Fix merge conflicts

Signed-off-by: shedaniel <daniel@shedaniel.me>
2026-04-02 05:27:43 -05:00 · 2021-09-18 14:00:14 +08:00
parent 3aa0e5f731
commit 7f54808315
25 changed files with 371 additions and 408 deletions
--- a/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingsNamespace.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/MappingsNamespace.java
@@ -43,6 +43,7 @@ public enum MappingsNamespace {
 	 * @see <a href="https://github.com/FabricMC/intermediary/">github.com/FabricMC/intermediary/</a>
 	 */
 	INTERMEDIARY,
+	SRG,

 	/**
 	 * Named mappings are the developer friendly names used to develop mods against.
--- a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
@@ -47,4 +47,6 @@ public interface LayeredMappingSpecBuilder {
 	}

 	LayeredMappingSpecBuilder parchment(Object object, Action<ParchmentMappingsSpecBuilder> action);
+
+	LayeredMappingSpecBuilder crane(Object object);
 }
--- a/src/main/java/net/fabricmc/loom/configuration/accesswidener/TransitiveAccessWidenerJarProcessor.java
+++ b/src/main/java/net/fabricmc/loom/configuration/accesswidener/TransitiveAccessWidenerJarProcessor.java
@@ -31,6 +31,7 @@ import java.util.List;
 import java.util.Set;

 import com.google.common.base.Preconditions;
+import dev.architectury.tinyremapper.TinyRemapper;
 import org.gradle.api.Project;

 import net.fabricmc.accesswidener.AccessWidener;
@@ -44,7 +45,6 @@ import net.fabricmc.loom.configuration.RemappedConfigurationEntry;
 import net.fabricmc.loom.configuration.processors.JarProcessor;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.TinyRemapperHelper;
-import net.fabricmc.tinyremapper.TinyRemapper;

 /**
 * Applies transitive access wideners that are inherited from mod and api dependencies.
--- a/src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java
+++ b/src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java
@@ -67,7 +67,7 @@ import net.fabricmc.loom.util.LoggerFilter;
 import net.fabricmc.loom.util.TinyRemapperHelper;
 import net.fabricmc.loom.util.srg.AtRemapper;
 import net.fabricmc.loom.util.srg.CoreModClassRemapper;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;

 public class ModProcessor {
 	public static void processMods(Project project, List<ModDependencyInfo> processList) throws IOException {
@@ -148,7 +148,7 @@ public class ModProcessor {
 		Stopwatch stopwatch = Stopwatch.createStarted();
 		project.getLogger().lifecycle(":remapping " + remapList.size() + " mods (TinyRemapper, " + fromM + " -> " + toM + ")");

-		TinyTree mappings = extension.isForge() ? mappingsProvider.getMappingsWithSrg() : mappingsProvider.getMappings();
+		MemoryMappingTree mappings = extension.isForge() ? mappingsProvider.getMappingsWithSrg() : mappingsProvider.getMappings();
 		LoggerFilter.replaceSystemOut();
 		TinyRemapper remapper = TinyRemapper.newRemapper()
 				.logger(project.getLogger()::lifecycle)
--- a/src/main/java/net/fabricmc/loom/configuration/providers/forge/FieldMigratedMappingsProvider.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/forge/FieldMigratedMappingsProvider.java
@@ -27,6 +27,7 @@ package net.fabricmc.loom.configuration.providers.forge;
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
+import java.io.StringWriter;
 import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -44,11 +45,6 @@ import com.google.common.collect.HashBasedTable;
 import com.google.common.collect.Table;
 import com.google.common.reflect.TypeToken;
 import com.google.gson.Gson;
-import dev.architectury.mappingslayers.api.mutable.MappingsEntry;
-import dev.architectury.mappingslayers.api.mutable.MutableClassDef;
-import dev.architectury.mappingslayers.api.mutable.MutableFieldDef;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
 import dev.architectury.refmapremapper.utils.DescriptorRemapper;
 import org.gradle.api.Project;
 import org.objectweb.asm.ClassReader;
@@ -58,14 +54,16 @@ import org.objectweb.asm.Opcodes;

 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.LoomGradlePlugin;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.providers.mappings.MappingsProviderImpl;
 import net.fabricmc.loom.util.FileSystemUtil;
 import net.fabricmc.loom.util.ThreadingUtils;
 import net.fabricmc.loom.util.srg.SrgMerger;
-import net.fabricmc.mapping.tree.ClassDef;
-import net.fabricmc.mapping.tree.FieldDef;
-import net.fabricmc.mapping.tree.TinyMappingFactory;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.MappingReader;
+import net.fabricmc.mappingio.format.Tiny2Writer;
+import net.fabricmc.mappingio.tree.MappingTree;
+import net.fabricmc.mappingio.tree.MappingTreeView;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;

 public class FieldMigratedMappingsProvider extends MappingsProviderImpl {
 	private List<Map.Entry<FieldMember, String>> migratedFields = new ArrayList<>();
@@ -148,27 +146,30 @@ public class FieldMigratedMappingsProvider extends MappingsProviderImpl {
 				fieldDescriptorMap.put(entry.getKey().owner, entry.getKey().field, entry.getValue());
 			}

-			MutableTinyTree mappings;
+			MemoryMappingTree mappings = new MemoryMappingTree();

 			try (BufferedReader reader = Files.newBufferedReader(rawTinyMappings)) {
-				mappings = MappingsUtils.copyAsMutable(TinyMappingFactory.loadWithDetection(reader));
+				MappingReader.read(reader, mappings);

