fix

core/src/main/java/art/arcane/iris/core/IrisStartupValidation.java

@@ -0,0 +1,154 @@
+package art.arcane.iris.core;
+
+import java.util.List;
+import java.util.Optional;
+
+public final class IrisStartupValidation {
+    private static volatile Snapshot snapshot = Snapshot.disabled();
+
+    private IrisStartupValidation() {
+    }
+
+    public static synchronized void begin() {
+        snapshot = new Snapshot(true, ValidationState.PENDING, ValidationState.PENDING, List.of(), List.of());
+    }
+
+    public static synchronized void disable() {
+        snapshot = Snapshot.disabled();
+    }
+
+    public static synchronized void beginDatapackValidation() {
+        if (!snapshot.enforced() || snapshot.datapacks() == ValidationState.RESTART_REQUIRED) {
+            return;
+        }
+        snapshot = new Snapshot(true, ValidationState.PENDING, snapshot.packs(), List.of(), snapshot.packFailures());
+    }
+
+    public static synchronized void markDatapacksReady() {
+        if (!snapshot.enforced() || snapshot.datapacks() == ValidationState.RESTART_REQUIRED) {
+            return;
+        }
+        snapshot = new Snapshot(true, ValidationState.READY, snapshot.packs(), List.of(), snapshot.packFailures());
+    }
+
+    public static synchronized void markDatapacksInvalid(String failure) {
+        if (!snapshot.enforced()) {
+            return;
+        }
+        snapshot = new Snapshot(
+                true,
+                ValidationState.INVALID,
+                snapshot.packs(),
+                List.of(normalizeFailure(failure, "External datapack validation failed.")),
+                snapshot.packFailures());
+    }
+
+    public static synchronized void requireRestart(String reason) {
+        if (!snapshot.enforced()) {
+            return;
+        }
+        snapshot = new Snapshot(
+                true,
+                ValidationState.RESTART_REQUIRED,
+                snapshot.packs(),
+                List.of(normalizeFailure(reason, "A restart is required to load validated datapacks.")),
+                snapshot.packFailures());
+    }
+
+    public static synchronized void markPacksReady() {
+        if (!snapshot.enforced()) {
+            return;
+        }
+        snapshot = new Snapshot(true, snapshot.datapacks(), ValidationState.READY, snapshot.datapackFailures(), List.of());
+    }
+
+    public static synchronized void markPacksInvalid(List<String> failures) {
+        if (!snapshot.enforced()) {
+            return;
+        }
+        List<String> normalized = failures == null || failures.isEmpty()
+                ? List.of("Iris dimension-pack validation failed.")
+                : failures.stream()
+                .map(failure -> normalizeFailure(failure, "Iris dimension-pack validation failed."))
+                .toList();
+        snapshot = new Snapshot(true, snapshot.datapacks(), ValidationState.INVALID,
+                snapshot.datapackFailures(), normalized);
+    }
+
+    public static boolean isReady() {
+        return isReady(snapshot);
+    }
+
+    public static Optional<String> denialReason() {
+        Snapshot current = snapshot;
+        if (!current.enforced() || isReady(current)) {
+            return Optional.empty();
+        }
+        if (current.datapacks() == ValidationState.RESTART_REQUIRED) {
+            return Optional.of(firstFailure(current.datapackFailures(),
+                    "Iris installed validated datapacks and requires a restart before the server is safe."));
+        }
+        if (current.datapacks() == ValidationState.INVALID) {
+            return Optional.of(firstFailure(current.datapackFailures(),
+                    "Iris external datapack validation failed."));
+        }
+        if (current.datapacks() == ValidationState.PENDING) {
+            return Optional.of("Iris is still validating external datapacks.");
+        }
+        if (current.packs() == ValidationState.INVALID) {
+            return Optional.of(firstFailure(current.packFailures(),
+                    "Iris dimension-pack validation failed."));
+        }
+        return Optional.of("Iris is still validating dimension packs.");
+    }
+
+    public static void requireWorldCreationReady() {
+        Optional<String> denial = denialReason();
+        if (denial.isPresent()) {
+            throw new IllegalStateException("Iris world creation is locked: " + denial.get());
+        }
+    }
+
+    static Snapshot snapshot() {
+        return snapshot;
+    }
+
+    private static String normalizeFailure(String failure, String fallback) {
+        return failure == null || failure.isBlank() ? fallback : failure.trim();
+    }
+
+    private static String firstFailure(List<String> failures, String fallback) {
+        return failures == null || failures.isEmpty() ? fallback : failures.getFirst();
+    }
+
+    private static boolean isReady(Snapshot current) {
+        return !current.enforced()
+                || current.datapacks() == ValidationState.READY
+                && current.packs() == ValidationState.READY;
+    }
+
+    enum ValidationState {
+        PENDING,
+        READY,
+        INVALID,
+        RESTART_REQUIRED,
+        DISABLED
+    }
+
+    record Snapshot(
+            boolean enforced,
+            ValidationState datapacks,
+            ValidationState packs,
+            List<String> datapackFailures,
+            List<String> packFailures
+    ) {
+        Snapshot {
+            datapackFailures = List.copyOf(datapackFailures);
+            packFailures = List.copyOf(packFailures);
+        }
+
+        private static Snapshot disabled() {
+            return new Snapshot(false, ValidationState.DISABLED, ValidationState.DISABLED, List.of(), List.of());
+        }
+    }
+}

core/src/main/java/art/arcane/iris/core/ServerConfigurator.java

@@ -161,6 +161,8 @@ public class ServerConfigurator {
             invalidateLoadedDatapackRuntime();
             loadedDatapackRestartRequired = true;
         }
+        IrisStartupValidation.requireRestart(
+                "Iris datapack changes require a restart before player admission or world creation.");
     }
 
     public static void restoreLoadedDatapackRuntimeIfUnchanged(

core/src/main/java/art/arcane/iris/core/datapack/DatapackIngestService.java

@@ -21,6 +21,7 @@ package art.arcane.iris.core.datapack;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisPlatforms;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
+import art.arcane.iris.core.IrisStartupValidation;
 import art.arcane.iris.core.IrisSettings;
 import art.arcane.iris.core.ServerConfigurator;
 import art.arcane.iris.core.datapack.ModrinthResolver.ResolvedDatapack;
@@ -62,6 +63,7 @@ import java.nio.channels.FileChannel;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.FileStore;
+import java.nio.file.FileSystems;
 import java.nio.file.LinkOption;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -97,8 +99,10 @@ public final class DatapackIngestService {
     private static final String TRANSACTION_DIRECTORY = ".iris-datapack-transactions";
     private static final String TRANSACTION_JOURNAL = "journal.json";
     private static final String TRANSACTION_JOURNAL_NEXT = "journal.next.json";
+    private static final String STARTUP_VALIDATION_CACHE = "startup-validation.json";
     private static final int OWNERSHIP_SCHEMA = 1;
     private static final int TRANSACTION_SCHEMA = 2;
+    private static final int STARTUP_VALIDATION_SCHEMA = 1;
     private static final int STRUCTURE_IMPORT_FORMAT_REVISION = 3;
     private static final int MAX_REDIRECTS = 5;
     private static final int MAX_ARCHIVE_ENTRIES = 100_000;
@@ -113,9 +117,12 @@ public final class DatapackIngestService {
     private static final long MAX_METADATA_BYTES = 1024L * 1024L;
     private static final long MAX_OWNERSHIP_BYTES = 1024L * 1024L;
     private static final int MAX_TRANSACTION_COUNT = 1_024;
+    private static final int MAX_SCRATCH_DELETE_ATTEMPTS = 3;
+    private static final int WINDOWS_LEGACY_PATH_LIMIT = 247;
     private static final Set<String> RESERVED_IDS = Set.of("iris");
     private static final ReentrantLock TRANSACTION_LOCK = new ReentrantLock();
     private static final Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+    private static volatile StartupValidationCache activeStartupValidation;
 
     private DatapackIngestService() {
     }
@@ -125,19 +132,367 @@ public final class DatapackIngestService {
     }
 
     public static void autoIngestOnStartup() {
-        boolean restarting = false;
-        if (IrisSettings.get().getGeneral().autoIngestDatapacks) {
-            KList<String> urls = collectConfiguredImports();
-            if (!urls.isEmpty()) {
-                IrisLogging.info("Auto-ingesting " + urls.size() + " external datapack import(s) from pack datapackImports...");
-                Report report = ingest(null, urls, true);
-                restarting = report.changed();
+        StartupValidationOutcome outcome = validateOnStartup();
+        if (outcome == StartupValidationOutcome.READY) {
+            runPostStartupTasks();
+        }
+    }
+
+    public static StartupValidationOutcome validateOnStartup() {
+        activeStartupValidation = null;
+        IrisStartupValidation.beginDatapackValidation();
+        KList<String> configured = collectConfiguredImports();
+        List<String> urls = configured.stream().sorted().toList();
+        boolean autoIngest = IrisSettings.get().getGeneral().autoIngestDatapacks;
+        boolean stripOverrides = resolveStripOverrides();
+        String mcVersion = serverMcVersion();
+        int irisVersion = IrisPlatforms.get().irisVersionNumber();
+        File root = IrisPlatforms.get().dataFolder("datapacks");
+        KList<File> worldFolders = ServerConfigurator.getDatapacksFolder();
+        Path cacheFile = new File(root, STARTUP_VALIDATION_CACHE).toPath();
+
+        try {
+            String localFingerprint = startupValidationFingerprint(root, worldFolders);
+            StartupValidationCache cached = readStartupValidationCache(cacheFile);
+            if (startupValidationCacheMatches(
+                    cached,
+                    mcVersion,
+                    irisVersion,
+                    autoIngest,
+                    stripOverrides,
+                    urls,
+                    localFingerprint)) {
+                activeStartupValidation = cached;
+                IrisLogging.info("External datapacks match the persisted startup validation; remote resolution and full revalidation were skipped.");
+                IrisStartupValidation.markDatapacksReady();
+                return StartupValidationOutcome.READY;
             }
+        } catch (IOException | RuntimeException exception) {
+            IrisLogging.warn("Persisted external datapack validation could not be reused: "
+                    + failureMessage(exception));
         }
-        if (!restarting) {
-            refreshWorkspaces();
-            autoImportDatapackStructures();
+
+        if (autoIngest && !configured.isEmpty()) {
+            IrisLogging.info("Validating " + configured.size()
+                    + " configured external datapack import(s) before player admission...");
+            Report report = ingest(null, configured, true);
+            if (!report.getFailed().isEmpty()) {
+                String failure = report.getFailed().getFirst();
+                IrisStartupValidation.markDatapacksInvalid(failure);
+                return StartupValidationOutcome.FAILED;
+            }
+            StartupValidationOutcome outcome = report.changed()
+                    ? StartupValidationOutcome.RESTART_REQUIRED
+                    : StartupValidationOutcome.READY;
+            activeStartupValidation = cacheStartupValidation(root, worldFolders, cacheFile, mcVersion, irisVersion,
+                    autoIngest, stripOverrides, urls);
+            if (outcome == StartupValidationOutcome.RESTART_REQUIRED) {
+                IrisStartupValidation.requireRestart(
+                        "Iris installed updated external datapacks; restart must complete before player admission or world creation.");
+            } else {
+                IrisStartupValidation.markDatapacksReady();
+            }
+            return outcome;
         }
+
+        ReapplyOutcome reapply = reapplyFromStaging(worldFolders);
+        if (!reapply.succeeded()) {
+            String failure = reapply.failure()
+                    .map(DatapackIngestService::failureMessage)
+                    .orElse("External datapack recovery failed.");
+            IrisStartupValidation.markDatapacksInvalid(failure);
+            return StartupValidationOutcome.FAILED;
+        }
+        activeStartupValidation = cacheStartupValidation(root, worldFolders, cacheFile, mcVersion, irisVersion,
+                autoIngest, stripOverrides, urls);
+        if (reapply.changed()) {
+            IrisStartupValidation.requireRestart(
+                    "Iris repaired external datapack files; restart must complete before player admission or world creation.");
+            return StartupValidationOutcome.RESTART_REQUIRED;
+        }
+        IrisStartupValidation.markDatapacksReady();
+        return StartupValidationOutcome.READY;
+    }
+
+    public static void runPostStartupTasks() {
+        refreshWorkspaces();
+        autoImportDatapackStructures();
+        refreshStartupValidationAfterMaintenance();
+    }
+
+    private static StartupValidationCache cacheStartupValidation(
+            File root,
+            KList<File> worldFolders,
+            Path cacheFile,
+            String mcVersion,
+            int irisVersion,
+            boolean autoIngest,
+            boolean stripOverrides,
+            List<String> urls
+    ) {
+        try {
+            StartupValidationCache cache = createStartupValidationCache(
+                    mcVersion,
+                    irisVersion,
+                    autoIngest,
+                    stripOverrides,
+                    urls,
+                    startupValidationFingerprint(root, worldFolders));
+            writeStartupValidationCache(cacheFile, cache);
+            return cache;
+        } catch (IOException | RuntimeException exception) {
+            IrisLogging.warn("Could not persist external datapack startup validation: "
+                    + failureMessage(exception));
+            return null;
+        }
+    }
+
+    private static void refreshStartupValidationAfterMaintenance() {
+        StartupValidationCache validated = activeStartupValidation;
+        if (validated == null || !IrisStartupValidation.isReady()) {
+            return;
+        }
+        KList<String> configured = collectConfiguredImports();
+        List<String> urls = configured.stream().sorted().toList();
+        boolean autoIngest = IrisSettings.get().getGeneral().autoIngestDatapacks;
+        boolean stripOverrides = resolveStripOverrides();
+        String mcVersion = serverMcVersion();
+        int irisVersion = IrisPlatforms.get().irisVersionNumber();
+        if (!startupValidationContextMatches(
+                validated, mcVersion, irisVersion, autoIngest, stripOverrides, urls)) {
+            return;
+        }
+        File root = IrisPlatforms.get().dataFolder("datapacks");
+        KList<File> worldFolders = ServerConfigurator.getDatapacksFolder();
+        Path cacheFile = new File(root, STARTUP_VALIDATION_CACHE).toPath();
+        TRANSACTION_LOCK.lock();
+        try {
+            recoverTransactions(root, worldFolders);
+            StartupValidationCache refreshed = refreshStartupValidationCache(
+                    validated, root, worldFolders);
+            writeStartupValidationCache(cacheFile, refreshed);
+            activeStartupValidation = refreshed;
+        } catch (IOException | RuntimeException exception) {
+            IrisLogging.warn("Could not refresh external datapack validation after startup maintenance: "
+                    + failureMessage(exception));
+        } finally {
+            TRANSACTION_LOCK.unlock();
+        }
+    }
+
+    static StartupValidationCache refreshStartupValidationCache(
+            StartupValidationCache validated,
+            File root,
+            KList<File> worldFolders
+    ) throws IOException {
+        Objects.requireNonNull(validated, "Validated external datapack startup state");
+        return createStartupValidationCache(
+                validated.minecraftVersion,
+                validated.irisVersion,
+                validated.autoIngest,
+                validated.stripOverrides,
+                validated.urls,
+                startupValidationFingerprint(root, worldFolders));
+    }
+
+    private static StartupValidationCache createStartupValidationCache(
+            String mcVersion,
+            int irisVersion,
+            boolean autoIngest,
+            boolean stripOverrides,
+            List<String> urls,
+            String localFingerprint
+    ) {
+        StartupValidationCache cache = new StartupValidationCache();
+        cache.schemaVersion = STARTUP_VALIDATION_SCHEMA;
+        cache.minecraftVersion = Objects.requireNonNullElse(mcVersion, "");
+        cache.irisVersion = irisVersion;
+        cache.autoIngest = autoIngest;
+        cache.stripOverrides = stripOverrides;
+        cache.urls = List.copyOf(urls);
+        cache.localFingerprint = localFingerprint;
+        return cache;
+    }
+
+    static boolean startupValidationContextMatches(
+            StartupValidationCache cache,
+            String mcVersion,
+            int irisVersion,
+            boolean autoIngest,
+            boolean stripOverrides,
+            List<String> urls
+    ) {
+        return cache != null
+                && cache.schemaVersion == STARTUP_VALIDATION_SCHEMA
+                && Objects.equals(cache.minecraftVersion, Objects.requireNonNullElse(mcVersion, ""))
+                && cache.irisVersion == irisVersion
+                && cache.autoIngest == autoIngest
+                && cache.stripOverrides == stripOverrides
+                && Objects.equals(cache.urls, urls);
+    }
+
+    static boolean startupValidationCacheMatches(
+            StartupValidationCache cache,
+            String mcVersion,
+            int irisVersion,
+            boolean autoIngest,
+            boolean stripOverrides,
+            List<String> urls,
+            String localFingerprint
+    ) {
+        return startupValidationContextMatches(
+                cache, mcVersion, irisVersion, autoIngest, stripOverrides, urls)
+                && localFingerprint != null && !localFingerprint.isBlank()
+                && Objects.equals(cache.localFingerprint, localFingerprint);
+    }
+
+    static StartupValidationCache readStartupValidationCache(Path cacheFile) {
+        if (cacheFile == null
+                || Files.isSymbolicLink(cacheFile)
+                || !Files.isRegularFile(cacheFile, LinkOption.NOFOLLOW_LINKS)) {
+            return null;
+        }
+        try {
+            if (Files.size(cacheFile) > MAX_METADATA_BYTES) {
+                return null;
+            }
+            StartupValidationCache cache = GSON.fromJson(
+                    readBoundedUtf8(cacheFile, MAX_METADATA_BYTES, "External datapack startup validation"),
+                    StartupValidationCache.class);
+            if (cache == null || cache.urls == null) {
+                return null;
+            }
+            List<String> sortedUrls = cache.urls.stream()
+                    .filter(Objects::nonNull)
+                    .sorted()
+                    .toList();
+            if (sortedUrls.size() != cache.urls.size()
+                    || new HashSet<>(sortedUrls).size() != sortedUrls.size()
+                    || !sortedUrls.equals(cache.urls)) {
+                return null;
+            }
+            cache.urls = sortedUrls;
+            return cache;
+        } catch (IOException | RuntimeException exception) {
+            return null;
+        }
+    }
+
+    private static void writeStartupValidationCache(Path cacheFile, StartupValidationCache cache) throws IOException {
+        Path absolute = cacheFile.toAbsolutePath().normalize();
+        Path parent = Objects.requireNonNull(absolute.getParent(), "External datapack startup validation parent");
+        Files.createDirectories(parent);
+        Path staged = Files.createTempFile(parent, ".startup-validation-", ".tmp");
+        try {
+            byte[] content = GSON.toJson(cache).getBytes(StandardCharsets.UTF_8);
+            if (content.length > MAX_METADATA_BYTES) {
+                throw new IOException("External datapack startup validation exceeds " + MAX_METADATA_BYTES + " bytes");
+            }
+            Files.write(staged, content, StandardOpenOption.TRUNCATE_EXISTING);
+            forceFile(staged);
+            try {
+                Files.move(staged, absolute, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(staged, absolute, StandardCopyOption.REPLACE_EXISTING);
+            }
+            forceDirectoryIfSupported(parent);
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
+    static String startupValidationFingerprint(File root, KList<File> worldFolders) throws IOException {
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            Path manifestPath = new File(root, "manifest.json").toPath();
+            updateFingerprintValue(digest, "manifest");
+            if (Files.exists(manifestPath, LinkOption.NOFOLLOW_LINKS)) {
+                if (Files.isSymbolicLink(manifestPath)
+                        || !Files.isRegularFile(manifestPath, LinkOption.NOFOLLOW_LINKS)) {
+                    throw new IOException("Invalid datapack manifest path " + manifestPath);
+                }
+                byte[] manifest = readBoundedBytes(
+                        manifestPath, MAX_MANIFEST_BYTES, "Datapack manifest fingerprint");
+                updateDigestLong(digest, manifest.length);
+                digest.update(manifest);
+            } else if (Files.notExists(manifestPath, LinkOption.NOFOLLOW_LINKS)) {
+                updateDigestLong(digest, -1L);
+            } else {
+                throw new IOException("Cannot determine datapack manifest state at " + manifestPath);
+            }
+
+            Manifest manifest = readCommittedManifest(root);
+            updateDirectoryFingerprint(digest, "staging", new File(root, "staging"));
+            updateDirectoryFingerprint(digest, "transactions", new File(root, TRANSACTION_DIRECTORY));
+            updateDirectoryFingerprint(
+                    digest,
+                    "storage-install-scratch",
+                    installScratchRoot(new File(root, "staging")));
+
+            List<Entry> entries = new ArrayList<>(manifest.entries);
+            entries.sort(Comparator.comparing(entry -> entry.id));
+            List<File> targets = new ArrayList<>(worldFolders == null ? List.of() : worldFolders);
+            targets.sort(Comparator.comparing(file -> file.toPath().toAbsolutePath().normalize().toString()));
+            for (File worldFolder : targets) {
+                String worldIdentity = worldFolder.toPath().toAbsolutePath().normalize().toString();
+                updateFingerprintValue(digest, "world:" + worldIdentity);
+                updateDirectoryFingerprint(
+                        digest,
+                        "world-install-scratch:" + worldIdentity,
+                        installScratchRoot(worldFolder));
+                for (Entry entry : entries) {
+                    updateDirectoryFingerprint(
+                            digest,
+                            "world-pack:" + worldIdentity + ":" + entry.id,
+                            new File(worldFolder, entry.id));
+                }
+            }
+            return hex(digest.digest());
+        } catch (NoSuchAlgorithmException exception) {
+            throw new IOException("SHA-256 algorithm unavailable", exception);
+        }
+    }
+
+    private static void updateDirectoryFingerprint(
+            MessageDigest digest,
+            String identity,
+            File directory
+    ) throws IOException {
+        updateFingerprintValue(digest, identity);
+        Path path = directory.toPath();
+        if (Files.notExists(path, LinkOption.NOFOLLOW_LINKS)) {
+            updateFingerprintValue(digest, "missing");
+            return;
+        }
+        if (!Files.exists(path, LinkOption.NOFOLLOW_LINKS)
+                || Files.isSymbolicLink(path)
+                || !Files.isDirectory(path, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IOException("Invalid external datapack validation directory " + path);
+        }
+        updateFingerprintValue(digest, directoryHash(directory));
+        Path ownership = new File(directory, OWNERSHIP_MARKER).toPath();
+        if (Files.isRegularFile(ownership, LinkOption.NOFOLLOW_LINKS) && !Files.isSymbolicLink(ownership)) {
+            byte[] marker = readBoundedBytes(
+                    ownership, MAX_OWNERSHIP_BYTES, "External datapack ownership fingerprint");
+            updateDigestLong(digest, marker.length);
+            digest.update(marker);
+        } else {
+            updateDigestLong(digest, -1L);
+        }
+    }
+
+    private static void updateFingerprintValue(MessageDigest digest, String value) {
+        byte[] bytes = Objects.requireNonNullElse(value, "").getBytes(StandardCharsets.UTF_8);
+        updateDigestInt(digest, bytes.length);
+        digest.update(bytes);
+    }
+
+    private static String failureMessage(Throwable exception) {
+        if (exception == null) {
+            return "unknown failure";
+        }
+        String message = exception.getMessage();
+        return message == null || message.isBlank() ? exception.getClass().getSimpleName() : message;
     }
 
     public static void refreshWorkspaces() {
@@ -158,6 +513,7 @@ public final class DatapackIngestService {
     }
 
     public static Report ingest(VolmitSender sender, KList<String> urls, boolean restart) {
+        IrisStartupValidation.beginDatapackValidation();
         ServerConfigurator.LoadedDatapackRuntimeInvalidation invalidation =
                 ServerConfigurator.invalidateLoadedDatapackRuntime();
         Report report;
@@ -176,6 +532,11 @@ public final class DatapackIngestService {
                 ServerConfigurator.requireDatapackRestart();
             }
         }
+        if (!report.getFailed().isEmpty()) {
+            IrisStartupValidation.markDatapacksInvalid(report.getFailed().getFirst());
+        } else if (!report.changed()) {
+            IrisStartupValidation.markDatapacksReady();
+        }
         return report;
     }
 
