Merged treasure loot fixes

- Failed container fills retain pending work for retry
- Loot events and inventory writes run on the owning thread
- Native loot tables resolve against the current registry
- Gameplay checks cover map destinations and copper containers

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

@@ -81,7 +81,6 @@ import org.bukkit.FluidCollisionMode;
 import org.bukkit.Location;
 import org.bukkit.World;
 import org.bukkit.entity.Player;
-import org.bukkit.event.inventory.InventoryType;
 import org.bukkit.inventory.Inventory;
 import org.bukkit.util.Vector;
 
@@ -309,23 +308,33 @@ public class CommandStudio implements DirectorExecutor {
         O<Integer> ta = new O<>();
         ta.set(-1);
 
-        var sender = sender();
-        var player = player();
-        var engine = engine();
+        VolmitSender sender = sender();
+        Player player = player();
+        Engine engine = engine();
 
-        ta.set(J.sr(() ->
-        {
-            if (!player.getOpenInventory().getType().equals(InventoryType.CHEST)) {
+        ta.set(J.sr(() -> {
+            if (!J.runEntity(player, () -> {
+                if (player.getOpenInventory().getTopInventory() != inv) {
+                    J.csr(ta.get());
+                    sender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STUDIO_OPENED_INVENTORY));
+                    return;
+                }
+                if (!add) {
+                    inv.clear();
+                }
+                Location location = player.getLocation();
+                try {
+                    EngineBukkitOps.addItems(engine, true, inv, tables, InventorySlotType.STORAGE,
+                            location.getWorld(), location.getBlockX(), location.getBlockY(), location.getBlockZ());
+                } catch (RuntimeException | Error failure) {
+                    J.csr(ta.get());
+                    Iris.reportError(failure);
+                    sender.sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_CANNOT_ADD_ITEMS_VIRTUAL_INVENTORY_BECAUSE,
+                            MessageArgument.untrusted("value", String.valueOf(failure.getMessage()))));
+                }
+            }, 0, () -> J.csr(ta.get()))) {
                 J.csr(ta.get());
-                sender.sendMessage(IrisLanguage.text(BukkitCommandMessages.COMMAND_STUDIO_OPENED_INVENTORY));
-                return;
             }
-
-            if (!add) {
-                inv.clear();
-            }
-
-            EngineBukkitOps.addItems(engine, true, inv, tables, InventorySlotType.STORAGE, player.getWorld(), player.getLocation().getBlockX(), player.getLocation().getBlockY(), player.getLocation().getBlockZ());
         }, fast ? 5 : 35));
 
         sender().sendMessage(IrisLanguage.text(BukkitCommandMessagesExtended.COMMAND_STUDIO_OPENING_INVENTORY_NOW));

adapters/bukkit/plugin/src/test/gameplay/native-lifecycle-fixture/resources/plugin.yml

@@ -2,6 +2,7 @@ name: IrisNativeLifecycleFixture
 version: 1.0.0
 main: art.arcane.iris.fixture.NativeLifecycleFixture
 api-version: '26.1.2'
+folia-supported: true
 depend: [Iris]
 commands:
   irislifecycle:

adapters/bukkit/plugin/src/test/gameplay/native-lifecycle-fixture/src/art/arcane/iris/fixture/NativeLifecycleFixture.java

@@ -1,8 +1,12 @@
 package art.arcane.iris.fixture;
 
+import art.arcane.iris.Iris;
 import art.arcane.volmlib.nativelib.NativeAdapters;
 import art.arcane.iris.world.runtime.RuntimeInjection;
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.structure.placement.IrisStructureLocator;
 import art.arcane.iris.world.IrisCreator;
+import art.arcane.iris.world.task.J;
 import art.arcane.iris.world.IrisToolbelt;
 import art.arcane.iris.world.IrisWorldStorage;
 import art.arcane.iris.world.WorldCreatorCompat;
@@ -13,6 +17,15 @@ import org.bukkit.entity.Player;
 import org.bukkit.configuration.file.YamlConfiguration;
 import org.bukkit.Material;
 import org.bukkit.block.Biome;
+import org.bukkit.block.Container;
+import org.bukkit.loot.Lootable;
+import org.bukkit.loot.LootTable;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.MapMeta;
+import org.bukkit.map.MapView;
+import org.bukkit.generator.structure.Structure;
+import org.bukkit.util.StructureSearchResult;
 import art.arcane.volmlib.nativelib.terrain.NativeTerrainAccess;
 import art.arcane.volmlib.nativelib.terrain.NativeStructureReader;
 import art.arcane.volmlib.nativelib.terrain.NativeWorldRuntime;
@@ -38,12 +51,15 @@ public final class NativeLifecycleFixture extends JavaPlugin implements WorldRun
     private static final NamespacedKey WORLD_KEY = NamespacedKey.minecraft("native_lifecycle_probe");
     private static final NamespacedKey TERRAIN_KEY = new NamespacedKey("iris", "native_terrain_probe");
     private static final NamespacedKey COMMAND_KEY = new NamespacedKey("iris", "lifecycle_probe");
+    private static final NamespacedKey TREASURE_KEY = new NamespacedKey("iris", "treasure_map_probe");
     private static final long WORLD_SEED = 78264193L;
     private NativeWorldRuntime runtime;
+    private TreasureLootChecks treasureLootChecks;
 
     @Override
     public void onEnable() {
         runtime = NativeAdapters.require(NativeWorldRuntime.class);
+        treasureLootChecks = new TreasureLootChecks(this);
         NativeTerrainAccess terrain = NativeAdapters.require(NativeTerrainAccess.class);
         getLogger().info("Native lifecycle ready: " + runtime.description()
                 + "; terrain provider=" + terrain.getClass().getName());
@@ -56,12 +72,32 @@ public final class NativeLifecycleFixture extends JavaPlugin implements WorldRun
 
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] arguments) {
-        if (arguments.length != 1) {
+        if (arguments.length == 0) {
             sender.sendMessage("Use /irislifecycle create|unload|status|structures|terrain-create|terrain-check|terrain-unload|lifecycle-status|lifecycle-entry");
             return true;
         }
         try {
             switch (arguments[0]) {
+                case "treasure-map-create" -> createTreasureMapWorld(sender);
+                case "treasure-map-limit" -> runTreasureRegion(sender, () -> checkTreasureMapLimit(sender));
+                case "treasure-map-chest" -> {
+                    if (arguments.length != 3) {
+                        throw new IllegalArgumentException("Use treasure-map-chest <destination> <CHEST|COPPER_CHEST>");
+                    }
+                    runTreasureRegion(sender, () -> prepareTreasureMapChest(sender, arguments[1], arguments[2]));
+                }
+                case "treasure-map-inspect" -> {
+                    if (arguments.length != 2) {
+                        throw new IllegalArgumentException("Use treasure-map-inspect <destination>");
+                    }
+                    runTreasureRegion(sender, () -> inspectTreasureMapChest(sender, arguments[1]));
+                }
+                case "treasure-map-check" -> runTreasureRegion(sender, () -> verifyTreasureMapLoot(sender));
+                case "treasure-extra-check" -> runTreasureRegion(sender, () -> treasureLootChecks.verify(sender));
+                case "treasure-region-check" -> runTreasureRegion(sender, () -> treasureLootChecks.verifyRegion(sender));
+                case "treasure-reload-before" -> runTreasureRegion(sender, () -> treasureLootChecks.verifyReload(sender, false));
+                case "treasure-reload-after" -> runTreasureRegion(sender, () -> treasureLootChecks.verifyReload(sender, true));
+                case "treasure-resources" -> treasureLootChecks.reportResourceReloads(sender);
                 case "create" -> create(sender);
                 case "unload" -> unload(sender);
                 case "structures" -> structures(sender);
@@ -80,6 +116,177 @@ public final class NativeLifecycleFixture extends JavaPlugin implements WorldRun
         return true;
     }
 
+    private void createTreasureMapWorld(CommandSender sender) {
+        if (!(sender instanceof Player player)) {
+            throw new IllegalStateException("Treasure map fixture requires a player");
+        }
+        runTreasureRegion(sender, () -> prepareTreasureMapWorld(player));
+    }
+
+    private void runTreasureRegion(CommandSender sender, Runnable task) {
+        ensureTreasureMapWorld()
+                .thenCompose(ignored -> J.runRegionFuture(Bukkit.getWorld(TREASURE_KEY), 0, 0, task))
+                .whenComplete((ignored, failure) -> {
+                    if (failure != null) {
+                        fail(sender, failure);
+                    }
+                });
+    }
+
+    private CompletableFuture<?> ensureTreasureMapWorld() {
+        if (Bukkit.getWorld(TREASURE_KEY) != null) {
+            return CompletableFuture.completedFuture(null);
+        }
+        if (WorldCreatorCompat.persistentLevelRoot(TREASURE_KEY).exists()) {
+            return Iris.instance.worldReconciler().loadWorld(ServerProperties.BUKKIT_YML, TREASURE_KEY.toString());
+        }
+        return runAsync(() -> {
+            try {
+                new IrisCreator().name(TREASURE_KEY.toString()).dimension("treasure-map-fixture")
+                        .seed(WORLD_SEED).create();
+            } catch (Exception failure) {
+                throw new IllegalStateException("Treasure map fixture creation failed", failure);
+            }
+        });
+    }
+
+    private void prepareTreasureMapWorld(Player player) {
+        World world = Bukkit.getWorld(TREASURE_KEY);
+        if (world == null || !IrisToolbelt.isIrisWorld(world) || world.getSeed() != WORLD_SEED
+                || !"treasure-map-fixture".equals(IrisToolbelt.access(world).getEngine().getDimension().getLoadKey())) {
+            throw new IllegalStateException("Treasure map fixture world identity is invalid");
+        }
+        for (int x = 0; x <= 8; x++) {
+            for (int z = 0; z <= 8; z++) {
+                world.getBlockAt(x, 160, z).setType(Material.STONE, false);
+                for (int y = 161; y <= 164; y++) {
+                    world.getBlockAt(x, y, z).setType(Material.AIR, false);
+                }
+            }
+        }
+        if (!J.runEntity(player, () -> player.teleportAsync(new Location(world, 0.5, 161, 0.5)).whenComplete((teleported, failure) -> {
+            if (failure != null) {
+                fail(player, failure);
+            } else if (!Boolean.TRUE.equals(teleported)) {
+                fail(player, new IllegalStateException("Treasure map fixture teleport failed"));
+            } else {
+                player.sendMessage("TREASURE_MAP_READY world=" + TREASURE_KEY
+                        + " version=" + Bukkit.getMinecraftVersion() + " folia=" + J.isFolia());
+            }
+        }))) {
+            throw new IllegalStateException("Could not schedule treasure map fixture teleport");
+        }
+    }
+
+    private void checkTreasureMapLimit(CommandSender sender) {
+        World world = Bukkit.getWorld(TREASURE_KEY);
+        if (world == null) {
+            throw new IllegalStateException("Treasure map fixture world is absent");
+        }
+        Engine engine = IrisToolbelt.access(world).getEngine();
+        IrisStructureLocator.LocateResult located = IrisStructureLocator.locateInPlacementRings(
+                engine, "minecraft:buried_treasure", 2, 2, 50, (x, z) -> true);
+        if (located.status() != IrisStructureLocator.LocateStatus.SEARCH_LIMIT_REACHED) {
+            throw new IllegalStateException("Blocked treasure placement returned " + located.status());
+        }
+        sender.sendMessage("TREASURE_MAP_LIMIT status=" + located.status());
+    }
+
+    private void prepareTreasureMapChest(CommandSender sender, String destination, String material) {
+        World world = Bukkit.getWorld(TREASURE_KEY);
+        treasureMapChest(world, destination, material);
+        sender.sendMessage("TREASURE_MAP_CHEST destination=" + destination + " material=" + material);
+    }
+
+    private Container treasureMapChest(World world, String destination, String material) {
+        requireTreasureDestination(destination);
+        if (!List.of("CHEST", "COPPER_CHEST").contains(material)) {
+            throw new IllegalArgumentException("Unknown treasure map container: " + material);
+        }
+        LootTable loot = Bukkit.getLootTable(new NamespacedKey("iris_qa", destination));
+        if (loot == null) {
+            throw new IllegalStateException("Treasure map loot table is absent: " + destination);
+        }
+        world.getBlockAt(2, 161, 2).setType(Material.AIR, false);
+        world.getBlockAt(2, 161, 2).setType(Material.valueOf(material), false);
+        Container chest = (Container) world.getBlockAt(2, 161, 2).getState();
+        ((Lootable) chest).setLootTable(loot);
+        ((Lootable) chest).setSeed(WORLD_SEED);
+        if (!chest.update(true, false)) {
+            throw new IllegalStateException("Treasure map loot chest was not installed");
+        }
+        return (Container) world.getBlockAt(2, 161, 2).getState();
+    }
+
+    private void verifyTreasureMapLoot(CommandSender sender) {
+        checkTreasureMapLimit(sender);
+        World world = Bukkit.getWorld(TREASURE_KEY);
+        for (String destination : List.of("blocked", "disabled", "found", "mixed")) {
+            Inventory inventory = treasureMapChest(world, destination, "CHEST").getInventory();
+            inspectTreasureMapChest(sender, destination);
+            inventory.remove(Material.DIAMOND);
+            Inventory reopened = ((Container) world.getBlockAt(2, 161, 2).getState()).getInventory();
+            if (reopened.contains(Material.DIAMOND)
+                    || !(reopened.contains(Material.FILLED_MAP) || reopened.contains(Material.MAP))) {
+                throw new IllegalStateException("Reopening changed " + destination + " chest loot");
+            }
+        }
+        sender.sendMessage("TREASURE_MAP_CHECK destinations=4 retained=true");
+    }
+
+    private void inspectTreasureMapChest(CommandSender sender, String destination) {
+        requireTreasureDestination(destination);
+        World world = Bukkit.getWorld(TREASURE_KEY);
+        Inventory inventory = ((Container) world.getBlockAt(2, 161, 2).getState()).getInventory();
+        ItemStack map = null;
+        int diamonds = 0;
+        for (ItemStack item : inventory.getContents()) {
+            if (item == null) {
+                continue;
+            }
+            if ((item.getType() == Material.MAP || item.getType() == Material.FILLED_MAP)
+                    && item.getAmount() == 1 && map == null) {
+                map = item;
+            } else if (item.getType() == Material.DIAMOND) {
+                diamonds += item.getAmount();
+            } else {
+                throw new IllegalStateException("Unexpected chest loot: " + item);
+            }
+        }
+        if (map == null || diamonds != 1) {
+            throw new IllegalStateException("Invalid " + destination + " chest: map=" + map + " diamonds=" + diamonds);
+        }
+        boolean expectedLocated = destination.equals("found") || destination.equals("mixed");
+        MapView view = map.getItemMeta() instanceof MapMeta meta && meta.hasMapView() ? meta.getMapView() : null;
+        if ((view != null) != expectedLocated) {
+            throw new IllegalStateException("Unexpected map data for " + destination + ": " + map);
+        }
+        String result = "TREASURE_MAP_INSPECT destination=" + destination + " diamonds=1 located=" + expectedLocated;
+        if (view != null) {
+            StructureSearchResult target = world.locateNearestStructure(
+                    new Location(world, 2, 161, 2), Structure.DESERT_PYRAMID, 50, false);
+            if (target == null || target.getStructure() != Structure.DESERT_PYRAMID) {
+                throw new IllegalStateException("Map has no verified pyramid target");
+            }
+            int targetX = target.getLocation().getBlockX();
+            int targetZ = target.getLocation().getBlockZ();
+            if (view.getWorld() != world || view.getScale() != MapView.Scale.CLOSEST
+                    || view.getCenterX() != Math.floorDiv(targetX + 64, 128) * 128
+                    || view.getCenterZ() != Math.floorDiv(targetZ + 64, 128) * 128) {
+                throw new IllegalStateException("Map data does not cover the verified pyramid at " + target.getLocation());
+            }
+            result += " mapId=" + view.getId() + " targetX=" + targetX + " targetZ=" + targetZ
+                    + " centerX=" + view.getCenterX() + " centerZ=" + view.getCenterZ();
+        }
+        sender.sendMessage(result);
+    }
+
+    private void requireTreasureDestination(String destination) {
+        if (!List.of("blocked", "disabled", "found", "mixed").contains(destination)) {
+            throw new IllegalArgumentException("Unknown treasure map destination: " + destination);
+        }
+    }
+
     private void lifecycleStatus(CommandSender sender) throws Exception {
         World world = Bukkit.getWorld(COMMAND_KEY);
         Path storage = WorldCreatorCompat.persistentLevelRoot(COMMAND_KEY).toPath();
@@ -282,11 +489,11 @@ public final class NativeLifecycleFixture extends JavaPlugin implements WorldRun
     }
 
