName(
-                    "art.arcane.iris.platform.agent.Installer", true, ClassLoader.getSystemClassLoader());
-            return Boolean.TRUE.equals(installer.getMethod("deferClassLoaderClose", ClassLoader.class)
-                    .invoke(null, loader));
-        }
-    }
-
-    private static class LevelStorageAccessAdvice {
-        @Advice.OnMethodEnter
-        static void enter(
-                @Advice.Argument(1) String levelId,
-                @Advice.Argument(value = 3, readOnly = false) ResourceKey<LevelStem> dimensionType
-        ) {
-            if (levelId == null || levelId.isBlank()) {
-                return;
-            }
-
-            ClassLoader pluginClassLoader;
-            Class<?> generatorType;
-            Class<?> stagingType;
-            try {
-                Plugin irisPlugin = Bukkit.getPluginManager().getPlugin("Iris");
-                if (irisPlugin == null) {
-                    return;
-                }
-                pluginClassLoader = irisPlugin.getClass().getClassLoader();
-                generatorType = Class.forName("art.arcane.iris.platform.generation.PlatformChunkGenerator", true, pluginClassLoader);
-                stagingType = Class.forName("art.arcane.iris.world.lifecycle.WorldLifecycleStaging", true, pluginClassLoader);
-            } catch (Throwable ignored) {
-                return;
-            }
-
-            Object generator;
-            try {
-                generator = stagingType
-                        .getDeclaredMethod("peekStemGenerator", String.class)
-                        .invoke(null, levelId);
-            } catch (Throwable e) {
-                throw new RuntimeException("Iris failed to inspect the staged world generator",
-                        e instanceof InvocationTargetException ex ? ex.getCause() : e);
-            }
-            if (generator == null || !generatorType.isInstance(generator)) {
-                return;
-            }
-
-            try {
-                Object target = generatorType.getMethod("getTarget").invoke(generator);
-                if (target == null) {
-                    throw new IllegalStateException("Iris generator has no engine target.");
-                }
-                Object world = target.getClass().getMethod("getWorld").invoke(target);
-                if (world == null) {
-                    throw new IllegalStateException("Iris generator target has no world identity.");
-                }
-                Object rawIdentity = world.getClass().getMethod("identity").invoke(world);
-                String worldIdentity = rawIdentity == null ? "" : rawIdentity.toString().trim();
-                Identifier worldIdentifier = Identifier.parse(worldIdentity);
-                if (!"iris".equals(worldIdentifier.getNamespace())
-                        && !"minecraft".equals(worldIdentifier.getNamespace())) {
-                    throw new IllegalStateException(
-                            "Iris generator has an unmanaged world identity: " + worldIdentity);
-                }
-                dimensionType = ResourceKey.create(Registries.LEVEL_STEM, worldIdentifier);
-            } catch (Throwable e) {
-                throw new RuntimeException("Iris failed to bind the staged world storage identity",
-                        e instanceof InvocationTargetException ex ? ex.getCause() : e);
-            }
-        }
-    }
-
-    private static class ServerLevelAdvice {
-        @Advice.OnMethodEnter
-        static void enter(
-                @Advice.Argument(0) MinecraftServer server,
-                @Advice.Argument(value = 4, readOnly = false) ResourceKey<Level> dimensionKey,
-                @Advice.Argument(value = 5, readOnly = false) LevelStem levelStem,
-                @Advice.AllArguments Object[] constructorArguments
-        ) {
-            if (dimensionKey == null)
-                return;
-
-            // This advice is inlined into every ServerLevel construction on the server. Until a
-            // world is proven Iris-owned, every failure must fail OPEN (keep the vanilla stem):
-            // Iris being unloaded or half-loaded must never break other plugins' world creation.
-            String levelId;
-            ClassLoader pluginClassLoader;
-            Class<?> generatorType;
-            Class<?> stagingType;
-            try {
-                levelId = dimensionKey.identifier().getPath();
-                if (levelId == null || levelId.isBlank()) {
-                    return;
-                }
-
-                Plugin irisPlugin = Bukkit.getPluginManager().getPlugin("Iris");
-                if (irisPlugin == null) {
-                    return;
-                }
-                pluginClassLoader = irisPlugin.getClass().getClassLoader();
-                generatorType = Class.forName("art.arcane.iris.platform.generation.PlatformChunkGenerator", true, pluginClassLoader);
-                stagingType = Class.forName("art.arcane.iris.world.lifecycle.WorldLifecycleStaging", true, pluginClassLoader);
-            } catch (Throwable ignored) {
-                // Iris absent or half-loaded: fail OPEN for a world we cannot prove ours.
-                return;
-            }
-
-            // From here Iris is present and its classes resolve; a failure resolving the
-            // staged generator must fail LOUD — silently handing a possibly-staged Iris world
-            // the vanilla stem corrupts generation.
-            ChunkGenerator gen = null;
-            try {
-                ChunkGenerator constructorGenerator = null;
-                for (Object argument : constructorArguments) {
-                    if (argument instanceof ChunkGenerator candidate) {
-                        constructorGenerator = candidate;
-                        break;
-                    }
-                }
-                Object generator = generatorType.isInstance(constructorGenerator) ? constructorGenerator : null;
-                if (generator == null) {
-                    generator = stagingType
-                            .getDeclaredMethod("consumeStemGenerator", String.class)
-                            .invoke(null, levelId);
-                }
-                if (generator instanceof ChunkGenerator owned && owned.getClass().getPackageName().startsWith("art.arcane.iris")) {
-                    gen = owned;
-                }
-            } catch (Throwable e) {
-                throw new RuntimeException("Iris failed to resolve the staged world generator",
-                        e instanceof InvocationTargetException ex ? ex.getCause() : e);
-            }
-            if (gen == null) {
-                return;
-            }
-
-            // Past the ownership gate the world is Iris-owned; silently handing back the
-            // vanilla stem would corrupt generation, so failures from here rethrow.
-            try {
-                Object bindings = Class.forName("art.arcane.iris.platform.bukkit.nms.INMS", true, pluginClassLoader)
-                        .getDeclaredMethod("get")
-                        .invoke(null);
-                if (bindings == null) {
-                    throw new IllegalStateException("Iris failed to resolve an INMSBinding instance.");
-                }
-
-                Method stemMethod = null;
-                for (Method candidate : bindings.getClass().getMethods()) {
-                    if (candidate.getName().equals("createRuntimeLevelStem") && candidate.getParameterCount() == 2) {
-                        stemMethod = candidate;
-                        break;
-                    }
-                }
-                if (stemMethod == null) {
-                    throw new IllegalStateException("Iris binding is missing createRuntimeLevelStem.");
-                }
-                Object target = generatorType.getMethod("getTarget").invoke(gen);
-                if (target == null) {
-                    throw new IllegalStateException("Iris generator has no engine target.");
-                }
-                Object world = target.getClass().getMethod("getWorld").invoke(target);
-                if (world == null) {
-                    throw new IllegalStateException("Iris generator target has no world identity.");
-                }
-                Object rawIdentity = world.getClass().getMethod("identity").invoke(world);
-                String worldIdentity = rawIdentity == null ? "" : rawIdentity.toString().trim();
-                Identifier worldIdentifier = Identifier.parse(worldIdentity);
-                if (!"iris".equals(worldIdentifier.getNamespace())
-                        && !"minecraft".equals(worldIdentifier.getNamespace())) {
-                    throw new IllegalStateException(
-                            "Iris generator has an unmanaged world identity: " + worldIdentity);
-                }
-                Object resolvedStem = stemMethod.invoke(bindings, server.registryAccess(), gen);
-                if (!(resolvedStem instanceof LevelStem runtimeStem)) {
-                    throw new IllegalStateException("Iris runtime LevelStem binding returned " + (resolvedStem == null ? "null" : resolvedStem.getClass().getName()) + ".");
-                }
-                dimensionKey = ResourceKey.create(Registries.DIMENSION, worldIdentifier);
-                levelStem = runtimeStem;
-            } catch (Throwable e) {
-                throw new RuntimeException("Iris failed to replace the levelStem", e instanceof InvocationTargetException ex ? ex.getCause() : e);
-            }
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/main/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/VanillaStructureBiomes.java

@@ -1,80 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.nativegen.NativeStructureGenerationKeys;
-import net.minecraft.core.Holder;
-import net.minecraft.core.Registry;
-import net.minecraft.core.RegistryAccess;
-import net.minecraft.core.registries.Registries;
-import net.minecraft.resources.Identifier;
-import net.minecraft.resources.ResourceKey;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.level.biome.Biome;
-import net.minecraft.world.level.biome.BiomeSource;
-import net.minecraft.world.level.levelgen.structure.Structure;
-
-import java.util.LinkedHashSet;
-import java.util.Optional;
-import java.util.Set;
-
-final class VanillaStructureBiomes {
-    private VanillaStructureBiomes() {
-    }
-
-    static Set<String> possibleBiomeKeys(BiomeSource source) {
-        if (source == null) {
-            throw new IllegalStateException("Minecraft chunk generator has no biome source");
-        }
-        Set<String> keys = new LinkedHashSet<>();
-        Set<Holder<Biome>> possibleBiomes = source instanceof CustomBiomeSource customBiomeSource
-                ? customBiomeSource.possibleStructureBiomes()
-                : source.possibleBiomes();
-        for (Holder<Biome> holder : possibleBiomes) {
-            Optional<ResourceKey<Biome>> key = holder.unwrapKey();
-            if (key.isPresent()) {
-                keys.add(key.get().identifier().toString());
-            }
-        }
-        if (keys.isEmpty()) {
-            throw new IllegalStateException("Minecraft biome source exposes no registered possible biomes");
-        }
-        return keys;
-    }
-
-    static Set<String> structureBiomeKeys(RegistryAccess access, String structureKey) {
-        if (access == null) {
-            throw new IllegalStateException("Minecraft registry access is unavailable");
-        }
-        if (structureKey == null || structureKey.isBlank()) {
-            throw new IllegalArgumentException("Registered structure key must not be blank");
-        }
-        Set<String> keys = new LinkedHashSet<>();
-        Registry<Structure> registry = access.lookupOrThrow(Registries.STRUCTURE);
-        Structure structure = registry.getValue(Identifier.parse(structureKey));
-        if (structure == null) {
-            throw new IllegalArgumentException("Registered structure does not exist: " + structureKey);
-        }
-        boolean hasFilterEntries = false;
-        for (Holder<Biome> holder : structure.biomes()) {
-            hasFilterEntries = true;
-            Optional<ResourceKey<Biome>> key = holder.unwrapKey();
-            if (key.isPresent()) {
-                keys.add(key.get().identifier().toString());
-            }
-        }
-        // An empty biome filter is legal datapack content (opt-in structures whose tags only
-        // reference absent modded biomes); the structure is unreachable, not an error state.
-        if (keys.isEmpty() && hasFilterEntries) {
-            throw new IllegalStateException("Registered structure '" + structureKey
-                    + "' has biome filter entries but none resolve to registered biome keys");
-        }
-        return keys;
-    }
-
-    static Set<String> reachableStructureKeys(ServerLevel level, BiomeSource source) {
-        if (level == null) {
-            throw new IllegalStateException("Minecraft server level is unavailable");
-        }
-        Set<String> possible = possibleBiomeKeys(source);
-        return NativeStructureGenerationKeys.reachable(level, possible);
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/IrisChunkGeneratorHeightCacheTest.java

@@ -1,12 +1,15 @@
 package art.arcane.iris.nativegen;
 
-import art.arcane.iris.platform.bukkit.nms.v26_2_R1.IrisChunkGenerator;
-import art.arcane.iris.generation.runtime.IrisComplex;
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeChunkGenerator;
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeTerrainColumns;
+import art.arcane.iris.platform.bukkit.nms.BukkitTerrainColumnPolicy;
+
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.generation.runtime.GenerationSessionLease;
 import art.arcane.iris.world.history.BoundaryColumnGeometry;
 import art.arcane.iris.world.history.TerrainBoundarySignature;
 import art.arcane.iris.testsupport.PlatformLeakGuard;
+import art.arcane.volmlib.nativelib.terrain.NativeTerrainColumnPolicy;
 import net.minecraft.SharedConstants;
 import net.minecraft.server.Bootstrap;
 import net.minecraft.world.level.LevelHeightAccessor;
@@ -21,7 +24,7 @@ import java.util.Optional;
 import java.util.OptionalInt;
 
 import static org.junit.Assert.assertEquals;
-import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.CALLS_REAL_METHODS;
 import static org.mockito.Mockito.mock;
@@ -29,6 +32,7 @@ import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
+import static org.mockito.Mockito.never;
 
 public final class IrisChunkGeneratorHeightCacheTest {
     @Rule
@@ -41,73 +45,76 @@ public final class IrisChunkGeneratorHeightCacheTest {
     }
 
     @Test
-    public void repeatedNativeHeightSurvivesResolvedTerrainEvictionAndRuntimeChange() throws Exception {
+    public void repeatedNativeHeightUsesLiveHeightQueriesAcrossRuntimeChanges() throws Exception {
         Fixture fixture = fixture();
         LevelHeightAccessor bounds = LevelHeightAccessor.create(-16, 32);
-        assertEquals(-11, fixture.generator().getBaseHeight(-1, -33, Heightmap.Types.WORLD_SURFACE, bounds, null));
-        when(fixture.complex().resolvedTerrainColumn(-1, -33))
-                .thenThrow(new IllegalStateException("Full terrain was evicted"));
-
+        when(fixture.engine().getHeight(-1, -33, false)).thenReturn(4);
         for (int index = 0; index < 100; index++) {
             assertEquals(-11, fixture.generator().getBaseHeight(
                     -1, -33, Heightmap.Types.WORLD_SURFACE, bounds, null));
         }
-        verify(fixture.complex(), times(1)).resolvedTerrainColumn(-1, -33);
+        verify(fixture.engine(), times(100)).getHeight(-1, -33, false);
 
         when(fixture.engine().getCacheID()).thenReturn(2);
-        doReturn(Optional.of(signature())).when(fixture.complex()).resolvedTerrainColumn(-1, -33);
-        assertEquals(-11, fixture.generator().getBaseHeight(-1, -33, Heightmap.Types.WORLD_SURFACE, bounds, null));
-        verify(fixture.complex(), times(2)).resolvedTerrainColumn(-1, -33);
+        when(fixture.engine().getHeight(-1, -33, false)).thenReturn(7);
+        assertEquals(-8, fixture.generator().getBaseHeight(-1, -33, Heightmap.Types.WORLD_SURFACE, bounds, null));
+        verify(fixture.engine(), never()).getComplex();
+        verify(fixture.engine(), never()).getMode();
     }
 
     @Test
-    public void ordinaryHeightRemainsLiveUntilResolvedTransitionTerrainExists() throws Exception {
+    public void nativeHeightPredicatesSelectFluidOrSolidHeightWithoutGeneratingTerrain() throws Exception {
         Fixture fixture = fixture();
         LevelHeightAccessor bounds = LevelHeightAccessor.create(-16, 32);
-        when(fixture.complex().resolvedTerrainColumn(0, 0))
-                .thenReturn(Optional.empty(), Optional.empty(), Optional.of(signature()));
         when(fixture.engine().getHeight(0, 0, false)).thenReturn(20, 25);
+        when(fixture.engine().getHeight(0, 0, true)).thenReturn(8);
 
         assertEquals(5, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
         assertEquals(10, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
-        assertEquals(-11, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
-        assertEquals(-11, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
+        assertEquals(-7, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.OCEAN_FLOOR, bounds, null));
         verify(fixture.engine(), times(2)).getHeight(0, 0, false);
-        verify(fixture.complex(), times(3)).resolvedTerrainColumn(0, 0);
+        verify(fixture.engine(), times(1)).getHeight(0, 0, true);
+        verify(fixture.engine(), never()).getComplex();
+        verify(fixture.engine(), never()).getMode();
     }
 
     @Test
     public void nativePredicatesAndAccessorBoundsRemainExact() throws Exception {
-        Fixture fixture = fixture();
+        NativeTerrainColumnPolicy policy = mock(NativeTerrainColumnPolicy.class);
+        NativeTerrainColumnPolicy.ColumnSession session = mock(NativeTerrainColumnPolicy.ColumnSession.class);
+        when(policy.openQuery(any())).thenReturn(session);
+        when(policy.placementKey(anyString())).thenAnswer(invocation -> invocation.getArgument(0));
+        doReturn(Optional.of(signature().geometry())).when(session).resolvedColumn();
+        NativeChunkGenerator<?, ?, ?, ?, ?> generator = generator(policy);
         LevelHeightAccessor bounds = LevelHeightAccessor.create(-16, 32);
         for (int repeat = 0; repeat < 2; repeat++) {
-            assertEquals(-11, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
-            assertEquals(-13, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.OCEAN_FLOOR, bounds, null));
-            assertEquals(-13, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING, bounds, null));
-            assertEquals(-14, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, bounds, null));
-            assertEquals(-14, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE,
+            assertEquals(-11, generator.getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
+            assertEquals(-13, generator.getBaseHeight(0, 0, Heightmap.Types.OCEAN_FLOOR, bounds, null));
+            assertEquals(-13, generator.getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING, bounds, null));
+            assertEquals(-14, generator.getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, bounds, null));
+            assertEquals(-14, generator.getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE,
                     LevelHeightAccessor.create(-16, 2), null));
-            assertEquals(-14, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES,
+            assertEquals(-14, generator.getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES,
                     LevelHeightAccessor.create(-14, 3), null));
         }
-        verify(fixture.complex(), times(6)).resolvedTerrainColumn(0, 0);
+        verify(session, times(6)).resolvedColumn();
     }
 
     private static Fixture fixture() throws Exception {
         Engine engine = mock(Engine.class);
-        IrisComplex complex = mock(IrisComplex.class);
-        when(engine.getComplex()).thenReturn(complex);
         when(engine.getCacheID()).thenReturn(1);
         when(engine.acquireGenerationLease(anyString())).thenReturn(GenerationSessionLease.noop());
-        when(complex.resolvedTerrainColumn(anyInt(), anyInt())).thenReturn(Optional.of(signature()));
-        IrisChunkGenerator generator = mock(IrisChunkGenerator.class, CALLS_REAL_METHODS);
-        set(generator, "engine", engine);
-        set(generator, "terrainHeights", new NativeTerrainHeightCache());
-        return new Fixture(generator, engine, complex);
+        return new Fixture(generator(new BukkitTerrainColumnPolicy(engine, null)), engine);
     }
 
-    private static void set(IrisChunkGenerator generator, String name, Object value) throws Exception {
-        Field field = IrisChunkGenerator.class.getDeclaredField(name);
+    private static NativeChunkGenerator<?, ?, ?, ?, ?> generator(NativeTerrainColumnPolicy policy) throws Exception {
+        NativeChunkGenerator<?, ?, ?, ?, ?> generator = mock(NativeChunkGenerator.class, CALLS_REAL_METHODS);
+        set(generator, "terrainColumns", new NativeTerrainColumns(policy));
+        return generator;
+    }
+
+    private static void set(NativeChunkGenerator<?, ?, ?, ?, ?> generator, String name, Object value) throws Exception {
+        Field field = NativeChunkGenerator.class.getDeclaredField(name);
         field.setAccessible(true);
         field.set(generator, value);
     }
@@ -125,6 +132,6 @@ public final class IrisChunkGeneratorHeightCacheTest {
                         new TerrainBoundarySignature.BiomeEncoding(List.of("minecraft:plains"), new short[]{0})), geometry);
     }
 
-    private record Fixture(IrisChunkGenerator generator, Engine engine, IrisComplex complex) {
+    private record Fixture(NativeChunkGenerator<?, ?, ?, ?, ?> generator, Engine engine) {
     }
 }

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeGenerationWriteGuardTest.java

@@ -1,5 +1,9 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.iris.structure.nativegen.GenerationWritePolicy;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeGenerationWriteGuard;
+
 import art.arcane.iris.generation.runtime.DimensionStackContext;
 import art.arcane.iris.generation.runtime.DimensionStackLayout;
 import art.arcane.iris.generation.runtime.IrisComplex;
@@ -45,11 +49,11 @@ public final class NativeGenerationWriteGuardTest {
         DimensionStackContext stack = mock(DimensionStackContext.class);
         when(objects.contains(-3, 74, -7)).thenReturn(true);
 
-        Predicate<BlockPos> protectedPositions = NativeGenerationWriteGuard.protectedPositions(objects, stack, -64);
+        Predicate<BlockPos> protectedPositions = NativeGenerationWriteGuard.protectedPositions(GenerationWritePolicy.protectedPositions(objects, stack, -64));
 
         assertTrue(protectedPositions.test(new BlockPos(-3, 10, -7)));
         verifyNoInteractions(stack);
-        assertFalse(NativeGenerationWriteGuard.protectedPositions(objects, null, -64)
+        assertFalse(NativeGenerationWriteGuard.protectedPositions(GenerationWritePolicy.protectedPositions(objects, null, -64))
                 .test(new BlockPos(-3, 11, -7)));
     }
 
@@ -65,7 +69,7 @@ public final class NativeGenerationWriteGuardTest {
         when(negative.isHostFeatureProtectedY(64)).thenReturn(true);
         when(positive.isHostFeatureProtectedY(65)).thenReturn(true);
 
-        Predicate<BlockPos> protectedPositions = NativeGenerationWriteGuard.protectedPositions(objects, stack, -64);
+        Predicate<BlockPos> protectedPositions = NativeGenerationWriteGuard.protectedPositions(GenerationWritePolicy.protectedPositions(objects, stack, -64));
 
         assertTrue(protectedPositions.test(new BlockPos(-1, 0, -1)));
         assertFalse(protectedPositions.test(new BlockPos(-1, 1, -1)));
@@ -85,10 +89,10 @@ public final class NativeGenerationWriteGuardTest {
         when(router.history()).thenReturn(history);
         when(history.activeActivation()).thenReturn(active);
         when(active.activationId()).thenReturn(4L);
-        assertTrue(NativeGenerationWriteGuard.isHistoricalStructure(engine, 3));
-        assertFalse(NativeGenerationWriteGuard.isHistoricalStructure(engine, 0));
-        assertFalse(NativeGenerationWriteGuard.isHistoricalStructure(engine, 4));
-        assertFalse(NativeGenerationWriteGuard.isHistoricalStructure(engine, 5));
+        assertTrue(GenerationWritePolicy.isHistoricalStructure(engine, 3));
+        assertFalse(GenerationWritePolicy.isHistoricalStructure(engine, 0));
+        assertFalse(GenerationWritePolicy.isHistoricalStructure(engine, 4));
+        assertFalse(GenerationWritePolicy.isHistoricalStructure(engine, 5));
     }
 
     @Test
@@ -100,11 +104,11 @@ public final class NativeGenerationWriteGuardTest {
         ChunkAccess partial = mock(ChunkAccess.class);
         when(partial.getPersistedStatus()).thenReturn(ChunkStatus.NOISE);
         when(region.getChunk(anyInt(), anyInt())).thenReturn(partial);
-        assertTrue(NativeGenerationWriteGuard.allowsDecoration(engine, region, new ChunkPos(0, 0)));
+        assertTrue(NativeGenerationWriteGuard.allowsDecoration(engine.getComplex()::allowsMantleChunkWrite, region, new ChunkPos(0, 0)));
         ChunkAccess complete = mock(ChunkAccess.class);
         when(complete.getPersistedStatus()).thenReturn(ChunkStatus.FULL);
         when(region.getChunk(1, -1)).thenReturn(complete);
-        assertFalse(NativeGenerationWriteGuard.allowsDecoration(engine, region, new ChunkPos(0, 0)));
+        assertFalse(NativeGenerationWriteGuard.allowsDecoration(engine.getComplex()::allowsMantleChunkWrite, region, new ChunkPos(0, 0)));
     }
 
     @Test
@@ -115,11 +119,11 @@ public final class NativeGenerationWriteGuardTest {
         ChunkAccess chunk = mock(ChunkAccess.class);
         when(chunk.getPos()).thenReturn(new ChunkPos(-2, 3));
         when(chunk.getPersistedStatus()).thenReturn(ChunkStatus.NOISE);
-        assertTrue(NativeGenerationWriteGuard.allowsPendingStage(engine, chunk, ChunkStatus.FEATURES));
-        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine, chunk, ChunkStatus.NOISE));
+        assertTrue(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.FEATURES));
+        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.NOISE));
         when(chunk.getPersistedStatus()).thenReturn(ChunkStatus.FEATURES);
-        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine, chunk, ChunkStatus.FEATURES));
+        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.FEATURES));
         when(chunk.getPersistedStatus()).thenReturn(ChunkStatus.FULL);
-        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine, chunk, ChunkStatus.SPAWN));
+        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.SPAWN));
     }
 }

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureFactoryTest.java

@@ -1,5 +1,19 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureStartInjector;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureFactory;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeJigsawMetadata;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.ForcedStructureChunkGenerator;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureTemplatePoolBounds;
+
 import art.arcane.iris.structure.jigsaw.IrisJigsawConfiguration;
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
 import com.mojang.datafixers.util.Either;
@@ -108,10 +122,10 @@ public class NativeStructureFactoryTest {
         distance.putInt("vertical", 64);
         axisSpecific.put("max_distance_from_center", distance);
 
-        assertEquals(80, NativeStructureFactory.sourceDistance(scalar, "horizontal"));
-        assertEquals(80, NativeStructureFactory.sourceDistance(scalar, "vertical"));
-        assertEquals(96, NativeStructureFactory.sourceDistance(axisSpecific, "horizontal"));
-        assertEquals(64, NativeStructureFactory.sourceDistance(axisSpecific, "vertical"));
+        assertEquals(80, NativeJigsawMetadata.sourceDistance(scalar, "horizontal"));
+        assertEquals(80, NativeJigsawMetadata.sourceDistance(scalar, "vertical"));
+        assertEquals(96, NativeJigsawMetadata.sourceDistance(axisSpecific, "horizontal"));
+        assertEquals(64, NativeJigsawMetadata.sourceDistance(axisSpecific, "vertical"));
     }
 
     @Test
@@ -121,8 +135,8 @@ public class NativeStructureFactoryTest {
                 .terrainAdapation(TerrainAdjustment.BEARD_BOX)
                 .build());
 
-        assertEquals(0, NativeStructureFactory.horizontalReferenceExpansion(none));
-        assertEquals(12, NativeStructureFactory.horizontalReferenceExpansion(beardBox));
+        assertEquals(0, NativeJigsawMetadata.horizontalReferenceExpansion(none));
+        assertEquals(12, NativeJigsawMetadata.horizontalReferenceExpansion(beardBox));
     }
 
     @Test

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureGenerationKeysContractTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureGenerationKeys;
+
 import net.minecraft.SharedConstants;
 import net.minecraft.core.Vec3i;
 import net.minecraft.server.Bootstrap;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureLocatePersistenceTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureLocatePersistence;
+
 import net.minecraft.SharedConstants;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.server.Bootstrap;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureOwnershipFingerprintTest.java

@@ -1,11 +1,19 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceRepair;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureOwnershipFingerprint;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceEnvelope;
+
 import art.arcane.iris.structure.nativegen.NativeStructureOwnershipRecord;
 import art.arcane.iris.structure.nativegen.NativeStructureStartPlan;
 import art.arcane.iris.structure.nativegen.IrisNativeStructure;
 import art.arcane.iris.structure.placement.IrisStructurePlacement;
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
-import art.arcane.iris.structure.placement.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
 import art.arcane.volmlib.util.collection.KList;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
@@ -65,7 +73,7 @@ public class NativeStructureOwnershipFingerprintTest {
                 generated, 0, 80, -64, 320);
         int alignedLocatorY = NativeStructureOwnershipFingerprint.locatorY(generated);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setMode(StructureTerrainMode.FORCE_CARVE)
                 .setHorizontalPadding(24);
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
                 generated,
@@ -85,11 +93,9 @@ public class NativeStructureOwnershipFingerprintTest {
         StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
         String afterReload = NativeStructureOwnershipFingerprint.fingerprint(
                 "minecraft:monument", reloaded);
-        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
-                "minecraft:monument",
-                wrapped,
-                plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()),
-                NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain));
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", wrapped, NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain)), plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()));
 
         assertEquals(beforeReload, afterReload);
         assertTrue(NativeStructureOwnershipFingerprint.matches(ownership, reloaded));
@@ -110,11 +116,9 @@ public class NativeStructureOwnershipFingerprintTest {
         for (StructurePiece piece : moved.getPieces()) {
             piece.move(1, 0, 0);
         }
-        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
-                "minecraft:monument",
-                expected,
-                plan(origin, NativeStructureReferenceEnvelope.contentBounds(expected).minY()),
-                expected.getBoundingBox());
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", expected, expected.getBoundingBox()), plan(origin, NativeStructureReferenceEnvelope.contentBounds(expected).minY()));
 
         assertFalse(NativeStructureOwnershipFingerprint.matches(ownership, moved));
     }
@@ -129,18 +133,16 @@ public class NativeStructureOwnershipFingerprintTest {
         NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
                 generated, 0, 80, -64, 320);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setMode(StructureTerrainMode.FORCE_CARVE)
                 .setHorizontalPadding(24);
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
                 generated,
                 structure,
                 0,
                 terrain);
-        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
-                "minecraft:monument",
-                wrapped,
-                plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()),
-                NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain));
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", wrapped, NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain)), plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()));
         PiecesContainer regeneratedPieces = OceanMonumentStructure.regeneratePiecesAfterLoad(
                 origin, seed, new PiecesContainer(wrapped.getPieces()));
         StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
@@ -263,13 +265,10 @@ public class NativeStructureOwnershipFingerprintTest {
 
     private static NativeStructureOwnershipRecord ownership(
             ChunkPos origin, StructureStart start, OceanMonumentStructure structure) {
-        return NativeStructureOwnershipFingerprint.capture(
-                "minecraft:monument",
-                start,
-                plan(origin, NativeStructureReferenceEnvelope.contentBounds(start).minY()),
-                NativeStructureReferenceEnvelope.referenceBounds(
-                        start, structure, new IrisStructureTerrain())
-        );
+        return NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", start, NativeStructureReferenceEnvelope.referenceBounds(
+                        start, structure, new IrisStructureTerrain())), plan(origin, NativeStructureReferenceEnvelope.contentBounds(start).minY()));
     }
 
     private static StructureStart poolStart(

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureOwnershipRecoveryTest.java

@@ -1,12 +1,22 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.terrain.structure.StructureOwnershipRecordView;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureOwnershipRecovery;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureOwnershipFingerprint;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceEnvelope;
+
 import art.arcane.iris.structure.nativegen.NativeStructureOwnershipRecord;
 import art.arcane.iris.structure.nativegen.NativeStructureStartPlan;
 import art.arcane.iris.structure.placement.StructurePlacementGrid;
 import art.arcane.iris.structure.nativegen.IrisNativeStructure;
 import art.arcane.iris.structure.placement.IrisStructurePlacement;
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
-import art.arcane.iris.structure.placement.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
 import art.arcane.volmlib.util.collection.KList;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.Direction;
@@ -63,7 +73,7 @@ public class NativeStructureOwnershipRecoveryTest {
         NativeStructureOwnershipRecord recovered =
                 NativeStructureOwnershipRecovery.proveCandidate(
                         "minecraft:monument", structure, reloaded,
-                        plan, expected, false);
+                        plan, expected, false, NativeStructureOwnershipRecord::capture);
 
         assertNotNull(recovered);
         assertEquals(StructurePlacementGrid.placementIdentity(plan.placement()),
@@ -71,7 +81,7 @@ public class NativeStructureOwnershipRecoveryTest {
         assertEquals(expectedLocatorY, recovered.locatorY());
         assertNotEquals(NativeStructureOwnershipFingerprint.locatorY(reloaded),
                 recovered.locatorY());
-        assertEquals(IrisStructureTerrainMode.FORCE_CARVE,
+        assertEquals(StructureTerrainMode.FORCE_CARVE,
                 recovered.restoredDecision().terrain().resolvedMode());
         assertEquals(24, recovered.restoredDecision().terrain().getHorizontalPadding());
         assertTrue(recovered.referenceMinChunkX()
@@ -89,7 +99,7 @@ public class NativeStructureOwnershipRecoveryTest {
         NativeStructureOwnershipRecord recovered =
                 NativeStructureOwnershipRecovery.proveCandidate(
                         "minecraft:monument", structure, natural,
-                        plan, natural, true);
+                        plan, natural, true, NativeStructureOwnershipRecord::capture);
 
         assertNull(recovered);
     }
@@ -114,10 +124,10 @@ public class NativeStructureOwnershipRecoveryTest {
                 StructurePlacementGrid.placementIdentity(changedIdentity.placement()));
         assertNull(NativeStructureOwnershipRecovery.proveCandidate(
                 "minecraft:monument", structure, expected,
-                changedIdentity, expected, false));
+                changedIdentity, expected, false, NativeStructureOwnershipRecord::capture));
         assertNull(NativeStructureOwnershipRecovery.proveCandidate(
                 "minecraft:monument", structure, changedGeometry,
-                plan(origin, "geometry-check", 0), expected, false));
+                plan(origin, "geometry-check", 0), expected, false, NativeStructureOwnershipRecord::capture));
     }
 
     @Test
@@ -129,7 +139,7 @@ public class NativeStructureOwnershipRecoveryTest {
         NativeStructureOwnershipRecord recovered =
                 NativeStructureOwnershipRecovery.proveCandidate(
                         "minecraft:monument", structure, expected,
-                        plan(origin, "fingerprint-check", 16), expected, false);
+                        plan(origin, "fingerprint-check", 16), expected, false, NativeStructureOwnershipRecord::capture);
         assertNotNull(recovered);
 
         StructureStart moved = monumentStart(structure, origin, seed);
@@ -148,10 +158,11 @@ public class NativeStructureOwnershipRecoveryTest {
         OceanMonumentStructure structure = structure();
         StructureStart start = monumentStart(structure, origin, seed);
         NativeStructureStartPlan plan = plan(
-                origin, "vacuum-envelope-refresh", IrisStructureTerrainMode.VACUUM, 0);
+                origin, "vacuum-envelope-refresh", StructureTerrainMode.VACUUM, 0);
         BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(start);
-        NativeStructureOwnershipRecord stale = NativeStructureOwnershipFingerprint.capture(
-                structureKey, start, plan, content);
+        NativeStructureOwnershipRecord stale = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, start, content), plan);
 
         NativeStructureOwnershipRecord refreshed =
                 NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
@@ -166,7 +177,7 @@ public class NativeStructureOwnershipRecoveryTest {
         assertEquals(stale.locatorY(), refreshed.locatorY());
         assertEquals(stale.contentFingerprint(), refreshed.contentFingerprint());
         assertEquals(stale.decision(), refreshed.decision());
-        assertEquals(IrisStructureTerrainMode.VACUUM,
+        assertEquals(StructureTerrainMode.VACUUM,
                 refreshed.restoredDecision().terrain().resolvedMode());
         BoundingBox expected = NativeStructureReferenceEnvelope.referenceBounds(
                 start, structure, plan.placement().resolvedTerrain(), structureKey);
@@ -187,10 +198,10 @@ public class NativeStructureOwnershipRecoveryTest {
         OceanMonumentStructure structure = structure();
         StructureStart expected = monumentStart(structure, origin, seed);
         NativeStructureStartPlan plan = plan(
-                origin, "vacuum-content-check", IrisStructureTerrainMode.VACUUM, 0);
-        NativeStructureOwnershipRecord stale = NativeStructureOwnershipFingerprint.capture(
-                structureKey, expected, plan,
-                NativeStructureReferenceEnvelope.contentBounds(expected));
+                origin, "vacuum-content-check", StructureTerrainMode.VACUUM, 0);
+        NativeStructureOwnershipRecord stale = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, expected, NativeStructureReferenceEnvelope.contentBounds(expected)), plan);
         StructureStart moved = monumentStart(structure, origin, seed);
         for (StructurePiece piece : moved.getPieces()) {
             piece.move(1, 0, 0);
@@ -210,8 +221,9 @@ public class NativeStructureOwnershipRecoveryTest {
         NativeStructureStartPlan plan = plan(origin, "current-force-carve", 24);
         BoundingBox envelope = NativeStructureReferenceEnvelope.referenceBounds(
                 start, structure, plan.placement().resolvedTerrain(), structureKey);
-        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
-                structureKey, start, plan, envelope);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, start, envelope), plan);
 
         assertSame(ownership, NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
                 structureKey, structure, start, ownership));
@@ -226,19 +238,20 @@ public class NativeStructureOwnershipRecoveryTest {
         StructureStart start = monumentStart(structure, origin, seed);
         BoundingBox initial = NativeStructureReferenceEnvelope.contentBounds(start);
         int maximumReferenceBlockX = ((origin.x()
-                + NativeStructureOwnershipRecord.MAX_REFERENCE_DISTANCE_CHUNKS) << 4) + 15;
+                + StructureOwnershipRecordView.MAX_REFERENCE_DISTANCE_CHUNKS) << 4) + 15;
         int shiftX = maximumReferenceBlockX - initial.maxX();
         for (StructurePiece piece : start.getPieces()) {
             piece.move(shiftX, 0, 0);
         }
         NativeStructureStartPlan plan = plan(
-                origin, "clipped-vacuum", IrisStructureTerrainMode.VACUUM, 0);
+                origin, "clipped-vacuum", StructureTerrainMode.VACUUM, 0);
         BoundingBox envelope = NativeStructureReferenceEnvelope.referenceBounds(
                 start, structure, plan.placement().resolvedTerrain(), structureKey);
-        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipFingerprint.capture(
-                structureKey, start, plan, envelope);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, start, envelope), plan);
 
-        assertEquals(origin.x() + NativeStructureOwnershipRecord.MAX_REFERENCE_DISTANCE_CHUNKS,
+        assertEquals(origin.x() + StructureOwnershipRecordView.MAX_REFERENCE_DISTANCE_CHUNKS,
                 ownership.referenceMaxChunkX());
         assertSame(ownership, NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
                 structureKey, structure, start, ownership));
@@ -270,12 +283,12 @@ public class NativeStructureOwnershipRecoveryTest {
                                                   String placementId,
                                                   int horizontalPadding) {
         return plan(origin, placementId,
-                IrisStructureTerrainMode.FORCE_CARVE, horizontalPadding);
+                StructureTerrainMode.FORCE_CARVE, horizontalPadding);
     }
 
     private static NativeStructureStartPlan plan(ChunkPos origin,
                                                   String placementId,
-                                                  IrisStructureTerrainMode terrainMode,
+                                                  StructureTerrainMode terrainMode,
                                                   int horizontalPadding) {
         IrisNativeStructure source = new IrisNativeStructure()
                 .setStructure("minecraft:monument")

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorEncaseTest.java

@@ -1,8 +1,18 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.terrain.structure.StructurePalette;
+
+import art.arcane.volmlib.nativelib.terrain.structure.StructureTerrainSettings;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureTerrainIntegrator;
+
 import art.arcane.iris.generation.terrain.IrisMaterialPalette;
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
-import art.arcane.iris.structure.placement.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
 import art.arcane.iris.structure.placement.IrisStructureYBand;
 import art.arcane.volmlib.util.math.RNG;
 import net.minecraft.SharedConstants;
@@ -76,7 +86,7 @@ public class NativeStructurePostProcessorEncaseTest {
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), area, "minecraft:stronghold", start,
                 new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.ENCASE)
+                        .setMode(StructureTerrainMode.ENCASE)
                         .setHorizontalPadding(1)
                         .setCeilingPadding(1)
                         .setFloorPadding(1),
@@ -100,7 +110,7 @@ public class NativeStructurePostProcessorEncaseTest {
 
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), bounds, "minecraft:stronghold", start,
-                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.ENCASE),
+                new IrisStructureTerrain().setMode(StructureTerrainMode.ENCASE),
                 null);
 
         assertEquals(-1, bounds.minY());
@@ -181,7 +191,7 @@ public class NativeStructurePostProcessorEncaseTest {
                         world(new HashMap<>()), area,
                         List.of(new NativeStructureTerrainIntegrator.TerrainTarget(
                                 "test:bounded-snapshot", start,
-                                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE))));
+                                new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE))));
 
         assertNotNull(sourceTerrain);
         assertEquals(23 * 16 * 16, sourceTerrain.sampledCells());
@@ -210,7 +220,7 @@ public class NativeStructurePostProcessorEncaseTest {
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), bounds, "minecraft:stronghold", start,
                 new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.ENCASE)
+                        .setMode(StructureTerrainMode.ENCASE)
                         .setEncasePalette(palette),
                 NativeStructurePostProcessorEncaseTest::tuffBlock);
 
@@ -221,10 +231,10 @@ public class NativeStructurePostProcessorEncaseTest {
     @Test
     public void omittedTerrainConfigurationRetainsSourceSemantics() {
         for (TerrainAdjustment adjustment : TerrainAdjustment.values()) {
-            IrisStructureTerrain resolved = NativeStructureTerrainIntegrator.resolveNativeTerrain(
+            StructureTerrainSettings resolved = NativeStructureTerrainIntegrator.resolveNativeTerrain(
                     start(adjustment, 64), null);
 
-            assertEquals(IrisStructureTerrainMode.SOURCE, resolved.resolvedMode());
+            assertEquals(StructureTerrainMode.SOURCE, resolved.resolvedMode());
         }
     }
 
@@ -240,7 +250,7 @@ public class NativeStructurePostProcessorEncaseTest {
 
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), area, "test:bury", start,
-                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE), null);
+                new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE), null);
 
         assertEquals(Blocks.STONE.defaultBlockState(),
                 state(blocks, bounds.minX() - 5, groundY, bounds.minZ()));
@@ -267,7 +277,7 @@ public class NativeStructurePostProcessorEncaseTest {
 
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), area, "test:encapsulate", start,
-                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE), null);
+                new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE), null);
 
         assertEquals(Blocks.STONE.defaultBlockState(),
                 state(blocks, bounds.minX() - 11, bounds.minY(), bounds.minZ()));
@@ -304,7 +314,7 @@ public class NativeStructurePostProcessorEncaseTest {
     @Test
     public void explicitTerrainConfigurationWinsOverAutoEncase() {
         IrisStructureTerrain configured = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.PRESERVE);
+                .setMode(StructureTerrainMode.PRESERVE);
 
         assertSame(configured, NativeStructureTerrainIntegrator.resolveNativeTerrain(
                 start(TerrainAdjustment.BURY, 64), configured));
@@ -313,11 +323,11 @@ public class NativeStructurePostProcessorEncaseTest {
     @Test
     public void legacyTemplateAirIsClearedAfterEveryTerrainFillPath() {
         IrisStructureTerrain source = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.SOURCE);
+                .setMode(StructureTerrainMode.SOURCE);
         IrisStructureTerrain preserve = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.PRESERVE);
+                .setMode(StructureTerrainMode.PRESERVE);
         IrisStructureTerrain encase = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.ENCASE);
+                .setMode(StructureTerrainMode.ENCASE);
 
         assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
                 start(TerrainAdjustment.BURY, 64), source));
@@ -337,7 +347,7 @@ public class NativeStructurePostProcessorEncaseTest {
         BoundingBox sourceBounds = generated.getBoundingBox();
         BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.ENCASE)
+                .setMode(StructureTerrainMode.ENCASE)
                 .setHorizontalPadding(4);
 
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
@@ -373,7 +383,7 @@ public class NativeStructurePostProcessorEncaseTest {
         StructureStart generated = start(TerrainAdjustment.BURY, 64);
         BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.ENCASE)
+                .setMode(StructureTerrainMode.ENCASE)
                 .setHorizontalPadding(112);
 
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
@@ -446,7 +456,7 @@ public class NativeStructurePostProcessorEncaseTest {
         assertEquals(minY, start.getBoundingBox().minY());
     }
 
-    private static BlockState tuffBlock(IrisMaterialPalette palette, RNG rng, int x, int y, int z) {
+    private static BlockState tuffBlock(StructurePalette palette, RNG rng, int x, int y, int z) {
         assertNotNull(palette);
         assertNotNull(rng);
         return Blocks.TUFF.defaultBlockState();

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorMonumentTest.java

@@ -1,7 +1,11 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceEnvelope;
+
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
-import art.arcane.iris.structure.placement.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.Direction;
 import net.minecraft.core.HolderSet;
@@ -95,7 +99,7 @@ public class NativeStructurePostProcessorMonumentTest {
                 start.getStructure(),
                 0,
                 new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                        .setMode(StructureTerrainMode.FORCE_CARVE)
                         .setHorizontalPadding(4));
 
         int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorScatteredFeatureTest.java

@@ -1,5 +1,11 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureSurfaceFitter;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReflection;
+
 import net.minecraft.SharedConstants;
 import net.minecraft.core.HolderSet;
 import net.minecraft.server.Bootstrap;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorSurfaceTerrainTest.java

@@ -1,9 +1,29 @@
 package art.arcane.iris.nativegen;
 
-import art.arcane.iris.generation.mantle.StructureCarvingFootprint;
-import art.arcane.iris.structure.placement.IrisStructureCarveShape;
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureTerrainIntegrator;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureFoundationBuilder;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureSurfaceSupportBuilder;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureSurfaceFitter;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVegetationClearer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureTemplateOccupancy;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReflection;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.WorldgenTerrainHeightmaps;
+
+import art.arcane.volmlib.util.structure.StructureCarvingFootprint;
+import art.arcane.volmlib.util.structure.StructureCarveShape;
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
-import art.arcane.iris.structure.placement.IrisStructureTerrainMode;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
 import com.mojang.datafixers.util.Either;
 import com.mojang.serialization.Codec;
 import net.minecraft.SharedConstants;
@@ -214,10 +234,10 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
             put(blocks, x, sourceY, 0, Blocks.GRASS_BLOCK.defaultBlockState());
         }
         assertTrue(NativeStructureSurfaceFitter.requiresFlattenTerrain(
-                surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)));
+                surfaceTarget(start, StructureTerrainMode.FLATTEN)));
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)),
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)),
                 (x, z) -> x < 2 ? groundY - 32 : groundY + 32);
 
         for (int x = 0; x <= 3; x++) {
@@ -240,7 +260,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         put(blocks, 0, groundY - 19, 0, Blocks.DIRT.defaultBlockState());
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)), (x, z) -> groundY);
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)), (x, z) -> groundY);
 
         for (int y = groundY - 19; y <= groundY; y++) {
             assertEquals(Blocks.DIRT.defaultBlockState(), state(blocks, 0, y, 0));
@@ -260,9 +280,9 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         Map<BlockPos, BlockState> originalSubmerged = new HashMap<>(submerged);
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(world(buried), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)), (x, z) -> 100);
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)), (x, z) -> 100);
         NativeStructureSurfaceFitter.prepareSurfaceStructures(world(submerged), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)), (x, z) -> groundY - 8);
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)), (x, z) -> groundY - 8);
 
         assertEquals(originalBuried, buried);
         assertEquals(originalSubmerged, submerged);
@@ -280,12 +300,12 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
             StructureStart start = new StructureStart(structure, new ChunkPos(0, 0), 0,
                     new PiecesContainer(desertStart().getPieces()));
             assertFalse(NativeStructureSurfaceFitter.requiresFlattenTerrain(
-                    surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)));
+                    surfaceTarget(start, StructureTerrainMode.FLATTEN)));
         }
         assertFalse(NativeStructureSurfaceFitter.requiresFlattenTerrain(
-                surfaceTarget(desertStart(TerrainAdjustment.BURY), IrisStructureTerrainMode.FLATTEN)));
+                surfaceTarget(desertStart(TerrainAdjustment.BURY), StructureTerrainMode.FLATTEN)));
         assertFalse(NativeStructureSurfaceFitter.requiresFlattenTerrain(
-                surfaceTarget(desertStart(TerrainAdjustment.ENCAPSULATE), IrisStructureTerrainMode.FLATTEN)));
+                surfaceTarget(desertStart(TerrainAdjustment.ENCAPSULATE), StructureTerrainMode.FLATTEN)));
     }
 
     @Test
@@ -294,8 +314,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                         block(0, 0, 0, Blocks.COBBLESTONE.defaultBlockState())))),
                 new BoundingBox(0, 128, 0, 0, 136, 0), 0, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(piece));
-        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, IrisStructureTerrainMode.FLATTEN);
-        target.terrain().setFlattenRange(32);
+        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, StructureTerrainMode.FLATTEN);
+        ((IrisStructureTerrain) target.terrain()).setFlattenRange(32);
         BoundingBox area = new BoundingBox(0, 0, 0, 0, 255, 0);
         Map<BlockPos, BlockState> blocks = new HashMap<>();
         put(blocks, 0, 94, 0, Blocks.GOLD_BLOCK.defaultBlockState());
@@ -323,7 +343,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                         block(0, 0, 0, Blocks.COBBLESTONE.defaultBlockState())))),
                 new BoundingBox(0, 64, 0, 0, 70, 0), 0, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(piece));
-        IrisStructureTerrain terrain = new IrisStructureTerrain().setMode(IrisStructureTerrainMode.FLATTEN)
+        IrisStructureTerrain terrain = new IrisStructureTerrain().setMode(StructureTerrainMode.FLATTEN)
                 .setHorizontalPadding(128).setFlattenRange(128);
 
         BoundingBox references = NativeStructureReferenceEnvelope.referenceBounds(start, start.getStructure(), terrain);
@@ -351,7 +371,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         Map<BlockPos, BlockState> blocks = supportTerrain(0, 0);
 
         Set<Long> written = NativeStructureSurfaceSupportBuilder.bridgeRigidPieceSupport(world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)),
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)),
                 NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager);
 
         assertEquals(Set.of(BlockPos.asLong(0, 63, 0)), written);
@@ -372,7 +392,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         put(blocks, 0, 80, 0, Blocks.STONE.defaultBlockState());
 
         Set<Long> written = NativeStructureSurfaceSupportBuilder.bridgeRigidPieceSupport(world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)),
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)),
                 NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager);
 
         assertTrue(written.isEmpty());
@@ -399,7 +419,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         }
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.FLATTEN)),
+                List.of(surfaceTarget(start, StructureTerrainMode.FLATTEN)),
                 (x, z) -> x == footprint.minX() ? 80 : 112);
 
         assertEquals(81, piece.getBoundingBox().minY());
@@ -421,8 +441,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                         List.of(), StructureTemplatePool.Projection.TERRAIN_MATCHING),
                 new BoundingBox(4, 65, 0, 4, 75, 0), 0, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(left, path, right));
-        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, IrisStructureTerrainMode.FLATTEN);
-        target.terrain().setHorizontalPadding(24);
+        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, StructureTerrainMode.FLATTEN);
+        ((IrisStructureTerrain) target.terrain()).setHorizontalPadding(24);
         BoundingBox area = new BoundingBox(0, 0, 0, 8, 128, 0);
         Map<BlockPos, BlockState> blocks = flatTerrain(area, 96);
         for (int x : List.of(0, 8)) {
@@ -472,8 +492,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                         List.of(), StructureTemplatePool.Projection.TERRAIN_MATCHING),
                 new BoundingBox(0, 65, 0, 8, 75, 0), 0, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(left, path, right));
-        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, IrisStructureTerrainMode.FLATTEN);
-        target.terrain().setHorizontalPadding(24);
+        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, StructureTerrainMode.FLATTEN);
+        ((IrisStructureTerrain) target.terrain()).setHorizontalPadding(24);
         BoundingBox area = new BoundingBox(0, 0, 0, 8, 127, 0);
         WorldGenLevel world = world(chunk);
 
@@ -532,8 +552,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                         List.of(), StructureTemplatePool.Projection.TERRAIN_MATCHING),
                 new BoundingBox(4, 65, 0, 6, 75, 0), 0, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(left, path, right));
-        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, IrisStructureTerrainMode.FLATTEN);
-        target.terrain().setHorizontalPadding(24).setFlattenRange(32);
+        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, StructureTerrainMode.FLATTEN);
+        ((IrisStructureTerrain) target.terrain()).setHorizontalPadding(24).setFlattenRange(32);
         BoundingBox area = new BoundingBox(0, 0, 0, 8, 127, 0);
         WorldGenLevel world = world(chunk);
 
@@ -579,8 +599,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
             }
         }
         StructureStart start = rigidSurfaceStart(pieces);
-        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, IrisStructureTerrainMode.FLATTEN);
-        target.terrain().setHorizontalPadding(24).setFlattenRange(64);
+        NativeStructureTerrainIntegrator.TerrainTarget target = surfaceTarget(start, StructureTerrainMode.FLATTEN);
+        ((IrisStructureTerrain) target.terrain()).setHorizontalPadding(24).setFlattenRange(64);
         BoundingBox area = new BoundingBox(0, 0, 0, 8, 127, 8);
         Map<BlockPos, BlockState> blocks = new HashMap<>();
         for (int x = 0; x <= 8; x++) {
@@ -667,11 +687,11 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         assertTrue(NativeStructureSurfaceFitter.requiresSurfaceTerrain(
                 new NativeStructureTerrainIntegrator.TerrainTarget(
                         "test:beard_box", start,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE))));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE))));
         assertFalse(NativeStructureSurfaceFitter.requiresSurfaceTerrain(
                 new NativeStructureTerrainIntegrator.TerrainTarget(
                         "test:beard_box", start,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.PRESERVE))));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.PRESERVE))));
     }
 
     @Test
@@ -681,15 +701,15 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         NativeStructureTerrainIntegrator.TerrainTarget sourceNone =
                 new NativeStructureTerrainIntegrator.TerrainTarget(
                         "test:none", none,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE));
         NativeStructureTerrainIntegrator.TerrainTarget vacuumNone =
                 new NativeStructureTerrainIntegrator.TerrainTarget(
                         "test:none", none,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.VACUUM));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.VACUUM));
         NativeStructureTerrainIntegrator.TerrainTarget vacuumBox =
                 new NativeStructureTerrainIntegrator.TerrainTarget(
                         "test:box", box,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.VACUUM));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.VACUUM));
 
         assertFalse(NativeStructureSurfaceFitter.requiresSurfaceTerrain(sourceNone));
         assertTrue(NativeStructureSurfaceFitter.requiresSurfaceTerrain(vacuumNone));
@@ -778,7 +798,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         List<NativeStructureTerrainIntegrator.TerrainTarget> targets = List.of(
                 new NativeStructureTerrainIntegrator.TerrainTarget(
                         "nova_structures:tavern_oak", start,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.SOURCE)));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE)));
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area, targets,
                 (x, z) -> 65);
@@ -886,7 +906,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(Blocks.AIR.defaultBlockState(), state(blocks, 0, 64, 0));
@@ -911,7 +931,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 0, 65, 0));
@@ -932,7 +952,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 80);
 
         for (int y = 61; y <= 74; y++) {
@@ -957,7 +977,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 79);
 
         for (int y = 61; y <= 74; y++) {
@@ -989,7 +1009,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         NativeStructureSurfaceFitter.SurfaceTerrainPlan plan =
                 NativeStructureSurfaceFitter.prepareSurfaceStructures(
                         world(blocks), area,
-                        List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                        List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                         (x, z) -> 60);
         for (int y = 61; y <= 64; y++) {
             put(blocks, 0, y, 0, Blocks.CAVE_AIR.defaultBlockState());
@@ -1029,7 +1049,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         NativeStructureSurfaceFitter.SurfaceTerrainPlan plan =
                 NativeStructureSurfaceFitter.prepareSurfaceStructures(
                         world(blocks), area,
-                        List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                        List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                         (x, z) -> 60);
         put(blocks, 0, 65, 0, Blocks.COBBLESTONE.defaultBlockState());
 
@@ -1051,7 +1071,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                 new BoundingBox(15, 65, 0, 16, 70, 0), 1, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(piece), TerrainAdjustment.NONE);
         NativeStructureTerrainIntegrator.TerrainTarget target =
-                surfaceTarget(start, IrisStructureTerrainMode.VACUUM);
+                surfaceTarget(start, StructureTerrainMode.VACUUM);
         BoundingBox wideArea = new BoundingBox(0, 54, 0, 31, 72, 15);
         BoundingBox westArea = new BoundingBox(0, 54, 0, 15, 72, 15);
         BoundingBox eastArea = new BoundingBox(16, 54, 0, 31, 72, 15);
@@ -1100,7 +1120,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(originalBlocks, blocks);
@@ -1121,7 +1141,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(originalBlocks, blocks);
@@ -1145,7 +1165,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 1, 66, 0));
@@ -1170,7 +1190,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(originalBlocks, blocks);
@@ -1190,7 +1210,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 0, 65, 0));
@@ -1215,7 +1235,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(originalBlocks, blocks);
@@ -1236,7 +1256,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 4, 61, 4));
@@ -1254,7 +1274,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 50);
 
         assertEquals(originalBlocks, blocks);
@@ -1273,7 +1293,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60, 1);
 
         assertEquals(originalBlocks, blocks);
@@ -1297,7 +1317,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureSurfaceFitter.prepareSurfaceStructures(
                 world(blocks), area,
-                List.of(surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 (x, z) -> 60);
 
         for (int y = 61; y <= 65; y++) {
@@ -1317,7 +1337,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                 new BoundingBox(15, 66, 0, 16, 72, 0), 1, Rotation.NONE);
         StructureStart start = rigidSurfaceStart(List.of(piece), TerrainAdjustment.NONE);
         NativeStructureTerrainIntegrator.TerrainTarget target =
-                surfaceTarget(start, IrisStructureTerrainMode.VACUUM);
+                surfaceTarget(start, StructureTerrainMode.VACUUM);
         BoundingBox wideArea = new BoundingBox(0, 54, 0, 31, 74, 15);
         BoundingBox westArea = new BoundingBox(0, 54, 0, 15, 74, 15);
         BoundingBox eastArea = new BoundingBox(16, 54, 0, 31, 74, 15);
@@ -1573,13 +1593,13 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         Set<Long> vacuumWritten = NativeStructureSurfaceSupportBuilder.bridgeRigidPieceSupport(
                 world(vacuumBlocks), area,
-                List.of(surfaceTarget(vacuumStart, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(vacuumStart, StructureTerrainMode.VACUUM)),
                 NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager);
 
         assertEquals(Set.of(BlockPos.asLong(0, 63, 0)), vacuumWritten);
         assertTrue(NativeStructureSurfaceSupportBuilder.bridgeRigidPieceSupport(
                 world(supportTerrain(0, 0)), area,
-                List.of(surfaceTarget(vacuumStart, IrisStructureTerrainMode.SOURCE)),
+                List.of(surfaceTarget(vacuumStart, StructureTerrainMode.SOURCE)),
                 NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager).isEmpty());
 
         PoolElementStructurePiece distantUpper = rigidTemplatePiece(
@@ -1589,7 +1609,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
                 List.of(lower, distantUpper), TerrainAdjustment.NONE);
         assertTrue(NativeStructureSurfaceSupportBuilder.bridgeRigidPieceSupport(
                 world(supportTerrain(0, 0)), area,
-                List.of(surfaceTarget(distantStart, IrisStructureTerrainMode.VACUUM)),
+                List.of(surfaceTarget(distantStart, StructureTerrainMode.VACUUM)),
                 NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager).isEmpty());
     }
 
@@ -1676,8 +1696,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         Set<Long> written = NativeStructureSurfaceSupportBuilder.bridgeRigidPieceSupport(
                 world(blocks), area, List.of(
-                        surfaceTarget(start, IrisStructureTerrainMode.PRESERVE),
-                        surfaceTarget(start, IrisStructureTerrainMode.VACUUM)),
+                        surfaceTarget(start, StructureTerrainMode.PRESERVE),
+                        surfaceTarget(start, StructureTerrainMode.VACUUM)),
                 NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager);
 
         assertEquals(Set.of(BlockPos.asLong(0, 63, 0)), written);
@@ -1875,6 +1895,72 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(raised, 0, 68, 0));
     }
 
+    @Test
+    public void loweredSnowSurfaceRemovesSolidSlabDecoration() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        for (int y = 82; y < 99; y++) {
+            put(blocks, 0, y, 0, Blocks.STONE.defaultBlockState());
+        }
+        put(blocks, 0, 99, 0, Blocks.SNOW_BLOCK.defaultBlockState());
+        put(blocks, 0, 100, 0, Blocks.COBBLESTONE_SLAB.defaultBlockState());
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world(blocks), new BlockPos.MutableBlockPos(),
+                0, 0, 99, 83, -64, 319);
+
+        assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, 82, 0));
+        assertEquals(Blocks.SNOW_BLOCK.defaultBlockState(), state(blocks, 0, 83, 0));
+        for (int y = 84; y <= 100; y++) {
+            assertEquals(Blocks.AIR.defaultBlockState(), state(blocks, 0, y, 0));
+        }
+    }
+
+    @Test
+    public void loweredSurfaceRemovesStackedSolidDecorationUntilAir() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        put(blocks, 0, 62, 0, Blocks.DIRT.defaultBlockState());
+        put(blocks, 0, 63, 0, Blocks.DIRT.defaultBlockState());
+        put(blocks, 0, 64, 0, Blocks.GRASS_BLOCK.defaultBlockState());
+        put(blocks, 0, 65, 0, Blocks.COBBLESTONE.defaultBlockState());
+        put(blocks, 0, 66, 0, Blocks.COBBLESTONE_STAIRS.defaultBlockState());
+        put(blocks, 0, 67, 0, Blocks.COBBLESTONE_WALL.defaultBlockState());
+        put(blocks, 0, 69, 0, Blocks.STONE.defaultBlockState());
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world(blocks), new BlockPos.MutableBlockPos(),
+                0, 0, 64, 62, -64, 319);
+
+        assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 0, 62, 0));
+        for (int y = 63; y <= 68; y++) {
+            assertEquals(Blocks.AIR.defaultBlockState(), state(blocks, 0, y, 0));
+        }
+        assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, 69, 0));
+    }
+
+    @Test
+    public void loweredSurfacePreservesTreeDecorationBoundary() {
+        for (BlockState tree : List.of(Blocks.OAK_LOG.defaultBlockState(), Blocks.OAK_LEAVES.defaultBlockState())) {
+            Map<BlockPos, BlockState> blocks = new HashMap<>();
+            put(blocks, 0, 62, 0, Blocks.DIRT.defaultBlockState());
+            put(blocks, 0, 63, 0, Blocks.DIRT.defaultBlockState());
+            put(blocks, 0, 64, 0, Blocks.GRASS_BLOCK.defaultBlockState());
+            put(blocks, 0, 65, 0, Blocks.COBBLESTONE_SLAB.defaultBlockState());
+            put(blocks, 0, 66, 0, tree);
+            put(blocks, 0, 67, 0, Blocks.STONE.defaultBlockState());
+
+            NativeStructureSurfaceFitter.applySurfaceColumn(
+                    world(blocks), new BlockPos.MutableBlockPos(),
+                    0, 0, 64, 62, -64, 319);
+
+            assertEquals(Blocks.GRASS_BLOCK.defaultBlockState(), state(blocks, 0, 62, 0));
+            for (int y = 63; y <= 65; y++) {
+                assertEquals(Blocks.AIR.defaultBlockState(), state(blocks, 0, y, 0));
+            }
+            assertEquals(tree, state(blocks, 0, 66, 0));
+            assertEquals(Blocks.STONE.defaultBlockState(), state(blocks, 0, 67, 0));
+        }
+    }
+
     @Test
     public void rigidSurfaceBaseClosesAOneBlockSubsurfaceGap() {
         Map<BlockPos, BlockState> blocks = new HashMap<>();
@@ -2033,7 +2119,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), bounds, "minecraft:desert_pyramid", start,
-                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.VACUUM), null);
+                new IrisStructureTerrain().setMode(StructureTerrainMode.VACUUM), null);
 
         assertEquals(Blocks.STONE.defaultBlockState(),
                 state(blocks, bounds.minX(), bounds.minY(), bounds.minZ()));
@@ -2055,7 +2141,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), area, "minecraft:desert_pyramid", start,
                 new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                        .setMode(StructureTerrainMode.FORCE_CARVE)
                         .setHorizontalPadding(1)
                         .setCeilingPadding(1), null);
 
@@ -2089,7 +2175,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), area, "minecraft:ancient_city", start,
-                new IrisStructureTerrain().setMode(IrisStructureTerrainMode.FORCE_CARVE), null);
+                new IrisStructureTerrain().setMode(StructureTerrainMode.FORCE_CARVE), null);
 
         assertEquals(Blocks.AIR.defaultBlockState(),
                 state(blocks, firstBounds.minX(), y, z));
@@ -2338,8 +2424,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         NativeStructureTerrainIntegrator.integrateTerrain(
                 world(blocks), area, "minecraft:ancient_city", start,
                 new IrisStructureTerrain()
-                        .setMode(IrisStructureTerrainMode.FORCE_CARVE)
-                        .setShape(IrisStructureCarveShape.ERODED)
+                        .setMode(StructureTerrainMode.FORCE_CARVE)
+                        .setShape(StructureCarveShape.ERODED)
                         .setHorizontalPadding(6)
                         .setCeilingPadding(8)
                         .setFloorPadding(0)
@@ -2378,7 +2464,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         StructureStart generated = desertStart();
         BoundingBox content = generated.getBoundingBox();
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setMode(StructureTerrainMode.FORCE_CARVE)
                 .setHorizontalPadding(24);
 
         StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
@@ -2403,7 +2489,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         StructureStart generated = desertStart(TerrainAdjustment.NONE);
         BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.VACUUM)
+                .setMode(StructureTerrainMode.VACUUM)
                 .setHorizontalPadding(64);
 
         BoundingBox references = NativeStructureReferenceEnvelope.referenceBounds(
@@ -2425,7 +2511,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         ChunkPos origin = generated.getChunkPos();
         BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
+                .setMode(StructureTerrainMode.FORCE_CARVE)
                 .setHorizontalPadding(124);
 
         BoundingBox references = NativeStructureReferenceEnvelope.referenceBounds(
@@ -2575,11 +2661,11 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
     private static NativeStructureTerrainIntegrator.TerrainTarget surfaceTarget(
             StructureStart start) {
-        return surfaceTarget(start, IrisStructureTerrainMode.SOURCE);
+        return surfaceTarget(start, StructureTerrainMode.SOURCE);
     }
 
     private static NativeStructureTerrainIntegrator.TerrainTarget surfaceTarget(
-            StructureStart start, IrisStructureTerrainMode mode) {
+            StructureStart start, StructureTerrainMode mode) {
         return new NativeStructureTerrainIntegrator.TerrainTarget(
                 "nova_structures:tavern_oak", start,
                 new IrisStructureTerrain().setMode(mode));
@@ -2619,8 +2705,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
     private static NativeStructureTerrainIntegrator.OrganicCarve organicCarve(
             StructureStart start, int horizontalPadding, double lobeStrength) {
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
-                .setShape(IrisStructureCarveShape.ERODED)
+                .setMode(StructureTerrainMode.FORCE_CARVE)
+                .setShape(StructureCarveShape.ERODED)
                 .setHorizontalPadding(horizontalPadding)
                 .setCeilingPadding(8)
                 .setFloorPadding(0)
@@ -2630,7 +2716,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
         return NativeStructureTerrainIntegrator.organicCarve(
                 NativeStructureTerrainIntegrator.carveFootprint(start, horizontalPadding,
                         NativeStructurePostProcessorSurfaceTerrainTest::forbiddenTemplateManager),
-                terrain, IrisStructureCarveShape.ERODED, TEST_SEED);
+                terrain, StructureCarveShape.ERODED, TEST_SEED);
     }
 