-				for (MutableClassDef classDef : mappings.getClassesMutable()) {
-					Map<String, String> row = fieldDescriptorMap.row(classDef.getIntermediary());
+				for (MappingTree.ClassMapping classDef : new ArrayList<>(mappings.getClasses())) {
+					Map<String, String> row = fieldDescriptorMap.row(classDef.getName(MappingsNamespace.INTERMEDIARY.toString()));

 					if (!row.isEmpty()) {
-						for (MutableFieldDef fieldDef : classDef.getFieldsMutable()) {
-							String newDescriptor = row.get(fieldDef.getIntermediary());
+						for (MappingTree.FieldMapping fieldDef : new ArrayList<>(classDef.getFields())) {
+							String newDescriptor = row.get(fieldDef.getName(MappingsNamespace.INTERMEDIARY.toString()));

 							if (newDescriptor != null) {
-								fieldDef.setDescriptor(MappingsEntry.NS_INTERMEDIARY, newDescriptor);
+								fieldDef.setSrcDesc(mappings.mapDesc(newDescriptor, mappings.getNamespaceId(MappingsNamespace.INTERMEDIARY.toString()), MappingTreeView.SRC_NAMESPACE_ID));
 							}
 						}
 					}
 				}
 			}

-			Files.writeString(tinyMappings, MappingsUtils.serializeToString(mappings), StandardOpenOption.CREATE);
+			StringWriter stringWriter = new StringWriter();
+			Tiny2Writer tiny2Writer = new Tiny2Writer(stringWriter, false);
+			mappings.accept(tiny2Writer);
+			Files.writeString(tinyMappings, stringWriter.toString(), StandardOpenOption.CREATE);
 		}
 	}

@@ -217,27 +218,28 @@ public class FieldMigratedMappingsProvider extends MappingsProviderImpl {
 		Map<FieldMember, String> migratedFields = new HashMap<>();

 		try (BufferedReader reader = Files.newBufferedReader(rawTinyMappingsWithSrg)) {
-			TinyTree mappings = TinyMappingFactory.loadWithDetection(reader);
+			MemoryMappingTree mappings = new MemoryMappingTree();
+			MappingReader.read(reader, mappings);
 			Map<String, String> srgToIntermediary = new HashMap<>();

-			for (ClassDef aClass : mappings.getClasses()) {
+			for (MappingTree.ClassMapping aClass : mappings.getClasses()) {
 				srgToIntermediary.put(aClass.getName("srg"), aClass.getName("intermediary"));
 			}

-			for (ClassDef classDef : mappings.getClasses()) {
+			for (MappingTree.ClassMapping classDef : mappings.getClasses()) {
 				String ownerSrg = classDef.getName("srg");
 				String ownerIntermediary = classDef.getName("intermediary");

-				for (FieldDef fieldDef : classDef.getFields()) {
+				for (MappingTree.FieldMapping fieldDef : classDef.getFields()) {
 					String fieldSrg = fieldDef.getName("srg");
-					String descriptorSrg = fieldDef.getDescriptor("srg");
+					String descriptorSrg = fieldDef.getDesc("srg");

 					FieldMember member = new FieldMember(ownerSrg, fieldSrg);
 					String newDescriptor = fieldDescriptorMap.get(member);

 					if (newDescriptor != null && !newDescriptor.equals(descriptorSrg)) {
 						String fieldIntermediary = fieldDef.getName("intermediary");
-						String descriptorIntermediary = fieldDef.getDescriptor("intermediary");
+						String descriptorIntermediary = fieldDef.getDesc("intermediary");
 						String newDescriptorRemapped = DescriptorRemapper.remapDescriptor(newDescriptor,
 								clazz -> srgToIntermediary.getOrDefault(clazz, clazz));
 						migratedFields.put(new FieldMember(ownerIntermediary, fieldIntermediary), newDescriptorRemapped);
--- a/src/main/java/net/fabricmc/loom/configuration/providers/forge/MinecraftPatchedProvider.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/forge/MinecraftPatchedProvider.java
@@ -32,6 +32,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.PrintStream;
+import java.io.StringReader;
 import java.io.UncheckedIOException;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
@@ -65,10 +66,6 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.hash.Hashing;
 import com.google.common.io.ByteSource;
 import de.oceanlabs.mcp.mcinjector.adaptors.ParameterAnnotationFixer;
-import dev.architectury.mappingslayers.api.mutable.MutableClassDef;
-import dev.architectury.mappingslayers.api.mutable.MutableMethodDef;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
 import dev.architectury.tinyremapper.InputTag;
 import dev.architectury.tinyremapper.OutputConsumerPath;
 import dev.architectury.tinyremapper.TinyRemapper;
@@ -92,25 +89,27 @@ import org.objectweb.asm.tree.ClassNode;
 import org.zeroturnaround.zip.ZipUtil;