@@ -304,6 +665,10 @@ public final class DatapackIngestService {
             ServerConfigurator.restoreLoadedDatapackRuntimeIfUnchanged(invalidation);
         } else if (outcome.changed()) {
             ServerConfigurator.requireDatapackRestart();
+        } else {
+            IrisStartupValidation.markDatapacksInvalid(outcome.failure()
+                    .map(DatapackIngestService::failureMessage)
+                    .orElse("External datapack recovery failed."));
         }
         return outcome;
     }
@@ -1279,7 +1644,7 @@ public final class DatapackIngestService {
         verifyPendingExtractionName(normalizedSource.getFileName().toString(), entry.id);
         validateManagedDirectory(verifiedSource, entry.id);
         validateScratchTree(normalizedSource);
-        if (!Objects.equals(Files.getFileStore(normalizedSource), Files.getFileStore(normalizedStagingRoot))) {
+        if (!sameScratchVolume(normalizedSource, normalizedStagingRoot)) {
             throw new IOException("Verified datapack extraction crosses a filesystem boundary");
         }
         String desiredHash = directoryHash(verifiedSource);
@@ -1338,8 +1703,9 @@ public final class DatapackIngestService {
 
     private static Path requireDirectoryIdentity(File directory, String purpose) throws IOException {
         Path normalized = directory.toPath().toAbsolutePath().normalize();
-        if (Files.isSymbolicLink(normalized)
-                || !Files.isDirectory(normalized, LinkOption.NOFOLLOW_LINKS)) {
+        BasicFileAttributes attributes = Files.readAttributes(
+                normalized, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
+        if (!isSupportedScratchDirectory(attributes)) {
             throw new IOException("Invalid " + purpose + " " + normalized);
         }
         normalized.toRealPath();
@@ -1350,9 +1716,17 @@ public final class DatapackIngestService {
         Path current = normalized.getRoot();
         for (Path component : normalized) {
             current = current == null ? component : current.resolve(component);
-            if (Files.isSymbolicLink(current)) {
+            BasicFileAttributes attributes = Files.readAttributes(
+                    current, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
+            if (attributes.isSymbolicLink()) {
                 throw new IOException("Refusing symbolic-link component in " + purpose + " " + normalized);
             }
+            if (attributes.isOther()) {
+                throw new IOException("Refusing special filesystem component in " + purpose + " " + normalized);
+            }
+            if (!isSupportedScratchDirectory(attributes)) {
+                throw new IOException("Refusing unsupported component in " + purpose + " " + normalized);
+            }
         }
     }
 
@@ -1677,7 +2051,7 @@ public final class DatapackIngestService {
 
     private static void validateInstallTree(File directory, File storeAnchor, String purpose) throws IOException {
         validateScratchTree(directory.toPath());
-        if (!Objects.equals(Files.getFileStore(directory.toPath()), Files.getFileStore(storeAnchor.toPath()))) {
+        if (!sameScratchVolume(directory.toPath(), storeAnchor.toPath())) {
             throw new IOException(purpose + " crosses a filesystem boundary at " + directory.getPath());
         }
     }
@@ -1990,21 +2364,26 @@ public final class DatapackIngestService {
         plan.pendingRoot.delete();
     }
 
-    private static void deleteInstallScratch(File scratch, String purpose) throws IOException {
-        if (Files.notExists(scratch.toPath(), LinkOption.NOFOLLOW_LINKS)) {
-            return;
-        }
-        if (!Files.exists(scratch.toPath(), LinkOption.NOFOLLOW_LINKS)
-                || Files.isSymbolicLink(scratch.toPath())
-                || !Files.isDirectory(scratch.toPath(), LinkOption.NOFOLLOW_LINKS)) {
-            throw new IOException("Refusing to remove unsafe " + purpose + " " + scratch.getPath());
-        }
+    static void deleteInstallScratch(File scratch, String purpose) throws IOException {
+        Path scratchPath = scratch.toPath();
         File parent = Objects.requireNonNull(scratch.getParentFile(), "datapack scratch parent");
-        validateInstallTree(scratch, parent, purpose);
-        IO.delete(scratch);
-        if (Files.exists(scratch.toPath(), LinkOption.NOFOLLOW_LINKS)) {
-            throw new IOException("Could not remove " + purpose + " " + scratch.getPath());
+        for (int attempt = 0; attempt < MAX_SCRATCH_DELETE_ATTEMPTS; attempt++) {
+            if (Files.notExists(scratchPath, LinkOption.NOFOLLOW_LINKS)) {
+                return;
+            }
+            if (!Files.exists(scratchPath, LinkOption.NOFOLLOW_LINKS)
+                    || Files.isSymbolicLink(scratchPath)
+                    || !Files.isDirectory(scratchPath, LinkOption.NOFOLLOW_LINKS)) {
+                throw new IOException("Refusing to remove unsafe " + purpose + " " + scratch.getPath());
+            }
+            validateInstallTree(scratch, parent, purpose);
+            removeFinderMetadata(scratch);
+            IO.delete(scratch);
+            if (Files.notExists(scratchPath, LinkOption.NOFOLLOW_LINKS)) {
+                return;
+            }
         }
+        throw new IOException("Could not remove " + purpose + " " + scratch.getPath());
     }
 
     private static boolean resolveStripOverrides() {
@@ -2271,6 +2650,7 @@ public final class DatapackIngestService {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
             Path rootPath = root.toPath().toAbsolutePath().normalize();
             Path rootMarker = rootPath.resolve(OWNERSHIP_MARKER);
+            FileStore rootStore = Files.getFileStore(rootPath);
             List<Path> entries = new ArrayList<>();
             try (Stream<Path> paths = Files.walk(rootPath)) {
                 Iterator<Path> iterator = paths.iterator();
@@ -2315,9 +2695,14 @@ public final class DatapackIngestService {
                         BasicFileAttributes.class,
                         LinkOption.NOFOLLOW_LINKS
                 );
-                if (!attributes.isDirectory() && !attributes.isRegularFile()) {
+                if (attributes.isSymbolicLink()
+                        || attributes.isOther()
+                        || !attributes.isDirectory() && !attributes.isRegularFile()) {
                     throw new IOException("Datapack entry changed while hashing: " + relative);
                 }
+                if (!sameScratchVolume(rootPath, rootStore, entry, Files.getFileStore(entry))) {
+                    throw new IOException("Datapack entry crosses a filesystem boundary: " + entry);
+                }
                 boolean directory = attributes.isDirectory();
                 digest.update((byte) (directory ? 1 : 2));
                 updateDigestInt(digest, relativeBytes.length);
@@ -3809,16 +4194,78 @@ public final class DatapackIngestService {
                 BasicFileAttributes attributes = Files.readAttributes(
                         entry, BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
                 if (attributes.isSymbolicLink()
+                        || attributes.isOther()
                         || (!attributes.isDirectory() && !attributes.isRegularFile())) {
                     throw new IOException("Datapack scratch contains an unsupported file: " + entry);
                 }
-                if (!Objects.equals(rootStore, Files.getFileStore(entry))) {
+                if (!sameScratchVolume(root, rootStore, entry, Files.getFileStore(entry))) {
                     throw new IOException("Datapack scratch crosses a filesystem boundary: " + entry);
                 }
             }
         }
     }
 
+    private static boolean sameScratchVolume(Path first, Path second) throws IOException {
+        return sameScratchVolume(first, Files.getFileStore(first), second, Files.getFileStore(second));
+    }
+
+    static boolean sameScratchVolume(
+            Path first,
+            FileStore firstStore,
+            Path second,
+            FileStore secondStore
+    ) {
+        if (Objects.equals(firstStore, secondStore)) {
+            return true;
+        }
+        if (!isDefaultWindowsPath(first) || !isDefaultWindowsPath(second)) {
+            return false;
+        }
+        Path firstAbsolute = first.toAbsolutePath().normalize();
+        Path secondAbsolute = second.toAbsolutePath().normalize();
+        if ((firstAbsolute.toString().length() > WINDOWS_LEGACY_PATH_LIMIT)
+                == (secondAbsolute.toString().length() > WINDOWS_LEGACY_PATH_LIMIT)) {
+            return false;
+        }
+        Path firstRoot = firstAbsolute.getRoot();
+        Path secondRoot = secondAbsolute.getRoot();
+        if (firstRoot == null || secondRoot == null) {
+            return false;
+        }
+        return sameWindowsVolume(
+                firstStore, firstRoot.toString(), secondStore, secondRoot.toString());
+    }
+
+    static boolean sameWindowsVolume(
+            FileStore firstStore,
+            String firstRoot,
+            FileStore secondStore,
+            String secondRoot
+    ) {
+        if (firstRoot == null || secondRoot == null || !firstRoot.equalsIgnoreCase(secondRoot)) {
+            return false;
+        }
+        try {
+            Object firstSerial = firstStore.getAttribute("volume:vsn");
+            Object secondSerial = secondStore.getAttribute("volume:vsn");
+            return firstSerial != null && firstSerial.equals(secondSerial);
+        } catch (IOException | RuntimeException exception) {
+            return false;
+        }
+    }
+
+    static boolean isSupportedScratchDirectory(BasicFileAttributes attributes) {
+        return attributes != null
+                && attributes.isDirectory()
+                && !attributes.isSymbolicLink()
+                && !attributes.isOther();
+    }
+
+    private static boolean isDefaultWindowsPath(Path path) {
+        return File.separatorChar == '\\'
+                && path.getFileSystem().equals(FileSystems.getDefault());
+    }
+
     private static Ownership verifyManagedScratchDirectory(File directory, String id) throws IOException {
         validateManagedDirectory(directory, id);
         Ownership ownership = readOwnership(directory);
@@ -4752,9 +5199,8 @@ public final class DatapackIngestService {
             if (!Objects.equals(legacyStagingSnapshot.normalizedTarget().getParent(), normalizedStagingRoot)
                     || !Files.isSameFile(
                     legacyStagingSnapshot.normalizedTarget().getParent(), normalizedStagingRoot)
-                    || !Objects.equals(
-                    Files.getFileStore(legacyStagingSnapshot.normalizedTarget()),
-                    Files.getFileStore(normalizedStagingRoot))) {
+                    || !sameScratchVolume(
+                    legacyStagingSnapshot.normalizedTarget(), normalizedStagingRoot)) {
                 throw new IOException("Changed or unsafe canonical legacy datapack staging target for " + id);
             }
             verifyDirectorySnapshot(
@@ -4831,6 +5277,22 @@ public final class DatapackIngestService {
         public Map<String, Map<String, String>> importedBundles = new HashMap<>();
     }
 
+    static final class StartupValidationCache {
+        int schemaVersion;
+        String minecraftVersion;
+        int irisVersion;
+        boolean autoIngest;
+        boolean stripOverrides;
+        List<String> urls;
+        String localFingerprint;
+    }
+
+    public enum StartupValidationOutcome {
+        READY,
+        RESTART_REQUIRED,
+        FAILED
+    }
+
     private static final class Manifest {
         private List<Entry> entries = new ArrayList<>();
 

core/src/main/java/art/arcane/iris/core/lifecycle/WorldLifecycleService.java

@@ -1,5 +1,6 @@
 package art.arcane.iris.core.lifecycle;
 
+import art.arcane.iris.core.IrisStartupValidation;
 import art.arcane.iris.core.ServerConfigurator;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.core.tools.IrisToolbelt;
@@ -76,6 +77,7 @@ public final class WorldLifecycleService {
     public CompletableFuture<World> create(WorldLifecycleRequest request) {
         WorldLifecycleBackend backend;
         try {
+            IrisStartupValidation.requireWorldCreationReady();
             backend = selectCreateBackend(request);
         } catch (Throwable e) {
             IrisLogging.reportError("WorldLifecycle create backend selection failed for world=\"" + request.worldName()

core/src/main/java/art/arcane/iris/core/pack/PackValidationCache.java

@@ -0,0 +1,201 @@
+package art.arcane.iris.core.pack;
+
+import art.arcane.iris.core.ServerConfigurator;
+import art.arcane.iris.spi.IrisPlatform;
+import art.arcane.iris.spi.IrisPlatforms;
+import art.arcane.iris.spi.PlatformRegistries;
+import art.arcane.iris.spi.PlatformStructureHooks;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.HexFormat;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+
+public final class PackValidationCache {
+    private static final int SCHEMA_VERSION = 1;
+    private static final long MAX_CACHE_BYTES = 16L * 1024L * 1024L;
+    private static final Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+
+    private PackValidationCache() {
+    }
+
+    public static String contentFingerprint(File packsRoot) {
+        return ServerConfigurator.computePackFingerprint(packsRoot);
+    }
+
+    public static String contextFingerprint() {
+        if (!IrisPlatforms.isBound()) {
+            return "";
+        }
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            IrisPlatform platform = IrisPlatforms.get();
+            update(digest, platform.platformName());
+            update(digest, platform.minecraftVersion());
+            update(digest, Integer.toString(platform.irisVersionNumber()));
+            update(digest, Boolean.toString(ContentKeyValidator.strictContent()));
+
+            PlatformRegistries registries = Objects.requireNonNull(
+                    platform.registries(), "Pack validation platform registries");
+            updateSorted(digest, registries.blockKeys());
+            updateSorted(digest, registries.biomeKeys());
+            updateSorted(digest, registries.itemKeys());
+            updateSorted(digest, registries.entityKeys());
+
+            PlatformStructureHooks hooks = Objects.requireNonNull(
+                    platform.structureHooks(), "Pack validation structure hooks");
+            updateSorted(digest, hooks.structureKeys());
+            updateSorted(digest, hooks.jigsawStructureKeys());
+            updateSorted(digest, hooks.templatePoolKeys());
+            updateSorted(digest, hooks.structureSetKeys());
+            updateSorted(digest, hooks.objectFeatureKeys());
+            return HexFormat.of().formatHex(digest.digest());
+        } catch (NoSuchAlgorithmException exception) {
+            throw new IllegalStateException("SHA-256 is unavailable", exception);
+        }
+    }
+
+    public static Optional<List<PackValidationResult>> load(
+            Path cacheFile,
+            String contentFingerprint,
+            String contextFingerprint,
+            List<String> expectedPackNames
+    ) {
+        if (cacheFile == null
+                || contentFingerprint == null || contentFingerprint.isBlank()
+                || contextFingerprint == null || contextFingerprint.isBlank()
+                || !Files.isRegularFile(cacheFile, LinkOption.NOFOLLOW_LINKS)
+                || Files.isSymbolicLink(cacheFile)) {
+            return Optional.empty();
+        }
+        try {
+            if (Files.size(cacheFile) > MAX_CACHE_BYTES) {
+                return Optional.empty();
+            }
+            CacheState state = GSON.fromJson(Files.readString(cacheFile, StandardCharsets.UTF_8), CacheState.class);
+            if (state == null
+                    || state.schemaVersion != SCHEMA_VERSION
+                    || !contentFingerprint.equals(state.contentFingerprint)
+                    || !contextFingerprint.equals(state.contextFingerprint)
+                    || state.results == null) {
+                return Optional.empty();
+            }
+            Set<String> expected = new HashSet<>(expectedPackNames == null ? List.of() : expectedPackNames);
+            List<PackValidationResult> results = new ArrayList<>(state.results.size());
+            Set<String> actual = new HashSet<>();
+            for (CachedResult cached : state.results) {
+                if (cached == null || cached.packName == null || cached.packName.isBlank()
+                        || cached.blockingErrors == null || cached.warnings == null
+                        || !actual.add(cached.packName)) {
+                    return Optional.empty();
+                }
+                results.add(new PackValidationResult(
+                        cached.packName,
+                        cached.blockingErrors,
+                        cached.warnings,
+                        cached.validatedAtMillis));
+            }
+            if (!expected.equals(actual)) {
+                return Optional.empty();
+            }
+            results.sort(Comparator.comparing(PackValidationResult::getPackName));
+            return Optional.of(List.copyOf(results));
+        } catch (IOException | RuntimeException exception) {
+            return Optional.empty();
+        }
+    }
+
+    public static void save(
+            Path cacheFile,
+            String contentFingerprint,
+            String contextFingerprint,
+            List<PackValidationResult> results
+    ) throws IOException {
+        if (cacheFile == null || contentFingerprint == null || contentFingerprint.isBlank()
+                || contextFingerprint == null || contextFingerprint.isBlank()) {
+            return;
+        }
+        List<PackValidationResult> sorted = new ArrayList<>(results == null ? List.of() : results);
+        sorted.sort(Comparator.comparing(PackValidationResult::getPackName));
+        CacheState state = new CacheState();
+        state.schemaVersion = SCHEMA_VERSION;
+        state.contentFingerprint = contentFingerprint;
+        state.contextFingerprint = contextFingerprint;
+        state.results = new ArrayList<>(sorted.size());
+        for (PackValidationResult result : sorted) {
+            CachedResult cached = new CachedResult();
+            cached.packName = result.getPackName();
+            cached.blockingErrors = List.copyOf(result.getBlockingErrors());
+            cached.warnings = List.copyOf(result.getWarnings());
+            cached.validatedAtMillis = result.getValidatedAtMillis();
+            state.results.add(cached);
+        }
+
+        Path absolute = cacheFile.toAbsolutePath().normalize();
+        Path parent = Objects.requireNonNull(absolute.getParent(), "Pack validation cache parent");
+        Files.createDirectories(parent);
+        Path staged = Files.createTempFile(parent, ".pack-validation-", ".tmp");
+        try {
+            byte[] content = GSON.toJson(state).getBytes(StandardCharsets.UTF_8);
+            if (content.length > MAX_CACHE_BYTES) {
+                throw new IOException("Pack validation cache exceeds " + MAX_CACHE_BYTES + " bytes");
+            }
+            Files.write(staged, content);
+            try {
+                Files.move(staged, absolute, StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(staged, absolute, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } finally {
+            Files.deleteIfExists(staged);
+        }
+    }
+
+    private static void updateSorted(MessageDigest digest, List<String> values) {
+        List<String> sorted = new ArrayList<>(Objects.requireNonNull(values, "Pack validation registry keys"));
+        sorted.sort(String::compareTo);
+        update(digest, Integer.toString(sorted.size()));
+        for (String value : sorted) {
+            update(digest, value);
+        }
+    }
+
+    private static void update(MessageDigest digest, String value) {
+        byte[] bytes = Objects.requireNonNullElse(value, "").getBytes(StandardCharsets.UTF_8);
+        digest.update((byte) (bytes.length >>> 24));
+        digest.update((byte) (bytes.length >>> 16));
+        digest.update((byte) (bytes.length >>> 8));
+        digest.update((byte) bytes.length);
+        digest.update(bytes);
+    }
+
+    private static final class CacheState {
+        private int schemaVersion;
+        private String contentFingerprint;
+        private String contextFingerprint;
+        private List<CachedResult> results;
+    }
+
+    private static final class CachedResult {
+        private String packName;
+        private List<String> blockingErrors;
+        private List<String> warnings;
+        private long validatedAtMillis;
+    }
+}

core/src/main/java/art/arcane/iris/core/runtime/StudioOpenCoordinator.java

@@ -218,9 +218,7 @@ public final class StudioOpenCoordinator {
             if (request.openKind().openWorkspace() && request.project() != null) {
                 new IrisCodeWorkspace(request.project()).openVSCode(request.sender());
             }
-            if (request.onDone() != null) {
-                request.onDone().accept(world);
-            }
+            runOpenFinalizer(request.onDone(), world);
             t = logStudioPhase(request, "finalize_open", t, openStart);
 
             IrisLogging.info("Studio open: " + world.getName() + " ready in "
@@ -272,6 +270,20 @@ public final class StudioOpenCoordinator {
         return now;
     }
 
+    private void runOpenFinalizer(Consumer<World> finalizer, World world)
+            throws InterruptedException, ExecutionException, TimeoutException {
+        if (finalizer == null) {
+            return;
+        }
+        if (J.isPrimaryThread()) {
+            finalizer.accept(world);
+            return;
+        }
+
+        CompletableFuture<Void> completion = J.sfut(() -> finalizer.accept(world));
+        completion.get(STUDIO_STRUCTURE_ACTIVATION_TIMEOUT_SECONDS, TimeUnit.SECONDS);
+    }
+
     private long elapsedMillis(long startedAtNanos) {
         return TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startedAtNanos);
     }

core/src/main/java/art/arcane/iris/core/runtime/jigsaw/JigsawStudioGraphEditor.java

