Gap-free object rotation

- Rotations off the right angles fill every target cell from the nearest source block
- Source blocks that no target cell samples still place at their rotated position
- Right-angle rotations keep the direct transform
- Markers, canopy and tile data follow their resampled source blocks
- Datapack export bakes off-angle variants with the same resampler
- The unused rotateCopy paths are removed
- Placement goldens match the resampled output

.gitignore

@@ -81,3 +81,5 @@ BUILDS/
 /docs/
 /.perf/
 /.codegraph/
+
+.superpowers/

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

@@ -0,0 +1,563 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+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.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.Aquifer;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.NoiseRouter;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.lang.management.ManagementFactory;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import java.util.concurrent.Callable;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+
+public final class DatapackCostProbe {
+    private static final String LOG_PREFIX = "[datapack-cost]";
+    static final String VANILLA_PRESET = "minecraft:normal";
+    private static final int WARMUP_ORIGIN = -4096;
+    private static final int MINIMUM_CALLS = 8;
+    private static final int TOP_OFFENDERS = 10;
+    private static final long ANALYSIS_STACK_BYTES = 1L << 30;
+    private static final double MEGABYTE = 1024.0 * 1024.0;
+    private static final double NANOS_PER_SECOND = 1_000_000_000.0;
+
+    private DatapackCostProbe() {
+    }
+
+    public static void main(String[] arguments) {
+        PrintStream diagnostics = System.err;
+        try {
+            execute(Configuration.parse(arguments));
+        } catch (Throwable failure) {
+            failure.printStackTrace(diagnostics);
+            diagnostics.flush();
+            System.exit(1);
+        }
+        System.out.flush();
+        System.exit(0);
+    }
+
+    private static void execute(Configuration configuration) throws Exception {
+        HeadlessNativeBootstrap.initialize();
+        Files.createDirectories(configuration.work());
+        Path work = Files.createTempDirectory(configuration.work(), "run-");
+        List<HeadlessNativeRegistries> loaded = new ArrayList<>(2);
+        try {
+            log("exporting " + configuration.dimension() + " from " + configuration.pack());
+            ExportRun export = export(configuration, work);
+            log(String.format(Locale.ROOT, "exported in %.1f s: %d files, %d density functions", export.stats().seconds(),
+                    export.stats().files(), export.stats().densityFunctions()));
+            DensityJsonBreakdown.Report densityJson = onLargeStack("density-json",
+                    () -> DensityJsonBreakdown.analyze(export.files(), configuration.dimension()).report());
+            Path datapack = work.resolve("datapack");
+            writeFiles(export.files(), datapack);
+            Path vanillaPack = Files.createDirectories(work.resolve("vanilla"));
+            ExportStats exportStats = export.stats();
+            export.files().clear();
+
+            long baseline = settledHeap();
+            long loadStarted = System.nanoTime();
+            HeadlessNativeRegistries vanilla = isolatedLoad(vanillaPack);
+            double vanillaLoad = (System.nanoTime() - loadStarted) / NANOS_PER_SECOND;
+            loaded.add(vanilla);
+            long vanillaHeap = settledHeap();
+            loadStarted = System.nanoTime();
+            HeadlessNativeRegistries exported = isolatedLoad(datapack);
+            double exportLoad = (System.nanoTime() - loadStarted) / NANOS_PER_SECOND;
+            loaded.add(exported);
+            long exportHeap = settledHeap();
+            log(String.format(Locale.ROOT, "registries loaded: vanilla %.2f s, export %.2f s", vanillaLoad, exportLoad));
+
+            WorldgenStageBench vanillaBench = new WorldgenStageBench(new WorldgenStageBench.Options("vanilla",
+                    presetOverworld(vanilla.registries(), VANILLA_PRESET), vanilla.registries(), configuration.seed()));
+            warm(vanillaBench, configuration);
+            long vanillaSamplers = settledHeap();
+            WorldgenStageBench exportBench = new WorldgenStageBench(new WorldgenStageBench.Options("export",
+                    exportedOverworld(exported.registries()), exported.registries(), configuration.seed()));
+            warm(exportBench, configuration);
+            long exportSamplers = settledHeap();
+
+            double loadStart = ManagementFactory.getOperatingSystemMXBean().getSystemLoadAverage();
+            Measurement vanillaMeasurement = new Measurement(vanillaBench);
+            Measurement exportMeasurement = new Measurement(exportBench);
+            measure(List.of(vanillaMeasurement, exportMeasurement), configuration);
+            double loadEnd = ManagementFactory.getOperatingSystemMXBean().getSystemLoadAverage();
+            Map<String, GeneratorStats> generators = new LinkedHashMap<>();
+            generators.put("vanilla", vanillaMeasurement.stats(vanillaLoad, vanillaHeap - baseline, vanillaSamplers - exportHeap));
+            generators.put("export", exportMeasurement.stats(exportLoad, exportHeap - vanillaHeap, exportSamplers - vanillaSamplers));
+
+            log("analyzing density function graphs");
+            Map<String, List<DensityCostAnalysis.RootCost>> roots = new LinkedHashMap<>();
+            roots.put("vanilla", onLargeStack("density-cost-vanilla", () -> analyzeRoots(vanillaBench.settings(), configuration.dimension())));
+            roots.put("export", onLargeStack("density-cost-export", () -> analyzeRoots(exportBench.settings(), configuration.dimension())));
+
+            Report report = new Report(configuration.pack().toString(), configuration.dimension(), configuration.seed(),
+                    configuration.rounds() * configuration.side() * configuration.side(), configuration.warmup() * configuration.warmup(),
+                    configuration.rounds(), new MachineLoad(Runtime.getRuntime().availableProcessors(), loadStart, loadEnd),
+                    "single thread for chunk stages and calls, vanilla and export interleaved per round; registry load uses HeadlessNativeRegistries' 4-thread loader; export uses Iris's own pools",
+                    "feature decoration not measured: Paper's applyBiomeDecoration needs a live ServerLevel and the headless feature world lives in test fixtures",
+                    exportStats, generators, densityJson, roots, definitions());
+            writeReport(report, configuration.output());
+            System.out.println(table(report));
+            log("report written to " + configuration.output());
+        } finally {
+            for (HeadlessNativeRegistries registries : loaded) {
+                registries.close();
+            }
+            deleteTree(work);
+        }
+    }
+
+    private static ExportRun export(Configuration configuration, Path work) throws Exception {
+        Path exportRoot = Files.createDirectories(work.resolve("exports"));
+        StageClock clock = new StageClock();
+        WorldgenExportResult result;
+        long started;
+        long finished;
+        try (RealPackProbeSupport.Workspace workspace = RealPackProbeSupport.openWorkspace(new RealPackProbeSupport.WorkspaceOptions(
+                configuration.pack().toFile(), configuration.dimension(), LOG_PREFIX, new HeadlessNativeRuntime(), work))) {
+            WorldgenExportRequest request = WorldgenExportRequest.builder()
+                    .pack(workspace.pack().toPath())
+                    .dimension(configuration.dimension())
+                    .exportRoot(exportRoot)
+                    .objects(true)
+                    .build();
+            started = System.nanoTime();
+            clock.start(started);
+            result = WorldgenDatapackExporter.create().export(request, clock);
+            finished = System.nanoTime();
+        }
+        if (!result.isSuccess()) {
+            throw new IllegalStateException("Export failed: " + result.message() + " " + result.diagnostics());
+        }
+        SortedMap<String, byte[]> files = zipEntries(result.output());
+        ExportStats stats = new ExportStats((finished - started) / NANOS_PER_SECOND, clock.seconds(finished), Files.size(result.output()),
+                files.size(), count(files, "/worldgen/density_function/"), bytes(files, "/worldgen/density_function/"),
+                count(files, "/worldgen/noise/"), count(files, "/worldgen/biome/"), result.diagnostics().size());
+        Files.delete(result.output());
+        return new ExportRun(stats, files);
+    }
+
+    private static void warm(WorldgenStageBench bench, Configuration configuration) {
+        long started = System.nanoTime();
+        bench.chunks(WARMUP_ORIGIN, WARMUP_ORIGIN, configuration.warmup(), new WorldgenStageBench.ChunkSamples());
+        WorldgenStageBench.CallBudget budget = new WorldgenStageBench.CallBudget(MINIMUM_CALLS * 4, MINIMUM_CALLS,
+                TimeUnit.SECONDS.toNanos(configuration.callSeconds()) / 4);
+        bench.uncachedBiome(budget, new WorldgenStageBench.CallSamples());
+        bench.baseHeight(budget, Heightmap.Types.WORLD_SURFACE_WG, new WorldgenStageBench.CallSamples());
+        bench.baseColumn(budget, new WorldgenStageBench.CallSamples());
+        log(String.format(Locale.ROOT, "%s warmed in %.1f s", bench.label(), (System.nanoTime() - started) / NANOS_PER_SECOND));
+    }
+
+    private static void measure(List<Measurement> measurements, Configuration configuration) {
+        int stride = configuration.side() + 4;
+        WorldgenStageBench.CallBudget budget = new WorldgenStageBench.CallBudget(
+                Math.max(1, configuration.calls() / configuration.rounds()), Math.max(1, MINIMUM_CALLS / configuration.rounds()),
+                TimeUnit.SECONDS.toNanos(configuration.callSeconds()) / configuration.rounds());
+        for (int round = 0; round < configuration.rounds(); round++) {
+            for (int index = 0; index < measurements.size(); index++) {
+                Measurement measurement = measurements.get((index + round) % measurements.size());
+                long started = System.nanoTime();
+                measurement.bench.chunks(round * stride, round * stride, configuration.side(), measurement.chunks);
+                measurement.bench.uncachedBiome(budget, measurement.uncachedBiome);
+                measurement.bench.baseHeight(budget, Heightmap.Types.WORLD_SURFACE_WG, measurement.surfaceHeight);
+                measurement.bench.baseHeight(budget, Heightmap.Types.OCEAN_FLOOR_WG, measurement.floorHeight);
+                measurement.bench.baseColumn(budget, measurement.column);
+                log(String.format(Locale.ROOT, "%s round %d measured in %.1f s", measurement.bench.label(), round,
+                        (System.nanoTime() - started) / NANOS_PER_SECOND));
+            }
+        }
+    }
+
+    private static List<DensityCostAnalysis.RootCost> analyzeRoots(NoiseGeneratorSettings settings, String dimension) {
+        DensityCostAnalysis analysis = new DensityCostAnalysis(id -> DensityJsonBreakdown.category(dimension, id), TOP_OFFENDERS);
+        Map<String, DensityFunction> roots = new LinkedHashMap<>();
+        NoiseRouter router = settings.noiseRouter();
+        roots.put("temperature", router.temperature());
+        roots.put("vegetation", router.vegetation());
+        roots.put("continents", router.continents());
+        roots.put("erosion", router.erosion());
+        roots.put("depth", router.depth());
+        roots.put("ridges", router.ridges());
+        roots.put("chunk_surface_level", router.chunkSurfaceLevel());
+        roots.put("final_density", router.finalDensity());
+        if (settings.aquifers().isPresent()) {
+            Aquifer.Config aquifer = settings.aquifers().get();
+            roots.put("aquifer.barrier", aquifer.barrierNoise());
+            roots.put("aquifer.fluid_level_floodedness", aquifer.fluidLevelFloodednessNoise());
+            roots.put("aquifer.fluid_level_spread", aquifer.fluidLevelSpreadNoise());
+            roots.put("aquifer.lava", aquifer.lavaNoise());
+            roots.put("aquifer.exclusion", aquifer.exclusion());
+            roots.put("aquifer.surface_level", aquifer.surfaceLevel());
+        }
+        List<DensityCostAnalysis.RootCost> costs = new ArrayList<>(roots.size());
+        for (Map.Entry<String, DensityFunction> root : roots.entrySet()) {
+            costs.add(analysis.analyze(root.getKey(), root.getValue()));
+        }
+        return costs;
+    }
+
+    static LevelStem presetOverworld(RegistryAccess registries, String preset) {
+        return registries.lookupOrThrow(Registries.WORLD_PRESET)
+                .getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, Identifier.parse(preset))).value().overworld()
+                .orElseThrow(() -> new IllegalStateException("World preset " + preset + " has no overworld"));
+    }
+
+    static LevelStem exportedOverworld(RegistryAccess registries) {
+        return registries.lookupOrThrow(Registries.LEVEL_STEM).getOrThrow(LevelStem.OVERWORLD).value();
+    }
+
+    private static HeadlessNativeRegistries isolatedLoad(Path directory) {
+        try (PaperRegistryScope scope = PaperRegistryScope.open()) {
+            return HeadlessNativeRegistries.load(directory);
+        }
+    }
+
+    private static long settledHeap() throws InterruptedException {
+        for (int pass = 0; pass < 4; pass++) {
+            System.gc();
+            Thread.sleep(200L);
+        }
+        return ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getUsed();
+    }
+
+    private static <T> T onLargeStack(String name, Callable<T> work) throws Exception {
+        AtomicReference<T> result = new AtomicReference<>();
+        AtomicReference<Throwable> failure = new AtomicReference<>();
+        Thread thread = new Thread(null, () -> {
+            try {
+                result.set(work.call());
+            } catch (Throwable problem) {
+                failure.set(problem);
+            }
+        }, name, ANALYSIS_STACK_BYTES);
+        thread.start();
+        thread.join();
+        if (failure.get() instanceof Exception exception) {
+            throw exception;
+        }
+        if (failure.get() instanceof Error error) {
+            throw error;
+        }
+        return result.get();
+    }
+
+    private static SortedMap<String, byte[]> zipEntries(Path zip) throws IOException {
+        SortedMap<String, byte[]> files = new TreeMap<>();
+        try (ZipFile archive = new ZipFile(zip.toFile())) {
+            Enumeration<? extends ZipEntry> entries = archive.entries();
+            while (entries.hasMoreElements()) {
+                ZipEntry entry = entries.nextElement();
+                if (!entry.isDirectory()) {
+                    files.put(entry.getName(), archive.getInputStream(entry).readAllBytes());
+                }
+            }
+        }
+        return files;
+    }
+
+    private static void writeFiles(SortedMap<String, byte[]> files, Path directory) throws IOException {
+        Files.createDirectories(directory);
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            Path target = directory.resolve(file.getKey()).normalize();
+            if (!target.startsWith(directory)) {
+                throw new IllegalArgumentException("Export file escapes the datapack root: " + file.getKey());
+            }
+            Files.createDirectories(target.getParent());
+            Files.write(target, file.getValue());
+        }
+    }
+
+    private static int count(SortedMap<String, byte[]> files, String folder) {
+        int count = 0;
+        for (String path : files.keySet()) {
+            if (path.contains(folder) && path.endsWith(".json")) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    private static long bytes(SortedMap<String, byte[]> files, String folder) {
+        long bytes = 0;
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            if (file.getKey().contains(folder) && file.getKey().endsWith(".json")) {
+                bytes += file.getValue().length;
+            }
+        }
+        return bytes;
+    }
+
+    private static void writeReport(Report report, Path output) throws IOException {
+        Files.createDirectories(output.getParent());
+        Gson gson = new GsonBuilder().setPrettyPrinting().serializeSpecialFloatingPointValues().create();
+        Files.writeString(output, gson.toJson(report), StandardCharsets.UTF_8);
+    }
+
+    private static Map<String, String> definitions() {
+        Map<String, String> definitions = new LinkedHashMap<>();
+        definitions.put("chunks", "per stage: wall ms and current-thread CPU ms per chunk; rounds of side x side chunks alternate vanilla and export");
+        definitions.put("chunks.biomes", "ChunkGenerator.createBiomes on a fresh ProtoChunk, ms per chunk over the grid plus a one-chunk ring");
+        definitions.put("chunks.noise", "NoiseChunk construction (aquifer init) plus NoiseBasedChunkGenerator.doFill, ms per chunk");
+        definitions.put("chunks.surface", "MaterialSystem.buildSurface with the fill's NoiseChunk and a region biome manager, ms per chunk");
+        definitions.put("chunks.carverBiome", "one uncached BiomeSource lookup at the chunk origin, as ChunkAccess.carverBiome memoizes per chunk, ms per chunk");
+        definitions.put("uncachedBiome", "BiomeSource.createUncachedResolver(...).getNoiseBiome at random quart positions within 32k blocks, wall us per call and mean thread CPU us per call");
+        definitions.put("baseHeight", "NoiseBasedChunkGenerator.getBaseHeight as structure placement calls it, us per call");
+        definitions.put("baseColumn", "NoiseBasedChunkGenerator.getBaseColumn, us per call");
+        definitions.put("retainedHeapBytes", "used heap after four System.gc passes, delta across the registry load");
+        definitions.put("samplerHeapBytes", "used heap delta across RandomState creation and warmup (compiled samplers and buffer pools)");
+        definitions.put("roots.dagNodes", "distinct non-constant density function and spline nodes reachable, references shared");
+        definitions.put("roots.cachedNodes", "non-constant evaluations per point with caches enabled: every distinct cache body once, all branches");
+        definitions.put("roots.expandedNodes", "non-constant evaluations per point with every reference and cache re-expanded, all branches");
+        definitions.put("roots.uncachedPointWorst", "worst single uncached point evaluation with lazy splines, interval_select and range_choice; interpolated off-lattice costs 8 corners at expanded cost; find_top_surface counts its probe steps");
+        definitions.put("roots.dagShare", "share of the distinct nodes by the category of the named file that holds them; offset copies are Grad2 and Taps duplicates");
+        definitions.put("roots.exclusive", "named density functions ranked by multiplicity x own nodes in the expanded tree");
+        definitions.put("roots.inclusive", "named density functions ranked by multiplicity x subtree nodes in the expanded tree");
+        definitions.put("densityJson.structurallyDuplicateBytes", "bytes beyond one file per JSON shape, with numbers, density function references and noise ids abstracted");
+        return definitions;
+    }
+
+    private static String table(Report report) {
+        StringBuilder out = new StringBuilder(4096);
+        GeneratorStats vanilla = report.generators().get("vanilla");
+        GeneratorStats export = report.generators().get("export");
+        out.append(String.format(Locale.ROOT, "%s %s seed %d: %d chunks in %d interleaved rounds after %d warmup chunks, one thread, load %.0f-%.0f on %d cores%n",
+                LOG_PREFIX, report.dimension(), report.seed(), report.chunks(), report.rounds(), report.warmupChunks(),
+                report.load().loadAverageStart(), report.load().loadAverageEnd(), report.load().processors()));
+        out.append(String.format(Locale.ROOT, "%-34s %10s %10s %8s %10s %10s %8s%n", "stage (mean)", "vanilla", "export", "ratio",
+                "cpu van", "cpu exp", "ratio"));
+        out.append(String.format(Locale.ROOT, "%-34s %10s %10.1f%n", "export (s)", "-", report.export().seconds()));
+        row(out, "registry load (s)", vanilla.registryLoadSeconds(), export.registryLoadSeconds());
+        row(out, "retained heap after load (MB)", vanilla.retainedHeapBytes() / MEGABYTE, export.retainedHeapBytes() / MEGABYTE);
+        row(out, "sampler heap after warmup (MB)", vanilla.samplerHeapBytes() / MEGABYTE, export.samplerHeapBytes() / MEGABYTE);
+        stage(out, "biome fill (ms/chunk)", vanilla.chunks().biomes(), export.chunks().biomes());
+        stage(out, "noise fill (ms/chunk)", vanilla.chunks().noise(), export.chunks().noise());
+        stage(out, "surface (ms/chunk)", vanilla.chunks().surface(), export.chunks().surface());
+        stage(out, "carver biome lookup (ms/chunk)", vanilla.chunks().carverBiome(), export.chunks().carverBiome());
+        row(out, "chunk total (ms/chunk)", vanilla.chunks().totalMean(), export.chunks().totalMean(),
+                vanilla.chunks().totalCpuMean(), export.chunks().totalCpuMean());
+        call(out, "uncached getNoiseBiome (us/call)", vanilla.uncachedBiome(), export.uncachedBiome());
+        call(out, "getBaseHeight WORLD_SURFACE (us)", vanilla.baseHeightSurface(), export.baseHeightSurface());
+        call(out, "getBaseHeight OCEAN_FLOOR (us)", vanilla.baseHeightFloor(), export.baseHeightFloor());
+        call(out, "getBaseColumn (us/call)", vanilla.baseColumn(), export.baseColumn());
+        out.append(String.format(Locale.ROOT, "%-24s %9s %9s %9s %10s %10s %10s %10s%n", "router root", "dag(v)", "dag",
+                "cached", "expand(v)", "expanded", "uncPt(v)", "uncachedPt"));
+        List<DensityCostAnalysis.RootCost> vanillaRoots = report.roots().get("vanilla");
+        List<DensityCostAnalysis.RootCost> exportRoots = report.roots().get("export");
+        for (DensityCostAnalysis.RootCost root : exportRoots) {
+            DensityCostAnalysis.RootCost reference = find(vanillaRoots, root.root());
+            out.append(String.format(Locale.ROOT, "%-24s %9s %9s %9s %10s %10s %10s %10s%n", root.root(),
+                    reference == null ? "-" : compact(reference.dagNodes()), compact(root.dagNodes()), compact(root.cachedNodes()),
+                    reference == null ? "-" : compact(reference.expandedNodes()), compact(root.expandedNodes()),
+                    reference == null ? "-" : compact(reference.uncachedPointWorst()), compact(root.uncachedPointWorst())));
+        }
+        out.append("top expanded offenders (exclusive share of root, multiplicity)\n");
+        for (DensityCostAnalysis.RootCost root : exportRoots) {
+            if (root.exclusive().isEmpty() || root.expandedNodes() < 1.0e4) {
+                continue;
+            }
+            StringBuilder line = new StringBuilder(String.format(Locale.ROOT, "  %-22s", root.root()));
+            for (int index = 0; index < Math.min(2, root.exclusive().size()); index++) {
+                DensityCostAnalysis.Offender offender = root.exclusive().get(index);
+                line.append(String.format(Locale.ROOT, " %4.1f%% %s x%s;", 100.0 * offender.contribution() / root.expandedNodes(),
+                        shortName(offender.name()), compact(offender.multiplicity())));
+            }
+            out.append(line).append('\n');
+        }
+        for (DensityCostAnalysis.RootCost root : exportRoots) {
+            if (root.dagNodes() < 1.0e4) {
+                continue;
+            }
+            List<Map.Entry<String, Double>> shares = new ArrayList<>(root.dagShare().entrySet());
+            shares.sort(Map.Entry.<String, Double>comparingByValue().reversed());
+            StringBuilder line = new StringBuilder(String.format(Locale.ROOT, "  dag %-18s", root.root()));
+            for (int index = 0; index < Math.min(3, shares.size()); index++) {
+                line.append(String.format(Locale.ROOT, " %4.1f%% %s;", 100.0 * shares.get(index).getValue(), shares.get(index).getKey()));
+            }
+            out.append(line).append('\n');
+        }
+        DensityJsonBreakdown.Report json = report.densityJson();
+        out.append(String.format(Locale.ROOT, "density function JSON %.0f MB in %d files, %d cellular instances in %d shapes%n",
+                json.bytes() / MEGABYTE, json.files(), json.cellularInstances(), json.cellularShapes().size()));
+        for (int index = 0; index < Math.min(9, json.categories().size()); index++) {
+            DensityJsonBreakdown.CategoryBytes category = json.categories().get(index);
+            out.append(String.format(Locale.ROOT, "  %-22s %8.1f MB %7d files %7d shapes %8.1f MB dup%n", category.category(),
+                    category.bytes() / MEGABYTE, category.files(), category.distinctShapes(), category.structurallyDuplicateBytes() / MEGABYTE));
+        }
+        for (int index = 0; index < Math.min(4, json.libraryOwners().size()); index++) {
+            DensityJsonBreakdown.Bytes owner = json.libraryOwners().get(index);
+            out.append(String.format(Locale.ROOT, "  %-48s %8.1f MB%n", owner.name(), owner.bytes() / MEGABYTE));
+        }
+        return out.toString();
+    }
+
+    private static void row(StringBuilder out, String label, double vanilla, double export) {
+        out.append(String.format(Locale.ROOT, "%-34s %10.3f %10.3f %8s%n", label, vanilla, export, ratio(vanilla, export)));
+    }
+
+    private static void row(StringBuilder out, String label, double vanilla, double export, double vanillaCpu, double exportCpu) {
+        out.append(String.format(Locale.ROOT, "%-34s %10.3f %10.3f %8s %10.3f %10.3f %8s%n", label, vanilla, export, ratio(vanilla, export),
+                vanillaCpu, exportCpu, ratio(vanillaCpu, exportCpu)));
+    }
+
+    private static void stage(StringBuilder out, String label, WorldgenStageBench.StageTiming vanilla, WorldgenStageBench.StageTiming export) {
+        row(out, label, vanilla.wall().mean(), export.wall().mean(), vanilla.cpu().mean(), export.cpu().mean());
+    }
+
+    private static void call(StringBuilder out, String label, WorldgenStageBench.CallTiming vanilla, WorldgenStageBench.CallTiming export) {
+        row(out, label, vanilla.wall().mean(), export.wall().mean(), vanilla.cpuMean(), export.cpuMean());
+    }
+
+    private static String ratio(double vanilla, double export) {
+        return vanilla > 0.0 ? String.format(Locale.ROOT, "%.1fx", export / vanilla) : "-";
+    }
+
+    private static DensityCostAnalysis.RootCost find(List<DensityCostAnalysis.RootCost> roots, String name) {
+        for (DensityCostAnalysis.RootCost root : roots) {
+            if (root.root().equals(name)) {
+                return root;
+            }
+        }
+        return null;
+    }
+
+    private static String shortName(String name) {
+        int separator = name.indexOf(':');
+        String path = separator < 0 ? name : name.substring(separator + 1);
+        return path.length() <= 34 ? path : "..." + path.substring(path.length() - 31);
+    }
+
+    private static String compact(double value) {
+        if (value < 1.0e4) {
+            return String.format(Locale.ROOT, "%.0f", value);
+        }
+        return String.format(Locale.ROOT, "%.2e", value);
+    }
+
+    private static void log(String message) {
+        System.out.println(LOG_PREFIX + " " + message);
+    }
+
+    private static void deleteTree(Path root) throws IOException {
+        if (!Files.exists(root)) {
+            return;
+        }
+        HeadlessNativeRegistries.delete(root);
+    }
+
+    record Configuration(Path pack, String dimension, long seed, int side, int rounds, int warmup, int calls, long callSeconds,
+                         Path output, Path work) {
+        Configuration {
+            if (side < 1 || rounds < 1 || warmup < 1 || calls < MINIMUM_CALLS || callSeconds < 1) {
+                throw new IllegalArgumentException("side, rounds, warmup and callSeconds must be positive and calls at least " + MINIMUM_CALLS);
+            }
+        }
+
+        static Configuration parse(String[] arguments) {
+            if (arguments.length != 10) {
+                throw new IllegalArgumentException("Usage: pack dimension seed side rounds warmupSide calls callSeconds output work");
+            }
+            return new Configuration(new File(arguments[0]).toPath().toAbsolutePath(), arguments[1], Long.parseLong(arguments[2]),
+                    Integer.parseInt(arguments[3]), Integer.parseInt(arguments[4]), Integer.parseInt(arguments[5]),
+                    Integer.parseInt(arguments[6]), Long.parseLong(arguments[7]), new File(arguments[8]).toPath().toAbsolutePath(),
+                    new File(arguments[9]).toPath().toAbsolutePath());
+        }
+    }
+
+    record ExportStats(double seconds, Map<String, Double> stageSeconds, long zipBytes, int files, int densityFunctions,
+                       long densityFunctionBytes, int noises, int biomes, int diagnostics) {
+    }
+
+    record GeneratorStats(double registryLoadSeconds, long retainedHeapBytes, long samplerHeapBytes, WorldgenStageBench.ChunkTimings chunks,
+                          WorldgenStageBench.CallTiming uncachedBiome, WorldgenStageBench.CallTiming baseHeightSurface,
+                          WorldgenStageBench.CallTiming baseHeightFloor, WorldgenStageBench.CallTiming baseColumn) {
+    }
+
+    record MachineLoad(int processors, double loadAverageStart, double loadAverageEnd) {
+    }
+
+    record Report(String pack, String dimension, long seed, int chunks, int warmupChunks, int rounds, MachineLoad load,
+                  String threading, String decoration,
+                  ExportStats export, Map<String, GeneratorStats> generators, DensityJsonBreakdown.Report densityJson,
+                  Map<String, List<DensityCostAnalysis.RootCost>> roots, Map<String, String> definitions) {
+    }
+
+    private record ExportRun(ExportStats stats, SortedMap<String, byte[]> files) {
+    }
+
+    private static final class Measurement {
+        private final WorldgenStageBench bench;
+        private final WorldgenStageBench.ChunkSamples chunks = new WorldgenStageBench.ChunkSamples();
+        private final WorldgenStageBench.CallSamples uncachedBiome = new WorldgenStageBench.CallSamples();
+        private final WorldgenStageBench.CallSamples surfaceHeight = new WorldgenStageBench.CallSamples();
+        private final WorldgenStageBench.CallSamples floorHeight = new WorldgenStageBench.CallSamples();
+        private final WorldgenStageBench.CallSamples column = new WorldgenStageBench.CallSamples();
+
+        private Measurement(WorldgenStageBench bench) {
+            this.bench = bench;
+        }
+
+        private GeneratorStats stats(double loadSeconds, long retainedHeap, long samplerHeap) {
+            return new GeneratorStats(loadSeconds, retainedHeap, samplerHeap, chunks.timings(), uncachedBiome.timing(),
+                    surfaceHeight.timing(), floorHeight.timing(), column.timing());
+        }
+    }
+
+    private static final class StageClock implements WorldgenExportProgress {
+        private final Map<String, Long> starts = new LinkedHashMap<>();
+        private long origin;
+
+        private void start(long nanos) {
+            origin = nanos;
+        }
+
+        @Override
+        public void stage(String stage) {
+            starts.put(stage, System.nanoTime());
+        }
+
+        @Override
+        public void resources(int done, int total) {
+        }
+
+        private Map<String, Double> seconds(long finished) {
+            Map<String, Double> seconds = new LinkedHashMap<>();
+            String previous = "setup";
+            long previousStart = origin;
+            for (Map.Entry<String, Long> entry : starts.entrySet()) {
+                seconds.put(previous, (entry.getValue() - previousStart) / NANOS_PER_SECOND);
+                previous = entry.getKey();
+                previousStart = entry.getValue();
+            }
+            seconds.put(previous, (finished - previousStart) / NANOS_PER_SECOND);
+            return seconds;
+        }
+    }
+}

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

@@ -0,0 +1,331 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.generation.concurrent.MultiBurst;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.pack.datapack.export.VanillaResourceIdentifier;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import art.arcane.iris.pack.datapack.export.WorldgenExportService;
+import art.arcane.iris.pack.datapack.export.compile.surface.MaterialProgramCompiler;
+import art.arcane.iris.pack.datapack.export.ir.ExportDiagnostic;
+import art.arcane.iris.probe.fidelity.BiomeShareReport;
+import art.arcane.iris.probe.fidelity.BiomeTypes;
+import art.arcane.iris.probe.fidelity.ColumnSource;
+import art.arcane.iris.probe.fidelity.ColumnSurvey;
+import art.arcane.iris.probe.fidelity.FidelityComparison;
+import art.arcane.iris.probe.fidelity.FidelityReport;
+import art.arcane.iris.probe.fidelity.FidelitySampling;
+import art.arcane.iris.probe.fidelity.FidelitySamples;
+import art.arcane.iris.probe.fidelity.FidelityScanner;
+import art.arcane.iris.probe.fidelity.FidelitySource;
+import art.arcane.iris.probe.fidelity.FidelityStats;
+import art.arcane.iris.probe.fidelity.FidelityThresholds;
+import art.arcane.iris.probe.fidelity.IrisEngineColumnSource;
+import art.arcane.iris.probe.fidelity.IrisEngineFidelitySource;
+import art.arcane.iris.probe.fidelity.SurveyWindow;
+import art.arcane.iris.probe.fidelity.VanillaNoiseColumnSource;
+import art.arcane.iris.probe.fidelity.VanillaNoiseFidelitySource;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Objects;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+public final class DatapackFidelityProbe {
+    private static final String LOG_PREFIX = "[datapack-fidelity]";
+    private static final String USAGE = "Usage: datapackFidelityProbe pack dimension seed radiusChunks stride output surveyBlocks surveyStride surveySeeds mode";
+    private static final String TARGET_VERSION = "26.3";
+    private static final String EXPORT_FORMAT = "directory";
+    private static final String EXPORT_OUTPUT = "export";
+    private static final int MAX_STRIDE = 16;
+    private static final int CHUNK_WIDTH = 16;
+    private static final int ARGUMENTS = 10;
+    private static final String COLUMN_SCOPE = "columns";
+    private static final String CHUNK_SCOPE = "chunks";
+    private static final int EXIT_ERROR = 1;
+    private static final int EXIT_FIDELITY_FAILED = 3;
+
+    private DatapackFidelityProbe() {
+    }
+
+    public static void main(String[] arguments) {
+        int status;
+        try {
+            status = execute(arguments, WorldgenDatapackExporter.create()).passed() ? 0 : EXIT_FIDELITY_FAILED;
+        } catch (Throwable failure) {
+            failure.printStackTrace(System.err);
+            status = EXIT_ERROR;
+        }
+        System.out.flush();
+        System.err.flush();
+        System.exit(status);
+    }
+
+    static FidelityReport execute(String[] arguments, WorldgenExportService exporter) throws Exception {
+        Objects.requireNonNull(exporter, "exporter");
+        Configuration configuration = Configuration.parse(arguments);
+        System.out.println(LOG_PREFIX + " pack=" + configuration.pack() + " dimension=" + configuration.dimension()
+                + " seed=" + configuration.seed() + " radiusChunks=" + configuration.radiusChunks() + " stride=" + configuration.stride()
+                + " surveyBlocks=" + configuration.survey().size() + " surveyStride=" + configuration.survey().stride()
+                + " surveySeeds=" + configuration.surveySeeds() + " mode=" + configuration.mode().label());
+        Outcome outcome = compare(configuration, exporter);
+        writeReport(configuration.output(), outcome.json());
+        System.out.print(outcome.table());
+        System.out.println(LOG_PREFIX + " report=" + configuration.output());
+        return outcome.report();
+    }
+
+    private static Outcome compare(Configuration configuration, WorldgenExportService exporter) throws Exception {
+        Path scratch = Files.createTempDirectory("iris-datapack-fidelity-");
+        try {
+            return compareIn(scratch, configuration, exporter);
+        } finally {
+            ProbeWorkspaceCleanup.deleteRecursively(scratch);
+        }
+    }
+
+    private static Outcome compareIn(Path scratch, Configuration configuration, WorldgenExportService exporter) throws Exception {
+        HeadlessNativeRuntime runtime = new HeadlessNativeRuntime();
+        try (RealPackProbeSupport.Workspace workspace = RealPackProbeSupport.openWorkspace(new RealPackProbeSupport.WorkspaceOptions(
+                configuration.pack().toFile(), configuration.dimension(), LOG_PREFIX, runtime, scratch))) {
+            WorldgenExportResult export = export(exporter, workspace.pack().toPath(), configuration.dimension(), scratch.resolve("exports"));
+            Target target = new Target(export.output(), WorldgenExportRequest.DEFAULT_NAMESPACE,
+                    VanillaResourceIdentifier.sanitizePath(configuration.dimension()), export.loadKeyByBiomeId());
+            return switch (configuration.mode()) {
+                case FULL -> Outcome.of(compareAll(workspace, target, configuration));
+                case BIOMES -> Outcome.of(compareBiomes(workspace, target, configuration));
+            };
+        }
+    }
+
+    private static FidelityReport compareAll(RealPackProbeSupport.Workspace workspace, Target target, Configuration configuration) throws Exception {
+        List<Long> seeds = configuration.surveySeeds();
+        FidelityStats irisColumns = null;
+        FidelityStats exportColumns = null;
+        FidelitySamples chunks = null;
+        for (long seed : seeds) {
+            try (RealPackProbeSupport.EngineSession session = workspace.openEngine(seed, false, "fidelity-" + seed)) {
+                Surveyed surveyed = survey(session.engine(), target, seed, configuration.survey());
+                irisColumns = irisColumns == null ? surveyed.iris() : irisColumns.merge(surveyed.iris());
+                exportColumns = exportColumns == null ? surveyed.export() : exportColumns.merge(surveyed.export());
+                if (seed == configuration.seed()) {
+                    chunks = scanChunks(session.engine(), target, configuration);
+                }
+            }
+        }
+        FidelitySampling columnSampling = new FidelitySampling(COLUMN_SCOPE, configuration.survey().size(), configuration.survey().stride(),
+                seeds, irisColumns.columns());
+        return FidelityComparison.compare(new FidelitySamples(irisColumns, exportColumns, columnSampling), chunks, FidelityThresholds.defaults());
+    }
+
+    private static BiomeShareReport compareBiomes(RealPackProbeSupport.Workspace workspace, Target target, Configuration configuration) throws Exception {
+        List<FidelitySamples> seeds = new ArrayList<>(configuration.seedCount());
+        Map<String, String> biomeTypes = Map.of();
+        for (long seed : configuration.surveySeeds()) {
+            try (RealPackProbeSupport.EngineSession session = workspace.openEngine(seed, false, "biomes-" + seed)) {
+                Engine engine = session.engine();
+                Surveyed surveyed = survey(engine, target, seed, configuration.survey());
+                if (biomeTypes.isEmpty()) {
+                    biomeTypes = BiomeTypes.of(engine.getDimension().getAllRegions(engine), key -> engine.getData().getBiomeLoader().load(key));
+                }
+                seeds.add(new FidelitySamples(surveyed.iris(), surveyed.export(), new FidelitySampling(COLUMN_SCOPE, configuration.survey().size(),
+                        configuration.survey().stride(), List.of(seed), surveyed.iris().columns())));
+            }
+        }
+        return FidelityComparison.compareBiomeShares(seeds, biomeTypes, FidelityThresholds.defaults());
+    }
+
+    private static Surveyed survey(Engine engine, Target target, long seed, SurveyWindow window) throws Exception {
+        try (ColumnSource iris = new IrisEngineColumnSource(engine);
+             ColumnSource vanilla = new VanillaNoiseColumnSource(target.sampler(seed), target.loadKeyByBiomeId())) {
+            requireSameHeightRange(iris.minY(), iris.maxY(), vanilla.minY(), vanilla.maxY());
+            return new Surveyed(surveyed(iris, window, seed), surveyed(vanilla, window, seed));
+        }
+    }
+
+    private static FidelityStats surveyed(ColumnSource source, SurveyWindow window, long seed) {
+        long started = System.nanoTime();
+        FidelityStats stats = ColumnSurvey.scan(source, window, MultiBurst.burst.parallelism());
+        System.out.println(LOG_PREFIX + " surveyed " + source.label() + " seed=" + seed + " columns=" + stats.columns()
+                + " in " + (System.nanoTime() - started) / 1_000_000L + "ms");
+        return stats;
+    }
+
+    private static FidelitySamples scanChunks(Engine engine, Target target, Configuration configuration) throws Exception {
+        try (IrisEngineFidelitySource iris = new IrisEngineFidelitySource(engine);
+             VanillaNoiseFidelitySource vanilla = new VanillaNoiseFidelitySource(target.sampler(configuration.seed()), target.loadKeyByBiomeId(),
+                     target.namespace() + ":" + MaterialProgramCompiler.WALL_SHELL)) {
+            requireSameHeightRange(iris.minY(), iris.maxY(), vanilla.minY(), vanilla.maxY());
+            FidelityStats irisStats = scan(iris, configuration);
+            FidelityStats exportStats = scan(vanilla, configuration);
+            FidelitySampling sampling = new FidelitySampling(CHUNK_SCOPE, (2 * configuration.radiusChunks() + 1) * CHUNK_WIDTH,
+                    configuration.stride(), List.of(configuration.seed()), irisStats.columns());
+            return new FidelitySamples(irisStats, exportStats, sampling);
+        }
+    }
+
+    private static WorldgenExportResult export(WorldgenExportService exporter, Path pack, String dimension, Path exportRoot) throws IOException {
+        Files.createDirectories(exportRoot);
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(pack)
+                .dimension(dimension)
+                .version(TARGET_VERSION)
+                .format(EXPORT_FORMAT)
+                .output(EXPORT_OUTPUT)
+                .exportRoot(exportRoot)
+                .build();
+        WorldgenExportResult result = exporter.export(request, WorldgenExportProgress.NONE);
+        if (!result.isSuccess()) {
+            throw new IllegalStateException("Datapack export of dimension '" + dimension + "' was " + result.status() + ": " + result.message());
+        }
+        System.out.println(LOG_PREFIX + " exported target=" + TARGET_VERSION + " biomes=" + result.loadKeyByBiomeId().size()
+                + " diagnostics=" + result.diagnostics().size() + " " + diagnosticCounts(result.diagnostics()));
+        return result;
+    }
+
+    private static FidelityStats scan(FidelitySource source, Configuration configuration) {
+        long started = System.nanoTime();
+        FidelityStats stats = FidelityScanner.scan(source, 0, 0, configuration.radiusChunks(), configuration.stride(),
+                MultiBurst.burst.parallelism());
+        System.out.println(LOG_PREFIX + " sampled " + source.label() + " columns=" + stats.columns() + " terrainColumns=" + stats.heightColumns()
+                + " in " + (System.nanoTime() - started) / 1_000_000L + "ms");
+        return stats;
+    }
+
+    private static void requireSameHeightRange(int irisMinY, int irisMaxY, int exportMinY, int exportMaxY) {
+        if (irisMinY != exportMinY || irisMaxY != exportMaxY) {
+            throw new IllegalStateException("Iris height range [" + irisMinY + ", " + irisMaxY
+                    + ") differs from the exported dimension range [" + exportMinY + ", " + exportMaxY + ")");
+        }
+    }
+
+    private static SortedMap<String, Integer> diagnosticCounts(List<ExportDiagnostic> diagnostics) {
+        SortedMap<String, Integer> counts = new TreeMap<>();
+        for (ExportDiagnostic diagnostic : diagnostics) {
+            counts.merge(diagnostic.limit().name(), 1, Integer::sum);
+        }
+        return counts;
+    }
+
+    private static void writeReport(Path output, String json) throws IOException {
+        Path parent = output.getParent();
+        Files.createDirectories(parent);
+        Path staged = Files.createTempFile(parent, ".datapack-fidelity-", ".json");
+        try {
+            Files.writeString(staged, json + "\n", StandardCharsets.UTF_8);
+            Files.move(staged, output, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
+    private enum Mode {
+        FULL,
+        BIOMES;
+
+        private static Mode parse(String value) {
+            String normalized = value.trim().toLowerCase(Locale.ROOT);
+            for (Mode mode : values()) {
+                if (mode.label().equals(normalized)) {
+                    return mode;
+                }
+            }
+            throw new IllegalArgumentException("mode must be full or biomes, got '" + value + "'");
+        }
+
+        private String label() {
+            return name().toLowerCase(Locale.ROOT);
+        }
+    }
+
+    private record Outcome(FidelityReport report, String json, String table) {
+        private static Outcome of(FidelityReport report) {
+            return new Outcome(report, report.toJson(), report.toTable());
+        }
+
+        private static Outcome of(BiomeShareReport report) {
+            return new Outcome(report.mean(), report.toJson(), report.toTable());
+        }
+    }
+
+    private record Surveyed(FidelityStats iris, FidelityStats export) {
+    }
+
+    private record Target(Path output, String namespace, String dimension, Map<String, String> loadKeyByBiomeId) {
+        private WorldgenExportSampler sampler(long seed) throws IOException {
+            return WorldgenExportSampler.open(output, WorldgenExportMode.OVERWORLD, namespace + ":" + dimension, seed);
+        }
+    }
+
+    private record Configuration(Path pack, String dimension, long seed, int radiusChunks, int stride, Path output, SurveyWindow survey,
+                                 int seedCount, Mode mode) {
+        private static Configuration parse(String[] arguments) {
+            if (arguments.length != ARGUMENTS) {
+                throw new IllegalArgumentException(USAGE);
+            }
+            Path pack = Path.of(arguments[0]).toAbsolutePath().normalize();
+            if (!Files.isDirectory(pack)) {
+                throw new IllegalArgumentException("Pack folder " + pack + " does not exist");
+            }
+            String dimension = arguments[1].trim();
+            if (dimension.isEmpty()) {
+                throw new IllegalArgumentException("Dimension key must not be blank");
+            }
+            long seed = parseLong(arguments[2], "seed");
+            int radiusChunks = parseInt(arguments[3], "radiusChunks");
+            if (radiusChunks < 0) {
+                throw new IllegalArgumentException("radiusChunks must be zero or positive, got " + radiusChunks);
+            }
+            int stride = parseInt(arguments[4], "stride");
+            if (stride < 1 || stride > MAX_STRIDE) {
+                throw new IllegalArgumentException("stride must be within [1, " + MAX_STRIDE + "], got " + stride);
+            }
+            Path output = Path.of(arguments[5]).toAbsolutePath().normalize();
+            if (Files.isDirectory(output)) {
+                throw new IllegalArgumentException("Report output " + output + " is a directory");
+            }
+            SurveyWindow survey = new SurveyWindow(0, 0, parseInt(arguments[6], "surveyBlocks"), parseInt(arguments[7], "surveyStride"));
+            int seedCount = parseInt(arguments[8], "surveySeeds");
+            if (seedCount < 1) {
+                throw new IllegalArgumentException("surveySeeds must be at least 1, got " + seedCount);
+            }
+            Mode mode = Mode.parse(arguments[9]);
+            return new Configuration(pack, dimension, seed, radiusChunks, stride, output, survey, seedCount, mode);
+        }
+
+        private List<Long> surveySeeds() {
+            List<Long> seeds = new ArrayList<>(seedCount);
+            for (int index = 0; index < seedCount; index++) {
+                seeds.add(seed + index);
+            }
+            return seeds;
+        }
+
+        private static long parseLong(String value, String name) {
+            try {
+                return Long.parseLong(value.trim());
+            } catch (NumberFormatException failure) {
+                throw new IllegalArgumentException(name + " must be an integer, got '" + value + "'", failure);
+            }
+        }
+
+        private static int parseInt(String value, String name) {
+            try {
+                return Integer.parseInt(value.trim());
+            } catch (NumberFormatException failure) {
+                throw new IllegalArgumentException(name + " must be an integer, got '" + value + "'", failure);
+            }
+        }
+    }
+}

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

@@ -0,0 +1,349 @@
+package art.arcane.iris.probe;
+
+import net.minecraft.core.Holder;
+import net.minecraft.util.CubicSpline;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunctions;
+import net.minecraft.world.level.levelgen.densityfunction.generator.ConstantFunction;
+import net.minecraft.world.level.levelgen.densityfunction.op.CacheFunction;
+import net.minecraft.world.level.levelgen.densityfunction.op.FindTopSurfaceFunction;
+import net.minecraft.world.level.levelgen.densityfunction.op.InterpolatedFunction;
+import net.minecraft.world.level.levelgen.densityfunction.op.IntervalSelectFunction;
+import net.minecraft.world.level.levelgen.densityfunction.op.RangeChoiceFunction;
+import net.minecraft.world.level.levelgen.densityfunction.op.SplineFunction;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.function.Function;
+
+final class DensityCostAnalysis {
+    private static final double LATTICE_CORNERS = 8.0;
+    private static final int MAX_SURFACE_STEPS = 4096;
+    private static final String INLINE = "<inline>";
+
+    private final Function<String, String> categories;
+    private final int topCount;
+    private final Map<Object, Costs> costs = new IdentityHashMap<>();
+    private final Map<DensityFunction, Body> bodies = new IdentityHashMap<>();
+    private final Map<DensityFunction, String> names = new IdentityHashMap<>();
+
+    DensityCostAnalysis(Function<String, String> categories, int topCount) {
+        this.categories = categories;
+        this.topCount = topCount;
+    }
+
+    RootCost analyze(String root, DensityFunction function) {
+        Costs total = cost(function);
+        Reach reach = new Reach();
+        reach(function, reach, categories.apply(rootName(function, root)));
+        double cached = total.cachedLocal();
+        for (CacheFunction cache : reach.caches.keySet()) {
+            cached += cost(cache.input()).cachedLocal();
+        }
+        Body rootBody = new Body();
+        local(function, rootBody, true);
+        Map<DensityFunction, Double> multiplicity = multiplicity(rootBody);
+        List<Offender> offenders = new ArrayList<>(multiplicity.size());
+        Map<String, Double> shares = new TreeMap<>();
+        double expanded = total.expanded();
+        shares.merge(categories.apply(rootName(function, root)), rootBody.self / expanded, Double::sum);
+        for (Map.Entry<DensityFunction, Double> entry : multiplicity.entrySet()) {
+            DensityFunction value = entry.getKey();
+            Body body = body(value);
+            String name = names.get(value);
+            String category = categories.apply(name);
+            double contribution = entry.getValue() * body.self;
+            shares.merge(category, contribution / expanded, Double::sum);
+            offenders.add(new Offender(name, category, entry.getValue(), body.self, cost(value).expanded(),
+                    contribution, entry.getValue() * cost(value).expanded()));
+        }
+        List<Offender> exclusive = top(offenders, Comparator.comparingDouble(Offender::contribution).reversed());
+        List<Offender> inclusive = top(offenders, Comparator.comparingDouble(Offender::inclusive).reversed());
+        Map<String, Double> dagShares = new TreeMap<>();
+        for (Map.Entry<String, Double> entry : reach.categories.entrySet()) {
+            dagShares.put(entry.getKey(), entry.getValue() / Math.max(1L, reach.nodes));
+        }
+        return new RootCost(root, reach.nodes, cached, expanded, total.lazy(), multiplicity.size(), exclusive, inclusive, shares, dagShares);
+    }
+
+    private List<Offender> top(List<Offender> offenders, Comparator<Offender> order) {
+        List<Offender> sorted = new ArrayList<>(offenders);
+        sorted.sort(order);
+        return List.copyOf(sorted.subList(0, Math.min(topCount, sorted.size())));
+    }
+
+    private String rootName(DensityFunction function, String root) {
+        if (function instanceof DensityFunctions.HolderHolder(Holder<DensityFunction> holder)) {
+            return name(holder);
+        }
+        return root;
+    }
+
+    private Costs cost(DensityFunction function) {
+        if (function instanceof DensityFunctions.HolderHolder(Holder<DensityFunction> holder)) {
+            DensityFunction value = holder.value();
+            names.putIfAbsent(value, name(holder));
+            return cost(value);
+        }
+        Costs known = costs.get(function);
+        if (known != null) {
+            return known;
+        }
+        Costs computed = compute(function);
+        costs.put(function, computed);
+        return computed;
+    }
+
+    private Costs compute(DensityFunction function) {
+        return switch (function) {
+            case ConstantFunction ignored -> new Costs(0.0, 0.0, 0.0);
+            case CacheFunction cache -> {
+                Costs input = cost(cache.input());
+                yield new Costs(1.0 + input.expanded(), 1.0 + input.lazy(), 1.0);
+            }
+            case SplineFunction spline -> {
+                Costs inner = spline(spline.spline());
+                yield new Costs(1.0 + inner.expanded(), 1.0 + inner.lazy(), 1.0 + inner.cachedLocal());
+            }
+            case IntervalSelectFunction select -> {
+                Costs input = cost(select.input());
+                double expanded = 1.0 + input.expanded();
+                double cached = 1.0 + input.cachedLocal();
+                double lazy = 0.0;
+                for (DensityFunction branch : select.functions()) {
+                    Costs branchCost = cost(branch);
+                    expanded += branchCost.expanded();
+                    cached += branchCost.cachedLocal();
+                    lazy = Math.max(lazy, branchCost.lazy());
+                }
+                yield new Costs(expanded, 1.0 + input.lazy() + lazy, cached);
+            }
+            case RangeChoiceFunction choice -> {
+                Costs input = cost(choice.input());
+                Costs inside = cost(choice.whenInRange());
+                Costs outside = cost(choice.whenOutOfRange());
+                yield new Costs(1.0 + input.expanded() + inside.expanded() + outside.expanded(),
+                        1.0 + input.lazy() + Math.max(inside.lazy(), outside.lazy()),
+                        1.0 + input.cachedLocal() + inside.cachedLocal() + outside.cachedLocal());
+            }
+            case InterpolatedFunction grid -> {
+                Costs input = cost(grid.input());
+                yield new Costs(1.0 + input.expanded(), 1.0 + LATTICE_CORNERS * input.expanded(), 1.0 + input.cachedLocal());
+            }
+            case FindTopSurfaceFunction surface -> {
+                Costs density = cost(surface.density());
+                Costs upper = cost(surface.upperBound());
+                double steps = surfaceSteps(surface);
+                yield new Costs(1.0 + density.expanded() + upper.expanded(), 1.0 + upper.lazy() + steps * density.lazy(),
+                        1.0 + density.cachedLocal() + upper.cachedLocal());
+            }
+            default -> {
+                double expanded = 1.0;
+                double lazy = 1.0;
+                double cached = 1.0;
+                for (DensityFunction child : children(function)) {
+                    Costs childCost = cost(child);
+                    expanded += childCost.expanded();
+                    lazy += childCost.lazy();
+                    cached += childCost.cachedLocal();
+                }
+                yield new Costs(expanded, lazy, cached);
+            }
+        };
+    }
+
+    private Costs spline(CubicSpline<SplineFunction.Coordinate> spline) {
+        if (!(spline instanceof CubicSpline.Multipoint<SplineFunction.Coordinate> multipoint)) {
+            return new Costs(0.0, 0.0, 0.0);
+        }
+        Costs known = costs.get(multipoint);
+        if (known != null) {
+            return known;
+        }
+        Costs coordinate = cost(multipoint.coordinate().function());
+        List<CubicSpline<SplineFunction.Coordinate>> values = multipoint.values();
+        double expanded = 1.0 + coordinate.expanded();
+        double cached = 1.0 + coordinate.cachedLocal();
+        double[] lazy = new double[values.size()];
+        for (int index = 0; index < values.size(); index++) {
+            Costs value = spline(values.get(index));
+            expanded += value.expanded();
+            cached += value.cachedLocal();
+            lazy[index] = value.lazy();
+        }
+        double worstPair = lazy.length == 1 ? lazy[0] : 0.0;
+        for (int index = 0; index + 1 < lazy.length; index++) {
+            worstPair = Math.max(worstPair, lazy[index] + lazy[index + 1]);
+        }
+        Costs computed = new Costs(expanded, 1.0 + coordinate.lazy() + worstPair, cached);
+        costs.put(multipoint, computed);
+        return computed;
+    }
+
+    private void reach(DensityFunction function, Reach reach, String category) {
+        if (function instanceof DensityFunctions.HolderHolder(Holder<DensityFunction> holder)) {
+            reach(holder.value(), reach, categories.apply(name(holder)));
+            return;
+        }
+        if (function instanceof ConstantFunction || reach.visited.put(function, Boolean.TRUE) != null) {
+            return;
+        }
+        reach.count(category);
+        if (function instanceof CacheFunction cache) {
+            reach.caches.put(cache, Boolean.TRUE);
+        }
+        if (function instanceof SplineFunction spline) {
+            reachSpline(spline.spline(), reach, category);
+            return;
+        }
+        for (DensityFunction child : children(function)) {
+            reach(child, reach, category);
+        }
+    }
+
+    private void reachSpline(CubicSpline<SplineFunction.Coordinate> spline, Reach reach, String category) {
+        if (!(spline instanceof CubicSpline.Multipoint<SplineFunction.Coordinate> multipoint)) {
+            return;
+        }
+        if (reach.visited.put(multipoint, Boolean.TRUE) != null) {
+            return;
+        }
+        reach.count(category);
+        reach(multipoint.coordinate().function(), reach, category);
+        for (CubicSpline<SplineFunction.Coordinate> value : multipoint.values()) {
+            reachSpline(value, reach, category);
+        }
+    }
+
+    private Body body(DensityFunction value) {
+        Body known = bodies.get(value);
+        if (known != null) {
+            return known;
+        }
+        Body body = new Body();
+        local(value, body, true);
+        bodies.put(value, body);
+        return body;
+    }
+
+    private void local(DensityFunction function, Body body, boolean top) {
+        if (function instanceof DensityFunctions.HolderHolder(Holder<DensityFunction> holder)) {
+            if (!top) {
+                DensityFunction value = holder.value();
+                names.putIfAbsent(value, name(holder));
+                body.references.merge(value, 1.0, Double::sum);
+                return;
+            }
+            local(holder.value(), body, true);
+            return;
+        }
+        if (function instanceof ConstantFunction) {
+            return;
+        }
+        body.self++;
+        if (function instanceof SplineFunction spline) {
+            localSpline(spline.spline(), body);
+            return;
+        }
+        for (DensityFunction child : children(function)) {
+            local(child, body, false);
+        }
+    }
+
+    private void localSpline(CubicSpline<SplineFunction.Coordinate> spline, Body body) {
+        if (!(spline instanceof CubicSpline.Multipoint<SplineFunction.Coordinate> multipoint)) {
+            return;
+        }
+        body.self++;
+        local(multipoint.coordinate().function(), body, false);
+        for (CubicSpline<SplineFunction.Coordinate> value : multipoint.values()) {
+            localSpline(value, body);
+        }
+    }
+
+    private Map<DensityFunction, Double> multiplicity(Body root) {
+        List<DensityFunction> order = new ArrayList<>();
+        Map<DensityFunction, Boolean> visited = new IdentityHashMap<>();
+        for (DensityFunction child : root.references.keySet()) {
+            postOrder(child, visited, order);
+        }
+        Collections.reverse(order);
+        Map<DensityFunction, Double> multiplicity = new IdentityHashMap<>(order.size() * 2);
+        for (Map.Entry<DensityFunction, Double> entry : root.references.entrySet()) {
+            multiplicity.merge(entry.getKey(), entry.getValue(), Double::sum);
+        }
+        for (DensityFunction value : order) {
+            double times = multiplicity.getOrDefault(value, 0.0);
+            for (Map.Entry<DensityFunction, Double> entry : body(value).references.entrySet()) {
+                multiplicity.merge(entry.getKey(), times * entry.getValue(), Double::sum);
+            }
+        }
+        return multiplicity;
+    }
+
+    private void postOrder(DensityFunction value, Map<DensityFunction, Boolean> visited, List<DensityFunction> order) {
+        if (visited.put(value, Boolean.TRUE) != null) {
+            return;
+        }
+        for (DensityFunction child : body(value).references.keySet()) {
+            postOrder(child, visited, order);
+        }
+        order.add(value);
+    }
+
+    private static double surfaceSteps(FindTopSurfaceFunction surface) {
+        double upper = surface.upperBound().range().max();
+        if (!Double.isFinite(upper)) {
+            return MAX_SURFACE_STEPS;
+        }
+        double steps = Math.floor((upper - surface.lowerBound()) / surface.cellHeight()) + 1.0;
+        return Math.clamp(steps, 1.0, MAX_SURFACE_STEPS);
+    }
+
+    private static List<DensityFunction> children(DensityFunction function) {
+        List<DensityFunction> children = new ArrayList<>(4);
+        function.rewriteChildren(child -> {
+            children.add(child);
+            return child;
+        });
+        return children;
+    }
+
+    private static String name(Holder<DensityFunction> holder) {
+        return holder.unwrapKey().map(key -> key.identifier().toString()).orElse(INLINE);
+    }
+
+    record Costs(double expanded, double lazy, double cachedLocal) {
+    }
+
+    record Offender(String name, String category, double multiplicity, double selfNodes, double subtreeNodes,
+                    double contribution, double inclusive) {
+    }
+
+    record RootCost(String root, long dagNodes, double cachedNodes, double expandedNodes, double uncachedPointWorst,
+                    int namedSubtrees, List<Offender> exclusive, List<Offender> inclusive, Map<String, Double> categoryShare,
+                    Map<String, Double> dagShare) {
+    }
+
+    private static final class Reach {
+        private final Map<Object, Boolean> visited = new IdentityHashMap<>();
+        private final Map<CacheFunction, Boolean> caches = new IdentityHashMap<>();
+        private final Map<String, Double> categories = new TreeMap<>();
+        private long nodes;
+
+        private void count(String category) {
+            nodes++;
+            categories.merge(category, 1.0, Double::sum);
+        }
+    }
+
+    private static final class Body {
+        private final Map<DensityFunction, Double> references = new IdentityHashMap<>();
+        private double self;
+    }
+}