 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.DependencyProvider;
 import net.fabricmc.loom.configuration.providers.MinecraftProviderImpl;
 import net.fabricmc.loom.configuration.providers.mappings.GradleMappingContext;
-import net.fabricmc.loom.configuration.providers.mappings.MappingNamespace;
 import net.fabricmc.loom.configuration.providers.mappings.mojmap.MojangMappingLayer;
 import net.fabricmc.loom.configuration.providers.mappings.mojmap.MojangMappingsSpec;
-import net.fabricmc.loom.configuration.providers.minecraft.MinecraftMappedProvider;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.DependencyDownloader;
 import net.fabricmc.loom.util.FileSystemUtil;
 import net.fabricmc.loom.util.MappingsProviderVerbose;
 import net.fabricmc.loom.util.ThreadingUtils;
-import net.fabricmc.loom.util.TinyRemapperMappingsHelper;
+import net.fabricmc.loom.util.TinyRemapperHelper;
 import net.fabricmc.loom.util.function.FsPathConsumer;
 import net.fabricmc.loom.util.srg.InnerClassRemapper;
 import net.fabricmc.loom.util.srg.SpecialSourceExecutor;
 import net.fabricmc.loom.util.srg.Tsrg2Utils;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.loom.util.srg.Tsrg2Writer;
+import net.fabricmc.mappingio.MappingReader;
 import net.fabricmc.mappingio.MappingVisitor;
+import net.fabricmc.mappingio.tree.MappingTree;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;

 public class MinecraftPatchedProvider extends DependencyProvider {
 	private static final String LOOM_PATCH_VERSION_KEY = "Loom-Patch-Version";
@@ -319,12 +318,12 @@ public class MinecraftPatchedProvider extends DependencyProvider {
 	}

 	private TinyRemapper buildRemapper(Path input) throws IOException {
-		Path[] libraries = MinecraftMappedProvider.getRemapClasspath(getProject());
-		TinyTree mappingsWithSrg = getExtension().getMappingsProvider().getMappingsWithSrg();
+		Path[] libraries = TinyRemapperHelper.getMinecraftDependencies(getProject());
+		MemoryMappingTree mappingsWithSrg = getExtension().getMappingsProvider().getMappingsWithSrg();
 		TinyRemapper remapper = TinyRemapper.newRemapper()
 				.logger(getProject().getLogger()::lifecycle)
 				.logUnknownInvokeDynamic(false)
-				.withMappings(TinyRemapperMappingsHelper.create(mappingsWithSrg, "srg", "official", true))
+				.withMappings(TinyRemapperHelper.create(mappingsWithSrg, "srg", "official", true))
 				.withMappings(InnerClassRemapper.of(InnerClassRemapper.readClassNames(input), mappingsWithSrg, "srg", "official"))
 				.renameInvalidLocals(true)
 				.rebuildSourceFilenames(true)
@@ -377,14 +376,14 @@ public class MinecraftPatchedProvider extends DependencyProvider {
 		GradleMappingContext context = new GradleMappingContext(project, "tmp-mojmap");

 		try {
-			FileUtils.deleteDirectory(context.workingDirectory("/"));
+			FileUtils.deleteDirectory(context.workingDirectory("/").toFile());
 			MojangMappingLayer layer = new MojangMappingsSpec(() -> true).createLayer(context);
 			layer.visit(visitor);
 		} catch (IOException e) {
 			throw new UncheckedIOException(e);
 		} finally {
 			try {
-				FileUtils.deleteDirectory(context.workingDirectory("/"));
+				FileUtils.deleteDirectory(context.workingDirectory("/").toFile());
 			} catch (IOException e) {
 				e.printStackTrace();
 			}
@@ -397,7 +396,7 @@ public class MinecraftPatchedProvider extends DependencyProvider {
 		if (Files.notExists(path)) {
 			try (BufferedWriter writer = Files.newBufferedWriter(path, StandardCharsets.UTF_8, StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING)) {
 				Tsrg2Utils.writeTsrg(visitor -> visitMojmap(visitor, project),
-						MappingNamespace.NAMED.stringValue(), false, writer);
+						MappingsNamespace.NAMED.toString(), false, writer);
 			}
 		}

@@ -409,7 +408,9 @@ public class MinecraftPatchedProvider extends DependencyProvider {

 		if (Files.notExists(path)) {
 			try (BufferedWriter writer = Files.newBufferedWriter(path, StandardCharsets.UTF_8, StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING)) {
-				Tsrg2Utils.writeTsrg2(visitor -> visitMojmap(visitor, project), writer);
+				MemoryMappingTree tree = new MemoryMappingTree();
+				visitMojmap(tree, project);
+				writer.write(Tsrg2Writer.serialize(tree));
 			}
 		}

@@ -432,15 +433,16 @@ public class MinecraftPatchedProvider extends DependencyProvider {
 					out.toAbsolutePath().toString()
 			});

-			MutableTinyTree mappings = MappingsUtils.deserializeFromTsrg2(FileUtils.readFileToString(out.toFile(), StandardCharsets.UTF_8));
+			MemoryMappingTree tree = new MemoryMappingTree();
+			MappingReader.read(new StringReader(FileUtils.readFileToString(out.toFile(), StandardCharsets.UTF_8)), tree);

-			for (MutableClassDef classDef : mappings.getClassesMutable()) {
-				for (MutableMethodDef methodDef : classDef.getMethodsMutable()) {
-					methodDef.getParametersMutable().clear();
+			for (MappingTree.ClassMapping classDef : tree.getClasses()) {
+				for (MappingTree.MethodMapping methodDef : classDef.getMethods()) {
+					methodDef.getArgs().clear();
 				}
 			}

-			Files.writeString(outTrimmed, MappingsUtils.serializeToTsrg2(mappings), StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
+			Files.writeString(outTrimmed, 	Tsrg2Writer.serialize(tree), StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);

 			mergedMojangTsrg2Files = new Path[]{out, outTrimmed};
 		}
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
@@ -46,26 +46,20 @@ public class LayeredMappingSpecBuilderImpl implements LayeredMappingSpecBuilder
 	@Nullable
 	private final LoomGradleExtensionAPI extension;

-	public LayeredMappingSpecBuilder(@Nullable LoomGradleExtensionAPI extension) {
+	public LayeredMappingSpecBuilderImpl(@Nullable LoomGradleExtensionAPI extension) {
 		this.extension = extension;
 	}