@@ -157,7 +157,9 @@ public final class JigsawStudioGraphEditor {
         IrisStructure structure = readStructure(
                 resolveOwnedResource(graph.root(), structureResource),
                 structureResource);
-        Map<String, JigsawPlanarArchetype> expectedSources = expectedThemeSetSources(structure);
+        Map<String, JigsawPlanarArchetype> expectedSources = expectedThemeSetSources(
+                structure,
+                requestedSources.keySet());
         requireExactThemeSetSources(requestedSources, expectedSources.keySet());
 
         Map<String, byte[]> resources = readOwnedResources(graph);
@@ -200,7 +202,9 @@ public final class JigsawStudioGraphEditor {
                         + "' is not owned by this jigsaw project");
             }
             String variantFolder = expectedArchetype == null
+                    ? expectedSources.size() == 1
                     ? "spatial"
+                    : "spatial/" + sourcePieceKey
                     : expectedArchetype.name().toLowerCase(Locale.ROOT);
             String targetPieceKey = graph.manifest().structure().path()
                     + "/variants/" + variantFolder + "/" + themeKey;
@@ -686,11 +690,23 @@ public final class JigsawStudioGraphEditor {
     }
 
     private static Map<String, JigsawPlanarArchetype> expectedThemeSetSources(
-            IrisStructure structure
+            IrisStructure structure,
+            Set<String> requestedStableIds
     ) throws IOException {
         Map<String, JigsawPlanarArchetype> expected = new LinkedHashMap<>();
         if (structure.resolvedMode() == IrisJigsawMode.SPATIAL_JIGSAW) {
-            expected.put(JigsawStudioLayout.SPATIAL_WORKCELL_ID, null);
+            if (requestedStableIds.isEmpty()) {
+                throw new IOException("A spatial theme set requires at least one workcell source");
+            }
+            List<String> stableIds = new ArrayList<>(requestedStableIds);
+            stableIds.sort(Comparator.naturalOrder());
+            for (String stableId : stableIds) {
+                if (!stableId.equals(JigsawStudioLayout.SPATIAL_WORKCELL_ID)
+                        && !stableId.startsWith(JigsawStudioLayout.SPATIAL_WORKCELL_ID + "/")) {
+                    throw new IOException("Invalid spatial workcell source '" + stableId + "'");
+                }
+                expected.put(stableId, null);
+            }
             return expected;
         }
         Map<IrisJigsawWorkcellArchetype, PlanarJigsawWorkcellResolver.ResolvedWorkcell> workcells;

core/src/main/java/art/arcane/iris/core/runtime/jigsaw/JigsawStudioLayout.java

@@ -27,6 +27,7 @@ public final class JigsawStudioLayout {
     private final JigsawStudioVariantCatalog variantCatalog;
     private final List<JigsawStudioBay> bays;
     private final Map<String, JigsawStudioBay> byStableId;
+    private final Map<String, String> spatialVariantByBay;
 
     private JigsawStudioLayout(
             JigsawStudioMode mode,
@@ -34,7 +35,8 @@ public final class JigsawStudioLayout {
             int columns,
             int gap,
             JigsawStudioVariantCatalog variantCatalog,
-            List<JigsawStudioBay> bays
+            List<JigsawStudioBay> bays,
+            Map<String, String> spatialVariantByBay
     ) {
         this.mode = mode;
         this.cellDimensions = cellDimensions;
@@ -50,6 +52,7 @@ public final class JigsawStudioLayout {
             }
         }
         this.byStableId = Collections.unmodifiableMap(index);
+        this.spatialVariantByBay = Collections.unmodifiableMap(new LinkedHashMap<>(spatialVariantByBay));
     }
 
     public static JigsawStudioLayout create(
@@ -87,20 +90,41 @@ public final class JigsawStudioLayout {
         validateCatalogMode(JigsawStudioMode.SPATIAL_JIGSAW, catalog);
         String resolvedDisplayName = displayName == null ? "" : displayName.trim();
 
-        List<JigsawStudioBay> workcells = new ArrayList<>();
-        workcells.add(new JigsawStudioBay(
-                SPATIAL_WORKCELL_ID,
-                JigsawStudioBayKind.SPATIAL_WORKCELL,
-                Optional.empty(),
-                resolvedDisplayName,
-                new JigsawStudioBounds(FIRST_ORIGIN, FLOOR_Y + 1, FIRST_ORIGIN, dimensions)));
+        List<JigsawStudioVariant> variants = catalog.spatialVariants();
+        List<JigsawStudioBay> workcells = new ArrayList<>(Math.max(1, variants.size()));
+        Map<String, String> variantsByWorkcell = new LinkedHashMap<>();
+        if (variants.isEmpty()) {
+            workcells.add(new JigsawStudioBay(
+                    SPATIAL_WORKCELL_ID,
+                    JigsawStudioBayKind.SPATIAL_WORKCELL,
+                    Optional.empty(),
+                    resolvedDisplayName,
+                    new JigsawStudioBounds(FIRST_ORIGIN, FLOOR_Y + 1, FIRST_ORIGIN, dimensions)));
+        } else {
+            int originX = FIRST_ORIGIN;
+            for (int index = 0; index < variants.size(); index++) {
+                JigsawStudioVariant variant = variants.get(index);
+                String stableId = index == 0
+                        ? SPATIAL_WORKCELL_ID
+                        : SPATIAL_WORKCELL_ID + "/" + variant.pieceKey();
+                workcells.add(new JigsawStudioBay(
+                        stableId,
+                        JigsawStudioBayKind.SPATIAL_WORKCELL,
+                        Optional.empty(),
+                        variant.resolvedDisplayName(),
+                        new JigsawStudioBounds(originX, FLOOR_Y + 1, FIRST_ORIGIN, dimensions)));
+                variantsByWorkcell.put(stableId, variant.pieceKey());
+                originX = Math.addExact(originX, Math.addExact(dimensions.width(), PLANAR_GAP));
+            }
+        }
         return new JigsawStudioLayout(
                 JigsawStudioMode.SPATIAL_JIGSAW,
                 dimensions,
-                1,
+                workcells.size(),
                 PLANAR_GAP,
                 catalog,
-                workcells);
+                workcells,
+                variantsByWorkcell);
     }
 
     public static JigsawStudioLayout createPlanar(
@@ -143,7 +167,8 @@ public final class JigsawStudioLayout {
                 PLANAR_COLUMNS,
                 PLANAR_GAP,
                 catalog,
-                workcells);
+                workcells,
+                Map.of());
     }
 
     public JigsawStudioMode mode() {
@@ -186,7 +211,11 @@ public final class JigsawStudioLayout {
     public List<JigsawStudioVariant> variants(JigsawStudioBay workcell) {
         JigsawStudioBay activeWorkcell = requireWorkcell(workcell);
         if (activeWorkcell.kind() == JigsawStudioBayKind.SPATIAL_WORKCELL) {
-            return variantCatalog.spatialVariants();
+            String pieceKey = spatialVariantByBay.get(activeWorkcell.stableId());
+            if (pieceKey == null) {
+                return variantCatalog.spatialVariants();
+            }
+            return variantCatalog.find(pieceKey).map(List::of).orElseGet(List::of);
         }
         return variantCatalog.variants(activeWorkcell.archetype().orElseThrow());
     }
@@ -203,11 +232,28 @@ public final class JigsawStudioLayout {
             return false;
         }
         if (activeWorkcell.kind() == JigsawStudioBayKind.SPATIAL_WORKCELL) {
-            return activeVariant.mode() == JigsawStudioMode.SPATIAL_JIGSAW;
+            return activeVariant.mode() == JigsawStudioMode.SPATIAL_JIGSAW
+                    && variants(activeWorkcell).contains(activeVariant);
         }
         return activeVariant.archetype().filter(activeWorkcell.archetype().orElseThrow()::equals).isPresent();
     }
 
+    public Optional<JigsawStudioBay> workcellForVariant(String pieceKey) {
+        Optional<JigsawStudioVariant> variant = variantCatalog.find(pieceKey);
+        if (variant.isEmpty()) {
+            return Optional.empty();
+        }
+        if (mode == JigsawStudioMode.PLANAR_JIGSAW) {
+            return variant.get().archetype().map(archetype -> get(archetype.stableId()));
+        }
+        for (Map.Entry<String, String> entry : spatialVariantByBay.entrySet()) {
+            if (entry.getValue().equals(variant.get().pieceKey())) {
+                return Optional.ofNullable(get(entry.getKey()));
+            }
+        }
+        return Optional.ofNullable(get(SPATIAL_WORKCELL_ID));
+    }
+
     public JigsawStudioControlPosition controlPosition() {
         return CONTROL_POSITION;
     }

core/src/main/java/art/arcane/iris/core/runtime/jigsaw/JigsawStudioProjectCreator.java

@@ -30,11 +30,19 @@ import com.google.gson.GsonBuilder;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.nio.file.Path;
+import java.util.List;
 import java.util.Locale;
 import java.util.Objects;
 
 public final class JigsawStudioProjectCreator {
     private static final Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+    private static final List<IrisDirection> SPATIAL_CONNECTOR_ORDER = List.of(
+            IrisDirection.NORTH_NEGATIVE_Z,
+            IrisDirection.SOUTH_POSITIVE_Z,
+            IrisDirection.EAST_POSITIVE_X,
+            IrisDirection.WEST_NEGATIVE_X,
+            IrisDirection.UP_POSITIVE_Y,
+            IrisDirection.DOWN_NEGATIVE_Y);
 
     private JigsawStudioProjectCreator() {
     }
@@ -73,7 +81,7 @@ public final class JigsawStudioProjectCreator {
         if (options.mode() == JigsawStudioMode.PLANAR_JIGSAW) {
             addPlanarDefaults(bundle, structure, pool, options);
         } else {
-            addSpatialDefault(bundle, pool, options);
+            addSpatialDefaults(bundle, pool, options);
         }
         bundle.textResource("jigsaw-pools/" + resourceKey + "/start.json", GSON.toJson(pool) + "\n");
         bundle.textResource("structures/" + resourceKey + ".json", GSON.toJson(structure) + "\n");
@@ -156,23 +164,82 @@ public final class JigsawStudioProjectCreator {
         bundle.textResource("jigsaw-pools/" + capPoolKey + ".json", GSON.toJson(capPool) + "\n");
     }
 
-    private static void addSpatialDefault(
+    private static void addSpatialDefaults(
             StructureResourceBundle.Builder bundle,
             IrisJigsawPool pool,
             Options options
     ) throws IOException {
-        String key = options.structureKey() + "/start";
         JigsawStudioCellDimensions dimensions = options.cellDimensions();
-        IrisJigsawPiece piece = new IrisJigsawPiece().setObject(key).setRotatable(true);
-        if (options.compatibilityTarget() == JigsawStudioCompatibilityTarget.IRIS_EXTENDED) {
-            piece.getThemes().add("variant-1");
+        String piecePoolKey = options.structureKey() + "/pieces";
+        IrisJigsawPool piecePool = new IrisJigsawPool();
+        for (int connectorCount = 0; connectorCount <= SPATIAL_CONNECTOR_ORDER.size(); connectorCount++) {
+            String key = options.structureKey() + "/"
+                    + (connectorCount == 0 ? "start" : "connectors-" + connectorCount);
+            IrisJigsawPiece piece = spatialPiece(
+                    key,
+                    piecePoolKey,
+                    dimensions,
+                    connectorCount);
+            if (options.compatibilityTarget() == JigsawStudioCompatibilityTarget.IRIS_EXTENDED) {
+                piece.getThemes().add("variant-1");
+            }
+            pool.getPieces().add(new IrisJigsawPieceEntry(key, 1));
+            if (connectorCount > 0) {
+                piecePool.getPieces().add(new IrisJigsawPieceEntry(key, 1));
+            }
+            bundle.resource("objects/" + key + ".iob", serialize(new IrisObject(
+                    dimensions.width(),
+                    dimensions.height(),
+                    dimensions.depth())));
+            bundle.textResource("jigsaw-pieces/" + key + ".json", GSON.toJson(piece) + "\n");
         }
-        pool.getPieces().add(new IrisJigsawPieceEntry(key, 1));
-        bundle.resource("objects/" + key + ".iob", serialize(new IrisObject(
-                dimensions.width(),
-                dimensions.height(),
-                dimensions.depth())));
-        bundle.textResource("jigsaw-pieces/" + key + ".json", GSON.toJson(piece) + "\n");
+        piecePool.getPieces().add(new IrisJigsawPieceEntry().setEmpty(true));
+        bundle.textResource("jigsaw-pools/" + piecePoolKey + ".json", GSON.toJson(piecePool) + "\n");
+    }
+
+    private static IrisJigsawPiece spatialPiece(
+            String objectKey,
+            String poolKey,
+            JigsawStudioCellDimensions dimensions,
+            int connectorCount
+    ) {
+        IrisJigsawPiece piece = new IrisJigsawPiece()
+                .setDisplayName(connectorCount + (connectorCount == 1 ? " Connector" : " Connectors"))
+                .setObject(objectKey)
+                .setRotatable(true)
+                .setRules(new IrisJigsawPieceRules().setMaximumPlacements(16));
+        for (int index = 0; index < connectorCount; index++) {
+            IrisDirection direction = SPATIAL_CONNECTOR_ORDER.get(index);
+            piece.getConnectors().add(new IrisJigsawConnector()
+                    .setPosition(spatialConnectorPosition(dimensions, direction))
+                    .setDirection(direction)
+                    .setTop(direction.isVertical()
+                            ? IrisDirection.NORTH_NEGATIVE_Z
+                            : IrisDirection.UP_POSITIVE_Y)
+                    .setPool(poolKey)
+                    .setName("iris:spatial")
+                    .setTargetName("iris:spatial")
+                    .setJoint(JigsawJoint.ROLLABLE)
+                    .setFinalState("minecraft:structure_void"));
+        }
+        return piece;
+    }
+
+    private static IrisPosition spatialConnectorPosition(
+            JigsawStudioCellDimensions dimensions,
+            IrisDirection direction
+    ) {
+        int centerX = dimensions.width() / 2;
+        int centerY = dimensions.height() / 2;
+        int centerZ = dimensions.depth() / 2;
+        return switch (direction) {
+            case NORTH_NEGATIVE_Z -> new IrisPosition(centerX, centerY, 0);
+            case SOUTH_POSITIVE_Z -> new IrisPosition(centerX, centerY, dimensions.depth() - 1);
+            case EAST_POSITIVE_X -> new IrisPosition(dimensions.width() - 1, centerY, centerZ);
+            case WEST_NEGATIVE_X -> new IrisPosition(0, centerY, centerZ);
+            case UP_POSITIVE_Y -> new IrisPosition(centerX, dimensions.height() - 1, centerZ);
+            case DOWN_NEGATIVE_Y -> new IrisPosition(centerX, 0, centerZ);
+        };
     }
 
     private static IrisJigsawPiece planarPiece(

core/src/main/java/art/arcane/iris/core/service/JigsawStudioDisabledWorkcellRenderer.java

@@ -1,272 +0,0 @@
-package art.arcane.iris.core.service;
-
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioBay;
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioBounds;
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioLayout;
-import art.arcane.iris.util.common.scheduling.J;
-import org.bukkit.Location;
-import org.bukkit.Material;
-import org.bukkit.World;
-import org.bukkit.entity.BlockDisplay;
-import org.bukkit.entity.Display;
-import org.bukkit.util.Transformation;
-import org.joml.Quaternionf;
-import org.joml.Vector3f;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Objects;
-import java.util.UUID;
-
-public final class JigsawStudioDisabledWorkcellRenderer {
-    private static final String ENTITY_TAG = "iris_jigsaw_disabled_workcell";
-
-    private final Map<UUID, RequestDisplays> requests = new HashMap<>();
-
-    public void reconcile(World world, UUID requestId, JigsawStudioLayout layout) {
-        World activeWorld = Objects.requireNonNull(world, "Jigsaw Studio display world");
-        UUID activeRequestId = Objects.requireNonNull(requestId, "Jigsaw Studio display request ID");
-        Map<String, Descriptor> desired = descriptors(Objects.requireNonNull(
-                layout,
-                "Jigsaw Studio display layout"));
-        List<BlockDisplay> removals = new ArrayList<>();
-        long generation;
-        synchronized (this) {
-            RequestDisplays state = requests.computeIfAbsent(
-                    activeRequestId,
-                    ignored -> new RequestDisplays(activeWorld.getUID()));
-            if (!state.worldId.equals(activeWorld.getUID())) {
-                removals.addAll(state.entities.values());
-                state = new RequestDisplays(activeWorld.getUID());
-                requests.put(activeRequestId, state);
-            }
-            generation = Math.incrementExact(state.generation);
-            state.generation = generation;
-            state.desired.clear();
-            state.desired.putAll(desired);
-            for (Map.Entry<String, BlockDisplay> entry : new ArrayList<>(state.entities.entrySet())) {
-                Descriptor descriptor = desired.get(entry.getKey());
-                if (descriptor == null || !descriptor.equals(state.rendered.get(entry.getKey()))) {
-                    state.entities.remove(entry.getKey());
-                    state.rendered.remove(entry.getKey());
-                    removals.add(entry.getValue());
-                }
-            }
-        }
-        remove(removals);
-        for (Descriptor descriptor : desired.values()) {
-            scheduleSpawn(activeWorld, activeRequestId, generation, descriptor);
-        }
-    }
-
-    public void unloadChunk(UUID requestId, int chunkX, int chunkZ) {
-        if (requestId == null) {
-            return;
-        }
-        List<BlockDisplay> removals;
-        synchronized (this) {
-            RequestDisplays state = requests.get(requestId);
-            if (state == null) {
-                return;
-            }
-            removals = detachChunkDisplays(state.entities, state.rendered, chunkX, chunkZ);
-        }
-        remove(removals);
-    }
-
-    public void removeRequest(UUID requestId) {
-        if (requestId == null) {
-            return;
-        }
-        RequestDisplays removed;
-        synchronized (this) {
-            removed = requests.remove(requestId);
-        }
-        if (removed != null) {
-            remove(new ArrayList<>(removed.entities.values()));
-        }
-    }
-
-    public void removeAll() {
-        List<BlockDisplay> removals = new ArrayList<>();
-        synchronized (this) {
-            for (RequestDisplays state : requests.values()) {
-                removals.addAll(state.entities.values());
-            }
-            requests.clear();
-        }
-        remove(removals);
-    }
-
-    static Map<String, Descriptor> descriptors(JigsawStudioLayout layout) {
-        Map<String, Descriptor> descriptors = new LinkedHashMap<>();
-        for (JigsawStudioBay bay : layout.bays()) {
-            if (bay.enabled()) {
-                continue;
-            }
-            JigsawStudioBounds bounds = bay.bounds();
-            descriptors.put(bay.stableId(), new Descriptor(
-                    bay.stableId(),
-                    bounds.originX(),
-                    bounds.originY(),
-                    bounds.originZ(),
-                    bounds.dimensions().width(),
-                    bounds.dimensions().height(),
-                    bounds.dimensions().depth()));
-        }
-        return Map.copyOf(descriptors);
-    }
-
-    synchronized int activeDisplayCount(UUID requestId) {
-        RequestDisplays state = requests.get(requestId);
-        return state == null ? 0 : state.entities.size();
-    }
-
-    static List<BlockDisplay> detachChunkDisplays(
-            Map<String, BlockDisplay> entities,
-            Map<String, Descriptor> rendered,
-            int chunkX,
-            int chunkZ
-    ) {
-        List<BlockDisplay> removals = new ArrayList<>();
-        for (Map.Entry<String, BlockDisplay> entry : new ArrayList<>(entities.entrySet())) {
-            Descriptor descriptor = rendered.get(entry.getKey());
-            if (descriptor == null
-                    || descriptor.originX() >> 4 != chunkX
-                    || descriptor.originZ() >> 4 != chunkZ) {
-                continue;
-            }
-            entities.remove(entry.getKey());
-            rendered.remove(entry.getKey());
-            removals.add(entry.getValue());
-        }
-        return List.copyOf(removals);
-    }
-
-    private void scheduleSpawn(
-            World world,
-            UUID requestId,
-            long generation,
-            Descriptor descriptor
-    ) {
-        synchronized (this) {
-            RequestDisplays state = requests.get(requestId);
-            if (state == null
-                    || state.generation != generation
-                    || state.entities.containsKey(descriptor.workcellId())
-                    || !descriptor.equals(state.desired.get(descriptor.workcellId()))) {
-                return;
-            }
-        }
-        J.runRegion(
-                world,
-                descriptor.originX() >> 4,
-                descriptor.originZ() >> 4,
-                () -> spawn(world, requestId, generation, descriptor));
-    }
-
-    private void spawn(
-            World world,
-            UUID requestId,
-            long generation,
-            Descriptor descriptor
-    ) {
-        if (!world.isChunkLoaded(descriptor.originX() >> 4, descriptor.originZ() >> 4)) {
-            return;
-        }
-        synchronized (this) {
-            RequestDisplays state = requests.get(requestId);
-            if (state == null
-                    || state.generation != generation
-                    || state.entities.containsKey(descriptor.workcellId())
-                    || !descriptor.equals(state.desired.get(descriptor.workcellId()))) {
-                return;
-            }
-        }
-        BlockDisplay display = world.spawn(
-                new Location(world, descriptor.originX(), descriptor.originY(), descriptor.originZ()),
-                BlockDisplay.class,
-                entity -> configure(entity, descriptor));
-        boolean retained;
-        synchronized (this) {
-            RequestDisplays state = requests.get(requestId);
-            retained = state != null
-                    && state.generation == generation
-                    && !state.entities.containsKey(descriptor.workcellId())
-                    && descriptor.equals(state.desired.get(descriptor.workcellId()));
-            if (retained) {
-                state.entities.put(descriptor.workcellId(), display);
-                state.rendered.put(descriptor.workcellId(), descriptor);
-            }
-        }
-        if (!retained) {
-            remove(display);
-        }
-    }
-
-    private static void configure(BlockDisplay display, Descriptor descriptor) {
-        display.setBlock(Material.RED_STAINED_GLASS.createBlockData());
-        display.setTransformation(new Transformation(
-                new Vector3f(),
-                new Quaternionf(),
-                new Vector3f(descriptor.width(), descriptor.height(), descriptor.depth()),
-                new Quaternionf()));
-        display.setBrightness(new Display.Brightness(15, 15));
-        display.setDisplayWidth(Math.max(descriptor.width(), descriptor.depth()));
-        display.setDisplayHeight(descriptor.height());
-        display.setViewRange(128.0F);
-        display.setShadowRadius(0.0F);
-        display.setShadowStrength(0.0F);
-        display.setInterpolationDuration(0);
-        display.setTeleportDuration(0);
-        display.setPersistent(false);
-        display.setInvulnerable(true);
-        display.setGravity(false);
-        display.setSilent(true);
-        display.addScoreboardTag(ENTITY_TAG);
-    }
-
-    private static void remove(List<BlockDisplay> displays) {
-        for (BlockDisplay display : displays) {
-            remove(display);
-        }
-    }
-
-    private static void remove(BlockDisplay display) {
-        if (display != null) {
-            J.runEntity(display, display::remove);
-        }
-    }
-
-    record Descriptor(
-            String workcellId,
-            int originX,
-            int originY,
-            int originZ,
-            int width,
-            int height,
-            int depth
-    ) {
-        Descriptor {
-            workcellId = Objects.requireNonNull(workcellId, "Jigsaw Studio display workcell ID");
-            if (width < 1 || height < 1 || depth < 1) {
-                throw new IllegalArgumentException("Jigsaw Studio display dimensions must be positive");
-            }
-        }
-    }
-
-    private static final class RequestDisplays {
-        private final UUID worldId;
-        private final Map<String, Descriptor> desired = new HashMap<>();
-        private final Map<String, Descriptor> rendered = new HashMap<>();
-        private final Map<String, BlockDisplay> entities = new HashMap<>();
-        private long generation;
-
-        private RequestDisplays(UUID worldId) {
-            this.worldId = worldId;
-        }
-    }
-}