     /**
@@ -2648,8 +2734,8 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
             return true;
         }, SLAB_PADDING, 1_000_000);
         IrisStructureTerrain terrain = new IrisStructureTerrain()
-                .setMode(IrisStructureTerrainMode.FORCE_CARVE)
-                .setShape(IrisStructureCarveShape.ERODED)
+                .setMode(StructureTerrainMode.FORCE_CARVE)
+                .setShape(StructureCarveShape.ERODED)
                 .setHorizontalPadding(SLAB_PADDING)
                 .setCeilingPadding(8)
                 .setFloorPadding(0)
@@ -2664,7 +2750,7 @@ public class NativeStructurePostProcessorSurfaceTerrainTest {
 
         NativeStructureTerrainIntegrator.carveOrganicColumns(world(blocks), area,
                 NativeStructureTerrainIntegrator.organicCarve(
-                        footprint, terrain, IrisStructureCarveShape.ERODED, TEST_SEED));
+                        footprint, terrain, StructureCarveShape.ERODED, TEST_SEED));
 
         int[] depths = new int[SLAB_DEPTH];
         for (int z = 0; z < SLAB_DEPTH; z++) {

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorVegetationTest.java

@@ -1,5 +1,11 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureSurfaceFitter;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVegetationClearer;
+
 import com.mojang.serialization.Codec;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
@@ -233,8 +239,8 @@ public class NativeStructurePostProcessorVegetationTest {
     }
 
     @Test
-    public void loweringSurfaceKeepsTreeAndSolidObjectBoundaries() {
-        for (BlockState boundary : List.of(Blocks.OAK_LOG.defaultBlockState(), Blocks.OAK_PLANKS.defaultBlockState())) {
+    public void loweringSurfaceKeepsTreeBoundaries() {
+        for (BlockState boundary : List.of(Blocks.OAK_LOG.defaultBlockState(), Blocks.OAK_LEAVES.defaultBlockState())) {
             ProtoChunk chunk = chunk();
             write(chunk, 4, 63, 4, Blocks.SAND.defaultBlockState());
             write(chunk, 4, 64, 4, Blocks.SAND.defaultBlockState());
@@ -251,6 +257,34 @@ public class NativeStructurePostProcessorVegetationTest {
         }
     }
 
+    @Test
+    public void loweringSurfaceRemovesUnsupportedPlankDecoration() {
+        ProtoChunk chunk = chunk();
+        for (int x : List.of(4, 5)) {
+            for (int y = 60; y <= 64; y++) {
+                write(chunk, x, y, 4, Blocks.SAND.defaultBlockState());
+            }
+            write(chunk, x, 65, 4, Blocks.OAK_PLANKS.defaultBlockState());
+            write(chunk, x, 66, 4, Blocks.CACTUS.defaultBlockState());
+            write(chunk, x, 67, 4, Blocks.CACTUS_FLOWER.defaultBlockState());
+        }
+        WorldGenLevel world = world(chunk);
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(), 4, 4, 64, 60, MIN_Y, MAX_Y);
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(), 5, 4, 64, 64, MIN_Y, MAX_Y);
+
+        assertEquals(Blocks.SAND.defaultBlockState(), chunk.getBlockState(new BlockPos(4, 60, 4)));
+        for (int y = 61; y <= 67; y++) {
+            assertTrue(chunk.getBlockState(new BlockPos(4, y, 4)).isAir());
+        }
+        assertEquals(Blocks.SAND.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 64, 4)));
+        assertEquals(Blocks.OAK_PLANKS.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 65, 4)));
+        assertEquals(Blocks.CACTUS.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 66, 4)));
+        assertEquals(Blocks.CACTUS_FLOWER.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 67, 4)));
+    }
+
     private static void clearVegetation(ProtoChunk chunk, StructureStart start) {
         NativeStructureVegetationClearer.clearIntersectingVegetation(
                 world(chunk), chunk, AREA, List.of(start));

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureTemplateOccupancyTest.java

@@ -1,5 +1,9 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureTemplateOccupancy;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureReflection;
+
 import com.mojang.datafixers.util.Either;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeTerrainHeightCacheTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeTerrainHeightCache;
+
 import net.minecraft.SharedConstants;
 import net.minecraft.server.Bootstrap;
 import net.minecraft.world.level.levelgen.Heightmap;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/nativegen/NativeTransitionColumnTest.java

@@ -1,10 +1,14 @@
 package art.arcane.iris.nativegen;
 
+import art.arcane.iris.world.history.TerrainNativeBlockKeys;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeTransitionColumn;
+
 import art.arcane.iris.world.history.BoundaryColumnGeometry;
 import art.arcane.iris.world.history.TerrainBoundarySignature;
 import art.arcane.iris.spi.IrisPlatform;
 import art.arcane.iris.spi.IrisPlatforms;
-import art.arcane.iris.spi.PlatformBlockState;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
 import art.arcane.iris.spi.PlatformRegistries;
 import art.arcane.iris.testsupport.PlatformLeakGuard;
 import net.minecraft.SharedConstants;
@@ -44,8 +48,8 @@ public final class NativeTransitionColumnTest {
     @Test
     public void customKeysUseCarrierForNativeColumnsAndHeightmaps() {
         String key = "itemsadder:rocks/ruby_ore";
-        PlatformBlockState custom = mock(PlatformBlockState.class);
-        PlatformBlockState carrier = mock(PlatformBlockState.class);
+        NativeBlockState custom = mock(NativeBlockState.class);
+        NativeBlockState carrier = mock(NativeBlockState.class);
         when(custom.placementBaseState()).thenReturn(carrier);
         when(carrier.key()).thenReturn("minecraft:oak_log[axis=z]");
         IrisPlatform platform = mock(IrisPlatform.class);
@@ -58,17 +62,17 @@ public final class NativeTransitionColumnTest {
         try (MockedStatic<IrisPlatforms> platforms = mockStatic(IrisPlatforms.class)) {
             platforms.when(IrisPlatforms::isBound).thenReturn(true);
             platforms.when(IrisPlatforms::get).thenReturn(platform);
-            NoiseColumn column = NativeTransitionColumn.column(signature, height);
+            NoiseColumn column = NativeTransitionColumn.column(signature.geometry(), height, TerrainNativeBlockKeys::placementKey);
 
             assertEquals(Direction.Axis.Z, column.getBlock(-15).getValue(RotatedPillarBlock.AXIS));
-            assertEquals(-14, NativeTransitionColumn.height(signature, Heightmap.Types.OCEAN_FLOOR_WG, height));
+            assertEquals(-14, NativeTransitionColumn.height(signature.geometry(), Heightmap.Types.OCEAN_FLOOR_WG, height, TerrainNativeBlockKeys::placementKey));
         }
     }
 
     @Test
     public void preservesNativePropertiesCavesAndFluids() {
-        NoiseColumn column = NativeTransitionColumn.column(signature("minecraft:oak_log[axis=x]"),
-                LevelHeightAccessor.create(-16, 32));
+        NoiseColumn column = NativeTransitionColumn.column(signature("minecraft:oak_log[axis=x]").geometry(),
+                LevelHeightAccessor.create(-16, 32), TerrainNativeBlockKeys::placementKey);
         assertEquals(Direction.Axis.X, column.getBlock(-15).getValue(RotatedPillarBlock.AXIS));
         assertTrue(column.getBlock(-14).is(Blocks.CAVE_AIR));
         assertEquals(Integer.valueOf(3), column.getBlock(-13).getValue(LiquidBlock.LEVEL));
@@ -79,14 +83,13 @@ public final class NativeTransitionColumnTest {
     public void usesNativeHeightmapPredicatesForWaterAndOpenSpace() {
         TerrainBoundarySignature signature = signature("minecraft:oak_log[axis=x]");
         LevelHeightAccessor height = LevelHeightAccessor.create(-16, 32);
-        assertEquals(-12, NativeTransitionColumn.height(signature, Heightmap.Types.WORLD_SURFACE_WG, height));
-        assertEquals(-14, NativeTransitionColumn.height(signature, Heightmap.Types.OCEAN_FLOOR_WG, height));
+        assertEquals(-12, NativeTransitionColumn.height(signature.geometry(), Heightmap.Types.WORLD_SURFACE_WG, height, TerrainNativeBlockKeys::placementKey));
+        assertEquals(-14, NativeTransitionColumn.height(signature.geometry(), Heightmap.Types.OCEAN_FLOOR_WG, height, TerrainNativeBlockKeys::placementKey));
     }
 
     @Test
     public void rejectsUnknownSavedStatesInsteadOfReplacingTerrain() {
-        assertThrows(IllegalArgumentException.class, () -> NativeTransitionColumn.column(
-                signature("missing:removed_block"), LevelHeightAccessor.create(-16, 32)));
+        assertThrows(IllegalArgumentException.class, () -> NativeTransitionColumn.column(signature("missing:removed_block").geometry(), LevelHeightAccessor.create(-16, 32), TerrainNativeBlockKeys::placementKey));
     }
 
     private static TerrainBoundarySignature signature(String solidState) {

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/CustomBiomeSourceStructureContractTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.iris.platform.bukkit.nms.BukkitBiomePolicy;
+
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.generation.terrain.IrisDimension;
 import net.minecraft.SharedConstants;
@@ -28,10 +30,10 @@ public class CustomBiomeSourceStructureContractTest {
         IrisDimension upper = new IrisDimension();
         upper.setLoadKey("Layers/Upper");
 
-        assertEquals("layers:upper/aurora", CustomBiomeSource.customBiomeKey(upper, "Aurora"));
+        assertEquals("layers:upper/aurora", BukkitBiomePolicy.customBiomeKey(upper, "Aurora"));
         assertNotEquals(
-                CustomBiomeSource.customBiomeKey(host, "Aurora"),
-                CustomBiomeSource.customBiomeKey(upper, "Aurora")
+                BukkitBiomePolicy.customBiomeKey(host, "Aurora"),
+                BukkitBiomePolicy.customBiomeKey(upper, "Aurora")
         );
     }
 
@@ -39,8 +41,8 @@ public class CustomBiomeSourceStructureContractTest {
     public void temporaryNaturalBiomeAnswersAreNotMemoized() {
         Engine temporary = engineAnsweringNaturalFallback(true, 12, -8);
         Engine stable = engineAnsweringNaturalFallback(false, 12, -8);
-        assertFalse(CustomBiomeSource.isBiomeCacheable(temporary, 12, -8));
-        assertTrue(CustomBiomeSource.isBiomeCacheable(stable, 12, -8));
+        assertFalse(BukkitBiomePolicy.isBiomeCacheable(temporary, 12, -8));
+        assertTrue(BukkitBiomePolicy.isBiomeCacheable(stable, 12, -8));
     }
 
     private static Engine engineAnsweringNaturalFallback(

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/IrisChunkGeneratorMonumentLocateContractTest.java

@@ -1,6 +1,6 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
-import art.arcane.iris.nativegen.NativeStructureLocateResults;
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureLocateResults;
 import com.mojang.datafixers.util.Pair;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Holder;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/IrisChunkGeneratorSpawnAdmissionTest.java

@@ -1,5 +1,10 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.iris.platform.bukkit.nms.BukkitGeneratorContext;
+import org.bukkit.World;
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeChunkGenerator;
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeBiomeSourceImpl;
+
 import art.arcane.iris.generation.runtime.IrisEngine;
 import art.arcane.iris.generation.runtime.GenerationSessionManager;
 import art.arcane.iris.generation.runtime.GenerationTransitionGate;
@@ -89,8 +94,8 @@ public class IrisChunkGeneratorSpawnAdmissionTest {
         }
     }
 
-    private static void setField(IrisChunkGenerator generator, String name, Object value) throws Exception {
-        Field field = IrisChunkGenerator.class.getDeclaredField(name);
+    private static void setField(NativeChunkGenerator<?, ?, ?, ?, ?> generator, String name, Object value) throws Exception {
+        Field field = NativeChunkGenerator.class.getDeclaredField(name);
         field.setAccessible(true);
         field.set(generator, value);
     }
@@ -98,7 +103,7 @@ public class IrisChunkGeneratorSpawnAdmissionTest {
     private static final class Fixture {
         private final GenerationSessionManager sessions = new GenerationSessionManager(true);
         private final IrisEngine engine = mock(IrisEngine.class);
-        private final IrisChunkGenerator generator = mock(IrisChunkGenerator.class, CALLS_REAL_METHODS);
+        private final NativeChunkGenerator<?, ?, ?, ?, ?> generator = mock(NativeChunkGenerator.class, CALLS_REAL_METHODS);
         private final Holder<Biome> biome = Holder.direct(mock(Biome.class));
         private final StructureManager structures = mock(StructureManager.class);
         private final WeightedList<MobSpawnSettings.SpawnerData> expected = mock(WeightedList.class);
@@ -110,7 +115,7 @@ public class IrisChunkGeneratorSpawnAdmissionTest {
             GenerationHistoryRuntimeRouter router = mock(GenerationHistoryRuntimeRouter.class);
             SavedBiomeRuntime saved = mock(SavedBiomeRuntime.class);
             ChunkGenerator delegate = mock(ChunkGenerator.class);
-            CustomBiomeSource source = mock(CustomBiomeSource.class);
+            NativeBiomeSourceImpl source = mock(NativeBiomeSourceImpl.class);
             when(engine.getGenerationSessions()).thenReturn(sessions);
             when(engine.getGenerationHistoryRuntimeRouter()).thenReturn(Optional.of(router));
             when(router.biomes()).thenReturn(saved);
@@ -126,7 +131,7 @@ public class IrisChunkGeneratorSpawnAdmissionTest {
             });
             when(delegate.getMobsAt(biome, structures, MobCategory.MONSTER, new BlockPos(0, 64, 0)))
                     .thenReturn(expected);
-            setField(generator, "engine", engine);
+            setField(generator, "context", new BukkitGeneratorContext(new BukkitGeneratorContext.Options(1L, engine, mock(World.class))));
             setField(generator, "delegate", delegate);
             setField(generator, "customBiomeSource", source);
         }

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NMSBindingDatapackStructureScopeTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeStructureSetFilter;
+
 import art.arcane.iris.pack.datapack.DatapackIngestService;
 import art.arcane.iris.pack.datapack.DatapackStructureScopeIndex;
 import art.arcane.iris.structure.nativegen.IrisImportedStructureControl;
@@ -59,9 +61,9 @@ public class NMSBindingDatapackStructureScopeTest {
                 List.of(),
                 List.of("managed:illager_barracks"));
 
-        DatapackStructureStateFilter.Selection vanilla = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection vanilla = NativeStructureSetFilter.filter(
                 List.of(managedSet), index, Set.of());
-        DatapackStructureStateFilter.Selection declaring = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection declaring = NativeStructureSetFilter.filter(
                 List.of(managedSet), index, index.declaredSources(List.of(SOURCE)));
 
         assertEquals(0, vanilla.structureSets().size());
@@ -80,9 +82,9 @@ public class NMSBindingDatapackStructureScopeTest {
                 List.of("managed:tavern"),
                 List.of());
 
-        DatapackStructureStateFilter.Selection vanilla = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection vanilla = NativeStructureSetFilter.filter(
                 List.of(vanillaSet), index, Set.of());
-        DatapackStructureStateFilter.Selection declaring = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection declaring = NativeStructureSetFilter.filter(
                 List.of(vanillaSet), index, index.declaredSources(List.of(SOURCE)));
 
         assertEquals(1, vanilla.structureSets().size());
@@ -100,7 +102,7 @@ public class NMSBindingDatapackStructureScopeTest {
                 "minecraft:custom", structureHolder("managed:only"));
         DatapackStructureScopeIndex index = index(List.of("managed:only"), List.of());
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(unmanagedSet), index, Set.of());
 
         assertEquals(0, selection.structureSets().size());
@@ -124,18 +126,18 @@ public class NMSBindingDatapackStructureScopeTest {
                         34, 8, RandomSpreadType.LINEAR, 14357620)));
         DatapackStructureScopeIndex scopeIndex = index(
                 List.of(), List.of("managed:illager_barracks"));
-        DatapackStructureStateFilter.StructureSetKeyIndex keyIndex =
-                DatapackStructureStateFilter.keyIndex(List.of(registered));
+        NativeStructureSetFilter.StructureSetKeyIndex keyIndex =
+                NativeStructureSetFilter.keyIndex(List.of(registered));
 
-        DatapackStructureStateFilter.Selection excluded =
-                DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection excluded =
+                NativeStructureSetFilter.filter(
                         List.of(spigotDirect),
                         scopeIndex,
                         Set.of(),
                         new IrisImportedStructureControl(),
                         keyIndex);
-        DatapackStructureStateFilter.Selection retained =
-                DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection retained =
+                NativeStructureSetFilter.filter(
                         List.of(spigotDirect),
                         scopeIndex,
                         scopeIndex.declaredSources(List.of(SOURCE)),
@@ -150,8 +152,8 @@ public class NMSBindingDatapackStructureScopeTest {
 
     @Test
     public void structureScopeDoesNotLinkPaperOnlyPlacementClasses() throws IOException {
-        InputStream classResource = NMSBindingDatapackStructureScopeTest.class
-                .getResourceAsStream("DatapackStructureStateFilter.class");
+        InputStream classResource = NativeStructureSetFilter.class
+                .getResourceAsStream("NativeStructureSetFilter.class");
         assertNotNull(classResource);
         try (InputStream input = classResource) {
             String classFile = new String(input.readAllBytes(), StandardCharsets.ISO_8859_1);
@@ -176,7 +178,7 @@ public class NMSBindingDatapackStructureScopeTest {
         IrisImportedStructureControl control = new IrisImportedStructureControl()
                 .setFrequencyOverrides(overrides);
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(complexes, fossils), index(List.of(), List.of()), Set.of(), control);
 
         RandomSpreadStructurePlacement scaledComplexes =
@@ -206,7 +208,7 @@ public class NMSBindingDatapackStructureScopeTest {
         IrisImportedStructureControl control = new IrisImportedStructureControl()
                 .setFrequencyOverrides(overrides);
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(custom), index(List.of(), List.of()), Set.of(), control);
 
         assertSame(custom, selection.structureSets().getFirst());
@@ -238,14 +240,14 @@ public class NMSBindingDatapackStructureScopeTest {
         IrisImportedStructureControl control = new IrisImportedStructureControl()
                 .setFrequencyOverrides(overrides);
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(dependent, target), index(List.of(), List.of()), Set.of(), control);
 
         Holder<StructureSet> scaledDependent = selection.structureSets().get(0);
         Holder<StructureSet> scaledTarget = selection.structureSets().get(1);
         assertNotSame(dependent, scaledDependent);
         assertNotSame(target, scaledTarget);
-        assertSame(scaledTarget, DatapackStructureStateFilter.exclusionZone(
+        assertSame(scaledTarget, NativeStructureSetFilter.exclusionZone(
                 scaledDependent.value().placement()).orElseThrow().otherSet());
         assertEquals(26, ((RandomSpreadStructurePlacement)
                 scaledTarget.value().placement()).spacing());
@@ -284,14 +286,14 @@ public class NMSBindingDatapackStructureScopeTest {
         IrisImportedStructureControl control = new IrisImportedStructureControl()
                 .setFrequencyOverrides(overrides);
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(first, second), index(List.of(), List.of()), Set.of(), control);
 
         Holder<StructureSet> scaledFirst = selection.structureSets().get(0);
         Holder<StructureSet> scaledSecond = selection.structureSets().get(1);
-        assertSame(scaledSecond, DatapackStructureStateFilter.exclusionZone(
+        assertSame(scaledSecond, NativeStructureSetFilter.exclusionZone(
                 scaledFirst.value().placement()).orElseThrow().otherSet());
-        assertSame(scaledFirst, DatapackStructureStateFilter.exclusionZone(
+        assertSame(scaledFirst, NativeStructureSetFilter.exclusionZone(
                 scaledSecond.value().placement()).orElseThrow().otherSet());
         assertEquals(26, ((RandomSpreadStructurePlacement)
                 scaledSecond.value().placement()).spacing());
@@ -310,7 +312,7 @@ public class NMSBindingDatapackStructureScopeTest {
         IrisImportedStructureControl control = new IrisImportedStructureControl()
                 .setFrequencyOverrides(overrides);
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(custom), index(List.of(), List.of()), Set.of(), control);
         StructurePlacement placement = selection.structureSets().getFirst().value().placement();
 
@@ -340,12 +342,12 @@ public class NMSBindingDatapackStructureScopeTest {
                 List.of("managed:blocked"),
                 List.of("managed:blocked"));
 
-        DatapackStructureStateFilter.Selection selection = DatapackStructureStateFilter.filter(
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
                 List.of(vanillaSet, managedSet), index, Set.of());
 
         assertEquals(1, selection.structureSets().size());
         StructurePlacement scopedPlacement = selection.structureSets().getFirst().value().placement();
-        assertEquals(0, DatapackStructureStateFilter.exclusionZone(scopedPlacement).stream().count());
+        assertEquals(0, NativeStructureSetFilter.exclusionZone(scopedPlacement).stream().count());
     }
 
     private static DatapackStructureScopeIndex index(

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NativeStructurePoiUpdatesTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeStructurePoiUpdates;
+
 import ca.spottedleaf.moonrise.common.util.TickThread;
 import com.mojang.serialization.Codec;
 import net.minecraft.SharedConstants;

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NativeStructureWorldgenAccessTest.java

@@ -1,9 +1,11 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeStructureWorldgenAccess;
+
 import art.arcane.iris.structure.placement.IrisStructureTerrain;
-import art.arcane.iris.structure.placement.IrisStructureTerrainMode;
-import art.arcane.iris.nativegen.NativeStructurePostProcessor;
-import art.arcane.iris.nativegen.NativeStructureTerrainIntegrator;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructurePostProcessor;
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureTerrainIntegrator;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
@@ -84,7 +86,7 @@ public class NativeStructureWorldgenAccessTest {
         StructureStart start = new StructureStart(structure, generationCenter(), 0, new PiecesContainer(List.of(piece)));
         List<NativeStructureTerrainIntegrator.TerrainTarget> targets = List.of(
                 new NativeStructureTerrainIntegrator.TerrainTarget("minecraft:village_plains", start,
-                        new IrisStructureTerrain().setMode(IrisStructureTerrainMode.FLATTEN)));
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.FLATTEN)));
         BoundingBox area = new BoundingBox(generationCenter().getMinBlockX(), -64, generationCenter().getMinBlockZ(),
                 generationCenter().getMaxBlockX(), 319, generationCenter().getMaxBlockZ());
         RecordingDelegate unbounded = new RecordingDelegate();

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsChunkIOFlushTest.java

@@ -1,5 +1,6 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeTerrainAccessImpl;
 import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO.RegionDataController;
 import net.minecraft.SharedConstants;
 import net.minecraft.server.Bootstrap;
@@ -83,7 +84,7 @@ public class NmsChunkIOFlushTest {
     }
 
     private static final class Fixture {
-        private final NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        private final NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         private final CraftWorld world = mock(CraftWorld.class);
         private final ServerLevel level = mock(ServerLevel.class);
         private final RegionDataController chunks = mock(RegionDataController.class);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsChunkRetentionTest.java

@@ -0,0 +1,84 @@
+package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
+
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeTerrainAccessImpl;
+import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkHolderManager;
+import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ChunkLevel;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.TicketType;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import java.lang.reflect.Field;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.isNull;
+import static org.mockito.ArgumentMatchers.same;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class NmsChunkRetentionTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void retentionRequestsNothingBeyondTheOuterRingOfAFullRequest() {
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        assertEquals(ChunkLevel.RADIUS_AROUND_FULL_CHUNK, binding.fullChunkDependencyRadius());
+        assertEquals(ChunkLevel.MAX_LEVEL, ChunkHolderManager.MAX_TICKET_LEVEL);
+        assertEquals(ChunkLevel.generationStatus(ChunkLevel.FULL_CHUNK_LEVEL + binding.fullChunkDependencyRadius()),
+                ChunkLevel.generationStatus(ChunkHolderManager.MAX_TICKET_LEVEL));
+        assertEquals(ChunkStatus.STRUCTURE_STARTS, ChunkLevel.generationStatus(ChunkHolderManager.MAX_TICKET_LEVEL));
+    }
+
+    @Test
+    public void retainAndReleaseUseOnePermanentNonPersistentTicketAtTheMaximumLevel() throws Exception {
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        CraftWorld world = mock(CraftWorld.class);
+        ServerLevel level = mock(ServerLevel.class);
+        ChunkTaskScheduler scheduler = mock(ChunkTaskScheduler.class);
+        ChunkHolderManager manager = mock(ChunkHolderManager.class);
+        Field managerField = ChunkTaskScheduler.class.getField("chunkHolderManager");
+        managerField.setAccessible(true);
+        managerField.set(scheduler, manager);
+        when(world.getHandle()).thenReturn(level);
+        when(level.moonrise$getChunkTaskScheduler()).thenReturn(scheduler);
+        when(manager.addTicketAtLevel(any(TicketType.class), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull()))
+                .thenReturn(true);
+        when(manager.removeTicketAtLevel(any(TicketType.class), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull()))
+                .thenReturn(true);
+
+        assertTrue(binding.retainChunk(world, 3, -4));
+        ArgumentCaptor<TicketType> type = ArgumentCaptor.forClass(TicketType.class);
+        verify(manager).addTicketAtLevel(type.capture(), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull());
+        assertEquals(TicketType.NO_TIMEOUT, type.getValue().timeout());
+        assertTrue(type.getValue().doesLoad());
+        assertFalse(type.getValue().doesSimulate());
+        assertFalse(type.getValue().persist());
+
+        assertTrue(binding.releaseChunk(world, 3, -4));
+        verify(manager).removeTicketAtLevel(same(type.getValue()), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull());
+
+        binding.retainChunk(world, 3, -4);
+        ArgumentCaptor<TicketType> again = ArgumentCaptor.forClass(TicketType.class);
+        verify(manager, times(2)).addTicketAtLevel(again.capture(), eq(3), eq(-4),
+                eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull());
+        assertSame(type.getValue(), again.getValue());
+    }
+}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsChunkTaskPollingTest.java

@@ -1,5 +1,6 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeTerrainAccessImpl;
 import art.arcane.volmlib.util.scheduling.FoliaScheduler;
 import net.minecraft.SharedConstants;
 import net.minecraft.server.Bootstrap;
@@ -41,7 +42,7 @@ public class NmsChunkTaskPollingTest {
         ServerLevel level = mock(ServerLevel.class);
         MinecraftServer server = mock(MinecraftServer.class);
         ServerChunkCache chunks = mock(ServerChunkCache.class);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         CompletableFuture<Void> completed = new CompletableFuture<>();
         when(world.getHandle()).thenReturn(level);
         when(level.getServer()).thenReturn(server);
@@ -66,7 +67,7 @@ public class NmsChunkTaskPollingTest {
         CraftWorld world = mock(CraftWorld.class);
         ServerLevel level = mock(ServerLevel.class);
         MinecraftServer server = mock(MinecraftServer.class);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         when(world.getHandle()).thenReturn(level);
         when(level.getServer()).thenReturn(server);
         when(server.getRunningThread()).thenReturn(new Thread("Other server owner"));
@@ -83,7 +84,7 @@ public class NmsChunkTaskPollingTest {
     public void foliaNeverUsesTheWorldWideTaskPump() {
         Server bukkitServer = mock(Server.class);
         CraftWorld world = mock(CraftWorld.class);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
              MockedStatic<FoliaScheduler> folia = mockStatic(FoliaScheduler.class)) {
             bukkit.when(Bukkit::getServer).thenReturn(bukkitServer);

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsEntitySpawnDifficultyTest.java

@@ -1,5 +1,6 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeTerrainAccessImpl;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.resources.Identifier;
@@ -41,7 +42,7 @@ public class NmsEntitySpawnDifficultyTest {
     public void peacefulRejectsEveryNativeForbiddenTypeBeforeBukkitCreatesIt() {
         CraftWorld world = mock(CraftWorld.class);
         when(world.getDifficulty()).thenReturn(Difficulty.PEACEFUL);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         Location location = new Location(world, 0.5, 80, 0.5);
         int rejected = 0;
 
@@ -64,7 +65,7 @@ public class NmsEntitySpawnDifficultyTest {
     public void peacefulPreservesPassiveAndNativeMonsterCategoryExceptions() {
         CraftWorld world = mock(CraftWorld.class);
         when(world.getDifficulty()).thenReturn(Difficulty.PEACEFUL);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         Location location = new Location(world, 0.5, 80, 0.5);
         Entity created = mock(Entity.class);
         doReturn(created).when(world).spawn(eq(location), any(Class.class), isNull(), eq(CreatureSpawnEvent.SpawnReason.NATURAL));
@@ -77,7 +78,7 @@ public class NmsEntitySpawnDifficultyTest {
     @Test
     public void nonPeacefulDifficultiesPreserveHostileSpawns() {
         CraftWorld world = mock(CraftWorld.class);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         Location location = new Location(world, 0.5, 80, 0.5);
         Entity created = mock(Entity.class);
         doReturn(created).when(world).spawn(eq(location), any(Class.class), isNull(), eq(CreatureSpawnEvent.SpawnReason.NATURAL));
@@ -92,7 +93,7 @@ public class NmsEntitySpawnDifficultyTest {
     public void unrelatedBukkitSpawnFailuresStillPropagate() {
         CraftWorld world = mock(CraftWorld.class);
         when(world.getDifficulty()).thenReturn(Difficulty.PEACEFUL);
-        NMSBinding binding = mock(NMSBinding.class, CALLS_REAL_METHODS);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
         Location location = new Location(world, 0.5, 80, 0.5);
         IllegalStateException failure = new IllegalStateException("Spawn rejected by platform");
         doThrow(failure).when(world).spawn(eq(location), any(Class.class), isNull(), eq(CreatureSpawnEvent.SpawnReason.NATURAL));

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsSavedTerrainCheckpointTest.java

@@ -1,114 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.world.history.SavedTerrainChunk;
-import ca.spottedleaf.concurrentutil.util.Priority;
-import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
-import net.minecraft.SharedConstants;
-import net.minecraft.server.Bootstrap;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.level.ChunkPos;
-import org.junit.BeforeClass;
-import org.junit.Test;
-import org.mockito.MockedStatic;
-
-import java.io.IOException;
-import java.nio.file.Path;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-import java.util.concurrent.atomic.AtomicBoolean;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThrows;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.mockStatic;
-import static org.mockito.Mockito.never;
-
-public class NmsSavedTerrainCheckpointTest {
-    @BeforeClass
-    public static void bootstrapMinecraftRegistries() {
-        SharedConstants.tryDetectVersion();
-        Bootstrap.bootStrap();
-    }
-
-    @Test
-    public void checkpointWaitsForDirtyAndUnloadedChunkWritesBeforeFlushAndVerification() throws Exception {
-        ServerLevel level = mock(ServerLevel.class);
-        Path root = Path.of("checkpoint-world");
-        byte[] receipt = new byte[]{1, 2, 3};
-        NmsSavedTerrainCapture.Checkpoint saved = new NmsSavedTerrainCapture.Checkpoint(new ChunkPos(4, -5),
-                new NmsSavedTerrainCapture.Verification("minecraft:full", receipt, 7L));
-        NmsSavedTerrainCapture.Checkpoint unloaded = NmsSavedTerrainCapture.checkpoint(-8, 9, null);
-        Set<ChunkPos> completed = new HashSet<>();
-        AtomicBoolean flushed = new AtomicBoolean();
-        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class);
-             MockedStatic<SavedTerrainChunk> terrain = mockStatic(SavedTerrainChunk.class)) {
-            io.when(() -> MoonriseRegionFileIO.getPriority(level, 4, -5, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
-                    .thenAnswer(invocation -> {
-                        completed.add(saved.chunk());
-                        return Priority.COMPLETING;
-                    });
-            io.when(() -> MoonriseRegionFileIO.getPriority(level, -8, 9, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
-                    .thenAnswer(invocation -> {
-                        completed.add(unloaded.chunk());
-                        return Priority.COMPLETING;
-                    });
-            io.when(() -> MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
-                    .thenAnswer(invocation -> {
-                        assertEquals(Set.of(saved.chunk(), unloaded.chunk()), completed);
-                        flushed.set(true);
-                        return null;
-                    });
-            terrain.when(() -> SavedTerrainChunk.verifyCheckpoint(root, 4, -5, "minecraft:full", receipt, 7L))
-                    .thenAnswer(invocation -> {
-                        assertTrue(flushed.get());
-                        return null;
-                    });
-
-            NmsSavedTerrainCapture.finishCheckpoint(level, root, List.of(saved, unloaded));
-
-            terrain.verify(() -> SavedTerrainChunk.verifyCheckpoint(root, 4, -5, "minecraft:full", receipt, 7L));
-            io.verify(() -> MoonriseRegionFileIO.flush(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA), never());
-            io.verify(() -> MoonriseRegionFileIO.getPriority(level, 100, 100, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA), never());
-            terrain.verifyNoMoreInteractions();
-        }
-    }
-
-    @Test
-    public void storageFlushFailureCannotCompleteTheCheckpoint() throws Exception {
-        ServerLevel level = mock(ServerLevel.class);
-        IOException failure = new IOException("storage flush failed");
-        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class);
-             MockedStatic<SavedTerrainChunk> terrain = mockStatic(SavedTerrainChunk.class)) {
-            io.when(() -> MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
-                    .thenThrow(failure);
-
-            assertSame(failure, assertThrows(IOException.class,
-                    () -> NmsSavedTerrainCapture.finishCheckpoint(level, Path.of("checkpoint-world"), List.of())));
-            terrain.verifyNoInteractions();
-        }
-    }
-
-    @Test
-    public void persistedReceiptMismatchCannotCompleteTheCheckpoint() throws Exception {
-        ServerLevel level = mock(ServerLevel.class);
-        Path root = Path.of("checkpoint-world");
-        byte[] receipt = new byte[]{4, 5};
-        IOException failure = new IOException("saved terrain receipt mismatch");
-        NmsSavedTerrainCapture.Checkpoint saved = new NmsSavedTerrainCapture.Checkpoint(new ChunkPos(1, 2),
-                new NmsSavedTerrainCapture.Verification("minecraft:noise", receipt, 3L));
-        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class);
-             MockedStatic<SavedTerrainChunk> terrain = mockStatic(SavedTerrainChunk.class)) {
-            io.when(() -> MoonriseRegionFileIO.getPriority(level, 1, 2, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
-                    .thenReturn(Priority.COMPLETING);
-            terrain.when(() -> SavedTerrainChunk.verifyCheckpoint(root, 1, 2, "minecraft:noise", receipt, 3L))
-                    .thenThrow(failure);
-
-            assertSame(failure, assertThrows(IOException.class,
-                    () -> NmsSavedTerrainCapture.finishCheckpoint(level, root, List.of(saved))));
-            io.verify(() -> MoonriseRegionFileIO.flushRegionStorages(level, MoonriseRegionFileIO.RegionFileType.CHUNK_DATA));
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsSavedTerrainSnapshotTest.java

@@ -1,223 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import art.arcane.iris.world.task.J;
-import ca.spottedleaf.concurrentutil.completable.Completable;
-import ca.spottedleaf.concurrentutil.executor.PrioritisedExecutor;
-import ca.spottedleaf.concurrentutil.executor.thread.BalancedPrioritisedThreadPool;
-import ca.spottedleaf.concurrentutil.util.Priority;
-import ca.spottedleaf.moonrise.common.PlatformHooks;
-import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
-import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkHolderManager;
-import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
-import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.NewChunkHolder;
-import net.minecraft.SharedConstants;
-import net.minecraft.nbt.CompoundTag;
-import net.minecraft.server.Bootstrap;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.level.ChunkPos;
-import net.minecraft.world.level.chunk.ChunkAccess;
-import net.minecraft.world.level.chunk.storage.SerializableChunkData;
-import org.bukkit.World;
-import org.junit.BeforeClass;
-import org.junit.Test;
-import org.mockito.MockedStatic;
-
-import java.io.File;
-import java.io.IOException;
-import java.lang.reflect.Field;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicInteger;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNotSame;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThrows;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.ArgumentMatchers.anyInt;
-import static org.mockito.ArgumentMatchers.eq;
-import static org.mockito.Mockito.doAnswer;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.mockStatic;
-import static org.mockito.Mockito.never;
-import static org.mockito.Mockito.times;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
-
-public class NmsSavedTerrainSnapshotTest {
-    @BeforeClass
-    public static void bootstrapMinecraftRegistries() {
-        SharedConstants.tryDetectVersion();
-        Bootstrap.bootStrap();
-    }
-
-    @Test
-    public void ownerReservesSaveOrderBeforeOffOwnerSerializationAndLaterAutosave() throws Exception {
-        try (SaveFixture fixture = new SaveFixture();
-             ExecutorService checkpoint = Executors.newSingleThreadExecutor();
-             MockedStatic<SerializableChunkData> snapshots = mockStatic(SerializableChunkData.class);
-             MockedStatic<PlatformHooks> hooks = mockStatic(PlatformHooks.class);
-             MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class)) {
-            Thread owner = Thread.currentThread();
-            ChunkAccess chunk = mock(ChunkAccess.class);
-            SerializableChunkData snapshot = mock(SerializableChunkData.class);
-            PlatformHooks platform = mock(PlatformHooks.class);
-            CompoundTag capturedData = new CompoundTag();
-            CompoundTag autosave = new CompoundTag();
-            List<String> submissions = new ArrayList<>();
-            when(chunk.getPos()).thenReturn(new ChunkPos(4, -9));
-            snapshots.when(() -> SerializableChunkData.copyOf(fixture.level, chunk)).thenAnswer(invocation -> {
-                assertSame(owner, Thread.currentThread());
-                return snapshot;
-            });
-            hooks.when(PlatformHooks::get).thenReturn(platform);
-            doAnswer(invocation -> {
-                assertSame(owner, Thread.currentThread());
-                return null;
-            }).when(platform).chunkSyncSave(fixture.level, chunk, snapshot);
-            when(snapshot.write()).thenAnswer(invocation -> {
-                assertNotSame(owner, Thread.currentThread());
-                assertEquals(List.of("checkpoint", "autosave"), submissions);
-                return capturedData;
-            });
-            io.when(() -> MoonriseRegionFileIO.scheduleSave(eq(fixture.level), eq(4), eq(-9),
-                    any(Completable.class), any(PrioritisedExecutor.PrioritisedTask.class),
-                    eq(MoonriseRegionFileIO.RegionFileType.CHUNK_DATA), eq(Priority.NORMAL)))
-                    .thenAnswer(invocation -> {
-                        assertSame(owner, Thread.currentThread());
-                        submissions.add("checkpoint");
-                        return null;
-                    });
-            io.when(() -> MoonriseRegionFileIO.scheduleSave(fixture.level, 4, -9, autosave,
-                    MoonriseRegionFileIO.RegionFileType.CHUNK_DATA)).thenAnswer(invocation -> {
-                submissions.add("autosave");
-                return null;
-            });
-
-            NmsSavedTerrainCapture.CapturedChunk captured = NmsSavedTerrainCapture.scheduleSnapshot(fixture.level, chunk);
-
-            assertEquals(List.of("checkpoint"), submissions);
-            assertFalse(captured.data().isDone());
-            verify(snapshot, never()).write();
-            verify(platform).chunkSyncSave(fixture.level, chunk, snapshot);
-            MoonriseRegionFileIO.scheduleSave(fixture.level, 4, -9, autosave,
-                    MoonriseRegionFileIO.RegionFileType.CHUNK_DATA);
-            Future<CompoundTag> result = checkpoint.submit(() -> NmsSavedTerrainCapture.awaitSnapshot(
-                    fixture.level, captured, System.nanoTime() + TimeUnit.SECONDS.toNanos(3)));
-
-            assertSame(capturedData, result.get(5, TimeUnit.SECONDS));
-            verify(snapshot).write();
-        }
-    }
-
-    @Test
-    public void failedOffOwnerSerializationCannotSucceedAsACheckpoint() throws Exception {
-        try (SaveFixture fixture = new SaveFixture();
-             ExecutorService checkpoint = Executors.newSingleThreadExecutor();
-             MockedStatic<SerializableChunkData> snapshots = mockStatic(SerializableChunkData.class);
-             MockedStatic<PlatformHooks> hooks = mockStatic(PlatformHooks.class);
-             MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class)) {
-            ChunkAccess chunk = mock(ChunkAccess.class);
-            SerializableChunkData snapshot = mock(SerializableChunkData.class);
-            IllegalStateException failure = new IllegalStateException("serialization failed");
-            when(chunk.getPos()).thenReturn(new ChunkPos(4, -9));
-            snapshots.when(() -> SerializableChunkData.copyOf(fixture.level, chunk)).thenReturn(snapshot);
-            hooks.when(PlatformHooks::get).thenReturn(mock(PlatformHooks.class));
-            when(snapshot.write()).thenThrow(failure);
-            NmsSavedTerrainCapture.CapturedChunk captured = NmsSavedTerrainCapture.scheduleSnapshot(fixture.level, chunk);
-
-            Future<IOException> result = checkpoint.submit(() -> assertThrows(IOException.class,
-                    () -> NmsSavedTerrainCapture.awaitSnapshot(fixture.level, captured,
-                            System.nanoTime() + TimeUnit.SECONDS.toNanos(3))));
-
-            assertSame(failure, result.get(5, TimeUnit.SECONDS).getCause());
-            assertTrue(captured.data().isCompletedExceptionally());
-        }
-    }
-
-    @Test
-    public void checkpointBoundsOwnerRequestsUntilPriorNativeWritesFinish() throws Exception {
-        try (SaveFixture fixture = new SaveFixture();
-             ExecutorService owner = Executors.newSingleThreadExecutor();
-             ExecutorService checkpoint = Executors.newSingleThreadExecutor()) {
-            World world = mock(World.class);
-            when(world.getWorldFolder()).thenReturn(new File("checkpoint-world"));
-            List<NewChunkHolder> holders = new ArrayList<>(129);
-            for (int index = 0; index < 129; index++) {
-                NewChunkHolder holder = mock(NewChunkHolder.class);
-                setField(holder, "chunkX", index);
-                holders.add(holder);
-            }
-            AtomicInteger requested = new AtomicInteger();
-            AtomicBoolean writesBlocked = new AtomicBoolean(true);
-            CountDownLatch firstBatchWaiting = new CountDownLatch(1);
-            Future<?> result = checkpoint.submit(() -> {
-                try (MockedStatic<J> scheduling = mockStatic(J.class);
-                     MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class)) {
-                    scheduling.when(() -> J.runRegionFuture(eq(world), anyInt(), anyInt(), any(Runnable.class)))
-                            .thenAnswer(invocation -> {
-                                requested.incrementAndGet();
-                                Runnable action = invocation.getArgument(3);
-                                return CompletableFuture.runAsync(action, owner);
-                            });
-                    io.when(() -> MoonriseRegionFileIO.getPriority(eq(fixture.level), anyInt(), anyInt(),
-                            eq(MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))).thenAnswer(invocation -> {
-                        firstBatchWaiting.countDown();
-                        return writesBlocked.get() ? Priority.NORMAL : Priority.COMPLETING;
-                    });
-                    NmsSavedTerrainCapture.flushSnapshots(world, fixture.level, holders);
-                    io.verify(() -> MoonriseRegionFileIO.getPriority(fixture.level, 128, 0,
-                            MoonriseRegionFileIO.RegionFileType.CHUNK_DATA), times(2));
-                    return null;
-                }
-            });
-            try {
-                assertTrue(firstBatchWaiting.await(5, TimeUnit.SECONDS));
-                assertEquals(64, requested.get());
-                assertTrue(owner.submit(() -> true).get(5, TimeUnit.SECONDS));
-                assertFalse(result.isDone());
-                writesBlocked.set(false);
-                result.get(5, TimeUnit.SECONDS);
-                assertEquals(129, requested.get());
-            } finally {
-                writesBlocked.set(false);
-            }
-        }
-    }
-
-    private static void setField(Object instance, String name, Object value) throws Exception {
-        Field field = instance.getClass().getField(name);
-        field.setAccessible(true);
-        field.set(instance, value);
-    }
-
-    private static final class SaveFixture implements AutoCloseable {
-        private final BalancedPrioritisedThreadPool pool = new BalancedPrioritisedThreadPool(
-                TimeUnit.MILLISECONDS.toNanos(1), Executors.defaultThreadFactory());
-        private final ServerLevel level = mock(ServerLevel.class);
-
-        private SaveFixture() throws Exception {
-            BalancedPrioritisedThreadPool.OrderedStreamGroup group = pool.createOrderedStreamGroup();
-            ChunkTaskScheduler scheduler = mock(ChunkTaskScheduler.class);
-            setField(scheduler, "saveExecutor", group.createExecutor());
-            setField(scheduler, "compressionExecutor", group.createExecutor());
-            setField(scheduler, "chunkHolderManager", mock(ChunkHolderManager.class));
-            when(level.moonrise$getChunkTaskScheduler()).thenReturn(scheduler);
-        }
-
-        @Override
-        public void close() throws Exception {
-            pool.halt(true);
-            assertTrue(pool.joinInterruptable(5_000));
-        }
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/NmsSavedTerrainWriteBarrierTest.java

@@ -1,135 +0,0 @@
-package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
-
-import ca.spottedleaf.concurrentutil.executor.thread.BalancedPrioritisedThreadPool;
-import ca.spottedleaf.concurrentutil.util.Priority;
-import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO;
-import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
-import net.minecraft.SharedConstants;
-import net.minecraft.server.Bootstrap;
-import net.minecraft.server.level.ServerLevel;
-import net.minecraft.world.level.ChunkPos;
-import org.junit.BeforeClass;
-import org.junit.Test;
-import org.mockito.MockedStatic;
-
-import java.io.IOException;
-import java.lang.reflect.Field;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.concurrent.atomic.AtomicReference;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThrows;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.mockStatic;
-import static org.mockito.Mockito.when;
-
-public class NmsSavedTerrainWriteBarrierTest {
-    @BeforeClass
-    public static void bootstrapMinecraftRegistries() {
-        SharedConstants.tryDetectVersion();
-        Bootstrap.bootStrap();
-    }
-
-    @Test
-    public void checkpointHelpsSaveAndCompressionWhileNativeGenerationOccupiesTheWorker() throws Exception {
-        BalancedPrioritisedThreadPool pool = new BalancedPrioritisedThreadPool(
-                TimeUnit.MILLISECONDS.toNanos(1), Executors.defaultThreadFactory());
-        BalancedPrioritisedThreadPool.OrderedStreamGroup group = pool.createOrderedStreamGroup();
-        BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue generation = group.createExecutor();
-        BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue saves = group.createExecutor();
-        BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue compression = group.createExecutor();
-        ServerLevel level = level(saves, compression);
-        ChunkPos chunk = new ChunkPos(4, -9);
-        CountDownLatch generationEntered = new CountDownLatch(1);
-        CountDownLatch releaseGeneration = new CountDownLatch(1);
-        AtomicBoolean pendingWrite = new AtomicBoolean(true);
-        AtomicInteger serialized = new AtomicInteger();
-        AtomicInteger compressed = new AtomicInteger();
-        AtomicReference<Thread> saveThread = new AtomicReference<>();
-        AtomicReference<Thread> compressionThread = new AtomicReference<>();
-        try (MockedStatic<MoonriseRegionFileIO> io = mockStatic(MoonriseRegionFileIO.class)) {
-            io.when(() -> MoonriseRegionFileIO.getPriority(level, chunk.x(), chunk.z(),
-                    MoonriseRegionFileIO.RegionFileType.CHUNK_DATA))
-                    .thenAnswer(invocation -> pendingWrite.get() ? Priority.NORMAL : Priority.COMPLETING);
-            generation.queueTask(() -> {
-                generationEntered.countDown();
-                try {
-                    assertTrue(releaseGeneration.await(5, TimeUnit.SECONDS));
-                } catch (InterruptedException interruption) {
-                    Thread.currentThread().interrupt();
-                    throw new AssertionError(interruption);
-                }
-            });
-            pool.adjustThreadCount(1);
-            assertTrue(generationEntered.await(5, TimeUnit.SECONDS));
-            saves.queueTask(() -> {
-                saveThread.set(Thread.currentThread());
-                serialized.incrementAndGet();
-                compression.queueTask(() -> {
-                    compressionThread.set(Thread.currentThread());
-                    compressed.incrementAndGet();
-                    pendingWrite.set(false);
-                });
-            });
-
-            NmsSavedTerrainCapture.awaitWrite(level, chunk, System.nanoTime() + TimeUnit.SECONDS.toNanos(3));
-
-            assertEquals(1L, releaseGeneration.getCount());
-            assertEquals(1, serialized.get());
-            assertEquals(1, compressed.get());
-            assertFalse(pendingWrite.get());
-            assertSame(Thread.currentThread(), saveThread.get());
-            assertSame(Thread.currentThread(), compressionThread.get());
-        } finally {
-            releaseGeneration.countDown();
-            pool.halt(true);
-            assertTrue(pool.joinInterruptable(5_000));
-        }
-    }
-
-    @Test
-    public void waitingForNativeWriteHonorsTheSharedDeadline() throws Exception {
-        ServerLevel level = mock(ServerLevel.class);
-        ChunkPos chunk = new ChunkPos(2, 3);
-        IOException failure = assertThrows(IOException.class,
-                () -> NmsSavedTerrainCapture.awaitWrite(level, chunk, System.nanoTime() - 1L));
-        assertTrue(failure.getMessage().contains("Timed out"));
-    }
-
-    @Test
-    public void interruptedNativeWriteWaitPreservesInterruption() throws Exception {
-        ServerLevel level = mock(ServerLevel.class);
-        ChunkPos chunk = new ChunkPos(2, 3);
-        Thread.currentThread().interrupt();
-        try {
-            IOException failure = assertThrows(IOException.class,
-                    () -> NmsSavedTerrainCapture.awaitWrite(level, chunk,
-                            System.nanoTime() + TimeUnit.SECONDS.toNanos(3)));
-            assertTrue(failure.getMessage().contains("Interrupted"));
-            assertTrue(Thread.currentThread().isInterrupted());
-        } finally {
-            Thread.interrupted();
-        }
-    }
-
-    private static ServerLevel level(BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue saves,
-                                     BalancedPrioritisedThreadPool.OrderedStreamGroup.Queue compression) throws Exception {
-        ServerLevel level = mock(ServerLevel.class);
-        ChunkTaskScheduler scheduler = mock(ChunkTaskScheduler.class);
-        Field savesField = ChunkTaskScheduler.class.getField("saveExecutor");
-        Field compressionField = ChunkTaskScheduler.class.getField("compressionExecutor");
-        savesField.setAccessible(true);
-        compressionField.setAccessible(true);
-        savesField.set(scheduler, saves);
-        compressionField.set(scheduler, compression);
-        when(level.moonrise$getChunkTaskScheduler()).thenReturn(scheduler);
-        return level;
-    }
-}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_2_R1/WorldgenTerrainHeightmapsTest.java

@@ -1,6 +1,8 @@
 package art.arcane.iris.platform.bukkit.nms.v26_2_R1;
 
-import art.arcane.iris.nativegen.WorldgenTerrainHeightmaps;
+import art.arcane.volmlib.nativelib.v26_2_R1.terrain.NativeTerrainPipeline;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.WorldgenTerrainHeightmaps;
 import com.mojang.serialization.Codec;
 import net.minecraft.SharedConstants;
 import net.minecraft.core.BlockPos;
@@ -68,7 +70,7 @@ public class WorldgenTerrainHeightmapsTest {
     public void authoringHeightmapsReadPlacedObjectsAndFluidsWithoutTerrainResolvers() {
         ProtoChunk chunk = terrainChunk(new ChunkPos(0, 0));
 
-        IrisChunkGenerator.primeAuthoringHeightmaps(chunk);
+        NativeTerrainPipeline.primeAuthoringHeightmaps(chunk);
 
         assertEquals(LAND_CANOPY_TOP, chunk.getHeight(Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
         assertEquals(LAND_CANOPY_TOP, chunk.getHeight(Heightmap.Types.OCEAN_FLOOR_WG, LAND_X, LAND_Z));

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/structure/VillageImporterListPoolElementRuntimeContractTest.java

@@ -18,6 +18,7 @@
 
 package art.arcane.iris.structure;
 
+import art.arcane.volmlib.nativelib.common.structure.StructureReaderFixture;
 import art.arcane.iris.structure.authoring.StructureCapability;
 import art.arcane.iris.structure.authoring.StructureLoss;
 import net.minecraft.SharedConstants;
@@ -33,7 +34,6 @@ import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 
 public class VillageImporterListPoolElementRuntimeContractTest {
@@ -54,7 +54,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 StructureTemplatePool.Projection.RIGID
         );
 
-        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(towers);
+        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(towers));
         Map<String, Object> entry = VillageImporter.piecePoolEntry(
                 "qa/pillager_outpost/piece/minecraft/pillager_outpost/watchtower",
                 1
@@ -85,7 +85,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 0,
                 List.of(Map.of("name", "minecraft:bottom")));
 
-        assertSame(tower, resolution.physicalElement());
+        assertEquals(tower.getClass().getSimpleName(), resolution.physicalElement().typeName());
         assertEquals("minecraft:pillager_outpost/watchtower", resolution.templateLocation());
         assertEquals(1, resolution.omittedElements());
         assertEquals("qa/pillager_outpost/piece/minecraft/pillager_outpost/watchtower", entry.get("piece"));
@@ -103,7 +103,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
         StructurePoolElement waystone = StructurePoolElement
                 .legacy("dungeons_and_taverns:waystones/waystone_scaffold")
                 .apply(StructureTemplatePool.Projection.RIGID);
-        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(waystone);
+        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(waystone));
         VillageImporter.PoolMemberNormalization normalization = VillageImporter.normalizePoolMember(
                 "dungeons_and_taverns:waystones",
                 "qa/pool/dungeons_and_taverns/waystones",
@@ -116,7 +116,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 0,
                 List.of());
 
-        assertSame(waystone, resolution.physicalElement());
+        assertEquals(waystone.getClass().getSimpleName(), resolution.physicalElement().typeName());
         assertEquals("dungeons_and_taverns:waystones/waystone_scaffold", resolution.templateLocation());
         assertEquals(VillageImporter.PoolMemberDisposition.EMPTY, normalization.disposition());
         assertEquals(true, normalization.poolEntry().get("empty"));
@@ -130,7 +130,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
         StructurePoolElement orphan = StructurePoolElement
                 .legacy("test:orphan_house")
                 .apply(StructureTemplatePool.Projection.RIGID);
-        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(orphan);
+        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(orphan));
         VillageImporter.PoolMemberNormalization normalization = VillageImporter.normalizePoolMember(
                 "test:orphan_pool",
                 "qa/pool/test/orphan_pool",
@@ -143,7 +143,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 37,
                 List.of());
 
-        assertSame(orphan, resolution.physicalElement());
+        assertEquals(orphan.getClass().getSimpleName(), resolution.physicalElement().typeName());
         assertEquals("test:orphan_house", resolution.templateLocation());
         assertEquals(VillageImporter.PoolMemberDisposition.OMITTED, normalization.disposition());
         assertTrue(normalization.poolEntry().isEmpty());
@@ -160,7 +160,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
         StructurePoolElement start = StructurePoolElement
                 .legacy("test:air_start")
                 .apply(StructureTemplatePool.Projection.RIGID);
-        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(start);
+        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(start));
         VillageImporter.PoolMemberNormalization normalization = VillageImporter.normalizePoolMember(
                 "test:start",
                 "qa/pool/test/start",
@@ -173,7 +173,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 0,
                 List.of());
 
-        assertSame(start, resolution.physicalElement());
+        assertEquals(start.getClass().getSimpleName(), resolution.physicalElement().typeName());
         assertEquals(VillageImporter.PoolMemberDisposition.PHYSICAL, normalization.disposition());
         assertEquals("qa/piece/test/air_start", normalization.poolEntry().get("piece"));
         assertTrue(normalization.losses().isEmpty());
@@ -184,7 +184,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
         StructurePoolElement inert = StructurePoolElement
                 .legacy("test:mixed_air_inert")
                 .apply(StructureTemplatePool.Projection.RIGID);
-        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(inert);
+        VillageImporter.PoolElementResolution resolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(inert));
         VillageImporter.PoolMemberNormalization normalization = VillageImporter.normalizePoolMember(
                 "test:mixed",
                 "qa/pool/test/mixed",
@@ -197,7 +197,7 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 0,
                 List.of());
 
-        assertSame(inert, resolution.physicalElement());
+        assertEquals(inert.getClass().getSimpleName(), resolution.physicalElement().typeName());
         assertEquals(VillageImporter.PoolMemberDisposition.OMITTED, normalization.disposition());
         assertTrue(normalization.poolEntry().isEmpty());
         assertEquals("connectorless_all_air_mixed_member_omitted",
@@ -214,8 +214,8 @@ public class VillageImporterListPoolElementRuntimeContractTest {
         StructurePoolElement nonAirElement = StructurePoolElement
                 .legacy("test:mixed_non_air_primary")
                 .apply(StructureTemplatePool.Projection.RIGID);
-        VillageImporter.PoolElementResolution allAirResolution = VillageImporter.resolvePoolElement(allAirElement);
-        VillageImporter.PoolElementResolution nonAirResolution = VillageImporter.resolvePoolElement(nonAirElement);
+        VillageImporter.PoolElementResolution allAirResolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(allAirElement));
+        VillageImporter.PoolElementResolution nonAirResolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(nonAirElement));
         VillageImporter.PoolMemberNormalization allAir = VillageImporter.normalizePoolMember(
                 "test:mixed",
                 "qa/pool/test/mixed",
@@ -239,8 +239,8 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 41,
                 List.of());
 
-        assertSame(allAirElement, allAirResolution.physicalElement());
-        assertSame(nonAirElement, nonAirResolution.physicalElement());
+        assertEquals(allAirElement.getClass().getSimpleName(), allAirResolution.physicalElement().typeName());
+        assertEquals(nonAirElement.getClass().getSimpleName(), nonAirResolution.physicalElement().typeName());
         assertEquals(VillageImporter.PoolMemberDisposition.PHYSICAL, allAir.disposition());
         assertEquals(VillageImporter.PoolMemberDisposition.PHYSICAL, nonAir.disposition());
         assertEquals("qa/piece/test/mixed_all_air_primary", allAir.poolEntry().get("piece"));
@@ -257,8 +257,8 @@ public class VillageImporterListPoolElementRuntimeContractTest {
         StructurePoolElement nonAirElement = StructurePoolElement
                 .legacy("test:non_air_primary")
                 .apply(StructureTemplatePool.Projection.RIGID);
-        VillageImporter.PoolElementResolution allAirResolution = VillageImporter.resolvePoolElement(allAirElement);
-        VillageImporter.PoolElementResolution nonAirResolution = VillageImporter.resolvePoolElement(nonAirElement);
+        VillageImporter.PoolElementResolution allAirResolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(allAirElement));
+        VillageImporter.PoolElementResolution nonAirResolution = VillageImporter.resolvePoolElement(StructureReaderFixture.element(nonAirElement));
         VillageImporter.PoolMemberNormalization allAir = VillageImporter.normalizePoolMember(
                 "test:primary",
                 "qa/pool/test/primary",
@@ -282,8 +282,8 @@ public class VillageImporterListPoolElementRuntimeContractTest {
                 29,
                 List.of());
 
-        assertSame(allAirElement, allAirResolution.physicalElement());
-        assertSame(nonAirElement, nonAirResolution.physicalElement());
+        assertEquals(allAirElement.getClass().getSimpleName(), allAirResolution.physicalElement().typeName());
+        assertEquals(nonAirElement.getClass().getSimpleName(), nonAirResolution.physicalElement().typeName());
         assertEquals(VillageImporter.PoolMemberDisposition.PHYSICAL, allAir.disposition());
         assertEquals(VillageImporter.PoolMemberDisposition.PHYSICAL, nonAir.disposition());
         assertEquals("qa/piece/test/all_air_primary", allAir.poolEntry().get("piece"));

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/iris/structure/nativegen/NativeStructureVolumeIndexTest.java

