v+

3.6.5

build.gradle

@@ -33,7 +33,7 @@ plugins {
 }
 
 
-version '3.6.2-1.20.1-1.21.4'
+version '3.6.5-1.20.1-1.21.4'
 
 // ADD YOURSELF AS A NEW LINE IF YOU WANT YOUR OWN BUILD TASK GENERATED
 // ======================== WINDOWS =============================

core/build.gradle

@@ -62,7 +62,7 @@ dependencies {
 
     // Third Party Integrations
     compileOnly 'com.ticxo.playeranimator:PlayerAnimator:R1.2.7'
-    compileOnly 'com.nexomc:nexo:0.6.0-dev.0'
+    compileOnly 'com.nexomc:nexo:1.0.0-dev.38'
     compileOnly 'com.github.LoneDev6:api-itemsadder:3.4.1-r4'
     compileOnly 'com.github.PlaceholderAPI:placeholderapi:2.11.3'
     compileOnly 'com.github.Ssomar-Developement:SCore:4.23.10.8'

core/src/main/java/com/volmit/iris/Iris.java

@@ -35,6 +35,7 @@ import com.volmit.iris.core.tools.IrisToolbelt;
 import com.volmit.iris.core.tools.IrisWorldCreator;
 import com.volmit.iris.engine.EnginePanic;
 import com.volmit.iris.engine.object.IrisCompat;
+import com.volmit.iris.engine.object.IrisContextInjector;
 import com.volmit.iris.engine.object.IrisDimension;
 import com.volmit.iris.engine.object.IrisWorld;
 import com.volmit.iris.engine.platform.BukkitChunkGenerator;
@@ -102,8 +103,6 @@ import static com.volmit.iris.core.safeguard.ServerBootSFG.passedserversoftware;
 
 @SuppressWarnings("CanBeFinal")
 public class Iris extends VolmitPlugin implements Listener {
-    public static final String OVERWORLD_TAG = "31010";
-
     private static final Queue<Runnable> syncJobs = new ShurikenQueue<>();
 
     public static Iris instance;
@@ -460,9 +459,12 @@ public class Iris extends VolmitPlugin implements Listener {
         initialize("com.volmit.iris.core.service").forEach((i) -> services.put((Class<? extends IrisService>) i.getClass(), (IrisService) i));
         INMS.get();
         IO.delete(new File("iris"));
+        compat = IrisCompat.configured(getDataFile("compat.json"));
+        ServerConfigurator.configure();
+        new IrisContextInjector();
         IrisSafeguard.IrisSafeguardSystem();
         getSender().setTag(getTag());
-        compat = IrisCompat.configured(getDataFile("compat.json"));
+        IrisSafeguard.earlySplash();
         linkMultiverseCore = new MultiverseCoreLink();
         linkMythicMobs = new MythicMobsLink();
         configWatcher = new FileWatcher(getDataFile("settings.json"));
@@ -517,11 +519,10 @@ public class Iris extends VolmitPlugin implements Listener {
                 Iris.info("Loading World: %s | Generator: %s", s, generator);
 
                 Iris.info(C.LIGHT_PURPLE + "Preparing Spawn for " + s + "' using Iris:" + generator + "...");
-                new WorldCreator(s)
-                        .type(IrisWorldCreator.IRIS)
+                WorldCreator c = new WorldCreator(s)
                         .generator(getDefaultWorldGenerator(s, generator))
-                        .environment(IrisData.loadAnyDimension(generator).getEnvironment())
-                        .createWorld();
+                        .environment(IrisData.loadAnyDimension(generator).getEnvironment());
+                INMS.get().createWorld(c);
                 Iris.info(C.LIGHT_PURPLE + "Loaded " + s + "!");
             }
         } catch (Throwable e) {

core/src/main/java/com/volmit/iris/core/IrisSettings.java

@@ -181,6 +181,7 @@ public class IrisSettings {
         public boolean splashLogoStartup = true;
         public boolean useConsoleCustomColors = true;
         public boolean useCustomColorsIngame = true;
+        public boolean adjustVanillaHeight = false;
         public String forceMainWorld = "";
         public int spinh = -20;
         public int spins = 7;

core/src/main/java/com/volmit/iris/core/ServerConfigurator.java

@@ -28,21 +28,24 @@ import com.volmit.iris.engine.object.IrisBiomeCustom;
 import com.volmit.iris.engine.object.IrisDimension;
 import com.volmit.iris.engine.object.IrisRange;
 import com.volmit.iris.util.collection.KList;
+import com.volmit.iris.util.collection.KMap;
 import com.volmit.iris.util.collection.KSet;
 import com.volmit.iris.util.format.C;
+import com.volmit.iris.util.misc.ServerProperties;
 import com.volmit.iris.util.plugin.VolmitSender;
 import com.volmit.iris.util.scheduling.J;
 import lombok.Data;
+import lombok.NonNull;
 import org.bukkit.Bukkit;
 import org.bukkit.configuration.InvalidConfigurationException;
 import org.bukkit.configuration.file.FileConfiguration;
 import org.bukkit.configuration.file.YamlConfiguration;
 import org.bukkit.entity.Player;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.io.IOException;
 import java.util.Arrays;
-import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
 
@@ -89,12 +92,13 @@ public class ServerConfigurator {
         }
     }
 
-    private static List<File> getDatapacksFolder() {
+    private static KList<File> getDatapacksFolder() {
         if (!IrisSettings.get().getGeneral().forceMainWorld.isEmpty()) {
             return new KList<File>().qadd(new File(Bukkit.getWorldContainer(), IrisSettings.get().getGeneral().forceMainWorld + "/datapacks"));
         }
         KList<File> worlds = new KList<>();
         Bukkit.getServer().getWorlds().forEach(w -> worlds.add(new File(w.getWorldFolder(), "datapacks")));
+        if (worlds.isEmpty()) worlds.add(new File(Bukkit.getWorldContainer(), ServerProperties.LEVEL_NAME + "/datapacks"));
         return worlds;
     }
 
@@ -105,14 +109,16 @@ public class ServerConfigurator {
     public static void installDataPacks(IDataFixer fixer, boolean fullInstall) {
         Iris.info("Checking Data Packs...");
         DimensionHeight height = new DimensionHeight(fixer);
+        KList<File> folders = getDatapacksFolder();
+        KMap<String, KSet<String>> biomes = new KMap<>();
 
         allPacks().flatMap(height::merge)
+                .parallel()
                 .forEach(dim -> {
-                    for (File dpack : getDatapacksFolder()) {
-                        Iris.verbose("  Checking Dimension " + dim.getLoadFile().getPath());
-                        dim.installDataPack(fixer, dim::getLoader, dpack, height);
-                    }
+                    Iris.verbose("  Checking Dimension " + dim.getLoadFile().getPath());
+                    dim.installBiomes(fixer, dim::getLoader, folders, biomes.computeIfAbsent(dim.getLoadKey(), k -> new KSet<>()));
                 });
+        IrisDimension.writeShared(folders, height);
 
         Iris.info("Data Packs Setup!");
 