 	@Override
 	public LayeredMappingSpecBuilder addLayer(MappingsSpec<?> mappingSpec) {
 		layers.add(mappingSpec);
-	public LayeredMappingSpecBuilder officialMojangMappings() {
-		layers.add(new MojangMappingsSpec(() -> extension != null && extension.isSilentMojangMappingsLicenseEnabled()));
-		return this;
-	}
-
-	public LayeredMappingSpecBuilder parchment(String mavenNotation) {
-		parchment(mavenNotation, parchmentMappingsSpecBuilder -> parchmentMappingsSpecBuilder.setRemovePrefix(true));
 		return this;
 	}

 	@Override
 	public LayeredMappingSpecBuilder officialMojangMappings() {
-		return addLayer(new MojangMappingsSpec());
+		layers.add(new MojangMappingsSpec(() -> extension != null && extension.isSilentMojangMappingsLicenseEnabled()));
+		return this;
 	}

 	@Override
@@ -75,8 +69,9 @@ public class LayeredMappingSpecBuilderImpl implements LayeredMappingSpecBuilder
 		return addLayer(builder.build());
 	}

-	public LayeredMappingSpecBuilder crane(String mavenNotation) {
-		layers.add(new CraneMappingsSpec(mavenNotation));
+	@Override
+	public LayeredMappingSpecBuilder crane(Object object) {
+		layers.add(new CraneMappingsSpec(FileSpec.create(object)));
 		return this;
 	}

--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
@@ -71,7 +71,6 @@ import net.fabricmc.loom.util.DownloadUtil;
 import net.fabricmc.loom.util.srg.MCPReader;
 import net.fabricmc.loom.util.srg.SrgMerger;
 import net.fabricmc.loom.util.srg.SrgNamedWriter;
-import net.fabricmc.mapping.reader.v2.TinyMetadata;
 import net.fabricmc.mappingio.MappingReader;
 import net.fabricmc.mappingio.adapter.MappingNsCompleter;
 import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
@@ -107,6 +106,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 	private boolean hasUnpickDefinitions;
 	private UnpickMetadata unpickMetadata;
 	private MemoryMappingTree mappingTree;
+	private MemoryMappingTree mappingTreeWithSrg;

 	public MappingsProviderImpl(Project project) {
 		super(project);
@@ -116,12 +116,8 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 		return Objects.requireNonNull(mappingTree, "Cannot get mappings before they have been read");
 	}

-	public TinyTree getMappingsWithSrg() throws IOException {
-		if (getExtension().shouldGenerateSrgTiny()) {
-			return MappingsCache.INSTANCE.get(tinyMappingsWithSrg);
-		}
-
-		throw new UnsupportedOperationException("Not running with Forge support / Tiny srg support.");
+	public MemoryMappingTree getMappingsWithSrg() throws IOException {
+		return Objects.requireNonNull(mappingTreeWithSrg, "Cannot get mappings before they have been read");
 	}

 	@Override
@@ -152,7 +148,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			patchedProvider.provide(dependency, postPopulationScheduler);
 		}

-		mappingTree = readMappings();
+		mappingTree = readMappings(tinyMappings);
 		manipulateMappings(mappingsJar.toPath());

 		if (getExtension().shouldGenerateSrgTiny()) {
@@ -162,6 +158,8 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			}
 		}

+		mappingTreeWithSrg = readMappings(tinyMappingsWithSrg);
+
 		if (Files.notExists(tinyMappingsJar) || isRefreshDeps()) {
 			ZipUtil.pack(new ZipEntrySource[] {new FileSource("mappings/mappings.tiny", tinyMappings.toFile())}, tinyMappingsJar.toFile());
 		}
@@ -318,9 +316,9 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 		}
 	}

-	private MemoryMappingTree readMappings() throws IOException {
+	private static MemoryMappingTree readMappings(Path file) throws IOException {
 		MemoryMappingTree mappingTree = new MemoryMappingTree();
-		MappingReader.read(tinyMappings, mappingTree);
+		MappingReader.read(file, mappingTree);
 		return mappingTree;
 	}

@@ -362,9 +360,8 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings

 	private static boolean areMappingsMergedV2(Path path) throws IOException {
 		try (BufferedReader reader = Files.newBufferedReader(path)) {
-			TinyMetadata metadata = TinyV2Factory.readMetadata(reader);
-			return metadata.getNamespaces().containsAll(Arrays.asList("named", "intermediary", "official"));
-		} catch (IllegalArgumentException | NoSuchFileException e) {
+			return MappingReader.detectFormat(reader) == MappingFormat.TINY_2 && MappingReader.getNamespaces(reader).containsAll(Arrays.asList("named", "intermediary", "official"));
+		} catch (NoSuchFileException e) {
 			return false;
 		}
 	}
@@ -374,6 +371,8 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			try (BufferedReader reader = Files.newBufferedReader(fs.getPath("mappings", "mappings.tiny"))) {
 				return MappingReader.detectFormat(reader) == MappingFormat.TINY_2;
 			}
+		} catch (NoSuchFileException e) {
+			return false;
 		}
 	}

@@ -466,10 +465,10 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			runCommand(command, intermediaryMappings.toAbsolutePath().toString(),
 					yarnMappings.toAbsolutePath().toString(),
 					newMergedMappings.toAbsolutePath().toString(),
-							MappingsNamespace.INTERMEDIARY.toString(), MappingsNamespace.OFFICIAL.toString());
+					MappingsNamespace.INTERMEDIARY.toString(), MappingsNamespace.OFFICIAL.toString());
 		} catch (Exception e) {
 			throw new RuntimeException("Could not merge mappings from " + intermediaryMappings.toString()
-					+ " with mappings from " + yarnMappings, e);
+			                           + " with mappings from " + yarnMappings, e);
 		}
 	}

