Merged wave1 into terrain bake

# Conflicts:
#	core/src/main/java/art/arcane/iris/generation/runtime/IrisComplex.java
#	probe/src/main/java/art/arcane/iris/probe/GenerationProbe.java

probe/build.gradle

@@ -171,10 +171,19 @@ tasks.register('genProbe', JavaExec) {
     systemProperty('iris.probe.expectedBackend', providers.gradleProperty('probeExpectedBackend').orElse('').get())
     systemProperty('iris.probe.requireNativeSamples', providers.gradleProperty('probeRequireNativeSamples').orElse('false').get())
     if (providers.gradleProperty('probeNativeLibrary').isPresent()) {
-        systemProperty('volmlib.noise.nativeBillowLibrary', providers.gradleProperty('probeNativeLibrary').get())
+        systemProperty('volmlib.native.library', providers.gradleProperty('probeNativeLibrary').get())
+    }
+    if (providers.gradleProperty('probeNativePolicy').isPresent()) {
+        systemProperty('volmlib.native', providers.gradleProperty('probeNativePolicy').get())
     }
     systemProperty('iris.probe.threads', providers.gradleProperty('probeThreads').orElse('1').get())
     systemProperty('iris.probe.pregenProfile', providers.gradleProperty('probePregenProfile').orElse('false').get())
+    systemProperty('iris.probe.hydrologyPreplan', providers.gradleProperty('probeHydrologyPreplan').orElse('false').get())
+    systemProperty('iris.probe.historyRouter', providers.gradleProperty('probeHistoryRouter').orElse('false').get())
+    systemProperty('iris.probe.productionBuffers', providers.gradleProperty('probeProductionBuffers').orElse('false').get())
+    String probeCounters = providers.gradleProperty('probeCounters').orElse('false').get()
+    systemProperty('iris.generation.counters', probeCounters)
+    systemProperty('volmlib.cache.countContention', probeCounters)
     dependsOn(':core:compileJava')
     doFirst {
         if (!probePack.isPresent() || probePack.get().isBlank()) {

probe/src/main/java/art/arcane/iris/probe/ChunkDump.java

@@ -20,6 +20,7 @@ package art.arcane.iris.probe;
 
 import art.arcane.volmlib.nativelib.terrain.NativeBiome;
 import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockVolume;
 import art.arcane.volmlib.util.hunk.Hunk;
 
 import java.io.BufferedInputStream;
@@ -84,11 +85,12 @@ public final class ChunkDump {
         char[] biomeIndices = new char[size];
         PaletteBuilder blockPalette = new PaletteBuilder();
         PaletteBuilder biomePalette = new PaletteBuilder();
+        NativeBlockVolume stored = blocks instanceof NativeBlockVolume volume ? volume : null;
         int index = 0;
         for (int x = 0; x < 16; x++) {
             for (int z = 0; z < 16; z++) {
                 for (int y = 0; y < height; y++) {
-                    NativeBlockState state = blocks.get(x, y, z);
+                    NativeBlockState state = stored == null ? blocks.get(x, y, z) : stored.getStoredRaw(x, y, z);
                     NativeBiome biome = biomes.get(x, y, z);
                     blockIndices[index] = blockPalette.indexOf(state, state == null ? NULL_BLOCK_KEY : null);
                     biomeIndices[index] = biomePalette.indexOf(biome, biome == null ? NULL_BIOME_KEY : null);

probe/src/main/java/art/arcane/iris/probe/GenerationProbe.java

@@ -20,6 +20,8 @@ package art.arcane.iris.probe;
 
 import art.arcane.iris.generation.bake.BakePlane;
 import art.arcane.iris.generation.bake.GeneratorEvaluations;
+import art.arcane.iris.generation.mantle.IrisCaveCarver3D;
+import art.arcane.iris.pack.datapack.DataVersion;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.pack.PackValidationResult;
 import art.arcane.iris.pack.PackValidator;
@@ -40,6 +42,9 @@ import art.arcane.iris.generation.hydrology.HydrologyTileCache;
 import art.arcane.iris.generation.hydrology.runtime.IrisHydrologyRuntime;
 import art.arcane.iris.generation.terrain.IrisDimension;
 import art.arcane.iris.world.IrisWorld;
+import art.arcane.iris.world.history.GenerationHistory;
+import art.arcane.iris.world.history.GenerationHistoryRuntimeRouter;
+import art.arcane.iris.world.history.IrisBoundarySignatureSampler;
 import art.arcane.iris.world.pregen.PregenPerformanceProfile;
 import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.spi.IrisServices;
@@ -63,6 +68,7 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -170,7 +176,8 @@ public final class GenerationProbe {
         }
     }
 
-    record ProbeOptions(int threads, Path dumpFile, boolean pregenProfile) {
+    record ProbeOptions(int threads, Path dumpFile, boolean pregenProfile, boolean hydrologyPreplan,
+                        boolean historyRouter, boolean productionBuffers, boolean counters) {
         ProbeOptions {
             if (threads < 1) {
                 throw new IllegalArgumentException("Thread count must be at least 1.");
@@ -185,7 +192,15 @@ public final class GenerationProbe {
             return new ProbeOptions(
                     Integer.parseInt(System.getProperty("iris.probe.threads", "1").trim()),
                     dump.isEmpty() ? null : Path.of(dump),
-                    Boolean.parseBoolean(System.getProperty("iris.probe.pregenProfile", "false").trim()));
+                    booleanProperty("iris.probe.pregenProfile"),
+                    booleanProperty("iris.probe.hydrologyPreplan"),
+                    booleanProperty("iris.probe.historyRouter"),
+                    booleanProperty("iris.probe.productionBuffers"),
+                    booleanProperty("iris.generation.counters"));
+        }
+
+        private static boolean booleanProperty(String key) {
+            return Boolean.parseBoolean(System.getProperty(key, "false").trim());
         }
 
         boolean parallel() {
@@ -304,6 +319,7 @@ public final class GenerationProbe {
         try {
             ProbeResult result = run(configuration, options);
             System.out.println(result.machineLine());
+            System.out.println(IrisCaveCarver3D.cellCounters().machineLine());
             exitCode = result.failedChunks() == 0 ? 0 : 1;
         } catch (Throwable e) {
             System.out.println("[genprobe] FAIL: probe execution failed");
@@ -356,7 +372,7 @@ public final class GenerationProbe {
         Throwable executionFailure = null;
         try {
             File pack = clonePack(configuration.packSource(), workRoot);
-            configureProbeRuntime(workRoot);
+            configureProbeRuntime(workRoot, options.historyRouter());
             validatePack(pack);
 