@@ -164,7 +170,7 @@ public class ServerConfigurator {
             Iris.warn("This will only happen when your pack changes (updates/first time setup)");
             Iris.warn("(You can disable this auto restart in iris settings)");
             J.s(() -> {
-                Iris.warn("Looks like the restart command diddn't work. Stopping the server instead!");
+                Iris.warn("Looks like the restart command didn't work. Stopping the server instead!");
                 Bukkit.shutdown();
             }, 100);
             Bukkit.dispatchCommand(Bukkit.getConsoleSender(), "restart");
@@ -172,22 +178,24 @@ public class ServerConfigurator {
     }
 
     public static boolean verifyDataPackInstalled(IrisDimension dimension) {
-        IrisData idm = IrisData.get(Iris.instance.getDataFolder("packs", dimension.getLoadKey()));
         KSet<String> keys = new KSet<>();
         boolean warn = false;
 
-        for (IrisBiome i : dimension.getAllBiomes(() -> idm)) {
+        for (IrisBiome i : dimension.getAllBiomes(dimension::getLoader)) {
             if (i.isCustom()) {
                 for (IrisBiomeCustom j : i.getCustomDerivitives()) {
                     keys.add(dimension.getLoadKey() + ":" + j.getId());
                 }
             }
         }
+        String key = getWorld(dimension.getLoader());
+        if (key == null) key = dimension.getLoadKey();
+        else key += "/" + dimension.getLoadKey();
 
         if (!INMS.get().supportsDataPacks()) {
             if (!keys.isEmpty()) {
                 Iris.warn("===================================================================================");
-                Iris.warn("Pack " + dimension.getLoadKey() + " has " + keys.size() + " custom biome(s). ");
+                Iris.warn("Pack " + key + " has " + keys.size() + " custom biome(s). ");
                 Iris.warn("Your server version does not yet support datapacks for iris.");
                 Iris.warn("The world will generate these biomes as backup biomes.");
                 Iris.warn("====================================================================================");
@@ -206,7 +214,7 @@ public class ServerConfigurator {
         }
 
         if (warn) {
-            Iris.error("The Pack " + dimension.getLoadKey() + " is INCAPABLE of generating custom biomes");
+            Iris.error("The Pack " + key + " is INCAPABLE of generating custom biomes");
             Iris.error("If not done automatically, restart your server before generating with this pack!");
         }
 
@@ -220,6 +228,17 @@ public class ServerConfigurator {
                 .map(IrisData::get);
     }
 
+    @Nullable
+    public static String getWorld(@NonNull IrisData data) {
+        String worldContainer = Bukkit.getWorldContainer().getAbsolutePath();
+        if (!worldContainer.endsWith(File.separator)) worldContainer += File.separator;
+        
+        String path = data.getDataFolder().getAbsolutePath();
+        if (!path.startsWith(worldContainer)) return null;
+        int l = path.endsWith(File.separator) ? 11 : 10;
+        return path.substring(worldContainer.length(), path.length() - l);
+    }
+
     private static Stream<File> listFiles(File parent) {
         var files = parent.listFiles();
         return files == null ? Stream.empty() : Arrays.stream(files);

core/src/main/java/com/volmit/iris/core/commands/CommandIris.java

@@ -21,6 +21,7 @@ package com.volmit.iris.core.commands;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.IrisSettings;
 import com.volmit.iris.core.loader.IrisData;
+import com.volmit.iris.core.nms.INMS;
 import com.volmit.iris.core.pregenerator.ChunkUpdater;
 import com.volmit.iris.core.service.StudioSVC;
 import com.volmit.iris.core.tools.IrisBenchmarking;
@@ -412,7 +413,7 @@ public class CommandIris implements DecreeExecutor {
     ) {
         sender().sendMessage(C.GREEN + "Downloading pack: " + pack + "/" + branch + (trim ? " trimmed" : "") + (overwrite ? " overwriting" : ""));
         if (pack.equals("overworld")) {
-            String url = "https://github.com/IrisDimensions/overworld/releases/download/" + Iris.OVERWORLD_TAG + "/overworld.zip";
+            String url = "https://github.com/IrisDimensions/overworld/releases/download/" + INMS.OVERWORLD_TAG + "/overworld.zip";
             Iris.service(StudioSVC.class).downloadRelease(sender(), url, trim, overwrite);
         } else {
             Iris.service(StudioSVC.class).downloadSearch(sender(), "IrisDimensions/" + pack + "/" + branch, trim, overwrite);
@@ -598,10 +599,10 @@ public class CommandIris implements DecreeExecutor {
                     continue;
                 }
                 Iris.info(C.LIGHT_PURPLE + "Preparing Spawn for " + s + "' using Iris:" + generator + "...");
-                new WorldCreator(s)
+                WorldCreator c = new WorldCreator(s)
                         .generator(getDefaultWorldGenerator(s, generator))
-                        .environment(IrisData.loadAnyDimension(generator).getEnvironment())
-                        .createWorld();
+                        .environment(IrisData.loadAnyDimension(generator).getEnvironment());
+                INMS.get().createWorld(c);
                 Iris.info(C.LIGHT_PURPLE + "Loaded " + s + "!");
             }
         } catch (Throwable e) {

core/src/main/java/com/volmit/iris/core/link/NexoDataProvider.java

@@ -125,7 +125,7 @@ public class NexoDataProvider extends ExternalDataProvider {
     @NotNull
     @Override
     public Identifier[] getBlockTypes() {
-        return Arrays.stream(NexoItems.itemNames())
+        return NexoItems.itemNames().stream()
                 .map(i -> new Identifier("nexo", i))
                 .filter(i -> {
                     try {
@@ -140,7 +140,7 @@ public class NexoDataProvider extends ExternalDataProvider {
     @NotNull
     @Override
     public Identifier[] getItemTypes() {
-        return Arrays.stream(NexoItems.itemNames())
+        return NexoItems.itemNames().stream()
                 .map(i -> new Identifier("nexo", i))
                 .filter(i -> {
                     try {

core/src/main/java/com/volmit/iris/core/nms/INMS.java

@@ -23,6 +23,7 @@ import com.volmit.iris.core.IrisSettings;
 import com.volmit.iris.core.nms.v1X.NMSBinding1X;
 import org.bukkit.Bukkit;
 
+import java.util.List;
 import java.util.Map;
 
 public class INMS {
@@ -35,8 +36,15 @@ public class INMS {
             "1.21.3", "v1_21_R2",
             "1.21.4", "v1_21_R3"
     );
+    private static final List<Version> PACKS = List.of(
+            new Version(21, 4, "31020"),
+            new Version(21, 2, "31000"),
+            new Version(20, 1, "3910")
+    );
+
     //@done
     private static final INMSBinding binding = bind();
+    public static final String OVERWORLD_TAG = getOverworldTag();
 
     public static INMSBinding get() {
         return binding;
@@ -87,4 +95,26 @@ public class INMS {
 
         return new NMSBinding1X();
     }
+
+    private static String getOverworldTag() {
+        var version = Bukkit.getServer().getBukkitVersion().split("-")[0].split("\\.", 3);
+        int major = 0;
+        int minor = 0;
+
+        if (version.length > 2) {
+            major = Integer.parseInt(version[1]);
+            minor = Integer.parseInt(version[2]);
+        } else if (version.length == 2) {
+            major = Integer.parseInt(version[1]);
+        }
+
+        for (var p : PACKS) {
+            if (p.major > major || p.minor > minor)
+                continue;
+            return p.tag;
+        }
+        return "3910";
+    }
+
+    private record Version(int major, int minor, String tag) {}
 }

core/src/main/java/com/volmit/iris/core/nms/INMSBinding.java

@@ -18,7 +18,9 @@
 
 package com.volmit.iris.core.nms;
 