core/src/main/java/art/arcane/iris/core/service/JigsawStudioMenuController.java

@@ -36,6 +36,8 @@ public final class JigsawStudioMenuController {
     static final int PLACEMENT_RULE_SHIFT_STEP = 16;
 
     private static final long DESTRUCTIVE_CONFIRM_NANOS = 10_000_000_000L;
+    private static final int WORKCELL_RESIZE_REFRESH_TICKS = 2;
+    private static final int WORKCELL_RESIZE_REFRESH_ATTEMPTS = 200;
     private static final int[] GRID_POSITIONS = {-3, -2, -1, 0, 1, 2, 3};
 
     private final JavaPlugin plugin;
@@ -44,6 +46,7 @@ public final class JigsawStudioMenuController {
     private final Map<UUID, PendingUnlink> pendingUnlinks = new ConcurrentHashMap<>();
     private final Map<UUID, PendingDelete> pendingDeletes = new ConcurrentHashMap<>();
     private final Map<UUID, PendingProjectDelete> pendingProjectDeletes = new ConcurrentHashMap<>();
+    private final Map<UUID, PendingWorkcellResize> pendingWorkcellResizes = new ConcurrentHashMap<>();
 
     public JigsawStudioMenuController(JavaPlugin plugin, Actions actions) {
         this.plugin = Objects.requireNonNull(plugin, "Jigsaw Studio menu plugin");
@@ -100,11 +103,13 @@ public final class JigsawStudioMenuController {
             pendingUnlinks.remove(playerId);
             pendingDeletes.remove(playerId);
             pendingProjectDeletes.remove(playerId);
+            pendingWorkcellResizes.remove(playerId);
         });
         windows.put(playerId, window);
         pendingUnlinks.remove(playerId);
         pendingDeletes.remove(playerId);
         pendingProjectDeletes.remove(playerId);
+        pendingWorkcellResizes.remove(playerId);
         renderMain(window, state, selected, 0);
         window.open();
         return true;
@@ -242,6 +247,7 @@ public final class JigsawStudioMenuController {
         pendingUnlinks.clear();
         pendingDeletes.clear();
         pendingProjectDeletes.clear();
+        pendingWorkcellResizes.clear();
         for (UIWindow window : activeWindows) {
             Player player = window.getViewer();
             if (J.isOwnedByCurrentRegion(player)) {
@@ -508,26 +514,38 @@ public final class JigsawStudioMenuController {
             JigsawStudioMenuState state,
             JigsawStudioMenuState.Workcell workcell
     ) {
+        PendingWorkcellResize pendingResize = pendingWorkcellResize(
+                window.getViewer().getUniqueId(),
+                state.requestId(),
+                workcell.stableId());
+        JigsawStudioMenuState.Workcell renderedWorkcell = pendingResize == null
+                ? workcell
+                : withCapacity(workcell, pendingResize.dimensions());
         window.batch(() -> {
             window.clearElements();
 
             UIElement back = element("settings-back", Material.ARROW, ChatColor.YELLOW + "Back to Variants");
-            back.onLeftClick(clicked -> refreshMain(
-                    window.getViewer(), state.requestId(), workcell.stableId(), 0));
+            back.onLeftClick(clicked -> leaveWorkcellSettings(
+                    window.getViewer(), state.requestId(), renderedWorkcell.stableId()));
             window.setElement(-4, 0, back);
 
             UIElement identity = element(
                     "settings-identity",
-                    workcell.enabled() ? Material.LIME_WOOL : Material.GRAY_WOOL,
-                    ChatColor.AQUA + safe(workcell.displayName()));
-            identity.addLore(ChatColor.DARK_GRAY + safe(workcell.stableId()));
-            identity.addLore(workcell.enabled()
+                    renderedWorkcell.enabled() ? Material.LIME_WOOL : Material.GRAY_WOOL,
+                    ChatColor.AQUA + safe(renderedWorkcell.displayName()));
+            identity.addLore(ChatColor.DARK_GRAY + safe(renderedWorkcell.stableId()));
+            identity.addLore(renderedWorkcell.enabled()
                     ? ChatColor.GREEN + "Enabled"
                     : ChatColor.RED + "Disabled for assembly and export");
-            if (!workcell.canonicalName().equals(workcell.displayName())) {
-                identity.addLore(ChatColor.GRAY + "Solver role: " + safe(workcell.canonicalName()));
+            if (!renderedWorkcell.canonicalName().equals(renderedWorkcell.displayName())) {
+                identity.addLore(ChatColor.GRAY + "Solver role: " + safe(renderedWorkcell.canonicalName()));
+            }
+            identity.addLore(ChatColor.GRAY + "Capacity: " + dimensions(renderedWorkcell.capacity()));
+            if (pendingResize != null) {
+                identity.addLore(pendingResize.applying()
+                        ? ChatColor.YELLOW + "Applying one live relayout"
+                        : ChatColor.GOLD + "Pending; apply when all dimensions are ready");
             }
-            identity.addLore(ChatColor.GRAY + "Capacity: " + dimensions(workcell.capacity()));
             identity.addLore(ChatColor.YELLOW + "Left-click for a rename stick");
             identity.addLore(ChatColor.GRAY + "Rename that stick in an anvil, then right-click it.");
             identity.addLore(ChatColor.GRAY + "Sneak-right-click the stick to reset this label.");
@@ -536,25 +554,25 @@ public final class JigsawStudioMenuController {
                     JigsawStudioToolPayload.workcell(
                             JigsawStudioToolAction.RENAME_WORKCELL,
                             state.requestId(),
-                            workcell.stableId())));
+                            renderedWorkcell.stableId())));
             window.setElement(0, 0, identity);
             window.setElement(4, 0, evaluationElement(state.evaluation()));
 
             if (state.mode() == JigsawStudioMode.PLANAR_JIGSAW) {
                 UIElement enabled = element(
                         "settings-enabled",
-                        workcell.enabled() ? Material.LEVER : Material.REDSTONE_TORCH,
-                        workcell.enabled()
+                        renderedWorkcell.enabled() ? Material.LEVER : Material.REDSTONE_TORCH,
+                        renderedWorkcell.enabled()
                                 ? ChatColor.GREEN + "Workcell Enabled"
                                 : ChatColor.RED + "Workcell Disabled");
                 enabled.addLore(ChatColor.GRAY + "Disabled workcells remain editable and keep their size.");
                 enabled.addLore(ChatColor.YELLOW + "Left-click to "
-                        + (workcell.enabled() ? "disable" : "enable"));
+                        + (renderedWorkcell.enabled() ? "disable" : "enable"));
                 enabled.onLeftClick(clicked -> setWorkcellEnabled(
                         window.getViewer(),
                         state.requestId(),
-                        workcell.stableId(),
-                        !workcell.enabled()));
+                        renderedWorkcell.stableId(),
+                        !renderedWorkcell.enabled()));
                 window.setElement(0, 1, enabled);
             } else {
                 UIElement spatial = element(
@@ -568,18 +586,18 @@ public final class JigsawStudioMenuController {
 
             UIElement connectors = element(
                     "settings-connectors",
-                    workcell.connectorsVisible() ? Material.JIGSAW : Material.STRUCTURE_VOID,
-                    workcell.connectorsVisible()
+                    renderedWorkcell.connectorsVisible() ? Material.JIGSAW : Material.STRUCTURE_VOID,
+                    renderedWorkcell.connectorsVisible()
                             ? ChatColor.GREEN + "Connector Blocks Visible"
                             : ChatColor.YELLOW + "Connector Blocks Hidden");
             connectors.addLore(ChatColor.GRAY + "Hidden connectors retain their metadata and final block state.");
             connectors.addLore(ChatColor.YELLOW + "Left-click to "
-                    + (workcell.connectorsVisible() ? "hide" : "show") + " connector blocks");
+                    + (renderedWorkcell.connectorsVisible() ? "hide" : "show") + " connector blocks");
             connectors.onLeftClick(clicked -> toggleConnectorBlocks(
                     window.getViewer(),
                     state.requestId(),
-                    workcell.stableId(),
-                    !workcell.connectorsVisible()));
+                    renderedWorkcell.stableId(),
+                    !renderedWorkcell.connectorsVisible()));
             window.setElement(2, 1, connectors);
 
             UIElement resetConnectors = element(
@@ -591,31 +609,57 @@ public final class JigsawStudioMenuController {
             resetConnectors.onLeftClick(clicked -> resetConnectorBlocks(
                     window.getViewer(),
                     state.requestId(),
-                    workcell.stableId()));
+                    renderedWorkcell.stableId()));
             window.setElement(4, 1, resetConnectors);
 
             window.setElement(-2, 2, axisElement(
                     window,
                     state,
-                    workcell,
+                    renderedWorkcell,
                     DimensionAxis.WIDTH,
                     Material.IRON_INGOT));
             window.setElement(0, 2, axisElement(
                     window,
                     state,
-                    workcell,
+                    renderedWorkcell,
                     DimensionAxis.HEIGHT,
                     Material.GOLD_INGOT));
             window.setElement(2, 2, axisElement(
                     window,
                     state,
-                    workcell,
+                    renderedWorkcell,
                     DimensionAxis.DEPTH,
                     Material.COPPER_INGOT));
 
+            if (pendingResize != null) {
+                UIElement apply = element(
+                        "settings-apply-capacity",
+                        pendingResize.applying() ? Material.CLOCK : Material.EMERALD_BLOCK,
+                        pendingResize.applying()
+                                ? ChatColor.YELLOW + "Applying Cell Size"
+                                : ChatColor.GREEN + "Apply Cell Size");
+                apply.addLore(ChatColor.WHITE + dimensions(pendingResize.dimensions()));
+                apply.addLore(ChatColor.GRAY + "Regenerates the layout once after all size edits.");
+                if (!pendingResize.applying()) {
+                    apply.onLeftClick(clicked -> applyWorkcellResize(
+                            window.getViewer(), state.requestId(), renderedWorkcell.stableId()));
+                }
+                window.setElement(0, 3, apply);
+
+                if (!pendingResize.applying()) {
+                    UIElement discard = element(
+                            "settings-discard-capacity",
+                            Material.BARRIER,
+                            ChatColor.RED + "Discard Size Changes");
+                    discard.onLeftClick(clicked -> discardWorkcellResize(
+                            window.getViewer(), state.requestId(), renderedWorkcell.stableId()));
+                    window.setElement(2, 3, discard);
+                }
+            }
+
             UIElement footerBack = element("settings-footer-back", Material.ARROW, ChatColor.YELLOW + "Back");
-            footerBack.onLeftClick(clicked -> refreshMain(
-                    window.getViewer(), state.requestId(), workcell.stableId(), 0));
+            footerBack.onLeftClick(clicked -> leaveWorkcellSettings(
+                    window.getViewer(), state.requestId(), renderedWorkcell.stableId()));
             window.setElement(-4, 5, footerBack);
 
             UIElement undo = element(
@@ -629,7 +673,7 @@ public final class JigsawStudioMenuController {
                     state.requestId()));
             window.setElement(0, 5, undo);
 
-            if (workcell.dirty() && !workcell.saving()) {
+            if (renderedWorkcell.dirty() && !renderedWorkcell.saving()) {
                 UIElement saveNow = element(
                         "save-now",
                         Material.EMERALD,
@@ -637,7 +681,7 @@ public final class JigsawStudioMenuController {
                 saveNow.addLore(ChatColor.GRAY + "Autosave is automatic.");
                 saveNow.addLore(ChatColor.GRAY + "Use this only to flush pending work or recover immediately.");
                 saveNow.onLeftClick(clicked -> flushNow(
-                        window.getViewer(), state.requestId(), workcell.stableId()));
+                        window.getViewer(), state.requestId(), renderedWorkcell.stableId()));
                 window.setElement(2, 5, saveNow);
             }
 
@@ -650,7 +694,7 @@ public final class JigsawStudioMenuController {
 
             UIElement toolbox = element("settings-toolbox", Material.STICK, ChatColor.AQUA + "Toolbox");
             toolbox.onLeftClick(clicked -> openToolbox(
-                    window.getViewer(), state.requestId(), workcell.stableId(), 0));
+                    window.getViewer(), state.requestId(), renderedWorkcell.stableId(), 0));
             window.setElement(4, 5, toolbox);
         });
     }
@@ -802,6 +846,7 @@ public final class JigsawStudioMenuController {
             if (themeEditingAvailable) {
                 createTheme.addLore(ChatColor.GRAY + "Creates one new owned variant for every enabled workcell.");
                 createTheme.addLore(ChatColor.GRAY + "All created variants join " + safe(nextThemeKey) + ".");
+                createTheme.addLore(ChatColor.GRAY + "One family is selected for the complete assembly.");
                 createTheme.addLore(ChatColor.YELLOW + "Left-click to create the complete set");
                 createTheme.onLeftClick(clicked -> duplicateActiveFamily(
                         window.getViewer(), state.requestId(), nextThemeKey));
@@ -884,6 +929,8 @@ public final class JigsawStudioMenuController {
                     state.irisExtended() ? Material.PURPLE_DYE : Material.GRAY_DYE,
                     (state.irisExtended() ? ChatColor.LIGHT_PURPLE : ChatColor.GRAY) + safe(themeSet.key()));
             element.addLore(ChatColor.WHITE + "Selection weight: " + themeSet.weight());
+            element.addLore(ChatColor.WHITE + "Whole-assembly chance: "
+                    + themeSelectionPercent(state.themeSets(), themeSet));
             if (state.irisExtended()) {
                 element.addLore(ChatColor.GREEN + "Left-click: weight +1");
                 element.addLore(ChatColor.YELLOW + "Right-click: weight -1");
@@ -919,7 +966,7 @@ public final class JigsawStudioMenuController {
         element.addLore(ChatColor.YELLOW + "Right-click: -1");
         element.addLore(ChatColor.GREEN + "Shift-left: +8");
         element.addLore(ChatColor.YELLOW + "Shift-right: -8");
-        element.addLore(ChatColor.GRAY + "The Studio layout regenerates after resizing.");
+        element.addLore(ChatColor.GRAY + "Changes stay in this menu until Apply Cell Size.");
         element.onLeftClick(clicked -> resizeWorkcell(
                 window.getViewer(), state.requestId(), workcell.stableId(), axis, 1));
         element.onRightClick(clicked -> resizeWorkcell(
@@ -1396,6 +1443,7 @@ public final class JigsawStudioMenuController {
             element.addLore(member
                     ? ChatColor.GREEN + "This variant belongs to the theme."
                     : ChatColor.GRAY + "This variant does not belong to the theme.");
+            element.addLore(ChatColor.GRAY + "Only variants in the selected family are eligible.");
             element.addLore(ChatColor.YELLOW + "Left-click to toggle membership");
             element.onLeftClick(clicked -> toggleVariantTheme(
                     window.getViewer(), state.requestId(), workcell, variant, themeSet.key()));
@@ -1702,17 +1750,162 @@ public final class JigsawStudioMenuController {
             stale(player);
             return;
         }
+        UUID playerId = player.getUniqueId();
+        PendingWorkcellResize existing = pendingWorkcellResize(playerId, requestId, workcellId);
+        if (existing != null && existing.applying()) {
+            player.sendMessage(ChatColor.YELLOW + "That cell size is already being applied.");
+            return;
+        }
+        JigsawStudioCellDimensions base = existing == null
+                ? workcell.capacity()
+                : existing.dimensions();
         Optional<JigsawStudioCellDimensions> adjusted = adjustedDimensions(
-                workcell.capacity(), axis, delta);
+                base, axis, delta);
         if (adjusted.isEmpty()) {
             player.sendMessage(ChatColor.RED + "That workcell size is outside Iris limits.");
             return;
         }
-        if (actions.updateWorkcellDimensions(player, workcellId, adjusted.get())) {
-            closeAfterAction(player);
+        PendingWorkcellResize pending = new PendingWorkcellResize(
+                requestId,
+                workcellId,
+                adjusted.get(),
+                false);
+        pendingWorkcellResizes.put(playerId, pending);
+        UIWindow window = windows.get(playerId);
+        if (window != null) {
+            renderWorkcellSettings(window, current.get(), withCapacity(workcell, pending.dimensions()));
         }
     }
 
+    private void applyWorkcellResize(Player player, UUID requestId, String workcellId) {
+        Optional<JigsawStudioMenuState> current = matchingState(player, requestId, true);
+        if (current.isEmpty()) {
+            return;
+        }
+        UUID playerId = player.getUniqueId();
+        PendingWorkcellResize pending = pendingWorkcellResize(playerId, requestId, workcellId);
+        JigsawStudioMenuState.Workcell workcell = current.get().workcell(workcellId);
+        if (pending == null || pending.applying() || workcell == null) {
+            return;
+        }
+        if (workcell.capacity().equals(pending.dimensions())) {
+            pendingWorkcellResizes.remove(playerId, pending);
+            refreshWorkcellSettings(player, requestId, workcellId);
+            return;
+        }
+        PendingWorkcellResize applying = new PendingWorkcellResize(
+                requestId,
+                workcellId,
+                pending.dimensions(),
+                true);
+        pendingWorkcellResizes.put(playerId, applying);
+        UIWindow window = windows.get(playerId);
+        if (window != null) {
+            renderWorkcellSettings(window, current.get(), withCapacity(workcell, applying.dimensions()));
+        }
+        if (!actions.updateWorkcellDimensions(player, workcellId, applying.dimensions())) {
+            pendingWorkcellResizes.replace(playerId, applying, pending);
+            refreshWorkcellSettings(player, requestId, workcellId);
+            return;
+        }
+        scheduleWorkcellResizeRefresh(player, applying, WORKCELL_RESIZE_REFRESH_ATTEMPTS);
+    }
+
+    private void scheduleWorkcellResizeRefresh(
+            Player player,
+            PendingWorkcellResize pending,
+            int attemptsRemaining
+    ) {
+        boolean scheduled = J.runEntity(
+                player,
+                () -> refreshAppliedWorkcellResize(player, pending, attemptsRemaining),
+                WORKCELL_RESIZE_REFRESH_TICKS);
+        if (!scheduled) {
+            pendingWorkcellResizes.remove(player.getUniqueId(), pending);
+        }
+    }
+
+    private void refreshAppliedWorkcellResize(
+            Player player,
+            PendingWorkcellResize pending,
+            int attemptsRemaining
+    ) {
+        UUID playerId = player.getUniqueId();
+        if (!pending.equals(pendingWorkcellResizes.get(playerId))) {
+            return;
+        }
+        Optional<JigsawStudioMenuState> current = matchingState(player, pending.requestId(), false);
+        JigsawStudioMenuState.Workcell workcell = current
+                .map(state -> state.workcell(pending.workcellId()))
+                .orElse(null);
+        if (workcell == null) {
+            pendingWorkcellResizes.remove(playerId, pending);
+            return;
+        }
+        if (workcell.capacity().equals(pending.dimensions())) {
+            pendingWorkcellResizes.remove(playerId, pending);
+            UIWindow window = windows.get(playerId);
+            if (window != null) {
+                renderWorkcellSettings(window, current.orElseThrow(), workcell);
+            }
+            return;
+        }
+        if (attemptsRemaining > 0) {
+            scheduleWorkcellResizeRefresh(player, pending, attemptsRemaining - 1);
+            return;
+        }
+        PendingWorkcellResize retry = new PendingWorkcellResize(
+                pending.requestId(),
+                pending.workcellId(),
+                pending.dimensions(),
+                false);
+        pendingWorkcellResizes.replace(playerId, pending, retry);
+        UIWindow window = windows.get(playerId);
+        if (window != null) {
+            renderWorkcellSettings(window, current.orElseThrow(), withCapacity(workcell, retry.dimensions()));
+        }
+        player.sendMessage(ChatColor.YELLOW
+                + "Cell resizing is still pending; use Apply Cell Size to retry after the current operation settles.");
+    }
+
+    private void discardWorkcellResize(Player player, UUID requestId, String workcellId) {
+        PendingWorkcellResize pending = pendingWorkcellResize(player.getUniqueId(), requestId, workcellId);
+        if (pending != null && !pending.applying()) {
+            pendingWorkcellResizes.remove(player.getUniqueId(), pending);
+        }
+        refreshWorkcellSettings(player, requestId, workcellId);
+    }
+
+    private void leaveWorkcellSettings(Player player, UUID requestId, String workcellId) {
+        PendingWorkcellResize pending = pendingWorkcellResize(player.getUniqueId(), requestId, workcellId);
+        if (pending != null && !pending.applying()) {
+            pendingWorkcellResizes.remove(player.getUniqueId(), pending);
+        }
+        refreshMain(player, requestId, workcellId, 0);
+    }
+
+    private void refreshWorkcellSettings(Player player, UUID requestId, String workcellId) {
+        Optional<JigsawStudioMenuState> current = matchingState(player, requestId, true);
+        UIWindow window = windows.get(player.getUniqueId());
+        JigsawStudioMenuState.Workcell workcell = current
+                .map(state -> state.workcell(workcellId))
+                .orElse(null);
+        if (window == null || workcell == null) {
+            return;
+        }
+        renderWorkcellSettings(window, current.orElseThrow(), workcell);
+    }
+
+    private PendingWorkcellResize pendingWorkcellResize(UUID playerId, UUID requestId, String workcellId) {
+        PendingWorkcellResize pending = pendingWorkcellResizes.get(playerId);
+        if (pending == null
+                || !pending.requestId().equals(requestId)
+                || !pending.workcellId().equals(workcellId)) {
+            return null;
+        }
+        return pending;
+    }
+
     private void resizeVariantAxis(
             Player player,
             UUID requestId,
@@ -2400,6 +2593,31 @@ public final class JigsawStudioMenuController {
         throw new IllegalStateException("Jigsaw Studio cannot allocate another numbered theme set");
     }
 