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

@@ -0,0 +1,409 @@
+package art.arcane.iris.probe;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.google.gson.JsonPrimitive;
+
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+final class DensityJsonBreakdown {
+    private static final String DENSITY_FUNCTIONS = "/worldgen/density_function/";
+    private static final String NOISES = "/worldgen/noise/";
+    private static final String JSON = ".json";
+    private static final String CELLULAR = "cellular";
+    private static final String NOISE_STYLE = "noise style";
+    private static final String UNREFERENCED = "unreferenced";
+    private static final String OFFSET_MARKER = "/offset_";
+    private static final String OFFSET_SUFFIX = " offset copies";
+    private static final int INSTANCE_SEGMENTS = 3;
+    private static final Set<String> ROUTER_ROOTS = Set.of("final_density", "temperature", "vegetation", "continents", "erosion",
+            "depth", "ridges", "chunk_surface_level", "barrier", "fluid_level_floodedness", "fluid_level_spread", "lava", "exclusion",
+            "surface_level", "spawn_elevation");
+    private static final long FNV_OFFSET = 0xcbf29ce484222325L;
+    private static final long FNV_PRIME = 0x100000001b3L;
+    private static final int TOP = 10;
+
+    private final String dimension;
+    private final String dimensionPrefix;
+    private final Map<String, Integer> categoryIndex = new HashMap<>();
+    private final List<String> categoryNames = new ArrayList<>();
+    private final Map<String, Entry> entries = new TreeMap<>();
+    private final Map<String, List<String>> parents = new HashMap<>();
+    private final Map<String, Long> owners = new HashMap<>();
+
+    private DensityJsonBreakdown(String dimension) {
+        this.dimension = dimension;
+        dimensionPrefix = dimension + "/";
+    }
+
+    static DensityJsonBreakdown analyze(SortedMap<String, byte[]> files, String dimension) {
+        DensityJsonBreakdown breakdown = new DensityJsonBreakdown(dimension);
+        breakdown.load(files);
+        return breakdown;
+    }
+
+    static String category(String dimension, String id) {
+        String base = baseCategory(dimension, id);
+        return id.contains(OFFSET_MARKER) ? base + OFFSET_SUFFIX : base;
+    }
+
+    private static String baseCategory(String dimension, String id) {
+        int separator = id.indexOf(':');
+        String path = separator < 0 ? id : id.substring(separator + 1);
+        String dimensionPrefix = dimension + "/";
+        if (path.startsWith(dimensionPrefix)) {
+            path = path.substring(dimensionPrefix.length());
+        }
+        if (ROUTER_ROOTS.contains(path)) {
+            return "router";
+        }
+        if (path.startsWith("cell/")) {
+            return CELLULAR;
+        }
+        if (path.startsWith("style/")) {
+            return NOISE_STYLE;
+        }
+        if (path.startsWith("biome/selector/")) {
+            return "biome selector";
+        }
+        if (path.startsWith("biome/carving/")) {
+            return "biome carving";
+        }
+        if (path.startsWith("biome/")) {
+            return "biome decision";
+        }
+        if (path.equals("height") || path.startsWith("height/") || path.startsWith("terrain/height/")) {
+            return "terrain height";
+        }
+        if (path.startsWith("terrain/generator/")) {
+            return "terrain generator";
+        }
+        if (path.startsWith("terrain/volume/")) {
+            return "terrain volumetric";
+        }
+        if (path.startsWith("terrain/")) {
+            return "terrain bands";
+        }
+        if (path.startsWith("cave")) {
+            return "caves";
+        }
+        if (path.startsWith("surface/")) {
+            return "surface";
+        }
+        int slash = path.indexOf('/');
+        return slash < 0 ? path : path.substring(0, slash);
+    }
+
+    Report report() {
+        Map<String, CategoryAccumulator> categories = new TreeMap<>();
+        Map<String, CategoryAccumulator> groups = new TreeMap<>();
+        Map<String, Long> libraryOwners = new TreeMap<>();
+        long totalBytes = 0;
+        long totalNodes = 0;
+        for (Map.Entry<String, Entry> item : entries.entrySet()) {
+            String id = item.getKey();
+            Entry entry = item.getValue();
+            totalBytes += entry.bytes;
+            totalNodes += entry.nodes;
+            String category = category(dimension, id);
+            categories.computeIfAbsent(category, ignored -> new CategoryAccumulator()).add(entry);
+            groups.computeIfAbsent(group(id), ignored -> new CategoryAccumulator()).add(entry);
+            if (isLibrary(category)) {
+                libraryOwners.merge(category + " via " + ownerLabel(owners(id)), entry.bytes, Long::sum);
+            }
+        }
+        List<CategoryBytes> categoryRows = rows(categories, Integer.MAX_VALUE);
+        List<CategoryBytes> groupRows = rows(groups, 40);
+        List<Bytes> ownerRows = new ArrayList<>();
+        for (Map.Entry<String, Long> owner : libraryOwners.entrySet()) {
+            ownerRows.add(new Bytes(owner.getKey(), owner.getValue()));
+        }
+        ownerRows.sort(Comparator.comparingLong(Bytes::bytes).reversed());
+        List<Bytes> largest = new ArrayList<>();
+        for (Map.Entry<String, Entry> item : entries.entrySet()) {
+            largest.add(new Bytes(item.getKey(), item.getValue().bytes));
+        }
+        largest.sort(Comparator.comparingLong(Bytes::bytes).reversed());
+        return new Report(entries.size(), totalBytes, totalNodes, categoryRows, groupRows, ownerRows,
+                List.copyOf(largest.subList(0, Math.min(TOP, largest.size()))), cellularInstances());
+    }
+
+    private void load(SortedMap<String, byte[]> files) {
+        Map<String, byte[]> bodies = new HashMap<>();
+        Set<String> noises = new HashSet<>();
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            String id = resourceId(file.getKey(), DENSITY_FUNCTIONS);
+            if (id != null) {
+                bodies.put(id, file.getValue());
+                continue;
+            }
+            String noise = resourceId(file.getKey(), NOISES);
+            if (noise != null) {
+                noises.add(noise);
+            }
+        }
+        for (Map.Entry<String, byte[]> body : bodies.entrySet()) {
+            JsonElement json = JsonParser.parseString(new String(body.getValue(), StandardCharsets.UTF_8));
+            Entry entry = new Entry(body.getValue().length);
+            entry.shape = shape(json, bodies.keySet(), noises, entry);
+            entries.put(body.getKey(), entry);
+            for (String reference : entry.references) {
+                parents.computeIfAbsent(reference, ignored -> new ArrayList<>()).add(body.getKey());
+            }
+        }
+    }
+
+    private long shape(JsonElement element, Set<String> functions, Set<String> noises, Entry entry) {
+        if (element.isJsonObject()) {
+            entry.nodes++;
+            JsonObject object = element.getAsJsonObject();
+            long hash = mix(FNV_OFFSET, '{');
+            for (String key : new TreeMap<>(object.asMap()).keySet()) {
+                hash = mix(mix(hash, key.hashCode()), shape(object.get(key), functions, noises, entry));
+            }
+            return mix(hash, '}');
+        }
+        if (element.isJsonArray()) {
+            JsonArray array = element.getAsJsonArray();
+            long hash = mix(FNV_OFFSET, '[');
+            for (JsonElement item : array) {
+                hash = mix(hash, shape(item, functions, noises, entry));
+            }
+            return mix(hash, ']');
+        }
+        if (element.isJsonPrimitive()) {
+            JsonPrimitive primitive = element.getAsJsonPrimitive();
+            if (primitive.isNumber()) {
+                return mix(FNV_OFFSET, 'N');
+            }
+            if (primitive.isString()) {
+                String value = primitive.getAsString();
+                if (functions.contains(value)) {
+                    entry.references.add(value);
+                    return mix(FNV_OFFSET, 'R');
+                }
+                if (noises.contains(value)) {
+                    return mix(FNV_OFFSET, 'Z');
+                }
+                return mix(FNV_OFFSET, value.hashCode());
+            }
+            return mix(FNV_OFFSET, primitive.getAsBoolean() ? 'T' : 'F');
+        }
+        return mix(FNV_OFFSET, '0');
+    }
+
+    private List<CellularShape> cellularInstances() {
+        Map<String, List<String>> instances = new TreeMap<>();
+        for (String id : entries.keySet()) {
+            if (!isLibrary(category(dimension, id)) || !id.contains(":cell/")) {
+                continue;
+            }
+            instances.computeIfAbsent(instanceKey(id), ignored -> new ArrayList<>()).add(id);
+        }
+        Map<Long, CellularAccumulator> shapes = new HashMap<>();
+        for (Map.Entry<String, List<String>> instance : instances.entrySet()) {
+            List<String> members = instance.getValue();
+            members.sort(String::compareTo);
+            long hash = FNV_OFFSET;
+            long bytes = 0;
+            long owner = 0L;
+            StringBuilder layout = new StringBuilder();
+            for (String member : members) {
+                Entry entry = entries.get(member);
+                String suffix = member.substring(instance.getKey().length());
+                hash = mix(mix(hash, suffix.hashCode()), entry.shape);
+                bytes += entry.bytes;
+                owner |= owners(member);
+                if (!layout.isEmpty()) {
+                    layout.append(',');
+                }
+                layout.append(suffix);
+            }
+            CellularAccumulator accumulator = shapes.computeIfAbsent(hash, ignored -> new CellularAccumulator(instance.getKey(), layout.toString()));
+            accumulator.instances++;
+            accumulator.bytes += bytes;
+            accumulator.owners |= owner;
+        }
+        List<CellularShape> rows = new ArrayList<>(shapes.size());
+        for (CellularAccumulator accumulator : shapes.values()) {
+            rows.add(new CellularShape(accumulator.example, accumulator.layout, accumulator.instances, accumulator.bytes, ownerLabel(accumulator.owners)));
+        }
+        rows.sort(Comparator.comparingLong(CellularShape::bytes).reversed());
+        return List.copyOf(rows);
+    }
+
+    private long owners(String id) {
+        Long known = owners.get(id);
+        if (known != null) {
+            return known;
+        }
+        owners.put(id, 0L);
+        long mask = 0L;
+        List<String> referrers = parents.get(id);
+        if (referrers == null) {
+            mask = bit(UNREFERENCED);
+        } else {
+            for (String parent : referrers) {
+                String category = category(dimension, parent);
+                mask |= isLibrary(category) ? owners(parent) : bit(category);
+            }
+        }
+        owners.put(id, mask);
+        return mask;
+    }
+
+    private long bit(String category) {
+        int index = categoryIndex.computeIfAbsent(category, name -> {
+            categoryNames.add(name);
+            return categoryNames.size() - 1;
+        });
+        if (index >= Long.SIZE) {
+            throw new IllegalStateException("More than " + Long.SIZE + " density function owner categories");
+        }
+        return 1L << index;
+    }
+
+    private String ownerLabel(long mask) {
+        if (mask == 0L) {
+            return UNREFERENCED;
+        }
+        List<String> labels = new ArrayList<>(Long.bitCount(mask));
+        for (int index = 0; index < categoryNames.size(); index++) {
+            if ((mask & (1L << index)) != 0L) {
+                labels.add(categoryNames.get(index));
+            }
+        }
+        labels.sort(String::compareTo);
+        return String.join("+", labels);
+    }
+
+    private String group(String id) {
+        int separator = id.indexOf(':');
+        String path = separator < 0 ? id : id.substring(separator + 1);
+        if (path.startsWith(dimensionPrefix)) {
+            path = path.substring(dimensionPrefix.length());
+        }
+        String[] segments = path.split("/");
+        if (segments.length == 1) {
+            return segments[0];
+        }
+        if (segments[0].equals("cell") || segments[0].equals("style")) {
+            return segments[0] + "/*/" + segments[segments.length - 1];
+        }
+        return segments[0] + "/" + segments[1];
+    }
+
+    private static boolean isLibrary(String category) {
+        return category.startsWith(CELLULAR) || category.startsWith(NOISE_STYLE);
+    }
+
+    private static String instanceKey(String id) {
+        int end = id.indexOf(':') + 1;
+        for (int segment = 0; segment < INSTANCE_SEGMENTS && end > 0; segment++) {
+            int slash = id.indexOf('/', end);
+            if (slash < 0) {
+                return id;
+            }
+            end = slash + 1;
+        }
+        return id.substring(0, end - 1);
+    }
+
+    private static List<CategoryBytes> rows(Map<String, CategoryAccumulator> accumulators, int limit) {
+        List<CategoryBytes> rows = new ArrayList<>(accumulators.size());
+        for (Map.Entry<String, CategoryAccumulator> item : accumulators.entrySet()) {
+            CategoryAccumulator accumulator = item.getValue();
+            long representative = 0;
+            for (long bytes : accumulator.representativeBytes.values()) {
+                representative += bytes;
+            }
+            rows.add(new CategoryBytes(item.getKey(), accumulator.files, accumulator.bytes, accumulator.nodes,
+                    accumulator.representativeBytes.size(), accumulator.bytes - representative));
+        }
+        rows.sort(Comparator.comparingLong(CategoryBytes::bytes).reversed());
+        return List.copyOf(rows.subList(0, Math.min(limit, rows.size())));
+    }
+
+    private static String resourceId(String path, String folder) {
+        int marker = path.indexOf(folder);
+        if (!path.startsWith("data/") || marker < 0 || !path.endsWith(JSON)) {
+            return null;
+        }
+        return path.substring("data/".length(), marker) + ":" + path.substring(marker + folder.length(), path.length() - JSON.length());
+    }
+
+    private static long mix(long hash, long value) {
+        long mixed = hash ^ value;
+        mixed *= FNV_PRIME;
+        return mixed ^ (mixed >>> 29);
+    }
+
+    record Report(int files, long bytes, long nodes, List<CategoryBytes> categories, List<CategoryBytes> groups,
+                  List<Bytes> libraryOwners, List<Bytes> largest, List<CellularShape> cellularShapes) {
+        int cellularInstances() {
+            int count = 0;
+            for (CellularShape shape : cellularShapes) {
+                count += shape.instances();
+            }
+            return count;
+        }
+    }
+
+    record CategoryBytes(String category, int files, long bytes, long nodes, int distinctShapes, long structurallyDuplicateBytes) {
+    }
+
+    record Bytes(String name, long bytes) {
+    }
+
+    record CellularShape(String example, String members, int instances, long bytes, String owners) {
+    }
+
+    private static final class Entry {
+        private final long bytes;
+        private final List<String> references = new ArrayList<>();
+        private long nodes;
+        private long shape;
+
+        private Entry(long bytes) {
+            this.bytes = bytes;
+        }
+    }
+
+    private static final class CategoryAccumulator {
+        private final Map<Long, Long> representativeBytes = new HashMap<>();
+        private int files;
+        private long bytes;
+        private long nodes;
+
+        private void add(Entry entry) {
+            files++;
+            bytes += entry.bytes;
+            nodes += entry.nodes;
+            representativeBytes.putIfAbsent(entry.shape, entry.bytes);
+        }
+    }
+
+    private static final class CellularAccumulator {
+        private final String example;
+        private final String layout;
+        private int instances;
+        private long bytes;
+        private long owners;
+
+        private CellularAccumulator(String example, String layout) {
+            this.example = example;
+            this.layout = layout;
+        }
+    }
+}

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

@@ -1,6 +1,7 @@
 package art.arcane.iris.probe;
 
 import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.platform.ClasspathVanillaDataSource;
 import art.arcane.iris.platform.bukkit.nms.BukkitGenerationRegistry;
 import art.arcane.iris.spi.IrisPlatform;
 import art.arcane.iris.spi.PlatformGenerationRegistry;
@@ -9,6 +10,7 @@ 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.iris.spi.VanillaDataSource;
 import art.arcane.volmlib.nativelib.entity.NativeEntityType;
 import art.arcane.volmlib.nativelib.item.NativeItem;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.ModdedBlockState;
@@ -35,6 +37,7 @@ final class HeadlessNativePlatform implements IrisPlatform, PlatformRegistries,
     private final NativeRegistryAccess nativeAccess;
     private final PlatformBiomeWriter biomeWriter;
     private final PlatformGenerationRegistry generationRegistry;
+    private final ClasspathVanillaDataSource vanillaData = new ClasspathVanillaDataSource(() -> SharedConstants.class);
     private final NativeBlockResolver blocks = new NativeBlockResolver(this);
     private final NativeBlockState air = blocks.getAir();
     private final ConcurrentHashMap<String, NativeBlockState> states = new ConcurrentHashMap<>();
@@ -215,6 +218,11 @@ final class HeadlessNativePlatform implements IrisPlatform, PlatformRegistries,
         return biomeWriter;
     }
 
+    @Override
+    public VanillaDataSource vanillaData() {
+        return vanillaData;
+    }
+
     @Override
     public File dataFolder() {
         return services.dataFolder();

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

@@ -4,6 +4,7 @@ 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.HolderLookup;
 import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.BuiltInRegistries;
 import net.minecraft.network.chat.Component;
@@ -25,6 +26,7 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.function.Function;
 import java.util.stream.Stream;
 
 final class HeadlessNativeRegistries implements AutoCloseable {
@@ -70,7 +72,7 @@ final class HeadlessNativeRegistries implements AutoCloseable {
         }
     }
 
-    private static HeadlessNativeRegistries load(Path directory) {
+    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(
@@ -78,12 +80,17 @@ final class HeadlessNativeRegistries implements AutoCloseable {
         try {
             RegistryAccess.Frozen builtins = RegistryAccess.fromRegistryOfRegistries(BuiltInRegistries.REGISTRY);
             RegistryAccess.Frozen loaded;
+            RegistryAccess.Frozen dimensions;
             try (ExecutorService executor = Executors.newFixedThreadPool(4)) {
                 loaded = RegistryDataLoader.load(resources, builtins.listRegistries().toList(),
                         RegistryDataLoader.WORLD_REGISTRIES, executor).join();
+                List<HolderLookup.RegistryLookup<?>> dimensionContext =
+                        Stream.concat(builtins.listRegistries(), loaded.listRegistries()).toList();
+                dimensions = RegistryDataLoader.load(resources, dimensionContext,
+                        RegistryDataLoader.DIMENSION_REGISTRIES, executor).join();
             }
-            RegistryAccess.Frozen registries = new RegistryAccess.ImmutableRegistryAccess(
-                    Stream.concat(builtins.registries(), loaded.registries())).freeze();
+            RegistryAccess.Frozen registries = new RegistryAccess.ImmutableRegistryAccess(Stream.of(
+                    builtins.registries(), loaded.registries(), dimensions.registries()).flatMap(Function.identity())).freeze();
             HeadlessNativeBootstrap.bindComponents(registries);
             return new HeadlessNativeRegistries(directory, resources, registries);
         } catch (RuntimeException failure) {
@@ -106,7 +113,7 @@ final class HeadlessNativeRegistries implements AutoCloseable {
         delete(directory);
     }
 
-    private static void delete(Path directory) throws IOException {
+    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

@@ -32,6 +32,7 @@ final class HeadlessNativeRuntime implements RealPackProbeSupport.RuntimeBinding
     private final Path stagingRoot;
     private NativeRegionTerrainWriter writer;
     private HeadlessNativeRegistries nativeRegistries;
+    private File preparedPack;
     private HolderLookup.Provider registries;
 
     HeadlessNativeRuntime() {
@@ -60,12 +61,16 @@ final class HeadlessNativeRuntime implements RealPackProbeSupport.RuntimeBinding
     @Override
     public void prepare(IrisData data, IrisDimension dimension) {
         try {
-            if (nativeRegistries != null) {
+            File pack = data.getDataFolder().getCanonicalFile();
+            if (nativeRegistries != null && !pack.equals(preparedPack)) {
                 throw new IllegalStateException("Headless native runtime supports one immutable pack per process");
             }
-            nativeRegistries = HeadlessNativeRegistries.compile(data.getDataFolder());
+            if (nativeRegistries == null) {
+                nativeRegistries = HeadlessNativeRegistries.compile(data.getDataFolder());
+                preparedPack = pack;
+                writer = new NativeRegionTerrainWriter(nativeRegistries.registries());
+            }
             registries = nativeRegistries.registries();
-            writer = new NativeRegionTerrainWriter(nativeRegistries.registries());
         } catch (IOException failure) {
             throw new UncheckedIOException("Cannot load native generation registries", failure);
         }
@@ -92,6 +97,7 @@ final class HeadlessNativeRuntime implements RealPackProbeSupport.RuntimeBinding
         if (nativeRegistries != null) {
             nativeRegistries.close();
             nativeRegistries = null;
+            preparedPack = null;
         }
     }
 

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

@@ -2,8 +2,9 @@ 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.generation.hydrology.engine.HydrologyPregeneration;
+import art.arcane.iris.generation.hydrology.plan.WindowKey;
+import art.arcane.iris.world.pregen.PregenHydrology;
 import art.arcane.iris.world.pregen.PregenPerformanceProfile;
 
 import net.minecraft.core.registries.Registries;
@@ -31,11 +32,16 @@ import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.nio.file.StandardOpenOption;
 import java.security.MessageDigest;
+import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.HexFormat;
 import java.util.List;
 import java.util.Locale;
+import java.util.Set;
 
 public final class OfflineRegionGenerator {
+    private static final int CHUNKS_PER_HYDROLOGY_REGION = WindowKey.SIZE >> 4;
+
     private OfflineRegionGenerator() {
     }
 
@@ -97,14 +103,13 @@ public final class OfflineRegionGenerator {
             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());
+            try (HydrologyPregeneration pregeneration = PregenHydrology.open(session.engine());
                  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)) {
+                PregenHydrology.prepareAll(pregeneration, configuration.hydrologyRegions());
                 HeadlessRegionTerrain.Session rolling = new HeadlessRegionTerrain.Session(workers);
                 Path regionDirectory = session.engine().getTarget().getWorld().worldFolder().toPath().resolve("region");
                 Files.createDirectory(regionDirectory);
@@ -239,14 +244,27 @@ public final class OfflineRegionGenerator {
             }
         }
 
-        HydrologyTileCache.PregenerationArea hydrologyArea() {
+        List<long[]> hydrologyRegions() {
             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);
+            Set<Long> seen = new HashSet<>();
+            List<long[]> regions = new ArrayList<>();
+            for (int row = 0; row < regionsZ; row++) {
+                for (int column = 0; column < regionsX; column++) {
+                    int regionX = row % 2 == 0 ? column : regionsX - column - 1;
+                    int minimumX = Math.floorDiv(chunkX + regionX * width - halo, CHUNKS_PER_HYDROLOGY_REGION);
+                    int maximumX = Math.floorDiv(chunkX + (regionX + 1) * width - 1 + halo, CHUNKS_PER_HYDROLOGY_REGION);
+                    int minimumZ = Math.floorDiv(chunkZ + row * width - halo, CHUNKS_PER_HYDROLOGY_REGION);
+                    int maximumZ = Math.floorDiv(chunkZ + (row + 1) * width - 1 + halo, CHUNKS_PER_HYDROLOGY_REGION);
+                    for (int hydrologyZ = minimumZ; hydrologyZ <= maximumZ; hydrologyZ++) {
+                        for (int hydrologyX = minimumX; hydrologyX <= maximumX; hydrologyX++) {
+                            if (seen.add(((long) hydrologyX << 32) | (hydrologyZ & 0xFFFFFFFFL))) {
+                                regions.add(new long[]{hydrologyX, hydrologyZ});
+                            }
+                        }
+                    }
+                }
+            }
+            return regions;
         }
 
         static Configuration parse(String[] arguments) throws IOException {

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

@@ -0,0 +1,39 @@
+package art.arcane.iris.probe;
+
+import io.papermc.paper.registry.PaperRegistryAccess;
+
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.Map;
+
+final class PaperRegistryScope implements AutoCloseable {
+    private final Map<Object, Object> registries;
+    private final Map<Object, Object> previous;
+
+    private PaperRegistryScope(Map<Object, Object> registries) {
+        this.registries = registries;
+        this.previous = new HashMap<>(registries);
+        registries.clear();
+    }
+
+    static PaperRegistryScope open() {
+        return new PaperRegistryScope(registries());
+    }
+
+    @Override
+    public void close() {
+        registries.clear();
+        registries.putAll(previous);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Map<Object, Object> registries() {
+        try {
+            Field field = PaperRegistryAccess.class.getDeclaredField("registries");
+            field.setAccessible(true);
+            return (Map<Object, Object>) field.get(PaperRegistryAccess.instance());
+        } catch (ReflectiveOperationException failure) {
+            throw new IllegalStateException("Paper registry access has no registries map to isolate", failure);
+        }
+    }
+}

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

@@ -0,0 +1,301 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import net.minecraft.core.Holder;
+import net.minecraft.core.QuartPos;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.datafix.DataFixers;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+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.biome.BiomeResolver;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.NoiseChunk;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.NoiseSettings;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.WorldGenerationContext;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+import net.minecraft.world.level.levelgen.densityfunction.DensityVolume;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import net.minecraft.world.level.levelgen.densityfunction.ScopedDensityBuffer;
+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 java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+
+public final class WorldgenExportSampler implements AutoCloseable {
+    private static final String DENSITY_FUNCTIONS = "/worldgen/density_function/";
+    private static final int CHUNK_WIDTH = 16;
+    private static final Method CREATE_NOISE_CHUNK = generatorMethod("createNoiseChunk", ChunkAccess.class, StructureManager.class, Blender.class,
+            RandomState.class, NoiseSettings.class);
+    private static final Method DO_FILL = generatorMethod("doFill", NoiseChunk.class, ChunkAccess.class);
+
+    private final HeadlessNativeRegistries loaded;
+    private final NoiseBasedChunkGenerator generator;
+    private final RandomState randomState;
+    private final ThreadLocal<BiomeResolver> resolvers;
+    private final LevelHeightAccessor heights;
+    private final SortedSet<String> densityFunctionIds;
+    private final ThreadLocal<SamplerContext> densityContexts = ThreadLocal.withInitial(() -> SamplerContext.builder().enableCaches().build());
+    private final PalettedContainerFactory containers;
+    private final long seed;
+    private final long biomeZoomSeed;
+
+    private WorldgenExportSampler(HeadlessNativeRegistries loaded, LevelStem stem, long seed, SortedSet<String> densityFunctionIds) {
+        this.loaded = loaded;
+        if (!(stem.generator() instanceof NoiseBasedChunkGenerator noiseGenerator)) {
+            throw new IllegalStateException("Exported dimension uses " + stem.generator().getClass().getSimpleName() + ", not a noise generator");
+        }
+        this.generator = noiseGenerator;
+        this.randomState = RandomState.create(loaded.registries().lookupOrThrow(Registries.NOISE), seed, noiseGenerator.generatorSettings().value());
+        this.resolvers = ThreadLocal.withInitial(() -> noiseGenerator.getBiomeSource().createCachingResolver(randomState));
+        DimensionType type = stem.type().value();
+        this.heights = LevelHeightAccessor.create(type.minY(), type.height());
+        this.densityFunctionIds = densityFunctionIds;
+        this.containers = PalettedContainerFactory.create(loaded.registries());
+        this.seed = seed;
+        this.biomeZoomSeed = BiomeManager.obfuscateSeed(seed);
+    }
+
+    public static WorldgenExportSampler open(Map<String, byte[]> files, WorldgenExportMode mode, String dimensionId, long seed) throws IOException {
+        Objects.requireNonNull(mode);
+        Identifier dimension = Identifier.parse(dimensionId);
+        HeadlessNativeBootstrap.initialize();
+        Path directory = Files.createTempDirectory("iris-worldgen-export-");
+        HeadlessNativeRegistries loaded;
+        try {
+            for (Map.Entry<String, byte[]> file : files.entrySet()) {
+                Path target = directory.resolve(file.getKey()).normalize();
+                if (!target.startsWith(directory)) {
+                    throw new IllegalArgumentException("Export file escapes the datapack root: " + file.getKey());
+                }
+                Files.createDirectories(target.getParent());
+                Files.write(target, file.getValue());
+            }
+            try (PaperRegistryScope scope = PaperRegistryScope.open()) {
+                loaded = HeadlessNativeRegistries.load(directory);
+            }
+        } catch (IOException | RuntimeException failure) {
+            HeadlessNativeRegistries.delete(directory);
+            throw failure;
+        }
+        try {
+            return new WorldgenExportSampler(loaded, stem(loaded.registries(), mode, dimension), seed, densityFunctionIds(files));
+        } catch (RuntimeException failure) {
+            loaded.close();
+            throw failure;
+        }
+    }
+
+    public static WorldgenExportSampler open(Path datapack, WorldgenExportMode mode, String dimensionId, long seed) throws IOException {
+        return open(files(datapack), mode, dimensionId, seed);
+    }
+
+    public float density(String functionId, int x, int y, int z) {
+        DensityFunction function = loaded.registries().lookupOrThrow(Registries.DENSITY_FUNCTION)
+                .getOrThrow(ResourceKey.create(Registries.DENSITY_FUNCTION, Identifier.parse(functionId))).value();
+        return randomState.getSampler(function).sampleValue(densityContexts.get(), x, y, z);
+    }
+
+    public float[] densityChunk(DensityFunction function, int chunkX, int chunkZ) {
+        DensityVolume volume = new DensityVolume(CHUNK_WIDTH, heights.getHeight(), CHUNK_WIDTH, chunkX * CHUNK_WIDTH, heights.getMinY(), chunkZ * CHUNK_WIDTH);
+        return sampleVolume(function, volume);
+    }
+
+    public DensityFunction finalDensity() {
+        return generator.generatorSettings().value().noiseRouter().finalDensity();
+    }
+
+    public int baseHeight(int x, int z) {
+        return generator.getBaseHeight(x, z, Heightmap.Types.WORLD_SURFACE_WG, heights, randomState);
+    }
+
+    public int floorHeight(int x, int z) {
+        return generator.getBaseHeight(x, z, Heightmap.Types.OCEAN_FLOOR_WG, heights, randomState);
+    }
+
+    public ProtoChunk terrainChunk(int chunkX, int chunkZ) {
+        ProtoChunk chunk = new ProtoChunk(new ChunkPos(chunkX, chunkZ), UpgradeData.EMPTY, heights, containers, null);
+        NoiseGeneratorSettings settings = generator.generatorSettings().value();
+        NoiseSettings noise = settings.noiseSettings().clampToHeightAccessor(chunk.getHeightAccessorForGeneration());
+        try (NoiseChunk noiseChunk = (NoiseChunk) invoke(CREATE_NOISE_CHUNK, chunk, NoStructures.INSTANCE, Blender.empty(), randomState, noise)) {
+            invoke(DO_FILL, noiseChunk, chunk);
+            randomState.surfaceSystem().buildSurface(randomState, new BiomeManager(resolvers.get(), biomeZoomSeed),
+                    new WorldGenerationContext(generator, chunk.getHeightAccessorForGeneration()), chunk, noiseChunk, settings.materialRule().value(), null);
+        }
+        return chunk;
+    }
+
+    public StructureStart structureStart(String structureId, int chunkX, int chunkZ) throws IOException {
+        Holder.Reference<Structure> structure = loaded.registries().lookupOrThrow(Registries.STRUCTURE)
+                .getOrThrow(ResourceKey.create(Registries.STRUCTURE, Identifier.parse(structureId)));
+        Path storageRoot = Files.createTempDirectory("iris-worldgen-export-structures-");
+        try (LevelStorageSource.LevelStorageAccess storage = LevelStorageSource.createDefault(storageRoot).createAccess("export")) {
+            StructureTemplateManager templates = new StructureTemplateManager(loaded.resources(), storage, DataFixers.getDataFixer(),
+                    loaded.registries().lookupOrThrow(Registries.BLOCK));
+            return structure.value().generate(structure, Level.OVERWORLD, loaded.registries(), generator, generator.getBiomeSource(),
+                    randomState.createClimateSampler(SamplerContext.builder().enableCaches().build()), randomState, templates, seed,
+                    new ChunkPos(chunkX, chunkZ), 0, heights, structure.value().biomes()::contains);
+        } finally {
+            HeadlessNativeRegistries.delete(storageRoot);
+        }
+    }
+
+    public String biome(int x, int y, int z) {
+        Holder<Biome> biome = resolvers.get().getNoiseBiome(QuartPos.fromBlock(x), QuartPos.fromBlock(y), QuartPos.fromBlock(z));
+        return biome.unwrapKey().orElseThrow().identifier().toString();
+    }
+
+    public Set<String> possibleBiomes() {
+        Set<String> biomes = new TreeSet<>();
+        for (Holder<Biome> biome : generator.getBiomeSource().possibleBiomes()) {
+            biomes.add(biome.unwrapKey().orElseThrow().identifier().toString());
+        }
+        return biomes;
+    }
+
+    public SortedSet<String> densityFunctionIds() {
+        return densityFunctionIds;
+    }
+
+    public int minY() {
+        return heights.getMinY();
+    }
+
+    public int height() {
+        return heights.getHeight();
+    }
+
+    public int seaLevel() {
+        return generator.getSeaLevel();
+    }
+
+    public RegistryAccess registries() {
+        return loaded.registries();
+    }
+
+    @Override
+    public void close() throws IOException {
+        loaded.close();
+    }
+
+    private float[] sampleVolume(DensityFunction function, DensityVolume volume) {
+        try (ScopedDensityBuffer buffer = randomState.getSampler(function).bind(densityContexts.get()).sampleVolume(volume)) {
+            float[] values = new float[volume.size()];
+            for (int index = 0; index < values.length; index++) {
+                values[index] = buffer.get(index);
+            }
+            return values;
+        }
+    }
+
+    private Object invoke(Method method, Object... arguments) {
+        try {
+            return method.invoke(generator, arguments);
+        } catch (InvocationTargetException failure) {
+            if (failure.getCause() instanceof RuntimeException runtime) {
+                throw runtime;
+            }
+            if (failure.getCause() instanceof Error error) {
+                throw error;
+            }
+            throw new IllegalStateException("Terrain stage " + method.getName() + " failed", failure.getCause());
+        } catch (IllegalAccessException failure) {
+            throw new IllegalStateException("Terrain stage " + method.getName() + " is not accessible", failure);
+        }
+    }
+
+    private static Method generatorMethod(String name, Class<?>... parameters) {
+        try {
+            Method method = NoiseBasedChunkGenerator.class.getDeclaredMethod(name, parameters);
+            method.setAccessible(true);
+            return method;
+        } catch (NoSuchMethodException failure) {
+            throw new IllegalStateException("NoiseBasedChunkGenerator has no terrain stage " + name, failure);
+        }
+    }
+
+    private static LevelStem stem(RegistryAccess registries, WorldgenExportMode mode, Identifier dimension) {
+        return switch (mode) {
+            case PRESET -> registries.lookupOrThrow(Registries.WORLD_PRESET)
+                    .getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, dimension)).value().overworld()
+                    .orElseThrow(() -> new IllegalStateException("World preset " + dimension + " has no overworld"));
+            case DIMENSION -> levelStem(registries, dimension);
+            case OVERWORLD -> levelStem(registries, LevelStem.OVERWORLD.identifier());
+        };
+    }
+
+    private static LevelStem levelStem(RegistryAccess registries, Identifier id) {
+        return registries.lookupOrThrow(Registries.LEVEL_STEM).getOrThrow(ResourceKey.create(Registries.LEVEL_STEM, id)).value();
+    }
+
+    private static SortedMap<String, byte[]> files(Path datapack) throws IOException {
+        if (!Files.isDirectory(datapack)) {
+            throw new IOException("Exported datapack " + datapack + " is not a directory");
+        }
+        SortedMap<String, byte[]> files = new TreeMap<>();
+        try (Stream<Path> paths = Files.walk(datapack)) {
+            List<Path> regular = paths.filter(Files::isRegularFile).toList();
+            for (Path file : regular) {
+                files.put(datapack.relativize(file).toString().replace('\\', '/'), Files.readAllBytes(file));
+            }
+        }
+        return files;
+    }
+
+    private static SortedSet<String> densityFunctionIds(Map<String, byte[]> files) {
+        SortedSet<String> ids = new TreeSet<>();
+        for (String path : files.keySet()) {
+            int marker = path.indexOf(DENSITY_FUNCTIONS);
+            if (path.startsWith("data/") && marker > 0 && path.endsWith(".json")) {
+                String namespace = path.substring("data/".length(), marker);
+                ids.add(namespace + ":" + path.substring(marker + DENSITY_FUNCTIONS.length(), path.length() - ".json".length()));
+            }
+        }
+        return ids;
+    }
+
+    private static final class NoStructures extends StructureManager {
+        private static final NoStructures INSTANCE = new NoStructures();
+
+        private NoStructures() {
+            super(null, null, null);
+        }
+
+        @Override
+        public List<StructureStart> startsForStructure(int chunkX, int chunkZ, Predicate<Structure> predicate) {
+            return List.of();
+        }
+    }
+}

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

@@ -0,0 +1,394 @@
+package art.arcane.iris.probe;
+
+import io.papermc.paper.configuration.WorldConfiguration;
+import net.minecraft.core.Holder;
+import net.minecraft.core.QuartPos;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.biome.BiomeResolver;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.Aquifer;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.NoiseChunk;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.NoiseSettings;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.WorldGenerationContext;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.densityfunction.DensityVolume;
+import net.minecraft.world.level.levelgen.material.rule.MaterialRule;
+import org.spigotmc.SpigotWorldConfig;
+
+import java.lang.management.ManagementFactory;
+import java.lang.management.ThreadMXBean;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SplittableRandom;
+import java.util.function.Supplier;
+
+final class WorldgenStageBench {
+    private static final int SAMPLE_RADIUS_BLOCKS = 32_768;
+    private static final double NANOS_PER_MILLI = 1_000_000.0;
+    private static final double NANOS_PER_MICRO = 1_000.0;
+    private static final ThreadMXBean THREADS = ManagementFactory.getThreadMXBean();
+
+    private final String label;
+    private final NoiseBasedChunkGenerator generator;
+    private final NoiseGeneratorSettings settings;
+    private final RandomState randomState;
+    private final LevelHeightAccessor heights;
+    private final PalettedContainerFactory containers;
+    private final long seed;
+    private final Method fill;
+    private final Aquifer.FluidPicker fluidPicker;
+    private final BiomeResolver uncached;
+    private final Level surfaceLevel;
+
+    WorldgenStageBench(Options options) {
+        label = options.label();
+        if (!(options.stem().generator() instanceof NoiseBasedChunkGenerator noiseGenerator)) {
+            throw new IllegalStateException(label + " uses " + options.stem().generator().getClass().getSimpleName() + ", not a noise generator");
+        }
+        generator = noiseGenerator;
+        settings = noiseGenerator.generatorSettings().value();
+        seed = options.seed();
+        randomState = RandomState.create(options.registries().lookupOrThrow(Registries.NOISE), seed, settings);
+        DimensionType type = options.stem().type().value();
+        heights = LevelHeightAccessor.create(type.minY(), type.height());
+        containers = PalettedContainerFactory.create(options.registries());
+        fill = fillMethod();
+        fluidPicker = fluidPicker(noiseGenerator);
+        uncached = noiseGenerator.getBiomeSource().createUncachedResolver(randomState);
+        surfaceLevel = paperConfiguredLevel();
+    }
+
+    String label() {
+        return label;
+    }
+
+    NoiseGeneratorSettings settings() {
+        return settings;
+    }
+
+    void chunks(int originChunkX, int originChunkZ, int side, ChunkSamples samples) {
+        int ring = side + 2;
+        Map<Long, ProtoChunk> chunks = new HashMap<>(ring * ring * 2);
+        for (int dz = -1; dz <= side; dz++) {
+            for (int dx = -1; dx <= side; dx++) {
+                ChunkPos position = new ChunkPos(originChunkX + dx, originChunkZ + dz);
+                ProtoChunk chunk = new ProtoChunk(position, UpgradeData.EMPTY, heights, containers, null);
+                long started = System.nanoTime();
+                long startedCpu = THREADS.getCurrentThreadCpuTime();
+                generator.createBiomes(randomState, Blender.empty(), null, chunk).join();
+                samples.biomes.add(System.nanoTime() - started, THREADS.getCurrentThreadCpuTime() - startedCpu);
+                chunk.setPersistedStatus(ChunkStatus.BIOMES);
+                chunks.put(ChunkPos.pack(position.x(), position.z()), chunk);
+            }
+        }
+        RegionBiomes region = new RegionBiomes(chunks, uncached);
+        BiomeManager biomeManager = new BiomeManager(region, BiomeManager.obfuscateSeed(seed));
+        MaterialRule materialRule = settings.materialRule().value();
+        for (int dz = 0; dz < side; dz++) {
+            for (int dx = 0; dx < side; dx++) {
+                int chunkX = originChunkX + dx;
+                int chunkZ = originChunkZ + dz;
+                ProtoChunk chunk = chunks.get(ChunkPos.pack(chunkX, chunkZ));
+                Set<Holder<Biome>> possible = possibleBiomes(chunks, chunkX, chunkZ);
+                long started = System.nanoTime();
+                long startedCpu = THREADS.getCurrentThreadCpuTime();
+                try (NoiseChunk noiseChunk = new NoiseChunk(randomState, null, settings, fluidPicker, Blender.empty(), volume(chunk))) {
+                    fill(noiseChunk, chunk);
+                    long filled = System.nanoTime();
+                    long filledCpu = THREADS.getCurrentThreadCpuTime();
+                    randomState.surfaceSystem().buildSurface(randomState, biomeManager,
+                            new WorldGenerationContext(generator, chunk.getHeightAccessorForGeneration(), surfaceLevel), chunk, noiseChunk, materialRule, possible);
+                    samples.surface.add(System.nanoTime() - filled, THREADS.getCurrentThreadCpuTime() - filledCpu);
+                    samples.noise.add(filled - started, filledCpu - startedCpu);
+                }
+                ChunkPos position = chunk.getPos();
+                long carverStarted = System.nanoTime();
+                long carverStartedCpu = THREADS.getCurrentThreadCpuTime();
+                uncached.getNoiseBiome(QuartPos.fromBlock(position.getMinBlockX()), 0, QuartPos.fromBlock(position.getMinBlockZ()));
+                samples.carverBiome.add(System.nanoTime() - carverStarted, THREADS.getCurrentThreadCpuTime() - carverStartedCpu);
+                samples.chunks++;
+            }
+        }
+        samples.biomeFallbacks += region.fallbacks();
+    }
+
+    void uncachedBiome(CallBudget budget, CallSamples samples) {
+        SplittableRandom random = new SplittableRandom(seed ^ 0x5DEECE66DL ^ samples.count);
+        int minQuart = QuartPos.fromBlock(heights.getMinY());
+        int quartHeight = QuartPos.fromBlock(heights.getHeight());
+        long deadline = System.nanoTime() + budget.limitNanos();
+        long startedCpu = THREADS.getCurrentThreadCpuTime();
+        int taken = 0;
+        while (taken < budget.calls() && (taken < budget.minimumCalls() || System.nanoTime() < deadline)) {
+            int quartX = QuartPos.fromBlock(random.nextInt(-SAMPLE_RADIUS_BLOCKS, SAMPLE_RADIUS_BLOCKS));
+            int quartY = minQuart + random.nextInt(quartHeight);
+            int quartZ = QuartPos.fromBlock(random.nextInt(-SAMPLE_RADIUS_BLOCKS, SAMPLE_RADIUS_BLOCKS));
+            long started = System.nanoTime();
+            uncached.getNoiseBiome(quartX, quartY, quartZ);
+            samples.wall.add(System.nanoTime() - started);
+            taken++;
+        }
+        samples.finish(taken, THREADS.getCurrentThreadCpuTime() - startedCpu);
+    }
+
+    void baseHeight(CallBudget budget, Heightmap.Types type, CallSamples samples) {
+        SplittableRandom random = new SplittableRandom(seed ^ type.ordinal() ^ 0x2545F4914F6CDD1DL ^ samples.count);
+        long deadline = System.nanoTime() + budget.limitNanos();
+        long startedCpu = THREADS.getCurrentThreadCpuTime();
+        int taken = 0;
+        while (taken < budget.calls() && (taken < budget.minimumCalls() || System.nanoTime() < deadline)) {
+            int x = random.nextInt(-SAMPLE_RADIUS_BLOCKS, SAMPLE_RADIUS_BLOCKS);
+            int z = random.nextInt(-SAMPLE_RADIUS_BLOCKS, SAMPLE_RADIUS_BLOCKS);
+            long started = System.nanoTime();
+            generator.getBaseHeight(x, z, type, heights, randomState);
+            samples.wall.add(System.nanoTime() - started);
+            taken++;
+        }
+        samples.finish(taken, THREADS.getCurrentThreadCpuTime() - startedCpu);
+    }
+
+    void baseColumn(CallBudget budget, CallSamples samples) {
+        SplittableRandom random = new SplittableRandom(seed ^ 0x9E3779B97F4A7C15L ^ samples.count);
+        long deadline = System.nanoTime() + budget.limitNanos();
+        long startedCpu = THREADS.getCurrentThreadCpuTime();
+        int taken = 0;
+        while (taken < budget.calls() && (taken < budget.minimumCalls() || System.nanoTime() < deadline)) {
+            int x = random.nextInt(-SAMPLE_RADIUS_BLOCKS, SAMPLE_RADIUS_BLOCKS);
+            int z = random.nextInt(-SAMPLE_RADIUS_BLOCKS, SAMPLE_RADIUS_BLOCKS);
+            long started = System.nanoTime();
+            generator.getBaseColumn(x, z, heights, randomState);
+            samples.wall.add(System.nanoTime() - started);
+            taken++;
+        }
+        samples.finish(taken, THREADS.getCurrentThreadCpuTime() - startedCpu);
+    }
+
+    private void fill(NoiseChunk noiseChunk, ChunkAccess chunk) {
+        try {
+            fill.invoke(generator, noiseChunk, chunk);
+        } catch (IllegalAccessException failure) {
+            throw new IllegalStateException("Cannot invoke NoiseBasedChunkGenerator.doFill for " + label, failure);
+        } catch (InvocationTargetException failure) {
+            if (failure.getCause() instanceof RuntimeException runtime) {
+                throw runtime;
+            }
+            throw new IllegalStateException("Noise fill failed for " + label, failure.getCause());
+        }
+    }
+
+    private DensityVolume volume(ChunkAccess chunk) {
+        NoiseSettings noise = settings.noiseSettings().clampToHeightAccessor(chunk.getHeightAccessorForGeneration());
+        ChunkPos position = chunk.getPos();
+        return new DensityVolume(16, noise.height(), 16, position.getMinBlockX(), noise.minY(), position.getMinBlockZ());
+    }
+
+    private static Set<Holder<Biome>> possibleBiomes(Map<Long, ProtoChunk> chunks, int chunkX, int chunkZ) {
+        Set<Holder<Biome>> possible = new HashSet<>();
+        for (int dz = -1; dz <= 1; dz++) {
+            for (int dx = -1; dx <= 1; dx++) {
+                chunks.get(ChunkPos.pack(chunkX + dx, chunkZ + dz)).collectBiomesInPalette(possible);
+            }
+        }
+        return possible;
+    }
+
+    private static Method fillMethod() {
+        try {
+            Method method = NoiseBasedChunkGenerator.class.getDeclaredMethod("doFill", NoiseChunk.class, ChunkAccess.class);
+            method.setAccessible(true);
+            return method;
+        } catch (NoSuchMethodException failure) {
+            throw new IllegalStateException("NoiseBasedChunkGenerator has no doFill(NoiseChunk, ChunkAccess)", failure);
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Aquifer.FluidPicker fluidPicker(NoiseBasedChunkGenerator generator) {
+        try {
+            Field field = NoiseBasedChunkGenerator.class.getDeclaredField("globalFluidPicker");
+            field.setAccessible(true);
+            return ((Supplier<Aquifer.FluidPicker>) field.get(generator)).get();
+        } catch (ReflectiveOperationException failure) {
+            throw new IllegalStateException("NoiseBasedChunkGenerator has no globalFluidPicker supplier", failure);
+        }
+    }
+
+    private static Level paperConfiguredLevel() {
+        try {
+            Constructor<WorldConfiguration> constructor = WorldConfiguration.class.getDeclaredConstructor(SpigotWorldConfig.class, Identifier.class);
+            constructor.setAccessible(true);
+            WorldConfiguration configuration = constructor.newInstance(null, Identifier.withDefaultNamespace("overworld"));
+            configuration.environment = configuration.new Environment();
+            Class<?> unsafeType = Class.forName("sun.misc.Unsafe");
+            Field unsafeField = unsafeType.getDeclaredField("theUnsafe");
+            unsafeField.setAccessible(true);
+            Method allocate = unsafeType.getMethod("allocateInstance", Class.class);
+            Level level = (Level) allocate.invoke(unsafeField.get(null), ServerLevel.class);
+            Field paperConfig = Level.class.getDeclaredField("paperConfig");
+            paperConfig.setAccessible(true);
+            paperConfig.set(level, configuration);
+            return level;
+        } catch (ReflectiveOperationException failure) {
+            throw new IllegalStateException("Cannot build the Paper world configuration that surface rules read", failure);
+        }
+    }
+
+    record Options(String label, LevelStem stem, RegistryAccess registries, long seed) {
+        Options {
+            Objects.requireNonNull(label, "label");
+            Objects.requireNonNull(stem, "stem");
+            Objects.requireNonNull(registries, "registries");
+        }
+    }
+
+    record CallBudget(int calls, int minimumCalls, long limitNanos) {
+    }
+
+    record ChunkTimings(int chunks, StageTiming biomes, StageTiming noise, StageTiming surface, StageTiming carverBiome,
+                        long biomeFallbacks) {
+        double totalMean() {
+            return biomes.wall().mean() + noise.wall().mean() + surface.wall().mean() + carverBiome.wall().mean();
+        }
+
+        double totalCpuMean() {
+            return biomes.cpu().mean() + noise.cpu().mean() + surface.cpu().mean() + carverBiome.cpu().mean();
+        }
+    }
+
+    record StageTiming(Summary wall, Summary cpu) {
+    }
+
+    record CallTiming(Summary wall, int calls, double cpuMean) {
+    }
+
+    record Summary(int count, double mean, double median, double p90, double min, double max) {
+        private static Summary of(long[] nanos, double unit) {
+            if (nanos.length == 0) {
+                return new Summary(0, Double.NaN, Double.NaN, Double.NaN, Double.NaN, Double.NaN);
+            }
+            long[] sorted = nanos.clone();
+            Arrays.sort(sorted);
+            double total = 0.0;
+            for (long value : sorted) {
+                total += value;
+            }
+            return new Summary(sorted.length, total / sorted.length / unit, percentile(sorted, 0.5) / unit,
+                    percentile(sorted, 0.9) / unit, sorted[0] / unit, sorted[sorted.length - 1] / unit);
+        }
+
+        private static double percentile(long[] sorted, double fraction) {
+            int index = (int) Math.min(sorted.length - 1, Math.round(fraction * (sorted.length - 1)));
+            return sorted[index];
+        }
+    }
+
+    static final class ChunkSamples {
+        private final StageSamples biomes = new StageSamples();
+        private final StageSamples noise = new StageSamples();
+        private final StageSamples surface = new StageSamples();
+        private final StageSamples carverBiome = new StageSamples();
+        private int chunks;
+        private long biomeFallbacks;
+
+        ChunkTimings timings() {
+            return new ChunkTimings(chunks, biomes.timing(), noise.timing(), surface.timing(), carverBiome.timing(), biomeFallbacks);
+        }
+    }
+
+    static final class CallSamples {
+        private final Samples wall = new Samples();
+        private int count;
+        private long cpuNanos;
+
+        CallTiming timing() {
+            return new CallTiming(Summary.of(wall.values(), NANOS_PER_MICRO), count,
+                    count == 0 ? Double.NaN : cpuNanos / (double) count / NANOS_PER_MICRO);
+        }
+
+        private void finish(int calls, long cpu) {
+            count += calls;
+            cpuNanos += cpu;
+        }
+    }
+
+    private static final class StageSamples {
+        private final Samples wall = new Samples();
+        private final Samples cpu = new Samples();
+
+        private void add(long wallNanos, long cpuNanos) {
+            wall.add(wallNanos);
+            cpu.add(cpuNanos);
+        }
+
+        private StageTiming timing() {
+            return new StageTiming(Summary.of(wall.values(), NANOS_PER_MILLI), Summary.of(cpu.values(), NANOS_PER_MILLI));
+        }
+    }
+
+    private static final class Samples {
+        private long[] values = new long[64];
+        private int size;
+
+        private void add(long value) {
+            if (size == values.length) {
+                values = Arrays.copyOf(values, size * 2);
+            }
+            values[size++] = value;
+        }
+
+        private long[] values() {
+            return Arrays.copyOf(values, size);
+        }
+    }
+
+    private static final class RegionBiomes implements BiomeResolver {
+        private final Map<Long, ProtoChunk> chunks;
+        private final BiomeResolver fallback;
+        private long fallbacks;
+
+        private RegionBiomes(Map<Long, ProtoChunk> chunks, BiomeResolver fallback) {
+            this.chunks = chunks;
+            this.fallback = fallback;
+        }
+
+        @Override
+        public Holder<Biome> getNoiseBiome(int quartX, int quartY, int quartZ) {
+            ProtoChunk chunk = chunks.get(ChunkPos.pack(QuartPos.toSection(quartX), QuartPos.toSection(quartZ)));
+            if (chunk == null) {
+                fallbacks++;
+                return fallback.getNoiseBiome(quartX, quartY, quartZ);
+            }
+            return chunk.getNoiseBiome(quartX, quartY, quartZ);
+        }
+
+        private long fallbacks() {
+            return fallbacks;
+        }
+    }
+}

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

@@ -0,0 +1,61 @@
+package art.arcane.iris.probe.fidelity;
+
+import art.arcane.iris.probe.WorldgenExportSampler;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Objects;
+
+public final class VanillaNoiseColumnSource implements ColumnSource {
+    private final WorldgenExportSampler sampler;
+    private final Map<String, String> loadKeyByBiomeId;
+    private final int minY;
+    private final int maxY;
+    private final int seaLevel;
+
+    public VanillaNoiseColumnSource(WorldgenExportSampler sampler, Map<String, String> loadKeyByBiomeId) {
+        this.sampler = Objects.requireNonNull(sampler, "sampler");
+        this.loadKeyByBiomeId = Map.copyOf(loadKeyByBiomeId);
+        this.minY = sampler.minY();
+        this.maxY = sampler.minY() + sampler.height();
+        this.seaLevel = sampler.seaLevel();
+    }
+
+    @Override
+    public String label() {
+        return "vanilla:26.3";
+    }
+
+    @Override
+    public int minY() {
+        return minY;
+    }
+
+    @Override
+    public int maxY() {
+        return maxY;
+    }
+
+    @Override
+    public FidelityColumn column(int x, int z) {
+        int floor = sampler.floorHeight(x, z);
+        int terrainY = floor - 1;
+        boolean wet = floor < seaLevel && sampler.baseHeight(x, z) > floor;
+        return new FidelityColumn(loadKey(x, Math.max(minY, terrainY), z), terrainY, wet);
+    }
+
+    @Override
+    public void close() throws IOException {
+        sampler.close();
+    }
+
+    private String loadKey(int x, int y, int z) {
+        String biomeId = sampler.biome(x, y, z);
+        String loadKey = loadKeyByBiomeId.get(biomeId);
+        if (loadKey == null) {
+            throw new IllegalStateException("Exported biome " + biomeId + " at " + x + "," + y + "," + z
+                    + " has no Iris load key in the export result");
+        }
+        return loadKey;
+    }
+}

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

@@ -0,0 +1,204 @@
+package art.arcane.iris.probe.fidelity;
+
+import art.arcane.iris.probe.WorldgenExportSampler;
+import net.minecraft.core.Holder;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunctions;
+import net.minecraft.world.level.levelgen.densityfunction.op.BinaryFunction;
+
+import java.io.IOException;
+import java.util.IdentityHashMap;
+import java.util.Map;
+import java.util.Objects;
+
+public final class VanillaNoiseFidelitySource implements FidelitySource {
+    private static final int CHUNK_WIDTH = 16;
+    private static final byte SOLID = 0;
+    private static final byte OPEN = 1;
+    private static final byte FLUID = 2;
+    private static final byte LAVA = 3;
+
+    private final WorldgenExportSampler sampler;
+    private final Map<String, String> loadKeyByBiomeId;
+    private final String wallShell;
+    private final DensityFunction massDensity;
+    private final boolean walls;
+    private final int minY;
+    private final int maxY;
+
+    public VanillaNoiseFidelitySource(WorldgenExportSampler sampler, Map<String, String> loadKeyByBiomeId, String wallShell) {
+        this.sampler = Objects.requireNonNull(sampler, "sampler");
+        this.loadKeyByBiomeId = Map.copyOf(loadKeyByBiomeId);
+        this.wallShell = Objects.requireNonNull(wallShell, "wallShell");
+        this.massDensity = terrainMass(sampler.finalDensity());
+        this.walls = sampler.densityFunctionIds().contains(wallShell);
+        this.minY = sampler.minY();
+        this.maxY = sampler.minY() + sampler.height();
+    }
+
+    @Override
+    public String label() {
+        return "vanilla:26.3";
+    }
+
+    @Override
+    public int minY() {
+        return minY;
+    }
+
+    @Override
+    public int maxY() {
+        return maxY;
+    }
+
+    @Override
+    public FidelityChunk sample(int chunkX, int chunkZ) {
+        return new TerrainChunk(sampler.terrainChunk(chunkX, chunkZ), chunkX * CHUNK_WIDTH, chunkZ * CHUNK_WIDTH);
+    }
+
+    @Override
+    public void close() throws IOException {
+        sampler.close();
+    }
+
+    private String loadKey(int x, int y, int z) {
+        String biomeId = sampler.biome(x, y, z);
+        String loadKey = loadKeyByBiomeId.get(biomeId);
+        if (loadKey == null) {
+            throw new IllegalStateException("Exported biome " + biomeId + " at " + x + "," + y + "," + z
+                    + " has no Iris load key in the export result");
+        }
+        return loadKey;
+    }
+
+    static DensityFunction terrainMass(DensityFunction finalDensity) {
+        DensityFunction root = finalDensity;
+        while (root instanceof DensityFunctions.HolderHolder(Holder<DensityFunction> holder)) {
+            root = holder.value();
+        }
+        return root instanceof BinaryFunction(BinaryFunction.Type type, DensityFunction terrain, DensityFunction ignored) && type == BinaryFunction.Type.MIN
+                ? terrain : root;
+    }
+
+    private static byte classify(Block block) {
+        String id = BuiltInRegistries.BLOCK.getKey(block).toString();
+        if (FidelityBlocks.open(id)) {
+            return OPEN;
+        }
+        if (FidelityBlocks.lava(id)) {
+            return LAVA;
+        }
+        return FidelityBlocks.fluid(id) ? FLUID : SOLID;
+    }
+
+    private record Column(int surfaceY, String biome, byte[] kinds) {
+    }
+
+    private final class TerrainChunk implements FidelityChunk {
+        private final ProtoChunk terrain;
+        private final int blockX;
+        private final int blockZ;
+        private final Column[] columns = new Column[CHUNK_WIDTH * CHUNK_WIDTH];
+        private final Map<Block, Byte> kinds = new IdentityHashMap<>();
+        private float[] masses;
+
+        private TerrainChunk(ProtoChunk terrain, int blockX, int blockZ) {
+            this.terrain = terrain;
+            this.blockX = blockX;
+            this.blockZ = blockZ;
+        }
+
+        @Override
+        public int surfaceY(int localX, int localZ) {
+            return column(localX, localZ).surfaceY();
+        }
+
+        @Override
+        public String surfaceBiome(int localX, int localZ) {
+            return column(localX, localZ).biome();
+        }
+
+        @Override
+        public boolean open(int localX, int y, int localZ) {
+            return kind(localX, y, localZ) == OPEN;
+        }
+
+        @Override
+        public boolean fluid(int localX, int y, int localZ) {
+            byte kind = kind(localX, y, localZ);
+            return kind == FLUID || kind == LAVA;
+        }
+
+        @Override
+        public boolean lava(int localX, int y, int localZ) {
+            return kind(localX, y, localZ) == LAVA;
+        }
+
+        @Override
+        public String block(int localX, int y, int localZ) {
+            return null;
+        }
+
+        @Override
+        public boolean terrainMass(int localX, int y, int localZ) {
+            if (y < minY || y >= maxY) {
+                throw new IllegalArgumentException("Y " + y + " is outside [" + minY + ", " + maxY + ")");
+            }
+            if (localX < 0 || localX >= CHUNK_WIDTH || localZ < 0 || localZ >= CHUNK_WIDTH) {
+                throw new IllegalArgumentException("Column " + localX + "," + localZ + " is outside the chunk");
+            }
+            if (masses == null) {
+                masses = sampler.densityChunk(massDensity, Math.floorDiv(blockX, CHUNK_WIDTH), Math.floorDiv(blockZ, CHUNK_WIDTH));
+            }
+            return masses[(localZ * CHUNK_WIDTH + localX) * (maxY - minY) + y - minY] > 0.0F;
+        }
+
+        @Override
+        public boolean wallsKnown() {
+            return walls;
+        }
+
+        @Override
+        public boolean wall(int localX, int y, int localZ) {
+            return walls && sampler.density(wallShell, blockX + localX, y, blockZ + localZ) > 0.0F;
+        }
+
+        private byte kind(int localX, int y, int localZ) {
+            if (y < minY || y >= maxY) {
+                throw new IllegalArgumentException("Y " + y + " is outside [" + minY + ", " + maxY + ")");
+            }
+            return column(localX, localZ).kinds()[y - minY];
+        }
+
+        private Column column(int localX, int localZ) {
+            if (localX < 0 || localX >= CHUNK_WIDTH || localZ < 0 || localZ >= CHUNK_WIDTH) {
+                throw new IllegalArgumentException("Column " + localX + "," + localZ + " is outside the chunk");
+            }
+            int index = localZ * CHUNK_WIDTH + localX;
+            Column column = columns[index];
+            if (column == null) {
+                column = sampleColumn(localX, localZ);
+                columns[index] = column;
+            }
+            return column;
+        }
+
+        private Column sampleColumn(int localX, int localZ) {
+            byte[] column = new byte[maxY - minY];
+            int surfaceY = minY - 1;
+            for (int y = maxY - 1; y >= minY; y--) {
+                LevelChunkSection section = terrain.getSection(terrain.getSectionIndex(y));
+                byte kind = kinds.computeIfAbsent(section.getBlockState(localX, y & (CHUNK_WIDTH - 1), localZ).getBlock(), VanillaNoiseFidelitySource::classify);
+                column[y - minY] = kind;
+                if (kind == SOLID && surfaceY < minY) {
+                    surfaceY = y;
+                }
+            }
+            return new Column(surfaceY, loadKey(blockX + localX, Math.max(minY, surfaceY), blockZ + localZ), column);
+        }
+    }
+}

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

@@ -0,0 +1,73 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.platform.bukkit.BukkitPlatform;
+import art.arcane.iris.spi.VanillaDataSource;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.packs.PackResources;
+import net.minecraft.server.packs.PackType;
+import net.minecraft.server.packs.repository.ServerPacksSource;
+import net.minecraft.server.packs.resources.IoSupplier;
+import org.bukkit.Bukkit;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collections;
+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.assertTrue;
+
+public final class BukkitVanillaDataTest {
+    private static final String PLAINS = "data/minecraft/worldgen/biome/plains.json";
+    private static final String BIOME_TAGS = "data/minecraft/tags/worldgen/biome";
+
+    @BeforeClass
+    public static void bootstrap() {
+        HeadlessNativeBootstrap.initialize();
+    }
+
+    @Test
+    public void bukkitPlatformReadsTheServerPlainsBiome() throws IOException {
+        byte[] plains = new BukkitPlatform().vanillaData().read(PLAINS).orElseThrow();
+        assertTrue(new String(plains, StandardCharsets.UTF_8).contains("\"temperature\""));
+        try (PackResources vanilla = ServerPacksSource.createVanillaPackSource().fullResources()) {
+            IoSupplier<InputStream> resource = vanilla.getResource(PackType.SERVER_DATA,
+                    Identifier.withDefaultNamespace("worldgen/biome/plains.json"));
+            try (InputStream input = resource.get()) {
+                assertArrayEquals(input.readAllBytes(), plains);
+            }
+        }
+        assertNull(Bukkit.getServer());
+    }
+
+    @Test
+    public void bukkitPlatformListsTheBiomeTagsTheGameLoads() {
+        List<String> expected = new ArrayList<>();
+        try (PackResources vanilla = ServerPacksSource.createVanillaPackSource().fullResources()) {
+            vanilla.listResources(PackType.SERVER_DATA, "minecraft", "tags/worldgen/biome",
+                    (id, resource) -> expected.add("data/" + id.getNamespace() + "/" + id.getPath()));
+        }
+        Collections.sort(expected);
+        List<String> listed = new BukkitPlatform().vanillaData().list(BIOME_TAGS);
+        assertFalse(listed.isEmpty());
+        assertTrue(listed.contains(BIOME_TAGS + "/is_overworld.json"));
+        assertEquals(expected, listed);
+    }
+
+    @Test
+    public void headlessPlatformReadsTheSameVanillaData() {
+        HeadlessNativePlatform platform = new HeadlessNativePlatform(new File("unused-native-platform"),
+                HeadlessNativeTestRegistries::get);
+        VanillaDataSource bukkit = new BukkitPlatform().vanillaData();
+        assertArrayEquals(bukkit.read(PLAINS).orElseThrow(), platform.vanillaData().read(PLAINS).orElseThrow());
+        assertEquals(bukkit.list(BIOME_TAGS), platform.vanillaData().list(BIOME_TAGS));
+    }
+}