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.core.nms.datapack.DataVersion;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
@@ -30,15 +32,12 @@ import com.volmit.iris.util.nbt.mca.palette.MCAPaletteAccess;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
-import org.bukkit.entity.Dolphin;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
 import org.bukkit.event.entity.CreatureSpawnEvent;
 import org.bukkit.generator.ChunkGenerator;
-import org.bukkit.generator.structure.Structure;
 import org.bukkit.inventory.ItemStack;
 
-import java.awt.*;
 import java.awt.Color;
 
 public interface INMSBinding {
@@ -91,7 +90,12 @@ public interface INMSBinding {
     MCABiomeContainer newBiomeContainer(int min, int max);
 
     default World createWorld(WorldCreator c) {
-        return c.createWorld();
+        if (missingDimensionTypes(true, true, true))
+            throw new IllegalStateException("Missing dimenstion types to create world");
+
+        try (var ignored = injectLevelStems()) {
+            return c.createWorld();
+        }
     }
 
     int countCustomBiomes();
@@ -125,4 +129,10 @@ public interface INMSBinding {
     }
 
     KList<String> getStructureKeys();
+
+    AutoClosing injectLevelStems();
+
+    Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end);
+
+    boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end);
 }

core/src/main/java/com/volmit/iris/core/nms/container/AutoClosing.java

@@ -0,0 +1,22 @@
+package com.volmit.iris.core.nms.container;
+
+import com.volmit.iris.util.function.NastyRunnable;
+import lombok.AllArgsConstructor;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+@AllArgsConstructor
+public class AutoClosing implements AutoCloseable {
+    private final AtomicBoolean closed = new AtomicBoolean();
+    private final NastyRunnable action;
+
+    @Override
+    public void close() {
+        if (closed.getAndSet(true)) return;
+        try {
+            action.run();
+        } catch (Throwable e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

core/src/main/java/com/volmit/iris/core/nms/datapack/IDataFixer.java

@@ -20,46 +20,6 @@ public interface IDataFixer {
         return obj;
     }
 
-    default JSONObject createPreset() {
-        return new JSONObject("""
-{
-  "dimensions": {
-    "minecraft:overworld": {
-      "type": "iris:overworld",
-      "generator": {
-        "type": "minecraft:noise",
-        "biome_source": {
-          "type": "minecraft:multi_noise",
-          "preset": "minecraft:overworld"
-        },
-        "settings": "minecraft:overworld"
-      }
-    },
-    "minecraft:the_end": {
-      "type": "iris:the_end",
-      "generator": {
-        "type": "minecraft:noise",
-        "biome_source": {
-          "type": "minecraft:the_end"
-        },
-        "settings": "minecraft:end"
-      }
-    },
-    "minecraft:the_nether": {
-      "type": "iris:the_nether",
-      "generator": {
-        "type": "minecraft:noise",
-        "biome_source": {
-          "type": "minecraft:multi_noise",
-          "preset": "minecraft:nether"
-        },
-        "settings": "minecraft:nether"
-      }
-    }
-  }
-}""");
-    }
-
     enum Dimension {
         OVERRWORLD,
         NETHER,

core/src/main/java/com/volmit/iris/core/nms/v1X/NMSBinding1X.java

@@ -20,7 +20,9 @@ package com.volmit.iris.core.nms.v1X;
 
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMSBinding;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.engine.framework.Engine;
 import com.volmit.iris.util.collection.KList;
 import com.volmit.iris.util.collection.KMap;
@@ -118,6 +120,21 @@ public class NMSBinding1X implements INMSBinding {
         return new KList<>(list);
     }
 
+    @Override
+    public AutoClosing injectLevelStems() {
+        return new AutoClosing(() -> {});
+    }
+
+    @Override
+    public Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        return new Pair<>(0, new AutoClosing(() -> {}));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        return false;
+    }
+
     @Override
     public CompoundTag serializeEntity(Entity location) {
         return null;

core/src/main/java/com/volmit/iris/core/safeguard/IrisSafeguard.java

@@ -1,6 +1,7 @@
 package com.volmit.iris.core.safeguard;
 
 import com.volmit.iris.Iris;
+import com.volmit.iris.core.IrisSettings;
 
 public class IrisSafeguard {
     public static boolean unstablemode = false;
@@ -11,5 +12,13 @@ public class IrisSafeguard {
         Iris.info("Enabled Iris SafeGuard");
         ServerBootSFG.BootCheck();
     }
+
+    public static void earlySplash() {
+        if (ServerBootSFG.safeguardPassed || IrisSettings.get().getGeneral().DoomsdayAnnihilationSelfDestructMode)
+            return;
+
+        Iris.instance.splash();
+        UtilsSFG.splash();
+    }
 }
 

core/src/main/java/com/volmit/iris/core/safeguard/ServerBootSFG.java

@@ -3,6 +3,7 @@ package com.volmit.iris.core.safeguard;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMS;
 import com.volmit.iris.core.nms.v1X.NMSBinding1X;
+import com.volmit.iris.engine.object.IrisContextInjector;
 import org.bukkit.Bukkit;
 import org.bukkit.plugin.Plugin;
 import org.bukkit.plugin.PluginManager;
@@ -29,6 +30,7 @@ public class ServerBootSFG {
     public static boolean isJRE = false;
     public static boolean hasPrivileges = true;
     public static boolean unsuportedversion = false;
+    public static boolean missingDimensionTypes = false;
     protected static boolean safeguardPassed;
     public static boolean passedserversoftware = true;
     protected static int count;
@@ -110,6 +112,12 @@ public class ServerBootSFG {
             severityMedium++;
         }
 