+    static String themeSelectionPercent(
+            List<JigsawStudioMenuState.ThemeSet> themeSets,
+            JigsawStudioMenuState.ThemeSet target
+    ) {
+        List<JigsawStudioMenuState.ThemeSet> activeThemeSets = Objects.requireNonNull(
+                themeSets,
+                "Jigsaw Studio theme sets");
+        JigsawStudioMenuState.ThemeSet activeTarget = Objects.requireNonNull(
+                target,
+                "Jigsaw Studio target theme set");
+        int totalWeight = 0;
+        for (JigsawStudioMenuState.ThemeSet themeSet : activeThemeSets) {
+            totalWeight = Math.addExact(totalWeight, Objects.requireNonNull(
+                    themeSet,
+                    "Jigsaw Studio theme set").weight());
+        }
+        if (totalWeight < 1) {
+            return "0.0%";
+        }
+        return String.format(
+                Locale.ROOT,
+                "%.1f%%",
+                activeTarget.weight() * 100.0D / totalWeight);
+    }
+
     static Optional<Integer> adjustedPositiveValue(int value, int delta) {
         if (value < 1 || delta == 0) {
             throw new IllegalArgumentException("Jigsaw Studio positive value adjustment is invalid");
@@ -2503,6 +2721,27 @@ public final class JigsawStudioMenuController {
         }
     }
 
+    static JigsawStudioMenuState.Workcell withCapacity(
+            JigsawStudioMenuState.Workcell workcell,
+            JigsawStudioCellDimensions capacity
+    ) {
+        JigsawStudioMenuState.Workcell source = Objects.requireNonNull(
+                workcell,
+                "Jigsaw Studio menu workcell");
+        return new JigsawStudioMenuState.Workcell(
+                source.stableId(),
+                source.canonicalName(),
+                source.displayName(),
+                Objects.requireNonNull(capacity, "Jigsaw Studio staged workcell capacity"),
+                source.enabled(),
+                source.activeVariantKey(),
+                source.dirty(),
+                source.saving(),
+                source.loading(),
+                source.connectorsVisible(),
+                source.variants());
+    }
+
     static List<ToolboxTool> toolboxTools(
             JigsawStudioMenuState state,
             JigsawStudioMenuState.Workcell workcell
@@ -3138,4 +3377,17 @@ public final class JigsawStudioMenuController {
 
     private record PendingProjectDelete(UUID requestId, long expiresAtNanos) {
     }
+
+    private record PendingWorkcellResize(
+            UUID requestId,
+            String workcellId,
+            JigsawStudioCellDimensions dimensions,
+            boolean applying
+    ) {
+        private PendingWorkcellResize {
+            requestId = Objects.requireNonNull(requestId, "Jigsaw Studio resize request ID");
+            workcellId = Objects.requireNonNull(workcellId, "Jigsaw Studio resize workcell ID");
+            dimensions = Objects.requireNonNull(dimensions, "Jigsaw Studio resize dimensions");
+        }
+    }
 }

core/src/main/java/art/arcane/iris/core/service/JigsawStudioService.java

@@ -67,6 +67,7 @@ import org.bukkit.Bukkit;
 import org.bukkit.ChatColor;
 import org.bukkit.Chunk;
 import org.bukkit.Color;
+import org.bukkit.GameRules;
 import org.bukkit.Location;
 import org.bukkit.Material;
 import org.bukkit.Particle;
@@ -100,6 +101,7 @@ import org.bukkit.event.block.BrewingStartEvent;
 import org.bukkit.event.block.CrafterCraftEvent;
 import org.bukkit.event.entity.EntityChangeBlockEvent;
 import org.bukkit.event.entity.EntityExplodeEvent;
+import org.bukkit.event.entity.CreatureSpawnEvent;
 import org.bukkit.event.inventory.BrewEvent;
 import org.bukkit.event.inventory.BrewingStandFuelEvent;
 import org.bukkit.event.inventory.FurnaceBurnEvent;
@@ -123,7 +125,6 @@ import org.bukkit.event.player.PlayerTeleportEvent;
 import org.bukkit.event.player.PlayerToggleSneakEvent;
 import org.bukkit.event.server.ServerCommandEvent;
 import org.bukkit.event.world.ChunkLoadEvent;
-import org.bukkit.event.world.ChunkUnloadEvent;
 import org.bukkit.event.world.StructureGrowEvent;
 import org.bukkit.event.world.WorldUnloadEvent;
 import org.bukkit.inventory.EquipmentSlot;
@@ -161,6 +162,7 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
     private static final List<Integer> AUTOSAVE_PERSISTENT_RETRY_DELAYS =
             List.of(40, 80, 160, 320, 600);
     private static final long PREVIEW_SEED = 1337L;
+    private static final int SPATIAL_PREVIEW_BASE_Y = JigsawStudioLayout.FLOOR_Y + 48;
     private static final JigsawStudioPieceRules DEFAULT_PIECE_RULES =
             new JigsawStudioPieceRules(0, 30, 0, 0, false);
     private static final long TOOL_CONFIRM_NANOS = 10_000_000_000L;
@@ -207,8 +209,6 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
     private final Map<UUID, JigsawStudioGraphEvaluation> evaluations = new ConcurrentHashMap<>();
     private final JigsawStudioTripleSneakTracker tripleSneakTracker = new JigsawStudioTripleSneakTracker();
     private final JigsawStudioToolCodec toolCodec = new JigsawStudioToolCodec();
-    private final JigsawStudioDisabledWorkcellRenderer disabledWorkcellRenderer =
-            new JigsawStudioDisabledWorkcellRenderer();
     private final JigsawStudioPreviewRenderer previewRenderer = new JigsawStudioPreviewRenderer();
     private final Object saveLifecycleLock = new Object();
     private final Set<UUID> savesInProgress = new HashSet<>();
@@ -258,7 +258,6 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         jigsawTileWatches.clear();
         toolConfirmations.clear();
         tripleSneakTracker.clearAll();
-        disabledWorkcellRenderer.removeAll();
         evaluations.clear();
         previewRenderer.removeAll();
         reopenRequiredRequests.clear();
@@ -329,16 +328,11 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
             unregisterRetries.remove(displacedRequestId);
             unregisterDrainWarnings.remove(displacedRequestId);
             tripleSneakTracker.clearRequest(displacedRequestId);
-            disabledWorkcellRenderer.removeRequest(displacedRequestId);
             evaluations.remove(displacedRequestId);
             previewRenderer.removeRequest(displacedRequestId);
         }
         IrisLogging.info("Jigsaw Studio authoring registered: world=%s structure=%s bays=%d",
                 world.getName(), activeGenerator.getSession().structureKey(), activeGenerator.getLayout().bays().size());
-        disabledWorkcellRenderer.reconcile(
-                world,
-                activeGenerator.getRequest().requestId(),
-                activeGenerator.getLayout());
         scheduleInitialEvaluation(next);
         scheduleOnlinePlayers(world.getUID());
     }
@@ -351,6 +345,7 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         if (studio == null || !requestId.equals(studio.generator().getRequest().requestId())) {
             return;
         }
+        disableNaturalStudioSpawning(world);
         scheduleInitialEvaluation(studio);
     }
 
@@ -429,7 +424,6 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         unregisterDrainWarnings.remove(request.requestId());
         toolConfirmations.entrySet().removeIf(entry -> entry.getValue().payload().requestId().equals(request.requestId()));
         tripleSneakTracker.clearRequest(request.requestId());
-        disabledWorkcellRenderer.removeRequest(request.requestId());
         evaluations.remove(request.requestId());
         previewRenderer.forgetRequest(request.requestId());
         JigsawStudioActivation.deactivate(request.packKey(), request.requestId());
@@ -1309,9 +1303,22 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                                 sourcePieceKey,
                                 pieceKey);
                     }
+                    JigsawStudioLayout updatedLayout = loadMappedLayout(studio);
+                    String targetWorkcellId = updatedLayout.workcellForVariant(pieceKey)
+                            .map(JigsawStudioBay::stableId)
+                            .orElseThrow(() -> new IOException(
+                                    "Created variant '" + pieceKey + "' has no Studio workcell"));
+                    if (updatedLayout.mode() == JigsawStudioMode.SPATIAL_JIGSAW) {
+                        return new CommandGraphMutationResult(
+                                updatedLayout,
+                                "",
+                                "",
+                                (duplicateActive ? "Duplicated" : "Created") + " variant '" + pieceKey
+                                        + "' in " + targetWorkcellId + ".");
+                    }
                     return new CommandGraphMutationResult(
-                            loadMappedLayout(studio),
-                            workcell.stableId(),
+                            updatedLayout,
+                            targetWorkcellId,
                             pieceKey,
                             (duplicateActive ? "Duplicated" : "Created") + " variant '" + pieceKey + "'.");
                 });
@@ -1548,11 +1555,15 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                         throw new IOException("Variant-family transaction failed with "
                                 + creation.writeResult().status());
                     }
+                    JigsawStudioLayout updatedLayout = loadMappedLayout(studio);
+                    Map<String, String> rebinds = updatedLayout.mode() == JigsawStudioMode.SPATIAL_JIGSAW
+                            ? Map.of()
+                            : creation.pieceKeysByWorkcell();
                     return new CommandGraphMutationResult(
-                            loadMappedLayout(studio),
+                            updatedLayout,
                             "",
                             "",
-                            creation.pieceKeysByWorkcell(),
+                            rebinds,
                             Optional.empty(),
                             "Duplicated every enabled workcell as coherent family '" + themeKey + "' with "
                                     + creation.pieceKeysByWorkcell().size() + " variant(s).");
@@ -2201,7 +2212,8 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         String activePieceKey = session.activeVariant(workcellId)
                 .map(JigsawStudioVariant::pieceKey)
                 .orElse("");
-        if (activePieceKey.equals(pieceKey)) {
+        if (session.layout().mode() == JigsawStudioMode.PLANAR_JIGSAW
+                && activePieceKey.equals(pieceKey)) {
             message(player, "Load another variant in this workcell before deleting '" + pieceKey + "'.");
             return false;
         }
@@ -2575,7 +2587,12 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                 IrisPosition origin = previewOrigin(studio.generator().getLayout(), structure);
                 StructureAssembler assembler = StructureAssembler.forCompilation(compilation, origin);
                 StructureAssemblyResult assembly = assembler.assemble(new RNG(PREVIEW_SEED));
-                computation = evaluationForAssembly(requestId, generation, compilation, assembly);
+                computation = evaluationForAssembly(
+                        requestId,
+                        generation,
+                        compilation,
+                        assembly,
+                        studio.generator().getLayout().mode());
             }
         } catch (Throwable exception) {
             IrisLogging.reportError(exception);
@@ -2588,7 +2605,8 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
             UUID requestId,
             long generation,
             StructureGraphCompilation compilation,
-            StructureAssemblyResult assembly
+            StructureAssemblyResult assembly,
+            JigsawStudioMode mode
     ) throws IOException {
         if (assembly.status().isFailure()) {
             return invalidEvaluation(
@@ -2611,7 +2629,7 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                             JigsawStudioPreviewRenderer.PreviewBounds.empty()),
                     JigsawStudioPreviewRenderer.PreviewPlan.empty());
         }
-        List<PlacedStructurePiece> aligned = alignPreviewPieces(assembly.pieces());
+        List<PlacedStructurePiece> aligned = alignPreviewPieces(assembly.pieces(), mode);
         JigsawStudioPreviewRenderer.PreviewPlan plan = JigsawStudioPreviewRenderer.plan(aligned);
         StructureGraphDiagnostic firstWarning = firstDiagnostic(
                 compilation,
@@ -2713,12 +2731,18 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                 Math.max(16, layout.extentZ() / 2));
     }
 
-    private static List<PlacedStructurePiece> alignPreviewPieces(List<PlacedStructurePiece> pieces) {
+    static List<PlacedStructurePiece> alignPreviewPieces(
+            List<PlacedStructurePiece> pieces,
+            JigsawStudioMode mode
+    ) {
         int minimumY = Integer.MAX_VALUE;
         for (PlacedStructurePiece piece : pieces) {
             minimumY = Math.min(minimumY, piece.getMinY());
         }
-        int shiftY = JigsawStudioLayout.FLOOR_Y + 1 - minimumY;
+        int baseY = mode == JigsawStudioMode.SPATIAL_JIGSAW
+                ? SPATIAL_PREVIEW_BASE_Y
+                : JigsawStudioLayout.FLOOR_Y + 1;
+        int shiftY = baseY - minimumY;
         List<PlacedStructurePiece> aligned = new ArrayList<>(pieces.size());
         for (PlacedStructurePiece piece : pieces) {
             aligned.add(new PlacedStructurePiece(
@@ -3534,7 +3558,6 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
             UUID requestId,
             CommandGraphMutationResult result
     ) {
-        disabledWorkcellRenderer.reconcile(studio.world(), requestId, result.layout());
         for (JigsawStudioBay workcell : result.layout().bays()) {
             refreshWorkcellContext(studio.worldId(), workcell.stableId());
         }
@@ -3801,28 +3824,6 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         ActiveStudio studio = studios.get(event.getWorld().getUID());
         if (studio != null) {
             markChunkAvailable(studio, event.getChunk().getX(), event.getChunk().getZ());
-            for (JigsawStudioBay bay : studio.generator().getLayout().bays()) {
-                if (!bay.enabled()
-                        && bay.bounds().originX() >> 4 == event.getChunk().getX()
-                        && bay.bounds().originZ() >> 4 == event.getChunk().getZ()) {
-                    disabledWorkcellRenderer.reconcile(
-                            studio.world(),
-                            studio.generator().getRequest().requestId(),
-                            studio.generator().getLayout());
-                    break;
-                }
-            }
-        }
-    }
-
-    @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
-    public void onChunkUnload(ChunkUnloadEvent event) {
-        ActiveStudio studio = studios.get(event.getWorld().getUID());
-        if (studio != null) {
-            disabledWorkcellRenderer.unloadChunk(
-                    studio.generator().getRequest().requestId(),
-                    event.getChunk().getX(),
-                    event.getChunk().getZ());
         }
     }
 
@@ -3922,6 +3923,14 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         reconcilePlayerContext(event.getPlayer(), event.getRespawnLocation());
     }
 
+    @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
+    public void onNaturalCreatureSpawn(CreatureSpawnEvent event) {
+        if (studios.containsKey(event.getLocation().getWorld().getUID())
+                && isNaturalStudioSpawn(event.getSpawnReason())) {
+            event.setCancelled(true);
+        }
+    }
+
     @EventHandler(priority = EventPriority.HIGHEST, ignoreCancelled = true)
     public void onUnauthorizedBlockPlace(BlockPlaceEvent event) {
         if (isUnauthorizedStudioEdit(event.getPlayer(), event.getBlockPlaced())) {
@@ -5947,6 +5956,11 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                     + " connector(s) from " + snapshots.size()
                     + " chunk(s); validating and writing the owned structure graph...");
             persistCapture(coordinator, capture, connectors);
+        } catch (WorkcellTopologyException exception) {
+            coordinator.failPersistent(
+                    "Jigsaw Studio cannot autosave this planar workcell: "
+                            + failureMessage(exception),
+                    null);
         } catch (Throwable exception) {
             coordinator.failPersistent(
                     "Jigsaw Studio capture assembly failed: " + failureMessage(exception),
@@ -6025,6 +6039,7 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
             String mutationNotice = unchanged ? "" : " Newer edits remain unsaved.";
             message(player, "Saved piece '" + coordinator.saveIdentity().variantKey() + "' and object '"
                     + assembly.objectKey() + "' atomically." + mutationNotice + cleanup);
+            playSaveSound(player);
             if (unchanged) {
                 scheduleEvaluation(studio);
             }
@@ -6518,21 +6533,29 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
                 case EAST_POSITIVE_X -> JigsawPlanarDirection.EAST.bit();
                 case SOUTH_POSITIVE_Z -> JigsawPlanarDirection.SOUTH.bit();
                 case WEST_NEGATIVE_X -> JigsawPlanarDirection.WEST.bit();
-                case UP_POSITIVE_Y, DOWN_NEGATIVE_Y -> throw new IOException(
-                        "Planar workcells cannot save vertical connectors");
+                case UP_POSITIVE_Y, DOWN_NEGATIVE_Y -> throw new WorkcellTopologyException(
+                        "Planar workcell '" + workcell.stableId()
+                                + "' cannot save a vertical connector. Remove it or use Reset Connector Blocks.");
             };
         }
         JigsawPlanarTopology sourceTopology = JigsawPlanarTopology.fromMask(mask);
         JigsawPlanarTopology displayedTopology = sourceTopology.rotateClockwise(displayRotationQuarterTurns);
         if (displayedTopology != expected.canonicalTopology()) {
-            throw new IOException("Workcell '" + workcell.stableId() + "' requires "
-                    + expected.canonicalTopology().name().toLowerCase(Locale.ROOT)
-                    + " connector orientation, but the edited markers form "
-                    + displayedTopology.name().toLowerCase(Locale.ROOT)
-                    + ". Keep the workcell's red floor glyph orientation; Iris rotates the saved variant automatically.");
+            throw new WorkcellTopologyException("Workcell '" + workcell.stableId() + "' requires "
+                    + topologyDescription(expected.canonicalTopology())
+                    + ", but the edited markers form "
+                    + topologyDescription(displayedTopology)
+                    + ". Use Reset Connector Blocks to restore the saved topology, or edit the markers to match the floor glyph.");
         }
     }
 
+    private static String topologyDescription(JigsawPlanarTopology topology) {
+        int connectorCount = topology.directions().size();
+        return topology.name().toLowerCase(Locale.ROOT).replace('_', ' ')
+                + " (" + connectorCount + " horizontal connector"
+                + (connectorCount == 1 ? "" : "s") + ")";
+    }
+
     static void storeConnectorFinalState(
             IrisObject object,
             int x,
@@ -7039,10 +7062,6 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
     private void reloadSessionLayout(ActiveStudio studio) throws IOException {
         JigsawStudioLayout layout = loadMappedLayout(studio);
         studio.generator().getSession().replaceLayout(layout);
-        disabledWorkcellRenderer.reconcile(
-                studio.world(),
-                studio.generator().getRequest().requestId(),
-                layout);
         for (JigsawStudioBay workcell : layout.bays()) {
             studio.generator().invalidateRender(workcell.stableId());
         }
@@ -7080,7 +7099,8 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         JigsawStudioSession session = studio.generator().getSession();
         JigsawStudioBay workcell = session.layout().findAt(
                 target.getBlockX(), target.getBlockY(), target.getBlockZ());
-        selectEnteredWorkcell(session, workcell, ownerMatches(player, studio));
+        boolean owner = ownerMatches(player, studio);
+        selectEnteredWorkcell(session, workcell, owner);
         String workcellId = workcell == null ? "" : workcell.stableId();
         playerWorkcells.put(player.getUniqueId(), new PlayerWorkcellContext(
                 studio.worldId(),
@@ -7115,6 +7135,14 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         return owner && workcell != null && session.selectBay(workcell.stableId());
     }
 
+    static boolean isNaturalStudioSpawn(CreatureSpawnEvent.SpawnReason reason) {
+        return reason == CreatureSpawnEvent.SpawnReason.NATURAL;
+    }
+
+    static void disableNaturalStudioSpawning(World world) {
+        Objects.requireNonNull(world, "world").setGameRule(GameRules.SPAWN_MOBS, false);
+    }
+
     public void refreshWorkcellContext(UUID worldId, String workcellId) {
         if (worldId == null || workcellId == null) {
             return;
@@ -7708,9 +7736,7 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
             if (!variant.pieceKey().equalsIgnoreCase(key)) {
                 continue;
             }
-            return variant.archetype()
-                    .map(archetype -> layout.get(archetype.stableId()))
-                    .orElse(layout.get(JigsawStudioLayout.SPATIAL_WORKCELL_ID));
+            return layout.workcellForVariant(variant.pieceKey()).orElse(null);
         }
         return null;
     }
@@ -7738,6 +7764,16 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         }
     }
 
+    static void playSaveSound(Player player) {
+        if (player != null) {
+            J.runEntity(player, () -> player.playSound(
+                    player.getLocation(),
+                    "minecraft:block.note_block.bell",
+                    0.65F,
+                    1.65F));
+        }
+    }
+
     private static void report(Player player, boolean enabled, String text) {
         if (enabled) {
             message(player, text);
@@ -8722,6 +8758,12 @@ public final class JigsawStudioService implements IrisService, JigsawStudioMenuC
         }
     }
 