     public boolean regionized() {
-        return false;
+        return J.isFolia();
     }
 
     public boolean primaryThread() {
-        return Bukkit.isPrimaryThread();
+        return J.isFolia() ? Bukkit.isGlobalTickThread() : Bukkit.isPrimaryThread();
     }
 
     public CompletableFuture<Void> runGlobal(Runnable task) {
@@ -299,10 +506,10 @@ public final class NativeLifecycleFixture extends JavaPlugin implements WorldRun
                 result.completeExceptionally(failure);
             }
         };
-        if (Bukkit.isPrimaryThread()) {
+        if (primaryThread()) {
             wrapped.run();
-        } else {
-            Bukkit.getScheduler().runTask(this, wrapped);
+        } else if (!J.runGlobal(wrapped)) {
+            result.completeExceptionally(new IllegalStateException("Could not schedule fixture task"));
         }
         return result;
     }

adapters/bukkit/plugin/src/test/gameplay/native-lifecycle-fixture/src/art/arcane/iris/fixture/TreasureLootChecks.java

@@ -0,0 +1,259 @@
+package art.arcane.iris.fixture;
+
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.platform.bukkit.BukkitBlockResolution;
+import art.arcane.iris.platform.generation.EngineBukkitOps;
+import art.arcane.iris.world.IrisToolbelt;
+import art.arcane.iris.world.loot.InventorySlotType;
+import art.arcane.iris.world.loot.IrisVanillaLootTable;
+import art.arcane.iris.world.loot.IrisLootTable;
+import art.arcane.volmlib.util.collection.KList;
+import art.arcane.volmlib.util.mantle.runtime.MantleChunk;
+import art.arcane.iris.world.task.J;
+import art.arcane.volmlib.util.matter.Matter;
+import io.papermc.paper.event.world.StructuresLocateEvent;
+import io.papermc.paper.event.server.ServerResourcesReloadedEvent;
+import io.papermc.paper.math.Position;
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.Material;
+import org.bukkit.NamespacedKey;
+import org.bukkit.World;
+import org.bukkit.block.Block;
+import org.bukkit.block.Container;
+import org.bukkit.block.Chest;
+import org.bukkit.command.CommandSender;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.world.LootGenerateEvent;
+import org.bukkit.generator.structure.Structure;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.plugin.java.JavaPlugin;
+import org.bukkit.util.StructureSearchResult;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Proxy;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public final class TreasureLootChecks implements Listener {
+    private static final NamespacedKey WORLD_KEY = new NamespacedKey("iris", "treasure_map_probe");
+    private static final List<String> CHESTS = List.of(
+            "CHEST", "COPPER_CHEST", "EXPOSED_COPPER_CHEST", "WEATHERED_COPPER_CHEST",
+            "OXIDIZED_COPPER_CHEST", "WAXED_COPPER_CHEST", "WAXED_EXPOSED_COPPER_CHEST",
+            "WAXED_WEATHERED_COPPER_CHEST", "WAXED_OXIDIZED_COPPER_CHEST");
+    private final IrisVanillaLootTable reloadTable = new IrisVanillaLootTable("iris_qa:reload");
+    private final AtomicInteger resourceReloads = new AtomicInteger();
+    private LocateAction locateAction = LocateAction.PASS;
+    private int locateEvents;
+    private int lootEvents;
+    private boolean lootEventsOwned = true;
+
+    public TreasureLootChecks(JavaPlugin plugin) {
+        Bukkit.getPluginManager().registerEvents(this, plugin);
+    }
+
+    public void verify(CommandSender sender) {
+        World world = requireWorld();
+        verifyCopperLoot(world);
+        sender.sendMessage("TREASURE_COPPER_LOOT variants=8 normal=true diamonds=1");
+        verifyInventoryRollback(world);
+        sender.sendMessage("TREASURE_LOOT_ROLLBACK contents=true nativeTable=true seed=true retry=true");
+        verifyLocateEvents(world);
+        sender.sendMessage("TREASURE_LOCATE_EVENTS cancelled=true replaced=true calls=2");
+        sender.sendMessage("TREASURE_EXTRA_CHECK variants=9 rollback=true locateEvents=true");
+    }
+
+    public void verifyRegion(CommandSender sender) {
+        World world = requireWorld();
+        if (!J.isOwnedByCurrentRegion(world, 0, 0)) {
+            throw new IllegalStateException("Fixture does not own its loot region");
+        }
+        lootEvents = 0;
+        lootEventsOwned = true;
+        verifyCopperLoot(world);
+        if (lootEvents != CHESTS.size() || !lootEventsOwned) {
+            throw new IllegalStateException("Loot event ownership failed: count=" + lootEvents
+                    + " owned=" + lootEventsOwned);
+        }
+        sender.sendMessage("TREASURE_REGION_LOOT copper=8 normal=1 events=" + lootEvents
+                + " owned=true folia=" + J.isFolia());
+    }
+
+    @EventHandler
+    public void onLoot(LootGenerateEvent event) {
+        if (event.getWorld().getKey().equals(WORLD_KEY) && event.isPlugin()) {
+            Location origin = event.getLootContext().getLocation();
+            lootEvents++;
+            lootEventsOwned &= J.isOwnedByCurrentRegion(event.getWorld(),
+                    origin.getBlockX() >> 4, origin.getBlockZ() >> 4);
+        }
+    }
+
+    public void verifyReload(CommandSender sender, boolean reloaded) {
+        World world = requireWorld();
+        Material expected = reloaded ? Material.EMERALD : Material.DIAMOND;
+        Collection<ItemStack> items = reloadTable.getLoot(
+                false, 783L, InventorySlotType.STORAGE, world, 2, 161, 2);
+        if (items.size() != 1 || items.iterator().next().getType() != expected) {
+            throw new IllegalStateException("Reloaded loot did not contain " + expected + ": " + items);
+        }
+        sender.sendMessage("TREASURE_RELOAD material=" + expected);
+    }
+
+    public void reportResourceReloads(CommandSender sender) {
+        sender.sendMessage("TREASURE_RESOURCES revision=" + resourceReloads.get());
+    }
+
+    @EventHandler
+    public void onResourcesReloaded(ServerResourcesReloadedEvent event) {
+        resourceReloads.incrementAndGet();
+    }
+
+    @EventHandler
+    public void onLocate(StructuresLocateEvent event) {
+        if (!event.getWorld().getKey().equals(WORLD_KEY) || locateAction == LocateAction.PASS) {
+            return;
+        }
+        locateEvents++;
+        if (locateAction == LocateAction.CANCEL) {
+            event.setCancelled(true);
+        } else {
+            event.setResult(new StructuresLocateEvent.Result(Position.block(123, 100, 456), Structure.DESERT_PYRAMID));
+        }
+    }
+
+    private void verifyCopperLoot(World world) {
+        Engine engine = IrisToolbelt.access(world).getEngine();
+        Block block = world.getBlockAt(4, 161, 4);
+        MantleChunk<Matter> mantle = engine.getMantle().getMantle().useChunk(block.getChunk());
+        try {
+            for (String name : CHESTS) {
+                block.setType(Material.AIR, false);
+                block.setType(Material.valueOf(name), false);
+                if (!BukkitBlockResolution.isStorageChest(block.getBlockData())) {
+                    throw new IllegalStateException("Chest is excluded from Iris loot: " + name);
+                }
+                EngineBukkitOps.update(engine, 4, 161, 4, block.getChunk(), mantle);
+                Container chest = (Container) block.getState();
+                int diamonds = 0;
+                for (ItemStack item : chest.getInventory().getContents()) {
+                    if (item == null) {
+                        continue;
+                    }
+                    if (item.getType() != Material.DIAMOND) {
+                        throw new IllegalStateException("Unexpected " + name + " loot: " + item);
+                    }
+                    diamonds += item.getAmount();
+                }
+                if (diamonds != 1) {
+                    throw new IllegalStateException(name + " contains " + diamonds + " diamonds");
+                }
+            }
+        } finally {
+            mantle.release();
+        }
+    }
+
+    private void verifyInventoryRollback(World world) {
+        Engine engine = IrisToolbelt.access(world).getEngine();
+        Block block = world.getBlockAt(6, 161, 4);
+        block.setType(Material.AIR, false);
+        block.setType(Material.CHEST, false);
+        Chest chest = (Chest) block.getState();
+        chest.getBlockInventory().setItem(0, new ItemStack(Material.EMERALD, 3));
+        chest = (Chest) block.getState();
+        NamespacedKey key = new NamespacedKey("iris_qa", "reload");
+        chest.setLootTable(Bukkit.getLootTable(key));
+        chest.setSeed(913L);
+        if (!chest.update(true, false)) {
+            throw new IllegalStateException("Could not set native loot for rollback check");
+        }
+        Inventory inventory = chest.getBlockInventory();
+        IllegalStateException injected = new IllegalStateException("Fixture insertion interruption");
+        Inventory interrupted = (Inventory) Proxy.newProxyInstance(Inventory.class.getClassLoader(),
+                new Class<?>[]{Inventory.class}, (proxy, method, arguments) -> {
+                    Object result;
+                    try {
+                        result = method.invoke(inventory, arguments);
+                    } catch (InvocationTargetException failure) {
+                        throw failure.getCause();
+                    }
+                    if (method.getName().equals("addItem")) {
+                        throw injected;
+                    }
+                    return result;
+                });
+        KList<IrisLootTable> tables = new KList<>();
+        tables.add(new IrisVanillaLootTable("iris_qa:reload"));
+        try {
+            EngineBukkitOps.addItems(engine, false, interrupted, tables, InventorySlotType.STORAGE,
+                    world, 6, 161, 4);
+            throw new IllegalStateException("Interrupted insertion did not fail");
+        } catch (IllegalStateException failure) {
+            if (failure != injected) {
+                throw failure;
+            }
+        }
+        Chest restored = (Chest) block.getState();
+        if (restored.getLootTable() == null || !restored.getLootTable().getKey().equals(key)
+                || restored.getSeed() != 913L) {
+            throw new IllegalStateException("Rollback lost the native loot table or seed");
+        }
+        ItemStack existing = restored.getSnapshotInventory().getItem(0);
+        if (existing == null || existing.getType() != Material.EMERALD || existing.getAmount() != 3) {
+            throw new IllegalStateException("Rollback lost the original contents: " + existing);
+        }
+        EngineBukkitOps.addItems(engine, false, restored.getBlockInventory(), tables, InventorySlotType.STORAGE,
+                world, 6, 161, 4);
+        int diamonds = 0;
+        int emeralds = 0;
+        for (ItemStack item : restored.getBlockInventory().getContents()) {
+            if (item == null) {
+                continue;
+            }
+            if (item.getType() == Material.DIAMOND) {
+                diamonds += item.getAmount();
+            } else if (item.getType() == Material.EMERALD) {
+                emeralds += item.getAmount();
+            }
+        }
+        if (diamonds != 2 || emeralds != 3 || ((Chest) block.getState()).getLootTable() != null) {
+            throw new IllegalStateException("Loot retry failed: diamonds=" + diamonds + " emeralds=" + emeralds);
+        }
+    }
+
+    private void verifyLocateEvents(World world) {
+        Location origin = new Location(world, 2, 161, 2);
+        locateEvents = 0;
+        try {
+            locateAction = LocateAction.CANCEL;
+            if (world.locateNearestStructure(origin, Structure.DESERT_PYRAMID, 50, false) != null) {
+                throw new IllegalStateException("Cancelled structure search returned a target");
+            }
+            locateAction = LocateAction.REPLACE;
+            StructureSearchResult result = world.locateNearestStructure(origin, Structure.DESERT_PYRAMID, 50, false);
+            if (result == null || result.getStructure() != Structure.DESERT_PYRAMID
+                    || result.getLocation().getBlockX() != 123 || result.getLocation().getBlockY() != 100
+                    || result.getLocation().getBlockZ() != 456 || locateEvents != 2) {
+                throw new IllegalStateException("Structure search ignored event result: " + result);
+            }
+        } finally {
+            locateAction = LocateAction.PASS;
+        }
+    }
+
+    private World requireWorld() {
+        World world = Bukkit.getWorld(WORLD_KEY);
+        if (world == null || !IrisToolbelt.isIrisWorld(world)) {
+            throw new IllegalStateException("Treasure map fixture world is absent");
+        }
+        return world;
+    }
+
+    private enum LocateAction {
+        PASS, CANCEL, REPLACE
+    }
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/loot_table/blocked.json