+        if (IrisContextInjector.isMissingDimensionTypes()) {
+            missingDimensionTypes = true;
+            joiner.add("Missing Dimension Types");
+            severityHigh++;
+        }
+
         allIncompatibilities = joiner.toString();
 
         safeguardPassed = (severityHigh == 0 && severityMedium == 0 && severityLow == 0);

core/src/main/java/com/volmit/iris/core/safeguard/UtilsSFG.java

@@ -39,6 +39,11 @@ public class UtilsSFG {
                 Iris.safeguard(C.RED + "Server Version");
                 Iris.safeguard(C.RED + "- Iris only supports 1.20.1 > 1.21.4");
             }
+            if (ServerBootSFG.missingDimensionTypes) {
+                Iris.safeguard(C.RED + "Dimension Types");
+                Iris.safeguard(C.RED + "- Required Iris dimension types were not loaded.");
+                Iris.safeguard(C.RED + "- If this still happens after a restart please contact support.");
+            }
             if (!ServerBootSFG.passedserversoftware) {
                 Iris.safeguard(C.YELLOW + "Unsupported Server Software");
                 Iris.safeguard(C.YELLOW + "- Please consider using Paper or Purpur instead.");

core/src/main/java/com/volmit/iris/core/service/StudioSVC.java

@@ -24,6 +24,7 @@ import com.volmit.iris.Iris;
 import com.volmit.iris.core.IrisSettings;
 import com.volmit.iris.core.ServerConfigurator;
 import com.volmit.iris.core.loader.IrisData;
+import com.volmit.iris.core.nms.INMS;
 import com.volmit.iris.core.pack.IrisPack;
 import com.volmit.iris.core.project.IrisProject;
 import com.volmit.iris.core.tools.IrisToolbelt;
@@ -64,7 +65,7 @@ public class StudioSVC implements IrisService {
             if (!f.exists()) {
                 Iris.info("Downloading Default Pack " + pack);
                 if (pack.equals("overworld")) {
-                    String url = "https://github.com/IrisDimensions/overworld/releases/download/" + Iris.OVERWORLD_TAG + "/overworld.zip";
+                    String url = "https://github.com/IrisDimensions/overworld/releases/download/" + INMS.OVERWORLD_TAG + "/overworld.zip";
                     Iris.service(StudioSVC.class).downloadRelease(Iris.getSender(), url, false, false);
                 } else {
                     downloadSearch(Iris.getSender(), pack, false);

core/src/main/java/com/volmit/iris/core/tools/IrisCreator.java

@@ -22,6 +22,7 @@ import com.google.common.util.concurrent.AtomicDouble;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.IrisSettings;
 import com.volmit.iris.core.ServerConfigurator;
+import com.volmit.iris.core.nms.INMS;
 import com.volmit.iris.core.pregenerator.PregenTask;
 import com.volmit.iris.core.service.StudioSVC;
 import com.volmit.iris.engine.object.IrisDimension;
@@ -170,7 +171,7 @@ public class IrisCreator {
 
         try {
             J.sfut(() -> {
-                world.set(wc.createWorld());
+                world.set(INMS.get().createWorld(wc));
             }).get();
         } catch (Throwable e) {
             e.printStackTrace();

core/src/main/java/com/volmit/iris/core/tools/IrisWorldCreator.java

@@ -32,8 +32,6 @@ import sun.misc.Unsafe;
 import java.io.File;
 
 public class IrisWorldCreator {
-    public static final WorldType IRIS;
-
     private String name;
     private boolean studio = false;
     private String dimensionName = null;
@@ -85,7 +83,6 @@ public class IrisWorldCreator {
 
 
         return new WorldCreator(name)
-                .type(IRIS)
                 .environment(findEnvironment())
                 .generateStructures(true)
                 .generator(g).seed(seed);
@@ -104,17 +101,4 @@ public class IrisWorldCreator {
         this.studio = studio;
         return this;
     }
-
-    static {
-        try {
-            var unsafe = new WrappedField<Unsafe, Unsafe>(Unsafe.class, "theUnsafe").get();
-            var iris = (WorldType) unsafe.allocateInstance(WorldType.class);
-            unsafe.putIntVolatile(iris, unsafe.objectFieldOffset(Enum.class.getDeclaredField("ordinal")), 0);
-            unsafe.putObjectVolatile(iris, unsafe.objectFieldOffset(Enum.class.getDeclaredField("name")), "IRIS");
-
-            IRIS = iris;
-        } catch (Throwable e) {
-            throw new ExceptionInInitializerError(e);
-        }
-    }
 }

core/src/main/java/com/volmit/iris/engine/object/IrisContextInjector.java

@@ -0,0 +1,77 @@
+package com.volmit.iris.engine.object;
+
+import com.volmit.iris.core.nms.INMS;
+import com.volmit.iris.core.nms.container.AutoClosing;
+import com.volmit.iris.util.misc.ServerProperties;
+import lombok.Getter;
+import org.bukkit.Bukkit;
+import org.bukkit.configuration.ConfigurationSection;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.world.WorldInitEvent;
+
+import java.util.List;
+
+import static com.volmit.iris.Iris.instance;
+
+public class IrisContextInjector implements Listener {
+    @Getter
+    private static boolean missingDimensionTypes = false;
+    private AutoClosing autoClosing = null;
+    private final int totalWorlds;
+    private int worldCounter = 0;
+
+    public IrisContextInjector() {
+        if (!Bukkit.getWorlds().isEmpty()) {
+            totalWorlds = 0;
+            return;
+        }
+
+        String levelName = ServerProperties.LEVEL_NAME;
+        List<String> irisWorlds = irisWorlds();
+        boolean overworld = irisWorlds.contains(levelName);
+        boolean nether = irisWorlds.contains(levelName + "_nether");
+        boolean end = irisWorlds.contains(levelName + "_end");
+
+        int i = 1;
+        if (Bukkit.getAllowNether()) i++;
+        if (Bukkit.getAllowEnd()) i++;
+
+        if (INMS.get().missingDimensionTypes(overworld, nether, end)) {
+            missingDimensionTypes = true;
+            totalWorlds = 0;
+            return;
+        }
+
+        if (overworld || nether || end) {
+            var pair = INMS.get().injectUncached(overworld, nether, end);
+            i += pair.getA() - 3;
+            autoClosing = pair.getB();
+        }
+
+        totalWorlds = i;
+        instance.registerListener(this);
+    }
+
+    @EventHandler
+    public void on(WorldInitEvent event) {
+        if (++worldCounter < totalWorlds) return;
+        if (autoClosing != null) {
+            autoClosing.close();
+            autoClosing = null;
+        }
+        instance.unregisterListener(this);
+    }
+
+    private List<String> irisWorlds() {
+        var config = YamlConfiguration.loadConfiguration(ServerProperties.BUKKIT_YML);
+        ConfigurationSection section = config.getConfigurationSection("worlds");
+        if (section == null) return List.of();
+
+        return section.getKeys(false)
+                .stream()
+                .filter(k -> section.getString(k + ".generator", "").startsWith("Iris"))
+                .toList();
+    }
+}

core/src/main/java/com/volmit/iris/engine/object/IrisDimension.java

@@ -19,6 +19,7 @@
 package com.volmit.iris.engine.object;
 
 import com.volmit.iris.Iris;
+import com.volmit.iris.core.IrisSettings;
 import com.volmit.iris.core.ServerConfigurator.DimensionHeight;
 import com.volmit.iris.core.loader.IrisData;
 import com.volmit.iris.core.loader.IrisRegistrant;
@@ -27,6 +28,7 @@ import com.volmit.iris.core.nms.datapack.IDataFixer;
 import com.volmit.iris.engine.data.cache.AtomicCache;
 import com.volmit.iris.engine.object.annotations.*;
 import com.volmit.iris.util.collection.KList;
+import com.volmit.iris.util.collection.KSet;
 import com.volmit.iris.util.data.DataProvider;
 import com.volmit.iris.util.io.IO;
 import com.volmit.iris.util.json.JSONObject;
@@ -377,60 +379,35 @@ public class IrisDimension extends IrisRegistrant {
         return landBiomeStyle;
     }
 
