Port to Hephaistos v2 (#424)

build.gradle

@@ -152,13 +152,13 @@ dependencies {
     api "org.jetbrains.kotlin:kotlin-reflect:${project.kotlinVersion}"
 
     // NBT parsing/manipulation/saving
-    api("com.github.jglrxavpok:Hephaistos:${project.hephaistosVersion}")
+    api("io.github.jglrxavpok.hephaistos:common:${project.hephaistosVersion}")
-    api("com.github.jglrxavpok:Hephaistos:${project.hephaistosVersion}:gson")
+    api("io.github.jglrxavpok.hephaistos:gson:${project.hephaistosVersion}")
-    api("com.github.jglrxavpok:Hephaistos:${project.hephaistosVersion}") {
+/*    api("io.github.jglrxavpok.hephaistos:common:${project.hephaistosVersion}") {
         capabilities {
-            requireCapability("org.jglrxavpok.nbt:Hephaistos-gson")
+            requireCapability("io.github.jglrxavpok.hephaistos:Hephaistos-gson")
         }
-    }
+    }*/
 
     api "com.github.Minestom:DependencyGetter:v1.0.1"
     implementation 'com.github.Minestom:MinestomDataGenerator:801b8007cf'

gradle.properties

@@ -3,6 +3,6 @@ mcVersion = 1.17
 
 asmVersion=9.2
 mixinVersion=0.8.4
-hephaistosVersion=v1.1.8
+hephaistosVersion=2.3.0
 kotlinVersion=1.5.31
-adventureVersion=4.9.3
+adventureVersion=4.9.3

src/main/java/net/minestom/server/adventure/MinestomAdventure.java

@@ -11,7 +11,7 @@ import java.util.Objects;
 
 import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
-import org.jglrxavpok.hephaistos.nbt.SNBTParser;
+import org.jglrxavpok.hephaistos.parser.SNBTParser;
 
 /**
  * Adventure related constants, etc.

src/main/java/net/minestom/server/adventure/provider/NBTLegacyHoverEventSerializer.java

@@ -16,6 +16,7 @@ import org.jglrxavpok.hephaistos.nbt.NBTException;
 import java.io.IOException;
 import java.util.Objects;
 import java.util.UUID;
+import java.util.concurrent.atomic.AtomicReference;
 
 final class NBTLegacyHoverEventSerializer implements LegacyHoverEventSerializer {
     static final NBTLegacyHoverEventSerializer INSTANCE = new NBTLegacyHoverEventSerializer();
@@ -66,17 +67,23 @@ final class NBTLegacyHoverEventSerializer implements LegacyHoverEventSerializer
 
     @Override
     public @NotNull Component serializeShowItem(HoverEvent.@NotNull ShowItem input) throws IOException {
-        final NBTCompound tag = new NBTCompound();
+        AtomicReference<NBTException> exception = new AtomicReference<>(null);
-        tag.setString(ITEM_TYPE, input.item().asString());
+        final NBTCompound tag = NBT.Compound(t -> {
-        tag.setByte(ITEM_COUNT, (byte) input.count());
+            t.setString(ITEM_TYPE, input.item().asString());
+            t.setByte(ITEM_COUNT, (byte) input.count());
 
-        final BinaryTagHolder nbt = input.nbt();
+            final BinaryTagHolder nbt = input.nbt();
-        if (nbt != null) {
+            if (nbt != null) {
-            try {
+                try {
-                tag.set(ITEM_TAG, nbt.get(MinestomAdventure.NBT_CODEC));
+                    t.set(ITEM_TAG, nbt.get(MinestomAdventure.NBT_CODEC));
-            } catch (NBTException e) {
+                } catch (NBTException e) {
-                throw new IOException(e);
+                    exception.set(e);
+                }
             }
+        });
+
+        if(exception.get() != null) {
+            throw new IOException(exception.get());
         }
 
         return Component.text(MinestomAdventure.NBT_CODEC.encode(tag));
@@ -84,14 +91,15 @@ final class NBTLegacyHoverEventSerializer implements LegacyHoverEventSerializer
 
     @Override
     public @NotNull Component serializeShowEntity(HoverEvent.@NotNull ShowEntity input, Codec.Encoder<Component, String, ? extends RuntimeException> componentEncoder) throws IOException {
-        final NBTCompound tag = new NBTCompound();
+        final NBTCompound tag = NBT.Compound(t -> {
-        tag.setString(ENTITY_ID, input.id().toString());
+            t.setString(ENTITY_ID, input.id().toString());
-        tag.setString(ENTITY_TYPE, input.type().asString());
+            t.setString(ENTITY_TYPE, input.type().asString());
 
-        final Component name = input.name();
+            final Component name = input.name();
-        if (name != null) {
+            if (name != null) {
-            tag.setString(ENTITY_NAME, componentEncoder.encode(name));
+                t.setString(ENTITY_NAME, componentEncoder.encode(name));
-        }
+            }
+        });
 
         return Component.text(MinestomAdventure.NBT_CODEC.encode(tag));
     }

src/main/java/net/minestom/server/command/ConsoleSender.java

@@ -9,6 +9,7 @@ import net.minestom.server.tag.Tag;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -23,7 +24,7 @@ public class ConsoleSender implements CommandSender {
     private static final Logger LOGGER = LoggerFactory.getLogger(ConsoleSender.class);
 
     private final Set<Permission> permissions = new CopyOnWriteArraySet<>();
-    private final NBTCompound nbtCompound = new NBTCompound();
+    private final MutableNBTCompound nbtCompound = new MutableNBTCompound();
 
     @Override
     public void sendMessage(@NotNull String message) {

src/main/java/net/minestom/server/command/ServerSender.java

@@ -7,6 +7,7 @@ import net.minestom.server.tag.Tag;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.util.Collections;
 import java.util.HashSet;
@@ -22,7 +23,7 @@ import java.util.Set;
 public class ServerSender implements CommandSender {
 
     private final Set<Permission> permissions = Collections.unmodifiableSet(new HashSet<>());
-    private final NBTCompound nbtCompound = new NBTCompound();
+    private final MutableNBTCompound nbtCompound = new MutableNBTCompound();
 
     @NotNull
     @Override

src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentItemStack.java

@@ -9,7 +9,7 @@ import net.minestom.server.network.packet.server.play.DeclareCommandsPacket;
 import org.jetbrains.annotations.NotNull;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
-import org.jglrxavpok.hephaistos.nbt.SNBTParser;
+import org.jglrxavpok.hephaistos.parser.SNBTParser;
 
 import java.io.StringReader;
 

src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentNbtCompoundTag.java

@@ -8,7 +8,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
-import org.jglrxavpok.hephaistos.nbt.SNBTParser;
+import org.jglrxavpok.hephaistos.parser.SNBTParser;
 
 import java.io.StringReader;
 

src/main/java/net/minestom/server/command/builder/arguments/minecraft/ArgumentNbtTag.java

@@ -7,7 +7,7 @@ import net.minestom.server.network.packet.server.play.DeclareCommandsPacket;
 import org.jetbrains.annotations.NotNull;
 import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
-import org.jglrxavpok.hephaistos.nbt.SNBTParser;
+import org.jglrxavpok.hephaistos.parser.SNBTParser;
 
 import java.io.StringReader;
 

src/main/java/net/minestom/server/entity/Entity.java

@@ -51,6 +51,7 @@ import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.time.Duration;
 import java.time.temporal.TemporalUnit;
@@ -143,7 +144,7 @@ public class Entity implements Viewable, Tickable, TagHandler, PermissionHandler
             this instanceof Player player ? entity -> entity.viewEngine.viewableOption.addition.accept(player) : null,
             this instanceof Player player ? entity -> entity.viewEngine.viewableOption.removal.accept(player) : null);
     protected final Set<Player> viewers = viewEngine.asSet();
-    private final NBTCompound nbtCompound = new NBTCompound();
+    private final MutableNBTCompound nbtCompound = new MutableNBTCompound();
     private final Set<Permission> permissions = new CopyOnWriteArraySet<>();
 
     protected UUID uuid;

src/main/java/net/minestom/server/entity/Metadata.java

@@ -161,7 +161,7 @@ public class Metadata {
         EMPTY_VALUES.set(TYPE_DIRECTION, Direction(Direction.DOWN));
         EMPTY_VALUES.set(TYPE_OPTUUID, OptUUID(null));
         EMPTY_VALUES.set(TYPE_OPTBLOCKID, OptBlockID(null));
-        EMPTY_VALUES.set(TYPE_NBT, NBT(new NBTEnd()));
+        EMPTY_VALUES.set(TYPE_NBT, NBT(NBTEnd.INSTANCE));
         //EMPTY_VALUES.set(TYPE_PARTICLE -> throw new UnsupportedOperationException();
         EMPTY_VALUES.set(TYPE_VILLAGERDATA, VillagerData(0, 0, 0));
         EMPTY_VALUES.set(TYPE_OPTVARINT, OptVarInt(null));

src/main/java/net/minestom/server/entity/Player.java

@@ -84,6 +84,7 @@ import org.jctools.queues.MpscUnboundedXaddArrayQueue;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.nio.charset.StandardCharsets;
@@ -237,11 +238,12 @@ public class Player extends LivingEntity implements CommandSender, Localizable,
     public void UNSAFE_init(@NotNull Instance spawnInstance) {
         this.dimensionType = spawnInstance.getDimensionType();
 
-        NBTCompound nbt = new NBTCompound();
+        NBTCompound nbt = NBT.Compound(n -> {
-        NBTCompound dimensions = MinecraftServer.getDimensionTypeManager().toNBT();
+            NBTCompound dimensions = MinecraftServer.getDimensionTypeManager().toNBT();
-        NBTCompound biomes = MinecraftServer.getBiomeManager().toNBT();
+            NBTCompound biomes = MinecraftServer.getBiomeManager().toNBT();
-        nbt.set("minecraft:dimension_type", dimensions);
+            n.set("minecraft:dimension_type", dimensions);
-        nbt.set("minecraft:worldgen/biome", biomes);
+            n.set("minecraft:worldgen/biome", biomes);
+        });
 
         final JoinGamePacket joinGamePacket = new JoinGamePacket(getEntityId(), gameMode.isHardcore(), gameMode, null,
                 List.of("minestom:world"), nbt, dimensionType.toNBT(), dimensionType.getName().asString(),

src/main/java/net/minestom/server/entity/damage/DamageType.java

@@ -10,6 +10,7 @@ import net.minestom.server.tag.TagHandler;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 /**
  * Represents a type of damage, required when calling {@link LivingEntity#damage(DamageType, float)}
@@ -29,7 +30,7 @@ public class DamageType implements TagHandler {
     };
     private final String identifier;
     private final Object nbtLock = new Object();
-    private final NBTCompound nbt = new NBTCompound();
+    private final MutableNBTCompound nbt = new MutableNBTCompound();
 
     /**
      * Creates a new damage type.