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

@@ -0,0 +1,146 @@
+package art.arcane.iris.probe;
+
+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.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.densityfunction.CachingDensitySampler;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+import net.minecraft.world.level.levelgen.densityfunction.DensitySampler;
+import net.minecraft.world.level.levelgen.material.rule.ConditionRule;
+import net.minecraft.world.level.levelgen.material.rule.MaterialRule;
+import net.minecraft.world.level.levelgen.material.rule.OreVeinRule;
+import net.minecraft.world.level.levelgen.material.rule.SequenceRule;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Deque;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+
+final class CompiledCaches {
+    private static final String MINECRAFT_PACKAGE = "net.minecraft.";
+    private static final String DENSITY_PACKAGE = "net.minecraft.world.level.levelgen.densityfunction.";
+    private static final String SPLINE_PACKAGE = "net.minecraft.util.";
+    private static final String SPLINE_NAME = "Spline";
+
+    private final RegistryAccess registries;
+    private final NoiseGeneratorSettings settings;
+    private final RandomState state;
+
+    private CompiledCaches(RegistryAccess registries, NoiseGeneratorSettings settings, long seed) {
+        this.registries = registries;
+        this.settings = settings;
+        this.state = RandomState.create(registries.lookupOrThrow(Registries.NOISE), seed, settings);
+    }
+
+    static CompiledCaches open(RegistryAccess registries, long seed) {
+        if (!(DatapackCostProbe.exportedOverworld(registries).generator() instanceof NoiseBasedChunkGenerator generator)) {
+            throw new IllegalStateException("Exported overworld has no noise generator");
+        }
+        return new CompiledCaches(registries, generator.generatorSettings().value(), seed);
+    }
+
+    DensityFunction finalDensity() {
+        return settings.noiseRouter().finalDensity();
+    }
+
+    DensityFunction function(String id) {
+        return registries.lookupOrThrow(Registries.DENSITY_FUNCTION)
+                .getOrThrow(ResourceKey.create(Registries.DENSITY_FUNCTION, Identifier.parse(id))).value();
+    }
+
+    List<OreVeinRule> oreVeins() {
+        List<OreVeinRule> veins = new ArrayList<>();
+        Deque<MaterialRule> pending = new ArrayDeque<>();
+        pending.push(settings.materialRule().value());
+        while (!pending.isEmpty()) {
+            MaterialRule rule = pending.pop();
+            switch (rule) {
+                case OreVeinRule vein -> veins.add(vein);
+                case SequenceRule sequence -> sequence.sequence().reversed().forEach(pending::push);
+                case ConditionRule condition -> pending.push(condition.thenRun());
+                default -> {
+                }
+            }
+        }
+        return veins;
+    }
+
+    int rootId(DensityFunction function) {
+        if (!(state.getSampler(function) instanceof CachingDensitySampler cache)) {
+            throw new IllegalStateException("Density function " + function + " does not compile to a cache");
+        }
+        return cache.id();
+    }
+
+    Set<Integer> ids(DensityFunction function) {
+        Set<Integer> ids = new TreeSet<>();
+        Set<Object> visited = Collections.newSetFromMap(new IdentityHashMap<>());
+        Deque<Object> pending = new ArrayDeque<>();
+        pending.push(state.getSampler(function));
+        while (!pending.isEmpty()) {
+            Object node = pending.pop();
+            if (node == null || !visited.add(node)) {
+                continue;
+            }
+            if (node instanceof CachingDensitySampler cache) {
+                ids.add(cache.id());
+            }
+            for (Object child : children(node)) {
+                pending.push(child);
+            }
+        }
+        return ids;
+    }
+
+    private static List<Object> children(Object node) {
+        List<Object> children = new ArrayList<>();
+        if (node instanceof Object[] array) {
+            Collections.addAll(children, array);
+            return children;
+        }
+        if (node instanceof Collection<?> collection) {
+            children.addAll(collection);
+            return children;
+        }
+        if (!traversed(node)) {
+            return children;
+        }
+        for (Class<?> type = node.getClass(); type != null && type.getName().startsWith(MINECRAFT_PACKAGE); type = type.getSuperclass()) {
+            for (Field field : type.getDeclaredFields()) {
+                if (Modifier.isStatic(field.getModifiers()) || field.getType().isPrimitive()) {
+                    continue;
+                }
+                children.add(read(field, node));
+            }
+        }
+        return children;
+    }
+
+    private static boolean traversed(Object node) {
+        if (node instanceof Enum<?>) {
+            return false;
+        }
+        String name = node.getClass().getName();
+        return node instanceof DensitySampler || name.startsWith(DENSITY_PACKAGE) || name.startsWith(SPLINE_PACKAGE) && name.contains(SPLINE_NAME);
+    }
+
+    private static Object read(Field field, Object owner) {
+        try {
+            field.setAccessible(true);
+            return field.get(owner);
+        } catch (IllegalAccessException | RuntimeException failure) {
+            throw new IllegalStateException("Cannot read " + field + " of " + owner.getClass().getName(), failure);
+        }
+    }
+}

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

@@ -0,0 +1,46 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.probe.fidelity.FidelityReport;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.nio.charset.StandardCharsets;
+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.assertTrue;
+
+public final class DatapackFidelityProbeBiomeModeTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    @Rule
+    public TemporaryFolder temporary = new TemporaryFolder();
+
+    @Test(timeout = 300_000L)
+    public void biomeModeJudgesTheSeedMeanWithoutTheChunkScan() throws Exception {
+        Path pack = DatapackFidelityProbeTest.pack(temporary);
+        Path output = temporary.getRoot().toPath().resolve("reports").resolve("biomes.json");
+
+        FidelityReport report = DatapackFidelityProbe.execute(
+                new String[]{pack.toString(), "main", "1337", "0", "1", output.toString(), "256", "32", "3", "biomes"}, DatapackFidelityProbeTest.exporter());
+
+        JsonObject json = JsonParser.parseString(Files.readString(output, StandardCharsets.UTF_8)).getAsJsonObject();
+        assertTrue(report.toTable(), report.passed());
+        assertTrue(json.get("passed").getAsBoolean());
+        assertEquals(1.0D, DatapackFidelityProbeTest.metric(report, "biome.share.plains").export(), 0.0D);
+        assertEquals(1, report.sampling().size());
+        assertEquals(List.of(1337L, 1338L, 1339L), report.sampling().getFirst().seeds());
+        assertEquals(3, json.getAsJsonArray("seeds").size());
+        assertEquals(3, json.getAsJsonObject("seedsPassing").getAsJsonObject("biome.share.plains").get("passing").getAsInt());
+        assertTrue(report.observations().stream().anyMatch(observation -> observation.name().equals("biome.type.land")
+                && observation.iris() == 1.0D && observation.export() == 1.0D));
+        assertTrue(RealPackProbeSupport.drainReported().isEmpty());
+    }
+}

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

@@ -0,0 +1,116 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.compile.DimensionStage;
+import art.arcane.iris.pack.datapack.export.compile.ImageMapStage;
+import art.arcane.iris.pack.datapack.export.compile.PackCompiler;
+import art.arcane.iris.pack.datapack.export.emit.WorldgenJsonWriter;
+import art.arcane.iris.probe.fidelity.FidelityMetric;
+import art.arcane.iris.probe.fidelity.FidelityReport;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.nio.charset.StandardCharsets;
+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.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public final class DatapackFidelityProbeTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    @Rule
+    public TemporaryFolder temporary = new TemporaryFolder();
+
+    @Test(timeout = 300_000L)
+    public void probeExportsTheSyntheticPackAndComparesBothGenerators() throws Exception {
+        Path pack = pack(temporary);
+        Path output = temporary.getRoot().toPath().resolve("reports").resolve("fidelity.json");
+
+        FidelityReport report = DatapackFidelityProbe.execute(
+                new String[]{pack.toString(), "main", "1337", "1", "8", output.toString(), "256", "32", "2", "full"}, exporter());
+
+        JsonObject json = JsonParser.parseString(Files.readString(output, StandardCharsets.UTF_8)).getAsJsonObject();
+        assertTrue(report.toTable(), report.passed());
+        assertTrue(json.get("passed").getAsBoolean());
+        assertEquals(report.metrics().size(), json.getAsJsonArray("metrics").size());
+        FidelityMetric biome = metric(report, "biome.share.plains");
+        assertEquals(1.0D, biome.iris(), 0.0D);
+        assertEquals(1.0D, biome.export(), 0.0D);
+        assertTrue(biome.pass());
+        assertEquals(0.0D, metric(report, "biome.totalVariation").delta(), 0.0D);
+        assertEquals(1.0D, metric(report, "height.landFraction").export(), 0.0D);
+        JsonObject columns = json.getAsJsonArray("sampling").get(0).getAsJsonObject();
+        assertEquals("columns", columns.get("scope").getAsString());
+        assertEquals(256, columns.get("windowBlocks").getAsInt());
+        assertEquals(32, columns.get("strideBlocks").getAsInt());
+        assertEquals(2, columns.getAsJsonArray("seeds").size());
+        assertEquals(128L, columns.get("columns").getAsLong());
+        JsonObject chunks = json.getAsJsonArray("sampling").get(1).getAsJsonObject();
+        assertEquals("chunks", chunks.get("scope").getAsString());
+        assertEquals(48, chunks.get("windowBlocks").getAsInt());
+        assertTrue(RealPackProbeSupport.drainReported().isEmpty());
+    }
+
+    @Test
+    public void malformedArgumentsAreRejectedBeforeThePackOpens() throws Exception {
+        Path pack = pack(temporary);
+        String output = temporary.getRoot().toPath().resolve("unused.json").toString();
+
+        IllegalArgumentException missing = assertThrows(IllegalArgumentException.class,
+                () -> DatapackFidelityProbe.execute(new String[]{pack.toString(), "main"}, exporter()));
+        IllegalArgumentException stride = assertThrows(IllegalArgumentException.class,
+                () -> DatapackFidelityProbe.execute(new String[]{pack.toString(), "main", "1337", "1", "17", output, "256", "32", "1", "full"}, exporter()));
+        IllegalArgumentException survey = assertThrows(IllegalArgumentException.class,
+                () -> DatapackFidelityProbe.execute(new String[]{pack.toString(), "main", "1337", "1", "8", output, "250", "32", "1", "full"}, exporter()));
+        IllegalArgumentException seeds = assertThrows(IllegalArgumentException.class,
+                () -> DatapackFidelityProbe.execute(new String[]{pack.toString(), "main", "1337", "1", "8", output, "256", "32", "0", "full"}, exporter()));
+        IllegalArgumentException mode = assertThrows(IllegalArgumentException.class,
+                () -> DatapackFidelityProbe.execute(new String[]{pack.toString(), "main", "1337", "1", "8", output, "256", "32", "1", "caves"}, exporter()));
+
+        assertTrue(missing.getMessage(), missing.getMessage().startsWith("Usage:"));
+        assertTrue(stride.getMessage(), stride.getMessage().contains("stride"));
+        assertTrue(survey.getMessage(), survey.getMessage().contains("multiple"));
+        assertTrue(seeds.getMessage(), seeds.getMessage().contains("surveySeeds"));
+        assertTrue(mode.getMessage(), mode.getMessage().contains("caves"));
+        assertFalse(Files.exists(Path.of(output)));
+    }
+
+    static WorldgenDatapackExporter exporter() {
+        return new WorldgenDatapackExporter(WorldgenJsonWriter::forTarget, new PackCompiler(List.of(new DimensionStage(), new ImageMapStage())));
+    }
+
+    static FidelityMetric metric(FidelityReport report, String name) {
+        for (FidelityMetric metric : report.metrics()) {
+            if (metric.name().equals(name)) {
+                return metric;
+            }
+        }
+        throw new AssertionError("Report has no metric " + name + ": " + report.toJson());
+    }
+
+    static Path pack(TemporaryFolder temporary) 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":"Fidelity","focus":"plains","regions":["owned"],"landChance":1,"carvingEnabled":false}
+                """);
+        Files.writeString(pack.resolve("regions/owned.json"), "{\"landBiomes\":[\"plains\"]}");
+        Files.writeString(pack.resolve("generators/flat.json"), "{\"composite\":[]}");
+        Files.writeString(pack.resolve("biomes/plains.json"), """
+                {"derivative":"minecraft:plains","generators":[{"generator":"flat","min":0,"max":0}]}
+                """);
+        return pack;
+    }
+}

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

@@ -0,0 +1,110 @@
+package art.arcane.iris.probe;
+
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public final class DensityCostAnalysisTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final double EPSILON = 1.0E-9;
+    private static final String LEAF = "{\"type\":\"noise\",\"noise\":\"minecraft:temperature\",\"xz_scale\":1.0,\"y_scale\":0.0}";
+
+    private static HeadlessNativeRegistries registries;
+
+    @BeforeClass
+    public static void loadGraphs() throws IOException {
+        Map<String, String> definitions = new LinkedHashMap<>();
+        definitions.put(path("leaf"), LEAF);
+        definitions.put(path("pair"), "{\"type\":\"add\",\"left\":\"t:leaf\",\"right\":\"t:leaf\"}");
+        definitions.put(path("quad"), "{\"type\":\"mul\",\"left\":\"t:pair\",\"right\":\"t:pair\"}");
+        definitions.put(path("cached"), "{\"type\":\"cache\",\"input\":\"t:pair\"}");
+        definitions.put(path("twice"), "{\"type\":\"add\",\"left\":\"t:cached\",\"right\":\"t:cached\"}");
+        definitions.put(path("select"), "{\"type\":\"interval_select\",\"input\":\"t:leaf\",\"thresholds\":[0.0],\"functions\":[\"t:quad\",\"t:pair\"]}");
+        definitions.put(path("spline"), "{\"type\":\"spline\",\"spline\":{\"coordinate\":\"t:leaf\",\"points\":["
+                + "{\"location\":-1.0,\"value\":" + nested("t:quad") + ",\"derivative\":0.0},"
+                + "{\"location\":0.0,\"value\":0.0,\"derivative\":0.0},"
+                + "{\"location\":1.0,\"value\":" + nested("t:quad") + ",\"derivative\":0.0}]}}");
+        definitions.put(path("grid"), "{\"type\":\"interpolated\",\"input\":\"t:pair\",\"cell_size_xz\":4,\"cell_size_y\":8}");
+        registries = HeadlessNativeRegistries.load(definitions);
+    }
+
+    @AfterClass
+    public static void closeRegistries() throws IOException {
+        if (registries != null) {
+            registries.close();
+        }
+    }
+
+    @Test
+    public void referencesExpandWhileTheDagSharesThem() {
+        DensityCostAnalysis.RootCost quad = analysis().analyze("quad", function("quad"));
+        assertEquals(3L, quad.dagNodes());
+        assertEquals(7.0, quad.expandedNodes(), EPSILON);
+        assertEquals(7.0, quad.cachedNodes(), EPSILON);
+        assertEquals(2, quad.namedSubtrees());
+        assertEquals("t:leaf", quad.exclusive().getFirst().name());
+        assertEquals(4.0, quad.exclusive().getFirst().multiplicity(), EPSILON);
+        assertEquals(4.0, quad.exclusive().getFirst().contribution(), EPSILON);
+        assertEquals("t:pair", quad.inclusive().getFirst().name());
+        assertEquals(6.0, quad.inclusive().getFirst().inclusive(), EPSILON);
+        assertEquals(1.0 / 3.0, quad.dagShare().get("leaf"), EPSILON);
+        assertEquals(1.0 / 3.0, quad.dagShare().get("quad"), EPSILON);
+    }
+
+    @Test
+    public void cachesEvaluateTheirBodyOnceWhenEnabled() {
+        DensityCostAnalysis.RootCost twice = analysis().analyze("twice", function("twice"));
+        assertEquals(4L, twice.dagNodes());
+        assertEquals(9.0, twice.expandedNodes(), EPSILON);
+        assertEquals(6.0, twice.cachedNodes(), EPSILON);
+    }
+
+    @Test
+    public void uncachedPointEvaluationTakesOneSelectedBranch() {
+        DensityCostAnalysis analysis = analysis();
+        DensityCostAnalysis.RootCost select = analysis.analyze("select", function("select"));
+        assertEquals(12.0, select.expandedNodes(), EPSILON);
+        assertEquals(9.0, select.uncachedPointWorst(), EPSILON);
+        DensityCostAnalysis.RootCost spline = analysis.analyze("spline", function("spline"));
+        assertEquals(19.0, spline.expandedNodes(), EPSILON);
+        assertEquals(11.0, spline.uncachedPointWorst(), EPSILON);
+    }
+
+    @Test
+    public void offLatticeGridPointsSampleEightCorners() {
+        DensityCostAnalysis.RootCost grid = analysis().analyze("grid", function("grid"));
+        assertEquals(4.0, grid.expandedNodes(), EPSILON);
+        assertEquals(25.0, grid.uncachedPointWorst(), EPSILON);
+    }
+
+    private static DensityCostAnalysis analysis() {
+        return new DensityCostAnalysis(id -> DensityJsonBreakdown.category("overworld", id), 10);
+    }
+
+    private static DensityFunction function(String name) {
+        return registries.registries().lookupOrThrow(Registries.DENSITY_FUNCTION)
+                .getOrThrow(ResourceKey.create(Registries.DENSITY_FUNCTION, Identifier.parse("t:" + name))).value();
+    }
+
+    private static String nested(String coordinate) {
+        return "{\"coordinate\":\"" + coordinate + "\",\"points\":[{\"location\":0.0,\"value\":1.0,\"derivative\":0.0},"
+                + "{\"location\":1.0,\"value\":2.0,\"derivative\":0.0}]}";
+    }
+
+    private static String path(String name) {
+        return "data/t/worldgen/density_function/" + name + ".json";
+    }
+}

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

@@ -0,0 +1,88 @@
+package art.arcane.iris.probe;
+
+import org.junit.Test;
+
+import java.nio.charset.StandardCharsets;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+import static org.junit.Assert.assertEquals;
+
+public final class DensityJsonBreakdownTest {
+    private static final String TEMPERATURE = "{\"type\":\"add\",\"left\":\"x:biome/selector/0\",\"right\":1.0}";
+    private static final String SELECTOR = "{\"type\":\"mul\",\"left\":\"x:cell/cellular/a/value\",\"right\":2.0}";
+    private static final String CELL_A = "{\"type\":\"noise\",\"noise\":\"x:hash_a\",\"xz_scale\":0.5,\"y_scale\":0.0}";
+    private static final String CELL_B = "{\"type\":\"noise\",\"noise\":\"x:hash_b\",\"xz_scale\":0.25,\"y_scale\":0.0}";
+    private static final String FINAL_DENSITY = "{\"type\":\"min\",\"left\":\"x:cell/cellular/b/value\",\"right\":0.0}";
+    private static final String NOISE = "{\"firstOctave\":-1,\"amplitudes\":[1.0]}";
+
+    @Test
+    public void categoriesFollowProducingCompilers() {
+        assertEquals("router", DensityJsonBreakdown.category("overworld", "x:overworld/final_density"));
+        assertEquals("cellular", DensityJsonBreakdown.category("overworld", "x:cell/cracks/abc/distance"));
+        assertEquals("biome selector", DensityJsonBreakdown.category("overworld", "x:biome/selector/12"));
+        assertEquals("biome decision", DensityJsonBreakdown.category("overworld", "x:biome/base_code"));
+        assertEquals("terrain height", DensityJsonBreakdown.category("overworld", "x:height"));
+        assertEquals("terrain bands", DensityJsonBreakdown.category("overworld", "x:terrain/plains/blend/3"));
+        assertEquals("noise style", DensityJsonBreakdown.category("overworld", "x:style/shared/ab12"));
+        assertEquals("cellular offset copies", DensityJsonBreakdown.category("overworld", "x:cell/cellular/abc/vx_0_0/offset_x4_z0"));
+        assertEquals("biome selector offset copies", DensityJsonBreakdown.category("overworld", "x:biome/selector/4/offset_x0_z4"));
+    }
+
+    @Test
+    public void reportsBytesShapesAndCellularOwners() {
+        SortedMap<String, byte[]> files = new TreeMap<>();
+        put(files, "density_function/overworld/temperature", TEMPERATURE);
+        put(files, "density_function/biome/selector/0", SELECTOR);
+        put(files, "density_function/cell/cellular/a/value", CELL_A);
+        put(files, "density_function/cell/cellular/b/value", CELL_B);
+        put(files, "density_function/overworld/final_density", FINAL_DENSITY);
+        put(files, "noise/hash_a", NOISE);
+        put(files, "noise/hash_b", NOISE);
+
+        DensityJsonBreakdown.Report report = DensityJsonBreakdown.analyze(files, "overworld").report();
+
+        assertEquals(5, report.files());
+        assertEquals(bytes(TEMPERATURE, SELECTOR, CELL_A, CELL_B, FINAL_DENSITY), report.bytes());
+        DensityJsonBreakdown.CategoryBytes cellular = category(report, "cellular");
+        assertEquals(2, cellular.files());
+        assertEquals(1, cellular.distinctShapes());
+        assertEquals(bytes(CELL_B), cellular.structurallyDuplicateBytes());
+        assertEquals(2, category(report, "router").files());
+        assertEquals(2, report.cellularInstances());
+        assertEquals(1, report.cellularShapes().size());
+        assertEquals("biome selector+router", report.cellularShapes().getFirst().owners());
+        assertEquals(bytes(CELL_A), owner(report, "cellular via biome selector"));
+        assertEquals(bytes(CELL_B), owner(report, "cellular via router"));
+    }
+
+    private static DensityJsonBreakdown.CategoryBytes category(DensityJsonBreakdown.Report report, String name) {
+        for (DensityJsonBreakdown.CategoryBytes category : report.categories()) {
+            if (category.category().equals(name)) {
+                return category;
+            }
+        }
+        throw new AssertionError("No category " + name + " in " + report.categories());
+    }
+
+    private static long owner(DensityJsonBreakdown.Report report, String name) {
+        for (DensityJsonBreakdown.Bytes owner : report.libraryOwners()) {
+            if (owner.name().equals(name)) {
+                return owner.bytes();
+            }
+        }
+        throw new AssertionError("No owner " + name + " in " + report.libraryOwners());
+    }
+
+    private static long bytes(String... bodies) {
+        long total = 0;
+        for (String body : bodies) {
+            total += body.getBytes(StandardCharsets.UTF_8).length;
+        }
+        return total;
+    }
+
+    private static void put(SortedMap<String, byte[]> files, String path, String body) {
+        files.put("data/x/worldgen/" + path + ".json", body.getBytes(StandardCharsets.UTF_8));
+    }
+}

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

@@ -137,7 +137,7 @@ public class HeadlessChunkGeneratorTest {
         }
         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}}}
+                 "landChance":1,"carvingEnabled":false}
                 """);
         Files.writeString(pack.resolve("regions/owned.json"), "{\"landBiomes\":[\"swamp\"]}");
         Files.writeString(pack.resolve("generators/flat.json"), "{\"composite\":[]}");

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

@@ -1,7 +1,6 @@
 package art.arcane.iris.probe;
 
 import art.arcane.iris.structure.nativegen.NativeStructureVolumeIndex;
-import art.arcane.iris.generation.hydrology.HydrologyTileCache;
 import art.arcane.volmlib.nativelib.terrain.structure.NativeStructureVolume;
 import art.arcane.volmlib.util.collection.KList;
 import net.minecraft.nbt.CompoundTag;
@@ -68,11 +67,10 @@ public final class HeadlessRegionTerrainTest {
                 OfflineRegionGenerator.Configuration export = new OfflineRegionGenerator.Configuration(
                         workspace.pack(), "main", 69420L, -3, 2, 1, 2, 3, 4, configuration,
                         "probe", Level.OVERWORLD, NoiseGeneratorSettings.OVERWORLD, root.resolve("export"));
-                HydrologyTileCache.PregenerationArea bounds = export.hydrologyArea();
-                assertEquals(-80L, bounds.minimumBlockX());
-                assertEquals(0L, bounds.minimumBlockZ());
-                assertEquals(15L, bounds.maximumBlockX());
-                assertEquals(111L, bounds.maximumBlockZ());
+                List<long[]> regions = export.hydrologyRegions();
+                assertEquals(2, regions.size());
+                assertArrayEquals(new long[]{-1L, 0L}, regions.get(0));
+                assertArrayEquals(new long[]{0L, 0L}, regions.get(1));
                 assertEquals(1, result.targetChunks());
                 assertEquals(529, result.chunks().size());
                 long terrain = result.chunks().stream().filter(chunk -> chunk.getPersistedStatus() == ChunkStatus.TERRAIN).count();
@@ -189,7 +187,7 @@ public final class HeadlessRegionTerrainTest {
         }
         Files.writeString(pack.resolve("dimensions/main.json"), """
                 {"name":"Native region","focus":"swamp","regions":["owned"],"fluidHeight":40,"logicalHeight":256,
-                 "landChance":1,"carvingEnabled":false,"hydrology":{"rivers":{"enabled":false}}}
+                 "landChance":1,"carvingEnabled":false}
                 """);
         Files.writeString(pack.resolve("regions/owned.json"), "{\"landBiomes\":[\"swamp\"]}");
         Files.writeString(pack.resolve("generators/flat.json"), "{\"composite\":[]}");

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

@@ -1,37 +1,19 @@
 package art.arcane.iris.probe;
 
-import io.papermc.paper.registry.PaperRegistryAccess;
 import org.junit.rules.TestRule;
 import org.junit.runner.Description;
 import org.junit.runners.model.Statement;
 
-import java.lang.reflect.Field;
-import java.util.HashMap;
-import java.util.Map;
-
 public final class PaperRegistryIsolation implements TestRule {
     @Override
     public Statement apply(Statement base, Description description) {
         return new Statement() {
             @Override
             public void evaluate() throws Throwable {
-                Map<Object, Object> registries = registries();
-                Map<Object, Object> previous = new HashMap<>(registries);
-                registries.clear();
-                try {
+                try (PaperRegistryScope scope = PaperRegistryScope.open()) {
                     base.evaluate();
-                } finally {
-                    registries.clear();
-                    registries.putAll(previous);
                 }
             }
         };
     }
-
-    @SuppressWarnings("unchecked")
-    private static Map<Object, Object> registries() throws ReflectiveOperationException {
-        Field field = PaperRegistryAccess.class.getDeclaredField("registries");
-        field.setAccessible(true);
-        return (Map<Object, Object>) field.get(PaperRegistryAccess.instance());
-    }
 }

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/VanillaBoundsParity263Test.java

@@ -0,0 +1,126 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.emit.DensityFunctionEmitter;
+import art.arcane.iris.pack.datapack.export.emit.FunctionTable;
+import art.arcane.iris.pack.datapack.export.ir.Axis;
+import art.arcane.iris.pack.datapack.export.ir.Field;
+import art.arcane.iris.pack.datapack.export.ir.NoiseDef;
+import art.arcane.iris.pack.datapack.export.ir.ValueRange;
+import art.arcane.iris.pack.datapack.export.lower.ExportCapabilities;
+import art.arcane.iris.pack.datapack.export.lower.VanillaBounds;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.Interval;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public final class VanillaBoundsParity263Test {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final String NAMESPACE = "iris_export";
+    private static final List<NoiseDef> NOISES = List.of(new NoiseDef("parity/base", -3, List.of(1.0, 0.5, 0.25)),
+            new NoiseDef("parity/sparse", 0, List.of(0.0, 1.5, 0.0, 0.7)));
+    private static final Field BASE = new Field.Noise(NAMESPACE + ":parity/base", 0.25, 0.0, null, null, null);
+    private static final Field SPARSE = new Field.Noise(NAMESPACE + ":parity/sparse", 0.5, 0.25, null, null, null);
+    private static final Field UNIT = new Field.Clamp(BASE, 0.0, 1.0);
+    private static final Field BAND = new Field.Clamp(SPARSE, 0.3, 0.9);
+
+    @Test
+    public void boundsMatchMinecraftForEveryEmittedNode() throws Exception {
+        List<Field> fields = fields();
+        VanillaBounds bounds = VanillaBounds.of(NAMESPACE, NOISES);
+        DensityFunctionEmitter emitter = DensityFunctionEmitter.forTarget(ExportCapabilities.forTarget(DataVersion.V26_3), NAMESPACE, bounds);
+        FunctionTable table = new FunctionTable(NAMESPACE);
+        List<String> references = new ArrayList<>(fields.size());
+        for (int index = 0; index < fields.size(); index++) {
+            JsonElement emitted = emitter.emit(fields.get(index), table);
+            boolean reference = emitted.isJsonPrimitive() && emitted.getAsJsonPrimitive().isString();
+            references.add(reference ? emitted.getAsString() : table.register("parity/field_" + index, emitted));
+        }
+        Map<String, String> definitions = new LinkedHashMap<>();
+        for (Map.Entry<String, JsonElement> function : table.files().entrySet()) {
+            definitions.put("data/" + NAMESPACE + "/worldgen/density_function/" + function.getKey() + ".json", function.getValue().toString());
+        }
+        for (NoiseDef noise : NOISES) {
+            definitions.put("data/" + NAMESPACE + "/worldgen/noise/" + noise.id() + ".json", noiseJson(noise).toString());
+        }
+        try (HeadlessNativeRegistries registries = HeadlessNativeRegistries.load(definitions)) {
+            for (int index = 0; index < fields.size(); index++) {
+                Interval vanilla = registries.registries().lookupOrThrow(Registries.DENSITY_FUNCTION)
+                        .getOrThrow(ResourceKey.create(Registries.DENSITY_FUNCTION, Identifier.parse(references.get(index)))).value().range();
+                Optional<ValueRange> modelled = bounds.range(fields.get(index));
+                assertTrue("field " + index + " " + fields.get(index) + " has no modelled range, Minecraft " + vanilla, modelled.isPresent());
+                assertEquals("field " + index + " " + fields.get(index), new ValueRange(vanilla.min(), vanilla.max()), modelled.get());
+            }
+        }
+    }
+
+    private static List<Field> fields() {
+        Field scaled = new Field.Binary(Field.BinaryOp.MUL, new Field.Const(0.3), BAND);
+        Field curve = new Field.Curve(new Field.Binary(Field.BinaryOp.MUL, BASE, new Field.Const(1.7)), List.of(
+                new Field.Knot(-1.0, new Field.Const(0.2), 0.75),
+                new Field.Knot(0.1, new Field.Curve(SPARSE, List.of(new Field.Knot(-0.5, new Field.Const(-1.0), 0.0),
+                        new Field.Knot(0.5, new Field.Const(1.3), 2.0))), 0.0),
+                new Field.Knot(0.8, new Field.Const(0.6), -1.5)));
+        List<Field> fields = new ArrayList<>();
+        fields.add(BASE);
+        fields.add(SPARSE);
+        fields.add(new Field.Const(0.1));
+        fields.add(new Field.Coord(Axis.Y, Field.Tiling.CLAMP, -64.0, 320.0, 1.5, -0.7));
+        fields.add(new Field.Clamp(BASE, -0.3, 0.8));
+        for (Field.BinaryOp op : Field.BinaryOp.values()) {
+            fields.add(new Field.Binary(op, BASE, new Field.Binary(Field.BinaryOp.ADD, BAND, new Field.Const(0.6))));
+        }
+        fields.add(new Field.Binary(Field.BinaryOp.POW, UNIT, new Field.Const(2.5)));
+        fields.add(new Field.Binary(Field.BinaryOp.MAX, scaled, new Field.Const(0.0)));
+        fields.add(new Field.Binary(Field.BinaryOp.MIN, new Field.Const(2.0), scaled));
+        fields.add(new Field.Binary(Field.BinaryOp.MIN, new Field.Const(0.2), scaled));
+        for (Field.UnaryOp op : Field.UnaryOp.values()) {
+            fields.add(new Field.Unary(op, new Field.Binary(Field.BinaryOp.SUB, SPARSE, new Field.Const(0.4))));
+        }
+        fields.add(new Field.Lerp(UNIT, BASE, new Field.Binary(Field.BinaryOp.MUL, SPARSE, new Field.Const(3.0))));
+        for (Field.RoundMode mode : Field.RoundMode.values()) {
+            fields.add(new Field.Round(mode, new Field.Binary(Field.BinaryOp.MUL, BASE, new Field.Const(10.3)), new Field.Const(2.5)));
+        }
+        fields.add(curve);
+        fields.add(new Field.Curve(UNIT, List.of(new Field.Knot(0.0, new Field.Const(0.0), -3.0), new Field.Knot(1.0, new Field.Const(1.0), -3.0))));
+        fields.add(new Field.Partition(BASE, List.of(-0.2, 0.4), List.of(new Field.Const(-3.0), new Field.Const(0.5), new Field.Const(7.25))));
+        fields.add(new Field.Mux(new Field.Binary(Field.BinaryOp.MUL, UNIT, new Field.Const(2.0)), List.of(new Field.Const(4.0), BAND, scaled)));
+        fields.add(new Field.Gate(BASE, new Field.Binary(Field.BinaryOp.ADD, BAND, new Field.Const(40.0))));
+        fields.add(new Field.RangeIf(BASE, -0.1, 0.2, new Field.Const(-2.0), BAND));
+        fields.add(new Field.Grid(new Field.Binary(Field.BinaryOp.ADD, BASE, SPARSE), 4, 8));
+        fields.add(new Field.Shared("parity/shared", new Field.Binary(Field.BinaryOp.SUB, BAND, BASE)));
+        fields.add(new Field.Slice(new Field.Binary(Field.BinaryOp.MUL, SPARSE, new Field.Const(-2.0)), Axis.Y, 64));
+        fields.add(new Field.TopSurface(new Field.Binary(Field.BinaryOp.SUB, BASE, new Field.Const(0.1)), 200, -48, 4));
+        return fields;
+    }
+
+    private static JsonObject noiseJson(NoiseDef noise) {
+        JsonArray modifiers = new JsonArray(noise.amplitudes().size());
+        for (double amplitude : noise.amplitudes()) {
+            modifiers.add(amplitude);
+        }
+        JsonObject json = new JsonObject();
+        json.addProperty("base_octave", noise.firstOctave());
+        json.addProperty("octave_count", noise.amplitudes().size());
+        json.add("amplitude_modifiers", modifiers);
+        json.addProperty("base_amplitude", 1.0);
+        json.addProperty("normalize", false);
+        return json;
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/VanillaNoiseModelParity263Test.java

@@ -0,0 +1,242 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.compile.noise.VanillaNoiseModel;
+import net.minecraft.core.HolderGetter;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.PositionalRandomFactory;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.XoroshiroRandomSource;
+import net.minecraft.world.level.levelgen.synth.Noise;
+import net.minecraft.world.level.levelgen.synth.NormalNoise;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.SplittableRandom;
+import java.util.stream.Collectors;
+
+import static org.junit.Assert.assertTrue;
+
+public final class VanillaNoiseModelParity263Test {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final int POINTS = 4096;
+    private static final double TOLERANCE = 1.0E-5D;
+    private static final double RUNTIME_TOLERANCE = 1.0E-4D;
+    private static final List<Long> WORLD_SEEDS = List.of(0L, 8_675_309L, -4_611_686_018_427_387_904L);
+    private static final List<ParityNoise> NOISES = List.of(
+            ParityNoise.mapped("iris_export:parity/single", -7, List.of(1.0D)),
+            ParityNoise.mapped("iris_export:parity/fbm", -9, List.of(1.0D, 1.0D, 0.5D, 0.25D)),
+            ParityNoise.mapped("iris_export:parity/sparse", -10, List.of(1.5D, 0.0D, 1.0D, 0.0D, 0.0D, 0.0D)),
+            ParityNoise.mapped("iris_export:parity/leading_zero", -6, List.of(0.0D, 0.0D, 1.0D, 2.0D)),
+            ParityNoise.mapped("iris_export:parity/positive", 2, List.of(1.0D, 0.5D)),
+            ParityNoise.profiled("iris_export:parity/enabled",
+                    "{\"base_octave\":-10,\"octave_count\":6,\"amplitude_modifiers\":[1.5,0.0,1.0,0.0,0.0,0.0],"
+                            + "\"base_amplitude\":1.2453007926713473}",
+                    new VanillaNoiseModel.OctaveProfile(-10, 6, List.of(1.5D, 0.0D, 1.0D, 0.0D, 0.0D, 0.0D),
+                            1.2453007926713473D, VanillaNoiseModel.Normalization.ENABLED)),
+            ParityNoise.profiled("iris_export:parity/legacy",
+                    "{\"base_octave\":-9,\"octave_count\":3,\"amplitude_modifiers\":[1.0,0.0,1.0],\"normalize\":\"legacy\"}",
+                    new VanillaNoiseModel.OctaveProfile(-9, 3, List.of(1.0D, 0.0D, 1.0D), 1.0D,
+                            VanillaNoiseModel.Normalization.LEGACY)),
+            ParityNoise.profiled("iris_export:parity/defaults", "{\"base_octave\":-5}",
+                    new VanillaNoiseModel.OctaveProfile(-5, 1, List.of(), 1.0D, VanillaNoiseModel.Normalization.ENABLED)),
+            ParityNoise.profiled("iris_export:parity/scaled",
+                    "{\"base_octave\":-6,\"octave_count\":2,\"normalize\":false,\"base_amplitude\":0.5}",
+                    new VanillaNoiseModel.OctaveProfile(-6, 2, List.of(), 0.5D, VanillaNoiseModel.Normalization.DISABLED)));
+
+    private static HeadlessNativeRegistries registries;
+
+    @BeforeClass
+    public static void loadNoiseDefinitions() throws IOException {
+        Map<String, String> definitions = new LinkedHashMap<>();
+        for (ParityNoise noise : NOISES) {
+            definitions.put(resourcePath(noise.id()), noise.json());
+        }
+        registries = HeadlessNativeRegistries.load(definitions);
+    }
+
+    @AfterClass
+    public static void closeRegistries() throws IOException {
+        if (registries != null) {
+            registries.close();
+        }
+    }
+
+    @Test
+    public void modelMatchesNoiseBuiltFromLoadedDefinitions() {
+        List<String> report = new ArrayList<>();
+        for (long seed : WORLD_SEEDS) {
+            PositionalRandomFactory world = new VanillaPrecisionRandom(new XoroshiroRandomSource(seed)).forkPositional();
+            for (ParityNoise noise : NOISES) {
+                NormalNoise definition = registries.registries().lookupOrThrow(Registries.NOISE).getOrThrow(key(noise.id())).value();
+                Noise real = definition.create(world.fromHashOf(Identifier.parse(noise.id())));
+                report.add(noise.id() + "@" + seed + "=" + assertParity(noise, seed, real, TOLERANCE));
+            }
+        }
+        System.out.println("26.3 vanilla-precision parity " + report);
+    }
+
+    @Test
+    public void modelMatchesRuntimeRandomStateNoise() {
+        List<String> report = new ArrayList<>();
+        for (long seed : WORLD_SEEDS) {
+            RandomState state = randomState(seed);
+            for (ParityNoise noise : NOISES) {
+                Noise real = state.getOrCreateNoise(key(noise.id()));
+                report.add(noise.id() + "@" + seed + "=" + assertParity(noise, seed, real, RUNTIME_TOLERANCE));
+            }
+        }
+        System.out.println("26.3 runtime parity " + report);
+    }
+
+    private static double assertParity(ParityNoise noise, long seed, Noise real, double tolerance) {
+        VanillaNoiseModel model = noise.model(seed);
+        SplittableRandom random = new SplittableRandom(seed ^ noise.id().hashCode());
+        double worst = 0.0D;
+        double peak = 0.0D;
+        for (int index = 0; index < POINTS; index++) {
+            double range = random.nextInt(4) == 0 ? 30_000_000.0D : 100_000.0D;
+            double x = random.nextDouble(-range, range);
+            double y = random.nextDouble(-2_048.0D, 2_048.0D);
+            double z = random.nextDouble(-range, range);
+            double expected = real.get(x, y, z);
+            worst = Math.max(worst, Math.abs(expected - model.sample(x, y, z)));
+            peak = Math.max(peak, Math.abs(expected));
+        }
+        assertTrue(noise.id() + " seed " + seed + " differs by " + worst, worst <= tolerance);
+        assertTrue(noise.id() + " seed " + seed + " is flat", peak > 0.05D);
+        return worst;
+    }
+
+    private static RandomState randomState(long seed) {
+        HolderGetter<NormalNoise> noises = registries.registries().lookupOrThrow(Registries.NOISE);
+        NoiseGeneratorSettings settings = registries.registries().lookupOrThrow(Registries.NOISE_SETTINGS)
+                .getOrThrow(NoiseGeneratorSettings.OVERWORLD).value();
+        return RandomState.create(noises, seed, settings);
+    }
+
+    private static ResourceKey<NormalNoise> key(String id) {
+        return ResourceKey.create(Registries.NOISE, Identifier.parse(id));
+    }
+
+    private static String resourcePath(String id) {
+        Identifier identifier = Identifier.parse(id);
+        return "data/" + identifier.getNamespace() + "/worldgen/noise/" + identifier.getPath() + ".json";
+    }
+
+    private record ParityNoise(String id, String json, int firstOctave, List<Double> amplitudes,
+                               VanillaNoiseModel.OctaveProfile profile) {
+        private static ParityNoise mapped(String id, int firstOctave, List<Double> amplitudes) {
+            String modifiers = amplitudes.stream().map(String::valueOf).collect(Collectors.joining(","));
+            String json = "{\"base_octave\":" + firstOctave + ",\"octave_count\":" + amplitudes.size()
+                    + ",\"amplitude_modifiers\":[" + modifiers + "],\"base_amplitude\":1.0,\"normalize\":false}";
+            return new ParityNoise(id, json, firstOctave, amplitudes, null);
+        }
+
+        private static ParityNoise profiled(String id, String json, VanillaNoiseModel.OctaveProfile profile) {
+            return new ParityNoise(id, json, 0, List.of(), profile);
+        }
+
+        private VanillaNoiseModel model(long seed) {
+            if (profile == null) {
+                return VanillaNoiseModel.create(id, firstOctave, amplitudes, seed, DataVersion.V26_3);
+            }
+            return VanillaNoiseModel.create(id, profile, seed);
+        }
+    }
+
+    private static final class VanillaPrecisionRandom implements RandomSource {
+        private static final double DOUBLE_UNIT = 1.1102230246251565E-16D;
+
+        private final RandomSource source;
+
+        private VanillaPrecisionRandom(RandomSource source) {
+            this.source = source;
+        }
+
+        @Override
+        public RandomSource fork() {
+            return new VanillaPrecisionRandom(source.fork());
+        }
+
+        @Override
+        public PositionalRandomFactory forkPositional() {
+            return new VanillaPrecisionPositional(source.forkPositional());
+        }
+
+        @Override
+        public void setSeed(long seed) {
+            source.setSeed(seed);
+        }
+
+        @Override
+        public int nextInt() {
+            return source.nextInt();
+        }
+
+        @Override
+        public int nextInt(int bound) {
+            return source.nextInt(bound);
+        }
+
+        @Override
+        public long nextLong() {
+            return source.nextLong();
+        }
+
+        @Override
+        public boolean nextBoolean() {
+            return source.nextBoolean();
+        }
+
+        @Override
+        public float nextFloat() {
+            return source.nextFloat();
+        }
+
+        @Override
+        public double nextDouble() {
+            return (source.nextLong() >>> 11) * DOUBLE_UNIT;
+        }
+
+        @Override
+        public double nextGaussian() {
+            return source.nextGaussian();
+        }
+    }
+
+    private record VanillaPrecisionPositional(PositionalRandomFactory factory) implements PositionalRandomFactory {
+        @Override
+        public RandomSource at(int x, int y, int z) {
+            return new VanillaPrecisionRandom(factory.at(x, y, z));
+        }
+
+        @Override
+        public RandomSource fromHashOf(String name) {
+            return new VanillaPrecisionRandom(factory.fromHashOf(name));
+        }
+
+        @Override
+        public RandomSource fromSeed(long seed) {
+            return new VanillaPrecisionRandom(factory.fromSeed(seed));
+        }
+
+        @Override
+        public void parityConfigString(StringBuilder builder) {
+            factory.parityConfigString(builder);
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/WorldgenExport263CodecTest.java

@@ -0,0 +1,700 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.AtomicDatapackPublisher;
+import art.arcane.iris.pack.datapack.export.DatapackExportFormat;
+import art.arcane.iris.pack.datapack.export.ExportIrFixtures;
+import art.arcane.iris.pack.datapack.export.GenerationCost;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import art.arcane.iris.pack.datapack.export.compile.PackCompiler;
+import art.arcane.iris.pack.datapack.export.compile.surface.MaterialProgramCompiler;
+import art.arcane.iris.pack.datapack.export.compile.terrain.FieldMacros;
+import art.arcane.iris.pack.datapack.export.compile.terrain.HeightCompiler;
+import art.arcane.iris.pack.datapack.export.emit.NestingSplitter;
+import art.arcane.iris.pack.datapack.export.emit.WorldgenJsonWriter;
+import art.arcane.iris.pack.datapack.export.ir.ExportDiagnostic;
+import art.arcane.iris.pack.datapack.export.ir.ExportIr;
+import art.arcane.iris.pack.datapack.export.ir.ExportLimit;
+import art.arcane.iris.pack.datapack.export.ir.Field;
+import art.arcane.iris.pack.datapack.export.ir.FieldEvaluator;
+import art.arcane.iris.pack.datapack.export.ir.NoiseDef;
+import art.arcane.iris.pack.datapack.export.lower.GenerationBudget;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+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.tags.WorldPresetTags;
+import net.minecraft.util.Interval;
+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.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.densityfunction.DensityFunction;
+import net.minecraft.world.level.levelgen.densityfunction.DfRewriteRule;
+import net.minecraft.world.level.levelgen.densityfunction.op.BinaryFunction;
+import net.minecraft.world.level.levelgen.material.rule.OreVeinRule;
+import net.minecraft.world.level.levelgen.presets.WorldPreset;
+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 org.junit.AfterClass;
+import org.junit.Assume;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Deque;
+import java.util.Enumeration;
+import java.util.EnumMap;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.zip.GZIPInputStream;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenExport263CodecTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    @ClassRule
+    public static final TemporaryFolder overworldFolder = new TemporaryFolder();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.DIMENSION;
+    private static final String HEIGHT_ID = ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.DIMENSION + "/height";
+    private static final double SURFACE_TOLERANCE = 2.0;
+    private static final String BIOME_PREFIX = "data/" + ExportIrFixtures.NAMESPACE + "/worldgen/biome/";
+    private static final int[] SAMPLE_Y = {-64, 0, 64, 200};
+    private static final int LATTICE = 16;
+    private static final int LATTICE_STEP = 61;
+    private static final int HEIGHT_POINTS = 8;
+    private static final int HEIGHT_STEP = 97;
+    private static final String PROBE_PACK = "iris.exportProbePack";
+    private static final String OVERWORLD = "overworld";
+    private static final String OVERWORLD_ID = WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + OVERWORLD;
+    private static final String OVERWORLD_BIOME_PREFIX = "data/" + WorldgenExportRequest.DEFAULT_NAMESPACE + "/worldgen/biome/";
+    private static final String LOG_PREFIX = "[worldgen-export]";
+    private static final int OVERWORLD_LATTICE = 4;
+    private static final int OVERWORLD_STEP = 509;
+    private static final int MAX_NESTING = 255;
+    private static final String CAVE_FIELD = "cave/field";
+    private static final String WALL_FALLBACK = "uses the nearest kept palette (minecraft:";
+    private static final double WALL_SHELL_BAND_LIMIT = 0.25;
+    private static final String DENSITY_FUNCTION_RESOURCE = "worldgen/density_function";
+    private static final double MEGABYTE = 1024.0 * 1024.0;
+    private static final int OVERWORLD_LAVA_Y = -248;
+    private static final int LAVA_LINE = -54;
+    private static final int DEEP_CHUNKS = 2;
+    private static final int DEEP_STRIDE = 4;
+    private static final int CHUNK_WIDTH = 16;
+    private static final float OPEN_MARGIN = 1.0e-3f;
+    private static final int LAVA_SEARCH_RADIUS = 1024;
+    private static final int LAVA_SEARCH_STEP = 16;
+    private static final int LAVA_CELLS = 4;
+    private static final int AGREEMENT_POINTS = 16;
+    private static final double AGREEMENT_TOLERANCE = 1.0;
+    private static final int AGREEMENT_OUTLIERS = 2;
+    private static final String SUBTERRAIN_STRUCTURES = "data/" + WorldgenExportRequest.DEFAULT_NAMESPACE + "/worldgen/structure/subterrain/";
+    private static final String SUBTERRAIN_TEMPLATES = "data/" + WorldgenExportRequest.DEFAULT_NAMESPACE + "/structure/subterrain/";
+    private static final int ROOM_GRID = 24;
+    private static final int ROOM_STEP_CHUNKS = 8;
+    private static final int ROOM_ATTEMPTS = 4;
+    private static final int ROOM_REACH = 128;
+    private static final Map<WorldgenExportMode, SortedMap<String, byte[]>> FILES = new EnumMap<>(WorldgenExportMode.class);
+    private static final Map<WorldgenExportMode, WorldgenExportSampler> SAMPLERS = new EnumMap<>(WorldgenExportMode.class);
+    private static SortedMap<String, byte[]> exportedOverworld;
+    private static WorldgenExportResult exportedOverworldResult;
+    private static ExportIr exportedOverworldIr;
+
+    @BeforeClass
+    public static void loadExports() throws IOException {
+        for (WorldgenExportMode mode : WorldgenExportMode.values()) {
+            SortedMap<String, byte[]> files = WorldgenJsonWriter.forTarget(DataVersion.V26_3).write(ExportIrFixtures.flatNoise(DataVersion.V26_3, mode));
+            FILES.put(mode, files);
+            SAMPLERS.put(mode, WorldgenExportSampler.open(files, mode, DIMENSION_ID, SEED));
+        }
+    }
+
+    @AfterClass
+    public static void closeExports() throws IOException {
+        for (WorldgenExportSampler sampler : SAMPLERS.values()) {
+            sampler.close();
+        }
+        SAMPLERS.clear();
+        FILES.clear();
+        exportedOverworld = null;
+        exportedOverworldResult = null;
+        exportedOverworldIr = null;
+    }
+
+    @Test
+    public void fixtureLoadsInEveryMode() {
+        for (WorldgenExportMode mode : WorldgenExportMode.values()) {
+            WorldgenExportSampler sampler = SAMPLERS.get(mode);
+            assertEquals(ExportIrFixtures.MIN_Y, sampler.minY());
+            assertEquals(ExportIrFixtures.HEIGHT, sampler.height());
+            assertEquals(ExportIrFixtures.SEA_LEVEL, sampler.seaLevel());
+            assertFalse(sampler.densityFunctionIds().isEmpty());
+            for (String id : sampler.densityFunctionIds()) {
+                assertTrue(mode + " " + id, sampler.registries().lookupOrThrow(Registries.DENSITY_FUNCTION).containsKey(Identifier.parse(id)));
+            }
+            assertTrue(sampler.registries().lookupOrThrow(Registries.NOISE_SETTINGS).containsKey(Identifier.parse(DIMENSION_ID)));
+            assertTrue(sampler.registries().lookupOrThrow(Registries.DIMENSION_TYPE).containsKey(Identifier.parse(DIMENSION_ID)));
+            assertTrue(sampler.registries().lookupOrThrow(Registries.MATERIAL_RULE).containsKey(Identifier.parse(DIMENSION_ID)));
+            boolean preset = sampler.registries().lookupOrThrow(Registries.WORLD_PRESET).containsKey(Identifier.parse(DIMENSION_ID));
+            boolean dimension = sampler.registries().lookupOrThrow(Registries.LEVEL_STEM).containsKey(Identifier.parse(DIMENSION_ID));
+            boolean overworld = sampler.registries().lookupOrThrow(Registries.LEVEL_STEM).containsKey(LevelStem.OVERWORLD.identifier());
+            assertEquals(mode.toString(), mode == WorldgenExportMode.PRESET, preset);
+            assertEquals(mode.toString(), mode == WorldgenExportMode.DIMENSION, dimension);
+            assertEquals(mode.toString(), mode == WorldgenExportMode.OVERWORLD, overworld);
+        }
+        WorldgenExportSampler presetSampler = SAMPLERS.get(WorldgenExportMode.PRESET);
+        Holder<WorldPreset> preset = presetSampler.registries().lookupOrThrow(Registries.WORLD_PRESET)
+                .getOrThrow(ResourceKey.create(Registries.WORLD_PRESET, Identifier.parse(DIMENSION_ID)));
+        assertTrue(preset.value().createWorldDimensions().get(LevelStem.NETHER).isPresent());
+        assertTrue(preset.value().createWorldDimensions().get(LevelStem.END).isPresent());
+        HolderSet.Named<WorldPreset> normal = presetSampler.registries().lookupOrThrow(Registries.WORLD_PRESET).getOrThrow(WorldPresetTags.NORMAL);
+        assertTrue(normal.contains(preset));
+    }
+
+    @Test
+    public void everyDensityFunctionEvaluatesFinite() {
+        for (WorldgenExportMode mode : WorldgenExportMode.values()) {
+            WorldgenExportSampler sampler = SAMPLERS.get(mode);
+            for (String id : sampler.densityFunctionIds()) {
+                for (int y : SAMPLE_Y) {
+                    for (int xIndex = 0; xIndex < LATTICE; xIndex++) {
+                        for (int zIndex = 0; zIndex < LATTICE; zIndex++) {
+                            int x = (xIndex - LATTICE / 2) * LATTICE_STEP;
+                            int z = (zIndex - LATTICE / 2) * LATTICE_STEP;
+                            float value = sampler.density(id, x, y, z);
+                            assertTrue(mode + " " + id + " at " + x + "," + y + "," + z + " = " + value, Float.isFinite(value));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    @Test
+    public void baseHeightWithinDimension() {
+        for (WorldgenExportMode mode : WorldgenExportMode.values()) {
+            WorldgenExportSampler sampler = SAMPLERS.get(mode);
+            Set<Integer> heights = new HashSet<>();
+            int land = 0;
+            for (int xIndex = 0; xIndex < HEIGHT_POINTS; xIndex++) {
+                for (int zIndex = 0; zIndex < HEIGHT_POINTS; zIndex++) {
+                    int x = (xIndex - HEIGHT_POINTS / 2) * HEIGHT_STEP;
+                    int z = (zIndex - HEIGHT_POINTS / 2) * HEIGHT_STEP;
+                    int height = sampler.baseHeight(x, z);
+                    assertTrue(mode + " height " + height + " at " + x + "," + z,
+                            height >= sampler.minY() && height <= sampler.minY() + sampler.height());
+                    float surface = sampler.density(HEIGHT_ID, x, 0, z);
+                    int floor = sampler.floorHeight(x, z);
+                    assertTrue(mode + " height " + height + " below floor " + floor, height >= floor);
+                    if (surface > sampler.seaLevel() + 1) {
+                        assertTrue(mode + " floor " + floor + " against surface " + surface, Math.abs(floor - surface) <= SURFACE_TOLERANCE);
+                        land++;
+                    }
+                    heights.add(height);
+                }
+            }
+            assertTrue(mode + " surface never varies", heights.size() > 1);
+            assertTrue(mode + " has no land column above sea level", land > 0);
+        }
+    }
+
+    @Test
+    public void resolverReturnsOnlyExportedBiomes() {
+        for (WorldgenExportMode mode : WorldgenExportMode.values()) {
+            WorldgenExportSampler sampler = SAMPLERS.get(mode);
+            Set<String> exported = exportedBiomes(FILES.get(mode), BIOME_PREFIX, ExportIrFixtures.NAMESPACE);
+            assertFalse(exported.isEmpty());
+            assertTrue(mode + " " + sampler.possibleBiomes(), exported.containsAll(sampler.possibleBiomes()));
+            for (int y : SAMPLE_Y) {
+                for (int xIndex = 0; xIndex < LATTICE; xIndex++) {
+                    for (int zIndex = 0; zIndex < LATTICE; zIndex++) {
+                        String biome = sampler.biome((xIndex - LATTICE / 2) * LATTICE_STEP, y, (zIndex - LATTICE / 2) * LATTICE_STEP);
+                        assertTrue(mode + " " + biome, exported.contains(biome));
+                    }
+                }
+            }
+        }
+    }
+
+    @Test
+    public void overworldPackLoads() throws Exception {
+        SortedMap<String, byte[]> files = overworldFiles();
+        assertGenerationBudget(exportedOverworldResult);
+        assertWallPalettesFallBack(exportedOverworldResult);
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            if (file.getKey().endsWith(".json")) {
+                int depth = NestingSplitter.depth(JsonParser.parseString(new String(file.getValue(), StandardCharsets.UTF_8)));
+                assertTrue(file.getKey() + " nests " + depth, depth <= MAX_NESTING);
+            }
+            if (file.getKey().endsWith(".nbt")) {
+                assertCompleteGzip(file.getKey(), file.getValue());
+            }
+        }
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(files, WorldgenExportMode.OVERWORLD, OVERWORLD_ID, SEED)) {
+            Set<String> roots = new TreeSet<>();
+            for (String id : sampler.densityFunctionIds()) {
+                if (id.startsWith(OVERWORLD_ID + "/")) {
+                    roots.add(id);
+                }
+            }
+            assertTrue(roots.toString(), roots.contains(OVERWORLD_ID + "/final_density"));
+            for (String id : roots) {
+                for (int y : SAMPLE_Y) {
+                    for (int xIndex = 0; xIndex < OVERWORLD_LATTICE; xIndex++) {
+                        for (int zIndex = 0; zIndex < OVERWORLD_LATTICE; zIndex++) {
+                            int x = (xIndex - OVERWORLD_LATTICE / 2) * OVERWORLD_STEP;
+                            int z = (zIndex - OVERWORLD_LATTICE / 2) * OVERWORLD_STEP;
+                            float value = sampler.density(id, x, y, z);
+                            assertTrue(id + " at " + x + "," + y + "," + z + " = " + value, Float.isFinite(value));
+                        }
+                    }
+                }
+            }
+            assertNaturalHeightMatchesTheEvaluator(exportedOverworldIr, sampler);
+            Set<String> exported = exportedBiomes(files, OVERWORLD_BIOME_PREFIX, WorldgenExportRequest.DEFAULT_NAMESPACE);
+            assertFalse(exported.isEmpty());
+            assertTrue(sampler.possibleBiomes().toString(), exported.containsAll(sampler.possibleBiomes()));
+            for (int xIndex = 0; xIndex < HEIGHT_POINTS; xIndex++) {
+                for (int zIndex = 0; zIndex < HEIGHT_POINTS; zIndex++) {
+                    int x = (xIndex - HEIGHT_POINTS / 2) * HEIGHT_STEP;
+                    int z = (zIndex - HEIGHT_POINTS / 2) * HEIGHT_STEP;
+                    int height = sampler.baseHeight(x, z);
+                    assertTrue("height " + height + " at " + x + "," + z, height >= sampler.minY() && height <= sampler.minY() + sampler.height());
+                    for (int y : SAMPLE_Y) {
+                        String biome = sampler.biome(x, y, z);
+                        assertTrue(biome + " at " + x + "," + y + "," + z, exported.contains(biome));
+                    }
+                }
+            }
+        }
+    }
+
+    @Test
+    public void overworldHasNoDisjointMinMax() throws Exception {
+        SortedMap<String, byte[]> files = overworldFiles();
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(files, WorldgenExportMode.OVERWORLD, OVERWORLD_ID, SEED)) {
+            MinMaxAudit audit = new MinMaxAudit();
+            for (String id : sampler.densityFunctionIds()) {
+                audit.rewrite(sampler.registries().lookupOrThrow(Registries.DENSITY_FUNCTION)
+                        .getOrThrow(ResourceKey.create(Registries.DENSITY_FUNCTION, Identifier.parse(id))).value());
+            }
+            System.out.println(LOG_PREFIX + " min/max nodes " + audit.checked() + ", disjoint " + audit.disjoint().size());
+            assertTrue(audit.checked() > 0);
+            assertTrue(audit.disjoint().size() + " disjoint min/max nodes: " + audit.disjoint(), audit.disjoint().isEmpty());
+        }
+    }
+
+    @Test
+    public void overworldDeepCavesOpenWithoutLava() throws Exception {
+        SortedMap<String, byte[]> files = overworldFiles();
+        String field = WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + CAVE_FIELD;
+        long open = 0L;
+        long lava = 0L;
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(files, WorldgenExportMode.OVERWORLD, OVERWORLD_ID, SEED)) {
+            assertTrue(field, sampler.densityFunctionIds().contains(field));
+            BlockPos.MutableBlockPos position = new BlockPos.MutableBlockPos();
+            for (int chunkX = -DEEP_CHUNKS; chunkX < DEEP_CHUNKS; chunkX++) {
+                for (int chunkZ = -DEEP_CHUNKS; chunkZ < DEEP_CHUNKS; chunkZ++) {
+                    ProtoChunk chunk = sampler.terrainChunk(chunkX, chunkZ);
+                    for (int x = 0; x < CHUNK_WIDTH; x++) {
+                        for (int z = 0; z < CHUNK_WIDTH; z++) {
+                            for (int y = OVERWORLD_LAVA_Y + 1; y < LAVA_LINE; y++) {
+                                BlockState state = chunk.getBlockState(position.set(x, y, z));
+                                assertFalse(state + " at chunk " + chunkX + "," + chunkZ + " " + x + "," + y + "," + z, state.is(Blocks.LAVA));
+                            }
+                        }
+                    }
+                    for (int x = 0; x < CHUNK_WIDTH; x += DEEP_STRIDE) {
+                        for (int z = 0; z < CHUNK_WIDTH; z += DEEP_STRIDE) {
+                            int blockX = (chunkX << 4) + x;
+                            int blockZ = (chunkZ << 4) + z;
+                            for (int y = OVERWORLD_LAVA_Y + 1; y < LAVA_LINE; y++) {
+                                if (sampler.density(field, blockX, y, blockZ) > -OPEN_MARGIN) {
+                                    continue;
+                                }
+                                BlockState state = chunk.getBlockState(position.set(x, y, z));
+                                assertTrue(state + " at " + blockX + "," + y + "," + blockZ, state.isAir());
+                                open++;
+                            }
+                        }
+                    }
+                }
+            }
+            for (BlockPos cell : openLavaBandCells(sampler, field)) {
+                ProtoChunk chunk = sampler.terrainChunk(cell.getX() >> 4, cell.getZ() >> 4);
+                BlockState state = chunk.getBlockState(position.set(cell.getX() & (CHUNK_WIDTH - 1), cell.getY(), cell.getZ() & (CHUNK_WIDTH - 1)));
+                assertTrue(state + " at " + cell, state.is(Blocks.LAVA));
+                lava++;
+            }
+        }
+        System.out.println(LOG_PREFIX + " deep cave cells open " + open + ", lava band cells " + lava);
+        assertTrue("no deep cave cell opened", open > 0L);
+        assertTrue("no lava band cell opened", lava > 0L);
+    }
+
+    @Test
+    public void overworldMaterialPassComputesTheCaveFieldOnce() throws Exception {
+        SortedMap<String, byte[]> files = overworldFiles();
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(files, WorldgenExportMode.OVERWORLD, OVERWORLD_ID, SEED)) {
+            CompiledCaches caches = CompiledCaches.open(sampler.registries(), SEED);
+            int field = caches.rootId(caches.function(WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + CAVE_FIELD));
+            List<OreVeinRule> veins = caches.oreVeins();
+            DensityFunction opening = veins.getFirst().density();
+            assertTrue(caches.ids(opening).contains(field));
+            assertTrue(caches.ids(caches.finalDensity()).contains(field));
+            Set<Integer> caveCaches = caches.ids(caches.function(WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + CAVE_FIELD));
+            int shells = 0;
+            for (OreVeinRule vein : veins) {
+                if (!vein.oreBlock().isAir()) {
+                    assertTrue("wall shell " + shells + " " + vein.oreBlock(), caches.ids(vein.density()).contains(field));
+                    assertTrue("wall shell " + shells + " " + vein.oreBlock(), caveCaches.containsAll(caches.ids(vein.density())));
+                    shells++;
+                }
+            }
+            JsonObject shell = JsonParser.parseString(new String(files.get("data/" + WorldgenExportRequest.DEFAULT_NAMESPACE + "/" + DENSITY_FUNCTION_RESOURCE
+                    + "/" + MaterialProgramCompiler.WALL_SHELL + ".json"), StandardCharsets.UTF_8)).getAsJsonObject();
+            double band = shell.get("max_exclusive").getAsDouble();
+            System.out.println(LOG_PREFIX + " material pass: " + veins.size() + " ore vein rules, " + shells + " wall shells read cave field cache " + field
+                    + " within band " + band);
+            assertTrue(String.valueOf(shells), shells > 0);
+            assertTrue(String.valueOf(band), band > 0.0 && band < WALL_SHELL_BAND_LIMIT);
+        }
+    }
+
+    @Test
+    public void overworldSubterrainRoomsPlace() throws Exception {
+        SortedMap<String, byte[]> files = overworldFiles();
+        SortedMap<String, JsonObject> structures = new TreeMap<>();
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            if (file.getKey().startsWith(SUBTERRAIN_STRUCTURES) && file.getKey().endsWith(".json")) {
+                String path = file.getKey().substring(SUBTERRAIN_STRUCTURES.length(), file.getKey().length() - ".json".length());
+                structures.put(WorldgenExportRequest.DEFAULT_NAMESPACE + ":subterrain/" + path,
+                        JsonParser.parseString(new String(file.getValue(), StandardCharsets.UTF_8)).getAsJsonObject());
+            }
+        }
+        long templateBytes = 0L;
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            if (file.getKey().startsWith(SUBTERRAIN_TEMPLATES)) {
+                templateBytes += file.getValue().length;
+            }
+        }
+        System.out.println(LOG_PREFIX + " subterrain structures " + structures.size() + ", structure sets "
+                + count(files, "/worldgen/structure_set/subterrain/", ".json") + ", templates " + count(files, "/structure/subterrain/", ".nbt")
+                + ", template bytes " + templateBytes);
+        assertFalse(structures.isEmpty());
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(files, WorldgenExportMode.OVERWORLD, OVERWORLD_ID, SEED)) {
+            for (Map.Entry<String, JsonObject> entry : structures.entrySet()) {
+                Structure structure = sampler.registries().lookupOrThrow(Registries.STRUCTURE)
+                        .getOrThrow(ResourceKey.create(Registries.STRUCTURE, Identifier.parse(entry.getKey()))).value();
+                JsonObject height = entry.getValue().getAsJsonObject("start_height");
+                int y = (height.getAsJsonObject("min_inclusive").get("absolute").getAsInt()
+                        + height.getAsJsonObject("max_inclusive").get("absolute").getAsInt()) / 2;
+                List<ChunkPos> matches = new ArrayList<>();
+                for (int xIndex = 0; xIndex < ROOM_GRID; xIndex++) {
+                    for (int zIndex = 0; zIndex < ROOM_GRID; zIndex++) {
+                        ChunkPos chunk = new ChunkPos((xIndex - ROOM_GRID / 2) * ROOM_STEP_CHUNKS, (zIndex - ROOM_GRID / 2) * ROOM_STEP_CHUNKS);
+                        String biome = sampler.biome(chunk.getMinBlockX(), y, chunk.getMinBlockZ());
+                        Holder<Biome> holder = sampler.registries().lookupOrThrow(Registries.BIOME)
+                                .getOrThrow(ResourceKey.create(Registries.BIOME, Identifier.parse(biome)));
+                        if (structure.biomes().contains(holder)) {
+                            matches.add(chunk);
+                        }
+                    }
+                }
+                System.out.println(String.format(Locale.ROOT, "%s subterrain %s biome match %d/%d at y %d", LOG_PREFIX, entry.getKey(),
+                        matches.size(), ROOM_GRID * ROOM_GRID, y));
+                assertFalse(entry.getKey() + " finds no biome at y " + y, matches.isEmpty());
+                StructureStart start = null;
+                for (ChunkPos chunk : matches.subList(0, Math.min(ROOM_ATTEMPTS, matches.size()))) {
+                    StructureStart candidate = sampler.structureStart(entry.getKey(), chunk.x(), chunk.z());
+                    if (candidate.isValid()) {
+                        start = candidate;
+                        BoundingBox box = start.getBoundingBox();
+                        assertTrue(entry.getKey() + " " + box, chunk.getMinBlockX() - box.minX() <= ROOM_REACH && box.maxX() - chunk.getMinBlockX() <= ROOM_REACH);
+                        assertTrue(entry.getKey() + " " + box, chunk.getMinBlockZ() - box.minZ() <= ROOM_REACH && box.maxZ() - chunk.getMinBlockZ() <= ROOM_REACH);
+                        assertTrue(entry.getKey() + " " + box, box.minY() >= sampler.minY() && box.maxY() < sampler.minY() + sampler.height());
+                        break;
+                    }
+                }
+                assertTrue(entry.getKey() + " never starts", start != null);
+            }
+        }
+    }
+
+    private static List<BlockPos> openLavaBandCells(WorldgenExportSampler sampler, String field) {
+        List<BlockPos> cells = new ArrayList<>(LAVA_CELLS);
+        for (int x = -LAVA_SEARCH_RADIUS; x < LAVA_SEARCH_RADIUS; x += LAVA_SEARCH_STEP) {
+            for (int z = -LAVA_SEARCH_RADIUS; z < LAVA_SEARCH_RADIUS; z += LAVA_SEARCH_STEP) {
+                for (int y = sampler.minY(); y <= OVERWORLD_LAVA_Y; y++) {
+                    if (sampler.density(field, x, y, z) > -OPEN_MARGIN) {
+                        continue;
+                    }
+                    cells.add(new BlockPos(x, y, z));
+                    if (cells.size() == LAVA_CELLS) {
+                        return cells;
+                    }
+                }
+            }
+        }
+        return cells;
+    }
+
+    private static synchronized SortedMap<String, byte[]> overworldFiles() throws Exception {
+        String probePack = System.getProperty(PROBE_PACK);
+        Assume.assumeTrue("Set -P" + PROBE_PACK + " to export a real pack", probePack != null && !probePack.isBlank());
+        if (exportedOverworld != null) {
+            return exportedOverworld;
+        }
+        Path root = overworldFolder.newFolder("exports").toPath();
+        SortedMap<String, byte[]> untrimmed = new TreeMap<>();
+        AtomicReference<ExportIr> compiled = new AtomicReference<>();
+        WorldgenExportResult result;
+        try (RealPackProbeSupport.Workspace workspace = RealPackProbeSupport.openWorkspace(new RealPackProbeSupport.WorkspaceOptions(
+                new File(probePack), OVERWORLD, LOG_PREFIX, new HeadlessNativeRuntime(), overworldFolder.newFolder("workspace").toPath()))) {
+            WorldgenExportRequest request = WorldgenExportRequest.builder()
+                    .pack(workspace.pack().toPath())
+                    .dimension(OVERWORLD)
+                    .exportRoot(root)
+                    .objects(true)
+                    .build();
+            result = new WorldgenDatapackExporter(target -> ir -> {
+                compiled.set(ir);
+                SortedMap<String, byte[]> written = WorldgenJsonWriter.forTarget(target).write(ir);
+                untrimmed.putAll(written);
+                return written;
+            }, PackCompiler.create()).export(request, WorldgenExportProgress.NONE);
+        }
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+        SortedMap<String, byte[]> files = zipEntries(result.output());
+        Path untrimmedZip = root.resolve("untrimmed.zip");
+        new AtomicDatapackPublisher().publish(untrimmed, untrimmedZip, DatapackExportFormat.ZIP, false, ".untrimmed-");
+        report(result, untrimmed, Files.size(untrimmedZip), files);
+        exportedOverworld = files;
+        exportedOverworldResult = result;
+        exportedOverworldIr = compiled.get();
+        return files;
+    }
+
+    private static void assertGenerationBudget(WorldgenExportResult result) {
+        GenerationCost cost = result.cost();
+        Set<String> flagged = new TreeSet<>();
+        for (ExportDiagnostic diagnostic : result.diagnostics()) {
+            if (diagnostic.limit() == ExportLimit.GENERATION_COST) {
+                flagged.add(diagnostic.resource());
+            }
+        }
+        for (GenerationCost.Root root : GenerationCost.Root.values()) {
+            GenerationCost.RootCost rootCost = cost.root(root).orElseThrow();
+            System.out.println(String.format(Locale.ROOT, "%s cost %s worst case %.3e expanded %.3e distinct %d", LOG_PREFIX, root.id(),
+                    rootCost.worstCaseNodes(), rootCost.expandedNodes(), rootCost.distinctNodes()));
+        }
+        for (GenerationCost.Root root : GenerationCost.Root.values()) {
+            if (!root.climate()) {
+                continue;
+            }
+            double limit = GenerationBudget.worstCaseLimit(root).orElseThrow();
+            double nodes = cost.root(root).orElseThrow().worstCaseNodes();
+            String resource = "noise_settings/" + OVERWORLD + "/" + root.id();
+            assertTrue(root.id() + " evaluates " + nodes + " nodes, budget " + limit, nodes <= limit);
+            assertFalse(resource + " " + flagged, flagged.contains(resource));
+        }
+        long finalDensity = cost.root(GenerationCost.Root.FINAL_DENSITY).orElseThrow().distinctNodes();
+        String finalResource = "noise_settings/" + OVERWORLD + "/" + GenerationCost.Root.FINAL_DENSITY.id();
+        System.out.println(String.format(Locale.ROOT, "%s final_density distinct %d of %d, density function JSON %.1f of %.1f MB", LOG_PREFIX, finalDensity,
+                GenerationBudget.FINAL_DENSITY_DISTINCT_NODES, cost.densityFunctionBytes() / MEGABYTE, GenerationBudget.DENSITY_FUNCTION_JSON_BYTES / MEGABYTE));
+        assertEquals(finalResource + " " + flagged, finalDensity > GenerationBudget.FINAL_DENSITY_DISTINCT_NODES, flagged.contains(finalResource));
+        assertTrue(cost.densityFunctionBytes() + " bytes", cost.densityFunctionBytes() > 0L);
+        assertTrue(cost.densityFunctionBytes() + " bytes", cost.densityFunctionBytes() <= GenerationBudget.DENSITY_FUNCTION_JSON_BYTES);
+        assertFalse(flagged.toString(), flagged.contains(DENSITY_FUNCTION_RESOURCE));
+    }
+
+    private static void assertWallPalettesFallBack(WorldgenExportResult result) {
+        int fallbacks = 0;
+        for (ExportDiagnostic diagnostic : result.diagnostics()) {
+            if (diagnostic.limit() == ExportLimit.WALL_PALETTE && diagnostic.severity() == ExportDiagnostic.Severity.WARNING) {
+                assertTrue(diagnostic.resource() + " " + diagnostic.message(), diagnostic.message().contains(WALL_FALLBACK));
+                fallbacks++;
+            }
+        }
+        System.out.println(LOG_PREFIX + " wall palettes over the ore vein budget " + fallbacks);
+    }
+
+    private static void assertNaturalHeightMatchesTheEvaluator(ExportIr ir, WorldgenExportSampler sampler) {
+        Field.Shared height = shared(ir.router().chunkSurfaceLevel(), HeightCompiler.HEIGHT);
+        Map<String, NoiseDef> noises = new HashMap<>();
+        for (NoiseDef noise : ir.noises()) {
+            noises.put(ir.namespace() + ":" + noise.id(), noise);
+        }
+        String heightId = ir.namespace() + ":" + HeightCompiler.HEIGHT;
+        int outliers = 0;
+        StringBuilder detail = new StringBuilder();
+        for (int xIndex = 0; xIndex < AGREEMENT_POINTS; xIndex++) {
+            for (int zIndex = 0; zIndex < AGREEMENT_POINTS; zIndex++) {
+                int x = (xIndex - AGREEMENT_POINTS / 2) * OVERWORLD_STEP;
+                int z = (zIndex - AGREEMENT_POINTS / 2) * OVERWORLD_STEP;
+                double evaluated = FieldEvaluator.sample(height.expr(), noises, SEED, DataVersion.V26_3, x, 0, z);
+                double exported = sampler.density(heightId, x, 0, z);
+                if (Math.abs(evaluated - exported) > AGREEMENT_TOLERANCE) {
+                    outliers++;
+                    detail.append(' ').append(x).append(',').append(z).append('=').append(evaluated).append('/').append(exported);
+                }
+            }
+        }
+        assertTrue(outliers + " columns differ:" + detail, outliers <= AGREEMENT_OUTLIERS);
+    }
+
+    private static Field.Shared shared(Field root, String name) {
+        Set<Field> visited = Collections.newSetFromMap(new IdentityHashMap<>());
+        Deque<Field> pending = new ArrayDeque<>();
+        pending.push(root);
+        while (!pending.isEmpty()) {
+            Field field = pending.pop();
+            if (!visited.add(field)) {
+                continue;
+            }
+            if (field instanceof Field.Shared candidate && candidate.name().equals(name)) {
+                return candidate;
+            }
+            for (Field child : FieldMacros.children(field)) {
+                pending.push(child);
+            }
+        }
+        throw new AssertionError("Router has no shared field " + name);
+    }
+
+    private static void assertCompleteGzip(String path, byte[] bytes) throws IOException {
+        try (InputStream input = new GZIPInputStream(new ByteArrayInputStream(bytes))) {
+            input.readAllBytes();
+            assertEquals(path, -1, input.read());
+        }
+    }
+
+    private static void report(WorldgenExportResult result, SortedMap<String, byte[]> untrimmed, long untrimmedZipBytes,
+                               SortedMap<String, byte[]> files) throws IOException {
+        SortedMap<ExportLimit, Integer> limits = new TreeMap<>();
+        for (ExportDiagnostic diagnostic : result.diagnostics()) {
+            limits.merge(diagnostic.limit(), 1, Integer::sum);
+        }
+        System.out.println(LOG_PREFIX + " untrimmed zip bytes " + untrimmedZipBytes + ", files " + untrimmed.size()
+                + ", trimmed zip bytes " + Files.size(result.output()) + ", files " + files.size() + ", trim " + result.trim());
+        System.out.println(LOG_PREFIX + " diagnostics " + result.diagnostics().size() + " " + limits);
+        reportCounts("untrimmed", untrimmed);
+        reportCounts("trimmed", files);
+    }
+
+    private static void reportCounts(String label, SortedMap<String, byte[]> files) {
+        System.out.println(LOG_PREFIX + " " + label + " templates " + count(files, "/structure/", ".nbt")
+                + ", structures " + count(files, "/worldgen/structure/", ".json")
+                + ", structure sets " + count(files, "/worldgen/structure_set/", ".json")
+                + ", placed features " + count(files, "/worldgen/placed_feature/", ".json")
+                + ", features " + count(files, "/worldgen/feature/", ".json")
+                + ", density functions " + count(files, "/worldgen/density_function/", ".json")
+                + ", noises " + count(files, "/worldgen/noise/", ".json")
+                + ", biomes " + count(files, "/worldgen/biome/", ".json"));
+    }
+
+    private static int count(SortedMap<String, byte[]> files, String folder, String suffix) {
+        int count = 0;
+        for (String path : files.keySet()) {
+            if (path.contains(folder) && path.endsWith(suffix)) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    private static SortedMap<String, byte[]> zipEntries(Path zip) throws IOException {
+        SortedMap<String, byte[]> files = new TreeMap<>();
+        try (ZipFile archive = new ZipFile(zip.toFile())) {
+            Enumeration<? extends ZipEntry> entries = archive.entries();
+            while (entries.hasMoreElements()) {
+                ZipEntry entry = entries.nextElement();
+                if (!entry.isDirectory()) {
+                    files.put(entry.getName(), archive.getInputStream(entry).readAllBytes());
+                }
+            }
+        }
+        return files;
+    }
+
+    private static Set<String> exportedBiomes(SortedMap<String, byte[]> files, String prefix, String namespace) {
+        Set<String> biomes = new TreeSet<>();
+        for (String path : files.keySet()) {
+            if (path.startsWith(prefix)) {
+                biomes.add(namespace + ":" + path.substring(prefix.length(), path.length() - ".json".length()));
+            }
+        }
+        return biomes;
+    }
+
+    private static final class MinMaxAudit implements DfRewriteRule {
+        private final Set<DensityFunction> visited = Collections.newSetFromMap(new IdentityHashMap<>());
+        private final List<String> disjoint = new ArrayList<>();
+        private int checked;
+
+        @Override
+        public DensityFunction rewrite(DensityFunction function) {
+            if (!visited.add(function)) {
+                return function;
+            }
+            if (function instanceof BinaryFunction binary && (binary.type() == BinaryFunction.Type.MIN || binary.type() == BinaryFunction.Type.MAX)) {
+                checked++;
+                Interval left = binary.left().range();
+                Interval right = binary.right().range();
+                if (left.max() < right.min() || right.max() < left.min()) {
+                    disjoint.add(binary.type() + " " + left + " " + right);
+                }
+            }
+            function.rewriteChildren(this);
+            return function;
+        }
+
+        private int checked() {
+            return checked;
+        }
+
+        private List<String> disjoint() {
+            return disjoint;
+        }
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/WorldgenExportDeepCaves263Test.java