-    public boolean installDataPack(IDataFixer fixer, DataProvider data, File datapacks, DimensionHeight height) {
-        boolean write = false;
-        boolean changed = false;
-
-        IO.delete(new File(datapacks, "iris/data/" + getLoadKey().toLowerCase()));
-
-        for (IrisBiome i : getAllBiomes(data)) {
-            if (i.isCustom()) {
-                write = true;
-
-                for (IrisBiomeCustom j : i.getCustomDerivitives()) {
-                    File output = new File(datapacks, "iris/data/" + getLoadKey().toLowerCase() + "/worldgen/biome/" + j.getId() + ".json");
-
-                    if (!output.exists()) {
-                        changed = true;
-                    }
-
-                    Iris.verbose("    Installing Data Pack Biome: " + output.getPath());
-                    output.getParentFile().mkdirs();
-                    try {
-                        IO.writeAll(output, j.generateJson(fixer));
-                    } catch (IOException e) {
-                        Iris.reportError(e);
-                        e.printStackTrace();
-                    }
-                }
-            }
-        }
-
-        Iris.verbose("    Installing Data Pack Dimension Types: \"iris:overworld\", \"iris:the_nether\", \"iris:the_end\"");
-        changed = writeDimensionType(changed, datapacks, height);
-
-        Iris.verbose("    Installing Data Pack World Preset: \"minecraft:iris\"");
-        changed = writeWorldPreset(changed, datapacks, fixer);
-
-        if (write) {
-            File mcm = new File(datapacks, "iris/pack.mcmeta");
-            try {
-                IO.writeAll(mcm, """
-                        {
-                            "pack": {
-                                "description": "Iris Data Pack. This pack contains all installed Iris Packs' resources.",
-                                "pack_format": {}
-                            }
+    public void installBiomes(IDataFixer fixer, DataProvider data, KList<File> folders, KSet<String> biomes) {
+        getAllBiomes(data)
+                .stream()
+                .filter(IrisBiome::isCustom)
+                .map(IrisBiome::getCustomDerivitives)
+                .flatMap(KList::stream)
+                .parallel()
+                .forEach(j -> {
+                    String json = j.generateJson(fixer);
+                    synchronized (biomes) {
+                        if (!biomes.add(j.getId())) {
+                            Iris.verbose("Duplicate Data Pack Biome: " + getLoadKey() + "/" + j.getId());
+                            return;
                         }
-                        """.replace("{}", INMS.get().getDataVersion().getPackFormat() + ""));
-            } catch (IOException e) {
-                Iris.reportError(e);
-                e.printStackTrace();
-            }
-            Iris.verbose("    Installing Data Pack MCMeta: " + mcm.getPath());
-        }
+                    }
 
-        return changed;
+                    for (File datapacks : folders) {
+                        File output = new File(datapacks, "iris/data/" + getLoadKey().toLowerCase() + "/worldgen/biome/" + j.getId() + ".json");
+
+                        Iris.verbose("    Installing Data Pack Biome: " + output.getPath());
+                        output.getParentFile().mkdirs();
+                        try {
+                            IO.writeAll(output, json);
+                        } catch (IOException e) {
+                            Iris.reportError(e);
+                            e.printStackTrace();
+                        }
+                    }
+                });
     }
 
     @Override
@@ -448,56 +425,55 @@ public class IrisDimension extends IrisRegistrant {
 
     }
 
-    public boolean writeDimensionType(boolean changed, File datapacks, DimensionHeight height) {
-        File dimTypeOverworld = new File(datapacks, "iris/data/iris/dimension_type/overworld.json");
-        if (!dimTypeOverworld.exists())
-            changed = true;
-        dimTypeOverworld.getParentFile().mkdirs();
-        try {
-            IO.writeAll(dimTypeOverworld, height.overworldType());
-        } catch (IOException e) {
-            Iris.reportError(e);
-            e.printStackTrace();
+    public static void writeShared(KList<File> folders, DimensionHeight height) {
+        Iris.verbose("    Installing Data Pack Dimension Types: \"iris:overworld\", \"iris:the_nether\", \"iris:the_end\"");
+        for (File datapacks : folders) {
+            write(datapacks, "overworld", height.overworldType());
+            write(datapacks, "the_nether", height.netherType());
+            write(datapacks, "the_end", height.endType());
         }
 
+        String raw = """
+                        {
+                            "pack": {
+                                "description": "Iris Data Pack. This pack contains all installed Iris Packs' resources.",
+                                "pack_format": {}
+                            }
+                        }
+                        """.replace("{}", INMS.get().getDataVersion().getPackFormat() + "");
 
-        File dimTypeNether = new File(datapacks, "iris/data/iris/dimension_type/the_nether.json");
-        if (!dimTypeNether.exists())
-            changed = true;
-        dimTypeNether.getParentFile().mkdirs();
-        try {
-            IO.writeAll(dimTypeNether, height.netherType());
-        } catch (IOException e) {
-            Iris.reportError(e);
-            e.printStackTrace();
+        for (File datapacks : folders) {
+            File mcm = new File(datapacks, "iris/pack.mcmeta");
+            try {
+                IO.writeAll(mcm, raw);
+            } catch (IOException e) {
+                Iris.reportError(e);
+                e.printStackTrace();
+            }
+            Iris.verbose("    Installing Data Pack MCMeta: " + mcm.getPath());
         }
-
-
-        File dimTypeEnd = new File(datapacks, "iris/data/iris/dimension_type/the_end.json");
-        if (!dimTypeEnd.exists())
-            changed = true;
-        dimTypeEnd.getParentFile().mkdirs();
-        try {
-            IO.writeAll(dimTypeEnd, height.endType());
-        } catch (IOException e) {
-            Iris.reportError(e);
-            e.printStackTrace();
-        }
-
-        return changed;
     }
 
-    public boolean writeWorldPreset(boolean changed, File datapacks, IDataFixer fixer) {
-        File worldPreset = new File(datapacks, "iris/data/minecraft/worldgen/world_preset/iris.json");
-        if (!worldPreset.exists())
-            changed = true;
+    private static void write(File datapacks, String type, String json) {
+        File dimType = new File(datapacks, "iris/data/iris/dimension_type/" + type + ".json");
+        File dimTypeVanilla = new File(datapacks, "iris/data/minecraft/dimension_type/" + type + ".json");
+
+        dimType.getParentFile().mkdirs();
         try {
-            IO.writeAll(worldPreset, fixer.createPreset());
+            IO.writeAll(dimType, json);
         } catch (IOException e) {
             Iris.reportError(e);
             e.printStackTrace();
         }
 