src/main/java/net/minestom/server/extensions/ExtensionManager.java

@@ -470,7 +470,7 @@ public class ExtensionManager {
 
             // While there are entries with no more elements (no more dependencies)
             while (!(
-                    loadableExtensions = dependencyMap.entrySet().stream().filter(entry -> isLoaded(entry.getValue())).collect(Collectors.toList())
+                    loadableExtensions = dependencyMap.entrySet().stream().filter(entry -> isLoaded(entry.getValue())).toList()
             ).isEmpty()
             ) {
                 // Get all "loadable" (not actually being loaded!) extensions and put them in the sorted list.

src/main/java/net/minestom/server/instance/AnvilLoader.java

@@ -6,6 +6,7 @@ import net.minestom.server.instance.block.Block;
 import net.minestom.server.instance.block.BlockHandler;
 import net.minestom.server.instance.block.BlockManager;
 import net.minestom.server.tag.Tag;
+import net.minestom.server.utils.NamespaceID;
 import net.minestom.server.utils.async.AsyncUtils;
 import net.minestom.server.world.biomes.Biome;
 import net.minestom.server.world.biomes.BiomeManager;
@@ -13,6 +14,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.mca.*;
 import org.jglrxavpok.hephaistos.nbt.*;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -22,8 +24,7 @@ import java.io.RandomAccessFile;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
-import java.util.Map;
+import java.util.*;
-import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -87,20 +88,31 @@ public class AnvilLoader implements IChunkLoader {
             return CompletableFuture.completedFuture(null);
 
         Chunk chunk = new DynamicChunk(instance, chunkX, chunkZ);
-        // TODO Biomes
+        // TODO: Parallelize block, block entities and biome loading
+
         if (fileChunk.getGenerationStatus().compareTo(ChunkColumn.GenerationStatus.Biomes) > 0) {
-            final int[] fileChunkBiomes = fileChunk.getBiomes();
+            HashMap<String, Biome> biomeCache = new HashMap<>();
-            for (int id : fileChunkBiomes) {
+
-                // ((y >> 2) & 63) << 4 | ((z >> 2) & 3) << 2 | ((x >> 2) & 3)
+            for (ChunkSection section : fileChunk.getSections().values()) {
-                final Biome biome = Objects.requireNonNullElse(BIOME_MANAGER.getById(id), BIOME);
+                for (int y = 0; y < Chunk.CHUNK_SECTION_SIZE; y++) {
-                chunk.setBiome(0, 0, 0, biome);
+                    for (int z = 0; z < Chunk.CHUNK_SIZE_Z; z++) {
+                        for (int x = 0; x < Chunk.CHUNK_SIZE_X; x++) {
+                            int finalX = fileChunk.getX() * Chunk.CHUNK_SIZE_X + x;
+                            int finalZ = fileChunk.getZ() * Chunk.CHUNK_SIZE_Z + z;
+                            int finalY = section.getY() * Chunk.CHUNK_SECTION_SIZE + y;
+                            String biomeName = section.getBiome(x, y, z);
+                            Biome biome = biomeCache.computeIfAbsent(biomeName, n -> Objects.requireNonNullElse(BIOME_MANAGER.getByName(NamespaceID.from(n)), BIOME));
+                            chunk.setBiome(finalX, finalY, finalZ, biome);
+                        }
+                    }
+                }
             }
         }
         // Blocks
         loadBlocks(chunk, fileChunk);
         loadTileEntities(chunk, fileChunk);
         // Lights
-        for (var chunkSection : fileChunk.getSections()) {
+        for (var chunkSection : fileChunk.getSections().values()) {
             Section section = chunk.getSection(chunkSection.getY());
             section.setSkyLight(chunkSection.getSkyLights());
             section.setBlockLight(chunkSection.getBlockLights());
@@ -127,7 +139,7 @@ public class AnvilLoader implements IChunkLoader {
     }
 
     private void loadBlocks(Chunk chunk, ChunkColumn fileChunk) {
-        for (var section : fileChunk.getSections()) {
+        for (var section : fileChunk.getSections().values()) {
             if (section.getEmpty()) continue;
             final int yOffset = Chunk.CHUNK_SECTION_SIZE * section.getY();
             for (int x = 0; x < Chunk.CHUNK_SECTION_SIZE; x++) {
@@ -172,12 +184,15 @@ public class AnvilLoader implements IChunkLoader {
                 block = block.withHandler(handler);
             }
             // Remove anvil tags
-            te.removeTag("id")
+            MutableNBTCompound mutableCopy = te.toMutableCompound();
-                    .removeTag("x").removeTag("y").removeTag("z")
+            mutableCopy.remove("id");
-                    .removeTag("keepPacked");
+            mutableCopy.remove("x");
+            mutableCopy.remove("y");
+            mutableCopy.remove("z");
+            mutableCopy.remove("keepPacked");
             // Place block
-            final var finalBlock = te.getSize() > 0 ?
+            final var finalBlock = mutableCopy.getSize() > 0 ?
-                    block.withNbt(te) : block;
+                    block.withNbt(mutableCopy.toCompound()) : block;
             loadedChunk.setBlock(x, y, z, finalBlock);
         }
     }
@@ -247,7 +262,7 @@ public class AnvilLoader implements IChunkLoader {
     }
 
     private void save(Chunk chunk, ChunkColumn chunkColumn) {
-        NBTList<NBTCompound> tileEntities = new NBTList<>(NBTTypes.TAG_Compound);
+        List<NBTCompound> tileEntities = new ArrayList<>();
         chunkColumn.setGenerationStatus(ChunkColumn.GenerationStatus.Full);
         for (int x = 0; x < Chunk.CHUNK_SIZE_X; x++) {
             for (int z = 0; z < Chunk.CHUNK_SIZE_Z; z++) {
@@ -255,13 +270,15 @@ public class AnvilLoader implements IChunkLoader {
                     final Block block = chunk.getBlock(x, y, z);
                     // Block
                     chunkColumn.setBlockState(x, y, z, new BlockState(block.name(), block.properties()));
-                    chunkColumn.setBiome(x, 0, z, chunk.getBiome(x, y, z).id());
+                    chunkColumn.setBiome(x, 0, z, chunk.getBiome(x, y, z).name().asString());
 
                     // Tile entity
-                    var nbt = block.nbt();
                     final BlockHandler handler = block.handler();
-                    if (nbt != null || handler != null) {
+                    var originalNBT = block.nbt();
-                        nbt = Objects.requireNonNullElseGet(nbt, NBTCompound::new);
+                    if (originalNBT != null || handler != null) {
+                        MutableNBTCompound nbt = originalNBT != null ?
+                                originalNBT.toMutableCompound() : new MutableNBTCompound();
+
                         if (handler != null) {
                             nbt.setString("id", handler.getNamespaceId().asString());
                         }
@@ -269,12 +286,12 @@ public class AnvilLoader implements IChunkLoader {
                         nbt.setInt("y", y);
                         nbt.setInt("z", z + Chunk.CHUNK_SIZE_Z * chunk.getChunkZ());
                         nbt.setByte("keepPacked", (byte) 0);
-                        tileEntities.add(nbt);
+                        tileEntities.add(nbt.toCompound());
                     }
                 }
             }
         }
-        chunkColumn.setTileEntities(tileEntities);
+        chunkColumn.setTileEntities(NBT.List(NBTType.TAG_Compound, tileEntities));
     }
 
     @Override

src/main/java/net/minestom/server/instance/Chunk.java

@@ -17,6 +17,7 @@ import net.minestom.server.world.biomes.Biome;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.util.Set;
 import java.util.UUID;
@@ -55,7 +56,7 @@ public abstract class Chunk implements Block.Getter, Block.Setter, Biome.Getter,
     protected PFColumnarSpace columnarSpace;
 
     // Data
-    private final NBTCompound nbt = new NBTCompound();
+    private final MutableNBTCompound nbt = new MutableNBTCompound();
 
     public Chunk(@NotNull Instance instance, int chunkX, int chunkZ, boolean shouldGenerate) {
         this.identifier = UUID.randomUUID();

src/main/java/net/minestom/server/instance/DynamicChunk.java

@@ -22,6 +22,7 @@ import net.minestom.server.utils.chunk.ChunkUtils;
 import net.minestom.server.world.biomes.Biome;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.*;
@@ -47,7 +48,7 @@ public class DynamicChunk extends Chunk {
     public DynamicChunk(@NotNull Instance instance, int chunkX, int chunkZ) {
         super(instance, chunkX, chunkZ, true);
         this.minSection = instance.getDimensionType().getMinY() / CHUNK_SECTION_SIZE;
-        this.maxSection = instance.getDimensionType().getHeight() / CHUNK_SECTION_SIZE;
+        this.maxSection = (instance.getDimensionType().getMinY() + instance.getDimensionType().getHeight()) / CHUNK_SECTION_SIZE;
         this.sections = new Section[maxSection - minSection];
         Arrays.setAll(sections, value -> new Section());
     }
@@ -121,7 +122,7 @@ public class DynamicChunk extends Chunk {
             }
         }
         // Retrieve the block from state id
-        final Section section = sections[ChunkUtils.getSectionAt(y) + minSection];
+        final Section section = sections[ChunkUtils.getSectionAt(y) - minSection];
         final int blockStateId = section.blockPalette()
                 .get(toChunkRelativeCoordinate(x), y, toChunkRelativeCoordinate(z));
         if (blockStateId == -1) return Block.AIR; // Section is empty
@@ -130,7 +131,7 @@ public class DynamicChunk extends Chunk {
 
     @Override
     public @NotNull Biome getBiome(int x, int y, int z) {
-        final Section section = sections[ChunkUtils.getSectionAt(y) + minSection];
+        final Section section = sections[ChunkUtils.getSectionAt(y) - minSection];
         final int id = section.biomePalette()
                 .get(toChunkRelativeCoordinate(x) / 4, y / 4, toChunkRelativeCoordinate(z) / 4);
         return MinecraftServer.getBiomeManager().getById(id);
@@ -186,9 +187,9 @@ public class DynamicChunk extends Chunk {
                 }
             }
             final int bitsForHeight = MathUtils.bitsToRepresent(dimensionHeight);
-            heightmapsNBT = new NBTCompound()
+            heightmapsNBT = NBT.Compound(Map.of(
-                    .setLongArray("MOTION_BLOCKING", Utils.encodeBlocks(motionBlocking, bitsForHeight))
+                    "MOTION_BLOCKING", NBT.LongArray(Utils.encodeBlocks(motionBlocking, bitsForHeight)),
-                    .setLongArray("WORLD_SURFACE", Utils.encodeBlocks(worldSurface, bitsForHeight));
+                    "WORLD_SURFACE", NBT.LongArray(Utils.encodeBlocks(worldSurface, bitsForHeight))));
         }
         // Data
         final BinaryWriter writer = new BinaryWriter();

src/main/java/net/minestom/server/instance/Instance.java

@@ -32,6 +32,7 @@ import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.time.Duration;
 import java.util.*;
@@ -84,7 +85,7 @@ public abstract class Instance implements Block.Getter, Block.Setter, Tickable,
 
     // instance custom data
     private final Object nbtLock = new Object();
-    private final NBTCompound nbt = new NBTCompound();
+    private final MutableNBTCompound nbt = new MutableNBTCompound();
 