--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/crane/CraneMappingLayer.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/crane/CraneMappingLayer.java
@@ -25,91 +25,24 @@
 package net.fabricmc.loom.configuration.providers.mappings.crane;

 import java.io.BufferedReader;
-import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
-import java.util.Collections;
+import java.nio.file.Path;

-import dev.architectury.mappingslayers.api.mutable.MutableClassDef;
-import dev.architectury.mappingslayers.api.mutable.MutableFieldDef;
-import dev.architectury.mappingslayers.api.mutable.MutableMethodDef;
-import dev.architectury.mappingslayers.api.mutable.MutableParameterDef;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
-import org.apache.commons.io.IOUtils;
-
-import net.fabricmc.loom.configuration.providers.mappings.MappingLayer;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
 import net.fabricmc.loom.util.FileSystemUtil;
-import net.fabricmc.mappingio.MappedElementKind;
 import net.fabricmc.mappingio.MappingVisitor;
+import net.fabricmc.mappingio.format.Tiny2Reader;

-public record CraneMappingLayer(File craneJar) implements MappingLayer {
+public record CraneMappingLayer(Path craneJar) implements MappingLayer {
 	private static final String TINY_FILE_NAME = "crane.tiny";

 	@Override
 	public void visit(MappingVisitor visitor) throws IOException {
-		try (FileSystemUtil.FileSystemDelegate fs = FileSystemUtil.getJarFileSystem(craneJar().toPath(), false)) {
+		try (FileSystemUtil.FileSystemDelegate fs = FileSystemUtil.getJarFileSystem(craneJar(), false)) {
 			try (BufferedReader reader = Files.newBufferedReader(fs.get().getPath(TINY_FILE_NAME), StandardCharsets.UTF_8)) {
-				// can't use this, it requires 2 namespaces
-				// Tiny2Reader.read(reader, mappingVisitor);
-				MutableTinyTree tree = MappingsUtils.deserializeFromString(IOUtils.toString(reader));
-
-				do {
-					if (visitor.visitHeader()) {
-						visitor.visitNamespaces(tree.getMetadata().getNamespaces().get(0), Collections.emptyList());
-					}
-
-					if (visitor.visitContent()) {
-						for (MutableClassDef classDef : tree.getClassesMutable()) {
-							if (visitor.visitClass(classDef.getName(0))) {
-								if (!visitor.visitElementContent(MappedElementKind.CLASS)) {
-									return;
-								}
-
-								for (MutableFieldDef fieldDef : classDef.getFieldsMutable()) {
-									if (visitor.visitField(fieldDef.getName(0), fieldDef.getDescriptor(0))) {
-										if (!visitor.visitElementContent(MappedElementKind.FIELD)) {
-											return;
-										}
-
-										if (fieldDef.getComment() != null) {
-											visitor.visitComment(MappedElementKind.FIELD, fieldDef.getComment());
-										}
-									}
-								}
-
-								for (MutableMethodDef methodDef : classDef.getMethodsMutable()) {
-									if (visitor.visitMethod(methodDef.getName(0), methodDef.getDescriptor(0))) {
-										if (!visitor.visitElementContent(MappedElementKind.METHOD)) {
-											return;
-										}
-
-										for (MutableParameterDef parameterDef : methodDef.getParametersMutable()) {
-											if (visitor.visitMethodArg(parameterDef.getLocalVariableIndex(), parameterDef.getLocalVariableIndex(), parameterDef.getName(0))) {
-												if (!visitor.visitElementContent(MappedElementKind.METHOD_ARG)) {
-													return;
-												}
-
-												if (parameterDef.getComment() != null) {
-													visitor.visitComment(MappedElementKind.METHOD_ARG, parameterDef.getComment());
-												}
-											}
-										}
-
-										if (methodDef.getComment() != null) {
-											visitor.visitComment(MappedElementKind.METHOD, methodDef.getComment());
-										}
-									}
-								}
-
-								if (classDef.getComment() != null) {
-									visitor.visitComment(MappedElementKind.FIELD, classDef.getComment());
-								}
-							}
-						}
-					}
-				} while (!visitor.visitEnd());
+				Tiny2Reader.read(reader, visitor);
 			}
 		}
 	}
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/crane/CraneMappingsSpec.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/crane/CraneMappingsSpec.java
@@ -24,12 +24,13 @@

 package net.fabricmc.loom.configuration.providers.mappings.crane;

-import net.fabricmc.loom.configuration.providers.mappings.MappingContext;
-import net.fabricmc.loom.configuration.providers.mappings.MappingsSpec;
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;