-        return changed;
+        if (IrisSettings.get().getGeneral().adjustVanillaHeight || dimTypeVanilla.exists()) {
+            dimTypeVanilla.getParentFile().mkdirs();
+            try {
+                IO.writeAll(dimTypeVanilla, json);
+            } catch (IOException e) {
+                Iris.reportError(e);
+                e.printStackTrace();
+            }
+        }
     }
 }

core/src/main/java/com/volmit/iris/util/misc/ServerProperties.java

@@ -0,0 +1,44 @@
+package com.volmit.iris.util.misc;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.Properties;
+
+public class ServerProperties {
+    public static final Properties DATA = new Properties();
+    public static final File SERVER_PROPERTIES;
+    public static final File BUKKIT_YML;
+
+    public static final String LEVEL_NAME;
+
+    static {
+        String[] args = ProcessHandle.current()
+                .info()
+                .arguments()
+                .orElse(new String[0]);
+
+        String propertiesPath = "server.properties";
+        String bukkitYml = "bukkit.yml";
+        String levelName = null;
+
+        for (int i = 0; i < args.length - 1; i++) {
+            switch (args[i]) {
+                case "-c", "--config" -> propertiesPath = args[i + 1];
+                case "-b", "--bukkit-settings" -> bukkitYml = args[i + 1];
+                case "-w", "--level-name", "--world" -> levelName = args[i + 1];
+            }
+        }
+
+        SERVER_PROPERTIES = new File(propertiesPath);
+        BUKKIT_YML = new File(bukkitYml);
+        try (FileInputStream in = new FileInputStream(SERVER_PROPERTIES)){
+            DATA.load(in);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+
+        if (levelName != null) LEVEL_NAME = levelName;
+        else LEVEL_NAME = DATA.getProperty("level-name", "world");
+    }
+}

nms/v1_20_R1/src/main/java/com/volmit/iris/core/nms/v1_20_R1/NMSBinding.java

@@ -2,8 +2,10 @@ package com.volmit.iris.core.nms.v1_20_R1;
 
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.Lifecycle;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMSBinding;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.engine.data.cache.AtomicCache;
 import com.volmit.iris.engine.framework.Engine;
@@ -20,27 +22,36 @@ import com.volmit.iris.util.nbt.mca.palette.*;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 import com.volmit.iris.util.scheduling.J;
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
+import lombok.SneakyThrows;
+import net.minecraft.core.*;
 import net.minecraft.core.Registry;
-import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.nbt.*;
 import net.minecraft.nbt.Tag;
+import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.entity.EntityDimensions;
 import net.minecraft.world.level.LevelReader;
 import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.Biomes;
 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.entity.BlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.ChunkStatus;
 import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -73,11 +84,10 @@ import java.io.DataOutputStream;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.Vector;
+import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
 public class NMSBinding implements INMSBinding {
 
@@ -85,9 +95,11 @@ public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -568,6 +580,9 @@ public class NMSBinding implements INMSBinding {
 
     public void inject(long seed, Engine engine, World world) {
         var chunkMap = ((CraftWorld)world).getHandle().getChunkSource().chunkMap;
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
         chunkMap.generator = new IrisChunkGenerator(chunkMap.generator, seed, engine, world);
     }
 
@@ -628,4 +643,120 @@ public class NMSBinding implements INMSBinding {
             }
         }
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public com.volmit.iris.core.nms.container.Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                        old.resources(),
+                        old.dataConfiguration(),
+                        old.datapackWorldgen(),
+                        createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().registryOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new com.volmit.iris.core.nms.container.Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), Lifecycle.stable());
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.registryKeySet().forEach(key -> {
+            var value = source.get(key);
+            var info = source.lifecycle(value);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R2/src/main/java/com/volmit/iris/core/nms/v1_20_R2/NMSBinding.java

@@ -8,21 +8,34 @@ import java.io.DataOutputStream;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.Vector;
+import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
 import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.Lifecycle;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.util.scheduling.J;
+import lombok.SneakyThrows;
+import net.minecraft.core.*;
+import net.minecraft.core.Registry;
 import net.minecraft.nbt.*;
 import net.minecraft.nbt.Tag;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -61,10 +74,6 @@ import com.volmit.iris.util.nbt.mca.palette.*;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
-import net.minecraft.core.Registry;
-import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
@@ -83,9 +92,11 @@ public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -538,6 +549,9 @@ public class NMSBinding implements INMSBinding {
 
     public void inject(long seed, Engine engine, World world) {
         var chunkMap = ((CraftWorld)world).getHandle().getChunkSource().chunkMap;
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
         chunkMap.generator = new IrisChunkGenerator(chunkMap.generator, seed, engine, world);
     }
 
@@ -630,4 +644,120 @@ public class NMSBinding implements INMSBinding {
     public static Holder<net.minecraft.world.level.biome.Biome> biomeToBiomeBase(Registry<net.minecraft.world.level.biome.Biome> registry, Biome biome) {
         return registry.getHolderOrThrow(ResourceKey.create(Registries.BIOME, CraftNamespacedKey.toMinecraft(biome.getKey())));
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public com.volmit.iris.core.nms.container.Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                        old.resources(),
+                        old.dataConfiguration(),
+                        old.datapackWorldgen(),
+                        createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().registryOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new com.volmit.iris.core.nms.container.Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), Lifecycle.stable());
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.registryKeySet().forEach(key -> {
+            var value = source.get(key);
+            var info = source.lifecycle(value);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R3/src/main/java/com/volmit/iris/core/nms/v1_20_R3/NMSBinding.java

@@ -8,21 +8,34 @@ import java.io.DataOutputStream;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.Vector;
+import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
 import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.Lifecycle;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.util.scheduling.J;
+import lombok.SneakyThrows;
+import net.minecraft.core.*;
+import net.minecraft.core.Registry;
 import net.minecraft.nbt.*;
 import net.minecraft.nbt.Tag;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -61,10 +74,6 @@ import com.volmit.iris.util.nbt.mca.palette.*;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
-import net.minecraft.core.Registry;
-import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
@@ -83,9 +92,11 @@ public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -538,6 +549,9 @@ public class NMSBinding implements INMSBinding {
 
     public void inject(long seed, Engine engine, World world) {
         var chunkMap = ((CraftWorld)world).getHandle().getChunkSource().chunkMap;
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
         chunkMap.generator = new IrisChunkGenerator(chunkMap.generator, seed, engine, world);
     }
 
@@ -631,4 +645,120 @@ public class NMSBinding implements INMSBinding {
     public static Holder<net.minecraft.world.level.biome.Biome> biomeToBiomeBase(Registry<net.minecraft.world.level.biome.Biome> registry, Biome biome) {
         return registry.getHolderOrThrow(ResourceKey.create(Registries.BIOME, CraftNamespacedKey.toMinecraft(biome.getKey())));
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public com.volmit.iris.core.nms.container.Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                        old.resources(),
+                        old.dataConfiguration(),
+                        old.datapackWorldgen(),
+                        createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().registryOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new com.volmit.iris.core.nms.container.Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), Lifecycle.stable());
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.registryKeySet().forEach(key -> {
+            var value = source.get(key);
+            var info = source.lifecycle(value);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_20_R4/src/main/java/com/volmit/iris/core/nms/v1_20_R4/NMSBinding.java