             System.out.println("[genprobe] pack: " + configuration.packSource().getAbsolutePath());
@@ -369,29 +385,48 @@ public final class GenerationProbe {
             System.out.println("[genprobe] studio: " + configuration.studio());
             System.out.println("[genprobe] threads: " + options.threads());
             System.out.println("[genprobe] pregen profile: " + options.pregenProfile());
+            System.out.println("[genprobe] hydrology preplan: " + options.hydrologyPreplan());
+            System.out.println("[genprobe] history router: " + options.historyRouter());
+            System.out.println("[genprobe] production buffers: " + options.productionBuffers());
+            System.out.println("[genprobe] counters: " + options.counters());
             System.out.println("[genprobe] dump file: " + (options.dumpFile() == null ? "none" : options.dumpFile()));
 
             long engineStart = System.nanoTime();
+            File worldFolder = new File(workRoot, "world");
             data = IrisData.get(pack);
-            IrisDimension dimension = data.getDimensionLoader().load(configuration.dimensionKey());
-            if (dimension == null) {
-                throw new IllegalStateException("Dimension '" + configuration.dimensionKey()
-                        + "' did not load from " + pack.getAbsolutePath());
+            IrisDimension dimension = loadDimension(data, configuration.dimensionKey());
+            GenerationHistory history = null;
+            if (options.historyRouter()) {
+                history = HeadlessGenerationHistorySession.create(new RealPackProbeSupport.HistoryRequest(
+                        worldFolder.toPath(), data, dimension, configuration.seed()), DataVersion.getLatest().get());
+                data.close();
+                data = IrisData.openRuntime(history.activePackRoot().toFile());
+                data.bindGenerationRegistryContract(history.activeEpoch().registryContract());
+                dimension = loadDimension(data, configuration.dimensionKey());
             }
             IrisWorld world = IrisWorld.builder()
                     .platformIdentity("iris:probe")
                     .name("probe")
                     .seed(configuration.seed())
-                    .worldFolder(new File(workRoot, "world"))
+                    .worldFolder(worldFolder)
                     .minHeight(dimension.getMinHeight())
                     .maxHeight(dimension.getMaxHeight())
                     .build();
             EngineTarget target = new EngineTarget(world, dimension, data);
-            engine = new IrisEngine(
-                    target,
-                    configuration.studio()
-                            ? IrisEngine.InitializationMode.STUDIO
-                            : IrisEngine.InitializationMode.RUNTIME);
+            IrisEngine.InitializationMode mode = configuration.studio()
+                    ? IrisEngine.InitializationMode.STUDIO
+                    : IrisEngine.InitializationMode.RUNTIME;
+            GenerationHistoryRuntimeRouter router = null;
+            if (history == null) {
+                engine = new IrisEngine(target, mode);
+            } else {
+                IrisEngine historyEngine = new IrisEngine(target, mode,
+                        history.paths().activationMantleRoot(history.activeActivation().activationId()),
+                        history.activeEpoch().kernelVersion(), null);
+                engine = historyEngine;
+                router = GenerationHistoryRuntimeRouter.attach(historyEngine, history, IrisBoundarySignatureSampler.INSTANCE);
+                router.preloadActiveRuntimes();
+            }
             long engineReadyNanos = System.nanoTime() - engineStart;
 
             List<Throwable> initNoise = settleAndDrain();
@@ -400,9 +435,16 @@ public final class GenerationProbe {
                     + " seed=" + engine.getSeedManager().getSeed()
                     + " minY=" + engine.getMinHeight() + " maxY=" + engine.getMaxHeight()
                     + " timeMs=" + String.format(Locale.ROOT, "%.3f", nanosToMillis(engineReadyNanos)));
+            System.out.println("IRIS_GENPROBE_MANTLE version=1 radius=" + engine.getMantle().getRadius()
+                    + " real_radius=" + engine.getMantle().getRealRadius());
+            ProbeChunkGenerator generator = new ProbeChunkGenerator(engine, router, options.productionBuffers());
             long nativeSamplesBefore = FractalBillowSimplexNoise.nativeSampleCount();
-            GenerationResult generation = generateWithProfile(engine, configuration, options);
+            GenerationResult generation = generateWithProfile(generator, configuration, options);
             verifyBackend(nativeSamplesBefore);
+            if (options.productionBuffers()) {
+                System.out.println("IRIS_GENPROBE_BUFFERS version=1 mode=production biome_expanded_chunks="
+                        + generator.expandedBiomeHunks());
+            }
             String status = generation.failedChunks() == 0 ? "PASS" : "FAIL";
             printGenerationFailures(generation);
             return new ProbeResult(
@@ -447,7 +489,16 @@ public final class GenerationProbe {
         }
     }
 
-    private static void configureProbeRuntime(File workRoot) {
+    private static IrisDimension loadDimension(IrisData data, String dimensionKey) {
+        IrisDimension dimension = data.getDimensionLoader().load(dimensionKey);
+        if (dimension == null) {
+            throw new IllegalStateException("Dimension '" + dimensionKey + "' did not load from "
+                    + data.getDataFolder().getAbsolutePath());
+        }
+        return dimension;
+    }
+
+    private static void configureProbeRuntime(File workRoot, boolean generationRegistry) {
         REPORTED.clear();
         StubPlatform.bindGenerationStateHandlers();
         StubPlatform.verbose(false);
@@ -458,7 +509,8 @@ public final class GenerationProbe {
         IrisServices.register(EngineEffectsProvider.class, (EngineEffectsProvider) InertEffects::new);
         IrisServices.register(EnginePlatformHooks.class, new InertPlatformHooks());
         IrisPlatforms.unbind();
-        IrisPlatforms.bind(new StubPlatform(new File(workRoot, "platform-data")));
+        IrisPlatforms.bind(new StubPlatform(new File(workRoot, "platform-data"),
+                generationRegistry ? ProbeGenerationRegistry.INSTANCE : null));
     }
 
     private static void validatePack(File pack) {
@@ -475,21 +527,35 @@ public final class GenerationProbe {
         System.out.println("[genprobe] offline pack validation: PASS");
     }
 