@@ -0,0 +1,604 @@
+package art.arcane.iris.structure.nativegen;
+
+import art.arcane.iris.structure.nativegen.IrisStructureVolumePolicy;
+
+import art.arcane.volmlib.nativelib.minecraft26_2.terrain.NativeStructureVolumeSource;
+
+import art.arcane.iris.structure.nativegen.NativeStructureVolumeIndex;
+
+import art.arcane.iris.generation.runtime.IrisEngine;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.volmlib.nativelib.terrain.structure.NativeStructureVolume;
+import art.arcane.iris.world.history.GenerationHistoryRuntimeRouter;
+import art.arcane.volmlib.util.collection.KList;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutPiece;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Proxy;
+import java.lang.reflect.Field;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.LockSupport;
+import java.util.function.IntConsumer;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeStructureVolumeIndexTest {
+    private static final String STRUCTURE_KEY = "minecraft:swamp_hut";
+
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void assembledPiecesBecomeWorldSpacePieceVolumes() {
+        StructureStart start = swampHut(0, 0, 4, 6);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+
+        KList<NativeStructureVolume> volumes = NativeStructureVolumeSource.appendPieces(null, STRUCTURE_KEY, start);
+
+        assertEquals(1, volumes.size());
+        NativeStructureVolume volume = volumes.getFirst();
+        assertEquals(STRUCTURE_KEY, volume.structure());
+        assertEquals(bounds.minX(), volume.minX());
+        assertEquals(bounds.minY(), volume.minY());
+        assertEquals(bounds.minZ(), volume.minZ());
+        assertEquals(bounds.maxX(), volume.maxX());
+        assertEquals(bounds.maxY(), volume.maxY());
+        assertEquals(bounds.maxZ(), volume.maxZ());
+    }
+
+    @Test
+    public void invalidStartsContributeNoVolumes() {
+        assertNull(NativeStructureVolumeSource.appendPieces(null, STRUCTURE_KEY, StructureStart.INVALID_START));
+        assertNull(NativeStructureVolumeSource.appendPieces(null, STRUCTURE_KEY, null));
+    }
+
+    @Test
+    public void coldAndCachedQueriesResolveIdenticalVolumes() {
+        CountingResolver resolver = new CountingResolver(0, 0);
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+
+        KList<NativeStructureVolume> cold = index.resolve(null, 0, 0, 15, 15);
+        int coldResolutions = resolver.resolutions();
+        KList<NativeStructureVolume> cached = index.resolve(null, 0, 0, 15, 15);
+
+        assertTrue(coldResolutions > 0);
+        assertFalse(cold.isEmpty());
+        assertEquals(cold, cached);
+        assertEquals(coldResolutions, resolver.resolutions());
+    }
+
+    @Test
+    public void completedOriginsRemainBoundedAndPendingBuildsAreReleased() throws Exception {
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(
+                (engine, chunkX, chunkZ) -> NativeStructureVolume.NONE);
+        for (int chunkX = -8_192; chunkX <= 8_192; chunkX++) {
+            index.originVolumes(null, chunkX, -17);
+        }
+        assertEquals(16_384, cache(index, "originCache").size());
+        assertTrue(cache(index, "originBuilds").isEmpty());
+        index.resolve(null, -16, -16, -1, -1);
+        assertEquals(16_384, cache(index, "originCache").size());
+        assertTrue(cache(index, "originBuilds").isEmpty());
+        assertTrue(cache(index, "queryBuilds").isEmpty());
+    }
+
+    @Test
+    public void runtimeBucketsStayIsolatedAndRetirementEvictsOnlyTheirEntries() {
+        AtomicInteger runtimeId = new AtomicInteger(1);
+        Engine engine = runtimeEngine(runtimeId);
+        CountingResolver resolver = new CountingResolver(0, 0);
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+
+        index.resolve(engine, 0, 0, 15, 15);
+        assertEquals(289, resolver.resolutions());
+        index.resolve(engine, 0, 0, 15, 15);
+        assertEquals(289, resolver.resolutions());
+
+        runtimeId.set(2);
+        index.resolve(engine, 0, 0, 15, 15);
+        assertEquals(578, resolver.resolutions());
+        index.resolve(engine, 0, 0, 15, 15);
+        assertEquals(578, resolver.resolutions());
+
+        index.evictRuntime(1);
+        runtimeId.set(1);
+        index.resolve(engine, 0, 0, 15, 15);
+        assertEquals(867, resolver.resolutions());
+    }
+
+    @Test
+    public void pinnedRuntimeReusesCachedOriginsWithoutOpeningCoordinateScopes() throws Exception {
+        ScopedEngine scoped = scopedEngine(true, 1);
+        CountingResolver resolver = new CountingResolver(0, 0);
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+
+        KList<NativeStructureVolume> first = index.resolve(scoped.engine(), 0, 0, 15, 15);
+        assertEquals(289, scoped.scopes().get());
+        index.resolve(scoped.engine(), 16, 0, 31, 15);
+        assertEquals(306, resolver.resolutions());
+        assertEquals(306, scoped.scopes().get());
+        assertEquals(first, index.resolve(scoped.engine(), 0, 0, 15, 15));
+        assertEquals(306, scoped.scopes().get());
+    }
+
+    @Test
+    public void absentOrMismatchedRuntimeOwnershipKeepsCoordinateRouting() throws Exception {
+        ScopedEngine detached = scopedEngine(true, 1);
+        when(detached.engine().getGenerationHistoryRuntimeRouter()).thenReturn(Optional.empty());
+        for (ScopedEngine scoped : List.of(scopedEngine(false, 1), scopedEngine(true, 0),
+                scopedEngine(true, 2), detached)) {
+            NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(new CountingResolver(0, 0));
+            index.resolve(scoped.engine(), 0, 0, 15, 15);
+            index.resolve(scoped.engine(), 16, 0, 31, 15);
+            assertEquals(578, scoped.scopes().get());
+        }
+    }
+
+    @Test
+    public void retiredPinnedOriginsRebuildThroughCoordinateScopes() throws Exception {
+        ScopedEngine scoped = scopedEngine(true, 1);
+        CountingResolver resolver = new CountingResolver(0, 0);
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+
+        KList<NativeStructureVolume> first = index.resolve(scoped.engine(), 0, 0, 15, 15);
+        index.evictRuntime(1);
+        assertEquals(first, index.resolve(scoped.engine(), 0, 0, 15, 15));
+        assertEquals(578, resolver.resolutions());
+        assertEquals(578, scoped.scopes().get());
+    }
+
+    @Test
+    public void invalidatedIndexReceivesRuntimeRetirementAndDetachesOnUninstall() throws Exception {
+        IrisEngine engine = mock(IrisEngine.class);
+        Set<IntConsumer> listeners = new CopyOnWriteArraySet<>();
+        doAnswer(invocation -> {
+            listeners.add(invocation.getArgument(0));
+            return null;
+        }).when(engine).addGenerationRuntimeRetirementListener(any());
+        doAnswer(invocation -> {
+            listeners.remove(invocation.getArgument(0));
+            return null;
+        }).when(engine).removeGenerationRuntimeRetirementListener(any());
+        NativeStructureVolumeSource.Context context = new NativeStructureVolumeSource.Context(
+                null, null, null, null, () -> null, () -> null, () -> null);
+        NativeStructureVolumeIndex.install(engine,
+                new NativeStructureVolumeSource<>(context, IrisStructureVolumePolicy.INSTANCE)::volumesAt);
+        try {
+            assertEquals(1, listeners.size());
+            IntConsumer original = listeners.iterator().next();
+            NativeStructureVolumeIndex.invalidate(engine);
+            assertEquals(1, listeners.size());
+            assertFalse(listeners.contains(original));
+
+            NativeStructureVolumeIndex.volumes(engine, 0, 0, 15, 15);
+            NativeStructureVolumeIndex current = installedIndexes().get(engine);
+            assertEquals(289, cache(current, "originCache").size());
+            assertEquals(1, cache(current, "queryCache").size());
+            for (IntConsumer listener : listeners) {
+                listener.accept(0);
+            }
+            assertTrue(cache(current, "originCache").isEmpty());
+            assertTrue(cache(current, "queryCache").isEmpty());
+        } finally {
+            NativeStructureVolumeIndex.uninstall(engine);
+        }
+        assertTrue(listeners.isEmpty());
+    }
+
+    @Test
+    public void retiringOriginBuildCannotRepublishWhileQueryEvictionWaits() throws Exception {
+        BlockingResolver resolver = new BlockingResolver();
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        Map<?, ?> origins = cache(index, "originCache");
+        Map<?, ?> queries = cache(index, "queryCache");
+        try {
+            Future<KList<NativeStructureVolume>> builder = executor.submit(() -> index.originVolumes(null, 0, 0));
+            assertTrue(resolver.awaitFirstEntry());
+            index.originVolumes(null, 1, 0);
+            assertEquals(1, origins.size());
+            Future<?> retirement;
+            synchronized (queries) {
+                retirement = executor.submit(() -> index.evictRuntime(0));
+                long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(5);
+                boolean cleared = false;
+                while (System.nanoTime() < deadline) {
+                    synchronized (origins) {
+                        cleared = origins.isEmpty();
+                    }
+                    if (cleared) {
+                        break;
+                    }
+                    LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(10L));
+                }
+                assertTrue("Origin eviction did not complete before the query cache lock", cleared);
+                resolver.release();
+                assertTrue(builder.get(5, TimeUnit.SECONDS).isEmpty());
+                synchronized (origins) {
+                    assertTrue("The retired in-flight origin was cached again", origins.isEmpty());
+                }
+            }
+            retirement.get(5, TimeUnit.SECONDS);
+            index.originVolumes(null, 0, 0);
+            assertEquals(3, resolver.resolutions());
+        } finally {
+            resolver.release();
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void independentIndexesResolveIdenticalVolumesFromTheSameSeed() {
+        NativeStructureVolumeIndex first = NativeStructureVolumeIndex.forTesting(new CountingResolver(0, 0));
+        NativeStructureVolumeIndex second = NativeStructureVolumeIndex.forTesting(new CountingResolver(0, 0));
+
+        assertEquals(first.resolve(null, 0, 0, 15, 15), second.resolve(null, 0, 0, 15, 15));
+        assertEquals(first.resolve(null, -32, -32, 47, 47), second.resolve(null, -32, -32, 47, 47));
+    }
+
+    @Test
+    public void volumesOutsideTheQueryRectAreExcluded() {
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(new CountingResolver(0, 0));
+        BoundingBox bounds = swampHut(0, 0, 4, 6).getPieces().getFirst().getBoundingBox();
+
+        KList<NativeStructureVolume> hit = index.resolve(null, bounds.minX(), bounds.minZ(), bounds.maxX(), bounds.maxZ());
+        KList<NativeStructureVolume> miss = index.resolve(null,
+                bounds.maxX() + 1, bounds.minZ(), bounds.maxX() + 8, bounds.maxZ());
+
+        assertEquals(1, hit.size());
+        assertTrue(miss.isEmpty());
+    }
+
+    @Test
+    public void startsWithinTheOriginReachContributeAndBeyondItDoNot() {
+        int reach = NativeStructureVolumeIndex.originReachChunks();
+        NativeStructureVolumeIndex reachable = NativeStructureVolumeIndex.forTesting(new CountingResolver(reach, 0));
+        NativeStructureVolumeIndex unreachable = NativeStructureVolumeIndex.forTesting(new CountingResolver(reach + 1, 0));
+
+        assertFalse(reachable.resolve(null, 0, 0, 15, 15).isEmpty());
+        assertTrue(unreachable.resolve(null, 0, 0, 15, 15).isEmpty());
+    }
+
+    @Test
+    public void overlappingColdQueriesResolveIndependentOriginsConcurrently() throws Exception {
+        BlockingResolver resolver = new BlockingResolver();
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        try {
+            Future<KList<NativeStructureVolume>> first = executor.submit(() -> index.resolve(null, 0, 0, 15, 15));
+            assertTrue(resolver.awaitFirstEntry());
+            Future<KList<NativeStructureVolume>> adjacent = executor.submit(() -> index.resolve(null, 16, 0, 31, 15));
+
+            assertTrue(resolver.awaitSecondEntry(5_000));
+            assertTrue(adjacent.get(5, TimeUnit.SECONDS).isEmpty());
+            resolver.release();
+            assertTrue(first.get(5, TimeUnit.SECONDS).isEmpty());
+            assertTrue(adjacent.get(5, TimeUnit.SECONDS).isEmpty());
+            assertEquals(306, resolver.resolutions());
+        } finally {
+            resolver.release();
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    public void overlappingNegativeQueriesPreserveEveryVolumeAndOriginOrder() throws Exception {
+        BlockingResolver coordination = new BlockingResolver();
+        NativeStructureVolumeIndex.OriginResolver volumes = (engine, chunkX, chunkZ) ->
+                new KList<>(new NativeStructureVolume(chunkX + ":" + chunkZ,
+                        -256, 0, -256, 256, 255, 256));
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting((engine, chunkX, chunkZ) -> {
+            coordination.volumesAt(engine, chunkX, chunkZ);
+            return volumes.volumesAt(engine, chunkX, chunkZ);
+        });
+        NativeStructureVolumeIndex sequential = NativeStructureVolumeIndex.forTesting(volumes);
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        try {
+            Future<KList<NativeStructureVolume>> negative = executor.submit(
+                    () -> index.resolve(null, -16, 0, -1, 15));
+            assertTrue(coordination.awaitFirstEntry());
+            Future<KList<NativeStructureVolume>> positive = executor.submit(
+                    () -> index.resolve(null, 0, 0, 15, 15));
+            assertTrue(coordination.awaitSecondEntry(5_000));
+            assertEquals(sequential.resolve(null, 0, 0, 15, 15), positive.get(5, TimeUnit.SECONDS));
+            coordination.release();
+            assertEquals(sequential.resolve(null, -16, 0, -1, 15), negative.get(5, TimeUnit.SECONDS));
+            assertEquals(306, coordination.resolutions());
+        } finally {
+            coordination.release();
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void sharedOriginWaitAllowsQueuedTerrainWorkToRun() throws Exception {
+        assertQueuedTerrainCanComplete(false);
+    }
+
+    @Test
+    public void interruptedOriginWaitPreservesInterruptAndResult() throws Exception {
+        assertQueuedTerrainCanComplete(true);
+    }
+
+    private static void assertQueuedTerrainCanComplete(boolean interruptWaiter) throws Exception {
+        CountDownLatch ownerEntered = new CountDownLatch(1);
+        CompletableFuture<Void> terrain = new CompletableFuture<>();
+        AtomicBoolean firstOrigin = new AtomicBoolean(true);
+        AtomicBoolean interruptedAfterQuery = new AtomicBoolean();
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting((engine, chunkX, chunkZ) -> {
+            if (firstOrigin.compareAndSet(true, false)) {
+                ownerEntered.countDown();
+                terrain.join();
+            }
+            return new KList<>(new NativeStructureVolume(chunkX + ":" + chunkZ,
+                    -256, 0, -256, 256, 100, 256));
+        });
+        ExecutorService owner = Executors.newSingleThreadExecutor();
+        ForkJoinPool workers = new ForkJoinPool(2);
+        AtomicReference<Thread> firstWaiter = new AtomicReference<>();
+        AtomicReference<Thread> secondWaiter = new AtomicReference<>();
+        try {
+            Future<KList<NativeStructureVolume>> original = owner.submit(
+                    () -> index.originVolumes(null, -6, -8));
+            assertTrue(ownerEntered.await(5, TimeUnit.SECONDS));
+            Future<KList<NativeStructureVolume>> adjacent = workers.submit(() -> {
+                firstWaiter.set(Thread.currentThread());
+                KList<NativeStructureVolume> result = index.resolve(null, 16, 0, 31, 15);
+                interruptedAfterQuery.set(Thread.currentThread().isInterrupted());
+                return result;
+            });
+            Future<KList<NativeStructureVolume>> next = workers.submit(() -> {
+                secondWaiter.set(Thread.currentThread());
+                return index.resolve(null, 32, 0, 47, 15);
+            });
+            awaitOriginWaiter(firstWaiter);
+            awaitOriginWaiter(secondWaiter);
+            if (interruptWaiter) {
+                firstWaiter.get().interrupt();
+            }
+
+            Future<?> terrainTask = workers.submit(() -> terrain.complete(null));
+            terrainTask.get(3, TimeUnit.SECONDS);
+            assertEquals(1, original.get(3, TimeUnit.SECONDS).size());
+            KList<NativeStructureVolume> adjacentVolumes = adjacent.get(3, TimeUnit.SECONDS);
+            assertEquals(289, adjacentVolumes.size());
+            assertEquals(adjacentVolumes, index.resolve(null, 16, 0, 31, 15));
+            assertEquals(289, next.get(3, TimeUnit.SECONDS).size());
+            assertEquals(interruptWaiter, interruptedAfterQuery.get());
+        } finally {
+            terrain.complete(null);
+            owner.shutdownNow();
+            workers.shutdownNow();
+            assertTrue(owner.awaitTermination(5, TimeUnit.SECONDS));
+            assertTrue(workers.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    private static void awaitOriginWaiter(AtomicReference<Thread> reference) {
+        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(5);
+        while (System.nanoTime() < deadline) {
+            Thread thread = reference.get();
+            if (thread != null && thread.getState() == Thread.State.WAITING) {
+                for (StackTraceElement frame : thread.getStackTrace()) {
+                    if (frame.getClassName().equals("art.arcane.volmlib.nativelib.terrain.NativeBuildFutures")
+                            && frame.getMethodName().equals("awaitBuild")) {
+                        return;
+                    }
+                }
+            }
+            LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(1));
+        }
+        throw new AssertionError("Native query did not wait for the shared origin");
+    }
+
+    @Test
+    public void distantColdQueriesCanResolveOriginsConcurrently() throws Exception {
+        BlockingResolver resolver = new BlockingResolver();
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(resolver);
+        int distantChunkX = 64;
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        try {
+            Future<KList<NativeStructureVolume>> first = executor.submit(() -> index.resolve(null, 0, 0, 15, 15));
+            assertTrue(resolver.awaitFirstEntry());
+            Future<KList<NativeStructureVolume>> distant = executor.submit(
+                    () -> index.resolve(null, distantChunkX << 4, 0, (distantChunkX << 4) + 15, 15));
+
+            assertTrue(resolver.awaitSecondEntry(5_000));
+            resolver.release();
+            assertTrue(first.get(5, TimeUnit.SECONDS).isEmpty());
+            assertTrue(distant.get(5, TimeUnit.SECONDS).isEmpty());
+        } finally {
+            resolver.release();
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    public void coordinatedResolutionPreservesCanonicalOriginOrder() {
+        NativeStructureVolumeIndex index = NativeStructureVolumeIndex.forTesting(new OrderedResolver());
+
+        KList<NativeStructureVolume> volumes = index.resolve(null, 0, 0, 15, 15);
+
+        assertEquals(289, volumes.size());
+        assertEquals("-8:-8", volumes.getFirst().structure());
+        assertEquals("0:0", volumes.get(144).structure());
+        assertEquals("8:8", volumes.getLast().structure());
+    }
+
+    private static ScopedEngine scopedEngine(boolean scoped, int ownerRuntimeId) throws Exception {
+        IrisEngine engine = mock(IrisEngine.class);
+        GenerationHistoryRuntimeRouter router = mock(GenerationHistoryRuntimeRouter.class);
+        when(engine.hasGenerationRuntimeScope()).thenReturn(scoped);
+        when(engine.getGenerationHistoryRuntimeRouter()).thenReturn(Optional.of(router));
+        when(engine.getCacheID()).thenReturn(1);
+        if (ownerRuntimeId != 0) {
+            IrisEngine.GenerationRuntimeBinding binding = mock(IrisEngine.GenerationRuntimeBinding.class);
+            when(binding.runtimeId()).thenReturn(ownerRuntimeId);
+            when(router.currentRuntimeOwnership()).thenReturn(Optional.of(
+                    new GenerationHistoryRuntimeRouter.RuntimeOwnership(1L, binding)));
+        }
+        AtomicInteger scopes = new AtomicInteger();
+        when(engine.openGenerationHistoryCoordinateScope(anyInt(), anyInt())).thenAnswer(invocation -> {
+            scopes.incrementAndGet();
+            return null;
+        });
+        return new ScopedEngine(engine, scopes);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Map<Engine, NativeStructureVolumeIndex> installedIndexes() throws Exception {
+        Field indexes = NativeStructureVolumeIndex.class.getDeclaredField("INDEXES");
+        indexes.setAccessible(true);
+        return (Map<Engine, NativeStructureVolumeIndex>) indexes.get(null);
+    }
+
+    private static Map<?, ?> cache(NativeStructureVolumeIndex index, String name) throws Exception {
+        Field field = NativeStructureVolumeIndex.class.getDeclaredField(name);
+        field.setAccessible(true);
+        return (Map<?, ?>) field.get(index);
+    }
+
+    private static StructureStart swampHut(int chunkX, int chunkZ, int x, int z) {
+        Structure source = new SwampHutStructure(new Structure.StructureSettings(HolderSet.empty()));
+        SwampHutPiece piece = new SwampHutPiece(RandomSource.create(17L), x, z);
+        return new StructureStart(source, new ChunkPos(chunkX, chunkZ), 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static Engine runtimeEngine(AtomicInteger runtimeId) {
+        return (Engine) Proxy.newProxyInstance(
+                Engine.class.getClassLoader(),
+                new Class<?>[]{Engine.class},
+                (proxy, method, arguments) -> {
+                    if (method.getName().equals("getCacheID")) {
+                        return runtimeId.get();
+                    }
+                    if (method.getName().equals("hashCode")) {
+                        return System.identityHashCode(proxy);
+                    }
+                    if (method.getName().equals("equals")) {
+                        return proxy == arguments[0];
+                    }
+                    if (method.getName().equals("toString")) {
+                        return "runtime-engine-" + runtimeId.get();
+                    }
+                    throw new UnsupportedOperationException(method.getName());
+                }
+        );
+    }
+
+    private static final class CountingResolver implements NativeStructureVolumeIndex.OriginResolver {
+        private final AtomicInteger resolutions = new AtomicInteger();
+        private final int originChunkX;
+        private final int originChunkZ;
+
+        private CountingResolver(int originChunkX, int originChunkZ) {
+            this.originChunkX = originChunkX;
+            this.originChunkZ = originChunkZ;
+        }
+
+        private int resolutions() {
+            return resolutions.get();
+        }
+
+        @Override
+        public KList<NativeStructureVolume> volumesAt(Engine engine, int chunkX, int chunkZ) {
+            resolutions.incrementAndGet();
+            if (chunkX != originChunkX || chunkZ != originChunkZ) {
+                return NativeStructureVolume.NONE;
+            }
+            return NativeStructureVolumeSource.appendPieces(null, STRUCTURE_KEY, swampHut(chunkX, chunkZ, 4, 6));
+        }
+    }
+
+    private static final class BlockingResolver implements NativeStructureVolumeIndex.OriginResolver {
+        private final AtomicInteger resolutions = new AtomicInteger();
+        private final CountDownLatch firstEntry = new CountDownLatch(1);
+        private final CountDownLatch secondEntry = new CountDownLatch(1);
+        private final CountDownLatch release = new CountDownLatch(1);
+
+        private int resolutions() {
+            return resolutions.get();
+        }
+
+        private boolean awaitFirstEntry() throws InterruptedException {
+            return firstEntry.await(5, TimeUnit.SECONDS);
+        }
+
+        private boolean awaitSecondEntry(long timeoutMillis) throws InterruptedException {
+            return secondEntry.await(timeoutMillis, TimeUnit.MILLISECONDS);
+        }
+
+        private void release() {
+            release.countDown();
+        }
+
+        @Override
+        public KList<NativeStructureVolume> volumesAt(Engine engine, int chunkX, int chunkZ) {
+            int resolution = resolutions.incrementAndGet();
+            if (resolution == 1) {
+                firstEntry.countDown();
+                try {
+                    if (!release.await(5, TimeUnit.SECONDS)) {
+                        throw new IllegalStateException("Timed out waiting to release native structure resolution");
+                    }
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                    throw new IllegalStateException("Interrupted while coordinating native structure resolution", e);
+                }
+            } else if (resolution == 2) {
+                secondEntry.countDown();
+            }
+            return NativeStructureVolume.NONE;
+        }
+    }
+
+    private static final class OrderedResolver implements NativeStructureVolumeIndex.OriginResolver {
+        @Override
+        public KList<NativeStructureVolume> volumesAt(Engine engine, int chunkX, int chunkZ) {
+            return new KList<>(new NativeStructureVolume(
+                    chunkX + ":" + chunkZ,
+                    0, 0, 0,
+                    15, 255, 15));
+        }
+    }
+    private record ScopedEngine(IrisEngine engine, AtomicInteger scopes) {
+    }
+}

adapters/bukkit/nms/v26_2_R1/src/test/java/art/arcane/volmlib/nativelib/common/structure/StructureReaderFixture.java

@@ -0,0 +1,12 @@
+package art.arcane.volmlib.nativelib.common.structure;
+
+import art.arcane.volmlib.nativelib.terrain.NativeStructureReader;
+
+public final class StructureReaderFixture {
+    private StructureReaderFixture() {
+    }
+
+    public static NativeStructureReader.Element element(Object handle) {
+        return new ReflectiveStructureReader.ElementView(handle, null, ReflectiveStructureReader::readDefaultConnectors);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessChunkGenerator.java

@@ -0,0 +1,111 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.IrisEngine;
+import art.arcane.iris.platform.bukkit.nms.BukkitBiomePolicy;
+import art.arcane.iris.platform.bukkit.nms.BukkitTerrainColumnPolicy;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeBiomeRegistryImpl;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeBiomeSourceImpl;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainColumns;
+import com.mojang.serialization.MapCodec;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+
+final class HeadlessChunkGenerator extends ChunkGenerator {
+    private final NativeTerrainColumns columns;
+    private final int minimumY;
+    private final int height;
+    private final int seaLevel;
+
+    HeadlessChunkGenerator(Options options) {
+        super(biomes(options));
+        Engine engine = options.engine();
+        columns = new NativeTerrainColumns(new BukkitTerrainColumnPolicy(engine, null));
+        minimumY = engine.getMinHeight();
+        height = engine.getHeight();
+        seaLevel = minimumY + engine.getDimension().getFluidHeight();
+        if (engine instanceof IrisEngine irisEngine) {
+            irisEngine.addGenerationRuntimeRetirementListener(columns::evictRuntime);
+        }
+    }
+
+    @Override
+    protected MapCodec<? extends ChunkGenerator> codec() {
+        return MapCodec.unit(this);
+    }
+
+    @Override
+    public int getGenDepth() {
+        return height;
+    }
+
+    @Override
+    public int getSeaLevel() {
+        return seaLevel;
+    }
+
+    @Override
+    public int getMinY() {
+        return minimumY;
+    }
+
+    @Override
+    public int getBaseHeight(int x, int z, Heightmap.Types type, LevelHeightAccessor accessor, RandomState random) {
+        return columns.baseHeight(x, z, type, accessor);
+    }
+
+    @Override
+    public NoiseColumn getBaseColumn(int x, int z, LevelHeightAccessor accessor, RandomState random) {
+        return columns.baseColumn(x, z, accessor);
+    }
+
+    @Override
+    public CompletableFuture<ChunkAccess> buildTerrain(ChunkAccess chunk, Blender blender, RandomState random,
+            StructureManager structures, BiomeManager biomes, WorldGenRegion region, Set<Holder<Biome>> possibleBiomes) {
+        throw new UnsupportedOperationException("Headless terrain must be generated through the Iris region pipeline");
+    }
+
+    @Override
+    public void spawnOriginalMobs(WorldGenRegion region) {
+        throw new UnsupportedOperationException("Headless native population is not installed");
+    }
+
+    @Override
+    public void addDebugScreenInfo(List<String> result, RandomState random, BlockPos position, SamplerContext context) {
+        result.add("Iris native structure terrain");
+    }
+
+    private static NativeBiomeSourceImpl biomes(Options options) {
+        NativeBiomeRegistryImpl registry = new NativeBiomeRegistryImpl(options.registries().lookupOrThrow(Registries.BIOME));
+        BukkitBiomePolicy<Holder<Biome>, Biome> policy = new BukkitBiomePolicy<>(
+                new BukkitBiomePolicy.RuntimeOptions<>(options.engine().getSeedManager().getSeed(), options.engine(),
+                        null, () -> registry), registry);
+        return new NativeBiomeSourceImpl(policy);
+    }
+
+    record Options(Engine engine, RegistryAccess registries) {
+        Options {
+            Objects.requireNonNull(engine, "engine");
+            Objects.requireNonNull(registries, "registries");
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessChunkLighting.java

@@ -0,0 +1,259 @@
+package art.arcane.iris.probe;
+
+import ca.spottedleaf.moonrise.patches.starlight.chunk.StarlightChunk;
+import ca.spottedleaf.moonrise.patches.starlight.light.SWMRNibbleArray;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.SectionPos;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.DataLayer;
+import net.minecraft.world.level.chunk.LightChunk;
+import net.minecraft.world.level.chunk.LightChunkGetter;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.lighting.BlockLightEngine;
+import net.minecraft.world.level.lighting.ChunkSkyLightSources;
+import net.minecraft.world.level.lighting.LayerLightEventListener;
+import net.minecraft.world.level.lighting.SkyLightEngine;
+import net.minecraft.world.level.material.FluidState;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.function.BiConsumer;
+
+final class HeadlessChunkLighting {
+    private static final int MAXIMUM_WINDOW_CHUNKS = 256;
+    private static final int HALO = 2;
+
+    private HeadlessChunkLighting() {
+    }
+
+    static void light(Request request) {
+        if (Thread.currentThread().isInterrupted()) {
+            throw new IllegalStateException("Offline lighting interrupted before initialization");
+        }
+        Window window = new Window(request);
+        BlockLightEngine block = new BlockLightEngine(window);
+        SkyLightEngine sky = request.skyLight() ? new SkyLightEngine(window) : null;
+        for (LightingChunk chunk : window.chunks.values()) {
+            ProtoChunk source = chunk.source;
+            for (int section = source.getMinSectionY(); section <= source.getMaxSectionY(); section++) {
+                SectionPos position = SectionPos.of(source.getPos(), section);
+                boolean empty = source.getSection(source.getSectionIndexFromSectionY(section)).hasOnlyAir();
+                block.updateSectionStatus(position, empty);
+                if (sky != null) {
+                    sky.updateSectionStatus(position, empty);
+                }
+            }
+        }
+        for (LightingChunk chunk : window.chunks.values()) {
+            block.propagateLightSources(chunk.source.getPos());
+            if (sky != null) {
+                sky.propagateLightSources(chunk.source.getPos());
+            }
+        }
+        drain(block);
+        if (sky != null) {
+            drain(sky);
+        }
+        for (ChunkPos position : request.targets()) {
+            ProtoChunk chunk = window.chunks.get(position.pack()).source;
+            StarlightChunk destination = (StarlightChunk) chunk;
+            destination.starlight$setBlockNibbles(copyLight(block, chunk));
+            destination.starlight$setSkyNibbles(copyLight(sky, chunk));
+            boolean[] emptySections = new boolean[chunk.getSectionsCount()];
+            for (int index = 0; index < emptySections.length; index++) {
+                emptySections[index] = chunk.getSection(index).hasOnlyAir();
+            }
+            destination.starlight$setBlockEmptinessMap(emptySections.clone());
+            destination.starlight$setSkyEmptinessMap(emptySections);
+            chunk.setPersistedStatus(ChunkStatus.LIGHT);
+            chunk.setLightCorrect(true);
+        }
+    }
+
+    private static void drain(LayerLightEventListener engine) {
+        while (engine.hasLightWork()) {
+            if (Thread.currentThread().isInterrupted()) {
+                throw new IllegalStateException("Offline lighting interrupted before completion");
+            }
+            engine.runLightUpdates();
+        }
+    }
+
+    private static SWMRNibbleArray[] copyLight(LayerLightEventListener engine, ProtoChunk chunk) {
+        SWMRNibbleArray[] result = new SWMRNibbleArray[chunk.getSectionsCount() + 2];
+        BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
+        for (int index = 0; index < result.length; index++) {
+            int sectionY = chunk.getMinSectionY() + index - 1;
+            DataLayer layer = engine == null ? new DataLayer() : engine.getDataLayerData(SectionPos.of(chunk.getPos(), sectionY));
+            if (layer == null) {
+                layer = new DataLayer();
+                for (int y = 0; y < 16; y++) {
+                    for (int z = 0; z < 16; z++) {
+                        for (int x = 0; x < 16; x++) {
+                            position.set(chunk.getPos().getMinBlockX() + x, (sectionY << 4) + y,
+                                    chunk.getPos().getMinBlockZ() + z);
+                            layer.set(x, y, z, engine.getLightValue(position));
+                        }
+                    }
+                }
+            }
+            result[index] = SWMRNibbleArray.fromVanilla(layer);
+        }
+        return result;
+    }
+
+    record Request(List<ProtoChunk> chunks, Set<ChunkPos> targets, boolean skyLight) {
+        Request {
+            chunks = List.copyOf(chunks);
+            targets = Set.copyOf(targets);
+            if (chunks.isEmpty() || chunks.size() > MAXIMUM_WINDOW_CHUNKS || targets.isEmpty()) {
+                throw new IllegalArgumentException("Offline lighting requires targets inside a bounded chunk window");
+            }
+        }
+    }
+
+    private static final class Window implements LightChunkGetter, BlockGetter {
+        private final Map<Long, LightingChunk> chunks;
+        private final int minimumY;
+        private final int height;
+
+        private Window(Request request) {
+            minimumY = request.chunks().getFirst().getMinY();
+            height = request.chunks().getFirst().getHeight();
+            chunks = new HashMap<>(request.chunks().size());
+            for (ProtoChunk chunk : request.chunks()) {
+                if (chunk.getMinY() != minimumY || chunk.getHeight() != height
+                        || chunk.getPersistedStatus() != ChunkStatus.FEATURES) {
+                    throw new IllegalArgumentException("Offline lighting requires matching heights and completed FEATURES chunks");
+                }
+                if (chunks.putIfAbsent(chunk.getPos().pack(), new LightingChunk(chunk)) != null) {
+                    throw new IllegalArgumentException("Duplicate lighting chunk: " + chunk.getPos());
+                }
+            }
+            for (ChunkPos target : request.targets()) {
+                for (int dz = -HALO; dz <= HALO; dz++) {
+                    for (int dx = -HALO; dx <= HALO; dx++) {
+                        if (!chunks.containsKey(ChunkPos.pack(Math.addExact(target.x(), dx), Math.addExact(target.z(), dz)))) {
+                            throw new IllegalArgumentException("Offline lighting target lacks its completed neighbor halo: " + target);
+                        }
+                    }
+                }
+            }
+        }
+
+        @Override
+        public LightChunk getChunkForLighting(int x, int z) {
+            return chunks.get(ChunkPos.pack(x, z));
+        }
+
+        @Override
+        public BlockGetter getLevel() {
+            return this;
+        }
+
+        @Override
+        public int getMinY() {
+            return minimumY;
+        }
+
+        @Override
+        public int getHeight() {
+            return height;
+        }
+
+        @Override
+        public BlockEntity getBlockEntity(BlockPos position) {
+            return requireChunk(position).getBlockEntity(position);
+        }
+
+        @Override
+        public BlockState getBlockState(BlockPos position) {
+            return requireChunk(position).getBlockState(position);
+        }
+
+        @Override
+        public BlockState getBlockStateIfLoaded(BlockPos position) {
+            LightingChunk chunk = chunks.get(ChunkPos.pack(position.getX() >> 4, position.getZ() >> 4));
+            return chunk == null ? null : chunk.getBlockState(position);
+        }
+
+        @Override
+        public FluidState getFluidState(BlockPos position) {
+            return getBlockState(position).getFluidState();
+        }
+
+        @Override
+        public FluidState getFluidIfLoaded(BlockPos position) {
+            BlockState state = getBlockStateIfLoaded(position);
+            return state == null ? null : state.getFluidState();
+        }
+
+        private LightingChunk requireChunk(BlockPos position) {
+            return Objects.requireNonNull(chunks.get(ChunkPos.pack(position.getX() >> 4, position.getZ() >> 4)),
+                    "Lighting query outside the supplied chunk window");
+        }
+    }
+
+    private static final class LightingChunk implements LightChunk {
+        private final ProtoChunk source;
+        private final ChunkSkyLightSources skySources;
+
+        private LightingChunk(ProtoChunk source) {
+            this.source = source;
+            skySources = new ChunkSkyLightSources(source);
+            skySources.fillFrom(source);
+        }
+
+        @Override
+        public void findBlockLightSources(BiConsumer<BlockPos, BlockState> consumer) {
+            source.findBlockLightSources(consumer);
+        }
+
+        @Override
+        public ChunkSkyLightSources getSkyLightSources() {
+            return skySources;
+        }
+
+        @Override
+        public BlockEntity getBlockEntity(BlockPos position) {
+            return source.getBlockEntity(position);
+        }
+
+        @Override
+        public BlockState getBlockState(BlockPos position) {
+            return source.getBlockState(position);
+        }
+
+        @Override
+        public BlockState getBlockStateIfLoaded(BlockPos position) {
+            return source.getBlockStateIfLoaded(position);
+        }
+
+        @Override
+        public FluidState getFluidState(BlockPos position) {
+            return source.getFluidState(position);
+        }
+
+        @Override
+        public FluidState getFluidIfLoaded(BlockPos position) {
+            return source.getFluidIfLoaded(position);
+        }
+
+        @Override
+        public int getMinY() {
+            return source.getMinY();
+        }
+
+        @Override
+        public int getHeight() {
+            return source.getHeight();
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessChunkSerialization.java

@@ -0,0 +1,126 @@
+package art.arcane.iris.probe;
+
+import ca.spottedleaf.moonrise.patches.starlight.chunk.StarlightChunk;
+import ca.spottedleaf.moonrise.patches.starlight.light.SWMRNibbleArray;
+import ca.spottedleaf.moonrise.patches.starlight.storage.StarlightSectionData;
+import it.unimi.dsi.fastutil.longs.LongSet;
+import it.unimi.dsi.fastutil.shorts.ShortArrayList;
+import it.unimi.dsi.fastutil.shorts.ShortList;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Registry;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.level.chunk.DataLayer;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkType;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+
+import java.util.ArrayList;
+import java.util.EnumMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+final class HeadlessChunkSerialization {
+    private HeadlessChunkSerialization() {
+    }
+
+    static SerializableChunkData copyOf(ProtoChunk chunk, Context context) {
+        if (!chunk.canBeSerialized() || chunk.getPersistedStatus().getChunkType() != ChunkType.PROTOCHUNK) {
+            throw new IllegalArgumentException("Headless serialization requires a serializable proto chunk");
+        }
+        List<CompoundTag> blockEntities = new ArrayList<>(chunk.getBlockEntitiesPos().size());
+        for (BlockPos position : chunk.getBlockEntitiesPos()) {
+            CompoundTag tag = chunk.getBlockEntityNbtForSaving(position, context.structures().registryAccess());
+            if (tag != null) {
+                blockEntities.add(tag.copy());
+            }
+        }
+        List<CompoundTag> entities = new ArrayList<>(chunk.getEntities().size());
+        for (CompoundTag entity : chunk.getEntities()) {
+            entities.add(entity.copy());
+        }
+        Map<Heightmap.Types, long[]> heightmaps = new EnumMap<>(Heightmap.Types.class);
+        for (Map.Entry<Heightmap.Types, Heightmap> entry : chunk.getHeightmaps()) {
+            heightmaps.put(entry.getKey(), entry.getValue().getRawData().clone());
+        }
+        ShortList[] postProcessing = new ShortList[chunk.getPostProcessing().length];
+        for (int i = 0; i < postProcessing.length; i++) {
+            ShortList source = chunk.getPostProcessing()[i];
+            if (source != null && !source.isEmpty()) {
+                postProcessing[i] = new ShortArrayList(source);
+            }
+        }
+        CompoundTag persistent = chunk.persistentDataContainer.isEmpty()
+                ? null : chunk.persistentDataContainer.toTagCompound().copy();
+        return new SerializableChunkData(context.containers(), chunk.getPos(), chunk.getMinSectionY(),
+                context.gameTime(), chunk.getInhabitedTime(), chunk.getPersistedStatus(),
+                chunk.getBlendingData() == null ? null : chunk.getBlendingData().pack(),
+                chunk.getBelowZeroRetrogen(), chunk.getUpgradeData().copy(), heightmaps,
+                chunk.getTicksForSerialization(context.gameTime()), postProcessing, chunk.isLightCorrect(),
+                sections(chunk), entities, blockEntities, structures(chunk, context.structures()), persistent);
+    }
+
+    private static List<SerializableChunkData.SectionData> sections(ProtoChunk chunk) {
+        LevelChunkSection[] blocks = chunk.getSections();
+        StarlightChunk light = (StarlightChunk) chunk;
+        SWMRNibbleArray[] blockLight = light.starlight$getBlockNibbles();
+        SWMRNibbleArray[] skyLight = light.starlight$getSkyNibbles();
+        List<SerializableChunkData.SectionData> sections = new ArrayList<>(blocks.length + 2);
+        for (int i = 0; i < blocks.length + 2; i++) {
+            LevelChunkSection blocksCopy = i > 0 && i <= blocks.length ? blocks[i - 1].copy() : null;
+            SWMRNibbleArray.SaveState blockState = blockLight[i].getSaveState();
+            SWMRNibbleArray.SaveState skyState = skyLight[i].getSaveState();
+            if (blocksCopy == null && blockState == null && skyState == null) {
+                continue;
+            }
+            SerializableChunkData.SectionData section = new SerializableChunkData.SectionData(
+                    chunk.getMinSectionY() + i - 1, blocksCopy, layer(blockState), layer(skyState));
+            if (blockState != null) {
+                ((StarlightSectionData) (Object) section).starlight$setBlockLightState(blockState.state);
+            }
+            if (skyState != null) {
+                ((StarlightSectionData) (Object) section).starlight$setSkyLightState(skyState.state);
+            }
+            sections.add(section);
+        }
+        return sections;
+    }
+
+    private static DataLayer layer(SWMRNibbleArray.SaveState state) {
+        return state == null || state.data == null ? null : new DataLayer(state.data);
+    }
+
+    private static CompoundTag structures(ProtoChunk chunk, StructurePieceSerializationContext context) {
+        Registry<Structure> registry = context.registryAccess().lookupOrThrow(Registries.STRUCTURE);
+        CompoundTag starts = new CompoundTag();
+        for (Map.Entry<Structure, StructureStart> entry : chunk.getAllStarts().entrySet()) {
+            starts.put(Objects.requireNonNull(registry.getKey(entry.getKey()), "structure key").toString(),
+                    entry.getValue().createTag(context, chunk.getPos()));
+        }
+        CompoundTag references = new CompoundTag();
+        for (Map.Entry<Structure, LongSet> entry : chunk.getAllReferences().entrySet()) {
+            if (!entry.getValue().isEmpty()) {
+                references.putLongArray(Objects.requireNonNull(registry.getKey(entry.getKey()), "structure key").toString(),
+                        entry.getValue().toLongArray());
+            }
+        }
+        CompoundTag result = new CompoundTag();
+        result.put("starts", starts);
+        result.put("References", references);
+        return result;
+    }
+
+    record Context(StructurePieceSerializationContext structures, PalettedContainerFactory containers, long gameTime) {
+        Context {
+            Objects.requireNonNull(structures, "structures");
+            Objects.requireNonNull(containers, "containers");
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessNativeBiomeWriter.java

@@ -0,0 +1,33 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.spi.PlatformBiomeWriter;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedBiome;
+import art.arcane.volmlib.nativelib.terrain.NativeBiome;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.Registry;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.biome.Biome;
+
+import java.util.List;
+import java.util.function.Supplier;
+
+record HeadlessNativeBiomeWriter(Supplier<HolderLookup.Provider> registries) implements PlatformBiomeWriter {
+    @Override
+    public int biomeIdFor(String key) {
+        Registry<Biome> registry = registry();
+        Biome biome = registry.getOrThrow(ResourceKey.create(Registries.BIOME, Identifier.parse(key))).value();
+        return registry.getId(biome);
+    }
+
+    @Override
+    public List<NativeBiome> allBiomes() {
+        return registry().listElements().map(holder -> (NativeBiome) ModdedBiome.of(
+                holder.value(), holder.key().identifier().toString())).toList();
+    }
+
+    private Registry<Biome> registry() {
+        return (Registry<Biome>) registries.get().lookupOrThrow(Registries.BIOME);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessNativeBootstrap.java

@@ -0,0 +1,47 @@
+package art.arcane.iris.probe;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.component.DataComponentInitializers;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.MultiPackResourceManager;
+import net.minecraft.tags.TagLoader;
+
+import java.util.List;
+
+final class HeadlessNativeBootstrap {
+    private static boolean initialized;
+
+    private HeadlessNativeBootstrap() {
+    }
+
+    static synchronized void bindComponents(HolderLookup.Provider registries) {
+        List<DataComponentInitializers.PendingComponents<?>> pending =
+                BuiltInRegistries.DATA_COMPONENT_INITIALIZERS.build(registries);
+        for (DataComponentInitializers.PendingComponents<?> components : pending) {
+            components.apply();
+        }
+    }
+
+    static synchronized void initialize() {
+        if (initialized) {
+            return;
+        }
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        try (MultiPackResourceManager resources = new MultiPackResourceManager(PackType.SERVER_DATA,
+                List.of(ServerPacksSource.createVanillaPackSource().fullResources()))) {
+            List<Registry.PendingTags<?>> pending = TagLoader.loadTagsForExistingRegistries(resources,
+                    RegistryAccess.fromRegistryOfRegistries(BuiltInRegistries.REGISTRY));
+            for (Registry.PendingTags<?> tags : pending) {
+                tags.apply();
+            }
+        }
+        initialized = true;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessNativePlatform.java

@@ -0,0 +1,273 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.platform.bukkit.nms.BukkitGenerationRegistry;
+import art.arcane.iris.spi.IrisPlatform;
+import art.arcane.iris.spi.PlatformGenerationRegistry;
+import art.arcane.iris.spi.LogLevel;
+import art.arcane.iris.spi.PlatformBiomeWriter;
+import art.arcane.iris.spi.PlatformRegistries;
+import art.arcane.iris.spi.PlatformScheduler;
+import art.arcane.iris.spi.PlatformStructureHooks;
+import art.arcane.volmlib.nativelib.entity.NativeEntityType;
+import art.arcane.volmlib.nativelib.item.NativeItem;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedBlockState;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeBlockResolver;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeRegistryAccess;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeGenerationRegistryImpl;
+import art.arcane.volmlib.nativelib.terrain.NativeBiome;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockProperty;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.nativelib.terrain.NativeWorld;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.RegistryAccess;
+
+import java.io.File;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Supplier;
+
+final class HeadlessNativePlatform implements IrisPlatform, PlatformRegistries, NativeBlockResolver.Policy {
+    private final StubPlatform services;
+    private final NativeRegistryAccess nativeAccess;
+    private final PlatformBiomeWriter biomeWriter;
+    private final PlatformGenerationRegistry generationRegistry;
+    private final NativeBlockResolver blocks = new NativeBlockResolver(this);
+    private final NativeBlockState air = blocks.getAir();
+    private final ConcurrentHashMap<String, NativeBlockState> states = new ConcurrentHashMap<>();
+
+    HeadlessNativePlatform(File root, Supplier<HolderLookup.Provider> registries) {
+        services = new StubPlatform(root);
+        biomeWriter = new HeadlessNativeBiomeWriter(registries);
+        generationRegistry = new BukkitGenerationRegistry(new NativeGenerationRegistryImpl(() -> {
+            HolderLookup.Provider lookup = registries.get();
+            if (lookup instanceof RegistryAccess access) {
+                return access;
+            }
+            throw new IllegalStateException("Generation registry contract requires loaded native registries");
+        }), "bukkit-generation-registry-v1");
+        nativeAccess = new NativeRegistryAccess(new NativeRegistryAccess.Configuration(registries,
+                () -> { throw new UnsupportedOperationException("Headless reloadable registries are not loaded"); },
+                message -> { throw new IllegalStateException("Unavailable native registry: " + message); }));
+    }
+
+    NativeBlockResolver blocks() {
+        return blocks;
+    }
+
+    @Override
+    public PlatformRegistries registries() {
+        return this;
+    }
+
+    @Override
+    public PlatformGenerationRegistry generationRegistry() {
+        return generationRegistry;
+    }
+
+    @Override
+    public String platformName() {
+        return "headless-native-core";
+    }
+
+    @Override
+    public String minecraftVersion() {
+        return SharedConstants.getCurrentVersion().name();
+    }
+
+    @Override
+    public NativeBlockState decodeBlockState(String key) {
+        return states.computeIfAbsent(key, NativeBlockResolver::strictParse);
+    }
+
+    @Override
+    public NativeBlockState block(String key) {
+        return states.computeIfAbsent(key, candidate -> Objects.requireNonNull(blocks.getOrNull(candidate, true),
+                "Unresolved native block: " + candidate));
+    }
+
+    @Override
+    public NativeBlockState blockOrNull(String key) {
+        return blocks.getOrNull(key);
+    }
+
+    @Override
+    public NativeBlockState blockOrNull(String key, boolean warn) {
+        return blocks.getOrNull(key, warn);
+    }
+
+    @Override
+    public NativeBlockState air() {
+        return air;
+    }
+
+    @Override
+    public ModdedBlockState resolveCustomBlock(String key) {
+        return null;
+    }
+
+    @Override
+    public boolean preventLeafDecay() {
+        return IrisSettings.get().getGenerator().isPreventLeafDecay();
+    }
+
+    @Override
+    public void reportError(String key, Throwable failure) {
+        services.reportError(failure);
+        failure.printStackTrace(System.err);
+    }
+
+    @Override
+    public void warnUnresolved(String key, String message) {
+        throw new IllegalArgumentException(message + ": " + key);
+    }
+
+    @Override
+    public void debug(String message) {
+        services.log(LogLevel.DEBUG, message);
+    }
+
+    @Override
+    public NativeBlockState deepSlateOre(NativeBlockState block, NativeBlockState ore) {
+        return nativeAccess.deepSlateOre(block, ore);
+    }
+
+    @Override
+    public NativeBiome biome(String key) {
+        return nativeAccess.biome(key);
+    }
+
+    @Override
+    public NativeItem item(String key) {
+        return nativeAccess.item(key);
+    }
+
+    @Override
+    public NativeEntityType entity(String key) {
+        return nativeAccess.entity(key);
+    }
+
+    @Override
+    public List<String> blockKeys() {
+        return nativeAccess.blockKeys();
+    }
+
+    @Override
+    public List<String> biomeKeys() {
+        return nativeAccess.biomeKeys();
+    }
+
+    @Override
+    public List<String> structureKeys() {
+        return nativeAccess.structureKeys();
+    }
+
+    @Override
+    public List<String> itemKeys() {
+        return nativeAccess.itemKeys();
+    }
+
+    @Override
+    public List<String> entityKeys() {
+        return nativeAccess.entityKeys();
+    }
+
+    @Override
+    public List<String> enchantmentKeys() {
+        return nativeAccess.enchantmentKeys();
+    }
+
+    @Override
+    public List<String> potionEffectKeys() {
+        return nativeAccess.potionEffectKeys();
+    }
+
+    @Override
+    public List<String> lootTableKeys() {
+        return nativeAccess.lootTableKeys();
+    }
+
+    @Override
+    public Map<String, List<NativeBlockProperty>> blockStateProperties() {
+        return nativeAccess.blockStateProperties();
+    }
+
+    @Override
+    public List<String> blockTypeKeys() {
+        return blockKeys();
+    }
+
+    @Override
+    public PlatformScheduler scheduler() {
+        return services.scheduler();
+    }
+
+    @Override
+    public PlatformStructureHooks structureHooks() {
+        return services.structureHooks();
+    }
+
+    @Override
+    public PlatformBiomeWriter biomeWriter() {
+        return biomeWriter;
+    }
+
+    @Override
+    public File dataFolder() {
+        return services.dataFolder();
+    }
+
+    @Override
+    public File dataFile(String... path) {
+        return services.dataFile(path);
+    }
+
+    @Override
+    public File pluginJar() {
+        return services.pluginJar();
+    }
+
+    @Override
+    public int irisVersionNumber() {
+        return services.irisVersionNumber();
+    }
+
+    @Override
+    public int minecraftVersionNumber() {
+        return Integer.parseInt(minecraftVersion().replace(".", ""));
+    }
+
+    @Override
+    public void callEvent(Object event) {
+        services.callEvent(event);
+    }
+
+    @Override
+    public void dispatchConsoleCommand(String command) {
+        services.dispatchConsoleCommand(command);
+    }
+
+    @Override
+    public boolean spawnEntity(NativeWorld world, String entityKey, double x, double y, double z) {
+        return services.spawnEntity(world, entityKey, x, y, z);
+    }
+
+    @Override
+    public void log(LogLevel level, String message) {
+        services.log(level, message);
+    }
+
+    @Override
+    public void msg(String message) {
+        services.msg(message);
+    }
+
+    @Override
+    public void reportError(Throwable error) {
+        services.reportError(error);
+    }
+
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessNativeRegistries.java

@@ -0,0 +1,116 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.IrisDatapackCompiler;
+import art.arcane.iris.pack.datapack.v263.DataFixerV263;
+import art.arcane.volmlib.util.collection.KList;
+
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.RegistryDataLoader;
+import net.minecraft.server.packs.PackLocationInfo;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.PathPackResources;
+import net.minecraft.server.packs.repository.PackSource;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.MultiPackResourceManager;
+
+import java.io.IOException;
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.stream.Stream;
+
+final class HeadlessNativeRegistries implements AutoCloseable {
+    private final Path directory;
+    private final MultiPackResourceManager resources;
+    private final RegistryAccess.Frozen registries;
+
+    private HeadlessNativeRegistries(Path directory, MultiPackResourceManager resources, RegistryAccess.Frozen registries) {
+        this.directory = directory;
+        this.resources = resources;
+        this.registries = registries;
+    }
+
+    static HeadlessNativeRegistries load(Map<String, String> definitions) throws IOException {
+        HeadlessNativeBootstrap.initialize();
+        Path directory = Files.createTempDirectory("iris-native-registry-");
+        try {
+            for (Map.Entry<String, String> definition : definitions.entrySet()) {
+                Path file = directory.resolve(definition.getKey()).normalize();
+                if (!file.startsWith(directory.resolve("data")) || !file.toString().endsWith(".json")) {
+                    throw new IllegalArgumentException("Invalid generated registry resource " + definition.getKey());
+                }
+                Files.createDirectories(file.getParent());
+                Files.writeString(file, definition.getValue());
+            }
+            return load(directory);
+        } catch (IOException | RuntimeException failure) {
+            delete(directory);
+            throw failure;
+        }
+    }
+
+    static HeadlessNativeRegistries compile(File pack) throws IOException {
+        HeadlessNativeBootstrap.initialize();
+        Path directory = Files.createTempDirectory("iris-native-pack-");
+        try {
+            IrisDatapackCompiler.compile(List.of(pack), new KList<>(directory.toFile()), List.of(),
+                    new DataFixerV263(), false);
+            return load(directory);
+        } catch (IOException | RuntimeException failure) {
+            delete(directory);
+            throw failure;
+        }
+    }
+
+    private static HeadlessNativeRegistries load(Path directory) {
+        PackLocationInfo location = new PackLocationInfo("iris-headless", Component.literal("Iris"),
+                PackSource.WORLD, Optional.empty());
+        MultiPackResourceManager resources = new MultiPackResourceManager(PackType.SERVER_DATA, List.of(
+                ServerPacksSource.createVanillaPackSource().fullResources(), new PathPackResources(location, directory)));
+        try {
+            RegistryAccess.Frozen builtins = RegistryAccess.fromRegistryOfRegistries(BuiltInRegistries.REGISTRY);
+            RegistryAccess.Frozen loaded;
+            try (ExecutorService executor = Executors.newFixedThreadPool(4)) {
+                loaded = RegistryDataLoader.load(resources, builtins.listRegistries().toList(),
+                        RegistryDataLoader.WORLD_REGISTRIES, executor).join();
+            }
+            RegistryAccess.Frozen registries = new RegistryAccess.ImmutableRegistryAccess(
+                    Stream.concat(builtins.registries(), loaded.registries())).freeze();
+            HeadlessNativeBootstrap.bindComponents(registries);
+            return new HeadlessNativeRegistries(directory, resources, registries);
+        } catch (RuntimeException failure) {
+            resources.close();
+            throw failure;
+        }
+    }
+
+    RegistryAccess.Frozen registries() {
+        return registries;
+    }
+
+    MultiPackResourceManager resources() {
+        return resources;
+    }
+
+    @Override
+    public void close() throws IOException {
+        resources.close();
+        delete(directory);
+    }
+
+    private static void delete(Path directory) throws IOException {
+        try (Stream<Path> paths = Files.walk(directory)) {
+            for (Path path : paths.sorted(Comparator.reverseOrder()).toList()) {
+                Files.delete(path);
+            }
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessNativeRuntime.java

@@ -0,0 +1,109 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.block.BlockDataMergeSupport;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.structure.nativegen.NativeStructureVolumeIndex;
+import art.arcane.volmlib.nativelib.terrain.structure.NativeStructureVolume;
+import art.arcane.volmlib.util.collection.KList;
+import art.arcane.iris.generation.block.TileData;
+import art.arcane.iris.generation.decoration.DecoratorPlatformHooks;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import art.arcane.iris.modded.ModdedDecoratorHooks;
+import art.arcane.iris.modded.ModdedStateRotator;
+import art.arcane.iris.modded.ModdedTileData;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeTileReader;
+import art.arcane.iris.pack.datapack.v263.DataFixerV263;
+import art.arcane.iris.pack.loading.IrisData;
+import art.arcane.iris.world.history.GenerationHistory;
+import art.arcane.iris.spi.IrisPlatform;
+import art.arcane.iris.structure.object.IrisObjectRotation;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeStateMerger;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Path;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.data.registries.VanillaRegistries;
+import net.minecraft.server.packs.resources.ResourceManager;
+
+final class HeadlessNativeRuntime implements RealPackProbeSupport.RuntimeBindings {
+    private final Path stagingRoot;
+    private NativeRegionTerrainWriter writer;
+    private HeadlessNativeRegistries nativeRegistries;
+    private HolderLookup.Provider registries;
+
+    HeadlessNativeRuntime() {
+        stagingRoot = null;
+    }
+
+    HeadlessNativeRuntime(Path stagingRoot) throws IOException {
+        this.stagingRoot = stagingRoot.toRealPath();
+    }
+
+    @Override
+    public IrisPlatform create(File root) {
+        HeadlessNativeBootstrap.initialize();
+        registries = VanillaRegistries.createWorldLookup();
+        HeadlessNativePlatform platform = new HeadlessNativePlatform(root, () -> registries);
+        ModdedDecoratorHooks decorators = new ModdedDecoratorHooks();
+        DecoratorPlatformHooks.bind(decorators, decorators);
+        IrisObjectRotation.bindPlatformRotator(new ModdedStateRotator());
+        BlockDataMergeSupport.bindPlatformMerger(new NativeStateMerger(platform.blocks())::merge);
+        NativeTileReader tiles = new NativeTileReader(() -> registries);
+        TileData.bindPlatformReader(input -> ModdedTileData.wrap(tiles.read(input)));
+        TileData.bindPlatformFactory(ModdedTileData::fromProperties);
+        return platform;
+    }
+
+    @Override
+    public void prepare(IrisData data, IrisDimension dimension) {
+        try {
+            if (nativeRegistries != null) {
+                throw new IllegalStateException("Headless native runtime supports one immutable pack per process");
+            }
+            nativeRegistries = HeadlessNativeRegistries.compile(data.getDataFolder());
+            registries = nativeRegistries.registries();
+            writer = new NativeRegionTerrainWriter(nativeRegistries.registries());
+        } catch (IOException failure) {
+            throw new UncheckedIOException("Cannot load native generation registries", failure);
+        }
+    }
+
+    @Override
+    public KList<NativeStructureVolume> nativeStructureVolumes(Engine engine, int minX, int minZ, int maxX, int maxZ) {
+        return NativeStructureVolumeIndex.volumes(engine, minX, minZ, maxX, maxZ);
+    }
+
+    @Override
+    public GenerationHistory createHistory(RealPackProbeSupport.HistoryRequest request) throws IOException {
+        if (stagingRoot != null) {
+            if (!request.worldRoot().getParent().toRealPath().startsWith(stagingRoot)) {
+                throw new IOException("Unpublished native generation must remain inside its private staging directory");
+            }
+            return HeadlessGenerationHistorySession.createUnpublished(request, new DataFixerV263());
+        }
+        return HeadlessGenerationHistorySession.create(request, new DataFixerV263());
+    }
+
+    @Override
+    public void close() throws IOException {
+        if (nativeRegistries != null) {
+            nativeRegistries.close();
+            nativeRegistries = null;
+        }
+    }
+
+    RegistryAccess.Frozen registries() {
+        return nativeRegistries.registries();
+    }
+
+    ResourceManager resources() {
+        return nativeRegistries.resources();
+    }
+
+    NativeRegionTerrainWriter writer() {
+        return writer;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessRegionTerrain.java

@@ -0,0 +1,211 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.context.IrisContext;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.GenerationSessionLease;
+import art.arcane.iris.generation.runtime.IrisEngine;
+import art.arcane.iris.structure.nativegen.NativeStructureOwnershipRecord;
+import art.arcane.iris.world.history.GenerationHistoryRuntimeRouter;
+import art.arcane.iris.world.history.NativeTerrainReceipt;
+import art.arcane.volmlib.nativelib.terrain.NativeBiome;
+import art.arcane.volmlib.nativelib.terrain.NativeBiomeSourcePolicy;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedBlockState;
+import art.arcane.volmlib.util.hunk.Hunk;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainPipeline;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.WorldgenTerrainHeightmaps;
+import net.minecraft.core.Holder;
+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.block.state.BlockState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.Heightmap;
+import org.bukkit.NamespacedKey;
+import org.bukkit.persistence.PersistentDataType;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.EnumSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
+
+final class HeadlessRegionTerrain {
+    private static final NamespacedKey STRUCTURE_ACTIVATION = new NamespacedKey("iris", "structure_activation");
+    private static final NamespacedKey NATURAL_TERRAIN = new NamespacedKey("iris", "natural_terrain");
+
+    private HeadlessRegionTerrain() {
+    }
+
+    static final class Session {
+        private final Map<Long, HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord>> chunks = new HashMap<>();
+        private final RegionGenerationWindow workers;
+        private HeadlessTerrainContext context;
+
+        Session(RegionGenerationWindow workers) {
+            this.workers = Objects.requireNonNull(workers, "workers");
+        }
+
+        Result generate(Request request, Consumer<String> progress) throws Exception {
+            workers.requireOpen();
+            if (context != null && context != request.context()) {
+                throw new IllegalArgumentException("Rolling regions require one native terrain context");
+            }
+            context = request.context();
+            List<NativeRegionPlan.PlannedChunk> plan = NativeRegionPlan.plan(
+                    request.chunkX(), request.chunkZ(), request.width());
+            Set<Long> retained = new HashSet<>(plan.size());
+            for (NativeRegionPlan.PlannedChunk planned : plan) {
+                retained.add(ChunkPos.pack(planned.x(), planned.z()));
+            }
+            chunks.keySet().retainAll(retained);
+            Map<Long, ChunkStatus> previous = new HashMap<>(chunks.size());
+            for (Map.Entry<Long, HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord>> entry : chunks.entrySet()) {
+                previous.put(entry.getKey(), entry.getValue().chunk().getPersistedStatus());
+            }
+            for (ChunkStatus status : List.of(ChunkStatus.STRUCTURE_STARTS, ChunkStatus.STRUCTURE_REFERENCES,
+                    ChunkStatus.BIOMES, ChunkStatus.TERRAIN)) {
+                List<NativeRegionPlan.PlannedChunk> eligible = new ArrayList<>();
+                for (NativeRegionPlan.PlannedChunk planned : plan) {
+                    HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord> existing =
+                            chunks.get(ChunkPos.pack(planned.x(), planned.z()));
+                    if (planned.status().isOrAfter(status)
+                            && (status != ChunkStatus.BIOMES || planned.status() == ChunkStatus.BIOMES)
+                            && (existing == null || existing.chunk().getPersistedStatus().isBefore(status))) {
+                        eligible.add(planned);
+                    }
+                }
+                if (eligible.isEmpty()) {
+                    continue;
+                }
+                long started = System.nanoTime();
+                AtomicInteger completed = new AtomicInteger();
+                workers.process(new RegionGenerationWindow.Request<>(eligible.size(), request.parallelism(),
+                        index -> apply(request.context(), eligible.get(index), status, chunks),
+                        (index, result) -> {
+                            if (status == ChunkStatus.STRUCTURE_STARTS) {
+                                chunks.put(result.chunk().getPos().pack(), result);
+                            }
+                            int count = completed.incrementAndGet();
+                            if (count % 128 == 0 || count == eligible.size()) {
+                                progress.accept("stage=" + status.getName() + " chunks=" + count + "/" + eligible.size()
+                                        + " seconds=" + (System.nanoTime() - started) / 1_000_000_000.0);
+                            }
+                        }));
+                failReported();
+            }
+            List<ProtoChunk> ordered = new ArrayList<>(plan.size());
+            List<ProtoChunk> updated = new ArrayList<>();
+            for (NativeRegionPlan.PlannedChunk planned : plan) {
+                ProtoChunk chunk = chunks.get(ChunkPos.pack(planned.x(), planned.z())).chunk();
+                if (chunk.getPersistedStatus().isBefore(planned.status())) {
+                    throw new IllegalStateException("Incomplete native stage at " + chunk.getPos());
+                }
+                ordered.add(chunk);
+                ChunkStatus prior = previous.get(chunk.getPos().pack());
+                if (prior == null || chunk.getPersistedStatus().isAfter(prior)) {
+                    updated.add(chunk);
+                }
+            }
+            return new Result(List.copyOf(ordered), List.copyOf(updated), request.width() * request.width());
+        }
+    }
+
+    private static HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord> apply(
+            HeadlessTerrainContext context, NativeRegionPlan.PlannedChunk planned, ChunkStatus status,
+            Map<Long, HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord>> chunks) throws Exception {
+        Engine engine = context.engine();
+        GenerationHistoryRuntimeRouter router = ((IrisEngine) engine).getGenerationHistoryRuntimeRouter().orElseThrow();
+        try (GenerationHistoryRuntimeRouter.RuntimeRoute route = router.openRoute(planned.x(), planned.z());
+             GenerationHistoryRuntimeRouter.RuntimeRoute.RuntimeScope scope = route.openRuntimeScope();
+             GenerationSessionLease lease = engine.acquireGenerationLease("headless_native_terrain");
+             IrisContext.Scope generation = IrisContext.open(engine, lease.sessionId(), null)) {
+            if (status == ChunkStatus.STRUCTURE_STARTS) {
+                HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord> result = HeadlessStructurePlanner.plan(
+                        context.structures(), context.policies(), new ChunkPos(planned.x(), planned.z()));
+                result.chunk().persistentDataContainer.set(STRUCTURE_ACTIVATION,
+                        PersistentDataType.LONG, route.activation().activationId());
+                return result;
+            }
+            HeadlessStructurePlanner.PlannedChunk<NativeStructureOwnershipRecord> result = Objects.requireNonNull(
+                    chunks.get(ChunkPos.pack(planned.x(), planned.z())), "planned structure chunk");
+            if (status == ChunkStatus.STRUCTURE_REFERENCES) {
+                HeadlessStructurePlanner.references(context.policies(), result, chunks);
+            } else if (status == ChunkStatus.BIOMES) {
+                biomes(context, result.chunk());
+            } else if (status == ChunkStatus.TERRAIN) {
+                if (result.chunk().getPersistedStatus().isBefore(ChunkStatus.BIOMES)) {
+                    biomes(context, result.chunk());
+                }
+                terrain(context, result.chunk(), route);
+            } else {
+                throw new IllegalArgumentException("Unsupported headless native stage " + status);
+            }
+            return result;
+        }
+    }
+
+    private static void biomes(HeadlessTerrainContext context, ProtoChunk chunk) {
+        context.biomes().prepareVisibleBiomeBatch();
+        NativeBiomeSourcePolicy.VisibleResolver<Holder<Biome>> resolver = context.biomes().visibleResolver();
+        chunk.fillBiomesFromNoise(resolver::biome);
+        chunk.setPersistedStatus(ChunkStatus.BIOMES);
+    }
+
+    private static void terrain(HeadlessTerrainContext context, ProtoChunk target,
+                                GenerationHistoryRuntimeRouter.RuntimeRoute route) throws Exception {
+        Engine engine = context.engine();
+        ChunkPos position = target.getPos();
+        Hunk<NativeBlockState> blocks = Hunk.newArrayHunk(16, engine.getHeight(), 16);
+        Hunk<NativeBiome> biomes = Hunk.newArrayHunk(16, engine.getHeight(), 16);
+        engine.generate(position.x() << 4, position.z() << 4, blocks, biomes, true);
+        context.writer().fill(target, new NativeRegionTerrainWriter.TerrainInput(position.x(), position.z(),
+                engine.getMinHeight(), engine.getHeight(),
+                (x, y, z) -> blockState(blocks.getRaw(x, y, z)),
+                (x, y, z) -> Objects.requireNonNull(biomes.getRaw(x, y, z), "Generated native biome").key(), List.of()));
+        NativeTerrainPipeline.claimGeneratedSemantics(route, target, engine.getMinHeight());
+        target.persistentDataContainer.set(NATURAL_TERRAIN, PersistentDataType.BYTE_ARRAY,
+                NativeTerrainReceipt.encode(route.naturalTerrain().orElseThrow(),
+                        route.activation().activationId(), route.epoch().epochId()));
+        WorldgenTerrainHeightmaps.primeTerrain(target,
+                (x, z) -> engine.getHeight(x, z, false) + engine.getMinHeight() + 1,
+                (x, z) -> engine.getHeight(x, z, true) + engine.getMinHeight() + 1);
+        Heightmap.primeHeightmaps(target, EnumSet.of(Heightmap.Types.MOTION_BLOCKING,
+                Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, Heightmap.Types.OCEAN_FLOOR, Heightmap.Types.WORLD_SURFACE));
+        target.setPersistedStatus(ChunkStatus.TERRAIN);
+        target.markUnsaved();
+    }
+
+    private static BlockState blockState(NativeBlockState state) {
+        return state == null ? Blocks.AIR.defaultBlockState() : ((ModdedBlockState) state).handle();
+    }
+
+    private static void failReported() {
+        List<Throwable> reports = RealPackProbeSupport.drainReported();
+        if (!reports.isEmpty()) {
+            IllegalStateException failure = new IllegalStateException("Native terrain generation reported errors");
+            for (Throwable report : reports) {
+                failure.addSuppressed(report);
+            }
+            throw failure;
+        }
+    }
+
+    record Request(HeadlessTerrainContext context, int chunkX, int chunkZ, int width, int parallelism) {
+        Request {
+            Objects.requireNonNull(context, "context");
+            if (parallelism < 1 || parallelism > 32) {
+                throw new IllegalArgumentException("Headless native parallelism must be 1..32");
+            }
+        }
+    }
+
+    record Result(List<ProtoChunk> chunks, List<ProtoChunk> updated, int targetChunks) {
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessStructureConfiguration.java

@@ -0,0 +1,104 @@
+package art.arcane.iris.probe;
+
+import net.kyori.adventure.key.Key;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.Level;
+import org.bukkit.Bukkit;
+import org.bukkit.configuration.ConfigurationSection;
+import org.bukkit.configuration.InvalidConfigurationException;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.spigotmc.SpigotConfig;
+import org.spigotmc.SpigotWorldConfig;
+
+import java.io.File;
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.Objects;
+
+final class HeadlessStructureConfiguration {
+    private static final int CONFIG_VERSION = 13;
+    private static final Field CONFIG_FILE = nativeField("CONFIG_FILE");
+    private static final Field VERSION = nativeField("version");
+
+    private HeadlessStructureConfiguration() {
+    }
+
+    static SpigotWorldConfig load(Options options) throws IOException {
+        if (Bukkit.getServer() != null) {
+            throw new IllegalStateException("Headless structure configuration cannot initialize inside a Bukkit server");
+        }
+        Files.createDirectories(options.stagingDirectory());
+        Path staged = Files.createTempFile(options.stagingDirectory(), "spigot-structures-", ".yml");
+        try {
+            Files.copy(options.source(), staged, StandardCopyOption.REPLACE_EXISTING);
+            YamlConfiguration configuration = new YamlConfiguration();
+            configuration.load(staged.toFile());
+            configuration.options().copyDefaults(true);
+            int version = configuration.getInt("config-version", CONFIG_VERSION);
+            String worldName = options.levelKey().identifier().toString();
+            prepareEnvironment(configuration, options.legacyWorldName(), worldName, version);
+            configuration.set("config-version", CONFIG_VERSION);
+            return initialize(options, staged, configuration);
+        } catch (InvalidConfigurationException | ReflectiveOperationException | RuntimeException failure) {
+            throw new IOException("Could not initialize native structure configuration from " + options.source(), failure);
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
+    private static void prepareEnvironment(YamlConfiguration configuration, String legacyWorldName,
+                                           String worldName, int version) {
+        if (version <= 12) {
+            ConfigurationSection legacy = configuration.getConfigurationSection("world-settings." + legacyWorldName);
+            if (legacy != null) {
+                configuration.set("world-settings." + legacyWorldName, null);
+                configuration.set("world-settings." + worldName, legacy);
+            }
+        }
+        String worldPath = "world-settings." + worldName + ".";
+        configuration.set(worldPath + "verbose", false);
+        configuration.set(worldPath + "view-distance", 3);
+        configuration.set(worldPath + "simulation-distance", 3);
+    }
+
+    private static SpigotWorldConfig initialize(Options options, Path staged, YamlConfiguration configuration)
+            throws ReflectiveOperationException {
+        synchronized (SpigotConfig.class) {
+            YamlConfiguration previousConfiguration = SpigotConfig.config;
+            File previousFile = (File) CONFIG_FILE.get(null);
+            int previousVersion = VERSION.getInt(null);
+            try {
+                SpigotConfig.config = configuration;
+                CONFIG_FILE.set(null, staged.toFile());
+                VERSION.setInt(null, CONFIG_VERSION);
+                return new SpigotWorldConfig(options.legacyWorldName(), Key.key(options.levelKey().identifier().toString()));
+            } finally {
+                SpigotConfig.config = previousConfiguration;
+                CONFIG_FILE.set(null, previousFile);
+                VERSION.setInt(null, previousVersion);
+            }
+        }
+    }
+
+    private static Field nativeField(String name) {
+        try {
+            Field field = SpigotConfig.class.getDeclaredField(name);
+            field.setAccessible(true);
+            return field;
+        } catch (ReflectiveOperationException failure) {
+            throw new ExceptionInInitializerError(failure);
+        }
+    }
+
+    record Options(Path source, String legacyWorldName, ResourceKey<Level> levelKey, Path stagingDirectory) {
+        Options {
+            Objects.requireNonNull(source, "source");
+            Objects.requireNonNull(legacyWorldName, "legacyWorldName");
+            Objects.requireNonNull(levelKey, "levelKey");
+            Objects.requireNonNull(stagingDirectory, "stagingDirectory");
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessStructurePlanner.java