@@ -6,12 +6,17 @@ import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
 import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.Lifecycle;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.datapack.DataVersion;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 import com.volmit.iris.util.scheduling.J;
+import lombok.SneakyThrows;
 import net.minecraft.core.*;
 import net.minecraft.core.Registry;
 import net.minecraft.core.component.DataComponents;
@@ -25,15 +30,24 @@ import net.minecraft.nbt.LongTag;
 import net.minecraft.nbt.ShortTag;
 import net.minecraft.nbt.StringTag;
 import net.minecraft.nbt.Tag;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.server.commands.data.DataCommands;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.block.entity.BlockEntityType;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -86,9 +100,11 @@ public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -544,6 +560,10 @@ public class NMSBinding implements INMSBinding {
 
     public void inject(long seed, Engine engine, World world) {
         var chunkMap = ((CraftWorld)world).getHandle().getChunkSource().chunkMap;
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
+
         chunkMap.generator = new IrisChunkGenerator(chunkMap.generator, seed, engine, world);
     }
 
@@ -650,4 +670,120 @@ public class NMSBinding implements INMSBinding {
 
         return keys;
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public com.volmit.iris.core.nms.container.Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                        old.resources(),
+                        old.dataConfiguration(),
+                        old.datapackWorldgen(),
+                        createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().registryOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new com.volmit.iris.core.nms.container.Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), RegistrationInfo.BUILT_IN);
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.registryKeySet().forEach(key -> {
+            var value = source.get(key);
+            var info = source.registrationInfo(key).orElse(null);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return new ResourceLocation("iris", key.location().getPath());
+    }
 }

nms/v1_21_R1/src/main/java/com/volmit/iris/core/nms/v1_21_R1/NMSBinding.java

@@ -10,22 +10,38 @@ import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
 import com.mojang.datafixers.util.Pair;
+import com.mojang.serialization.Lifecycle;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
 import com.volmit.iris.core.nms.datapack.DataVersion;
 import com.volmit.iris.util.scheduling.J;
+import lombok.SneakyThrows;
+import net.minecraft.core.*;
+import net.minecraft.core.Registry;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.nbt.*;
 import net.minecraft.nbt.Tag;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.server.level.ChunkMap;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -64,10 +80,6 @@ import com.volmit.iris.util.nbt.mca.palette.*;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
-import net.minecraft.core.BlockPos;
-import net.minecraft.core.Holder;
-import net.minecraft.core.Registry;
-import net.minecraft.core.RegistryAccess;
 import net.minecraft.core.registries.Registries;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
@@ -85,9 +97,11 @@ public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -546,6 +560,9 @@ public class NMSBinding implements INMSBinding {
         var worldGenContextField = getField(chunkMap.getClass(), WorldGenContext.class);
         worldGenContextField.setAccessible(true);
         var worldGenContext = (WorldGenContext) worldGenContextField.get(chunkMap);
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
 
         var newContext = new WorldGenContext(
                 worldGenContext.level(), new IrisChunkGenerator(worldGenContext.generator(), seed, engine, world),
@@ -657,4 +674,120 @@ public class NMSBinding implements INMSBinding {
 
         return keys;
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public com.volmit.iris.core.nms.container.Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                        old.resources(),
+                        old.dataConfiguration(),
+                        old.datapackWorldgen(),
+                        createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().registryOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new com.volmit.iris.core.nms.container.Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().registryOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.registryOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.registry(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.registryOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.getHolder(ResourceKey.create(Registries.DIMENSION_TYPE, loc)).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), RegistrationInfo.BUILT_IN);
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.registryKeySet().forEach(key -> {
+            var value = source.get(key);
+            var info = source.registrationInfo(key).orElse(null);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath());
+    }
 }

nms/v1_21_R2/src/main/java/com/volmit/iris/core/nms/v1_21_R2/NMSBinding.java

@@ -6,22 +6,37 @@ import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
+import com.mojang.serialization.Lifecycle;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.core.nms.datapack.DataVersion;
 import com.volmit.iris.util.scheduling.J;
+import lombok.SneakyThrows;
 import net.minecraft.core.*;
 import net.minecraft.core.Registry;
 import net.minecraft.core.component.DataComponents;
 import net.minecraft.nbt.*;
 import net.minecraft.nbt.Tag;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.block.Blocks;
 import net.minecraft.world.level.block.EntityBlock;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -72,9 +87,11 @@ public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -533,6 +550,9 @@ public class NMSBinding implements INMSBinding {
         var worldGenContextField = getField(chunkMap.getClass(), WorldGenContext.class);
         worldGenContextField.setAccessible(true);
         var worldGenContext = (WorldGenContext) worldGenContextField.get(chunkMap);
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
 
         var newContext = new WorldGenContext(
                 worldGenContext.level(), new IrisChunkGenerator(worldGenContext.generator(), seed, engine, world),
@@ -644,4 +664,120 @@ public class NMSBinding implements INMSBinding {
 
         return keys;
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                        old.resources(),
+                        old.dataConfiguration(),
+                        old.datapackWorldgen(),
+                        createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().lookupOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().lookupOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.lookupOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.lookup(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.lookupOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.get(loc).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), RegistrationInfo.BUILT_IN);
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.listElementIds().forEach(key -> {
+            var value = source.getValue(key);
+            var info = source.registrationInfo(key).orElse(null);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath());
+    }
 }

nms/v1_21_R3/src/main/java/com/volmit/iris/core/nms/v1_21_R3/NMSBinding.java

@@ -1,9 +1,12 @@
 package com.volmit.iris.core.nms.v1_21_R3;
 
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import com.mojang.serialization.Lifecycle;
 import com.volmit.iris.Iris;
 import com.volmit.iris.core.nms.INMSBinding;
+import com.volmit.iris.core.nms.container.AutoClosing;
 import com.volmit.iris.core.nms.container.BiomeColor;
+import com.volmit.iris.core.nms.container.Pair;
 import com.volmit.iris.core.nms.datapack.DataVersion;
 import com.volmit.iris.engine.data.cache.AtomicCache;
 import com.volmit.iris.engine.framework.Engine;
@@ -19,6 +22,7 @@ import com.volmit.iris.util.nbt.mca.palette.*;
 import com.volmit.iris.util.nbt.tag.CompoundTag;
 import com.volmit.iris.util.scheduling.J;
 import it.unimi.dsi.fastutil.objects.Object2IntMap;
+import lombok.SneakyThrows;
 import net.minecraft.core.Registry;
 import net.minecraft.core.*;
 import net.minecraft.core.component.DataComponents;
@@ -27,13 +31,17 @@ import net.minecraft.nbt.Tag;
 import net.minecraft.nbt.*;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.WorldLoader;
 import net.minecraft.server.commands.data.BlockDataAccessor;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.tags.TagKey;
 import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.item.component.CustomData;
 import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.biome.Biomes;
 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.entity.BlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
@@ -41,6 +49,11 @@ import net.minecraft.world.level.chunk.ChunkAccess;
 import net.minecraft.world.level.chunk.LevelChunk;
 import net.minecraft.world.level.chunk.status.ChunkStatus;
 import net.minecraft.world.level.chunk.status.WorldGenContext;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
 import org.bukkit.*;
 import org.bukkit.block.Biome;
 import org.bukkit.block.data.BlockData;
@@ -66,14 +79,18 @@ import java.lang.reflect.Modifier;
 import java.util.List;
 import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Function;
 
 public class NMSBinding implements INMSBinding {
     private final KMap<Biome, Object> baseBiomeCache = new KMap<>();
     private final BlockData AIR = Material.AIR.createBlockData();
     private final AtomicCache<MCAIdMap<net.minecraft.world.level.biome.Biome>> biomeMapCache = new AtomicCache<>();
+    private final AtomicCache<WorldLoader.DataLoadContext> dataLoadContext = new AtomicCache<>();
     private final AtomicCache<MCAIdMapper<BlockState>> registryCache = new AtomicCache<>();
     private final AtomicCache<MCAPalette<BlockState>> globalCache = new AtomicCache<>();
     private final AtomicCache<RegistryAccess> registryAccess = new AtomicCache<>();
+    private final ReentrantLock dataContextLock = new ReentrantLock(true);
     private final AtomicCache<Method> byIdRef = new AtomicCache<>();
     private Field biomeStorageCache = null;
 