     // the explosion supplier
     private ExplosionSupplier explosionSupplier;

src/main/java/net/minestom/server/instance/block/BlockImpl.java

@@ -9,6 +9,7 @@ import net.minestom.server.utils.block.BlockUtils;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.time.Duration;
 import java.util.*;
@@ -105,9 +106,9 @@ final class BlockImpl implements Block {
 
     @Override
     public @NotNull <T> Block withTag(@NotNull Tag<T> tag, @Nullable T value) {
-        var temporaryNbt = nbt != null ? nbt.deepClone() : new NBTCompound();
+        var temporaryNbt = new MutableNBTCompound(Objects.requireNonNullElse(nbt, NBTCompound.EMPTY));
         tag.write(temporaryNbt, value);
-        final var finalNbt = temporaryNbt.getSize() > 0 ? NBT_CACHE.get(temporaryNbt, Function.identity()) : null;
+        final var finalNbt = temporaryNbt.getSize() > 0 ? NBT_CACHE.get(temporaryNbt.toCompound(), Function.identity()) : null;
         return new BlockImpl(registry, propertyEntry, properties, finalNbt, handler);
     }
 

src/main/java/net/minestom/server/inventory/AbstractInventory.java

@@ -10,6 +10,7 @@ import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -32,7 +33,7 @@ public sealed abstract class AbstractInventory implements InventoryClickHandler,
     protected final InventoryClickProcessor clickProcessor = new InventoryClickProcessor();
 
     private final Object nbtLock = new Object();
-    private final NBTCompound nbt = new NBTCompound();
+    private final MutableNBTCompound nbt = new MutableNBTCompound();
 
     protected AbstractInventory(int size) {
         this.size = size;

src/main/java/net/minestom/server/item/ItemMeta.java

@@ -119,7 +119,7 @@ public class ItemMeta implements TagReadable, Writeable {
     }
 
     public @NotNull NBTCompound toNBT() {
-        return nbt.deepClone();
+        return nbt;
     }
 
     public @NotNull String toSNBT() {

src/main/java/net/minestom/server/item/ItemMetaBuilder.java

@@ -12,6 +12,7 @@ import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.*;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 import java.util.*;
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
@@ -75,7 +76,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
                 final String name = GsonComponentSerializer.gson().serialize(displayName);
                 nbtCompound.setString("Name", name);
             } else {
-                nbtCompound.removeTag("Name");
+                nbtCompound.remove("Name");
             }
         });
         return this;
@@ -85,10 +86,11 @@ public abstract class ItemMetaBuilder implements TagWritable {
     public @NotNull ItemMetaBuilder lore(@NotNull List<@NotNull Component> lore) {
         this.lore = new ArrayList<>(lore);
         handleCompound("display", nbtCompound -> {
-            final NBTList<NBTString> loreNBT = new NBTList<>(NBTTypes.TAG_String);
+            final NBTList<NBTString> loreNBT = NBT.List(NBTType.TAG_String,
-            for (Component line : lore) {
+                    lore.stream()
-                loreNBT.add(new NBTString(GsonComponentSerializer.gson().serialize(line)));
+                            .map(line -> new NBTString(GsonComponentSerializer.gson().serialize(line)))
-            }
+                            .toList()
+            );
             nbtCompound.set("Lore", loreNBT);
         });
         return this;
@@ -104,8 +106,9 @@ public abstract class ItemMetaBuilder implements TagWritable {
     public @NotNull ItemMetaBuilder enchantments(@NotNull Map<Enchantment, Short> enchantments) {
         this.enchantmentMap = new HashMap<>(enchantments);
         handleMap(enchantmentMap, "Enchantments", () -> {
-            NBTUtils.writeEnchant(nbt, "Enchantments", enchantmentMap);
+            MutableNBTCompound mutableCopy = new MutableNBTCompound(nbt);
-            return nbt.get("Enchantments");
+            NBTUtils.writeEnchant(mutableCopy, "Enchantments", enchantmentMap);
+            return mutableCopy.get("Enchantments");
         });
         return this;
     }
@@ -127,22 +130,19 @@ public abstract class ItemMetaBuilder implements TagWritable {
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder attributes(@NotNull List<@NotNull ItemAttribute> attributes) {
         this.attributes = new ArrayList<>(attributes);
-        handleCollection(attributes, "AttributeModifiers", () -> {
+
-            NBTList<NBTCompound> attributesNBT = new NBTList<>(NBTTypes.TAG_Compound);
+        handleCollection(attributes, "AttributeModifiers", () -> NBT.List(
-            for (ItemAttribute itemAttribute : attributes) {
+                NBTType.TAG_Compound,
-                final UUID uuid = itemAttribute.getUuid();
+                attributes.stream()
-                attributesNBT.add(
+                        .map(itemAttribute -> NBT.Compound(Map.of(
-                        new NBTCompound()
+                                "UUID", NBT.IntArray(Utils.uuidToIntArray(itemAttribute.getUuid())),
-                                .setIntArray("UUID", Utils.uuidToIntArray(uuid))
+                                "Amount", NBT.Double(itemAttribute.getValue()),
-                                .setDouble("Amount", itemAttribute.getValue())
+                                "Slot", NBT.String(itemAttribute.getSlot().name().toLowerCase()),
-                                .setString("Slot", itemAttribute.getSlot().name().toLowerCase())
+                                "AttributeName", NBT.String(itemAttribute.getAttribute().getKey()),
-                                .setString("AttributeName", itemAttribute.getAttribute().getKey())
+                                "Operation", NBT.Int(itemAttribute.getOperation().getId()),
-                                .setInt("Operation", itemAttribute.getOperation().getId())
+                                "Name", NBT.String(itemAttribute.getInternalName()))))
-                                .setString("Name", itemAttribute.getInternalName())
+                        .toList()
-                );
+        ));
-            }
-            return attributesNBT;
-        });
 
         return this;
     }
@@ -157,11 +157,12 @@ public abstract class ItemMetaBuilder implements TagWritable {
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder canPlaceOn(@NotNull Set<@NotNull Block> blocks) {
         this.canPlaceOn = new HashSet<>(blocks);
-        handleCollection(canPlaceOn, "CanPlaceOn", () -> {
+        handleCollection(canPlaceOn, "CanPlaceOn", () -> NBT.List(
-            NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
+                NBTType.TAG_String,
-            canPlaceOn.forEach(block -> list.add(new NBTString(block.name())));
+                canPlaceOn.stream()
-            return list;
+                        .map(block -> new NBTString(block.name()))
-        });
+                        .toList()
+        ));
         return this;
     }
 
@@ -173,11 +174,12 @@ public abstract class ItemMetaBuilder implements TagWritable {
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder canDestroy(@NotNull Set<@NotNull Block> blocks) {
         this.canDestroy = new HashSet<>(blocks);
-        handleCollection(canDestroy, "CanDestroy", () -> {
+        handleCollection(canPlaceOn, "CanPlaceOn", () -> NBT.List(
-            NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
+                NBTType.TAG_String,
-            canDestroy.forEach(block -> list.add(new NBTString(block.name())));
+                canDestroy.stream()
-            return list;
+                        .map(block -> new NBTString(block.name()))
-        });
+                        .toList()
+        ));
         return this;
     }
 
@@ -203,13 +205,16 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     protected abstract @NotNull Supplier<@NotNull ItemMetaBuilder> getSupplier();
 
-    protected synchronized void mutateNbt(Consumer<NBTCompound> consumer) {
+    protected synchronized void mutateNbt(Consumer<MutableNBTCompound> consumer) {
+        MutableNBTCompound copy = new MutableNBTCompound(nbt);
+        consumer.accept(copy);
         if (built) {
             built = false;
             final var currentNbt = nbt;
-            NBT_UPDATER.compareAndSet(this, currentNbt, currentNbt.deepClone());
+            NBT_UPDATER.compareAndSet(this, currentNbt, copy.toCompound());
+        } else {
+            nbt = copy.toCompound();
         }
-        consumer.accept(nbt);
     }
 
     protected synchronized NBTCompound nbt() {
@@ -222,28 +227,16 @@ public abstract class ItemMetaBuilder implements TagWritable {
     }
 
     protected void handleCompound(@NotNull String key,
-                                  @NotNull Consumer<@NotNull NBTCompound> consumer) {
+                                  @NotNull Consumer<@NotNull MutableNBTCompound> consumer) {
         mutateNbt(nbt -> {
-            NBTCompound compound = null;
+            MutableNBTCompound compoundToModify = nbt.get(key) instanceof NBTCompound compound ?
-            boolean newNbt = false;
+                    compound.toMutableCompound() : new MutableNBTCompound();
-            if (nbt.containsKey(key)) {
+
-                NBT dNbt = nbt.get(key);
+            consumer.accept(compoundToModify);
-                if (dNbt instanceof NBTCompound) {
+            if (compoundToModify.isEmpty()) {
-                    compound = (NBTCompound) dNbt;
+                nbt.remove(key);
-                }
             } else {
-                compound = new NBTCompound();
+                nbt.set(key, compoundToModify.toCompound());
-                newNbt = true;
-            }
-
-            if (compound != null) {
-                consumer.accept(compound);
-
-                if (newNbt && compound.getSize() > 0) {
-                    this.nbt.set(key, compound);
-                } else if (!newNbt && compound.getSize() == 0) {
-                    this.nbt.removeTag(key);
-                }
             }
         });
     }
@@ -255,7 +248,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
             if (value != null) {
                 compound.set(key, supplier.get());
             } else {
-                compound.removeTag(key);
+                compound.remove(key);
             }
         });
     }
@@ -267,7 +260,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
             if (!objects.isEmpty()) {
                 compound.set(key, supplier.get());
             } else {
-                compound.removeTag(key);
+                compound.remove(key);
             }
         });
     }
@@ -279,7 +272,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
             if (!objects.isEmpty()) {
                 compound.set(key, supplier.get());
             } else {
-                compound.removeTag(key);
+                compound.remove(key);
             }
         });
     }
@@ -287,7 +280,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
     @Contract(value = "_, _ -> new", pure = true)
     public static @NotNull ItemMetaBuilder fromNBT(@NotNull ItemMetaBuilder src, @NotNull NBTCompound nbtCompound) {
         ItemMetaBuilder dest = src.getSupplier().get();
-        dest.nbt = nbtCompound.deepClone();
+        dest.nbt = nbtCompound;
         NBTUtils.loadDataIntoMeta(dest, dest.nbt);
         return dest;
     }

src/main/java/net/minestom/server/item/ItemStack.java

@@ -12,9 +12,11 @@ import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.function.Consumer;
 import java.util.function.IntUnaryOperator;
@@ -254,11 +256,10 @@ public final class ItemStack implements TagReadable, HoverEventSource<HoverEvent
      */
     @ApiStatus.Experimental
     public @NotNull NBTCompound toItemNBT() {
-        final NBTCompound nbtCompound = new NBTCompound();
+        return NBT.Compound(Map.of(
-        nbtCompound.setString("id", getMaterial().name());
+                "id", NBT.String(getMaterial().name()),
-        nbtCompound.setByte("Count", (byte) getAmount());
+                "Count", NBT.Byte(getAmount()),
-        nbtCompound.set("tag", getMeta().toNBT());
+                "tag", getMeta().toNBT()));
-        return nbtCompound;
     }
 