-public record CraneMappingsSpec(String mavenNotation) implements MappingsSpec<CraneMappingLayer> {
+public record CraneMappingsSpec(FileSpec fileSpec) implements MappingsSpec<CraneMappingLayer> {
 	@Override
 	public CraneMappingLayer createLayer(MappingContext context) {
-		return new CraneMappingLayer(context.mavenFile(mavenNotation()));
+		return new CraneMappingLayer(fileSpec().get(context));
 	}
 }
--- a/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
@@ -32,12 +32,10 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;

 import com.google.common.base.Stopwatch;
-import com.google.common.collect.ImmutableMap;
 import dev.architectury.tinyremapper.IMappingProvider;
 import dev.architectury.tinyremapper.InputTag;
 import dev.architectury.tinyremapper.NonClassCopyMode;
@@ -61,15 +59,9 @@ import net.fabricmc.loom.util.TinyRemapperHelper;
 import net.fabricmc.loom.util.srg.AtRemapper;
 import net.fabricmc.loom.util.srg.CoreModClassRemapper;
 import net.fabricmc.loom.util.srg.InnerClassRemapper;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;

 public class MinecraftMappedProvider extends DependencyProvider {
-	public static final Map<String, String> JSR_TO_JETBRAINS = new ImmutableMap.Builder<String, String>()
-			.put("javax/annotation/Nullable", "org/jetbrains/annotations/Nullable")
-			.put("javax/annotation/Nonnull", "org/jetbrains/annotations/NotNull")
-			.put("javax/annotation/concurrent/Immutable", "org/jetbrains/annotations/Unmodifiable")
-			.build();
-
 	private File inputJar;
 	private File inputForgeJar;
 	private File minecraftMappedJar;
@@ -177,14 +169,6 @@ public class MinecraftMappedProvider extends DependencyProvider {
 		}
 	}

-	private TinyRemapper buildRemapper() throws IOException {
-		Path[] libraries = getRemapClasspath(getProject());
-		TinyRemapper remapper = getTinyRemapper();
-		remapper.readClassPath(libraries);
-		remapper.prepareClasses();
-		return remapper;
-	}
-
 	private byte[][] inputBytes(Path input) throws IOException {
 		List<byte[]> inputByteList = new ArrayList<>();

@@ -244,7 +228,7 @@ public class MinecraftMappedProvider extends DependencyProvider {
 		Info vanilla = new Info(vanillaAssets, input, outputMapped, outputIntermediary, outputSrg);
 		Info forge = getExtension().isForgeAndNotOfficial() ? new Info(forgeAssets, inputForge, forgeOutputMapped, forgeOutputIntermediary, forgeOutputSrg) : null;

-		TinyRemapper remapper = remapperArray[0] = buildRemapper();
+		TinyRemapper remapper = remapperArray[0] = TinyRemapperHelper.getTinyRemapper(getProject());

 		assetsOut(input, vanillaAssets);

@@ -295,60 +279,34 @@ public class MinecraftMappedProvider extends DependencyProvider {
 				OutputRemappingHandler.remap(remapper, forge.assets, outputForge, null, forgeTag);
 			}

-			// TODO TinyRemapperHelper
 			getProject().getLogger().lifecycle(":remapped minecraft (TinyRemapper, " + fromM + " -> " + toM + ") in " + stopwatch);
 			remapper.removeInput();

 			if (getExtension().isForge() && !"srg".equals(toM)) {
 				getProject().getLogger().info(":running minecraft finalising tasks");

-				TinyTree yarnWithSrg = getExtension().getMappingsProvider().getMappingsWithSrg();
+				MemoryMappingTree yarnWithSrg = getExtension().getMappingsProvider().getMappingsWithSrg();
 				AtRemapper.remap(getProject().getLogger(), output, yarnWithSrg);
 				CoreModClassRemapper.remapJar(output, yarnWithSrg, getProject().getLogger());
 			}
 		}
 	}

-	public TinyRemapper getTinyRemapper() throws IOException {
-		TinyRemapper.Builder builder = TinyRemapper.newRemapper()
-				.renameInvalidLocals(true)
-				.logUnknownInvokeDynamic(false)
-				.ignoreConflicts(getExtension().isForge())
-				.cacheMappings(true)
-				.threads(Runtime.getRuntime().availableProcessors())
-				.logger(getProject().getLogger()::lifecycle)
-				.rebuildSourceFilenames(true);
-
-		if (getExtension().isForge()) {
-			/* FORGE: Required for classes like aej$OptionalNamedTag (1.16.4) which are added by Forge patches.
-			 * They won't get remapped to their proper packages, so IllegalAccessErrors will happen without ._.
-			 */
-			builder.fixPackageAccess(true);
-		}
-
-		return builder.build();
-	}
-
 	public Set<IMappingProvider> getMappings(@Nullable Set<String> fromClassNames, String fromM, String toM) throws IOException {
 		Set<IMappingProvider> providers = new HashSet<>();
-		providers.add(TinyRemapperMappingsHelper.create(getExtension().isForge() ? getExtension().getMappingsProvider().getMappingsWithSrg() : getExtension().getMappingsProvider().getMappings(), fromM, toM, true));
+		providers.add(TinyRemapperHelper.create(getExtension().isForge() ? getExtension().getMappingsProvider().getMappingsWithSrg() : getExtension().getMappingsProvider().getMappings(), fromM, toM, true));

 		if (getExtension().isForge()) {
 			if (fromClassNames != null) {
 				providers.add(InnerClassRemapper.of(fromClassNames, getExtension().getMappingsProvider().getMappingsWithSrg(), fromM, toM));
 			}
 		} else {
-			providers.add(out -> JSR_TO_JETBRAINS.forEach(out::acceptClass));
+			providers.add(out -> TinyRemapperHelper.JSR_TO_JETBRAINS.forEach(out::acceptClass));
 		}

 		return providers;
 	}

-	public static Path[] getRemapClasspath(Project project) {
-		return project.getConfigurations().getByName(Constants.Configurations.MINECRAFT_DEPENDENCIES).getFiles()
-				.stream().map(File::toPath).toArray(Path[]::new);
-	}
-
 	protected void addDependencies(DependencyInfo dependency, Consumer<Runnable> postPopulationScheduler) {
 		getProject().getDependencies().add(Constants.Configurations.MINECRAFT_NAMED,
 				getProject().getDependencies().module("net.minecraft:" + minecraftProvider.getJarPrefix() + "minecraft-mapped:" + getMinecraftProvider().minecraftVersion() + "/" + getExtension().getMappingsProvider().mappingsIdentifier()));
--- a/src/main/java/net/fabricmc/loom/configuration/sources/ForgeSourcesRemapper.java
+++ b/src/main/java/net/fabricmc/loom/configuration/sources/ForgeSourcesRemapper.java
@@ -48,13 +48,13 @@ import org.zeroturnaround.zip.ZipUtil;