@@ -0,0 +1,33 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:map",
+          "functions": [
+            {
+              "destination": "iris_qa:blocked",
+              "decoration": "minecraft:red_x",
+              "zoom": 0,
+              "search_radius": 50,
+              "skip_existing_chunks": false,
+              "function": "minecraft:exploration_map"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/loot_table/disabled.json

@@ -0,0 +1,33 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:map",
+          "functions": [
+            {
+              "destination": "iris_qa:disabled",
+              "decoration": "minecraft:red_x",
+              "zoom": 0,
+              "search_radius": 50,
+              "skip_existing_chunks": false,
+              "function": "minecraft:exploration_map"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/loot_table/found.json

@@ -0,0 +1,33 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:map",
+          "functions": [
+            {
+              "destination": "iris_qa:found",
+              "decoration": "minecraft:red_x",
+              "zoom": 0,
+              "search_radius": 50,
+              "skip_existing_chunks": false,
+              "function": "minecraft:exploration_map"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/loot_table/mixed.json

@@ -0,0 +1,33 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:map",
+          "functions": [
+            {
+              "destination": "iris_qa:mixed",
+              "decoration": "minecraft:red_x",
+              "zoom": 0,
+              "search_radius": 50,
+              "skip_existing_chunks": false,
+              "function": "minecraft:exploration_map"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/loot_table/reload.json

@@ -0,0 +1,14 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/tags/worldgen/structure/blocked.json

@@ -0,0 +1,5 @@
+{
+  "values": [
+    "minecraft:buried_treasure"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/tags/worldgen/structure/disabled.json

@@ -0,0 +1,5 @@
+{
+  "values": [
+    "minecraft:mansion"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/tags/worldgen/structure/found.json

@@ -0,0 +1,5 @@
+{
+  "values": [
+    "minecraft:desert_pyramid"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/data/iris_qa/tags/worldgen/structure/mixed.json

@@ -0,0 +1,6 @@
+{
+  "values": [
+    "minecraft:buried_treasure",
+    "minecraft:desert_pyramid"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack-26.2/pack.mcmeta

@@ -0,0 +1,13 @@
+{
+  "pack": {
+    "description": "Treasure map gameplay fixtures",
+    "min_format": [
+      107,
+      1
+    ],
+    "max_format": [
+      107,
+      1
+    ]
+  }
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/loot_table/blocked.json

@@ -0,0 +1,31 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:filled_map",
+          "modifier": {
+            "destination": "#iris_qa:blocked",
+            "decoration": "minecraft:red_x",
+            "zoom": 0,
+            "search_radius": 50,
+            "skip_existing_chunks": false,
+            "type": "minecraft:exploration_map"
+          }
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/loot_table/disabled.json

@@ -0,0 +1,31 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:filled_map",
+          "modifier": {
+            "destination": "#iris_qa:disabled",
+            "decoration": "minecraft:red_x",
+            "zoom": 0,
+            "search_radius": 50,
+            "skip_existing_chunks": false,
+            "type": "minecraft:exploration_map"
+          }
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/loot_table/found.json

@@ -0,0 +1,31 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:filled_map",
+          "modifier": {
+            "destination": "#iris_qa:found",
+            "decoration": "minecraft:red_x",
+            "zoom": 0,
+            "search_radius": 50,
+            "skip_existing_chunks": false,
+            "type": "minecraft:exploration_map"
+          }
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/loot_table/mixed.json

@@ -0,0 +1,31 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:filled_map",
+          "modifier": {
+            "destination": "#iris_qa:mixed",
+            "decoration": "minecraft:red_x",
+            "zoom": 0,
+            "search_radius": 50,
+            "skip_existing_chunks": false,
+            "type": "minecraft:exploration_map"
+          }
+        }
+      ]
+    },
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/loot_table/reload.json

@@ -0,0 +1,14 @@
+{
+  "type": "minecraft:chest",
+  "pools": [
+    {
+      "rolls": 1,
+      "entries": [
+        {
+          "type": "minecraft:item",
+          "name": "minecraft:diamond"
+        }
+      ]
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/tags/worldgen/structure/blocked.json

@@ -0,0 +1,5 @@
+{
+  "values": [
+    "minecraft:buried_treasure"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/tags/worldgen/structure/disabled.json

@@ -0,0 +1,5 @@
+{
+  "values": [
+    "minecraft:mansion"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/tags/worldgen/structure/found.json

@@ -0,0 +1,5 @@
+{
+  "values": [
+    "minecraft:desert_pyramid"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/data/iris_qa/tags/worldgen/structure/mixed.json

@@ -0,0 +1,6 @@
+{
+  "values": [
+    "minecraft:buried_treasure",
+    "minecraft:desert_pyramid"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-datapack/pack.mcmeta

@@ -0,0 +1,13 @@
+{
+  "pack": {
+    "description": "Treasure map gameplay fixtures",
+    "min_format": [
+      121,
+      0
+    ],
+    "max_format": [
+      121,
+      0
+    ]
+  }
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-pack/biomes/flat.json

@@ -0,0 +1,32 @@
+{
+  "name": "Flat",
+  "derivative": "minecraft:plains",
+  "vanillaDerivative": "minecraft:plains",
+  "layers": [
+    {
+      "minHeight": 1,
+      "maxHeight": 1,
+      "palette": [
+        {
+          "block": "minecraft:lime_wool"
+        }
+      ]
+    },
+    {
+      "minHeight": 384,
+      "maxHeight": 384,
+      "palette": [
+        {
+          "block": "minecraft:green_concrete"
+        }
+      ]
+    }
+  ],
+  "generators": [
+    {
+      "generator": "flat",
+      "min": 96,
+      "max": 96
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-pack/dimensions/treasure-map-fixture.json

@@ -0,0 +1,64 @@
+{
+  "name": "Treasure Map Fixture",
+  "version": 1,
+  "mode": {
+    "type": "OVERWORLD"
+  },
+  "regions": [
+    "flat"
+  ],
+  "focusRegion": "flat",
+  "focus": "flat",
+  "landChance": 1,
+  "environment": "NORMAL",
+  "dimensionHeight": {
+    "min": -64,
+    "max": 320
+  },
+  "logicalHeight": 384,
+  "fluidHeight": 0,
+  "bedrock": false,
+  "rockPalette": {
+    "palette": [
+      {
+        "block": "minecraft:red_concrete"
+      }
+    ]
+  },
+  "importedStructures": {
+    "disabled": [
+      "minecraft:"
+    ]
+  },
+  "structures": [
+    {
+      "placementId": "blocked-treasure",
+      "nativeStructures": [
+        {
+          "structure": "minecraft:buried_treasure"
+        }
+      ],
+      "distribution": "RANDOM_SPREAD",
+      "spacing": 1,
+      "separation": 0,
+      "minHeight": 0,
+      "maxHeight": 0
+    },
+    {
+      "placementId": "reachable-pyramid",
+      "nativeStructures": [
+        {
+          "structure": "minecraft:desert_pyramid"
+        }
+      ],
+      "distribution": "RANDOM_SPREAD",
+      "spacing": 16,
+      "separation": 4
+    }
+  ],
+  "loot": {
+    "tables": [
+      "fixture-diamond"
+    ]
+  }
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-pack/generators/flat.json

@@ -0,0 +1,15 @@
+{
+  "interpolator": {
+    "function": "NONE",
+    "horizontalScale": 1
+  },
+  "seed": 310,
+  "composite": [
+    {
+      "seed": 310,
+      "style": {
+        "style": "FLAT"
+      }
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-pack/loot/fixture-diamond.json

@@ -0,0 +1,15 @@
+{
+  "name": "Fixture Diamond",
+  "rarity": 1,
+  "minPicked": 1,
+  "maxPicked": 1,
+  "maxTries": 1,
+  "loot": [
+    {
+      "type": "diamond",
+      "rarity": 1,
+      "minAmount": 1,
+      "maxAmount": 1
+    }
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-map-pack/regions/flat.json

@@ -0,0 +1,12 @@
+{
+  "name": "Flat",
+  "landBiomes": [
+    "flat"
+  ],
+  "seaBiomes": [
+    "flat"
+  ],
+  "shoreBiomes": [
+    "flat"
+  ]
+}