     @Contract(value = "-> new", pure = true)

src/main/java/net/minestom/server/item/firework/FireworkEffect.java

@@ -2,6 +2,8 @@ package net.minestom.server.item.firework;
 
 import net.minestom.server.color.Color;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.collections.ImmutableIntArray;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.ArrayList;
@@ -47,14 +49,14 @@ public class FireworkEffect {
         List<Color> secondaryColor = new ArrayList<>();
 
         if (compound.containsKey("Colors")) {
-            final int[] color = compound.getIntArray("Colors");
+            ImmutableIntArray color = compound.getIntArray("Colors");
             for (int j : color) {
                 primaryColor.add(new Color(j));
             }
         }
 
         if (compound.containsKey("FadeColors")) {
-            final int[] fadeColor = compound.getIntArray("FadeColors");
+            ImmutableIntArray fadeColor = compound.getIntArray("FadeColors");
             for (int j : fadeColor) {
                 secondaryColor.add(new Color(j));
             }
@@ -137,15 +139,14 @@ public class FireworkEffect {
      * @return The firework effect as a nbt compound.
      */
     public NBTCompound asCompound() {
-        NBTCompound explosionCompound = new NBTCompound();
+        return NBT.Compound(explosionCompound -> {
-        explosionCompound.setByte("Flicker", this.getFlicker());
+            explosionCompound.setByte("Flicker", this.getFlicker());
-        explosionCompound.setByte("Trail", this.getTrail());
+            explosionCompound.setByte("Trail", this.getTrail());
-        explosionCompound.setByte("Type", this.getType());
+            explosionCompound.setByte("Type", this.getType());
 
-        explosionCompound.setIntArray("Colors", this.getColors());
+            explosionCompound.setIntArray("Colors", this.getColors());
-        explosionCompound.setIntArray("FadeColors", this.getFadeColors());
+            explosionCompound.setIntArray("FadeColors", this.getFadeColors());
-
+        });
-        return explosionCompound;
     }
 
     /**

src/main/java/net/minestom/server/item/metadata/BundleMeta.java

@@ -5,9 +5,7 @@ import net.minestom.server.item.ItemMetaBuilder;
 import net.minestom.server.item.ItemStack;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
-import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.*;
-import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -58,11 +56,7 @@ public class BundleMeta extends ItemMeta implements ItemMetaBuilder.Provider<Bun
 
         private void updateItems() {
             mutateNbt(compound -> {
-                NBTList<NBTCompound> itemList = new NBTList<>(NBTTypes.TAG_Compound);
+                compound.set("Items", NBT.List(NBTType.TAG_Compound, items.size(), i -> items.get(i).toItemNBT()));
-                for (ItemStack item : items) {
-                    itemList.add(item.toItemNBT());
-                }
-                compound.set("Items", itemList);
             });
         }
 

src/main/java/net/minestom/server/item/metadata/CompassMeta.java

@@ -6,6 +6,7 @@ import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemMetaBuilder;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.function.Supplier;
@@ -57,7 +58,7 @@ public class CompassMeta extends ItemMeta implements ItemMetaBuilder.Provider<Co
                 if (lodestoneDimension != null) {
                     compound.setString("LodestoneDimension", lodestoneDimension);
                 } else {
-                    compound.removeTag("LodestoneDimension");
+                    compound.remove("LodestoneDimension");
                 }
             });
 
@@ -69,13 +70,13 @@ public class CompassMeta extends ItemMeta implements ItemMetaBuilder.Provider<Co
 
             mutateNbt(compound -> {
                 if (lodestonePosition != null) {
-                    NBTCompound posCompound = new NBTCompound();
+                    compound.set("LodestonePos", NBT.Compound(posCompound -> {
-                    posCompound.setInt("X", lodestonePosition.blockX());
+                        posCompound.setInt("X", lodestonePosition.blockX());
-                    posCompound.setInt("Y", lodestonePosition.blockY());
+                        posCompound.setInt("Y", lodestonePosition.blockY());
-                    posCompound.setInt("Z", lodestonePosition.blockZ());
+                        posCompound.setInt("Z", lodestonePosition.blockZ());
-                    compound.set("LodestonePos", posCompound);
+                    }));
                 } else {
-                    compound.removeTag("LodestonePos");
+                    compound.remove("LodestonePos");
                 }
             });
 

src/main/java/net/minestom/server/item/metadata/CrossbowMeta.java

@@ -6,9 +6,10 @@ import net.minestom.server.item.ItemStack;
 import net.minestom.server.item.Material;
 import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -94,11 +95,9 @@ public class CrossbowMeta extends ItemMeta implements ItemMetaBuilder.Provider<S
             this.projectile1 = projectile;
             this.triple = false;
 
-            NBTList<NBTCompound> chargedProjectiles = new NBTList<>(NBTTypes.TAG_Compound);
+            List<NBTCompound> chargedProjectiles =
-            if (!projectile.isAir()) {
+                    projectile.isAir() ? List.of() : List.of(getItemCompound(projectile));
-                chargedProjectiles.add(getItemCompound(projectile));
+            mutateNbt(compound -> compound.set("ChargedProjectiles", NBT.List(NBTType.TAG_Compound, chargedProjectiles)));
-            }
-            mutateNbt(compound -> compound.set("ChargedProjectiles", chargedProjectiles));
 
             return this;
         }
@@ -120,11 +119,9 @@ public class CrossbowMeta extends ItemMeta implements ItemMetaBuilder.Provider<S
             this.projectile3 = projectile3;
             this.triple = true;
 
-            NBTList<NBTCompound> chargedProjectiles = new NBTList<>(NBTTypes.TAG_Compound);
+            List<NBTCompound> chargedProjectiles =
-            chargedProjectiles.add(getItemCompound(projectile1));
+                    List.of(getItemCompound(projectile1), getItemCompound(projectile2), getItemCompound(projectile3));
-            chargedProjectiles.add(getItemCompound(projectile2));
+            mutateNbt(compound -> compound.set("ChargedProjectiles", NBT.List(NBTType.TAG_Compound, chargedProjectiles)));
-            chargedProjectiles.add(getItemCompound(projectile3));
-            mutateNbt(compound -> compound.set("ChargedProjectiles", chargedProjectiles));
 
             return this;
         }
@@ -181,9 +178,10 @@ public class CrossbowMeta extends ItemMeta implements ItemMetaBuilder.Provider<S
 
         private @NotNull NBTCompound getItemCompound(@NotNull ItemStack itemStack) {
             NBTCompound compound = itemStack.getMeta().toNBT();
-            compound.setByte("Count", (byte) itemStack.getAmount());
+            return compound.modify(n -> {
-            compound.setString("id", itemStack.getMaterial().name());
+                n.setByte("Count", (byte) itemStack.getAmount());
-            return compound;
+                n.setString("id", itemStack.getMaterial().name());
+            });
         }
     }
 }

src/main/java/net/minestom/server/item/metadata/FireworkMeta.java

@@ -4,15 +4,17 @@ import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemMetaBuilder;
 import net.minestom.server.item.firework.FireworkEffect;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 public class FireworkMeta extends ItemMeta implements ItemMetaBuilder.Provider<FireworkMeta.Builder> {
 
@@ -42,11 +44,12 @@ public class FireworkMeta extends ItemMeta implements ItemMetaBuilder.Provider<F
         public Builder effects(List<FireworkEffect> effects) {
             this.effects = effects;
             handleCompound("Fireworks", nbtCompound -> {
-                NBTList<NBTCompound> explosions = new NBTList<>(NBTTypes.TAG_Compound);
+                nbtCompound.set("Explosions", NBT.List(
-                for (FireworkEffect effect : this.effects) {
+                        NBTType.TAG_Compound,
-                    explosions.add(effect.asCompound());
+                        effects.stream()
-                }
+                                .map(FireworkEffect::asCompound)
-                nbtCompound.set("Explosions", explosions);
+                                .toList()
+                ));
             });
             return this;
         }

src/main/java/net/minestom/server/item/metadata/LeatherArmorMeta.java

@@ -32,7 +32,7 @@ public class LeatherArmorMeta extends ItemMeta implements ItemMetaBuilder.Provid
                 if (color != null) {
                     nbtCompound.setInt("color", color.asRGB());
                 } else {
-                    nbtCompound.removeTag("color");
+                    nbtCompound.remove("color");
                 }
             });
             return this;

src/main/java/net/minestom/server/item/metadata/MapMeta.java

@@ -6,12 +6,14 @@ import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemMetaBuilder;
 import net.minestom.server.utils.clone.PublicCloneable;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Supplier;
 
@@ -92,17 +94,17 @@ public class MapMeta extends ItemMeta implements ItemMetaBuilder.Provider<MapMet
         public Builder decorations(List<MapDecoration> value) {
             this.decorations = new ArrayList<>(value);
 
-            NBTList<NBTCompound> decorationsList = new NBTList<>(NBTTypes.TAG_Compound);
+            NBTList<NBTCompound> decorationsList = NBT.List(
-            for (MapDecoration decoration : decorations) {
+                    NBTType.TAG_Compound,
-                NBTCompound decorationCompound = new NBTCompound();
+                    decorations.stream()
-                decorationCompound.setString("id", decoration.getId());
+                            .map(decoration -> NBT.Compound(Map.of(
-                decorationCompound.setByte("type", decoration.getType());
+                                    "id", NBT.String(decoration.getId()),
-                decorationCompound.setByte("x", decoration.getX());
+                                    "type", NBT.Byte(decoration.getType()),
-                decorationCompound.setByte("z", decoration.getZ());
+                                    "x", NBT.Byte(decoration.getX()),
-                decorationCompound.setDouble("rot", decoration.getRotation());
+                                    "z", NBT.Byte(decoration.getZ()),
-
+                                    "rot", NBT.Double(decoration.getRotation()))))
-                decorationsList.add(decorationCompound);
+                            .toList()
-            }
+            );
             mutateNbt(compound -> compound.set("Decorations", decorationsList));
 
             return this;
@@ -111,14 +113,7 @@ public class MapMeta extends ItemMeta implements ItemMetaBuilder.Provider<MapMet
         public Builder mapColor(Color value) {
             this.mapColor = value;
 
-            mutateNbt(nbt -> {
+            handleCompound("display", displayCompound -> {
-                NBTCompound displayCompound;
-                if (nbt.containsKey("display")) {
-                    displayCompound = nbt.getCompound("display");
-                } else {
-                    displayCompound = new NBTCompound();
-                    nbt.set("display", displayCompound);
-                }
                 displayCompound.setInt("MapColor", mapColor.asRGB());
             });
 

src/main/java/net/minestom/server/item/metadata/PlayerHeadMeta.java

@@ -6,10 +6,13 @@ import net.minestom.server.item.ItemMetaBuilder;
 import net.minestom.server.utils.Utils;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
+import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.UUID;
 import java.util.function.Supplier;
@@ -50,15 +53,17 @@ public class PlayerHeadMeta extends ItemMeta implements ItemMetaBuilder.Provider
             this.playerSkin = playerSkin;
             handleCompound("SkullOwner", nbtCompound -> {
                 if (playerSkin == null) {
-                    nbtCompound.removeTag("Properties");
+                    nbtCompound.remove("Properties");
                     return;
                 }
 