@@ -0,0 +1,136 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.ExportTestPacks;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import net.minecraft.core.BlockPos;
+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.levelgen.densityfunction.DensityFunction;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenExportDeepCaves263Test {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String NAMESPACE = WorldgenExportRequest.DEFAULT_NAMESPACE;
+    private static final String DIMENSION_ID = NAMESPACE + ":" + ExportTestPacks.DIMENSION;
+    private static final int MIN_Y = -64;
+    private static final int LAVA_Y = -62;
+    private static final int LAVA_LINE = -54;
+    private static final int CAVE_TOP = -14;
+    private static final int CHUNK_WIDTH = 16;
+    private static final String CAVE_FIELD = "cave/field";
+    private static final String DIMENSION = """
+            {
+              "regions": ["region"],
+              "dimensionHeight": {"min": -64, "max": 192},
+              "fluidHeight": 63,
+              "caveLavaHeight": 2,
+              "caveProfile": {
+                "enabled": true,
+                "verticalRange": {"min": 0, "max": 50},
+                "verticalEdgeFade": 0,
+                "baseDensityStyle": {"style": "SIMPLEX", "zoom": 0.6},
+                "detailDensityStyle": {"style": "SIMPLEX", "zoom": 0.3},
+                "baseWeight": 1.0,
+                "detailWeight": 0.0,
+                "densityThreshold": {"min": 5.0, "max": 5.0, "style": {"style": "SIMPLEX"}},
+                "thresholdBias": 0.0,
+                "surfaceClearance": 0,
+                "allowSurfaceBreak": false,
+                "allowFluid": false,
+                "allowLava": true,
+                "modules": []
+              }
+            }
+            """;
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Rule
+    public ExportTestPacks.BoundPlatform platform = new ExportTestPacks.BoundPlatform();
+
+    @Test
+    public void deepCavesOpenAsAirAboveTheIrisLavaBand() throws IOException {
+        WorldgenExportResult result = export();
+
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+        JsonObject head = JsonParser.parseString(Files.readString(result.output().resolve("data/" + NAMESPACE + "/worldgen/material_rule/"
+                + ExportTestPacks.DIMENSION + ".json"), StandardCharsets.UTF_8)).getAsJsonObject().getAsJsonArray("sequence").get(0).getAsJsonObject();
+        assertEquals("minecraft:ore_vein", head.get("type").getAsString());
+        String opening = head.get("density").getAsString();
+        assertTrue(opening, Files.isRegularFile(densityFunction(result.output(), opening)));
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(result.output(), WorldgenExportMode.OVERWORLD, DIMENSION_ID, SEED)) {
+            ProtoChunk chunk = sampler.terrainChunk(0, 0);
+            for (int x = 0; x < CHUNK_WIDTH; x++) {
+                for (int z = 0; z < CHUNK_WIDTH; z++) {
+                    for (int y = MIN_Y; y <= CAVE_TOP; y++) {
+                        BlockState state = chunk.getBlockState(new BlockPos(x, y, z));
+                        String where = state + " at " + x + "," + y + "," + z;
+                        if (y <= LAVA_Y) {
+                            assertTrue(where, state.is(Blocks.LAVA));
+                        } else {
+                            assertTrue(where, state.isAir());
+                        }
+                    }
+                }
+            }
+            assertTrue(chunk.getBlockState(new BlockPos(0, LAVA_LINE - 1, 0)).isAir());
+        }
+    }
+
+    @Test
+    public void deepCaveRuleSharesTheCaveFieldCacheWithTheFinalDensity() throws IOException {
+        WorldgenExportResult result = export();
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(result.output(), WorldgenExportMode.OVERWORLD, DIMENSION_ID, SEED)) {
+            CompiledCaches caches = CompiledCaches.open(sampler.registries(), SEED);
+            DensityFunction opening = caches.oreVeins().getFirst().density();
+            int field = caches.rootId(caches.function(NAMESPACE + ":" + CAVE_FIELD));
+            Set<Integer> finalDensity = caches.ids(caches.finalDensity());
+
+            assertTrue(caches.ids(opening).toString(), caches.ids(opening).contains(field));
+            assertTrue(finalDensity.toString(), finalDensity.contains(field));
+            assertTrue(finalDensity.toString(), finalDensity.contains(caches.rootId(opening)));
+        }
+    }
+
+    private WorldgenExportResult export() throws IOException {
+        File pack = ExportTestPacks.withDimension(temporaryFolder.newFolder("pack"), DIMENSION);
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(pack.toPath())
+                .dimension(ExportTestPacks.DIMENSION)
+                .exportRoot(temporaryFolder.newFolder("exports").toPath())
+                .format("directory")
+                .build();
+        return WorldgenDatapackExporter.create().export(request, WorldgenExportProgress.NONE);
+    }
+
+    private static Path densityFunction(Path datapack, String id) {
+        int separator = id.indexOf(':');
+        return datapack.resolve("data/" + id.substring(0, separator) + "/worldgen/density_function/" + id.substring(separator + 1) + ".json");
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/WorldgenExportPipeline263Test.java

@@ -0,0 +1,75 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.ExportTestPacks;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenExportPipeline263Test {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + ExportTestPacks.DIMENSION;
+    private static final int[] SAMPLE_Y = {-64, 0, 64, 200};
+    private static final int LATTICE = 8;
+    private static final int LATTICE_STEP = 61;
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Rule
+    public ExportTestPacks.BoundPlatform platform = new ExportTestPacks.BoundPlatform();
+
+    @Test
+    public void exportedPackLoadsAndSamples() throws IOException {
+        File pack = ExportTestPacks.basic(temporaryFolder.newFolder("pack"));
+        Path root = temporaryFolder.newFolder("exports").toPath();
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(pack.toPath())
+                .dimension(ExportTestPacks.DIMENSION)
+                .exportRoot(root)
+                .format("directory")
+                .build();
+
+        WorldgenExportResult result = WorldgenDatapackExporter.create().export(request, WorldgenExportProgress.NONE);
+
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(result.output(), WorldgenExportMode.OVERWORLD, DIMENSION_ID, SEED)) {
+            assertFalse(sampler.densityFunctionIds().isEmpty());
+            for (String id : sampler.densityFunctionIds()) {
+                for (int y : SAMPLE_Y) {
+                    for (int xIndex = 0; xIndex < LATTICE; xIndex++) {
+                        for (int zIndex = 0; zIndex < LATTICE; zIndex++) {
+                            int x = (xIndex - LATTICE / 2) * LATTICE_STEP;
+                            int z = (zIndex - LATTICE / 2) * LATTICE_STEP;
+                            float value = sampler.density(id, x, y, z);
+                            assertTrue(id + " at " + x + "," + y + "," + z + " = " + value, Float.isFinite(value));
+                        }
+                    }
+                }
+            }
+            for (int xIndex = 0; xIndex < LATTICE; xIndex++) {
+                for (int zIndex = 0; zIndex < LATTICE; zIndex++) {
+                    int x = (xIndex - LATTICE / 2) * LATTICE_STEP;
+                    int z = (zIndex - LATTICE / 2) * LATTICE_STEP;
+                    int height = sampler.baseHeight(x, z);
+                    assertTrue("height " + height + " at " + x + "," + z, height >= sampler.minY() && height <= sampler.minY() + sampler.height());
+                }
+            }
+        }
+    }
+}

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

@@ -0,0 +1,97 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.ExportTestPacks;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenExportSamplerThreadsTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + ExportTestPacks.DIMENSION;
+    private static final String FINAL_DENSITY_ID = DIMENSION_ID + "/final_density";
+    private static final int THREADS = 8;
+    private static final int POINTS = 2048;
+    private static final int ROW = 64;
+    private static final int STEP = 37;
+    private static final int ROUNDS = 3;
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Rule
+    public ExportTestPacks.BoundPlatform platform = new ExportTestPacks.BoundPlatform();
+
+    @Test
+    public void concurrentSamplingMatchesSequentialSampling() throws Exception {
+        File pack = ExportTestPacks.basic(temporaryFolder.newFolder("pack"));
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(pack.toPath())
+                .dimension(ExportTestPacks.DIMENSION)
+                .exportRoot(temporaryFolder.newFolder("exports").toPath())
+                .format("directory")
+                .build();
+        WorldgenExportResult result = WorldgenDatapackExporter.create().export(request, WorldgenExportProgress.NONE);
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(result.output(), WorldgenExportMode.OVERWORLD, DIMENSION_ID, SEED)) {
+            assertTrue(sampler.densityFunctionIds().toString(), sampler.densityFunctionIds().contains(FINAL_DENSITY_ID));
+            Sample expected = sweep(sampler, 0, 1).call();
+            ExecutorService executor = Executors.newFixedThreadPool(THREADS);
+            try {
+                List<Future<Sample>> futures = new ArrayList<>(THREADS);
+                for (int thread = 0; thread < THREADS; thread++) {
+                    futures.add(executor.submit(sweep(sampler, thread * (POINTS / THREADS), ROUNDS)));
+                }
+                for (Future<Sample> future : futures) {
+                    Sample sample = future.get();
+                    assertArrayEquals(expected.density(), sample.density(), 0.0F);
+                    assertEquals(List.of(expected.biome()), List.of(sample.biome()));
+                }
+            } finally {
+                executor.shutdownNow();
+            }
+        }
+    }
+
+    private static Callable<Sample> sweep(WorldgenExportSampler sampler, int offset, int rounds) {
+        return () -> {
+            float[] density = new float[POINTS];
+            String[] biome = new String[POINTS];
+            for (int round = 0; round < rounds; round++) {
+                for (int step = 0; step < POINTS; step++) {
+                    int index = (offset + step) % POINTS;
+                    int x = (index % ROW - ROW / 2) * STEP;
+                    int y = (index * 7) % 256 - 64;
+                    int z = (index / ROW - POINTS / ROW / 2) * STEP;
+                    density[index] = sampler.density(FINAL_DENSITY_ID, x, y, z);
+                    biome[index] = sampler.biome(x, y, z);
+                }
+            }
+            return new Sample(density, biome);
+        };
+    }
+
+    private record Sample(float[] density, String[] biome) {
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/WorldgenExportSeaLevel263Test.java

@@ -0,0 +1,90 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.ExportTestPacks;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import art.arcane.iris.testsupport.CompatTestPlatform;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenExportSeaLevel263Test {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + ExportTestPacks.DIMENSION;
+    private static final int FLUID_HEIGHT = 40;
+    private static final int SEA_FLOOR = 28;
+    private static final int CHUNK_WIDTH = 16;
+    private static final String DIMENSION = """
+            {
+              "regions": ["region"],
+              "dimensionHeight": {"min": -64, "max": 192},
+              "fluidHeight": 40,
+              "landChance": 0,
+              "carvingEnabled": false
+            }
+            """;
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Rule
+    public ExportTestPacks.BoundPlatform platform = new ExportTestPacks.BoundPlatform();
+
+    @Test
+    public void waterFillsThroughTheIrisFluidHeight() throws IOException {
+        WorldgenExportResult result = export();
+
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(result.output(), WorldgenExportMode.OVERWORLD, DIMENSION_ID, SEED)) {
+            ProtoChunk chunk = sampler.terrainChunk(0, 0);
+            for (int x = 0; x < CHUNK_WIDTH; x++) {
+                for (int z = 0; z < CHUNK_WIDTH; z++) {
+                    assertSolid(chunk.getBlockState(new BlockPos(x, SEA_FLOOR, z)), x, z);
+                    for (int y = SEA_FLOOR + 1; y <= FLUID_HEIGHT; y++) {
+                        BlockState state = chunk.getBlockState(new BlockPos(x, y, z));
+                        assertTrue(state + " at " + x + "," + y + "," + z, state.is(Blocks.WATER));
+                    }
+                    BlockState above = chunk.getBlockState(new BlockPos(x, FLUID_HEIGHT + 1, z));
+                    assertTrue(above + " above the fluid height at " + x + "," + z, above.isAir());
+                }
+            }
+            assertEquals(FLUID_HEIGHT + 1, sampler.seaLevel());
+        }
+    }
+
+    private static void assertSolid(BlockState state, int x, int z) {
+        assertTrue(state + " sea floor at " + x + "," + z, !state.isAir() && state.getFluidState().isEmpty());
+    }
+
+    private WorldgenExportResult export() throws IOException {
+        File pack = ExportTestPacks.withDimension(temporaryFolder.newFolder("pack"), DIMENSION);
+        CompatTestPlatform.write(pack, "generators/flat.json", "{\"composite\":[]}");
+        CompatTestPlatform.write(pack, "biomes/ocean.json", """
+                {"name":"Ocean","generators":[{"generator":"flat","min":-12,"max":-12}]}
+                """);
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(pack.toPath())
+                .dimension(ExportTestPacks.DIMENSION)
+                .exportRoot(temporaryFolder.newFolder("exports").toPath())
+                .format("directory")
+                .build();
+        return WorldgenDatapackExporter.create().export(request, WorldgenExportProgress.NONE);
+    }
+}

adapters/bukkit/nms/v26_3_R1/src/test/java/art/arcane/iris/probe/WorldgenExportSubterrain263Test.java

@@ -0,0 +1,165 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.export.ExportTestPacks;
+import art.arcane.iris.pack.datapack.export.WorldgenDatapackExporter;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtAccounter;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.Rotation;
+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.StructureSet;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.pools.ListPoolElement;
+import net.minecraft.world.level.levelgen.structure.structures.JigsawStructure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplate;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenExportSubterrain263Test {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = WorldgenExportRequest.DEFAULT_NAMESPACE + ":" + ExportTestPacks.DIMENSION;
+    private static final String POOLS = WorldgenExportRequest.DEFAULT_NAMESPACE + ":subterrain/pools";
+    private static final String TUBES = WorldgenExportRequest.DEFAULT_NAMESPACE + ":subterrain/tubes";
+    private static final String ANCHOR = WorldgenExportRequest.DEFAULT_NAMESPACE + ":subterrain/anchor";
+    private static final String TEMPLATES = "data/" + WorldgenExportRequest.DEFAULT_NAMESPACE + "/structure/subterrain/";
+    private static final int CHUNK_X = 3;
+    private static final int CHUNK_Z = -2;
+    private static final int POOLS_CENTER_Y = -49;
+    private static final int POOLS_BELOW_CENTER = 10;
+    private static final int POOLS_EXTENT = 10;
+    private static final int MAX_REACH = 128;
+    private static final String DIMENSION = """
+            {"regions": ["region"], "subterrainFeatures": [
+              {"id": "pools", "family": "CENOTE", "worldYRange": {"min": -60, "max": -40}, "spacing": 64, "probability": 1.0,
+               "radius": 8, "height": 12, "fluid": "WATER", "fluidDepth": 2, "shapeWarp": 0.5, "pillarSpacing": 0,
+               "formationFraction": 0.0, "solid": "minecraft:stone"},
+              {"id": "tubes", "family": "LAVA_TUBE", "allowedRegions": ["region"], "worldYRange": {"min": -60, "max": 40},
+               "spacing": 320, "probability": 0.5, "length": 300, "radius": 6, "height": 8, "fluidDepth": 2, "chimneyHeight": 0,
+               "shapeWarp": 0.0, "pillarSpacing": 0, "formationFraction": 0.0, "solid": "minecraft:stone"}]}
+            """;
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Rule
+    public ExportTestPacks.BoundPlatform platform = new ExportTestPacks.BoundPlatform();
+
+    @Test
+    public void subterrainRoomsLoadAndPlaceThroughRealCodecs() throws IOException {
+        File pack = ExportTestPacks.withDimension(temporaryFolder.newFolder("pack"), DIMENSION);
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(pack.toPath())
+                .dimension(ExportTestPacks.DIMENSION)
+                .exportRoot(temporaryFolder.newFolder("exports").toPath())
+                .format("directory")
+                .build();
+
+        WorldgenExportResult result = WorldgenDatapackExporter.create().export(request, WorldgenExportProgress.NONE);
+
+        assertTrue(result.message() + " " + result.diagnostics(), result.isSuccess());
+        try (WorldgenExportSampler sampler = WorldgenExportSampler.open(result.output(), WorldgenExportMode.OVERWORLD, DIMENSION_ID, SEED)) {
+            assertRegistered(sampler, POOLS, 4, 2);
+            assertRegistered(sampler, TUBES, 20, 10);
+            int cornerX = CHUNK_X << 4;
+            int cornerZ = CHUNK_Z << 4;
+
+            BoundingBox pools = placedBox(sampler, POOLS);
+            assertEquals(cornerX - POOLS_EXTENT, pools.minX());
+            assertEquals(cornerX + POOLS_EXTENT, pools.maxX());
+            assertEquals(cornerZ - POOLS_EXTENT, pools.minZ());
+            assertEquals(cornerZ + POOLS_EXTENT, pools.maxZ());
+            assertEquals(POOLS_CENTER_Y - POOLS_BELOW_CENTER, pools.minY());
+
+            BoundingBox tubes = placedBox(sampler, TUBES);
+            assertEquals(2 * MAX_REACH + 1, Math.max(tubes.getXSpan(), tubes.getZSpan()));
+            assertTrue(tubes.toString(), tubes.minX() >= cornerX - MAX_REACH && tubes.maxX() <= cornerX + MAX_REACH);
+            assertTrue(tubes.toString(), tubes.minZ() >= cornerZ - MAX_REACH && tubes.maxZ() <= cornerZ + MAX_REACH);
+            assertTrue(tubes.toString(), tubes.minY() >= -60 && tubes.maxY() <= 40);
+        }
+        assertTemplatesResolve(result.output());
+    }
+
+    private static void assertRegistered(WorldgenExportSampler sampler, String id, int spacing, int separation) {
+        Identifier identifier = Identifier.parse(id);
+        Structure structure = sampler.registries().lookupOrThrow(Registries.STRUCTURE)
+                .getOrThrow(ResourceKey.create(Registries.STRUCTURE, identifier)).value();
+        assertTrue(id, structure instanceof JigsawStructure);
+        assertEquals(id, GenerationStep.Decoration.UNDERGROUND_STRUCTURES, structure.step());
+        StructureSet set = sampler.registries().lookupOrThrow(Registries.STRUCTURE_SET)
+                .getOrThrow(ResourceKey.create(Registries.STRUCTURE_SET, identifier)).value();
+        RandomSpreadStructurePlacement placement = (RandomSpreadStructurePlacement) set.placement();
+        assertEquals(id, spacing, placement.spacing());
+        assertEquals(id, separation, placement.separation());
+        assertTrue(id, sampler.registries().lookupOrThrow(Registries.TEMPLATE_POOL).containsKey(identifier));
+    }
+
+    private static BoundingBox placedBox(WorldgenExportSampler sampler, String id) throws IOException {
+        StructureStart start = sampler.structureStart(id, CHUNK_X, CHUNK_Z);
+        assertTrue(id, start.isValid());
+        assertEquals(id, 1, start.getPieces().size());
+        PoolElementStructurePiece piece = (PoolElementStructurePiece) start.getPieces().getFirst();
+        assertTrue(id + " " + piece.getElement(), piece.getElement() instanceof ListPoolElement);
+        return start.getBoundingBox();
+    }
+
+    private static void assertTemplatesResolve(Path datapack) throws IOException {
+        List<Path> templates;
+        try (Stream<Path> paths = Files.walk(datapack.resolve(TEMPLATES))) {
+            templates = paths.filter(path -> path.toString().endsWith(".nbt")).sorted().toList();
+        }
+        assertEquals(12, templates.size());
+        boolean lava = false;
+        for (Path path : templates) {
+            CompoundTag tag;
+            try (InputStream input = Files.newInputStream(path)) {
+                tag = NbtIo.readCompressed(input, NbtAccounter.unlimitedHeap());
+            }
+            StructureTemplate template = new StructureTemplate();
+            template.load(BuiltInRegistries.BLOCK, tag);
+            StructurePlaceSettings settings = new StructurePlaceSettings();
+            assertTrue(path.toString(), template.filterBlocks(BlockPos.ZERO, settings, Blocks.AIR).isEmpty());
+            if (path.getFileName().toString().endsWith("_core.nbt")) {
+                assertFalse(path.toString(), template.filterBlocks(BlockPos.ZERO, settings, Blocks.CAVE_AIR).isEmpty());
+                List<StructureTemplate.JigsawBlockInfo> jigsaws = template.getJigsaws(BlockPos.ZERO, Rotation.NONE);
+                assertEquals(path.toString(), 1, jigsaws.size());
+                assertEquals(ANCHOR, jigsaws.getFirst().name().toString());
+                lava |= !template.filterBlocks(BlockPos.ZERO, settings, Blocks.LAVA).isEmpty();
+            } else {
+                assertFalse(path.toString(), template.filterBlocks(BlockPos.ZERO, settings, Blocks.STONE).isEmpty());
+            }
+        }
+        assertTrue("no lava tube template holds lava", lava);
+    }
+}

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

@@ -0,0 +1,111 @@
+package art.arcane.iris.probe;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.ExportIrFixtures;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.emit.WorldgenJsonWriter;
+import net.minecraft.world.level.levelgen.Heightmap;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.SortedMap;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public final class WorldgenStageBenchTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final int SIDE = 2;
+    private static final WorldgenStageBench.CallBudget BUDGET = new WorldgenStageBench.CallBudget(32, 8, 0L);
+
+    private static HeadlessNativeRegistries loaded;
+
+    @BeforeClass
+    public static void loadFixture() throws IOException {
+        HeadlessNativeBootstrap.initialize();
+        SortedMap<String, byte[]> files = WorldgenJsonWriter.forTarget(DataVersion.V26_3)
+                .write(ExportIrFixtures.flatNoise(DataVersion.V26_3, WorldgenExportMode.PRESET));
+        Path directory = Files.createTempDirectory("iris-stage-bench-");
+        for (Map.Entry<String, byte[]> file : files.entrySet()) {
+            Path target = directory.resolve(file.getKey());
+            Files.createDirectories(target.getParent());
+            Files.write(target, file.getValue());
+        }
+        try (PaperRegistryScope scope = PaperRegistryScope.open()) {
+            loaded = HeadlessNativeRegistries.load(directory);
+        }
+    }
+
+    @AfterClass
+    public static void closeFixture() throws IOException {
+        if (loaded != null) {
+            loaded.close();
+        }
+    }
+
+    @Test
+    public void exportedFixtureRunsEveryStage() {
+        assertStages(bench("export", ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.DIMENSION));
+    }
+
+    @Test
+    public void vanillaOverworldRunsEveryStage() {
+        assertStages(bench("vanilla", DatapackCostProbe.VANILLA_PRESET));
+    }
+
+    private static void assertStages(WorldgenStageBench bench) {
+        WorldgenStageBench.ChunkSamples samples = new WorldgenStageBench.ChunkSamples();
+        bench.chunks(0, 0, SIDE, samples);
+        bench.chunks(SIDE + 4, 0, SIDE, samples);
+        WorldgenStageBench.ChunkTimings timings = samples.timings();
+        assertEquals(2 * SIDE * SIDE, timings.chunks());
+        assertEquals(2 * (SIDE + 2) * (SIDE + 2), timings.biomes().wall().count());
+        assertEquals(2 * SIDE * SIDE, timings.noise().cpu().count());
+        assertEquals(2 * SIDE * SIDE, timings.surface().wall().count());
+        assertEquals(2 * SIDE * SIDE, timings.carverBiome().wall().count());
+        assertEquals(0L, timings.biomeFallbacks());
+        assertTrue(Double.isFinite(timings.totalMean()));
+        assertTrue(Double.isFinite(timings.totalCpuMean()));
+        assertCalls(samples(bench, Call.UNCACHED_BIOME));
+        assertCalls(samples(bench, Call.BASE_HEIGHT));
+        assertCalls(samples(bench, Call.BASE_COLUMN));
+    }
+
+    private static void assertCalls(WorldgenStageBench.CallTiming timing) {
+        assertEquals(2 * BUDGET.minimumCalls(), timing.calls());
+        assertEquals(2 * BUDGET.minimumCalls(), timing.wall().count());
+        assertTrue(Double.isFinite(timing.cpuMean()));
+    }
+
+    private static WorldgenStageBench.CallTiming samples(WorldgenStageBench bench, Call call) {
+        WorldgenStageBench.CallSamples samples = new WorldgenStageBench.CallSamples();
+        for (int round = 0; round < 2; round++) {
+            switch (call) {
+                case UNCACHED_BIOME -> bench.uncachedBiome(BUDGET, samples);
+                case BASE_HEIGHT -> bench.baseHeight(BUDGET, Heightmap.Types.WORLD_SURFACE_WG, samples);
+                case BASE_COLUMN -> bench.baseColumn(BUDGET, samples);
+            }
+        }
+        return samples.timing();
+    }
+
+    private static WorldgenStageBench bench(String label, String preset) {
+        return new WorldgenStageBench(new WorldgenStageBench.Options(label,
+                DatapackCostProbe.presetOverworld(loaded.registries(), preset), loaded.registries(), SEED));
+    }
+
+    private enum Call {
+        UNCACHED_BIOME,
+        BASE_HEIGHT,
+        BASE_COLUMN
+    }
+}

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

@@ -0,0 +1,99 @@
+package art.arcane.iris.probe.fidelity;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.ExportIrFixtures;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.emit.WorldgenJsonWriter;
+import art.arcane.iris.pack.datapack.export.ir.AquiferDef;
+import art.arcane.iris.pack.datapack.export.ir.Axis;
+import art.arcane.iris.pack.datapack.export.ir.BiomeDef;
+import art.arcane.iris.pack.datapack.export.ir.ClimateLayout;
+import art.arcane.iris.pack.datapack.export.ir.DimensionDef;
+import art.arcane.iris.pack.datapack.export.ir.ExportIr;
+import art.arcane.iris.pack.datapack.export.ir.Field;
+import art.arcane.iris.pack.datapack.export.ir.MaterialProgram;
+import art.arcane.iris.pack.datapack.export.ir.RouterDef;
+import art.arcane.iris.probe.PaperRegistryIsolation;
+import art.arcane.iris.probe.WorldgenExportSampler;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import java.util.SortedMap;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+public final class VanillaNoiseColumnSourceTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.DIMENSION;
+    private static final String BIOME_ID = ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.BIOME;
+    private static final String LOAD_KEY = "Flat Plains";
+    private static final int LAND_HEIGHT = 80;
+    private static final int SEA_FLOOR_HEIGHT = 40;
+    private static final int MAX_Y = ExportIrFixtures.MIN_Y + ExportIrFixtures.HEIGHT;
+
+    @Test
+    public void landColumnsReportTheTopSolidBlockAndStayDry() throws IOException {
+        try (VanillaNoiseColumnSource source = new VanillaNoiseColumnSource(open(LAND_HEIGHT), Map.of(BIOME_ID, LOAD_KEY))) {
+            assertEquals(ExportIrFixtures.MIN_Y, source.minY());
+            assertEquals(MAX_Y, source.maxY());
+            for (int x : new int[]{-37, 0, 113}) {
+                FidelityColumn column = source.column(x, -x);
+                assertEquals(new FidelityColumn(LOAD_KEY, LAND_HEIGHT - 1, false), column);
+            }
+        }
+    }
+
+    @Test
+    public void seaColumnsReportTheFloorUnderWater() throws IOException {
+        WorldgenExportSampler sampler = open(SEA_FLOOR_HEIGHT);
+        try (VanillaNoiseColumnSource source = new VanillaNoiseColumnSource(sampler, Map.of(BIOME_ID, LOAD_KEY))) {
+            FidelityStats stats = new FidelityStats(source.minY(), source.maxY());
+            for (int x : new int[]{-37, 0, 113}) {
+                FidelityColumn column = source.column(x, x);
+                assertEquals(new FidelityColumn(LOAD_KEY, sampler.floorHeight(x, x) - 1, true), column);
+                assertTrue(column.terrainY() + " under sea level", column.terrainY() < ExportIrFixtures.SEA_LEVEL - 1);
+                assertEquals(ExportIrFixtures.SEA_LEVEL, sampler.baseHeight(x, x));
+                stats.accept(column);
+            }
+
+            assertEquals(0.0D, stats.landFraction(), 0.0D);
+        }
+    }
+
+    @Test
+    public void exportedBiomeWithoutALoadKeyIsRejected() throws IOException {
+        try (VanillaNoiseColumnSource source = new VanillaNoiseColumnSource(open(LAND_HEIGHT), Map.of())) {
+            IllegalStateException failure = assertThrows(IllegalStateException.class, () -> source.column(0, 0));
+
+            assertTrue(failure.getMessage(), failure.getMessage().contains(BIOME_ID));
+        }
+    }
+
+    private static WorldgenExportSampler open(int height) throws IOException {
+        return WorldgenExportSampler.open(flatExport(height), WorldgenExportMode.PRESET, DIMENSION_ID, SEED);
+    }
+
+    private static SortedMap<String, byte[]> flatExport(int height) {
+        Field zero = new Field.Const(0.0);
+        Field level = new Field.Const(height);
+        Field y = new Field.Coord(Axis.Y, Field.Tiling.CLAMP, -4064.0, 4062.0, -4064.0, 4062.0);
+        Field finalDensity = new Field.Grid(new Field.Binary(Field.BinaryOp.MUL, new Field.Const(0.125),
+                new Field.Binary(Field.BinaryOp.SUB, level, y)), 4, 8);
+        RouterDef router = new RouterDef(zero, zero, zero, zero, zero, zero, new Field.Grid(level, 16, 1), finalDensity, AquiferDef.dry(level));
+        DimensionDef dimension = new DimensionDef(ExportIrFixtures.DIMENSION, ExportIrFixtures.MIN_Y, ExportIrFixtures.HEIGHT,
+                ExportIrFixtures.HEIGHT, ExportIrFixtures.FLUID_HEIGHT, "minecraft:stone", "minecraft:water", ExportIrFixtures.dimensionType());
+        ClimateLayout climate = new ClimateLayout(List.of(new ClimateLayout.ClimateEntry(BIOME_ID, ClimateLayout.ClimateAxis.TEMPERATURE, -2.0, 2.0)));
+        ExportIr ir = new ExportIr(ExportIrFixtures.NAMESPACE, DataVersion.V26_3, WorldgenExportMode.PRESET, dimension, List.of(), router, climate,
+                List.of(new BiomeDef(ExportIrFixtures.BIOME, ExportIrFixtures.biome())), MaterialProgram.rock("minecraft:stone"),
+                List.of(), List.of(), List.of());
+        return WorldgenJsonWriter.forTarget(DataVersion.V26_3).write(ir);
+    }
+}

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

@@ -0,0 +1,189 @@
+package art.arcane.iris.probe.fidelity;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.ExportIrFixtures;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.emit.WorldgenJsonWriter;
+import art.arcane.iris.pack.datapack.export.ir.AquiferDef;
+import art.arcane.iris.pack.datapack.export.ir.Axis;
+import art.arcane.iris.pack.datapack.export.ir.BiomeDef;
+import art.arcane.iris.pack.datapack.export.ir.ClimateLayout;
+import art.arcane.iris.pack.datapack.export.ir.DimensionDef;
+import art.arcane.iris.pack.datapack.export.ir.ExportIr;
+import art.arcane.iris.pack.datapack.export.ir.Field;
+import art.arcane.iris.pack.datapack.export.ir.JsonResource;
+import art.arcane.iris.pack.datapack.export.ir.MaterialProgram;
+import art.arcane.iris.pack.datapack.export.ir.RouterDef;
+import art.arcane.iris.probe.PaperRegistryIsolation;
+import art.arcane.iris.probe.WorldgenExportSampler;
+import com.google.gson.JsonParser;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import java.util.SortedMap;
+
+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 VanillaNoiseFidelitySourceTest {
+    @ClassRule
+    public static final PaperRegistryIsolation registryIsolation = new PaperRegistryIsolation();
+
+    private static final long SEED = 1337L;
+    private static final String DIMENSION_ID = ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.DIMENSION;
+    private static final String BIOME_ID = ExportIrFixtures.NAMESPACE + ":" + ExportIrFixtures.BIOME;
+    private static final String LOAD_KEY = "Flat Plains";
+    private static final int LAND_HEIGHT = 80;
+    private static final int MAX_Y = ExportIrFixtures.MIN_Y + ExportIrFixtures.HEIGHT;
+    private static final String WALL_SHELL = ExportIrFixtures.NAMESPACE + ":cave/wall_shell";
+    private static final int WALL_MIN_Y = 10;
+    private static final int WALL_MAX_Y = 20;
+    private static final int CARVED_HEIGHT = 120;
+    private static final int VOID_MIN_Y = 96;
+    private static final int CAVE_MIN_Y = 64;
+    private static final Field BLOCK_Y = new Field.Coord(Axis.Y, Field.Tiling.CLAMP, -4064.0, 4062.0, -4064.0, 4062.0);
+
+    @Test
+    public void flatExportReportsTheConstantSurface() throws IOException {
+        WorldgenExportSampler sampler = open(LAND_HEIGHT);
+        try (VanillaNoiseFidelitySource source = new VanillaNoiseFidelitySource(sampler, Map.of(BIOME_ID, LOAD_KEY), WALL_SHELL)) {
+            assertEquals(ExportIrFixtures.MIN_Y, source.minY());
+            assertEquals(MAX_Y, source.maxY());
+            for (int x : new int[]{-37, 0, 113}) {
+                assertEquals(LAND_HEIGHT, sampler.baseHeight(x, -x));
+            }
+            for (int[] chunkPosition : new int[][]{{0, 0}, {-3, 5}}) {
+                FidelityChunk chunk = source.sample(chunkPosition[0], chunkPosition[1]);
+                for (int x = 0; x < 16; x++) {
+                    for (int z = 0; z < 16; z++) {
+                        assertEquals(LAND_HEIGHT - 1, chunk.surfaceY(x, z));
+                        assertEquals(LOAD_KEY, chunk.surfaceBiome(x, z));
+                        assertTrue(chunk.open(x, LAND_HEIGHT, z));
+                        assertNull(chunk.block(x, LAND_HEIGHT - 1, z));
+                    }
+                }
+                for (int y = ExportIrFixtures.MIN_Y; y < LAND_HEIGHT; y++) {
+                    assertFalse("y " + y, chunk.open(7, y, 9));
+                    assertFalse("y " + y, chunk.fluid(7, y, 9));
+                }
+            }
+
+            FidelityStats stats = FidelityScanner.scan(source, 0, 0, 1, 4, 2);
+
+            assertEquals(144L, stats.heightColumns());
+            assertEquals(LAND_HEIGHT - 1, stats.heightQuantile(0.1D), 0.0D);
+            assertEquals(LAND_HEIGHT - 1, stats.heightQuantile(0.9D), 0.0D);
+            assertEquals(1.0D, stats.landFraction(), 0.0D);
+            assertEquals(Map.of(LOAD_KEY, 144L), stats.biomeColumns());
+            assertEquals(0L, stats.blockColumns());
+            assertEquals(0L, stats.wallSolidVoxels());
+        }
+    }
+
+    @Test
+    public void wallShellDensityMarksWallVoxels() throws IOException {
+        WorldgenExportSampler sampler = WorldgenExportSampler.open(flatExport(LAND_HEIGHT, wallShell()), WorldgenExportMode.PRESET, DIMENSION_ID, SEED);
+        try (VanillaNoiseFidelitySource source = new VanillaNoiseFidelitySource(sampler, Map.of(BIOME_ID, LOAD_KEY), WALL_SHELL)) {
+            FidelityChunk chunk = source.sample(2, -1);
+
+            assertTrue(chunk.wallsKnown());
+            assertTrue(chunk.wall(7, WALL_MIN_Y, 9));
+            assertTrue(chunk.wall(7, WALL_MAX_Y - 1, 9));
+            assertFalse(chunk.wall(7, WALL_MIN_Y - 1, 9));
+            assertFalse(chunk.wall(7, WALL_MAX_Y, 9));
+
+            FidelityStats stats = FidelityScanner.scan(source, 0, 0, 1, 4, 2);
+
+            long interiorColumns = 9L * 9L;
+            assertEquals(interiorColumns * (LAND_HEIGHT - 1 - ExportIrFixtures.MIN_Y), stats.wallSolidVoxels());
+            assertEquals(interiorColumns * (WALL_MAX_Y - WALL_MIN_Y), stats.wallVoxels());
+        }
+    }
+
+    @Test
+    public void openSpaceOutsideTheTerrainOperandIsATerrainVoid() throws IOException {
+        WorldgenExportSampler sampler = WorldgenExportSampler.open(carvedExport(), WorldgenExportMode.PRESET, DIMENSION_ID, SEED);
+        try (VanillaNoiseFidelitySource source = new VanillaNoiseFidelitySource(sampler, Map.of(BIOME_ID, LOAD_KEY), WALL_SHELL)) {
+            FidelityChunk chunk = source.sample(1, -2);
+
+            assertEquals(CARVED_HEIGHT - 1, chunk.surfaceY(7, 9));
+            assertTrue(chunk.open(7, VOID_MIN_Y, 9));
+            assertFalse(chunk.terrainMass(7, VOID_MIN_Y, 9));
+            assertTrue(chunk.open(7, CAVE_MIN_Y + 3, 9));
+            assertTrue(chunk.terrainMass(7, CAVE_MIN_Y + 3, 9));
+            assertFalse(chunk.open(7, VOID_MIN_Y - 4, 9));
+            assertTrue(chunk.terrainMass(7, VOID_MIN_Y - 4, 9));
+
+            FidelityStats stats = FidelityScanner.scan(source, 0, 0, 1, 4, 2);
+
+            int voidBand = (VOID_MIN_Y - ExportIrFixtures.MIN_Y) / 16;
+            int caveBand = (CAVE_MIN_Y - ExportIrFixtures.MIN_Y) / 16;
+            assertEquals(1.0D, stats.voidShare(voidBand), 0.0D);
+            assertEquals(0.0D, stats.caveShare(voidBand), 0.0D);
+            assertEquals(1.0D, stats.caveShare(caveBand), 0.0D);
+            assertEquals(0.0D, stats.voidShare(caveBand), 0.0D);
+        }
+    }
+
+    @Test
+    public void exportWithoutAWallShellReportsNoWalls() throws IOException {
+        try (VanillaNoiseFidelitySource source = new VanillaNoiseFidelitySource(open(LAND_HEIGHT), Map.of(BIOME_ID, LOAD_KEY), WALL_SHELL)) {
+            assertFalse(source.sample(0, 0).wallsKnown());
+        }
+    }
+
+    @Test
+    public void exportedBiomeWithoutALoadKeyIsRejected() throws IOException {
+        try (VanillaNoiseFidelitySource source = new VanillaNoiseFidelitySource(open(LAND_HEIGHT), Map.of(), WALL_SHELL)) {
+            FidelityChunk chunk = source.sample(0, 0);
+
+            IllegalStateException failure = assertThrows(IllegalStateException.class, () -> chunk.surfaceBiome(0, 0));
+
+            assertTrue(failure.getMessage(), failure.getMessage().contains(BIOME_ID));
+        }
+    }
+
+    private static WorldgenExportSampler open(int height) throws IOException {
+        return WorldgenExportSampler.open(flatExport(height), WorldgenExportMode.PRESET, DIMENSION_ID, SEED);
+    }
+
+    private static JsonResource wallShell() {
+        return new JsonResource("data/" + ExportIrFixtures.NAMESPACE + "/worldgen/density_function/cave/wall_shell.json", JsonParser.parseString(
+                "{\"type\":\"minecraft:range_choice\",\"input\":{\"type\":\"minecraft:gradient\",\"axis\":\"y\",\"tiling\":\"clamp_to_edge\","
+                        + "\"from_coordinate\":-4064,\"to_coordinate\":4062,\"from_value\":-4064.0,\"to_value\":4062.0},"
+                        + "\"min_inclusive\":" + WALL_MIN_Y + ".0,\"max_exclusive\":" + WALL_MAX_Y + ".0,\"when_in_range\":1.0,\"when_out_of_range\":0.0}"));
+    }
+
+    private static SortedMap<String, byte[]> flatExport(int height, JsonResource... resources) {
+        Field level = new Field.Const(height);
+        Field finalDensity = new Field.Grid(new Field.Binary(Field.BinaryOp.MUL, new Field.Const(0.125),
+                new Field.Binary(Field.BinaryOp.SUB, level, BLOCK_Y)), 4, 8);
+        return export(height, finalDensity, resources);
+    }
+
+    private static SortedMap<String, byte[]> carvedExport() {
+        Field ramp = new Field.Binary(Field.BinaryOp.MUL, new Field.Const(0.125), new Field.Binary(Field.BinaryOp.SUB, new Field.Const(CARVED_HEIGHT), BLOCK_Y));
+        Field terrain = new Field.RangeIf(BLOCK_Y, VOID_MIN_Y, VOID_MIN_Y + 16, new Field.Const(-1.0), ramp);
+        Field caves = new Field.RangeIf(BLOCK_Y, CAVE_MIN_Y, CAVE_MIN_Y + 16, new Field.Const(-1.0), new Field.Const(1.0));
+        return export(CARVED_HEIGHT, new Field.Binary(Field.BinaryOp.MIN, terrain, caves));
+    }
+
+    private static SortedMap<String, byte[]> export(int height, Field finalDensity, JsonResource... resources) {
+        Field zero = new Field.Const(0.0);
+        Field level = new Field.Const(height);
+        RouterDef router = new RouterDef(zero, zero, zero, zero, zero, zero, new Field.Grid(level, 16, 1), finalDensity, AquiferDef.dry(level));
+        DimensionDef dimension = new DimensionDef(ExportIrFixtures.DIMENSION, ExportIrFixtures.MIN_Y, ExportIrFixtures.HEIGHT,
+                ExportIrFixtures.HEIGHT, ExportIrFixtures.FLUID_HEIGHT, "minecraft:stone", "minecraft:water", ExportIrFixtures.dimensionType());
+        ClimateLayout climate = new ClimateLayout(List.of(new ClimateLayout.ClimateEntry(BIOME_ID, ClimateLayout.ClimateAxis.TEMPERATURE, -2.0, 2.0)));
+        ExportIr ir = new ExportIr(ExportIrFixtures.NAMESPACE, DataVersion.V26_3, WorldgenExportMode.PRESET, dimension, List.of(), router, climate,
+                List.of(new BiomeDef(ExportIrFixtures.BIOME, ExportIrFixtures.biome())), MaterialProgram.rock("minecraft:stone"),
+                List.of(), List.of(resources), List.of());
+        return WorldgenJsonWriter.forTarget(DataVersion.V26_3).write(ir);
+    }
+}

adapters/bukkit/plugin/build.gradle

@@ -14,7 +14,7 @@ dependencies {
     // log4j-core Filter interface, so its constructor reference needs the type resolvable.
     compileOnly(libs.log4j.core)
     testImplementation('junit:junit:4.13.2')
-    testImplementation('org.mockito:mockito-core:5.23.0')
+    testImplementation(libs.mockito.core)
     testImplementation(libs.paper.api)
     testImplementation(libs.bstats)
     testImplementation(project(':core'))
@@ -28,6 +28,16 @@ dependencies {
     }
 }
 
+String lwjglVersion = libs.versions.lwjgl.get()
+List<String> mavenLibraries = [
+    "org.lwjgl:lwjgl:${lwjglVersion}",
+    "org.lwjgl:lwjgl:jar:natives-linux:${lwjglVersion}",
+    "org.lwjgl:lwjgl-opengl:${lwjglVersion}",
+    "org.lwjgl:lwjgl-opengl:jar:natives-linux:${lwjglVersion}",
+    "org.lwjgl:lwjgl-egl:${lwjglVersion}",
+    "org.lwjgl:lwjgl-jawt:${lwjglVersion}",
+].collect { GString coordinate -> coordinate.toString() }
+
 tasks.named('processResources').configure {
     def pluginProperties = [
         name      : rootProject.name,
@@ -35,6 +45,7 @@ tasks.named('processResources').configure {
         apiVersion: apiVersion,
         main      : mainClass,
         bootstrapper: bootstrapperClass,
+        libraries : mavenLibraries.collect { String coordinate -> "'${coordinate}'" }.join(', '),
     ]
     inputs.properties(pluginProperties)
     filesMatching(['**/paper-plugin.yml', '**/plugin.yml']) {

adapters/bukkit/plugin/src/main/java/art/arcane/iris/Iris.java

@@ -57,9 +57,12 @@ import art.arcane.iris.localization.IrisLanguage;
 import art.arcane.volmlib.util.director.help.DirectorMiniMenu;
 import art.arcane.volmlib.util.localization.BukkitLanguageSwitcher;
 import art.arcane.iris.integration.MultiverseCoreLink;
+import art.arcane.iris.platform.agent.Agent;
+import art.arcane.iris.platform.agent.AttachSignal;
 import art.arcane.iris.platform.bukkit.nms.INMS;
 import art.arcane.volmlib.nativelib.terrain.ServerShutdownBoundary;
 import art.arcane.iris.studio.view.BukkitGuiHost;
+import art.arcane.iris.studio.view.GuiHost;
 import art.arcane.iris.studio.view.PregeneratorJob;
 import art.arcane.iris.platform.bukkit.BoardSVC;
 import art.arcane.iris.command.CommandSVC;
@@ -200,10 +203,10 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
     private final AtomicBoolean postStopFinisherStarted = new AtomicBoolean(false);
     private final AtomicBoolean serverStopTeardownDeferred = new AtomicBoolean(false);
     private final AtomicBoolean servicesDisabled = new AtomicBoolean(false);
+    private final AtomicBoolean runtimeTeardownFailed = new AtomicBoolean(false);
     private final AtomicBoolean sharedRuntimeClosed = new AtomicBoolean(false);
     private final AtomicBoolean startupBoundaryRestart = new AtomicBoolean(false);
     private final AtomicBoolean terminalCleanupCompleted = new AtomicBoolean(false);
-    private final AtomicBoolean runtimeTeardownFailed = new AtomicBoolean(false);
     private volatile boolean generatorDrainCompleted;
     private volatile boolean enableFailed;
     private volatile PlaceholderRegistration papiRegistration;
@@ -224,6 +227,7 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
     private BukkitDebugDump debugDump;
     private volatile SettingsHotloadWatch settingsHotloadWatch;
     private volatile ServerShutdownBoundary serverShutdownBoundary;
+    private boolean shutdownProtectionInitialized;
 
     public static VolmitSender getSender() {
         VolmitSender current = sender;
@@ -473,10 +477,16 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         }
 
         if (debug) {
-            String n = e.getClass().getCanonicalName() + "-" + e.getStackTrace()[0].getClassName() + "-" + e.getStackTrace()[0].getLineNumber();
+            String n = e.getClass().getName();
+            StackTraceElement[] trace = e.getStackTrace();
+            if (trace.length > 0) {
+                n += "-" + trace[0].getClassName() + "-" + trace[0].getLineNumber();
+            }
 
             if (e.getCause() != null) {
-                n += "-" + e.getCause().getStackTrace()[0].getClassName() + "-" + e.getCause().getStackTrace()[0].getLineNumber();
+                StackTraceElement[] causeTrace = e.getCause().getStackTrace();
+                n += "-" + (causeTrace.length == 0 ? e.getCause().getClass().getName()
+                        : causeTrace[0].getClassName() + "-" + causeTrace[0].getLineNumber());
             }
 