adapters/bukkit/plugin/src/test/gameplay/treasure-maps.mjs

@@ -0,0 +1,211 @@
+import { readFile, writeFile } from 'node:fs/promises'
+import path from 'node:path'
+
+const simplifyNbt = value => {
+  if (Array.isArray(value)) return value.map(simplifyNbt)
+  if (value === null || typeof value !== 'object') return value
+  if ('type' in value && 'value' in value) return simplifyNbt(value.value)
+  return Object.fromEntries(Object.entries(value).map(([key, entry]) => [key, simplifyNbt(entry)]))
+}
+
+const completeClientTicks = context => {
+  const client = context.bot._client
+  context.expect(context.bot.supportFeature('sendsClientTickEndPacket'), 'Fixture client supports tick delimiters')
+  let tickTimer
+  const finishTick = () => {
+    clearTimeout(tickTimer)
+    client.write('tick_end', {})
+    tickTimer = setTimeout(finishTick, 50)
+  }
+  context.bot.on('move', finishTick)
+  finishTick()
+  context.signal.addEventListener('abort', () => {
+    clearTimeout(tickTimer)
+    context.bot.removeListener('move', finishTick)
+  }, { once: true })
+}
+
+export default {
+  name: 'iris-treasure-maps',
+  description: 'Verify exploration-map targets, bounded misses, retained loot, and normal/copper storage on Iris.',
+  async run(context) {
+    completeClientTicks(context)
+    context.bot.physicsEnabled = false
+    context.bot.clearControlStates()
+    context.bot.entity.velocity.set(0, 0, 0)
+    const source = await readFile(path.join(context.server.directory, '.server-source'), 'utf8')
+    context.expect(/^isolated=true\s*$/m.test(source), 'Treasure map fixtures require an isolated instance')
+    const command = async (operation, expected, timeoutMs = 30000) => {
+      const token = expected.split(' ')[0]
+      const response = await context.command(`/irislifecycle ${operation}`,
+        new RegExp(`${token}|NATIVE_FAILED|TREASURE_.*_FAILED`), timeoutMs)
+      context.expect(response.includes(expected), response)
+      return response
+    }
+    const bounded = (label, action) => context.waitUntil(async () => {
+      await action()
+      return true
+    }, { label, timeoutMs: 10000 })
+    let lastActivation = 0
+    const openChest = async material => {
+      const position = context.bot.entity.position.clone().set(2, 161, 2)
+      await context.waitUntil(() => context.bot.blockAt(position)?.name === material, {
+        label: `${material} reached the client`, timeoutMs: 10000
+      })
+      const delay = 150 - (performance.now() - lastActivation)
+      if (delay > 0) await context.sleep(delay)
+      const opened = context.waitForEvent('windowOpen', undefined, 30000)
+      await bounded(`Activate ${material}`, () => context.bot.activateBlock(context.bot.blockAt(position)))
+      lastActivation = performance.now()
+      const [window] = await opened
+      return window
+    }
+    const chestItems = window => window.slots.slice(0, window.inventoryStart).filter(Boolean)
+    const mapId = item => item.componentMap?.get('map_id')?.data
+    let missItem
+    await context.step('create and enter the Iris treasure map world', async () => {
+      const response = await command('treasure-map-create', 'TREASURE_MAP_READY world=iris:treasure_map_probe', 180000)
+      const version = response.match(/version=(\S+)/)?.[1]
+      context.expect(/^26\.[23](?:[.-]|$)/.test(version ?? ''), 'Fixture requires its matching 26.2 or 26.3 data pack', { version })
+      missItem = version.startsWith('26.2') ? 'map' : 'filled_map'
+      context.report.treasurePlatform = { version, folia: response.includes('folia=true'), missItem }
+      await context.waitUntil(() => context.bot.entity.position.distanceTo(
+        context.bot.entity.position.clone().set(0.5, 161, 0.5)
+      ) < 2, { label: 'Fixture teleport reached the client', timeoutMs: 30000 })
+    })
+    await context.step('confirm the missing target exhausts the placement search budget', async () => {
+      await command('treasure-map-limit', 'TREASURE_MAP_LIMIT status=SEARCH_LIMIT_REACHED', 120000)
+    })
+    for (const material of ['chest', 'copper_chest']) {
+      for (const destination of ['blocked', 'disabled', 'found', 'mixed']) {
+        await context.step(`open ${material} with ${destination} map target and retain all loot`, async () => {
+          const evidence = { destination, material, phase: 'prepare' }
+          context.report.treasureMaps ??= []
+          context.report.treasureMaps.push(evidence)
+          const located = destination === 'found' || destination === 'mixed'
+          const mapName = located ? 'filled_map' : missItem
+          await command(`treasure-map-chest ${destination} ${material.toUpperCase()}`,
+            `TREASURE_MAP_CHEST destination=${destination} material=${material.toUpperCase()}`)
+          evidence.phase = 'open'
+          const window = await openChest(material)
+          evidence.windowType = window.type
+          evidence.inventoryStart = window.inventoryStart
+          let targetId
+          let diamondType
+          let diamondsBefore
+          let marker
+          let verified
+          try {
+            await context.waitUntil(() => {
+              const items = chestItems(window)
+              return items.some(item => item.name === mapName) && items.some(item => item.name === 'diamond')
+            }, { label: `${destination} chest contains map and diamond`, timeoutMs: 30000 })
+            const items = chestItems(window)
+            const map = items.find(item => item.name === mapName)
+            const diamond = items.find(item => item.name === 'diamond')
+            targetId = mapId(map)
+            context.expect(items.length === 2 && map.count === 1 && diamond.count === 1,
+              'Loot table must produce exactly one map and one diamond')
+            context.expect((targetId !== undefined) === located, 'Only reachable destinations receive map data', {
+              destination, components: map.components
+            })
+            const response = await command(`treasure-map-inspect ${destination}`,
+              `TREASURE_MAP_INSPECT destination=${destination} diamonds=1 located=${located}`, 120000)
+            verified = Object.fromEntries([...response.matchAll(/(mapId|targetX|targetZ|centerX|centerZ)=(-?\d+)/g)]
+              .map(([, key, value]) => [key, Number(value)]))
+            const decorations = simplifyNbt(map.componentMap?.get('map_decorations')?.data)
+            marker = decorations?.['+']
+            if (located) {
+              context.expect(targetId === verified.mapId, 'Client and saved map IDs agree', { targetId, verified })
+              context.expect(marker?.type === 'minecraft:red_x'
+                && marker.x === verified.targetX && marker.z === verified.targetZ,
+              'Map marker points to the verified pyramid', { marker, verified, components: map.components })
+            } else {
+              context.expect(marker === undefined, 'Missing destinations must not invent a map marker', { decorations })
+            }
+            diamondType = diamond.type
+            diamondsBefore = context.bot.inventory.count(diamondType)
+            evidence.phase = 'withdraw'
+            evidence.diamondSlot = diamond.slot
+            await bounded(`Withdraw diamond from ${material} ${destination}`,
+              () => context.bot.clickWindow(diamond.slot, 0, 1))
+            evidence.phase = 'withdrawn'
+            await context.waitUntil(() => chestItems(window).every(item => item.name !== 'diamond'), {
+              label: 'Diamond transferred out of the chest', timeoutMs: 10000
+            })
+          } finally {
+            context.bot.closeWindow(window)
+          }
+          evidence.phase = 'reopen'
+          const reopened = await openChest(material)
+          try {
+            await context.waitUntil(() => chestItems(reopened).some(item => item.name === mapName), {
+              label: 'Saved map remains in the reopened chest', timeoutMs: 10000
+            })
+            const retained = chestItems(reopened)
+            context.expect(retained.length === 1 && retained[0].name === mapName && retained[0].count === 1,
+              'Reopening must not regenerate chest loot')
+            context.expect(mapId(retained[0]) === targetId, 'Reopening must retain the same map data')
+            context.expect(JSON.stringify(simplifyNbt(retained[0].componentMap?.get('map_decorations')?.data)?.['+'])
+              === JSON.stringify(marker), 'Reopening must retain the same destination marker')
+            await context.waitUntil(() => context.bot.inventory.count(diamondType) === diamondsBefore + 1, {
+              label: 'Chest awards exactly one diamond', timeoutMs: 10000
+            })
+            Object.assign(evidence, { phase: 'complete', mapItem: mapName,
+              mapId: targetId ?? null, marker: marker ?? null, verified, reopened: true })
+          } finally {
+            context.bot.closeWindow(reopened)
+          }
+        })
+      }
+    }
+    await context.step('verify storage variants, insertion rollback, and locate event results', async () => {
+      await command('treasure-extra-check', 'TREASURE_EXTRA_CHECK variants=9 rollback=true locateEvents=true', 120000)
+    })
+    await context.step('verify plugin loot runs on its owning region', async () => {
+      await command('treasure-region-check', 'TREASURE_REGION_LOOT copper=8 normal=1 events=9 owned=true', 120000)
+    })
+    await context.step('verify native loot table reload support', async () => {
+      await command('treasure-reload-before', 'TREASURE_RELOAD material=DIAMOND')
+      if (context.report.treasurePlatform.folia) {
+        const response = await context.command('/minecraft:reload', /Unknown or incomplete command|Reloading/i, 10000)
+        context.expect(response.includes('Unknown or incomplete command'),
+          'Folia fixture expects its unavailable data pack reload command', { response })
+        context.report.treasureReload = { status: 'unavailable', before: 'diamond', evidence: response }
+        return
+      }
+      const properties = await readFile(path.join(context.server.directory, 'server.properties'), 'utf8')
+      const levelName = properties.match(/^level-name=(.+)$/m)?.[1].trim() ?? 'world'
+      const tablePath = path.join(context.server.directory, levelName, 'datapacks', 'iris_treasure',
+        'data', 'iris_qa', 'loot_table', 'reload.json')
+      const original = await readFile(tablePath, 'utf8')
+      const replacement = JSON.parse(original)
+      context.expect(replacement.pools[0].entries[0].name === 'minecraft:diamond',
+        'Reload fixture must start with its diamond table')
+      const revision = async () => {
+        const response = await command('treasure-resources', 'TREASURE_RESOURCES revision=')
+        return Number(response.match(/revision=(\d+)/)?.[1])
+      }
+      const reload = async () => {
+        const before = await revision()
+        await context.command('/minecraft:reload', /Reloading/i, 30000)
+        await context.waitUntil(async () => await revision() > before, {
+          label: 'Server resource reload completed', timeoutMs: 120000, intervalMs: 500
+        })
+      }
+      replacement.pools[0].entries[0].name = 'minecraft:emerald'
+      try {
+        await writeFile(tablePath, `${JSON.stringify(replacement, null, 2)}\n`)
+        await reload()
+        await command('treasure-reload-after', 'TREASURE_RELOAD material=EMERALD')
+        context.report.treasureReload = { status: 'passed', before: 'diamond', after: 'emerald' }
+      } finally {
+        await writeFile(tablePath, original)
+        if (!context.signal.aborted) {
+          await reload()
+          await command('treasure-reload-before', 'TREASURE_RELOAD material=DIAMOND')
+        }
+      }
+    })
+  }
+}

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

@@ -30,7 +30,6 @@ import art.arcane.iris.studio.view.PregeneratorJob;
 import art.arcane.iris.integration.Identifier;
 import art.arcane.iris.generation.cache.Cache;
 import art.arcane.iris.generation.runtime.Engine;
-import art.arcane.iris.generation.runtime.GenerationFailures;
 import art.arcane.iris.generation.block.TileData;
 import art.arcane.iris.modded.IrisModdedChunkGenerator;
 import art.arcane.iris.modded.ModdedBlockResolution;
@@ -382,16 +381,7 @@ public final class ModdedChunkUpdateService implements ModdedTickableService {
             if (!state.isStorageChest()) {
                 return;
             }
-            try {
-                ModdedLootApplier.apply(engine, level, pos, state, chunk);
-            } catch (SavedBiomeUnavailableException unavailable) {
-                GenerationFailures.rethrowEngineFailure(unavailable);
-                IrisLogging.warnOnce("chunk-update-loot:" + level.name() + ":" + unavailable.getMessage(),
-                        "Iris left the container at " + pos + " in " + level.name() + " without loot: " + unavailable.getMessage());
-            } catch (Throwable e) {
-                GenerationFailures.rethrowEngineFailure(e);
-                IrisLogging.reportError(e);
-            }
+            ModdedLootApplier.apply(engine, level, pos, state, chunk);
         } else {
             NativeWorldMaintenance.refresh(level, pos);
         }

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

@@ -8,9 +8,12 @@ import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
 import art.arcane.volmlib.util.hunk.Hunk;
 
 import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
 import net.minecraft.server.Bootstrap;
+import net.minecraft.world.RandomizableContainer;
 import net.minecraft.world.level.block.Block;
 import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.block.SpeleothemBlock;
 import net.minecraft.world.level.block.state.properties.SpeleothemThickness;
 import org.junit.BeforeClass;
@@ -62,6 +65,42 @@ public class ModdedBlockResolutionContractTest {
         assertEquals(Blocks.OAK_LOG, state.handle().getBlock());
     }
 
+    @Test
+    public void copperChestVariantsReceiveIrisLootAndPostLoadUpdates() {
+        for (String key : new String[]{"copper_chest", "exposed_copper_chest", "weathered_copper_chest",
+                "oxidized_copper_chest", "waxed_copper_chest", "waxed_exposed_copper_chest",
+                "waxed_weathered_copper_chest", "waxed_oxidized_copper_chest"}) {
+            ModdedBlockState state = ModdedBlockResolution.BLOCKS.getOrNull("minecraft:" + key);
+            assertNotNull(key, state);
+            assertTrue(key, state.isStorage());
+            assertTrue(key, state.isStorageChest());
+            assertTrue(key, NativeBlockProperties.isUpdatable(state.handle()));
+            assertTrue(key, ((EntityBlock) state.handle().getBlock()).newBlockEntity(BlockPos.ZERO, state.handle())
+                    instanceof RandomizableContainer);
+        }
+    }
+
+    @Test
+    public void lootContainerClassificationPreservesExistingContainerBoundaries() {
+        for (String key : new String[]{"chest", "trapped_chest", "barrel", "shulker_box",
+                "blue_shulker_box", "dispenser", "dropper", "hopper"}) {
+            ModdedBlockState state = ModdedBlockResolution.BLOCKS.getOrNull("minecraft:" + key);
+            assertNotNull(key, state);
+            assertTrue(key, state.isStorage());
+            assertTrue(key, state.isStorageChest());
+        }
+        for (Block block : new Block[]{Blocks.FURNACE, Blocks.BLAST_FURNACE, Blocks.SMOKER}) {
+            assertTrue(block.toString(), NativeBlockProperties.isStorage(block.defaultBlockState()));
+            assertFalse(block.toString(), NativeBlockProperties.isStorageChest(block.defaultBlockState()));
+        }
+        for (String key : new String[]{"stone", "air", "ender_chest", "copper_block"}) {
+            ModdedBlockState state = ModdedBlockResolution.BLOCKS.getOrNull("minecraft:" + key);
+            assertNotNull(key, state);
+            assertFalse(key, state.isStorage());
+            assertFalse(key, state.isStorageChest());
+        }
+    }
+
     @Test
     public void cactusPlacementRequiresNativeCactusSupport() {
         assertTrue(NativeBlockProperties.canPlaceOnto(Blocks.CACTUS, Blocks.CACTUS));

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

@@ -1,33 +1,64 @@
 package art.arcane.iris.modded;
 
-import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeContainerLoot;
-
 import art.arcane.iris.structure.placement.LootResolver;
 import art.arcane.iris.world.loot.IrisLootMode;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeContainerLoot;
+import art.arcane.volmlib.nativelib.minecraft26_2.modded.NativeItemStack;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockPoint;
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import art.arcane.volmlib.nativelib.terrain.NativeWorld;
 import art.arcane.volmlib.util.math.RNG;
-import net.minecraft.resources.Identifier;
-import net.minecraft.resources.ResourceKey;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.registries.Registries;
-import net.minecraft.world.RandomizableContainer;
-import net.minecraft.world.SimpleContainer;
-import net.minecraft.world.item.ItemStack;
-import net.minecraft.world.level.storage.loot.LootTable;
-import org.junit.Test;
-
+import java.lang.reflect.Proxy;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
-import java.lang.reflect.Proxy;
 import java.util.concurrent.atomic.AtomicBoolean;
+import net.minecraft.SharedConstants;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.component.DataComponentMap;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.Bootstrap;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.CompoundContainer;
+import net.minecraft.world.RandomizableContainer;
+import net.minecraft.world.SimpleContainer;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.ChestBlock;
+import net.minecraft.world.level.block.entity.ChestBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.properties.ChestType;
+import net.minecraft.world.level.storage.loot.LootTable;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.MockedStatic;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
 
 public class ModdedLootApplierTest {
+    @BeforeClass
+    public static void bootstrapMinecraftRegistries() {
+        SharedConstants.tryDetectVersion();
+        Bootstrap.bootStrap();
+        if (!Items.DIAMOND.builtInRegistryHolder().areComponentsBound()) {
+            Items.DIAMOND.builtInRegistryHolder().bindComponents(DataComponentMap.EMPTY);
+        }
+    }
+
     @Test
     public void addAppendsSourcesInOrder() {
         List<String> sources = new ArrayList<>(List.of("placement-native"));
@@ -171,6 +202,152 @@ public class ModdedLootApplierTest {
         assertTrue(NativeContainerLoot.hasNativeLootTable(nativeLoot));
     }
 