-                NBTList<NBTCompound> textures = new NBTList<>(NBTTypes.TAG_Compound);
                 final String value = Objects.requireNonNullElse(this.playerSkin.textures(), "");
                 final String signature = Objects.requireNonNullElse(this.playerSkin.signature(), "");
-                textures.add(new NBTCompound().setString("Value", value).setString("Signature", signature));
+                NBTList<NBTCompound> textures = new NBTList<>(NBTType.TAG_Compound,
-                nbtCompound.set("Properties", new NBTCompound().set("textures", textures));
+                        List.of(NBT.Compound(Map.of(
+                                "Value", NBT.String(value),
+                                "Signature", NBT.String(signature)))));
+                nbtCompound.set("Properties", NBT.Compound(Map.of("textures", textures)));
             });
             return this;
         }
@@ -74,7 +79,7 @@ public class PlayerHeadMeta extends ItemMeta implements ItemMetaBuilder.Provider
                 NBTCompound skullOwnerCompound = nbtCompound.getCompound("SkullOwner");
 
                 if (skullOwnerCompound.containsKey("Id")) {
-                    skullOwner(Utils.intArrayToUuid(skullOwnerCompound.getIntArray("Id")));
+                    skullOwner(Utils.intArrayToUuid(skullOwnerCompound.getIntArray("Id").copyArray()));
                 }
 
                 if (skullOwnerCompound.containsKey("Properties")) {

src/main/java/net/minestom/server/item/metadata/PotionMeta.java

@@ -7,14 +7,16 @@ import net.minestom.server.potion.CustomPotionEffect;
 import net.minestom.server.potion.PotionType;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 public class PotionMeta extends ItemMeta implements ItemMetaBuilder.Provider<PotionMeta.Builder> {
 
@@ -58,18 +60,19 @@ public class PotionMeta extends ItemMeta implements ItemMetaBuilder.Provider<Pot
         public Builder effects(@NotNull List<CustomPotionEffect> customPotionEffects) {
             this.customPotionEffects = customPotionEffects;
 
-            NBTList<NBTCompound> potionList = new NBTList<>(NBTTypes.TAG_Compound);
+            NBTList<NBTCompound> potionList = NBT.List(
-            for (CustomPotionEffect customPotionEffect : customPotionEffects) {
+                    NBTType.TAG_Compound,
-                NBTCompound potionCompound = new NBTCompound();
+                    customPotionEffects.stream()
-                potionCompound.setByte("Id", customPotionEffect.getId());
+                            .map(customPotionEffect -> NBT.Compound(potionCompound -> {
-                potionCompound.setByte("Amplifier", customPotionEffect.getAmplifier());
+                                potionCompound.setByte("Id", customPotionEffect.getId());
-                potionCompound.setInt("Duration", customPotionEffect.getDuration());
+                                potionCompound.setByte("Amplifier", customPotionEffect.getAmplifier());
-                potionCompound.setByte("Ambient", (byte) (customPotionEffect.isAmbient() ? 1 : 0));
+                                potionCompound.setInt("Duration", customPotionEffect.getDuration());
-                potionCompound.setByte("ShowParticles", (byte) (customPotionEffect.showParticles() ? 1 : 0));
+                                potionCompound.setByte("Ambient", (byte) (customPotionEffect.isAmbient() ? 1 : 0));
-                potionCompound.setByte("ShowIcon", (byte) (customPotionEffect.showIcon() ? 1 : 0));
+                                potionCompound.setByte("ShowParticles", (byte) (customPotionEffect.showParticles() ? 1 : 0));
-
+                                potionCompound.setByte("ShowIcon", (byte) (customPotionEffect.showIcon() ? 1 : 0));
-                potionList.add(potionCompound);
+                            }))
-            }
+                            .toList()
+            );
             mutateNbt(compound -> compound.set("CustomPotionEffects", potionList));
 
             return this;

src/main/java/net/minestom/server/item/metadata/WritableBookMeta.java

@@ -6,16 +6,14 @@ import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemMetaBuilder;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.*;
-import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTString;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 public class WritableBookMeta extends ItemMeta implements ItemMetaBuilder.Provider<WritableBookMeta.Builder> {
 
@@ -67,13 +65,12 @@ public class WritableBookMeta extends ItemMeta implements ItemMetaBuilder.Provid
         public Builder pages(@NotNull List<@NotNull Component> pages) {
             this.pages = new ArrayList<>(pages);
 
-            handleCollection(pages, "pages", () -> {
+            handleCollection(pages, "pages", () -> NBT.List(
-                NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
+                    NBTType.TAG_String,
-                for (Component page : pages) {
+                    pages.stream()
-                    list.add(new NBTString(LegacyComponentSerializer.legacySection().serialize(page)));
+                            .map(page -> new NBTString(LegacyComponentSerializer.legacySection().serialize(page)))
-                }
+                            .toList()
-                return list;
+            ));
-            });
 
             return this;
         }

src/main/java/net/minestom/server/item/metadata/WrittenBookMeta.java

@@ -14,6 +14,7 @@ import org.jglrxavpok.hephaistos.nbt.*;
 
 import java.util.*;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 public class WrittenBookMeta extends ItemMeta implements ItemMetaBuilder.Provider<WrittenBookMeta.Builder> {
 
@@ -115,13 +116,12 @@ public class WrittenBookMeta extends ItemMeta implements ItemMetaBuilder.Provide
         public Builder pages(@NotNull List<@NotNull Component> pages) {
             this.pages = new ArrayList<>(pages);
 
-            handleCollection(pages, "pages", () -> {
+            handleCollection(pages, "pages", () -> NBT.List(
-                NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
+                    NBTType.TAG_String,
-                for (Component page : pages) {
+                    pages.stream()
-                    list.add(new NBTString(GsonComponentSerializer.gson().serialize(page)));
+                            .map(page -> new NBTString(GsonComponentSerializer.gson().serialize(page)))
-                }
+                            .toList()
-                return list;
+            ));
-            });
 
             return this;
         }

src/main/java/net/minestom/server/network/packet/server/play/JoinGamePacket.java

@@ -6,6 +6,7 @@ import net.minestom.server.network.packet.server.ServerPacketIdentifier;
 import net.minestom.server.utils.binary.BinaryReader;
 import net.minestom.server.utils.binary.BinaryWriter;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.List;

src/main/java/net/minestom/server/network/packet/server/play/data/ChunkData.java

@@ -9,6 +9,7 @@ import net.minestom.server.utils.binary.BinaryWriter;
 import net.minestom.server.utils.binary.Writeable;
 import net.minestom.server.utils.chunk.ChunkUtils;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.HashMap;
@@ -18,7 +19,6 @@ import java.util.Objects;
 public record ChunkData(@NotNull NBTCompound heightmaps, byte @NotNull [] data,
                         @NotNull Map<Integer, Block> blockEntities) implements Writeable {
     public ChunkData {
-        heightmaps = heightmaps.deepClone();
         data = data.clone();
         blockEntities = Map.copyOf(blockEntities);
     }
@@ -56,15 +56,16 @@ public record ChunkData(@NotNull NBTCompound heightmaps, byte @NotNull [] data,
             // Append handler tags
             final BlockHandler handler = block.handler();
             if (handler != null) {
-                resultNbt = new NBTCompound();
+                resultNbt = NBT.Compound(nbt -> {
-                final NBTCompound blockNbt = Objects.requireNonNullElseGet(block.nbt(), NBTCompound::new);
+                    final NBTCompound blockNbt = Objects.requireNonNullElseGet(block.nbt(), NBTCompound::new);
-                for (Tag<?> tag : handler.getBlockEntityTags()) {
+                    for (Tag<?> tag : handler.getBlockEntityTags()) {
-                    final var value = tag.read(blockNbt);
+                        final var value = tag.read(blockNbt);
-                    if (value != null) {
+                        if (value != null) {
-                        // Tag is present and valid
+                            // Tag is present and valid
-                        tag.writeUnsafe(resultNbt, value);
+                            tag.writeUnsafe(nbt, value);
+                        }
                     }
-                }
+                });
             } else {
                 // Complete nbt shall be sent if the block has no handler
                 // Necessary to support all vanilla blocks

src/main/java/net/minestom/server/permission/PermissionHandler.java

@@ -3,7 +3,7 @@ package net.minestom.server.permission;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
-import org.jglrxavpok.hephaistos.nbt.SNBTParser;
+import org.jglrxavpok.hephaistos.parser.SNBTParser;
 
 import java.util.Set;
 

src/main/java/net/minestom/server/tag/Tag.java

@@ -1,13 +1,16 @@
 package net.minestom.server.tag;
 
+import net.minestom.server.MinecraftServer;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.NBTCompoundLike;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
-import org.jglrxavpok.hephaistos.nbt.SNBTParser;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
+import org.jglrxavpok.hephaistos.parser.SNBTParser;
 
 import java.io.StringReader;
 import java.util.Objects;
@@ -31,16 +34,15 @@ public class Tag<T> {
      * Writing will override all tags. Proceed with caution.
      */
     @ApiStatus.Experimental
-    public static final Tag<String> SNBT = new Tag<>(null, NBTCompound::toSNBT, (original, snbt) -> {
+    public static final Tag<String> SNBT = new Tag<>(null, n -> n.toCompound().toSNBT(), (original, snbt) -> {
         try {
             final var updated = new SNBTParser(new StringReader(snbt)).parse();
             if (!(updated instanceof NBTCompound updatedCompound))
                 throw new IllegalArgumentException("'" + snbt + "' is not a compound!");
             original.clear();
-            updatedCompound.getKeys().forEach(s ->
+            updatedCompound.forEach(original::set);
-                    original.set(s, Objects.requireNonNull(updatedCompound.get(s))));
         } catch (NBTException e) {
-            e.printStackTrace();
+            MinecraftServer.getExceptionManager().handleException(e);
         }
     }, null);
 
@@ -50,20 +52,20 @@ public class Tag<T> {
      * Writing will override all tags. Proceed with caution.
      */
     @ApiStatus.Experimental
-    public static final Tag<NBTCompound> NBT = new Tag<>(null, NBTCompound::deepClone, (original, updated) -> {
+    public static final Tag<NBTCompound> NBT = new Tag<>(null, NBTCompoundLike::toCompound, (original, updated) -> {
         original.clear();
-        updated.getKeys().forEach(s -> original.set(s, Objects.requireNonNull(updated.get(s))));
+        updated.forEach(original::set);
     }, null);
 
     private final String key;
-    private final Function<NBTCompound, T> readFunction;
+    private final Function<NBTCompoundLike, T> readFunction;
-    private final BiConsumer<NBTCompound, T> writeConsumer;
+    private final BiConsumer<MutableNBTCompound, T> writeConsumer;
 
     private final Supplier<T> defaultValue;
 
     protected Tag(@Nullable String key,
-                  @NotNull Function<NBTCompound, T> readFunction,
+                  @NotNull Function<NBTCompoundLike, T> readFunction,
-                  @Nullable BiConsumer<NBTCompound, T> writeConsumer,
+                  @Nullable BiConsumer<MutableNBTCompound, T> writeConsumer,
                   @Nullable Supplier<T> defaultValue) {
         this.key = key;
         this.readFunction = readFunction;
@@ -73,8 +75,8 @@ public class Tag<T> {
     }
 
     protected Tag(@Nullable String key,
-                  @NotNull Function<NBTCompound, T> readFunction,
+                  @NotNull Function<NBTCompoundLike, T> readFunction,
-                  @Nullable BiConsumer<NBTCompound, T> writeConsumer) {
+                  @Nullable BiConsumer<MutableNBTCompound, T> writeConsumer) {
         this(key, readFunction, writeConsumer, null);
     }
 