-    private static GenerationResult generateWithProfile(Engine engine, ProbeConfiguration configuration,
+    private static GenerationResult generateWithProfile(ProbeChunkGenerator generator, ProbeConfiguration configuration,
                                                         ProbeOptions options) throws Exception {
+        Engine engine = generator.engine();
         if (!options.pregenProfile()) {
-            return generate(engine, configuration, options);
+            preplanHydrology(engine, configuration, options);
+            return generate(generator, configuration, options);
         }
         PregenPerformanceProfile.apply(engine);
         IrisHydrologyRuntime hydrology = engine.getComplex().getHydrologyRuntime();
         try (HydrologyTileCache.PregenerationScope ignored = hydrology == null ? null
                 : hydrology.preparePregeneration(pregenerationArea(configuration))) {
-            return generate(engine, configuration, options);
+            preplanHydrology(engine, configuration, options);
+            return generate(generator, configuration, options);
         } finally {
             PregenPerformanceProfile.restore();
         }
     }
 
+    private static void preplanHydrology(Engine engine, ProbeConfiguration configuration, ProbeOptions options)
+            throws Exception {
+        if (!options.hydrologyPreplan()) {
+            return;
+        }
+        Optional<ProbeHydrologyPreplan> preplan = ProbeHydrologyPreplan.run(engine, configuration);
+        printDistinctCauses("hydrology preplan reported errors", drainReported());
+        System.out.println(preplan.map(ProbeHydrologyPreplan::machineLine)
+                .orElse("IRIS_GENPROBE_HYDROLOGY_PREPLAN version=1 tiles=0 skipped=no-hydrology"));
+    }
+
     static HydrologyTileCache.PregenerationArea pregenerationArea(ProbeConfiguration configuration) {
         List<ChunkCoordinate> coordinates = scheduleCoordinates(
                 configuration.warmupChunks() + configuration.measuredChunks(),
@@ -533,8 +599,9 @@ public final class GenerationProbe {
         return Math.atan2(coordinate.z() - centerChunkZ, coordinate.x() - centerChunkX);
     }
 
-    private static GenerationResult generate(Engine engine, ProbeConfiguration configuration,
+    private static GenerationResult generate(ProbeChunkGenerator generator, ProbeConfiguration configuration,
                                              ProbeOptions options) throws Exception {
+        Engine engine = generator.engine();
         int totalChunks = configuration.warmupChunks() + configuration.measuredChunks();
         List<ChunkCoordinate> coordinates = scheduleCoordinates(
                 totalChunks, configuration.centerChunkX(), configuration.centerChunkZ());
@@ -543,31 +610,44 @@ public final class GenerationProbe {
                 engine.getMinHeight(), height);
         try (OutcomeSink sink = new OutcomeSink(options.dumpFile(), header, configuration.measuredChunks())) {
             if (options.parallel()) {
-                generateParallel(engine, configuration, options, coordinates, sink);
+                generateParallel(generator, configuration, options, coordinates, sink);
             } else {
-                generateSequential(engine, configuration, coordinates, sink);
+                generateSequential(generator, configuration, options, coordinates, sink);
             }
             return sink.result(configuration);
         }
     }
 
-    private static void generateSequential(Engine engine, ProbeConfiguration configuration,
-                                           List<ChunkCoordinate> coordinates, OutcomeSink sink) throws IOException {
+    private static void generateSequential(ProbeChunkGenerator generator, ProbeConfiguration configuration,
+                                           ProbeOptions options, List<ChunkCoordinate> coordinates,
+                                           OutcomeSink sink) throws IOException {
         int totalChunks = coordinates.size();
         long measuredStartEpochMillis = 0L;
+        ProbeWindowMetrics measuredStart = null;
         GeneratorEvaluations.Snapshot measuredStartEvaluations = GeneratorEvaluations.snapshot();
         for (int index = 0; index < totalChunks; index++) {
             if (index == configuration.warmupChunks()) {
                 measuredStartEpochMillis = System.currentTimeMillis();
                 measuredStartEvaluations = GeneratorEvaluations.snapshot();
+                measuredStart = ProbeWindowMetrics.capture(generator.engine(), options.counters());
             }
             drainReported();
-            ChunkOutcome outcome = generateChunk(engine, index, coordinates.get(index), configuration.multicore());
+            ChunkOutcome outcome = generator.generate(index, coordinates.get(index), configuration.multicore());
             outcome.failures().addAll(drainReported());
             sink.accept(outcome, index >= configuration.warmupChunks());
             printProgress(configuration, index + 1, totalChunks);
         }
-        printWindow(engine, measuredStartEpochMillis, System.currentTimeMillis(), measuredStartEvaluations);
+        printWindow(generator.engine(), measuredStartEpochMillis, System.currentTimeMillis(), measuredStartEvaluations);
+        printWindowMetrics(measuredStart, ProbeWindowMetrics.capture(generator.engine(), options.counters()),
+                configuration.measuredChunks(), options);
+    }
+
+    private static void printWindowMetrics(ProbeWindowMetrics start, ProbeWindowMetrics end, int chunks,
+                                           ProbeOptions options) {
+        System.out.println(ProbeWindowMetrics.stagesLine(start, end, chunks, options.threads()));
+        if (options.counters()) {
+            System.out.println(ProbeWindowMetrics.countersLine(start, end, chunks));
+        }
     }
 
     private static void printWindow(Engine engine, long startEpochMillis, long endEpochMillis, GeneratorEvaluations.Snapshot startEvaluations) {
@@ -585,8 +665,9 @@ public final class GenerationProbe {
         System.out.println(planes);
     }
 
-    private static void generateParallel(Engine engine, ProbeConfiguration configuration, ProbeOptions options,
-                                         List<ChunkCoordinate> coordinates, OutcomeSink sink) throws Exception {
+    private static void generateParallel(ProbeChunkGenerator generator, ProbeConfiguration configuration,
+                                         ProbeOptions options, List<ChunkCoordinate> coordinates,
+                                         OutcomeSink sink) throws Exception {
         ChunkOutcome[] outcomes = new ChunkOutcome[coordinates.size()];
         ExecutorService executor = Executors.newFixedThreadPool(options.threads());
         long warmupWallNanos;
@@ -599,7 +680,7 @@ public final class GenerationProbe {
                 warmup.add(index);
             }
             long warmupStarted = System.nanoTime();
-            runPhase(executor, engine, configuration, coordinates, warmup, outcomes);
+            runPhase(executor, generator, configuration, coordinates, warmup, outcomes);
             warmupWallNanos = System.nanoTime() - warmupStarted;
             unattributed.addAll(drainReported());
             System.out.println("[genprobe] warmup complete: " + configuration.warmupChunks() + " chunks on "
@@ -607,12 +688,15 @@ public final class GenerationProbe {
 