+    @Test
+    public void failedFillRestoresContentsAndDoesNotDuplicateLootOnRetry() {
+        RejectingContainer container = new RejectingContainer();
+        container.setItem(0, diamondStack(2));
+        assertEquals(2, container.getItem(0).getCount());
+        container.reject = true;
+        ItemStack reward = diamondStack(7);
+
+        assertThrows(IllegalStateException.class,
+                () -> NativeContainerLoot.fillContainer(container, List.of(reward), new RNG(17), message -> {}));
+
+        assertEquals(2, container.getItem(0).getCount());
+        assertTrue(container.getItem(1).isEmpty());
+        assertEquals(7, reward.getCount());
+        NativeContainerLoot.fillContainer(container, List.of(reward), new RNG(17), message -> {});
+        assertEquals(9, container.getItem(0).getCount() + container.getItem(1).getCount());
+        assertEquals(7, reward.getCount());
+    }
+
+    @Test
+    public void failedNativeUnpackRestoresTheLootTableSeedAndPriorContents() {
+        DeferredLootChest container = new DeferredLootChest(BlockPos.ZERO, Blocks.CHEST.defaultBlockState());
+        container.setItem(0, diamondStack(2));
+        container.reject = true;
+        ResourceKey<LootTable> table = ResourceKey.create(Registries.LOOT_TABLE, Identifier.parse("minecraft:chests/simple_dungeon"));
+        container.setLootTable(table, 41L);
+
+        assertThrows(IllegalStateException.class, () -> NativeContainerLoot.fillContainer(container,
+                List.of(new ItemStack(Items.DIAMOND)), new RNG(17), message -> {}));
+
+        assertSame(table, container.getLootTable());
+        assertEquals(41L, container.getLootTableSeed());
+        container.setLootTable(null);
+        assertEquals(2, container.getItem(0).getCount());
+        for (int slot = 1; slot < container.getContainerSize(); slot++) {
+            assertTrue(container.getItem(slot).isEmpty());
+        }
+    }
+
+    @Test
+    public void failedDoubleChestFillRestoresBothDeferredHalvesBeforeRetry() {
+        BlockPos leftPos = new BlockPos(0, 64, 0);
+        BlockPos rightPos = new BlockPos(1, 64, 0);
+        BlockState leftState = Blocks.CHEST.defaultBlockState().setValue(ChestBlock.TYPE, ChestType.LEFT);
+        BlockState rightState = Blocks.CHEST.defaultBlockState().setValue(ChestBlock.TYPE, ChestType.RIGHT);
+        DeferredLootChest left = new DeferredLootChest(leftPos, leftState);
+        DeferredLootChest right = new DeferredLootChest(rightPos, rightState);
+        left.setItem(0, diamondStack(2));
+        right.setItem(0, diamondStack(3));
+        right.reject = true;
+        ResourceKey<LootTable> table = ResourceKey.create(Registries.LOOT_TABLE, Identifier.parse("minecraft:chests/simple_dungeon"));
+        left.setLootTable(table, 41L);
+        right.setLootTable(table, 42L);
+        ServerLevel level = mock(ServerLevel.class);
+        NativeWorld world = mock(NativeWorld.class);
+        NativeBlockState state = mock(NativeBlockState.class);
+        when(world.nativeHandle()).thenReturn(level);
+        when(state.nativeHandle()).thenReturn(leftState);
+        when(level.getBlockEntity(leftPos)).thenReturn(left);
+        when(level.getBlockEntity(rightPos)).thenReturn(right);
+        CompoundContainer inventory = new CompoundContainer(left, right);
+        ItemStack reward = diamondStack(7);
+        try (MockedStatic<ChestBlock> chests = mockStatic(ChestBlock.class)) {
+            chests.when(() -> ChestBlock.getContainer((ChestBlock) Blocks.CHEST, leftState, level, leftPos, true))
+                    .thenReturn(inventory);
+            chests.when(() -> ChestBlock.getConnectedBlockPos(leftPos, leftState)).thenReturn(rightPos);
+            NativeContainerLoot access = new NativeContainerLoot(new NativeContainerLoot.Target(
+                    world, new NativeBlockPoint(0, 64, 0), state));
+            NativeContainerLoot.Session session = access.open();
+            assertNotNull(session);
+            session.add(List.of(NativeItemStack.of(reward)));
+
+            assertThrows(IllegalStateException.class, () -> session.fill(new RNG(17), message -> {}));
+
+            assertSame(table, left.getLootTable());
+            assertSame(table, right.getLootTable());
+            assertEquals(41L, left.getLootTableSeed());
+            assertEquals(42L, right.getLootTableSeed());
+            left.setLootTable(null);
+            right.setLootTable(null);
+            assertEquals(2, countItems(left));
+            assertEquals(3, countItems(right));
+            assertEquals(7, reward.getCount());
+            left.setLootTable(table, 41L);
+            right.setLootTable(table, 42L);
+            right.reject = false;
+
+            session.fill(new RNG(17), message -> {});
+
+            assertNull(left.getLootTable());
+            assertNull(right.getLootTable());
+            assertEquals(15, countItems(left) + countItems(right));
+            assertEquals(7, reward.getCount());
+        }
+    }
+
+    private static int countItems(ChestBlockEntity container) {
+        int total = 0;
+        for (int slot = 0; slot < container.getContainerSize(); slot++) {
+            total += container.getItem(slot).getCount();
+        }
+        return total;
+    }
+
+    private static ItemStack diamondStack(int count) {
+        ItemStack stack = new ItemStack(Items.DIAMOND, count);
+        stack.set(DataComponents.MAX_STACK_SIZE, 64);
+        return stack;
+    }
+
+    private static final class RejectingContainer extends SimpleContainer {
+        private boolean reject;
+
+        private RejectingContainer() {
+            super(2);
+        }
+
+        @Override
+        public void setItem(int slot, ItemStack stack) {
+            super.setItem(slot, stack);
+            if (reject) {
+                reject = false;
+                throw new IllegalStateException("Inventory write failed");
+            }
+        }
+    }
+
+    private static final class DeferredLootChest extends ChestBlockEntity {
+        private boolean reject;
+
+        private DeferredLootChest(BlockPos position, BlockState state) {
+            super(position, state);
+        }
+
+        @Override
+        public void unpackLootTable(Player player) {
+            if (getLootTable() != null) {
+                setLootTable(null);
+                setItem(0, diamondStack(4));
+                if (reject) {
+                    throw new IllegalStateException("Native loot failed");
+                }
+            }
+        }
+    }
+
     private RandomizableContainer containerWithLootTable(ResourceKey<LootTable> key) {
         return (RandomizableContainer) Proxy.newProxyInstance(
                 RandomizableContainer.class.getClassLoader(),

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

@@ -57,7 +57,6 @@ import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
-import static org.mockito.ArgumentMatchers.contains;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.inOrder;
@@ -171,7 +170,7 @@ public class ModdedChunkUpdateServiceTest {
     }
 
     @Test
-    public void permanentSavedBiomeUnavailabilityCompletesThePassWithAWarning() {
+    public void permanentSavedBiomeUnavailabilityRetainsPendingLoot() {
         ChestUpdateMantleChunk chunk = new ChestUpdateMantleChunk();
         Engine engine = updateEngine(chunk);
         NativeWorld level = chestLevel();
@@ -187,13 +186,46 @@ public class ModdedChunkUpdateServiceTest {
                 return null;
             });
 
-            new ModdedChunkUpdateService().updateRegeneratedChunk(engine, level, 0, 0);
+            assertThrows(SavedBiomeUnavailableException.class,
+                    () -> new ModdedChunkUpdateService().updateRegeneratedChunk(engine, level, 0, 0));
+
+            assertFalse(chunk.isFlagged(MantleFlag.ETCHED));
+            assertFalse(chunk.isFlagged(MantleFlag.UPDATE));
+            assertFalse(chunk.deleted());
+            verify(chunk.slice, never()).set(2, 5, 2, null);
+
+        }
+    }
+
+    @Test
+    public void ordinaryLootFailureRetainsPendingWorkAndRetries() {
+        ChestUpdateMantleChunk chunk = new ChestUpdateMantleChunk();
+        Engine engine = updateEngine(chunk);
+        NativeWorld level = chestLevel();
+        AtomicInteger attempts = new AtomicInteger();
+        ModdedChunkUpdateService service = new ModdedChunkUpdateService();
+        IllegalStateException failure = new IllegalStateException("Loot provider unavailable");
+        try (MockedStatic<ModdedLootApplier> loot = mockStatic(ModdedLootApplier.class)) {
+            loot.when(() -> ModdedLootApplier.apply(any(), any(), any(), any(), any())).thenAnswer(invocation -> {
+                NativeBlockPoint position = invocation.getArgument(2);
+                if (position.x() == 2 && attempts.getAndIncrement() == 0) {
+                    throw failure;
+                }
+                return null;
+            });
+
+            assertSame(failure, assertThrows(IllegalStateException.class,
+                    () -> service.updateRegeneratedChunk(engine, level, 0, 0)));
+            assertFalse(chunk.isFlagged(MantleFlag.UPDATE));
+            assertFalse(chunk.isFlagged(MantleFlag.ETCHED));
+            assertFalse(chunk.deleted());
+            verify(chunk.slice, never()).set(2, 5, 2, null);
+
+            service.updateRegeneratedChunk(engine, level, 0, 0);
 
             assertTrue(chunk.isFlagged(MantleFlag.ETCHED));
             assertTrue(chunk.deleted());
-            logging.verify(() -> IrisLogging.warnOnce(anyString(), contains(reason)));
-            logging.verify(() -> IrisLogging.reportError(any(Throwable.class)), never());
-            logging.verify(() -> IrisLogging.reportError(anyString(), any(Throwable.class)), never());
+            assertEquals(2, attempts.get());
         }
     }
 

core/src/main/java/art/arcane/iris/generation/runtime/WorldChunkMaintenance.java

@@ -289,6 +289,8 @@ final class WorldChunkMaintenance {
             boolean scheduled = J.runRegion(world, chunkX, chunkZ, manager.managedTask("bukkit_world_manager_chunk_update", () -> {
                 try {
                     updateChunkRegion(world, chunkX, chunkZ);
+                } catch (RuntimeException | Error failure) {
+                    reportMaterializationFailure(new MaterializationTarget(world, chunkX, chunkZ), failure);
                 } finally {
                     chunkUpdateQueue.remove(key);
                 }
@@ -508,6 +510,13 @@ final class WorldChunkMaintenance {
         return loadedChunkPositions;
     }
 
+    private void reportMaterializationFailure(MaterializationTarget target, Throwable failure) {
+        String context = "Failed to materialize chunk " + target.x() + "," + target.z() + " in " + target.world().getName() + ".";
+        if (IrisLogging.errorOnce("chunk-materialization:" + target.world().getUID() + ":" + target.x() + "," + target.z() + ":" + failure, context)) {
+            IrisLogging.reportError(context, failure);
+        }
+    }
+
     private record MaterializationTarget(World world, int x, int z) {
         private long key() {
             return Cache.key(x, z);
@@ -614,7 +623,7 @@ final class WorldChunkMaintenance {
                 }
                 spawnInitially(chunk);
             } catch (Throwable failure) {
-                IrisLogging.reportError("Failed to materialize saved chunk at " + target.x() + "," + target.z() + ".", failure);
+                reportMaterializationFailure(target, failure);
             } finally {
                 synchronized (this) {
                     applying = false;

core/src/main/java/art/arcane/iris/platform/generation/EngineBukkitOps.java

@@ -20,7 +20,6 @@ package art.arcane.iris.platform.generation;
 
 import art.arcane.iris.world.history.GenerationFindCatalog;
 
-import art.arcane.iris.platform.bukkit.BukkitWorldBinding;
 import art.arcane.iris.world.event.IrisLootEvent;
 import art.arcane.iris.integration.Identifier;
 import art.arcane.iris.integration.ExternalDataSVC;
@@ -73,6 +72,7 @@ import org.bukkit.World;
 import org.bukkit.block.Block;
 import org.bukkit.block.BlockFace;
 import org.bukkit.block.BlockState;
+import org.bukkit.block.DoubleChest;
 import org.bukkit.block.data.BlockData;
 import org.bukkit.block.data.type.Chest;
 import org.bukkit.entity.Player;
@@ -82,6 +82,8 @@ import org.bukkit.inventory.ItemStack;
 import org.bukkit.loot.Lootable;
 
 import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.CompletableFuture;
@@ -89,9 +91,7 @@ import java.util.concurrent.CompletionException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.atomic.AtomicLong;
-import java.util.function.BooleanSupplier;
 import java.util.function.Consumer;
-import java.util.function.Predicate;
 
 import art.arcane.iris.localization.BukkitRuntimeMessages;
 import art.arcane.iris.localization.IrisLanguage;
@@ -124,14 +124,7 @@ public final class EngineBukkitOps {
         }
 
         if (!J.isFolia() && !J.isPrimaryThread()) {
-            CompletableFuture<?> scheduled = J.sfut(() -> updateChunk(engine, c, mantle));
-            if (scheduled != null) {
-                try {
-                    scheduled.join();
-                } catch (Throwable e) {
-                    IrisLogging.reportError(e);
-                }
-            }
+            awaitMaterialization(J.sfut(() -> updateChunk(engine, c, mantle)));
             return;
         }
 
@@ -303,21 +296,25 @@ public final class EngineBukkitOps {
         });
 
         if (!scheduled) {
-            if (J.isPrimaryThread()) {
-                runnable.run();
-            }
-            return;
+            throw new IllegalStateException("Failed to schedule chunk materialization for "
+                    + contextChunk.getWorld().getName() + " at chunk " + contextChunk.getX() + "," + contextChunk.getZ() + ".");
         }
 
+        awaitMaterialization(completion);
+    }
+
+    private static void awaitMaterialization(CompletableFuture<?> completion) {
         try {
             completion.join();
         } catch (CompletionException error) {
             Throwable cause = error.getCause();
-            IrisLogging.reportError(
-                    "Failed deferred chunk materialization for " + contextChunk.getWorld().getName()
-                            + " at chunk " + contextChunk.getX() + "," + contextChunk.getZ() + ".",
-                    cause == null ? error : cause
-            );
+            if (cause instanceof RuntimeException runtimeFailure) {
+                throw runtimeFailure;
+            }
+            if (cause instanceof Error fatalFailure) {
+                throw fatalFailure;
+            }
+            throw error;
         }
     }
 