@@ -126,7 +128,7 @@ public class Tag<T> {
                 });
     }
 
-    public @Nullable T read(@NotNull NBTCompound nbtCompound) {
+    public @Nullable T read(@NotNull NBTCompoundLike nbtCompound) {
         T result = readFunction.apply(nbtCompound);
         if (result == null) {
             final var supplier = defaultValue;
@@ -135,15 +137,15 @@ public class Tag<T> {
         return result;
     }
 
-    public void write(@NotNull NBTCompound nbtCompound, @Nullable T value) {
+    public void write(@NotNull MutableNBTCompound nbtCompound, @Nullable T value) {
         if (key == null || value != null) {
             this.writeConsumer.accept(nbtCompound, value);
         } else {
-            nbtCompound.removeTag(key);
+            nbtCompound.remove(key);
         }
     }
 
-    public void writeUnsafe(@NotNull NBTCompound nbtCompound, @Nullable Object value) {
+    public void writeUnsafe(@NotNull MutableNBTCompound nbtCompound, @Nullable Object value) {
         write(nbtCompound, (T) value);
     }
 
@@ -185,7 +187,7 @@ public class Tag<T> {
 
     public static @NotNull Tag<byte[]> ByteArray(@NotNull String key) {
         return new Tag<>(key,
-                nbtCompound -> nbtCompound.getByteArray(key),
+                nbtCompound -> nbtCompound.getByteArray(key).copyArray(),
                 (nbtCompound, value) -> nbtCompound.setByteArray(key, value));
     }
 
@@ -199,24 +201,20 @@ public class Tag<T> {
         return new Tag<>(key,
                 nbt -> {
                     final var currentNBT = nbt.get(key);
-                    // Avoid a NPE when cloning a null variable.
+                    return (T) currentNBT;
-                    if (currentNBT == null) {
-                        return null;
-                    }
-                    return (T) currentNBT.deepClone();
                 },
-                ((nbt, value) -> nbt.set(key, value.deepClone())));
+                ((nbt, value) -> nbt.set(key, value)));
     }
 
     public static @NotNull Tag<int[]> IntArray(@NotNull String key) {
         return new Tag<>(key,
-                nbtCompound -> nbtCompound.getIntArray(key),
+                nbtCompound -> nbtCompound.getIntArray(key).copyArray(),
                 (nbtCompound, value) -> nbtCompound.setIntArray(key, value));
     }
 
     public static @NotNull Tag<long[]> LongArray(@NotNull String key) {
         return new Tag<>(key,
-                nbtCompound -> nbtCompound.getLongArray(key),
+                nbtCompound -> nbtCompound.getLongArray(key).copyArray(),
                 (nbtCompound, value) -> nbtCompound.setLongArray(key, value));
     }
 
@@ -231,19 +229,15 @@ public class Tag<T> {
     public static <T> @NotNull Tag<T> Structure(@NotNull String key, @NotNull TagSerializer<T> serializer) {
         return new Tag<>(key,
                 nbtCompound -> {
-                    final var compound = nbtCompound.getCompound(key);
+                    final NBTCompound compound = nbtCompound.getCompound(key);
-                    if (compound == null) {
+                    if (compound == null) return null;
-                        return null;
-                    }
                     return serializer.read(TagReadable.fromCompound(compound));
                 },
                 (nbtCompound, value) -> {
-                    var compound = nbtCompound.getCompound(key);
+                    MutableNBTCompound mutableCopy = nbtCompound.get(key) instanceof NBTCompound c ?
-                    if (compound == null) {
+                            c.toMutableCompound() : new MutableNBTCompound();
-                        compound = new NBTCompound();
+                    serializer.write(TagWritable.fromCompound(mutableCopy), value);
-                        nbtCompound.set(key, compound);
+                    nbtCompound.set(key, mutableCopy.toCompound());
-                    }
-                    serializer.write(TagWritable.fromCompound(compound), value);
                 });
     }
 

src/main/java/net/minestom/server/tag/TagReadable.java

@@ -3,6 +3,8 @@ package net.minestom.server.tag;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.NBTCompoundGetters;
+import org.jglrxavpok.hephaistos.nbt.NBTCompoundLike;
 
 /**
  * Represents an element which can read {@link Tag tags}.
@@ -34,7 +36,7 @@ public interface TagReadable {
      * @param compound the compound to convert
      * @return a {@link TagReadable} capable of reading {@code compound}
      */
-    static @NotNull TagReadable fromCompound(@NotNull NBTCompound compound) {
+    static @NotNull TagReadable fromCompound(@NotNull NBTCompoundLike compound) {
         return new TagReadable() {
             @Override
             public <T> @Nullable T getTag(@NotNull Tag<T> tag) {

src/main/java/net/minestom/server/tag/TagWritable.java

@@ -3,6 +3,7 @@ package net.minestom.server.tag;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 
 /**
  * Represents an element which can write {@link Tag tags}.
@@ -28,7 +29,7 @@ public interface TagWritable {
      * @param compound the compound to convert
      * @return a {@link TagWritable} capable of writing {@code compound}
      */
-    static @NotNull TagWritable fromCompound(@NotNull NBTCompound compound) {
+    static @NotNull TagWritable fromCompound(@NotNull MutableNBTCompound compound) {
         return new TagWritable() {
             @Override
             public <T> void setTag(@NotNull Tag<T> tag, @Nullable T value) {

src/main/java/net/minestom/server/utils/NBTUtils.java

@@ -20,10 +20,12 @@ import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.*;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
+import java.util.stream.Collectors;
 
 // for lack of a better name
 public final class NBTUtils {
@@ -79,34 +81,35 @@ public final class NBTUtils {
         }
     }
 
-    public static void saveAllItems(@NotNull NBTList<NBTCompound> list, @NotNull Inventory inventory) {
+    public static void saveAllItems(@NotNull List<NBTCompound> list, @NotNull Inventory inventory) {
         for (int i = 0; i < inventory.getSize(); i++) {
             final ItemStack stack = inventory.getItemStack(i);
-            NBTCompound nbt = new NBTCompound();
 
             NBTCompound tag = stack.getMeta().toNBT();
 
-            nbt.set("tag", tag);
+            final int slotIndex = i;
-            nbt.setByte("Slot", (byte) i);
+            list.add(NBT.Compound(nbt -> {
-            nbt.setByte("Count", (byte) stack.getAmount());
+                nbt.set("tag", tag);
-            nbt.setString("id", stack.getMaterial().name());
+                nbt.setByte("Slot", (byte) slotIndex);
-
+                nbt.setByte("Count", (byte) stack.getAmount());
-            list.add(nbt);
+                nbt.setString("id", stack.getMaterial().name());
+            }));
         }
     }
 
-    public static void writeEnchant(@NotNull NBTCompound nbt, @NotNull String listName,
+    public static void writeEnchant(@NotNull MutableNBTCompound nbt, @NotNull String listName,
                                     @NotNull Map<Enchantment, Short> enchantmentMap) {
-        NBTList<NBTCompound> enchantList = new NBTList<>(NBTTypes.TAG_Compound);
+        nbt.set(listName, NBT.List(
-        for (var entry : enchantmentMap.entrySet()) {
+                NBTType.TAG_Compound,
-            final Enchantment enchantment = entry.getKey();
+                enchantmentMap.entrySet().stream()
-            final short level = entry.getValue();
+                        .map(entry ->
-            enchantList.add(new NBTCompound()
+                            NBT.Compound(n -> {
-                    .setShort("lvl", level)
+                                n.setShort("lvl", entry.getValue());
-                    .setString("id", enchantment.name())
+                                n.setString("id", entry.getKey().name());
-            );
+                            })
-        }
+                        )
-        nbt.set(listName, enchantList);
+                        .toList()
+        ));
     }
 
     public static @NotNull ItemStack readItemStack(@NotNull BinaryReader reader) {
@@ -134,7 +137,7 @@ public final class NBTUtils {
         if (nbt.containsKey("display")) {
             final NBTCompound display = nbt.getCompound("display");
             if (display.containsKey("Name")) {
-                final String rawName = StringUtils.unescapeJavaString(display.getString("Name"));
+                final String rawName = display.getString("Name");
                 final Component displayName = GsonComponentSerializer.gson().deserialize(rawName);
                 metaBuilder.displayName(displayName);
             }
@@ -142,7 +145,7 @@ public final class NBTUtils {
                 NBTList<NBTString> loreList = display.getList("Lore");
                 List<Component> lore = new ArrayList<>();
                 for (NBTString s : loreList) {
-                    final String rawLore = StringUtils.unescapeJavaString(s.getValue());
+                    final String rawLore = s.getValue();
                     lore.add(GsonComponentSerializer.gson().deserialize(rawLore));
                 }
                 metaBuilder.lore(lore);
@@ -161,7 +164,7 @@ public final class NBTUtils {
             for (NBTCompound attributeNBT : nbtAttributes) {
                 final UUID uuid;
                 {
-                    final int[] uuidArray = attributeNBT.getIntArray("UUID");
+                    final int[] uuidArray = attributeNBT.getIntArray("UUID").copyArray();
                     uuid = Utils.intArrayToUuid(uuidArray);
                 }
 

src/main/java/net/minestom/server/utils/SerializerUtils.java

@@ -15,7 +15,7 @@ public final class SerializerUtils {
 
     public static Point longToBlockPosition(long value) {
         final int x = (int) (value >> 38);
-        final int y = (int) (value & 0xFFF);
+        final int y = (int) (value << 52 >> 52);
         final int z = (int) (value << 26 >> 38);
         return new Vec(x, y, z);
     }

src/main/java/net/minestom/server/utils/binary/BinaryReader.java

@@ -10,6 +10,7 @@ import net.minestom.server.utils.SerializerUtils;
 import net.minestom.server.utils.Utils;
 import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.CompressedProcesser;
 import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
 import org.jglrxavpok.hephaistos.nbt.NBTReader;
@@ -32,7 +33,7 @@ import java.util.function.Supplier;
  */
 public class BinaryReader extends InputStream {
     private final ByteBuffer buffer;
-    private NBTReader nbtReader;
+    private NBTReader nbtReader = null;
 
     public BinaryReader(@NotNull ByteBuffer buffer) {
         this.buffer = buffer;
@@ -257,7 +258,7 @@ public class BinaryReader extends InputStream {
     public NBT readTag() {
         NBTReader reader = this.nbtReader;
         if (reader == null) {
-            reader = new NBTReader(this, false);
+            reader = new NBTReader(this, CompressedProcesser.NONE);
             this.nbtReader = reader;
         }
         try {

src/main/java/net/minestom/server/utils/binary/BinaryWriter.java

@@ -9,6 +9,7 @@ import net.minestom.server.utils.SerializerUtils;
 import net.minestom.server.utils.Utils;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.CompressedProcesser;
 import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTWriter;
 
