Bind generation context

- Resolve first-generation engine binding from authoritative published level context.
- Validate generator identity and recover canonical Overworld binding from stale snapshots.
- Add shared loader regression tests and their Mockito test dependency.

adapters/fabric/build.gradle

@@ -114,6 +114,7 @@ dependencies {
     minecraft("com.mojang:minecraft:${minecraftVersion}")
     implementation("net.fabricmc:fabric-loader:${fabricLoaderVersion}")
     testImplementation('junit:junit:4.13.2')
+    testImplementation('org.mockito:mockito-core:5.23.0')
     // registrySync and resourceLoader are LOAD-BEARING despite zero imports anywhere in Iris:
     //   fabric-registry-sync-v0   delays registry freeze past mod init, which is what lets
     //                             IrisFabricBootstrap register the CHUNK_GENERATOR codec in

adapters/forge/build.gradle

@@ -131,6 +131,7 @@ configurations.testRuntimeClasspath.extendsFrom(configurations.runtimeClasspath,
 dependencies {
     implementation minecraft.dependency("net.minecraftforge:forge:${forgeVersion}")
     testImplementation('junit:junit:4.13.2')
+    testImplementation('org.mockito:mockito-core:5.23.0')
     compileOnly('org.slf4j:slf4j-api:2.0.17')
     compileOnly(libs.spigot) {
         transitive = false

adapters/modded-common/src/main/java/art/arcane/iris/modded/IrisModdedChunkGenerator.java

@@ -331,34 +331,113 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
         if (server == null) {
             return null;
         }
-        // Snapshot, never server.getAllLevels(): this runs off the server thread from data queries.
-        for (ServerLevel level : ModdedServerLevels.levels(server)) {
+        ServerLevel resolved = resolveBoundLevel(server, ModdedServerLevels.levels(server));
+        if (resolved != null) {
+            boundLevel = resolved;
+        }
+        return resolved;
+    }
+
+    ServerLevel resolveBoundLevel(MinecraftServer server, List<ServerLevel> snapshot) {
+        for (ServerLevel level : snapshot) {
             if (level.getChunkSource().getGenerator() == this) {
-                boundLevel = level;
                 return level;
             }
         }
-        return null;
+        ServerLevel overworld = server.getLevel(Level.OVERWORLD);
+        return overworld != null && overworld.getChunkSource().getGenerator() == this ? overworld : null;
     }
 
     Engine engine() {
-        requireBindingAllowed();
-        Engine cached = engine;
-        requireCompletedShutdown(cached);
-        if (cached != null && !cached.isClosed()) {
+        Engine cached = readyEngine();
+        if (cached != null) {
             return cached;
         }
         ServerLevel level = boundLevel();
         if (level == null) {
             throw new IllegalStateException("Iris generator '" + dimensionKey + "' has no bound ServerLevel yet");
         }
-        return bindEngine(level);
+        return bindGenerationLevel(level);
+    }
+
+    private Engine engine(ResourceKey<Level> levelKey) {
+        Engine cached = readyEngine();
+        if (cached != null) {
+            return cached;
+        }
+        ServerLevel level = boundLevel;
+        if (level == null) {
+            level = requirePublishedLevel(ModdedEngineBootstrap.currentServer(), levelKey);
+        } else {
+            requireGeneratorLevel(level, levelKey);
+        }
+        return bindGenerationLevel(level);
+    }
+
+    private Engine engine(ServerLevel generationLevel) {
+        Engine cached = readyEngine();
+        if (cached != null) {
+            return cached;
+        }
+        ServerLevel level = boundLevel == null ? generationLevel : boundLevel;
+        requireGeneratorLevel(level, generationLevel.dimension());
+        return bindGenerationLevel(level);
+    }
+
+    private Engine readyEngine() {
+        requireBindingAllowed();
+        Engine cached = engine;
+        requireCompletedShutdown(cached);
+        if (cached != null && !cached.isClosed()) {
+            return cached;
+        }
+        return null;
+    }
+
+    private Engine bindGenerationLevel(ServerLevel level) {
+        bindLevel(level);
+        Engine bound = readyEngine();
+        if (bound == null) {
+            throw new IllegalStateException("Iris generator '" + dimensionKey
+                    + "' completed generation binding without a ready engine");
+        }
+        return bound;
+    }
+
+    ServerLevel requirePublishedLevel(MinecraftServer server, ResourceKey<Level> levelKey) {
+        if (server == null) {
+            throw new IllegalStateException("Iris generator '" + dimensionKey
+                    + "' cannot resolve level '" + levelKey.identifier() + "': server is unavailable");
+        }
+        ServerLevel level = server.getLevel(levelKey);
+        if (level == null) {
+            throw new IllegalStateException("Iris generator '" + dimensionKey
+                    + "' has no published ServerLevel for '" + levelKey.identifier() + "'");
+        }
+        requireGeneratorLevel(level, levelKey);
+        return level;
+    }
+
+    private void requireGeneratorLevel(ServerLevel level, ResourceKey<Level> levelKey) {
+        if (!levelKey.equals(level.dimension())) {
+            throw new IllegalStateException("Iris generator '" + dimensionKey + "' resolved level '"
+                    + level.dimension().identifier() + "' while binding '" + levelKey.identifier() + "'");
+        }
+        ChunkGenerator publishedGenerator = level.getChunkSource().getGenerator();
+        if (publishedGenerator != this) {
+            throw new IllegalStateException("Published ServerLevel '" + levelKey.identifier()
+                    + "' does not use Iris generator '" + dimensionKey + "'");
+        }
     }
 
