made it work, at least for a command

build.gradle

@@ -1,9 +1,10 @@
 plugins {
-    id 'fabric-loom' version '1.6.12'
+    id 'fabric-loom' version '1.6-SNAPSHOT'
+    id 'maven-publish'
 }
 
 version = "1.0.0"
-group = "dev.chipper"
+group = "net.Chipperfluff"
 
 repositories {
     mavenCentral()
@@ -11,10 +12,16 @@ repositories {
 
 dependencies {
     minecraft "com.mojang:minecraft:1.20.1"
+
     mappings "net.fabricmc:yarn:1.20.1+build.10:v2"
     modImplementation "net.fabricmc:fabric-loader:0.15.11"
+
+    // 🔴 THIS LINE IS THE FIX
+    modImplementation "net.fabricmc.fabric-api:fabric-api:0.92.2+1.20.1"
 }
 
 java {
-    toolchain.languageVersion = JavaLanguageVersion.of(17)
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(17)
+    }
 }

main/java/dev/chipper/dimension/ChipperDimensionMod.java

@@ -1,11 +0,0 @@
-package dev.chipper.dimension;
-
-import net.fabricmc.api.ModInitializer;
-
-public class ChipperDimensionMod implements ModInitializer {
-
-    @Override
-    public void onInitialize() {
-        ChipperDimensions.init();
-    }
-}

main/java/dev/chipper/dimension/ChipperDimensions.java

@@ -1,30 +0,0 @@
-package dev.chipper.dimension;
-
-import net.minecraft.block.Blocks;
-import net.minecraft.server.world.ServerWorld;
-import net.minecraft.util.Identifier;
-import net.minecraft.util.math.BlockPos;
-import net.minecraft.registry.RegistryKey;
-import net.minecraft.registry.RegistryKeys;
-import net.minecraft.world.World;
-
-public class ChipperDimensions {
-
-    public static final RegistryKey<World> CHIPPER_WORLD =
-            RegistryKey.of(RegistryKeys.WORLD, new Identifier("chipperdimension", "chipper"));
-
-    public static void init() {
-        // JSON handles dimension creation
-    }
-
-    public static void ensureSpawnPlatform(ServerWorld world) {
-        BlockPos center = new BlockPos(0, 64, 0);
-
-        for (int x = -5; x < 5; x++) {
-            for (int z = -5; z < 5; z++) {
-                world.setBlockState(center.add(x, 0, z),
-                        Blocks.STONE.getDefaultState());
-            }
-        }
-    }
-}

main/resources/data/chipperdimension/worldgen/dimension/chipper.json

@@ -1,11 +0,0 @@
-{
-  "type": "chipperdimension:chipper",
-  "generator": {
-    "type": "minecraft:noise",
-    "settings": "minecraft:overworld",
-    "biome_source": {
-      "type": "minecraft:fixed",
-      "biome": "minecraft:the_void"
-    }
-  }
-}

main/resources/data/chipperdimension/worldgen/dimension_type/chipper.json

@@ -1,25 +0,0 @@
-{
-  "ultrawarm": false,
-  "natural": false,
-  "coordinate_scale": 1.0,
-  "has_skylight": true,
-  "has_ceiling": false,
-  "ambient_light": 0.0,
-  "fixed_time": 6000,
-  "monster_spawn_light_level": {
-    "type": "minecraft:uniform",
-    "value": {
-      "min_inclusive": 0,
-      "max_inclusive": 7
-    }
-  },
-  "monster_spawn_block_light_limit": 0,
-  "piglin_safe": false,
-  "bed_works": true,
-  "respawn_anchor_works": false,
-  "infiniburn": "#minecraft:infiniburn_overworld",
-  "effects": "minecraft:overworld",
-  "min_y": 0,
-  "height": 256,
-  "logical_height": 256
-}

main/resources/fabric.mod.json

@@ -1,19 +0,0 @@
-{
-  "schemaVersion": 1,
-  "id": "chipperdimension",
-  "version": "1.0.0",
-  "name": "The Chipper Dimension",
-  "description": "A void dimension for testing.",
-  "authors": ["you"],
-  "environment": "*",
-  "entrypoints": {
-    "main": [
-      "dev.chipper.dimension.ChipperDimensionMod"
-    ]
-  },
-  "depends": {
-    "fabricloader": ">=0.15.0",
-    "minecraft": "1.20.1",
-    "java": ">=17"
-  }
-}

main/resources/pack.mcmeta

@@ -1,6 +0,0 @@
-{
-  "pack": {
-    "pack_format": 15,
-    "description": "The Chipper Dimension"
-  }
-}

src/main/java/net/Chipperfluff/chipi/ChipiMod.java

@@ -0,0 +1,17 @@
+package net.Chipperfluff.chipi;
+
+import net.fabricmc.api.ModInitializer;
+import net.fabricmc.fabric.api.command.v2.CommandRegistrationCallback;
+import net.Chipperfluff.chipi.command.ChipperCommand;
+
+public class ChipiMod implements ModInitializer {
+
+    @Override
+    public void onInitialize() {
+        CommandRegistrationCallback.EVENT.register(
+            (dispatcher, registryAccess, environment) -> {
+                ChipperCommand.register(dispatcher);
+            }
+        );
+    }
+}

src/main/java/net/Chipperfluff/chipi/command/ChipperCommand.java

@@ -0,0 +1,23 @@
+package net.Chipperfluff.chipi.command;
+
+import com.mojang.brigadier.CommandDispatcher;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.text.Text;
+
+import static net.minecraft.server.command.CommandManager.literal;
+
+public class ChipperCommand {
+
+    public static void register(CommandDispatcher<ServerCommandSource> dispatcher) {
+        dispatcher.register(
+            literal("chipper")
+                .executes(context -> {
+                    context.getSource().sendFeedback(
+                        () -> Text.literal("This is a test command!"),
+                        false
+                    );
+                    return 1;
+                })
+        );
+    }
+}

src/main/resources/fabric.mod.json

@@ -0,0 +1,22 @@
+{
+  "schemaVersion": 1,
+  "id": "chipi",
+  "version": "1.0.0",
+
+  "name": "Chipi Mod",
+  "description": "Test mod with a command",
+  "authors": ["You"],
+
+  "environment": "*",
+  "entrypoints": {
+    "main": [
+      "net.Chipperfluff.chipi.ChipiMod"
+    ]
+  },
+
+  "depends": {
+    "fabricloader": ">=0.14.0",
+    "minecraft": ">=1.20",
+    "fabric-api": "*"
+  }
+}

src/main/resources/pack.mcmeta

@@ -0,0 +1,8 @@
+{
+  "pack": {
+    "description": {
+      "text": "${mod_id} resources"
+    },
+    "pack_format": 15
+  }
+}