@@ -0,0 +1,333 @@
+package art.arcane.iris.probe;
+
+import art.arcane.volmlib.nativelib.terrain.NativeGenerationScope;
+import art.arcane.volmlib.nativelib.terrain.structure.StructureInjectionPolicy;
+import art.arcane.volmlib.nativelib.terrain.structure.StructureOwnershipRecordView;
+import art.arcane.volmlib.nativelib.terrain.structure.StructurePlacementDecision;
+import art.arcane.volmlib.nativelib.terrain.structure.StructureReferencePolicy;
+import art.arcane.volmlib.nativelib.terrain.structure.StructureStartPlan;
+import art.arcane.volmlib.nativelib.terrain.structure.StructureTerrainSettings;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureFactory;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureOwnershipFingerprint;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceEnvelope;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceRepair;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureTerrainIntegrator;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVegetationClearer;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+import it.unimi.dsi.fastutil.longs.LongOpenHashSet;
+import it.unimi.dsi.fastutil.longs.LongSet;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Holder;
+import net.minecraft.core.Registry;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Climate;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.WorldOptions;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.placement.StructurePlacement;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.Predicate;
+
+final class HeadlessStructurePlanner {
+    private HeadlessStructurePlanner() {
+    }
+
+    static <P extends StructureStartPlan, O extends StructureOwnershipRecordView<O>> PlannedChunk<O> plan(
+            NativeContext context, Policies<P, O> policies, ChunkPos position) {
+        ProtoChunk chunk = new ProtoChunk(position, UpgradeData.EMPTY,
+                LevelHeightAccessor.create(context.generator().getMinY(), context.generator().getGenDepth()),
+                PalettedContainerFactory.create(context.registries()), null);
+        if (!context.enabled()) {
+            chunk.setPersistedStatus(ChunkStatus.STRUCTURE_STARTS);
+            return new PlannedChunk<O>(context, chunk, Map.of(), Map.of());
+        }
+        try (NativeGenerationScope scope = policies.references().openOriginScope(chunk.getPos().x(), chunk.getPos().z())) {
+            generateNaturalStarts(context, chunk);
+            Map<Structure, O> ownership = inject(context, policies, chunk);
+            Map<Structure, StructureTerrainSettings> terrain = adjust(context, policies, chunk, ownership);
+            chunk.setPersistedStatus(ChunkStatus.STRUCTURE_STARTS);
+            return new PlannedChunk<>(context, chunk, Map.copyOf(ownership), Map.copyOf(terrain));
+        }
+    }
+
+    static <P extends StructureStartPlan, O extends StructureOwnershipRecordView<O>> void references(
+            Policies<P, O> policies, PlannedChunk<O> target, Map<Long, PlannedChunk<O>> grid) {
+        ChunkPos position = target.chunk().getPos();
+        List<PlannedChunk<O>> origins = new ArrayList<>(289);
+        if (target.chunk().getPersistedStatus() != ChunkStatus.STRUCTURE_STARTS) {
+            throw new IllegalArgumentException("Structure references require an unreferenced planned chunk: " + position);
+        }
+        if (!target.context().adapterEnabled()) {
+            target.chunk().setPersistedStatus(ChunkStatus.STRUCTURE_REFERENCES);
+            return;
+        }
+        for (int x = position.x() - 8; x <= position.x() + 8; x++) {
+            for (int z = position.z() - 8; z <= position.z() + 8; z++) {
+                PlannedChunk<O> origin = grid.get(ChunkPos.pack(x, z));
+                if (origin == null || origin.context() != target.context()
+                        || origin.chunk().getPos().x() != x || origin.chunk().getPos().z() != z
+                        || !origin.chunk().getPersistedStatus().isOrAfter(ChunkStatus.STRUCTURE_STARTS)) {
+                    throw new IllegalArgumentException("Missing matching structure origin at " + x + "," + z);
+                }
+                origins.add(origin);
+            }
+        }
+        Map<Structure, LongSet> references = new HashMap<>();
+        Registry<Structure> registry = target.context().registries().lookupOrThrow(Registries.STRUCTURE);
+        for (PlannedChunk<O> origin : origins) {
+            ChunkPos source = origin.chunk().getPos();
+            try (NativeGenerationScope scope = policies.references().openOriginScope(source.x(), source.z())) {
+                for (Map.Entry<Structure, StructureStart> entry : origin.chunk().getAllStarts().entrySet()) {
+                    StructureStart start = entry.getValue();
+                    if (!start.isValid()) {
+                        continue;
+                    }
+                    String key = Objects.requireNonNull(registry.getKey(entry.getKey()), "structure key").toString();
+                    if (!NativeStructureReferenceEnvelope.contentFitsReferenceRange(start)) {
+                        throw new IllegalStateException("Planned structure exceeds its reference range: " + key);
+                    }
+                    O ownership = origin.ownership().get(entry.getKey());
+                    boolean relevant = ownership == null
+                            ? NativeStructureReferenceRepair.requiresNaturalReference(policies.references(), position,
+                            key, entry.getKey(), start)
+                            : NativeStructureReferenceRepair.requiresReference(position, key, start, ownership);
+                    if (relevant) {
+                        references.computeIfAbsent(entry.getKey(), ignored -> new LongOpenHashSet()).add(source.pack());
+                    }
+                }
+            }
+        }
+        target.chunk().setAllReferences(references);
+        target.chunk().setPersistedStatus(ChunkStatus.STRUCTURE_REFERENCES);
+    }
+
+    private static <P extends StructureStartPlan, O extends StructureOwnershipRecordView<O>> Map<Structure, O> inject(
+            NativeContext context, Policies<P, O> policies, ProtoChunk chunk) {
+        Registry<Structure> registry = context.registries().lookupOrThrow(Registries.STRUCTURE);
+        Map<Structure, O> ownership = new LinkedHashMap<>();
+        for (P plan : policies.injection().plansAt(chunk.getPos().x(), chunk.getPos().z())) {
+            Holder.Reference<Structure> holder = registry.getOrThrow(ResourceKey.create(Registries.STRUCTURE,
+                    Identifier.parse(plan.structureKey())));
+            Structure structure = holder.value();
+            if (ownership.containsKey(structure)) {
+                policies.injection().duplicate(plan.structureKey());
+                continue;
+            }
+            StructureStart existing = chunk.getStartForStructure(structure);
+            boolean replace = plan.replacesSource() || existing != null && existing.isValid()
+                    && policies.injection().sourceReplaced(plan.structureKey(),
+                    NativeStructureVegetationClearer.isUndergroundStep(structure.step()));
+            if (!replace && existing != null && existing.isValid()) {
+                continue;
+            }
+            int references = existing != null && existing.isValid() ? existing.getReferences() : 0;
+            StructureStart generated = NativeStructureFactory.generate(new NativeStructureFactory.GenerationContext(
+                    context.registries(), context.generator(), context.generator().getBiomeSource(),
+                    context.structureState().randomState(), context.templates(), context.structureState().getLevelSeed(),
+                    context.levelKey(), chunk, biome -> true, context.generator().getSeaLevel(),
+                    policies.injection()::surfaceHeight), holder, plan, references);
+            if (!generated.isValid()) {
+                if (replace) {
+                    chunk.setStartForStructure(structure, StructureStart.INVALID_START);
+                }
+                policies.injection().discard(plan.structureKey(), chunk.getPos().x(), chunk.getPos().z());
+                continue;
+            }
+            BoundingBox envelope = NativeStructureReferenceEnvelope.referenceBounds(generated, structure,
+                    plan.terrain(), plan.structureKey());
+            policies.injection().record(plan, NativeStructureOwnershipFingerprint.capture(plan.structureKey(), generated, envelope));
+            O recorded;
+            try {
+                recorded = policies.references().findPersisted(plan.structureKey(), chunk.getPos().x(), chunk.getPos().z());
+                if (!NativeStructureOwnershipFingerprint.matches(recorded, generated)) {
+                    throw new IllegalStateException("Configured structure ownership was not retained: " + plan.structureKey());
+                }
+                chunk.setStartForStructure(structure, generated);
+            } catch (RuntimeException | Error failure) {
+                try {
+                    policies.injection().discard(plan.structureKey(), chunk.getPos().x(), chunk.getPos().z());
+                } catch (RuntimeException | Error cleanupFailure) {
+                    failure.addSuppressed(cleanupFailure);
+                }
+                throw failure;
+            }
+            ownership.put(structure, recorded);
+        }
+        return ownership;
+    }
+
+    private static <P extends StructureStartPlan, O extends StructureOwnershipRecordView<O>> Map<Structure, StructureTerrainSettings> adjust(
+            NativeContext context, Policies<P, O> policies, ProtoChunk chunk, Map<Structure, O> ownership) {
+        Registry<Structure> registry = context.registries().lookupOrThrow(Registries.STRUCTURE);
+        Map<Structure, StructureTerrainSettings> terrain = new HashMap<>();
+        for (Map.Entry<Structure, StructureStart> entry : chunk.getAllStarts().entrySet()) {
+            Structure structure = entry.getKey();
+            StructureStart start = entry.getValue();
+            if (!start.isValid()) {
+                continue;
+            }
+            String key = Objects.requireNonNull(registry.getKey(structure), "structure key").toString();
+            if (!policies.allowsFootprint().test(start.getBoundingBox())) {
+                chunk.setStartForStructure(structure, StructureStart.INVALID_START);
+                if (ownership.remove(structure) != null) {
+                    policies.references().discard(key, chunk.getPos().x(), chunk.getPos().z());
+                }
+                continue;
+            }
+            O recorded = ownership.get(structure);
+            if (recorded != null) {
+                terrain.put(structure, NativeStructureTerrainIntegrator.resolveNativeTerrain(start, recorded.terrain()));
+                continue;
+            }
+            boolean underground = NativeStructureVegetationClearer.isUndergroundStep(structure.step());
+            StructurePlacementDecision decision = policies.references().resolve(key, underground);
+            if (!decision.generate()) {
+                chunk.setStartForStructure(structure, StructureStart.INVALID_START);
+                continue;
+            }
+            NativeStructureVerticalPlacer.applyVerticalPlacement(start, key, decision.yShift(),
+                    context.generator().getSeaLevel(), chunk.getMinY(), chunk.getMinY() + chunk.getHeight(),
+                    underground, decision.preserveSourceY(), decision.yBand(), policies.injection()::surfaceHeight);
+            StructureTerrainSettings resolved = NativeStructureTerrainIntegrator.resolveNativeTerrain(start, decision.terrain());
+            StructureStart wrapped = NativeStructureReferenceEnvelope.wrapForPublication(start, structure,
+                    start.getReferences(), resolved, key);
+            chunk.setStartForStructure(structure, wrapped);
+            if (wrapped.isValid()) {
+                terrain.put(structure, resolved);
+            }
+        }
+        return terrain;
+    }
+
+    static void generateNaturalStarts(NativeContext context, ChunkAccess chunk) {
+        if (!context.enabled() || SharedConstants.DEBUG_DISABLE_STRUCTURES) {
+            return;
+        }
+        RandomState random = context.structureState().randomState();
+        Climate.Sampler climate = random.createClimateSampler(SamplerContext.builder().enableCaches().build());
+        for (Holder<StructureSet> holder : context.structureState().possibleStructureSets()) {
+            generateSet(context, chunk, holder.value(), climate);
+        }
+    }
+
+    private static void generateSet(NativeContext context, ChunkAccess chunk, StructureSet set, Climate.Sampler climate) {
+        List<StructureSet.StructureSelectionEntry> entries = set.structures();
+        for (StructureSet.StructureSelectionEntry entry : entries) {
+            StructureStart existing = chunk.getStartForStructure(entry.structure().value());
+            if (existing != null && existing.isValid()) {
+                return;
+            }
+        }
+        StructurePlacement placement = set.placement();
+        ChunkPos position = chunk.getPos();
+        ResourceKey<StructureSet> key = placement instanceof ChunkGeneratorStructureState.KeyedRandomSpreadStructurePlacement keyed
+                ? keyed.key : null;
+        if (!placement.isStructureChunk(context.structureState(), position.x(), position.z(), key)) {
+            return;
+        }
+        if (entries.size() == 1) {
+            generate(context, chunk, entries.getFirst(), climate);
+            return;
+        }
+        ArrayList<StructureSet.StructureSelectionEntry> remaining = new ArrayList<>(entries);
+        WorldgenRandom random = new WorldgenRandom(new LegacyRandomSource(0L));
+        random.setLargeFeatureSeed(context.structureState().getLevelSeed(), position.x(), position.z());
+        int weight = 0;
+        for (StructureSet.StructureSelectionEntry entry : remaining) {
+            weight += entry.weight();
+        }
+        while (!remaining.isEmpty()) {
+            int selection = random.nextInt(weight);
+            int index = 0;
+            for (StructureSet.StructureSelectionEntry entry : remaining) {
+                selection -= entry.weight();
+                if (selection < 0) {
+                    break;
+                }
+                index++;
+            }
+            StructureSet.StructureSelectionEntry selected = remaining.get(index);
+            if (generate(context, chunk, selected, climate)) {
+                return;
+            }
+            remaining.remove(index);
+            weight -= selected.weight();
+        }
+    }
+
+    private static boolean generate(NativeContext context, ChunkAccess chunk,
+                                    StructureSet.StructureSelectionEntry entry, Climate.Sampler climate) {
+        Structure structure = entry.structure().value();
+        StructureStart existing = chunk.getStartForStructure(structure);
+        int references = existing == null ? 0 : existing.getReferences();
+        StructureStart generated = structure.generate(entry.structure(), context.levelKey(), context.registries(),
+                context.generator(), context.generator().getBiomeSource(), climate, context.structureState().randomState(),
+                context.templates(), context.structureState().getLevelSeed(), chunk.getPos(), references, chunk,
+                structure.biomes()::contains);
+        if (!generated.isValid()) {
+            return false;
+        }
+        chunk.setStartForStructure(structure, generated);
+        return true;
+    }
+
+    record NativeContext(RegistryAccess registries, ChunkGenerator generator,
+                         ChunkGeneratorStructureState structureState, StructureTemplateManager templates,
+                         ResourceKey<Level> levelKey, WorldOptions worldOptions, boolean adapterEnabled) {
+        NativeContext {
+            Objects.requireNonNull(registries, "registries");
+            Objects.requireNonNull(generator, "generator");
+            Objects.requireNonNull(structureState, "structureState");
+            Objects.requireNonNull(templates, "templates");
+            Objects.requireNonNull(levelKey, "levelKey");
+            Objects.requireNonNull(worldOptions, "worldOptions");
+            if (worldOptions.seed() != structureState.getLevelSeed()) {
+                throw new IllegalArgumentException("Structure state seed differs from world options");
+            }
+        }
+
+        boolean enabled() {
+            return worldOptions.generateStructures() && adapterEnabled;
+        }
+    }
+
+    record Policies<P extends StructureStartPlan, O extends StructureOwnershipRecordView<O>>(
+            StructureInjectionPolicy<P> injection, StructureReferencePolicy<P, O> references,
+            Predicate<BoundingBox> allowsFootprint) {
+        Policies {
+            Objects.requireNonNull(injection, "injection");
+            Objects.requireNonNull(references, "references");
+            Objects.requireNonNull(allowsFootprint, "allowsFootprint");
+        }
+    }
+
+    record PlannedChunk<O extends StructureOwnershipRecordView<O>>(NativeContext context, ProtoChunk chunk,
+            Map<Structure, O> ownership, Map<Structure, StructureTerrainSettings> terrain) {
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/HeadlessTerrainContext.java

@@ -0,0 +1,159 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.platform.bukkit.nms.BukkitBiomePolicy;
+import art.arcane.iris.structure.nativegen.IrisStructurePolicy;
+import art.arcane.iris.structure.nativegen.IrisStructureVolumePolicy;
+import art.arcane.iris.structure.nativegen.NativeStructureOwnershipRecord;
+import art.arcane.iris.structure.nativegen.NativeStructureStartPlan;
+import art.arcane.iris.structure.nativegen.NativeStructureVolumeIndex;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeBiomeRegistryImpl;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVolumeSource;
+import net.minecraft.core.Holder;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.datafix.DataFixers;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.WorldOptions;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.minecraft.world.level.levelgen.structure.placement.ConcentricRingsStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import net.minecraft.world.level.storage.LevelStorageSource;
+import org.spigotmc.SpigotWorldConfig;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.Objects;
+
+final class HeadlessTerrainContext implements AutoCloseable {
+    private final Engine engine;
+    private final LevelStorageSource.LevelStorageAccess storage;
+    private final HeadlessStructurePlanner.NativeContext structures;
+    private final HeadlessStructurePlanner.Policies<NativeStructureStartPlan, NativeStructureOwnershipRecord> policies;
+    private final BukkitBiomePolicy<Holder<Biome>, Biome> biomes;
+    private final HeadlessChunkSerialization.Context serialization;
+    private final NativeRegionTerrainWriter writer;
+
+    private HeadlessTerrainContext(Options options, LevelStorageSource.LevelStorageAccess storage) {
+        engine = options.engine();
+        this.storage = storage;
+        HeadlessNativeRuntime runtime = options.runtime();
+        writer = runtime.writer();
+        HeadlessChunkGenerator generator = new HeadlessChunkGenerator(new HeadlessChunkGenerator.Options(
+                engine, runtime.registries()));
+        long seed = engine.getSeedManager().getSeed();
+        NoiseGeneratorSettings settings = runtime.registries().lookupOrThrow(Registries.NOISE_SETTINGS)
+                .getOrThrow(options.noiseSettings()).value();
+        RandomState random = RandomState.create(runtime.registries().lookupOrThrow(Registries.NOISE), seed, settings);
+        ChunkGeneratorStructureState state = generator.createState(
+                runtime.registries().lookupOrThrow(Registries.STRUCTURE_SET), random, seed, options.configuration());
+        initializeStructureState(state);
+        StructureTemplateManager templates = new StructureTemplateManager(runtime.resources(), storage,
+                DataFixers.getDataFixer(), BuiltInRegistries.BLOCK);
+        structures = new HeadlessStructurePlanner.NativeContext(runtime.registries(), generator, state,
+                templates, options.levelKey(), new WorldOptions(seed, true, false), true);
+        IrisStructurePolicy policy = new IrisStructurePolicy(engine);
+        policies = new HeadlessStructurePlanner.Policies<>(policy, policy,
+                bounds -> engine.getComplex().allowsNewGenerationFootprint(
+                        bounds.minX(), bounds.minZ(), bounds.maxX(), bounds.maxZ()));
+        NativeBiomeRegistryImpl registry = new NativeBiomeRegistryImpl(runtime.registries().lookupOrThrow(Registries.BIOME));
+        biomes = new BukkitBiomePolicy<>(new BukkitBiomePolicy.RuntimeOptions<>(seed, engine, null, () -> registry), registry);
+        serialization = new HeadlessChunkSerialization.Context(new StructurePieceSerializationContext(
+                runtime.resources(), runtime.registries(), templates), PalettedContainerFactory.create(runtime.registries()), 0L);
+        NativeStructureVolumeSource<Engine, NativeStructureStartPlan> volumes = new NativeStructureVolumeSource<>(
+                new NativeStructureVolumeSource.Context(runtime.registries(), templates, options.levelKey(),
+                        LevelHeightAccessor.create(engine.getMinHeight(), engine.getHeight()),
+                        () -> generator, generator::getBiomeSource, () -> state), IrisStructureVolumePolicy.INSTANCE);
+        NativeStructureVolumeIndex.install(engine, volumes::volumesAt);
+    }
+
+    static HeadlessTerrainContext create(Options options) throws IOException {
+        LevelStorageSource.LevelStorageAccess storage = LevelStorageSource.createDefault(options.templateStorage())
+                .createAccess("native-templates");
+        try {
+            return new HeadlessTerrainContext(options, storage);
+        } catch (RuntimeException | Error failure) {
+            try {
+                storage.close();
+            } catch (IOException closeFailure) {
+                failure.addSuppressed(closeFailure);
+            }
+            throw failure;
+        }
+    }
+
+    private static void initializeStructureState(ChunkGeneratorStructureState state) {
+        state.ensureStructuresGenerated();
+        Throwable failure = null;
+        for (Holder<StructureSet> structureSet : state.possibleStructureSets()) {
+            if (!(structureSet.value().placement() instanceof ConcentricRingsStructurePlacement rings)) {
+                continue;
+            }
+            try {
+                state.getRingPositionsFor(rings);
+            } catch (RuntimeException | Error problem) {
+                if (failure == null) {
+                    failure = problem;
+                } else {
+                    failure.addSuppressed(problem);
+                }
+            }
+        }
+        if (failure instanceof RuntimeException exception) {
+            throw exception;
+        }
+        if (failure instanceof Error error) {
+            throw error;
+        }
+    }
+
+    @Override
+    public void close() throws IOException {
+        NativeStructureVolumeIndex.uninstall(engine);
+        storage.close();
+    }
+
+    Engine engine() {
+        return engine;
+    }
+
+    HeadlessStructurePlanner.NativeContext structures() {
+        return structures;
+    }
+
+    HeadlessStructurePlanner.Policies<NativeStructureStartPlan, NativeStructureOwnershipRecord> policies() {
+        return policies;
+    }
+
+    BukkitBiomePolicy<Holder<Biome>, Biome> biomes() {
+        return biomes;
+    }
+
+    HeadlessChunkSerialization.Context serialization() {
+        return serialization;
+    }
+
+    NativeRegionTerrainWriter writer() {
+        return writer;
+    }
+
+    record Options(Engine engine, HeadlessNativeRuntime runtime, Path templateStorage, ResourceKey<Level> levelKey,
+                   ResourceKey<NoiseGeneratorSettings> noiseSettings, SpigotWorldConfig configuration) {
+        Options {
+            Objects.requireNonNull(engine, "engine");
+            Objects.requireNonNull(runtime, "runtime");
+            Objects.requireNonNull(templateStorage, "templateStorage");
+            Objects.requireNonNull(levelKey, "levelKey");
+            Objects.requireNonNull(noiseSettings, "noiseSettings");
+            Objects.requireNonNull(configuration, "configuration");
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/NativeRegionPlan.java

@@ -0,0 +1,56 @@
+package art.arcane.iris.probe;
+
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.status.ChunkPyramid;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.status.ChunkStep;
+
+import java.util.ArrayList;
+import java.util.List;
+
+final class NativeRegionPlan {
+    private NativeRegionPlan() {
+    }
+
+    static List<PlannedChunk> plan(int chunkX, int chunkZ, int width) {
+        if (width < 1 || width > 32) {
+            throw new IllegalArgumentException("Native terrain tile width must be 1..32 chunks");
+        }
+        ChunkStep target = ChunkPyramid.GENERATION_PYRAMID.getStepTo(ChunkStatus.FULL);
+        int halo = target.accumulatedDependencies().size() - 1;
+        int maximumX = Math.addExact(chunkX, width - 1);
+        int maximumZ = Math.addExact(chunkZ, width - 1);
+        if (!new ChunkPos(Math.subtractExact(chunkX, halo), Math.subtractExact(chunkZ, halo)).isValid()
+                || !new ChunkPos(Math.addExact(maximumX, halo), Math.addExact(maximumZ, halo)).isValid()) {
+            throw new IllegalArgumentException("Native terrain tile exceeds supported chunk bounds");
+        }
+        List<PlannedChunk> result = new ArrayList<>((width + halo * 2) * (width + halo * 2));
+        for (int z = Math.subtractExact(chunkZ, halo); z <= Math.addExact(maximumZ, halo); z++) {
+            for (int x = Math.subtractExact(chunkX, halo); x <= Math.addExact(maximumX, halo); x++) {
+                int distance = Math.max(distance(x, chunkX, maximumX), distance(z, chunkZ, maximumZ));
+                ChunkStatus required = distance == 0 ? ChunkStatus.FULL : target.accumulatedDependencies().get(distance);
+                ChunkStatus status = required.isAfter(ChunkStatus.TERRAIN) ? ChunkStatus.TERRAIN : required;
+                result.add(new PlannedChunk(x, z, status, distance == 0));
+            }
+        }
+        return List.copyOf(result);
+    }
+
+    static int terrainHalo() {
+        ChunkStep target = ChunkPyramid.GENERATION_PYRAMID.getStepTo(ChunkStatus.FULL);
+        int radius = 0;
+        for (int distance = 1; distance < target.accumulatedDependencies().size(); distance++) {
+            if (target.accumulatedDependencies().get(distance).isOrAfter(ChunkStatus.TERRAIN)) {
+                radius = distance;
+            }
+        }
+        return radius;
+    }
+
+    private static int distance(int value, int minimum, int maximum) {
+        return Math.max(0, Math.max(minimum - value, value - maximum));
+    }
+
+    record PlannedChunk(int x, int z, ChunkStatus status, boolean target) {
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/NativeRegionTerrainWriter.java

@@ -0,0 +1,223 @@
+package art.arcane.iris.probe;
+
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import it.unimi.dsi.fastutil.shorts.ShortList;
+import net.minecraft.commands.arguments.blocks.BlockStateParser;
+import net.minecraft.core.Holder;
+import net.minecraft.core.BlockPos;
+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.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.nbt.NbtOps;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.util.ProblemReporter;
+import net.minecraft.world.level.storage.TagValueInput;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.PalettedContainer;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.concurrent.ConcurrentHashMap;
+
+final class NativeRegionTerrainWriter {
+    private final Registry<Biome> biomes;
+    private final RegistryAccess registries;
+    private final PalettedContainerFactory containers;
+    private final Map<String, BlockState> tileStates = new ConcurrentHashMap<>();
+    private final Map<String, Holder<Biome>> biomeHolders = new ConcurrentHashMap<>();
+
+    NativeRegionTerrainWriter(RegistryAccess registries) {
+        this.registries = Objects.requireNonNull(registries, "registries");
+        biomes = registries.lookupOrThrow(Registries.BIOME);
+        containers = PalettedContainerFactory.create(registries);
+    }
+
+    RegistryAccess registries() {
+        return registries;
+    }
+
+    CompoundTag encode(TerrainInput input) {
+        TerrainData terrain = terrain(input, null);
+        SerializableChunkData data = new SerializableChunkData(containers,
+                new ChunkPos(input.chunkX(), input.chunkZ()), input.minimumY() >> 4, 0L, 0L,
+                ChunkStatus.EMPTY, null, null, UpgradeData.EMPTY, Map.of(),
+                new ChunkAccess.PackedTicks(List.of(), List.of()), new ShortList[input.height() >> 4], false,
+                terrain.sections(), List.of(), terrain.blockEntities(), new CompoundTag(), null);
+        CompoundTag tag = data.write();
+        tag.putString("iris:checkpoint", "iris:terrain_checkpoint");
+        return tag;
+    }
+
+
+    void fill(ProtoChunk chunk, TerrainInput input) {
+        if (chunk.getPos().x() != input.chunkX() || chunk.getPos().z() != input.chunkZ()
+                || chunk.getMinY() != input.minimumY() || chunk.getHeight() != input.height()) {
+            throw new IllegalArgumentException("Generated terrain does not match its planned chunk");
+        }
+        TerrainData terrain = terrain(input, chunk.getSections());
+        for (int i = 0; i < terrain.sections().size(); i++) {
+            chunk.getSections()[i] = terrain.sections().get(i).chunkSection();
+        }
+        for (CompoundTag entity : terrain.blockEntities()) {
+            chunk.setBlockEntityNbt(entity);
+        }
+        chunk.markUnsaved();
+    }
+
+    private TerrainData terrain(TerrainInput input, LevelChunkSection[] existingBiomes) {
+        Int2ObjectOpenHashMap<TileInput> tiles = new Int2ObjectOpenHashMap<>(input.tiles().size());
+        for (TileInput tile : input.tiles()) {
+            if (tile.y() >= input.height() || tiles.put(tile.x() | tile.z() << 4 | tile.y() << 8, tile) != null) {
+                throw new IllegalArgumentException("Duplicate or out-of-bounds tile data");
+            }
+        }
+        List<CompoundTag> blockEntities = new ArrayList<>();
+        List<SerializableChunkData.SectionData> sections = new ArrayList<>(input.height() >> 4);
+        for (int sectionY = 0; sectionY < input.height(); sectionY += 16) {
+            PalettedContainer<BlockState> blocks = containers.createForBlockStates();
+            PalettedContainer<Holder<Biome>> sectionBiomes = existingBiomes == null
+                    ? containers.createForBiomes() : existingBiomes[sectionY >> 4].getBiomes().copy();
+            for (int y = 0; y < 16; y++) {
+                for (int z = 0; z < 16; z++) {
+                    for (int x = 0; x < 16; x++) {
+                        BlockState state = Objects.requireNonNull(input.blocks().state(x, sectionY + y, z), "block state");
+                        TileInput tile = tiles.isEmpty() ? null : tiles.get(x | z << 4 | (sectionY + y) << 8);
+                        if (tile == null && state == Blocks.AIR.defaultBlockState()) {
+                            continue;
+                        }
+                        if (tile != null) {
+                            state = tileStates.computeIfAbsent(tile.stateKey(), NativeRegionTerrainWriter::resolveState);
+                        }
+                        blocks.set(x, y, z, state);
+                        if (state.hasBlockEntity()) {
+                            BlockPos position = new BlockPos((input.chunkX() << 4) + x,
+                                    input.minimumY() + sectionY + y, (input.chunkZ() << 4) + z);
+                            CompoundTag entity = encodeBlockEntity(state, position, tile);
+                            if (entity != null) {
+                                blockEntities.add(entity);
+                            }
+                        } else if (tile != null) {
+                            throw new IllegalArgumentException("Tile data has no native block entity at " + x + "," + y + "," + z);
+                        }
+                    }
+                }
+            }
+            if (existingBiomes == null) {
+                for (int y = 0; y < 4; y++) {
+                    for (int z = 0; z < 4; z++) {
+                        for (int x = 0; x < 4; x++) {
+                            String key = Objects.requireNonNull(input.biomes().key(x << 2, sectionY + (y << 2), z << 2), "biome key");
+                            sectionBiomes.set(x, y, z, biomeHolders.computeIfAbsent(key, this::resolveBiome));
+                        }
+                    }
+                }
+            }
+            sections.add(new SerializableChunkData.SectionData((input.minimumY() + sectionY) >> 4,
+                    new LevelChunkSection(blocks, sectionBiomes), null, null));
+        }
+        return new TerrainData(sections, blockEntities);
+    }
+
+    private CompoundTag encodeBlockEntity(BlockState state, BlockPos position, TileInput tile) {
+        BlockEntity entity = ((EntityBlock) state.getBlock()).newBlockEntity(position, state);
+        if (entity == null) {
+            if (tile != null) {
+                throw new IllegalStateException("Native block did not create a tile entity at " + position);
+            }
+            return null;
+        }
+        if (tile != null) {
+            CompoundTag merged = entity.saveWithoutMetadata(registries);
+            merged.merge(tile.payload());
+            entity.loadWithComponents(TagValueInput.create(ProblemReporter.DISCARDING, registries, merged));
+        }
+        return entity.saveWithFullMetadata(registries);
+    }
+
+    BlockState readBlock(CompoundTag tag, int x, int y, int z) {
+        for (CompoundTag section : tag.getListOrEmpty("sections").compoundStream().toList()) {
+            if (section.getByteOr("Y", (byte) 0) == y >> 4) {
+                return containers.blockStatesContainerCodec().parse(NbtOps.INSTANCE,
+                        section.getCompoundOrEmpty("block_states")).getOrThrow().get(x & 15, y & 15, z & 15);
+            }
+        }
+        throw new IllegalArgumentException("Missing section at " + y);
+    }
+
+    static void write(RegionFile region, CompoundTag tag) throws IOException {
+        ChunkPos position = new ChunkPos(tag.getIntOr("xPos", 0), tag.getIntOr("zPos", 0));
+        try (DataOutputStream output = region.getChunkDataOutputStream(position)) {
+            NbtIo.write(tag, output);
+        }
+    }
+
+    private static BlockState resolveState(String key) {
+        try {
+            return BlockStateParser.parseForBlock(BuiltInRegistries.BLOCK, key, false).blockState();
+        } catch (CommandSyntaxException failure) {
+            throw new IllegalArgumentException("Unsupported native block state: " + key, failure);
+        }
+    }
+
+    private Holder<Biome> resolveBiome(String key) {
+        return biomes.get(ResourceKey.create(Registries.BIOME, Identifier.parse(key)))
+                .orElseThrow(() -> new IllegalArgumentException("Unsupported native biome: " + key));
+    }
+
+    record TerrainInput(int chunkX, int chunkZ, int minimumY, int height, BlockLookup blocks, KeyLookup biomes, List<TileInput> tiles) {
+        TerrainInput {
+            if ((minimumY & 15) != 0 || (height & 15) != 0 || height < 16
+                    || minimumY < -2032 || (long) minimumY + height > 2032) {
+                throw new IllegalArgumentException("Terrain bounds must be section aligned within the native height range");
+            }
+            Objects.requireNonNull(blocks, "blocks");
+            Objects.requireNonNull(biomes, "biomes");
+            tiles = List.copyOf(tiles);
+        }
+    }
+
+    record TileInput(int x, int y, int z, String stateKey, CompoundTag payload) {
+        TileInput {
+            if (x < 0 || x > 15 || z < 0 || z > 15 || y < 0) {
+                throw new IllegalArgumentException("Tile position is outside its chunk");
+            }
+            Objects.requireNonNull(stateKey, "stateKey");
+            payload = Objects.requireNonNull(payload, "payload").copy();
+        }
+    }
+
+    private record TerrainData(List<SerializableChunkData.SectionData> sections, List<CompoundTag> blockEntities) {
+    }
+
+    @FunctionalInterface
+    interface BlockLookup {
+        BlockState state(int x, int y, int z);
+    }
+
+    @FunctionalInterface
+    interface KeyLookup {
+        String key(int x, int y, int z);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/OfflineRegionGenerator.java

@@ -0,0 +1,264 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.generation.concurrent.MultiBurst;
+import art.arcane.iris.generation.hydrology.HydrologyTileCache;
+import art.arcane.iris.generation.hydrology.runtime.IrisHydrologyRuntime;
+import art.arcane.iris.world.pregen.PregenPerformanceProfile;
+
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import org.spigotmc.SpigotWorldConfig;
+import org.bukkit.NamespacedKey;
+import org.bukkit.Bukkit;
+import org.bukkit.persistence.PersistentDataType;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileLock;
+import java.nio.file.Files;
+import java.nio.file.FileVisitResult;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.nio.file.StandardOpenOption;
+import java.security.MessageDigest;
+import java.util.HexFormat;
+import java.util.List;
+import java.util.Locale;
+
+public final class OfflineRegionGenerator {
+    private OfflineRegionGenerator() {
+    }
+
+    public static void main(String[] arguments) {
+        PrintStream diagnostics = System.err;
+        try {
+            execute(arguments);
+        } catch (Throwable failure) {
+            failure.printStackTrace(diagnostics);
+            diagnostics.flush();
+            System.exit(1);
+        }
+    }
+
+    private static void execute(String[] arguments) throws Exception {
+        if (arguments.length == 1 && arguments[0].equals("--help")) {
+            System.out.println("Usage: iris-offline pack dimension seed chunkX chunkZ width regionsX regionsZ parallelism spigot worldName levelKey noiseSettings output");
+            System.out.println("Java 25; width 1..32 chunks; parallelism 1..32. Output must be a new absolute directory.");
+            System.out.println("Generates fresh TERRAIN checkpoints and immutable Iris history. Native server completion is required for features, population and lighting.");
+            return;
+        }
+        if (Bukkit.getServer() != null) {
+            throw new IllegalStateException("Offline generation requires a separate process without a running Bukkit server");
+        }
+        long processStarted = System.nanoTime();
+        HeadlessNativeBootstrap.initialize();
+        Configuration configuration = Configuration.parse(arguments);
+        Files.createDirectory(configuration.output());
+        force(configuration.output());
+        try (FileChannel channel = FileChannel.open(configuration.output().resolve("checkpoint.lock"),
+                StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
+             FileLock lock = channel.lock()) {
+            if (!lock.isValid()) {
+                throw new IllegalStateException("Headless checkpoint lock is invalid");
+            }
+            run(configuration);
+            System.out.println("processSeconds=" + (System.nanoTime() - processStarted) / 1_000_000_000.0);
+        }
+    }
+
+    private static void run(Configuration configuration) throws Exception {
+        Path staged = Files.createDirectory(configuration.output().resolve("incomplete"));
+        byte[] configurationBytes = Files.readAllBytes(configuration.spigot());
+        Path capturedConfiguration = staged.resolve("spigot.yml");
+        Files.write(capturedConfiguration, configurationBytes, StandardOpenOption.CREATE_NEW);
+        String configurationHash = HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(configurationBytes));
+        HeadlessNativeRuntime runtime = new HeadlessNativeRuntime(staged);
+        long started = System.nanoTime();
+        long writes = 0;
+        long terrainWrites = 0;
+        double generationSeconds = 0;
+        double serializationSeconds = 0;
+        try (RealPackProbeSupport.Workspace workspace = RealPackProbeSupport.openWorkspace(new RealPackProbeSupport.WorkspaceOptions(configuration.pack(),
+                configuration.dimension(), "[headless-native-region]", runtime, staged));
+             RealPackProbeSupport.EngineSession session = workspace.openEngine(configuration.seed(), false, "native-region")) {
+            session.retainWorld(staged.resolve("world"));
+            SpigotWorldConfig spigot = HeadlessStructureConfiguration.load(new HeadlessStructureConfiguration.Options(
+                    capturedConfiguration, configuration.worldName(), configuration.levelKey(), staged.resolve("configuration")));
+            PregenPerformanceProfile.apply(session.engine());
+            System.out.println("generationProfile=pregen noiseCacheSize=" + IrisSettings.get().getPerformance().getNoiseCacheSize()
+                    + " burstParallelism=" + MultiBurst.burst.parallelism() + " multicore=true");
+            IrisHydrologyRuntime hydrology = session.engine().getComplex().getHydrologyRuntime();
+            try (HydrologyTileCache.PregenerationScope hydrologyScope = hydrology == null ? null
+                    : hydrology.preparePregeneration(configuration.hydrologyArea());
+                 HeadlessTerrainContext context = HeadlessTerrainContext.create(new HeadlessTerrainContext.Options(
+                    session.engine(), runtime, staged.resolve("templates"), configuration.levelKey(),
+                    configuration.noiseSettings(), spigot));
+                 RegionGenerationWindow workers = new RegionGenerationWindow(configuration.parallelism(),
+                         RegionGenerationWindow.Policy.STANDALONE)) {
+                HeadlessRegionTerrain.Session rolling = new HeadlessRegionTerrain.Session(workers);
+                Path regionDirectory = session.engine().getTarget().getWorld().worldFolder().toPath().resolve("region");
+                Files.createDirectory(regionDirectory);
+                OfflineRegionWriter writer = new OfflineRegionWriter(new OfflineRegionWriter.Options(
+                        context, regionDirectory, workers));
+                for (int row = 0; row < configuration.regionsZ(); row++) {
+                    for (int column = 0; column < configuration.regionsX(); column++) {
+                        int regionX = row % 2 == 0 ? column : configuration.regionsX() - column - 1;
+                        int chunkX = Math.addExact(configuration.chunkX(), Math.multiplyExact(regionX, configuration.width()));
+                        int chunkZ = Math.addExact(configuration.chunkZ(), Math.multiplyExact(row, configuration.width()));
+                        RegionResult generated = generateRegion(new RegionRequest(context, rolling, writer, chunkX, chunkZ,
+                                configuration.width(), configuration.parallelism(),
+                                staged.resolve("receipts.properties")));
+                        writes += generated.written().chunks();
+                        terrainWrites += generated.written().terrainChunks();
+                        generationSeconds += generated.generationSeconds();
+                        serializationSeconds += generated.serializationSeconds();
+                        System.out.println("region=" + regionX + "," + row + " residentChunks=" + generated.residentChunks()
+                                + " upgradedChunks=" + generated.upgradedChunks() + " writtenChunks=" + generated.written().chunks());
+                    }
+                }
+            } finally {
+                PregenPerformanceProfile.restore();
+            }
+        }
+        double wallSeconds = (System.nanoTime() - started) / 1_000_000_000.0;
+        String report = String.format(Locale.ROOT,
+                "format=iris-native-terrain-checkpoint\nplatform=headless-native\nstatus=minecraft:terrain\ncomplete=false\n"
+                        + "targetChunks=%d\nchunkWrites=%d\nterrainWrites=%d\nparallelism=%d\nseed=%d\nchunkX=%d\nchunkZ=%d\nwidth=%d\nregionsX=%d\nregionsZ=%d\n"
+                        + "levelKey=%s\nworldName=%s\nnoiseSettings=%s\nspigotSha256=%s\npipelineWallSeconds=%.3f\ngenerationSeconds=%.3f\nserializationSeconds=%.3f\n"
+                        + "limitations=Fresh offline world checkpoint only. Native features, population, lighting, POI, entities and scheduled ticks require native completion. No live plugin events are dispatched. Authored tile payloads remain in retained mantle for native completion. No transitions or existing chunks are imported.\n",
+                Math.multiplyExact(Math.multiplyExact(configuration.width(), configuration.width()),
+                        Math.multiplyExact(configuration.regionsX(), configuration.regionsZ())), writes, terrainWrites,
+                configuration.parallelism(), configuration.seed(), configuration.chunkX(), configuration.chunkZ(),
+                configuration.width(), configuration.regionsX(), configuration.regionsZ(), configuration.levelKey().identifier(),
+                configuration.worldName(), configuration.noiseSettings().identifier(), configurationHash,
+                wallSeconds, generationSeconds, serializationSeconds);
+        Files.writeString(staged.resolve("checkpoint.properties"), report, StandardOpenOption.CREATE_NEW);
+        long publicationStarted = System.nanoTime();
+        publish(staged, configuration.output().resolve("native-terrain-checkpoint"));
+        System.out.println(report);
+        System.out.println("publicationSeconds=" + (System.nanoTime() - publicationStarted) / 1_000_000_000.0);
+        System.out.println("totalSeconds=" + (System.nanoTime() - started) / 1_000_000_000.0);
+    }
+
+    private static RegionResult generateRegion(RegionRequest request) throws Exception {
+        long generationStarted = System.nanoTime();
+        HeadlessRegionTerrain.Result generated = request.rolling().generate(new HeadlessRegionTerrain.Request(
+                request.context(), request.chunkX(), request.chunkZ(), request.width(), request.parallelism()), System.out::println);
+        double generationSeconds = (System.nanoTime() - generationStarted) / 1_000_000_000.0;
+        long serializationStarted = System.nanoTime();
+        OfflineRegionWriter.Result written = request.writer().write(generated);
+        writeReceipts(generated, request.receipts());
+        return new RegionResult(written, generated.chunks().size(), generated.updated().size(), generationSeconds,
+                (System.nanoTime() - serializationStarted) / 1_000_000_000.0);
+    }
+
+    private record RegionRequest(HeadlessTerrainContext context, HeadlessRegionTerrain.Session rolling, OfflineRegionWriter writer,
+                                 int chunkX, int chunkZ, int width, int parallelism, Path receipts) {
+    }
+
+    private record RegionResult(OfflineRegionWriter.Result written, int residentChunks, int upgradedChunks,
+                                double generationSeconds, double serializationSeconds) {
+    }
+
+    private static void writeReceipts(HeadlessRegionTerrain.Result generated, Path path) throws Exception {
+        NamespacedKey key = new NamespacedKey("iris", "natural_terrain");
+        MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        StringBuilder receipts = new StringBuilder();
+        for (ProtoChunk chunk : generated.updated()) {
+            if (!chunk.getPersistedStatus().isOrAfter(ChunkStatus.TERRAIN)) {
+                continue;
+            }
+            byte[] receipt = chunk.persistentDataContainer.get(key, PersistentDataType.BYTE_ARRAY);
+            if (receipt == null) {
+                throw new IllegalStateException("Native TERRAIN checkpoint has no receipt at " + chunk.getPos());
+            }
+            receipts.append(chunk.getPos().x()).append(',').append(chunk.getPos().z()).append('=')
+                    .append(HexFormat.of().formatHex(digest.digest(receipt))).append('\n');
+        }
+        Files.writeString(path, receipts, StandardOpenOption.CREATE, StandardOpenOption.APPEND);
+    }
+
+    private static void forceTree(Path directory) throws IOException {
+        Files.walkFileTree(directory, new SimpleFileVisitor<>() {
+            @Override
+            public FileVisitResult visitFile(Path file, BasicFileAttributes attributes) throws IOException {
+                force(file);
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult postVisitDirectory(Path path, IOException failure) throws IOException {
+                if (failure != null) {
+                    throw failure;
+                }
+                force(path);
+                return FileVisitResult.CONTINUE;
+            }
+        });
+    }
+
+    static void publish(Path staged, Path destination) throws IOException {
+        forceTree(staged);
+        Files.move(staged, destination, StandardCopyOption.ATOMIC_MOVE);
+        force(destination.getParent());
+    }
+
+    private static void force(Path path) throws IOException {
+        try (FileChannel channel = FileChannel.open(path, Files.isDirectory(path)
+                ? StandardOpenOption.READ : StandardOpenOption.WRITE)) {
+            channel.force(true);
+        }
+    }
+
+    record Configuration(File pack, String dimension, long seed, int chunkX, int chunkZ, int width,
+                         int regionsX, int regionsZ, int parallelism, Path spigot, String worldName, ResourceKey<Level> levelKey,
+                         ResourceKey<NoiseGeneratorSettings> noiseSettings, Path output) {
+        Configuration {
+            if (regionsX < 1 || regionsZ < 1) {
+                throw new IllegalArgumentException("Region dimensions must be positive");
+            }
+            Math.multiplyExact(Math.multiplyExact(width, width), Math.multiplyExact(regionsX, regionsZ));
+            NativeRegionPlan.plan(chunkX, chunkZ, width);
+            NativeRegionPlan.plan(Math.addExact(chunkX, Math.multiplyExact(regionsX - 1, width)),
+                    Math.addExact(chunkZ, Math.multiplyExact(regionsZ - 1, width)), width);
+            if (parallelism < 1 || parallelism > 32 || !Files.isRegularFile(spigot)) {
+                throw new IllegalArgumentException("Parallelism must be 1..32 and Spigot configuration must exist");
+            }
+            if (!output.isAbsolute() || Files.exists(output) || !Files.isDirectory(output.getParent())) {
+                throw new IllegalArgumentException("Output must be a new absolute directory under an existing parent");
+            }
+        }
+
+        HydrologyTileCache.PregenerationArea hydrologyArea() {
+            int halo = NativeRegionPlan.terrainHalo();
+            long minimumX = ((long) chunkX - halo) * 16L;
+            long minimumZ = ((long) chunkZ - halo) * 16L;
+            long maximumX = ((long) chunkX + (long) width * regionsX + halo) * 16L - 1L;
+            long maximumZ = ((long) chunkZ + (long) width * regionsZ + halo) * 16L - 1L;
+            return new HydrologyTileCache.PregenerationArea(Math.toIntExact((minimumX + maximumX) / 2L),
+                    Math.toIntExact((minimumZ + maximumZ) / 2L), minimumX, minimumZ, maximumX, maximumZ);
+        }
+
+        static Configuration parse(String[] arguments) throws IOException {
+            if (arguments.length != 14) {
+                throw new IllegalArgumentException("Expected pack dimension seed chunkX chunkZ width regionsX regionsZ parallelism spigot worldName levelKey noiseSettings output");
+            }
+            return new Configuration(new File(arguments[0]).getCanonicalFile(), arguments[1], Long.parseLong(arguments[2]),
+                    Integer.parseInt(arguments[3]), Integer.parseInt(arguments[4]), Integer.parseInt(arguments[5]),
+                    Integer.parseInt(arguments[6]), Integer.parseInt(arguments[7]), Integer.parseInt(arguments[8]),
+                    Path.of(arguments[9]), arguments[10],
+                    ResourceKey.create(Registries.DIMENSION, Identifier.parse(arguments[11])),
+                    ResourceKey.create(Registries.NOISE_SETTINGS, Identifier.parse(arguments[12])), Path.of(arguments[13]));
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/OfflineRegionWriter.java

@@ -0,0 +1,161 @@
+package art.arcane.iris.probe;
+
+import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO.RegionDataController.IORunnable;
+import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO.RegionDataController.WriteData;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+final class OfflineRegionWriter {
+    private static final int MAXIMUM_PREPARATION_WORKERS = 8;
+    private static final int MAXIMUM_STATUS_REGIONS = 64;
+
+    private final Options options;
+    private final Map<Long, int[]> published = new LinkedHashMap<>(MAXIMUM_STATUS_REGIONS, 0.75F, true) {
+        @Override
+        protected boolean removeEldestEntry(Map.Entry<Long, int[]> eldest) {
+            return size() > MAXIMUM_STATUS_REGIONS;
+        }
+    };
+
+    OfflineRegionWriter(Options options) {
+        this.options = Objects.requireNonNull(options, "options");
+    }
+
+    Result write(HeadlessRegionTerrain.Result generated) throws Exception {
+        options.workers().requireOpen();
+        try (OpenRegions regions = new OpenRegions(options)) {
+            List<ChunkWrite> pending = new ArrayList<>(generated.updated().size());
+            for (ProtoChunk chunk : generated.updated()) {
+                ChunkPos position = chunk.getPos();
+                long regionKey = ChunkPos.pack(position.x() >> 5, position.z() >> 5);
+                int[] statuses = published.computeIfAbsent(regionKey, ignored -> new int[1024]);
+                int index = (position.x() & 31) + ((position.z() & 31) << 5);
+                int status = chunk.getPersistedStatus().getIndex() + 2;
+                if (statuses[index] >= status) {
+                    continue;
+                }
+                RegionFile region = regions.get(position);
+                if (statuses[index] == 0) {
+                    statuses[index] = readStatus(region, position);
+                    if (statuses[index] >= status) {
+                        continue;
+                    }
+                }
+                pending.add(new ChunkWrite(chunk, region, statuses, index, status));
+            }
+            if (pending.isEmpty()) {
+                return new Result(0, 0);
+            }
+            int[] counts = new int[2];
+            options.workers().process(new RegionGenerationWindow.Request<>(pending.size(),
+                    Math.min(options.workers().parallelism(), MAXIMUM_PREPARATION_WORKERS),
+                    index -> prepare(pending.get(index)),
+                    (index, prepared) -> {
+                        ChunkWrite chunk = prepared.chunk();
+                        prepared.commit().run(chunk.region());
+                        chunk.statuses()[chunk.index()] = chunk.status();
+                        counts[0]++;
+                        if (chunk.chunk().getPersistedStatus().isOrAfter(ChunkStatus.TERRAIN)) {
+                            counts[1]++;
+                        }
+                    }));
+            return new Result(counts[0], counts[1]);
+        }
+    }
+
+    private PreparedWrite prepare(ChunkWrite chunk) throws IOException {
+        CompoundTag tag = HeadlessChunkSerialization.copyOf(chunk.chunk(), options.context().serialization()).write();
+        WriteData prepared = chunk.region().moonrise$startWrite(tag, chunk.chunk().getPos());
+        try (DataOutputStream output = prepared.output()) {
+            NbtIo.write(tag, output);
+        }
+        return new PreparedWrite(chunk, prepared.write());
+    }
+
+    private static int readStatus(RegionFile region, ChunkPos position) throws IOException {
+        try (DataInputStream input = region.getChunkDataInputStream(position)) {
+            if (input == null) {
+                return 1;
+            }
+            ChunkStatus status = ChunkStatus.byName(NbtIo.read(input).getStringOr("Status", ""));
+            if (status == null) {
+                throw new IOException("Invalid native chunk status at " + position);
+            }
+            return status.getIndex() + 2;
+        }
+    }
+
+    record Options(HeadlessTerrainContext context, Path directory, RegionGenerationWindow workers) {
+        Options {
+            Objects.requireNonNull(context, "context");
+            Objects.requireNonNull(directory, "directory");
+            Objects.requireNonNull(workers, "workers");
+        }
+    }
+
+    record Result(int chunks, int terrainChunks) {
+    }
+
+    private record ChunkWrite(ProtoChunk chunk, RegionFile region, int[] statuses, int index, int status) {
+    }
+
+    private record PreparedWrite(ChunkWrite chunk, IORunnable commit) {
+    }
+
+    private static final class OpenRegions implements AutoCloseable {
+        private final Options options;
+        private final Map<Long, RegionFile> regions = new HashMap<>();
+
+        private OpenRegions(Options options) {
+            this.options = options;
+        }
+
+        private RegionFile get(ChunkPos position) throws IOException {
+            long key = ChunkPos.pack(position.x() >> 5, position.z() >> 5);
+            RegionFile region = regions.get(key);
+            if (region != null) {
+                return region;
+            }
+            Path path = options.directory().resolve("r." + (position.x() >> 5) + "." + (position.z() >> 5) + ".mca");
+            region = new RegionFile(new RegionStorageInfo("headless-native-terrain",
+                    options.context().structures().levelKey(), "chunk"), path, options.directory(), false);
+            regions.put(key, region);
+            return region;
+        }
+
+        @Override
+        public void close() throws IOException {
+            IOException failure = null;
+            for (RegionFile region : regions.values()) {
+                try {
+                    region.close();
+                } catch (IOException exception) {
+                    if (failure == null) {
+                        failure = exception;
+                    } else {
+                        failure.addSuppressed(exception);
+                    }
+                }
+            }
+            if (failure != null) {
+                throw failure;
+            }
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/offline/java/art/arcane/iris/probe/RegionGenerationWindow.java

@@ -0,0 +1,176 @@
+package art.arcane.iris.probe;
+
+import java.time.Duration;
+import java.util.HashSet;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ExecutorCompletionService;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+final class RegionGenerationWindow implements AutoCloseable {
+    private static final int UNRESPONSIVE_WORKER_EXIT = 70;
+
+    private final int parallelism;
+    private final Policy policy;
+    private final ExecutorService workers;
+    private boolean closed;
+    private boolean processing;
+
+    RegionGenerationWindow(int parallelism, Policy policy) {
+        if (parallelism < 1 || parallelism > 32) {
+            throw new IllegalArgumentException("Generation workers must be 1..32");
+        }
+        this.parallelism = parallelism;
+        this.policy = Objects.requireNonNull(policy, "policy");
+        workers = Executors.newFixedThreadPool(parallelism);
+    }
+
+    @Override
+    public synchronized void close() {
+        if (processing) {
+            throw new IllegalStateException("Cannot close generation workers from an active batch");
+        }
+        if (closed) {
+            return;
+        }
+        closed = true;
+        workers.shutdown();
+        drain(workers, policy, null);
+    }
+
+    int parallelism() {
+        return parallelism;
+    }
+
+    synchronized void requireOpen() {
+        if (closed) {
+            throw new IllegalStateException("Generation workers are closed");
+        }
+    }
+
+    synchronized <T> void process(Request<T> request) throws Exception {
+        requireOpen();
+        if (processing || request.parallelism() > parallelism) {
+            throw new IllegalArgumentException("Generation batch requires idle workers within the session limit");
+        }
+        ExecutorCompletionService<Completed<T>> completions = new ExecutorCompletionService<>(workers);
+        Set<Future<Completed<T>>> active = new HashSet<>(request.parallelism());
+        processing = true;
+        try {
+            int submitted = 0;
+            for (; submitted < Math.min(request.count(), request.parallelism()); submitted++) {
+                active.add(submit(completions, request.generator(), submitted));
+            }
+            for (int completed = 0; completed < request.count(); completed++) {
+                Future<Completed<T>> pending = completions.poll(policy.completionTimeout().toNanos(), TimeUnit.NANOSECONDS);
+                if (pending == null) {
+                    throw new TimeoutException("No generation worker completed within " + policy.completionTimeout());
+                }
+                active.remove(pending);
+                Completed<T> result = pending.get();
+                if (submitted < request.count()) {
+                    active.add(submit(completions, request.generator(), submitted++));
+                }
+                request.sink().accept(result.index(), result.value());
+            }
+        } catch (Exception | Error failure) {
+            closed = true;
+            for (Future<Completed<T>> future : active) {
+                future.cancel(true);
+            }
+            workers.shutdownNow();
+            drain(workers, policy, failure);
+            throw failure;
+        } finally {
+            processing = false;
+        }
+    }
+
+    private static void drain(ExecutorService workers, Policy policy, Throwable failure) {
+        boolean interrupted = Thread.interrupted() || failure instanceof InterruptedException;
+        long deadline = System.nanoTime() + policy.drainTimeout().toNanos();
+        try {
+            while (!workers.isTerminated()) {
+                long remaining = deadline - System.nanoTime();
+                if (remaining <= 0L) {
+                    break;
+                }
+                try {
+                    workers.awaitTermination(remaining, TimeUnit.NANOSECONDS);
+                } catch (InterruptedException interruption) {
+                    interrupted = true;
+                }
+            }
+            if (workers.isTerminated()) {
+                return;
+            }
+            IllegalStateException stalled = new IllegalStateException(
+                    "Generation workers did not stop within " + policy.drainTimeout()
+                            + "; generation resources remain open and no checkpoint will be published", failure);
+            stalled.printStackTrace(System.err);
+            if (policy.haltOnUnresponsiveWorkers()) {
+                System.err.println("Terminating offline generation; incomplete output is retained for inspection");
+                System.err.flush();
+                Runtime.getRuntime().halt(UNRESPONSIVE_WORKER_EXIT);
+            }
+            System.err.println("Waiting for embedded generation workers to stop before releasing their resources");
+            while (!workers.isTerminated()) {
+                try {
+                    workers.awaitTermination(1L, TimeUnit.DAYS);
+                } catch (InterruptedException interruption) {
+                    interrupted = true;
+                }
+            }
+        } finally {
+            if (interrupted) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
+
+    private static <T> Future<Completed<T>> submit(ExecutorCompletionService<Completed<T>> completions,
+                                                  Generator<T> generator, int index) {
+        return completions.submit(() -> new Completed<>(index, generator.generate(index)));
+    }
+
+    record Policy(Duration completionTimeout, Duration drainTimeout, boolean haltOnUnresponsiveWorkers) {
+        static final Policy EMBEDDED = new Policy(Duration.ofMinutes(5), Duration.ofSeconds(30), false);
+        static final Policy STANDALONE = new Policy(Duration.ofMinutes(5), Duration.ofSeconds(30), true);
+
+        Policy {
+            Objects.requireNonNull(completionTimeout, "completionTimeout");
+            Objects.requireNonNull(drainTimeout, "drainTimeout");
+            if (completionTimeout.isNegative() || completionTimeout.isZero()
+                    || drainTimeout.isNegative() || drainTimeout.isZero()) {
+                throw new IllegalArgumentException("Worker completion and drain timeouts must be positive");
+            }
+            completionTimeout.toNanos();
+            drainTimeout.toNanos();
+        }
+    }
+
+    record Request<T>(int count, int parallelism, Generator<T> generator, Sink<T> sink) {
+        Request {
+            if (count < 1 || count > 4096 || parallelism < 1 || parallelism > 32) {
+                throw new IllegalArgumentException("Generation window requires 1..4096 tasks and 1..32 workers");
+            }
+        }
+    }
+
+    private record Completed<T>(int index, T value) {
+    }
+
+    @FunctionalInterface
+    interface Generator<T> {
+        T generate(int index) throws Exception;
+    }
+
+    @FunctionalInterface
+    interface Sink<T> {
+        void accept(int index, T value) throws Exception;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/IrisChunkGeneratorHeightCacheTest.java

@@ -0,0 +1,144 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeChunkGenerator;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainColumns;
+import art.arcane.iris.platform.bukkit.nms.BukkitTerrainColumnPolicy;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.GenerationSessionLease;
+import art.arcane.iris.world.history.BoundaryColumnGeometry;
+import art.arcane.iris.world.history.TerrainBoundarySignature;
+import art.arcane.iris.testsupport.PlatformLeakGuard;
+import art.arcane.volmlib.nativelib.terrain.NativeTerrainColumnPolicy;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.levelgen.Heightmap;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.util.List;
+import java.util.Optional;
+import java.util.OptionalInt;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import static org.mockito.Mockito.never;
+
+public final class IrisChunkGeneratorHeightCacheTest {
+    @Rule
+    public final PlatformLeakGuard leakGuard = PlatformLeakGuard.clean();
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        NativeBlockTags.bindHeightmapFixtures();
+    }
+
+    @AfterClass
+    public static void restoreBlockTags() {
+        NativeBlockTags.restoreTags();
+    }
+
+    @Test
+    public void repeatedNativeHeightUsesLiveHeightQueriesAcrossRuntimeChanges() throws Exception {
+        Fixture fixture = fixture();
+        LevelHeightAccessor bounds = LevelHeightAccessor.create(-16, 32);
+        when(fixture.engine().getHeight(-1, -33, false)).thenReturn(4);
+        for (int index = 0; index < 100; index++) {
+            assertEquals(-11, fixture.generator().getBaseHeight(
+                    -1, -33, Heightmap.Types.WORLD_SURFACE, bounds, null));
+        }
+        verify(fixture.engine(), times(100)).getHeight(-1, -33, false);
+
+        when(fixture.engine().getCacheID()).thenReturn(2);
+        when(fixture.engine().getHeight(-1, -33, false)).thenReturn(7);
+        assertEquals(-8, fixture.generator().getBaseHeight(-1, -33, Heightmap.Types.WORLD_SURFACE, bounds, null));
+        verify(fixture.engine(), never()).getComplex();
+        verify(fixture.engine(), never()).getMode();
+    }
+
+    @Test
+    public void nativeHeightPredicatesSelectFluidOrSolidHeightWithoutGeneratingTerrain() throws Exception {
+        Fixture fixture = fixture();
+        LevelHeightAccessor bounds = LevelHeightAccessor.create(-16, 32);
+        when(fixture.engine().getHeight(0, 0, false)).thenReturn(20, 25);
+        when(fixture.engine().getHeight(0, 0, true)).thenReturn(8);
+
+        assertEquals(5, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
+        assertEquals(10, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
+        assertEquals(-7, fixture.generator().getBaseHeight(0, 0, Heightmap.Types.OCEAN_FLOOR, bounds, null));
+        verify(fixture.engine(), times(2)).getHeight(0, 0, false);
+        verify(fixture.engine(), times(1)).getHeight(0, 0, true);
+        verify(fixture.engine(), never()).getComplex();
+        verify(fixture.engine(), never()).getMode();
+    }
+
+    @Test
+    public void nativePredicatesAndAccessorBoundsRemainExact() throws Exception {
+        NativeTerrainColumnPolicy policy = mock(NativeTerrainColumnPolicy.class);
+        NativeTerrainColumnPolicy.ColumnSession session = mock(NativeTerrainColumnPolicy.ColumnSession.class);
+        when(policy.openQuery(any())).thenReturn(session);
+        when(policy.placementKey(anyString())).thenAnswer(invocation -> invocation.getArgument(0));
+        doReturn(Optional.of(signature().geometry())).when(session).resolvedColumn();
+        NativeChunkGenerator<?, ?, ?, ?, ?> generator = generator(policy);
+        LevelHeightAccessor bounds = LevelHeightAccessor.create(-16, 32);
+        for (int repeat = 0; repeat < 2; repeat++) {
+            assertEquals(-11, generator.getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE, bounds, null));
+            assertEquals(-13, generator.getBaseHeight(0, 0, Heightmap.Types.OCEAN_FLOOR, bounds, null));
+            assertEquals(-13, generator.getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING, bounds, null));
+            assertEquals(-14, generator.getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, bounds, null));
+            assertEquals(-14, generator.getBaseHeight(0, 0, Heightmap.Types.WORLD_SURFACE,
+                    LevelHeightAccessor.create(-16, 2), null));
+            assertEquals(-14, generator.getBaseHeight(0, 0, Heightmap.Types.MOTION_BLOCKING_NO_LEAVES,
+                    LevelHeightAccessor.create(-14, 3), null));
+        }
+        verify(session, times(6)).resolvedColumn();
+    }
+
+    private static Fixture fixture() throws Exception {
+        Engine engine = mock(Engine.class);
+        when(engine.getCacheID()).thenReturn(1);
+        when(engine.acquireGenerationLease(anyString())).thenReturn(GenerationSessionLease.noop());
+        return new Fixture(generator(new BukkitTerrainColumnPolicy(engine, null)), engine);
+    }
+
+    private static NativeChunkGenerator<?, ?, ?, ?, ?> generator(NativeTerrainColumnPolicy policy) throws Exception {
+        NativeChunkGenerator<?, ?, ?, ?, ?> generator = mock(NativeChunkGenerator.class, CALLS_REAL_METHODS);
+        set(generator, "terrainColumns", new NativeTerrainColumns(policy));
+        return generator;
+    }
+
+    private static void set(NativeChunkGenerator<?, ?, ?, ?, ?> generator, String name, Object value) throws Exception {
+        Field field = NativeChunkGenerator.class.getDeclaredField(name);
+        field.setAccessible(true);
+        field.set(generator, value);
+    }
+
+    private static TerrainBoundarySignature signature() {
+        BoundaryColumnGeometry geometry = BoundaryColumnGeometry.fromVoxels(-16, List.of(
+                new BoundaryColumnGeometry.Voxel("minecraft:stone", BoundaryColumnGeometry.Phase.SOLID, "", false),
+                new BoundaryColumnGeometry.Voxel("minecraft:water", BoundaryColumnGeometry.Phase.FLUID, "minecraft:water", false),
+                new BoundaryColumnGeometry.Voxel("minecraft:oak_leaves[persistent=true]", BoundaryColumnGeometry.Phase.SOLID, "", false),
+                new BoundaryColumnGeometry.Voxel("minecraft:short_grass", BoundaryColumnGeometry.Phase.SOLID, "", false),
+                new BoundaryColumnGeometry.Voxel("minecraft:light[level=15]", BoundaryColumnGeometry.Phase.SOLID, "", false)));
+        return new TerrainBoundarySignature(
+                new TerrainBoundarySignature.Column(0, 0, 4, 4, OptionalInt.of(1), OptionalInt.empty()),
+                new TerrainBoundarySignature.Samples(new TerrainBoundarySignature.VerticalLayout(-16, 5, 1),
+                        new TerrainBoundarySignature.BiomeEncoding(List.of("minecraft:plains"), new short[]{0})), geometry);
+    }
+
+    private record Fixture(NativeChunkGenerator<?, ?, ?, ?, ?> generator, Engine engine) {
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeGenerationWriteGuardTest.java

@@ -0,0 +1,129 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.iris.structure.nativegen.GenerationWritePolicy;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeGenerationWriteGuard;
+
+import art.arcane.iris.generation.runtime.DimensionStackContext;
+import art.arcane.iris.generation.runtime.DimensionStackLayout;
+import art.arcane.iris.generation.runtime.IrisComplex;
+import art.arcane.iris.generation.runtime.IrisEngine;
+import art.arcane.iris.world.history.GenerationActivation;
+import art.arcane.iris.world.history.GenerationHistory;
+import art.arcane.iris.world.history.GenerationHistoryRuntimeRouter;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.structure.object.IrisStaticObjectLayer;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Optional;
+import java.util.function.Predicate;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
+
+public final class NativeGenerationWriteGuardTest {
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void staticObjectsProtectRelativeHeightBeforeStackSampling() {
+        IrisStaticObjectLayer objects = mock(IrisStaticObjectLayer.class);
+        DimensionStackContext stack = mock(DimensionStackContext.class);
+        when(objects.contains(-3, 74, -7)).thenReturn(true);
+
+        Predicate<BlockPos> protectedPositions = NativeGenerationWriteGuard.protectedPositions(GenerationWritePolicy.protectedPositions(objects, stack, -64));
+
+        assertTrue(protectedPositions.test(new BlockPos(-3, 10, -7)));
+        verifyNoInteractions(stack);
+        assertFalse(NativeGenerationWriteGuard.protectedPositions(GenerationWritePolicy.protectedPositions(objects, null, -64))
+                .test(new BlockPos(-3, 11, -7)));
+    }
+
+    @Test
+    public void emptyStaticLayerSkipsContainsAndCachesEachSignedColumn() {
+        IrisStaticObjectLayer objects = mock(IrisStaticObjectLayer.class);
+        DimensionStackContext stack = mock(DimensionStackContext.class);
+        DimensionStackLayout negative = mock(DimensionStackLayout.class);
+        DimensionStackLayout positive = mock(DimensionStackLayout.class);
+        when(objects.isEmpty()).thenReturn(true);
+        when(stack.sample(-1, -1)).thenReturn(negative);
+        when(stack.sample(-1, 1)).thenReturn(positive);
+        when(negative.isHostFeatureProtectedY(64)).thenReturn(true);
+        when(positive.isHostFeatureProtectedY(65)).thenReturn(true);
+
+        Predicate<BlockPos> protectedPositions = NativeGenerationWriteGuard.protectedPositions(GenerationWritePolicy.protectedPositions(objects, stack, -64));
+
+        assertTrue(protectedPositions.test(new BlockPos(-1, 0, -1)));
+        assertFalse(protectedPositions.test(new BlockPos(-1, 1, -1)));
+        assertTrue(protectedPositions.test(new BlockPos(-1, 1, 1)));
+        verify(stack, times(1)).sample(-1, -1);
+        verify(stack, times(1)).sample(-1, 1);
+        verify(objects, never()).contains(anyInt(), anyInt(), anyInt());
+    }
+
+    @Test
+    public void preTerrainSavedStampDistinguishesEarlierNativeStarts() {
+        IrisEngine engine = mock(IrisEngine.class);
+        GenerationHistoryRuntimeRouter router = mock(GenerationHistoryRuntimeRouter.class);
+        GenerationHistory history = mock(GenerationHistory.class);
+        GenerationActivation active = mock(GenerationActivation.class);
+        when(engine.getGenerationHistoryRuntimeRouter()).thenReturn(Optional.of(router));
+        when(router.history()).thenReturn(history);
+        when(history.activeActivation()).thenReturn(active);
+        when(active.activationId()).thenReturn(4L);
+        assertTrue(GenerationWritePolicy.isHistoricalStructure(engine, 3));
+        assertFalse(GenerationWritePolicy.isHistoricalStructure(engine, 0));
+        assertFalse(GenerationWritePolicy.isHistoricalStructure(engine, 4));
+        assertFalse(GenerationWritePolicy.isHistoricalStructure(engine, 5));
+    }
+
+    @Test
+    public void partialNeighborsMayFinishButCompletedHistoricalNeighborRejectsPass() {
+        Engine engine = mock(Engine.class);
+        IrisComplex complex = mock(IrisComplex.class);
+        when(engine.getComplex()).thenReturn(complex);
+        WorldGenLevel region = mock(WorldGenLevel.class);
+        ChunkAccess partial = mock(ChunkAccess.class);
+        when(partial.getPersistedStatus()).thenReturn(ChunkStatus.TERRAIN);
+        when(region.getChunk(anyInt(), anyInt())).thenReturn(partial);
+        assertTrue(NativeGenerationWriteGuard.allowsDecoration(engine.getComplex()::allowsMantleChunkWrite, region, new ChunkPos(0, 0)));
+        ChunkAccess complete = mock(ChunkAccess.class);
+        when(complete.getPersistedStatus()).thenReturn(ChunkStatus.FULL);
+        when(region.getChunk(1, -1)).thenReturn(complete);
+        assertFalse(NativeGenerationWriteGuard.allowsDecoration(engine.getComplex()::allowsMantleChunkWrite, region, new ChunkPos(0, 0)));
+    }
+
+    @Test
+    public void historicalNoiseMayFinishFeaturesButNeverReplaysNoiseOrCompletedStage() {
+        Engine engine = mock(Engine.class);
+        IrisComplex complex = mock(IrisComplex.class);
+        when(engine.getComplex()).thenReturn(complex);
+        ChunkAccess chunk = mock(ChunkAccess.class);
+        when(chunk.getPos()).thenReturn(new ChunkPos(-2, 3));
+        when(chunk.getPersistedStatus()).thenReturn(ChunkStatus.TERRAIN);
+        assertTrue(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.FEATURES));
+        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.TERRAIN));
+        when(chunk.getPersistedStatus()).thenReturn(ChunkStatus.FEATURES);
+        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.FEATURES));
+        when(chunk.getPersistedStatus()).thenReturn(ChunkStatus.FULL);
+        assertFalse(NativeGenerationWriteGuard.allowsPendingStage(engine.getComplex()::allowsMantleChunkWrite, chunk, ChunkStatus.SPAWN));
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureFactoryTest.java

@@ -0,0 +1,476 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureStartInjector;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureFactory;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeJigsawMetadata;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.ForcedStructureChunkGenerator;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureTemplatePoolBounds;
+
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import java.util.Set;
+import art.arcane.iris.structure.jigsaw.IrisJigsawConfiguration;
+import art.arcane.iris.structure.placement.IrisStructureTerrain;
+import com.mojang.datafixers.util.Either;
+import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.MapCodec;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderOwner;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.Vec3i;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.IntTag;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.biome.FixedBiomeSource;
+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.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.EmptyPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.ListPoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElementType;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.pools.alias.PoolAliasBinding;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutPiece;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessorList;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureFactoryTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void genericSourceDoesNotRequireJigsawType() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+
+        Structure configured = NativeStructureFactory.configure(
+                null, source, null, false, 80);
+
+        assertSame(source, configured);
+    }
+
+    @Test
+    public void jigsawOptionsFailClosedForNonJigsawSource() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+
+        assertThrows(IllegalStateException.class, () -> NativeStructureFactory.configure(
+                null, source, new IrisJigsawConfiguration(), false, 80));
+    }
+
+    @Test
+    public void sourceMetadataReadsScalarAndAxisSpecificJigsawRanges() {
+        CompoundTag scalar = new CompoundTag();
+        scalar.putInt("max_distance_from_center", 80);
+        CompoundTag axisSpecific = new CompoundTag();
+        CompoundTag distance = new CompoundTag();
+        distance.putInt("horizontal", 96);
+        distance.putInt("vertical", 64);
+        axisSpecific.put("max_distance_from_center", distance);
+
+        assertEquals(80, NativeJigsawMetadata.sourceDistance(scalar, "horizontal"));
+        assertEquals(80, NativeJigsawMetadata.sourceDistance(scalar, "vertical"));
+        assertEquals(96, NativeJigsawMetadata.sourceDistance(axisSpecific, "horizontal"));
+        assertEquals(64, NativeJigsawMetadata.sourceDistance(axisSpecific, "vertical"));
+    }
+
+    @Test
+    public void sourceMetadataIncludesAdjustBoundingBoxExpansion() {
+        Structure none = new SwampHutStructure(new Structure.StructureSettings(HolderSet.empty()));
+        Structure beardBox = new SwampHutStructure(new Structure.StructureSettings.Builder(HolderSet.empty())
+                .terrainAdapation(TerrainAdjustment.BEARD_BOX)
+                .build());
+
+        assertEquals(0, NativeJigsawMetadata.horizontalReferenceExpansion(none));
+        assertEquals(12, NativeJigsawMetadata.horizontalReferenceExpansion(beardBox));
+    }
+
+    @Test
+    public void templatePoolSpanIncludesWeightedListsFallbacksAndRotations() {
+        StructurePoolElement narrow = inlineElement(30, 8, 70);
+        StructurePoolElement wide = inlineElement(96, 8, 12);
+        ListPoolElement list = new ListPoolElement(
+                List.of(narrow, wide, EmptyPoolElement.INSTANCE),
+                StructureTemplatePool.Projection.RIGID);
+        BoundPoolHolder fallbackHolder = new BoundPoolHolder("test:fallback");
+        StructureTemplatePool fallback = new StructureTemplatePool(
+                fallbackHolder,
+                List.of(Pair.of(inlineElement(110, 8, 20), 1)));
+        fallbackHolder.bind(fallback);
+        BoundPoolHolder startHolder = new BoundPoolHolder("test:start");
+        StructureTemplatePool start = new StructureTemplatePool(
+                fallbackHolder,
+                List.of(Pair.of(list, 5), Pair.of(EmptyPoolElement.INSTANCE, 1)));
+        startHolder.bind(start);
+
+        assertEquals(110, NativeStructureTemplatePoolBounds.horizontalSpan(start, null));
+    }
+
+    @Test
+    public void oversizedInlineStartTemplateReportsItsFullSpan() {
+        BoundPoolHolder holder = new BoundPoolHolder("test:oversized");
+        StructureTemplatePool pool = new StructureTemplatePool(
+                holder,
+                List.of(Pair.of(inlineElement(160, 8, 9), 1)));
+        holder.bind(pool);
+
+        assertEquals(160, NativeStructureTemplatePoolBounds.horizontalSpan(pool, null));
+    }
+
+    @Test
+    public void sourceSpanIncludesOnlyAliasesThatCanReplaceTheStartPool() {
+        BoundPoolHolder emptyHolder = new BoundPoolHolder("test:empty");
+        StructureTemplatePool empty = new StructureTemplatePool(emptyHolder, List.of());
+        emptyHolder.bind(empty);
+        BoundPoolHolder startHolder = new BoundPoolHolder("test:start");
+        StructureTemplatePool start = new StructureTemplatePool(
+                emptyHolder, List.of(Pair.of(inlineElement(20, 8, 12), 1)));
+        startHolder.bind(start);
+        BoundPoolHolder replacementHolder = new BoundPoolHolder("test:replacement");
+        StructureTemplatePool replacement = new StructureTemplatePool(
+                emptyHolder, List.of(Pair.of(inlineElement(30, 8, 12), 1)));
+        replacementHolder.bind(replacement);
+        BoundPoolHolder unrelatedHolder = new BoundPoolHolder("test:unrelated");
+        StructureTemplatePool unrelated = new StructureTemplatePool(
+                emptyHolder, List.of(Pair.of(inlineElement(200, 8, 12), 1)));
+        unrelatedHolder.bind(unrelated);
+        ResourceKey<StructureTemplatePool> startKey = startHolder.unwrapKey().orElseThrow();
+        ResourceKey<StructureTemplatePool> replacementKey = replacementHolder.unwrapKey().orElseThrow();
+        ResourceKey<StructureTemplatePool> unrelatedKey = unrelatedHolder.unwrapKey().orElseThrow();
+        ResourceKey<StructureTemplatePool> childAlias = ResourceKey.create(
+                Registries.TEMPLATE_POOL, Identifier.parse("test:child_alias"));
+        List<PoolAliasBinding> aliases = List.of(
+                PoolAliasBinding.direct(startKey, replacementKey),
+                PoolAliasBinding.direct(childAlias, unrelatedKey));
+        Map<ResourceKey<StructureTemplatePool>, StructureTemplatePool> pools = Map.of(
+                replacementKey, replacement,
+                unrelatedKey, unrelated);
+
+        assertEquals(30, NativeStructureTemplatePoolBounds.sourceHorizontalSpan(
+                null, start, startKey, aliases, pools::get));
+    }
+
+    @Test
+    public void sourceStartSpanDoesNotIncludeItsFallbackPool() {
+        BoundPoolHolder fallbackHolder = new BoundPoolHolder("test:large_fallback");
+        StructureTemplatePool fallback = new StructureTemplatePool(
+                fallbackHolder, List.of(Pair.of(inlineElement(180, 8, 10), 1)));
+        fallbackHolder.bind(fallback);
+        BoundPoolHolder startHolder = new BoundPoolHolder("test:small_start");
+        StructureTemplatePool start = new StructureTemplatePool(
+                fallbackHolder, List.of(Pair.of(inlineElement(24, 8, 10), 1)));
+        startHolder.bind(start);
+
+        assertEquals(180, NativeStructureTemplatePoolBounds.horizontalSpan(start, null));
+        assertEquals(24, NativeStructureTemplatePoolBounds.sourceHorizontalSpan(
+                null, start, startHolder.unwrapKey().orElseThrow(), List.of(), ignored -> null));
+    }
+
+    @Test
+    public void customPoolElementUsesItsBoundingBoxCapability() {
+        BoundPoolHolder fallbackHolder = new BoundPoolHolder("test:custom_fallback");
+        StructureTemplatePool fallback = new StructureTemplatePool(fallbackHolder, List.of());
+        fallbackHolder.bind(fallback);
+        BoundPoolHolder poolHolder = new BoundPoolHolder("test:custom");
+        StructureTemplatePool pool = new StructureTemplatePool(
+                fallbackHolder, List.of(Pair.of(new BoundingPoolElement(37, 11), 1)));
+        poolHolder.bind(pool);
+
+        assertEquals(37, NativeStructureTemplatePoolBounds.horizontalSpan(pool, null));
+    }
+
+    @Test
+    public void forcedGeneratorBypassesBiomeEligibilityWithoutFabricatingTerrain() {
+        ChunkGenerator delegate = new TestChunkGenerator();
+        Holder<Biome> biome = Holder.direct((Biome) null);
+        LevelHeightAccessor heightAccessor = LevelHeightAccessor.create(-64, 384);
+        ForcedStructureChunkGenerator generator = new ForcedStructureChunkGenerator(
+                delegate, biome);
+
+        assertEquals(63, generator.getSeaLevel());
+        assertEquals(64, generator.getBaseHeight(
+                0, 0, Heightmap.Types.WORLD_SURFACE_WG, heightAccessor, null));
+        NoiseColumn column = generator.getBaseColumn(
+                0, 0, heightAccessor, null);
+        assertSame(Blocks.STONE, column.getBlock(80).getBlock());
+        assertSame(Blocks.STONE, column.getBlock(81).getBlock());
+        assertNotSame(delegate.getBiomeSource(), generator.getBiomeSource());
+    }
+
+    @Test
+    public void undergroundRelocationMovesGenericPiecesAndReturnsFreshStart() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+        SwampHutPiece piece = new SwampHutPiece(RandomSource.create(17L), 0, 0);
+        StructureStart start = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(piece))
+        );
+
+        StructureStart relocated = NativeStructureVerticalPlacer.relocateToMinY(
+                start, source, -20, LevelHeightAccessor.create(-64, 384));
+
+        assertNotSame(start, relocated);
+        assertEquals(-20, relocated.getPieces().getFirst().getBoundingBox().minY());
+        assertEquals(-20, relocated.getBoundingBox().minY());
+    }
+
+    @Test
+    public void invalidGeneratedStartIsANormalSkippedCandidate() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+        StructureStart valid = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(
+                        new SwampHutPiece(RandomSource.create(23L), 0, 0)))
+        );
+
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(
+                StructureStart.INVALID_START));
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(null));
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(
+                new StructureStart(source, new ChunkPos(0, 0), 0,
+                        new PiecesContainer(List.of()))));
+        assertTrue(NativeStructureStartInjector.isUsableGeneratedStart(valid));
+    }
+
+    @Test
+    public void unrepresentableGeneratedContentBecomesAnUnpublishedInvalidStart() {
+        Structure source = new SwampHutStructure(
+                new Structure.StructureSettings(HolderSet.empty()));
+        SwampHutPiece boundaryPiece = new SwampHutPiece(RandomSource.create(29L), 0, 0);
+        boundaryPiece.move(143 - boundaryPiece.getBoundingBox().maxX(), 0, 0);
+        StructureStart boundary = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(boundaryPiece))
+        );
+        SwampHutPiece oversizedPiece = new SwampHutPiece(RandomSource.create(31L), 0, 0);
+        oversizedPiece.move(144 - oversizedPiece.getBoundingBox().maxX(), 0, 0);
+        StructureStart oversized = new StructureStart(
+                source,
+                new ChunkPos(0, 0),
+                0,
+                new PiecesContainer(List.of(oversizedPiece))
+        );
+
+        StructureStart boundaryResult = NativeStructureReferenceEnvelope.wrapForPublication(
+                boundary, source, 0, new IrisStructureTerrain(), "test:boundary_content");
+
+        StructureStart result = NativeStructureReferenceEnvelope.wrapForPublication(
+                oversized, source, 0,
+                new IrisStructureTerrain(),
+                "test:oversized_content");
+
+        assertTrue(boundaryResult.isValid());
+        assertSame(StructureStart.INVALID_START, result);
+        assertFalse(NativeStructureStartInjector.isUsableGeneratedStart(result));
+        assertEquals(1, oversized.getPieces().size());
+    }
+
+    private static final class TestChunkGenerator extends ChunkGenerator {
+        private TestChunkGenerator() {
+            super(new FixedBiomeSource(Holder.direct((Biome) null)));
+        }
+
+        @Override
+        protected MapCodec<? extends ChunkGenerator> codec() {
+            return MapCodec.unit(this);
+        }
+
+        @Override
+        public void spawnOriginalMobs(WorldGenRegion worldGenRegion) {
+        }
+
+        @Override
+        public int getGenDepth() {
+            return 384;
+        }
+
+        @Override
+        public CompletableFuture<ChunkAccess> buildTerrain(
+                ChunkAccess centerChunk, Blender blender, RandomState randomState,
+                StructureManager structureManager, BiomeManager biomeManager, WorldGenRegion region, Set<Holder<Biome>> possibleBiomes) {
+            return CompletableFuture.completedFuture(centerChunk);
+        }
+
+        @Override
+        public int getSeaLevel() {
+            return 63;
+        }
+
+        @Override
+        public int getMinY() {
+            return -64;
+        }
+
+        @Override
+        public int getBaseHeight(int x, int z, Heightmap.Types type,
+                                 LevelHeightAccessor heightAccessor, RandomState randomState) {
+            return 64;
+        }
+
+        @Override
+        public NoiseColumn getBaseColumn(int x, int z, LevelHeightAccessor heightAccessor,
+                                         RandomState randomState) {
+            BlockState[] states = new BlockState[heightAccessor.getHeight()];
+            for (int index = 0; index < states.length; index++) {
+                states[index] = Blocks.STONE.defaultBlockState();
+            }
+            return new NoiseColumn(heightAccessor.getMinY(), states);
+        }
+
+        @Override
+        public void addDebugScreenInfo(List<String> result, RandomState randomState,
+                                       BlockPos feetPos, SamplerContext samplerContext) {
+        }
+    }
+
+    private static StructurePoolElement inlineElement(int sizeX, int sizeY, int sizeZ) {
+        StructureTemplate template = new StructureTemplate();
+        CompoundTag tag = new CompoundTag();
+        ListTag size = new ListTag();
+        size.add(IntTag.valueOf(sizeX));
+        size.add(IntTag.valueOf(sizeY));
+        size.add(IntTag.valueOf(sizeZ));
+        tag.put("size", size);
+        template.load(BuiltInRegistries.BLOCK, tag);
+        return new InlinePoolElement(template);
+    }
+
+    private static final class InlinePoolElement extends SinglePoolElement {
+        private final StructureTemplate inlineTemplate;
+
+        private InlinePoolElement(StructureTemplate template) {
+            super(Either.right(template), Holder.direct(new StructureProcessorList(List.of())),
+                    StructureTemplatePool.Projection.RIGID, Optional.<LiquidSettings>empty());
+            inlineTemplate = template;
+        }
+
+        @Override
+        public BoundingBox getBoundingBox(StructureTemplateManager templateManager,
+                                          BlockPos position, Rotation rotation) {
+            return inlineTemplate.getBoundingBox(
+                    new StructurePlaceSettings().setRotation(rotation), position);
+        }
+    }
+
+    private static final class BoundingPoolElement extends StructurePoolElement {
+        private final int width;
+        private final int depth;
+
+        private BoundingPoolElement(int width, int depth) {
+            super(StructureTemplatePool.Projection.RIGID);
+            this.width = width;
+            this.depth = depth;
+        }
+
+        @Override
+        public Vec3i getSize(StructureTemplateManager templateManager, Rotation rotation) {
+            return new Vec3i(width, 1, depth);
+        }
+
+        @Override
+        public List<StructureTemplate.JigsawBlockInfo> getShuffledJigsawBlocks(
+                StructureTemplateManager templateManager, BlockPos position,
+                Rotation rotation, RandomSource random) {
+            return List.of();
+        }
+
+        @Override
+        public BoundingBox getBoundingBox(StructureTemplateManager templateManager,
+                                          BlockPos position, Rotation rotation) {
+            return new BoundingBox(
+                    position.getX(), position.getY(), position.getZ(),
+                    position.getX() + width - 1, position.getY(),
+                    position.getZ() + depth - 1);
+        }
+
+        @Override
+        public boolean place(StructureTemplateManager templateManager,
+                             WorldGenLevel world,
+                             StructureManager structureManager, ChunkGenerator chunkGenerator,
+                             BlockPos position, BlockPos pivot, Rotation rotation,
+                             BoundingBox area, RandomSource random,
+                             LiquidSettings liquidSettings, boolean keepJigsaws) {
+            return true;
+        }
+
+        @Override
+        public StructurePoolElementType<?> getType() {
+            return StructurePoolElementType.EMPTY;
+        }
+    }
+
+    private static final class BoundPoolHolder extends Holder.Reference<StructureTemplatePool> {
+        private BoundPoolHolder(String key) {
+            super(Type.STAND_ALONE, new HolderOwner<>() {
+            }, ResourceKey.create(Registries.TEMPLATE_POOL, Identifier.parse(key)), null);
+        }
+
+        private void bind(StructureTemplatePool pool) {
+            bindValue(pool);
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureGenerationKeysContractTest.java

@@ -0,0 +1,46 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureGenerationKeys;
+
+import net.minecraft.world.level.levelgen.structure.placement.AbstractSpreadingStructurePlacement;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Vec3i;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadType;
+import net.minecraft.world.level.levelgen.structure.placement.StructurePlacement;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Optional;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureGenerationKeysContractTest {
+    @BeforeClass
+    public static void bootstrapMinecraft() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void frequencyGateUsesMappedAccessorAndRejectsNonPositivePlacements() {
+        assertFalse(NativeStructureGenerationKeys.isEnabledPlacement(placement(0.0F)));
+        assertFalse(NativeStructureGenerationKeys.isEnabledPlacement(placement(-0.1F)));
+        assertFalse(NativeStructureGenerationKeys.isEnabledPlacement(placement(Float.NaN)));
+        assertTrue(NativeStructureGenerationKeys.isEnabledPlacement(placement(0.25F)));
+    }
+
+    private static RandomSpreadStructurePlacement placement(float frequency) {
+        return new RandomSpreadStructurePlacement(
+                Vec3i.ZERO,
+                AbstractSpreadingStructurePlacement.FrequencyReductionMethod.DEFAULT,
+                frequency,
+                1,
+                Optional.empty(),
+                2,
+                1,
+                RandomSpreadType.LINEAR);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureLocatePersistenceTest.java

@@ -0,0 +1,199 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureLocatePersistence;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureLocatePersistenceTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void storageProbeScansEachCandidateOnlyOnce() {
+        AtomicInteger reads = new AtomicInteger();
+        CompoundTag chunk = new CompoundTag();
+        chunk.putInt("DataVersion", SharedConstants.getCurrentVersion().dataVersion().version());
+        chunk.putString("Status", "full");
+        CompoundTag start = new CompoundTag();
+        start.putString("id", "minecraft:village_plains");
+        start.putInt("references", 0);
+        CompoundTag starts = new CompoundTag();
+        starts.put("minecraft:village_plains", start);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+        NativeStructureLocatePersistence.ProbeBudget budget =
+                new NativeStructureLocatePersistence.ProbeBudget(
+                        512,
+                        (chunkPos, visitor) -> {
+                            reads.incrementAndGet();
+                            chunk.acceptAsRoot(visitor);
+                            return CompletableFuture.completedFuture(null);
+                        });
+        ChunkPos chunkPos = new ChunkPos(7, -11);
+
+        assertTrue(budget.acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+        assertTrue(budget.acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+        assertEquals(1, reads.get());
+        assertEquals(1, budget.used());
+    }
+
+    @Test
+    public void legacyStoredChunkIsDatafixedBeforeItsStartIsClassified() {
+        AtomicBoolean datafixed = new AtomicBoolean();
+        CompoundTag legacy = new CompoundTag();
+        legacy.putInt("DataVersion", 100);
+        legacy.putString("Status", "full");
+        NativeStructureLocatePersistence.ProbeBudget budget =
+                new NativeStructureLocatePersistence.ProbeBudget(
+                        512,
+                        (chunkPos, visitor) -> {
+                            legacy.acceptAsRoot(visitor);
+                            return CompletableFuture.completedFuture(null);
+                        },
+                        (level, storedChunk) -> {
+                            datafixed.set(true);
+                            CompoundTag fixed = storedChunk.copy();
+                            fixed.putInt("DataVersion",
+                                    SharedConstants.getCurrentVersion().dataVersion().version());
+                            CompoundTag start = new CompoundTag();
+                            start.putString("id", "minecraft:village_plains");
+                            start.putInt("references", 1);
+                            CompoundTag starts = new CompoundTag();
+                            starts.put("minecraft:village_plains", start);
+                            CompoundTag structures = new CompoundTag();
+                            structures.put("starts", starts);
+                            fixed.put("structures", structures);
+                            return fixed;
+                        });
+
+        assertFalse(budget.acceptsStored(
+                null, new ChunkPos(3, 4), "minecraft:village_plains", true));
+        assertTrue(datafixed.get());
+    }
+
+    @Test
+    public void partialDatafixFailureFallsBackToSelectedChunkVerification() {
+        CompoundTag legacy = new CompoundTag();
+        legacy.putInt("DataVersion", 100);
+        NativeStructureLocatePersistence.ProbeBudget budget =
+                new NativeStructureLocatePersistence.ProbeBudget(
+                        512,
+                        (chunkPos, visitor) -> {
+                            legacy.acceptAsRoot(visitor);
+                            return CompletableFuture.completedFuture(null);
+                        },
+                        (level, storedChunk) -> {
+                            throw new IllegalStateException("broken partial datafix");
+                        });
+
+        assertTrue(budget.acceptsStored(
+                null, new ChunkPos(9, -2), "minecraft:village_plains", true));
+    }
+
+    @Test
+    public void missingStartsContainerFallsBackToSelectedChunkVerification() {
+        CompoundTag chunk = currentChunk();
+        NativeStructureLocatePersistence.ProbeBudget budget = budget(chunk);
+
+        assertTrue(budget.acceptsStored(
+                null, new ChunkPos(5, 8), "minecraft:village_plains", false));
+        assertTrue(budget.acceptsStored(
+                null, new ChunkPos(5, 8), "minecraft:village_plains", true));
+    }
+
+    @Test
+    public void presentEmptyStartsContainerRejectsTheCandidateWithoutLoading() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", new CompoundTag());
+        chunk.put("structures", structures);
+        NativeStructureLocatePersistence.ProbeBudget budget = budget(chunk);
+
+        assertFalse(budget.acceptsStored(
+                null, new ChunkPos(-3, 2), "minecraft:village_plains", false));
+    }
+
+    @Test
+    public void collisionTombstoneIsRejectedForNormalAndUnexploredLocate() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag tombstone = new CompoundTag();
+        tombstone.putString("id", "INVALID");
+        CompoundTag starts = new CompoundTag();
+        starts.put("minecraft:village_plains", tombstone);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+        ChunkPos chunkPos = new ChunkPos(12, -9);
+
+        assertFalse(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", false));
+        assertFalse(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+    }
+
+    @Test
+    public void malformedNonCompoundStartIsRejectedWithoutLoading() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag starts = new CompoundTag();
+        starts.putInt("minecraft:village_plains", 1);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+
+        assertFalse(budget(chunk).acceptsStored(
+                null, new ChunkPos(1, 1), "minecraft:village_plains", false));
+    }
+
+    @Test
+    public void referencedStoredStartIsOnlyRejectedForUnexploredLocate() {
+        CompoundTag chunk = currentChunk();
+        CompoundTag start = new CompoundTag();
+        start.putString("id", "minecraft:village_plains");
+        start.putInt("references", 1);
+        CompoundTag starts = new CompoundTag();
+        starts.put("minecraft:village_plains", start);
+        CompoundTag structures = new CompoundTag();
+        structures.put("starts", starts);
+        chunk.put("structures", structures);
+        ChunkPos chunkPos = new ChunkPos(-4, -7);
+
+        assertTrue(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", false));
+        assertFalse(budget(chunk).acceptsStored(
+                null, chunkPos, "minecraft:village_plains", true));
+    }
+
+    private static CompoundTag currentChunk() {
+        CompoundTag chunk = new CompoundTag();
+        chunk.putInt("DataVersion", SharedConstants.getCurrentVersion().dataVersion().version());
+        return chunk;
+    }
+
+    private static NativeStructureLocatePersistence.ProbeBudget budget(CompoundTag chunk) {
+        return new NativeStructureLocatePersistence.ProbeBudget(
+                512,
+                (chunkPos, visitor) -> {
+                    chunk.acceptAsRoot(visitor);
+                    return CompletableFuture.completedFuture(null);
+                });
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureOwnershipFingerprintTest.java

@@ -0,0 +1,345 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceRepair;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureOwnershipFingerprint;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.iris.structure.nativegen.NativeStructureOwnershipRecord;
+import art.arcane.iris.structure.nativegen.NativeStructureStartPlan;
+import art.arcane.iris.structure.nativegen.IrisNativeStructure;
+import art.arcane.iris.structure.placement.IrisStructurePlacement;
+import art.arcane.iris.structure.placement.IrisStructureTerrain;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
+import art.arcane.volmlib.util.collection.KList;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.Vec3i;
+import net.minecraft.nbt.ListTag;
+import net.minecraft.server.Bootstrap;
+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.Rotation;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomSupport;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElementType;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureOwnershipFingerprintTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void monumentFingerprintSurvivesSourceYRegenerationWithoutSyntheticPieces() {
+        long seed = 8372619L;
+        ChunkPos origin = new ChunkPos(9, -4);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart generated = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                generated, 0, 80, -64, 320);
+        int alignedLocatorY = NativeStructureOwnershipFingerprint.locatorY(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated,
+                structure,
+                0,
+                terrain);
+        String beforeReload = NativeStructureOwnershipFingerprint.fingerprint(
+                "minecraft:monument", wrapped);
+
+        ListTag serializedPieces = (ListTag) new PiecesContainer(wrapped.getPieces()).save(null);
+        PiecesContainer loadedPieces = PiecesContainer.load(serializedPieces, null);
+        assertEquals(1, loadedPieces.pieces().size());
+        assertTrue(loadedPieces.pieces().getFirst()
+                instanceof OceanMonumentPieces.MonumentBuilding);
+        PiecesContainer regeneratedPieces = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                origin, seed, loadedPieces);
+        StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
+        String afterReload = NativeStructureOwnershipFingerprint.fingerprint(
+                "minecraft:monument", reloaded);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", wrapped, NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain)), plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()));
+
+        assertEquals(beforeReload, afterReload);
+        assertTrue(NativeStructureOwnershipFingerprint.matches(ownership, reloaded));
+        assertNotEquals(alignedLocatorY, NativeStructureOwnershipFingerprint.locatorY(reloaded));
+        assertEquals(alignedLocatorY, ownership.locatorY());
+        assertEquals(1, reloaded.getPieces().size());
+        assertEquals(1, wrapped.getPieces().size());
+    }
+
+    @Test
+    public void sameKeyAndOriginStillRequiresMatchingContentIdentity() {
+        long seed = 18273L;
+        ChunkPos origin = new ChunkPos(2, 3);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart expected = monumentStart(structure, origin, seed);
+        StructureStart moved = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : moved.getPieces()) {
+            piece.move(1, 0, 0);
+        }
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", expected, expected.getBoundingBox()), plan(origin, NativeStructureReferenceEnvelope.contentBounds(expected).minY()));
+
+        assertFalse(NativeStructureOwnershipFingerprint.matches(ownership, moved));
+    }
+
+    @Test
+    public void persistedEnvelopeRepairsReloadedMonumentReferenceOutsideLiveBounds() {
+        long seed = 772931L;
+        ChunkPos origin = new ChunkPos(4, -7);
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        StructureStart generated = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                generated, 0, 80, -64, 320);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.FORCE_CARVE)
+                .setHorizontalPadding(24);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated,
+                structure,
+                0,
+                terrain);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", wrapped, NativeStructureReferenceEnvelope.referenceBounds(wrapped, structure, terrain)), plan(origin, NativeStructureReferenceEnvelope.contentBounds(wrapped).minY()));
+        PiecesContainer regeneratedPieces = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                origin, seed, new PiecesContainer(wrapped.getPieces()));
+        StructureStart reloaded = new StructureStart(structure, origin, 0, regeneratedPieces);
+        ChunkPos target = outsideLiveBounds(ownership, reloaded);
+
+        assertNotNull(target);
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                target, "minecraft:monument", reloaded, ownership));
+        assertFalse(NativeStructureReferenceRepair.requiresReference(
+                target, "minecraft:monument", reloaded, null));
+    }
+
+    @Test
+    public void overlappingManualStartsSixteenChunksApartRemainIndependentlyReferenced() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos westOrigin = new ChunkPos(0, 0);
+        ChunkPos eastOrigin = new ChunkPos(16, 0);
+        StructureStart west = monumentStart(structure, westOrigin, 317L);
+        StructureStart east = monumentStart(structure, eastOrigin, 941L);
+        west.getPieces().getFirst().move(112, 0, 0);
+        east.getPieces().getFirst().move(-96, 0, 0);
+        NativeStructureOwnershipRecord westOwnership = ownership(westOrigin, west, structure);
+        NativeStructureOwnershipRecord eastOwnership = ownership(eastOrigin, east, structure);
+        ChunkPos shared = new ChunkPos(8, 0);
+
+        assertTrue(NativeStructureReferenceEnvelope.contentBounds(west).intersects(
+                NativeStructureReferenceEnvelope.contentBounds(east)));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", west, westOwnership));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", east, eastOwnership));
+    }
+
+    @Test
+    public void denseAdjacentManualStartsDoNotSuppressEachOther() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos firstOrigin = new ChunkPos(0, 0);
+        ChunkPos secondOrigin = new ChunkPos(1, 0);
+        StructureStart first = monumentStart(structure, firstOrigin, 17L);
+        StructureStart second = monumentStart(structure, secondOrigin, 23L);
+        NativeStructureOwnershipRecord firstOwnership = ownership(firstOrigin, first, structure);
+        NativeStructureOwnershipRecord secondOwnership = ownership(secondOrigin, second, structure);
+        ChunkPos shared = new ChunkPos(0, 0);
+
+        assertTrue(NativeStructureReferenceEnvelope.contentBounds(first).intersects(
+                NativeStructureReferenceEnvelope.contentBounds(second)));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", first, firstOwnership));
+        assertTrue(NativeStructureReferenceRepair.requiresReference(
+                shared, "minecraft:monument", second, secondOwnership));
+    }
+
+    @Test
+    public void customPoolElementIdentityDoesNotDependOnProcessLocalToString() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos origin = new ChunkPos(3, -2);
+        StructureStart first = poolStart(structure, origin, new IdentityStringPoolElement());
+        StructureStart reloaded = poolStart(structure, origin, new IdentityStringPoolElement());
+
+        assertEquals(
+                NativeStructureOwnershipFingerprint.fingerprint("test:custom_pool", first),
+                NativeStructureOwnershipFingerprint.fingerprint("test:custom_pool", reloaded));
+    }
+
+    @Test
+    public void namedPoolTemplateRemainsPartOfTheStableFingerprint() {
+        OceanMonumentStructure structure = new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+        ChunkPos origin = new ChunkPos(3, -2);
+        StructurePoolElement firstElement = StructurePoolElement.single("test:first")
+                .apply(StructureTemplatePool.Projection.RIGID);
+        StructurePoolElement secondElement = StructurePoolElement.single("test:second")
+                .apply(StructureTemplatePool.Projection.RIGID);
+
+        assertNotEquals(
+                NativeStructureOwnershipFingerprint.fingerprint(
+                        "test:named_pool", poolStart(structure, origin, firstElement)),
+                NativeStructureOwnershipFingerprint.fingerprint(
+                        "test:named_pool", poolStart(structure, origin, secondElement)));
+    }
+
+    private static StructureStart monumentStart(OceanMonumentStructure structure,
+                                                  ChunkPos origin, long seed) {
+        WorldgenRandom random = new WorldgenRandom(
+                new LegacyRandomSource(RandomSupport.generateUniqueSeed()));
+        random.setLargeFeatureSeed(seed, origin.x(), origin.z());
+        Direction orientation = Direction.Plane.HORIZONTAL.getRandomDirection(random);
+        OceanMonumentPieces.MonumentBuilding building = new OceanMonumentPieces.MonumentBuilding(
+                random,
+                origin.getMinBlockX() - 29,
+                origin.getMinBlockZ() - 29,
+                orientation
+        );
+        return new StructureStart(
+                structure,
+                origin,
+                0,
+                new PiecesContainer(List.of(building))
+        );
+    }
+
+    private static NativeStructureStartPlan plan(ChunkPos origin, int baseY) {
+        IrisNativeStructure source = new IrisNativeStructure()
+                .setStructure("minecraft:monument")
+                .setWeight(1);
+        IrisStructurePlacement placement = new IrisStructurePlacement()
+                .setPlacementId("monument-test")
+                .setNativeStructures(new KList<IrisNativeStructure>().qadd(source));
+        return new NativeStructureStartPlan(
+                placement,
+                source,
+                origin.x(),
+                origin.z(),
+                baseY
+        );
+    }
+
+    private static NativeStructureOwnershipRecord ownership(
+            ChunkPos origin, StructureStart start, OceanMonumentStructure structure) {
+        return NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        "minecraft:monument", start, NativeStructureReferenceEnvelope.referenceBounds(
+                        start, structure, new IrisStructureTerrain())), plan(origin, NativeStructureReferenceEnvelope.contentBounds(start).minY()));
+    }
+
+    private static StructureStart poolStart(
+            OceanMonumentStructure structure, ChunkPos origin, StructurePoolElement element) {
+        BlockPos position = new BlockPos(
+                origin.getMiddleBlockX(), 64, origin.getMiddleBlockZ());
+        PoolElementStructurePiece piece = new PoolElementStructurePiece(
+                null, element, position, 0, Rotation.NONE,
+                new BoundingBox(position), LiquidSettings.APPLY_WATERLOGGING);
+        return new StructureStart(
+                structure, origin, 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static final class IdentityStringPoolElement extends StructurePoolElement {
+        private IdentityStringPoolElement() {
+            super(StructureTemplatePool.Projection.RIGID);
+        }
+
+        @Override
+        public Vec3i getSize(StructureTemplateManager templateManager, Rotation rotation) {
+            return new Vec3i(1, 1, 1);
+        }
+
+        @Override
+        public List<StructureTemplate.JigsawBlockInfo> getShuffledJigsawBlocks(
+                StructureTemplateManager templateManager, BlockPos position,
+                Rotation rotation, RandomSource random) {
+            return List.of();
+        }
+
+        @Override
+        public BoundingBox getBoundingBox(StructureTemplateManager templateManager,
+                                          BlockPos position, Rotation rotation) {
+            return new BoundingBox(position);
+        }
+
+        @Override
+        public boolean place(StructureTemplateManager templateManager,
+                             WorldGenLevel world, StructureManager structureManager,
+                             ChunkGenerator chunkGenerator, BlockPos position, BlockPos pivot,
+                             Rotation rotation, BoundingBox area, RandomSource random,
+                             LiquidSettings liquidSettings, boolean keepJigsaws) {
+            return true;
+        }
+
+        @Override
+        public StructurePoolElementType<?> getType() {
+            return StructurePoolElementType.EMPTY;
+        }
+
+        @Override
+        public String toString() {
+            return "IdentityStringPoolElement@"
+                    + Integer.toHexString(System.identityHashCode(this));
+        }
+    }
+
+    private static ChunkPos outsideLiveBounds(NativeStructureOwnershipRecord ownership,
+                                              StructureStart start) {
+        for (int chunkX = ownership.referenceMinChunkX();
+             chunkX <= ownership.referenceMaxChunkX(); chunkX++) {
+            for (int chunkZ = ownership.referenceMinChunkZ();
+                 chunkZ <= ownership.referenceMaxChunkZ(); chunkZ++) {
+                ChunkPos candidate = new ChunkPos(chunkX, chunkZ);
+                if (!start.getBoundingBox().intersects(
+                        candidate.getMinBlockX(), candidate.getMinBlockZ(),
+                        candidate.getMaxBlockX(), candidate.getMaxBlockZ())) {
+                    return candidate;
+                }
+            }
+        }
+        return null;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureOwnershipRecoveryTest.java

@@ -0,0 +1,327 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.terrain.structure.StructureOwnershipRecordView;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureOwnershipRecovery;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureOwnershipFingerprint;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.iris.structure.nativegen.NativeStructureOwnershipRecord;
+import art.arcane.iris.structure.nativegen.NativeStructureStartPlan;
+import art.arcane.iris.structure.placement.StructurePlacementGrid;
+import art.arcane.iris.structure.nativegen.IrisNativeStructure;
+import art.arcane.iris.structure.placement.IrisStructurePlacement;
+import art.arcane.iris.structure.placement.IrisStructureTerrain;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
+import art.arcane.volmlib.util.collection.KList;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomSupport;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureOwnershipRecoveryTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void missingSidecarRecoversExactPolicyEnvelopeAndLocatorAfterReload() {
+        long seed = 5519231L;
+        ChunkPos origin = new ChunkPos(7, -5);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        NativeStructureVerticalPlacer.alignOceanMonumentToSeaLevel(
+                expected, 0, 80, -64, 320);
+        int expectedLocatorY = NativeStructureOwnershipFingerprint.locatorY(expected);
+        NativeStructureStartPlan plan = plan(origin, "recovery-exact", 24);
+        StructureStart reloaded = new StructureStart(
+                structure,
+                origin,
+                expected.getReferences(),
+                OceanMonumentStructure.regeneratePiecesAfterLoad(
+                        origin, seed, new PiecesContainer(expected.getPieces()))
+        );
+
+        NativeStructureOwnershipRecord recovered =
+                NativeStructureOwnershipRecovery.proveCandidate(
+                        "minecraft:monument", structure, reloaded,
+                        plan, expected, false, NativeStructureOwnershipRecord::capture);
+
+        assertNotNull(recovered);
+        assertEquals(StructurePlacementGrid.placementIdentity(plan.placement()),
+                recovered.placementIdentity());
+        assertEquals(expectedLocatorY, recovered.locatorY());
+        assertNotEquals(NativeStructureOwnershipFingerprint.locatorY(reloaded),
+                recovered.locatorY());
+        assertEquals(StructureTerrainMode.FORCE_CARVE,
+                recovered.restoredDecision().terrain().resolvedMode());
+        assertEquals(24, recovered.restoredDecision().terrain().getHorizontalPadding());
+        assertTrue(recovered.referenceMinChunkX()
+                < NativeStructureReferenceEnvelope.contentBounds(reloaded).minX() >> 4);
+    }
+
+    @Test
+    public void naturalSameKeyStartRemainsUnownedWhenOriginIsAmbiguous() {
+        long seed = 22817L;
+        ChunkPos origin = new ChunkPos(-3, 6);
+        OceanMonumentStructure structure = structure();
+        StructureStart natural = monumentStart(structure, origin, seed);
+        NativeStructureStartPlan plan = plan(origin, "natural-ambiguous", 0);
+
+        NativeStructureOwnershipRecord recovered =
+                NativeStructureOwnershipRecovery.proveCandidate(
+                        "minecraft:monument", structure, natural,
+                        plan, natural, true, NativeStructureOwnershipRecord::capture);
+
+        assertNull(recovered);
+    }
+
+    @Test
+    public void changedPlacementIdentityOrGeometryCannotRecoverOwnership() {
+        long seed = 991723L;
+        ChunkPos origin = new ChunkPos(2, 4);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        StructureStart changedGeometry = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : changedGeometry.getPieces()) {
+            piece.move(1, 0, 0);
+        }
+        NativeStructureStartPlan originalIdentity = plan(
+                origin, "original-identity", 0);
+        NativeStructureStartPlan changedIdentity = plan(
+                new ChunkPos(origin.x() + 1, origin.z()), "changed-identity", 0);
+
+        assertNotEquals(
+                StructurePlacementGrid.placementIdentity(originalIdentity.placement()),
+                StructurePlacementGrid.placementIdentity(changedIdentity.placement()));
+        assertNull(NativeStructureOwnershipRecovery.proveCandidate(
+                "minecraft:monument", structure, expected,
+                changedIdentity, expected, false, NativeStructureOwnershipRecord::capture));
+        assertNull(NativeStructureOwnershipRecovery.proveCandidate(
+                "minecraft:monument", structure, changedGeometry,
+                plan(origin, "geometry-check", 0), expected, false, NativeStructureOwnershipRecord::capture));
+    }
+
+    @Test
+    public void recoveredEnvelopeStillRequiresExactFingerprint() {
+        long seed = 81337L;
+        ChunkPos origin = new ChunkPos(-8, -9);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        NativeStructureOwnershipRecord recovered =
+                NativeStructureOwnershipRecovery.proveCandidate(
+                        "minecraft:monument", structure, expected,
+                        plan(origin, "fingerprint-check", 16), expected, false, NativeStructureOwnershipRecord::capture);
+        assertNotNull(recovered);
+
+        StructureStart moved = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : moved.getPieces()) {
+            piece.move(0, 0, 1);
+        }
+
+        assertFalse(NativeStructureOwnershipFingerprint.matches(recovered, moved));
+    }
+
+    @Test
+    public void staleVacuumEnvelopeRefreshesWithoutReplacingOwnershipIdentity() {
+        String structureKey = "minecraft:monument";
+        long seed = 648231L;
+        ChunkPos origin = new ChunkPos(5, -6);
+        OceanMonumentStructure structure = structure();
+        StructureStart start = monumentStart(structure, origin, seed);
+        NativeStructureStartPlan plan = plan(
+                origin, "vacuum-envelope-refresh", StructureTerrainMode.VACUUM, 0);
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(start);
+        NativeStructureOwnershipRecord stale = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, start, content), plan);
+
+        NativeStructureOwnershipRecord refreshed =
+                NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
+                        structureKey, structure, start, stale);
+
+        assertNotNull(refreshed);
+        assertNotEquals(stale, refreshed);
+        assertEquals(stale.schema(), refreshed.schema());
+        assertEquals(stale.ownershipKey(), refreshed.ownershipKey());
+        assertEquals(stale.placementIdentity(), refreshed.placementIdentity());
+        assertEquals(stale.baseY(), refreshed.baseY());
+        assertEquals(stale.locatorY(), refreshed.locatorY());
+        assertEquals(stale.contentFingerprint(), refreshed.contentFingerprint());
+        assertEquals(stale.decision(), refreshed.decision());
+        assertEquals(StructureTerrainMode.VACUUM,
+                refreshed.restoredDecision().terrain().resolvedMode());
+        BoundingBox expected = NativeStructureReferenceEnvelope.referenceBounds(
+                start, structure, plan.placement().resolvedTerrain(), structureKey);
+        assertEquals(expected.minX() >> 4, refreshed.referenceMinChunkX());
+        assertEquals(expected.maxX() >> 4, refreshed.referenceMaxChunkX());
+        assertEquals(expected.minZ() >> 4, refreshed.referenceMinChunkZ());
+        assertEquals(expected.maxZ() >> 4, refreshed.referenceMaxChunkZ());
+        assertTrue(hasExpandedCoverage(stale, refreshed));
+        assertSame(refreshed, NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
+                structureKey, structure, start, refreshed));
+    }
+
+    @Test
+    public void staleEnvelopeCannotRefreshAgainstDifferentContent() {
+        String structureKey = "minecraft:monument";
+        long seed = 412987L;
+        ChunkPos origin = new ChunkPos(-2, 7);
+        OceanMonumentStructure structure = structure();
+        StructureStart expected = monumentStart(structure, origin, seed);
+        NativeStructureStartPlan plan = plan(
+                origin, "vacuum-content-check", StructureTerrainMode.VACUUM, 0);
+        NativeStructureOwnershipRecord stale = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, expected, NativeStructureReferenceEnvelope.contentBounds(expected)), plan);
+        StructureStart moved = monumentStart(structure, origin, seed);
+        for (StructurePiece piece : moved.getPieces()) {
+            piece.move(1, 0, 0);
+        }
+
+        assertNull(NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
+                structureKey, structure, moved, stale));
+    }
+
+    @Test
+    public void currentNonVacuumEnvelopeRemainsThePersistedAuthority() {
+        String structureKey = "minecraft:monument";
+        long seed = 927451L;
+        ChunkPos origin = new ChunkPos(3, 8);
+        OceanMonumentStructure structure = structure();
+        StructureStart start = monumentStart(structure, origin, seed);
+        NativeStructureStartPlan plan = plan(origin, "current-force-carve", 24);
+        BoundingBox envelope = NativeStructureReferenceEnvelope.referenceBounds(
+                start, structure, plan.placement().resolvedTerrain(), structureKey);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, start, envelope), plan);
+
+        assertSame(ownership, NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
+                structureKey, structure, start, ownership));
+    }
+
+    @Test
+    public void clippedVacuumEnvelopeRemainsStableAtTheReferenceLimit() {
+        String structureKey = "minecraft:monument";
+        long seed = 381729L;
+        ChunkPos origin = new ChunkPos(0, 0);
+        OceanMonumentStructure structure = structure();
+        StructureStart start = monumentStart(structure, origin, seed);
+        BoundingBox initial = NativeStructureReferenceEnvelope.contentBounds(start);
+        int maximumReferenceBlockX = ((origin.x()
+                + StructureOwnershipRecordView.MAX_REFERENCE_DISTANCE_CHUNKS) << 4) + 15;
+        int shiftX = maximumReferenceBlockX - initial.maxX();
+        for (StructurePiece piece : start.getPieces()) {
+            piece.move(shiftX, 0, 0);
+        }
+        NativeStructureStartPlan plan = plan(
+                origin, "clipped-vacuum", StructureTerrainMode.VACUUM, 0);
+        BoundingBox envelope = NativeStructureReferenceEnvelope.referenceBounds(
+                start, structure, plan.placement().resolvedTerrain(), structureKey);
+        NativeStructureOwnershipRecord ownership = NativeStructureOwnershipRecord.capture(
+                NativeStructureOwnershipFingerprint.capture(
+                        structureKey, start, envelope), plan);
+
+        assertEquals(origin.x() + StructureOwnershipRecordView.MAX_REFERENCE_DISTANCE_CHUNKS,
+                ownership.referenceMaxChunkX());
+        assertSame(ownership, NativeStructureOwnershipRecovery.refreshReferenceEnvelope(
+                structureKey, structure, start, ownership));
+    }
+
+    private static OceanMonumentStructure structure() {
+        return new OceanMonumentStructure(
+                new OceanMonumentStructure.StructureSettings(HolderSet.empty()));
+    }
+
+    private static StructureStart monumentStart(OceanMonumentStructure structure,
+                                                 ChunkPos origin, long seed) {
+        WorldgenRandom random = new WorldgenRandom(
+                new LegacyRandomSource(RandomSupport.generateUniqueSeed()));
+        random.setLargeFeatureSeed(seed, origin.x(), origin.z());
+        Direction orientation = Direction.Plane.HORIZONTAL.getRandomDirection(random);
+        OceanMonumentPieces.MonumentBuilding building =
+                new OceanMonumentPieces.MonumentBuilding(
+                        random,
+                        origin.getMinBlockX() - 29,
+                        origin.getMinBlockZ() - 29,
+                        orientation
+                );
+        return new StructureStart(
+                structure, origin, 0, new PiecesContainer(List.of(building)));
+    }
+
+    private static NativeStructureStartPlan plan(ChunkPos origin,
+                                                  String placementId,
+                                                  int horizontalPadding) {
+        return plan(origin, placementId,
+                StructureTerrainMode.FORCE_CARVE, horizontalPadding);
+    }
+
+    private static NativeStructureStartPlan plan(ChunkPos origin,
+                                                  String placementId,
+                                                  StructureTerrainMode terrainMode,
+                                                  int horizontalPadding) {
+        IrisNativeStructure source = new IrisNativeStructure()
+                .setStructure("minecraft:monument")
+                .setWeight(1);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(terrainMode)
+                .setHorizontalPadding(horizontalPadding);
+        IrisStructurePlacement placement = new IrisStructurePlacement()
+                .setPlacementId(placementId)
+                .setTerrain(terrain)
+                .setNativeStructures(new KList<IrisNativeStructure>().qadd(source));
+        return new NativeStructureStartPlan(
+                placement,
+                source,
+                origin.x(),
+                origin.z(),
+                NativeStructureReferenceEnvelope.contentBounds(
+                        monumentStart(structure(), origin, 1L)).minY()
+        );
+    }
+
+    private static boolean hasExpandedCoverage(
+            NativeStructureOwnershipRecord stale,
+            NativeStructureOwnershipRecord refreshed) {
+        for (int chunkX = refreshed.referenceMinChunkX();
+             chunkX <= refreshed.referenceMaxChunkX(); chunkX++) {
+            for (int chunkZ = refreshed.referenceMinChunkZ();
+                 chunkZ <= refreshed.referenceMaxChunkZ(); chunkZ++) {
+                if (!stale.covers(chunkX, chunkZ)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorEncaseTest.java

@@ -0,0 +1,542 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.terrain.structure.StructurePalette;
+
+import art.arcane.volmlib.nativelib.terrain.structure.StructureTerrainSettings;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureTerrainIntegrator;
+
+import art.arcane.iris.generation.terrain.IrisMaterialPalette;
+import art.arcane.iris.structure.placement.IrisStructureTerrain;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
+import art.arcane.iris.structure.placement.IrisStructureYBand;
+import art.arcane.volmlib.util.math.RNG;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.WorldGenLevel;
+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.dimension.BuiltinDimensionTypes;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.BlockIgnoreProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessorList;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Proxy;
+import java.util.BitSet;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructurePostProcessorEncaseTest {
+    private static final long TEST_SEED = 1234L;
+
+    @BeforeClass
+    public static void bootstrapMinecraft() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void encaseFillsAirAndLiquidWithoutOverwritingExistingTerrain() {
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        BoundingBox area = new BoundingBox(
+                bounds.minX() - 1, bounds.minY() - 1, bounds.minZ() - 1,
+                bounds.maxX() + 1, bounds.maxY() + 1, bounds.maxZ() + 1);
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        put(blocks, bounds.minX(), bounds.minY(), bounds.minZ(), Blocks.DIRT.defaultBlockState());
+        put(blocks, bounds.maxX(), bounds.minY(), bounds.maxZ(), Blocks.WATER.defaultBlockState());
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), area, "minecraft:stronghold", start,
+                new IrisStructureTerrain()
+                        .setMode(StructureTerrainMode.ENCASE)
+                        .setHorizontalPadding(1)
+                        .setCeilingPadding(1)
+                        .setFloorPadding(1),
+                null);
+
+        assertEquals(Blocks.DIRT.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.maxX(), bounds.minY(), bounds.maxZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX() - 1, bounds.minY() - 1, bounds.minZ() - 1));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.maxX() + 1, bounds.maxY() + 1, bounds.maxZ() + 1));
+    }
+
+    @Test
+    public void defaultEncasePaletteSplitsStoneAboveZeroAndDeepslateBelow() {
+        StructureStart start = start(TerrainAdjustment.BURY, -1);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), bounds, "minecraft:stronghold", start,
+                new IrisStructureTerrain().setMode(StructureTerrainMode.ENCASE),
+                null);
+
+        assertEquals(-1, bounds.minY());
+        assertEquals(Blocks.DEEPSLATE.defaultBlockState(),
+                state(blocks, bounds.minX(), -1, bounds.minZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX(), 0, bounds.minZ()));
+    }
+
+    @Test
+    public void defaultEncaseMaterialFollowsVanillaDimensionTerrain() {
+        assertEquals(Blocks.NETHERRACK.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(Level.NETHER, 64));
+        assertEquals(Blocks.END_STONE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(Level.END, 64));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(Level.OVERWORLD, 64));
+    }
+
+    @Test
+    public void sourceEncaseMaterialFollowsNearbyIrisTerrain() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(4, 64, 8);
+        put(blocks, fill.getX() + 3, fill.getY(), fill.getZ(), Blocks.TUFF.defaultBlockState());
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(world(blocks), fill));
+    }
+
+    @Test
+    public void sourceMaterialSnapshotIgnoresPreviouslyDecoratedAdjacentChunks() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(0, 64, 8);
+        put(blocks, -1, 64, 8, Blocks.OAK_PLANKS.defaultBlockState());
+        put(blocks, 3, 64, 8, Blocks.TUFF.defaultBlockState());
+        WorldGenLevel world = world(blocks);
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                sourceSnapshot(world, new BoundingBox(0, 64, 0, 15, 64, 15));
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(
+                        world, fill, sourceTerrain));
+    }
+
+    @Test
+    public void sourceMaterialSnapshotIsStableAcrossEarlierFillsInTheSameChunk() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(0, 64, 8);
+        put(blocks, 3, 64, 8, Blocks.TUFF.defaultBlockState());
+        WorldGenLevel world = world(blocks);
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                sourceSnapshot(world, new BoundingBox(0, 64, 0, 15, 64, 15));
+        put(blocks, 1, 64, 8, Blocks.OAK_PLANKS.defaultBlockState());
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(
+                        world, fill, sourceTerrain));
+    }
+
+    @Test
+    public void sourceMaterialRejectsStructureBlocksAndOresBeforeDimensionFallback() {
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        BlockPos fill = new BlockPos(4, -20, 8);
+        put(blocks, 3, -20, 8, Blocks.OAK_PLANKS.defaultBlockState());
+        put(blocks, 5, -20, 8, Blocks.STONE_BRICKS.defaultBlockState());
+        put(blocks, 4, -20, 7, Blocks.IRON_ORE.defaultBlockState());
+
+        assertEquals(Blocks.DEEPSLATE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.sourceEncaseBlock(world(blocks), fill));
+    }
+
+    @Test
+    public void sourceMaterialSnapshotOnlyAllocatesActualFillLayers() {
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox area = new BoundingBox(0, -2032, 0, 15, 2030, 15);
+        NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceTerrain =
+                NativeStructureTerrainIntegrator.captureSourceTerrain(
+                        world(new HashMap<>()), area,
+                        List.of(new NativeStructureTerrainIntegrator.TerrainTarget(
+                                "test:bounded-snapshot", start,
+                                new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE))));
+
+        assertNotNull(sourceTerrain);
+        assertEquals(23 * 16 * 16, sourceTerrain.sampledCells());
+    }
+
+    @Test
+    public void customDimensionKeyUsesRegisteredVanillaDimensionType() {
+        ResourceKey<Level> customDimension = ResourceKey.create(
+                Registries.DIMENSION, Identifier.parse("iris:custom_nether"));
+
+        assertEquals(Blocks.NETHERRACK.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(
+                        customDimension, BuiltinDimensionTypes.NETHER, null, 64));
+        assertEquals(Blocks.END_STONE.defaultBlockState(),
+                NativeStructureTerrainIntegrator.defaultEncaseBlock(
+                        customDimension, BuiltinDimensionTypes.END, null, 64));
+    }
+
+    @Test
+    public void configuredEncasePaletteReplacesTheDefaultMaterial() {
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+        IrisMaterialPalette palette = new IrisMaterialPalette().qclear().qadd("minecraft:tuff");
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), bounds, "minecraft:stronghold", start,
+                new IrisStructureTerrain()
+                        .setMode(StructureTerrainMode.ENCASE)
+                        .setEncasePalette(palette),
+                NativeStructurePostProcessorEncaseTest::tuffBlock);
+
+        assertEquals(Blocks.TUFF.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.minY(), bounds.minZ()));
+    }
+
+    @Test
+    public void omittedTerrainConfigurationRetainsSourceSemantics() {
+        for (TerrainAdjustment adjustment : TerrainAdjustment.values()) {
+            StructureTerrainSettings resolved = NativeStructureTerrainIntegrator.resolveNativeTerrain(
+                    start(adjustment, 64), null);
+
+            assertEquals(StructureTerrainMode.SOURCE, resolved.resolvedMode());
+        }
+    }
+
+    @Test
+    public void sourceBuryUsesTheVanillaSixByTwelveInfluenceEnvelope() {
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        int groundY = bounds.minY();
+        BoundingBox area = new BoundingBox(
+                bounds.minX() - 7, groundY - 13, bounds.minZ(),
+                bounds.maxX(), groundY + 13, bounds.maxZ());
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), area, "test:bury", start,
+                new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE), null);
+
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX() - 5, groundY, bounds.minZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX(), groundY + 11, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 6, groundY, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), groundY + 12, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 7, groundY, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), groundY + 13, bounds.minZ()));
+    }
+
+    @Test
+    public void sourceEncapsulateWrapsTheFullPieceBounds() {
+        StructureStart start = start(TerrainAdjustment.ENCAPSULATE, 64);
+        BoundingBox bounds = start.getPieces().getFirst().getBoundingBox();
+        BoundingBox area = new BoundingBox(
+                bounds.minX() - 13, bounds.minY(), bounds.minZ(),
+                bounds.maxX(), bounds.maxY() + 13, bounds.maxZ());
+        Map<BlockPos, BlockState> blocks = new HashMap<>();
+
+        NativeStructureTerrainIntegrator.integrateTerrain(
+                world(blocks), area, "test:encapsulate", start,
+                new IrisStructureTerrain().setMode(StructureTerrainMode.SOURCE), null);
+
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX() - 11, bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.STONE.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.maxY() + 11, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 12, bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.maxY() + 12, bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX() - 13, bounds.minY(), bounds.minZ()));
+        assertEquals(Blocks.AIR.defaultBlockState(),
+                state(blocks, bounds.minX(), bounds.maxY() + 13, bounds.minZ()));
+    }
+
+    @Test
+    public void sourceTerrainDensityOnlyUsesRigidPoolPieces() {
+        PoolElementStructurePiece terrainMatching = poolPiece(StructureTemplatePool.Projection.TERRAIN_MATCHING);
+        PoolElementStructurePiece rigid = poolPiece(StructureTemplatePool.Projection.RIGID);
+
+        assertFalse(NativeStructureTerrainIntegrator.isSourceRigidPiece(terrainMatching));
+        assertTrue(NativeStructureTerrainIntegrator.isSourceRigidPiece(rigid));
+    }
+
+    @Test
+    public void sourceJunctionTerrainUsesTheStrictLowerTwelveBlockEnvelope() {
+        assertTrue(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, -1, 0));
+        assertTrue(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, -11, 0));
+        assertFalse(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, 0, 0));
+        assertFalse(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(0, -12, 0));
+        assertFalse(NativeStructureTerrainIntegrator.insideSourceJunctionEnvelope(12, -1, 0));
+    }
+
+    @Test
+    public void explicitTerrainConfigurationWinsOverAutoEncase() {
+        IrisStructureTerrain configured = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.PRESERVE);
+
+        assertSame(configured, NativeStructureTerrainIntegrator.resolveNativeTerrain(
+                start(TerrainAdjustment.BURY, 64), configured));
+    }
+
+    @Test
+    public void legacyTemplateAirIsClearedAfterEveryTerrainFillPath() {
+        IrisStructureTerrain source = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.SOURCE);
+        IrisStructureTerrain preserve = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.PRESERVE);
+        IrisStructureTerrain encase = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.ENCASE);
+
+        assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.BURY, 64), source));
+        assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.BEARD_BOX, 64), source));
+        assertTrue(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.NONE, 64), encase));
+        assertFalse(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.NONE, 64), source));
+        assertFalse(NativeStructureTerrainIntegrator.clearsLegacyTemplateAir(
+                start(TerrainAdjustment.BURY, 64), preserve));
+    }
+
+    @Test
+    public void encaseReservesTheNeighborChunkEnvelope() {
+        StructureStart generated = start(TerrainAdjustment.BURY, 64);
+        BoundingBox sourceBounds = generated.getBoundingBox();
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.ENCASE)
+                .setHorizontalPadding(4);
+
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated,
+                generated.getStructure(),
+                0,
+                terrain);
+        BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                wrapped, wrapped.getStructure(), terrain);
+
+        assertEquals(sourceBounds, wrapped.getBoundingBox());
+        assertEquals(content.minX() - 4, referenceBounds.minX());
+        assertEquals(content.maxX() + 4, referenceBounds.maxX());
+        assertEquals(content.minZ() - 4, referenceBounds.minZ());
+        assertEquals(content.maxZ() + 4, referenceBounds.maxZ());
+        assertEquals(generated.getPieces().size(), wrapped.getPieces().size());
+    }
+
+    @Test
+    public void referenceEnvelopeRejectsChunkCoordinateOverflow() {
+        StructureStart generated = start(TerrainAdjustment.NONE, 64);
+        StructureStart extreme = new StructureStart(
+                generated.getStructure(), new ChunkPos(Integer.MAX_VALUE, 0), 0,
+                new PiecesContainer(generated.getPieces()));
+
+        assertThrows(IllegalStateException.class, () ->
+                NativeStructureReferenceEnvelope.referenceBounds(
+                        extreme, extreme.getStructure(), new IrisStructureTerrain()));
+    }
+
+    @Test
+    public void explicitTerrainEnvelopeDoesNotInheritSourceAdjustment() {
+        StructureStart generated = start(TerrainAdjustment.BURY, 64);
+        BoundingBox content = NativeStructureReferenceEnvelope.contentBounds(generated);
+        IrisStructureTerrain terrain = new IrisStructureTerrain()
+                .setMode(StructureTerrainMode.ENCASE)
+                .setHorizontalPadding(112);
+
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                generated, generated.getStructure(), 0, terrain);
+        BoundingBox referenceBounds = NativeStructureReferenceEnvelope.referenceBounds(
+                wrapped, wrapped.getStructure(), terrain);
+
+        assertEquals(content.minX() - 112, referenceBounds.minX());
+        assertEquals(content.maxX() + 112, referenceBounds.maxX());
+    }
+
+    @Test
+    public void yBandRelocatesTheStartMidpointDeterministically() {
+        IrisStructureYBand band = new IrisStructureYBand().setMin(-120).setMax(-20);
+        StructureStart first = start(TerrainAdjustment.BURY, 64);
+        StructureStart second = start(TerrainAdjustment.BURY, 64);
+
+        NativeStructureVerticalPlacer.applyVerticalShift(
+                first, -64, -256, 320, true, false, band, (x, z) -> 40);
+        NativeStructureVerticalPlacer.applyVerticalShift(
+                second, -64, -256, 320, true, false, band, (x, z) -> 40);
+
+        BoundingBox bounds = first.getBoundingBox();
+        assertEquals(bounds.minY(), second.getBoundingBox().minY());
+        assertTrue(bounds.minY() >= -120);
+        assertTrue(bounds.maxY() <= -20);
+
+        int repeated = NativeStructureVerticalPlacer.applyVerticalShift(
+                first, -64, -256, 320, true, false, band, (x, z) -> 40);
+        assertEquals(0, repeated);
+    }
+
+    @Test
+    public void yBandClampsWhenTheBandCannotContainTheStructure() {
+        IrisStructureYBand band = new IrisStructureYBand().setMin(-50).setMax(-45);
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+
+        NativeStructureVerticalPlacer.applyVerticalShift(
+                start, 0, -256, 320, true, false, band, (x, z) -> 40);
+
+        BoundingBox bounds = start.getBoundingBox();
+        int midpoint = bounds.minY() + (bounds.maxY() - bounds.minY()) / 2;
+        assertTrue(midpoint >= -50);
+        assertTrue(midpoint <= -45);
+    }
+
+    @Test
+    public void yBandReplacesBothTheBlindShiftAndBurial() {
+        IrisStructureYBand band = new IrisStructureYBand().setMin(-64).setMax(-64);
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        BoundingBox bounds = start.getBoundingBox();
+        int height = bounds.maxY() - bounds.minY();
+
+        NativeStructureVerticalPlacer.applyVerticalShift(
+                start, -200, -256, 320, true, false, band, (x, z) -> 40);
+
+        assertEquals(-64 - height / 2, start.getBoundingBox().minY());
+    }
+
+    @Test
+    public void preserveSourceYWinsOverTheConfiguredBand() {
+        IrisStructureYBand band = new IrisStructureYBand().setMin(-120).setMax(-20);
+        StructureStart start = start(TerrainAdjustment.BURY, 64);
+        int minY = start.getBoundingBox().minY();
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalShift(
+                start, 0, -256, 320, true, true, band, (x, z) -> 40);
+
+        assertEquals(0, offset);
+        assertEquals(minY, start.getBoundingBox().minY());
+    }
+
+    private static BlockState tuffBlock(StructurePalette palette, RNG rng, int x, int y, int z) {
+        assertNotNull(palette);
+        assertNotNull(rng);
+        return Blocks.TUFF.defaultBlockState();
+    }
+
+    private static StructureStart start(TerrainAdjustment adjustment, int minY) {
+        Structure structure = new DesertPyramidStructure(new Structure.StructureSettings(
+                HolderSet.empty(), Map.of(), GenerationStep.Decoration.STRONGHOLDS, adjustment));
+        StructurePiece piece = new DesertPyramidPiece(RandomSource.create(7L), 0, 0);
+        piece.move(0, minY - piece.getBoundingBox().minY(), 0);
+        return new StructureStart(
+                structure, new ChunkPos(0, 0), 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static PoolElementStructurePiece poolPiece(StructureTemplatePool.Projection projection) {
+        BlockPos position = new BlockPos(0, 64, 0);
+        StructurePoolElement element = StructurePoolElement.single(
+                "minecraft:empty",
+                Holder.direct(new StructureProcessorList(List.of(
+                        BlockIgnoreProcessor.STRUCTURE_AND_AIR))),
+                LiquidSettings.APPLY_WATERLOGGING
+        ).apply(projection);
+        return new PoolElementStructurePiece(
+                null,
+                element,
+                position,
+                0,
+                Rotation.NONE,
+                new BoundingBox(position),
+                LiquidSettings.APPLY_WATERLOGGING);
+    }
+
+    private static WorldGenLevel world(Map<BlockPos, BlockState> blocks) {
+        InvocationHandler handler = (proxy, method, arguments) -> {
+            String methodName = method.getName();
+            if (methodName.equals("getBlockState")) {
+                BlockPos position = (BlockPos) arguments[0];
+                return state(blocks, position.getX(), position.getY(), position.getZ());
+            }
+            if (methodName.equals("setBlock")) {
+                BlockPos position = (BlockPos) arguments[0];
+                BlockState blockState = (BlockState) arguments[1];
+                put(blocks, position.getX(), position.getY(), position.getZ(), blockState);
+                return true;
+            }
+            if (methodName.equals("getSeed")) {
+                return TEST_SEED;
+            }
+            if (methodName.equals("getLevel")) {
+                return null;
+            }
+            if (methodName.equals("hashCode")) {
+                return System.identityHashCode(proxy);
+            }
+            if (methodName.equals("equals")) {
+                return proxy == arguments[0];
+            }
+            if (methodName.equals("toString")) {
+                return "encase-test-world";
+            }
+            throw new UnsupportedOperationException(method.toString());
+        };
+        return (WorldGenLevel) Proxy.newProxyInstance(
+                WorldGenLevel.class.getClassLoader(), new Class<?>[]{WorldGenLevel.class}, handler);
+    }
+
+    private static NativeStructureTerrainIntegrator.SourceTerrainSnapshot sourceSnapshot(
+            WorldGenLevel world, BoundingBox area) {
+        BitSet requiredLayers = new BitSet(area.getYSpan());
+        requiredLayers.set(0, area.getYSpan());
+        return NativeStructureTerrainIntegrator.SourceTerrainSnapshot.capture(
+                world, area, requiredLayers);
+    }
+
+    private static void put(Map<BlockPos, BlockState> blocks,
+                           int x, int y, int z, BlockState state) {
+        blocks.put(new BlockPos(x, y, z), state);
+    }
+
+    private static BlockState state(Map<BlockPos, BlockState> blocks, int x, int y, int z) {
+        return blocks.getOrDefault(new BlockPos(x, y, z), Blocks.AIR.defaultBlockState());
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorMonumentTest.java