             File f = instance.getDataFile("debug", "caught-exceptions", n + ".txt");
@@ -570,6 +580,17 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
                 this::getIrisVersion,
                 this::getMCVersion));
         SlimJar.load();
+        restoreAttachSignal();
+    }
+
+    private static void restoreAttachSignal() {
+        try {
+            if (AttachSignal.restoreJvmHandler()) {
+                info("Restored the JVM SIGQUIT handler that the server console replaced");
+            }
+        } catch (RuntimeException failure) {
+            reportError("Could not restore the JVM SIGQUIT handler; the Iris agent may fail to attach.", failure);
+        }
     }
 
     private static void bridgeLog(LogLevel level, String message) {
@@ -626,10 +647,10 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         postStopFinisherStarted.set(false);
         serverStopTeardownDeferred.set(false);
         servicesDisabled.set(false);
+        runtimeTeardownFailed.set(false);
         sharedRuntimeClosed.set(false);
         startupBoundaryRestart.set(false);
         terminalCleanupCompleted.set(false);
-        runtimeTeardownFailed.set(false);
         generatorDrainCompleted = false;
         deferredShutdownGenerators.clear();
         MultiBurst.burst.reopen();
@@ -910,6 +931,7 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
 
     public void onEnable() {
         enableFailed = false;
+        shutdownProtectionInitialized = false;
         IrisStartupValidation.begin();
         Bukkit.getPluginManager().registerEvents(new IrisStartupAdmissionListener(), this);
         try {
@@ -921,13 +943,14 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
                 refuseUnsupportedServer();
                 return;
             }
+            initializeShutdownProtection();
             enable();
         } catch (Throwable failure) {
+            enableFailed = true;
             if (!FailedEnableLock.engage(failure, FailedEnableLock.irisWorldsPresent(),
                     generatorResolver.refusals().startupWorldsCreated())) {
                 throw failure;
             }
-            enableFailed = true;
             return;
         }
         BukkitGuiHost.install();
@@ -945,6 +968,17 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         reportLockedRuntime();
     }
 
+    private void initializeShutdownProtection() {
+        if (!INMS.get().supportsIrisWorldGeneration()) {
+            return;
+        }
+        if (!Agent.install()) {
+            throw new IllegalStateException("Iris Java agent is unavailable; shutdown protection cannot be installed.");
+        }
+        INMS.get().initializeLifecycle(getClass().getClassLoader());
+        shutdownProtectionInitialized = true;
+    }
+
     private void refuseUnsupportedServer() {
         Throwable bindFailure = INMS.bindFailure();
         IllegalStateException failure = new IllegalStateException("Iris cannot start: " + (bindFailure == null
@@ -988,6 +1022,8 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
     }
 
     public void onDisable() {
+        pendingWorldReplacements.awaitStagingForShutdown();
+        GuiHost.shutdown();
         preservePendingBlockDrops();
         papiLifecycleActive = false;
         if (updateNotifier != null) {
@@ -1004,7 +1040,8 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         }
         IrisLanguage.shutdown();
         teardownPapi();
-        boolean deferToServerStop = FailedEnableLock.defersTeardownToServerStop(enableFailed, IrisToolbelt.isServerStopping());
+        boolean deferToServerStop = FailedEnableLock.defersTeardownToServerStop(enableFailed, IrisToolbelt.isServerStopping())
+                && tryDeferPluginClassLoaderClose();
         boolean restartingAtStartupBoundary = startupBoundaryRestart.get();
         if (restartingAtStartupBoundary) {
             teardownRuntime("startup-boundary-restart", 30L);
@@ -1036,7 +1073,7 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         preservePendingBlockDrops();
         papiLifecycleActive = false;
         teardownPapi();
-        if (IrisToolbelt.isServerStopping()) {
+        if (IrisToolbelt.isServerStopping() && tryDeferPluginClassLoaderClose()) {
             quiesceRuntimeForServerShutdown("pre-unload:" + reason);
             startPostStopFinisher();
             Iris.debug("Pre-unload hook deferred generator teardown until Paper closes its chunk schedulers.");
@@ -1051,6 +1088,19 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         return CompletableFuture.completedFuture(null);
     }
 
+    private boolean tryDeferPluginClassLoaderClose() {
+        if (!shutdownProtectionInitialized) {
+            return false;
+        }
+        try {
+            INMS.get().deferPluginClassLoaderClose();
+            return true;
+        } catch (RuntimeException | LinkageError failure) {
+            Iris.reportError("Failed to retain the Iris plugin class loader; draining shutdown inline.", failure);
+            return false;
+        }
+    }
+
     /**
      * Drains the world generators exactly once. Serialized against the JVM shutdown hook so a
      * second caller cannot rip the pools or services out from under an in-flight drain.
@@ -1097,19 +1147,16 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
             try {
                 MultiBurst.burst.close();
             } catch (Throwable failure) {
-                runtimeTeardownFailed.set(true);
                 Iris.reportError("Failed to close Iris generation workers.", failure);
             }
             try {
                 MultiBurst.hydrology.close();
             } catch (Throwable failure) {
-                runtimeTeardownFailed.set(true);
                 Iris.reportError("Failed to close Iris hydrology workers.", failure);
             }
             try {
                 MultiBurst.ioBurst.close();
             } catch (Throwable failure) {
-                runtimeTeardownFailed.set(true);
                 Iris.reportError("Failed to close Iris I/O workers.", failure);
             }
             clearQueues();
@@ -1128,7 +1175,6 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
 
     private void quiesceRuntimeForServerShutdown(String reason) {
         serverStopTeardownDeferred.set(true);
-        INMS.get().deferPluginClassLoaderClose();
         JigsawStudioService jigsawStudioService = IrisServices.getOrNull(JigsawStudioService.class);
         if (jigsawStudioService != null) {
             try {
@@ -1226,30 +1272,37 @@ public class Iris extends VolmitPlugin implements Listener, ReloadAware {
         if (!terminalCleanupCompleted.compareAndSet(false, true)) {
             return;
         }
-        J.attempt(() -> INMS.get().uninjectBukkit());
+        try {
+            if (INMS.isBound()) {
+                INMS.get().uninjectBukkit();
+            }
+        } catch (Throwable failure) {
+            Iris.reportError("Failed to remove Iris world-generation hooks.", failure);
+        }
         try {
             runPostShutdown();
         } catch (Throwable e) {
             runtimeTeardownFailed.set(true);
             Iris.reportError("Failed to run Iris post-shutdown cleanup.", e);
         } finally {
-            if (serverStopTeardownDeferred.get() && hasActiveShutdownResources()) {
-                runtimeTeardownFailed.set(true);
-                SHUTDOWN_ERRORS.println("[Iris] Owned background work remains active after cleanup; retaining the plugin class loader until JVM exit.");
-            }
+            boolean activeResources = serverStopTeardownDeferred.get()
+                    && (runtimeTeardownFailed.get() || hasActiveShutdownResources());
             IrisPlatforms.unbind();
-            if (serverStopTeardownDeferred.get() && runtimeTeardownFailed.get()) {
-                SHUTDOWN_ERRORS.println("[Iris] Runtime cleanup failed; retaining the plugin class loader until JVM exit.");
+            BukkitPlatform.releaseHost();
+            if (activeResources) {
+                SHUTDOWN_ERRORS.println("[Iris] Owned background work has not completed cleanup; retaining the plugin class loader until JVM exit.");
             } else {
                 try {
-                    INMS.get().releasePluginClassLoaderClose();
-                    SlimJar.closeNativeProviders();
+                    if (shutdownProtectionInitialized) {
+                        INMS.get().releasePluginClassLoaderClose();
+                    } else {
+                        SlimJar.closeNativeProviders();
+                    }
                 } catch (Throwable failure) {
                     SHUTDOWN_ERRORS.println("[Iris] Failed to release the plugin class loader after runtime cleanup.");
                     failure.printStackTrace(SHUTDOWN_ERRORS);
                 }
             }
-            BukkitPlatform.releaseHost();
         }
     }
 

adapters/bukkit/plugin/src/main/java/art/arcane/iris/IrisPluginLoader.java

@@ -6,12 +6,22 @@ import io.papermc.paper.plugin.bootstrap.PluginProviderContext;
 import io.papermc.paper.plugin.loader.PluginClasspathBuilder;
 import io.papermc.paper.plugin.loader.PluginLoader;
 import io.papermc.paper.plugin.loader.library.impl.JarLibrary;
+import io.papermc.paper.plugin.loader.library.impl.MavenLibraryResolver;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.eclipse.aether.artifact.DefaultArtifact;
+import org.eclipse.aether.graph.Dependency;
+import org.eclipse.aether.repository.RemoteRepository;
 
 import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
 import java.util.stream.Stream;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
 
 @SuppressWarnings("UnstableApiUsage")
 public final class IrisPluginLoader implements PluginLoader {
@@ -40,6 +50,21 @@ public final class IrisPluginLoader implements PluginLoader {
                 classpathBuilder.addLibrary(new JarLibrary(library));
             }
         }
+        classpathBuilder.addLibrary(mavenResolver(mavenLibraries(context.getPluginSource())));
+    }
+
+    static List<String> mavenLibraries(Path pluginJar) {
+        try (ZipFile jar = new ZipFile(pluginJar.toFile())) {
+            ZipEntry descriptor = jar.getEntry("plugin.yml");
+            if (descriptor == null) {
+                throw new IllegalStateException("The Iris jar " + pluginJar + " has no plugin.yml library list.");
+            }
+            try (Reader reader = new InputStreamReader(jar.getInputStream(descriptor), StandardCharsets.UTF_8)) {
+                return YamlConfiguration.loadConfiguration(reader).getStringList("libraries");
+            }
+        } catch (IOException failure) {
+            throw new IllegalStateException("Unable to read the Iris library list from " + pluginJar + ".", failure);
+        }
     }
 
     static List<Path> relocatedLibraries(Path libraryRoot) {
@@ -59,6 +84,16 @@ public final class IrisPluginLoader implements PluginLoader {
         }
     }
 
+    private static MavenLibraryResolver mavenResolver(List<String> coordinates) {
+        MavenLibraryResolver resolver = new MavenLibraryResolver();
+        resolver.addRepository(new RemoteRepository.Builder("central", "default",
+                MavenLibraryResolver.MAVEN_CENTRAL_DEFAULT_MIRROR).build());
+        for (String coordinate : coordinates) {
+            resolver.addDependency(new Dependency(new DefaultArtifact(coordinate), null));
+        }
+        return resolver;
+    }
+
     private static boolean isRelocatedLibrary(Path path) {
         int count = path.getNameCount();
         for (int i = 0; i < count - 2; i++) {

adapters/bukkit/plugin/src/main/java/art/arcane/iris/command/CommandDatapack.java

@@ -18,21 +18,41 @@
 
 package art.arcane.iris.command;
 
-import art.arcane.iris.pack.datapack.DatapackIngestService;
-import art.arcane.volmlib.util.collection.KList;
+import art.arcane.iris.Iris;
+import art.arcane.iris.command.handlers.DimensionHandler;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import art.arcane.iris.localization.BukkitCommandMessages;
 import art.arcane.iris.localization.C;
+import art.arcane.iris.localization.DirectorCommandMessages;
+import art.arcane.iris.localization.IrisLanguage;
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.DatapackIngestService;
+import art.arcane.iris.pack.datapack.export.DatapackExportDestinations;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import art.arcane.iris.pack.datapack.export.WorldgenExportService;
+import art.arcane.iris.pack.datapack.export.WorldgenExportServices;
+import art.arcane.iris.pack.datapack.export.WorldgenExportTargets;
+import art.arcane.iris.pack.datapack.export.ir.ExportDiagnostic;
 import art.arcane.iris.platform.bukkit.plugin.VolmitSender;
+import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.world.task.J;
+import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.director.annotations.Director;
 import art.arcane.volmlib.util.director.annotations.Param;
+import art.arcane.volmlib.util.localization.LanguageAudience;
+import art.arcane.volmlib.util.localization.MessageArgument;
+import art.arcane.volmlib.util.localization.TextKey;
 
 import java.util.List;
+import java.util.UUID;
 
-import art.arcane.iris.localization.IrisLanguage;
-import art.arcane.iris.localization.BukkitCommandMessages;
-import art.arcane.volmlib.util.localization.MessageArgument;
 @Director(name = "datapack", aliases = {"datapacks", "dp"}, description = "Download & manage external datapack imports", descriptionKey = "iris.director.commanddatapack.director.download_manage_external_datapack_imports_modrinth")
 public class CommandDatapack implements DirectorExecutor {
+    private static final int RESOURCE_REPORTS = 4;
+
     @Director(description = "Download/update every datapack listed in a pack dimension's 'datapackImports' and install it into the world so its structures register like vanilla", descriptionKey = "iris.director.commanddatapack.director.download_update_every_datapack_listed_pack_dimension_s_datapackimports_install_it_into", aliases = {"pull"})
     public void ingest(
             @Param(description = "Restart the server when new datapacks are installed (required for new structures to register and generate)", descriptionKey = "iris.director.commanddatapack.param.restart_server_when_new_datapacks_are_installed_required_new_structures_register_generate", defaultValue = "false")
@@ -71,4 +91,128 @@ public class CommandDatapack implements DirectorExecutor {
     ) {
         DatapackIngestService.remove(sender(), id);
     }
+
+    @Director(description = "Export a dimension as a vanilla worldgen datapack", descriptionKey = "iris.director.commanddatapack.director.export_dimension_vanilla_worldgen_datapack")
+    public void export(
+            @Param(name = "dimension", description = "The dimension to export", descriptionKey = "iris.director.commanddatapack.param.export_dimension", customHandler = DimensionHandler.class)
+            IrisDimension dimension,
+            @Param(name = "version", description = "Target Minecraft version, 26.3 or later (blank uses the latest)", descriptionKey = "iris.director.commanddatapack.param.export_version", defaultValue = "")
+            String version,
+            @Param(name = "mode", description = "Output mode: preset, dimension, or overworld", descriptionKey = "iris.director.commanddatapack.param.export_mode", defaultValue = WorldgenExportRequest.DEFAULT_MODE)
+            String mode,
+            @Param(name = "namespace", description = "Namespace for the exported resources", descriptionKey = "iris.director.commanddatapack.param.export_namespace", defaultValue = WorldgenExportRequest.DEFAULT_NAMESPACE)
+            String namespace,
+            @Param(name = "output", description = "Output name in the datapack exports folder (blank uses the dimension and version)", descriptionKey = "iris.director.commanddatapack.param.export_output", defaultValue = "")
+            String output,
+            @Param(name = "format", description = "zip or directory", descriptionKey = "iris.director.commanddatapack.param.export_format", defaultValue = WorldgenExportRequest.DEFAULT_FORMAT)
+            String format,
+            @Param(name = "objects", description = "Include objects as structure templates", descriptionKey = "iris.director.commanddatapack.param.export_objects", defaultValue = "true")
+            boolean objects,
+            @Param(name = "replace", description = "Replace an existing export with the same name", descriptionKey = "iris.director.commanddatapack.param.export_replace", defaultValue = "false")
+            boolean replace
+    ) {
+        VolmitSender sender = sender();
+        WorldgenExportRequest request = WorldgenExportRequest.builder()
+                .pack(dimension.getLoader().getDataFolder().toPath())
+                .dimension(dimension.getLoadKey())
+                .version(version)
+                .mode(mode)
+                .namespace(namespace)
+                .output(output)
+                .format(format)
+                .objects(objects)
+                .replace(replace)
+                .exportRoot(IrisPlatforms.get().dataFolder("exports", "datapacks").toPath())
+                .build();
+        DataVersion target;
+        try {
+            target = validateExport(request);
+        } catch (IllegalArgumentException invalid) {
+            sender.sendMessage(C.RED + IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_INVALID, MessageArgument.untrusted("reason", invalid.getMessage())));
+            return;
+        }
+        WorldgenExportService service = WorldgenExportServices.get();
+        sender.sendMessage(C.GRAY + IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_STARTED, MessageArgument.untrusted("dimension", request.dimension()), MessageArgument.untrusted("version", target.getVersion())));
+        UUID audience = LanguageAudience.current();
+        ExportFeedback feedback = new ExportFeedback(sender);
+        J.a(() -> LanguageAudience.run(audience, () -> runExport(service, request, feedback)));
+    }
+
+    static DataVersion validateExport(WorldgenExportRequest request) {
+        DataVersion target = WorldgenExportTargets.resolve(request.version());
+        WorldgenExportMode.parse(request.mode());
+        DatapackExportDestinations.parseFormat(request.format());
+        return target;
+    }
+
+    private static void runExport(WorldgenExportService service, WorldgenExportRequest request, ExportFeedback feedback) {
+        WorldgenExportResult result;
+        try {
+            result = service.export(request, feedback);
+        } catch (Throwable failure) {
+            Iris.reportError("Datapack export failed for '" + request.dimension() + "'.", failure);
+            feedback.send(C.RED, IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_FAILED, MessageArgument.untrusted("reason", IrisLanguage.errorDetail(failure))));
+            return;
+        }
+        reportExport(feedback, result);
+    }
+
+    private static void reportExport(ExportFeedback feedback, WorldgenExportResult result) {
+        for (ExportDiagnostic diagnostic : result.diagnostics()) {
+            feedback.send(diagnosticColor(diagnostic.severity()), IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_DIAGNOSTIC, MessageArgument.untrusted("key", diagnosticLabel(diagnostic)), MessageArgument.untrusted("message", diagnostic.message())));
+        }
+        if (result.isSuccess()) {
+            feedback.send(C.GREEN, IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_EXPORTED, MessageArgument.untrusted("path", result.output())));
+            return;
+        }
+        TextKey outcome = result.status() == WorldgenExportResult.Status.REJECTED
+                ? DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_REJECTED
+                : DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_FAILED;
+        feedback.send(C.RED, IrisLanguage.text(outcome, MessageArgument.untrusted("reason", result.message())));
+    }
+
+    private static C diagnosticColor(ExportDiagnostic.Severity severity) {
+        return switch (severity) {
+            case ERROR -> C.RED;
+            case WARNING -> C.YELLOW;
+            case INFO -> C.GRAY;
+        };
+    }
+
+    private static String diagnosticLabel(ExportDiagnostic diagnostic) {
+        return diagnostic.resource().isEmpty()
+                ? diagnostic.limit().name()
+                : diagnostic.limit().name() + " " + diagnostic.resource();
+    }
+
+    private static final class ExportFeedback implements WorldgenExportProgress {
+        private final VolmitSender sender;
+
+        private ExportFeedback(VolmitSender sender) {
+            this.sender = sender;
+        }
+
+        @Override
+        public void stage(String stage) {
+            send(C.GRAY, IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_STAGE, MessageArgument.untrusted("stage", stage)));
+        }
+
+        @Override
+        public void resources(int done, int total) {
+            int stride = Math.max(1, total / RESOURCE_REPORTS);
+            if (done != total && done % stride != 0) {
+                return;
+            }
+            send(C.GRAY, IrisLanguage.text(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_RESOURCES, MessageArgument.untrusted("done", done), MessageArgument.untrusted("total", total)));
+        }
+
+        private void send(C color, String message) {
+            String line = color + message;
+            if (sender.isPlayer()) {
+                J.runEntity(sender.player(), () -> sender.sendMessage(line));
+                return;
+            }
+            sender.sendMessage(line);
+        }
+    }
 }

adapters/bukkit/plugin/src/main/java/art/arcane/iris/command/CommandFind.java

@@ -31,8 +31,7 @@ import art.arcane.iris.structure.placement.IrisStructureLocator;
 import art.arcane.iris.structure.nativegen.NativeStructureGenerationPolicy;
 import art.arcane.iris.structure.placement.StructureReachability;
 import art.arcane.iris.world.history.GenerationSemanticQueries;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureQuery;
-import art.arcane.iris.generation.hydrology.runtime.IrisHydrologyRuntime;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureType;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.iris.structure.nativegen.IrisNativeStructureDecision;
 import art.arcane.iris.generation.terrain.IrisRegion;
@@ -196,9 +195,9 @@ public class CommandFind implements DirectorExecutor {
         EngineBukkitOps.gotoPOI(e, type, player(), teleport);
     }
 
-    @Director(description = "Find an accepted hydrology feature", sync = true)
+    @Director(description = "Find a hydrology water feature", sync = true)
     public void river(
-            @Param(description = "Feature type: surface, waterfall, underground, grotto, mouth, or a deep-fluid id", customHandler = HydrologyTypeHandler.class)
+            @Param(description = "Feature type: stream, river, major_river, cascade, waterfall, mouth, pond, lake, dam, sea_inlet or cave_pool", customHandler = HydrologyTypeHandler.class)
             String type,
             @Param(description = "Should you be teleported", defaultValue = "true")
             boolean teleport
@@ -212,42 +211,32 @@ public class CommandFind implements DirectorExecutor {
             }
             return;
         }
-        IrisHydrologyRuntime runtime = activeEngine.getComplex().getHydrologyRuntime();
-        HydrologyFeatureQuery query;
+        HydrologyFeatureType featureType;
         try {
-            query = HydrologyFeatureQuery.parse(type);
+            featureType = HydrologyFeatureType.parse(type);
         } catch (IllegalArgumentException error) {
             commandSender.sendMessage(C.RED + error.getMessage());
             return;
         }
+        String label = featureType.key().replace('_', ' ');
         Location origin = target.getLocation();
         World originWorld = origin.getWorld();
-        int requestedDistance = runtime == null
-                ? 8192
-                : Math.min(8192, runtime.settings().routing().tileSize() * 15);
-        int maximumDistance = runtime == null
-                ? requestedDistance
-                : runtime.maximumFeatureSearchDistance(
-                        origin.getBlockX(), origin.getBlockZ(), requestedDistance);
-        commandSender.sendMessage(C.GRAY + "Searching accepted hydrology plans for " + type + "...");
+        int maximumDistance = GenerationSemanticQueries.RIVER_SEARCH_DISTANCE;
+        commandSender.sendMessage(C.GRAY + GenerationSemanticQueries.riverSearchMessage(featureType, maximumDistance));
         J.a(() -> {
             try {
                 GenerationSemanticQueries.RiverResult feature = GenerationSemanticQueries.nearestRiver(
                         activeEngine,
-                        query,
+                        featureType,
                         origin.getBlockX(),
                         origin.getBlockZ(),
-                        maximumDistance,
-                        (int visited) -> sendStructureMessage(target, commandSender,
-                                C.GRAY + "Searched " + visited + " hydrology tiles for " + type + "...")
+                        maximumDistance
                 ).orElse(null);
                 if (feature == null) {
                     sendStructureMessage(target, commandSender,
-                            C.YELLOW + "No accepted " + type + " hydrology feature found within "
-                                    + maximumDistance + " blocks.");
+                            C.YELLOW + GenerationSemanticQueries.riverNotFoundMessage(featureType, maximumDistance));
                     return;
                 }
-                String label = type + " hydrology feature";
                 if (!teleport) {
                     sendStructureMessage(target, commandSender,
                             C.GREEN + "Found " + label + " at " + feature.x() + ", " + feature.y() + ", " + feature.z() + ".");
@@ -259,8 +248,9 @@ public class CommandFind implements DirectorExecutor {
                         target, originWorld, commandSender, label, destination, true);
             } catch (Throwable error) {
                 sendStructureMessage(target, commandSender,
-                        C.RED + "Could not locate " + type + " hydrology: " + error.getClass().getSimpleName());
-                Iris.reportError("Could not locate accepted hydrology feature '" + type + "'.", error);
+                        C.RED + "Could not search for " + label + ": " + error.getClass().getSimpleName()
+                                + (error.getMessage() == null ? "" : " - " + error.getMessage()));
+                Iris.reportError("Could not locate hydrology feature '" + featureType.key() + "'.", error);
             }
         });
     }

adapters/bukkit/plugin/src/main/java/art/arcane/iris/command/CommandJigsaw.java

@@ -21,8 +21,10 @@ import art.arcane.iris.structure.StructureImporter;
 import art.arcane.iris.structure.VillageImporter;
 import art.arcane.iris.structure.authoring.StructureKey;
 import art.arcane.iris.structure.authoring.StructureWriteResult;
-import art.arcane.iris.structure.export.VanillaJigsawExportFormat;
+import art.arcane.iris.pack.datapack.export.DatapackExportDestinations;
+import art.arcane.iris.pack.datapack.export.DatapackExportFormat;
 import art.arcane.iris.structure.export.VanillaJigsawExportRequest;
+import art.arcane.iris.structure.export.VanillaJigsawExportSettings;
 import art.arcane.iris.structure.export.VanillaJigsawExportSource;
 import art.arcane.iris.structure.graph.PlanarJigsawWorkcellResolver;
 import art.arcane.iris.generation.terrain.IrisDimension;
@@ -419,9 +421,9 @@ public class CommandJigsaw implements DirectorExecutor {
             sendError("Wait for the pending autosave or discard the edits before exporting the on-disk graph.");
             return;
         }
-        VanillaJigsawExportFormat exportFormat;
+        DatapackExportFormat exportFormat;
         try {
-            exportFormat = CommandJigsawExports.parseFormat(format);
+            exportFormat = DatapackExportDestinations.parseFormat(format);
         } catch (IllegalArgumentException exception) {
             sendError(exception.getMessage());
             return;
@@ -430,20 +432,21 @@ public class CommandJigsaw implements DirectorExecutor {
                 .toPath().toAbsolutePath().normalize();
         Path destination;
         try {
-            destination = CommandJigsawExports.resolveExportDestination(exportRoot, output, exportFormat);
+            destination = DatapackExportDestinations.resolve(exportRoot, output, exportFormat);
         } catch (IllegalArgumentException exception) {
             sendError(exception.getMessage());
             return;
         }
         VanillaJigsawExportRequest request;
         try {
-            request = VanillaJigsawExportRequest.builder(
-                            VanillaJigsawExportSource.forData(
-                                    context.request().source(), context.request().structureKey()), destination)
+            VanillaJigsawExportSource source = VanillaJigsawExportSource.forData(
+                    context.request().source(), context.request().structureKey());
+            request = VanillaJigsawExportRequest.builder(source, destination)
                     .namespace(namespace)
                     .resourcePath(context.request().structureKey())
                     .format(exportFormat)
                     .replaceExisting(replace)
+                    .settings(VanillaJigsawExportSettings.runtimeDefaults(source.loadStructure()))
                     .build();
         } catch (IllegalArgumentException exception) {
             sendError(exception.getMessage());

adapters/bukkit/plugin/src/main/java/art/arcane/iris/command/CommandJigsawExports.java

@@ -4,7 +4,7 @@ import art.arcane.iris.Iris;
 import art.arcane.iris.studio.jigsaw.JigsawStudioService;
 import art.arcane.iris.structure.export.VanillaJigsawDatapackExporter;
 import art.arcane.iris.structure.export.VanillaJigsawExportDiagnostic;
-import art.arcane.iris.structure.export.VanillaJigsawExportFormat;
+import art.arcane.iris.pack.datapack.export.DatapackExportDestinations;
 import art.arcane.iris.structure.export.VanillaJigsawExportRequest;
 import art.arcane.iris.structure.export.VanillaJigsawExportResult;
 import art.arcane.iris.localization.C;
@@ -13,18 +13,14 @@ import art.arcane.iris.world.task.J;
 import org.bukkit.entity.Player;
 
 import java.nio.file.Path;
-import java.util.Locale;
 import java.util.Objects;
 import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.regex.Pattern;
 
 final class CommandJigsawExports {
-    private static final Pattern EXPORT_OUTPUT_NAME = Pattern.compile("[a-zA-Z0-9_-][a-zA-Z0-9._-]{0,127}");
     private static final Set<UUID> EXPORTING_PLAYERS = ConcurrentHashMap.newKeySet();
-    private static final Set<Path> EXPORT_DESTINATIONS = ConcurrentHashMap.newKeySet();
 
     private CommandJigsawExports() {
     }
@@ -45,11 +41,11 @@ final class CommandJigsawExports {
 
     static boolean beginExport(UUID playerId, Path destination) {
         Objects.requireNonNull(playerId);
-        Path normalizedDestination = Objects.requireNonNull(destination).toAbsolutePath().normalize();
+        Objects.requireNonNull(destination);
         if (!EXPORTING_PLAYERS.add(playerId)) {
             return false;
         }
-        if (EXPORT_DESTINATIONS.add(normalizedDestination)) {
+        if (DatapackExportDestinations.claim(destination)) {
             return true;
         }
         EXPORTING_PLAYERS.remove(playerId);
@@ -58,7 +54,7 @@ final class CommandJigsawExports {
 
     static void finishExport(UUID playerId, Path destination) {
         EXPORTING_PLAYERS.remove(Objects.requireNonNull(playerId));
-        EXPORT_DESTINATIONS.remove(Objects.requireNonNull(destination).toAbsolutePath().normalize());
+        DatapackExportDestinations.release(destination);
     }
 
     static void runExport(ExportOperation operation) {
@@ -102,35 +98,6 @@ final class CommandJigsawExports {
                 + result.status() + ": " + result.output());
     }
 
-    static VanillaJigsawExportFormat parseFormat(String value) {
-        return switch (value.trim().toLowerCase(Locale.ROOT)) {
-            case "zip" -> VanillaJigsawExportFormat.ZIP;
-            case "directory", "dir", "folder" -> VanillaJigsawExportFormat.DIRECTORY;
-            default -> throw new IllegalArgumentException("Export format must be directory or zip.");
-        };
-    }
-
-    static Path resolveExportDestination(
-            Path exportRoot,
-            String output,
-            VanillaJigsawExportFormat format
-    ) {
-        Path root = Objects.requireNonNull(exportRoot, "Jigsaw export root").toAbsolutePath().normalize();
-        String requested = Objects.requireNonNull(output, "Jigsaw export output name");
-        String name = requested.trim();
-        if (!name.equals(requested) || !EXPORT_OUTPUT_NAME.matcher(name).matches()) {
-            throw new IllegalArgumentException(
-                    "Export output must be one file name using letters, numbers, '.', '_', or '-'.");
-        }
-        String fileName = format == VanillaJigsawExportFormat.ZIP && !name.endsWith(".zip")
-                ? name + ".zip" : name;
-        Path destination = root.resolve(fileName).normalize();
-        if (destination.equals(root) || !root.equals(destination.getParent())) {
-            throw new IllegalArgumentException("Export output must be one artifact inside the Studio exports folder.");
-        }
-        return destination;
-    }
-
     record ExportOperation(
             Player player,
             VolmitSender sender,

adapters/bukkit/plugin/src/main/java/art/arcane/iris/command/CommandStudio.java

@@ -21,10 +21,9 @@ package art.arcane.iris.command;
 import art.arcane.iris.Iris;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.studio.map.MapWindow;
+import art.arcane.iris.studio.map.PaletteExplorerStart;
 import art.arcane.iris.studio.view.GuiHost;
-import art.arcane.iris.studio.view.ImageMapStudioGUI;
-import art.arcane.iris.studio.view.NoiseExplorerGUI;
-import art.arcane.iris.studio.view.VisionGUI;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.studio.workspace.IrisProject;
 import art.arcane.iris.studio.workspace.IrisCodeWorkspace;
@@ -98,11 +97,14 @@ import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
 
 import art.arcane.iris.localization.IrisLanguage;
 import art.arcane.iris.localization.BukkitCommandMessages;
 import art.arcane.volmlib.util.localization.MessageArgument;
+import art.arcane.volmlib.util.localization.LanguageAudience;
 import art.arcane.iris.localization.BukkitCommandMessagesExtended;
 @Director(name = "studio", aliases = {"std", "s"}, description = "Studio Commands", descriptionKey = "iris.director.commandstudio.director.studio_commands")
 public class CommandStudio implements DirectorExecutor {
@@ -202,6 +204,22 @@ public class CommandStudio implements DirectorExecutor {
         }));
     }
 
+    @Director(description = "Hotload the active Studio pack", descriptionKey = "iris.director.commandstudio.director.hotload_active_studio_pack", aliases = {"refresh"}, origin = DirectorOrigin.BOTH)
+    public void hotload() {
+        VolmitSender commandSender = sender();
+        IrisProject project = Iris.service(StudioSVC.class).getActiveProject();
+        PlatformChunkGenerator generator = project == null ? null : project.getActiveProvider();
+        if (generator == null) {
+            commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STUDIO_NO_OPEN_STUDIO_PROJECTS));
+            return;
+        }
+
+        UUID audience = LanguageAudience.current();
+        commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STUDIO_HOTLOADING));
+        generator.hotloadAsync().whenComplete((ignored, failure) ->
+                LanguageAudience.run(audience, () -> sendHotloadResult(commandSender, failure)));
+    }
+
     @Director(description = "Toggle your Studio debug scoreboard", descriptionKey = "iris.director.commandstudio.director.toggle_your_studio_debug_scoreboard", aliases = {"board", "sidebar", "sb"}, origin = DirectorOrigin.PLAYER)
     public void scoreboard() {
         Player target = player();
@@ -255,15 +273,10 @@ public class CommandStudio implements DirectorExecutor {
             long seed
     ) {
         if (noGUI()) return;
-        sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_OPENING_NOISE_EXPLORER));
-
-        if (generator == null) {
-            NoiseExplorerGUI.launch();
-            return;
-        }
-
-        String generatorKey = generator.getLoadKey();
-        NoiseExplorerGUI.launchGeneratorKey(generatorKey, generator, seed);
+        VolmitSender commandSender = sender();
+        UUID openerId = commandSender.isPlayer() ? commandSender.player().getUniqueId() : null;
+        MapWindow.NoiseSelection selection = new MapWindow.NoiseSelection(generator == null ? null : generator.getLoadKey(), generator, seed);
+        withPlayerContext(opener -> openNoiseAtPlayer(commandSender, openerId, opener, selection));
     }
 
     @Director(description = "Open the image-map studio (External GUI)", descriptionKey = "iris.director.commandstudio.director.open_image_map_studio_external_gui", aliases = {"imap"})
@@ -279,8 +292,7 @@ public class CommandStudio implements DirectorExecutor {
             return;
         }
 
-        Engine activeEngine = IrisToolbelt.access(world).getEngine();
-        ImageMapStudioGUI.launch(activeEngine);
+        requestMapStart(world, MapWindow::openImageMaps);
         sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_OPENING_IMAGE_MAP_STUDIO));
     }
 
@@ -420,11 +432,61 @@ public class CommandStudio implements DirectorExecutor {
             return;
         }
 
-        UUID openerId = sender().isPlayer() ? player().getUniqueId() : null;
-        VisionGUI.launch(IrisToolbelt.access(world).getEngine(), openerId);
+        requestMapStart(world, MapWindow::openMap);
         sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_OPENING_MAP));
     }
 
+    // The map opens where the player stands when they are in that world, otherwise at the world origin.
+    private PaletteExplorerStart mapStartIn(World world, Player opener, UUID openerId) {
+        Location center = opener != null && opener.getWorld().equals(world) ? opener.getLocation() : null;
+        return new PaletteExplorerStart(
+                IrisToolbelt.access(world).getEngine(),
+                world.getUID(),
+                openerId,
+                null,
+                center == null ? 0D : center.getX(),
+                center == null ? 0D : center.getZ()
+        );
+    }
+
+    private void requestMapStart(World world, Consumer<PaletteExplorerStart> launch) {
+        UUID openerId = sender().isPlayer() ? player().getUniqueId() : null;
+        withPlayerContext(opener -> launch.accept(mapStartIn(world, opener, openerId)));
+    }
+
+    private void openNoiseAtPlayer(VolmitSender commandSender, UUID openerId, Player opener, MapWindow.NoiseSelection selection) {
+        World world = opener == null ? null : opener.getWorld();
+        PlatformChunkGenerator worldGenerator = world == null ? null : IrisToolbelt.access(world);
+        Engine engine = worldGenerator == null ? GuiHost.get().findActiveEngine() : worldGenerator.getEngine();
+        if (engine == null) {
+            commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_YOU_NEED_BE_SPECIFY_IRIS_GENERATED_WORLD));
+            return;
+        }
+        PaletteExplorerStart start = worldGenerator == null
+                ? new PaletteExplorerStart(engine, null, openerId, null, 0D, 0D)
+                : mapStartIn(world, opener, openerId);
+        MapWindow.openNoise(start, selection);
+        commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_OPENING_NOISE_EXPLORER));
+    }
+
+    private void withPlayerContext(Consumer<Player> action) {
+        Player opener = sender().isPlayer() ? player() : null;
+        if (opener == null) {
+            action.accept(null);
+            return;
+        }
+        AtomicBoolean completed = new AtomicBoolean();
+        Consumer<Player> complete = player -> {
+            if (completed.compareAndSet(false, true)) {
+                action.accept(player);
+            }
+        };
+        Runnable retired = () -> complete.accept(null);
+        if (!J.runEntity(opener, () -> complete.accept(opener.isOnline() ? opener : null), 0, retired)) {
+            retired.run();
+        }
+    }
+
     @Director(description = "Profiles the performance of a dimension", descriptionKey = "iris.director.commandstudio.director.profiles_performance_dimension", origin = DirectorOrigin.PLAYER)
     public void profile(
             @Param(description = "The dimension to profile", descriptionKey = "iris.director.commandstudio.param.dimension_profile", contextual = true, contextualOverride = true, defaultValue = "default", customHandler = DimensionHandler.class)
@@ -597,6 +659,16 @@ public class CommandStudio implements DirectorExecutor {
         sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_DONE, MessageArgument.untrusted("value", report.getPath())));
     }
 
+    private void sendHotloadResult(VolmitSender commandSender, Throwable failure) {
+        if (failure != null) {
+            Iris.reportError(failure);
+            commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STUDIO_HOTLOAD_FAILED,
+                    MessageArgument.untrusted("value", String.valueOf(failure.getMessage()))));
+            return;
+        }
+        commandSender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STUDIO_HOTLOADED));
+    }
+
     private PlatformChunkGenerator resolveProfileGenerator(IrisDimension dimension) {
         StudioSVC studioService = Iris.service(StudioSVC.class);
         if (studioService != null && studioService.isProjectOpen()) {

adapters/bukkit/plugin/src/main/java/art/arcane/iris/platform/agent/AttachSignal.java

@@ -0,0 +1,50 @@
+package art.arcane.iris.platform.agent;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.Linker;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
+import java.util.Locale;
+
+public final class AttachSignal {
+    private static final int SIGQUIT = 3;
+    private static final int SIGTERM = 15;
+    private static final long ACTION_BYTES = 256;
+    private static final long SIG_IGN = 1L;
+
+    private AttachSignal() {
+    }
+
+    public static boolean restoreJvmHandler() {
+        if (System.getProperty("os.name", "").toLowerCase(Locale.ROOT).contains("win")) {
+            return false;
+        }
+        Linker linker = Linker.nativeLinker();
+        MethodHandle sigaction = linker.downcallHandle(
+                linker.defaultLookup().find("sigaction")
+                        .orElseThrow(() -> new IllegalStateException("sigaction is unavailable")),
+                FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS));
+        try (Arena arena = Arena.ofConfined()) {
+            MemorySegment jvm = arena.allocate(ACTION_BYTES);
+            MemorySegment quit = arena.allocate(ACTION_BYTES);
+            if ((int) sigaction.invokeExact(SIGTERM, MemorySegment.NULL, jvm) != 0
+                    || (int) sigaction.invokeExact(SIGQUIT, MemorySegment.NULL, quit) != 0) {
+                throw new IllegalStateException("sigaction could not read the SIGTERM and SIGQUIT handlers");
+            }
+            long handler = jvm.get(ValueLayout.JAVA_LONG, 0);
+            if (handler == 0L || handler == SIG_IGN || quit.get(ValueLayout.JAVA_LONG, 0) == handler) {
+                return false;
+            }
+            if ((int) sigaction.invokeExact(SIGQUIT, jvm, MemorySegment.NULL) != 0) {
+                throw new IllegalStateException("sigaction could not restore the JVM SIGQUIT handler");
+            }
+            return true;
+        } catch (RuntimeException | Error failure) {
+            throw failure;
+        } catch (Throwable failure) {
+            throw new IllegalStateException("Unable to restore the JVM SIGQUIT handler", failure);
+        }
+    }
+}

adapters/bukkit/plugin/src/main/java/art/arcane/iris/platform/bukkit/api/IrisTerrainSVC.java

@@ -17,8 +17,7 @@ import art.arcane.iris.platform.bukkit.terrain.IrisSampleLimits;
 import art.arcane.iris.platform.bukkit.terrain.IrisSurfaceClassifier;
 import art.arcane.iris.platform.bukkit.terrain.IrisWorldInfoFactory;
 import art.arcane.iris.generation.runtime.Engine;
-import art.arcane.iris.generation.hydrology.HydrologyColumnLayer;
-import art.arcane.iris.generation.hydrology.HydrologyColumnSample;
+import art.arcane.iris.generation.hydrology.raster.WaterRole;
 import art.arcane.iris.generation.terrain.InferredType;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.iris.generation.terrain.IrisRegion;
@@ -108,15 +107,15 @@ public class IrisTerrainSVC implements IrisService, IrisTerrainService {
 
         try {
             int surface = engine.getHeight(blockX, blockZ);
-            HydrologyColumnSample hydrology = hydrologySample(engine, blockX, blockZ);
+            WaterRole role = engine.getComplex().getWaterRoleStream().get(blockX, blockZ);
             int fluid = (int) Math.round(
-                    engine.getComplex().getRiverWaterSurfaceStream().get(blockX, blockZ));
+                    engine.getComplex().getWaterHeadStream().get(blockX, blockZ));
             InferredType inferredType = null;
             if (IrisSurfaceClassifier.requiresSurfaceBiome(surface, fluid)) {
                 IrisBiome biome = engine.getSurfaceBiome(blockX, blockZ);
                 inferredType = biome == null ? null : biome.getInferredType();
             }
-            return IrisSurfaceClassifier.classify(surface, fluid, inferredType, hydrology);
+            return IrisSurfaceClassifier.classify(surface, fluid, inferredType, role);
         } catch (Throwable error) {
             reportQueryFault("surfaceKind", world, error);
             return IrisSurfaceKind.UNKNOWN;
@@ -266,12 +265,12 @@ public class IrisTerrainSVC implements IrisService, IrisTerrainService {
                     return false;
                 }
 
-                HydrologyColumnSample hydrology = wantRiver
-                        ? hydrologySample(engine, blockX, blockZ)
-                        : null;
+                WaterRole role = wantRiver
+                        ? engine.getComplex().getWaterRoleStream().get(blockX, blockZ)
+                        : WaterRole.NONE;
                 int surface = wantHeight || wantKind ? engine.getHeight(blockX, blockZ) : 0;
                 int fluid = wantRiver
-                        ? (int) Math.round(engine.getComplex().getRiverWaterSurfaceStream().get(blockX, blockZ))
+                        ? (int) Math.round(engine.getComplex().getWaterHeadStream().get(blockX, blockZ))
                         : engine.getDimension().getFluidHeight();
                 boolean needsBiome = wantBiome
                         || (wantKind && IrisSurfaceClassifier.requiresSurfaceBiome(surface, fluid));
@@ -281,29 +280,23 @@ public class IrisTerrainSVC implements IrisService, IrisTerrainService {
                                 surface,
                                 fluid,
                                 biome == null ? null : biome.getInferredType(),
-                                hydrology
+                                role
                         )
                         : IrisSurfaceKind.UNKNOWN;
                 String biomeKey = wantBiome && biome != null ? biome.getLoadKey() : null;
                 int natural = wantNaturalHeight
                         ? (int) Math.round(engine.getComplex().getNaturalHeightStream().get(blockX, blockZ)) + minHeight
                         : IrisColumnSample.UNAVAILABLE_HEIGHT;
-                HydrologyColumnLayer surfaceLayer = hydrology == null
-                        ? null
-                        : hydrology.primarySurfaceLayer().orElse(null);
-                boolean riverPresent = surfaceLayer != null;
                 IrisRiverState riverState = wantRiverState
-                        ? riverState(hydrology)
+                        ? riverState(role)
                         : IrisRiverState.NONE;
-                double riverDistance = wantRiverDistance && riverPresent
-                        ? engine.getComplex().getRiverDistanceStream().get(blockX, blockZ)
+                double riverDistance = wantRiverDistance
+                        ? riverDistance(role)
                         : IrisColumnSample.UNAVAILABLE_RIVER_DISTANCE;
-                int riverFlow = wantRiverFlow && riverPresent
-                        ? (int) Math.round(engine.getComplex().getRiverFlowStream().get(blockX, blockZ))
+                int riverFlow = wantRiverFlow
+                        ? riverFlow(role)
                         : IrisColumnSample.UNAVAILABLE_RIVER_FLOW;
-                int riverWaterSurfaceY = wantRiverWaterSurface
-                        && surfaceLayer != null
-                        && surfaceLayer.connectedFluid()
+                int riverWaterSurfaceY = wantRiverWaterSurface && role.wet()
                         ? fluid + minHeight
                         : IrisColumnSample.UNAVAILABLE_HEIGHT;
                 sink.accept(new IrisColumnSample(
@@ -327,21 +320,25 @@ public class IrisTerrainSVC implements IrisService, IrisTerrainService {
         }
     }
 
-    static IrisRiverState riverState(HydrologyColumnSample hydrology) {
-        HydrologyColumnLayer layer = hydrology == null
-                ? null
-                : hydrology.primarySurfaceLayer().orElse(null);
-        if (layer == null || !layer.channel()) {
-            return IrisRiverState.NONE;
-        }
-        return layer.connectedFluid() ? IrisRiverState.WET : IrisRiverState.DRY;
+    static IrisRiverState riverState(WaterRole role) {
+        return role.wet() ? IrisRiverState.WET : IrisRiverState.NONE;
     }
 
-    private static HydrologyColumnSample hydrologySample(Engine engine, int blockX, int blockZ) {
-        if (engine.getComplex().getHydrologyRuntime() == null) {
-            return null;
-        }
-        return engine.getComplex().getHydrologyRuntime().sample(blockX, blockZ).orElse(null);
+    static double riverDistance(WaterRole role) {
+        return switch (role) {
+            case NONE -> IrisColumnSample.UNAVAILABLE_RIVER_DISTANCE;
+            case CHANNEL, POND, MOUTH, CASCADE, WATERFALL, INLET -> 0D;
+            case SHORE, POND_SHORE -> 1D;
+            case BANK, DAM -> 2D;
+        };
+    }
+
+    static int riverFlow(WaterRole role) {
+        return switch (role) {
+            case NONE, SHORE, POND_SHORE, BANK, DAM -> IrisColumnSample.UNAVAILABLE_RIVER_FLOW;
+            case CHANNEL, MOUTH, CASCADE, WATERFALL -> 1;
+            case POND, INLET -> 0;
+        };
     }
 
     private static Optional<String> key(IrisBiome biome) {

adapters/bukkit/plugin/src/main/java/art/arcane/iris/platform/bukkit/terrain/IrisSurfaceClassifier.java

@@ -1,8 +1,7 @@
 package art.arcane.iris.platform.bukkit.terrain;
 
 import art.arcane.iris.api.terrain.IrisSurfaceKind;
-import art.arcane.iris.generation.hydrology.HydrologyColumnLayer;
-import art.arcane.iris.generation.hydrology.HydrologyColumnSample;
+import art.arcane.iris.generation.hydrology.raster.WaterRole;
 import art.arcane.iris.generation.terrain.InferredType;
 
 public final class IrisSurfaceClassifier {
@@ -29,25 +28,16 @@ public final class IrisSurfaceClassifier {
             int engineSurfaceHeight,
             int engineFluidHeight,
             InferredType inferredType,
-            HydrologyColumnSample hydrology
+            WaterRole role
     ) {
         if (engineSurfaceHeight <= 0) {
             return IrisSurfaceKind.VOID;
         }
-        HydrologyColumnLayer layer = hydrology == null
-                ? null
-                : hydrology.primarySurfaceLayer().orElse(null);
-        if (layer != null) {
-            if (layer.shore()) {
-                return IrisSurfaceKind.RIVER_SHORE;
-            }
-            if (layer.channel()) {
-                return layer.connectedFluid() ? IrisSurfaceKind.RIVER : IrisSurfaceKind.DRY_CHANNEL;
-            }
-            if (layer.grading()) {
-                return IrisSurfaceKind.LAND;
-            }
-        }
-        return classify(engineSurfaceHeight, engineFluidHeight, inferredType);
+        return switch (role) {
+            case NONE -> classify(engineSurfaceHeight, engineFluidHeight, inferredType);
+            case SHORE, POND_SHORE -> IrisSurfaceKind.RIVER_SHORE;
+            case BANK, DAM -> IrisSurfaceKind.LAND;
+            case CHANNEL, POND, MOUTH, CASCADE, WATERFALL, INLET -> IrisSurfaceKind.RIVER;
+        };
     }
 }

adapters/bukkit/plugin/src/main/java/art/arcane/iris/studio/view/BukkitGuiHost.java

@@ -23,6 +23,8 @@ import art.arcane.iris.world.event.IrisEngineHotloadEvent;
 import art.arcane.iris.world.IrisToolbelt;
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.platform.generation.PlatformChunkGenerator;
+import art.arcane.iris.studio.StudioSVC;
+import art.arcane.iris.studio.workspace.IrisProject;
 import org.bukkit.Bukkit;
 import org.bukkit.World;
 import org.bukkit.event.EventHandler;
@@ -40,16 +42,21 @@ public final class BukkitGuiHost implements GuiHost.Provider {
         GuiHost.set(new BukkitGuiHost());
     }
 
+    /**
+     * The engine of the open studio project, which reads the pack folder being edited, or else the first
+     * Iris world. A normal Iris world runs on its own copy of the pack, made when the world was created.
+     */
     @Override
     public Engine findActiveEngine() {
+        Engine studioEngine = findStudioEngine();
+        if (studioEngine != null) {
+            return studioEngine;
+        }
         try {
             for (World world : new ArrayList<>(Bukkit.getWorlds())) {
-                try {
-                    PlatformChunkGenerator access = IrisToolbelt.access(world);
-                    if (access != null && access.getEngine() != null && !access.getEngine().isClosed()) {
-                        return access.getEngine();
-                    }
-                } catch (Throwable ignored) {
+                Engine engine = engineOf(world);
+                if (engine != null) {
+                    return engine;
                 }
             }
         } catch (Throwable ignored) {
@@ -57,6 +64,35 @@ public final class BukkitGuiHost implements GuiHost.Provider {
         return null;
     }
 
+    @Override
+    public Engine findEngine(UUID worldId) {
+        World world = worldId == null ? null : Bukkit.getWorld(worldId);
+        return world == null ? null : engineOf(world);
+    }
+
+    private static Engine findStudioEngine() {
+        try {
+            StudioSVC studio = Iris.service(StudioSVC.class);
+            IrisProject project = studio == null || !studio.isProjectOpen() ? null : studio.getActiveProject();
+            PlatformChunkGenerator provider = project == null ? null : project.getActiveProvider();
+            Engine engine = provider == null ? null : provider.getEngine();
+            return engine == null || engine.isClosed() ? null : engine;
+        } catch (Throwable ignored) {
+            return null;
+        }
+    }
+
+    private static Engine engineOf(World world) {
+        try {
+            PlatformChunkGenerator access = IrisToolbelt.access(world);
+            if (access != null && access.getEngine() != null && !access.getEngine().isClosed()) {
+                return access.getEngine();
+            }
+        } catch (Throwable ignored) {
+        }
+        return null;
+    }
+
     @Override
     public void registerHotloadHook(Runnable onHotload) {
         Listener listener = new HotloadListener(onHotload);

adapters/bukkit/plugin/src/main/java/art/arcane/iris/studio/view/BukkitVisionOverlay.java

@@ -18,23 +18,19 @@
 
 package art.arcane.iris.studio.view;
 
-import art.arcane.volmlib.nativelib.view.WorldMarker;
-
-import art.arcane.iris.generation.runtime.IrisComplex;
 import art.arcane.iris.generation.runtime.Engine;
-import art.arcane.iris.studio.render.RenderType;
 import art.arcane.iris.world.IrisWorld;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.world.task.J;
 import art.arcane.volmlib.util.format.Form;
+import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.World;
 import org.bukkit.entity.LivingEntity;
 import org.bukkit.entity.Player;
 
-import java.io.File;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -56,7 +52,7 @@ public final class BukkitVisionOverlay implements GuiOverlay {
     private final AtomicBoolean playerRefreshQueued = new AtomicBoolean();
     private final AtomicLong teleportSequence = new AtomicLong();
     private final AtomicReference<VisionTeleportRequest> latestTeleport = new AtomicReference<>();
-    private volatile List<WorldMarker> playerMarkers = List.of();
+    private volatile List<GuiMarker> playerMarkers = List.of();
 
     public BukkitVisionOverlay(Engine engine, UUID openerId) {
         this.engine = engine;
@@ -68,7 +64,7 @@ public final class BukkitVisionOverlay implements GuiOverlay {
      * built by a server thread.
      */
     @Override
-    public List<WorldMarker> players() {
+    public List<GuiMarker> players() {
         queuePlayerRefresh();
         return playerMarkers;
     }
@@ -78,26 +74,48 @@ public final class BukkitVisionOverlay implements GuiOverlay {
             return;
         }
 
-        boolean scheduled = J.runGlobal(() -> {
-            try {
-                List<WorldMarker> markers = new ArrayList<>();
-                for (Player player : BukkitWorldBinding.players(engine.getWorld())) {
-                    Location at = player.getLocation();
-                    markers.add(WorldMarker.player(player.getName(), at.getX(), at.getZ()));
-                }
-                playerMarkers = List.copyOf(markers);
-            } finally {
-                playerRefreshQueued.set(false);
-            }
-        });
+        boolean scheduled = J.runGlobal(this::refreshPlayers);
 
         if (!scheduled) {
             playerRefreshQueued.set(false);
         }
     }
 
+    private void refreshPlayers() {
+        World world = BukkitWorldBinding.world(engine.getWorld());
+        List<Player> players = BukkitWorldBinding.players(engine.getWorld());
+        if (players.isEmpty() || world == null) {
+            playerMarkers = List.of();
+            playerRefreshQueued.set(false);
+            return;
+        }
+        List<GuiMarker> markers = Collections.synchronizedList(new ArrayList<>(players.size()));
+        AtomicInteger pending = new AtomicInteger(players.size());
+        for (Player player : players) {
+            AtomicBoolean completed = new AtomicBoolean();
+            Runnable complete = () -> {
+                if (completed.compareAndSet(false, true) && pending.decrementAndGet() == 0) {
+                    playerMarkers = List.copyOf(markers);
+                    playerRefreshQueued.set(false);
+                }
+            };
+            if (!J.runEntity(player, () -> {
+                try {
+                    if (player.isOnline() && player.getWorld() == world) {
+                        Location at = player.getLocation();
+                        markers.add(GuiMarker.player(player.getName(), at.getX(), at.getZ(), at.getYaw()));
+                    }
+                } finally {
+                    complete.run();
+                }
+            }, 0, complete)) {
+                complete.run();
+            }
+        }
+    }
+
     @Override
-    public void requestEntities(Consumer<List<WorldMarker>> sink) {
+    public void requestEntities(Consumer<List<GuiMarker>> sink) {
         J.runGlobal(() -> {
             IrisWorld target = engine.getWorld();
             World world = BukkitWorldBinding.world(target);
@@ -118,7 +136,7 @@ public final class BukkitVisionOverlay implements GuiOverlay {
                 return;
             }
 
-            List<WorldMarker> collected = Collections.synchronizedList(new ArrayList<>(living.size()));
+            List<GuiMarker> collected = Collections.synchronizedList(new ArrayList<>(living.size()));
             AtomicInteger pending = new AtomicInteger(living.size());
             Runnable complete = () -> {
                 if (pending.decrementAndGet() == 0) {
@@ -144,22 +162,22 @@ public final class BukkitVisionOverlay implements GuiOverlay {
         });
     }
 
-    private WorldMarker marker(LivingEntity entity, Location at) {
+    private GuiMarker marker(LivingEntity entity, Location at) {
         String label = Form.capitalizeWords(entity.getType().name().toLowerCase(Locale.ROOT).replaceAll("\\Q_\\E", " "));
         double maxHealth = 0;
         try {
             maxHealth = entity.getAttribute(MAX_HEALTH).getValue();
         } catch (Throwable ignored) {
         }
-        return WorldMarker.entity(label, at.getX(), at.getY(), at.getZ(), entity.getHealth(), maxHealth);
+        return GuiMarker.entity(label, at.getX(), at.getY(), at.getZ(), entity.getHealth(), maxHealth);
     }
 
     @Override
     public void teleport(double worldX, double worldZ) {
         VisionTeleportRequest request = new VisionTeleportRequest(
                 teleportSequence.incrementAndGet(),
-                VisionGUI.floorWorldCoordinate(worldX),
-                VisionGUI.floorWorldCoordinate(worldZ));
+                (int) StrictMath.floor(worldX),
+                (int) StrictMath.floor(worldZ));
         latestTeleport.set(request);
         startTeleport(request);
     }
@@ -212,6 +230,46 @@ public final class BukkitVisionOverlay implements GuiOverlay {
         }
     }
 
+    @Override
+    public void requestOpenerPosition(Consumer<OpenerPosition> sink) {
+        AtomicBoolean completed = new AtomicBoolean();
+        Consumer<OpenerPosition> complete = position -> {
+            if (completed.compareAndSet(false, true)) {
+                sink.accept(position);
+            }
+        };
+        if (openerId == null) {
+            complete.accept(OpenerPosition.OFFLINE);
+            return;
+        }
+        boolean scheduled = J.runGlobal(() -> {
+            Player player = Bukkit.getPlayer(openerId);
+            if (player == null) {
+                complete.accept(OpenerPosition.OFFLINE);
+                return;
+            }
+            Runnable retired = () -> complete.accept(OpenerPosition.OFFLINE);
+            if (!J.runEntity(player, () -> complete.accept(positionOf(player,
+                    BukkitWorldBinding.world(engine.getWorld()))), 0, retired)) {
+                retired.run();
+            }
+        });
+        if (!scheduled) {
+            complete.accept(OpenerPosition.OFFLINE);
+        }
+    }
+
+    private static OpenerPosition positionOf(Player player, World world) {
+        if (!player.isOnline()) {
+            return OpenerPosition.OFFLINE;
+        }
+        if (world == null || player.getWorld() != world) {
+            return OpenerPosition.IN_OTHER_WORLD;
+        }
+        Location at = player.getLocation();
+        return OpenerPosition.inWorld(at.getX(), at.getY(), at.getZ());
+    }
+
     private Player selectPlayer(List<Player> players) {
         if (openerId == null) {
             return players.isEmpty() ? null : players.get(0);
@@ -316,21 +374,6 @@ public final class BukkitVisionOverlay implements GuiOverlay {
                 + blockX + "," + blockZ + ".", failure);
     }
 
-    @Override
-    public String openInEditor(double worldX, double worldZ, RenderType type) {
-        IrisComplex complex = engine.getComplex();
-        File file = switch (type) {
-            case BIOME, LAYER_LOAD, DECORATOR_LOAD, OBJECT_LOAD, HEIGHT, RIVER ->
-                    complex.getTrueBiomeStream().get(worldX, worldZ).openInVSCode();
-            case BIOME_LAND -> complex.getLandBiomeStream().get(worldX, worldZ).openInVSCode();
-            case BIOME_SEA -> complex.getSeaBiomeStream().get(worldX, worldZ).openInVSCode();
-            case REGION -> complex.getRegionStream().get(worldX, worldZ).openInVSCode();
-            case CAVE_LAND -> complex.getCaveBiomeStream().get(worldX, worldZ).openInVSCode();
-            default -> null;
-        };
-        return file == null ? null : file.getName();
-    }
-
     private static final class VisionTeleportRequest {
         private final long sequence;
         private final int blockX;

adapters/bukkit/plugin/src/main/java/art/arcane/iris/world/PendingWorldReplacementManager.java

@@ -58,6 +58,7 @@ import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
@@ -78,6 +79,9 @@ public final class PendingWorldReplacementManager implements Listener {
     private volatile UUID overworldEntryAwaitingVerification;
     private volatile World overworldEntryWorld;
     private volatile boolean paperEntryListenerRegistered;
+    private final Object stagingMonitor = new Object();
+    private boolean stagingAdmissionOpen = true;
+    private StagingAdmission activeStaging;
 
     public PendingWorldReplacementManager(Iris plugin) {
         this.plugin = Objects.requireNonNull(plugin, "plugin");
@@ -135,7 +139,8 @@ public final class PendingWorldReplacementManager implements Listener {
                 LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
                 LifecycleOperationCoordinator.OperationKind.WORLD_REPLACE,
                 requiredWorldKey.toString()
-        ); WorldReplacementProgress progress = WorldReplacementProgress.start(
+        ); StagingAdmission ignoredAdmission = admitStaging(requiredWorldKey);
+             WorldReplacementProgress progress = WorldReplacementProgress.start(
                 requiredSender, requiredWorldKey.toString())) {
             synchronized (this) {
                 IrisStartupValidation.requireWorldReplacementStagingReady();
@@ -271,6 +276,29 @@ public final class PendingWorldReplacementManager implements Listener {
         }
     }
 
+    public void awaitStagingForShutdown() {
+        StagingAdmission staging;
+        synchronized (stagingMonitor) {
+            stagingAdmissionOpen = false;
+            staging = activeStaging;
+        }
+        if (staging == null) {
+            return;
+        }
+        Iris.warn("Waiting for the replacement of " + staging.worldKey + " to finish staging before Iris shuts down.");
+        boolean interrupted = false;
+        while (staging.finished.getCount() > 0L) {
+            try {
+                staging.finished.await();
+            } catch (InterruptedException e) {
+                interrupted = true;
+            }
+        }
+        if (interrupted) {
+            Thread.currentThread().interrupt();
+        }
+    }
+
     public synchronized void processPendingStartupReplacements() {
         ArrayList<String> failures = new ArrayList<>();
         ArrayList<String> restartBoundaries = new ArrayList<>();
@@ -1048,6 +1076,17 @@ public final class PendingWorldReplacementManager implements Listener {
         return plugin.getDataFolder().toPath().toAbsolutePath().normalize();
     }
 
+    private StagingAdmission admitStaging(NamespacedKey worldKey) throws IOException {
+        synchronized (stagingMonitor) {
+            if (!stagingAdmissionOpen) {
+                throw new IOException("Iris is shutting down. Run the replacement again after the server starts.");
+            }
+            StagingAdmission staging = new StagingAdmission(worldKey);
+            activeStaging = staging;
+            return staging;
+        }
+    }
+
     private synchronized void loadOverworldEntryGuard() throws IOException {
         ExactWorldSlotPathPolicy.Target target = resolveTarget(OVERWORLD_KEY);
         Optional<WorldReplacementEntryGuard.Entry> loaded = WorldReplacementEntryGuard.load(target.worldDirectory());
@@ -1218,6 +1257,25 @@ public final class PendingWorldReplacementManager implements Listener {
     record SavedLocationInspection(boolean safe, Throwable failure) {
     }
 