             List<Integer> measured = spiralOrder(coordinates, configuration.warmupChunks(),
                     configuration.centerChunkX(), configuration.centerChunkZ());
+            ProbeWindowMetrics measuredStart = ProbeWindowMetrics.capture(generator.engine(), options.counters());
             long measuredStartEpochMillis = System.currentTimeMillis();
             GeneratorEvaluations.Snapshot measuredStartEvaluations = GeneratorEvaluations.snapshot();
             long measuredStarted = System.nanoTime();
-            runPhase(executor, engine, configuration, coordinates, measured, outcomes);
+            runPhase(executor, generator, configuration, coordinates, measured, outcomes);
             measuredWallNanos = System.nanoTime() - measuredStarted;
-            printWindow(engine, measuredStartEpochMillis, System.currentTimeMillis(), measuredStartEvaluations);
+            printWindow(generator.engine(), measuredStartEpochMillis, System.currentTimeMillis(), measuredStartEvaluations);
+            printWindowMetrics(measuredStart, ProbeWindowMetrics.capture(generator.engine(), options.counters()),
+                    configuration.measuredChunks(), options);
             unattributed.addAll(drainReported());
             System.out.println("[genprobe] measured progress: " + configuration.measuredChunks() + "/"
                     + configuration.measuredChunks());
@@ -646,13 +730,13 @@ public final class GenerationProbe {
         System.out.println(throughput.machineLine());
     }
 
-    private static void runPhase(ExecutorService executor, Engine engine, ProbeConfiguration configuration,
-                                 List<ChunkCoordinate> coordinates, List<Integer> order,
-                                 ChunkOutcome[] outcomes) throws Exception {
+    private static void runPhase(ExecutorService executor, ProbeChunkGenerator generator,
+                                 ProbeConfiguration configuration, List<ChunkCoordinate> coordinates,
+                                 List<Integer> order, ChunkOutcome[] outcomes) throws Exception {
         List<Future<ChunkOutcome>> futures = new ArrayList<>(order.size());
         for (int index : order) {
             ChunkCoordinate coordinate = coordinates.get(index);
-            futures.add(executor.submit(() -> generateChunk(engine, index, coordinate, configuration.multicore())));
+            futures.add(executor.submit(() -> generator.generate(index, coordinate, configuration.multicore())));
         }
         for (Future<ChunkOutcome> future : futures) {
             ChunkOutcome outcome;
@@ -672,21 +756,6 @@ public final class GenerationProbe {
         }
     }
 
-    private static ChunkOutcome generateChunk(Engine engine, int index, ChunkCoordinate coordinate,
-                                              boolean multicore) {
-        int height = engine.getTarget().getHeight();
-        List<Throwable> failures = new ArrayList<>();
-        Hunk<NativeBlockState> blocks = Hunk.newArrayHunk(16, height, 16);
-        Hunk<NativeBiome> biomes = Hunk.newArrayHunk(16, height, 16);
-        long started = System.nanoTime();
-        try {
-            engine.generate(coordinate.x() << 4, coordinate.z() << 4, blocks, biomes, multicore);
-        } catch (Throwable e) {
-            failures.add(e);
-        }
-        return new ChunkOutcome(index, coordinate, System.nanoTime() - started, blocks, biomes, failures);
-    }
-
     private static void printProgress(ProbeConfiguration configuration, int completed, int totalChunks) {
         if (completed == configuration.warmupChunks()) {
             System.out.println("[genprobe] warmup complete: " + configuration.warmupChunks() + " chunks");

probe/src/main/java/art/arcane/iris/probe/ProbeChunkGenerator.java

@@ -0,0 +1,99 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.chunk.SectionBuffer;
+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.spi.IrisPlatforms;
+import art.arcane.iris.world.history.GenerationHistoryRuntimeRouter;
+import art.arcane.volmlib.nativelib.terrain.NativeBiome;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.util.hunk.Hunk;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+final class ProbeChunkGenerator {
+    private final Engine engine;
+    private final GenerationHistoryRuntimeRouter router;
+    private final boolean productionBuffers;
+    private final AtomicInteger expandedBiomeHunks = new AtomicInteger();
+
+    ProbeChunkGenerator(Engine engine, GenerationHistoryRuntimeRouter router, boolean productionBuffers) {
+        this.engine = engine;
+        this.router = router;
+        this.productionBuffers = productionBuffers;
+    }
+
+    Engine engine() {
+        return engine;
+    }
+
+    int expandedBiomeHunks() {
+        return expandedBiomeHunks.get();
+    }
+
+    GenerationProbe.ChunkOutcome generate(int index, GenerationProbe.ChunkCoordinate coordinate, boolean multicore) {
+        int height = engine.getTarget().getHeight();
+        List<Throwable> failures = new ArrayList<>();
+        Hunk<NativeBlockState> blocks = newBlocks(height);
+        Hunk<NativeBiome> biomes = newBiomes(height);
+        long started = System.nanoTime();
+        try {
+            generateInto(coordinate.x() << 4, coordinate.z() << 4, blocks, biomes, multicore);
+        } catch (Throwable e) {
+            failures.add(e);
+        }
+        long elapsed = System.nanoTime() - started;
+        if (biomes instanceof ProductionBiomeHunk production && production.expanded()) {
+            expandedBiomeHunks.incrementAndGet();
+        }
+        return new GenerationProbe.ChunkOutcome(index, coordinate, elapsed, blocks, biomes, failures);
+    }
+
+    private Hunk<NativeBlockState> newBlocks(int height) {
+        return productionBuffers ? new SectionBuffer(height) : Hunk.newArrayHunk(16, height, 16);
+    }
+
+    private Hunk<NativeBiome> newBiomes(int height) {
+        return productionBuffers ? new ProductionBiomeHunk(height, ProbeChunkGenerator::plainsBiome)
+                : Hunk.newArrayHunk(16, height, 16);
+    }
+
+    private void generateInto(int blockX, int blockZ, Hunk<NativeBlockState> blocks, Hunk<NativeBiome> biomes,
+                              boolean multicore) throws Exception {
+        if (router == null) {
+            engine.generate(blockX, blockZ, blocks, biomes, multicore);
+            return;
+        }
+        try (GenerationHistoryRuntimeRouter.CoordinateScope historyScope = router.openCoordinateScope(blockX, blockZ);
+             GenerationSessionLease lease = engine.acquireGenerationLease("probe_terrain_stage");
+             IrisContext.Scope ignored = IrisContext.open(engine, lease.sessionId(), null)) {
+            engine.generate(blockX, blockZ, blocks, biomes, multicore);
+            historyScope.claimGeneratedSemantics();
+        }
+    }
+
+    private static NativeBiome plainsBiome() {
+        return IrisPlatforms.get().registries().biome("minecraft:plains");
+    }
+}