+    static final class WorkcellTopologyException extends IOException {
+        WorkcellTopologyException(String message) {
+            super(message);
+        }
+    }
+
     private static final class ParticleBudget {
         private int remaining;
 

core/src/main/java/art/arcane/iris/core/service/StudioSVC.java

@@ -22,6 +22,7 @@ import com.google.gson.JsonSyntaxException;
 import art.arcane.iris.spi.IrisLogging;
 import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.core.IrisSettings;
+import art.arcane.iris.core.IrisStartupValidation;
 import art.arcane.iris.core.IrisWorldStorage;
 import art.arcane.iris.core.ServerConfigurator;
 import art.arcane.iris.core.DatapackInstallResult;
@@ -33,6 +34,7 @@ import art.arcane.iris.core.pack.PackDirectoryResolver;
 import art.arcane.iris.core.pack.PackDownloader;
 import art.arcane.iris.core.pack.PackValidationRegistry;
 import art.arcane.iris.core.pack.PackValidationResult;
+import art.arcane.iris.core.pack.PackValidator;
 import art.arcane.iris.core.project.IrisProject;
 import art.arcane.iris.core.project.IrisPackageCompiler;
 import art.arcane.iris.core.project.IrisCodeWorkspace;
@@ -69,6 +71,7 @@ import java.nio.file.StandardCopyOption;
 import java.util.Comparator;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Locale;
 import java.util.Objects;
 import java.util.UUID;
@@ -471,12 +474,24 @@ public class StudioSVC implements IrisService {
     }
 
     private static boolean blockIfPackBroken(VolmitSender sender, String dimm) {
-        PackValidationResult validation = PackValidationRegistry.get(dimm);
-        if (validation == null || validation.isLoadable()) {
+        Optional<String> startupDenial = IrisStartupValidation.denialReason();
+        if (startupDenial.isPresent()) {
+            sender.sendMessage(startupDenial.get());
+            return true;
+        }
+        IrisDimension dimension = IrisToolbelt.getDimension(dimm);
+        String packName = dimension == null || dimension.getLoader() == null
+                ? dimm
+                : dimension.getLoader().getDataFolder().getName();
+        PackValidationResult validation = PackValidationRegistry.get(packName);
+        if (validation != null && validation.isLoadable()) {
             return false;
         }
         sender.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.STUDIO_S_V_C_CANNOT_OPEN_STUDIO_PACK_HAS_BLOCKING_ERRORS, MessageArgument.untrusted("dimm", String.valueOf(dimm))));
-        for (String reason : validation.getBlockingErrors()) {
+        List<String> failures = validation == null
+                ? List.of("Required pack validation has not completed. Studio creation fails closed until validation succeeds.")
+                : validation.getBlockingErrors();
+        for (String reason : failures) {
             sender.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.STUDIO_S_V_C_MESSAGE, MessageArgument.untrusted("reason", String.valueOf(reason))));
         }
         sender.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.STUDIO_S_V_C_FIX_PACK_RUN_IRIS_PACK_VALIDATE_REVALIDATE, MessageArgument.untrusted("dimm", String.valueOf(dimm))));
@@ -829,6 +844,11 @@ public class StudioSVC implements IrisService {
     }
 
     private void createProject(VolmitSender sender, String requestedName, String requestedTemplate, File selectedTemplatePack) {
+        Optional<String> startupDenial = IrisStartupValidation.denialReason();
+        if (startupDenial.isPresent()) {
+            sender.sendMessage("Studio project creation refused: " + startupDenial.get());
+            return;
+        }
         String normalizedName;
         String templateName;
         File workspace;
@@ -881,12 +901,24 @@ public class StudioSVC implements IrisService {
                     sender.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.STUDIO_S_V_C_MISSING_IMPORTED_DIMENSION_FILE));
                     return;
                 }
+                PackValidationRegistry.requireLoadable(importPack.getName());
 
                 sender.sendMessage(IrisLanguage.text(BukkitRuntimeMessages.STUDIO_S_V_C_IMPORTING_INTO_NEW_PROJECT, MessageArgument.untrusted("downloadable", String.valueOf(templateName)), MessageArgument.untrusted("s", String.valueOf(projectName))));
                 createFrom(importPack, templateName, projectName);
             }
             projectPublished = true;
 
+            PackValidationResult createdValidation = PackValidator.validate(newPack);
+            PackValidationRegistry.publish(createdValidation);
+            if (!createdValidation.isLoadable()) {
+                rollbackCreatedProject(sender, newPack,
+                        "Studio project validation failed; the new project was rolled back.");
+                for (String reason : createdValidation.getBlockingErrors()) {
+                    sender.sendMessage(reason);
+                }
+                return;
+            }
+
             DatapackInstallResult installResult = ServerConfigurator.installDataPacksIfChanged(true);
             CreationOutcome installOutcome = switch (installResult.status()) {
                 case FAILED -> CreationOutcome.FAILED;

core/src/main/java/art/arcane/iris/core/tools/IrisCreator.java

@@ -26,6 +26,7 @@ import art.arcane.iris.spi.IrisServices;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
 import art.arcane.iris.core.link.MultiverseCoreLink;
 import art.arcane.iris.core.IrisRuntimeSchedulerMode;
+import art.arcane.iris.core.IrisStartupValidation;
 import art.arcane.iris.core.DatapackInstallResult;
 import art.arcane.iris.core.IrisWorldStorage;
 import art.arcane.iris.core.IrisWorlds;
@@ -41,6 +42,7 @@ import art.arcane.iris.core.localization.RuntimeProgressMessages;
 import art.arcane.iris.core.nms.INMS;
 import art.arcane.iris.core.pregenerator.PregenTask;
 import art.arcane.iris.core.pack.AtomicDirectoryPublisher;
+import art.arcane.iris.core.pack.PackValidationRegistry;
 import art.arcane.iris.core.runtime.WorldDeletionQueue;
 import art.arcane.iris.core.service.StudioSVC;
 import art.arcane.iris.engine.object.IrisDimension;
@@ -172,6 +174,9 @@ public class IrisCreator {
             if (resolvedDimension == null) {
                 throw new IrisException("Dimension cannot be found for id " + dimension());
             }
+            IrisStartupValidation.requireWorldCreationReady();
+            PackValidationRegistry.requireLoadable(
+                    resolvedDimension.getLoader().getDataFolder().getName());
             worldLease = coordinator.acquire(
                     LifecycleOperationCoordinator.Domain.WORLD_MUTATION,
                     LifecycleOperationCoordinator.OperationKind.WORLD_CREATE,

core/src/main/java/art/arcane/iris/engine/platform/studio/generators/JigsawStudioGenerator.java

@@ -73,7 +73,7 @@ public final class JigsawStudioGenerator extends EnginedStudioGenerator {
                 session,
                 B.getState("minecraft:smooth_stone"),
                 B.getState("minecraft:polished_deepslate"),
-                B.getState("minecraft:smooth_quartz"),
+                B.getState("minecraft:white_concrete"),
                 B.getState("minecraft:light_gray_wool"),
                 B.getState("minecraft:red_wool"),
                 B.getState("minecraft:sea_lantern"),
@@ -289,41 +289,56 @@ public final class JigsawStudioGenerator extends EnginedStudioGenerator {
             int chunkWorldZ
     ) {
         JigsawStudioBounds bounds = workcell.bounds();
-        int minX = bounds.originX() - 1;
-        int maxX = bounds.maxX() + 1;
-        int minZ = bounds.originZ() - 1;
-        int maxZ = bounds.maxZ() + 1;
+        int minimumX = bounds.originX() - 1;
+        int maximumX = bounds.maxX() + 1;
+        int minimumZ = bounds.originZ() - 1;
+        int maximumZ = bounds.maxZ() + 1;
         int bottomY = bounds.originY();
         int topY = bounds.maxY() + 1;
 
-        paintRectangle(terrainChunk, minX, maxX, bottomY, minZ, maxZ, frame, chunkWorldX, chunkWorldZ);
-        paintRectangle(terrainChunk, minX, maxX, topY, minZ, maxZ, frame, chunkWorldX, chunkWorldZ);
+        paintRectangle(
+                terrainChunk,
+                minimumX,
+                maximumX,
+                bottomY,
+                minimumZ,
+                maximumZ,
+                chunkWorldX,
+                chunkWorldZ);
+        paintRectangle(
+                terrainChunk,
+                minimumX,
+                maximumX,
+                topY,
+                minimumZ,
+                maximumZ,
+                chunkWorldX,
+                chunkWorldZ);
         for (int y = bottomY + 1; y < topY; y++) {
-            setWorldBlock(terrainChunk, minX, y, minZ, frame, chunkWorldX, chunkWorldZ);
-            setWorldBlock(terrainChunk, maxX, y, minZ, frame, chunkWorldX, chunkWorldZ);
-            setWorldBlock(terrainChunk, minX, y, maxZ, frame, chunkWorldX, chunkWorldZ);
-            setWorldBlock(terrainChunk, maxX, y, maxZ, frame, chunkWorldX, chunkWorldZ);
+            setWorldBlock(terrainChunk, minimumX, y, minimumZ, frame, chunkWorldX, chunkWorldZ);
+            setWorldBlock(terrainChunk, maximumX, y, minimumZ, frame, chunkWorldX, chunkWorldZ);
+            setWorldBlock(terrainChunk, minimumX, y, maximumZ, frame, chunkWorldX, chunkWorldZ);
+            setWorldBlock(terrainChunk, maximumX, y, maximumZ, frame, chunkWorldX, chunkWorldZ);
         }
     }
 
     private void paintRectangle(
             TerrainChunk terrainChunk,
-            int minX,
-            int maxX,
+            int minimumX,
+            int maximumX,
             int y,
-            int minZ,
-            int maxZ,
-            PlatformBlockState block,
+            int minimumZ,
+            int maximumZ,
             int chunkWorldX,
             int chunkWorldZ
     ) {
-        for (int x = minX; x <= maxX; x++) {
-            setWorldBlock(terrainChunk, x, y, minZ, block, chunkWorldX, chunkWorldZ);
-            setWorldBlock(terrainChunk, x, y, maxZ, block, chunkWorldX, chunkWorldZ);
+        for (int x = minimumX; x <= maximumX; x++) {
+            setWorldBlock(terrainChunk, x, y, minimumZ, frame, chunkWorldX, chunkWorldZ);
+            setWorldBlock(terrainChunk, x, y, maximumZ, frame, chunkWorldX, chunkWorldZ);
         }
-        for (int z = minZ + 1; z < maxZ; z++) {
-            setWorldBlock(terrainChunk, minX, y, z, block, chunkWorldX, chunkWorldZ);
-            setWorldBlock(terrainChunk, maxX, y, z, block, chunkWorldX, chunkWorldZ);
+        for (int z = minimumZ + 1; z < maximumZ; z++) {
+            setWorldBlock(terrainChunk, minimumX, y, z, frame, chunkWorldX, chunkWorldZ);
+            setWorldBlock(terrainChunk, maximumX, y, z, frame, chunkWorldX, chunkWorldZ);
         }
     }
 

core/src/test/java/art/arcane/iris/core/IrisStartupValidationTest.java

@@ -0,0 +1,97 @@
+package art.arcane.iris.core;
+
+import org.junit.After;
+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;
+import static org.junit.Assert.fail;
+
+public class IrisStartupValidationTest {
+    @After
+    public void disableValidation() {
+        IrisStartupValidation.disable();
+    }
+
+    @Test
+    public void disabledValidationAllowsCreation() {
+        IrisStartupValidation.disable();
+
+        assertTrue(IrisStartupValidation.isReady());
+        assertTrue(IrisStartupValidation.denialReason().isEmpty());
+        IrisStartupValidation.requireWorldCreationReady();
+    }
+
+    @Test
+    public void pendingValidationDeniesCreation() {
+        IrisStartupValidation.begin();
+
+        assertFalse(IrisStartupValidation.isReady());
+        assertTrue(IrisStartupValidation.denialReason().orElseThrow().contains("external datapacks"));
+        try {
+            IrisStartupValidation.requireWorldCreationReady();
+            fail("Expected pending startup validation to lock world creation");
+        } catch (IllegalStateException expected) {
+            assertTrue(expected.getMessage().contains("world creation is locked"));
+        }
+    }
+
+    @Test
+    public void bothValidationPhasesMustComplete() {
+        IrisStartupValidation.begin();
+        IrisStartupValidation.markDatapacksReady();
+
+        assertFalse(IrisStartupValidation.isReady());
+        assertTrue(IrisStartupValidation.denialReason().orElseThrow().contains("dimension packs"));
+
+        IrisStartupValidation.markPacksReady();
+
+        assertTrue(IrisStartupValidation.isReady());
+        assertTrue(IrisStartupValidation.denialReason().isEmpty());
+    }
+
+    @Test
+    public void invalidDatapacksExposeTheFailure() {
+        IrisStartupValidation.begin();
+        IrisStartupValidation.markDatapacksInvalid("broken managed datapack");
+        IrisStartupValidation.markPacksReady();
+
+        assertEquals("broken managed datapack", IrisStartupValidation.denialReason().orElseThrow());
+    }
+
+    @Test
+    public void restartRequirementCannotBeDowngradedToReady() {
+        IrisStartupValidation.begin();
+        IrisStartupValidation.requireRestart("restart required for registry load");
+        IrisStartupValidation.markDatapacksReady();
+        IrisStartupValidation.markPacksReady();
+
+        assertFalse(IrisStartupValidation.isReady());
+        assertEquals("restart required for registry load", IrisStartupValidation.denialReason().orElseThrow());
+    }
+
+    @Test
+    public void repeatedValidationCannotClearRestartRequirement() {
+        IrisStartupValidation.begin();
+        IrisStartupValidation.requireRestart("restart boundary");
+
+        IrisStartupValidation.beginDatapackValidation();
+        IrisStartupValidation.markDatapacksReady();
+        IrisStartupValidation.markPacksReady();
+
+        assertFalse(IrisStartupValidation.isReady());
+        assertEquals("restart boundary", IrisStartupValidation.denialReason().orElseThrow());
+    }
+
+    @Test
+    public void packValidationInfrastructureFailureDeniesCreation() {
+        IrisStartupValidation.begin();
+        IrisStartupValidation.markDatapacksReady();
+        IrisStartupValidation.markPacksInvalid(List.of("pack registry unavailable"));
+
+        assertEquals("pack registry unavailable", IrisStartupValidation.denialReason().orElseThrow());
+    }
+}

core/src/test/java/art/arcane/iris/core/datapack/DatapackIngestServiceTest.java

@@ -29,9 +29,11 @@ import java.net.StandardProtocolFamily;
 import java.net.UnixDomainSocketAddress;
 import java.nio.channels.ServerSocketChannel;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.FileStore;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.attribute.FileTime;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
@@ -75,6 +77,174 @@ public class DatapackIngestServiceTest {
         assertEquals("1.21.4", DatapackIngestService.serverMcVersion(server));
     }
 
+    @Test
+    public void windowsLongPathAliasAcceptsTheSameVolumeSerialAndRoot() throws Exception {
+        FileStore shortPathStore = mock(FileStore.class);
+        FileStore longPathStore = mock(FileStore.class);
+        when(shortPathStore.getAttribute("volume:vsn")).thenReturn(41234L);
+        when(longPathStore.getAttribute("volume:vsn")).thenReturn(41234L);
+
+        assertTrue(DatapackIngestService.sameWindowsVolume(
+                shortPathStore, "C:\\", longPathStore, "c:\\"));
+    }
+
+    @Test
+    public void windowsLongPathAliasRejectsDifferentRootsAndVolumeSerials() throws Exception {
+        FileStore firstStore = mock(FileStore.class);
+        FileStore secondStore = mock(FileStore.class);
+        when(firstStore.getAttribute("volume:vsn")).thenReturn(1L);
+        when(secondStore.getAttribute("volume:vsn")).thenReturn(2L);
+
+        assertFalse(DatapackIngestService.sameWindowsVolume(
+                firstStore, "C:\\", secondStore, "C:\\"));
+
+        when(secondStore.getAttribute("volume:vsn")).thenReturn(1L);
+        assertFalse(DatapackIngestService.sameWindowsVolume(
+                firstStore, "C:\\", secondStore, "D:\\"));
+    }
+
+    @Test
+    public void scratchDirectoryRejectsJunctionLikeOtherAttributes() {
+        BasicFileAttributes attributes = mock(BasicFileAttributes.class);
+        when(attributes.isDirectory()).thenReturn(true);
+        when(attributes.isOther()).thenReturn(true);
+
+        assertFalse(DatapackIngestService.isSupportedScratchDirectory(attributes));
+
+        when(attributes.isOther()).thenReturn(false);
+        assertTrue(DatapackIngestService.isSupportedScratchDirectory(attributes));
+    }
+
+    @Test
+    public void startupValidationCacheRequiresEveryInputAndLocalFingerprint() {
+        DatapackIngestService.StartupValidationCache cache = new DatapackIngestService.StartupValidationCache();
+        cache.schemaVersion = 1;
+        cache.minecraftVersion = "26.2";
+        cache.irisVersion = 4000;
+        cache.autoIngest = true;
+        cache.stripOverrides = false;
+        cache.urls = List.of("https://modrinth.com/datapack/example");
+        cache.localFingerprint = "fingerprint";
+
+        assertTrue(DatapackIngestService.startupValidationCacheMatches(
+                cache,
+                "26.2",
+                4000,
+                true,
+                false,
+                List.of("https://modrinth.com/datapack/example"),
+                "fingerprint"));
+        assertFalse(DatapackIngestService.startupValidationCacheMatches(
+                cache,
+                "26.3",
+                4000,
+                true,
+                false,
+                cache.urls,
+                "fingerprint"));
+        assertFalse(DatapackIngestService.startupValidationCacheMatches(
+                cache,
+                "26.2",
+                4000,
+                true,
+                true,
+                cache.urls,
+                "fingerprint"));
+        assertFalse(DatapackIngestService.startupValidationCacheMatches(
+                cache,
+                "26.2",
+                4000,
+                true,
+                false,
+                List.of("https://modrinth.com/datapack/changed"),
+                "fingerprint"));
+        assertFalse(DatapackIngestService.startupValidationCacheMatches(
+                cache,
+                "26.2",
+                4000,
+                true,
+                false,
+                cache.urls,
+                "changed"));
+    }
+
+    @Test
+    public void startupValidationFingerprintChangesWithStagedContent() throws Exception {
+        File root = temporaryFolder.newFolder("startup-validation-fingerprint");
+        File staged = new File(root, "staging/managed");
+        assertTrue(staged.mkdirs());
+        Path content = new File(staged, "value.txt").toPath();
+        Files.writeString(content, "alpha", StandardCharsets.UTF_8);
+        KList<File> worldFolders = new KList<>();
+        String before = DatapackIngestService.startupValidationFingerprint(root, worldFolders);
+
+        Files.writeString(content, "bravo", StandardCharsets.UTF_8);
+        String after = DatapackIngestService.startupValidationFingerprint(root, worldFolders);
+
+        assertFalse(before.equals(after));
+    }
+
+    @Test
+    public void authorizedStartupMaintenanceRefreshesOnlyTheLocalFingerprint() throws Exception {
+        File root = temporaryFolder.newFolder("startup-validation-maintenance");
+        File staging = new File(root, "staging/managed");
+        assertTrue(staging.mkdirs());
+        Path content = new File(staging, "value.txt").toPath();
+        Files.writeString(content, "before", StandardCharsets.UTF_8);
+        KList<File> worldFolders = new KList<>();
+
+        DatapackIngestService.StartupValidationCache validated = new DatapackIngestService.StartupValidationCache();
+        validated.schemaVersion = 1;
+        validated.minecraftVersion = "26.2";
+        validated.irisVersion = 4000;
+        validated.autoIngest = true;
+        validated.stripOverrides = false;
+        validated.urls = List.of("https://modrinth.com/datapack/example");
+        validated.localFingerprint = DatapackIngestService.startupValidationFingerprint(root, worldFolders);
+
+        Files.writeString(content, "after", StandardCharsets.UTF_8);
+        assertFalse(DatapackIngestService.startupValidationCacheMatches(
+                validated,
+                "26.2",
+                4000,
+                true,
+                false,
+                validated.urls,
+                DatapackIngestService.startupValidationFingerprint(root, worldFolders)));
+
+        DatapackIngestService.StartupValidationCache refreshed =
+                DatapackIngestService.refreshStartupValidationCache(validated, root, worldFolders);
+
+        assertTrue(DatapackIngestService.startupValidationCacheMatches(
+                refreshed,
+                "26.2",
+                4000,
+                true,
+                false,
+                validated.urls,
+                DatapackIngestService.startupValidationFingerprint(root, worldFolders)));
+        assertEquals(validated.urls, refreshed.urls);
+    }
+
+    @Test
+    public void startupMaintenanceDoesNotAuthorizeChangedValidationInputs() {
+        DatapackIngestService.StartupValidationCache validated = new DatapackIngestService.StartupValidationCache();
+        validated.schemaVersion = 1;
+        validated.minecraftVersion = "26.2";
+        validated.irisVersion = 4000;
+        validated.autoIngest = true;
+        validated.stripOverrides = false;
+        validated.urls = List.of("https://modrinth.com/datapack/example");
+
+        assertTrue(DatapackIngestService.startupValidationContextMatches(
+                validated, "26.2", 4000, true, false, validated.urls));
+        assertFalse(DatapackIngestService.startupValidationContextMatches(
+                validated, "26.2", 4000, true, false,
+                List.of("https://modrinth.com/datapack/changed")));
+        assertFalse(DatapackIngestService.startupValidationContextMatches(
+                validated, "26.2", 4000, true, true, validated.urls));
+    }
+
     @Test
     public void packMetadataMustContainAValidPackContract() throws Exception {
         File valid = temporaryFolder.newFolder("valid");
@@ -1974,6 +2144,38 @@ public class DatapackIngestServiceTest {
         assertFalse(scratch.exists());
     }
 