     synchronized void bindLevel(ServerLevel level) {
         if (level.getChunkSource().getGenerator() != this) {
             throw new IllegalArgumentException("ServerLevel does not use Iris generator '" + dimensionKey + "'");
         }
+        Engine current = engineIfBound();
+        if (boundLevel == level && current != null && current.getComplex() != null) {
+            return;
+        }
         requireCompletedShutdown(engine);
         unloading = false;
         Engine bound = bindEngine(level);
@@ -853,7 +932,6 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
     @Override
     public void applyBiomeDecoration(WorldGenLevel level, ChunkAccess chunk, StructureManager structureManager) {
         Engine current = engine();
-        // Self-heal for an engine bound through a data-query path instead of bindLevel; a no-op once prepared.
         importedFeatures.prepare(current);
         try (GenerationSessionLease lease = requireGenerationLease(current, "modded_biome_decoration");
              IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
@@ -867,7 +945,7 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
 
     @Override
     public void createStructures(RegistryAccess registryAccess, ChunkGeneratorStructureState structureState, StructureManager structureManager, ChunkAccess chunk, StructureTemplateManager templateManager, ResourceKey<Level> levelKey) {
-        Engine current = engine();
+        Engine current = engine(levelKey);
         try (GenerationSessionLease lease = requireGenerationLease(current, "modded_create_structures");
              IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
             Map<Structure, StructureStart> previousStarts = new HashMap<>(chunk.getAllStarts());
@@ -891,7 +969,7 @@ public final class IrisModdedChunkGenerator extends ChunkGenerator {
 
     @Override
     public void createReferences(WorldGenLevel level, StructureManager structureManager, ChunkAccess chunk) {
-        Engine current = engine();
+        Engine current = engine(level.getLevel());
         try (GenerationSessionLease lease = requireGenerationLease(current, "modded_create_references");
              IrisContext.Scope ignored = IrisContext.open(current, lease.sessionId(), null)) {
             NativeStructureReferenceRepair.createReferences(

adapters/modded-common/src/test/java/art/arcane/iris/modded/ModdedGenerationBootstrapBindingTest.java