@@ -0,0 +1,206 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReferenceEnvelope;
+
+import art.arcane.iris.structure.placement.IrisStructureTerrain;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Direction;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentPieces;
+import net.minecraft.world.level.levelgen.structure.structures.OceanMonumentStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructurePostProcessorMonumentTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void vanillaSeaLevelKeepsTheVanillaMonumentHeight() {
+        StructureStart start = monumentStart(1337L);
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:monument", 0, 63, -64, 320, false, false, null, (x, z) -> 0);
+
+        assertEquals(0, offset);
+        assertEquals(39, start.getBoundingBox().minY());
+        assertEquals(61, start.getBoundingBox().maxY());
+    }
+
+    @Test
+    public void shiftedSeaLevelMovesTheShellAndEveryRoomTogether() {
+        StructureStart start = monumentStart(1337L);
+        OceanMonumentPieces.MonumentBuilding building = monumentBuilding(start);
+        List<StructurePiece> children = NativeStructureVerticalPlacer.monumentChildPieces(building);
+        int[] childMinY = minimumYs(children);
+        BoundingBox cachedBounds = start.getBoundingBox();
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:monument", 0, 50, -256, 512, false, false, null, (x, z) -> 0);
+
+        assertEquals(-13, offset);
+        assertSame(cachedBounds, start.getBoundingBox());
+        assertEquals(26, building.getBoundingBox().minY());
+        assertEquals(48, building.getBoundingBox().maxY());
+        assertEquals(26, start.getBoundingBox().minY());
+        assertEquals(48, start.getBoundingBox().maxY());
+        assertTrue(children.size() > 20);
+        for (int i = 0; i < children.size(); i++) {
+            assertEquals(childMinY[i] - 13, children.get(i).getBoundingBox().minY());
+        }
+
+        int repeatedOffset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:monument", 0, 50, -256, 512, false, false, null, (x, z) -> 0);
+        assertEquals(0, repeatedOffset);
+    }
+
+    @Test
+    public void configuredOffsetIsRelativeToTheActualSeaLevel() {
+        StructureStart start = monumentStart(1337L);
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:monument", 3, 50, -256, 512, false, false, null, (x, z) -> 0);
+
+        assertEquals(-10, offset);
+        assertEquals(29, start.getBoundingBox().minY());
+        assertEquals(51, start.getBoundingBox().maxY());
+    }
+
+    @Test
+    public void referenceEnvelopeDoesNotAddMonumentPieces() {
+        StructureStart start = monumentStart(1337L);
+        StructureStart wrapped = NativeStructureReferenceEnvelope.wrap(
+                start,
+                start.getStructure(),
+                0,
+                new IrisStructureTerrain()
+                        .setMode(StructureTerrainMode.FORCE_CARVE)
+                        .setHorizontalPadding(4));
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                wrapped, "minecraft:monument", 0, 63, -64, 320,
+                false, false, null, (x, z) -> 0);
+
+        assertEquals(0, offset);
+        assertEquals(1, wrapped.getPieces().size());
+    }
+
+    @Test
+    public void vanillaReloadRegenerationIsRealignedBeforePlacement() {
+        long seed = 1337L;
+        ChunkPos chunkPos = new ChunkPos(0, 0);
+        StructureStart initial = monumentStart(seed);
+        NativeStructureVerticalPlacer.applyVerticalPlacement(
+                initial, "minecraft:monument", 0, 50, -256, 512, false, false, null, (x, z) -> 0);
+
+        PiecesContainer regenerated = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                chunkPos, seed, new PiecesContainer(initial.getPieces()));
+        StructureStart reloaded = new StructureStart(
+                monumentStructure(), chunkPos, 0, regenerated);
+
+        assertEquals(39, reloaded.getBoundingBox().minY());
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                reloaded, "minecraft:monument", 0, 50, -256, 512, false, false, null, (x, z) -> 0);
+        assertEquals(-13, offset);
+        assertEquals(26, reloaded.getBoundingBox().minY());
+        assertEquals(48, reloaded.getBoundingBox().maxY());
+    }
+
+    @Test
+    public void neighboringChunkPlacementRealignsReloadedMonumentOnce() throws Exception {
+        long seed = 1337L;
+        ChunkPos chunkPos = new ChunkPos(0, 0);
+        StructureStart initial = monumentStart(seed);
+        NativeStructureVerticalPlacer.applyVerticalPlacement(
+                initial, "minecraft:monument", 0, 50, -256, 512,
+                false, false, null, (x, z) -> 0);
+        PiecesContainer regenerated = OceanMonumentStructure.regeneratePiecesAfterLoad(
+                chunkPos, seed, new PiecesContainer(initial.getPieces()));
+        StructureStart reloaded = new StructureStart(
+                monumentStructure(), chunkPos, 0, regenerated);
+        ExecutorService executor = Executors.newFixedThreadPool(8);
+        CountDownLatch release = new CountDownLatch(1);
+        List<Future<?>> futures = new ArrayList<>();
+        try {
+            for (int task = 0; task < 16; task++) {
+                futures.add(executor.submit(() -> {
+                    release.await();
+                    NativeStructureVerticalPlacer.ensureMonumentSeaLevelAlignment(
+                            reloaded, "minecraft:monument", 0, 50, -256, 512);
+                    return null;
+                }));
+            }
+            release.countDown();
+            for (Future<?> future : futures) {
+                future.get();
+            }
+        } finally {
+            executor.shutdownNow();
+        }
+
+        assertEquals(26, reloaded.getBoundingBox().minY());
+        assertEquals(48, reloaded.getBoundingBox().maxY());
+    }
+
+    @Test
+    public void impossibleSeaLevelAlignmentFailsInsteadOfClippingTheMonument() {
+        StructureStart start = monumentStart(1337L);
+        try {
+            NativeStructureVerticalPlacer.applyVerticalPlacement(
+                    start, "minecraft:monument", 0, -50, -64, 320, false, false, null, (x, z) -> 0);
+        } catch (IllegalStateException error) {
+            assertTrue(error.getMessage().contains("cannot align"));
+            return;
+        }
+        throw new AssertionError("Expected an out-of-bounds monument alignment to fail");
+    }
+
+    private static StructureStart monumentStart(long seed) {
+        ChunkPos chunkPos = new ChunkPos(0, 0);
+        OceanMonumentPieces.MonumentBuilding building = new OceanMonumentPieces.MonumentBuilding(
+                RandomSource.create(seed), -29, -29, Direction.NORTH);
+        return new StructureStart(
+                monumentStructure(), chunkPos, 0, new PiecesContainer(List.of(building)));
+    }
+
+    private static OceanMonumentStructure monumentStructure() {
+        return new OceanMonumentStructure(new Structure.StructureSettings(HolderSet.empty()));
+    }
+
+    private static OceanMonumentPieces.MonumentBuilding monumentBuilding(StructureStart start) {
+        return (OceanMonumentPieces.MonumentBuilding) start.getPieces().get(0);
+    }
+
+    private static int[] minimumYs(List<StructurePiece> pieces) {
+        int[] ys = new int[pieces.size()];
+        for (int i = 0; i < pieces.size(); i++) {
+            ys[i] = pieces.get(i).getBoundingBox().minY();
+        }
+        return ys;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorScatteredFeatureTest.java

@@ -0,0 +1,204 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureSurfaceFitter;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReflection;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelAccessor;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.ScatteredFeaturePiece;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructurePiece;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
+import net.minecraft.world.level.levelgen.structure.structures.JungleTemplePiece;
+import net.minecraft.world.level.levelgen.structure.structures.JungleTempleStructure;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutPiece;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructurePostProcessorScatteredFeatureTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void desertPyramidUsesTheLowestFootprintSurfaceAndLocksVanillaReanchor() {
+        TestDesertPyramidPiece piece = new TestDesertPyramidPiece(RandomSource.create(11L), 0, 0);
+        StructureStart start = desertStart(piece);
+        BoundingBox cachedBounds = start.getBoundingBox();
+        BoundingBox footprint = piece.getBoundingBox();
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:desert_pyramid", 0, 63, -64, 320, false, false, null,
+                (x, z) -> x == footprint.maxX() && z == footprint.maxZ() ? 64 : 92);
+
+        assertEquals(1, offset);
+        assertSame(cachedBounds, start.getBoundingBox());
+        assertEquals(65, piece.getBoundingBox().minY());
+        assertEquals(65, start.getBoundingBox().minY());
+        assertTrue(piece.attemptVanillaAlignment(-2));
+        assertEquals(65, piece.getBoundingBox().minY());
+    }
+
+    @Test
+    public void jungleTempleUsesAverageFootprintSurfaceAndHonorsConfiguredShift() {
+        TestJungleTemplePiece piece = new TestJungleTemplePiece(RandomSource.create(19L), 32, -16);
+        StructureStart start = jungleStart(piece);
+        BoundingBox footprint = piece.getBoundingBox();
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:jungle_pyramid", 4, 63, -64, 320, false, false, null,
+                (x, z) -> x == footprint.minX() && z == footprint.minZ() ? 88 : 70);
+
+        assertEquals(11, offset);
+        assertEquals(75, piece.getBoundingBox().minY());
+        assertTrue(piece.attemptVanillaAlignment());
+        assertEquals(75, piece.getBoundingBox().minY());
+    }
+
+    @Test
+    public void repeatedAlignmentIsIdempotent() {
+        TestDesertPyramidPiece piece = new TestDesertPyramidPiece(RandomSource.create(23L), 0, 0);
+        StructureStart start = desertStart(piece);
+
+        int initialOffset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:desert_pyramid", 0, 63, -64, 320, false, false, null, (x, z) -> 80);
+        int repeatedOffset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:desert_pyramid", 0, 63, -64, 320, false, false, null, (x, z) -> 80);
+
+        assertEquals(17, initialOffset);
+        assertEquals(0, repeatedOffset);
+        assertEquals(81, piece.getBoundingBox().minY());
+    }
+
+    @Test
+    public void scatteredAlignmentStaysInsideWorldBounds() {
+        TestDesertPyramidPiece piece = new TestDesertPyramidPiece(RandomSource.create(29L), 0, 0);
+        StructureStart start = desertStart(piece);
+
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                start, "minecraft:desert_pyramid", 0, 63, -64, 320, false, false, null, (x, z) -> 318);
+
+        assertEquals(241, offset);
+        assertEquals(305, piece.getBoundingBox().minY());
+        assertEquals(319, start.getBoundingBox().maxY());
+    }
+
+    @Test
+    public void scatteredStructuresDoNotOptIntoFullFootprintSurfaceFitting() {
+        TestDesertPyramidPiece desert = new TestDesertPyramidPiece(RandomSource.create(31L), 0, 0);
+        TestJungleTemplePiece jungle = new TestJungleTemplePiece(RandomSource.create(37L), 0, 0);
+        SwampHutPiece swamp = new SwampHutPiece(RandomSource.create(41L), 0, 0);
+        StructureStart desertStart = desertStart(desert);
+        StructureStart jungleStart = jungleStart(jungle);
+        StructureStart swampStart = swampStart(swamp);
+
+        assertFalse(NativeStructureSurfaceFitter.requiresSurfaceTerrain(desertStart));
+        assertFalse(NativeStructureSurfaceFitter.requiresSurfaceTerrain(jungleStart));
+        assertFalse(NativeStructureSurfaceFitter.requiresSurfaceTerrain(swampStart));
+
+        AtomicInteger terrainQueries = new AtomicInteger();
+        int offset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                swampStart, "minecraft:swamp_hut", 0, 63, -64, 320, false, false, null,
+                (x, z) -> terrainQueries.incrementAndGet());
+        assertEquals(0, offset);
+        assertEquals(0, terrainQueries.get());
+        assertEquals(64, swamp.getBoundingBox().minY());
+    }
+
+    @Test
+    public void scatteredHeightFieldMatchesTheRuntimeContract() {
+        Field field = NativeStructureReflection.resolveScatteredHeightPositionField();
+
+        assertEquals(ScatteredFeaturePiece.class, field.getDeclaringClass());
+        assertEquals(int.class, field.getType());
+        assertTrue(Modifier.isProtected(field.getModifiers()));
+        assertFalse(Modifier.isFinal(field.getModifiers()));
+        assertFalse(Modifier.isStatic(field.getModifiers()));
+        assertTrue(field.trySetAccessible());
+    }
+
+    @Test
+    public void datapackOverridesOfSpecialVanillaIdsUseGenericPlacement() {
+        StructureStart pyramidOverride = swampStart(
+                new SwampHutPiece(RandomSource.create(43L), 0, 0));
+        int pyramidMinY = pyramidOverride.getBoundingBox().minY();
+        int pyramidOffset = NativeStructureVerticalPlacer.applyVerticalPlacement(
+                pyramidOverride, "minecraft:desert_pyramid", 5,
+                63, -64, 320, false, false, null, (x, z) -> 200);
+
+        assertEquals(5, pyramidOffset);
+        assertEquals(pyramidMinY + 5, pyramidOverride.getBoundingBox().minY());
+
+        StructureStart monumentOverride = swampStart(
+                new SwampHutPiece(RandomSource.create(47L), 0, 0));
+        int monumentMinY = monumentOverride.getBoundingBox().minY();
+        NativeStructureVerticalPlacer.ensureMonumentSeaLevelAlignment(
+                monumentOverride, "minecraft:monument", 0, 40, -64, 320);
+
+        assertEquals(monumentMinY, monumentOverride.getBoundingBox().minY());
+    }
+
+    private static StructureStart desertStart(StructurePiece piece) {
+        Structure structure = new DesertPyramidStructure(new Structure.StructureSettings(HolderSet.empty()));
+        return start(structure, piece);
+    }
+
+    private static StructureStart jungleStart(StructurePiece piece) {
+        Structure structure = new JungleTempleStructure(new Structure.StructureSettings(HolderSet.empty()));
+        return start(structure, piece);
+    }
+
+    private static StructureStart swampStart(StructurePiece piece) {
+        Structure structure = new SwampHutStructure(new Structure.StructureSettings(HolderSet.empty()));
+        return start(structure, piece);
+    }
+
+    private static StructureStart start(Structure structure, StructurePiece piece) {
+        return new StructureStart(
+                structure, new ChunkPos(0, 0), 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static final class TestDesertPyramidPiece extends DesertPyramidPiece {
+        private TestDesertPyramidPiece(RandomSource random, int west, int north) {
+            super(random, west, north);
+        }
+
+        private boolean attemptVanillaAlignment(int offset) {
+            return updateHeightPositionToLowestGroundHeight((LevelAccessor) null, offset);
+        }
+    }
+
+    private static final class TestJungleTemplePiece extends JungleTemplePiece {
+        private TestJungleTemplePiece(RandomSource random, int west, int north) {
+            super(random, west, north);
+        }
+
+        private boolean attemptVanillaAlignment() {
+            return updateAverageGroundHeight((LevelAccessor) null, null, 0);
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructurePostProcessorVegetationTest.java

@@ -0,0 +1,388 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVerticalPlacer;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureSurfaceFitter;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureVegetationClearer;
+
+import com.mojang.serialization.Codec;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.IdMapper;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.PalettedContainer;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.Strategy;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidPiece;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Proxy;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructurePostProcessorVegetationTest {
+    private static final long TEST_SEED = 1234L;
+    private static final int MIN_Y = -64;
+    private static final int MAX_Y = 319;
+    private static final int GROUND_Y = 64;
+    private static final BoundingBox AREA = new BoundingBox(0, MIN_Y, 0, 15, MAX_Y, 15);
+
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void canopyAboveTheStructureRoofSurvivesVegetationClearing() {
+        ProtoChunk chunk = chunk();
+        StructureStart start = desertStart(0, 0, GROUND_Y + 15);
+        BoundingBox bounds = start.getBoundingBox();
+        for (int y = bounds.maxY() - 1; y <= GROUND_Y + 40; y++) {
+            fillLayer(chunk, y, leaves());
+        }
+        write(chunk, 4, bounds.minY() - 1, 4, log());
+
+        clearVegetation(chunk, start);
+
+        for (int z = 0; z < 16; z++) {
+            for (int x = 0; x < 16; x++) {
+                assertEquals(leaves(), chunk.getBlockState(new BlockPos(x, GROUND_Y + 40, z)));
+                assertEquals(leaves(), chunk.getBlockState(new BlockPos(x, bounds.maxY() + 1, z)));
+                assertEquals(air(), chunk.getBlockState(new BlockPos(x, bounds.maxY(), z)));
+                assertEquals(air(), chunk.getBlockState(new BlockPos(x, bounds.maxY() - 1, z)));
+            }
+        }
+        assertEquals(air(), chunk.getBlockState(new BlockPos(4, bounds.minY() - 1, 4)));
+    }
+
+    @Test
+    public void buriedStructuresPreserveTheForestAboveThem() {
+        ProtoChunk chunk = chunk();
+        StructureStart start = desertStart(0, 0, -20);
+        write(chunk, 8, GROUND_Y + 1, 8, log());
+        write(chunk, 8, GROUND_Y + 2, 8, log());
+        write(chunk, 8, GROUND_Y + 3, 8, log());
+        write(chunk, 8, GROUND_Y + 4, 8, leaves());
+
+        clearVegetation(chunk, start);
+
+        assertEquals(log(), chunk.getBlockState(new BlockPos(8, GROUND_Y + 1, 8)));
+        assertEquals(log(), chunk.getBlockState(new BlockPos(8, GROUND_Y + 2, 8)));
+        assertEquals(log(), chunk.getBlockState(new BlockPos(8, GROUND_Y + 3, 8)));
+        assertEquals(leaves(), chunk.getBlockState(new BlockPos(8, GROUND_Y + 4, 8)));
+    }
+
+    @Test
+    public void columnsOutsideThePieceFootprintKeepEveryTreeBlock() {
+        ProtoChunk chunk = chunk();
+        StructureStart start = desertStart(8, 8, GROUND_Y + 15);
+        BoundingBox bounds = start.getBoundingBox();
+        int inside = bounds.minY() + 4;
+        write(chunk, 0, inside, 0, log());
+        write(chunk, 0, GROUND_Y + 40, 0, leaves());
+        write(chunk, 12, inside, 12, log());
+        write(chunk, 12, GROUND_Y + 40, 12, leaves());
+
+        clearVegetation(chunk, start);
+
+        assertEquals(log(), chunk.getBlockState(new BlockPos(0, inside, 0)));
+        assertEquals(leaves(), chunk.getBlockState(new BlockPos(0, GROUND_Y + 40, 0)));
+        assertEquals(air(), chunk.getBlockState(new BlockPos(12, inside, 12)));
+        assertEquals(leaves(), chunk.getBlockState(new BlockPos(12, GROUND_Y + 40, 12)));
+    }
+
+    @Test
+    public void clearingStopsAtThePieceEnvelopeBoundaries() {
+        ProtoChunk chunk = chunk();
+        StructureStart start = desertStart(0, 0, GROUND_Y + 15);
+        BoundingBox bounds = start.getBoundingBox();
+        write(chunk, 4, bounds.maxY() + 1, 4, log());
+        write(chunk, 4, bounds.maxY(), 4, log());
+        write(chunk, 4, bounds.minY() - 1, 4, log());
+        write(chunk, 4, bounds.minY() - 2, 4, log());
+
+        clearVegetation(chunk, start);
+
+        assertEquals(log(), chunk.getBlockState(new BlockPos(4, bounds.maxY() + 1, 4)));
+        assertEquals(air(), chunk.getBlockState(new BlockPos(4, bounds.maxY(), 4)));
+        assertEquals(air(), chunk.getBlockState(new BlockPos(4, bounds.minY() - 1, 4)));
+        assertEquals(log(), chunk.getBlockState(new BlockPos(4, bounds.minY() - 2, 4)));
+    }
+
+    @Test
+    public void overlappingPieceEnvelopesMergeIntoOneClearedRange() {
+        ProtoChunk chunk = chunk();
+        StructureStart low = desertStart(0, 0, GROUND_Y);
+        StructureStart high = desertStart(0, 0, GROUND_Y + 40);
+        int between = GROUND_Y + 20;
+        write(chunk, 4, between, 4, log());
+        write(chunk, 4, high.getBoundingBox().maxY() + 1, 4, log());
+        write(chunk, 4, low.getBoundingBox().minY() - 2, 4, log());
+
+        NativeStructureVegetationClearer.clearIntersectingVegetation(
+                world(chunk), chunk, AREA, List.of(low, high));
+
+        assertEquals(air(), chunk.getBlockState(new BlockPos(4, between, 4)));
+        assertEquals(log(), chunk.getBlockState(
+                new BlockPos(4, high.getBoundingBox().maxY() + 1, 4)));
+        assertEquals(log(), chunk.getBlockState(
+                new BlockPos(4, low.getBoundingBox().minY() - 2, 4)));
+    }
+
+    @Test
+    public void validStartsReachIntersectionProcessing() {
+        assertTrue(NativeStructureVegetationClearer.shouldProcessStart(
+                desertStart(0, 0, GROUND_Y + 15)));
+        assertFalse(NativeStructureVegetationClearer.shouldProcessStart(
+                StructureStart.INVALID_START));
+    }
+
+    @Test
+    public void allUndergroundGenerationStepsShareOneClassification() {
+        assertTrue(NativeStructureVegetationClearer.isUndergroundStep(
+                GenerationStep.Decoration.UNDERGROUND_STRUCTURES));
+        assertTrue(NativeStructureVegetationClearer.isUndergroundStep(
+                GenerationStep.Decoration.UNDERGROUND_DECORATION));
+        assertTrue(NativeStructureVegetationClearer.isUndergroundStep(
+                GenerationStep.Decoration.STRONGHOLDS));
+        assertFalse(NativeStructureVegetationClearer.isUndergroundStep(
+                GenerationStep.Decoration.SURFACE_STRUCTURES));
+    }
+
+    @Test
+    public void undergroundStructuresUseTheLowestTerrainColumn() {
+        BoundingBox bounds = new BoundingBox(0, 60, 0, 1, 80, 0);
+        int offset = NativeStructureVerticalPlacer.resolveBuriedOffset(
+                bounds, 0, -64, 320, (x, z) -> x == 1 ? 76 : 100);
+        assertEquals(-5, offset);
+    }
+
+    @Test
+    public void undergroundBurialClampsToTheWorldFloorInsteadOfFailing() {
+        BoundingBox bounds = new BoundingBox(0, 60, 0, 1, 80, 0);
+        assertEquals(-2, NativeStructureVerticalPlacer.resolveBuriedOffset(
+                bounds, 0, 58, 320, (x, z) -> x == 1 ? 76 : 100));
+    }
+
+    @Test
+    public void loweringSurfaceRemovesCactusStacksAndTheirFlowers() {
+        ProtoChunk chunk = chunk();
+        for (int y = 80; y <= 102; y++) {
+            write(chunk, 4, y, 4, Blocks.SAND.defaultBlockState());
+        }
+        for (int y = 103; y <= 105; y++) {
+            write(chunk, 4, y, 4, Blocks.CACTUS.defaultBlockState());
+        }
+        write(chunk, 4, 106, 4, Blocks.CACTUS_FLOWER.defaultBlockState());
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world(chunk), new BlockPos.MutableBlockPos(), 4, 4, 102, 93, MIN_Y, MAX_Y);
+
+        assertEquals(Blocks.SAND.defaultBlockState(), chunk.getBlockState(new BlockPos(4, 93, 4)));
+        for (int y = 94; y <= 106; y++) {
+            assertTrue("Unsupported decoration at " + y, chunk.getBlockState(new BlockPos(4, y, 4)).isAir());
+        }
+    }
+
+    @Test
+    public void loweringSurfacePreservesCactusOnUnchangedColumns() {
+        ProtoChunk chunk = chunk();
+        for (int x : List.of(4, 5)) {
+            for (int y = 60; y <= 64; y++) {
+                write(chunk, x, y, 4, Blocks.SAND.defaultBlockState());
+            }
+            write(chunk, x, 65, 4, Blocks.CACTUS.defaultBlockState());
+            write(chunk, x, 66, 4, Blocks.CACTUS_FLOWER.defaultBlockState());
+        }
+        WorldGenLevel world = world(chunk);
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(), 4, 4, 64, 60, MIN_Y, MAX_Y);
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(), 5, 4, 64, 64, MIN_Y, MAX_Y);
+
+        assertTrue(chunk.getBlockState(new BlockPos(4, 65, 4)).isAir());
+        assertTrue(chunk.getBlockState(new BlockPos(4, 66, 4)).isAir());
+        assertEquals(Blocks.SAND.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 64, 4)));
+        assertEquals(Blocks.CACTUS.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 65, 4)));
+        assertEquals(Blocks.CACTUS_FLOWER.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 66, 4)));
+    }
+
+    @Test
+    public void loweringSurfaceKeepsTreeBoundaries() {
+        for (BlockState boundary : List.of(Blocks.OAK_LOG.defaultBlockState(), Blocks.OAK_LEAVES.defaultBlockState())) {
+            ProtoChunk chunk = chunk();
+            write(chunk, 4, 63, 4, Blocks.SAND.defaultBlockState());
+            write(chunk, 4, 64, 4, Blocks.SAND.defaultBlockState());
+            write(chunk, 4, 65, 4, boundary);
+            write(chunk, 4, 66, 4, Blocks.CACTUS.defaultBlockState());
+            write(chunk, 4, 67, 4, Blocks.CACTUS_FLOWER.defaultBlockState());
+
+            NativeStructureSurfaceFitter.applySurfaceColumn(
+                    world(chunk), new BlockPos.MutableBlockPos(), 4, 4, 64, 60, MIN_Y, MAX_Y);
+
+            assertEquals(boundary, chunk.getBlockState(new BlockPos(4, 65, 4)));
+            assertEquals(Blocks.CACTUS.defaultBlockState(), chunk.getBlockState(new BlockPos(4, 66, 4)));
+            assertEquals(Blocks.CACTUS_FLOWER.defaultBlockState(), chunk.getBlockState(new BlockPos(4, 67, 4)));
+        }
+    }
+
+    @Test
+    public void loweringSurfaceRemovesUnsupportedPlankDecoration() {
+        ProtoChunk chunk = chunk();
+        for (int x : List.of(4, 5)) {
+            for (int y = 60; y <= 64; y++) {
+                write(chunk, x, y, 4, Blocks.SAND.defaultBlockState());
+            }
+            write(chunk, x, 65, 4, Blocks.OAK_PLANKS.defaultBlockState());
+            write(chunk, x, 66, 4, Blocks.CACTUS.defaultBlockState());
+            write(chunk, x, 67, 4, Blocks.CACTUS_FLOWER.defaultBlockState());
+        }
+        WorldGenLevel world = world(chunk);
+
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(), 4, 4, 64, 60, MIN_Y, MAX_Y);
+        NativeStructureSurfaceFitter.applySurfaceColumn(
+                world, new BlockPos.MutableBlockPos(), 5, 4, 64, 64, MIN_Y, MAX_Y);
+
+        assertEquals(Blocks.SAND.defaultBlockState(), chunk.getBlockState(new BlockPos(4, 60, 4)));
+        for (int y = 61; y <= 67; y++) {
+            assertTrue(chunk.getBlockState(new BlockPos(4, y, 4)).isAir());
+        }
+        assertEquals(Blocks.SAND.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 64, 4)));
+        assertEquals(Blocks.OAK_PLANKS.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 65, 4)));
+        assertEquals(Blocks.CACTUS.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 66, 4)));
+        assertEquals(Blocks.CACTUS_FLOWER.defaultBlockState(), chunk.getBlockState(new BlockPos(5, 67, 4)));
+    }
+
+    private static void clearVegetation(ProtoChunk chunk, StructureStart start) {
+        NativeStructureVegetationClearer.clearIntersectingVegetation(
+                world(chunk), chunk, AREA, List.of(start));
+    }
+
+    private static StructureStart desertStart(int originX, int originZ, int topY) {
+        Structure structure = new DesertPyramidStructure(
+                new Structure.StructureSettings(
+                        HolderSet.empty(), Map.of(),
+                        GenerationStep.Decoration.SURFACE_STRUCTURES, TerrainAdjustment.NONE));
+        DesertPyramidPiece piece = new DesertPyramidPiece(RandomSource.create(7L), originX, originZ);
+        piece.move(0, topY - piece.getBoundingBox().maxY(), 0);
+        return new StructureStart(
+                structure, new ChunkPos(0, 0), 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static ProtoChunk chunk() {
+        return new ProtoChunk(
+                new ChunkPos(0, 0), UpgradeData.EMPTY,
+                LevelHeightAccessor.create(MIN_Y, MAX_Y - MIN_Y + 1), containerFactory(), null);
+    }
+
+    private static void fillLayer(ProtoChunk chunk, int y, BlockState state) {
+        for (int z = 0; z < 16; z++) {
+            for (int x = 0; x < 16; x++) {
+                write(chunk, x, y, z, state);
+            }
+        }
+    }
+
+    private static void write(ProtoChunk chunk, int x, int y, int z, BlockState state) {
+        LevelChunkSection section = chunk.getSection(chunk.getSectionIndex(y));
+        section.setBlockState(x, y & 15, z, state, false);
+    }
+
+    private static BlockState log() {
+        return Blocks.OAK_LOG.defaultBlockState();
+    }
+
+    private static BlockState leaves() {
+        return Blocks.OAK_LEAVES.defaultBlockState();
+    }
+
+    private static BlockState air() {
+        return Blocks.AIR.defaultBlockState();
+    }
+
+    private static WorldGenLevel world(ChunkAccess chunk) {
+        InvocationHandler handler = (proxy, method, arguments) -> {
+            String methodName = method.getName();
+            if (methodName.equals("getBlockState")) {
+                return chunk.getBlockState((BlockPos) arguments[0]);
+            }
+            if (methodName.equals("setBlock")) {
+                return chunk.setBlockState(
+                        ((BlockPos) arguments[0]).immutable(),
+                        (BlockState) arguments[1], (int) arguments[2]) != null;
+            }
+            if (methodName.equals("getSeed")) {
+                return TEST_SEED;
+            }
+            if (methodName.equals("getLevel")) {
+                return null;
+            }
+            if (methodName.equals("holderLookup")) {
+                return BuiltInRegistries.BLOCK;
+            }
+            if (methodName.equals("hashCode")) {
+                return System.identityHashCode(proxy);
+            }
+            if (methodName.equals("equals")) {
+                return proxy == arguments[0];
+            }
+            if (methodName.equals("toString")) {
+                return "vegetation-test-world";
+            }
+            throw new UnsupportedOperationException(method.toString());
+        };
+        return (WorldGenLevel) Proxy.newProxyInstance(
+                WorldGenLevel.class.getClassLoader(), new Class<?>[]{WorldGenLevel.class}, handler);
+    }
+
+    private static PalettedContainerFactory containerFactory() {
+        Strategy<BlockState> blockStates = Strategy.createForBlockStates(Block.BLOCK_STATE_REGISTRY);
+        BlockState air = Blocks.AIR.defaultBlockState();
+        IdMapper<Holder<Biome>> biomeIds = new IdMapper<>();
+        Holder<Biome> defaultBiome = Holder.direct((Biome) null);
+        biomeIds.add(defaultBiome);
+        Strategy<Holder<Biome>> biomes = Strategy.createForBiomes(biomeIds);
+        Codec<Holder<Biome>> biomeCodec = Codec.STRING.xmap(
+                name -> defaultBiome, holder -> "iris-test-biome");
+        return new PalettedContainerFactory(
+                blockStates,
+                air,
+                PalettedContainer.codecRW(BlockState.CODEC, blockStates, air),
+                biomes,
+                defaultBiome,
+                PalettedContainer.codecRO(biomeCodec, biomes, defaultBiome),
+                PalettedContainer.codecRW(biomeCodec, biomes, defaultBiome));
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeStructureTemplateOccupancyTest.java

@@ -0,0 +1,240 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureTemplateOccupancy;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureReflection;
+
+import com.mojang.datafixers.util.Either;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.tags.TagKey;
+import net.minecraft.util.valueproviders.ConstantInt;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
+import net.minecraft.world.level.levelgen.structure.pools.SinglePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.templatesystem.BlackstoneReplaceProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.BlockAgeProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.BlockIgnoreProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.CappedProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.GravityProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.JigsawReplacementProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LavaSubmergedBlockProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.NopProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.ProtectedBlockProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.RuleProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureProcessorList;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import org.junit.Assume;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.TreeSet;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureTemplateOccupancyTest {
+    private static final BoundingBox PROCESSING_AREA = new BoundingBox(0, 56, 0, 15, 80, 0);
+    private static final int TEMPLATE_WIDTH = 32;
+    private static final int TERRAIN_HEIGHT = 64;
+
+    @BeforeClass
+    public static void bootstrapMinecraft() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void straddlingGravityPieceHeightReadsHonorTheVanillaClipContract() throws Exception {
+        ColumnRecorder recorder = new ColumnRecorder();
+
+        resolve(straddlingPiece(
+                List.of(new GravityProcessor(Heightmap.Types.WORLD_SURFACE_WG, 0))), recorder);
+
+        // 26.2 vanilla clips processor evaluation to the placement bounding box; 26.1.2 vanilla
+        // runs processors across the whole piece. Iris mirrors the pinned version's semantics.
+        assertEquals(expectedClippedColumns(), recorder.heightColumns);
+    }
+
+    @Test
+    public void cappedStraddlingPieceRunsProcessorsAcrossTheWholePiece() throws Exception {
+        ColumnRecorder recorder = new ColumnRecorder();
+
+        resolve(straddlingPiece(List.of(
+                new GravityProcessor(Heightmap.Types.WORLD_SURFACE_WG, 0),
+                new CappedProcessor(NopProcessor.INSTANCE, ConstantInt.of(0)))), recorder);
+
+        assertEquals(columns(0, TEMPLATE_WIDTH - 1), recorder.heightColumns);
+    }
+
+    @Test
+    public void cappedProcessorIsTheOnlyProcessorThatDisablesTheProcessingAreaClip() throws Exception {
+        Method contract = clipContractMethod();
+        Assume.assumeTrue("evaluatesEntirePieceState only exists on 26.2+", contract != null);
+
+        for (StructureProcessor processor : List.of(
+                BlockIgnoreProcessor.STRUCTURE_BLOCK,
+                JigsawReplacementProcessor.INSTANCE,
+                LavaSubmergedBlockProcessor.INSTANCE,
+                NopProcessor.INSTANCE,
+                BlackstoneReplaceProcessor.INSTANCE,
+                new GravityProcessor(Heightmap.Types.WORLD_SURFACE_WG, 0),
+                new RuleProcessor(List.of()),
+                new BlockAgeProcessor(0.5F),
+                protectedBlockProcessor())) {
+            assertFalse(processor.getClass().getName(),
+                    (Boolean) contract.invoke(processor));
+        }
+        assertTrue((Boolean) contract.invoke(
+                new CappedProcessor(NopProcessor.INSTANCE, ConstantInt.of(4))));
+    }
+
+    @Test
+    public void placementSettingsCarryTheProcessingAreaAsTheirClipBox() throws Exception {
+        PoolElementStructurePiece piece = straddlingPiece(List.of());
+
+        StructurePlaceSettings settings = NativeStructureReflection.resolvePlacementSettings(
+                (SinglePoolElement) piece.getElement(), piece, PROCESSING_AREA);
+
+        assertEquals(PROCESSING_AREA, settings.getBoundingBox());
+    }
+
+    private static void resolve(PoolElementStructurePiece piece, ColumnRecorder recorder) {
+        NativeStructureTemplateOccupancy.resolve(
+                world(recorder), piece, piece.getPosition(), PROCESSING_AREA,
+                NativeStructureTemplateOccupancyTest::forbiddenTemplateManager,
+                PROCESSING_AREA::isInside, amount -> {
+                });
+    }
+
+    private static PoolElementStructurePiece straddlingPiece(
+            List<StructureProcessor> processors) throws Exception {
+        BoundingBox bounds = new BoundingBox(0, 70, 0, TEMPLATE_WIDTH - 1, 76, 0);
+        return new PoolElementStructurePiece(
+                null, new InlineSinglePoolElement(template(), processors),
+                new BlockPos(bounds.minX(), bounds.minY(), bounds.minZ()),
+                1, Rotation.NONE, bounds, LiquidSettings.APPLY_WATERLOGGING);
+    }
+
+    private static Set<Integer> columns(int minimumX, int maximumX) {
+        Set<Integer> columns = new TreeSet<>();
+        for (int x = minimumX; x <= maximumX; x++) {
+            columns.add(x);
+        }
+        return columns;
+    }
+
+    private static Method clipContractMethod() {
+        try {
+            return StructureProcessor.class.getMethod("evaluatesEntirePieceState");
+        } catch (NoSuchMethodException absent) {
+            return null;
+        }
+    }
+
+    private static Set<Integer> expectedClippedColumns() {
+        return clipContractMethod() != null
+                ? columns(PROCESSING_AREA.minX(), PROCESSING_AREA.maxX())
+                : columns(0, TEMPLATE_WIDTH - 1);
+    }
+
+    private static StructureProcessor protectedBlockProcessor() throws Exception {
+        // Constructed reflectively: the constructor takes HolderSet on 26.2 and TagKey on 26.1.2.
+        Constructor<?> constructor = ProtectedBlockProcessor.class.getConstructors()[0];
+        Class<?> parameter = constructor.getParameterTypes()[0];
+        Object argument = parameter == HolderSet.class
+                ? HolderSet.empty()
+                : TagKey.create(Registries.BLOCK, Identifier.fromNamespaceAndPath("minecraft", "air"));
+        return (StructureProcessor) constructor.newInstance(argument);
+    }
+
+    private static StructureTemplateManager forbiddenTemplateManager() {
+        throw new AssertionError("Inline templates must not resolve a template manager");
+    }
+
+    private static StructureTemplate template() throws Exception {
+        List<StructureTemplate.StructureBlockInfo> blocks = new ArrayList<>();
+        for (int x = 0; x < TEMPLATE_WIDTH; x++) {
+            blocks.add(new StructureTemplate.StructureBlockInfo(
+                    new BlockPos(x, 0, 0), Blocks.COBBLESTONE.defaultBlockState(), null));
+        }
+        Constructor<StructureTemplate.Palette> constructor =
+                StructureTemplate.Palette.class.getDeclaredConstructor(List.class);
+        assertTrue(constructor.trySetAccessible());
+        StructureTemplate template = new StructureTemplate();
+        template.palettes.add(constructor.newInstance(blocks));
+        return template;
+    }
+
+    private static WorldGenLevel world(ColumnRecorder recorder) {
+        InvocationHandler handler = (proxy, method, arguments) -> {
+            String methodName = method.getName();
+            if (methodName.equals("getHeight") && arguments.length == 3) {
+                recorder.heightColumns.add((Integer) arguments[1]);
+                return TERRAIN_HEIGHT;
+            }
+            if (methodName.equals("getBlockState")) {
+                recorder.stateColumns.add(((BlockPos) arguments[0]).getX());
+                return Blocks.STONE.defaultBlockState();
+            }
+            if (methodName.equals("getLevel")) {
+                return null;
+            }
+            if (methodName.equals("holderLookup")) {
+                return BuiltInRegistries.BLOCK;
+            }
+            if (methodName.equals("hashCode")) {
+                return System.identityHashCode(proxy);
+            }
+            if (methodName.equals("equals")) {
+                return proxy == arguments[0];
+            }
+            if (methodName.equals("toString")) {
+                return "occupancy-test-world";
+            }
+            throw new UnsupportedOperationException(method.toString());
+        };
+        return (WorldGenLevel) Proxy.newProxyInstance(
+                WorldGenLevel.class.getClassLoader(),
+                new Class<?>[]{WorldGenLevel.class}, handler);
+    }
+
+    private static final class ColumnRecorder {
+        private final Set<Integer> heightColumns = new TreeSet<>();
+        private final Set<Integer> stateColumns = new TreeSet<>();
+    }
+
+    private static final class InlineSinglePoolElement extends SinglePoolElement {
+        private InlineSinglePoolElement(
+                StructureTemplate template, List<StructureProcessor> processors) {
+            super(Either.right(template),
+                    Holder.direct(new StructureProcessorList(processors)),
+                    StructureTemplatePool.Projection.RIGID,
+                    Optional.<LiquidSettings>empty());
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeTerrainHeightCacheTest.java

@@ -0,0 +1,131 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainHeightCache;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.levelgen.Heightmap;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.OptionalInt;
+import java.util.function.IntSupplier;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public final class NativeTerrainHeightCacheTest {
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void coordinatesRuntimePredicatesAndBoundsHaveSeparateEntries() {
+        NativeTerrainHeightCache cache = new NativeTerrainHeightCache();
+        AtomicInteger calls = new AtomicInteger();
+        NativeTerrainHeightCache.Query[] queries = {
+                query(1, -1, 1),
+                query(1, 1, -1),
+                query(2, -1, 1),
+                new NativeTerrainHeightCache.Query(1, -1, 1, Heightmap.Types.OCEAN_FLOOR, -256, 768),
+                new NativeTerrainHeightCache.Query(1, -1, 1, Heightmap.Types.WORLD_SURFACE, -64, 768),
+                new NativeTerrainHeightCache.Query(1, -1, 1, Heightmap.Types.WORLD_SURFACE, -256, 256)
+        };
+        for (int index = 0; index < queries.length; index++) {
+            assertEquals(index + 1, cached(cache, queries[index], calls::incrementAndGet));
+        }
+        for (int index = 0; index < queries.length; index++) {
+            assertEquals(index + 1, cached(cache, queries[index], calls::incrementAndGet));
+        }
+        assertEquals(queries.length, calls.get());
+        cache.evictRuntime(1);
+        assertEquals(3, cached(cache, queries[2], calls::incrementAndGet));
+        assertEquals(7, cached(cache, queries[0], calls::incrementAndGet));
+    }
+
+    @Test
+    public void allIntegerResultsAreCacheable() {
+        NativeTerrainHeightCache cache = new NativeTerrainHeightCache();
+        NativeTerrainHeightCache.Query query = query(1, 0, 0);
+        assertEquals(Integer.MIN_VALUE, cached(cache, query, () -> Integer.MIN_VALUE));
+        assertEquals(Integer.MIN_VALUE, cached(cache, query, () -> 0));
+    }
+
+    @Test
+    public void failedResolutionCanBeRetried() {
+        NativeTerrainHeightCache cache = new NativeTerrainHeightCache();
+        NativeTerrainHeightCache.Query query = query(1, 0, 0);
+        assertThrows(IllegalStateException.class, () -> cached(cache, query, () -> {
+            throw new IllegalStateException("terrain unavailable");
+        }));
+        assertEquals(42, cached(cache, query, () -> 42));
+    }
+
+    @Test
+    public void coldResolutionDoesNotHoldCacheMonitor() throws Exception {
+        NativeTerrainHeightCache cache = new NativeTerrainHeightCache();
+        CountDownLatch entered = new CountDownLatch(1);
+        CountDownLatch release = new CountDownLatch(1);
+        ExecutorService executor = Executors.newFixedThreadPool(2);
+        try {
+            Future<Integer> slow = executor.submit(() -> cached(cache, query(1, 0, 0), () -> {
+                entered.countDown();
+                try {
+                    assertTrue(release.await(5, TimeUnit.SECONDS));
+                } catch (InterruptedException interruption) {
+                    Thread.currentThread().interrupt();
+                    throw new IllegalStateException(interruption);
+                }
+                return 9;
+            }));
+            assertTrue(entered.await(5, TimeUnit.SECONDS));
+            Future<Integer> independent = executor.submit(() -> cached(cache, query(1, 1, 0), () -> 17));
+            assertEquals(Integer.valueOf(17), independent.get(1, TimeUnit.SECONDS));
+            release.countDown();
+            assertEquals(Integer.valueOf(9), slow.get(5, TimeUnit.SECONDS));
+        } finally {
+            release.countDown();
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(5, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void boundedCacheKeepsRecentlyReadCoordinates() {
+        NativeTerrainHeightCache cache = new NativeTerrainHeightCache();
+        for (int x = 0; x < 65_536; x++) {
+            cached(cache, query(1, x, 0), () -> 8);
+        }
+        assertEquals(8, cached(cache, query(1, 0, 0), () -> 99));
+        cached(cache, query(1, 65_536, 0), () -> 9);
+        assertEquals(8, cached(cache, query(1, 0, 0), () -> 99));
+        assertEquals(99, cached(cache, query(1, 1, 0), () -> 99));
+    }
+
+    @Test
+    public void unavailableResolvedHeightIsNotCached() {
+        NativeTerrainHeightCache cache = new NativeTerrainHeightCache();
+        NativeTerrainHeightCache.Query query = query(1, 0, 0);
+        assertTrue(cache.resolvedHeight(query, OptionalInt::empty).isEmpty());
+        assertEquals(42, cache.resolvedHeight(query, () -> OptionalInt.of(42)).orElseThrow());
+        assertEquals(42, cache.resolvedHeight(query, OptionalInt::empty).orElseThrow());
+    }
+
+    private static int cached(NativeTerrainHeightCache cache, NativeTerrainHeightCache.Query query,
+                              IntSupplier resolver) {
+        return cache.resolvedHeight(query, () -> OptionalInt.of(resolver.getAsInt())).orElseThrow();
+    }
+
+    private static NativeTerrainHeightCache.Query query(int runtimeId, int x, int z) {
+        return new NativeTerrainHeightCache.Query(runtimeId, x, z, Heightmap.Types.WORLD_SURFACE, -256, 768);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/NativeTransitionColumnTest.java

@@ -0,0 +1,115 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import art.arcane.iris.world.history.TerrainNativeBlockKeys;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTransitionColumn;
+
+import art.arcane.iris.world.history.BoundaryColumnGeometry;
+import art.arcane.iris.world.history.TerrainBoundarySignature;
+import art.arcane.iris.spi.IrisPlatform;
+import art.arcane.iris.spi.IrisPlatforms;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.iris.spi.PlatformRegistries;
+import art.arcane.iris.testsupport.PlatformLeakGuard;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Direction;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.RotatedPillarBlock;
+import net.minecraft.world.level.block.LiquidBlock;
+import net.minecraft.world.level.levelgen.Heightmap;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.List;
+import java.util.OptionalInt;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public final class NativeTransitionColumnTest {
+    @Rule
+    public final PlatformLeakGuard leakGuard = PlatformLeakGuard.clean();
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        NativeBlockTags.bindHeightmapFixtures();
+    }
+
+    @AfterClass
+    public static void restoreBlockTags() {
+        NativeBlockTags.restoreTags();
+    }
+
+    @Test
+    public void customKeysUseCarrierForNativeColumnsAndHeightmaps() {
+        String key = "itemsadder:rocks/ruby_ore";
+        NativeBlockState custom = mock(NativeBlockState.class);
+        NativeBlockState carrier = mock(NativeBlockState.class);
+        when(custom.placementBaseState()).thenReturn(carrier);
+        when(carrier.key()).thenReturn("minecraft:oak_log[axis=z]");
+        IrisPlatform platform = mock(IrisPlatform.class);
+        PlatformRegistries registries = mock(PlatformRegistries.class);
+        when(platform.registries()).thenReturn(registries);
+        when(registries.blockOrNull(key)).thenReturn(custom);
+        LevelHeightAccessor height = LevelHeightAccessor.create(-16, 32);
+        TerrainBoundarySignature signature = signature(key);
+
+        try (MockedStatic<IrisPlatforms> platforms = mockStatic(IrisPlatforms.class)) {
+            platforms.when(IrisPlatforms::isBound).thenReturn(true);
+            platforms.when(IrisPlatforms::get).thenReturn(platform);
+            NoiseColumn column = NativeTransitionColumn.column(signature.geometry(), height, TerrainNativeBlockKeys::placementKey);
+
+            assertEquals(Direction.Axis.Z, column.getBlock(-15).getValue(RotatedPillarBlock.AXIS));
+            assertEquals(-14, NativeTransitionColumn.height(signature.geometry(), Heightmap.Types.OCEAN_FLOOR_WG, height, TerrainNativeBlockKeys::placementKey));
+        }
+    }
+
+    @Test
+    public void preservesNativePropertiesCavesAndFluids() {
+        NoiseColumn column = NativeTransitionColumn.column(signature("minecraft:oak_log[axis=x]").geometry(),
+                LevelHeightAccessor.create(-16, 32), TerrainNativeBlockKeys::placementKey);
+        assertEquals(Direction.Axis.X, column.getBlock(-15).getValue(RotatedPillarBlock.AXIS));
+        assertTrue(column.getBlock(-14).is(Blocks.CAVE_AIR));
+        assertEquals(Integer.valueOf(3), column.getBlock(-13).getValue(LiquidBlock.LEVEL));
+        assertTrue(column.getBlock(0).isAir());
+    }
+
+    @Test
+    public void usesNativeHeightmapPredicatesForWaterAndOpenSpace() {
+        TerrainBoundarySignature signature = signature("minecraft:oak_log[axis=x]");
+        LevelHeightAccessor height = LevelHeightAccessor.create(-16, 32);
+        assertEquals(-12, NativeTransitionColumn.height(signature.geometry(), Heightmap.Types.WORLD_SURFACE_WG, height, TerrainNativeBlockKeys::placementKey));
+        assertEquals(-14, NativeTransitionColumn.height(signature.geometry(), Heightmap.Types.OCEAN_FLOOR_WG, height, TerrainNativeBlockKeys::placementKey));
+    }
+
+    @Test
+    public void rejectsUnknownSavedStatesInsteadOfReplacingTerrain() {
+        assertThrows(IllegalArgumentException.class, () -> NativeTransitionColumn.column(signature("missing:removed_block").geometry(), LevelHeightAccessor.create(-16, 32), TerrainNativeBlockKeys::placementKey));
+    }
+
+    private static TerrainBoundarySignature signature(String solidState) {
+        BoundaryColumnGeometry geometry = BoundaryColumnGeometry.fromVoxels(-16, List.of(
+                new BoundaryColumnGeometry.Voxel("minecraft:stone", BoundaryColumnGeometry.Phase.SOLID, "", false),
+                new BoundaryColumnGeometry.Voxel(solidState, BoundaryColumnGeometry.Phase.SOLID, "", false),
+                new BoundaryColumnGeometry.Voxel("minecraft:cave_air", BoundaryColumnGeometry.Phase.AIR, "", false),
+                new BoundaryColumnGeometry.Voxel("minecraft:water[level=3]", BoundaryColumnGeometry.Phase.FLUID,
+                        "minecraft:water[level=3]", false)));
+        return new TerrainBoundarySignature(
+                new TerrainBoundarySignature.Column(0, 0, 3, 1, OptionalInt.of(3), OptionalInt.empty()),
+                new TerrainBoundarySignature.Samples(new TerrainBoundarySignature.VerticalLayout(-16, 4, 1),
+                        new TerrainBoundarySignature.BiomeEncoding(List.of("minecraft:plains"), new short[]{0})),
+                geometry);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/nativegen/v26_3_R1/NativeBlockTags.java

@@ -0,0 +1,45 @@
+package art.arcane.iris.nativegen.v26_3_R1;
+
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.tags.TagLoader;
+import net.minecraft.tags.TagKey;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public final class NativeBlockTags {
+    private static Map<TagKey<Block>, List<Holder<Block>>> originalTags;
+
+    private NativeBlockTags() {
+    }
+
+    public static void bindHeightmapFixtures() {
+        originalTags = new HashMap<>();
+        for (HolderSet.Named<Block> tag : BuiltInRegistries.BLOCK.getTags().toList()) {
+            originalTags.put(tag.key(), tag.stream().toList());
+        }
+        List<Holder<Block>> solid = List.of(Blocks.STONE.builtInRegistryHolder(),
+                Blocks.OAK_LOG.builtInRegistryHolder(), Blocks.SPRUCE_LOG.builtInRegistryHolder());
+        List<Holder<Block>> canopy = List.of(Blocks.STONE.builtInRegistryHolder(),
+                Blocks.OAK_LOG.builtInRegistryHolder(), Blocks.SPRUCE_LOG.builtInRegistryHolder(),
+                Blocks.OAK_LEAVES.builtInRegistryHolder(), Blocks.SPRUCE_LEAVES.builtInRegistryHolder());
+        BuiltInRegistries.BLOCK.prepareTagReload(new TagLoader.LoadResult<>(Registries.BLOCK, Map.of(
+                BlockTags.BLOCKS_MOTION_IN_HEIGHTMAP, canopy,
+                BlockTags.BLOCKS_MOTION_IN_HEIGHTMAP_NO_LEAVES, solid))).apply();
+    }
+
+    public static void restoreTags() {
+        if (originalTags == null) {
+            return;
+        }
+        BuiltInRegistries.BLOCK.prepareTagReload(new TagLoader.LoadResult<>(Registries.BLOCK, originalTags)).apply();
+        originalTags = null;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/CustomBiomeCodecTest.java

@@ -0,0 +1,60 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.iris.generation.biome.IrisBiomeCustom;
+import art.arcane.iris.generation.biome.IrisBiomeCustomSpawn;
+import art.arcane.iris.generation.biome.IrisBiomeCustomSpawnType;
+import art.arcane.iris.pack.datapack.v263.DataFixerV263;
+import art.arcane.volmlib.util.collection.KList;
+import com.google.gson.JsonParser;
+import com.mojang.serialization.JsonOps;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.data.registries.VanillaRegistries;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.attribute.EnvironmentAttributes;
+import net.minecraft.world.attribute.modifier.MobSpawnSettingsModifier;
+import net.minecraft.world.entity.MobCategory;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.MobSpawnSettings;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class CustomBiomeCodecTest {
+    private static HolderLookup.Provider registries;
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        registries = VanillaRegistries.createWorldLookup();
+    }
+
+    @Test
+    public void nativeCodecAcceptsCustomColorsAndSpawnCounts() {
+        IrisBiomeCustom custom = new IrisBiomeCustom();
+        custom.setId("codec_test");
+        custom.setWaterColor("#102030");
+        custom.setFogColor("#405060");
+        custom.setSpawnRarity(2);
+        IrisBiomeCustomSpawn spawn = new IrisBiomeCustomSpawn();
+        spawn.setType("minecraft:zombie");
+        spawn.setGroup(IrisBiomeCustomSpawnType.MONSTER);
+        spawn.setMinCount(2);
+        spawn.setMaxCount(4);
+        spawn.setWeight(7);
+        custom.setSpawns(new KList<>(spawn));
+        Biome biome = Biome.DIRECT_CODEC.parse(RegistryOps.create(JsonOps.INSTANCE, registries),
+                JsonParser.parseString(custom.generateJson(new DataFixerV263()))).getOrThrow();
+        MobSpawnSettings settings = biome.getAttributes().applyModifier(EnvironmentAttributes.NATURAL_MOB_SPAWNS,
+                EnvironmentAttributes.NATURAL_MOB_SPAWNS.defaultValue());
+        MobSpawnSettings.SpawnerData decoded = settings.getMobsToSpawn(MobCategory.MONSTER).unwrap().getFirst().value();
+        assertEquals(2, decoded.count().minInclusive());
+        assertEquals(4, decoded.count().maxInclusive());
+        assertEquals(0x102030, biome.getWaterColor() & 0xFFFFFF);
+        assertEquals(MobSpawnSettingsModifier.overlay(),
+                biome.getAttributes().get(EnvironmentAttributes.NATURAL_MOB_SPAWNS).modifier());
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/CustomBiomeSourceStructureContractTest.java

@@ -0,0 +1,66 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.iris.platform.bukkit.nms.BukkitBiomePolicy;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Proxy;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+
+public class CustomBiomeSourceStructureContractTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void stackedCustomBiomesUseTheirOwningDimensionNamespace() {
+        IrisDimension host = new IrisDimension();
+        host.setLoadKey("Host");
+        IrisDimension upper = new IrisDimension();
+        upper.setLoadKey("Layers/Upper");
+
+        assertEquals("layers:upper/aurora", BukkitBiomePolicy.customBiomeKey(upper, "Aurora"));
+        assertNotEquals(
+                BukkitBiomePolicy.customBiomeKey(host, "Aurora"),
+                BukkitBiomePolicy.customBiomeKey(upper, "Aurora")
+        );
+    }
+
+    @Test
+    public void temporaryNaturalBiomeAnswersAreNotMemoized() {
+        Engine temporary = engineAnsweringNaturalFallback(true, 12, -8);
+        Engine stable = engineAnsweringNaturalFallback(false, 12, -8);
+        assertFalse(BukkitBiomePolicy.isBiomeCacheable(temporary, 12, -8));
+        assertTrue(BukkitBiomePolicy.isBiomeCacheable(stable, 12, -8));
+    }
+
+    private static Engine engineAnsweringNaturalFallback(
+            boolean naturalFallback,
+            int expectedX,
+            int expectedZ
+    ) {
+        return (Engine) Proxy.newProxyInstance(
+                Engine.class.getClassLoader(),
+                new Class<?>[]{Engine.class},
+                (proxy, method, arguments) -> {
+                    if (!method.getName().equals("answersFromNaturalTerrain")) {
+                        throw new UnsupportedOperationException(method.getName());
+                    }
+                    assertEquals(Integer.valueOf(expectedX), arguments[0]);
+                    assertEquals(Integer.valueOf(expectedZ), arguments[1]);
+                    return naturalFallback;
+                }
+        );
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/IrisChunkGeneratorFailureContractTest.java

@@ -0,0 +1,97 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import org.junit.Test;
+
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.LockSupport;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class IrisChunkGeneratorFailureContractTest {
+    @Test
+    public void releasedNoiseAdmissionLetsSynchronousDependentWaitForQueuedExclusive() throws Exception {
+        Semaphore admission = new Semaphore(1, true);
+        admission.acquire();
+        CountDownLatch exclusiveEntered = new CountDownLatch(1);
+        CountDownLatch releaseExclusive = new CountDownLatch(1);
+        AtomicBoolean dependentFinished = new AtomicBoolean(false);
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+        boolean stageReleased = false;
+
+        try {
+            Future<?> exclusive = executor.submit(() -> {
+                boolean acquired = false;
+                try {
+                    admission.acquire();
+                    acquired = true;
+                    exclusiveEntered.countDown();
+                    assertTrue(releaseExclusive.await(2, TimeUnit.SECONDS));
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                    throw new IllegalStateException(e);
+                } finally {
+                    if (acquired) {
+                        admission.release();
+                    }
+                }
+            });
+            awaitQueueLength(admission, 1);
+            CompletableFuture<Void> outward = new CompletableFuture<>();
+            outward.thenRun(() -> {
+                try {
+                    assertTrue(exclusiveEntered.await(2, TimeUnit.SECONDS));
+                    dependentFinished.set(true);
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                    throw new IllegalStateException(e);
+                }
+            });
+
+            admission.release();
+            stageReleased = true;
+            assertTrue(outward.complete(null));
+            assertTrue(dependentFinished.get());
+            releaseExclusive.countDown();
+            exclusive.get(2, TimeUnit.SECONDS);
+            assertEquals(1, admission.availablePermits());
+        } finally {
+            if (!stageReleased) {
+                admission.release();
+            }
+            releaseExclusive.countDown();
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    public void transformedDelegateCancellationIsDetectedThroughItsCompletionFailure() {
+        CompletableFuture<Void> delegate = new CompletableFuture<>();
+        CompletableFuture<Void> transformed = delegate.thenApply(value -> value);
+
+        assertTrue(delegate.cancel(false));
+        assertFalse(transformed.isCancelled());
+        CompletionException failure = assertThrows(CompletionException.class, transformed::join);
+        assertTrue(failure.getCause() instanceof CancellationException);
+    }
+
+    private static void awaitQueueLength(Semaphore semaphore, int expected) {
+        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(2);
+        while (semaphore.getQueueLength() < expected && System.nanoTime() < deadline) {
+            LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(1));
+        }
+        assertTrue("Expected at least " + expected + " queued semaphore threads",
+                semaphore.getQueueLength() >= expected);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/IrisChunkGeneratorMonumentLocateContractTest.java

@@ -0,0 +1,58 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureLocateResults;
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import org.junit.Test;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+public class IrisChunkGeneratorMonumentLocateContractTest {
+    @Test
+    public void mixedLocateSelectsNearestProviderAndPrefersNativeOnTie() {
+        BlockPos origin = BlockPos.ZERO;
+        Pair<BlockPos, Holder<Structure>> irisNear = Pair.of(new BlockPos(4, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeFar = Pair.of(new BlockPos(8, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeNear = Pair.of(new BlockPos(2, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeTie = Pair.of(new BlockPos(0, 70, 4), null);
+
+        assertSame(irisNear, NativeStructureLocateResults.nearest(origin, irisNear, nativeFar));
+        assertSame(nativeNear, NativeStructureLocateResults.nearest(origin, irisNear, nativeNear));
+        assertSame(nativeTie, NativeStructureLocateResults.nearest(origin, irisNear, nativeTie));
+    }
+
+    @Test
+    public void mixedUnexploredLocateReferencesOnlyTheSelectedProvider() {
+        BlockPos origin = BlockPos.ZERO;
+        Pair<BlockPos, Holder<Structure>> irisNear = Pair.of(new BlockPos(4, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeFar = Pair.of(new BlockPos(8, 70, 0), null);
+        AtomicInteger irisReferences = new AtomicInteger();
+        AtomicInteger nativeReferences = new AtomicInteger();
+
+        Pair<BlockPos, Holder<Structure>> irisSelected =
+                NativeStructureLocateResults.selectAndReference(
+                        origin,
+                        irisNear, () -> irisReferences.incrementAndGet(),
+                        nativeFar, () -> nativeReferences.incrementAndGet());
+
+        assertSame(irisNear, irisSelected);
+        assertEquals(1, irisReferences.get());
+        assertEquals(0, nativeReferences.get());
+
+        Pair<BlockPos, Holder<Structure>> nativeNear = Pair.of(new BlockPos(2, 70, 0), null);
+        Pair<BlockPos, Holder<Structure>> nativeSelected =
+                NativeStructureLocateResults.selectAndReference(
+                        origin,
+                        irisNear, () -> irisReferences.incrementAndGet(),
+                        nativeNear, () -> nativeReferences.incrementAndGet());
+
+        assertSame(nativeNear, nativeSelected);
+        assertEquals(1, irisReferences.get());
+        assertEquals(1, nativeReferences.get());
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/IrisChunkGeneratorSpawnAdmissionTest.java