probe/src/main/java/art/arcane/iris/probe/ProbeGenerationRegistry.java

@@ -0,0 +1,51 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.probe;
+
+import art.arcane.iris.spi.PlatformGenerationRegistry;
+
+import java.util.List;
+import java.util.Locale;
+
+final class ProbeGenerationRegistry implements PlatformGenerationRegistry {
+    static final ProbeGenerationRegistry INSTANCE = new ProbeGenerationRegistry();
+
+    private ProbeGenerationRegistry() {
+    }
+
+    @Override
+    public String runtimeIdentity() {
+        return "iris-probe";
+    }
+
+    @Override
+    public List<String> legacyCustomBiomeResourceKeys(String packName, String dimensionKey, String customBiomeId) {
+        return List.of(dimensionKey.toLowerCase(Locale.ROOT) + ":" + customBiomeId.toLowerCase(Locale.ROOT));
+    }
+
+    @Override
+    public String dimensionTypeResourceKey(String packName, String dimensionKey, String dimensionTypeKey) {
+        return "iris:" + dimensionTypeKey.toLowerCase(Locale.ROOT);
+    }
+
+    @Override
+    public Definition definition(String registryKey, String resourceKey) {
+        return Definition.resourceIdentity(registryKey, resourceKey);
+    }
+}

probe/src/main/java/art/arcane/iris/probe/ProbeHydrologyPreplan.java

@@ -0,0 +1,109 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.hydrology.HydrologyPlannerSettings;
+import art.arcane.iris.generation.hydrology.HydrologyTileCache;
+import art.arcane.iris.generation.hydrology.HydrologyTileKey;
+import art.arcane.iris.generation.hydrology.runtime.IrisHydrologyRuntime;
+import art.arcane.iris.generation.runtime.Engine;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Locale;
+import java.util.Optional;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+record ProbeHydrologyPreplan(int tiles, int tileSize, int publicationRadius, int reachChunks, long elapsedNanos) {
+    private static final int PLANNING_THREADS = 4;
+
+    static Optional<ProbeHydrologyPreplan> run(Engine engine, GenerationProbe.ProbeConfiguration configuration)
+            throws Exception {
+        IrisHydrologyRuntime hydrology = engine.getComplex().getHydrologyRuntime();
+        if (hydrology == null) {
+            return Optional.empty();
+        }
+        HydrologyPlannerSettings settings = hydrology.settings();
+        int tileSize = settings.routing().tileSize();
+        int publicationRadius = settings.publicationRadius();
+        int reachChunks = Math.max(engine.getMantle().getRadius(), engine.getMantle().getRealRadius());
+        List<HydrologyTileKey> keys = tiles(configuration, tileSize, publicationRadius, reachChunks);
+        long started = System.nanoTime();
+        ExecutorService executor = Executors.newFixedThreadPool(Math.min(keys.size(), PLANNING_THREADS));
+        try {
+            List<Future<?>> plans = new ArrayList<>(keys.size());
+            for (HydrologyTileKey key : keys) {
+                plans.add(executor.submit(() -> hydrology.tile(key)));
+            }
+            for (Future<?> plan : plans) {
+                await(plan);
+            }
+        } finally {
+            executor.shutdown();
+        }
+        return Optional.of(new ProbeHydrologyPreplan(keys.size(), tileSize, publicationRadius, reachChunks,
+                System.nanoTime() - started));
+    }
+
+    static List<HydrologyTileKey> tiles(GenerationProbe.ProbeConfiguration configuration, int tileSize,
+                                        int publicationRadius, int reachChunks) {
+        HydrologyTileCache.PregenerationArea area = GenerationProbe.pregenerationArea(configuration);
+        long reach = (long) reachChunks * 16L + publicationRadius;
+        int minimumX = Math.toIntExact(Math.floorDiv(area.minimumBlockX() - reach, tileSize)) - 1;
+        int minimumZ = Math.toIntExact(Math.floorDiv(area.minimumBlockZ() - reach, tileSize)) - 1;
+        int maximumX = Math.toIntExact(Math.floorDiv(area.maximumBlockX() + reach, tileSize)) + 1;
+        int maximumZ = Math.toIntExact(Math.floorDiv(area.maximumBlockZ() + reach, tileSize)) + 1;
+        int centerX = Math.floorDiv(area.centerBlockX(), tileSize);
+        int centerZ = Math.floorDiv(area.centerBlockZ(), tileSize);
+        List<HydrologyTileKey> keys = new ArrayList<>((maximumX - minimumX + 1) * (maximumZ - minimumZ + 1));
+        for (int tileZ = minimumZ; tileZ <= maximumZ; tileZ++) {
+            for (int tileX = minimumX; tileX <= maximumX; tileX++) {
+                keys.add(new HydrologyTileKey(tileX, tileZ));
+            }
+        }
+        keys.sort(Comparator.comparingInt((HydrologyTileKey key) ->
+                Math.max(Math.abs(key.tileX() - centerX), Math.abs(key.tileZ() - centerZ))));
+        return keys;
+    }
+
+    String machineLine() {
+        return String.format(Locale.ROOT,
+                "IRIS_GENPROBE_HYDROLOGY_PREPLAN version=1 tiles=%d tile_size=%d publication_radius=%d reach_chunks=%d planned_ms=%.3f",
+                tiles, tileSize, publicationRadius, reachChunks, elapsedNanos / 1_000_000D);
+    }
+
+    private static void await(Future<?> plan) throws Exception {
+        try {
+            plan.get();
+        } catch (ExecutionException failure) {
+            Throwable cause = failure.getCause();
+            if (cause instanceof Error error) {
+                throw error;
+            }
+            if (cause instanceof Exception exception) {
+                throw exception;
+            }
+            throw new IllegalStateException(cause);
+        }
+    }
+}