+    @Test
+    public void installScratchDeletionRetriesATransientDirectoryFailure() throws Exception {
+        File root = temporaryFolder.newFolder("transient-install-scratch-delete-root");
+        DeleteAttemptFile scratch = new DeleteAttemptFile(
+                new File(root, "managed-" + UUID.randomUUID()).getPath(), 2);
+        assertTrue(scratch.mkdir());
+        Files.writeString(new File(scratch, ".DS_Store").toPath(), "finder", StandardCharsets.UTF_8);
+
+        DatapackIngestService.deleteInstallScratch(scratch, "test datapack install scratch");
+
+        assertFalse(scratch.exists());
+        assertEquals(2, scratch.deleteAttempts());
+    }
+
+    @Test
+    public void installScratchDeletionStillFailsAfterBoundedRetries() throws Exception {
+        File root = temporaryFolder.newFolder("persistent-install-scratch-delete-root");
+        DeleteAttemptFile scratch = new DeleteAttemptFile(
+                new File(root, "managed-" + UUID.randomUUID()).getPath(), Integer.MAX_VALUE);
+        assertTrue(scratch.mkdir());
+
+        try {
+            DatapackIngestService.deleteInstallScratch(scratch, "test datapack install scratch");
+            fail("Expected persistent scratch deletion failure");
+        } catch (IOException expected) {
+            assertTrue(expected.getMessage().contains("Could not remove test datapack install scratch"));
+        }
+
+        assertTrue(scratch.exists());
+        assertEquals(3, scratch.deleteAttempts());
+    }
+
     @Test
     public void recoveryRejectsFinderMetadataDirectoryInInstallScratch() throws Exception {
         File root = temporaryFolder.newFolder("orphan-install-finder-directory-root");
@@ -3173,4 +3375,26 @@ public class DatapackIngestServiceTest {
             DatapackIngestService.VerifiedStagingInstall authorization
     ) {
     }
+
+    private static final class DeleteAttemptFile extends File {
+        private static final long serialVersionUID = 1L;
+
+        private final int successfulAttempt;
+        private int deleteAttempts;
+
+        private DeleteAttemptFile(String pathname, int successfulAttempt) {
+            super(pathname);
+            this.successfulAttempt = successfulAttempt;
+        }
+
+        @Override
+        public boolean delete() {
+            deleteAttempts++;
+            return deleteAttempts >= successfulAttempt && super.delete();
+        }
+
+        private int deleteAttempts() {
+            return deleteAttempts;
+        }
+    }
 }

core/src/test/java/art/arcane/iris/core/lifecycle/WorldLifecycleSelectionTest.java

@@ -1,12 +1,24 @@
 package art.arcane.iris.core.lifecycle;
 
+import art.arcane.iris.core.IrisStartupValidation;
 import org.bukkit.NamespacedKey;
 import org.bukkit.World;
+import org.junit.After;
 import org.junit.Test;
 
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.atomic.AtomicInteger;
+
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
 
 public class WorldLifecycleSelectionTest {
+    @After
+    public void disableStartupValidation() {
+        IrisStartupValidation.disable();
+    }
+
     @Test
     public void studioSelectsPaperLikeBackendOnPaper() {
         WorldLifecycleService service = new WorldLifecycleService(CapabilitySnapshot.forTesting(ServerFamily.PAPER, false, false, true));
@@ -86,4 +98,67 @@ public class WorldLifecycleSelectionTest {
         service.rememberBackend(NamespacedKey.minecraft("studio"), "paper_like_runtime");
         assertEquals("paper_like_runtime", service.selectUnloadBackend("minecraft:studio").backendName());
     }
+
+    @Test
+    public void pendingStartupValidationStopsCreateBeforeBackendSelection() {
+        CountingBackend selected = new CountingBackend("selected", true);
+        CountingBackend inactive = new CountingBackend("inactive", false);
+        WorldLifecycleService service = new WorldLifecycleService(
+                CapabilitySnapshot.forTesting(ServerFamily.PAPER, false, false, true),
+                selected,
+                inactive,
+                inactive);
+        WorldLifecycleRequest request = new WorldLifecycleRequest(
+                "blocked",
+                NamespacedKey.minecraft("blocked"),
+                World.Environment.NORMAL,
+                null,
+                null,
+                null,
+                true,
+                false,
+                1337L,
+                false,
+                false,
+                WorldLifecycleCaller.CREATE);
+        IrisStartupValidation.begin();
+
+        CompletionException failure = assertThrows(CompletionException.class, () -> service.create(request).join());
+
+        assertEquals(IllegalStateException.class, failure.getCause().getClass());
+        assertEquals(0, selected.createCount.get());
+    }
+
+    private static final class CountingBackend implements WorldLifecycleBackend {
+        private final String name;
+        private final boolean supported;
+        private final AtomicInteger createCount;
+
+        private CountingBackend(String name, boolean supported) {
+            this.name = name;
+            this.supported = supported;
+            this.createCount = new AtomicInteger();
+        }
+
+        @Override
+        public boolean supports(WorldLifecycleRequest request, CapabilitySnapshot capabilities) {
+            return supported;
+        }
+
+        @Override
+        public CompletableFuture<World> create(WorldLifecycleRequest request) {
+            createCount.incrementAndGet();
+            return CompletableFuture.completedFuture(null);
+        }
+
+        @Override
+        public CompletableFuture<Boolean> unloadAsync(World world, boolean save) {
+            return CompletableFuture.completedFuture(false);
+        }
+
+        @Override
+        public String backendName() {
+            return name;
+        }
+    }
 }

core/src/test/java/art/arcane/iris/core/pack/PackValidationCacheTest.java

@@ -0,0 +1,146 @@
+package art.arcane.iris.core.pack;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.Assume;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
+import java.util.List;
+import java.util.Optional;
+
+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.Assert.fail;
+
+public class PackValidationCacheTest {
+    @Rule
+    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+    @Test
+    public void cacheRoundTripsSuccessfulAndFailedResultsInStableOrder() throws Exception {
+        Path cache = new File(temporaryFolder.newFolder("round-trip"), "validation.json").toPath();
+        PackValidationResult valid = new PackValidationResult(
+                "z-valid", List.of(), List.of("warning"), 20L);
+        PackValidationResult invalid = new PackValidationResult(
+                "a-invalid", List.of("broken reference"), List.of(), 10L);
+
+        PackValidationCache.save(cache, "content", "context", List.of(valid, invalid));
+        List<PackValidationResult> loaded = PackValidationCache.load(
+                cache,
+                "content",
+                "context",
+                List.of("z-valid", "a-invalid")).orElseThrow();
+
+        assertEquals(List.of("a-invalid", "z-valid"), loaded.stream()
+                .map(PackValidationResult::getPackName)
+                .toList());
+        assertFalse(loaded.getFirst().isLoadable());
+        assertEquals(List.of("broken reference"), loaded.getFirst().getBlockingErrors());
+        assertTrue(loaded.getLast().isLoadable());
+        assertEquals(List.of("warning"), loaded.getLast().getWarnings());
+    }
+
+    @Test
+    public void cacheRejectsContentContextAndPackSetChanges() throws Exception {
+        Path cache = new File(temporaryFolder.newFolder("mismatch"), "validation.json").toPath();
+        PackValidationCache.save(cache, "content", "context", List.of(
+                new PackValidationResult("overworld", List.of(), List.of(), 1L)));
+
+        assertTrue(PackValidationCache.load(
+                cache, "changed", "context", List.of("overworld")).isEmpty());
+        assertTrue(PackValidationCache.load(
+                cache, "content", "changed", List.of("overworld")).isEmpty());
+        assertTrue(PackValidationCache.load(
+                cache, "content", "context", List.of("other")).isEmpty());
+    }
+
+    @Test
+    public void corruptCacheIsIgnored() throws Exception {
+        Path cache = new File(temporaryFolder.newFolder("corrupt"), "validation.json").toPath();
+        Files.writeString(cache, "not-json", StandardCharsets.UTF_8);
+
+        Optional<List<PackValidationResult>> loaded = PackValidationCache.load(
+                cache, "content", "context", List.of());
+
+        assertTrue(loaded.isEmpty());
+    }
+
+    @Test
+    public void duplicateResultsAreRejected() throws Exception {
+        Path cache = new File(temporaryFolder.newFolder("duplicate"), "validation.json").toPath();
+        Files.writeString(cache, """
+                {
+                  "schemaVersion": 1,
+                  "contentFingerprint": "content",
+                  "contextFingerprint": "context",
+                  "results": [
+                    {"packName":"overworld","blockingErrors":[],"warnings":[],"validatedAtMillis":1},
+                    {"packName":"overworld","blockingErrors":[],"warnings":[],"validatedAtMillis":2}
+                  ]
+                }
+                """, StandardCharsets.UTF_8);
+
+        assertTrue(PackValidationCache.load(
+                cache, "content", "context", List.of("overworld")).isEmpty());
+    }
+
+    @Test
+    public void symbolicLinkCacheIsRejected() throws Exception {
+        Path directory = temporaryFolder.newFolder("symbolic-cache").toPath();
+        Path target = directory.resolve("target.json");
+        Files.writeString(target, "{}", StandardCharsets.UTF_8);
+        Path link = directory.resolve("validation.json");
+        try {
+            Files.createSymbolicLink(link, target.getFileName());
+        } catch (Exception unavailable) {
+            Assume.assumeNoException(unavailable);
+        }
+
+        assertTrue(PackValidationCache.load(
+                link, "content", "context", List.of()).isEmpty());
+    }
+
+    @Test
+    public void contentFingerprintChangesWhenSizeAndTimestampAreRestored() throws Exception {
+        File packsRoot = temporaryFolder.newFolder("content-fingerprint");
+        File pack = new File(packsRoot, "overworld");
+        assertTrue(pack.mkdirs());
+        Path dimension = new File(pack, "dimensions/overworld.json").toPath();
+        Files.createDirectories(dimension.getParent());
+        Files.writeString(dimension, "alpha", StandardCharsets.UTF_8);
+        FileTime originalTime = Files.getLastModifiedTime(dimension);
+        String before = PackValidationCache.contentFingerprint(packsRoot);
+
+        Files.writeString(dimension, "bravo", StandardCharsets.UTF_8);
+        Files.setLastModifiedTime(dimension, originalTime);
+        String after = PackValidationCache.contentFingerprint(packsRoot);
+
+        assertNotEquals(before, after);
+    }
+
+    @Test
+    public void cachedFailureRemainsFailClosedWhenPublished() throws Exception {
+        Path cache = new File(temporaryFolder.newFolder("failed-result"), "validation.json").toPath();
+        PackValidationCache.save(cache, "content", "context", List.of(
+                new PackValidationResult("overworld", List.of("missing structure"), List.of(), 1L)));
+        PackValidationResult loaded = PackValidationCache.load(
+                cache, "content", "context", List.of("overworld")).orElseThrow().getFirst();
+        PackValidationRegistry.clear();
+        PackValidationRegistry.publish(loaded);
+        try {
+            PackValidationRegistry.requireLoadable("overworld");
+            fail("Expected a persisted failed validation to remain blocking");
+        } catch (BrokenPackException expected) {
+            assertEquals(List.of("missing structure"), expected.getReasons());
+        } finally {
+            PackValidationRegistry.clear();
+        }
+    }
+}

core/src/test/java/art/arcane/iris/core/runtime/StudioOpenCoordinatorOpenKindTest.java

@@ -131,4 +131,24 @@ public class StudioOpenCoordinatorOpenKindTest {
         assertTrue(method.contains("CompletableFuture<Void> abandonment = J.sfut("));
         assertTrue(method.contains("abandonment.get(STUDIO_STRUCTURE_ACTIVATION_TIMEOUT_SECONDS"));
     }
+
+    @Test
+    public void openFinalizerReturnsToTheServerThreadBeforeCompletion() throws Exception {
+        String source = Files.readString(Path.of(
+                "src/main/java/art/arcane/iris/core/runtime/StudioOpenCoordinator.java"));
+        int finalizerCall = source.indexOf("runOpenFinalizer(request.onDone(), world);");
+        int futureCompletion = source.indexOf(
+                "future.complete(new StudioOpenResult(world, safeEntry))", finalizerCall);
+        int methodStart = source.indexOf(
+                "private void runOpenFinalizer(Consumer<World> finalizer, World world)");
+        int methodEnd = source.indexOf("private long elapsedMillis", methodStart);
+        String method = source.substring(methodStart, methodEnd);
+
+        assertTrue(finalizerCall >= 0);
+        assertTrue(futureCompletion > finalizerCall);
+        assertTrue(method.contains("if (J.isPrimaryThread())"));
+        assertTrue(method.contains("J.sfut(() -> finalizer.accept(world))"));
+        assertTrue(method.contains(
+                "completion.get(STUDIO_STRUCTURE_ACTIVATION_TIMEOUT_SECONDS, TimeUnit.SECONDS)"));
+    }
 }

core/src/test/java/art/arcane/iris/core/runtime/jigsaw/JigsawStudioLayoutTest.java

@@ -96,20 +96,31 @@ public class JigsawStudioLayoutTest {
     }
 
     @Test
-    public void spatialLayoutHasOneActiveWorkcell() {
+    public void spatialVariantsReceiveDedicatedAdjacentWorkcells() {
         JigsawStudioVariant hall = spatialVariant("stronghold/hall");
+        JigsawStudioVariant stairs = spatialVariant("stronghold/stairs");
+        JigsawStudioVariant tower = spatialVariant("stronghold/tower");
         JigsawStudioLayout layout = JigsawStudioLayout.create(
                 JigsawStudioMode.SPATIAL_JIGSAW,
                 CELL,
-                new JigsawStudioVariantCatalog(List.of(hall)));
+                new JigsawStudioVariantCatalog(List.of(hall, stairs, tower)));
 
-        assertEquals(1, layout.bays().size());
+        assertEquals(3, layout.bays().size());
         JigsawStudioBay workcell = layout.bays().getFirst();
+        JigsawStudioBay second = layout.bays().get(1);
+        JigsawStudioBay third = layout.bays().get(2);
         assertEquals(JigsawStudioLayout.SPATIAL_WORKCELL_ID, workcell.stableId());
         assertEquals(JigsawStudioBayKind.SPATIAL_WORKCELL, workcell.kind());
         assertTrue(workcell.archetype().isEmpty());
         assertTrue(workcell.topology().isEmpty());
         assertSame(hall, layout.defaultVariant(workcell).orElseThrow());
+        assertSame(stairs, layout.defaultVariant(second).orElseThrow());
+        assertSame(tower, layout.defaultVariant(third).orElseThrow());
+        assertEquals(1, second.bounds().originX() - workcell.bounds().maxX() - 1);
+        assertEquals(1, third.bounds().originX() - second.bounds().maxX() - 1);
+        assertTrue(layout.accepts(second, stairs));
+        assertFalse(layout.accepts(second, hall));
+        assertSame(second, layout.workcellForVariant(stairs.pieceKey()).orElseThrow());
         assertNull(layout.findAt(-1, JigsawStudioLayout.FLOOR_Y + 1, -1));
     }
 

core/src/test/java/art/arcane/iris/core/runtime/jigsaw/JigsawStudioPersistenceEditorsTest.java

@@ -448,7 +448,7 @@ public class JigsawStudioPersistenceEditorsTest {
     }
 
     @Test
-    public void createsSpatialThemeSetFromTheSingleSpatialWorkcellSource() throws Exception {
+    public void createsSpatialThemeSetFromTheSelectedSpatialWorkcellSource() throws Exception {
         Path packRoot = temporaryFolder.newFolder("spatial-theme").toPath();
         JigsawStudioProjectCreator.Options options = new JigsawStudioProjectCreator.Options(
                 "spatial/theme",
@@ -468,7 +468,39 @@ public class JigsawStudioPersistenceEditorsTest {
                 "spatial/theme/variants/spatial/variant-2",
                 creation.pieceKeysByWorkcell().get(JigsawStudioLayout.SPATIAL_WORKCELL_ID));
         JsonObject pool = readJson(packRoot.resolve("jigsaw-pools/spatial/theme/start.json"));
-        assertEquals(2, pool.getAsJsonArray("pieces").size());
+        assertEquals(8, pool.getAsJsonArray("pieces").size());
+    }
+
+    @Test
+    public void createsSpatialThemeSetAcrossEveryDedicatedSpatialWorkcell() throws Exception {
+        Path packRoot = temporaryFolder.newFolder("spatial-theme-row").toPath();
+        JigsawStudioProjectCreator.Options options = new JigsawStudioProjectCreator.Options(
+                "spatial/row",
+                JigsawStudioMode.SPATIAL_JIGSAW,
+                JigsawStudioCompatibilityTarget.IRIS_EXTENDED,
+                new JigsawStudioCellDimensions(15, 15, 15));
+        assertTrue(JigsawStudioProjectCreator.create(packRoot, options).successful());
+
+        Map<String, String> sources = new LinkedHashMap<>();
+        sources.put(JigsawStudioLayout.SPATIAL_WORKCELL_ID, "spatial/row/start");
+        for (int connectorCount = 1; connectorCount <= 6; connectorCount++) {
+            String pieceKey = "spatial/row/connectors-" + connectorCount;
+            sources.put(JigsawStudioLayout.SPATIAL_WORKCELL_ID + "/" + pieceKey, pieceKey);
+        }
+        JigsawStudioGraphEditor.VariantFamilyCreation creation = JigsawStudioGraphEditor.duplicateActiveFamily(
+                packRoot,
+                "spatial/row",
+                sources,
+                "variant-2");
+
+        assertTrue(creation.writeResult().successful());
+        assertEquals(7, creation.pieceKeysByWorkcell().size());
+        for (String targetPieceKey : creation.pieceKeysByWorkcell().values()) {
+            assertTrue(Files.isRegularFile(packRoot.resolve("jigsaw-pieces/" + targetPieceKey + ".json")));
+            assertTrue(Files.isRegularFile(packRoot.resolve("objects/" + targetPieceKey + ".iob")));
+        }
+        JsonObject pool = readJson(packRoot.resolve("jigsaw-pools/spatial/row/start.json"));
+        assertEquals(14, pool.getAsJsonArray("pieces").size());
     }
 
     @Test

core/src/test/java/art/arcane/iris/core/runtime/jigsaw/JigsawStudioProjectCreatorTest.java

@@ -206,6 +206,64 @@ public class JigsawStudioProjectCreatorTest {
         }
     }
 
+    @Test
+    public void spatialProjectSeedsZeroThroughSixConnectorVariants() throws Exception {
+        Path temporaryDirectory = temporaryFolder.getRoot().toPath();
+        JigsawStudioProjectCreator.Options options = new JigsawStudioProjectCreator.Options(
+                "stronghold/gallery",
+                JigsawStudioMode.SPATIAL_JIGSAW,
+                JigsawStudioCompatibilityTarget.IRIS_EXTENDED,
+                new JigsawStudioCellDimensions(15, 15, 15));
+
+        StructureWriteResult result = JigsawStudioProjectCreator.create(temporaryDirectory, options);
+
+        assertTrue(result.successful());
+        JsonObject startPool = JsonParser.parseString(Files.readString(
+                temporaryDirectory.resolve("jigsaw-pools/stronghold/gallery/start.json"),
+                StandardCharsets.UTF_8)).getAsJsonObject();
+        JsonObject piecePool = JsonParser.parseString(Files.readString(
+                temporaryDirectory.resolve("jigsaw-pools/stronghold/gallery/pieces.json"),
+                StandardCharsets.UTF_8)).getAsJsonObject();
+        assertEquals(7, startPool.getAsJsonArray("pieces").size());
+        assertEquals(7, piecePool.getAsJsonArray("pieces").size());
+        assertEquals("stronghold/gallery/connectors-1", piecePool.getAsJsonArray("pieces").get(0)
+                .getAsJsonObject().get("piece").getAsString());
+        assertTrue(piecePool.getAsJsonArray("pieces").get(6).getAsJsonObject()
+                .get("empty").getAsBoolean());
+        for (int connectorCount = 0; connectorCount <= 6; connectorCount++) {
+            String pieceName = connectorCount == 0 ? "start" : "connectors-" + connectorCount;
+            JsonObject piece = JsonParser.parseString(Files.readString(
+                    temporaryDirectory.resolve("jigsaw-pieces/stronghold/gallery/"
+                            + pieceName + ".json"),
+                    StandardCharsets.UTF_8)).getAsJsonObject();
+            assertEquals(connectorCount, piece.getAsJsonArray("connectors").size());
+            assertEquals(connectorCount + (connectorCount == 1 ? " Connector" : " Connectors"),
+                    piece.get("displayName").getAsString());
+            assertEquals(16, piece.getAsJsonObject("rules").get("maximumPlacements").getAsInt());
+            assertEquals(new IrisBlockVector(15, 15, 15), IrisObject.sampleSize(
+                    temporaryDirectory.resolve("objects/stronghold/gallery/"
+                            + pieceName + ".iob").toFile()));
+        }
+        JsonObject six = JsonParser.parseString(Files.readString(
+                temporaryDirectory.resolve("jigsaw-pieces/stronghold/gallery/connectors-6.json"),
+                StandardCharsets.UTF_8)).getAsJsonObject();
+        assertEquals("NORTH_NEGATIVE_Z", six.getAsJsonArray("connectors").get(0)
+                .getAsJsonObject().get("direction").getAsString());
+        assertEquals("DOWN_NEGATIVE_Y", six.getAsJsonArray("connectors").get(5)
+                .getAsJsonObject().get("direction").getAsString());
+        assertEquals(0, six.getAsJsonArray("connectors").get(5)
+                .getAsJsonObject().getAsJsonObject("position").get("y").getAsInt());
+
+        StructureGraphCompilation compilation = StructureResourceBundleGraphCompiler.compile(
+                JigsawStudioProjectCreator.bundle(options)).getFirst();
+        StructureAssemblyResult preview = StructureAssembler.forCompilation(
+                compilation,
+                new IrisPosition(0, 0, 0)).assemble(new RNG(1337L));
+        assertEquals(preview.detail(), StructureAssemblyStatus.COMPLETE, preview.status());
+        assertTrue(preview.pieces().size() > 1);
+        assertTrue(preview.pieces().size() <= 96);
+    }
+
     @Test
     public void updatesOwnedPoolThroughWholeGraphTransaction() throws Exception {
         Path temporaryDirectory = temporaryFolder.getRoot().toPath();
@@ -337,10 +395,10 @@ public class JigsawStudioProjectCreatorTest {
         JsonObject pool = JsonParser.parseString(Files.readString(
                 temporaryDirectory.resolve("jigsaw-pools/stronghold/test/start.json"),
                 StandardCharsets.UTF_8)).getAsJsonObject();
-        assertEquals(2, pool.getAsJsonArray("pieces").size());
-        assertEquals("stronghold/test/hall", pool.getAsJsonArray("pieces").get(1)
+        assertEquals(8, pool.getAsJsonArray("pieces").size());
+        assertEquals("stronghold/test/hall", pool.getAsJsonArray("pieces").get(7)
                 .getAsJsonObject().get("piece").getAsString());
-        assertEquals(3, pool.getAsJsonArray("pieces").get(1)
+        assertEquals(3, pool.getAsJsonArray("pieces").get(7)
                 .getAsJsonObject().get("weight").getAsInt());
 