@@ -0,0 +1,153 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.iris.platform.bukkit.nms.BukkitGeneratorContext;
+import org.bukkit.World;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeChunkGenerator;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeBiomeSourceImpl;
+
+import net.minecraft.server.level.ServerLevel;
+import art.arcane.iris.generation.runtime.IrisEngine;
+import art.arcane.iris.generation.runtime.GenerationSessionManager;
+import art.arcane.iris.generation.runtime.GenerationTransitionGate;
+import art.arcane.iris.world.history.GenerationHistoryRuntimeRouter;
+import art.arcane.iris.world.history.NativeBiomeSpawnSelection;
+import art.arcane.iris.world.history.SavedBiomeRuntime;
+import art.arcane.iris.generation.context.IrisContext;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.random.WeightedList;
+import net.minecraft.world.entity.MobCategory;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.MobSpawnSettings;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class IrisChunkGeneratorSpawnAdmissionTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void tickSpawnQueryLeavesOwnerThreadAvailableForBoundaryCheckpoint() throws Exception {
+        Fixture fixture = new Fixture();
+        ExecutorService owner = Executors.newSingleThreadExecutor();
+        ExecutorService reloader = Executors.newSingleThreadExecutor();
+        AtomicInteger snapshots = new AtomicInteger();
+        long previousSession = fixture.sessions.currentSessionId();
+        try {
+            assertSame(fixture.expected, owner.submit(fixture::query).get(2L, TimeUnit.SECONDS));
+            assertEquals(previousSession, fixture.readSession.get());
+            CompletableFuture<Void> cutover = CompletableFuture.runAsync(() -> {
+                try (GenerationTransitionGate.Transition ignored = fixture.sessions.transitionGate().beginTransition(2_000L)) {
+                    fixture.sessions.sealAndAwait("Studio generation cutover", 2_000L);
+                    Future<?> query = owner.submit(() -> {
+                        assertTrue(fixture.query().isEmpty());
+                        assertNull(IrisContext.get());
+                    });
+                    owner.submit(snapshots::incrementAndGet).get(2L, TimeUnit.SECONDS);
+                    query.get(2L, TimeUnit.SECONDS);
+                    assertEquals(1, fixture.savedReads.get());
+                    assertEquals(1, fixture.routes.get());
+                    fixture.sessions.activateNextSession();
+                } catch (Exception failure) {
+                    throw new IllegalStateException(failure);
+                }
+            }, reloader);
+
+            cutover.get(3L, TimeUnit.SECONDS);
+            assertEquals(1, snapshots.get());
+            assertEquals(0, fixture.sessions.activeLeases());
+            assertSame(fixture.expected, owner.submit(fixture::query).get(2L, TimeUnit.SECONDS));
+            assertEquals(fixture.sessions.currentSessionId(), fixture.readSession.get());
+            assertTrue(fixture.readSession.get() > previousSession);
+            assertEquals(2, fixture.savedReads.get());
+            assertEquals(2, fixture.routes.get());
+            assertEquals(0, fixture.sessions.activeLeases());
+        } finally {
+            owner.shutdownNow();
+            reloader.shutdownNow();
+            assertTrue(owner.awaitTermination(2L, TimeUnit.SECONDS));
+            assertTrue(reloader.awaitTermination(2L, TimeUnit.SECONDS));
+        }
+    }
+
+    private static void setField(NativeChunkGenerator<?, ?, ?, ?, ?> generator, String name, Object value) throws Exception {
+        Field field = NativeChunkGenerator.class.getDeclaredField(name);
+        field.setAccessible(true);
+        field.set(generator, value);
+    }
+
+    private static final class Fixture {
+        private final GenerationSessionManager sessions = new GenerationSessionManager(true);
+        private final IrisEngine engine = mock(IrisEngine.class);
+        private final NativeChunkGenerator<?, ?, ?, ?, ?> generator = mock(NativeChunkGenerator.class, CALLS_REAL_METHODS);
+        private final Holder<Biome> biome = Holder.direct(mock(Biome.class));
+        private final StructureManager structures = mock(StructureManager.class);
+        private final WeightedList<MobSpawnSettings.SpawnerData> expected = mock(WeightedList.class);
+        private final ServerLevel level = mock(ServerLevel.class);
+        private final AtomicInteger savedReads = new AtomicInteger();
+        private final AtomicInteger routes = new AtomicInteger();
+        private final AtomicLong readSession = new AtomicLong();
+
+        private Fixture() throws Exception {
+            GenerationHistoryRuntimeRouter router = mock(GenerationHistoryRuntimeRouter.class);
+            SavedBiomeRuntime saved = mock(SavedBiomeRuntime.class);
+            ChunkGenerator delegate = mock(ChunkGenerator.class);
+            NativeBiomeSourceImpl source = mock(NativeBiomeSourceImpl.class);
+            when(level.getBiome(new BlockPos(0, 64, 0))).thenReturn(biome);
+            setField(generator, "runtimeLevel", level);
+            when(engine.getGenerationSessions()).thenReturn(sessions);
+            when(engine.getGenerationHistoryRuntimeRouter()).thenReturn(Optional.of(router));
+            when(router.biomes()).thenReturn(saved);
+            when(saved.nativeSpawnSelection(0, 64, 0, "")).thenAnswer(invocation -> {
+                assertAdmitted();
+                savedReads.incrementAndGet();
+                return new NativeBiomeSpawnSelection(NativeBiomeSpawnSelection.Mode.RETAINED, "minecraft:plains");
+            });
+            when(engine.openGenerationHistoryCoordinateScope(0, 0)).thenAnswer(invocation -> {
+                assertAdmitted();
+                routes.incrementAndGet();
+                return null;
+            });
+            when(delegate.getMobsAt(level, structures, MobCategory.MONSTER, new BlockPos(0, 64, 0)))
+                    .thenReturn(expected);
+            setField(generator, "context", new BukkitGeneratorContext(new BukkitGeneratorContext.Options(1L, engine, mock(World.class))));
+            setField(generator, "delegate", delegate);
+            setField(generator, "customBiomeSource", source);
+        }
+
+        private WeightedList<MobSpawnSettings.SpawnerData> query() {
+            return generator.getMobsAt(level, structures, MobCategory.MONSTER, new BlockPos(0, 64, 0));
+        }
+
+        private void assertAdmitted() {
+            assertEquals(1, sessions.activeLeases());
+            assertSame(engine, IrisContext.get().getEngine());
+            readSession.set(IrisContext.get().getGenerationSessionId());
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NMSBindingDatapackStructureScopeTest.java

@@ -0,0 +1,439 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureSetFilter;
+
+import net.minecraft.world.level.levelgen.structure.placement.AbstractSpreadingStructurePlacement;
+import art.arcane.iris.pack.datapack.DatapackIngestService;
+import art.arcane.iris.pack.datapack.DatapackStructureScopeIndex;
+import art.arcane.iris.structure.nativegen.IrisImportedStructureControl;
+import art.arcane.iris.structure.placement.IrisStructureSetFrequencyOverride;
+import art.arcane.volmlib.util.collection.KList;
+import com.mojang.datafixers.util.Either;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderOwner;
+import net.minecraft.core.Vec3i;
+import net.minecraft.core.component.DataComponentMap;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.tags.TagKey;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadType;
+import net.minecraft.world.level.levelgen.structure.placement.StructurePlacement;
+import com.mojang.serialization.MapCodec;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import org.junit.Test;
+import org.junit.BeforeClass;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+
+public class NMSBindingDatapackStructureScopeTest {
+    private static final String SOURCE = "https://example.test/managed.zip";
+
+    @BeforeClass
+    public static void bootstrapMinecraft() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void managedSetContainingVanillaStructureIsAbsentOutsideDeclaringDimension() {
+        Holder<Structure> vanillaStructure = structureHolder("minecraft:pillager_outpost");
+        Holder<StructureSet> managedSet = structureSetHolder(
+                "managed:illager_barracks", vanillaStructure);
+        DatapackStructureScopeIndex index = index(
+                List.of(),
+                List.of("managed:illager_barracks"));
+
+        NativeStructureSetFilter.Selection vanilla = NativeStructureSetFilter.filter(
+                List.of(managedSet), index, Set.of());
+        NativeStructureSetFilter.Selection declaring = NativeStructureSetFilter.filter(
+                List.of(managedSet), index, index.declaredSources(List.of(SOURCE)));
+
+        assertEquals(0, vanilla.structureSets().size());
+        assertEquals(1, vanilla.excludedManagedSets());
+        assertEquals(1, declaring.structureSets().size());
+        assertSame(managedSet, declaring.structureSets().getFirst());
+    }
+
+    @Test
+    public void unmanagedSetRetainsOnlyDefinitionsAllowedInTheWorld() {
+        Holder<Structure> vanillaStructure = structureHolder("minecraft:village_plains");
+        Holder<Structure> managedStructure = structureHolder("managed:tavern");
+        Holder<StructureSet> vanillaSet = structureSetHolder(
+                "minecraft:villages", vanillaStructure, managedStructure);
+        DatapackStructureScopeIndex index = index(
+                List.of("managed:tavern"),
+                List.of());
+
+        NativeStructureSetFilter.Selection vanilla = NativeStructureSetFilter.filter(
+                List.of(vanillaSet), index, Set.of());
+        NativeStructureSetFilter.Selection declaring = NativeStructureSetFilter.filter(
+                List.of(vanillaSet), index, index.declaredSources(List.of(SOURCE)));
+
+        assertEquals(1, vanilla.structureSets().size());
+        assertEquals(1, vanilla.structureSets().getFirst().value().structures().size());
+        assertSame(vanillaStructure,
+                vanilla.structureSets().getFirst().value().structures().getFirst().structure());
+        assertSame(vanillaSet.value().placement(),
+                vanilla.structureSets().getFirst().value().placement());
+        assertSame(vanillaSet, declaring.structureSets().getFirst());
+    }
+
+    @Test
+    public void setWithNoAllowedDefinitionsIsRemoved() {
+        Holder<StructureSet> unmanagedSet = structureSetHolder(
+                "minecraft:custom", structureHolder("managed:only"));
+        DatapackStructureScopeIndex index = index(List.of("managed:only"), List.of());
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(unmanagedSet), index, Set.of());
+
+        assertEquals(0, selection.structureSets().size());
+    }
+
+    @Test
+    public void spigotDirectHolderRecoversItsRegistryKeyFromSharedEntries() {
+        ResourceKey<StructureSet> key = ResourceKey.create(
+                Registries.STRUCTURE_SET,
+                Identifier.parse("managed:illager_barracks"));
+        List<StructureSet.StructureSelectionEntry> entries = List.of(
+                new StructureSet.StructureSelectionEntry(
+                        structureHolder("minecraft:pillager_outpost"), 1));
+        Holder<StructureSet> registered = new KeyedHolder<>(key, new StructureSet(
+                entries,
+                new RandomSpreadStructurePlacement(
+                        34, 8, RandomSpreadType.LINEAR, 10387312)));
+        Holder<StructureSet> spigotDirect = Holder.direct(new StructureSet(
+                entries,
+                new RandomSpreadStructurePlacement(
+                        34, 8, RandomSpreadType.LINEAR, 14357620)));
+        DatapackStructureScopeIndex scopeIndex = index(
+                List.of(), List.of("managed:illager_barracks"));
+        NativeStructureSetFilter.StructureSetKeyIndex keyIndex =
+                NativeStructureSetFilter.keyIndex(List.of(registered));
+
+        NativeStructureSetFilter.Selection excluded =
+                NativeStructureSetFilter.filter(
+                        List.of(spigotDirect),
+                        scopeIndex,
+                        Set.of(),
+                        new IrisImportedStructureControl(),
+                        keyIndex);
+        NativeStructureSetFilter.Selection retained =
+                NativeStructureSetFilter.filter(
+                        List.of(spigotDirect),
+                        scopeIndex,
+                        scopeIndex.declaredSources(List.of(SOURCE)),
+                        new IrisImportedStructureControl(),
+                        keyIndex);
+
+        assertEquals(0, excluded.structureSets().size());
+        assertEquals(1, excluded.excludedManagedSets());
+        assertSame(spigotDirect, retained.structureSets().getFirst());
+        assertEquals(1, retained.retainedManagedSets());
+    }
+
+    @Test
+    public void structureScopeDoesNotLinkPaperOnlyPlacementClasses() throws IOException {
+        InputStream classResource = NativeStructureSetFilter.class
+                .getResourceAsStream("NativeStructureSetFilter.class");
+        assertNotNull(classResource);
+        try (InputStream input = classResource) {
+            String classFile = new String(input.readAllBytes(), StandardCharsets.ISO_8859_1);
+            assertFalse(classFile.contains("KeyedRandomSpreadStructurePlacement"));
+        }
+    }
+
+    @Test
+    public void exactFrequencyOverridesScaleOnlyTheNamedNativeStructureSet() {
+        Holder<StructureSet> complexes = structureSetHolder(
+                "minecraft:nether_complexes",
+                new RandomSpreadStructurePlacement(27, 4, RandomSpreadType.LINEAR, 30084232),
+                structureHolder("minecraft:fortress"));
+        Holder<StructureSet> fossils = structureSetHolder(
+                "minecraft:nether_fossils",
+                new RandomSpreadStructurePlacement(2, 1, RandomSpreadType.LINEAR, 14357921),
+                structureHolder("minecraft:nether_fossil"));
+        KList<IrisStructureSetFrequencyOverride> overrides = new KList<>();
+        overrides.add(new IrisStructureSetFrequencyOverride()
+                .setStructureSet("minecraft:nether_complexes")
+                .setMultiplier(1.1D));
+        IrisImportedStructureControl control = new IrisImportedStructureControl()
+                .setFrequencyOverrides(overrides);
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(complexes, fossils), index(List.of(), List.of()), Set.of(), control);
+
+        RandomSpreadStructurePlacement scaledComplexes =
+                (RandomSpreadStructurePlacement) selection.structureSets().get(0).value().placement();
+        RandomSpreadStructurePlacement unchangedFossils =
+                (RandomSpreadStructurePlacement) selection.structureSets().get(1).value().placement();
+        assertEquals(26, scaledComplexes.spacing());
+        assertEquals(4, scaledComplexes.separation());
+        assertEquals(2, unchangedFossils.spacing());
+        assertSame(fossils, selection.structureSets().get(1));
+        assertEquals(27, ((RandomSpreadStructurePlacement) complexes.value().placement()).spacing());
+    }
+
+    @Test
+    public void frequencyOnlyPassLeavesUnrelatedCustomPlacementUntouched() {
+        Holder<StructureSet> exclusionTarget = structureSetHolder(
+                "example:target", structureHolder("example:target"));
+        Holder<StructureSet> custom = structureSetHolder(
+                "example:custom",
+                new UnsupportedPlacement(Optional.of(
+                        new AbstractSpreadingStructurePlacement.ExclusionZone(exclusionTarget, 1))),
+                structureHolder("example:custom"));
+        KList<IrisStructureSetFrequencyOverride> overrides = new KList<>();
+        overrides.add(new IrisStructureSetFrequencyOverride()
+                .setStructureSet("minecraft:nether_complexes")
+                .setMultiplier(1.1D));
+        IrisImportedStructureControl control = new IrisImportedStructureControl()
+                .setFrequencyOverrides(overrides);
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(custom), index(List.of(), List.of()), Set.of(), control);
+
+        assertSame(custom, selection.structureSets().getFirst());
+    }
+
+    @Test
+    public void frequencyOnlyPassRebindsDependentExclusionTarget() {
+        Holder<StructureSet> target = structureSetHolder(
+                "example:target",
+                new RandomSpreadStructurePlacement(27, 4, RandomSpreadType.LINEAR, 30084232),
+                structureHolder("example:target"));
+        RandomSpreadStructurePlacement dependentPlacement = new RandomSpreadStructurePlacement(
+                Vec3i.ZERO,
+                AbstractSpreadingStructurePlacement.FrequencyReductionMethod.DEFAULT,
+                1.0F,
+                4567,
+                Optional.of(new AbstractSpreadingStructurePlacement.ExclusionZone(target, 1)),
+                32,
+                8,
+                RandomSpreadType.LINEAR);
+        Holder<StructureSet> dependent = structureSetHolder(
+                "example:dependent",
+                dependentPlacement,
+                structureHolder("example:dependent"));
+        KList<IrisStructureSetFrequencyOverride> overrides = new KList<>();
+        overrides.add(new IrisStructureSetFrequencyOverride()
+                .setStructureSet("example:target")
+                .setMultiplier(1.1D));
+        IrisImportedStructureControl control = new IrisImportedStructureControl()
+                .setFrequencyOverrides(overrides);
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(dependent, target), index(List.of(), List.of()), Set.of(), control);
+
+        Holder<StructureSet> scaledDependent = selection.structureSets().get(0);
+        Holder<StructureSet> scaledTarget = selection.structureSets().get(1);
+        assertNotSame(dependent, scaledDependent);
+        assertNotSame(target, scaledTarget);
+        assertSame(scaledTarget, NativeStructureSetFilter.exclusionZone(
+                scaledDependent.value().placement()).orElseThrow().otherSet());
+        assertEquals(26, ((RandomSpreadStructurePlacement)
+                scaledTarget.value().placement()).spacing());
+    }
+
+    @Test
+    public void frequencyOnlyPassRebindsAffectedExclusionCycle() {
+        MutableStructureSetHolder first = new MutableStructureSetHolder("example:first");
+        MutableStructureSetHolder second = new MutableStructureSetHolder("example:second");
+        first.bind(structureSet(
+                new RandomSpreadStructurePlacement(
+                        Vec3i.ZERO,
+                        AbstractSpreadingStructurePlacement.FrequencyReductionMethod.DEFAULT,
+                        1.0F,
+                        101,
+                        Optional.of(new AbstractSpreadingStructurePlacement.ExclusionZone(second, 1)),
+                        32,
+                        8,
+                        RandomSpreadType.LINEAR),
+                "example:first"));
+        second.bind(structureSet(
+                new RandomSpreadStructurePlacement(
+                        Vec3i.ZERO,
+                        AbstractSpreadingStructurePlacement.FrequencyReductionMethod.DEFAULT,
+                        1.0F,
+                        102,
+                        Optional.of(new AbstractSpreadingStructurePlacement.ExclusionZone(first, 1)),
+                        27,
+                        4,
+                        RandomSpreadType.LINEAR),
+                "example:second"));
+        KList<IrisStructureSetFrequencyOverride> overrides = new KList<>();
+        overrides.add(new IrisStructureSetFrequencyOverride()
+                .setStructureSet("example:second")
+                .setMultiplier(1.1D));
+        IrisImportedStructureControl control = new IrisImportedStructureControl()
+                .setFrequencyOverrides(overrides);
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(first, second), index(List.of(), List.of()), Set.of(), control);
+
+        Holder<StructureSet> scaledFirst = selection.structureSets().get(0);
+        Holder<StructureSet> scaledSecond = selection.structureSets().get(1);
+        assertSame(scaledSecond, NativeStructureSetFilter.exclusionZone(
+                scaledFirst.value().placement()).orElseThrow().otherSet());
+        assertSame(scaledFirst, NativeStructureSetFilter.exclusionZone(
+                scaledSecond.value().placement()).orElseThrow().otherSet());
+        assertEquals(26, ((RandomSpreadStructurePlacement)
+                scaledSecond.value().placement()).spacing());
+    }
+
+    @Test
+    public void randomSpreadSubtypeUsesTheCanonicalPlacementContract() {
+        Holder<StructureSet> custom = structureSetHolder(
+                "example:custom",
+                new CustomRandomSpreadPlacement(),
+                structureHolder("example:custom"));
+        KList<IrisStructureSetFrequencyOverride> overrides = new KList<>();
+        overrides.add(new IrisStructureSetFrequencyOverride()
+                .setStructureSet("example:custom")
+                .setMultiplier(1.1D));
+        IrisImportedStructureControl control = new IrisImportedStructureControl()
+                .setFrequencyOverrides(overrides);
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(custom), index(List.of(), List.of()), Set.of(), control);
+        StructurePlacement placement = selection.structureSets().getFirst().value().placement();
+
+        assertEquals(RandomSpreadStructurePlacement.class, placement.getClass());
+        assertEquals(26, ((RandomSpreadStructurePlacement) placement).spacing());
+    }
+
+    @Test
+    public void excludedManagedSetCannotSuppressAnAllowedSetThroughExclusionZone() {
+        Holder<StructureSet> managedSet = structureSetHolder(
+                "managed:blocked",
+                structureHolder("managed:blocked"));
+        RandomSpreadStructurePlacement originalPlacement = new RandomSpreadStructurePlacement(
+                Vec3i.ZERO,
+                AbstractSpreadingStructurePlacement.FrequencyReductionMethod.DEFAULT,
+                1.0F,
+                4567,
+                Optional.of(new AbstractSpreadingStructurePlacement.ExclusionZone(managedSet, 1)),
+                32,
+                8,
+                RandomSpreadType.LINEAR);
+        Holder<StructureSet> vanillaSet = structureSetHolder(
+                "minecraft:allowed",
+                originalPlacement,
+                structureHolder("minecraft:village_plains"));
+        DatapackStructureScopeIndex index = index(
+                List.of("managed:blocked"),
+                List.of("managed:blocked"));
+
+        NativeStructureSetFilter.Selection selection = NativeStructureSetFilter.filter(
+                List.of(vanillaSet, managedSet), index, Set.of());
+
+        assertEquals(1, selection.structureSets().size());
+        StructurePlacement scopedPlacement = selection.structureSets().getFirst().value().placement();
+        assertEquals(0, NativeStructureSetFilter.exclusionZone(scopedPlacement).stream().count());
+    }
+
+    private static DatapackStructureScopeIndex index(
+            List<String> structureKeys,
+            List<String> structureSetKeys
+    ) {
+        return DatapackStructureScopeIndex.create(List.of(
+                new DatapackIngestService.StructureScopeResources(
+                        SOURCE,
+                        structureKeys,
+                        structureSetKeys)));
+    }
+
+    private static Holder<Structure> structureHolder(String key) {
+        return new KeyedHolder<>(ResourceKey.create(Registries.STRUCTURE, Identifier.parse(key)), null);
+    }
+
+    private static Holder<StructureSet> structureSetHolder(
+            String key,
+            Holder<Structure>... structures
+    ) {
+        return structureSetHolder(
+                key,
+                new RandomSpreadStructurePlacement(32, 8, RandomSpreadType.LINEAR, 12345),
+                structures);
+    }
+
+    private static Holder<StructureSet> structureSetHolder(
+            String key,
+            StructurePlacement placement,
+            Holder<Structure>... structures
+    ) {
+        List<StructureSet.StructureSelectionEntry> entries = Stream.of(structures)
+                .map(structure -> new StructureSet.StructureSelectionEntry(structure, 1))
+                .toList();
+        StructureSet value = new StructureSet(entries, placement);
+        return new KeyedHolder<>(
+                ResourceKey.create(Registries.STRUCTURE_SET, Identifier.parse(key)),
+                value);
+    }
+
+    private static StructureSet structureSet(StructurePlacement placement, String structureKey) {
+        return new StructureSet(
+                List.of(new StructureSet.StructureSelectionEntry(
+                        structureHolder(structureKey), 1)),
+                placement);
+    }
+
+    private static final class KeyedHolder<T> extends Holder.Reference<T> {
+        private KeyedHolder(ResourceKey<T> key, T value) {
+            super(Type.STAND_ALONE, new HolderOwner<>() {}, key, null);
+            bindValue(value);
+        }
+    }
+
+    private static final class UnsupportedPlacement extends AbstractSpreadingStructurePlacement {
+        private UnsupportedPlacement(Optional<ExclusionZone> exclusionZone) {
+            super(Vec3i.ZERO, FrequencyReductionMethod.DEFAULT, 1F, 1, exclusionZone);
+        }
+
+        @Override
+        protected boolean isPlacementChunk(ChunkGeneratorStructureState state, int x, int z) {
+            return false;
+        }
+
+        @Override
+        public MapCodec<? extends AbstractSpreadingStructurePlacement> codec() {
+            return null;
+        }
+    }
+
+    private static final class MutableStructureSetHolder extends Holder.Reference<StructureSet> {
+        private MutableStructureSetHolder(String key) {
+            super(Type.STAND_ALONE, new HolderOwner<>() {
+            }, ResourceKey.create(Registries.STRUCTURE_SET, Identifier.parse(key)), null);
+        }
+
+        private void bind(StructureSet structureSet) {
+            bindValue(structureSet);
+        }
+    }
+
+    private static final class CustomRandomSpreadPlacement extends RandomSpreadStructurePlacement {
+        private CustomRandomSpreadPlacement() {
+            super(27, 4, RandomSpreadType.LINEAR, 30084232);
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NativeStructurePoiUpdatesTest.java

@@ -0,0 +1,252 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructurePoiUpdates;
+
+import ca.spottedleaf.moonrise.common.util.TickThread;
+import com.mojang.serialization.Codec;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.IdMapper;
+import net.minecraft.core.SectionPos;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.ai.village.poi.PoiManager;
+import net.minecraft.world.entity.ai.village.poi.PoiRecord;
+import net.minecraft.world.entity.ai.village.poi.PoiSection;
+import net.minecraft.world.entity.ai.village.poi.PoiType;
+import net.minecraft.world.entity.ai.village.poi.PoiTypes;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ImposterProtoChunk;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.PalettedContainer;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.Strategy;
+import net.minecraft.world.level.chunk.UpgradeData;
+import org.bukkit.NamespacedKey;
+import org.bukkit.craftbukkit.persistence.CraftPersistentDataTypeRegistry;
+import org.bukkit.craftbukkit.persistence.DirtyCraftPersistentDataContainer;
+import org.bukkit.persistence.PersistentDataType;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.FutureTask;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeStructurePoiUpdatesTest {
+    private static final NamespacedKey DIRTY_SECTIONS = new NamespacedKey("iris", "native_poi_sections");
+
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void generationRecordsIntentBeforeSuppressingNativePoiCallbacks() {
+        Fixture fixture = new Fixture();
+        BlockPos position = new BlockPos(-31, 5, 49);
+        doAnswer(call -> {
+            assertNotNull(fixture.proto.persistentDataContainer.get(DIRTY_SECTIONS, PersistentDataType.LONG_ARRAY));
+            assertEquals(Block.UPDATE_CLIENTS | 4096, (int) call.getArgument(2));
+            fixture.proto.setBlockState(position, call.getArgument(1), 0);
+            return true;
+        }).when(fixture.world).setBlock(any(), any(), anyInt(), anyInt());
+
+        assertTrue(fixture.updates.setBlock(fixture.world, position,
+                Blocks.COMPOSTER.defaultBlockState(), Block.UPDATE_CLIENTS, 17));
+        assertArrayEquals(new long[]{16L}, fixture.marker());
+    }
+
+    @Test
+    public void denseWritesStoreOneSectionBitAndSurvivePersistentDataRoundTrip() throws Exception {
+        Fixture fixture = new Fixture();
+        for (int z = 0; z < 16; z++) {
+            for (int x = 0; x < 16; x++) {
+                fixture.write(new BlockPos(-32 + x, 5, 48 + z), Blocks.COMPOSTER.defaultBlockState());
+            }
+        }
+        assertArrayEquals(new long[]{16L}, fixture.marker());
+        DirtyCraftPersistentDataContainer restored = new DirtyCraftPersistentDataContainer(new CraftPersistentDataTypeRegistry());
+        restored.putAll(fixture.proto.persistentDataContainer.toTagCompound());
+        fixture.loaded.persistentDataContainer = restored;
+
+        onOwner(() -> NativeStructurePoiUpdates.reconcile(fixture.loaded));
+
+        assertEquals(256L, fixture.records().getRecords(type -> true, PoiManager.Occupancy.ANY).count());
+        assertFalse(restored.has(DIRTY_SECTIONS));
+    }
+
+    @Test
+    public void validSectionsReconcileFinalStatesAndKeepMatchingClaimedTickets() throws Exception {
+        Fixture fixture = new Fixture();
+        BlockPos retained = new BlockPos(-31, 5, 49);
+        BlockPos replaced = new BlockPos(-30, 5, 49);
+        BlockPos removed = new BlockPos(-29, 5, 49);
+        Holder<PoiType> farmer = PoiTypes.forState(Blocks.COMPOSTER.defaultBlockState()).orElseThrow();
+        PoiSection existing = new PoiSection.Packed(true, List.of(
+                new PoiRecord.Packed(retained, farmer, 0),
+                new PoiRecord.Packed(replaced, farmer, 1),
+                new PoiRecord.Packed(removed, farmer, 1))).unpack(() -> {});
+        fixture.pois.put(SectionPos.of(retained).asLong(), existing);
+        PoiRecord retainedRecord = existing.getRecords(type -> true, PoiManager.Occupancy.ANY)
+                .filter(record -> record.getPos().equals(retained)).findFirst().orElseThrow();
+        for (BlockPos position : List.of(retained, replaced, removed)) {
+            fixture.proto.setBlockState(position, Blocks.COMPOSTER.defaultBlockState(), 0);
+        }
+        fixture.write(replaced, Blocks.BARREL.defaultBlockState());
+        fixture.write(removed, Blocks.AIR.defaultBlockState());
+
+        onOwner(() -> NativeStructurePoiUpdates.reconcile(fixture.loaded));
+
+        assertEquals(PoiTypes.forState(Blocks.BARREL.defaultBlockState()), existing.getType(replaced));
+        assertTrue(existing.getType(removed).isEmpty());
+        assertSame(retainedRecord, existing.getRecords(type -> true, PoiManager.Occupancy.ANY)
+                .filter(record -> record.getPos().equals(retained)).findFirst().orElseThrow());
+        assertEquals(0, existing.getFreeTickets(retained));
+        onOwner(() -> NativeStructurePoiUpdates.reconcile(fixture.loaded));
+        assertEquals(0, existing.getFreeTickets(retained));
+    }
+
+    @Test
+    public void failedReconciliationRetainsIntentForRetry() throws Exception {
+        Fixture fixture = new Fixture();
+        fixture.write(new BlockPos(-31, 5, 49), Blocks.COMPOSTER.defaultBlockState());
+        IllegalStateException failure = new IllegalStateException("POI storage failure");
+        doThrow(failure).when(fixture.manager).add(any(), any());
+
+        onOwner(() -> assertSame(failure, assertThrows(IllegalStateException.class,
+                () -> NativeStructurePoiUpdates.reconcile(fixture.loaded))));
+
+        assertArrayEquals(new long[]{16L}, fixture.marker());
+        fixture.allowPoiAdds();
+        onOwner(() -> NativeStructurePoiUpdates.reconcile(fixture.loaded));
+        assertFalse(fixture.proto.persistentDataContainer.has(DIRTY_SECTIONS));
+    }
+
+    @Test
+    public void explicitPoiSuppressionAndReadOnlyFullChunksDoNotCreateIntent() {
+        Fixture fixture = new Fixture();
+        BlockPos position = new BlockPos(-31, 5, 49);
+        fixture.updates.setBlock(fixture.world, position, Blocks.COMPOSTER.defaultBlockState(),
+                4096, 17);
+        assertFalse(fixture.proto.persistentDataContainer.has(DIRTY_SECTIONS));
+        ImposterProtoChunk full = mock(ImposterProtoChunk.class);
+        when(fixture.world.getChunk(any(BlockPos.class))).thenReturn(full);
+        fixture.updates.setBlock(fixture.world, position, Blocks.BARREL.defaultBlockState(), 2, 17);
+        assertFalse(fixture.proto.persistentDataContainer.has(DIRTY_SECTIONS));
+    }
+
+    @Test
+    public void invalidSectionBitsRetainTheStoredRecord() throws Exception {
+        Fixture fixture = new Fixture();
+        fixture.proto.persistentDataContainer.set(DIRTY_SECTIONS, PersistentDataType.LONG_ARRAY, new long[]{1L << 24});
+        onOwner(() -> assertThrows(IllegalArgumentException.class,
+                () -> NativeStructurePoiUpdates.reconcile(fixture.loaded)));
+        assertArrayEquals(new long[]{1L << 24}, fixture.marker());
+    }
+
+    private static void onOwner(Runnable action) throws Exception {
+        FutureTask<Void> task = new FutureTask<>(action, null);
+        new TickThread(task, "Native POI test").start();
+        task.get(5L, TimeUnit.SECONDS);
+    }
+
+    private static PalettedContainerFactory containerFactory() {
+        Strategy<BlockState> blocks = Strategy.createForBlockStates(Block.BLOCK_STATE_REGISTRY);
+        BlockState air = Blocks.AIR.defaultBlockState();
+        IdMapper<Holder<Biome>> biomeIds = new IdMapper<>();
+        Holder<Biome> biome = Holder.direct((Biome) null);
+        biomeIds.add(biome);
+        Strategy<Holder<Biome>> biomes = Strategy.createForBiomes(biomeIds);
+        Codec<Holder<Biome>> biomeCodec = Codec.STRING.xmap(name -> biome, holder -> "iris-test-biome");
+        return new PalettedContainerFactory(blocks, air, PalettedContainer.codecRW(BlockState.CODEC, blocks, air),
+                biomes, biome, PalettedContainer.codecRO(biomeCodec, biomes, biome),
+                PalettedContainer.codecRW(biomeCodec, biomes, biome));
+    }
+
+    private static final class Fixture {
+        private final NativeStructurePoiUpdates updates = new NativeStructurePoiUpdates(4096);
+        private final ProtoChunk proto = new ProtoChunk(new ChunkPos(-2, 3), UpgradeData.EMPTY,
+                LevelHeightAccessor.create(-64, 384), containerFactory(), null);
+        private final LevelChunk loaded = mock(LevelChunk.class);
+        private final WorldGenLevel world = mock(WorldGenLevel.class);
+        private final PoiManager manager = mock(PoiManager.class);
+        private final Map<Long, PoiSection> pois = new HashMap<>();
+
+        private Fixture() {
+            ServerLevel level = mock(ServerLevel.class);
+            when(level.getPoiManager()).thenReturn(manager);
+            loaded.persistentDataContainer = proto.persistentDataContainer;
+            when(loaded.getLevel()).thenReturn(level);
+            when(loaded.getPos()).thenReturn(proto.getPos());
+            when(loaded.getSectionsCount()).thenReturn(proto.getSectionsCount());
+            when(loaded.getSectionYFromSectionIndex(anyInt())).thenAnswer(call -> proto.getSectionYFromSectionIndex(call.getArgument(0)));
+            when(loaded.getSection(anyInt())).thenAnswer(call -> proto.getSection(call.getArgument(0)));
+            when(loaded.getBlockState(any())).thenAnswer(call -> proto.getBlockState(call.getArgument(0)));
+            when(world.getChunk(any(BlockPos.class))).thenReturn(proto);
+            when(world.setBlock(any(), any(), anyInt(), anyInt())).thenAnswer(call -> {
+                proto.setBlockState(call.getArgument(0), call.getArgument(1), call.getArgument(2));
+                return true;
+            });
+            when(manager.getOrLoad(anyLong())).thenAnswer(call -> Optional.ofNullable(pois.get((long) call.getArgument(0))));
+            when(manager.getType(any())).thenAnswer(call -> {
+                BlockPos position = call.getArgument(0);
+                PoiSection section = pois.get(SectionPos.of(position).asLong());
+                return section == null ? Optional.empty() : section.getType(position);
+            });
+            doAnswer(call -> {
+                BlockPos position = call.getArgument(0);
+                pois.get(SectionPos.of(position).asLong()).remove(position);
+                return null;
+            }).when(manager).remove(any());
+            allowPoiAdds();
+        }
+
+        private void allowPoiAdds() {
+            doAnswer(call -> {
+                BlockPos position = call.getArgument(0);
+                return pois.computeIfAbsent(SectionPos.of(position).asLong(), ignored -> new PoiSection(() -> {}))
+                        .add(position, call.getArgument(1));
+            }).when(manager).add(any(), any());
+        }
+
+        private void write(BlockPos position, BlockState state) {
+            updates.setBlock(world, position, state, Block.UPDATE_CLIENTS, Block.UPDATE_LIMIT);
+        }
+
+        private long[] marker() {
+            return proto.persistentDataContainer.get(DIRTY_SECTIONS, PersistentDataType.LONG_ARRAY);
+        }
+
+        private PoiSection records() {
+            return pois.get(SectionPos.of(new BlockPos(-31, 5, 49)).asLong());
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NativeStructureWorldgenAccessTest.java

@@ -0,0 +1,466 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureWorldgenAccess;
+
+import art.arcane.iris.structure.placement.IrisStructureTerrain;
+import art.arcane.volmlib.util.structure.StructureTerrainMode;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructurePostProcessor;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeStructureTerrainIntegrator;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeManager;
+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.chunk.status.ChunkStatus;
+import net.minecraft.world.level.entity.EntityTypeTest;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.structure.BoundingBox;
+import net.minecraft.world.level.levelgen.structure.PoolElementStructurePiece;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.TerrainAdjustment;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pools.StructurePoolElement;
+import net.minecraft.world.level.levelgen.structure.pools.StructureTemplatePool;
+import net.minecraft.world.level.levelgen.structure.structures.DesertPyramidStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.GravityProcessor;
+import net.minecraft.world.level.levelgen.structure.templatesystem.LiquidSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import net.minecraft.world.level.material.Fluid;
+import net.minecraft.world.level.material.FluidState;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.phys.Vec3;
+import net.minecraft.world.ticks.LevelTickAccess;
+import net.minecraft.world.ticks.ScheduledTick;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public class NativeStructureWorldgenAccessTest {
+    private static final int GENERATION_CENTER_X = 60;
+    private static final int GENERATION_CENTER_Z = 15;
+    private static final int SURFACE_FIRST_FREE_Y = 80;
+    private static final int FLOOR_FIRST_FREE_Y = 70;
+
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void ordinaryWorldFlattenPreparationHandlesReferencedVillagePiecesBeyondEightChunks() {
+        int farX = (GENERATION_CENTER_X - 9) << 4;
+        int farZ = (GENERATION_CENTER_Z + 4) << 4;
+        BoundingBox bounds = new BoundingBox(farX, 64, farZ, farX + 4, 90, farZ + 4);
+        PoolElementStructurePiece piece = new PoolElementStructurePiece(
+                null, StructurePoolElement.single("minecraft:empty").apply(StructureTemplatePool.Projection.RIGID),
+                new BlockPos(farX, 64, farZ), 1, Rotation.NONE, bounds, LiquidSettings.APPLY_WATERLOGGING);
+        Structure structure = new DesertPyramidStructure(new Structure.StructureSettings(
+                HolderSet.empty(), Map.of(), GenerationStep.Decoration.SURFACE_STRUCTURES, TerrainAdjustment.BEARD_BOX));
+        StructureStart start = new StructureStart(structure, generationCenter(), 0, new PiecesContainer(List.of(piece)));
+        List<NativeStructureTerrainIntegrator.TerrainTarget> targets = List.of(
+                new NativeStructureTerrainIntegrator.TerrainTarget("minecraft:village_plains", start,
+                        new IrisStructureTerrain().setMode(StructureTerrainMode.FLATTEN)));
+        BoundingBox area = new BoundingBox(generationCenter().getMinBlockX(), -64, generationCenter().getMinBlockZ(),
+                generationCenter().getMaxBlockX(), 319, generationCenter().getMaxBlockZ());
+        RecordingDelegate unbounded = new RecordingDelegate();
+        unbounded.rejectDistantTerrainReads = true;
+
+        assertThrows(IllegalStateException.class, () -> NativeStructurePostProcessor.prepareTerrain(
+                unbounded.world(), area, targets, (palette, rng, x, y, z) -> Blocks.STONE.defaultBlockState()));
+
+        RecordingDelegate recording = new RecordingDelegate();
+        recording.rejectDistantTerrainReads = true;
+        NativeStructureWorldgenAccess access = access(recording);
+        NativeStructurePostProcessor.prepareTerrain(
+                access, area, targets, (palette, rng, x, y, z) -> Blocks.STONE.defaultBlockState());
+
+        assertEquals(0, recording.heightReads);
+        assertEquals(0, recording.chunkReads);
+        assertEquals(0, recording.terrainReads);
+        assertEquals(0, recording.mutations);
+        assertEquals(91, access.getHeight(Heightmap.Types.WORLD_SURFACE_WG,
+                generationCenter().getMinBlockX(), generationCenter().getMinBlockZ()));
+        assertEquals(1, recording.heightReads);
+    }
+
+    @Test
+    public void projectedTemplatePrefiltersUseRemoteTerrainAndRetainLocalHeightmaps() {
+        RecordingDelegate recording = new RecordingDelegate();
+        recording.rejectDistantTerrainReads = true;
+        NativeStructureWorldgenAccess access = access(recording);
+        GravityProcessor gravity = new GravityProcessor(Heightmap.Types.WORLD_SURFACE_WG, -1);
+        BlockPos remote = new BlockPos((GENERATION_CENTER_X - 9) << 4, 64, (GENERATION_CENTER_Z + 4) << 4);
+        StructureTemplate.StructureBlockInfo raw = new StructureTemplate.StructureBlockInfo(
+                new BlockPos(0, 4, 0), Blocks.DIRT_PATH.defaultBlockState(), null);
+        StructurePlaceSettings settings = new StructurePlaceSettings().addProcessor(gravity);
+
+        StructureTemplate.StructureBlockInfo projected = StructureTemplate.processBlockInfos(
+                access, remote, BlockPos.ZERO, settings, List.of(raw)).getFirst();
+
+        assertEquals(remote.atY(SURFACE_FIRST_FREE_Y + 3), projected.pos());
+        assertEquals(0, recording.heightReads);
+        BlockPos local = generationCenter().getMiddleBlockPosition(64);
+        StructureTemplate.StructureBlockInfo localBlock = new StructureTemplate.StructureBlockInfo(
+                BlockPos.ZERO, Blocks.DIRT_PATH.defaultBlockState(), null);
+        StructureTemplate.StructureBlockInfo localProjection = StructureTemplate.processBlockInfos(
+                access, local, BlockPos.ZERO, settings, List.of(localBlock)).getFirst();
+        assertEquals(local.atY(90), localProjection.pos());
+        assertEquals(1, recording.heightReads);
+        assertEquals(0, recording.chunkReads);
+    }
+
+    @Test
+    public void distanceTwoTerrainReadsNeverReachTheDelegate() {
+        RecordingDelegate recording = new RecordingDelegate();
+        NativeStructureWorldgenAccess access = access(recording);
+        ChunkPos generationCenter = generationCenter();
+        int x = generationCenter.getMiddleBlockX();
+        int z = (generationCenter.z() + 2) << 4;
+
+        assertSame(Blocks.STONE, access.getBlockState(new BlockPos(x, FLOOR_FIRST_FREE_Y - 1, z)).getBlock());
+        assertSame(Blocks.WATER, access.getBlockState(new BlockPos(x, FLOOR_FIRST_FREE_Y, z)).getBlock());
+        assertSame(Blocks.AIR, access.getBlockState(new BlockPos(x, SURFACE_FIRST_FREE_Y, z)).getBlock());
+        assertSame(Blocks.WATER.defaultBlockState().getFluidState(),
+                access.getFluidState(new BlockPos(x, FLOOR_FIRST_FREE_Y, z)));
+        assertEquals(SURFACE_FIRST_FREE_Y, access.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z));
+        assertEquals(FLOOR_FIRST_FREE_Y, access.getHeight(Heightmap.Types.OCEAN_FLOOR_WG, x, z));
+        assertNull(access.getBlockStateIfLoaded(new BlockPos(x, FLOOR_FIRST_FREE_Y, z)));
+        assertNull(access.getChunk(generationCenter.x(), generationCenter.z() + 2, ChunkStatus.FEATURES, false));
+        assertNull(access.getChunkIfLoadedImmediately(
+                generationCenter.x(), generationCenter.z() + 2));
+        List<BlockState> streamed = access.getBlockStates(new AABB(
+                x, FLOOR_FIRST_FREE_Y, z, x, FLOOR_FIRST_FREE_Y, z)).toList();
+
+        assertEquals(1, streamed.size());
+        assertSame(Blocks.WATER, streamed.getFirst().getBlock());
+        assertEquals(0, recording.terrainReads);
+        assertEquals(0, recording.heightReads);
+        assertEquals(0, recording.chunkReads);
+    }
+
+    @Test
+    public void distanceTwoMutationsAndSideEffectsNeverReachTheDelegate() {
+        RecordingDelegate recording = new RecordingDelegate();
+        NativeStructureWorldgenAccess access = access(recording);
+        ChunkPos generationCenter = generationCenter();
+        BlockPos position = new BlockPos(
+                generationCenter.getMiddleBlockX(),
+                FLOOR_FIRST_FREE_Y,
+                (generationCenter.z() + 2) << 4);
+
+        assertFalse(access.ensureCanWrite(position));
+        assertFalse(access.setBlock(position, Blocks.DIRT.defaultBlockState(), 2));
+        assertFalse(access.removeBlock(position, false));
+        assertFalse(access.destroyBlock(position, false));
+        access.updateNeighborsAt(position, Blocks.DIRT);
+        access.neighborShapeChanged(
+                Direction.NORTH, position, position.north(),
+                Blocks.DIRT.defaultBlockState(), 2, 512);
+        access.levelEvent(null, 2001, position, 0);
+        access.gameEvent(null, Vec3.atCenterOf(position), null);
+        access.addParticle(null, position.getX(), position.getY(), position.getZ(), 0, 0, 0);
+        access.getBlockTicks().schedule(new ScheduledTick<>(
+                Blocks.DIRT, position, 1L, 0L));
+
+        assertEquals(0, recording.mutations);
+        assertEquals(0, recording.events);
+        assertEquals(0, recording.blockTicks.count());
+    }
+
+    @Test
+    public void radiusOneReadsWritesAndTicksRemainUnchanged() {
+        RecordingDelegate recording = new RecordingDelegate();
+        NativeStructureWorldgenAccess access = access(recording);
+        ChunkPos generationCenter = generationCenter();
+        BlockPos position = new BlockPos(
+                (generationCenter.x() + 1) << 4,
+                FLOOR_FIRST_FREE_Y,
+                (generationCenter.z() - 1) << 4);
+
+        assertTrue(access.isInsideGenerationRegion(
+                generationCenter.x() + 1, generationCenter.z() - 1));
+        assertSame(Blocks.DIRT, access.getBlockState(position).getBlock());
+        assertEquals(91, access.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, position.getX(), position.getZ()));
+        assertTrue(access.ensureCanWrite(position));
+        assertTrue(access.setBlock(position, Blocks.STONE.defaultBlockState(), 2));
+        assertTrue(access.removeBlock(position, false));
+        assertTrue(access.destroyBlock(position, false));
+        access.getBlockTicks().schedule(new ScheduledTick<>(
+                Blocks.DIRT, position, 1L, 0L));
+
+        assertEquals(1, recording.terrainReads);
+        assertEquals(1, recording.heightReads);
+        assertEquals(4, recording.mutations);
+        assertEquals(1, recording.blockTicks.count());
+    }
+
+    @Test
+    public void virtualizedHeightsHideInRegionTerrainFromTheDelegate() {
+        RecordingDelegate recording = new RecordingDelegate();
+        ChunkPos generationCenter = generationCenter();
+        NativeStructureWorldgenAccess access = NativeStructureWorldgenAccess.create(
+                recording.world(), generationCenter,
+                (x, z) -> SURFACE_FIRST_FREE_Y,
+                (x, z) -> FLOOR_FIRST_FREE_Y,
+                true,
+                position -> false);
+        int x = generationCenter.getMiddleBlockX();
+        int z = generationCenter.getMiddleBlockZ();
+
+        assertEquals(SURFACE_FIRST_FREE_Y, access.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z));
+        assertEquals(FLOOR_FIRST_FREE_Y, access.getHeight(Heightmap.Types.OCEAN_FLOOR_WG, x, z));
+        assertEquals(0, recording.heightReads);
+    }
+
+    @Test
+    public void protectedCellsRemainReadableButRejectWritesTilesAndTicks() {
+        RecordingDelegate recording = new RecordingDelegate();
+        BlockPos position = generationCenter().getMiddleBlockPosition(70);
+        NativeStructureWorldgenAccess access = NativeStructureWorldgenAccess.create(
+                recording.world(), generationCenter(),
+                (x, z) -> SURFACE_FIRST_FREE_Y,
+                (x, z) -> FLOOR_FIRST_FREE_Y,
+                false,
+                position::equals);
+
+        assertSame(Blocks.DIRT, access.getBlockState(position).getBlock());
+        assertFalse(access.ensureCanWrite(position));
+        assertFalse(access.setBlock(position, Blocks.STONE.defaultBlockState(), 2));
+        assertFalse(access.removeBlock(position, false));
+        assertFalse(access.destroyBlock(position, false));
+        assertNull(access.getBlockEntity(position));
+        assertTrue(access.getBlockEntity(position, null).isEmpty());
+        access.getBlockTicks().schedule(new ScheduledTick<>(Blocks.DIRT, position, 1L, 0L));
+        access.updateNeighborsAt(position.east(), Blocks.DIRT);
+        access.neighborShapeChanged(
+                Direction.EAST, position, position.east(), Blocks.DIRT.defaultBlockState(), 2, 512);
+
+        assertEquals(1, recording.terrainReads);
+        assertEquals(0, recording.mutations);
+        assertEquals(0, recording.blockTicks.count());
+        assertTrue(access.setBlock(position.above(), Blocks.STONE.defaultBlockState(), 2));
+        assertEquals(1, recording.mutations);
+    }
+
+    @Test
+    public void statuslessChunkReadsPreserveWorldgenDelegateSemantics() {
+        RecordingDelegate recording = new RecordingDelegate();
+        NativeStructureWorldgenAccess access = access(recording);
+        ChunkPos generationCenter = generationCenter();
+
+        assertNull(access.getChunk(generationCenter.getWorldPosition()));
+
+        assertEquals(1, recording.statuslessChunkReads);
+        assertEquals(0, recording.statusChunkReads);
+    }
+
+    @Test
+    public void entityQueriesRejectDisjointAreasAndClampOverlaps() {
+        RecordingDelegate recording = new RecordingDelegate();
+        NativeStructureWorldgenAccess access = access(recording);
+        ChunkPos generationCenter = generationCenter();
+        int safeMaxX = generationCenter.getMaxBlockX() + 17;
+        int safeMinZ = generationCenter.getMinBlockZ() - 16;
+        int safeMaxZ = generationCenter.getMaxBlockZ() + 17;
+        AABB disjoint = new AABB(
+                safeMaxX, -64, safeMinZ,
+                safeMaxX + 16, 320, safeMaxZ);
+        AABB overlap = new AABB(
+                safeMaxX - 8, -128, safeMinZ - 8,
+                safeMaxX + 16, 400, safeMaxZ + 8);
+        EntityTypeTest<Entity, Entity> type = EntityTypeTest.forClass(Entity.class);
+
+        assertTrue(access.getEntities((Entity) null, disjoint, entity -> true).isEmpty());
+        assertTrue(access.getEntities(type, disjoint, entity -> true).isEmpty());
+        access.getEntities((Entity) null, overlap, entity -> true);
+        access.getEntities(type, overlap, entity -> true);
+
+        assertEquals(2, recording.entityAreas.size());
+        for (AABB delegatedArea : recording.entityAreas) {
+            assertEquals(safeMaxX - 8, delegatedArea.minX, 0D);
+            assertEquals(-64, delegatedArea.minY, 0D);
+            assertEquals(safeMinZ, delegatedArea.minZ, 0D);
+            assertEquals(safeMaxX, delegatedArea.maxX, 0D);
+            assertEquals(320, delegatedArea.maxY, 0D);
+            assertEquals(safeMaxZ, delegatedArea.maxZ, 0D);
+        }
+    }
+
+    private static NativeStructureWorldgenAccess access(RecordingDelegate recording) {
+        return NativeStructureWorldgenAccess.create(
+                recording.world(), generationCenter(),
+                (x, z) -> SURFACE_FIRST_FREE_Y,
+                (x, z) -> FLOOR_FIRST_FREE_Y,
+                false,
+                position -> false);
+    }
+
+    private static ChunkPos generationCenter() {
+        return new ChunkPos(GENERATION_CENTER_X, GENERATION_CENTER_Z);
+    }
+
+    private static final class RecordingDelegate implements InvocationHandler {
+        private final Holder<Biome> biome;
+        private final BiomeManager biomeManager;
+        private final RecordingTicks<Block> blockTicks;
+        private final RecordingTicks<Fluid> fluidTicks;
+        private final List<AABB> entityAreas;
+        private int terrainReads;
+        private int heightReads;
+        private int chunkReads;
+        private int statuslessChunkReads;
+        private int statusChunkReads;
+        private int mutations;
+        private int events;
+        private boolean rejectDistantTerrainReads;
+
+        private RecordingDelegate() {
+            this.biome = Holder.direct((Biome) null);
+            this.biomeManager = new BiomeManager((x, y, z) -> biome, 13L);
+            this.blockTicks = new RecordingTicks<>();
+            this.fluidTicks = new RecordingTicks<>();
+            this.entityAreas = new ArrayList<>();
+        }
+
+        private WorldGenLevel world() {
+            return (WorldGenLevel) Proxy.newProxyInstance(
+                    WorldGenLevel.class.getClassLoader(),
+                    new Class<?>[]{WorldGenLevel.class}, this);
+        }
+
+        @Override
+        public Object invoke(Object proxy, Method method, Object[] arguments) {
+            String name = method.getName();
+            if (name.equals("getSeaLevel")) {
+                return 63;
+            }
+            if (name.equals("getBiome")) {
+                return biome;
+            }
+            if (name.equals("getBiomeManager")) {
+                return biomeManager;
+            }
+            if (name.equals("getBlockTicks")) {
+                return blockTicks;
+            }
+            if (name.equals("getFluidTicks")) {
+                return fluidTicks;
+            }
+            if (name.equals("getMinY")) {
+                return -64;
+            }
+            if (name.equals("getHeight") && arguments == null) {
+                return 384;
+            }
+            if (name.equals("getHeight")) {
+                if (rejectDistantTerrainReads
+                        && (Math.abs(((int) arguments[1] >> 4) - GENERATION_CENTER_X) > 1
+                        || Math.abs(((int) arguments[2] >> 4) - GENERATION_CENTER_Z) > 1)) {
+                    throw new IllegalStateException("Requested chunk unavailable during world generation");
+                }
+                heightReads++;
+                return 91;
+            }
+            if (name.equals("getBlockState")) {
+                terrainReads++;
+                return Blocks.DIRT.defaultBlockState();
+            }
+            if (name.equals("getFluidState")) {
+                terrainReads++;
+                return Blocks.WATER.defaultBlockState().getFluidState();
+            }
+            if (name.equals("getChunk")) {
+                chunkReads++;
+                if (arguments.length == 2) {
+                    statuslessChunkReads++;
+                } else {
+                    statusChunkReads++;
+                }
+                return null;
+            }
+            if (name.equals("getChunkIfLoadedImmediately")) {
+                chunkReads++;
+                return null;
+            }
+            if (name.equals("getEntities")) {
+                entityAreas.add((AABB) arguments[1]);
+                return List.of();
+            }
+            if (name.equals("ensureCanWrite") || name.equals("setBlock")
+                    || name.equals("removeBlock") || name.equals("destroyBlock")) {
+                mutations++;
+                return true;
+            }
+            if (name.equals("updateNeighborsAt") || name.equals("neighborShapeChanged")) {
+                mutations++;
+                return null;
+            }
+            if (name.equals("levelEvent") || name.equals("gameEvent") || name.equals("addParticle")) {
+                events++;
+                return null;
+            }
+            if (name.equals("hashCode")) {
+                return System.identityHashCode(proxy);
+            }
+            if (name.equals("equals")) {
+                return proxy == arguments[0];
+            }
+            if (name.equals("toString")) {
+                return "native-structure-worldgen-test-delegate";
+            }
+            throw new UnsupportedOperationException(method.toString());
+        }
+    }
+
+    private static final class RecordingTicks<T> implements LevelTickAccess<T> {
+        private int count;
+
+        @Override
+        public void schedule(ScheduledTick<T> tick) {
+            count++;
+        }
+
+        @Override
+        public boolean hasScheduledTick(BlockPos position, T type) {
+            return false;
+        }
+
+        @Override
+        public int count() {
+            return count;
+        }
+
+        @Override
+        public boolean willTickThisTick(BlockPos position, T type) {
+            return false;
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NmsChunkIOFlushTest.java

@@ -0,0 +1,101 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainAccessImpl;
+import ca.spottedleaf.moonrise.patches.chunk_system.io.MoonriseRegionFileIO.RegionDataController;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NmsChunkIOFlushTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void nativeDrainCanWaitOffOwnerUntilChunkPoiAndEntityIoFinish() throws Exception {
+        Fixture fixture = new Fixture();
+        AtomicBoolean chunkPending = new AtomicBoolean(true);
+        AtomicBoolean poiPending = new AtomicBoolean(true);
+        AtomicBoolean entityPending = new AtomicBoolean(true);
+        CountDownLatch chunkDrain = new CountDownLatch(1);
+        CountDownLatch poiDrain = new CountDownLatch(1);
+        CountDownLatch entityDrain = new CountDownLatch(1);
+        when(fixture.chunks.hasTasks()).thenAnswer(invocation -> {
+            chunkDrain.countDown();
+            return chunkPending.get();
+        });
+        when(fixture.pois.hasTasks()).thenAnswer(invocation -> {
+            poiDrain.countDown();
+            return poiPending.get();
+        });
+        when(fixture.entities.hasTasks()).thenAnswer(invocation -> {
+            entityDrain.countDown();
+            return entityPending.get();
+        });
+        ExecutorService io = Executors.newSingleThreadExecutor();
+        try {
+            Future<?> drain = io.submit(() -> fixture.binding.flushChunkIO(fixture.world));
+            assertTrue(chunkDrain.await(5L, TimeUnit.SECONDS));
+            assertFalse(drain.isDone());
+            chunkPending.set(false);
+            assertTrue(poiDrain.await(5L, TimeUnit.SECONDS));
+            assertFalse(drain.isDone());
+            poiPending.set(false);
+            assertTrue(entityDrain.await(5L, TimeUnit.SECONDS));
+            assertFalse(drain.isDone());
+            entityPending.set(false);
+            drain.get(5L, TimeUnit.SECONDS);
+        } finally {
+            chunkPending.set(false);
+            poiPending.set(false);
+            entityPending.set(false);
+            io.shutdownNow();
+            assertTrue(io.awaitTermination(5L, TimeUnit.SECONDS));
+        }
+    }
+
+    @Test
+    public void nativeDrainFailurePropagatesToItsCompletionReceipt() {
+        Fixture fixture = new Fixture();
+        IllegalStateException failure = new IllegalStateException("native IO failed");
+        when(fixture.chunks.hasTasks()).thenThrow(failure);
+        assertSame(failure, assertThrows(IllegalStateException.class,
+                () -> fixture.binding.flushChunkIO(fixture.world)));
+    }
+
+    private static final class Fixture {
+        private final NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        private final CraftWorld world = mock(CraftWorld.class);
+        private final ServerLevel level = mock(ServerLevel.class);
+        private final RegionDataController chunks = mock(RegionDataController.class);
+        private final RegionDataController pois = mock(RegionDataController.class);
+        private final RegionDataController entities = mock(RegionDataController.class);
+
+        private Fixture() {
+            when(world.getHandle()).thenReturn(level);
+            when(level.moonrise$getChunkDataController()).thenReturn(chunks);
+            when(level.moonrise$getPoiChunkDataController()).thenReturn(pois);
+            when(level.moonrise$getEntityChunkDataController()).thenReturn(entities);
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NmsChunkRetentionTest.java

@@ -0,0 +1,84 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainAccessImpl;
+import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkHolderManager;
+import ca.spottedleaf.moonrise.patches.chunk_system.scheduling.ChunkTaskScheduler;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ChunkLevel;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.TicketType;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import java.lang.reflect.Field;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.isNull;
+import static org.mockito.ArgumentMatchers.same;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class NmsChunkRetentionTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void retentionRequestsNothingBeyondTheOuterRingOfAFullRequest() {
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        assertEquals(ChunkLevel.RADIUS_AROUND_FULL_CHUNK, binding.fullChunkDependencyRadius());
+        assertEquals(ChunkLevel.MAX_LEVEL, ChunkHolderManager.MAX_TICKET_LEVEL);
+        assertEquals(ChunkLevel.generationStatus(ChunkLevel.FULL_CHUNK_LEVEL + binding.fullChunkDependencyRadius()),
+                ChunkLevel.generationStatus(ChunkHolderManager.MAX_TICKET_LEVEL));
+        assertEquals(ChunkStatus.STRUCTURE_STARTS, ChunkLevel.generationStatus(ChunkHolderManager.MAX_TICKET_LEVEL));
+    }
+
+    @Test
+    public void retainAndReleaseUseOnePermanentNonPersistentTicketAtTheMaximumLevel() throws Exception {
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        CraftWorld world = mock(CraftWorld.class);
+        ServerLevel level = mock(ServerLevel.class);
+        ChunkTaskScheduler scheduler = mock(ChunkTaskScheduler.class);
+        ChunkHolderManager manager = mock(ChunkHolderManager.class);
+        Field managerField = ChunkTaskScheduler.class.getField("chunkHolderManager");
+        managerField.setAccessible(true);
+        managerField.set(scheduler, manager);
+        when(world.getHandle()).thenReturn(level);
+        when(level.moonrise$getChunkTaskScheduler()).thenReturn(scheduler);
+        when(manager.addTicketAtLevel(any(TicketType.class), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull()))
+                .thenReturn(true);
+        when(manager.removeTicketAtLevel(any(TicketType.class), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull()))
+                .thenReturn(true);
+
+        assertTrue(binding.retainChunk(world, 3, -4));
+        ArgumentCaptor<TicketType> type = ArgumentCaptor.forClass(TicketType.class);
+        verify(manager).addTicketAtLevel(type.capture(), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull());
+        assertEquals(TicketType.NO_TIMEOUT, type.getValue().timeout());
+        assertTrue(type.getValue().doesLoad());
+        assertFalse(type.getValue().doesSimulate());
+        assertFalse(type.getValue().persist());
+
+        assertTrue(binding.releaseChunk(world, 3, -4));
+        verify(manager).removeTicketAtLevel(same(type.getValue()), eq(3), eq(-4), eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull());
+
+        binding.retainChunk(world, 3, -4);
+        ArgumentCaptor<TicketType> again = ArgumentCaptor.forClass(TicketType.class);
+        verify(manager, times(2)).addTicketAtLevel(again.capture(), eq(3), eq(-4),
+                eq(ChunkHolderManager.MAX_TICKET_LEVEL), isNull());
+        assertSame(type.getValue(), again.getValue());
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NmsChunkTaskPollingTest.java

@@ -0,0 +1,96 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainAccessImpl;
+import art.arcane.volmlib.util.scheduling.FoliaScheduler;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerChunkCache;
+import net.minecraft.server.level.ServerLevel;
+import org.bukkit.Bukkit;
+import org.bukkit.Server;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.concurrent.CompletableFuture;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
+
+public class NmsChunkTaskPollingTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void serverOwnerPumpsOnlyTheTargetWorldQueue() {
+        Server bukkitServer = mock(Server.class);
+        CraftWorld world = mock(CraftWorld.class);
+        ServerLevel level = mock(ServerLevel.class);
+        MinecraftServer server = mock(MinecraftServer.class);
+        ServerChunkCache chunks = mock(ServerChunkCache.class);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        CompletableFuture<Void> completed = new CompletableFuture<>();
+        when(world.getHandle()).thenReturn(level);
+        when(level.getServer()).thenReturn(server);
+        when(server.getRunningThread()).thenReturn(Thread.currentThread());
+        when(level.getChunkSource()).thenReturn(chunks);
+        when(chunks.pollTask()).thenAnswer(invocation -> completed.complete(null)).thenReturn(false);
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+             MockedStatic<FoliaScheduler> folia = mockStatic(FoliaScheduler.class)) {
+            bukkit.when(Bukkit::getServer).thenReturn(bukkitServer);
+            folia.when(() -> FoliaScheduler.isRegionizedRuntime(bukkitServer)).thenReturn(false);
+            assertTrue(binding.pollChunkTask(world));
+            assertTrue(completed.isDone());
+            assertFalse(binding.pollChunkTask(world));
+        }
+        verify(chunks, times(2)).pollTask();
+        verify(server, never()).executeAllRecentInternalTasks();
+    }
+
+    @Test
+    public void nonOwnerIsRejectedBeforeAccessingTheChunkQueue() {
+        Server bukkitServer = mock(Server.class);
+        CraftWorld world = mock(CraftWorld.class);
+        ServerLevel level = mock(ServerLevel.class);
+        MinecraftServer server = mock(MinecraftServer.class);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        when(world.getHandle()).thenReturn(level);
+        when(level.getServer()).thenReturn(server);
+        when(server.getRunningThread()).thenReturn(new Thread("Other server owner"));
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+             MockedStatic<FoliaScheduler> folia = mockStatic(FoliaScheduler.class)) {
+            bukkit.when(Bukkit::getServer).thenReturn(bukkitServer);
+            folia.when(() -> FoliaScheduler.isRegionizedRuntime(bukkitServer)).thenReturn(false);
+            assertThrows(IllegalStateException.class, () -> binding.pollChunkTask(world));
+        }
+        verify(level, never()).getChunkSource();
+    }
+
+    @Test
+    public void foliaNeverUsesTheWorldWideTaskPump() {
+        Server bukkitServer = mock(Server.class);
+        CraftWorld world = mock(CraftWorld.class);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+             MockedStatic<FoliaScheduler> folia = mockStatic(FoliaScheduler.class)) {
+            bukkit.when(Bukkit::getServer).thenReturn(bukkitServer);
+            folia.when(() -> FoliaScheduler.isRegionizedRuntime(bukkitServer)).thenReturn(true);
+            assertFalse(binding.pollChunkTask(world));
+        }
+        verifyNoInteractions(world);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/NmsEntitySpawnDifficultyTest.java

@@ -0,0 +1,104 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainAccessImpl;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.Bootstrap;
+import org.bukkit.Difficulty;
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.EntityType;
+import org.bukkit.event.entity.CreatureSpawnEvent;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.isNull;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class NmsEntitySpawnDifficultyTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void peacefulRejectsEveryNativeForbiddenTypeBeforeBukkitCreatesIt() {
+        CraftWorld world = mock(CraftWorld.class);
+        when(world.getDifficulty()).thenReturn(Difficulty.PEACEFUL);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        Location location = new Location(world, 0.5, 80, 0.5);
+        int rejected = 0;
+
+        for (EntityType type : EntityType.values()) {
+            if (type.getEntityClass() == null) {
+                continue;
+            }
+            if (BuiltInRegistries.ENTITY_TYPE.getValue(Identifier.parse(type.getKey().toString())).isAllowedInPeaceful()) {
+                continue;
+            }
+            assertNull(type.name(), binding.spawnEntity(location, type, CreatureSpawnEvent.SpawnReason.NATURAL));
+            rejected++;
+        }
+
+        assertTrue(rejected > 20);
+        verify(world, never()).spawn(any(Location.class), any(Class.class), isNull(), any(CreatureSpawnEvent.SpawnReason.class));
+    }
+
+    @Test
+    public void peacefulPreservesPassiveAndNativeMonsterCategoryExceptions() {
+        CraftWorld world = mock(CraftWorld.class);
+        when(world.getDifficulty()).thenReturn(Difficulty.PEACEFUL);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        Location location = new Location(world, 0.5, 80, 0.5);
+        Entity created = mock(Entity.class);
+        doReturn(created).when(world).spawn(eq(location), any(Class.class), isNull(), eq(CreatureSpawnEvent.SpawnReason.NATURAL));
+
+        for (EntityType type : List.of(EntityType.COW, EntityType.VILLAGER, EntityType.WOLF, EntityType.PIGLIN, EntityType.SHULKER)) {
+            assertSame(type.name(), created, binding.spawnEntity(location, type, CreatureSpawnEvent.SpawnReason.NATURAL));
+        }
+    }
+
+    @Test
+    public void nonPeacefulDifficultiesPreserveHostileSpawns() {
+        CraftWorld world = mock(CraftWorld.class);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        Location location = new Location(world, 0.5, 80, 0.5);
+        Entity created = mock(Entity.class);
+        doReturn(created).when(world).spawn(eq(location), any(Class.class), isNull(), eq(CreatureSpawnEvent.SpawnReason.NATURAL));
+
+        for (Difficulty difficulty : List.of(Difficulty.EASY, Difficulty.NORMAL, Difficulty.HARD)) {
+            when(world.getDifficulty()).thenReturn(difficulty);
+            assertSame(created, binding.spawnEntity(location, EntityType.ZOMBIE, CreatureSpawnEvent.SpawnReason.NATURAL));
+        }
+    }
+
+    @Test
+    public void unrelatedBukkitSpawnFailuresStillPropagate() {
+        CraftWorld world = mock(CraftWorld.class);
+        when(world.getDifficulty()).thenReturn(Difficulty.PEACEFUL);
+        NativeTerrainAccessImpl binding = mock(NativeTerrainAccessImpl.class, CALLS_REAL_METHODS);
+        Location location = new Location(world, 0.5, 80, 0.5);
+        IllegalStateException failure = new IllegalStateException("Spawn rejected by platform");
+        doThrow(failure).when(world).spawn(eq(location), any(Class.class), isNull(), eq(CreatureSpawnEvent.SpawnReason.NATURAL));
+
+        assertSame(failure, assertThrows(IllegalStateException.class,
+                () -> binding.spawnEntity(location, EntityType.COW, CreatureSpawnEvent.SpawnReason.NATURAL)));
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/platform/bukkit/nms/v26_3_R1/WorldgenTerrainHeightmapsTest.java