@@ -0,0 +1,150 @@
+package art.arcane.iris.modded;
+
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerChunkCache;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+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;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+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 ModdedGenerationBootstrapBindingTest {
+    private static final String SOURCE_ROOT_PROPERTY = "iris.moddedCommonSources";
+
+    @Test
+    public void publishedLevelRequiresCurrentGeneratorIdentity() {
+        IrisModdedChunkGenerator generator = mock(IrisModdedChunkGenerator.class, CALLS_REAL_METHODS);
+        MinecraftServer server = mock(MinecraftServer.class);
+        ServerLevel level = mock(ServerLevel.class);
+        ServerChunkCache chunkSource = mock(ServerChunkCache.class);
+        when(server.getLevel(Level.OVERWORLD)).thenReturn(level);
+        when(level.dimension()).thenReturn(Level.OVERWORLD);
+        when(level.getChunkSource()).thenReturn(chunkSource);
+        when(chunkSource.getGenerator()).thenReturn(generator);
+
+        assertSame(level, generator.requirePublishedLevel(server, Level.OVERWORLD));
+
+        ChunkGenerator otherGenerator = mock(ChunkGenerator.class);
+        when(chunkSource.getGenerator()).thenReturn(otherGenerator);
+        IllegalStateException mismatch = assertThrows(IllegalStateException.class,
+                () -> generator.requirePublishedLevel(server, Level.OVERWORLD));
+        assertTrue(mismatch.getMessage().contains("does not use Iris generator"));
+    }
+
+    @Test
+    public void publishedLevelRejectsMissingServerAndWorld() {
+        IrisModdedChunkGenerator generator = mock(IrisModdedChunkGenerator.class, CALLS_REAL_METHODS);
+        IllegalStateException missingServer = assertThrows(IllegalStateException.class,
+                () -> generator.requirePublishedLevel(null, Level.OVERWORLD));
+        assertTrue(missingServer.getMessage().contains("server is unavailable"));
+
+        MinecraftServer server = mock(MinecraftServer.class);
+        IllegalStateException missingWorld = assertThrows(IllegalStateException.class,
+                () -> generator.requirePublishedLevel(server, Level.OVERWORLD));
+        assertTrue(missingWorld.getMessage().contains("no published ServerLevel"));
+    }
+
+    @Test
+    public void staleSnapshotResolvesOnlyCanonicalOverworldOwnedByGenerator() {
+        IrisModdedChunkGenerator generator = mock(IrisModdedChunkGenerator.class, CALLS_REAL_METHODS);
+        MinecraftServer server = mock(MinecraftServer.class);
+        ServerLevel overworld = mock(ServerLevel.class);
+        ServerChunkCache chunkSource = mock(ServerChunkCache.class);
+        when(server.getLevel(Level.OVERWORLD)).thenReturn(overworld);
+        when(overworld.getChunkSource()).thenReturn(chunkSource);
+        when(chunkSource.getGenerator()).thenReturn(generator);
+
+        assertSame(overworld, generator.resolveBoundLevel(server, List.of()));
+
+        ChunkGenerator otherGenerator = mock(ChunkGenerator.class);
+        when(chunkSource.getGenerator()).thenReturn(otherGenerator);
+        assertNull(generator.resolveBoundLevel(server, List.of()));
+        verify(server, never()).getLevel(Level.NETHER);
+    }
+
+    @Test
+    public void dynamicLevelStillResolvesFromSnapshotWithoutCanonicalLookup() {
+        IrisModdedChunkGenerator generator = mock(IrisModdedChunkGenerator.class, CALLS_REAL_METHODS);
+        MinecraftServer server = mock(MinecraftServer.class);
+        ServerLevel dynamicLevel = mock(ServerLevel.class);
+        ServerChunkCache chunkSource = mock(ServerChunkCache.class);
+        when(dynamicLevel.getChunkSource()).thenReturn(chunkSource);
+        when(chunkSource.getGenerator()).thenReturn(generator);
+
+        assertSame(dynamicLevel, generator.resolveBoundLevel(server, List.of(dynamicLevel)));
+        verify(server, never()).getLevel(Level.OVERWORLD);
+    }
+
+    @Test
+    public void firstGenerationStagesProvideAuthoritativeLevelContext() throws IOException {
+        String source = source("IrisModdedChunkGenerator.java");
+        String structures = method(source, "public void createStructures(");
+        String references = method(source, "public void createReferences(");
+        assertTrue(structures.contains("Engine current = engine(levelKey);"));
+        assertTrue(references.contains("Engine current = engine(level.getLevel());"));
+
+        String publishedBinding = method(source, "private Engine engine(ResourceKey<Level> levelKey)");
+        assertTrue(publishedBinding.contains("requirePublishedLevel(ModdedEngineBootstrap.currentServer(), levelKey)"));
+        assertTrue(publishedBinding.contains("return bindGenerationLevel(level);"));
+        assertFalse(publishedBinding.contains("ModdedServerLevels.level("));
+
+        String fullBinding = method(source, "private Engine bindGenerationLevel(ServerLevel level)");
+        assertTrue(fullBinding.contains("bindLevel(level);"));
+        assertTrue(fullBinding.contains("Engine bound = readyEngine();"));
+
+        String genericBinding = method(source, "Engine engine()");
+        assertTrue(genericBinding.contains("return bindGenerationLevel(level);"));
+    }
+
+    @Test
+    public void constructorMixinIsNotPartOfGenerationBootstrap() throws IOException {
+        String sourceRoot = System.getProperty(SOURCE_ROOT_PROPERTY);
+        assertTrue(sourceRoot != null && !sourceRoot.isBlank());
+        Path root = Path.of(sourceRoot);
+        assertFalse(Files.exists(root.resolve(Path.of("art", "arcane", "iris", "modded", "mixin",
+                "ServerLevelBindingMixin.java"))));
+        String mixinConfig = Files.readString(root.getParent().resolve("resources/irisworldgen.entity.mixins.json"));
+        assertFalse(mixinConfig.contains("ServerLevelBindingMixin"));
+    }
+
+    private String source(String fileName) throws IOException {
+        String sourceRoot = System.getProperty(SOURCE_ROOT_PROPERTY);
+        assertTrue(sourceRoot != null && !sourceRoot.isBlank());
+        return Files.readString(Path.of(sourceRoot, "art", "arcane", "iris", "modded", fileName));
+    }
+
+    private String method(String source, String signature) {
+        int start = source.indexOf(signature);
+        assertTrue(start >= 0);
+        int body = source.indexOf('{', start);
+        assertTrue(body >= 0);
+        int depth = 0;
+        for (int index = body; index < source.length(); index++) {
+            char token = source.charAt(index);
+            if (token == '{') {
+                depth++;
+            } else if (token == '}') {
+                depth--;
+                if (depth == 0) {
+                    return source.substring(start, index + 1);
+                }
+            }
+        }
+        throw new IllegalArgumentException("Unclosed source contract method: " + signature);
+    }
+}

adapters/neoforge/build.gradle

@@ -105,6 +105,7 @@ configurations.testRuntimeClasspath.extendsFrom(configurations.runtimeClasspath,
 
 dependencies {
     testImplementation('junit:junit:4.13.2')
+    testImplementation('org.mockito:mockito-core:5.23.0')
     testRuntimeOnly('org.junit.platform:junit-platform-launcher:6.1.2')
     testRuntimeOnly('org.junit.vintage:junit-vintage-engine:6.1.2')
     compileOnly('org.slf4j:slf4j-api:2.0.17')