@@ -303,7 +304,7 @@ public class BinaryWriter extends OutputStream {
 
     public void writeNBT(@NotNull String name, @NotNull NBT tag) {
         if (nbtWriter == null) {
-            this.nbtWriter = new NBTWriter(this, false);
+            this.nbtWriter = new NBTWriter(this, CompressedProcesser.NONE);
         }
         try {
             nbtWriter.writeNamed(name, tag);

src/main/java/net/minestom/server/world/DimensionType.java

@@ -3,8 +3,10 @@ package net.minestom.server.world;
 import net.minestom.server.utils.NamespaceID;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
+import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -26,8 +28,9 @@ public class DimensionType {
             .ceilingEnabled(false)
             .fixedTime(null)
             .ambientLight(0.0f)
-            .height(256)
+            .height(384)
-            .logicalHeight(256)
+            .minY(-64)
+            .logicalHeight(384)
             .infiniburn(NamespaceID.from("minecraft:infiniburn_overworld"))
             .build();
 
@@ -107,35 +110,33 @@ public class DimensionType {
 
     @NotNull
     public NBTCompound toIndexedNBT() {
-        NBTCompound nbt = new NBTCompound();
+        return NBT.Compound(Map.of(
-        NBTCompound element = toNBT();
+                "name", NBT.String(name.toString()),
-        nbt.setString("name", name.toString());
+                "id", NBT.Int(id),
-        nbt.setInt("id", id);
+                "element", toNBT()));
-        nbt.set("element", element);
-        return nbt;
     }
 
     @NotNull
     public NBTCompound toNBT() {
-        NBTCompound nbt = new NBTCompound()
+        return NBT.Compound(nbt -> {
-                .setFloat("ambient_light", ambientLight)
+            nbt.setFloat("ambient_light", ambientLight);
-                .setString("infiniburn", infiniburn.toString())
+            nbt.setString("infiniburn", infiniburn.toString());
-                .setByte("natural", (byte) (natural ? 0x01 : 0x00))
+            nbt.setByte("natural", (byte) (natural ? 0x01 : 0x00));
-                .setByte("has_ceiling", (byte) (ceilingEnabled ? 0x01 : 0x00))
+            nbt.setByte("has_ceiling", (byte) (ceilingEnabled ? 0x01 : 0x00));
-                .setByte("has_skylight", (byte) (skylightEnabled ? 0x01 : 0x00))
+            nbt.setByte("has_skylight", (byte) (skylightEnabled ? 0x01 : 0x00));
-                .setByte("ultrawarm", (byte) (ultrawarm ? 0x01 : 0x00))
+            nbt.setByte("ultrawarm", (byte) (ultrawarm ? 0x01 : 0x00));
-                .setByte("has_raids", (byte) (raidCapable ? 0x01 : 0x00))
+            nbt.setByte("has_raids", (byte) (raidCapable ? 0x01 : 0x00));
-                .setByte("respawn_anchor_works", (byte) (respawnAnchorSafe ? 0x01 : 0x00))
+            nbt.setByte("respawn_anchor_works", (byte) (respawnAnchorSafe ? 0x01 : 0x00));
-                .setByte("bed_works", (byte) (bedSafe ? 0x01 : 0x00))
+            nbt.setByte("bed_works", (byte) (bedSafe ? 0x01 : 0x00));
-                .setString("effects", effects)
+            nbt.setString("effects", effects);
-                .setByte("piglin_safe", (byte) (piglinSafe ? 0x01 : 0x00))
+            nbt.setByte("piglin_safe", (byte) (piglinSafe ? 0x01 : 0x00));
-                .setInt("min_y", minY)
+            nbt.setInt("min_y", minY);
-                .setInt("height", height)
+            nbt.setInt("height", height);
-                .setInt("logical_height", logicalHeight)
+            nbt.setInt("logical_height", logicalHeight);
-                .setInt("coordinate_scale", coordinateScale)
+            nbt.setInt("coordinate_scale", coordinateScale);
-                .setString("name", name.toString());
+            nbt.setString("name", name.toString());
-        if (fixedTime != null) nbt.setLong("fixed_time", fixedTime);
+            if (fixedTime != null) nbt.setLong("fixed_time", fixedTime);
-        return nbt;
+        });
     }
 
     @Override

src/main/java/net/minestom/server/world/DimensionTypeManager.java

@@ -3,13 +3,15 @@ package net.minestom.server.world;
 import net.minestom.server.utils.NamespaceID;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.stream.Collectors;
 
 /**
  * Allows servers to register custom dimensions. Also used during player login to send the list of all existing dimensions.
@@ -88,13 +90,14 @@ public final class DimensionTypeManager {
      * @return an nbt compound containing the registered dimensions
      */
     public @NotNull NBTCompound toNBT() {
-        NBTCompound dimensions = new NBTCompound();
+        return NBT.Compound(dimensions -> {
-        dimensions.setString("type", "minecraft:dimension_type");
+            dimensions.setString("type", "minecraft:dimension_type");
-        NBTList<NBTCompound> dimensionList = new NBTList<>(NBTTypes.TAG_Compound);
+            dimensions.set("value", NBT.List(
-        for (DimensionType dimensionType : dimensionTypes) {
+                    NBTType.TAG_Compound,
-            dimensionList.add(dimensionType.toIndexedNBT());
+                    dimensionTypes.stream()
-        }
+                            .map(DimensionType::toIndexedNBT)
-        dimensions.set("value", dimensionList);
+                            .toList()
-        return dimensions;
+            ));
+        });
     }
 }

src/main/java/net/minestom/server/world/biomes/Biome.java

@@ -4,6 +4,7 @@ import net.minestom.server.coordinate.Point;
 import net.minestom.server.utils.NamespaceID;
 import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.Locale;
@@ -61,22 +62,22 @@ public final class Biome {
         Check.notNull(name, "The biome namespace cannot be null");
         Check.notNull(effects, "The biome effects cannot be null");
 
-        NBTCompound nbt = new NBTCompound();
+        return NBT.Compound(nbt -> {
-        nbt.setString("name", name.toString());
+            nbt.setString("name", name.toString());
-        nbt.setInt("id", id());
+            nbt.setInt("id", id());
 
-        NBTCompound element = new NBTCompound();
+            nbt.set("element", NBT.Compound(element -> {
-        element.setFloat("depth", depth);
+                element.setFloat("depth", depth);
-        element.setFloat("temperature", temperature);
+                element.setFloat("temperature", temperature);
-        element.setFloat("scale", scale);
+                element.setFloat("scale", scale);
-        element.setFloat("downfall", downfall);
+                element.setFloat("downfall", downfall);
-        element.setString("category", category.name().toLowerCase(Locale.ROOT));
+                element.setString("category", category.name().toLowerCase(Locale.ROOT));
-        element.setString("precipitation", precipitation.name().toLowerCase(Locale.ROOT));
+                element.setString("precipitation", precipitation.name().toLowerCase(Locale.ROOT));
-        if (temperatureModifier != TemperatureModifier.NONE)
+                if (temperatureModifier != TemperatureModifier.NONE)
-            element.setString("temperature_modifier", temperatureModifier.name().toLowerCase(Locale.ROOT));
+                    element.setString("temperature_modifier", temperatureModifier.name().toLowerCase(Locale.ROOT));
-        element.set("effects", effects.toNbt());
+                element.set("effects", effects.toNbt());
-        nbt.set("element", element);
+            }));
-        return nbt;
+        });
     }
 
     public int id() {

src/main/java/net/minestom/server/world/biomes/BiomeEffects.java

@@ -2,9 +2,11 @@ package net.minestom.server.world.biomes;
 
 import net.minestom.server.utils.NamespaceID;
 import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.Locale;
+import java.util.Map;
 
 public record BiomeEffects(int fogColor, int skyColor, int waterColor, int waterFogColor, int foliageColor,
                            int grassColor,
@@ -17,26 +19,28 @@ public record BiomeEffects(int fogColor, int skyColor, int waterColor, int water
     }
 
     public NBTCompound toNbt() {
-        NBTCompound nbt = new NBTCompound();
+        return NBT.Compound(nbt -> {
-        nbt.setInt("fog_color", fogColor);
+            nbt.setInt("fog_color", fogColor);
-        if (foliageColor != -1) nbt.setInt("foliage_color", foliageColor);
+            if (foliageColor != -1)
-        if (grassColor != -1) nbt.setInt("grass_color", grassColor);
+                nbt.setInt("foliage_color", foliageColor);
-        nbt.setInt("sky_color", skyColor);
+            if (grassColor != -1)
-        nbt.setInt("water_color", waterColor);
+                nbt.setInt("grass_color", grassColor);
-        nbt.setInt("water_fog_color", waterFogColor);
+            nbt.setInt("sky_color", skyColor);
-        if (grassColorModifier != null)
+            nbt.setInt("water_color", waterColor);
-            nbt.setString("grass_color_modifier", grassColorModifier.name().toLowerCase(Locale.ROOT));
+            nbt.setInt("water_fog_color", waterFogColor);
-        if (biomeParticle != null)
+            if (grassColorModifier != null)
-            nbt.set("particle", biomeParticle.toNbt());
+                nbt.setString("grass_color_modifier", grassColorModifier.name().toLowerCase(Locale.ROOT));
-        if (ambientSound != null)
+            if (biomeParticle != null)
-            nbt.setString("ambient_sound", ambientSound.toString());
+                nbt.set("particle", biomeParticle.toNbt());
-        if (moodSound != null)
+            if (ambientSound != null)
-            nbt.set("mood_sound", moodSound.toNbt());
+                nbt.setString("ambient_sound", ambientSound.toString());
-        if (additionsSound != null)
+            if (moodSound != null)
-            nbt.set("additions_sound", additionsSound.toNbt());
+                nbt.set("mood_sound", moodSound.toNbt());
-        if (music != null)
+            if (additionsSound != null)
-            nbt.set("music", music.toNbt());
+                nbt.set("additions_sound", additionsSound.toNbt());
-        return nbt;
+            if (music != null)
+                nbt.set("music", music.toNbt());
+        });
     }
 
     public enum GrassColorModifier {
@@ -45,32 +49,29 @@ public record BiomeEffects(int fogColor, int skyColor, int waterColor, int water
 