@@ -532,6 +549,9 @@ public class NMSBinding implements INMSBinding {
         var worldGenContextField = getField(chunkMap.getClass(), WorldGenContext.class);
         worldGenContextField.setAccessible(true);
         var worldGenContext = (WorldGenContext) worldGenContextField.get(chunkMap);
+        var dimensionType = chunkMap.level.dimensionTypeRegistration().unwrapKey().orElse(null);
+        if (dimensionType != null && !dimensionType.location().getNamespace().equals("iris"))
+            Iris.error("Loaded world %s with invalid dimension type! (%s)", world.getName(), dimensionType.location().toString());
 
         var newContext = new WorldGenContext(
                 worldGenContext.level(), new IrisChunkGenerator(worldGenContext.generator(), seed, engine, world),
@@ -643,4 +663,120 @@ public class NMSBinding implements INMSBinding {
 
         return keys;
     }
+
+    @Override
+    public AutoClosing injectLevelStems() {
+        return inject(this::supplier);
+    }
+
+    @Override
+    @SneakyThrows
+    public Pair<Integer, AutoClosing> injectUncached(boolean overworld, boolean nether, boolean end) {
+        var reg = registry();
+        var field = getField(RegistryAccess.ImmutableRegistryAccess.class, Map.class);
+        field.setAccessible(true);
+
+        AutoClosing closing = inject(old -> new WorldLoader.DataLoadContext(
+                    old.resources(),
+                    old.dataConfiguration(),
+                    old.datapackWorldgen(),
+                    createRegistryAccess(old.datapackDimensions(), true, overworld, nether, end)
+                )
+        );
+
+        var injected = ((CraftServer) Bukkit.getServer()).getServer().worldLoader.datapackDimensions().lookupOrThrow(Registries.LEVEL_STEM);
+        var old = (Map<ResourceKey<? extends Registry<?>>, Registry<?>>) field.get(reg);
+        var fake = new HashMap<>(old);
+        fake.put(Registries.LEVEL_STEM, injected);
+        field.set(reg, fake);
+
+        return new Pair<>(
+                injected.size(),
+                new AutoClosing(() -> {
+                    closing.close();
+                    field.set(reg, old);
+                }));
+    }
+
+    @Override
+    public boolean missingDimensionTypes(boolean overworld, boolean nether, boolean end) {
+        var registry = registry().lookupOrThrow(Registries.DIMENSION_TYPE);
+        if (overworld) overworld = !registry.containsKey(createIrisKey(LevelStem.OVERWORLD));
+        if (nether) nether = !registry.containsKey(createIrisKey(LevelStem.NETHER));
+        if (end) end = !registry.containsKey(createIrisKey(LevelStem.END));
+        return overworld || nether || end;
+    }
+
+    private WorldLoader.DataLoadContext supplier(WorldLoader.DataLoadContext old) {
+        return dataLoadContext.aquire(() -> new WorldLoader.DataLoadContext(
+                old.resources(),
+                old.dataConfiguration(),
+                old.datapackWorldgen(),
+                createRegistryAccess(old.datapackDimensions(), false, true, true, true)
+        ));
+    }
+
+    @SneakyThrows
+    private AutoClosing inject(Function<WorldLoader.DataLoadContext, WorldLoader.DataLoadContext> transformer) {
+        if (!dataContextLock.tryLock()) throw new IllegalStateException("Failed to inject data context!");
+
+        var server = ((CraftServer) Bukkit.getServer());
+        var field = getField(MinecraftServer.class, WorldLoader.DataLoadContext.class);
+        var nmsServer = server.getServer();
+        var old = nmsServer.worldLoader;
+
+        field.setAccessible(true);
+        field.set(nmsServer, transformer.apply(old));
+
+        return new AutoClosing(() -> {
+            field.set(nmsServer, old);
+            dataContextLock.unlock();
+        });
+    }
+
+    private RegistryAccess.Frozen createRegistryAccess(RegistryAccess.Frozen datapack, boolean copy, boolean overworld, boolean nether, boolean end) {
+        var access = registry();
+        var dimensions = access.lookupOrThrow(Registries.DIMENSION_TYPE);
+
+        var settings = new FlatLevelGeneratorSettings(
+                Optional.empty(),
+                access.lookupOrThrow(Registries.BIOME).getOrThrow(Biomes.THE_VOID),
+                List.of()
+        );
+        settings.getLayersInfo().add(new FlatLayerInfo(1, Blocks.AIR));
+        settings.updateLayers();
+
+        var source = new FlatLevelSource(settings);
+        var fake = new MappedRegistry<>(Registries.LEVEL_STEM, Lifecycle.experimental());
+        if (overworld) register(fake, dimensions, source, LevelStem.OVERWORLD);
+        if (nether) register(fake, dimensions, source, LevelStem.NETHER);
+        if (end) register(fake, dimensions, source, LevelStem.END);
+        copy(fake, datapack.lookup(Registries.LEVEL_STEM).orElse(null));
+
+        if (copy) copy(fake, access.lookupOrThrow(Registries.LEVEL_STEM));
+
+        return new RegistryAccess.Frozen.ImmutableRegistryAccess(List.of(fake.freeze())).freeze();
+    }
+
+    private void register(MappedRegistry<LevelStem> target, Registry<DimensionType> dimensions, FlatLevelSource source, ResourceKey<LevelStem> key) {
+        var loc = createIrisKey(key);
+        target.register(key, new LevelStem(
+                dimensions.get(loc).orElseThrow(() -> new IllegalStateException("Missing dimension type " + loc + " in " + dimensions.keySet())),
+                source
+        ), RegistrationInfo.BUILT_IN);
+    }
+
+    private void copy(MappedRegistry<LevelStem> target, Registry<LevelStem> source) {
+        if (source == null) return;
+        source.listElementIds().forEach(key -> {
+            var value = source.getValue(key);
+            var info = source.registrationInfo(key).orElse(null);
+            if (value != null && info != null && !target.containsKey(key))
+                target.register(key, value, info);
+        });
+    }
+
+    private ResourceLocation createIrisKey(ResourceKey<LevelStem> key) {
+        return ResourceLocation.fromNamespaceAndPath("iris", key.location().getPath());
+    }
 }