 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.build.ModCompileRemapper;
-import net.fabricmc.loom.configuration.providers.minecraft.MinecraftMappedProvider;
 import net.fabricmc.loom.task.GenerateSourcesTask;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.DeletingFileVisitor;
 import net.fabricmc.loom.util.FileSystemUtil;
 import net.fabricmc.loom.util.SourceRemapper;
 import net.fabricmc.loom.util.ThreadingUtils;
+import net.fabricmc.loom.util.TinyRemapperHelper;
 import net.fabricmc.lorenztiny.TinyMappingsReader;

 public class ForgeSourcesRemapper {
@@ -171,7 +171,7 @@ public class ForgeSourcesRemapper {

 		MappingSet mappings = new TinyMappingsReader(extension.getMappingsProvider().getMappingsWithSrg(), "srg", "named").read();

-		for (Map.Entry<String, String> entry : MinecraftMappedProvider.JSR_TO_JETBRAINS.entrySet()) {
+		for (Map.Entry<String, String> entry : TinyRemapperHelper.JSR_TO_JETBRAINS.entrySet()) {
 			mappings.getOrCreateClassMapping(entry.getKey()).setDeobfuscatedName(entry.getValue());
 		}

--- a/src/main/java/net/fabricmc/loom/task/RemapJarTask.java
+++ b/src/main/java/net/fabricmc/loom/task/RemapJarTask.java
@@ -88,7 +88,6 @@ import org.zeroturnaround.zip.transform.StreamZipEntryTransformer;
 import org.zeroturnaround.zip.transform.ZipEntryTransformerEntry;

 import net.fabricmc.loom.LoomGradleExtension;
-import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.build.JarRemapper;
 import net.fabricmc.loom.build.MixinRefmapHelper;
 import net.fabricmc.loom.build.nesting.EmptyNestedJarProvider;
@@ -109,10 +108,7 @@ import net.fabricmc.loom.util.TinyRemapperHelper;
 import net.fabricmc.loom.util.ZipReprocessorUtil;
 import net.fabricmc.loom.util.aw2at.Aw2At;
 import net.fabricmc.lorenztiny.TinyMappingsReader;
-import net.fabricmc.mapping.tree.ClassDef;
-import net.fabricmc.mapping.tree.FieldDef;
-import net.fabricmc.mapping.tree.MethodDef;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MappingTree;
 import net.fabricmc.stitch.util.Pair;

 public class RemapJarTask extends Jar {
@@ -169,7 +165,7 @@ public class RemapJarTask extends Jar {
 	}

 	private ReferenceRemapper createReferenceRemapper(LoomGradleExtension extension, String from, String to) throws IOException {
-		TinyTree mappings = extension.shouldGenerateSrgTiny() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings();
+		MappingTree mappings = extension.shouldGenerateSrgTiny() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings();

 		return new SimpleReferenceRemapper(new SimpleReferenceRemapper.Remapper() {
 			@Override
@@ -186,13 +182,13 @@ public class RemapJarTask extends Jar {
 			@Nullable
 			public String mapMethod(@Nullable String className, String methodName, String methodDescriptor) {
 				if (className != null) {
-					Optional<ClassDef> classDef = mappings.getClasses().stream()
+					Optional<MappingTree.ClassMapping> classDef = (Optional<MappingTree.ClassMapping>) mappings.getClasses().stream()
 							.filter(c -> Objects.equals(c.getName(from), className))
 							.findFirst();

 					if (classDef.isPresent()) {
-						for (MethodDef methodDef : classDef.get().getMethods()) {
-							if (Objects.equals(methodDef.getName(from), methodName) && Objects.equals(methodDef.getDescriptor(from), methodDescriptor)) {
+						for (MappingTree.MethodMapping methodDef : classDef.get().getMethods()) {
+							if (Objects.equals(methodDef.getName(from), methodName) && Objects.equals(methodDef.getDesc(from), methodDescriptor)) {
 								return methodDef.getName(to);
 							}
 						}
@@ -201,7 +197,7 @@ public class RemapJarTask extends Jar {

 				return mappings.getClasses().stream()
 						.flatMap(classDef -> classDef.getMethods().stream())
-						.filter(methodDef -> Objects.equals(methodDef.getName(from), methodName) && Objects.equals(methodDef.getDescriptor(from), methodDescriptor))
+						.filter(methodDef -> Objects.equals(methodDef.getName(from), methodName) && Objects.equals(methodDef.getDesc(from), methodDescriptor))
 						.findFirst()
 						.map(methodDef -> methodDef.getName(to))
 						.orElse(null);
@@ -211,13 +207,13 @@ public class RemapJarTask extends Jar {
 			@Nullable
 			public String mapField(@Nullable String className, String fieldName, String fieldDescriptor) {
 				if (className != null) {
-					Optional<ClassDef> classDef = mappings.getClasses().stream()
+					Optional<MappingTree.ClassMapping> classDef = (Optional<MappingTree.ClassMapping>) mappings.getClasses().stream()
 							.filter(c -> Objects.equals(c.getName(from), className))
 							.findFirst();