probe/src/main/java/art/arcane/iris/probe/ProbeWindowMetrics.java

@@ -0,0 +1,67 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.EngineMetrics;
+import art.arcane.iris.generation.runtime.GenerationCounter;
+import art.arcane.volmlib.util.cache.CacheContention;
+
+import java.util.LinkedHashMap;
+import java.util.Locale;
+import java.util.Map;
+
+record ProbeWindowMetrics(Map<String, EngineMetrics.StageTotal> stages, Map<String, Long> counters) {
+    static ProbeWindowMetrics capture(Engine engine, boolean counters) {
+        return new ProbeWindowMetrics(engine.getMetrics().stageTotals(), counters ? counterValues() : Map.of());
+    }
+
+    static String stagesLine(ProbeWindowMetrics start, ProbeWindowMetrics end, int chunks, int threads) {
+        StringBuilder line = new StringBuilder(512);
+        line.append("IRIS_GENPROBE_STAGES version=1 chunks=").append(chunks).append(" threads=").append(threads);
+        for (Map.Entry<String, EngineMetrics.StageTotal> entry : end.stages().entrySet()) {
+            EngineMetrics.StageTotal earlier = start.stages().get(entry.getKey());
+            EngineMetrics.StageTotal window = earlier == null ? entry.getValue() : entry.getValue().since(earlier);
+            line.append(' ').append(entry.getKey()).append('=')
+                    .append(String.format(Locale.ROOT, "%.3f", window.millis()));
+        }
+        return line.toString();
+    }
+
+    static String countersLine(ProbeWindowMetrics start, ProbeWindowMetrics end, int chunks) {
+        StringBuilder line = new StringBuilder(256);
+        line.append("IRIS_GENPROBE_COUNTERS version=1 chunks=").append(chunks);
+        for (Map.Entry<String, Long> entry : end.counters().entrySet()) {
+            long window = entry.getValue() - start.counters().getOrDefault(entry.getKey(), 0L);
+            line.append(' ').append(entry.getKey()).append('=').append(window)
+                    .append(' ').append(entry.getKey()).append("_per_chunk=")
+                    .append(String.format(Locale.ROOT, "%.1f", chunks == 0 ? 0D : window / (double) chunks));
+        }
+        return line.toString();
+    }
+
+    private static Map<String, Long> counterValues() {
+        Map<String, Long> values = new LinkedHashMap<>();
+        for (GenerationCounter counter : GenerationCounter.values()) {
+            values.put(counter.key(), counter.sum());
+        }
+        values.put("cache_duplicate_computations", CacheContention.duplicateComputations());
+        return values;
+    }
+}

probe/src/main/java/art/arcane/iris/probe/ProductionBiomeHunk.java

@@ -0,0 +1,112 @@
+/*
+ * Iris is a World Generator for Minecraft Servers
+ * Copyright (c) 2026 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package art.arcane.iris.probe;
+
+import art.arcane.volmlib.nativelib.terrain.NativeBiome;
+import art.arcane.volmlib.util.hunk.HunkMutationSupport;
+import art.arcane.volmlib.util.hunk.storage.StorageHunk;
+
+import java.util.function.Supplier;
+
+final class ProductionBiomeHunk extends StorageHunk<NativeBiome> {
+    private static final int CHUNK_SIZE = 16;
+
+    private final NativeBiome[] columns = new NativeBiome[CHUNK_SIZE * CHUNK_SIZE];
+    private final Supplier<NativeBiome> fallback;
+    private NativeBiome[] cells;
+    private volatile NativeBiome defaultBiome;
+
+    ProductionBiomeHunk(int height, Supplier<NativeBiome> fallback) {
+        super(CHUNK_SIZE, height, CHUNK_SIZE);
+        this.fallback = fallback;
+    }
+
+    @Override
+    public void set(int x1, int y1, int z1, int x2, int y2, int z2, NativeBiome biome) {
+        if (x1 == x2 && z1 == z2 && y1 == 0 && y2 == getHeight() - 1) {
+            fillColumn(x1, z1, biome);
+            return;
+        }
+        HunkMutationSupport.setRangeInclusive(this, x1, y1, z1, x2, y2, z2, biome);
+    }
+
+    @Override
+    public void setRaw(int x, int y, int z, NativeBiome biome) {
+        NativeBiome[] storage = cells == null ? expand() : cells;
+        storage[cellIndex(x, y, z)] = biome;
+    }
+
+    @Override
+    public NativeBiome getRaw(int x, int y, int z) {
+        NativeBiome[] storage = cells;
+        NativeBiome biome = storage == null ? columns[columnIndex(x, z)] : storage[cellIndex(x, y, z)];
+        if (biome != null) {
+            return biome;
+        }
+        NativeBiome resolved = defaultBiome;
+        if (resolved == null) {
+            resolved = fallback.get();
+            defaultBiome = resolved;
+        }
+        return resolved;
+    }
+
+    boolean expanded() {
+        return cells != null;
+    }
+
+    private void fillColumn(int x, int z, NativeBiome biome) {
+        NativeBiome[] storage = cells;
+        if (storage == null) {
+            columns[columnIndex(x, z)] = biome;
+            return;
+        }
+        int stride = CHUNK_SIZE * CHUNK_SIZE;
+        int index = columnIndex(x, z);
+        for (int y = 0; y < getHeight(); y++) {
+            storage[index] = biome;
+            index += stride;
+        }
+    }
+
+    private NativeBiome[] expand() {
+        NativeBiome[] storage = new NativeBiome[CHUNK_SIZE * getHeight() * CHUNK_SIZE];
+        int stride = CHUNK_SIZE * CHUNK_SIZE;
+        for (int column = 0; column < stride; column++) {
+            NativeBiome biome = columns[column];
+            if (biome == null) {
+                continue;
+            }
+            for (int index = column; index < storage.length; index += stride) {
+                storage[index] = biome;
+            }
+        }
+        cells = storage;
+        return storage;
+    }
+
+    private static int columnIndex(int x, int z) {
+        return ((z & (CHUNK_SIZE - 1)) * CHUNK_SIZE) + (x & (CHUNK_SIZE - 1));
+    }
+
+    private int cellIndex(int x, int y, int z) {
+        int clampedY = Math.max(0, Math.min(getHeight() - 1, y));
+        return (clampedY * CHUNK_SIZE * CHUNK_SIZE) + columnIndex(x, z);
+    }
+}

probe/src/main/java/art/arcane/iris/probe/StubPlatform.java

@@ -26,6 +26,7 @@ import art.arcane.iris.spi.IrisPlatform;
 import art.arcane.iris.spi.LogLevel;
 import art.arcane.volmlib.nativelib.terrain.NativeBiome;
 import art.arcane.iris.spi.PlatformBiomeWriter;
+import art.arcane.iris.spi.PlatformGenerationRegistry;
 import art.arcane.volmlib.nativelib.terrain.NativeBlockProperty;
 import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
 import art.arcane.volmlib.nativelib.entity.NativeEntityType;
@@ -78,7 +79,7 @@ public final class StubPlatform implements IrisPlatform {
         return StubBlockState.of(key);
     }
 