@@ -0,0 +1,353 @@
+package art.arcane.iris.platform.bukkit.nms.v26_3_R1;
+
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeTerrainPipeline;
+
+import art.arcane.iris.nativegen.v26_3_R1.NativeBlockTags;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.WorldgenTerrainHeightmaps;
+import com.mojang.serialization.Codec;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.IdMapper;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.PalettedContainer;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.Strategy;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.structures.IglooPieces;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutPiece;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutStructure;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Proxy;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.IntBinaryOperator;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class WorldgenTerrainHeightmapsTest {
+    private static final int MIN_Y = -64;
+    private static final int HEIGHT = 384;
+    private static final int LAND_TERRAIN_TOP = 70;
+    private static final int LAND_CANOPY_TOP = 80;
+    private static final int OCEAN_FLOOR_TOP = 60;
+    private static final int OCEAN_FLUID_TOP = 64;
+    private static final int LAND_X = 3;
+    private static final int LAND_Z = 5;
+    private static final int OCEAN_X = 8;
+    private static final int OCEAN_Z = 8;
+    private static final int TERRAIN_SLAB_DEPTH = 4;
+
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        NativeBlockTags.bindHeightmapFixtures();
+    }
+
+    @AfterClass
+    public static void restoreBlockTags() {
+        NativeBlockTags.restoreTags();
+    }
+
+    @Test
+    public void authoringHeightmapsReadPlacedObjectsAndFluidsWithoutTerrainResolvers() {
+        ProtoChunk chunk = terrainChunk(new ChunkPos(0, 0));
+
+        NativeTerrainPipeline.primeAuthoringHeightmaps(chunk);
+
+        assertEquals(LAND_CANOPY_TOP, chunk.getHeight(Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+        assertEquals(LAND_CANOPY_TOP, chunk.getHeight(Heightmap.Types.OCEAN_FLOOR_WG, LAND_X, LAND_Z));
+        assertEquals(LAND_CANOPY_TOP, chunk.getHeight(Heightmap.Types.MOTION_BLOCKING, LAND_X, LAND_Z));
+        assertEquals(LAND_TERRAIN_TOP + 6,
+                chunk.getHeight(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, LAND_X, LAND_Z));
+        assertEquals(OCEAN_FLUID_TOP, chunk.getHeight(Heightmap.Types.WORLD_SURFACE_WG, OCEAN_X, OCEAN_Z));
+        assertEquals(OCEAN_FLOOR_TOP, chunk.getHeight(Heightmap.Types.OCEAN_FLOOR_WG, OCEAN_X, OCEAN_Z));
+    }
+
+    @Test
+    public void primeTerrainWritesEngineSurfaceAndOceanFloorHeights() {
+        ProtoChunk chunk = terrainChunk(new ChunkPos(0, 0));
+
+        assertFalse(chunk.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+        assertFalse(chunk.hasPrimedHeightmap(Heightmap.Types.OCEAN_FLOOR_WG));
+
+        WorldgenTerrainHeightmaps.primeTerrain(chunk, surfaceFirstFreeY(), floorFirstFreeY());
+
+        assertTrue(chunk.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+        assertTrue(chunk.hasPrimedHeightmap(Heightmap.Types.OCEAN_FLOOR_WG));
+        assertEquals(LAND_TERRAIN_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+        assertEquals(LAND_TERRAIN_TOP, chunk.getHeight(
+                Heightmap.Types.OCEAN_FLOOR_WG, LAND_X, LAND_Z));
+        assertEquals(OCEAN_FLUID_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, OCEAN_X, OCEAN_Z));
+        assertEquals(OCEAN_FLOOR_TOP, chunk.getHeight(
+                Heightmap.Types.OCEAN_FLOOR_WG, OCEAN_X, OCEAN_Z));
+    }
+
+    @Test
+    public void finalHeightmapPrimingDoesNotClobberTheWorldgenHeightmaps() {
+        ProtoChunk chunk = terrainChunk(new ChunkPos(0, 0));
+
+        WorldgenTerrainHeightmaps.primeTerrain(chunk, surfaceFirstFreeY(), floorFirstFreeY());
+        Heightmap.primeHeightmaps(chunk, ChunkStatus.FINAL_HEIGHTMAPS);
+
+        assertEquals(LAND_TERRAIN_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+        assertEquals(LAND_TERRAIN_TOP, chunk.getHeight(
+                Heightmap.Types.OCEAN_FLOOR_WG, LAND_X, LAND_Z));
+        assertEquals(LAND_CANOPY_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE, LAND_X, LAND_Z));
+    }
+
+    @Test
+    public void unprimedWorldgenHeightmapResolvesTheIrisCanopyInstead() {
+        ProtoChunk chunk = terrainChunk(new ChunkPos(0, 0));
+
+        assertEquals(LAND_CANOPY_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+    }
+
+    @Test
+    public void primeTerrainOverwritesAnAlreadyLazyPrimedCanopyHeight() {
+        ProtoChunk chunk = terrainChunk(new ChunkPos(0, 0));
+
+        assertEquals(LAND_CANOPY_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+        WorldgenTerrainHeightmaps.primeTerrain(chunk, surfaceFirstFreeY(), floorFirstFreeY());
+
+        assertEquals(LAND_TERRAIN_TOP, chunk.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+    }
+
+    @Test
+    public void structurePlacementPrimesTheWestNeighbourAnIglooEntranceReads() {
+        Map<Long, ChunkAccess> chunks = new HashMap<>();
+        chunks.put(ChunkPos.pack(0, 0), terrainChunk(new ChunkPos(0, 0)));
+        chunks.put(ChunkPos.pack(-1, 0), terrainChunk(new ChunkPos(-1, 0)));
+        WorldGenLevel world = world(chunks);
+        StructureStart start = startInOrigin();
+
+        int canopySnap = IglooPieces.GENERATION_HEIGHT + iglooSnapOffset(world);
+        WorldgenTerrainHeightmaps.primeStructurePlacement(
+                world, new ChunkPos(0, 0), List.of(start), surfaceFirstFreeY(), floorFirstFreeY());
+        int terrainSnap = IglooPieces.GENERATION_HEIGHT + iglooSnapOffset(world);
+
+        assertEquals(LAND_TERRAIN_TOP + 1, world.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, -2, 5));
+        assertEquals(LAND_TERRAIN_TOP, terrainSnap);
+        assertEquals(LAND_CANOPY_TOP, canopySnap);
+        assertEquals(LAND_CANOPY_TOP - LAND_TERRAIN_TOP, canopySnap - terrainSnap);
+    }
+
+    @Test
+    public void structurePlacementPrimesEveryChunkTheStartFootprintTouches() {
+        Map<Long, ChunkAccess> chunks = new HashMap<>();
+        for (int chunkX = -1; chunkX <= 1; chunkX++) {
+            for (int chunkZ = -1; chunkZ <= 1; chunkZ++) {
+                chunks.put(ChunkPos.pack(chunkX, chunkZ), terrainChunk(new ChunkPos(chunkX, chunkZ)));
+            }
+        }
+        WorldGenLevel world = world(chunks);
+
+        WorldgenTerrainHeightmaps.primeStructurePlacement(
+                world, new ChunkPos(0, 0), List.of(startInOrigin()),
+                surfaceFirstFreeY(), floorFirstFreeY());
+
+        for (ChunkAccess chunk : chunks.values()) {
+            assertTrue(chunk.getPos().toString(),
+                    chunk.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+            assertTrue(chunk.getPos().toString(),
+                    chunk.hasPrimedHeightmap(Heightmap.Types.OCEAN_FLOOR_WG));
+            assertEquals(LAND_TERRAIN_TOP, chunk.getHeight(
+                    Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+        }
+    }
+
+    @Test
+    public void structurePlacementDoesNotPrimeALoadedDistanceTwoChunk() {
+        Map<Long, ChunkAccess> chunks = new HashMap<>();
+        ProtoChunk origin = terrainChunk(new ChunkPos(0, 0));
+        ProtoChunk neighbour = terrainChunk(new ChunkPos(1, 0));
+        ProtoChunk distanceTwo = terrainChunk(new ChunkPos(2, 0));
+        chunks.put(ChunkPos.pack(0, 0), origin);
+        chunks.put(ChunkPos.pack(1, 0), neighbour);
+        chunks.put(ChunkPos.pack(2, 0), distanceTwo);
+        WorldGenLevel world = world(chunks);
+        StructureStart shifted = startInOrigin();
+        shifted.getPieces().forEach(piece -> piece.move(16, 0, 0));
+
+        WorldgenTerrainHeightmaps.primeStructurePlacement(
+                world, new ChunkPos(0, 0), List.of(shifted),
+                surfaceFirstFreeY(), floorFirstFreeY());
+
+        assertTrue(origin.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+        assertTrue(neighbour.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+        assertFalse(distanceTwo.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+    }
+
+    @Test
+    public void structurePlacementSkipsChunksOutsideTheGenerationRegion() {
+        Map<Long, ChunkAccess> chunks = new HashMap<>();
+        ProtoChunk origin = terrainChunk(new ChunkPos(0, 0));
+        chunks.put(ChunkPos.pack(0, 0), origin);
+        WorldGenLevel world = world(chunks);
+
+        WorldgenTerrainHeightmaps.primeStructurePlacement(
+                world, new ChunkPos(0, 0), List.of(startInOrigin()),
+                surfaceFirstFreeY(), floorFirstFreeY());
+
+        assertTrue(origin.hasPrimedHeightmap(Heightmap.Types.WORLD_SURFACE_WG));
+        assertEquals(LAND_TERRAIN_TOP, origin.getHeight(
+                Heightmap.Types.WORLD_SURFACE_WG, LAND_X, LAND_Z));
+    }
+
+    private static int iglooSnapOffset(WorldGenLevel world) {
+        return world.getHeight(Heightmap.Types.WORLD_SURFACE_WG, -2, 5)
+                - IglooPieces.GENERATION_HEIGHT - 1;
+    }
+
+    private static StructureStart startInOrigin() {
+        Structure structure = new SwampHutStructure(new Structure.StructureSettings(HolderSet.empty()));
+        SwampHutPiece piece = new SwampHutPiece(RandomSource.create(13L), 0, 0);
+        return new StructureStart(
+                structure, new ChunkPos(0, 0), 0, new PiecesContainer(List.of(piece)));
+    }
+
+    private static IntBinaryOperator surfaceFirstFreeY() {
+        return (x, z) -> isOcean(x, z) ? OCEAN_FLUID_TOP + 1 : LAND_TERRAIN_TOP + 1;
+    }
+
+    private static IntBinaryOperator floorFirstFreeY() {
+        return (x, z) -> isOcean(x, z) ? OCEAN_FLOOR_TOP + 1 : LAND_TERRAIN_TOP + 1;
+    }
+
+    private static boolean isOcean(int x, int z) {
+        return Math.floorMod(x, 16) == OCEAN_X && Math.floorMod(z, 16) == OCEAN_Z;
+    }
+
+    private static ProtoChunk terrainChunk(ChunkPos pos) {
+        ProtoChunk chunk = new ProtoChunk(
+                pos, UpgradeData.EMPTY, LevelHeightAccessor.create(MIN_Y, HEIGHT),
+                containerFactory(), null);
+        for (int x = 0; x < 16; x++) {
+            for (int z = 0; z < 16; z++) {
+                boolean ocean = isOcean(pos.getMinBlockX() + x, pos.getMinBlockZ() + z);
+                int stoneTop = ocean ? OCEAN_FLOOR_TOP : LAND_TERRAIN_TOP;
+                for (int y = stoneTop - TERRAIN_SLAB_DEPTH; y <= stoneTop; y++) {
+                    write(chunk, x, y, z, Blocks.STONE.defaultBlockState());
+                }
+                if (ocean) {
+                    for (int y = OCEAN_FLOOR_TOP + 1; y <= OCEAN_FLUID_TOP; y++) {
+                        write(chunk, x, y, z, Blocks.WATER.defaultBlockState());
+                    }
+                    continue;
+                }
+                for (int y = LAND_TERRAIN_TOP + 1; y <= LAND_TERRAIN_TOP + 6; y++) {
+                    write(chunk, x, y, z, Blocks.SPRUCE_LOG.defaultBlockState());
+                }
+                for (int y = LAND_TERRAIN_TOP + 7; y <= LAND_CANOPY_TOP; y++) {
+                    write(chunk, x, y, z, Blocks.SPRUCE_LEAVES.defaultBlockState());
+                }
+            }
+        }
+        return chunk;
+    }
+
+    private static void write(ProtoChunk chunk, int x, int y, int z, BlockState state) {
+        LevelChunkSection section = chunk.getSection(chunk.getSectionIndex(y));
+        section.setBlockState(x, y & 15, z, state, false);
+    }
+
+    private static PalettedContainerFactory containerFactory() {
+        Strategy<BlockState> blockStates = Strategy.createForBlockStates(Block.BLOCK_STATE_REGISTRY);
+        BlockState air = Blocks.AIR.defaultBlockState();
+        IdMapper<Holder<Biome>> biomeIds = new IdMapper<>();
+        Holder<Biome> defaultBiome = Holder.direct((Biome) null);
+        biomeIds.add(defaultBiome);
+        Strategy<Holder<Biome>> biomes = Strategy.createForBiomes(biomeIds);
+        Codec<Holder<Biome>> biomeCodec = Codec.STRING.xmap(
+                name -> defaultBiome, holder -> "iris-test-biome");
+        return new PalettedContainerFactory(
+                blockStates,
+                air,
+                PalettedContainer.codecRW(BlockState.CODEC, blockStates, air),
+                biomes,
+                defaultBiome,
+                PalettedContainer.codecRO(biomeCodec, biomes, defaultBiome),
+                PalettedContainer.codecRW(biomeCodec, biomes, defaultBiome));
+    }
+
+    private static WorldGenLevel world(Map<Long, ChunkAccess> chunks) {
+        InvocationHandler handler = (proxy, method, arguments) -> {
+            String methodName = method.getName();
+            if (methodName.equals("hasChunk")) {
+                return chunks.containsKey(ChunkPos.pack((int) arguments[0], (int) arguments[1]));
+            }
+            if (methodName.equals("getChunk") && arguments.length == 2) {
+                ChunkAccess chunk = chunks.get(ChunkPos.pack((int) arguments[0], (int) arguments[1]));
+                if (chunk == null) {
+                    throw new AssertionError("Heightmap priming requested an unavailable chunk "
+                            + arguments[0] + "," + arguments[1]);
+                }
+                return chunk;
+            }
+            if (methodName.equals("getHeight") && arguments.length == 3) {
+                Heightmap.Types type = (Heightmap.Types) arguments[0];
+                int x = (int) arguments[1];
+                int z = (int) arguments[2];
+                ChunkAccess chunk = chunks.get(ChunkPos.pack(x >> 4, z >> 4));
+                if (chunk == null) {
+                    throw new AssertionError("Heightmap read requested an unavailable chunk at "
+                            + x + "," + z);
+                }
+                return chunk.getHeight(type, x & 15, z & 15) + 1;
+            }
+            if (methodName.equals("getBlockState")) {
+                BlockPos position = (BlockPos) arguments[0];
+                ChunkAccess chunk = chunks.get(ChunkPos.pack(position.getX() >> 4, position.getZ() >> 4));
+                if (chunk == null) {
+                    throw new AssertionError("Block read requested an unavailable chunk at " + position);
+                }
+                return chunk.getBlockState(position);
+            }
+            if (methodName.equals("hashCode")) {
+                return System.identityHashCode(proxy);
+            }
+            if (methodName.equals("equals")) {
+                return proxy == arguments[0];
+            }
+            if (methodName.equals("toString")) {
+                return "worldgen-heightmap-test-world";
+            }
+            throw new UnsupportedOperationException(method.toString());
+        };
+        return (WorldGenLevel) Proxy.newProxyInstance(
+                WorldGenLevel.class.getClassLoader(), new Class<?>[]{WorldGenLevel.class}, handler);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/BareMobSpawnHistoryTest.java

@@ -0,0 +1,160 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.biome.IrisBiomeCustom;
+import art.arcane.iris.generation.biome.IrisBiomeCustomSpawn;
+import art.arcane.iris.generation.biome.IrisBiomeCustomSpawnType;
+import art.arcane.iris.pack.datapack.v263.DataFixerV263;
+import art.arcane.iris.spi.PlatformGenerationRegistry;
+import art.arcane.iris.world.history.GenerationRegistryContract;
+import art.arcane.iris.world.history.GenerationRegistryContractFactory;
+import art.arcane.volmlib.util.collection.KList;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import org.bukkit.Bukkit;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+
+public final class BareMobSpawnHistoryTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final String LEGACY_RENDERER_IDENTITY = "bukkit-v26_3_R1-generated-registry-json-v1";
+    private static final String NATURAL_MOB_SPAWNS = "minecraft:gameplay/natural_mob_spawns";
+    private static final GenerationRegistryContract.PhysicalResourceKey INSTALLED =
+            new GenerationRegistryContract.PhysicalResourceKey(
+                    GenerationRegistryContractFactory.BIOME_REGISTRY,
+                    "iris:biomes/" + "c".repeat(64)
+            );
+    private static HeadlessNativeRegistries loaded;
+    private static PlatformGenerationRegistry registry;
+
+    @BeforeClass
+    public static void installOverlayRendering() throws IOException {
+        assertNull(Bukkit.getServer());
+        loaded = HeadlessNativeRegistries.load(Map.of(
+                "data/iris/worldgen/biome/biomes/" + "c".repeat(64) + ".json",
+                spawningBiome().generateJson(new DataFixerV263())
+        ));
+        registry = new HeadlessNativePlatform(new File("unused-native-platform"), loaded::registries)
+                .generationRegistry();
+    }
+
+    @AfterClass
+    public static void closeRegistries() throws IOException {
+        if (loaded != null) {
+            loaded.close();
+        }
+    }
+
+    @Test
+    public void bareMobSpawnHistoryValidatesAgainstTheInstalledOverlayRendering() throws IOException {
+        GenerationRegistryContract legacy = legacyContract(INSTALLED, spawningBiome());
+        GenerationRegistryContract.GeneratedSource source = legacy.generatedSources().get(INSTALLED);
+        assertEquals(GenerationRegistryContract.FINGERPRINT_SCHEMA_VERSION_ONE, legacy.fingerprintSchema());
+        assertEquals(LEGACY_RENDERER_IDENTITY, source.rendererIdentity());
+        assertNotEquals(
+                JsonParser.parseString(source.sourceJson()),
+                JsonParser.parseString(registry.generatedDefinition(
+                        INSTALLED.registryKey(),
+                        INSTALLED.resourceKey()
+                ).value())
+        );
+
+        GenerationRegistryContract available = GenerationRegistryContractFactory.captureRequiredDefinitions(
+                Set.of(legacy),
+                new DataFixerV263(),
+                registry
+        );
+
+        legacy.requireDefinitionsAvailableIn(available);
+    }
+
+    @Test
+    public void bareMobSpawnHistoryStillRejectsDifferentSemantics() throws IOException {
+        GenerationRegistryContract changed = legacyContract(INSTALLED, spawningBiome().setTemperature(0.2D));
+
+        IOException failure = assertThrows(IOException.class,
+                () -> GenerationRegistryContractFactory.captureRequiredDefinitions(
+                        Set.of(changed),
+                        new DataFixerV263(),
+                        registry
+                ));
+
+        assertEquals("Historical generated registry definition changed for minecraft:worldgen/biome / "
+                + INSTALLED.resourceKey() + ".", failure.getMessage());
+    }
+
+    @Test
+    public void bareMobSpawnHistoryStillRejectsAMissingDefinition() throws IOException {
+        GenerationRegistryContract missing = legacyContract(new GenerationRegistryContract.PhysicalResourceKey(
+                GenerationRegistryContractFactory.BIOME_REGISTRY,
+                "iris:biomes/" + "d".repeat(64)
+        ), spawningBiome());
+
+        assertThrows(IOException.class, () -> GenerationRegistryContractFactory.captureRequiredDefinitions(
+                Set.of(missing),
+                new DataFixerV263(),
+                registry
+        ));
+    }
+
+    private static GenerationRegistryContract legacyContract(
+            GenerationRegistryContract.PhysicalResourceKey key,
+            IrisBiomeCustom biome
+    ) {
+        JsonObject rendered = JsonParser.parseString(biome.generateJson(new DataFixerV263())).getAsJsonObject();
+        JsonObject attributes = rendered.getAsJsonObject("attributes");
+        attributes.add(NATURAL_MOB_SPAWNS, attributes.getAsJsonObject(NATURAL_MOB_SPAWNS).get("argument"));
+        String captured = registry.canonicalDefinition(key.registryKey(), key.resourceKey(), rendered.toString())
+                .value();
+        String semantic = GenerationRegistryContractFactory.customBiomeEffectiveSemanticJson(biome, null);
+        GenerationRegistryContract.GeneratedSource source = new GenerationRegistryContract.GeneratedSource(
+                GenerationRegistryContractFactory.CUSTOM_BIOME_EFFECTIVE_SOURCE_SCHEMA,
+                GenerationRegistryContractFactory.fingerprintCustomBiomeAuthoredDefinition(semantic),
+                semantic,
+                LEGACY_RENDERER_IDENTITY,
+                GenerationRegistryContractFactory.fingerprintDefinition(
+                        key,
+                        PlatformGenerationRegistry.Definition.exactJson(captured),
+                        "generated"
+                ),
+                captured
+        );
+        return GenerationRegistryContract.fromDefinitionsAndGeneratedSources(
+                Map.of(key, GenerationRegistryContractFactory.fingerprintGeneratedSemantic(key, source)),
+                Map.of(key, source)
+        );
+    }
+
+    private static IrisBiomeCustom spawningBiome() {
+        return new IrisBiomeCustom()
+                .setId("tester")
+                .setSpawnRarity(2)
+                .setSpawns(new KList<>(
+                        new IrisBiomeCustomSpawn()
+                                .setType("minecraft:zombie")
+                                .setGroup(IrisBiomeCustomSpawnType.MONSTER)
+                                .setMinCount(2)
+                                .setMaxCount(4)
+                                .setWeight(7),
+                        new IrisBiomeCustomSpawn()
+                                .setType("minecraft:cow")
+                                .setGroup(IrisBiomeCustomSpawnType.CREATURE)
+                                .setMinCount(3)
+                                .setMaxCount(3)
+                                .setWeight(5)
+                ));
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/DetachedNativeTerrain.java

@@ -0,0 +1,235 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.probe.NativeRegionPlan.PlannedChunk;
+
+import net.minecraft.nbt.CompoundTag;
+import org.bukkit.NamespacedKey;
+import org.bukkit.persistence.PersistentDataType;
+import net.minecraft.server.level.ChunkMap;
+import net.minecraft.server.level.GenerationChunkHolder;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.StaticCache2D;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.status.ChunkPyramid;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.status.ChunkStep;
+import net.minecraft.world.level.chunk.status.WorldGenContext;
+import net.minecraft.world.level.chunk.storage.RegionFile;
+import net.minecraft.world.level.chunk.storage.RegionStorageInfo;
+import net.minecraft.world.level.chunk.storage.SerializableChunkData;
+
+import java.io.IOException;
+import java.lang.reflect.Field;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.HexFormat;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Consumer;
+import java.util.concurrent.atomic.AtomicInteger;
+
+final class DetachedNativeTerrain {
+    private static final NamespacedKey NATURAL_TERRAIN = new NamespacedKey("iris", "natural_terrain");
+
+    private DetachedNativeTerrain() {
+    }
+
+    static Result generate(Request request, Consumer<String> progress) throws Exception {
+        List<PlannedChunk> plan = NativeRegionPlan.plan(request.chunkX(), request.chunkZ(), request.width());
+        Path output = Files.createDirectory(request.output());
+        WorldGenContext context = context(request.level().getChunkSource().chunkMap);
+        Map<Long, DetachedHolder> holders = new HashMap<>(plan.size());
+        for (PlannedChunk planned : plan) {
+            ChunkPos position = new ChunkPos(planned.x(), planned.z());
+            holders.put(position.pack(), new DetachedHolder(new ProtoChunk(position, UpgradeData.EMPTY,
+                    request.level(), request.level().palettedContainerFactory(), null)));
+        }
+        long started = System.nanoTime();
+        try (RegionGenerationWindow workers = new RegionGenerationWindow(request.parallelism(), RegionGenerationWindow.Policy.EMBEDDED)) {
+            for (ChunkStatus status : ChunkStatus.getStatusList()) {
+                if (status == ChunkStatus.EMPTY) {
+                    continue;
+                }
+                if (status.isAfter(ChunkStatus.TERRAIN)) {
+                    break;
+                }
+                ChunkStep step = ChunkPyramid.GENERATION_PYRAMID.getStepTo(status);
+                executeStage(new Stage(context, step, plan, holders, request.parallelism()), workers, progress);
+            }
+        }
+        long serializationStarted = System.nanoTime();
+        write(request.level(), output, plan, holders);
+        progress.accept("stage=native_serialization seconds=" + (System.nanoTime() - serializationStarted) / 1_000_000_000.0);
+        double seconds = (System.nanoTime() - started) / 1_000_000_000.0;
+        return new Result(request.width() * request.width(), plan.size(), seconds);
+    }
+
+    private static void executeStage(Stage stage, RegionGenerationWindow workers, Consumer<String> progress) throws Exception {
+        long started = System.nanoTime();
+        List<PlannedChunk> eligible = new ArrayList<>();
+        for (PlannedChunk planned : stage.plan()) {
+            if (planned.status().isOrAfter(stage.step().targetStatus())) {
+                eligible.add(planned);
+            }
+        }
+        AtomicInteger completed = new AtomicInteger();
+        AtomicInteger targetCompleted = new AtomicInteger();
+        workers.process(new RegionGenerationWindow.Request<>(eligible.size(), stage.parallelism(),
+                index -> {
+                    PlannedChunk planned = eligible.get(index);
+                    apply(stage, planned);
+                    return planned;
+                }, (index, planned) -> {
+                    int count = completed.incrementAndGet();
+                    if (planned.target()) {
+                        targetCompleted.incrementAndGet();
+                    }
+                    if (count % 128 == 0) {
+                        progress.accept("stage=" + stage.step().targetStatus().getName() + " completed=" + count
+                                + " elapsedSeconds=" + (System.nanoTime() - started) / 1_000_000_000.0);
+                    }
+                }));
+        progress.accept("stage=" + stage.step().targetStatus().getName() + " chunks=" + completed.get()
+                + " targetChunks=" + targetCompleted.get() + " haloChunks=" + (completed.get() - targetCompleted.get())
+                + " seconds=" + (System.nanoTime() - started) / 1_000_000_000.0);
+    }
+
+    private static void apply(Stage stage, PlannedChunk planned) {
+        DetachedHolder center = requireHolder(stage.holders(), planned.x(), planned.z());
+        StaticCache2D<GenerationChunkHolder> cache = StaticCache2D.create(planned.x(), planned.z(),
+                stage.step().directDependencies().size() - 1, (x, z) -> requireHolder(stage.holders(), x, z));
+        ChunkAccess result = stage.step().apply(stage.context(), cache, center.chunk).join();
+        if (result != center.chunk || result.getPersistedStatus() != stage.step().targetStatus()) {
+            throw new IllegalStateException("Native stage did not retain its detached chunk: " + stage.step().targetStatus());
+        }
+    }
+
+    private static DetachedHolder requireHolder(Map<Long, DetachedHolder> holders, int x, int z) {
+        DetachedHolder holder = holders.get(ChunkPos.pack(x, z));
+        if (holder == null) {
+            throw new IllegalStateException("Native dependency escaped the terrain halo at " + x + "," + z);
+        }
+        return holder;
+    }
+
+    private static WorldGenContext context(ChunkMap map) throws ReflectiveOperationException {
+        for (Field field : ChunkMap.class.getDeclaredFields()) {
+            if (field.getType() == WorldGenContext.class) {
+                field.setAccessible(true);
+                return (WorldGenContext) field.get(map);
+            }
+        }
+        throw new IllegalStateException("Native world generation context is unavailable");
+    }
+
+    private static void write(ServerLevel level, Path output, List<PlannedChunk> plan,
+                              Map<Long, DetachedHolder> holders) throws IOException {
+        List<PlannedChunk> ordered = new ArrayList<>(plan);
+        ordered.sort(Comparator.comparingInt((PlannedChunk chunk) -> chunk.z() >> 5)
+                .thenComparingInt(chunk -> chunk.x() >> 5).thenComparingInt(PlannedChunk::z).thenComparingInt(PlannedChunk::x));
+        StringBuilder receipts = new StringBuilder();
+        RegionFile region = null;
+        long currentRegion = Long.MIN_VALUE;
+        try {
+            for (PlannedChunk planned : ordered) {
+                if (planned.status() == ChunkStatus.EMPTY) {
+                    continue;
+                }
+                long key = ChunkPos.pack(planned.x() >> 5, planned.z() >> 5);
+                if (key != currentRegion) {
+                    if (region != null) {
+                        region.close();
+                    }
+                    Path file = output.resolve("r." + (planned.x() >> 5) + "." + (planned.z() >> 5) + ".mca");
+                    region = new RegionFile(new RegionStorageInfo(level.serverLevelData.getLevelName(),
+                            level.dimension(), "chunk"), file, output, false);
+                    currentRegion = key;
+                }
+                ChunkAccess chunk = holders.get(ChunkPos.pack(planned.x(), planned.z())).chunk;
+                if (planned.status() == ChunkStatus.TERRAIN) {
+                    receipts.append(planned.x()).append(",").append(planned.z()).append("=")
+                            .append(receiptHash(chunk)).append("\n");
+                }
+                CompoundTag tag = SerializableChunkData.copyOf(level, chunk).write();
+                NativeRegionTerrainWriter.write(region, tag);
+            }
+            Files.writeString(output.resolve("receipts.properties"), receipts.toString(), StandardCharsets.UTF_8);
+        } finally {
+            if (region != null) {
+                region.close();
+            }
+        }
+    }
+
+
+    static String receiptHash(ChunkAccess chunk) {
+        byte[] receipt = chunk.persistentDataContainer.get(NATURAL_TERRAIN,
+                PersistentDataType.BYTE_ARRAY);
+        if (receipt == null || receipt.length == 0) {
+            throw new IllegalStateException("Missing Iris natural terrain receipt at " + chunk.getPos());
+        }
+        try {
+            return HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(receipt));
+        } catch (NoSuchAlgorithmException failure) {
+            throw new IllegalStateException(failure);
+        }
+    }
+
+    record Request(ServerLevel level, int chunkX, int chunkZ, int width, int parallelism, Path output) {
+        Request {
+            if (parallelism < 1 || parallelism > 16) {
+                throw new IllegalArgumentException("Native terrain worker count must be 1..16");
+            }
+        }
+    }
+
+    private record Stage(WorldGenContext context, ChunkStep step, List<PlannedChunk> plan,
+                         Map<Long, DetachedHolder> holders, int parallelism) {
+    }
+
+    record Result(int terrainChunks, int dependencyChunks, double seconds) {
+    }
+
+
+    private static final class DetachedHolder extends GenerationChunkHolder {
+        private final ProtoChunk chunk;
+
+        private DetachedHolder(ProtoChunk chunk) {
+            super(chunk.getPos());
+            this.chunk = chunk;
+        }
+
+        @Override
+        public ChunkAccess getChunkIfPresentUnchecked(ChunkStatus status) {
+            if (chunk.getPersistedStatus().isBefore(status)) {
+                throw new IllegalStateException("Native dependency is not ready: " + getPos() + " needs " + status);
+            }
+            return chunk;
+        }
+
+        @Override
+        protected void addSaveDependency(CompletableFuture<?> dependency) {
+            throw new UnsupportedOperationException("Detached chunks have no live save queue");
+        }
+
+        @Override
+        public int getTicketLevel() {
+            throw new UnsupportedOperationException("Detached chunks have no live tickets");
+        }
+
+        @Override
+        public int getQueueLevel() {
+            throw new UnsupportedOperationException("Detached chunks have no live queue");
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/DetachedNativeTerrainTest.java

@@ -0,0 +1,57 @@
+package art.arcane.iris.probe;
+
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.status.ChunkPyramid;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.chunk.status.ChunkStep;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public final class DetachedNativeTerrainTest {
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void fullRegionPlanSatisfiesEveryNativeStageDependency() {
+        List<NativeRegionPlan.PlannedChunk> plan = NativeRegionPlan.plan(-32, 64, 32);
+        Map<Long, ChunkStatus> statuses = new HashMap<>();
+        int terrain = 0;
+        for (NativeRegionPlan.PlannedChunk chunk : plan) {
+            statuses.put(ChunkPos.pack(chunk.x(), chunk.z()), chunk.status());
+            if (chunk.status() == ChunkStatus.TERRAIN) {
+                terrain++;
+            }
+        }
+        assertEquals(1296, terrain);
+        assertEquals(2916, plan.size());
+        assertTrue(plan.size() < 4096);
+        for (NativeRegionPlan.PlannedChunk chunk : plan) {
+            for (ChunkStatus status : ChunkStatus.getStatusList()) {
+                if (status == ChunkStatus.EMPTY || status.isAfter(chunk.status())) {
+                    continue;
+                }
+                ChunkStep step = ChunkPyramid.GENERATION_PYRAMID.getStepTo(status);
+                int radius = step.directDependencies().size() - 1;
+                for (int z = -radius; z <= radius; z++) {
+                    for (int x = -radius; x <= radius; x++) {
+                        ChunkStatus required = step.directDependencies().get(Math.max(Math.abs(x), Math.abs(z)));
+                        ChunkStatus available = statuses.get(ChunkPos.pack(chunk.x() + x, chunk.z() + z));
+                        assertTrue("Missing native stage dependency", available != null && available.isOrAfter(required));
+                    }
+                }
+            }
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/HeadlessChunkGeneratorTest.java

@@ -0,0 +1,149 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.volmlib.nativelib.v26_3_R1.terrain.NativeBiomeSourceImpl;
+import net.minecraft.core.Holder;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.MultiPackResourceManager;
+import net.minecraft.util.datafix.DataFixers;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.RandomState;
+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.templatesystem.StructureTemplateManager;
+import net.minecraft.world.level.storage.LevelStorageSource;
+import org.junit.Rule;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.bukkit.craftbukkit.generator.CustomChunkGenerator;
+
+import java.lang.reflect.Method;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.clearInvocations;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+public class HeadlessChunkGeneratorTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    @Rule
+    public TemporaryFolder temporary = new TemporaryFolder();
+
+    @Test
+    public void nativeStructureStateAndOriginMatchThePaperGeneratorDefaults() throws Exception {
+        int checked = 0;
+        for (Method method : CustomChunkGenerator.class.getMethods()) {
+            if (!method.getName().equals("getOrigin") && !method.getName().equals("createState")) {
+                continue;
+            }
+            assertEquals(ChunkGenerator.class, method.getDeclaringClass());
+            assertEquals(method, HeadlessChunkGenerator.class.getMethod(method.getName(), method.getParameterTypes()));
+            checked++;
+        }
+        assertEquals(2, checked);
+    }
+
+    @Test
+    public void nativeSwampHutQueriesRealPackHeightsAndBiomesWithoutAServer() throws Exception {
+        long seed = 69420L;
+        HeadlessNativeRuntime runtime = new HeadlessNativeRuntime();
+        try (RealPackProbeSupport.Workspace workspace = RealPackProbeSupport.openWorkspace(new RealPackProbeSupport.WorkspaceOptions(
+                pack().toFile(), "main", "[native-column-test]", runtime, temporary.getRoot().toPath()));
+             RealPackProbeSupport.EngineSession session = workspace.openEngine(seed, false, "columns");
+             MultiPackResourceManager resources = new MultiPackResourceManager(PackType.SERVER_DATA,
+                     List.of(ServerPacksSource.createVanillaPackSource().fullResources()));
+             LevelStorageSource.LevelStorageAccess storage = LevelStorageSource.createDefault(
+                     temporary.newFolder().toPath()).createAccess("native")) {
+            Engine engine = session.engine();
+            HeadlessChunkGenerator generator = spy(new HeadlessChunkGenerator(
+                    new HeadlessChunkGenerator.Options(engine, runtime.registries())));
+            assertTrue(generator.getBiomeSource() instanceof NativeBiomeSourceImpl);
+            assertEquals(engine.getMinHeight(), generator.getMinY());
+            assertEquals(engine.getHeight(), generator.getGenDepth());
+            assertEquals(engine.getMinHeight() + engine.getDimension().getFluidHeight(), generator.getSeaLevel());
+            Holder<NoiseGeneratorSettings> settings = runtime.registries().lookupOrThrow(Registries.NOISE_SETTINGS)
+                    .getOrThrow(NoiseGeneratorSettings.OVERWORLD);
+            RandomState random = RandomState.create(runtime.registries().lookupOrThrow(Registries.NOISE), seed, settings.value());
+            LevelHeightAccessor height = LevelHeightAccessor.create(generator.getMinY(), generator.getGenDepth());
+            Holder<Biome> swamp = runtime.registries().lookupOrThrow(Registries.BIOME).getOrThrow(
+                    ResourceKey.create(Registries.BIOME, Identifier.parse("minecraft:swamp")));
+            assertTrue(generator.getBiomeSource().possibleBiomes().contains(swamp));
+            for (int x : new int[]{-33, 0, 49}) {
+                int z = -x - 7;
+                int expected = engine.getMinHeight() + engine.getHeight(x, z, true) + 1;
+                assertTrue(expected > generator.getSeaLevel());
+                assertEquals(expected, generator.getBaseHeight(x, z, Heightmap.Types.OCEAN_FLOOR_WG, height, random));
+                NoiseColumn column = generator.getBaseColumn(x, z, height, random);
+                assertFalse(column.getBlock(expected - 1).isAir());
+                assertTrue(column.getBlock(expected).isAir());
+                assertEquals(swamp, generator.getBiomeSource().createResolver(
+                        random.createClimateSampler(SamplerContext.builder().enableCaches().build()))
+                        .getNoiseBiome(x >> 2, expected >> 2, z >> 2));
+            }
+            Holder.Reference<Structure> hut = runtime.registries().lookupOrThrow(Registries.STRUCTURE).getOrThrow(
+                    ResourceKey.create(Registries.STRUCTURE, Identifier.parse("minecraft:swamp_hut")));
+            StructureTemplateManager templates = new StructureTemplateManager(resources, storage,
+                    DataFixers.getDataFixer(), BuiltInRegistries.BLOCK);
+            ChunkPos position = new ChunkPos(-3, 2);
+            ProtoChunk chunk = new ProtoChunk(position, UpgradeData.EMPTY, height,
+                    PalettedContainerFactory.create(runtime.registries()), null);
+            clearInvocations(generator);
+            StructureStart start = hut.value().generate(hut, Level.OVERWORLD, runtime.registries(), generator,
+                    generator.getBiomeSource(), random.createClimateSampler(SamplerContext.builder().enableCaches().build()),
+                    random, templates, seed, position, 0, chunk, hut.value().biomes()::contains);
+            assertTrue(start.isValid());
+            assertFalse(start.getPieces().isEmpty());
+            verify(generator, atLeastOnce()).getBaseHeight(anyInt(), anyInt(), any(Heightmap.Types.class),
+                    any(LevelHeightAccessor.class), any(RandomState.class));
+            StructureStart excluded = hut.value().generate(hut, Level.OVERWORLD, runtime.registries(), generator,
+                    generator.getBiomeSource(), random.createClimateSampler(SamplerContext.builder().enableCaches().build()),
+                    random, templates, seed, position, 0, chunk, selected -> !selected.equals(swamp));
+            assertFalse(excluded.isValid());
+            assertTrue(RealPackProbeSupport.drainReported().isEmpty());
+        }
+    }
+
+    private Path pack() throws Exception {
+        Path pack = temporary.newFolder().toPath();
+        for (String directory : List.of("dimensions", "regions", "biomes", "generators")) {
+            Files.createDirectories(pack.resolve(directory));
+        }
+        Files.writeString(pack.resolve("dimensions/main.json"), """
+                {"name":"Native columns","focus":"swamp","regions":["owned"],"fluidHeight":40,"logicalHeight":256,
+                 "landChance":1,"carvingEnabled":false,"hydrology":{"rivers":{"enabled":false}}}
+                """);
+        Files.writeString(pack.resolve("regions/owned.json"), "{\"landBiomes\":[\"swamp\"]}");
+        Files.writeString(pack.resolve("generators/flat.json"), "{\"composite\":[]}");
+        Files.writeString(pack.resolve("biomes/swamp.json"), """
+                {"derivative":"minecraft:swamp","generators":[{"generator":"flat","min":35,"max":35}]}
+                """);
+        return pack;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/HeadlessChunkLightingTest.java

@@ -0,0 +1,264 @@
+package art.arcane.iris.probe;
+
+import ca.spottedleaf.moonrise.patches.starlight.chunk.StarlightChunk;
+import ca.spottedleaf.moonrise.patches.starlight.light.StarLightInterface;
+import ca.spottedleaf.moonrise.patches.starlight.light.SWMRNibbleArray;
+import ca.spottedleaf.moonrise.patches.starlight.util.SaveUtil;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtAccounter;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.MultiPackResourceManager;
+import net.minecraft.util.datafix.DataFixers;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.LightChunk;
+import net.minecraft.world.level.chunk.LightChunkGetter;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+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.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import net.minecraft.world.level.storage.LevelStorageSource;
+import org.bukkit.Bukkit;
+import org.junit.Rule;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public final class HeadlessChunkLightingTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    @Rule
+    public TemporaryFolder temporary = new TemporaryFolder();
+
+    @Test
+    public void nativeLightCrossesChunkEdgesAndRoundTripsSavedNibblesWithoutServer() throws Exception {
+        Fixture fixture = new Fixture(-1, -2);
+        int edgeX = fixture.target.x() * 16;
+        int z = fixture.target.z() * 16 + 8;
+        for (ProtoChunk chunk : fixture.chunks) {
+            for (int x = 0; x < 16; x++) {
+                for (int localZ = 0; localZ < 16; localZ++) {
+                    chunk.setBlockState(new BlockPos(chunk.getPos().getMinBlockX() + x, 0,
+                            chunk.getPos().getMinBlockZ() + localZ), Blocks.STONE.defaultBlockState(), 0);
+                }
+            }
+        }
+        fixture.set(new BlockPos(edgeX - 1, 0, z), Blocks.AIR.defaultBlockState());
+        fixture.set(new BlockPos(edgeX - 1, -12, z), Blocks.GLOWSTONE.defaultBlockState());
+        fixture.finishFeatures();
+        assertNull(Bukkit.getServer());
+        HeadlessChunkLighting.light(fixture.request(true));
+        ProtoChunk target = fixture.chunk(fixture.target);
+        assertEquals(14, light(target, false, new BlockPos(edgeX, -12, z)));
+        assertEquals(13, light(target, false, new BlockPos(edgeX + 1, -12, z)));
+        assertEquals(14, light(target, true, new BlockPos(edgeX, -1, z)));
+        assertEquals(15, light(target, true, new BlockPos(edgeX, 1, z)));
+        assertEquals(0, light(target, true, new BlockPos(edgeX + 15, -1, z)));
+        assertEquals(ChunkStatus.LIGHT, target.getPersistedStatus());
+        assertTrue(target.isLightCorrect());
+        assertEquals(ChunkStatus.FEATURES, fixture.chunk(new ChunkPos(fixture.target.x() - 2, fixture.target.z())).getPersistedStatus());
+        assertFalse(fixture.chunk(new ChunkPos(fixture.target.x() - 2, fixture.target.z())).isLightCorrect());
+
+        try (MultiPackResourceManager resources = new MultiPackResourceManager(PackType.SERVER_DATA,
+                List.of(ServerPacksSource.createVanillaPackSource().fullResources()));
+             LevelStorageSource.LevelStorageAccess storage = LevelStorageSource.createDefault(
+                     temporary.newFolder().toPath()).createAccess("lighting")) {
+            StructureTemplateManager templates = new StructureTemplateManager(resources, storage,
+                    DataFixers.getDataFixer(), BuiltInRegistries.BLOCK);
+            HeadlessChunkSerialization.Context context = new HeadlessChunkSerialization.Context(
+                    new StructurePieceSerializationContext(resources, fixture.registries, templates), fixture.containers, 0L);
+            CompoundTag tag = HeadlessChunkSerialization.copyOf(target, context).write();
+            assertEquals("minecraft:light", tag.getStringOr("Status", ""));
+            assertEquals(SaveUtil.STARLIGHT_LIGHT_VERSION, tag.getIntOr(SaveUtil.STARLIGHT_VERSION_TAG, -1));
+            assertTrue(tag.contains("isLightOn"));
+            assertFalse(tag.getBooleanOr("isLightOn", true));
+            assertThrows(ClassCastException.class, () -> SerializableChunkData.parse(target, fixture.containers, tag));
+            ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+            NbtIo.writeCompressed(tag, bytes);
+            CompoundTag restored = NbtIo.readCompressed(new ByteArrayInputStream(bytes.toByteArray()), NbtAccounter.unlimitedHeap());
+            assertEquals(tag, restored);
+            List<CompoundTag> sections = restored.getListOrEmpty("sections").compoundStream().toList();
+            assertEquals(target.getSectionsCount() + 2, sections.size());
+            for (CompoundTag section : sections) {
+                int index = section.getByteOr("Y", (byte) 0) - target.getMinSectionY() + 1;
+                assertTrue(section.contains(SaveUtil.BLOCKLIGHT_STATE_TAG));
+                assertTrue(section.contains(SaveUtil.SKYLIGHT_STATE_TAG));
+                SWMRNibbleArray block = new SWMRNibbleArray(section.getByteArray("BlockLight").orElse(null),
+                        section.getIntOr(SaveUtil.BLOCKLIGHT_STATE_TAG, 0));
+                SWMRNibbleArray sky = new SWMRNibbleArray(section.getByteArray("SkyLight").orElse(null),
+                        section.getIntOr(SaveUtil.SKYLIGHT_STATE_TAG, 0));
+                assertNibbleEquals(((StarlightChunk) target).starlight$getBlockNibbles()[index], block);
+                assertNibbleEquals(((StarlightChunk) target).starlight$getSkyNibbles()[index], sky);
+            }
+        }
+        assertNull(Bukkit.getServer());
+    }
+
+    @Test
+    public void nativeOpacityAndShapeRulesApplyAcrossTheBoundaryWithoutSkylight() {
+        for (BlockState barrier : List.of(Blocks.GLASS.defaultBlockState(), Blocks.TINTED_GLASS.defaultBlockState(),
+                Blocks.STONE_SLAB.defaultBlockState(), Blocks.STONE.defaultBlockState())) {
+            Fixture fixture = new Fixture(0, 0);
+            for (int x = -2; x <= 3; x++) {
+                for (int y = -13; y <= -11; y++) {
+                    for (int z = 7; z <= 9; z++) {
+                        fixture.set(new BlockPos(x, y, z), Blocks.STONE.defaultBlockState());
+                    }
+                }
+            }
+            for (int x = -1; x <= 2; x++) {
+                fixture.set(new BlockPos(x, -12, 8), Blocks.AIR.defaultBlockState());
+            }
+            fixture.set(new BlockPos(-1, -12, 8), Blocks.GLOWSTONE.defaultBlockState());
+            fixture.set(new BlockPos(0, -12, 8), barrier);
+            fixture.finishFeatures();
+            HeadlessChunkLighting.light(fixture.request(false));
+            ProtoChunk target = fixture.chunk(fixture.target);
+            int expected = barrier.is(Blocks.GLASS) || barrier.is(Blocks.STONE_SLAB) ? 13 : 0;
+            assertEquals(barrier.toString(), expected, light(target, false, new BlockPos(1, -12, 8)));
+            assertEquals(0, light(target, true, new BlockPos(1, 20, 8)));
+        }
+        assertNull(Bukkit.getServer());
+    }
+
+    @Test
+    public void emptySectionsRetainImplicitSkyLightAcrossFullHeightAndPadding() {
+        for (boolean sky : List.of(true, false)) {
+            Fixture fixture = new Fixture(0, 0);
+            fixture.finishFeatures();
+            HeadlessChunkLighting.light(fixture.request(sky));
+            ProtoChunk target = fixture.chunk(fixture.target);
+            for (int y = target.getMinY() - 16; y <= target.getMaxY() + 16; y++) {
+                assertEquals("sky y=" + y, sky ? 15 : 0, light(target, true, new BlockPos(8, y, 8)));
+                assertEquals("block y=" + y, 0, light(target, false, new BlockPos(8, y, 8)));
+            }
+        }
+    }
+
+    @Test
+    public void interruptionLeavesChunkUnlitAndRetainsInterrupt() {
+        Fixture fixture = new Fixture(0, 0);
+        fixture.finishFeatures();
+        Thread.currentThread().interrupt();
+        try {
+            assertThrows(IllegalStateException.class, () -> HeadlessChunkLighting.light(fixture.request(true)));
+            assertTrue(Thread.currentThread().isInterrupted());
+            assertFalse(fixture.chunk(fixture.target).isLightCorrect());
+            assertEquals(ChunkStatus.FEATURES, fixture.chunk(fixture.target).getPersistedStatus());
+        } finally {
+            Thread.interrupted();
+        }
+    }
+
+    @Test
+    public void rejectsIncompleteNeighborsBeforePromotingOrMutatingLight() {
+        Fixture fixture = new Fixture(0, 0);
+        fixture.finishFeatures();
+        fixture.chunks.removeFirst();
+        ProtoChunk target = fixture.chunk(fixture.target);
+        SWMRNibbleArray[] previous = ((StarlightChunk) target).starlight$getBlockNibbles();
+        assertThrows(IllegalArgumentException.class, () -> HeadlessChunkLighting.light(fixture.request(true)));
+        assertEquals(ChunkStatus.FEATURES, target.getPersistedStatus());
+        assertFalse(target.isLightCorrect());
+        assertArrayEquals(previous, ((StarlightChunk) target).starlight$getBlockNibbles());
+        fixture.chunks.add(new ProtoChunk(new ChunkPos(-2, -2), UpgradeData.EMPTY, target, fixture.containers, null));
+        assertThrows(IllegalArgumentException.class, () -> HeadlessChunkLighting.light(fixture.request(true)));
+    }
+
+    @Test
+    public void directStarlightRequiresLevelButNativeLightEnginesDoNot() {
+        Fixture fixture = new Fixture(0, 0);
+        ProtoChunk chunk = fixture.chunk(fixture.target);
+        LightChunkGetter source = new LightChunkGetter() {
+            @Override
+            public LightChunk getChunkForLighting(int x, int z) {
+                return chunk;
+            }
+
+            @Override
+            public BlockGetter getLevel() {
+                return chunk;
+            }
+        };
+        assertThrows(ClassCastException.class, () -> new StarLightInterface(source, true, true, null));
+        assertNull(Bukkit.getServer());
+    }
+
+    private static int light(ProtoChunk chunk, boolean sky, BlockPos position) {
+        StarlightChunk light = (StarlightChunk) chunk;
+        SWMRNibbleArray[] nibbles = sky ? light.starlight$getSkyNibbles() : light.starlight$getBlockNibbles();
+        return nibbles[(position.getY() >> 4) - chunk.getMinSectionY() + 1]
+                .getVisible(position.getX(), position.getY(), position.getZ());
+    }
+
+    private static void assertNibbleEquals(SWMRNibbleArray expected, SWMRNibbleArray actual) {
+        for (int index = 0; index < 4096; index++) {
+            assertEquals(expected.getVisible(index), actual.getVisible(index));
+        }
+    }
+
+    private static final class Fixture {
+        private final RegistryAccess registries = HeadlessNativeTestRegistries.get();
+        private final PalettedContainerFactory containers = PalettedContainerFactory.create(registries);
+        private final List<ProtoChunk> chunks = new ArrayList<>();
+        private final ChunkPos target;
+
+        private Fixture(int x, int z) {
+            target = new ChunkPos(x, z);
+            LevelHeightAccessor height = LevelHeightAccessor.create(-64, 128);
+            for (int dz = -2; dz <= 2; dz++) {
+                for (int dx = -2; dx <= 2; dx++) {
+                    chunks.add(new ProtoChunk(new ChunkPos(x + dx, z + dz), UpgradeData.EMPTY, height, containers, null));
+                }
+            }
+        }
+
+        private ProtoChunk chunk(ChunkPos position) {
+            for (ProtoChunk chunk : chunks) {
+                if (chunk.getPos().equals(position)) {
+                    return chunk;
+                }
+            }
+            throw new IllegalArgumentException("Missing fixture chunk " + position);
+        }
+
+        private void set(BlockPos position, BlockState state) {
+            chunk(new ChunkPos(position.getX() >> 4, position.getZ() >> 4)).setBlockState(position, state, 0);
+        }
+
+        private void finishFeatures() {
+            for (ProtoChunk chunk : chunks) {
+                chunk.setPersistedStatus(ChunkStatus.FEATURES);
+            }
+        }
+
+        private HeadlessChunkLighting.Request request(boolean sky) {
+            return new HeadlessChunkLighting.Request(chunks, Set.of(target), sky);
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/HeadlessChunkSerializationTest.java

@@ -0,0 +1,161 @@
+package art.arcane.iris.probe;
+
+import ca.spottedleaf.moonrise.patches.starlight.chunk.StarlightChunk;
+import it.unimi.dsi.fastutil.longs.LongOpenHashSet;
+import it.unimi.dsi.fastutil.shorts.ShortArrayList;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.MultiPackResourceManager;
+import net.minecraft.util.RandomSource;
+import net.minecraft.util.datafix.DataFixers;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+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.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.pieces.PiecesContainer;
+import net.minecraft.world.level.levelgen.structure.pieces.StructurePieceSerializationContext;
+import net.minecraft.world.level.levelgen.structure.structures.SwampHutPiece;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import net.minecraft.world.level.material.Fluids;
+import net.minecraft.world.level.storage.LevelStorageSource;
+import net.minecraft.world.ticks.ScheduledTick;
+import org.bukkit.NamespacedKey;
+import org.bukkit.persistence.PersistentDataType;
+import org.junit.Rule;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.util.EnumSet;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class HeadlessChunkSerializationTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    @Rule
+    public TemporaryFolder temporary = new TemporaryFolder();
+
+    @Test
+    public void snapshotMatchesNativeCopyOfIncludingStructuresLightAndReceipts() throws Exception {
+        RegistryAccess registries = HeadlessNativeTestRegistries.get();
+        PalettedContainerFactory containers = PalettedContainerFactory.create(registries);
+        LevelHeightAccessor height = LevelHeightAccessor.create(-64, 384);
+        ProtoChunk chunk = new ProtoChunk(new ChunkPos(-33, 17), UpgradeData.EMPTY, height, containers, null);
+        BlockPos block = new BlockPos(-528, -40, 272);
+        chunk.setBlockState(block, Blocks.CHEST.defaultBlockState(), 0);
+        CompoundTag chest = new CompoundTag();
+        chest.putString("id", "minecraft:chest");
+        chest.putInt("x", block.getX());
+        chest.putInt("y", block.getY());
+        chest.putInt("z", block.getZ());
+        chest.putString("LootTable", "minecraft:chests/simple_dungeon");
+        chunk.setBlockEntityNbt(chest);
+        CompoundTag entity = new CompoundTag();
+        entity.putString("id", "minecraft:pig");
+        chunk.addEntity(entity);
+        chunk.getBlockTicks().schedule(new ScheduledTick<>(Blocks.CHEST, block, 37L, 2L));
+        chunk.getFluidTicks().schedule(new ScheduledTick<>(Fluids.WATER, block.above(), 41L, 3L));
+        chunk.addPackedPostProcess(new ShortArrayList(new short[]{17, 2049}), 1);
+        chunk.setInhabitedTime(192L);
+        Heightmap.primeHeightmaps(chunk, EnumSet.allOf(Heightmap.Types.class));
+        chunk.setPersistedStatus(ChunkStatus.TERRAIN);
+        chunk.persistentDataContainer.set(new NamespacedKey("iris", "natural_terrain"),
+                PersistentDataType.BYTE_ARRAY, new byte[]{1, -8, 92, 0});
+        StarlightChunk light = (StarlightChunk) chunk;
+        light.starlight$getBlockNibbles()[1].setFull();
+        light.starlight$getBlockNibbles()[1].updateVisible();
+        light.starlight$getSkyNibbles()[0].setFull();
+        light.starlight$getSkyNibbles()[0].updateVisible();
+        chunk.setLightCorrect(true);
+        Structure hut = registries.lookupOrThrow(Registries.STRUCTURE).getOrThrow(
+                ResourceKey.create(Registries.STRUCTURE, Identifier.parse("minecraft:swamp_hut"))).value();
+        StructureStart start = new StructureStart(hut, chunk.getPos(), 2,
+                new PiecesContainer(List.of(new SwampHutPiece(RandomSource.create(69420L), block.getX(), block.getZ()))));
+        start.persistentDataContainer.set(new NamespacedKey("iris", "structure_activation"), PersistentDataType.LONG, 73L);
+        chunk.setAllStarts(Map.of(hut, start));
+        chunk.setAllReferences(Map.of(hut, new LongOpenHashSet(new long[]{ChunkPos.pack(-32, 17)})));
+        try (MultiPackResourceManager resources = new MultiPackResourceManager(PackType.SERVER_DATA,
+                List.of(ServerPacksSource.createVanillaPackSource().fullResources()));
+             LevelStorageSource.LevelStorageAccess storage = LevelStorageSource.createDefault(
+                     temporary.newFolder().toPath()).createAccess("serialization")) {
+            StructureTemplateManager templates = new StructureTemplateManager(resources, storage,
+                    DataFixers.getDataFixer(), BuiltInRegistries.BLOCK);
+            StructurePieceSerializationContext structures = new StructurePieceSerializationContext(resources, registries, templates);
+            HeadlessChunkSerialization.Context context = new HeadlessChunkSerialization.Context(structures, containers, 29L);
+            MinecraftServer server = mock(MinecraftServer.class);
+            when(server.getResourceManager()).thenReturn(resources);
+            when(server.registryAccess()).thenReturn(registries.freeze());
+            when(server.getStructureTemplateManager()).thenReturn(templates);
+            ServerLevel level = mock(ServerLevel.class);
+            when(level.getServer()).thenReturn(server);
+            when(level.registryAccess()).thenReturn(registries);
+            when(level.palettedContainerFactory()).thenReturn(containers);
+            when(level.getGameTime()).thenReturn(29L);
+            when(level.getMinSectionY()).thenReturn(height.getMinSectionY());
+            when(level.getMaxSectionY()).thenReturn(height.getMaxSectionY());
+            CompoundTag nativeTag = SerializableChunkData.copyOf(level, chunk).write();
+            SerializableChunkData snapshot = HeadlessChunkSerialization.copyOf(chunk, context);
+            CompoundTag headless = snapshot.write();
+            assertEquals(nativeTag, headless);
+            assertEquals("minecraft:terrain", headless.getStringOr("Status", ""));
+            assertEquals(29L, headless.getLongOr("LastUpdate", -1L));
+            assertEquals(192L, headless.getLongOr("InhabitedTime", -1L));
+            assertArrayEquals(new byte[]{1, -8, 92, 0}, headless.getCompoundOrEmpty("ChunkBukkitValues")
+                    .getByteArray("iris:natural_terrain").orElseThrow());
+            assertFalse(headless.getListOrEmpty("block_entities").isEmpty());
+            assertFalse(headless.getListOrEmpty("block_ticks").isEmpty());
+            assertFalse(headless.getListOrEmpty("fluid_ticks").isEmpty());
+            assertTrue(headless.getCompoundOrEmpty("structures").getCompoundOrEmpty("starts").contains("minecraft:swamp_hut"));
+            CompoundTag serializedStart = headless.getCompoundOrEmpty("structures").getCompoundOrEmpty("starts")
+                    .getCompoundOrEmpty("minecraft:swamp_hut");
+            StructureStart restored = StructureStart.loadStaticStart(structures, serializedStart, 69420L);
+            assertTrue(restored.isValid());
+            assertEquals(start.getBoundingBox(), restored.getBoundingBox());
+            assertEquals(73L, serializedStart.getCompoundOrEmpty("StructureBukkitValues")
+                    .getLongOr("iris:structure_activation", -1L));
+            chunk.getSection(1).setBlockState(0, 8, 0, Blocks.AIR.defaultBlockState());
+            chunk.getPostProcessing()[1].clear();
+            chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE).getRawData()[0] = 0L;
+            assertEquals(headless, snapshot.write());
+            for (ChunkStatus status : List.of(ChunkStatus.EMPTY, ChunkStatus.STRUCTURE_STARTS,
+                    ChunkStatus.STRUCTURE_REFERENCES, ChunkStatus.BIOMES, ChunkStatus.TERRAIN)) {
+                ProtoChunk fresh = new ProtoChunk(new ChunkPos(0, -1), UpgradeData.EMPTY, height, containers, null);
+                fresh.setPersistedStatus(status);
+                CompoundTag freshTag = HeadlessChunkSerialization.copyOf(fresh, context).write();
+                assertEquals(SerializableChunkData.copyOf(level, fresh).write(), freshTag);
+                assertEquals(status, SerializableChunkData.getChunkStatusFromTag(freshTag));
+                assertFalse(freshTag.contains("ChunkBukkitValues"));
+                assertTrue(freshTag.getListOrEmpty("entities").isEmpty());
+                assertTrue(freshTag.getListOrEmpty("block_entities").isEmpty());
+            }
+            chunk.setPersistedStatus(ChunkStatus.FULL);
+            assertThrows(IllegalArgumentException.class, () -> HeadlessChunkSerialization.copyOf(chunk, context));
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/HeadlessGenerationRegistryTest.java

@@ -0,0 +1,45 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.spi.PlatformGenerationRegistry;
+import net.minecraft.data.registries.VanillaRegistries;
+import org.bukkit.Bukkit;
+import org.junit.Test;
+
+import java.io.File;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+
+public final class HeadlessGenerationRegistryTest {
+    @Test
+    public void capturesGeneratedDefinitionsThroughNativeCodecs() throws Exception {
+        HeadlessNativeBootstrap.initialize();
+        String biome = HeadlessNativeTestRegistries.generatedBiome();
+        String dimension = HeadlessNativeTestRegistries.generatedDimension();
+        HeadlessNativePlatform platform = new HeadlessNativePlatform(new File("unused-native-platform"),
+            HeadlessNativeTestRegistries::get);
+        PlatformGenerationRegistry registry = platform.generationRegistry();
+        assertEquals("bukkit-generation-registry-v1", registry.runtimeIdentity());
+        assertEquals(registry.canonicalDefinition("minecraft:worldgen/biome", "iris:native_test", biome),
+                registry.generatedDefinition("minecraft:worldgen/biome", "iris:native_test"));
+        assertEquals(registry.canonicalDefinition("minecraft:dimension_type", "iris:native_test", dimension),
+                registry.generatedDefinition("minecraft:dimension_type", "iris:native_test"));
+        assertEquals(PlatformGenerationRegistry.Definition.resourceIdentity("minecraft:block", "minecraft:stone"),
+                registry.definition("minecraft:block", "minecraft:stone"));
+        assertThrows(IllegalStateException.class,
+                () -> registry.generatedDefinition("minecraft:worldgen/biome", "iris:absent"));
+        assertThrows(IllegalArgumentException.class,
+                () -> registry.canonicalDefinition("minecraft:worldgen/biome", "iris:invalid", "{}"));
+        assertNull(Bukkit.getServer());
+    }
+
+    @Test
+    public void rejectsContractCaptureBeforeCoherentRegistriesLoad() {
+        HeadlessNativeBootstrap.initialize();
+        HeadlessNativePlatform platform = new HeadlessNativePlatform(new File("unused-native-platform"),
+            VanillaRegistries::createWorldLookup);
+        assertThrows(IllegalStateException.class,
+            () -> platform.generationRegistry().definition("minecraft:block", "minecraft:stone"));
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/HeadlessMantleInspection.java

@@ -0,0 +1,90 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.block.TileData;
+import art.arcane.iris.world.storage.matter.TileWrapper;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.IrisEngineMantle;
+import art.arcane.volmlib.util.matter.Matter;
+import art.arcane.volmlib.util.mantle.runtime.Mantle;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.util.Comparator;
+import java.util.HexFormat;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Stream;
+
+public final class HeadlessMantleInspection {
+    private HeadlessMantleInspection() {
+    }
+
+    public static void main(String[] arguments) throws Exception {
+        if (arguments.length != 6) {
+            throw new IllegalArgumentException("Expected pack, dimension, seed, world, regionX, regionZ");
+        }
+        Path temporary = Files.createTempDirectory("iris-mantle-inspection-");
+        Path copied = temporary.resolve("mantle");
+        try {
+            Process copy = new ProcessBuilder("cp", "-Rc", Path.of(arguments[3]).resolve("mantle-hydrology").toString(),
+                    copied.toString()).inheritIO().start();
+            if (copy.waitFor() != 0) {
+                throw new IllegalStateException("Could not clone retained mantle for read-only inspection");
+            }
+            inspect(arguments, copied);
+        } finally {
+            try (Stream<Path> paths = Files.walk(temporary)) {
+                for (Path path : paths.sorted(Comparator.reverseOrder()).toList()) {
+                    Files.delete(path);
+                }
+            }
+        }
+    }
+
+    private static void inspect(String[] arguments, Path copied) throws Exception {
+        HeadlessNativeRuntime runtime = new HeadlessNativeRuntime();
+        try (RealPackProbeSupport.Workspace workspace = RealPackProbeSupport.openWorkspace(new RealPackProbeSupport.WorkspaceOptions(
+                new File(arguments[0]), arguments[1], "[mantle-inspection]", runtime,
+                Path.of(System.getProperty("java.io.tmpdir"))));
+             RealPackProbeSupport.EngineSession session = workspace.openEngine(Long.parseLong(arguments[2]), false, "inspect")) {
+            Engine engine = session.engine();
+            Mantle<Matter> mantle = IrisEngineMantle.createMantle(engine, copied, engine::getData);
+            try {
+                AtomicInteger tiles = new AtomicInteger();
+                Map<String, Integer> materials = new TreeMap<>();
+                MessageDigest digest = MessageDigest.getInstance("SHA-256");
+                int minimumX = Integer.parseInt(arguments[4]) << 5;
+                int minimumZ = Integer.parseInt(arguments[5]) << 5;
+                for (int z = minimumZ; z < minimumZ + 32; z++) {
+                    for (int x = minimumX; x < minimumX + 32; x++) {
+                        mantle.iterateChunk(x, z, TileWrapper.class, (localX, y, localZ, wrapper) -> {
+                            TileData tile = wrapper.getData();
+                            tiles.incrementAndGet();
+                            materials.merge(tile.getMaterialKey(), 1, Integer::sum);
+                            digest.update(encoded(tile));
+                        });
+                    }
+                }
+                System.out.println("retainedMantleTiles=" + tiles.get() + " materials=" + materials
+                        + " sha256=" + HexFormat.of().formatHex(digest.digest()));
+            } finally {
+                mantle.close();
+            }
+        }
+    }
+
+    private static byte[] encoded(TileData tile) {
+        try (ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+             DataOutputStream output = new DataOutputStream(bytes)) {
+            tile.toBinary(output);
+            return bytes.toByteArray();
+        } catch (Exception failure) {
+            throw new IllegalStateException("Cannot serialize retained tile " + tile.getMaterialKey(), failure);
+        }
+    }
+}