+    private final class StagingAdmission implements AutoCloseable {
+        private final NamespacedKey worldKey;
+        private final CountDownLatch finished = new CountDownLatch(1);
+
+        private StagingAdmission(NamespacedKey worldKey) {
+            this.worldKey = worldKey;
+        }
+
+        @Override
+        public void close() {
+            synchronized (stagingMonitor) {
+                if (activeStaging == this) {
+                    activeStaging = null;
+                }
+            }
+            finished.countDown();
+        }
+    }
+
     private static final class RestartBoundaryRequired extends IOException {
         private RestartBoundaryRequired(String message) {
             super(message);

adapters/bukkit/plugin/src/main/resources/plugin.yml

@@ -27,3 +27,4 @@ permissions:
     description: Allows survival players to fell Iris-managed trees with an axe.
     default: op
 api-version: '${apiVersion}'
+libraries: [ ${libraries} ]

adapters/bukkit/plugin/src/test/gameplay/studio-manual-hotload.mjs

@@ -0,0 +1,72 @@
+import { readFile, writeFile } from 'node:fs/promises'
+import path from 'node:path'
+import { setup, openStudio, closeStudio, sampleTerrain, readJson, writeJson,
+  logPosition, logSince } from './studio-support.mjs'
+
+async function hotload(context, fixture, active, command) {
+  const before = await readJson(fixture.manifestPath(active.key))
+  const response = await context.command(command, /^Studio hotloaded\.$|^Studio hotload failed:/, 90000)
+  context.expect(response === 'Studio hotloaded.', 'The manual Studio command did not complete successfully', { command, response })
+  const after = await readJson(fixture.manifestPath(active.key))
+  context.expect(after.pendingActivationId === null, 'The manual hotload completed with a pending activation')
+  context.report.iris.manualHotloads.push({ command, response,
+    before: before.activeActivationId, after: after.activeActivationId })
+  return after
+}
+
+export default {
+  name: 'iris-studio-manual-hotload',
+  description: 'Refresh an open Studio through hotload and its refresh alias, verify terrain, and reject commands without a Studio.',
+  async run(context) {
+    const fixture = await setup(context)
+    const biomeFile = path.join(fixture.pack, 'biomes', 'flat.json')
+    const original = await readFile(biomeFile, 'utf8')
+    const logOffset = await logPosition(fixture)
+    const processId = (await context.observe()).processId
+    context.report.iris.manualHotloads = []
+    let active
+    try {
+      await context.step('Reject hotload without an open Studio', async () => {
+        await context.command('/iris studio hotload', /^No open studio projects\.$/, 10000)
+      })
+      await context.step('Open Studio and hotload an unchanged pack', async () => {
+        active = await openStudio(context, fixture)
+        await sampleTerrain(context, fixture, 0, fixture.state.material)
+        await hotload(context, fixture, active, '/iris studio hotload')
+        await sampleTerrain(context, fixture, 4096, fixture.state.material)
+      })
+      await context.step('Refresh an edited pack and inspect newly generated terrain', async () => {
+        const before = await readJson(fixture.manifestPath(active.key))
+        const biome = await readJson(biomeFile)
+        biome.name = 'Manual hotload terrain'
+        biome.layers[0].palette[0].block = 'minecraft:gold_block'
+        await writeJson(biomeFile, biome)
+        await hotload(context, fixture, active, '/iris studio refresh')
+        const after = await fixture.wait(async () => {
+          const manifest = await readJson(fixture.manifestPath(active.key))
+          return manifest.activeActivationId !== before.activeActivationId && manifest.pendingActivationId === null ? manifest : false
+        }, 'The edited Studio pack did not become active', 90000)
+        context.report.iris.activations.push({ before: before.activeActivationId,
+          after: after.activeActivationId, material: 'gold_block' })
+        await sampleTerrain(context, fixture, 16384, 'gold_block')
+        await sampleTerrain(context, fixture, 0, fixture.state.material)
+      })
+      await context.step('Close Studio and reject another refresh', async () => {
+        await closeStudio(context, fixture, active)
+        active = undefined
+        await context.command('/iris studio refresh', /^No open studio projects\.$/, 10000)
+        await context.command('/minecraft:seed', /Seed:/i, 10000)
+      })
+      context.expect((await context.observe()).processId === processId, 'The server restarted during manual Studio hotload')
+      const log = await logSince(fixture, logOffset)
+      context.expect(!/Studio generation update failed|Studio hotload failed|Unable to (capture terrain|save the terrain boundary)|ClosedChannelException|Chunk system error|server has stopped responding|could not acquire its engine runtime|Failed to list files/i.test(log),
+        'Manual Studio hotload emitted a generation, snapshot, storage, or watchdog failure')
+    } finally {
+      try {
+        if (active) await closeStudio(context, fixture, active)
+      } finally {
+        await writeFile(biomeFile, original)
+      }
+    }
+  }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/FailedEnableLockTest.java

@@ -148,6 +148,9 @@ public class FailedEnableLockTest {
         try (EnableFixture fixture = new EnableFixture(false)) {
             IllegalStateException failure = assertThrows(IllegalStateException.class, plugin::onEnable);
             assertTrue(failure.getMessage(), failure.getMessage().contains("already bound"));
+            Field failed = Iris.class.getDeclaredField("enableFailed");
+            failed.setAccessible(true);
+            assertTrue(failed.getBoolean(plugin));
         }
     }
 

adapters/bukkit/plugin/src/test/java/art/arcane/iris/IrisErrorReportingTest.java

@@ -0,0 +1,80 @@
+package art.arcane.iris;
+
+import art.arcane.iris.configuration.IrisSettings;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.mockito.MockedStatic;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.PrintStream;
+import java.lang.reflect.Field;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public class IrisErrorReportingTest {
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void debugReportingPreservesStacklessFailures() throws Exception {
+        ArrayIndexOutOfBoundsException failure = new ArrayIndexOutOfBoundsException("raster index");
+        failure.setStackTrace(new StackTraceElement[0]);
+
+        String output = reportWithDebug(failure);
+
+        assertEquals(1L, output.lines().filter(line -> line.contains("raster index")).count());
+    }
+
+    @Test
+    public void debugReportingPreservesFailureWithStacklessCause() throws Exception {
+        ArrayIndexOutOfBoundsException cause = new ArrayIndexOutOfBoundsException("raster index");
+        cause.setStackTrace(new StackTraceElement[0]);
+        IllegalStateException failure = new IllegalStateException("Hydrology failed", cause);
+
+        String output = reportWithDebug(failure);
+
+        assertEquals(1L, output.lines().filter(line -> line.contains("Hydrology failed")).count());
+        assertTrue(output.contains("Caused by: java.lang.ArrayIndexOutOfBoundsException: raster index"));
+        assertTrue(output.contains("IrisErrorReportingTest.debugReportingPreservesFailureWithStacklessCause"));
+    }
+
+    private String reportWithDebug(Throwable failure) throws Exception {
+        Iris previousPlugin = Iris.instance;
+        IrisSettings previousSettings = IrisSettings.settings;
+        PrintStream previousError = System.err;
+        Iris plugin = mock(Iris.class);
+        Field deferred = Iris.class.getDeclaredField("serverStopTeardownDeferred");
+        deferred.setAccessible(true);
+        deferred.set(plugin, new AtomicBoolean());
+        File report = new File(temporaryFolder.getRoot(), "failure.txt");
+        when(plugin.getDataFile(any(String[].class))).thenReturn(report);
+        ByteArrayOutputStream output = new ByteArrayOutputStream();
+        try (PrintStream errors = new PrintStream(output, true, StandardCharsets.UTF_8);
+             MockedStatic<Iris> iris = mockStatic(Iris.class)) {
+            Iris.instance = plugin;
+            IrisSettings.settings = new IrisSettings();
+            IrisSettings.settings.getGeneral().setDebug(true);
+            System.setErr(errors);
+            iris.when(() -> Iris.reportError(failure)).thenCallRealMethod();
+
+            Iris.reportError(failure);
+
+            assertTrue(Files.readString(report.toPath()).contains(failure.toString()));
+            return output.toString(StandardCharsets.UTF_8);
+        } finally {
+            System.setErr(previousError);
+            IrisSettings.settings = previousSettings;
+            Iris.instance = previousPlugin;
+        }
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/IrisPluginLoaderTest.java

@@ -4,9 +4,13 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
+import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
 
 import static org.junit.Assert.assertEquals;
 
@@ -31,4 +35,19 @@ public class IrisPluginLoaderTest {
 
         assertEquals(List.of(relocatedCaffeine, relocatedGson), libraries);
     }
+
+    @Test
+    public void readsMavenLibrariesFromTheSpigotDescriptorInThePluginJar() throws Exception {
+        Path jar = temporaryFolder.getRoot().toPath().resolve("Iris.jar");
+        try (OutputStream file = Files.newOutputStream(jar); ZipOutputStream zip = new ZipOutputStream(file)) {
+            zip.putNextEntry(new ZipEntry("plugin.yml"));
+            zip.write("name: Iris\nlibraries: [ 'org.lwjgl:lwjgl:3.4.3', 'org.lwjgl:lwjgl:jar:natives-linux:3.4.3' ]\n"
+                    .getBytes(StandardCharsets.UTF_8));
+            zip.closeEntry();
+        }
+
+        List<String> libraries = IrisPluginLoader.mavenLibraries(jar);
+
+        assertEquals(List.of("org.lwjgl:lwjgl:3.4.3", "org.lwjgl:lwjgl:jar:natives-linux:3.4.3"), libraries);
+    }
 }

adapters/bukkit/plugin/src/test/java/art/arcane/iris/IrisShutdownMaintenanceTest.java

@@ -1,7 +1,17 @@
 package art.arcane.iris;
 
 import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.generation.concurrent.MultiBurst;
 import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.platform.agent.Agent;
+import art.arcane.iris.platform.bootstrap.SlimJar;
+import art.arcane.iris.platform.bukkit.BukkitPlatform;
+import art.arcane.iris.platform.bukkit.plugin.IrisService;
+import art.arcane.iris.platform.bukkit.plugin.VolmitPlugin;
+import art.arcane.iris.spi.IrisPlatforms;
+import art.arcane.iris.world.lifecycle.IrisRuntimeStatics;
+import art.arcane.volmlib.util.collection.KList;
+import art.arcane.volmlib.util.collection.KMap;
 import art.arcane.iris.generation.runtime.GenerationSessionLease;
 import art.arcane.iris.generation.runtime.GenerationSessionManager;
 import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
@@ -17,6 +27,7 @@ import art.arcane.iris.world.WorldMaintenance;
 import art.arcane.iris.world.runtime.BukkitEnginePlatformHooks;
 import art.arcane.iris.world.task.J;
 import art.arcane.volmlib.nativelib.terrain.ServerShutdownBoundary;
+import art.arcane.volmlib.integration.ReloadAware;
 import org.bukkit.Bukkit;
 import org.bukkit.NamespacedKey;
 import org.bukkit.World;
@@ -26,10 +37,13 @@ import org.mockito.MockedStatic;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.lang.reflect.InvocationTargetException;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
@@ -37,10 +51,16 @@ import java.util.concurrent.atomic.AtomicReference;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.CALLS_REAL_METHODS;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doCallRealMethod;
+import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mockStatic;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
@@ -109,8 +129,6 @@ public class IrisShutdownMaintenanceTest {
                 }
                 verify(fixture.generator).quiesceForServerShutdown();
                 verify(fixture.generator, never()).closeAsync();
-                fixture.nms.verify(INMS::get);
-                verify(fixture.binding).deferPluginClassLoaderClose();
                 verify(fixture.binding, never()).releasePluginClassLoaderClose();
             }
             assertEquals(0, sessions.activeLeases());
@@ -151,6 +169,229 @@ public class IrisShutdownMaintenanceTest {
         }
     }
 
+    @Test
+    public void startupEnsuresAgentReadinessBeforeLifecycleProtectionWithoutWorldInjection() throws Exception {
+        try (Fixture fixture = new Fixture(); MockedStatic<Agent> agent = mockStatic(Agent.class)) {
+            when(fixture.binding.supportsIrisWorldGeneration()).thenReturn(true);
+            agent.when(Agent::install).thenReturn(true);
+            doAnswer(invocation -> {
+                agent.verify(Agent::install);
+                assertSame(fixture.plugin.getClass().getClassLoader(), invocation.getArgument(0));
+                return null;
+            }).when(fixture.binding).initializeLifecycle(fixture.plugin.getClass().getClassLoader());
+            invoke(fixture.plugin, "initializeShutdownProtection");
+            verify(fixture.binding).initializeLifecycle(fixture.plugin.getClass().getClassLoader());
+            verify(fixture.binding, never()).injectBukkit();
+        }
+    }
+
+    @Test
+    public void unavailableAgentStopsLifecycleInitialization() throws Exception {
+        try (Fixture fixture = new Fixture(); MockedStatic<Agent> agent = mockStatic(Agent.class)) {
+            when(fixture.binding.supportsIrisWorldGeneration()).thenReturn(true);
+            InvocationTargetException failure = assertThrows(InvocationTargetException.class,
+                    () -> invoke(fixture.plugin, "initializeShutdownProtection"));
+            assertTrue(failure.getCause() instanceof IllegalStateException);
+            verify(fixture.binding, never()).initializeLifecycle(fixture.plugin.getClass().getClassLoader());
+        }
+    }
+
+    @Test
+    public void worldHookTeardownFailureReleasesProtectionAfterServicesAndWorkersStop() throws Exception {
+        try (Fixture fixture = new Fixture();
+             MockedStatic<Iris> iris = mockStatic(Iris.class);
+             MockedStatic<IrisRuntimeStatics> statics = mockStatic(IrisRuntimeStatics.class);
+             MockedStatic<IrisPlatforms> platforms = mockStatic(IrisPlatforms.class);
+             MockedStatic<BukkitPlatform> bukkitPlatform = mockStatic(BukkitPlatform.class);
+             MockedStatic<SlimJar> providers = mockStatic(SlimJar.class)) {
+            IrisService service = mock(IrisService.class);
+            IllegalStateException failure = new IllegalStateException("world hook teardown failed");
+            fixture.nms.when(INMS::isBound).thenReturn(true);
+            doThrow(failure).when(fixture.binding).uninjectBukkit();
+            setField(fixture.plugin, "services", new KMap<Class<? extends IrisService>, IrisService>());
+            setField(fixture.plugin, "enabledServices", List.of(service));
+            doAnswer(invocation -> {
+                platforms.verify(IrisPlatforms::unbind);
+                bukkitPlatform.verify(BukkitPlatform::releaseHost);
+                assertTrue(MultiBurst.burst.isTerminated());
+                assertTrue(MultiBurst.hydrology.isTerminated());
+                assertTrue(MultiBurst.ioBurst.isTerminated());
+                return null;
+            }).when(fixture.binding).releasePluginClassLoaderClose();
+            fixture.quiesce();
+            try {
+                fixture.finish(5L);
+                fixture.finish(5L);
+                verify(service).onDisable();
+                iris.verify(() -> Iris.reportError("Failed to remove Iris world-generation hooks.", failure));
+                assertTrue(MultiBurst.burst.isTerminated());
+                assertTrue(MultiBurst.hydrology.isTerminated());
+                assertTrue(MultiBurst.ioBurst.isTerminated());
+                verify(fixture.binding).releasePluginClassLoaderClose();
+                platforms.verify(IrisPlatforms::unbind);
+                bukkitPlatform.verify(BukkitPlatform::releaseHost);
+            } finally {
+                MultiBurst.burst.reopen();
+                MultiBurst.hydrology.reopen();
+                MultiBurst.ioBurst.reopen();
+            }
+        }
+    }
+
+    @Test
+    public void failedServiceWithAnOwnedExecutorRetainsTheClassLoader() throws Exception {
+        ExecutorService ownedExecutor = Executors.newSingleThreadExecutor();
+        CountDownLatch started = new CountDownLatch(1);
+        CountDownLatch finish = new CountDownLatch(1);
+        ownedExecutor.submit(() -> {
+            started.countDown();
+            finish.await();
+            return null;
+        });
+        try (Fixture fixture = new Fixture();
+             MockedStatic<Iris> iris = mockStatic(Iris.class);
+             MockedStatic<IrisRuntimeStatics> statics = mockStatic(IrisRuntimeStatics.class);
+             MockedStatic<IrisPlatforms> platforms = mockStatic(IrisPlatforms.class);
+             MockedStatic<BukkitPlatform> bukkitPlatform = mockStatic(BukkitPlatform.class)) {
+            assertTrue(started.await(5, TimeUnit.SECONDS));
+            IrisService service = mock(IrisService.class);
+            IllegalStateException failure = new IllegalStateException("service teardown failed");
+            doThrow(failure).when(service).onDisable();
+            setField(fixture.plugin, "services", new KMap<Class<? extends IrisService>, IrisService>());
+            setField(fixture.plugin, "enabledServices", List.of(service));
+            fixture.quiesce();
+            fixture.finish(5L);
+            verify(service).onDisable();
+            iris.verify(() -> Iris.reportError("Failed to disable " + service.getClass().getSimpleName() + ".", failure));
+            assertFalse(ownedExecutor.isTerminated());
+            verify(fixture.binding, never()).releasePluginClassLoaderClose();
+        } finally {
+            finish.countDown();
+            ownedExecutor.shutdownNow();
+            assertTrue(ownedExecutor.awaitTermination(5, TimeUnit.SECONDS));
+            MultiBurst.burst.reopen();
+            MultiBurst.hydrology.reopen();
+            MultiBurst.ioBurst.reopen();
+        }
+    }
+
+    @Test
+    public void failedPostShutdownCallbackRetainsTheClassLoaderForSkippedCleanup() throws Exception {
+        ExecutorService ownedExecutor = Executors.newSingleThreadExecutor();
+        CountDownLatch started = new CountDownLatch(1);
+        CountDownLatch finish = new CountDownLatch(1);
+        ownedExecutor.submit(() -> {
+            started.countDown();
+            finish.await();
+            return null;
+        });
+        try (Fixture fixture = new Fixture();
+             MockedStatic<Iris> iris = mockStatic(Iris.class);
+             MockedStatic<IrisRuntimeStatics> statics = mockStatic(IrisRuntimeStatics.class);
+             MockedStatic<IrisPlatforms> platforms = mockStatic(IrisPlatforms.class);
+             MockedStatic<BukkitPlatform> bukkitPlatform = mockStatic(BukkitPlatform.class)) {
+            assertTrue(started.await(5, TimeUnit.SECONDS));
+            IllegalStateException failure = new IllegalStateException("post-shutdown callback failed");
+            AtomicBoolean cleanupAttempted = new AtomicBoolean();
+            KList<Runnable> callbacks = new KList<>();
+            callbacks.add(() -> { throw failure; });
+            callbacks.add(() -> {
+                cleanupAttempted.set(true);
+                ownedExecutor.shutdown();
+            });
+            Field callbacksField = VolmitPlugin.class.getDeclaredField("postShutdown");
+            callbacksField.setAccessible(true);
+            callbacksField.set(fixture.plugin, callbacks);
+            Method runCallbacks = VolmitPlugin.class.getDeclaredMethod("runPostShutdown");
+            runCallbacks.setAccessible(true);
+            runCallbacks.invoke(doCallRealMethod().when(fixture.plugin));
+            fixture.quiesce();
+            fixture.finish(5L);
+            iris.verify(() -> Iris.reportError("Failed to run Iris post-shutdown cleanup.", failure));
+            assertFalse(cleanupAttempted.get());
+            assertFalse(ownedExecutor.isShutdown());
+            assertFalse(ownedExecutor.isTerminated());
+            verify(fixture.binding, never()).releasePluginClassLoaderClose();
+        } finally {
+            finish.countDown();
+            ownedExecutor.shutdownNow();
+            assertTrue(ownedExecutor.awaitTermination(5, TimeUnit.SECONDS));
+            MultiBurst.burst.reopen();
+            MultiBurst.hydrology.reopen();
+            MultiBurst.ioBurst.reopen();
+        }
+    }
+
+    @Test
+    public void incompleteDrainRetainsServicesWorkersAndClassLoader() throws Exception {
+        try (Fixture fixture = new Fixture(); MockedStatic<Iris> iris = mockStatic(Iris.class)) {
+            IrisService service = mock(IrisService.class);
+            setField(fixture.plugin, "services", new KMap<Class<? extends IrisService>, IrisService>());
+            setField(fixture.plugin, "enabledServices", List.of(service));
+            when(fixture.generator.closeAsync()).thenReturn(new CompletableFuture<>());
+            fixture.quiesce();
+            fixture.finish(0L);
+            verify(service, never()).onDisable();
+            verify(fixture.binding, never()).releasePluginClassLoaderClose();
+            verify(fixture.binding, never()).uninjectBukkit();
+        }
+    }
+
+    @Test
+    public void serverStopPreUnloadDefersTeardownWhileTheClassLoaderIsHeld() throws Exception {
+        try (Fixture fixture = new Fixture()) {
+            setField(fixture.plugin, "postStopFinisherStarted", new AtomicBoolean(true));
+            try {
+                fixture.commitReloadDuringServerStop();
+                verify(fixture.binding).deferPluginClassLoaderClose();
+                verify(fixture.generator).quiesceForServerShutdown();
+                verify(fixture.generator, never()).closeAsync();
+                assertTrue(fixture.serverStopTeardownDeferred());
+            } finally {
+                WorldMaintenance.endWorldMaintenance(fixture.identity, "pre-unload:HOT_UNLOAD");
+            }
+        }
+    }
+
+    @Test
+    public void serverStopPreUnloadDrainsInlineWhenTheClassLoaderCannotBeHeld() throws Exception {
+        try (Fixture fixture = new Fixture(); MockedStatic<Iris> iris = mockStatic(Iris.class)) {
+            IllegalStateException failure = new IllegalStateException("class loader hold failed");
+            doThrow(failure).when(fixture.binding).deferPluginClassLoaderClose();
+            try {
+                fixture.commitReloadDuringServerStop();
+                verify(fixture.generator).closeAsync();
+                verify(fixture.generator, never()).quiesceForServerShutdown();
+                assertFalse(fixture.serverStopTeardownDeferred());
+                iris.verify(() -> Iris.reportError("Failed to retain the Iris plugin class loader; draining shutdown inline.", failure));
+            } finally {
+                WorldMaintenance.endWorldMaintenance(fixture.identity, "pre-unload:HOT_UNLOAD", true);
+            }
+        }
+    }
+
+    @Test
+    public void serverStopPreUnloadDrainsInlineWithoutInitializedProtection() throws Exception {
+        try (Fixture fixture = new Fixture()) {
+            setField(fixture.plugin, "shutdownProtectionInitialized", false);
+            try {
+                fixture.commitReloadDuringServerStop();
+                verify(fixture.binding, never()).deferPluginClassLoaderClose();
+                verify(fixture.generator).closeAsync();
+                verify(fixture.generator, never()).quiesceForServerShutdown();
+                assertFalse(fixture.serverStopTeardownDeferred());
+            } finally {
+                WorldMaintenance.endWorldMaintenance(fixture.identity, "pre-unload:HOT_UNLOAD", true);
+            }
+        }
+    }
+
+    private static void invoke(Iris plugin, String name) throws ReflectiveOperationException {
+        Method method = Iris.class.getDeclaredMethod(name);
+        method.setAccessible(true);
+        method.invoke(plugin);
+    }
+
     private static void setField(Iris plugin, String name, Object value) throws ReflectiveOperationException {
         Field field = Iris.class.getDeclaredField(name);
         field.setAccessible(true);
@@ -178,6 +419,12 @@ public class IrisShutdownMaintenanceTest {
 
         private Fixture() throws ReflectiveOperationException {
             IrisSettings.settings = new IrisSettings();
+            setField(plugin, "shutdownProtectionInitialized", true);
+            setField(plugin, "alreadyDrained", new AtomicBoolean());
+            setField(plugin, "servicesDisabled", new AtomicBoolean());
+            setField(plugin, "runtimeTeardownFailed", new AtomicBoolean());
+            setField(plugin, "sharedRuntimeClosed", new AtomicBoolean());
+            setField(plugin, "terminalCleanupCompleted", new AtomicBoolean());
             setField(plugin, "serverStopTeardownDeferred", new AtomicBoolean());
             setField(plugin, "postStopFinisherStarted", new AtomicBoolean());
             setField(plugin, "deferredShutdownGenerators", new CopyOnWriteArrayList<PlatformChunkGenerator>());
@@ -206,6 +453,26 @@ public class IrisShutdownMaintenanceTest {
             method.invoke(plugin, "manual_disable", 5L);
         }
 
+        private void commitReloadDuringServerStop() throws ReflectiveOperationException {
+            setField(plugin, "alreadyDrained", new AtomicBoolean());
+            toolbelt.when(IrisToolbelt::isServerStopping).thenReturn(true);
+            doCallRealMethod().when(plugin).commitReload(any());
+            plugin.commitReload(ReloadAware.PreUnloadReason.HOT_UNLOAD);
+        }
+
+        private boolean serverStopTeardownDeferred() throws ReflectiveOperationException {
+            Field field = Iris.class.getDeclaredField("serverStopTeardownDeferred");
+            field.setAccessible(true);
+            return ((AtomicBoolean) field.get(plugin)).get();
+        }
+
+
+        private void finish(long timeoutSeconds) throws ReflectiveOperationException {
+            Method method = Iris.class.getDeclaredMethod("finishDeferredRuntimeTeardown", String.class, long.class);
+            method.setAccessible(true);
+            method.invoke(plugin, "test_shutdown", timeoutSeconds);
+        }
+
         private void startFinisher() throws ReflectiveOperationException {
             Method method = Iris.class.getDeclaredMethod("startPostStopFinisher");
             method.setAccessible(true);

adapters/bukkit/plugin/src/test/java/art/arcane/iris/command/CommandDatapackExportContractTest.java

@@ -0,0 +1,104 @@
+package art.arcane.iris.command;
+
+import art.arcane.iris.command.handlers.DimensionHandler;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import art.arcane.iris.localization.IrisLanguage;
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.volmlib.util.director.annotations.Director;
+import art.arcane.volmlib.util.director.annotations.Param;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+
+public class CommandDatapackExportContractTest {
+    private static final List<String> NAMES = List.of(
+            "dimension", "version", "mode", "namespace", "output", "format", "objects", "replace");
+    private static final List<String> DEFAULTS = List.of(
+            Param.NO_DEFAULT, "", "overworld", "iris_export", "", "zip", "true", "false");
+
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void exportParametersAreNamedInOrder() throws Exception {
+        List<String> names = new ArrayList<>();
+        for (Parameter parameter : exportMethod().getParameters()) {
+            names.add(parameter.getAnnotation(Param.class).name());
+        }
+
+        assertEquals(NAMES, names);
+    }
+
+    @Test
+    public void dimensionIsPositionalAndEveryOtherParameterIsKeyedWithItsDefault() throws Exception {
+        Parameter[] parameters = exportMethod().getParameters();
+        List<String> defaults = new ArrayList<>();
+        for (Parameter parameter : parameters) {
+            defaults.add(parameter.getAnnotation(Param.class).defaultValue());
+        }
+
+        assertEquals(DEFAULTS, defaults);
+        assertEquals(DimensionHandler.class, parameters[0].getAnnotation(Param.class).customHandler());
+    }
+
+    @Test
+    public void exportCommandAndParametersUseRegisteredDescriptions() throws Exception {
+        Method export = exportMethod();
+        Director director = export.getAnnotation(Director.class);
+
+        assertNotNull(director);
+        assertEquals(0L, Arrays.stream(director.aliases()).filter((String alias) -> !alias.isBlank()).count());
+        assertNotNull(director.descriptionKey(), IrisLanguage.catalog().key(director.descriptionKey()));
+        for (Parameter parameter : export.getParameters()) {
+            String key = parameter.getAnnotation(Param.class).descriptionKey();
+            assertNotNull(key, IrisLanguage.catalog().key(key));
+        }
+    }
+
+    @Test
+    public void validRequestResolvesItsTarget() {
+        assertSame(DataVersion.V26_3, CommandDatapack.validateExport(request().build()));
+        assertSame(DataVersion.V26_3, CommandDatapack.validateExport(request().version("26.3").build()));
+    }
+
+    @Test
+    public void unsupportedArgumentsAreRejectedWithSharedMessages() {
+        assertEquals("Unsupported datapack export version '1.21.1'. Supported: 26.3",
+                reason(request().version("1.21.1").build()));
+        assertEquals("Unsupported datapack export version '26.2'. Supported: 26.3",
+                reason(request().version("26.2").build()));
+        assertEquals("Unknown export mode 'nether'. Expected: preset, dimension, overworld",
+                reason(request().mode("nether").build()));
+        assertEquals("Export format must be directory or zip.", reason(request().format("rar").build()));
+    }
+
+    private WorldgenExportRequest.Builder request() {
+        Path root = temporaryFolder.getRoot().toPath();
+        return WorldgenExportRequest.builder()
+                .pack(root.resolve("packs").resolve("overworld"))
+                .dimension("overworld")
+                .exportRoot(root.resolve("exports"));
+    }
+
+    private static String reason(WorldgenExportRequest request) {
+        return assertThrows(IllegalArgumentException.class, () -> CommandDatapack.validateExport(request)).getMessage();
+    }
+
+    private static Method exportMethod() throws NoSuchMethodException {
+        return CommandDatapack.class.getDeclaredMethod("export", IrisDimension.class, String.class, String.class,
+                String.class, String.class, String.class, boolean.class, boolean.class);
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/command/CommandFindHydrologyTest.java

@@ -1,7 +1,7 @@
 package art.arcane.iris.command;
 
 import art.arcane.iris.Iris;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureType;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureType;
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.generation.runtime.IrisComplex;
 import art.arcane.iris.localization.IrisLanguage;
@@ -22,6 +22,7 @@ import java.util.OptionalLong;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.atomic.AtomicReference;
 
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
@@ -45,7 +46,7 @@ public class CommandFindHydrologyTest {
     @Test
     public void worldChangeDuringSearchDoesNotLoadOrTeleportIntoTheNewWorld() {
         try (Fixture fixture = new Fixture()) {
-            fixture.command.river("surface", true);
+            fixture.command.river("river", true);
             when(fixture.player.getWorld()).thenReturn(mock(World.class));
             fixture.search.get().run();
 
@@ -58,7 +59,7 @@ public class CommandFindHydrologyTest {
     @Test
     public void disconnectDuringSearchDoesNotLoadTheDestination() {
         try (Fixture fixture = new Fixture()) {
-            fixture.command.river("surface", true);
+            fixture.command.river("river", true);
             when(fixture.player.isOnline()).thenReturn(false);
             fixture.search.get().run();
 
@@ -69,7 +70,7 @@ public class CommandFindHydrologyTest {
     @Test
     public void worldChangeWhileLoadingTheDestinationCancelsTeleport() {
         try (Fixture fixture = new Fixture()) {
-            fixture.command.river("surface", true);
+            fixture.command.river("river", true);
             fixture.search.get().run();
             when(fixture.player.getWorld()).thenReturn(mock(World.class));
             fixture.chunk.complete(mock(Chunk.class));
@@ -82,7 +83,7 @@ public class CommandFindHydrologyTest {
     @Test
     public void successIsReportedOnlyAfterTeleportCompletes() {
         try (Fixture fixture = new Fixture()) {
-            fixture.command.river("surface", true);
+            fixture.command.river("river", true);
             fixture.search.get().run();
             fixture.chunk.complete(mock(Chunk.class));
 
@@ -95,7 +96,7 @@ public class CommandFindHydrologyTest {
     @Test
     public void rejectedTeleportReportsFailureWithoutSuccess() {
         try (Fixture fixture = new Fixture()) {
-            fixture.command.river("surface", true);
+            fixture.command.river("river", true);
             fixture.search.get().run();
             fixture.chunk.complete(mock(Chunk.class));
             fixture.teleport.complete(false);
@@ -109,7 +110,7 @@ public class CommandFindHydrologyTest {
     public void failedTeleportReportsTheFullCauseWithoutSuccess() {
         try (Fixture fixture = new Fixture()) {
             IllegalStateException failure = new IllegalStateException("destination unloaded");
-            fixture.command.river("surface", true);
+            fixture.command.river("river", true);
             fixture.search.get().run();
             fixture.chunk.complete(mock(Chunk.class));
             fixture.teleport.completeExceptionally(failure);
@@ -120,6 +121,72 @@ public class CommandFindHydrologyTest {
         }
     }
 
+    @Test
+    public void everyFeatureTypeIsSearchedOffTheCommandThreadAtTheRuntimeRadius() {
+        for (HydrologyFeatureType type : HydrologyFeatureType.values()) {
+            try (Fixture fixture = new Fixture()) {
+                fixture.command.river(type.key(), false);
+                fixture.queries.verify(() -> GenerationSemanticQueries.nearestRiver(any(), any(), anyInt(), anyInt(), anyInt()), never());
+                fixture.search.get().run();
+
+                fixture.queries.verify(() -> GenerationSemanticQueries.nearestRiver(fixture.engine, type, 0, 0,
+                        GenerationSemanticQueries.RIVER_SEARCH_DISTANCE));
+                verify(fixture.sender).sendMessage(contains("Found " + type.key().replace('_', ' ') + " at 32, 63, 32."));
+            }
+        }
+    }
+
+    @Test
+    public void unknownTypeIsRejectedWithTheAcceptedTypesBeforeAnySearch() {
+        try (Fixture fixture = new Fixture()) {
+            fixture.command.river("surface", true);
+
+            verify(fixture.sender).sendMessage(contains("Use one of: stream, river, major_river, cascade, waterfall, mouth, pond, lake, dam, sea_inlet, cave_pool."));
+            assertNull(fixture.search.get());
+        }
+    }
+
+    @Test
+    public void missingCavePoolIsReportedAsNotFoundInGeneratedChunks() {
+        try (Fixture fixture = new Fixture()) {
+            fixture.queries.when(() -> GenerationSemanticQueries.nearestRiver(eq(fixture.engine), any(), eq(0), eq(0), anyInt()))
+                    .thenReturn(Optional.empty());
+            fixture.command.river("cave_pool", true);
+            fixture.search.get().run();
+
+            verify(fixture.sender).sendMessage(contains("Searching generated chunks for the nearest cave pool within 7168 blocks"));
+            verify(fixture.sender).sendMessage(contains("No cave pool found in generated chunks within 7168 blocks."));
+        }
+    }
+
+    @Test
+    public void missingFeatureIsReportedAsNotFound() {
+        try (Fixture fixture = new Fixture()) {
+            fixture.queries.when(() -> GenerationSemanticQueries.nearestRiver(eq(fixture.engine), any(), eq(0), eq(0), anyInt()))
+                    .thenReturn(Optional.empty());
+            fixture.command.river("sea_inlet", true);
+            fixture.search.get().run();
+
+            verify(fixture.sender).sendMessage(contains("No sea inlet found within 7168 blocks."));
+            fixture.platform.verify(() -> BukkitPlatform.chunkAtAsync(any(World.class), anyInt(), anyInt(), eq(true)), never());
+        }
+    }
+
+    @Test
+    public void plannerFailureIsReportedAsAnErrorNotAsNotFound() {
+        try (Fixture fixture = new Fixture()) {
+            IllegalStateException failure = new IllegalStateException("window planner exploded");
+            fixture.queries.when(() -> GenerationSemanticQueries.nearestRiver(eq(fixture.engine), any(), eq(0), eq(0), anyInt()))
+                    .thenThrow(failure);
+            fixture.command.river("lake", true);
+            fixture.search.get().run();
+
+            verify(fixture.sender).sendMessage(contains("Could not search for lake: IllegalStateException - window planner exploded"));
+            verify(fixture.sender, never()).sendMessage(contains("No lake found"));
+            fixture.logging.verify(() -> Iris.reportError(any(String.class), eq(failure)));
+        }
+    }
+
     private static final class Fixture implements AutoCloseable {
         private final CommandFind command = mock(CommandFind.class, CALLS_REAL_METHODS);
         private final Engine engine = mock(Engine.class);
@@ -132,7 +199,7 @@ public class CommandFindHydrologyTest {
         private final CompletableFuture<Boolean> teleport = new CompletableFuture<>();
         private final MockedStatic<J> scheduler = mockStatic(J.class);
         private final MockedStatic<BukkitPlatform> platform = mockStatic(BukkitPlatform.class);
-        private final MockedStatic<GenerationSemanticQueries> queries = mockStatic(GenerationSemanticQueries.class);
+        private final MockedStatic<GenerationSemanticQueries> queries = mockStatic(GenerationSemanticQueries.class, CALLS_REAL_METHODS);
         private final MockedStatic<IrisLanguage> language = mockStatic(IrisLanguage.class, invocation -> "teleported");
         private final MockedStatic<Iris> logging = mockStatic(Iris.class);
 
@@ -160,10 +227,10 @@ public class CommandFindHydrologyTest {
             });
             platform.when(() -> BukkitPlatform.chunkAtAsync(any(World.class), anyInt(), anyInt(), eq(true))).thenReturn(chunk);
             platform.when(() -> BukkitPlatform.teleportAsync(eq(player), any(Location.class))).thenReturn(teleport);
-            queries.when(() -> GenerationSemanticQueries.nearestRiver(eq(engine), any(), eq(0), eq(0), anyInt(), any()))
+            queries.when(() -> GenerationSemanticQueries.nearestRiver(eq(engine), any(), eq(0), eq(0), anyInt()))
                     .thenReturn(Optional.of(new GenerationSemanticQueries.RiverResult(
                             GenerationSemanticQueries.RiverSource.ACTIVE_PREDICTION,
-                            HydrologyFeatureType.RIFFLE, Optional.empty(), 1L, 32, 63, 32, OptionalLong.empty())));
+                            HydrologyFeatureType.RIVER, 1L, 32, 63, 32, OptionalLong.empty())));
         }
 
         @Override

adapters/bukkit/plugin/src/test/java/art/arcane/iris/command/CommandJigsawContractTest.java

@@ -17,7 +17,6 @@ import art.arcane.iris.structure.authoring.StructureOwnershipManifest;
 import art.arcane.iris.structure.authoring.StructureSource;
 import art.arcane.iris.structure.authoring.StructureTransactionWriter;
 import art.arcane.iris.structure.conversion.IrisStructureAdoptionInputKind;
-import art.arcane.iris.structure.export.VanillaJigsawExportFormat;
 import art.arcane.iris.world.IrisCreator;
 import art.arcane.iris.generation.terrain.IrisDimension;
 import art.arcane.iris.pack.value.IrisDirection;
@@ -413,24 +412,6 @@ public class CommandJigsawContractTest {
         }
     }
 
-    @Test
-    public void exportOutputIsOneSafeChildArtifact() {
-        Path root = Path.of("build", "jigsaw-exports").toAbsolutePath().normalize();
-
-        assertEquals(root.resolve("village.zip"), CommandJigsawExports.resolveExportDestination(
-                root, "village", VanillaJigsawExportFormat.ZIP));
-        assertEquals(root.resolve("village"), CommandJigsawExports.resolveExportDestination(
-                root, "village", VanillaJigsawExportFormat.DIRECTORY));
-        assertThrows(IllegalArgumentException.class, () -> CommandJigsawExports.resolveExportDestination(
-                root, "", VanillaJigsawExportFormat.DIRECTORY));
-        assertThrows(IllegalArgumentException.class, () -> CommandJigsawExports.resolveExportDestination(
-                root, ".", VanillaJigsawExportFormat.DIRECTORY));
-        assertThrows(IllegalArgumentException.class, () -> CommandJigsawExports.resolveExportDestination(
-                root, "../all-exports", VanillaJigsawExportFormat.DIRECTORY));
-        assertThrows(IllegalArgumentException.class, () -> CommandJigsawExports.resolveExportDestination(
-                root, "nested/export", VanillaJigsawExportFormat.DIRECTORY));
-    }
-
     @Test
     public void exportLeaseRejectsDuplicatePlayerAndDestination() {
         UUID firstPlayer = UUID.randomUUID();

adapters/bukkit/plugin/src/test/java/art/arcane/iris/command/CommandObjectFluidHeightTest.java

@@ -20,26 +20,26 @@ import static org.mockito.Mockito.when;
 
 public class CommandObjectFluidHeightTest {
     @Test
-    public void absoluteObjectPlacementShiftsTheColumnRiverHeadFromNegativeMinY() {
+    public void absoluteObjectPlacementShiftsTheColumnWaterHeadFromNegativeMinY() {
         World world = mock(World.class);
         Engine engine = mock(Engine.class);
         IrisDimension dimension = mock(IrisDimension.class);
         IrisComplex complex = mock(IrisComplex.class);
         @SuppressWarnings("unchecked")
-        ProceduralStream<Double> riverHead = mock(ProceduralStream.class);
+        ProceduralStream<Double> waterHead = mock(ProceduralStream.class);
         Map<Block, BlockData> future = new HashMap<>();
 
         when(engine.getMinHeight()).thenReturn(-64);
         when(engine.getDimension()).thenReturn(dimension);
         when(engine.getComplex()).thenReturn(complex);
         when(dimension.getFluidHeight()).thenReturn(127);
-        when(complex.getRiverWaterSurfaceStream()).thenReturn(riverHead);
-        when(riverHead.get(12, -7)).thenReturn(131D);
+        when(complex.getWaterHeadStream()).thenReturn(waterHead);
+        when(waterHead.get(12, -7)).thenReturn(131D);
 
         IObjectPlacer placer = CommandObject.createPlacer(world, future, engine);
 
         assertEquals(63, placer.getFluidHeight());
         assertEquals(67, placer.getFluidHeight(12, -7));
-        verify(riverHead).get(12, -7);
+        verify(waterHead).get(12, -7);
     }
 }

adapters/bukkit/plugin/src/test/java/art/arcane/iris/command/CommandStudioHotloadTest.java

@@ -0,0 +1,112 @@
+package art.arcane.iris.command;
+
+import art.arcane.iris.Iris;
+import art.arcane.iris.platform.bukkit.plugin.VolmitSender;
+import art.arcane.iris.platform.generation.PlatformChunkGenerator;
+import art.arcane.iris.studio.StudioSVC;
+import art.arcane.iris.studio.workspace.IrisProject;
+import art.arcane.volmlib.util.director.annotations.Director;
+import art.arcane.volmlib.util.localization.LanguageAudience;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.lang.reflect.Method;
+import java.io.File;
+import java.util.concurrent.CompletableFuture;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class CommandStudioHotloadTest {
+    @Test
+    public void hotloadAndRefreshReportWhenNoStudioIsOpen() throws Exception {
+        RecordingSender sender = new RecordingSender();
+        StudioSVC studio = mock(StudioSVC.class);
+        Method hotload = CommandStudio.class.getDeclaredMethod("hotload");
+        assertTrue(List.of(hotload.getAnnotation(Director.class).aliases()).contains("refresh"));
+
+        try (MockedStatic<Iris> iris = mockStatic(Iris.class)) {
+            iris.when(() -> Iris.service(StudioSVC.class)).thenReturn(studio);
+            hotload.invoke(new TestCommand(sender));
+            assertTrue(sender.messages.getLast(), sender.messages.getLast().contains("No open studio"));
+        }
+    }
+
+    @Test
+    public void completionFeedbackWaitsForTheHotload() {
+        assertCompletionFeedback(null, "Studio hotloaded.");
+    }
+
+    @Test
+    public void failedHotloadReportsFailureAndLogsTheCause() {
+        assertCompletionFeedback(new IllegalStateException("Invalid pack"), "Studio hotload failed: Invalid pack");
+    }
+
+    private void assertCompletionFeedback(Throwable failure, String expected) {
+        RecordingSender sender = new RecordingSender();
+        StudioSVC studio = mock(StudioSVC.class);
+        PlatformChunkGenerator generator = mock(PlatformChunkGenerator.class);
+        IrisProject project = new IrisProject(new File("tutorial"));
+        project.setActiveProvider(generator);
+        CompletableFuture<Void> pending = new CompletableFuture<>();
+        UUID audience = UUID.randomUUID();
+        when(studio.getActiveProject()).thenReturn(project);
+        when(generator.hotloadAsync()).thenReturn(pending);
+
+        try (MockedStatic<Iris> iris = mockStatic(Iris.class)) {
+            iris.when(() -> Iris.service(StudioSVC.class)).thenReturn(studio);
+            LanguageAudience.run(audience, () -> new TestCommand(sender).hotload());
+            assertNull(LanguageAudience.current());
+
+            verify(generator).hotloadAsync();
+            assertEquals(1, sender.messages.size());
+            assertTrue(sender.messages.getFirst().contains("Hotloading Studio"));
+            if (failure == null) {
+                pending.complete(null);
+            } else {
+                pending.completeExceptionally(failure);
+                iris.verify(() -> Iris.reportError(failure));
+            }
+            assertEquals(2, sender.messages.size());
+            assertTrue(sender.messages.getLast(), sender.messages.getLast().contains(expected));
+            assertEquals(List.of(audience, audience), sender.audiences);
+            assertNull(LanguageAudience.current());
+        }
+    }
+
+    private static final class TestCommand extends CommandStudio {
+        private final VolmitSender sender;
+
+        private TestCommand(VolmitSender sender) {
+            this.sender = sender;
+        }
+
+        @Override
+        public VolmitSender sender() {
+            return sender;
+        }
+    }
+
+    private static final class RecordingSender extends VolmitSender {
+        private final List<String> messages = new ArrayList<>();
+        private final List<UUID> audiences = new ArrayList<>();
+
+        private RecordingSender() {
+            super(null);
+        }
+
+        @Override
+        public void sendMessage(String message) {
+            messages.add(message);
+            audiences.add(LanguageAudience.current());
+        }
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/command/StudioMapPositionTest.java

@@ -0,0 +1,99 @@
+package art.arcane.iris.command;
+
+import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.platform.bukkit.plugin.VolmitSender;
+import art.arcane.iris.platform.generation.PlatformChunkGenerator;
+import art.arcane.iris.studio.map.MapWindow;
+import art.arcane.iris.studio.map.PaletteExplorerStart;
+import art.arcane.iris.studio.view.GuiHost;
+import art.arcane.iris.world.IrisToolbelt;
+import art.arcane.iris.world.task.J;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.entity.Player;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.same;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public class StudioMapPositionTest {
+    @Test
+    public void mapCapturesItsStartingPositionOnThePlayerScheduler() {
+        IrisSettings previous = IrisSettings.settings;
+        IrisSettings.settings = new IrisSettings();
+        IrisSettings.settings.getGui().setUseServerLaunchedGuis(true);
+        World world = mock(World.class);
+        Player player = mock(Player.class);
+        VolmitSender sender = mock(VolmitSender.class);
+        PlatformChunkGenerator generator = mock(PlatformChunkGenerator.class);
+        Engine engine = mock(Engine.class);
+        UUID playerId = UUID.randomUUID();
+        UUID worldId = UUID.randomUUID();
+        AtomicBoolean owned = new AtomicBoolean();
+        AtomicReference<Runnable> task = new AtomicReference<>();
+        AtomicReference<PaletteExplorerStart> start = new AtomicReference<>();
+        when(world.getUID()).thenReturn(worldId);
+        when(player.getUniqueId()).thenReturn(playerId);
+        when(player.isOnline()).thenReturn(true);
+        when(player.getWorld()).thenAnswer(invocation -> {
+            assertTrue("world read must use the player scheduler", owned.get());
+            return world;
+        });
+        when(player.getLocation()).thenAnswer(invocation -> {
+            assertTrue("location read must use the player scheduler", owned.get());
+            return new Location(world, 33.25D, 91D, -72.5D);
+        });
+        when(sender.isPlayer()).thenReturn(true);
+        when(sender.player()).thenReturn(player);
+        when(generator.getEngine()).thenReturn(engine);
+        CommandStudio command = new CommandStudio() {
+            @Override
+            public VolmitSender sender() {
+                return sender;
+            }
+        };
+        try (MockedStatic<GuiHost> host = mockStatic(GuiHost.class);
+             MockedStatic<IrisToolbelt> toolbelt = mockStatic(IrisToolbelt.class);
+             MockedStatic<J> scheduling = mockStatic(J.class);
+             MockedStatic<MapWindow> windows = mockStatic(MapWindow.class)) {
+            host.when(GuiHost::isAvailable).thenReturn(true);
+            toolbelt.when(() -> IrisToolbelt.isIrisWorld(world)).thenReturn(true);
+            toolbelt.when(() -> IrisToolbelt.access(world)).thenReturn(generator);
+            scheduling.when(() -> J.runEntity(same(player), any(Runnable.class), eq(0), any(Runnable.class)))
+                    .thenAnswer(invocation -> {
+                        task.set(invocation.getArgument(1));
+                        return true;
+                    });
+            windows.when(() -> MapWindow.openMap(any(PaletteExplorerStart.class))).thenAnswer(invocation -> {
+                start.set(invocation.getArgument(0));
+                return null;
+            });
+
+            command.map(world);
+            assertNull(start.get());
+            owned.set(true);
+            task.get().run();
+
+            assertEquals(engine, start.get().engine());
+            assertEquals(playerId, start.get().playerId());
+            assertEquals(worldId, start.get().worldId());
+            assertEquals(33.25D, start.get().centerX(), 0D);
+            assertEquals(-72.5D, start.get().centerZ(), 0D);
+        } finally {
+            IrisSettings.settings = previous;
+        }
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/platform/agent/AttachSignalTest.java

@@ -0,0 +1,57 @@
+package art.arcane.iris.platform.agent;
+
+import org.junit.Test;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.Linker;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
+import java.util.Locale;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeFalse;
+
+public class AttachSignalTest {
+    private static final int SIGQUIT = 3;
+    private static final int SIGTERM = 15;
+    private static final long ACTION_BYTES = 256;
+    private static final MethodHandle SIGACTION = Linker.nativeLinker().downcallHandle(
+            Linker.nativeLinker().defaultLookup().find("sigaction").orElseThrow(),
+            FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS));
+
+    @Test
+    public void aConsoleThatResetsQuitGetsTheJvmHandlerBack() throws Throwable {
+        assumeFalse(System.getProperty("os.name").toLowerCase(Locale.ROOT).contains("win"));
+        long jvmHandler = handler(SIGTERM);
+        assertNotEquals(0L, jvmHandler);
+        try (Arena arena = Arena.ofConfined()) {
+            MemorySegment original = arena.allocate(ACTION_BYTES);
+            assertEquals(0, (int) SIGACTION.invokeExact(SIGQUIT, MemorySegment.NULL, original));
+            try {
+                MemorySegment reset = arena.allocate(ACTION_BYTES);
+                assertEquals(0, (int) SIGACTION.invokeExact(SIGQUIT, reset, MemorySegment.NULL));
+                assertEquals(0L, handler(SIGQUIT));
+
+                assertTrue(AttachSignal.restoreJvmHandler());
+
+                assertEquals(jvmHandler, handler(SIGQUIT));
+                assertFalse(AttachSignal.restoreJvmHandler());
+            } finally {
+                assertEquals(0, (int) SIGACTION.invokeExact(SIGQUIT, original, MemorySegment.NULL));
+            }
+        }
+    }
+
+    private static long handler(int signal) throws Throwable {
+        try (Arena arena = Arena.ofConfined()) {
+            MemorySegment action = arena.allocate(ACTION_BYTES);
+            assertEquals(0, (int) SIGACTION.invokeExact(signal, MemorySegment.NULL, action));
+            return action.get(ValueLayout.JAVA_LONG, 0);
+        }
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/platform/bukkit/api/IrisTerrainSVCTest.java

@@ -9,16 +9,18 @@ import art.arcane.iris.configuration.IrisSettings;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.iris.generation.runtime.BiomeEnvironment;
 import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.IrisComplex;
+import art.arcane.iris.generation.terrain.InferredType;
 import art.arcane.iris.generation.terrain.IrisDimension;
 import art.arcane.iris.generation.terrain.IrisRegion;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.platform.generation.PlatformChunkGenerator;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.world.history.SavedBiomeUnavailableException;
-import art.arcane.iris.generation.hydrology.HydrologyColumnLayer;
-import art.arcane.iris.generation.hydrology.HydrologyColumnSample;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureRef;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureType;
+import art.arcane.volmlib.util.stream.ProceduralStream;
+import art.arcane.volmlib.util.stream.interpolation.Interpolated;
+import art.arcane.iris.api.terrain.IrisColumnSample;
+import art.arcane.iris.generation.hydrology.raster.WaterRole;
 import art.arcane.iris.platform.bukkit.plugin.IrisService;
 import org.bukkit.World;
 import org.bukkit.generator.ChunkGenerator;
@@ -26,6 +28,7 @@ import org.junit.Test;
 import org.mockito.MockedStatic;
 
 import java.lang.reflect.Field;
+import java.util.ArrayList;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Optional;
@@ -112,10 +115,32 @@ public class IrisTerrainSVCTest {
     }
 
     @Test
-    public void acceptedHydrologyMapsToThePublicDiagnosticStates() {
-        assertEquals(IrisRiverState.NONE, IrisTerrainSVC.riverState(null));
-        assertEquals(IrisRiverState.WET, IrisTerrainSVC.riverState(river(true)));
-        assertEquals(IrisRiverState.DRY, IrisTerrainSVC.riverState(river(false)));
+    public void waterRolesMapToThePublicRiverFields() {
+        for (WaterRole role : WaterRole.values()) {
+            assertEquals(role.name(), role.wet() ? IrisRiverState.WET : IrisRiverState.NONE, IrisTerrainSVC.riverState(role));
+            double distance = switch (role) {
+                case NONE -> IrisColumnSample.UNAVAILABLE_RIVER_DISTANCE;
+                case CHANNEL, POND, MOUTH, CASCADE, WATERFALL, INLET -> 0D;
+                case SHORE, POND_SHORE -> 1D;
+                case BANK, DAM -> 2D;
+            };
+            assertEquals(role.name(), distance, IrisTerrainSVC.riverDistance(role), 0D);
+            int flow = switch (role) {
+                case NONE, SHORE, POND_SHORE, BANK, DAM -> IrisColumnSample.UNAVAILABLE_RIVER_FLOW;
+                case CHANNEL, MOUTH, CASCADE, WATERFALL -> 1;
+                case POND, INLET -> 0;
+            };
+            assertEquals(role.name(), flow, IrisTerrainSVC.riverFlow(role));
+        }
+    }
+
+    @Test
+    public void columnSamplesReportTheWaterRoleOfEachColumn() throws Exception {
+        assertEquals(List.of("RIVER", "WET", "0.0", "1", "6"), sampled(WaterRole.CHANNEL, 70));
+        assertEquals(List.of("RIVER", "WET", "0.0", "0", "6"), sampled(WaterRole.POND, 70));
+        assertEquals(List.of("RIVER_SHORE", "NONE", "1.0", "-1", "unavailable"), sampled(WaterRole.SHORE, 50));
+        assertEquals(List.of("LAND", "NONE", "2.0", "-1", "unavailable"), sampled(WaterRole.BANK, 50));
+        assertEquals(List.of("LAND", "NONE", "NaN", "-1", "unavailable"), sampled(WaterRole.NONE, 50));
     }
 
     @Test
@@ -219,6 +244,33 @@ public class IrisTerrainSVCTest {
         }
     }
 
+    private static List<String> sampled(WaterRole role, int head) throws Exception {
+        Engine engine = mock(Engine.class);
+        IrisComplex complex = mock(IrisComplex.class);
+        IrisBiome biome = mock(IrisBiome.class);
+        when(biome.getInferredType()).thenReturn(InferredType.LAND);
+        when(engine.getComplex()).thenReturn(complex);
+        when(engine.getDimension()).thenReturn(mock(IrisDimension.class));
+        when(engine.getHeight(0, 0)).thenReturn(60);
+        when(engine.getMinHeight()).thenReturn(-64);
+        when(engine.getSurfaceBiome(0, 0)).thenReturn(biome);
+        when(complex.getWaterRoleStream()).thenReturn(ProceduralStream.of((x, z) -> role, Interpolated.of(value -> 0D, value -> role)));
+        when(complex.getWaterHeadStream()).thenReturn(ProceduralStream.ofDouble((x, z) -> (double) head));
+        IrisColumnQuery query = IrisColumnQuery.rect(0, 0, 0, 0, 1, EnumSet.of(IrisColumnField.SURFACE_KIND,
+                IrisColumnField.RIVER_STATE, IrisColumnField.RIVER_DISTANCE, IrisColumnField.RIVER_FLOW,
+                IrisColumnField.RIVER_WATER_SURFACE_Y));
+        List<IrisColumnSample> samples = new ArrayList<>();
+        try (MockedStatic<IrisSettings> settings = mockStatic(IrisSettings.class)) {
+            settings.when(IrisSettings::get).thenReturn(new IrisSettings());
+            assertTrue(enabledService().sampleColumns(world(engine), query, samples::add));
+        }
+        assertEquals(1, samples.size());
+        IrisColumnSample sample = samples.get(0);
+        return List.of(sample.surfaceKind().name(), sample.riverState().name(), String.valueOf(sample.riverDistance()),
+                String.valueOf(sample.riverFlow()),
+                sample.riverWaterSurfaceY() == IrisColumnSample.UNAVAILABLE_HEIGHT ? "unavailable" : String.valueOf(sample.riverWaterSurfaceY()));
+    }
+
     private static World world(Engine engine) {
         World world = mock(World.class);
         ChunkGenerator generator = mock(ChunkGenerator.class, withSettings().extraInterfaces(PlatformChunkGenerator.class));
@@ -235,41 +287,4 @@ public class IrisTerrainSVCTest {
         ((AtomicBoolean) enabled.get(service)).set(true);
         return service;
     }
-
-    private static HydrologyColumnSample river(boolean connectedFluid) {
-        HydrologyFeatureRef feature = new HydrologyFeatureRef(
-                1L,
-                HydrologyFeatureType.SURFACE_POOL,
-                2L,
-                3L,
-                0,
-                63,
-                0,
-                1,
-                0,
-                false
-        );
-        HydrologyColumnLayer layer = new HydrologyColumnLayer(
-                feature,
-                60,
-                63,
-                63,
-                true,
-                false,
-                false,
-                connectedFluid,
-                false,
-                false,
-                true,
-                connectedFluid,
-                false,
-                "water",
-                "river",
-                "mouth",
-                "shore",
-                "dry",
-                "cave"
-        );
-        return new HydrologyColumnSample(0, 0, 70, 63, false, "parent", List.of(layer));
-    }
 }

adapters/bukkit/plugin/src/test/java/art/arcane/iris/platform/bukkit/terrain/IrisSurfaceClassifierTest.java

@@ -1,15 +1,10 @@
 package art.arcane.iris.platform.bukkit.terrain;
 
 import art.arcane.iris.api.terrain.IrisSurfaceKind;
-import art.arcane.iris.generation.hydrology.HydrologyColumnLayer;
-import art.arcane.iris.generation.hydrology.HydrologyColumnSample;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureRef;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureType;
+import art.arcane.iris.generation.hydrology.raster.WaterRole;
 import art.arcane.iris.generation.terrain.InferredType;
 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.assertTrue;
@@ -69,98 +64,28 @@ public class IrisSurfaceClassifierTest {
     }
 
     @Test
-    public void acceptedSurfaceRolesOverrideGenericOceanAndLandKinds() {
-        assertEquals(IrisSurfaceKind.RIVER, IrisSurfaceClassifier.classify(
-                60,
-                63,
-                InferredType.SEA,
-                hydrology(HydrologyFeatureType.SURFACE_POOL, true, false, true)
-        ));
-        assertEquals(IrisSurfaceKind.RIVER, IrisSurfaceClassifier.classify(
-                60,
-                63,
-                InferredType.SEA,
-                hydrology(HydrologyFeatureType.MOUTH, true, false, true)
-        ));
-        assertEquals(IrisSurfaceKind.RIVER_SHORE, IrisSurfaceClassifier.classify(
-                64,
-                63,
-                InferredType.SHORE,
-                hydrology(HydrologyFeatureType.SURFACE_POOL, false, true, false)
-        ));
-        assertEquals(IrisSurfaceKind.DRY_CHANNEL, IrisSurfaceClassifier.classify(
-                60,
-                60,
-                InferredType.LAND,
-                hydrology(HydrologyFeatureType.SURFACE_POOL, true, false, false)
-        ));
-        assertEquals(IrisSurfaceKind.LAND, IrisSurfaceClassifier.classify(
-                60,
-                60,
-                InferredType.LAND,
-                hydrology(HydrologyFeatureType.SURFACE_POOL, false, false, false)
-        ));
+    public void waterRolesOverrideGenericOceanAndLandKinds() {
+        for (WaterRole role : WaterRole.values()) {
+            IrisSurfaceKind expected = switch (role) {
+                case NONE -> IrisSurfaceKind.OCEAN;
+                case SHORE, POND_SHORE -> IrisSurfaceKind.RIVER_SHORE;
+                case BANK, DAM -> IrisSurfaceKind.LAND;
+                case CHANNEL, POND, MOUTH, CASCADE, WATERFALL, INLET -> IrisSurfaceKind.RIVER;
+            };
+            assertEquals(role.name(), expected, IrisSurfaceClassifier.classify(60, 63, InferredType.SEA, role));
+        }
     }
 
     @Test
-    public void voidClassificationWinsOverAcceptedRiverGeometry() {
-        assertEquals(IrisSurfaceKind.VOID, IrisSurfaceClassifier.classify(
-                0,
-                63,
-                InferredType.LAND,
-                hydrology(HydrologyFeatureType.SURFACE_POOL, true, false, true)
-        ));
+    public void voidClassificationWinsOverWaterRoles() {
+        for (WaterRole role : WaterRole.values()) {
+            assertEquals(role.name(), IrisSurfaceKind.VOID, IrisSurfaceClassifier.classify(0, 63, InferredType.LAND, role));
+        }
     }
 
     @Test
-    public void absentRejectedCandidatesDoNotCreatePublicRiverKinds() {
-        assertEquals(IrisSurfaceKind.LAND, IrisSurfaceClassifier.classify(
-                64,
-                63,
-                InferredType.LAND,
-                null
-        ));
-    }
-
-    private static HydrologyColumnSample hydrology(
-            HydrologyFeatureType type,
-            boolean channel,
-            boolean shore,
-            boolean connectedFluid
-    ) {
-        HydrologyFeatureRef feature = new HydrologyFeatureRef(
-                1L,
-                type,
-                2L,
-                3L,
-                0,
-                63,
-                0,
-                1,
-                0,
-                false
-        );
-        HydrologyColumnLayer layer = new HydrologyColumnLayer(
-                feature,
-                60,
-                63,
-                63,
-                channel,
-                shore,
-                !channel && !shore,
-                connectedFluid,
-                false,
-                false,
-                true,
-                connectedFluid && channel,
-                false,
-                "water",
-                "river",
-                "mouth",
-                "shore",
-                "dry",
-                "cave"
-        );
-        return new HydrologyColumnSample(0, 0, 70, 63, false, "parent", List.of(layer));
+    public void columnsWithoutAWaterRoleKeepTheGenericKinds() {
+        assertEquals(IrisSurfaceKind.LAND, IrisSurfaceClassifier.classify(64, 63, InferredType.LAND, WaterRole.NONE));
+        assertEquals(IrisSurfaceKind.SHORE, IrisSurfaceClassifier.classify(64, 63, InferredType.SHORE, WaterRole.NONE));
     }
 }

adapters/bukkit/plugin/src/test/java/art/arcane/iris/studio/view/BukkitOpenerPositionTest.java