@@ -351,8 +348,12 @@ public final class EngineBukkitOps {
                     InventoryHolder m = (InventoryHolder) block.getState();
                     addItems(engine, false, m.getInventory(), tables, slot, c.getWorld(), worldX, y, worldZ);
 
-                } catch (Throwable e) {
-                    IrisLogging.reportError(e);
+                } catch (RuntimeException | Error failure) {
+                    if (IrisLogging.errorOnce("container-loot:" + world.getUID() + ":" + worldX + "," + y + "," + worldZ + ":" + failure,
+                            "Failed to populate loot at " + world.getName() + " [" + worldX + "," + y + "," + worldZ + "].")) {
+                        IrisLogging.reportError(failure);
+                    }
+                    throw failure;
                 }
             }
         } else {
@@ -515,6 +516,10 @@ public final class EngineBukkitOps {
     }
 
     public static void addItems(Engine engine, boolean debug, Inventory inv, KList<IrisLootTable> tables, InventorySlotType slot, World world, int x, int y, int z) {
+        if (!J.isOwnedByCurrentRegion(world, x >> 4, z >> 4)) {
+            throw new IllegalStateException("Loot inventory mutation requires the owning region at "
+                    + world.getName() + " [" + x + "," + y + "," + z + "].");
+        }
         KList<ItemStack> items = new KList<>();
 
         for (IrisLootTable i : tables) {
@@ -525,57 +530,69 @@ public final class EngineBukkitOps {
         if (IrisLootEvent.callLootEvent(items, inv, world, x, y, z))
             return;
 
-        if (PaperLib.isPaper() && engine.getWorld().hasPlatformWorld()) {
-            PaperLib.getChunkAtAsync(BukkitWorldBinding.world(engine.getWorld()), x >> 4, z >> 4).thenAccept((c) -> {
-                Runnable mutation = () -> {
-                    for (ItemStack i : items) {
-                        inv.addItem(i);
-                    }
+        populateInventory(engine, inv, items, LootResolver.containerRng(engine.getSeedManager().getLoot(), x, y, z));
+    }
 
-                    scramble(engine, inv, LootResolver.containerRng(engine.getSeedManager().getLoot(), x, y, z));
-                };
-
-                LootMutationTask task = new LootMutationTask(world, x >> 4, z >> 4, mutation);
-                boolean scheduled = dispatchLootMutation(
-                        task,
-                        J.isFolia(),
-                        Bukkit::isPrimaryThread,
-                        regionTask -> J.runRegion(
-                                regionTask.world(),
-                                regionTask.chunkX(),
-                                regionTask.chunkZ(),
-                                regionTask.mutation()),
-                        J::s
-                );
-                if (!scheduled) {
-                    IrisLogging.error("Failed to schedule loot inventory mutation for " + world.getName() + "@" + (x >> 4) + "," + (z >> 4) + ".");
-                }
-            });
+    static void populateInventory(Engine engine, Inventory inv, List<ItemStack> items, RNG rng) {
+        List<BlockState> states = new ArrayList<>(2);
+        InventoryHolder holder = inv.getHolder();
+        if (holder instanceof DoubleChest chest) {
+            snapshotContainer(states, chest.getLeftSide());
+            snapshotContainer(states, chest.getRightSide());
         } else {
-            for (ItemStack i : items) {
-                inv.addItem(i);
+            snapshotContainer(states, holder);
+        }
+        ItemStack[] contents = null;
+        try {
+            if (states.isEmpty()) {
+                contents = copyContents(inv.getContents());
             }
-
-            scramble(engine, inv, LootResolver.containerRng(engine.getSeedManager().getLoot(), x, y, z));
+            for (ItemStack i : items) {
+                if (i != null) {
+                    inv.addItem(i.clone());
+                }
+            }
+            scramble(engine, inv, rng);
+        } catch (RuntimeException | Error failure) {
+            if (states.isEmpty()) {
+                if (contents != null) {
+                    try {
+                        inv.setContents(contents);
+                    } catch (RuntimeException | Error rollbackFailure) {
+                        if (rollbackFailure != failure) {
+                            failure.addSuppressed(rollbackFailure);
+                        }
+                    }
+                }
+            } else {
+                for (BlockState state : states) {
+                    try {
+                        if (!state.update(true, false)) {
+                            throw new IllegalStateException("Failed to restore loot container at " + state.getLocation());
+                        }
+                    } catch (RuntimeException | Error rollbackFailure) {
+                        if (rollbackFailure != failure) {
+                            failure.addSuppressed(rollbackFailure);
+                        }
+                    }
+                }
+            }
+            throw failure;
         }
     }
 
-    static boolean dispatchLootMutation(
-            LootMutationTask task,
-            boolean folia,
-            BooleanSupplier primaryThread,
-            Predicate<LootMutationTask> regionScheduler,
-            Consumer<Runnable> syncScheduler) {
-        if (folia) {
-            return regionScheduler.test(task);
+    private static void snapshotContainer(List<BlockState> snapshots, InventoryHolder holder) {
+        if (holder instanceof BlockState state) {
+            snapshots.add(state.getBlock().getState());
         }
+    }
 
-        if (primaryThread.getAsBoolean()) {
-            task.mutation().run();
-        } else {
-            syncScheduler.accept(task.mutation());
+    private static ItemStack[] copyContents(ItemStack[] contents) {
+        ItemStack[] copy = new ItemStack[contents.length];
+        for (int index = 0; index < contents.length; index++) {
+            copy[index] = contents[index] == null ? null : contents[index].clone();
         }
-        return true;
+        return copy;
     }
 
     public static IrisBiome getBiome(Engine engine, Location l) {
@@ -838,6 +855,4 @@ public final class EngineBukkitOps {
         }
     }
 
-    record LootMutationTask(World world, int chunkX, int chunkZ, Runnable mutation) {
-    }
 }

core/src/main/java/art/arcane/iris/structure/object/WorldObjectPlacer.java

@@ -93,8 +93,10 @@ public class WorldObjectPlacer implements IObjectPlacer {
             }
             InventoryHolder holder = (InventoryHolder) block.getState();
             EngineBukkitOps.addItems(engine, false, holder.getInventory(), tables, InventorySlotType.STORAGE, world, x, y, z);
-        } catch (Throwable e) {
-            IrisLogging.reportError(e);
+        } catch (RuntimeException | Error failure) {
+            IrisLogging.reportError("Failed to populate placed container at " + world.getName()
+                    + " [" + x + "," + y + "," + z + "].", failure);
+            throw failure;
         }
     }
 

core/src/main/java/art/arcane/iris/world/event/IrisLootEvent.java

@@ -4,7 +4,6 @@ import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.world.loot.InventorySlotType;
 import art.arcane.iris.world.loot.IrisLootTable;
 import art.arcane.iris.platform.bukkit.BukkitPlatform;
-import art.arcane.iris.spi.IrisLogging;
 import art.arcane.volmlib.util.collection.KList;
 import art.arcane.iris.world.task.J;
 import lombok.Getter;
@@ -92,6 +91,10 @@ public class IrisLootEvent extends Event {
      * @return true when the event was canceled
      */
     public static boolean callLootEvent(KList<ItemStack> loot, Inventory inv, World world, int x, int y, int z) {
+        if (!J.isOwnedByCurrentRegion(world, x >> 4, z >> 4)) {
+            throw new IllegalStateException("LootGenerateEvent requires the owning region at "
+                    + world.getName() + " [" + x + "," + y + "," + z + "].");
+        }
         InventoryHolder holder = inv.getHolder();
         Location loc = new Location(world, x, y, z);
         if (holder == null) {
@@ -106,39 +109,8 @@ public class IrisLootEvent extends Event {
 
         LootContext context = new LootContext.Builder(loc).build();
         LootGenerateEvent event = new LootGenerateEvent(world, null, holder, EMPTY, context, loot, true);
-        if (!Bukkit.isPrimaryThread()) {
-            IrisLogging.warn("LootGenerateEvent was not called on the main thread, please report this issue.");
-            Thread.dumpStack();
-            J.sfut(() -> {
-                try {
-                    Bukkit.getPluginManager().callEvent(event);
-                } catch (Throwable e) {
-                    IrisLogging.reportError("LootGenerateEvent dispatch failed at "
-                            + world.getName() + " [" + x + "," + y + "," + z + "].", e);
-                    if (e instanceof RuntimeException runtimeException) {
-                        throw runtimeException;
-                    }
-                    if (e instanceof Error error) {
-                        throw error;
-                    }
-                    throw new IllegalStateException(e);
-                }
-            }).join();
-        } else {
-            try {
-                Bukkit.getPluginManager().callEvent(event);
-            } catch (Throwable e) {
-                IrisLogging.reportError("LootGenerateEvent dispatch failed at "
-                        + world.getName() + " [" + x + "," + y + "," + z + "].", e);
-                if (e instanceof RuntimeException runtimeException) {
-                    throw runtimeException;
-                }
-                if (e instanceof Error error) {
-                    throw error;
-                }
-                throw new IllegalStateException(e);
-            }
-        }
+
+        Bukkit.getPluginManager().callEvent(event);
 
         return event.isCancelled();
     }

core/src/main/java/art/arcane/iris/world/loot/IrisVanillaLootTable.java

@@ -33,13 +33,12 @@ public class IrisVanillaLootTable extends IrisLootTable {
     private final String lootTableKey;
 
     /**
-     * The resolved table, looked up once. Every chest pull resolved it again - a NamespacedKey parse plus a registry
-     * lookup per container, and a dungeon room is a lot of containers.
+     * Cache the parsed key; resolve its table from the current registry for every container.
      * <p>
      * Transient for the same reason the field above is a String: it keeps the Bukkit type argument out of the Gson
      * field walk and out of the pack purity gate, both of which resolve generic field types for the fields they visit.
      */
-    private final transient AtomicCache<LootTable> resolvedTable = new AtomicCache<>();
+    private final transient AtomicCache<NamespacedKey> resolvedKey = new AtomicCache<>();
 
     @Override
     public String getName() {
@@ -83,10 +82,8 @@ public class IrisVanillaLootTable extends IrisLootTable {
     }
 
     private LootTable resolveTable() {
-        return resolvedTable.aquire(() -> {
-            NamespacedKey key = NamespacedKey.fromString(lootTableKey);
-            return key == null ? null : Bukkit.getLootTable(key);
-        });
+        NamespacedKey key = resolvedKey.aquire(() -> NamespacedKey.fromString(lootTableKey));
+        return key == null ? null : Bukkit.getLootTable(key);
     }
 
     @Override

core/src/test/java/art/arcane/iris/generation/runtime/WorldChunkMaintenanceRoutingTest.java

@@ -175,6 +175,7 @@ public class WorldChunkMaintenanceRoutingTest {
     public void failedMaterializationRetainsRetryAndReportsTheFailure() throws Exception {
         try (Fixture fixture = new Fixture()) {
             IllegalStateException failure = new IllegalStateException("Provider placement failed");
+            fixture.logging.when(() -> IrisLogging.errorOnce(anyString(), anyString())).thenReturn(true, false);
             fixture.updates.when(() -> EngineBukkitOps.updateChunk(fixture.engine, fixture.chunk, fixture.savedMantle)).thenThrow(failure);
             fixture.schedule();
             fixture.prepare();
@@ -182,6 +183,10 @@ public class WorldChunkMaintenanceRoutingTest {
             fixture.apply();
             fixture.awaitRelease();
 
+            fixture.schedule();
+            fixture.prepare();
+            fixture.apply();
+            fixture.awaitRelease();
             fixture.logging.verify(() -> IrisLogging.reportError(anyString(), eq(failure)));
             fixture.schedule();
             assertEquals(1, fixture.async.size());

core/src/test/java/art/arcane/iris/platform/bukkit/BukkitStorageClassificationTest.java

@@ -0,0 +1,54 @@
+package art.arcane.iris.platform.bukkit;
+
+import art.arcane.volmlib.util.data.BSupport;
+import org.bukkit.Bukkit;
+import org.bukkit.Material;
+import org.bukkit.block.data.BlockData;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.when;
+
+public class BukkitStorageClassificationTest {
+    @Test
+    public void copperChestsAndExistingLootContainersReceiveStorageUpdates() {
+        BlockData air = blockData(Material.AIR);
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class)) {
+            bukkit.when(() -> Bukkit.createBlockData(Material.AIR)).thenReturn(air);
+            BSupport<Object> support = new BSupport<Object>() {
+            };
+            for (Material material : new Material[]{Material.COPPER_CHEST, Material.EXPOSED_COPPER_CHEST,
+                    Material.WEATHERED_COPPER_CHEST, Material.OXIDIZED_COPPER_CHEST,
+                    Material.WAXED_COPPER_CHEST, Material.WAXED_EXPOSED_COPPER_CHEST,
+                    Material.WAXED_WEATHERED_COPPER_CHEST, Material.WAXED_OXIDIZED_COPPER_CHEST,
+                    Material.CHEST, Material.TRAPPED_CHEST, Material.BARREL, Material.SHULKER_BOX,
+                    Material.BLUE_SHULKER_BOX, Material.DISPENSER, Material.DROPPER, Material.HOPPER}) {
+                BlockData state = blockData(material);
+                assertTrue(material.name(), support.isStorage(state));
+                assertTrue(material.name(), support.isStorageChest(state));
+                assertTrue(material.name(), support.isUpdatable(state));
+            }
+            for (Material material : new Material[]{Material.FURNACE, Material.BLAST_FURNACE, Material.SMOKER}) {
+                BlockData state = blockData(material);
+                assertTrue(material.name(), support.isStorage(state));
+                assertFalse(material.name(), support.isStorageChest(state));
+            }
+            for (Material material : new Material[]{Material.STONE, Material.AIR, Material.ENDER_CHEST,
+                    Material.COPPER_BLOCK, Material.COPPER_CHESTPLATE}) {
+                BlockData state = blockData(material);
+                assertFalse(material.name(), support.isStorage(state));
+                assertFalse(material.name(), support.isStorageChest(state));
+            }
+        }
+    }
+
+    private static BlockData blockData(Material material) {
+        BlockData state = mock(BlockData.class);
+        when(state.getMaterial()).thenReturn(material);
+        return state;
+    }
+}

core/src/test/java/art/arcane/iris/platform/generation/EngineBukkitOpsLootTest.java