-    private final StubRegistries registries = new StubRegistries();
+    private final StubRegistries registries;
     private final StubScheduler scheduler = new StubScheduler();
     private final StubStructureHooks structureHooks = new StubStructureHooks();
     private final StubBiomeWriter biomeWriter = new StubBiomeWriter();
@@ -89,7 +90,12 @@ public final class StubPlatform implements IrisPlatform {
     }
 
     public StubPlatform(File dataFolder) {
+        this(dataFolder, null);
+    }
+
+    public StubPlatform(File dataFolder, PlatformGenerationRegistry generationRegistry) {
         this.dataFolder = dataFolder;
+        this.registries = new StubRegistries(generationRegistry);
     }
 
     private static final class StubBlockState implements NativeBlockState {
@@ -620,6 +626,20 @@ public final class StubPlatform implements IrisPlatform {
     }
 
     private static final class StubRegistries implements PlatformRegistries {
+        private final PlatformGenerationRegistry generationRegistry;
+
+        private StubRegistries(PlatformGenerationRegistry generationRegistry) {
+            this.generationRegistry = generationRegistry;
+        }
+
+        @Override
+        public PlatformGenerationRegistry generationRegistry() {
+            if (generationRegistry == null) {
+                return PlatformRegistries.super.generationRegistry();
+            }
+            return generationRegistry;
+        }
+
         @Override
         public NativeBlockState decodeBlockState(String key) {
             return blockOrNull(key);

probe/src/test/java/art/arcane/iris/probe/GenerationProbeTest.java

@@ -1,15 +1,20 @@
 package art.arcane.iris.probe;
 
 import art.arcane.iris.generation.hydrology.HydrologyTileCache;
+import art.arcane.iris.generation.hydrology.HydrologyTileKey;
+import art.arcane.iris.generation.runtime.EngineMetrics;
 import org.junit.Test;
 
 import java.io.File;
 import java.nio.file.Path;
 import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThrows;
@@ -128,7 +133,96 @@ public final class GenerationProbeTest {
         GenerationProbe.ProbeOptions defaults = GenerationProbe.ProbeOptions.fromSystemProperties();
         assertEquals(1, defaults.threads());
         assertNull(defaults.dumpFile());
-        assertThrows(IllegalArgumentException.class, () -> new GenerationProbe.ProbeOptions(0, null, false));
+        assertThrows(IllegalArgumentException.class,
+                () -> new GenerationProbe.ProbeOptions(0, null, false, false, false, false, false));
+        assertFalse(defaults.hydrologyPreplan());
+        assertFalse(defaults.historyRouter());
+        assertFalse(defaults.productionBuffers());
+        assertFalse(defaults.counters());
+    }
+
+    @Test
+    public void readsHarnessFidelityOptionsFromSystemProperties() {
+        System.setProperty("iris.probe.hydrologyPreplan", "true");
+        System.setProperty("iris.probe.historyRouter", "true");
+        System.setProperty("iris.probe.productionBuffers", "true");
+        System.setProperty("iris.generation.counters", "true");
+        try {
+            GenerationProbe.ProbeOptions options = GenerationProbe.ProbeOptions.fromSystemProperties();
+            assertTrue(options.hydrologyPreplan());
+            assertTrue(options.historyRouter());
+            assertTrue(options.productionBuffers());
+            assertTrue(options.counters());
+            assertFalse(options.parallel());
+        } finally {
+            System.clearProperty("iris.probe.hydrologyPreplan");
+            System.clearProperty("iris.probe.historyRouter");
+            System.clearProperty("iris.probe.productionBuffers");
+            System.clearProperty("iris.generation.counters");
+        }
+    }
+
+    @Test
+    public void stageLineReportsOnlyTheMeasuredWindow() {
+        Map<String, EngineMetrics.StageTotal> before = new LinkedHashMap<>();
+        before.put("total", new EngineMetrics.StageTotal(100D, 10L));
+        before.put("context.prefill.height", new EngineMetrics.StageTotal(0D, 0L));
+        Map<String, EngineMetrics.StageTotal> after = new LinkedHashMap<>();
+        after.put("total", new EngineMetrics.StageTotal(350.25D, 20L));
+        after.put("context.prefill.height", new EngineMetrics.StageTotal(12.5D, 10L));
+
+        String line = ProbeWindowMetrics.stagesLine(new ProbeWindowMetrics(before, Map.of()),
+                new ProbeWindowMetrics(after, Map.of()), 10, 1);
+
+        assertEquals("IRIS_GENPROBE_STAGES version=1 chunks=10 threads=1 total=250.250 context.prefill.height=12.500", line);
+    }
+
+    @Test
+    public void counterLineReportsWindowTotalsAndPerChunkRates() {
+        Map<String, Long> before = new LinkedHashMap<>();
+        before.put("generator_evaluations", 1_000L);
+        before.put("corner_starcasts", 0L);
+        Map<String, Long> after = new LinkedHashMap<>();
+        after.put("generator_evaluations", 5_000L);
+        after.put("corner_starcasts", 330L);
+
+        String line = ProbeWindowMetrics.countersLine(new ProbeWindowMetrics(Map.of(), before),
+                new ProbeWindowMetrics(Map.of(), after), 2);
+
+        assertEquals("IRIS_GENPROBE_COUNTERS version=1 chunks=2 generator_evaluations=4000"
+                + " generator_evaluations_per_chunk=2000.0 corner_starcasts=330 corner_starcasts_per_chunk=165.0", line);
+    }
+
+    @Test
+    public void hydrologyPreplanCoversEveryTileAScheduledChunkComposesFromPlusTheNeighbourRing() {
+        GenerationProbe.ProbeConfiguration configuration = new GenerationProbe.ProbeConfiguration(
+                new File("/tmp/pack"), "overworld", 256, 1024, 2048, 2048, false, false, 1337L);
+        int tileSize = 512;
+        int publicationRadius = 96;
+        int reachChunks = 13;
+        List<HydrologyTileKey> keys = ProbeHydrologyPreplan.tiles(configuration, tileSize, publicationRadius, reachChunks);
+        Set<HydrologyTileKey> planned = new HashSet<>(keys);
+
+        assertEquals(keys.size(), planned.size());
+        for (GenerationProbe.ChunkCoordinate chunk : GenerationProbe.scheduleCoordinates(1280, 2048, 2048)) {
+            for (int offsetX = -reachChunks; offsetX <= reachChunks; offsetX++) {
+                for (int offsetZ = -reachChunks; offsetZ <= reachChunks; offsetZ++) {
+                    long minimumX = (long) (chunk.x() + offsetX) * 16L;
+                    long minimumZ = (long) (chunk.z() + offsetZ) * 16L;
+                    int firstX = Math.floorDiv(Math.toIntExact(minimumX - publicationRadius), tileSize) - 1;
+                    int lastX = Math.floorDiv(Math.toIntExact(minimumX + 15L + publicationRadius), tileSize) + 1;
+                    int firstZ = Math.floorDiv(Math.toIntExact(minimumZ - publicationRadius), tileSize) - 1;
+                    int lastZ = Math.floorDiv(Math.toIntExact(minimumZ + 15L + publicationRadius), tileSize) + 1;
+                    for (int tileX = firstX; tileX <= lastX; tileX++) {
+                        for (int tileZ = firstZ; tileZ <= lastZ; tileZ++) {
+                            assertTrue(planned.contains(new HydrologyTileKey(tileX, tileZ)));
+                        }
+                    }
+                }
+            }
+        }
+        HydrologyTileKey first = keys.getFirst();
+        assertEquals(new HydrologyTileKey(Math.floorDiv(2048 * 16 + 8, tileSize), Math.floorDiv(2048 * 16 + 8, tileSize)), first);
     }
 