@@ -0,0 +1,165 @@
+package art.arcane.iris.studio.view;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
+import art.arcane.iris.world.IrisWorld;
+import art.arcane.iris.world.task.J;
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.entity.Player;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.same;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public class BukkitOpenerPositionTest {
+    @Test
+    public void playerMarkersAreCapturedOnTheirEntitySchedulers() {
+        try (Harness harness = new Harness()) {
+            harness.binding.when(() -> BukkitWorldBinding.players(harness.target)).thenReturn(List.of(harness.player));
+            when(harness.player.getName()).thenReturn("Explorer");
+            assertTrue(harness.overlay.players().isEmpty());
+
+            harness.runEntity();
+
+            List<GuiMarker> markers = harness.overlay.players();
+            assertEquals(1, markers.size());
+            assertEquals("Explorer", markers.getFirst().label());
+            assertEquals(18.5D, markers.getFirst().worldX(), 0D);
+            assertEquals(-4.25D, markers.getFirst().worldZ(), 0D);
+        }
+    }
+
+    @Test
+    public void positionIsCapturedOnlyOnTheOwningEntityTask() {
+        try (Harness harness = new Harness()) {
+            harness.overlay.requestOpenerPosition(harness.results::add);
+            assertTrue(harness.results.isEmpty());
+
+            harness.runEntity();
+
+            assertEquals(List.of(OpenerPosition.inWorld(18.5D, 72D, -4.25D)), harness.results);
+        }
+    }
+
+    @Test
+    public void retiredEntityCompletesTheRequestOnce() {
+        try (Harness harness = new Harness()) {
+            harness.overlay.requestOpenerPosition(harness.results::add);
+            assertTrue("retirement callback must be registered", harness.retired != null);
+
+            harness.retired.run();
+            harness.retired.run();
+
+            assertEquals(List.of(OpenerPosition.OFFLINE), harness.results);
+        }
+    }
+
+    @Test
+    public void disconnectBeforeCaptureCompletesAsOfflineAndReconnectCanRefresh() {
+        try (Harness harness = new Harness()) {
+            harness.overlay.requestOpenerPosition(harness.results::add);
+            when(harness.player.isOnline()).thenReturn(false);
+            harness.runEntity();
+            assertEquals(List.of(OpenerPosition.OFFLINE), harness.results);
+
+            when(harness.player.isOnline()).thenReturn(true);
+            harness.overlay.requestOpenerPosition(harness.results::add);
+            harness.runEntity();
+            assertEquals(List.of(OpenerPosition.OFFLINE, OpenerPosition.inWorld(18.5D, 72D, -4.25D)), harness.results);
+        }
+    }
+
+    @Test
+    public void rejectedEntityTaskCompletesOnceEvenIfRetirementAlreadyRan() {
+        try (Harness harness = new Harness()) {
+            harness.reject = true;
+            harness.overlay.requestOpenerPosition(harness.results::add);
+            assertEquals(List.of(OpenerPosition.OFFLINE), harness.results);
+        }
+    }
+
+    @Test
+    public void changingWorldBeforeCaptureReportsOtherWorld() {
+        try (Harness harness = new Harness()) {
+            harness.overlay.requestOpenerPosition(harness.results::add);
+            when(harness.player.getWorld()).thenReturn(mock(World.class));
+            harness.runEntity();
+            assertEquals(List.of(OpenerPosition.IN_OTHER_WORLD), harness.results);
+        }
+    }
+
+    private static final class Harness implements AutoCloseable {
+        private final Player player = mock(Player.class);
+        private final World world = mock(World.class);
+        private final Engine engine = mock(Engine.class);
+        private final IrisWorld target = mock(IrisWorld.class);
+        private final UUID opener = UUID.randomUUID();
+        private final List<OpenerPosition> results = new ArrayList<>();
+        private final MockedStatic<J> scheduling = mockStatic(J.class);
+        private final MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+        private final MockedStatic<BukkitWorldBinding> binding = mockStatic(BukkitWorldBinding.class);
+        private final BukkitVisionOverlay overlay = new BukkitVisionOverlay(engine, opener);
+        private Runnable task;
+        private Runnable retired;
+        private boolean entityOwned;
+        private boolean reject;
+
+        private Harness() {
+            when(engine.getWorld()).thenReturn(target);
+            when(player.isOnline()).thenReturn(true);
+            when(player.getWorld()).thenReturn(world);
+            when(player.getLocation()).thenAnswer(invocation -> {
+                assertTrue("location read outside owning entity task", entityOwned);
+                return new Location(world, 18.5D, 72D, -4.25D);
+            });
+            bukkit.when(() -> Bukkit.getPlayer(opener)).thenReturn(player);
+            binding.when(() -> BukkitWorldBinding.world(target)).thenReturn(world);
+            scheduling.when(() -> J.runGlobal(any(Runnable.class))).thenAnswer(invocation -> {
+                invocation.getArgument(0, Runnable.class).run();
+                return true;
+            });
+            scheduling.when(() -> J.runEntity(same(player), any(Runnable.class))).thenAnswer(invocation -> {
+                task = invocation.getArgument(1);
+                return !reject;
+            });
+            scheduling.when(() -> J.runEntity(same(player), any(Runnable.class), eq(0), any(Runnable.class)))
+                    .thenAnswer(invocation -> {
+                        task = invocation.getArgument(1);
+                        retired = invocation.getArgument(3);
+                        if (reject) {
+                            retired.run();
+                        }
+                        return !reject;
+                    });
+        }
+
+        private void runEntity() {
+            entityOwned = true;
+            try {
+                task.run();
+            } finally {
+                entityOwned = false;
+            }
+        }
+
+        @Override
+        public void close() {
+            binding.close();
+            bukkit.close();
+            scheduling.close();
+        }
+    }
+}

adapters/bukkit/plugin/src/test/java/art/arcane/iris/world/PendingWorldReplacementAdmissionTest.java

@@ -11,12 +11,16 @@ import art.arcane.iris.platform.bukkit.plugin.VolmitSender;
 import org.bukkit.NamespacedKey;
 import org.junit.Test;
 
+import java.io.IOException;
 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.AtomicReference;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.assertThrows;
 import static org.mockito.Mockito.mock;
 
@@ -42,4 +46,55 @@ public class PendingWorldReplacementAdmissionTest {
             executor.awaitTermination(5L, TimeUnit.SECONDS);
         }
     }
+
+    @Test
+    public void shutdownRejectsReplacementsThatStartAfterIt() {
+        PendingWorldReplacementManager manager = new PendingWorldReplacementManager(mock(Iris.class));
+        manager.awaitStagingForShutdown();
+
+        IOException rejected = assertThrows(IOException.class, () -> manager.stageReplacement(
+                mock(VolmitSender.class), NamespacedKey.minecraft("overworld"), mock(IrisDimension.class), null));
+
+        assertTrue(rejected.getMessage().contains("shutting down"));
+        assertTrue(LifecycleOperationCoordinator.get().isIdle());
+    }
+
+    @Test
+    public void shutdownWaitsForTheReplacementBeingStaged() throws Exception {
+        PendingWorldReplacementManager manager = new PendingWorldReplacementManager(mock(Iris.class));
+        AtomicReference<Throwable> stagingFailure = new AtomicReference<>();
+        Thread staging = new Thread(() -> {
+            try {
+                manager.stageReplacement(mock(VolmitSender.class), NamespacedKey.minecraft("overworld"),
+                        mock(IrisDimension.class), null);
+            } catch (Throwable failure) {
+                stagingFailure.set(failure);
+            }
+        });
+        Thread shutdown = new Thread(manager::awaitStagingForShutdown);
+        synchronized (manager) {
+            staging.start();
+            awaitState(staging, Thread.State.BLOCKED);
+            shutdown.start();
+            awaitState(shutdown, Thread.State.WAITING);
+            assertTrue(staging.isAlive());
+        }
+        shutdown.join(TimeUnit.SECONDS.toMillis(10L));
+        staging.join(TimeUnit.SECONDS.toMillis(10L));
+
+        assertFalse(shutdown.isAlive());
+        assertFalse(staging.isAlive());
+        assertTrue(stagingFailure.get() instanceof Exception);
+        assertTrue(LifecycleOperationCoordinator.get().isIdle());
+    }
+
+    private static void awaitState(Thread thread, Thread.State state) throws InterruptedException {
+        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(5L);
+        while (thread.getState() != state) {
+            if (System.nanoTime() > deadline) {
+                throw new AssertionError(thread.getName() + " never reached " + state + "; it is " + thread.getState());
+            }
+            Thread.sleep(5L);
+        }
+    }
 }

adapters/fabric/build.gradle

@@ -62,7 +62,7 @@ apply from: file('../../gradle/java21-runtime-exclusions.gradle')
 
 Properties rootProperties = new Properties()
 file('../../gradle.properties').withInputStream { InputStream stream -> rootProperties.load(stream) }
-String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.5'))
+String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.7'))
 String minecraftVersion = providers.gradleProperty('minecraftVersion').getOrElse(rootProperties.getProperty('minecraftVersion', '26.3'))
 String fabricLoaderVersion = providers.gradleProperty('fabricLoaderVersion').getOrElse(irisModTarget.fabricLoader.toString())
 Closure<String> irisArtifactName = { String platform, String targetVersion ->
@@ -131,6 +131,8 @@ configurations.named('bundle').configure {
     exclude(group: 'de.crazydev22.slimjar.helper')
     exclude(group: 'de.crazydev22.slimjar')
     exclude(group: 'io.github.slimjar')
+    // The game ships its own LWJGL; without the modules it leaves out, the map's 3D views draw in software.
+    exclude(group: 'org.lwjgl')
 }
 
 configurations.compileClasspath.extendsFrom(configurations.devBundle)
@@ -153,7 +155,7 @@ dependencies {
     String modConfiguration = irisModTarget.fabricRemap ? 'modImplementation' : 'implementation'
     add(modConfiguration, "net.fabricmc:fabric-loader:${fabricLoaderVersion}")
     testImplementation('junit:junit:4.13.2')
-    testImplementation('org.mockito:mockito-core:5.23.0')
+    testImplementation(libs.mockito.core)
     testImplementation(testFixtures('art.arcane:core'))
     testImplementation(libs.spigot) {
         transitive = false
@@ -216,7 +218,9 @@ dependencies {
         libs.caffeine,
         'com.fulcrumgenomics:jlibdeflate:0.2.0',
         libs.dom4j,
-        libs.jaxen
+        libs.jaxen,
+        libs.flatlaf,
+        libs.flatlaf.extras
     ]
     shared.each { Object notation ->
         ['bundle', 'devBundle'].each { String configuration ->
@@ -236,6 +240,8 @@ tasks.named('compileJava', JavaCompile).configure {
     options.release.set((int) irisModTarget.java)
 }
 
+apply from: file('../../gradle/mockito-agent.gradle')
+
 tasks.named('test').configure {
 }
 

adapters/forge/build.gradle

@@ -61,7 +61,7 @@ apply from: file('../../gradle/java21-runtime-exclusions.gradle')
 
 Properties rootProperties = new Properties()
 file('../../gradle.properties').withInputStream { InputStream stream -> rootProperties.load(stream) }
-String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.5'))
+String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.7'))
 String minecraftVersion = providers.gradleProperty('minecraftVersion').getOrElse(rootProperties.getProperty('minecraftVersion', '26.3'))
 String forgeVersion = providers.gradleProperty('forgeVersion').getOrElse(irisModTarget.forge.toString())
 String buildLane = gradle.extensions.extraProperties.has('irisBuildLane')
@@ -152,12 +152,16 @@ configurations.named('bundle').configure {
     exclude(group: 'de.crazydev22.slimjar.helper')
     exclude(group: 'de.crazydev22.slimjar')
     exclude(group: 'io.github.slimjar')
+    // The game ships its own LWJGL; without the modules it leaves out, the map's 3D views draw in software.
+    exclude(group: 'org.lwjgl')
 }
 
 configurations.named('runBundle').configure {
     exclude(group: 'de.crazydev22.slimjar.helper')
     exclude(group: 'de.crazydev22.slimjar')
     exclude(group: 'io.github.slimjar')
+    // The game ships its own LWJGL; without the modules it leaves out, the map's 3D views draw in software.
+    exclude(group: 'org.lwjgl')
 }
 
 configurations.compileClasspath.extendsFrom(configurations.devBundle)
@@ -178,7 +182,7 @@ dependencies {
         ? minecraft.dependency("net.minecraftforge:forge:${forgeVersion}")
         : minecraft.dependency("iris-${buildLane}", "net.minecraftforge:forge:${forgeVersion}"))
     testImplementation('junit:junit:4.13.2')
-    testImplementation('org.mockito:mockito-core:5.23.0')
+    testImplementation(libs.mockito.core)
     testImplementation(testFixtures('art.arcane:core'))
     testImplementation(libs.spigot) {
         transitive = false
@@ -215,7 +219,9 @@ dependencies {
         libs.caffeine,
         'com.fulcrumgenomics:jlibdeflate:0.2.0',
         libs.dom4j,
-        libs.jaxen
+        libs.jaxen,
+        libs.flatlaf,
+        libs.flatlaf.extras
     ]
     shared.each { Object notation ->
         ['bundle', 'devBundle', 'runBundle'].each { String configuration ->
@@ -272,6 +278,8 @@ tasks.named('compileJava', JavaCompile).configure {
     options.release.set((int) irisModTarget.java)
 }
 
+apply from: file('../../gradle/mockito-agent.gradle')
+
 tasks.named('test').configure {
 }
 

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

@@ -105,6 +105,7 @@ import java.util.Objects;
 import java.util.OptionalLong;
 import java.util.Set;
 import java.util.TreeSet;
+import java.util.UUID;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.IntConsumer;
@@ -946,6 +947,14 @@ public final class IrisModdedChunkGenerator implements NativeGeneratorOwner, Nat
                         + " requires an attached generation-history runtime router."));
     }
 
+    private String structureStateKey() {
+        Engine current = boundEngineOrNull();
+        if (current == null || allowsGenerationHistoryBypass(current)) {
+            return "transient:" + UUID.randomUUID();
+        }
+        return "epoch:" + requireHistoryRouter(current, "structure state key").history().activeEpoch().epochId();
+    }
+
     boolean allowsGenerationHistoryBypass(Engine current) {
         if (generationMode != ModdedGenerationMode.TRANSIENT_STUDIO) {
             return false;
@@ -985,7 +994,7 @@ public final class IrisModdedChunkGenerator implements NativeGeneratorOwner, Nat
         ModdedBiomePolicy<H, S> policy = new ModdedBiomePolicy<>(source);
         policy.bind(new ModdedBiomePolicy.RuntimeCallbacks(this::boundEngineOrNull, this::awaitStructureEngine,
                 this::allowsGenerationHistoryBypass, this::configuredStructureBiomeKeys,
-                IrisModdedChunkGenerator::retainedBiomeKeys, this::visibleBiomeSeed));
+                IrisModdedChunkGenerator::retainedBiomeKeys, this::visibleBiomeSeed, this::structureStateKey));
         return policy;
     }
 

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

@@ -1395,6 +1395,11 @@ final class ModdedBiomePolicy<H, S> implements NativeModdedBiomePolicy<H, S> {
         return requireConfiguredStructureBiomeKeys(exactStructureBiomeKeys());
     }
 
+    @Override
+    public String structureStateKey() {
+        return Objects.requireNonNull(runtime, "runtime").structureStateKey().get();
+    }
+
     @Override
     public int horizontalSearchStep(int blockY, int searchRadius) {
         return horizontalBiomeSearchQuartStep(blockY, searchRadius);
@@ -1402,6 +1407,7 @@ final class ModdedBiomePolicy<H, S> implements NativeModdedBiomePolicy<H, S> {
 
     record RuntimeCallbacks(Supplier<Engine> currentEngine, Supplier<Engine> awaitEngine,
                             Predicate<Engine> historyBypass, Supplier<Set<String>> configuredStructureKeys,
-                            Function<Engine, Set<String>> retainedBiomeKeys, LongSupplier visibleBiomeSeed) {
+                            Function<Engine, Set<String>> retainedBiomeKeys, LongSupplier visibleBiomeSeed,
+                            Supplier<String> structureStateKey) {
     }
 }

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

@@ -227,6 +227,7 @@ public final class ModdedEngineBootstrap {
         failure = runStopStage(failure, "wand service", ModdedWandService::clearAll);
         failure = runStopStage(failure, "block break handler", ModdedBlockBreakHandler::clear);
         failure = runStopStage(failure, "studio commands", ModdedStudioCommands::clear);
+        failure = runStopStage(failure, "gui windows", GuiHost::shutdown);
         failure = runStopStage(failure, "gui host", ModdedGuiHost::clear);
         failure = runStopStage(failure, "services", () -> services().disableAll());
         reportStopFailure("stopping", failure);

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

@@ -25,6 +25,7 @@ import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeEntitySpawns;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedLoader;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeBiomeRegistry;
 import art.arcane.iris.BuildConstants;
+import art.arcane.iris.platform.ClasspathVanillaDataSource;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandExecutor;
 import art.arcane.iris.spi.PlatformGenerationRegistry;
@@ -35,6 +36,7 @@ import art.arcane.volmlib.nativelib.entity.NativeEntityType;
 import art.arcane.iris.spi.PlatformRegistries;
 import art.arcane.iris.spi.PlatformScheduler;
 import art.arcane.iris.spi.PlatformStructureHooks;
+import art.arcane.iris.spi.VanillaDataSource;
 import art.arcane.volmlib.nativelib.terrain.NativeWorld;
 
 import java.io.File;
@@ -56,6 +58,7 @@ public final class ModdedPlatform implements IrisPlatform {
     private final ModdedScheduler scheduler;
     private final ModdedStructureHooks structureHooks;
     private final ModdedBiomeWriter biomeWriter;
+    private final ClasspathVanillaDataSource vanillaData;
 
     public ModdedPlatform(NativeModdedLoader loader) {
         this.loader = loader;
@@ -65,6 +68,7 @@ public final class ModdedPlatform implements IrisPlatform {
         this.scheduler = new ModdedScheduler();
         this.structureHooks = new ModdedStructureHooks(ModdedEngineBootstrap::currentServer);
         this.biomeWriter = new ModdedBiomeWriter(new NativeBiomeRegistry(ModdedEngineBootstrap::currentServer, "minecraft:plains"));
+        this.vanillaData = new ClasspathVanillaDataSource(() -> overworldClass(ModdedEngineBootstrap.currentServer()));
     }
 
     public static void errorSink(Consumer<Throwable> sink) {
@@ -110,6 +114,11 @@ public final class ModdedPlatform implements IrisPlatform {
         return biomeWriter;
     }
 
+    @Override
+    public VanillaDataSource vanillaData() {
+        return vanillaData;
+    }
+
     @Override
     public File dataFolder() {
         File folder = loader.configDir().resolve("iris").toFile();
@@ -365,4 +374,15 @@ public final class ModdedPlatform implements IrisPlatform {
                 "modded-generation-registry-v1");
     }
 
+    static Class<?> overworldClass(NativeModdedServer server) {
+        if (server == null) {
+            throw new IllegalStateException("Vanilla data needs a running Minecraft server.");
+        }
+        NativeWorld overworld = server.overworld();
+        if (overworld == null) {
+            throw new IllegalStateException("Vanilla data needs the Minecraft server overworld to be loaded.");
+        }
+        return overworld.nativeHandle().getClass();
+    }
+
 }

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

@@ -150,6 +150,7 @@ final class ModdedCommandHelp {
                 Entry.command("close", "", ModdedHelpMessages.COMMAND_CLOSE_CLOSE_THE_OPEN_STUDIO_DIMENSION_AND_DISCARD_ITS_WORLD, "x"),
                 Entry.command("tpstudio", "", ModdedHelpMessages.COMMAND_TPSTUDIO_TELEPORT_INTO_THE_OPEN_STUDIO_DIMENSION, "stp"),
                 Entry.command("status", "", ModdedHelpMessages.COMMAND_STATUS_SHOW_THE_OPEN_STUDIO_DIMENSION_AND_ITS_PACK),
+                Entry.command("hotload", "", ModdedHelpMessages.COMMAND_HOTLOAD_REFRESH_THE_OPEN_STUDIO, "refresh"),
                 Entry.command("noise", "[generator] [seed]", ModdedHelpMessages.COMMAND_NOISE_OPEN_THE_NOISE_EXPLORER_GUI_ON_THE_SERVER_DISPLAY, "nmap"),
                 Entry.command("map", "", ModdedHelpMessages.COMMAND_MAP_OPEN_THE_VISION_MAP_GUI_ON_THE_SERVER_DISPLAY, "render"),
                 Entry.command("vscode", "[pack]", ModdedHelpMessages.COMMAND_VSCODE_REGENERATE_THE_CODE_WORKSPACE_FOR_A_PACK_AND_OPEN_IT_IN_YOUR, "vsc"),
@@ -188,7 +189,8 @@ final class ModdedCommandHelp {
                 Entry.command("install", "", ModdedHelpMessages.COMMAND_INSTALL_INSTALL_DIMENSION_TYPE_OVERRIDES_FOR_LOADED_IRIS_DIMENSIONS),
                 Entry.command("list", "", ModdedHelpMessages.COMMAND_LIST_LIST_CONFIGURED_AND_INSTALLED_DATAPACKS, "ls"),
                 Entry.command("ingest", "", ModdedHelpMessages.COMMAND_INGEST_EXPLAIN_BUKKIT_DATAPACK_INGEST_WORKFLOW, "pull"),
-                Entry.command("remove", "<id>", ModdedHelpMessages.COMMAND_REMOVE_EXPLAIN_DATAPACK_REMOVAL_WORKFLOW, "rm")
+                Entry.command("remove", "<id>", ModdedHelpMessages.COMMAND_REMOVE_EXPLAIN_DATAPACK_REMOVAL_WORKFLOW, "rm"),
+                Entry.command("export", "<dimension> [version=] [mode=overworld] [namespace=iris_export] [output=] [format=zip] [objects=true] [replace=false]", ModdedHelpMessages.COMMAND_EXPORT_EXPORT_A_DIMENSION_AS_A_VANILLA_WORLDGEN_DATAPACK)
         ));
         SECTIONS.put("datapacks", SECTIONS.get("datapack"));
         SECTIONS.put("dp", SECTIONS.get("datapack"));

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

@@ -25,7 +25,7 @@ import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.structure.placement.IrisStructureLocator;
 import art.arcane.iris.structure.nativegen.NativeStructureGenerationPolicy;
 import art.arcane.iris.structure.placement.StructureReachability;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureQuery;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureType;
 import art.arcane.iris.world.history.GenerationFindCatalog;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.iris.structure.nativegen.IrisNativeStructureDecision;
@@ -61,7 +61,7 @@ final class ModdedCommandSuggestions {
     static final SuggestionProvider<NativeCommandSource> OBJECT_KEYS = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> suggestObjectKeys(context, builder);
     static final SuggestionProvider<NativeCommandSource> STRUCTURE_KEYS = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> suggestStructureKeys(context, builder);
     static final SuggestionProvider<NativeCommandSource> POI_TYPES = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> NativeCommandRegistration.suggest(List.of("buried_treasure"), builder);
-    static final SuggestionProvider<NativeCommandSource> HYDROLOGY_TYPES = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> suggestHydrologyTypes(context, builder);
+    static final SuggestionProvider<NativeCommandSource> HYDROLOGY_TYPES = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> NativeCommandRegistration.suggest(HydrologyFeatureType.keys(), builder);
     static final SuggestionProvider<NativeCommandSource> PACK_NAMES = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> suggestPackNames(context, builder);
     static final SuggestionProvider<NativeCommandSource> DIMENSION_NAMES = (CommandContext<NativeCommandSource> context, SuggestionsBuilder builder) -> suggestDimensionNames(context, builder);
 
@@ -87,24 +87,6 @@ final class ModdedCommandSuggestions {
         return builder.buildFuture();
     }
 
-    private static CompletableFuture<Suggestions> suggestHydrologyTypes(
-            CommandContext<NativeCommandSource> context,
-            SuggestionsBuilder builder
-    ) {
-        ModdedCommandFeedback.tab(context.getSource());
-        try {
-            Engine engine = IrisModdedCommands.engineFor(context.getSource().world());
-            if (engine != null && engine.getComplex().getHydrologyRuntime() != null) {
-                return NativeCommandRegistration.suggest(
-                        engine.getComplex().getHydrologyRuntime().featureQueryKeys(), builder);
-            }
-        } catch (Throwable error) {
-            warnTabFailure("hydrology types", context.getSource(), error);
-        }
-        return NativeCommandRegistration.suggest(
-                HydrologyFeatureQuery.suggestions(List.of()), builder);
-    }
-
     static Set<String> reachableBiomeKeys(Engine engine) {
         return reachableBiomeKeys(GenerationFindCatalog.biomes(engine));
     }

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

@@ -18,7 +18,14 @@
 
 package art.arcane.iris.modded.command;
 
+import art.arcane.iris.modded.ModdedEngineBootstrap;
 import art.arcane.iris.modded.ModdedIrisLog;
+import art.arcane.iris.pack.datapack.export.WorldgenExportProgress;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportResult;
+import art.arcane.iris.pack.datapack.export.WorldgenExportService;
+import art.arcane.iris.pack.datapack.export.WorldgenExportServices;
+import art.arcane.iris.pack.datapack.export.ir.ExportDiagnostic;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.pack.datapack.DataVersion;
 import art.arcane.iris.pack.PackDirectoryResolver;
@@ -33,6 +40,7 @@ import com.mojang.brigadier.context.CommandContext;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandSource;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandRegistration;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandText;
 import art.arcane.volmlib.nativelib.terrain.NativeWorld;
 import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldDimensions;
 
@@ -40,6 +48,7 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -47,15 +56,20 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Set;
+import java.util.UUID;
 import java.util.function.Predicate;
 
+import art.arcane.iris.localization.DirectorCommandMessages;
 import art.arcane.iris.localization.IrisLanguage;
 import art.arcane.iris.modded.localization.ModdedCommandMessages;
 import art.arcane.iris.localization.RuntimeUiMessages;
+import art.arcane.volmlib.util.localization.LanguageAudience;
 import art.arcane.volmlib.util.localization.MessageArgument;
+import art.arcane.volmlib.util.localization.TextKey;
 public final class ModdedDatapackCommands {
     private static final Predicate<NativeCommandSource> GATE = NativeCommandRegistration.GAMEMASTERS;
     private static final String WORLD_PACK_NAME = "iris";
+    private static final int RESOURCE_REPORTS = 4;
 
     private ModdedDatapackCommands() {
     }
@@ -79,6 +93,11 @@ public final class ModdedDatapackCommands {
         root.then(message("ingest", "Managed Modrinth datapack ingest is Bukkit-only. On modded servers install the datapack folder or zip in world/datapacks, enable it, restart, then use /iris datapack list to confirm it is enabled. Registered structures generate natively in Iris dimensions."));
         root.then(message("pull", "Managed Modrinth datapack ingest is Bukkit-only. On modded servers install the datapack folder or zip in world/datapacks, enable it, restart, then use /iris datapack list to confirm it is enabled. Registered structures generate natively in Iris dimensions."));
 
+        root.then(NativeCommandRegistration.literal("export")
+                .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> export(context.getSource(), "")))
+                .then(NativeCommandRegistration.argument("args", StringArgumentType.greedyString())
+                        .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> export(context.getSource(), StringArgumentType.getString(context, "args"))))));
+
         root.then(message("remove", "Managed datapack removal is Bukkit-only. On modded servers disable the pack, delete its folder or zip from world/datapacks, and restart."));
         root.then(message("rm", "Managed datapack removal is Bukkit-only. On modded servers disable the pack, delete its folder or zip from world/datapacks, and restart."));
 
@@ -291,4 +310,107 @@ public final class ModdedDatapackCommands {
         }
         return null;
     }
+
+    private static int export(NativeCommandSource source, String raw) {
+        ModdedDatapackExportArguments arguments;
+        try {
+            arguments = ModdedDatapackExportArguments.parse(raw);
+        } catch (IllegalArgumentException invalid) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_INVALID, MessageArgument.untrusted("reason", invalid.getMessage())));
+            return 0;
+        }
+        File packsRoot = ModdedPackCommands.packsRoot();
+        File pack = PackDirectoryResolver.resolveExisting(packsRoot, arguments.dimension());
+        if (pack == null) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_STUDIO_COMMANDS_PACK_NOT_FOUND_UNDER, MessageArgument.untrusted("name", arguments.dimension()), MessageArgument.untrusted("value", packsRoot.getAbsolutePath())));
+            return 0;
+        }
+        WorldgenExportService service = WorldgenExportServices.get();
+        WorldgenExportRequest request = arguments.toRequest(pack.toPath(), exportRoot());
+        IrisModdedCommands.ok(source, IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_STARTED, MessageArgument.untrusted("dimension", request.dimension()), MessageArgument.untrusted("version", arguments.target().getVersion())));
+        ExportFeedback feedback = new ExportFeedback(source);
+        Thread worker = new Thread(() -> runExport(service, request, feedback), "Iris Datapack Export");
+        worker.setDaemon(true);
+        worker.start();
+        return 1;
+    }
+
+    private static Path exportRoot() {
+        return ModdedEngineBootstrap.loader().configDir().resolve("irisworldgen").resolve("exports").resolve("datapacks");
+    }
+
+    private static void runExport(WorldgenExportService service, WorldgenExportRequest request, ExportFeedback feedback) {
+        WorldgenExportResult result;
+        try {
+            result = service.export(request, feedback);
+        } catch (Throwable failure) {
+            ModdedIrisLog.error("Iris datapack export failed for " + request.dimension(), failure);
+            feedback.post(() -> IrisModdedCommands.fail(feedback.source, IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_FAILED, MessageArgument.untrusted("reason", IrisLanguage.errorDetail(failure)))));
+            return;
+        }
+        feedback.post(() -> reportExport(feedback.source, result));
+    }
+
+    private static void reportExport(NativeCommandSource source, WorldgenExportResult result) {
+        for (ExportDiagnostic diagnostic : result.diagnostics()) {
+            String line = IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_DIAGNOSTIC, MessageArgument.untrusted("key", diagnosticLabel(diagnostic)), MessageArgument.untrusted("message", diagnostic.message()));
+            ModdedCommandFeedback.send(source, NativeCommandText.literal(line).withStyle(diagnosticFormat(diagnostic.severity())));
+        }
+        if (result.isSuccess()) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_EXPORTED, MessageArgument.untrusted("path", result.output())));
+            return;
+        }
+        TextKey outcome = result.status() == WorldgenExportResult.Status.REJECTED
+                ? DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_REJECTED
+                : DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_FAILED;
+        IrisModdedCommands.fail(source, IrisLanguage.plain(outcome, MessageArgument.untrusted("reason", result.message())));
+    }
+
+    private static NativeCommandText.Format diagnosticFormat(ExportDiagnostic.Severity severity) {
+        return switch (severity) {
+            case ERROR -> NativeCommandText.Format.RED;
+            case WARNING -> NativeCommandText.Format.YELLOW;
+            case INFO -> NativeCommandText.Format.GRAY;
+        };
+    }
+
+    private static String diagnosticLabel(ExportDiagnostic diagnostic) {
+        return diagnostic.resource().isEmpty()
+                ? diagnostic.limit().name()
+                : diagnostic.limit().name() + " " + diagnostic.resource();
+    }
+
+    private static final class ExportFeedback implements WorldgenExportProgress {
+        private final NativeCommandSource source;
+        private final NativeModdedServer server;
+        private final UUID audience;
+
+        private ExportFeedback(NativeCommandSource source) {
+            this.source = source;
+            this.server = source.server();
+            this.audience = source.playerId();
+        }
+
+        @Override
+        public void stage(String stage) {
+            post(() -> progress(IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_STAGE, MessageArgument.untrusted("stage", stage))));
+        }
+
+        @Override
+        public void resources(int done, int total) {
+            int stride = Math.max(1, total / RESOURCE_REPORTS);
+            if (done != total && done % stride != 0) {
+                return;
+            }
+            post(() -> progress(IrisLanguage.plain(DirectorCommandMessages.COMMAND_DATAPACK_EXPORT_RESOURCES, MessageArgument.untrusted("done", done), MessageArgument.untrusted("total", total))));
+        }
+
+        private void post(Runnable task) {
+            server.execute(() -> LanguageAudience.run(audience, task));
+        }
+
+        private void progress(String message) {
+            ModdedCommandFeedback.send(source, NativeCommandText.literal(message).withStyle(NativeCommandText.Format.GRAY));
+        }
+    }
 }

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

@@ -0,0 +1,128 @@
+/*
+ * 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.modded.command;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.DatapackExportDestinations;
+import art.arcane.iris.pack.datapack.export.WorldgenExportMode;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import art.arcane.iris.pack.datapack.export.WorldgenExportTargets;
+
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.regex.Pattern;
+
+record ModdedDatapackExportArguments(String dimension, String version, String mode, String namespace, String output,
+                                     String format, boolean objects, boolean replace) {
+    private static final Pattern DIMENSION = Pattern.compile("[A-Za-z0-9_/.-]+");
+    private static final String VERSION_KEY = "version";
+    private static final String MODE_KEY = "mode";
+    private static final String NAMESPACE_KEY = "namespace";
+    private static final String OUTPUT_KEY = "output";
+    private static final String FORMAT_KEY = "format";
+    private static final String OBJECTS_KEY = "objects";
+    private static final String REPLACE_KEY = "replace";
+    private static final Set<String> OPTIONS = Set.of(VERSION_KEY, MODE_KEY, NAMESPACE_KEY, OUTPUT_KEY, FORMAT_KEY,
+            OBJECTS_KEY, REPLACE_KEY);
+
+    ModdedDatapackExportArguments {
+        Objects.requireNonNull(dimension, "dimension");
+        Objects.requireNonNull(version, "version");
+        Objects.requireNonNull(mode, "mode");
+        Objects.requireNonNull(namespace, "namespace");
+        Objects.requireNonNull(output, "output");
+        Objects.requireNonNull(format, "format");
+    }
+
+    static ModdedDatapackExportArguments parse(String raw) {
+        String trimmed = raw == null ? "" : raw.trim();
+        String[] tokens = trimmed.isEmpty() ? new String[0] : trimmed.split("\\s+");
+        String dimension = null;
+        Map<String, String> options = new HashMap<>(OPTIONS.size());
+        for (String token : tokens) {
+            int equals = token.indexOf('=');
+            if (equals < 0) {
+                if (dimension != null) {
+                    throw new IllegalArgumentException("unexpected argument '" + token + "'");
+                }
+                dimension = token;
+                continue;
+            }
+            String key = token.substring(0, equals);
+            if (!OPTIONS.contains(key)) {
+                throw new IllegalArgumentException("unknown option '" + key + "'");
+            }
+            if (options.putIfAbsent(key, token.substring(equals + 1)) != null) {
+                throw new IllegalArgumentException("option '" + key + "' given twice");
+            }
+        }
+        if (dimension == null) {
+            throw new IllegalArgumentException("missing dimension");
+        }
+        if (!DIMENSION.matcher(dimension).matches() || dimension.contains("..")) {
+            throw new IllegalArgumentException("invalid dimension key '" + dimension + "'");
+        }
+        ModdedDatapackExportArguments arguments = new ModdedDatapackExportArguments(
+                dimension,
+                options.getOrDefault(VERSION_KEY, ""),
+                options.getOrDefault(MODE_KEY, WorldgenExportRequest.DEFAULT_MODE),
+                options.getOrDefault(NAMESPACE_KEY, WorldgenExportRequest.DEFAULT_NAMESPACE),
+                options.getOrDefault(OUTPUT_KEY, ""),
+                options.getOrDefault(FORMAT_KEY, WorldgenExportRequest.DEFAULT_FORMAT),
+                flag(OBJECTS_KEY, options.get(OBJECTS_KEY), true),
+                flag(REPLACE_KEY, options.get(REPLACE_KEY), false));
+        arguments.target();
+        WorldgenExportMode.parse(arguments.mode());
+        DatapackExportDestinations.parseFormat(arguments.format());
+        return arguments;
+    }
+
+    DataVersion target() {
+        return WorldgenExportTargets.resolve(version);
+    }
+
+    WorldgenExportRequest toRequest(Path pack, Path exportRoot) {
+        return WorldgenExportRequest.builder()
+                .pack(pack)
+                .dimension(dimension)
+                .version(version)
+                .mode(mode)
+                .namespace(namespace)
+                .output(output)
+                .format(format)
+                .objects(objects)
+                .replace(replace)
+                .exportRoot(exportRoot)
+                .build();
+    }
+
+    private static boolean flag(String key, String raw, boolean fallback) {
+        if (raw == null) {
+            return fallback;
+        }
+        return switch (raw) {
+            case "true" -> true;
+            case "false" -> false;
+            default -> throw new IllegalArgumentException(key + " must be true or false");
+        };
+    }
+}

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

@@ -39,8 +39,7 @@ import art.arcane.iris.structure.placement.StructureReachability;
 import art.arcane.iris.generation.runtime.WrongEngineBroException;
 import art.arcane.iris.world.history.GenerationSemanticQueries;
 import art.arcane.iris.world.history.GenerationFindCatalog;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureQuery;
-import art.arcane.iris.generation.hydrology.runtime.IrisHydrologyRuntime;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureType;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.iris.structure.nativegen.IrisNativeStructureDecision;
 import art.arcane.iris.generation.terrain.IrisRegion;
@@ -143,39 +142,31 @@ final class ModdedLocateCommands {
             IrisModdedCommands.fail(source, "This dimension is not generated by Iris.");
             return 0;
         }
-        IrisHydrologyRuntime runtime = engine.getComplex().getHydrologyRuntime();
-        HydrologyFeatureQuery query;
+        HydrologyFeatureType featureType;
         try {
-            query = HydrologyFeatureQuery.parse(type);
+            featureType = HydrologyFeatureType.parse(type);
         } catch (IllegalArgumentException error) {
             IrisModdedCommands.fail(source, error.getMessage());
             return 0;
         }
+        String label = featureType.key().replace('_', ' ');
         int originX = player.blockX();
         int originZ = player.blockZ();
-        int requestedDistance = runtime == null
-                ? 8192
-                : Math.min(8192, runtime.settings().routing().tileSize() * 15);
-        int maximumDistance = runtime == null
-                ? requestedDistance
-                : runtime.maximumFeatureSearchDistance(originX, originZ, requestedDistance);
+        int maximumDistance = GenerationSemanticQueries.RIVER_SEARCH_DISTANCE;
         NativeModdedServer server = source.server();
-        IrisModdedCommands.ok(source, "Searching accepted hydrology plans for " + type + "...");
+        IrisModdedCommands.ok(source, GenerationSemanticQueries.riverSearchMessage(featureType, maximumDistance));
         MultiBurst.burst.completeValueAsync(() -> GenerationSemanticQueries.nearestRiver(
-                        engine, query, originX, originZ, maximumDistance,
-                        (int visited) -> server.execute(() -> IrisModdedCommands.ok(source,
-                                "Searched " + visited + " hydrology tiles for " + type + "..."))).orElse(null))
+                        engine, featureType, originX, originZ, maximumDistance).orElse(null))
                 .whenComplete((GenerationSemanticQueries.RiverResult feature, Throwable error) -> server.execute(() -> {
                     if (error != null) {
-                        ModdedIrisLog.error("Hydrology locate failed for {}", type, error);
-                        IrisModdedCommands.fail(source,
-                                "Could not locate " + type + " hydrology: " + error.getClass().getSimpleName());
+                        Throwable cause = error instanceof CompletionException && error.getCause() != null ? error.getCause() : error;
+                        ModdedIrisLog.error("Hydrology locate failed for {}", featureType.key(), cause);
+                        IrisModdedCommands.fail(source, "Could not search for " + label + ": " + cause.getClass().getSimpleName()
+                                + (cause.getMessage() == null ? "" : " - " + cause.getMessage()));
                         return;
                     }
                     if (feature == null) {
-                        IrisModdedCommands.fail(source,
-                                "No accepted " + type + " hydrology feature found within "
-                                        + maximumDistance + " blocks.");
+                        IrisModdedCommands.fail(source, GenerationSemanticQueries.riverNotFoundMessage(featureType, maximumDistance));
                         return;
                     }
                     teleportToStructure(
@@ -185,7 +176,7 @@ final class ModdedLocateCommands {
                             feature.x(),
                             feature.y() + 2,
                             feature.z(),
-                            type + " hydrology feature"
+                            label
                     );
                 }));
         return 1;

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

@@ -23,6 +23,7 @@ import art.arcane.volmlib.nativelib.terrain.NativePregenRuntime;
 import art.arcane.volmlib.nativelib.terrain.NativePregenRuntime.ChunkLoad;
 import art.arcane.iris.configuration.IrisSettings;
 import art.arcane.iris.world.pregen.MantleHeapPressure;
+import art.arcane.iris.world.pregen.PregenHydrology;
 import art.arcane.iris.world.pregen.PregenListener;
 import art.arcane.iris.world.pregen.PregenMantleBackpressure;
 import art.arcane.iris.world.pregen.PregeneratorMethod;
@@ -30,6 +31,7 @@ import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.modded.ModdedGenPool;
 import art.arcane.volmlib.util.mantle.runtime.Mantle;
 
+import java.util.List;
 import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
@@ -71,6 +73,8 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
     private final PregenMantleBackpressure backpressure;
     private final PauseWhenEmptyGuard pauseGuard;
     private final LongSupplier clock;
+    private final AtomicBoolean closing = new AtomicBoolean();
+    private final PregenHydrology hydrology;
 
     public ModdedPregenMethod(Configuration configuration) {
         this(configuration, System::nanoTime);
@@ -80,6 +84,7 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
         this.clock = Objects.requireNonNull(clock);
         runtime = configuration.runtime();
         engine = configuration.engine();
+        hydrology = new PregenHydrology(() -> engine);
         sync = configuration.sync();
         pauseGuard = new PauseWhenEmptyGuard(runtime);
         IrisSettings.IrisSettingsPregen pregen = IrisSettings.get().getPregen();
@@ -121,6 +126,8 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
 
     @Override
     public void close() {
+        closing.set(true);
+        hydrology.close();
         try {
             awaitPendingChunks();
             ModdedIrisLog.info("Iris modded pregen closing: dim={} completed={} pending={} peakInFlight={} finalLimit={}",
@@ -341,6 +348,18 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
         return false;
     }
 
+    @Override
+    public void onRegionBounds(int minRegionX, int minRegionZ, int maxRegionX, int maxRegionZ) {
+        hydrology.bound(minRegionX, minRegionZ, maxRegionX, maxRegionZ);
+    }
+
+    @Override
+    public void onRegionsAhead(List<long[]> regions) {
+        if (!closing.get()) {
+            hydrology.prepare(regions);
+        }
+    }
+
     @Override
     public String getMethod(int x, int z) {
         return "Modded";

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

@@ -23,10 +23,9 @@ import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeWorldView;
 
 import art.arcane.iris.modded.ModdedIrisLog;
 import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.studio.map.MapWindow;
+import art.arcane.iris.studio.map.PaletteExplorerStart;
 import art.arcane.iris.studio.view.GuiHost;
-import art.arcane.iris.studio.view.ImageMapStudioGUI;
-import art.arcane.iris.studio.view.NoiseExplorerGUI;
-import art.arcane.iris.studio.view.VisionGUI;
 import art.arcane.iris.pack.loading.IrisData;
 import art.arcane.iris.pack.StructurePackageClosure;
 import art.arcane.iris.pack.ImageMapPackageClosure;
@@ -38,6 +37,7 @@ import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.iris.generation.biome.IrisBiomeGeneratorLink;
 import art.arcane.iris.generation.terrain.IrisDimension;
 import art.arcane.iris.world.entity.IrisEntitySpawn;
+import art.arcane.iris.world.IrisWorld;
 import art.arcane.iris.generation.noise.IrisGenerator;
 import art.arcane.iris.pack.PackExportClosure;
 import art.arcane.iris.world.entity.IrisEntity;
@@ -49,6 +49,7 @@ import art.arcane.iris.modded.ModdedDimensionManager;
 import art.arcane.iris.modded.ModdedEngineBootstrap;
 import art.arcane.iris.modded.ModdedScheduler;
 import art.arcane.iris.modded.ModdedWorkspaceGenerator;
+import art.arcane.iris.modded.service.ModdedStudioHotloadService;
 import art.arcane.iris.generation.concurrent.BurstExecutor;
 import art.arcane.iris.generation.concurrent.MultiBurst;
 import art.arcane.volmlib.util.collection.KMap;
@@ -85,6 +86,7 @@ import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Predicate;
 import java.util.regex.Pattern;
@@ -92,6 +94,7 @@ import java.util.stream.Stream;
 
 import art.arcane.iris.localization.IrisLanguage;
 import art.arcane.iris.modded.localization.ModdedCommandMessages;
+import art.arcane.volmlib.util.localization.LanguageAudience;
 import art.arcane.volmlib.util.localization.MessageArgument;
 public final class ModdedStudioCommands {
     private static final Predicate<NativeCommandSource> GATE = NativeCommandRegistration.GAMEMASTERS;
@@ -152,6 +155,10 @@ public final class ModdedStudioCommands {
                 .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> tpStudio(context.getSource()))));
         root.then(NativeCommandRegistration.literal("status")
                 .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> status(context.getSource()))));
+        root.then(NativeCommandRegistration.literal("hotload")
+                .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> hotload(context.getSource()))));
+        root.then(NativeCommandRegistration.literal("refresh")
+                .executes(ModdedCommandTree.localized((CommandContext<NativeCommandSource> context) -> hotload(context.getSource()))));
         root.then(workspaceTree("vscode", true));
         root.then(workspaceTree("vsc", true));
         root.then(workspaceTree("update", false));
@@ -247,8 +254,9 @@ public final class ModdedStudioCommands {
             NativeProtocolPlayer player = source.player();
             ModdedGuiHost.bindContext(worldView(source.server(), level), engine, player == null ? null : player.id());
         }
-        if (generatorKey == null || generatorKey.isBlank()) {
-            NoiseExplorerGUI.launch();
+        Engine mapEngine = engine != null ? engine : GuiHost.get().findActiveEngine();
+        if ((generatorKey == null || generatorKey.isBlank()) && mapEngine != null) {
+            MapWindow.openNoise(mapStart(mapEngine, source.player()), new MapWindow.NoiseSelection(null, null, seed));
             IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_STUDIO_COMMANDS_OPENING_NOISE_EXPLORER_ON_SERVER_DISPLAY));
             return 1;
         }
@@ -262,7 +270,7 @@ public final class ModdedStudioCommands {
             return 0;
         }
         String selectedGeneratorKey = generatorKey.trim();
-        NoiseExplorerGUI.launchGeneratorKey(selectedGeneratorKey, generator, seed);
+        MapWindow.openNoise(mapStart(engine, source.player()), new MapWindow.NoiseSelection(selectedGeneratorKey, generator, seed));
         IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_STUDIO_COMMANDS_OPENING_NOISE_EXPLORER_GENERATOR_SEED, MessageArgument.untrusted("value", generatorKey.trim()), MessageArgument.untrusted("seed", seed)));
         return 1;
     }
@@ -280,11 +288,20 @@ public final class ModdedStudioCommands {
         }
         NativeProtocolPlayer player = source.player();
         ModdedGuiHost.bindContext(worldView(source.server(), level), engine, player == null ? null : player.id());
-        VisionGUI.launch(engine, player == null ? null : player.id());
+        MapWindow.openMap(mapStart(engine, player));
         IrisModdedCommands.ok(source, IrisLanguage.plain(ModdedCommandMessages.MODDED_STUDIO_COMMANDS_OPENING_VISION_MAP_ON_SERVER_DISPLAY, MessageArgument.untrusted("value", level.name())));
         return 1;
     }
 
+    // Modded worlds have no Bukkit world id; the map finds the engine again through the bound GUI context.
+    private static PaletteExplorerStart mapStart(Engine engine, NativeProtocolPlayer player) {
+        IrisWorld world = engine.getWorld();
+        NativeWorld level = world == null ? null : world.platformWorld();
+        boolean inWorld = player != null && player.connected() && level != null && player.inWorld(level);
+        return new PaletteExplorerStart(engine, null, player == null ? null : player.id(), null,
+                inWorld ? player.x() : 0D, inWorld ? player.z() : 0D);
+    }
+
     private static int imageMap(NativeCommandSource source) {
         NativeWorld level = source.world();
         Engine engine = IrisModdedCommands.engineFor(level);
@@ -294,13 +311,13 @@ public final class ModdedStudioCommands {
             ));
             return 0;
         }
-        if (!ImageMapStudioGUI.isAvailable()) {
+        if (!GuiHost.isAvailable() || !IrisSettings.get().getGui().isUseServerLaunchedGuis()) {
             IrisModdedCommands.fail(source, guiUnavailableMessage());
             return 0;
         }
         NativeProtocolPlayer player = source.player();
         ModdedGuiHost.bindContext(worldView(source.server(), level), engine, player == null ? null : player.id());
-        ImageMapStudioGUI.launch(engine);
+        MapWindow.openImageMaps(mapStart(engine, player));
         IrisModdedCommands.ok(source, IrisLanguage.plain(
                 ModdedCommandMessages.MODDED_STUDIO_COMMANDS_OPENING_IMAGE_MAP_STUDIO_ON_SERVER_DISPLAY,
                 MessageArgument.untrusted("value", level.name())
@@ -643,6 +660,72 @@ public final class ModdedStudioCommands {
         return transition;
     }
 
+    private static int hotload(NativeCommandSource source) {
+        NativeProtocolPlayer player = source.player();
+        NativeModdedServer server = source.server();
+        UUID owner = player == null ? CONSOLE_OWNER : player.id();
+        UUID audience = source.playerId();
+        Executor feedback = task -> server.execute(() -> LanguageAudience.run(audience, task));
+        CompletableFuture<Void> transition = TRANSITIONS.submit(owner, () -> hotloadTransition(source, owner, feedback));
+        transition.whenComplete((ignored, failure) -> {
+            if (failure == null) {
+                return;
+            }
+            Throwable cause = unwrapFailure(failure);
+            ModdedIrisLog.error("Iris Studio hotload command failed", cause);
+            feedback.execute(() -> IrisModdedCommands.fail(source, IrisLanguage.plain(
+                    ModdedCommandMessages.MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_FAILED,
+                    MessageArgument.trusted("errorMessage", IrisLanguage.errorDetail(cause)))));
+        });
+        return 1;
+    }
+
+    private static CompletableFuture<Void> hotloadTransition(
+            NativeCommandSource source,
+            UUID owner,
+            Executor feedback
+    ) {
+        return CompletableFuture.supplyAsync(() -> hotloadStudio(source, owner, feedback), feedback)
+                .thenCompose(request -> request);
+    }
+
+    private static CompletableFuture<Void> hotloadStudio(
+            NativeCommandSource source,
+            UUID owner,
+            Executor feedback
+    ) {
+        String dimensionId = STUDIOS.get(owner);
+        if (dimensionId == null) {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(
+                    ModdedCommandMessages.MODDED_STUDIO_COMMANDS_YOU_DO_NOT_HAVE_OPEN_STUDIO_USE_IRIS_STUDIO_OPEN));
+            return CompletableFuture.completedFuture(null);
+        }
+        NativeWorld studio = ModdedDimensionManager.level(source.server(), dimensionId);
+        if (studio == null) {
+            STUDIOS.remove(owner, dimensionId);
+            IrisModdedCommands.fail(source, IrisLanguage.plain(
+                    ModdedCommandMessages.MODDED_STUDIO_COMMANDS_YOUR_STUDIO_DIMENSION_IS_NO_LONGER_LOADED_USE_IRIS_STUDIO));
+            return CompletableFuture.completedFuture(null);
+        }
+        Engine engine = IrisModdedCommands.engineFor(studio);
+        ModdedStudioHotloadService service = ModdedEngineBootstrap.services().service(ModdedStudioHotloadService.class);
+        if (engine == null || service == null) {
+            throw new IllegalStateException("The Studio engine or hotload service is unavailable.");
+        }
+        return service.requestHotload(dimensionId, engine)
+                .thenAcceptAsync(completed -> sendHotloadResult(source, completed), feedback);
+    }
+
+    private static void sendHotloadResult(NativeCommandSource source, boolean completed) {
+        if (completed) {
+            IrisModdedCommands.ok(source, IrisLanguage.plain(
+                    ModdedCommandMessages.MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_COMPLETE));
+        } else {
+            IrisModdedCommands.fail(source, IrisLanguage.plain(
+                    ModdedCommandMessages.MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_BUSY));
+        }
+    }
+
     private static int status(NativeCommandSource source) {
         NativeModdedServer server = source.server();
         List<ModdedDimensionManager.Handle> handles = ModdedDimensionManager.handles();

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

@@ -18,21 +18,22 @@
 
 package art.arcane.iris.modded.command;
 
-import art.arcane.iris.studio.view.GuiHost;
-import art.arcane.volmlib.nativelib.view.WorldMarker;
+import art.arcane.iris.studio.view.GuiMarker;
 import art.arcane.iris.studio.view.GuiOverlay;
-import art.arcane.iris.generation.runtime.IrisComplex;
+import art.arcane.iris.studio.view.OpenerPosition;
 import art.arcane.iris.generation.runtime.Engine;
-import art.arcane.iris.studio.render.RenderType;
 import art.arcane.iris.modded.ModdedIrisLog;
 import art.arcane.iris.modded.ModdedTeleportDeadline;
+import art.arcane.iris.world.IrisWorld;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeProtocolPlayer;
+import art.arcane.volmlib.nativelib.terrain.NativeWorld;
+import art.arcane.volmlib.nativelib.view.WorldView;
 
-import java.awt.Desktop;
-import java.io.File;
 import java.util.List;
 import java.util.Optional;
-import art.arcane.volmlib.nativelib.view.WorldView;
 import java.util.UUID;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.function.Consumer;
 
 public final class ModdedVisionOverlay implements GuiOverlay {
@@ -46,14 +47,33 @@ public final class ModdedVisionOverlay implements GuiOverlay {
         opener = context.opener();
     }
 
+    // WorldView doesn't report which way a player faces, so their markers all face south.
     @Override
-    public List<WorldMarker> players() {
-        return world.players();
+    public List<GuiMarker> players() {
+        return world.players().stream()
+                .map(player -> GuiMarker.player(player.label(), player.worldX(), player.worldZ(), 0F))
+                .toList();
     }
 
     @Override
-    public void requestEntities(Consumer<List<WorldMarker>> sink) {
-        world.requestEntities(sink);
+    public void requestEntities(Consumer<List<GuiMarker>> sink) {
+        world.requestEntities(entities -> sink.accept(entities.stream()
+                .map(entity -> GuiMarker.entity(entity.label(), entity.worldX(), entity.worldY(), entity.worldZ(),
+                        entity.health(), entity.maxHealth()))
+                .toList()));
+    }
+
+    @Override
+    public void requestOpenerPosition(Consumer<OpenerPosition> sink) {
+        if (opener == null) {
+            sink.accept(OpenerPosition.OFFLINE);
+            return;
+        }
+        try {
+            world.execute(() -> sink.accept(openerPosition()));
+        } catch (RejectedExecutionException failure) {
+            sink.accept(OpenerPosition.OFFLINE);
+        }
     }
 
     @Override
@@ -80,23 +100,25 @@ public final class ModdedVisionOverlay implements GuiOverlay {
         });
     }
 
-    @Override
-    public String openInEditor(double worldX, double worldZ, RenderType type) {
-        if (!GuiHost.isAvailable() || !Desktop.isDesktopSupported()) {
-            return null;
+    private OpenerPosition openerPosition() {
+        IrisWorld target = engine.getWorld();
+        if (target == null || engine.isClosing() || engine.isClosed()) {
+            return OpenerPosition.OFFLINE;
         }
-        IrisComplex complex = engine.getComplex();
-        File file = switch (type) {
-            case BIOME, LAYER_LOAD, DECORATOR_LOAD, OBJECT_LOAD, HEIGHT, RIVER ->
-                    complex.getTrueBiomeStream().get(worldX, worldZ).openInVSCode();
-            case BIOME_LAND -> complex.getLandBiomeStream().get(worldX, worldZ).openInVSCode();
-            case BIOME_SEA -> complex.getSeaBiomeStream().get(worldX, worldZ).openInVSCode();
-            case REGION -> complex.getRegionStream().get(worldX, worldZ).openInVSCode();
-            case CAVE_LAND -> complex.getCaveBiomeStream().get(worldX, worldZ).openInVSCode();
-            default -> null;
-        };
-        return file == null ? null : file.getName();
+        NativeWorld level = target.platformWorld();
+        if (level == null) {
+            return OpenerPosition.OFFLINE;
+        }
+        NativeProtocolPlayer player = NativeModdedServer.forWorld(level).player(opener);
+        if (player == null || !player.connected()) {
+            return OpenerPosition.OFFLINE;
+        }
+        if (!player.inWorld(level)) {
+            return OpenerPosition.IN_OTHER_WORLD;
+        }
+        return OpenerPosition.inWorld(player.x(), player.y(), player.z());
     }
+
     public record Context(WorldView world, Engine engine, UUID opener) {
     }
 

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

@@ -1016,6 +1016,18 @@ public final class ModdedCommandMessages {
             "iris.modded.moddedstudiocommands.studio_close_failed",
             "Studio close failed: " + "{value}" + "{errorMessage}"
     );
+    public static final TextKey MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_COMPLETE = TextKey.of(
+            "iris.modded.moddedstudiocommands.studio_hotload_complete",
+            "Studio hotloaded."
+    );
+    public static final TextKey MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_BUSY = TextKey.of(
+            "iris.modded.moddedstudiocommands.studio_hotload_busy",
+            "Studio is already checking or hotloading its pack. Try again after it finishes."
+    );
+    public static final TextKey MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_FAILED = TextKey.of(
+            "iris.modded.moddedstudiocommands.studio_hotload_failed",
+            "Studio hotload failed{errorMessage}"
+    );
     public static final TextKey MODDED_STUDIO_COMMANDS_STUDIO_CLOSED_WAS_EVACUATED_UNLOADED_ITS_REGION_DATA_DELETED = TextKey.of(
             "iris.modded.moddedstudiocommands.studio_closed_was_evacuated_unloaded_its_region_data_deleted",
             "Studio closed: " + "{dimensionId}" + " was evacuated, unloaded and its region data deleted."
@@ -1530,6 +1542,9 @@ public final class ModdedCommandMessages {
             MODDED_STUDIO_COMMANDS_STUDIO_OPEN_NOW_RUNS_SEED_USE_IRIS_STUDIO_CLOSE_WHEN,
             MODDED_STUDIO_COMMANDS_YOU_DO_NOT_HAVE_OPEN_STUDIO_USE_IRIS_STUDIO_OPEN,
             MODDED_STUDIO_COMMANDS_STUDIO_CLOSE_FAILED,
+            MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_COMPLETE,
+            MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_BUSY,
+            MODDED_STUDIO_COMMANDS_STUDIO_HOTLOAD_FAILED,
             MODDED_STUDIO_COMMANDS_STUDIO_CLOSED_WAS_EVACUATED_UNLOADED_ITS_REGION_DATA_DELETED,
             MODDED_STUDIO_COMMANDS_NO_STUDIO_DIMENSIONS_ARE_CURRENTLY_OPEN,
             MODDED_STUDIO_COMMANDS_ACTIVE_STUDIO_DIMENSION_S,

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

@@ -242,6 +242,10 @@ public final class ModdedHelpMessages {
             "iris.modded.help.entry.command.status_studio",
             "Show the open studio dimension and its pack"
     );
+    public static final TextKey COMMAND_HOTLOAD_REFRESH_THE_OPEN_STUDIO = TextKey.of(
+            "iris.modded.help.entry.command.hotload_studio",
+            "Reload the open Studio pack for newly generated terrain"
+    );
     public static final TextKey COMMAND_NOISE_OPEN_THE_NOISE_EXPLORER_GUI_ON_THE_SERVER_DISPLAY = TextKey.of(
             "iris.modded.help.entry.command.noise",
             "Open the Noise Explorer GUI on the server display"
@@ -326,6 +330,10 @@ public final class ModdedHelpMessages {
             "iris.modded.help.entry.command.remove",
             "Explain datapack removal workflow"
     );
+    public static final TextKey COMMAND_EXPORT_EXPORT_A_DIMENSION_AS_A_VANILLA_WORLDGEN_DATAPACK = TextKey.of(
+            "iris.modded.help.entry.command.export_datapack",
+            "Export a dimension as a vanilla worldgen datapack"
+    );
     public static final TextKey COMMAND_LIST_REGENERATE_STRUCTURE_INDEX_JSON = TextKey.of(
             "iris.modded.help.entry.command.list_structures",
             "Regenerate structure-index.json"
@@ -479,6 +487,7 @@ public final class ModdedHelpMessages {
             COMMAND_CLOSE_CLOSE_THE_OPEN_STUDIO_DIMENSION_AND_DISCARD_ITS_WORLD,
             COMMAND_TPSTUDIO_TELEPORT_INTO_THE_OPEN_STUDIO_DIMENSION,
             COMMAND_STATUS_SHOW_THE_OPEN_STUDIO_DIMENSION_AND_ITS_PACK,
+            COMMAND_HOTLOAD_REFRESH_THE_OPEN_STUDIO,
             COMMAND_NOISE_OPEN_THE_NOISE_EXPLORER_GUI_ON_THE_SERVER_DISPLAY,
             COMMAND_MAP_OPEN_THE_VISION_MAP_GUI_ON_THE_SERVER_DISPLAY,
             COMMAND_VSCODE_REGENERATE_THE_CODE_WORKSPACE_FOR_A_PACK_AND_OPEN_IT_IN_YOUR,
@@ -500,6 +509,7 @@ public final class ModdedHelpMessages {
             COMMAND_LIST_LIST_CONFIGURED_AND_INSTALLED_DATAPACKS,
             COMMAND_INGEST_EXPLAIN_BUKKIT_DATAPACK_INGEST_WORKFLOW,
             COMMAND_REMOVE_EXPLAIN_DATAPACK_REMOVAL_WORKFLOW,
+            COMMAND_EXPORT_EXPORT_A_DIMENSION_AS_A_VANILLA_WORLDGEN_DATAPACK,
             COMMAND_LIST_REGENERATE_STRUCTURE_INDEX_JSON,
             COMMAND_INFO_RESOLVE_AN_IRIS_STRUCTURE_GRAPH_AND_REPORT_BOUNDS,
             COMMAND_PLACE_ASSEMBLE_AND_PLACE_AN_IRIS_STRUCTURE_AT_YOUR_LOCATION,

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

@@ -123,6 +123,33 @@ public final class ModdedStudioHotloadService implements ModdedTickableService,
         watches.clear();
     }
 
+    public CompletableFuture<Boolean> requestHotload(String dimensionId, Engine engine) {
+        if (!dimensionId.startsWith(STUDIO_DIMENSION_PREFIX) || !engine.isStudio()) {
+            return CompletableFuture.failedFuture(new IllegalArgumentException("Only Studio worlds can be hotloaded."));
+        }
+        ExecutorService active = executor;
+        if (active == null || active.isShutdown()) {
+            return CompletableFuture.failedFuture(new IllegalStateException("Iris Studio hotload is unavailable."));
+        }
+        Watch watch = watches.computeIfAbsent(dimensionId, (String key) -> new Watch());
+        if (!watch.busy.compareAndSet(false, true)) {
+            return CompletableFuture.completedFuture(false);
+        }
+        try {
+            return CompletableFuture.supplyAsync(() -> {
+                try {
+                    hotload(dimensionId, engine);
+                    return true;
+                } finally {
+                    watch.busy.set(false);
+                }
+            }, active);
+        } catch (RejectedExecutionException rejected) {
+            watch.busy.set(false);
+            return CompletableFuture.failedFuture(rejected);
+        }
+    }
+
     @Override
     public void refreshWorkspace(Engine engine) {
         writeWorkspace(engine, "workspace refresh");
@@ -254,7 +281,7 @@ public final class ModdedStudioHotloadService implements ModdedTickableService,
             try {
                 active.execute(() -> {
                     try {
-                        poll(dimensionId, watch, generator, engine);
+                        poll(dimensionId, watch, engine);
                     } finally {
                         watch.busy.set(false);
                     }
@@ -332,14 +359,14 @@ public final class ModdedStudioHotloadService implements ModdedTickableService,
         return isPregeneratorActive(engine);
     }
 