     public record MoodSound(NamespaceID sound, int tickDelay, int blockSearchExtent, double offset) {
         public @NotNull NBTCompound toNbt() {
-            NBTCompound nbt = new NBTCompound();
+            return NBT.Compound(Map.of(
-            nbt.setString("sound", sound.toString());
+                    "sound", NBT.String(sound.toString()),
-            nbt.setInt("tick_delay", tickDelay);
+                    "tick_delay", NBT.Int(tickDelay),
-            nbt.setInt("block_search_extent", blockSearchExtent);
+                    "block_search_extent", NBT.Int(blockSearchExtent),
-            nbt.setDouble("offset", offset);
+                    "offset", NBT.Double(offset)));
-            return nbt;
         }
     }
 
     public record AdditionsSound(NamespaceID sound, double tickChance) {
         public @NotNull NBTCompound toNbt() {
-            NBTCompound nbt = new NBTCompound();
+            return NBT.Compound(Map.of(
-            nbt.setString("sound", sound.toString());
+                    "sound", NBT.String(sound.toString()),
-            nbt.setDouble("tick_chance", tickChance);
+                    "tick_chance", NBT.Double(tickChance)));
-            return nbt;
         }
     }
 
     public record Music(NamespaceID sound, int minDelay, int maxDelay, boolean replaceCurrentMusic) {
         public @NotNull NBTCompound toNbt() {
-            NBTCompound nbt = new NBTCompound();
+            return NBT.Compound(Map.of(
-            nbt.setString("sound", sound.toString());
+                    "sound", NBT.String(sound.toString()),
-            nbt.setInt("min_delay", minDelay);
+                    "min_delay", NBT.Int(minDelay),
-            nbt.setInt("max_delay", maxDelay);
+                    "max_delay", NBT.Int(maxDelay),
-            nbt.setByte("replace_current_music", replaceCurrentMusic ? (byte) 1 : (byte) 0);
+                    "replace_current_music", NBT.Boolean(replaceCurrentMusic)));
-            return nbt;
         }
     }
 

src/main/java/net/minestom/server/world/biomes/BiomeManager.java

@@ -3,12 +3,14 @@ package net.minestom.server.world.biomes;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 import net.minestom.server.utils.NamespaceID;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
-import org.jglrxavpok.hephaistos.nbt.NBTList;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
 
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Map;
+
 
 /**
  * Allows servers to register custom dimensions. Also used during player joining to send the list of all existing dimensions.
@@ -71,13 +73,8 @@ public final class BiomeManager {
     }
 
     public synchronized NBTCompound toNBT() {
-        NBTCompound biomes = new NBTCompound();
+        return NBT.Compound(Map.of(
-        biomes.setString("type", "minecraft:worldgen/biome");
+                "type", NBT.String("minecraft:worldgen/biome"),
-        NBTList<NBTCompound> biomesList = new NBTList<>(NBTTypes.TAG_Compound);
+                "value", NBT.List(NBTType.TAG_Compound, biomes.values().stream().map(Biome::toNbt).toList())));
-        for (Biome biome : this.biomes.values()) {
-            biomesList.add(biome.toNbt());
-        }
-        biomes.set("value", biomesList);
-        return biomes;
     }
 }

src/main/java/net/minestom/server/world/biomes/BiomeParticle.java

@@ -3,16 +3,16 @@ package net.minestom.server.world.biomes;
 import net.minestom.server.instance.block.Block;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.utils.NamespaceID;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.Map;
 
 public record BiomeParticle(float probability, Option option) {
     public NBTCompound toNbt() {
-        NBTCompound nbt = new NBTCompound();
+        return NBT.Compound(Map.of(
-        nbt.setFloat("probability", probability);
+                "probability", NBT.Float(probability),
-        nbt.set("options", option.toNbt());
+                "options", option.toNbt()));
-        return nbt;
     }
 
     public interface Option {
@@ -25,16 +25,16 @@ public record BiomeParticle(float probability, Option option) {
 
         @Override
         public NBTCompound toNbt() {
-            NBTCompound nbtCompound = new NBTCompound();
+            return NBT.Compound(nbtCompound -> {
-            nbtCompound.setString("type", type);
+                nbtCompound.setString("type", type);
-            nbtCompound.setString("Name", block.name());
+                nbtCompound.setString("Name", block.name());
-            Map<String, String> propertiesMap = block.properties();
+                Map<String, String> propertiesMap = block.properties();
-            if (propertiesMap.size() != 0) {
+                if (propertiesMap.size() != 0) {
-                NBTCompound properties = new NBTCompound();
+                    nbtCompound.set("Properties", NBT.Compound(p -> {
-                propertiesMap.forEach(properties::setString);
+                        propertiesMap.forEach(p::setString);
-                nbtCompound.set("Properties", properties);
+                    }));
-            }
+                }
-            return nbtCompound;
+            });
         }
     }
 
@@ -43,13 +43,12 @@ public record BiomeParticle(float probability, Option option) {
 
         @Override
         public NBTCompound toNbt() {
-            NBTCompound nbtCompound = new NBTCompound();
+            return NBT.Compound(Map.of(
-            nbtCompound.setString("type", type);
+                    "type", NBT.String(type),
-            nbtCompound.setFloat("r", red);
+                    "r", NBT.Float(red),
-            nbtCompound.setFloat("g", green);
+                    "g", NBT.Float(green),
-            nbtCompound.setFloat("b", blue);
+                    "b", NBT.Float(blue),
-            nbtCompound.setFloat("scale", scale);
+                    "scale", NBT.Float(scale)));
-            return nbtCompound;
         }
     }
 
@@ -60,17 +59,16 @@ public record BiomeParticle(float probability, Option option) {
         public NBTCompound toNbt() {
             //todo test count might be wrong type
             NBTCompound nbtCompound = item.getMeta().toNBT();
-            nbtCompound.setString("type", type);
+            return nbtCompound.modify(n -> {
-            return nbtCompound;
+                n.setString("type", type);
+            });
         }
     }
 
     public record NormalOption(NamespaceID type) implements Option {
         @Override
         public NBTCompound toNbt() {
-            NBTCompound nbtCompound = new NBTCompound();
+            return NBT.Compound(Map.of("type", NBT.String(type.toString())));
-            nbtCompound.setString("type", type.toString());
-            return nbtCompound;
         }
     }
 }

src/test/java/demo/block/CampfireHandler.java

@@ -10,13 +10,15 @@ import net.minestom.server.tag.TagWritable;
 import net.minestom.server.utils.NamespaceID;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTList;
-import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+import org.jglrxavpok.hephaistos.nbt.NBTType;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.stream.Collectors;
 
 public class CampfireHandler implements BlockHandler {
 
@@ -44,15 +46,16 @@ public class CampfireHandler implements BlockHandler {
                 writer.removeTag(internal);
                 return;
             }
-            NBTList<NBTCompound> items = new NBTList<>(NBTTypes.TAG_Compound);
+            writer.setTag(internal, NBT.List(
-            for (var item : value) {
+                    NBTType.TAG_Compound,
-                NBTCompound compound = new NBTCompound()
+                    value.stream()
-                        .setByte("Count", (byte) item.getAmount())
+                            .map(item -> NBT.Compound(nbt -> {
-                        .setByte("Slot", (byte) 1)
+                                nbt.setByte("Count", (byte) item.getAmount());
-                        .setString("id", item.getMaterial().name());
+                                nbt.setByte("Slot", (byte) 1);
-                items.add(compound);
+                                nbt.setString("id", item.getMaterial().name());
-            }
+                            }))
-            writer.setTag(internal, items);
+                            .toList()
+            ));
         }
     });
 

src/test/java/permissions/TestPermissions.java

@@ -3,6 +3,7 @@ package permissions;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.entity.Player;
 import net.minestom.server.permission.Permission;
+import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -36,9 +37,11 @@ public class TestPermissions {
         };
 
         permission1 = new Permission("perm.name",
-                new NBTCompound()
+                NBT.Compound(nbt -> {
-                        .setString("name", "Minestom")
+                    nbt.setString("name", "Minestom");
-                        .setInt("amount", 5));
+                    nbt.setInt("amount", 5);
+                })
+        );
 
         permission2 = new Permission("perm.name2");
     }

src/test/java/regressions/ItemMetaBuilderRegressions.java

@@ -0,0 +1,95 @@
+package regressions;
+
+import net.minestom.server.item.ItemMeta;
+import net.minestom.server.item.ItemMetaBuilder;
+import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.NBTShort;
+import org.jglrxavpok.hephaistos.nbt.NBTString;
+import org.jglrxavpok.hephaistos.nbt.mutable.MutableNBTCompound;
+import org.junit.jupiter.api.Test;
+
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ItemMetaBuilderRegressions {
+
+    private static class BasicMetaBuilder extends ItemMetaBuilder {
+        @Override
+        public @NotNull ItemMeta build() {
+            return new ItemMeta(this) {};
+        }
+
+        @Override
+        public void read(@NotNull NBTCompound nbtCompound) {
+            // don't care
+        }
+
+        @Override
+        protected @NotNull Supplier<@NotNull ItemMetaBuilder> getSupplier() {
+            // don't care
+            return () -> this;
+        }
+
+        @Override
+        public void handleCompound(@NotNull String key, @NotNull Consumer<@NotNull MutableNBTCompound> consumer) {
+            super.handleCompound(key, consumer);
+        }
+    }
+
+    @Test
+    public void handleCompoundShouldUsePreviousValue() {
+        BasicMetaBuilder builder = new BasicMetaBuilder();
+
+        builder.handleCompound("test", nbt -> {
+            nbt.setString("my_key", "AAA");
+        });
+
+        NBTCompound nbt = builder.build().toNBT().getCompound("test");
+
+        assertTrue(nbt.contains("my_key"));
+        assertEquals(1, nbt.getSize());
+        assertTrue(nbt.get("my_key") instanceof NBTString);
+        assertEquals("AAA", nbt.getString("my_key"));
+
+        builder.handleCompound("test", n -> {
+            n.setString("my_other_key", "BBB");
+        });
+
+        nbt = builder.build().toNBT().getCompound("test");
+
+        assertTrue(nbt.contains("my_key"));
+        assertTrue(nbt.contains("my_other_key"));
+        assertEquals(2, nbt.getSize());
+        assertTrue(nbt.get("my_key") instanceof NBTString);
+        assertTrue(nbt.get("my_other_key") instanceof NBTString);
+        assertEquals("AAA", nbt.getString("my_key"));
+        assertEquals("BBB", nbt.getString("my_other_key"));
+    }
+
+    @Test
+    public void clearingShouldRemoveData() {
+        BasicMetaBuilder builder = new BasicMetaBuilder();
+
+        builder.handleCompound("test", nbt -> {
+            nbt.setString("my_key", "AAA");
+        });
+
+        NBTCompound nbt = builder.build().toNBT().getCompound("test");
+        assertTrue(nbt.contains("my_key"));
+        assertEquals(1, nbt.getSize());
+        assertTrue(nbt.get("my_key") instanceof NBTString);
+        assertEquals("AAA", nbt.getString("my_key"));
+
+        builder.handleCompound("test", n -> {
+            n.clear();
+        });
+
+        NBTCompound rootNBT = builder.build().toNBT();
+
+        assertFalse(rootNBT.contains("test"));
+        assertEquals(0, rootNBT.getSize());
+    }
+}