     @Test

probe/src/test/java/art/arcane/iris/probe/ProductionHunkTest.java

@@ -0,0 +1,127 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.chunk.SectionBuffer;
+import art.arcane.volmlib.nativelib.terrain.NativeBiome;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.util.hunk.Hunk;
+import org.junit.Test;
+
+import java.util.List;
+
+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.assertSame;
+import static org.junit.Assert.assertTrue;
+
+public final class ProductionHunkTest {
+    private static final int HEIGHT = 24;
+
+    @Test
+    public void blockHunkIgnoresNullWritesAndTracksTheHighestStoredCellPerColumn() {
+        SectionBuffer blocks = new SectionBuffer(HEIGHT);
+        NativeBlockState stone = StubPlatform.blockStateForTest("minecraft:stone");
+        NativeBlockState dirt = StubPlatform.blockStateForTest("minecraft:dirt");
+
+        blocks.setRaw(3, 5, 7, stone);
+        blocks.setRaw(3, 9, 7, dirt);
+        blocks.setRaw(3, 2, 7, stone);
+        blocks.setRaw(3, 9, 7, null);
+
+        assertSame(dirt, blocks.getStoredRaw(3, 9, 7));
+        assertSame(stone, blocks.getStoredRaw(3, 5, 7));
+        assertNull(blocks.getStoredRaw(3, 6, 7));
+        assertEquals(9, blocks.highestStoredY(3, 7));
+        assertEquals(-1, blocks.highestStoredY(7, 3));
+    }
+
+    @Test
+    public void dumpCaptureOfTheBlockHunkMatchesAnArrayHunkHoldingTheSameWrites() {
+        SectionBuffer production = new SectionBuffer(HEIGHT);
+        Hunk<NativeBlockState> array = Hunk.newArrayHunk(16, HEIGHT, 16);
+        Hunk<NativeBiome> biomes = Hunk.newArrayHunk(16, HEIGHT, 16);
+        NativeBlockState stone = StubPlatform.blockStateForTest("minecraft:stone");
+        NativeBlockState water = StubPlatform.blockStateForTest("minecraft:water");
+        for (int x = 0; x < 16; x++) {
+            for (int z = 0; z < 16; z++) {
+                int top = (x * 7 + z * 3) % HEIGHT;
+                for (int y = 0; y <= top; y++) {
+                    NativeBlockState state = y == top ? water : stone;
+                    production.setRaw(x, y, z, state);
+                    array.setRaw(x, y, z, state);
+                }
+            }
+        }
+
+        ChunkDump.ChunkSnapshot fromProduction = ChunkDump.capture(4, -9, production, biomes, HEIGHT);
+        ChunkDump.ChunkSnapshot fromArray = ChunkDump.capture(4, -9, array, biomes, HEIGHT);
+
+        assertArrayEquals(fromArray.blockPalette(), fromProduction.blockPalette());
+        assertArrayEquals(fromArray.blocks(), fromProduction.blocks());
+        assertTrue(List.of(fromProduction.blockPalette()).contains(ChunkDump.NULL_BLOCK_KEY));
+    }
+
+    @Test
+    public void biomeHunkKeepsWholeColumnWritesPerColumnAndReadsLikeAnArrayHunk() {
+        ProductionBiomeHunk production = new ProductionBiomeHunk(HEIGHT, () -> biome("minecraft:plains"));
+        Hunk<NativeBiome> array = Hunk.newArrayHunk(16, HEIGHT, 16);
+        NativeBiome forest = biome("minecraft:forest");
+        NativeBiome desert = biome("minecraft:desert");
+        for (int x = 0; x < 16; x++) {
+            for (int z = 0; z < 16; z++) {
+                NativeBiome column = ((x + z) & 1) == 0 ? forest : desert;
+                production.set(x, 0, z, x, HEIGHT - 1, z, column);
+                array.set(x, 0, z, x, HEIGHT - 1, z, column);
+            }
+        }
+
+        assertFalse(production.expanded());
+        assertSameCells(array, production);
+
+        production.setRaw(2, 4, 9, desert);
+        array.setRaw(2, 4, 9, desert);
+        production.set(5, 0, 5, 5, HEIGHT - 1, 5, desert);
+        array.set(5, 0, 5, 5, HEIGHT - 1, 5, desert);
+
+        assertTrue(production.expanded());
+        assertSameCells(array, production);
+    }
+
+    @Test
+    public void biomeHunkReadsTheFallbackOnlyForUnwrittenCells() {
+        NativeBiome plains = biome("minecraft:plains");
+        ProductionBiomeHunk production = new ProductionBiomeHunk(HEIGHT, () -> plains);
+        NativeBiome forest = biome("minecraft:forest");
+        production.set(1, 0, 1, 1, HEIGHT - 1, 1, forest);
+
+        assertSame(forest, production.getRaw(1, HEIGHT - 1, 1));
+        assertSame(plains, production.getRaw(0, 0, 0));
+    }
+
+    private static void assertSameCells(Hunk<NativeBiome> expected, Hunk<NativeBiome> actual) {
+        for (int x = 0; x < 16; x++) {
+            for (int z = 0; z < 16; z++) {
+                for (int y = 0; y < HEIGHT; y++) {
+                    assertSame(expected.get(x, y, z), actual.get(x, y, z));
+                }
+            }
+        }
+    }
+
+    private static NativeBiome biome(String key) {
+        return new TestBiome(key);
+    }
+
+    private record TestBiome(String key) implements NativeBiome {
+        @Override
+        public String namespace() {
+            return key.substring(0, key.indexOf(':'));
+        }
+
+        @Override
+        public Object nativeHandle() {
+            return key;
+        }
+    }
+}