@@ -1,20 +1,66 @@
 package art.arcane.iris.platform.generation;
 
-import org.bukkit.World;
-import org.bukkit.block.Block;
-import org.bukkit.block.BlockFace;
-import org.bukkit.block.data.type.Chest;
-import org.bukkit.loot.LootTable;
-import org.junit.Test;
-
+import art.arcane.iris.generation.runtime.Engine;
+import art.arcane.iris.generation.runtime.EngineMetrics;
+import art.arcane.iris.platform.bukkit.BukkitBlockResolution;
+import art.arcane.iris.spi.IrisLogging;
+import art.arcane.iris.testsupport.BukkitTestServer;
+import art.arcane.iris.world.event.IrisLootEvent;
+import art.arcane.iris.world.loot.InventorySlotType;
+import art.arcane.iris.world.loot.IrisLootTable;
+import art.arcane.iris.world.task.J;
+import art.arcane.volmlib.util.collection.KList;
+import art.arcane.volmlib.util.function.Consumer4;
+import art.arcane.volmlib.util.mantle.flag.MantleFlag;
+import art.arcane.volmlib.util.mantle.runtime.MantleChunk;
+import art.arcane.volmlib.util.mantle.runtime.MantleDataAdapter;
+import art.arcane.volmlib.util.mantle.runtime.MantleHooks;
+import art.arcane.volmlib.util.math.RNG;
+import art.arcane.volmlib.util.matter.Matter;
+import art.arcane.volmlib.util.matter.MatterUpdate;
+import art.arcane.volmlib.util.matter.slices.UpdateMatter;
+import io.papermc.paper.registry.RegistryAccess;
+import java.util.HashMap;
+import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
+import org.bukkit.Bukkit;
+import org.bukkit.Chunk;
+import org.bukkit.Material;
+import org.bukkit.World;
+import org.bukkit.block.Barrel;
+import org.bukkit.block.Block;
+import org.bukkit.block.BlockFace;
+import org.bukkit.block.BlockState;
+import org.bukkit.block.DoubleChest;
+import org.bukkit.block.data.BlockData;
+import org.bukkit.block.data.type.Chest;
+import org.bukkit.event.world.LootGenerateEvent;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.loot.LootTable;
+import org.bukkit.plugin.PluginManager;
+import org.junit.Test;
+import org.mockito.MockedStatic;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.RETURNS_DEEP_STUBS;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 
 public class EngineBukkitOpsLootTest {
@@ -46,117 +92,314 @@ public class EngineBukkitOpsLootTest {
     }
 
     @Test
-    public void foliaLootMutationUsesOwningRegionOnly() {
-        World world = mock(World.class);
-        AtomicInteger primaryChecks = new AtomicInteger();
-        AtomicInteger regionSchedules = new AtomicInteger();
-        AtomicInteger syncSchedules = new AtomicInteger();
-        AtomicBoolean mutated = new AtomicBoolean();
-        Runnable mutation = () -> mutated.set(true);
-        EngineBukkitOps.LootMutationTask task = new EngineBukkitOps.LootMutationTask(world, 12, -3, mutation);
+    public void failedInsertionRestoresExistingLootBeforeRetry() {
+        Inventory inventory = mock(Inventory.class);
+        AtomicReference<ItemStack[]> contents = new AtomicReference<>(new ItemStack[]{item(2), null});
+        AtomicBoolean reject = new AtomicBoolean(true);
+        when(inventory.getSize()).thenReturn(2);
+        when(inventory.getContents()).thenAnswer(invocation -> contents.get());
+        doAnswer(invocation -> {
+            contents.set(invocation.getArgument(0));
+            return null;
+        }).when(inventory).setContents(any(ItemStack[].class));
+        doAnswer(invocation -> {
+            ItemStack incoming = invocation.getArgument(0);
+            contents.get()[0].setAmount(contents.get()[0].getAmount() + incoming.getAmount());
+            if (reject.getAndSet(false)) {
+                throw new IllegalStateException("Insertion failed");
+            }
+            return new HashMap<Integer, ItemStack>();
+        }).when(inventory).addItem(any(ItemStack.class));
+        ItemStack reward = item(7);
 
-        boolean scheduled = EngineBukkitOps.dispatchLootMutation(
-                task,
-                true,
-                () -> {
-                    primaryChecks.incrementAndGet();
-                    return true;
-                },
-                regionTask -> {
-                    regionSchedules.incrementAndGet();
-                    assertSame(world, regionTask.world());
-                    assertEquals(12, regionTask.chunkX());
-                    assertEquals(-3, regionTask.chunkZ());
-                    assertSame(mutation, regionTask.mutation());
-                    regionTask.mutation().run();
-                    return true;
-                },
-                runnable -> syncSchedules.incrementAndGet()
-        );
+        assertThrows(IllegalStateException.class,
+                () -> EngineBukkitOps.populateInventory(null, inventory, List.of(reward), new RNG(17)));
 
-        assertTrue(scheduled);
-        assertTrue(mutated.get());
-        assertEquals(1, regionSchedules.get());
-        assertEquals(0, primaryChecks.get());
-        assertEquals(0, syncSchedules.get());
+        assertEquals(2, contents.get()[0].getAmount());
+        EngineBukkitOps.populateInventory(null, inventory, List.of(reward), new RNG(17));
+        int total = 0;
+        for (ItemStack item : contents.get()) {
+            total += item == null ? 0 : item.getAmount();
+        }
+        assertEquals(9, total);
+        assertEquals(7, reward.getAmount());
     }
 
     @Test
-    public void failedFoliaRegionScheduleDoesNotMutateInventoryElsewhere() {
-        World world = mock(World.class);
-        AtomicInteger primaryChecks = new AtomicInteger();
-        AtomicInteger syncSchedules = new AtomicInteger();
-        AtomicBoolean mutated = new AtomicBoolean();
-        EngineBukkitOps.LootMutationTask task = new EngineBukkitOps.LootMutationTask(world, 1, 2, () -> mutated.set(true));
+    public void failedNativeInventoryAccessRestoresBothChestSnapshots() {
+        Inventory inventory = mock(Inventory.class);
+        DoubleChest holder = mock(DoubleChest.class);
+        org.bukkit.block.Chest left = mock(org.bukkit.block.Chest.class);
+        org.bukkit.block.Chest right = mock(org.bukkit.block.Chest.class);
+        Block leftBlock = mock(Block.class);
+        Block rightBlock = mock(Block.class);
+        BlockState leftSnapshot = mock(BlockState.class);
+        BlockState rightSnapshot = mock(BlockState.class);
+        when(inventory.getHolder()).thenReturn(holder);
+        when(holder.getLeftSide()).thenReturn(left);
+        when(holder.getRightSide()).thenReturn(right);
+        when(left.getBlock()).thenReturn(leftBlock);
+        when(right.getBlock()).thenReturn(rightBlock);
+        when(leftBlock.getState()).thenReturn(leftSnapshot);
+        when(rightBlock.getState()).thenReturn(rightSnapshot);
+        when(leftSnapshot.update(true, false)).thenReturn(true);
+        when(rightSnapshot.update(true, false)).thenReturn(true);
+        IllegalStateException failure = new IllegalStateException("Native loot failed");
+        doThrow(failure).when(inventory).addItem(any(ItemStack.class));
 
-        boolean scheduled = EngineBukkitOps.dispatchLootMutation(
-                task,
-                true,
-                () -> {
-                    primaryChecks.incrementAndGet();
-                    return true;
-                },
-                regionTask -> false,
-                runnable -> syncSchedules.incrementAndGet()
-        );
+        assertSame(failure, assertThrows(IllegalStateException.class,
+                () -> EngineBukkitOps.populateInventory(null, inventory,
+                        List.of(item(1)), new RNG(17))));
 
-        assertFalse(scheduled);
-        assertFalse(mutated.get());
-        assertEquals(0, primaryChecks.get());
-        assertEquals(0, syncSchedules.get());
+        verify(leftSnapshot).update(true, false);
+        verify(rightSnapshot).update(true, false);
     }
 
     @Test
-    public void nonFoliaPrimaryThreadMutatesInline() {
-        World world = mock(World.class);
-        AtomicInteger regionSchedules = new AtomicInteger();
-        AtomicInteger syncSchedules = new AtomicInteger();
-        AtomicBoolean mutated = new AtomicBoolean();
-        EngineBukkitOps.LootMutationTask task = new EngineBukkitOps.LootMutationTask(world, 4, 5, () -> mutated.set(true));
+    public void failedBarrelFillRestoresItsBlockSnapshot() {
+        Inventory inventory = mock(Inventory.class);
+        Barrel holder = mock(Barrel.class);
+        Block block = mock(Block.class);
+        Barrel snapshot = mock(Barrel.class);
+        when(inventory.getHolder()).thenReturn(holder);
+        when(holder.getBlock()).thenReturn(block);
+        when(block.getState()).thenReturn(snapshot);
+        when(snapshot.update(true, false)).thenReturn(true);
+        IllegalStateException failure = new IllegalStateException("Native barrel loot failed");
+        when(inventory.getContents()).thenThrow(failure);
 
-        boolean scheduled = EngineBukkitOps.dispatchLootMutation(
-                task,
-                false,
-                () -> true,
-                regionTask -> {
-                    regionSchedules.incrementAndGet();
-                    return true;
-                },
-                runnable -> syncSchedules.incrementAndGet()
-        );
+        assertSame(failure, assertThrows(IllegalStateException.class,
+                () -> EngineBukkitOps.populateInventory(null, inventory, List.of(), new RNG(17))));
 
-        assertTrue(scheduled);
-        assertTrue(mutated.get());
-        assertEquals(0, regionSchedules.get());
-        assertEquals(0, syncSchedules.get());
+        verify(snapshot).update(true, false);
     }
 
     @Test
-    public void nonFoliaAsyncCompletionUsesSyncScheduler() {
+    public void failedRollbackPreservesTheCauseAndRestoresTheOtherHalf() {
+        Inventory inventory = mock(Inventory.class);
+        DoubleChest holder = mock(DoubleChest.class);
+        org.bukkit.block.Chest left = mock(org.bukkit.block.Chest.class, RETURNS_DEEP_STUBS);
+        org.bukkit.block.Chest right = mock(org.bukkit.block.Chest.class, RETURNS_DEEP_STUBS);
+        BlockState leftSnapshot = mock(BlockState.class);
+        BlockState rightSnapshot = mock(BlockState.class);
+        when(inventory.getHolder()).thenReturn(holder);
+        when(holder.getLeftSide()).thenReturn(left);
+        when(holder.getRightSide()).thenReturn(right);
+        when(left.getBlock().getState()).thenReturn(leftSnapshot);
+        when(right.getBlock().getState()).thenReturn(rightSnapshot);
+        when(rightSnapshot.update(true, false)).thenReturn(true);
+        IllegalStateException failure = new IllegalStateException("Native loot failed");
+        IllegalStateException rollbackFailure = new IllegalStateException("Snapshot restore failed");
+        when(leftSnapshot.update(true, false)).thenThrow(rollbackFailure);
+        doThrow(failure).when(inventory).addItem(any(ItemStack.class));
+
+        assertSame(failure, assertThrows(IllegalStateException.class,
+                () -> EngineBukkitOps.populateInventory(null, inventory, List.of(item(1)), new RNG(17))));
+
+        assertEquals(1, failure.getSuppressed().length);
+        assertSame(rollbackFailure, failure.getSuppressed()[0]);
+        verify(rightSnapshot).update(true, false);
+    }
+
+    @Test
+    public void cancelledLootLeavesTheInventoryUntouched() {
+        Engine engine = mock(Engine.class, RETURNS_DEEP_STUBS);
+        Inventory inventory = mock(Inventory.class);
         World world = mock(World.class);
-        AtomicInteger regionSchedules = new AtomicInteger();
-        AtomicInteger syncSchedules = new AtomicInteger();
-        AtomicBoolean mutated = new AtomicBoolean();
-        EngineBukkitOps.LootMutationTask task = new EngineBukkitOps.LootMutationTask(world, 6, 7, () -> mutated.set(true));
+        try (MockedStatic<J> scheduling = mockStatic(J.class);
+             MockedStatic<IrisLootEvent> events = mockStatic(IrisLootEvent.class)) {
+            scheduling.when(() -> J.isOwnedByCurrentRegion(world, 2, -2)).thenReturn(true);
+            events.when(() -> IrisLootEvent.callLootEvent(any(), eq(inventory), eq(world), eq(33), eq(64), eq(-17)))
+                    .thenReturn(true);
 
-        boolean scheduled = EngineBukkitOps.dispatchLootMutation(
-                task,
-                false,
-                () -> false,
-                regionTask -> {
-                    regionSchedules.incrementAndGet();
-                    return true;
-                },
-                runnable -> {
-                    syncSchedules.incrementAndGet();
-                    runnable.run();
-                }
-        );
+            EngineBukkitOps.addItems(engine, false, inventory, new KList<>(), InventorySlotType.STORAGE, world, 33, 64, -17);
 