         StructureWriteResult resized = JigsawStudioStructureEditor.updateCellSize(
@@ -360,10 +418,10 @@ public class JigsawStudioProjectCreatorTest {
                 new JigsawStudioCellDimensions(16, 12, 18)).writeResult().successful());
         IrisBlockVector hallSize = IrisObject.sampleSize(
                 temporaryDirectory.resolve("objects/stronghold/test/hall.iob").toFile());
-        IrisBlockVector startSize = IrisObject.sampleSize(
+        IrisBlockVector starterSize = IrisObject.sampleSize(
                 temporaryDirectory.resolve("objects/stronghold/test/start.iob").toFile());
         assertEquals(new IrisBlockVector(16, 12, 18), hallSize);
-        assertEquals(new IrisBlockVector(12, 10, 14), startSize);
+        assertEquals(new IrisBlockVector(12, 10, 14), starterSize);
 
         StructureWriteResult limited = JigsawStudioStructureEditor.updateLimits(
                 temporaryDirectory,

core/src/test/java/art/arcane/iris/core/service/JigsawStudioDisabledWorkcellRendererTest.java

@@ -1,89 +0,0 @@
-package art.arcane.iris.core.service;
-
-import art.arcane.iris.core.runtime.jigsaw.JigsawPlanarArchetype;
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioCellDimensions;
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioLayout;
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioVariantCatalog;
-import art.arcane.iris.core.runtime.jigsaw.JigsawStudioWorkcellSpec;
-import org.bukkit.entity.BlockDisplay;
-import org.junit.Test;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verifyNoInteractions;
-
-public class JigsawStudioDisabledWorkcellRendererTest {
-    @Test
-    public void disabledWorkcellProducesOneFullVolumeDescriptor() {
-        JigsawStudioLayout layout = layoutWithDisabled(JigsawPlanarArchetype.TEE);
-
-        Map<String, JigsawStudioDisabledWorkcellRenderer.Descriptor> descriptors =
-                JigsawStudioDisabledWorkcellRenderer.descriptors(layout);
-
-        assertEquals(1, descriptors.size());
-        JigsawStudioDisabledWorkcellRenderer.Descriptor descriptor =
-                descriptors.get(JigsawPlanarArchetype.TEE.stableId());
-        assertEquals(11, descriptor.width());
-        assertEquals(5, descriptor.height());
-        assertEquals(7, descriptor.depth());
-        assertEquals(JigsawStudioLayout.FLOOR_Y + 1, descriptor.originY());
-    }
-
-    @Test
-    public void enabledWorkcellsNeverProduceRedGlassDescriptors() {
-        JigsawStudioLayout layout = layoutWithDisabled(null);
-
-        Map<String, JigsawStudioDisabledWorkcellRenderer.Descriptor> descriptors =
-                JigsawStudioDisabledWorkcellRenderer.descriptors(layout);
-
-        assertTrue(descriptors.isEmpty());
-        assertFalse(layout.bays().isEmpty());
-    }
-
-    @Test
-    public void chunkUnloadDetachesOnlyDisplaysWhoseOriginsBelongToThatChunk() {
-        BlockDisplay target = mock(BlockDisplay.class);
-        BlockDisplay retained = mock(BlockDisplay.class);
-        JigsawStudioDisabledWorkcellRenderer.Descriptor targetDescriptor =
-                new JigsawStudioDisabledWorkcellRenderer.Descriptor("workcell/tee", 31, 65, -1, 3, 3, 3);
-        JigsawStudioDisabledWorkcellRenderer.Descriptor retainedDescriptor =
-                new JigsawStudioDisabledWorkcellRenderer.Descriptor("workcell/cross", 32, 65, -1, 3, 3, 3);
-        Map<String, BlockDisplay> entities = new HashMap<>(Map.of(
-                targetDescriptor.workcellId(), target,
-                retainedDescriptor.workcellId(), retained));
-        Map<String, JigsawStudioDisabledWorkcellRenderer.Descriptor> rendered = new HashMap<>(Map.of(
-                targetDescriptor.workcellId(), targetDescriptor,
-                retainedDescriptor.workcellId(), retainedDescriptor));
-
-        List<BlockDisplay> removals = JigsawStudioDisabledWorkcellRenderer.detachChunkDisplays(
-                entities, rendered, 1, -1);
-
-        assertEquals(List.of(target), removals);
-        assertFalse(entities.containsKey(targetDescriptor.workcellId()));
-        assertFalse(rendered.containsKey(targetDescriptor.workcellId()));
-        assertEquals(retained, entities.get(retainedDescriptor.workcellId()));
-        assertEquals(retainedDescriptor, rendered.get(retainedDescriptor.workcellId()));
-        verifyNoInteractions(target, retained);
-    }
-
-    private static JigsawStudioLayout layoutWithDisabled(JigsawPlanarArchetype disabled) {
-        List<JigsawStudioWorkcellSpec> specs = new ArrayList<>();
-        for (JigsawPlanarArchetype archetype : JigsawPlanarArchetype.values()) {
-            JigsawStudioCellDimensions dimensions = archetype == JigsawPlanarArchetype.TEE
-                    ? new JigsawStudioCellDimensions(11, 5, 7)
-                    : new JigsawStudioCellDimensions(3, 3, 3);
-            specs.add(new JigsawStudioWorkcellSpec(archetype, "", dimensions, archetype != disabled));
-        }
-        return JigsawStudioLayout.createPlanar(
-                new JigsawStudioCellDimensions(3, 3, 3),
-                specs,
-                JigsawStudioVariantCatalog.empty());
-    }
-}

core/src/test/java/art/arcane/iris/core/service/JigsawStudioLifecycleTest.java

@@ -16,12 +16,16 @@ import art.arcane.iris.engine.platform.studio.generators.JigsawStudioGenerator;
 import art.arcane.iris.util.common.scheduling.J;
 import art.arcane.volmlib.util.collection.KMap;
 import org.bukkit.World;
+import org.bukkit.event.entity.CreatureSpawnEvent;
 import org.junit.After;
 import org.junit.Test;
 import org.mockito.MockedStatic;
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -70,6 +74,33 @@ public class JigsawStudioLifecycleTest {
         assertFalse(JigsawStudioActivation.tryBeginOpen(OTHER_OWNER));
     }
 
+    @Test
+    public void studioRejectsNaturalCreatureSpawns() {
+        assertTrue(JigsawStudioService.isNaturalStudioSpawn(
+                CreatureSpawnEvent.SpawnReason.NATURAL));
+        assertFalse(JigsawStudioService.isNaturalStudioSpawn(
+                CreatureSpawnEvent.SpawnReason.CUSTOM));
+        assertFalse(JigsawStudioService.isNaturalStudioSpawn(
+                CreatureSpawnEvent.SpawnReason.SPAWNER));
+    }
+
+    @Test
+    public void committedStudioActivationDisablesNaturalMobSpawning() throws IOException {
+        String source = Files.readString(Path.of(
+                "src/main/java/art/arcane/iris/core/service/JigsawStudioService.java"));
+        int registerStart = source.indexOf("public void register(");
+        int commitStart = source.indexOf("public void activationCommitted(", registerStart);
+        int commitEnd = source.indexOf("public void markChunkGenerated(", commitStart);
+        int helperStart = source.indexOf("static void disableNaturalStudioSpawning(", commitEnd);
+        String register = source.substring(registerStart, commitStart);
+        String commit = source.substring(commitStart, commitEnd);
+        String helper = source.substring(helperStart);
+
+        assertFalse(register.contains("disableNaturalStudioSpawning(world)"));
+        assertTrue(commit.contains("disableNaturalStudioSpawning(world)"));
+        assertTrue(helper.contains("setGameRule(GameRules.SPAWN_MOBS, false)"));
+    }
+
     @Test
     public void closeAuthorizationChecksOwnerDirtyStateAndSaveBarrierAtomically() {
         assertTrue(JigsawStudioActivation.tryBeginOpen(OWNER));
@@ -91,10 +122,10 @@ public class JigsawStudioLifecycleTest {
                 service.tryBeginClose(request.requestId(), OWNER, false));
         assertTrue(service.closeProtectionFailure(request.requestId()).contains("autosave"));
 
-        JigsawStudioSession.VariantSwitchToken switchToken = session.beginVariantSwitch(
-                JigsawStudioLayout.SPATIAL_WORKCELL_ID,
-                "stronghold/tower",
-                true).token().orElseThrow();
+        String towerWorkcellId = session.layout().workcellForVariant("stronghold/tower")
+                .orElseThrow().stableId();
+        JigsawStudioSession.VariantSwitchToken switchToken = session.beginVariantReload(
+                towerWorkcellId).token().orElseThrow();
         assertEquals(
                 JigsawStudioService.CloseStart.OPERATION_IN_PROGRESS,
                 service.tryBeginClose(request.requestId(), OWNER, true));

core/src/test/java/art/arcane/iris/core/service/JigsawStudioMenuControllerTest.java

@@ -19,6 +19,7 @@ import org.junit.Test;
 import org.mockito.MockedStatic;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
@@ -30,9 +31,11 @@ import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.same;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
@@ -239,6 +242,87 @@ public class JigsawStudioMenuControllerTest {
                 0));
     }
 
+    @Test
+    public void stagesMultipleCellSizeEditsAndAppliesOneRelayoutWithoutClosing() throws Exception {
+        UUID playerId = UUID.fromString("55555555-5555-5555-5555-555555555555");
+        Player player = mock(Player.class);
+        JigsawStudioMenuController.Actions actions = mock(JigsawStudioMenuController.Actions.class);
+        JigsawStudioMenuState.Variant active = variant("pieces/corner", true, List.of(), List.of());
+        JigsawStudioMenuState.Workcell workcell = workcell(active);
+        JigsawStudioMenuState state = state(JigsawStudioMenuState.Evaluation.pending(), workcell);
+        JigsawStudioMenuController controller = new JigsawStudioMenuController(
+                mock(JavaPlugin.class),
+                actions);
+        Method resize = JigsawStudioMenuController.class.getDeclaredMethod(
+                "resizeWorkcell",
+                Player.class,
+                UUID.class,
+                String.class,
+                JigsawStudioMenuController.DimensionAxis.class,
+                int.class);
+        Method apply = JigsawStudioMenuController.class.getDeclaredMethod(
+                "applyWorkcellResize",
+                Player.class,
+                UUID.class,
+                String.class);
+        resize.setAccessible(true);
+        apply.setAccessible(true);
+        when(player.getUniqueId()).thenReturn(playerId);
+        when(actions.menuState(player)).thenReturn(Optional.of(state));
+        when(actions.updateWorkcellDimensions(
+                player,
+                workcell.stableId(),
+                new JigsawStudioCellDimensions(25, 20, 18))).thenReturn(true);
+
+        resize.invoke(
+                controller,
+                player,
+                REQUEST_ID,
+                workcell.stableId(),
+                JigsawStudioMenuController.DimensionAxis.WIDTH,
+                1);
+        resize.invoke(
+                controller,
+                player,
+                REQUEST_ID,
+                workcell.stableId(),
+                JigsawStudioMenuController.DimensionAxis.HEIGHT,
+                8);
+
+        verify(actions, never()).updateWorkcellDimensions(
+                player,
+                workcell.stableId(),
+                new JigsawStudioCellDimensions(25, 20, 18));
+        try (MockedStatic<J> scheduling = mockStatic(J.class)) {
+            scheduling.when(() -> J.runEntity(
+                    same(player),
+                    any(Runnable.class),
+                    eq(2))).thenReturn(true);
+
+            apply.invoke(controller, player, REQUEST_ID, workcell.stableId());
+
+            verify(actions).updateWorkcellDimensions(
+                    player,
+                    workcell.stableId(),
+                    new JigsawStudioCellDimensions(25, 20, 18));
+        }
+    }
+
+    @Test
+    public void stagedCapacityPreservesEveryOtherWorkcellProperty() {
+        JigsawStudioMenuState.Variant active = variant("pieces/corner", true, List.of(), List.of());
+        JigsawStudioMenuState.Workcell source = workcell(active);
+        JigsawStudioCellDimensions capacity = new JigsawStudioCellDimensions(31, 19, 27);
+
+        JigsawStudioMenuState.Workcell staged = JigsawStudioMenuController.withCapacity(source, capacity);
+
+        assertEquals(capacity, staged.capacity());
+        assertEquals(source.stableId(), staged.stableId());
+        assertEquals(source.enabled(), staged.enabled());
+        assertEquals(source.activeVariantKey(), staged.activeVariantKey());
+        assertEquals(source.variants(), staged.variants());
+    }
+
     @Test
     public void allocatesNumberedThemeSetsAndAdjustsPositiveWeights() {
         List<JigsawStudioMenuState.ThemeSet> themeSets = List.of(
@@ -254,6 +338,20 @@ public class JigsawStudioMenuControllerTest {
                 () -> JigsawStudioMenuController.adjustedPositiveValue(4, 0));
     }
 
+    @Test
+    public void themeWeightsExposeWholeAssemblySelectionChance() {
+        List<JigsawStudioMenuState.ThemeSet> themes = List.of(
+                new JigsawStudioMenuState.ThemeSet("variant-1", 3),
+                new JigsawStudioMenuState.ThemeSet("variant-2", 1));
+
+        assertEquals("75.0%", JigsawStudioMenuController.themeSelectionPercent(
+                themes,
+                themes.getFirst()));
+        assertEquals("25.0%", JigsawStudioMenuController.themeSelectionPercent(
+                themes,
+                themes.getLast()));
+    }
+
     @Test
     public void editsPieceRuleFieldsWithinRuntimeBounds() {
         assertEquals(

core/src/test/java/art/arcane/iris/core/service/JigsawStudioPreviewRendererTest.java

@@ -1,5 +1,7 @@
 package art.arcane.iris.core.service;
 
+import art.arcane.iris.core.runtime.jigsaw.JigsawStudioLayout;
+import art.arcane.iris.core.runtime.jigsaw.JigsawStudioMode;
 import art.arcane.iris.engine.framework.PlacedStructurePiece;
 import art.arcane.iris.engine.object.IrisJigsawPiece;
 import art.arcane.iris.engine.object.IrisObject;
@@ -68,6 +70,28 @@ public class JigsawStudioPreviewRendererTest {
         assertTrue(plan.bounds().isEmpty());
     }
 
+    @Test
+    public void spatialPreviewFloatsAboveThePlanarEditingFloor() {
+        PlacedStructurePiece source = piece(
+                new IrisObject(3, 3, 3),
+                10,
+                10,
+                10,
+                IrisObjectRotation.of(0, 0, 0));
+
+        PlacedStructurePiece planar = JigsawStudioService.alignPreviewPieces(
+                List.of(source),
+                JigsawStudioMode.PLANAR_JIGSAW).getFirst();
+        PlacedStructurePiece spatial = JigsawStudioService.alignPreviewPieces(
+                List.of(source),
+                JigsawStudioMode.SPATIAL_JIGSAW).getFirst();
+
+        assertEquals(JigsawStudioLayout.FLOOR_Y + 1, planar.getMinY());
+        assertEquals(JigsawStudioLayout.FLOOR_Y + 48, spatial.getMinY());
+        assertEquals(planar.getMinX(), spatial.getMinX());
+        assertEquals(planar.getMinZ(), spatial.getMinZ());
+    }
+
     @Test
     public void uncertainPositionIsReappliedWhenSuccessivePlansMatch() {
         JigsawStudioPreviewRenderer.BlockPosition position =

core/src/test/java/art/arcane/iris/core/service/JigsawStudioResourceBundleAssemblerTest.java

@@ -63,7 +63,7 @@ public class JigsawStudioResourceBundleAssemblerTest {
                         List.of(connector),
                         false);
 
-        assertEquals(4, assembly.bundle().resources().size());
+        assertEquals(17, assembly.bundle().resources().size());
         assertEquals("fort/start", assembly.objectKey());
         assertEquals(1, assembly.piece().getConnectors().size());
         StructureWriteResult result = new StructureTransactionWriter(packRoot)

core/src/test/java/art/arcane/iris/core/service/JigsawStudioServiceCaptureTest.java

@@ -41,6 +41,7 @@ import art.arcane.iris.util.common.scheduling.J;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.volmlib.util.collection.KMap;
 import org.bukkit.Chunk;
+import org.bukkit.Location;
 import org.bukkit.Material;
 import org.bukkit.World;
 import org.bukkit.block.Block;
@@ -103,6 +104,7 @@ import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.ArgumentMatchers.same;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.mockStatic;
@@ -112,6 +114,24 @@ import static org.mockito.Mockito.when;
 
 public class JigsawStudioServiceCaptureTest {
 
+    @Test
+    public void successfulStudioSavePlaysOneOwnerLocalBell() {
+        Player player = mock(Player.class);
+        Location location = mock(Location.class);
+        when(player.getLocation()).thenReturn(location);
+
+        try (MockedStatic<J> scheduling = mockStatic(J.class)) {
+            scheduling.when(() -> J.runEntity(same(player), any(Runnable.class))).thenAnswer(invocation -> {
+                invocation.getArgument(1, Runnable.class).run();
+                return true;
+            });
+
+            JigsawStudioService.playSaveSound(player);
+
+            verify(player).playSound(location, "minecraft:block.note_block.bell", 0.65F, 1.65F);
+        }
+    }
+
     @Test
     public void hiddenConnectorResetRestoresOnlyItsSavedOrdinaryBlock() throws Exception {
         World world = mock(World.class);
@@ -741,10 +761,23 @@ public class JigsawStudioServiceCaptureTest {
                 layout.get("workcell/end"),
                 List.of(eastSource),
                 3);
-        assertThrows(IOException.class, () -> JigsawStudioService.requireWorkcellTopology(
-                layout.get("workcell/end"),
-                List.of(southDisplayed),
-                0));
+        JigsawStudioService.WorkcellTopologyException wrongDirection = assertThrows(
+                JigsawStudioService.WorkcellTopologyException.class,
+                () -> JigsawStudioService.requireWorkcellTopology(
+                        layout.get("workcell/end"),
+                        List.of(southDisplayed),
+                        0));
+        assertTrue(wrongDirection.getMessage().contains("south end (1 horizontal connector)"));
+        assertTrue(wrongDirection.getMessage().contains("Reset Connector Blocks"));
+
+        JigsawStudioService.WorkcellTopologyException missingTee = assertThrows(
+                JigsawStudioService.WorkcellTopologyException.class,
+                () -> JigsawStudioService.requireWorkcellTopology(
+                        layout.get("workcell/tee"),
+                        List.of(),
+                        0));
+        assertTrue(missingTee.getMessage().contains("north east west tee (3 horizontal connectors)"));
+        assertTrue(missingTee.getMessage().contains("blank (0 horizontal connectors)"));
     }
 
     @Test
@@ -1233,6 +1266,9 @@ public class JigsawStudioServiceCaptureTest {
         when(world.getUID()).thenReturn(worldId);
         JigsawStudioGenerator generator = mock(JigsawStudioGenerator.class);
         when(generator.getLayout()).thenReturn(layout);
+        JigsawStudioActivation.Request request = mock(JigsawStudioActivation.Request.class);
+        when(request.requestId()).thenReturn(UUID.randomUUID());
+        when(generator.getRequest()).thenReturn(request);
         when(generator.renderBay(any(JigsawStudioBay.class)))
                 .thenReturn(JigsawStudioGenerator.RenderedBay.empty(dimensions));
         Class<?> studioType = Class.forName(JigsawStudioService.class.getName() + "$ActiveStudio");

core/src/test/java/art/arcane/iris/engine/platform/studio/generators/JigsawStudioGeneratorTest.java

@@ -212,6 +212,32 @@ public class JigsawStudioGeneratorTest {
                 fixture.generator(), control.worldX(), control.worldY(), control.worldZ()));
     }
 
+    @Test
+    public void paintsEveryWorkcellAsAWhiteConcreteEdgeCuboid() {
+        GeneratorFixture fixture = fixture(
+                JigsawStudioMode.PLANAR_JIGSAW,
+                new JigsawStudioCellDimensions(5, 4, 3),
+                JigsawStudioVariantCatalog.empty());
+        JigsawStudioBay workcell = fixture.layout().get("workcell/blank");
+        int minimumX = workcell.bounds().originX() - 1;
+        int maximumX = workcell.bounds().maxX() + 1;
+        int minimumZ = workcell.bounds().originZ() - 1;
+        int maximumZ = workcell.bounds().maxZ() + 1;
+        int bottomY = workcell.bounds().originY();
+        int topY = workcell.bounds().maxY() + 1;
+
+        assertSame(fixture.frame(), stateAt(fixture.generator(), minimumX, bottomY, minimumZ));
+        assertSame(fixture.frame(), stateAt(fixture.generator(), maximumX, bottomY, maximumZ));
+        assertSame(fixture.frame(), stateAt(fixture.generator(), minimumX, topY, maximumZ));
+        assertSame(fixture.frame(), stateAt(fixture.generator(), maximumX, topY, minimumZ));
+        assertSame(fixture.frame(), stateAt(fixture.generator(), minimumX, bottomY + 1, minimumZ));
+        assertFalse(fixture.frame() == stateAt(
+                fixture.generator(),
+                workcell.bounds().originX(),
+                bottomY + 1,
+                workcell.bounds().originZ()));
+    }
+
     @Test
     public void glyphMathHandlesAllArchetypesAndSmallEvenAndOddCells() {
         int[] sizes = {1, 2, 3, 4, 7, 16};
@@ -521,6 +547,7 @@ public class JigsawStudioGeneratorTest {
         return new GeneratorFixture(
                 generator,
                 layout,
+                frame,
                 topologyBase,
                 topologyPath,
                 connectorCap,
@@ -559,6 +586,7 @@ public class JigsawStudioGeneratorTest {
     private record GeneratorFixture(
             JigsawStudioGenerator generator,
             JigsawStudioLayout layout,
+            PlatformBlockState frame,
             PlatformBlockState topologyBase,
             PlatformBlockState topologyPath,
             PlatformBlockState connectorCap,