-    private void poll(String dimensionId, Watch watch, IrisModdedChunkGenerator generator, Engine engine) {
+    private void poll(String dimensionId, Watch watch, Engine engine) {
         try {
             if (watch.engine != engine) {
                 watch.close();
                 watch.engine = engine;
                 watch.folder = new ReactiveFolder(
                         engine.getData().getDataFolder(),
-                        (KList<File> created, KList<File> changed, KList<File> deleted) -> hotload(dimensionId, generator, engine),
+                        (KList<File> created, KList<File> changed, KList<File> deleted) -> hotload(dimensionId, engine),
                         new KList<>(".iob", ".json"),
                         new KList<>(".iris"),
                         new KList<>());
@@ -354,12 +381,12 @@ public final class ModdedStudioHotloadService implements ModdedTickableService,
         }
     }
 
-    private void hotload(String dimensionId, IrisModdedChunkGenerator generator, Engine engine) {
-        if (engine.isClosed()) {
-            return;
-        }
+    private void hotload(String dimensionId, Engine engine) {
         long start = System.currentTimeMillis();
         try {
+            if (engine.isClosed() || engine.isClosing()) {
+                throw new IllegalStateException("The Studio world is closing or closed.");
+            }
             engine.hotloadSilently();
             ModdedIrisLog.info("Iris studio hotload {} pack={} {}ms", dimensionId, engine.getDimension().getLoadKey(), System.currentTimeMillis() - start);
         } catch (Throwable e) {

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

@@ -102,6 +102,15 @@ public class ModdedBiomePolicyTest {
         assertSame(desert, policy.orderedPossibleBiomes().getFirst());
     }
 
+    @Test
+    public void structureStateKeyComesFromTheBoundRuntime() {
+        ModdedBiomePolicy<BiomeToken, Object> policy = new ModdedBiomePolicy<>(new Access(new ArrayList<>()));
+        policy.bind(new ModdedBiomePolicy.RuntimeCallbacks(() -> null, () -> null, engine -> false,
+                Set::of, engine -> Set.of(), () -> 0L, () -> "epoch:example"));
+
+        assertEquals("epoch:example", policy.structureStateKey());
+    }
+
     @Test
     public void missingRequiredStructureBiomesFailBeforePublishingAPartialSet() {
         AtomicReference<Set<String>> configured = new AtomicReference<>(Set.of("example:missing"));
@@ -130,7 +139,7 @@ public class ModdedBiomePolicyTest {
         ModdedBiomePolicy<BiomeToken, Object> policy = new ModdedBiomePolicy<>(
                 new Access(new ArrayList<>(List.of(forest))));
         policy.bind(new ModdedBiomePolicy.RuntimeCallbacks(() -> engine, () -> engine, bound -> true,
-                () -> Set.of(forest.key()), bound -> Set.of(), () -> 0L));
+                () -> Set.of(forest.key()), bound -> Set.of(), () -> 0L, () -> "transient:test"));
 
         assertSame(forest, policy.requiredStructureBiome(6000, 0, -6000, null));
         assertSame(forest, policy.requiredStructureBiome(6000, -30, -6000, null));
@@ -212,7 +221,7 @@ public class ModdedBiomePolicyTest {
         ModdedBiomePolicy<BiomeToken, Object> policy = new ModdedBiomePolicy<>(
                 new Access(new ArrayList<>(List.of(plains, mirage))));
         policy.bind(new ModdedBiomePolicy.RuntimeCallbacks(() -> engine, () -> engine, bound -> false,
-                () -> Set.of(plains.key(), mirage.key()), bound -> Set.of(), () -> 0L));
+                () -> Set.of(plains.key(), mirage.key()), bound -> Set.of(), () -> 0L, () -> "transient:test"));
         int[] columns = {0, 1024, 2048, 3072, 4096, 5120};
 
         NativeBiomeSourcePolicy.BiomeLocation<BiomeToken> found = policy.findClosestBiome3d(
@@ -241,7 +250,7 @@ public class ModdedBiomePolicyTest {
     private static ModdedBiomePolicy<BiomeToken, Object> boundTo(Engine engine) {
         ModdedBiomePolicy<BiomeToken, Object> policy = new ModdedBiomePolicy<>(new Access(new ArrayList<>()));
         policy.bind(new ModdedBiomePolicy.RuntimeCallbacks(() -> engine, () -> engine, bound -> true,
-                Set::of, bound -> Set.of(), () -> 0L));
+                Set::of, bound -> Set.of(), () -> 0L, () -> "transient:test"));
         return policy;
     }
 
@@ -249,7 +258,7 @@ public class ModdedBiomePolicyTest {
                                                                AtomicReference<Set<String>> configured) {
         ModdedBiomePolicy<BiomeToken, Object> policy = new ModdedBiomePolicy<>(new Access(entries));
         policy.bind(new ModdedBiomePolicy.RuntimeCallbacks(() -> null, () -> null, engine -> false,
-                configured::get, engine -> Set.of(), () -> 0L));
+                configured::get, engine -> Set.of(), () -> 0L, () -> "transient:test"));
         return policy;
     }
 

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

@@ -0,0 +1,50 @@
+package art.arcane.iris.modded;
+
+import art.arcane.iris.platform.ClasspathVanillaDataSource;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.terrain.NativeWorld;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.nio.charset.StandardCharsets;
+
+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.when;
+
+public class ModdedVanillaDataTest {
+    private static final String PLAINS = "data/minecraft/worldgen/biome/plains.json";
+    private static final String BIOME_TAGS = "data/minecraft/tags/worldgen/biome";
+
+    @BeforeClass
+    public static void bootstrapRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void overworldLevelClassReadsTheGameVanillaData() {
+        NativeModdedServer server = mock(NativeModdedServer.class);
+        NativeWorld overworld = mock(NativeWorld.class);
+        when(overworld.nativeHandle()).thenReturn(mock(ServerLevel.class));
+        when(server.overworld()).thenReturn(overworld);
+        Class<?> anchor = ModdedPlatform.overworldClass(server);
+        assertSame(ServerLevel.class, anchor);
+        ClasspathVanillaDataSource source = new ClasspathVanillaDataSource(() -> anchor);
+        String plains = new String(source.read(PLAINS).orElseThrow(), StandardCharsets.UTF_8);
+        assertTrue(plains.contains("\"temperature\""));
+        assertTrue(source.list(BIOME_TAGS).contains(BIOME_TAGS + "/is_overworld.json"));
+    }
+
+    @Test
+    public void vanillaDataNeedsALoadedOverworld() {
+        NativeModdedServer server = mock(NativeModdedServer.class);
+        assertThrows(IllegalStateException.class, () -> ModdedPlatform.overworldClass(null));
+        assertThrows(IllegalStateException.class, () -> ModdedPlatform.overworldClass(server));
+    }
+}

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

@@ -63,6 +63,9 @@ public class IrisModdedCommandParityTest {
         CommandNode<CommandSourceStack> studio = child(iris, "studio");
         child(studio, "package");
         child(studio, "pkg");
+        CommandNode<CommandSourceStack> datapackExport = child(child(iris, "datapack"), "export");
+        assertNotNull(datapackExport.getCommand());
+        assertNotNull(child(datapackExport, "args").getCommand());
 
         CommandNode<CommandSourceStack> download = child(iris, "download");
         CommandNode<CommandSourceStack> source = child(download, "source");
@@ -211,6 +214,8 @@ public class IrisModdedCommandParityTest {
         assertTrue(root.stream().anyMatch((String line) -> line.startsWith("/iris teleport <dimension> [player] (tp) - ")));
         assertTrue(ModdedCommandHelp.consoleLines("pregen").stream().anyMatch((String line) ->
                 line.startsWith("/iris pregen start <radius> [dimension] [at] [x] [z] [gui] [sync] [nocache] - ")));
+        assertTrue(ModdedCommandHelp.consoleLines("datapack").stream().anyMatch((String line) ->
+                line.startsWith("/iris datapack export <dimension> [version=] [mode=overworld] [namespace=iris_export] [output=] [format=zip] [objects=true] [replace=false] - ")));
     }
 
     private static CommandNode<CommandSourceStack> child(

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

@@ -0,0 +1,87 @@
+package art.arcane.iris.modded.command;
+
+import art.arcane.iris.pack.datapack.DataVersion;
+import art.arcane.iris.pack.datapack.export.WorldgenExportRequest;
+import org.junit.Test;
+
+import java.nio.file.Path;
+
+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;
+
+public class ModdedDatapackExportArgumentsTest {
+    @Test
+    public void unknownKeyFails() {
+        assertEquals("unknown option 'seed'", reason("overworld seed=1"));
+        assertEquals("unknown option 'Version'", reason("overworld Version=26.3"));
+    }
+
+    @Test
+    public void duplicateKeyFails() {
+        assertEquals("option 'replace' given twice", reason("overworld replace=true replace=false"));
+        assertEquals("option 'version' given twice", reason("overworld version= version=26.3"));
+    }
+
+    @Test
+    public void firstBareTokenIsDimension() {
+        ModdedDatapackExportArguments arguments = ModdedDatapackExportArguments.parse(
+                "  version=26.3 overworld   mode=dimension namespace=worlds output=export_one format=directory objects=false replace=true ");
+
+        assertEquals("overworld", arguments.dimension());
+        assertEquals("26.3", arguments.version());
+        assertEquals("dimension", arguments.mode());
+        assertEquals("worlds", arguments.namespace());
+        assertEquals("export_one", arguments.output());
+        assertEquals("directory", arguments.format());
+        assertFalse(arguments.objects());
+        assertTrue(arguments.replace());
+        assertSame(DataVersion.V26_3, arguments.target());
+        assertEquals("unexpected argument 'underworld'", reason("overworld underworld"));
+        assertEquals("missing dimension", reason("   "));
+        assertEquals("missing dimension", reason("version=26.3"));
+    }
+
+    @Test
+    public void defaultsMatchBukkit() {
+        ModdedDatapackExportArguments arguments = ModdedDatapackExportArguments.parse("overworld");
+
+        assertEquals("", arguments.version());
+        assertEquals("overworld", arguments.mode());
+        assertEquals("iris_export", arguments.namespace());
+        assertEquals("", arguments.output());
+        assertEquals("zip", arguments.format());
+        assertTrue(arguments.objects());
+        assertFalse(arguments.replace());
+        assertSame(DataVersion.V26_3, arguments.target());
+
+        Path pack = Path.of("packs", "overworld");
+        Path exportRoot = Path.of("exports", "datapacks");
+        WorldgenExportRequest expected = WorldgenExportRequest.builder()
+                .pack(pack)
+                .dimension("overworld")
+                .exportRoot(exportRoot)
+                .build();
+        assertEquals(expected, arguments.toRequest(pack, exportRoot));
+    }
+
+    @Test
+    public void unsupportedValuesFailWithSharedMessages() {
+        assertEquals("Unsupported datapack export version '1.21.1'. Supported: 26.3",
+                reason("overworld version=1.21.1"));
+        assertEquals("Unsupported datapack export version '26.2'. Supported: 26.3",
+                reason("overworld version=26.2"));
+        assertEquals("Unknown export mode 'nether'. Expected: preset, dimension, overworld",
+                reason("overworld mode=nether"));
+        assertEquals("Export format must be directory or zip.", reason("overworld format=rar"));
+        assertEquals("objects must be true or false", reason("overworld objects=yes"));
+        assertEquals("replace must be true or false", reason("overworld replace=1"));
+        assertEquals("invalid dimension key 'a..b'", reason("a..b"));
+    }
+
+    private static String reason(String raw) {
+        return assertThrows(IllegalArgumentException.class, () -> ModdedDatapackExportArguments.parse(raw)).getMessage();
+    }
+}

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

@@ -0,0 +1,149 @@
+package art.arcane.iris.modded.command;
+
+import art.arcane.iris.generation.hydrology.engine.HydrologyRuntime;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureQuery;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureRef;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureType;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.IrisComplex;
+import art.arcane.iris.generation.terrain.IrisDimension;
+import art.arcane.iris.world.history.GenerationSemanticQueries;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandSource;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeProtocolPlayer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeStructureQueries;
+import art.arcane.volmlib.nativelib.terrain.NativeWorld;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+import org.mockito.MockedConstruction;
+import org.mockito.MockedStatic;
+
+import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyDouble;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockConstruction;
+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 ModdedLocateRiverTest {
+    private static final int DISTANCE = GenerationSemanticQueries.RIVER_SEARCH_DISTANCE;
+
+    @Test
+    public void unknownTypeFailsBeforeSearching() {
+        Fixture fixture = new Fixture();
+        try (MockedStatic<IrisModdedCommands> commands = fixture.commands()) {
+            assertEquals(0, ModdedLocateCommands.gotoRiver(fixture.source, "ocean_trench"));
+
+            commands.verify(() -> IrisModdedCommands.fail(eq(fixture.source), anyString()));
+            commands.verify(() -> IrisModdedCommands.ok(eq(fixture.source), anyString()), never());
+            verify(fixture.server, never()).execute(any());
+            verify(fixture.runtime, never()).nearestFeature(anyInt(), anyInt(), any(), anyInt(), any());
+        }
+    }
+
+    @Test
+    public void missingFeatureReportsNotFound() throws Exception {
+        Fixture fixture = new Fixture();
+        when(fixture.runtime.nearestFeature(anyInt(), anyInt(), any(), anyInt(), any())).thenReturn(Optional.empty());
+        try (MockedStatic<IrisModdedCommands> commands = fixture.commands()) {
+            assertEquals(1, ModdedLocateCommands.gotoRiver(fixture.source, "river"));
+            fixture.finishOnServerThread();
+
+            commands.verify(() -> IrisModdedCommands.fail(fixture.source, "No river found within " + DISTANCE + " blocks."));
+            verify(fixture.player, never()).teleport(any(), anyDouble(), anyDouble(), anyDouble());
+        }
+    }
+
+    @Test
+    public void plannerFailureIsReportedAsAnErrorNotAsNotFound() throws Exception {
+        Fixture fixture = new Fixture();
+        when(fixture.runtime.nearestFeature(anyInt(), anyInt(), any(), anyInt(), any()))
+                .thenThrow(new IllegalStateException("window planner exploded"));
+        try (MockedStatic<IrisModdedCommands> commands = fixture.commands()) {
+            assertEquals(1, ModdedLocateCommands.gotoRiver(fixture.source, "major_river"));
+            fixture.finishOnServerThread();
+
+            commands.verify(() -> IrisModdedCommands.fail(fixture.source,
+                    "Could not search for major river: IllegalStateException - window planner exploded"));
+            commands.verify(() -> IrisModdedCommands.fail(eq(fixture.source), eq("No major river found within " + DISTANCE + " blocks.")),
+                    never());
+            verify(fixture.player, never()).teleport(any(), anyDouble(), anyDouble(), anyDouble());
+        }
+    }
+
+    @Test
+    public void foundFeatureTeleportsAboveItFromThePlayersPosition() throws Exception {
+        Fixture fixture = new Fixture();
+        when(fixture.runtime.nearestFeature(anyInt(), anyInt(), any(), anyInt(), any()))
+                .thenReturn(Optional.of(new HydrologyFeatureRef(9L, HydrologyFeatureType.WATERFALL, 400, 130, -250)));
+        when(fixture.player.teleport(fixture.world, 400.5D, 68D, -249.5D)).thenReturn(true);
+        try (MockedStatic<IrisModdedCommands> commands = fixture.commands();
+             MockedConstruction<NativeStructureQueries> queries = mockConstruction(NativeStructureQueries.class)) {
+            assertEquals(1, ModdedLocateCommands.gotoRiver(fixture.source, "waterfall"));
+            fixture.finishOnServerThread();
+
+            ArgumentCaptor<HydrologyFeatureQuery> query = ArgumentCaptor.forClass(HydrologyFeatureQuery.class);
+            verify(fixture.runtime).nearestFeature(eq(120), eq(-75), query.capture(), eq(DISTANCE), any());
+            assertEquals(HydrologyFeatureQuery.of(HydrologyFeatureType.WATERFALL), query.getValue());
+            verify(queries.constructed().getFirst()).loadChunk(400 >> 4, -250 >> 4);
+            verify(fixture.player).teleport(fixture.world, 400.5D, 68D, -249.5D);
+            commands.verify(() -> IrisModdedCommands.ok(eq(fixture.source), anyString()), times(2));
+            commands.verify(() -> IrisModdedCommands.fail(eq(fixture.source), anyString()), never());
+        }
+    }
+
+    private static final class Fixture {
+        private final NativeCommandSource source = mock(NativeCommandSource.class);
+        private final NativeWorld world = mock(NativeWorld.class);
+        private final NativeProtocolPlayer player = mock(NativeProtocolPlayer.class);
+        private final NativeModdedServer server = mock(NativeModdedServer.class);
+        private final Engine engine = mock(Engine.class);
+        private final HydrologyRuntime runtime = mock(HydrologyRuntime.class);
+        private final CompletableFuture<Runnable> completion = new CompletableFuture<>();
+
+        private Fixture() {
+            IrisComplex complex = mock(IrisComplex.class);
+            IrisDimension dimension = mock(IrisDimension.class);
+            when(source.player()).thenReturn(player);
+            when(source.world()).thenReturn(world);
+            when(source.server()).thenReturn(server);
+            when(player.blockX()).thenReturn(120);
+            when(player.blockZ()).thenReturn(-75);
+            when(player.connected()).thenReturn(true);
+            when(player.inWorld(world)).thenReturn(true);
+            when(world.minHeight()).thenReturn(-64);
+            when(world.maxHeight()).thenReturn(320);
+            when(engine.getComplex()).thenReturn(complex);
+            when(engine.getDimension()).thenReturn(dimension);
+            when(dimension.getMinHeight()).thenReturn(-64);
+            when(complex.getHydrologyRuntime()).thenReturn(runtime);
+            when(runtime.enabled()).thenReturn(true);
+            doAnswer(invocation -> {
+                completion.complete(invocation.getArgument(0));
+                return null;
+            }).when(server).execute(any());
+        }
+
+        private MockedStatic<IrisModdedCommands> commands() {
+            MockedStatic<IrisModdedCommands> commands = mockStatic(IrisModdedCommands.class);
+            commands.when(() -> IrisModdedCommands.engineFor(world)).thenReturn(engine);
+            return commands;
+        }
+
+        private void finishOnServerThread() throws Exception {
+            completion.get(10L, TimeUnit.SECONDS).run();
+        }
+    }
+}

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

@@ -1,6 +1,7 @@
 package art.arcane.iris.modded.command;
 
 import art.arcane.iris.configuration.IrisSettings;
+import art.arcane.iris.generation.hydrology.engine.HydrologyPregeneration;
 import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.modded.ModdedGenPool;
 import art.arcane.iris.world.pregen.MantleHeapPressure;
@@ -11,8 +12,10 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
+import org.mockito.InOrder;
 import org.mockito.MockedStatic;
 
+import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
@@ -31,9 +34,11 @@ import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyList;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.RETURNS_DEEP_STUBS;
 import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.mockStatic;
 import static org.mockito.Mockito.never;
@@ -89,6 +94,25 @@ public class ModdedPregenMethodLifecycleTest {
         verify(runtime, never()).execute(any());
     }
 
+    @Test
+    public void closeWithdrawsQueuedHydrologyPrefetchAndRefusesLaterAnnouncements() {
+        HydrologyPregeneration epoch = mock(HydrologyPregeneration.class);
+        when(engine.getComplex().getHydrologyRuntime().openPregeneration()).thenReturn(epoch);
+        when(runtime.isServerThread()).thenReturn(true);
+        assertTrue(method.deferFinalSaveToServerThread());
+        List<long[]> ahead = List.of(new long[]{0L, 0L}, new long[]{1L, 0L});
+
+        method.onRegionsAhead(ahead);
+        method.close();
+        method.onRegionsAhead(ahead);
+
+        InOrder order = inOrder(epoch);
+        order.verify(epoch).prepare(ahead);
+        order.verify(epoch).close();
+        verify(epoch, times(1)).prepare(anyList());
+        method.completeDeferredFinalSave();
+    }
+
     @Test
     public void asynchronousCallerCannotClaimTheShutdownSave() {
         assertFalse(method.deferFinalSaveToServerThread());

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

@@ -0,0 +1,113 @@
+package art.arcane.iris.modded.command;
+
+import art.arcane.iris.localization.IrisLanguage;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandSource;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeCommandText;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeProtocolPlayer;
+import art.arcane.volmlib.util.localization.LanguageAudience;
+import com.mojang.brigadier.CommandDispatcher;
+import net.minecraft.SharedConstants;
+import net.minecraft.server.Bootstrap;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class ModdedStudioHotloadLanguageTest {
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    private final UUID playerId = UUID.randomUUID();
+    private File dataFolder;
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Before
+    public void setUp() throws Exception {
+        dataFolder = temporaryFolder.newFolder();
+        assertTrue(IrisLanguage.reload(dataFolder, "en_US"));
+        Files.writeString(dataFolder.toPath().resolve("languages/de_DE.toml"),
+                "\"iris.modded.moddedstudiocommands.you_do_not_have_open_studio_use_iris_studio_open\" = \"Kein Studio geöffnet.\"\n");
+        IrisLanguage.start();
+        IrisLanguage.selections().selectPlayer(playerId, "de_DE").get(5L, TimeUnit.SECONDS);
+        ModdedStudioCommands.clear();
+    }
+
+    @After
+    public void tearDown() {
+        ModdedStudioCommands.clear();
+        IrisLanguage.shutdown();
+        assertTrue(IrisLanguage.reload(dataFolder, "en_US"));
+    }
+
+    @Test
+    public void delayedHotloadFeedbackKeepsThePlayersLanguage() throws Exception {
+        assertEquals(List.of("Kein Studio geöffnet."), runCommand("studio hotload", true));
+    }
+
+    @Test
+    public void delayedConsoleRefreshUsesTheServerLanguage() throws Exception {
+        assertEquals(List.of("You do not have an open studio. Use /iris studio open <pack> first."),
+                runCommand("studio refresh", false));
+    }
+
+    private List<String> runCommand(String command, boolean playerCommand) throws Exception {
+        NativeModdedServer server = mock(NativeModdedServer.class);
+        List<Runnable> tasks = new ArrayList<>();
+        doAnswer(invocation -> {
+            tasks.add(invocation.getArgument(0));
+            return null;
+        }).when(server).execute(any(Runnable.class));
+        NativeCommandSource source = mock(NativeCommandSource.class);
+        when(source.server()).thenReturn(server);
+        when(source.isGameMaster()).thenReturn(true);
+        if (playerCommand) {
+            NativeProtocolPlayer player = mock(NativeProtocolPlayer.class);
+            when(player.id()).thenReturn(playerId);
+            when(source.player()).thenReturn(player);
+            when(source.playerId()).thenReturn(playerId);
+        }
+        List<String> messages = new ArrayList<>();
+        doAnswer(invocation -> {
+            NativeCommandText text = invocation.getArgument(0);
+            messages.add(text.getString());
+            return null;
+        }).when(source).sendFailure(any());
+        CommandDispatcher<NativeCommandSource> dispatcher = new CommandDispatcher<>();
+        dispatcher.register(ModdedStudioCommands.tree("studio"));
+
+        assertEquals(1, dispatcher.execute(command, source));
+        assertTrue(messages.isEmpty());
+        assertNull(LanguageAudience.current());
+        UUID ambientAudience = playerCommand ? UUID.randomUUID() : playerId;
+        try (LanguageAudience.Scope audience = LanguageAudience.open(ambientAudience)) {
+            while (!tasks.isEmpty()) {
+                tasks.removeFirst().run();
+                assertEquals(ambientAudience, LanguageAudience.current());
+            }
+        }
+        return messages;
+    }
+}

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

@@ -1,25 +1,98 @@
 package art.arcane.iris.modded.command;
 
 import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.studio.view.OpenerPosition;
+import art.arcane.iris.world.IrisWorld;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeModdedServer;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeProtocolPlayer;
+import art.arcane.volmlib.nativelib.terrain.NativeWorld;
 import art.arcane.volmlib.nativelib.view.WorldView;
 import org.junit.Test;
+import org.mockito.MockedStatic;
 import org.mockito.invocation.InvocationOnMock;
 
 import java.util.Optional;
 import java.util.UUID;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertNull;
 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.doThrow;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
 import static org.mockito.Mockito.when;
 
 public class ModdedVisionOverlayTest {
+    @Test
+    public void rejectedServerTaskCompletesThePositionRequestAsOffline() {
+        WorldView world = mock(WorldView.class);
+        doThrow(new RejectedExecutionException("Server stopped")).when(world).execute(any(Runnable.class));
+        ModdedVisionOverlay overlay = new ModdedVisionOverlay(new ModdedVisionOverlay.Context(world,
+                mock(Engine.class), UUID.randomUUID()));
+        AtomicReference<OpenerPosition> position = new AtomicReference<>();
+
+        overlay.requestOpenerPosition(position::set);
+
+        assertEquals(OpenerPosition.OFFLINE, position.get());
+    }
+
+    @Test
+    public void openerPositionRunsOnTheServerAndTracksDisconnectAndWorldChanges() {
+        WorldView world = mock(WorldView.class);
+        AtomicReference<Runnable> scheduled = new AtomicReference<>();
+        doAnswer(invocation -> {
+            scheduled.set(invocation.getArgument(0));
+            return null;
+        }).when(world).execute(any(Runnable.class));
+        Engine engine = mock(Engine.class);
+        IrisWorld irisWorld = mock(IrisWorld.class);
+        NativeWorld level = mock(NativeWorld.class);
+        NativeModdedServer server = mock(NativeModdedServer.class);
+        NativeProtocolPlayer player = mock(NativeProtocolPlayer.class);
+        UUID opener = UUID.randomUUID();
+        when(engine.getWorld()).thenReturn(irisWorld);
+        when(irisWorld.platformWorld()).thenReturn(level);
+        when(server.player(opener)).thenReturn(player);
+        when(player.connected()).thenReturn(true);
+        when(player.inWorld(level)).thenReturn(true);
+        when(player.x()).thenReturn(21.5D);
+        when(player.y()).thenReturn(85.25D);
+        when(player.z()).thenReturn(-39.5D);
+        ModdedVisionOverlay overlay = new ModdedVisionOverlay(new ModdedVisionOverlay.Context(world, engine, opener));
+        AtomicReference<OpenerPosition> position = new AtomicReference<>();
+        try (MockedStatic<NativeModdedServer> nativeServer = mockStatic(NativeModdedServer.class)) {
+            nativeServer.when(() -> NativeModdedServer.forWorld(level)).thenReturn(server);
+
+            overlay.requestOpenerPosition(position::set);
+            assertNull("position reads must wait for the server task", position.get());
+            scheduled.get().run();
+            assertEquals(OpenerPosition.inWorld(21.5D, 85.25D, -39.5D), position.get());
+
+            overlay.requestOpenerPosition(position::set);
+            when(player.connected()).thenReturn(false);
+            scheduled.get().run();
+            assertEquals(OpenerPosition.OFFLINE, position.get());
+
+            when(player.connected()).thenReturn(true);
+            when(player.inWorld(level)).thenReturn(false);
+            overlay.requestOpenerPosition(position::set);
+            scheduled.get().run();
+            assertEquals(OpenerPosition.IN_OTHER_WORLD, position.get());
+
+            when(player.inWorld(level)).thenReturn(true);
+            overlay.requestOpenerPosition(position::set);
+            scheduled.get().run();
+            assertEquals(OpenerPosition.inWorld(21.5D, 85.25D, -39.5D), position.get());
+        }
+    }
+
     /**
      * A Vision click can land anywhere in the world, so the destination chunk is usually cold and gets the same
      * bounded deadline as /iris tp.

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

@@ -1,5 +1,6 @@
 package art.arcane.iris.modded.service;
 
+import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.generation.terrain.IrisDimension;
 import art.arcane.iris.modded.ModdedScheduler;
 import art.arcane.volmlib.util.collection.KList;
@@ -8,19 +9,130 @@ import org.mockito.InOrder;
 
 import java.lang.reflect.Field;
 import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.doAnswer;
+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 ModdedStudioHotloadServiceTest {
+    @Test
+    public void manualHotloadRunsWithoutAFileChangeOnTheWorker() throws Exception {
+        ModdedStudioHotloadService service = new ModdedStudioHotloadService();
+        Engine engine = studioEngine();
+        Thread caller = Thread.currentThread();
+        doAnswer(invocation -> {
+            assertNotSame(caller, Thread.currentThread());
+            return null;
+        }).when(engine).hotloadSilently();
+        service.onEnable();
+        try {
+            assertTrue(service.requestHotload("irisworldgen:studio_test", engine).get(5L, TimeUnit.SECONDS));
+            verify(engine).hotloadSilently();
+        } finally {
+            service.onDisable();
+        }
+    }
+
+    @Test
+    public void overlappingManualHotloadIsRejected() throws Exception {
+        ModdedStudioHotloadService service = new ModdedStudioHotloadService();
+        Engine engine = studioEngine();
+        CountDownLatch entered = new CountDownLatch(1);
+        CountDownLatch release = new CountDownLatch(1);
+        doAnswer(invocation -> {
+            entered.countDown();
+            assertTrue(release.await(5L, TimeUnit.SECONDS));
+            return null;
+        }).when(engine).hotloadSilently();
+        service.onEnable();
+        try {
+            CompletableFuture<Boolean> first = service.requestHotload("irisworldgen:studio_test", engine);
+            assertTrue(entered.await(5L, TimeUnit.SECONDS));
+            assertFalse(service.requestHotload("irisworldgen:studio_test", engine).get(5L, TimeUnit.SECONDS));
+            release.countDown();
+            assertTrue(first.get(5L, TimeUnit.SECONDS));
+            verify(engine).hotloadSilently();
+        } finally {
+            release.countDown();
+            service.onDisable();
+        }
+    }
+
+    @Test
+    public void closingStudioIsNotHotloadedAfterWaitingInTheQueue() throws Exception {
+        ModdedStudioHotloadService service = new ModdedStudioHotloadService();
+        Engine engine = studioEngine();
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+        CountDownLatch release = new CountDownLatch(1);
+        executor.submit(() -> {
+            try {
+                assertTrue(release.await(5L, TimeUnit.SECONDS));
+            } catch (InterruptedException failure) {
+                Thread.currentThread().interrupt();
+                throw new IllegalStateException(failure);
+            }
+        });
+        setExecutor(service, executor);
+        try {
+            CompletableFuture<Boolean> requested = service.requestHotload("irisworldgen:studio_test", engine);
+            when(engine.isClosing()).thenReturn(true);
+            release.countDown();
+            assertThrows(ExecutionException.class, () -> requested.get(5L, TimeUnit.SECONDS));
+            verify(engine, never()).hotloadSilently();
+        } finally {
+            release.countDown();
+            service.onDisable();
+        }
+    }
+
+    @Test
+    public void manualHotloadRejectsProductionWorlds() throws Exception {
+        ModdedStudioHotloadService service = new ModdedStudioHotloadService();
+        Engine engine = studioEngine();
+        service.onEnable();
+        try {
+            assertThrows(ExecutionException.class, () -> service.requestHotload("irisworldgen:production", engine)
+                    .get(5L, TimeUnit.SECONDS));
+            when(engine.isStudio()).thenReturn(false);
+            assertThrows(ExecutionException.class, () -> service.requestHotload("irisworldgen:studio_test", engine)
+                    .get(5L, TimeUnit.SECONDS));
+            verify(engine, never()).hotloadSilently();
+        } finally {
+            service.onDisable();
+        }
+    }
+
+    @Test
+    public void failedManualHotloadReleasesTheWatchForRetry() throws Exception {
+        ModdedStudioHotloadService service = new ModdedStudioHotloadService();
+        Engine engine = studioEngine();
+        doThrow(new IllegalStateException("Invalid pack")).doNothing().when(engine).hotloadSilently();
+        service.onEnable();
+        try {
+            assertThrows(ExecutionException.class, () -> service.requestHotload("irisworldgen:studio_test", engine)
+                    .get(5L, TimeUnit.SECONDS));
+            assertTrue(service.requestHotload("irisworldgen:studio_test", engine).get(5L, TimeUnit.SECONDS));
+        } finally {
+            service.onDisable();
+        }
+    }
+
     @Test
     public void shutdownDrainsWorkerBeforeAllowingRestart() throws Exception {
         ModdedStudioHotloadService service = new ModdedStudioHotloadService();
@@ -102,4 +214,11 @@ public class ModdedStudioHotloadServiceTest {
         field.set(service, executor);
     }
 
+    private static Engine studioEngine() {
+        Engine engine = mock(Engine.class);
+        when(engine.isStudio()).thenReturn(true);
+        when(engine.getDimension()).thenReturn(new IrisDimension());
+        return engine;
+    }
+
 }

adapters/modded-common/src/test/java/art/arcane/volmlib/nativelib/minecraft26_2/modded/NativeModdedBiomeSourceCodecTest.java

@@ -0,0 +1,64 @@
+package art.arcane.volmlib.nativelib.minecraft26_2.modded;
+
+import art.arcane.volmlib.nativelib.terrain.NativeModdedBiomePolicy;
+import com.google.gson.JsonElement;
+import com.mojang.serialization.DataResult;
+import com.mojang.serialization.JsonOps;
+import com.mojang.serialization.MapCodec;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.Holder;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.Climate;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.Constructor;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeModdedBiomeSourceCodecTest {
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void runtimeSourceEncodeReportsErrorInsteadOfThrowing() {
+        DataResult<JsonElement> result = BiomeSource.CODEC.encodeStart(JsonOps.INSTANCE, runtimeSource("epoch:unused"));
+        assertTrue(result.isError());
+    }
+
+    @Test
+    @SuppressWarnings("unchecked")
+    public void structureStateSourceEncodesItsGenerationKey() throws ReflectiveOperationException {
+        BiomeSource structureState = structureState(runtimeSource("epoch:example"));
+        MapCodec<BiomeSource> codec = (MapCodec<BiomeSource>) NativeModdedBiomeSource.STRUCTURE_STATE_CODEC;
+
+        JsonElement encoded = codec.codec().encodeStart(JsonOps.INSTANCE, structureState).getOrThrow();
+
+        assertEquals("epoch:example", encoded.getAsJsonObject().get("generation").getAsString());
+        assertTrue(codec.codec().parse(JsonOps.INSTANCE, encoded).isError());
+    }
+
+    private static BiomeSource structureState(NativeModdedBiomeSource<?> source) throws ReflectiveOperationException {
+        Class<?> type = Class.forName(NativeModdedBiomeSource.class.getName() + "$StructureStateBiomeSource");
+        Constructor<?> constructor = type.getDeclaredConstructor(NativeModdedBiomeSource.class, Set.class);
+        constructor.setAccessible(true);
+        return (BiomeSource) constructor.newInstance(source, Set.<Holder<Biome>>of());
+    }
+
+    @SuppressWarnings("unchecked")
+    private static NativeModdedBiomeSource<NativeModdedBiomePolicy<Holder<Biome>, Climate.Sampler>> runtimeSource(String key) {
+        NativeModdedBiomePolicy<Holder<Biome>, Climate.Sampler> policy = mock(NativeModdedBiomePolicy.class);
+        when(policy.structureStateKey()).thenReturn(key);
+        return new NativeModdedBiomeSource<>(new NativeModdedBiomeSource.Options<>(
+                mock(BiomeSource.class), () -> null, access -> policy));
+    }
+}

adapters/modded-common/src/test/java/art/arcane/volmlib/nativelib/minecraft26_2/modded/NativeModdedChunkGeneratorTerrainWriteTest.java

@@ -0,0 +1,104 @@
+package art.arcane.volmlib.nativelib.minecraft26_2.modded;
+
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+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.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeGenerationSettings;
+import net.minecraft.world.level.biome.BiomeSpecialEffects;
+import net.minecraft.world.level.biome.MobSpawnSettings;
+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.PalettedContainer;
+import net.minecraft.world.level.chunk.PalettedContainerFactory;
+import net.minecraft.world.level.chunk.PalettedContainerRO;
+import net.minecraft.world.level.chunk.ProtoChunk;
+import net.minecraft.world.level.chunk.Strategy;
+import net.minecraft.world.level.chunk.UpgradeData;
+import org.junit.Assume;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertSame;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeModdedChunkGeneratorTerrainWriteTest {
+    private static final int MIN_Y = -64;
+    private static final int HEIGHT = 384;
+    private static final int SURFACE = 10;
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void freshSectionsInstallWithoutSelfLockingTheirContainers() throws Exception {
+        BlockState stone = Blocks.STONE.defaultBlockState();
+        Assume.assumeTrue("block-state ids are not baked on this classpath",
+                Block.BLOCK_STATE_REGISTRY.getId(stone) >= 0);
+        NativeBlockState nativeStone = mock(NativeBlockState.class);
+        when(nativeStone.nativeHandle()).thenReturn(stone);
+        NativeModdedGeneratorPolicy.BlockBuffer blocks = (x, y, z) -> y + MIN_Y < SURFACE ? nativeStone : null;
+        ProtoChunk chunk = newChunk();
+        Method writeBlocks = NativeModdedChunkGenerator.class.getDeclaredMethod("writeBlocks", ChunkAccess.class,
+                NativeModdedGeneratorPolicy.BlockBuffer.class, int.class, int.class);
+        writeBlocks.setAccessible(true);
+
+        CompletableFuture.runAsync(() -> invoke(writeBlocks, chunk, blocks)).get(30, TimeUnit.SECONDS);
+
+        assertSame(stone, chunk.getBlockState(new BlockPos(3, SURFACE - 1, 5)));
+        assertSame(stone, chunk.getBlockState(new BlockPos(0, MIN_Y, 0)));
+        assertSame(Blocks.AIR.defaultBlockState(), chunk.getBlockState(new BlockPos(3, SURFACE, 5)));
+    }
+
+    private static void invoke(Method writeBlocks, ChunkAccess chunk, NativeModdedGeneratorPolicy.BlockBuffer blocks) {
+        try {
+            writeBlocks.invoke(null, chunk, blocks, MIN_Y, HEIGHT);
+        } catch (IllegalAccessException | InvocationTargetException failure) {
+            throw new IllegalStateException(failure);
+        }
+    }
+
+    private static ProtoChunk newChunk() {
+        return new ProtoChunk(new ChunkPos(0, 0), UpgradeData.EMPTY, LevelHeightAccessor.create(MIN_Y, HEIGHT),
+                palettedContainerFactory(), null);
+    }
+
+    private static PalettedContainerFactory palettedContainerFactory() {
+        Strategy<BlockState> blockStrategy = Strategy.createForBlockStates(Block.BLOCK_STATE_REGISTRY);
+        Codec<PalettedContainer<BlockState>> blockCodec = PalettedContainer.codecRW(
+                BlockState.CODEC, blockStrategy, Blocks.AIR.defaultBlockState());
+        Biome biome = new Biome.BiomeBuilder()
+                .hasPrecipitation(false)
+                .temperature(0.8F)
+                .downfall(0.4F)
+                .specialEffects(new BiomeSpecialEffects.Builder().waterColor(0x3F76E4).build())
+                .mobSpawnSettings(MobSpawnSettings.EMPTY)
+                .generationSettings(BiomeGenerationSettings.EMPTY)
+                .build();
+        Holder<Biome> biomeHolder = Holder.direct(biome);
+        IdMapper<Holder<Biome>> biomeIds = new IdMapper<>(1);
+        biomeIds.add(biomeHolder);
+        Strategy<Holder<Biome>> biomeStrategy = Strategy.createForBiomes(biomeIds);
+        Codec<PalettedContainerRO<Holder<Biome>>> biomeCodec = PalettedContainer.codecRO(
+                Biome.CODEC, biomeStrategy, biomeHolder);
+        return new PalettedContainerFactory(blockStrategy, Blocks.AIR.defaultBlockState(), blockCodec,
+                biomeStrategy, biomeHolder, biomeCodec);
+    }
+}

adapters/modded-common/src/versions/1.21.1/test/java/art/arcane/volmlib/nativelib/minecraft26_2/modded/NativeModdedChunkGeneratorTerrainWriteTest.java

@@ -0,0 +1,98 @@
+package art.arcane.volmlib.nativelib.minecraft26_2.modded;
+
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import com.mojang.serialization.Lifecycle;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.MappedRegistry;
+import net.minecraft.core.RegistrationInfo;
+import net.minecraft.core.Registry;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeGenerationSettings;
+import net.minecraft.world.level.biome.BiomeSpecialEffects;
+import net.minecraft.world.level.biome.MobSpawnSettings;
+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.ProtoChunk;
+import net.minecraft.world.level.chunk.UpgradeData;
+import org.junit.Assume;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.Assert.assertSame;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NativeModdedChunkGeneratorTerrainWriteTest {
+    private static final int MIN_Y = -64;
+    private static final int HEIGHT = 384;
+    private static final int SURFACE = 10;
+
+    @BeforeClass
+    public static void bootstrap() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+    }
+
+    @Test
+    public void freshSectionsInstallWithoutSelfLockingTheirContainers() throws Exception {
+        BlockState stone = Blocks.STONE.defaultBlockState();
+        Assume.assumeTrue("block-state ids are not baked on this classpath",
+                Block.BLOCK_STATE_REGISTRY.getId(stone) >= 0);
+        NativeBlockState nativeStone = mock(NativeBlockState.class);
+        when(nativeStone.nativeHandle()).thenReturn(stone);
+        NativeModdedGeneratorPolicy.BlockBuffer blocks = (x, y, z) -> y + MIN_Y < SURFACE ? nativeStone : null;
+        ProtoChunk chunk = newChunk();
+        Method writeBlocks = NativeModdedChunkGenerator.class.getDeclaredMethod("writeBlocks", ChunkAccess.class,
+                NativeModdedGeneratorPolicy.BlockBuffer.class, int.class, int.class);
+        writeBlocks.setAccessible(true);
+
+        CompletableFuture.runAsync(() -> invoke(writeBlocks, chunk, blocks)).get(30, TimeUnit.SECONDS);
+
+        assertSame(stone, chunk.getBlockState(new BlockPos(3, SURFACE - 1, 5)));
+        assertSame(stone, chunk.getBlockState(new BlockPos(0, MIN_Y, 0)));
+        assertSame(Blocks.AIR.defaultBlockState(), chunk.getBlockState(new BlockPos(3, SURFACE, 5)));
+    }
+
+    private static void invoke(Method writeBlocks, ChunkAccess chunk, NativeModdedGeneratorPolicy.BlockBuffer blocks) {
+        try {
+            writeBlocks.invoke(null, chunk, blocks, MIN_Y, HEIGHT);
+        } catch (IllegalAccessException | InvocationTargetException failure) {
+            throw new IllegalStateException(failure);
+        }
+    }
+
+    private static ProtoChunk newChunk() {
+        return new ProtoChunk(new ChunkPos(0, 0), UpgradeData.EMPTY, LevelHeightAccessor.create(MIN_Y, HEIGHT),
+                biomeRegistry(), null);
+    }
+
+    private static Registry<Biome> biomeRegistry() {
+        Biome biome = new Biome.BiomeBuilder()
+                .hasPrecipitation(false)
+                .temperature(0.8F)
+                .downfall(0.4F)
+                .specialEffects(new BiomeSpecialEffects.Builder().fogColor(0).waterColor(0x3F76E4)
+                        .waterFogColor(0).skyColor(0).build())
+                .mobSpawnSettings(MobSpawnSettings.EMPTY)
+                .generationSettings(BiomeGenerationSettings.EMPTY)
+                .build();
+        MappedRegistry<Biome> registry = new MappedRegistry<>(Registries.BIOME, Lifecycle.stable());
+        registry.register(ResourceKey.create(Registries.BIOME, ResourceLocation.withDefaultNamespace("plains")),
+                biome, RegistrationInfo.BUILT_IN);
+        return registry.freeze();
+    }
+}

adapters/neoforge/build.gradle

@@ -60,7 +60,7 @@ apply from: file('../../gradle/java21-runtime-exclusions.gradle')
 
 Properties rootProperties = new Properties()
 file('../../gradle.properties').withInputStream { InputStream stream -> rootProperties.load(stream) }
-String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.5'))
+String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.7'))
 String minecraftVersion = providers.gradleProperty('minecraftVersion').getOrElse(rootProperties.getProperty('minecraftVersion', '26.3'))
 String neoForgeVersion = providers.gradleProperty('neoForgeVersion').getOrElse(irisModTarget.neoForge.toString())
 Closure<String> irisArtifactName = { String platform, String targetVersion ->
@@ -132,6 +132,8 @@ configurations.named('bundle').configure {
     exclude(group: 'de.crazydev22.slimjar.helper')
     exclude(group: 'de.crazydev22.slimjar')
     exclude(group: 'io.github.slimjar')
+    // The game ships its own LWJGL; without the modules it leaves out, the map's 3D views draw in software.
+    exclude(group: 'org.lwjgl')
 }
 
 configurations.compileClasspath.extendsFrom(configurations.devBundle)
@@ -141,7 +143,7 @@ configurations.testRuntimeClasspath.extendsFrom(configurations.runtimeClasspath,
 
 dependencies {
     testImplementation('junit:junit:4.13.2')
-    testImplementation('org.mockito:mockito-core:5.23.0')
+    testImplementation(libs.mockito.core)
     testImplementation(testFixtures('art.arcane:core'))
     testImplementation(libs.spigot) {
         transitive = false
@@ -173,7 +175,9 @@ dependencies {
         libs.caffeine,
         'com.fulcrumgenomics:jlibdeflate:0.2.0',
         libs.dom4j,
-        libs.jaxen
+        libs.jaxen,
+        libs.flatlaf,
+        libs.flatlaf.extras
     ]
     add('bundle', libs.asm)
     add('devBundle', 'org.ow2.asm:asm') {
@@ -261,6 +265,8 @@ tasks.named('compileJava', JavaCompile).configure {
     options.release.set((int) irisModTarget.java)
 }
 
+apply from: file('../../gradle/mockito-agent.gradle')
+
 tasks.named('test').configure {
     useJUnitPlatform()
     classpath = classpath.minus(developmentModLibraries).plus(sourceSets.modLibraries.output)

build.gradle

@@ -55,7 +55,7 @@ apply from: file('gradle/runtime-relocations.gradle')
 apply from: file('gradle/volmlib-stamp.gradle')
 
 group = 'art.arcane'
-version = providers.gradleProperty('irisVersion').getOrElse('4.3.5')
+version = providers.gradleProperty('irisVersion').getOrElse('4.3.7')
 
 project(':core') {
     group = 'art.arcane'
@@ -89,7 +89,6 @@ Closure<String> irisArtifactName = { String platform, String targetVersion ->
 String bukkitArtifactName = irisArtifactName('CraftBukkit', bukkitMinecraftRange)
 Map<String, String> runtimeDownloadRelocations = (Map<String, String>) ext.runtimeDownloadRelocations
 List<String> runtimeDownloadedPrefixes = (List<String>) ext.runtimeDownloadedPrefixes
-File bukkitArtifact = layout.buildDirectory.file("libs/${bukkitArtifactName}").get().asFile
 apply plugin: ApiGenerator
 
 List<String> nmsBindings = ['v26_2_R1', 'v26_3_R1']
@@ -127,7 +126,7 @@ nmsBindings.each { String key ->
             compileOnly(rootProject.libs.annotations)
             compileOnly(rootProject.libs.byteBuddy.core)
             testImplementation('junit:junit:4.13.2')
-            testImplementation('org.mockito:mockito-core:5.23.0')
+            testImplementation(rootProject.libs.mockito.core)
             if (key == 'v26_3_R1') {
                 testImplementation(project(':probe'))
             }
@@ -194,6 +193,7 @@ tasks.named('jar', Jar).configure {
     includeEmptyDirs = false
     from(jarJar)
     from(provider { included.resolve().collect { zipTree(it) } }) {
+        exclude('META-INF/INDEX.LIST')
         exclude('languages/**')
         exclude('com/fren_gor/**')
 
@@ -534,19 +534,20 @@ List<String> requiredBukkitArtifactEntries = [
 tasks.register('verifyBukkitArtifact') {
     group = 'verification'
     dependsOn('jar')
-    File artifact = bukkitArtifact
+    Provider<RegularFile> artifact = tasks.named('jar', Jar).flatMap { Jar task -> task.archiveFile }
     inputs.file(artifact)
     inputs.files(nativeRuntime)
     inputs.files(commandHandlerSources)
     inputs.files(mantleComponentSources)
     doLast {
+        File archive = artifact.get().asFile
         BukkitArtifactVerifier.verify(
-                artifact,
+                archive,
                 requiredBukkitArtifactEntries,
                 16,
                 runtimeDownloadedPrefixes)
-        NativeRuntimeArtifacts.verify(artifact, nativeRuntimeModules, embeddedNatives())
-        logger.lifecycle("Verified ${artifact.name} packaging and class reference graph")
+        NativeRuntimeArtifacts.verify(archive, nativeRuntimeModules, embeddedNatives())
+        logger.lifecycle("Verified ${archive.name} packaging and class reference graph")
     }
 }
 
@@ -586,11 +587,14 @@ allprojects {
         layout.buildDirectory.set(layout.projectDirectory.dir("build/${runtimeOutputVariant}"))
     }
 
+    apply from: rootProject.file('gradle/mockito-agent.gradle')
+
     tasks.withType(Test).configureEach {
         int moduleForks = project.path.startsWith(':adapters:bukkit:') ? Math.min(2, testForks)
             : project.path == ':probe' ? Math.min(4, testForks) : testForks
         maxParallelForks = Math.min(gradle.startParameter.maxWorkerCount, moduleForks)
         jvmArgs('-XX:ParallelGCThreads=2', '-XX:ConcGCThreads=1', '-XX:CICompilerCount=2')
+        timeout = java.time.Duration.ofMinutes(60)
     }
 
     java {
@@ -731,6 +735,7 @@ pluginPackaging {
             policyName = 'Iris Bukkit'
             packed = true
             packedJarAccessors = ['art/arcane/iris/platform/bukkit/plugin/VolmitPlugin#getJarFile']
+            packedPayloadOnlyPrefixes = ['iris-language-guides/']
             stripDirectories = true
             stripLocalVariables = true
             releaseCompression = providers.gradleProperty('compactRelease')
@@ -816,6 +821,13 @@ project(':adapters:bukkit:nms:v26_3_R1') {
     }
     sourceSets.test.compileClasspath += sourceSets.offline.output
     sourceSets.test.runtimeClasspath += sourceSets.offline.output
+    tasks.named('test').configure {
+        String exportProbePack = providers.gradleProperty('iris.exportProbePack').orNull
+        if (exportProbePack != null) {
+            systemProperty('iris.exportProbePack', exportProbePack)
+            maxHeapSize = '6g'
+        }
+    }
 
     TaskProvider<Jar> offlineJar = tasks.register('offlineJar', Jar) {
         dependsOn(offlineClasses)
@@ -843,6 +855,30 @@ project(':adapters:bukkit:nms:v26_3_R1') {
         }
     }
 
+    tasks.register('datapackCostProbe', JavaExec) {
+        group = 'verification'
+        description = 'Exports an Iris dimension as a 26.3 worldgen datapack and measures its load, chunk and density function cost against vanilla.'
+        dependsOn(offlineClasses)
+        mainClass = 'art.arcane.iris.probe.DatapackCostProbe'
+        classpath = sourceSets.offline.runtimeClasspath
+        maxHeapSize = providers.gradleProperty('probeHeap').getOrElse('24G')
+        jvmArgs('--add-modules', 'jdk.incubator.vector', '-Djava.awt.headless=true')
+        doFirst {
+            String dimension = providers.gradleProperty('probeDimension').getOrElse('overworld')
+            String output = providers.gradleProperty('probeOutput')
+                    .getOrElse(layout.buildDirectory.file("reports/datapack-cost/${dimension}.json").get().asFile.absolutePath)
+            args([rootProject.file(providers.gradleProperty('probePack').get()).absolutePath, dimension,
+                    providers.gradleProperty('probeSeed').getOrElse('1337'),
+                    providers.gradleProperty('probeChunkSide').getOrElse('6'),
+                    providers.gradleProperty('probeRounds').getOrElse('4'),
+                    providers.gradleProperty('probeWarmupSide').getOrElse('6'),
+                    providers.gradleProperty('probeCalls').getOrElse('256'),
+                    providers.gradleProperty('probeCallSeconds').getOrElse('60'),
+                    rootProject.file(output).absolutePath,
+                    layout.buildDirectory.dir('tmp/datapack-cost').get().asFile.absolutePath])
+        }
+    }
+
     tasks.register('regionMantleInspection', JavaExec) {
         group = 'verification'
         dependsOn(testClasses)
@@ -872,6 +908,32 @@ project(':adapters:bukkit:nms:v26_3_R1') {
         }
     }
 
+    tasks.register('datapackFidelityProbe', JavaExec) {
+        group = 'verification'
+        description = 'Exports an Iris dimension as a 26.3 worldgen datapack and compares both generators on the same seed.'
+        dependsOn(offlineClasses)
+        mainClass = 'art.arcane.iris.probe.DatapackFidelityProbe'
+        classpath = sourceSets.offline.runtimeClasspath
+        maxHeapSize = '8G'
+        jvmArgs('--add-modules', 'jdk.incubator.vector', '-Djava.awt.headless=true')
+        doFirst {
+            String dimension = providers.gradleProperty('probeDimension').get()
+            String seed = providers.gradleProperty('probeSeed').get()
+            String mode = providers.gradleProperty('probeMode').getOrElse('full')
+            boolean biomes = mode == 'biomes'
+            String output = providers.gradleProperty('probeOutput')
+                    .getOrElse(layout.buildDirectory.file("reports/datapack-fidelity/${dimension}-${seed}${biomes ? '-biomes' : ''}.json").get().asFile.absolutePath)
+            args([rootProject.file(providers.gradleProperty('probePack').get()).absolutePath, dimension, seed,
+                    biomes ? providers.gradleProperty('probeRadiusChunks').getOrElse('0') : providers.gradleProperty('probeRadiusChunks').get(),
+                    biomes ? providers.gradleProperty('probeStride').getOrElse('1') : providers.gradleProperty('probeStride').get(),
+                    rootProject.file(output).absolutePath,
+                    providers.gradleProperty('probeSurveyBlocks').getOrElse('65536'),
+                    providers.gradleProperty('probeSurveyStride').getOrElse('256'),
+                    providers.gradleProperty('probeSurveySeeds').getOrElse(biomes ? '7' : '1'),
+                    mode])
+        }
+    }
+
 
 }
 

core/build.gradle

@@ -108,6 +108,10 @@ dependencies {
     compileOnly(libs.log4j.api)
     compileOnly(libs.log4j.core)
     compileOnly(libs.guava)
+    compileOnly(libs.lwjgl)
+    compileOnly(libs.lwjgl.opengl)
+    compileOnly(libs.lwjgl.egl)
+    compileOnly(libs.lwjgl.jawt)
 
     // Third Party Integrations
     compileOnly(libs.nexo)
@@ -161,25 +165,38 @@ dependencies {
     slim(libs.byteBuddy.agent)
     slim(libs.dom4j)
     slim(libs.jaxen)
+    slim(libs.flatlaf)
+    slim(libs.flatlaf.extras)
 
     testFixturesImplementation('junit:junit:4.13.2')
-    testFixturesImplementation('org.mockito:mockito-core:5.23.0')
+    testFixturesImplementation(libs.mockito.core)
     testFixturesCompileOnly(libs.paper.api)
 
     testImplementation('junit:junit:4.13.2')
-    testImplementation('org.mockito:mockito-core:5.23.0')
+    testImplementation(libs.mockito.core)
     testImplementation(libs.paper.api)
     testImplementation(libs.log4j.core)
     testRuntimeOnly(libs.paper.api)
     testImplementation(libs.multiverseCore)
     testImplementation(libs.annotations)
     testImplementation(libs.mythic)
+    testRuntimeOnly(libs.lwjgl)
+    testRuntimeOnly(libs.lwjgl.opengl)
+    testRuntimeOnly(libs.lwjgl.egl)
+    testRuntimeOnly(libs.lwjgl.jawt)
+    testRuntimeOnly(variantOf(libs.lwjgl) { classifier('natives-linux') })
+    testRuntimeOnly(variantOf(libs.lwjgl.opengl) { classifier('natives-linux') })
 }
 
 tasks.named('test').configure {
-    maxHeapSize = '1g'
+    timeout = java.time.Duration.ofMinutes(60)
+    maxHeapSize = '2g'
     jvmArgs('-XX:+ExitOnOutOfMemoryError')
     systemProperty('iris.generation.counters', 'true')
+    String exportProbePack = providers.gradleProperty('iris.exportProbePack').orNull
+    if (exportProbePack != null) {
+        systemProperty('iris.exportProbePack', exportProbePack)
+    }
 }
 
 java {
@@ -347,14 +364,9 @@ List<String> unusedVolmLibPackages = [
 ]
 
 List<String> unusedVolmLibClasses = [
-    'art/arcane/volmlib/util/nbt/io/ParseException',
-    'art/arcane/volmlib/util/nbt/io/SNBTDeserializer',
-    'art/arcane/volmlib/util/nbt/io/SNBTParser',
     'art/arcane/volmlib/util/nbt/io/SNBTSerializer',
     'art/arcane/volmlib/util/nbt/io/SNBTUtil',
     'art/arcane/volmlib/util/nbt/io/SNBTWriter',
-    'art/arcane/volmlib/util/nbt/io/StringPointer',
-    'art/arcane/volmlib/util/io/StringDeserializer',
     'art/arcane/volmlib/util/io/StringSerializer',
     'art/arcane/volmlib/util/json/EnumType',
     'art/arcane/volmlib/util/json/HTTP',

core/purity-allowlist.txt

@@ -26,7 +26,6 @@ art/arcane/iris/generation/decoration/IrisSpeleothems.java
 art/arcane/iris/generation/decoration/IrisSurface.java
 art/arcane/iris/generation/decoration/tree/IrisTree.java
 art/arcane/iris/generation/geometry/AxisAlignedBB.java
-art/arcane/iris/generation/mantle/MantleWriter.java
 art/arcane/iris/generation/runtime/BukkitEngineWorldManager.java
 art/arcane/iris/generation/runtime/EngineAssignedWorldManager.java
 art/arcane/iris/generation/runtime/EnginePlayer.java
@@ -57,7 +56,6 @@ art/arcane/iris/integration/data/NexoDataProvider.java
 art/arcane/iris/integration/data/OraxenDataProvider.java
 art/arcane/iris/localization/C.java
 art/arcane/iris/pack/IrisConverter.java
-art/arcane/iris/pack/IrisPack.java
 art/arcane/iris/pack/IrisPackBenchmarking.java
 art/arcane/iris/pack/datapack/DatapackIngestService.java
 art/arcane/iris/pack/datapack/ServerConfigurator.java
@@ -121,13 +119,17 @@ art/arcane/iris/studio/StudioSVC.java
 art/arcane/iris/studio/edit/BlockSignal.java
 art/arcane/iris/studio/edit/DustRevealer.java
 art/arcane/iris/studio/generation/JigsawStudioGenerator.java
+art/arcane/iris/studio/jigsaw/JigsawStudioConnectorTool.java
+art/arcane/iris/studio/jigsaw/JigsawStudioFloorPainter.java
 art/arcane/iris/studio/generation/ObjectStudioGenerator.java
 art/arcane/iris/studio/jigsaw/JigsawStudioAutosaveScheduler.java
 art/arcane/iris/studio/jigsaw/JigsawStudioCapture.java
 art/arcane/iris/studio/jigsaw/JigsawStudioCaptureScheduler.java
 art/arcane/iris/studio/jigsaw/JigsawStudioChunkWriter.java
+art/arcane/iris/studio/jigsaw/JigsawStudioConnectorTool.java
 art/arcane/iris/studio/jigsaw/JigsawStudioDetailsMenu.java
 art/arcane/iris/studio/jigsaw/JigsawStudioDirtyTracker.java
+art/arcane/iris/studio/jigsaw/JigsawStudioFloorPainter.java
 art/arcane/iris/studio/jigsaw/JigsawStudioGraphMutations.java
 art/arcane/iris/studio/jigsaw/JigsawStudioMainMenu.java
 art/arcane/iris/studio/jigsaw/JigsawStudioMarkerParser.java

core/src/main/java/art/arcane/iris/command/specialhandlers/HydrologyTypeHandler.java

@@ -1,25 +1,14 @@
 package art.arcane.iris.command.specialhandlers;
 
-import art.arcane.iris.generation.runtime.Engine;
-import art.arcane.iris.generation.hydrology.HydrologyFeatureQuery;
-import art.arcane.iris.generation.hydrology.runtime.IrisHydrologyRuntime;
 import art.arcane.iris.command.DirectorParameterHandler;
+import art.arcane.iris.generation.hydrology.query.HydrologyFeatureType;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.director.exceptions.DirectorParsingException;
 
-import java.util.List;
-
 public final class HydrologyTypeHandler implements DirectorParameterHandler<String> {
     @Override
     public KList<String> getPossibilities() {
-        Engine activeEngine = engine();
-        if (activeEngine == null) {
-            return new KList<>(HydrologyFeatureQuery.suggestions(List.of()));
-        }
-        IrisHydrologyRuntime runtime = activeEngine.getComplex().getHydrologyRuntime();
-        return new KList<>(runtime == null
-                ? HydrologyFeatureQuery.suggestions(List.of())
-                : runtime.featureQueryKeys());
+        return new KList<>(HydrologyFeatureType.keys());
     }
 
     @Override
@@ -29,16 +18,11 @@ public final class HydrologyTypeHandler implements DirectorParameterHandler<Stri
 
     @Override
     public String parse(String input, boolean force) throws DirectorParsingException {
-        String normalized = input == null ? "" : input.trim();
-        if (normalized.isEmpty()) {
-            throw new DirectorParsingException("Hydrology feature type must not be blank.");
+        try {
+            return HydrologyFeatureType.parse(input).key();
+        } catch (IllegalArgumentException error) {
+            throw new DirectorParsingException(error.getMessage());
         }
-        for (String possibility : getPossibilities(normalized)) {
-            if (possibility.equalsIgnoreCase(normalized)) {
-                return possibility;
-            }
-        }
-        return normalized;
     }
 
     @Override
@@ -48,6 +32,6 @@ public final class HydrologyTypeHandler implements DirectorParameterHandler<Stri
 
     @Override
     public String getRandomDefault() {
-        return "surface";
+        return HydrologyFeatureType.RIVER.key();
     }
 }

core/src/main/java/art/arcane/iris/configuration/IrisSettings.java

@@ -373,6 +373,7 @@ public class IrisSettings {
         public boolean useServerLaunchedGuis = true;
         public boolean maximumPregenGuiFPS = false;
         public boolean colorMode = true;
+        public String theme = "auto";
     }
 
     @Data