-        assertTrue(scheduled);
-        assertTrue(mutated.get());
-        assertEquals(0, regionSchedules.get());
-        assertEquals(1, syncSchedules.get());
+            verifyNoInteractions(inventory);
+        }
+    }
+
+    @Test
+    public void offRegionLootDoesNotRollOrTouchInventory() {
+        Engine engine = mock(Engine.class);
+        Inventory inventory = mock(Inventory.class);
+        World world = mock(World.class);
+        IrisLootTable table = mock(IrisLootTable.class);
+        try (MockedStatic<J> scheduling = mockStatic(J.class)) {
+            assertThrows(IllegalStateException.class, () -> EngineBukkitOps.addItems(engine, false, inventory,
+                    new KList<>(table), InventorySlotType.STORAGE, world, 33, 64, -17));
+
+            scheduling.verify(() -> J.isOwnedByCurrentRegion(world, 2, -2));
+            verifyNoInteractions(table, inventory, engine);
+        }
+    }
+
+    @Test
+    public void owningRegionLootCompletesInlineWithoutGlobalDispatch() {
+        Engine engine = mock(Engine.class, RETURNS_DEEP_STUBS);
+        Inventory inventory = mock(Inventory.class);
+        World world = mock(World.class);
+        when(inventory.getContents()).thenReturn(new ItemStack[0]);
+        try (MockedStatic<J> scheduling = mockStatic(J.class);
+             MockedStatic<IrisLootEvent> events = mockStatic(IrisLootEvent.class)) {
+            scheduling.when(() -> J.isOwnedByCurrentRegion(world, 2, -2)).thenReturn(true);
+
+            EngineBukkitOps.addItems(engine, false, inventory, new KList<>(), InventorySlotType.STORAGE, world, 33, 64, -17);
+
+            verify(inventory).setContents(any(ItemStack[].class));
+            scheduling.verify(() -> J.isOwnedByCurrentRegion(world, 2, -2));
+            scheduling.verifyNoMoreInteractions();
+        }
+    }
+
+    @Test
+    public void foliaLootEventRunsOnTheOwningRegionWithoutGlobalDispatch() {
+        World world = mock(World.class);
+        Inventory inventory = mock(Inventory.class);
+        PluginManager manager = mock(PluginManager.class);
+        Thread owner = Thread.currentThread();
+        AtomicInteger eventCalls = new AtomicInteger();
+        try (MockedStatic<J> scheduling = mockStatic(J.class);
+             MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class)) {
+            scheduling.when(() -> J.isOwnedByCurrentRegion(world, 2, -2)).thenReturn(true);
+            bukkit.when(Bukkit::getPluginManager).thenReturn(manager);
+            doAnswer(invocation -> {
+                assertSame(owner, Thread.currentThread());
+                eventCalls.incrementAndGet();
+                return null;
+            }).when(manager).callEvent(any(LootGenerateEvent.class));
+
+            assertFalse(IrisLootEvent.callLootEvent(new KList<>(), inventory, world, 33, 64, -17));
+
+            assertEquals(1, eventCalls.get());
+            scheduling.verify(() -> J.isOwnedByCurrentRegion(world, 2, -2));
+            scheduling.verifyNoMoreInteractions();
+        }
+    }
+
+    @Test
+    public void lootEventRetainsListenerChangesAndCancellation() {
+        World world = mock(World.class);
+        Inventory inventory = mock(Inventory.class);
+        PluginManager manager = mock(PluginManager.class);
+        ItemStack original = item(2);
+        ItemStack replacement = item(3);
+        KList<ItemStack> items = new KList<>(original);
+        try (MockedStatic<J> scheduling = mockStatic(J.class);
+             MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class)) {
+            scheduling.when(() -> J.isOwnedByCurrentRegion(world, 2, -2)).thenReturn(true);
+            bukkit.when(Bukkit::getPluginManager).thenReturn(manager);
+            doAnswer(invocation -> {
+                LootGenerateEvent event = invocation.getArgument(0);
+                event.setLoot(List.of(replacement));
+                event.setCancelled(true);
+                return null;
+            }).when(manager).callEvent(any(LootGenerateEvent.class));
+
+            assertTrue(IrisLootEvent.callLootEvent(items, inventory, world, 33, 64, -17));
+
+            assertEquals(List.of(replacement), items);
+        }
+    }
+
+    @Test
+    @SuppressWarnings("unchecked")
+    public void failedLootRollKeepsPendingMarkerUntilSuccessfulRetry() {
+        BukkitTestServer.install();
+        AtomicBoolean pending = new AtomicBoolean(true);
+        AtomicInteger attempts = new AtomicInteger();
+        Engine engine = mock(Engine.class, RETURNS_DEEP_STUBS);
+        when(engine.getMetrics()).thenReturn(new EngineMetrics(8));
+        World world = mock(World.class);
+        when(world.getMaxHeight()).thenReturn(256);
+        Chunk chunk = mock(Chunk.class);
+        when(chunk.getWorld()).thenReturn(world);
+        Block block = mock(Block.class);
+        BlockData state = mock(BlockData.class);
+        org.bukkit.block.Chest chest = mock(org.bukkit.block.Chest.class);
+        Inventory inventory = mock(Inventory.class);
+        when(chunk.getBlock(1, 64, 1)).thenReturn(block);
+        when(block.getBlockData()).thenReturn(state);
+        when(block.getX()).thenReturn(1);
+        when(block.getZ()).thenReturn(1);
+        when(block.getState()).thenReturn(chest);
+        when(chest.getInventory()).thenReturn(inventory);
+        when(inventory.getContents()).thenReturn(new ItemStack[0]);
+        MantleChunk<Matter> mantle = spy(new MantleChunk<>(16, 0, 0, mock(MantleDataAdapter.class), MantleHooks.NONE));
+        doAnswer(invocation -> {
+            if (pending.get()) {
+                Consumer4<Integer, Integer, Integer, MatterUpdate> visitor = invocation.getArgument(1);
+                visitor.accept(1, 64, 1, UpdateMatter.ON);
+            }
+            return null;
+        }).when(mantle).iterate(eq(MatterUpdate.class), any());
+        doAnswer(invocation -> {
+            pending.set(false);
+            return null;
+        }).when(mantle).deleteSlices(MatterUpdate.class);
+        IrisLootTable table = mock(IrisLootTable.class);
+        IllegalStateException failure = new IllegalStateException("Loot provider unavailable");
+        when(table.getLoot(false, 0L, InventorySlotType.STORAGE, world, 1, 64, 1)).thenAnswer(invocation -> {
+            if (attempts.getAndIncrement() < 2) {
+                throw failure;
+            }
+            return new KList<ItemStack>();
+        });
+        KList<IrisLootTable> tables = new KList<>(table);
+        PluginManager manager = mock(PluginManager.class);
+        try (MockedStatic<RegistryAccess> registries = mockStatic(RegistryAccess.class)) {
+            registries.when(RegistryAccess::registryAccess).thenReturn(BukkitTestServer.registryAccess());
+            try (MockedStatic<EngineBukkitOps> operations = mockStatic(EngineBukkitOps.class);
+                 MockedStatic<BukkitBlockResolution> resolution = mockStatic(BukkitBlockResolution.class);
+                 MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+                 MockedStatic<IrisLootEvent> events = mockStatic(IrisLootEvent.class);
+                 MockedStatic<J> scheduling = mockStatic(J.class);
+                 MockedStatic<IrisLogging> logging = mockStatic(IrisLogging.class)) {
+                bukkit.when(Bukkit::getPluginManager).thenReturn(manager);
+                logging.when(() -> IrisLogging.errorOnce(anyString(), anyString())).thenReturn(true, false);
+                scheduling.when(() -> J.isOwnedByCurrentRegion(world, 0, 0)).thenReturn(true);
+                resolution.when(() -> BukkitBlockResolution.isStorage(state)).thenReturn(true);
+                resolution.when(() -> BukkitBlockResolution.isStorageChest(state)).thenReturn(true);
+                operations.when(() -> EngineBukkitOps.isCanonicalContainer(block)).thenReturn(true);
+                operations.when(() -> EngineBukkitOps.getLootTables(eq(engine), any(RNG.class), eq(block), eq(mantle), eq(false))).thenReturn(tables);
+                operations.when(() -> EngineBukkitOps.addItems(engine, false, inventory, tables, InventorySlotType.STORAGE, world, 1, 64, 1)).thenCallRealMethod();
+                operations.when(() -> EngineBukkitOps.populateInventory(eq(engine), eq(inventory), any(), any())).thenCallRealMethod();
+                operations.when(() -> EngineBukkitOps.update(engine, 1, 64, 1, chunk, mantle)).thenCallRealMethod();
+                operations.when(() -> EngineBukkitOps.materializeUpdates(engine, chunk, mantle)).thenCallRealMethod();
+                operations.when(() -> EngineBukkitOps.materializeUpdates(eq(engine), eq(chunk), eq(mantle), any(EngineBukkitOps.UpdateDispatcher.class))).thenCallRealMethod();
+                operations.when(() -> EngineBukkitOps.runMaterializationPasses(eq(mantle), any(Runnable.class), any(Runnable.class), any(Runnable.class))).thenCallRealMethod();
+                Runnable pass = () -> EngineBukkitOps.runMaterializationPasses(mantle, () -> {}, () -> {},
+                        () -> EngineBukkitOps.materializeUpdates(engine, chunk, mantle));
+
+                assertSame(failure, assertThrows(IllegalStateException.class, pass::run));
+                assertTrue(pending.get());
+                assertFalse(mantle.isFlagged(MantleFlag.UPDATE));
+                assertFalse(mantle.isFlagged(MantleFlag.ETCHED));
+                assertSame(failure, assertThrows(IllegalStateException.class, pass::run));
+                assertTrue(pending.get());
+                logging.verify(() -> IrisLogging.reportError(failure));
+
+                pass.run();
+                pass.run();
+
+                assertFalse(pending.get());
+                assertTrue(mantle.isFlagged(MantleFlag.UPDATE));
+                assertTrue(mantle.isFlagged(MantleFlag.ETCHED));
+                assertEquals(3, attempts.get());
+            }
+        }
+    }
+
+    private ItemStack item(int amount) {
+        ItemStack item = mock(ItemStack.class);
+        AtomicInteger count = new AtomicInteger(amount);
+        when(item.getType()).thenReturn(Material.DIAMOND);
+        when(item.getAmount()).thenAnswer(invocation -> count.get());
+        when(item.clone()).thenAnswer(invocation -> item(count.get()));
+        doAnswer(invocation -> {
+            count.set(invocation.getArgument(0));
+            return null;
+        }).when(item).setAmount(anyInt());
+        return item;
     }
 
     private Block chestBlock(int x, int z, Chest.Type type, BlockFace facing) {

core/src/test/java/art/arcane/iris/world/loot/IrisVanillaLootTableTest.java

@@ -0,0 +1,76 @@
+package art.arcane.iris.world.loot;
+
+import art.arcane.iris.spi.IrisLogging;
+import org.bukkit.Bukkit;
+import org.bukkit.NamespacedKey;
+import org.bukkit.World;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.loot.LootTable;
+import org.junit.Test;
+import org.mockito.MockedStatic;
+
+import java.util.List;
+
+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.Mockito.mock;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class IrisVanillaLootTableTest {
+    @Test
+    public void registryReplacementRemovalAndRestorationApplyToTheNextContainer() {
+        NamespacedKey key = new NamespacedKey("test", "reloadable_loot");
+        World world = mock(World.class);
+        LootTable before = mock(LootTable.class);
+        LootTable after = mock(LootTable.class);
+        ItemStack previousItem = mock(ItemStack.class);
+        ItemStack currentItem = mock(ItemStack.class);
+        when(before.populateLoot(any(), any())).thenReturn(List.of(previousItem));
+        when(after.populateLoot(any(), any())).thenReturn(List.of(currentItem));
+
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class);
+             MockedStatic<IrisLogging> logging = mockStatic(IrisLogging.class)) {
+            IrisVanillaLootTable table = new IrisVanillaLootTable(key.toString());
+            bukkit.when(() -> Bukkit.getLootTable(key)).thenReturn(before);
+            assertSame(previousItem, table.getLoot(false, 1L, InventorySlotType.STORAGE, world, 0, 64, 0).getFirst());
+
+            bukkit.when(() -> Bukkit.getLootTable(key)).thenReturn(after);
+            assertSame(currentItem, table.getLoot(false, 1L, InventorySlotType.STORAGE, world, 1, 64, 0).getFirst());
+
+            bukkit.when(() -> Bukkit.getLootTable(key)).thenReturn(null);
+            assertTrue(table.getLoot(false, 1L, InventorySlotType.STORAGE, world, 2, 64, 0).isEmpty());
+
+            bukkit.when(() -> Bukkit.getLootTable(key)).thenReturn(after);
+            assertSame(currentItem, table.getLoot(false, 1L, InventorySlotType.STORAGE, world, 3, 64, 0).getFirst());
+            verify(before).populateLoot(any(), any());
+            verify(after, times(2)).populateLoot(any(), any());
+        }
+    }
+
+    @Test
+    public void failedTableGenerationDoesNotRetainTheReplacedTable() {
+        NamespacedKey key = new NamespacedKey("test", "repaired_loot");
+        World world = mock(World.class);
+        LootTable failed = mock(LootTable.class);
+        LootTable repaired = mock(LootTable.class);
+        ItemStack item = mock(ItemStack.class);
+        IllegalStateException failure = new IllegalStateException("Loot generation failed");
+        when(failed.populateLoot(any(), any())).thenThrow(failure);
+        when(repaired.populateLoot(any(), any())).thenReturn(List.of(item));
+
+        try (MockedStatic<Bukkit> bukkit = mockStatic(Bukkit.class)) {
+            IrisVanillaLootTable table = new IrisVanillaLootTable(key.toString());
+            bukkit.when(() -> Bukkit.getLootTable(key)).thenReturn(failed);
+            assertSame(failure, assertThrows(IllegalStateException.class,
+                    () -> table.getLoot(false, 1L, InventorySlotType.STORAGE, world, 0, 64, 0)));
+
+            bukkit.when(() -> Bukkit.getLootTable(key)).thenReturn(repaired);
+            assertSame(item, table.getLoot(false, 1L, InventorySlotType.STORAGE, world, 0, 64, 0).getFirst());
+        }
+    }
+}