 					if (classDef.isPresent()) {
-						for (FieldDef fieldDef : classDef.get().getFields()) {
-							if (Objects.equals(fieldDef.getName(from), fieldName) && Objects.equals(fieldDef.getDescriptor(from), fieldDescriptor)) {
+						for (MappingTree.FieldMapping fieldDef : classDef.get().getFields()) {
+							if (Objects.equals(fieldDef.getName(from), fieldName) && Objects.equals(fieldDef.getDesc(from), fieldDescriptor)) {
 								return fieldDef.getName(to);
 							}
 						}
@@ -226,7 +222,7 @@ public class RemapJarTask extends Jar {

 				return mappings.getClasses().stream()
 						.flatMap(classDef -> classDef.getFields().stream())
-						.filter(fieldDef -> Objects.equals(fieldDef.getName(from), fieldName) && Objects.equals(fieldDef.getDescriptor(from), fieldDescriptor))
+						.filter(fieldDef -> Objects.equals(fieldDef.getName(from), fieldName) && Objects.equals(fieldDef.getDesc(from), fieldDescriptor))
 						.findFirst()
 						.map(fieldDef -> fieldDef.getName(to))
 						.orElse(null);
@@ -407,7 +403,7 @@ public class RemapJarTask extends Jar {
 	}

 	private IMappingProvider remapToSrg(LoomGradleExtension extension, IMappingProvider parent, String from, String to) throws IOException {
-		TinyTree mappings = extension.shouldGenerateSrgTiny() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings();
+		MappingTree mappings = extension.shouldGenerateSrgTiny() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings();

 		return sink -> {
 			parent.load(new IMappingProvider.MappingAcceptor() {
@@ -507,7 +503,7 @@ public class RemapJarTask extends Jar {
 			}

 			LoomGradleExtension extension = LoomGradleExtension.get(getProject());
-			TinyTree mappings = extension.shouldGenerateSrgTiny() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings();
+			MappingTree mappings = extension.shouldGenerateSrgTiny() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings();

 			try (TinyMappingsReader reader = new TinyMappingsReader(mappings, fromM.get(), toM.get())) {
 				MappingSet mappingSet = reader.read();
--- a/src/main/java/net/fabricmc/loom/util/MappingsProviderVerbose.java
+++ b/src/main/java/net/fabricmc/loom/util/MappingsProviderVerbose.java
@@ -25,20 +25,23 @@
 package net.fabricmc.loom.util;

 import java.io.IOException;
+import java.io.StringWriter;
+import java.io.UncheckedIOException;
 import java.lang.reflect.Field;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
-import java.util.Arrays;
-import java.util.HashMap;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Set;

-import dev.architectury.mappingslayers.api.mutable.MutableTinyMetadata;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
 import dev.architectury.tinyremapper.IMappingProvider;
 import dev.architectury.tinyremapper.TinyRemapper;

+import net.fabricmc.mappingio.adapter.RegularAsFlatMappingVisitor;
+import net.fabricmc.mappingio.format.Tiny2Writer;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;
+
 public class MappingsProviderVerbose {
 	public static void saveFile(TinyRemapper providers) throws IOException {
 		try {
@@ -52,26 +55,38 @@ public class MappingsProviderVerbose {
 	}

 	public static void saveFile(Iterable<IMappingProvider> providers) throws IOException {
-		MutableTinyTree tree = MappingsUtils.create(MutableTinyMetadata.create(2, 0, Arrays.asList("from", "to"), new HashMap<>()));
+		MemoryMappingTree tree = new MemoryMappingTree();
+		tree.setSrcNamespace("from");
+		tree.setDstNamespaces(new ArrayList<>(Collections.singletonList("to")));
+		RegularAsFlatMappingVisitor flatVisitor = new RegularAsFlatMappingVisitor(tree);

 		for (IMappingProvider provider : providers) {
 			provider.load(new IMappingProvider.MappingAcceptor() {
 				@Override
 				public void acceptClass(String from, String to) {
-					tree.getOrCreateClass(from).setName(1, to);
+					try {
+						flatVisitor.visitClass(from, to);
+					} catch (IOException e) {
+						throw new UncheckedIOException(e);
+					}
 				}

 				@Override
 				public void acceptMethod(IMappingProvider.Member from, String to) {
-					tree.getOrCreateClass(from.owner).getOrCreateMethod(from.name, from.desc)
-							.setName(1, to);
+					try {
+						flatVisitor.visitMethod(from.owner, from.name, from.desc, to);
+					} catch (IOException e) {
+						throw new UncheckedIOException(e);
+					}
 				}

 				@Override
 				public void acceptMethodArg(IMappingProvider.Member from, int lvIndex, String to) {
-					tree.getOrCreateClass(from.owner).getOrCreateMethod(from.name, from.desc)
-							.getOrCreateParameter(lvIndex, "")
-							.setName(1, to);
+					try {
+						flatVisitor.visitMethodArg(from.owner, from.name, from.desc, lvIndex, lvIndex, "", to);
+					} catch (IOException e) {
+						throw new UncheckedIOException(e);
+					}
 				}

 				@Override
@@ -81,14 +96,20 @@ public class MappingsProviderVerbose {

 				@Override
 				public void acceptField(IMappingProvider.Member from, String to) {
-					tree.getOrCreateClass(from.owner).getOrCreateField(from.name, from.desc)
-							.setName(1, to);
+					try {
+						flatVisitor.visitField(from.owner, from.name, from.desc, to);
+					} catch (IOException e) {
+						throw new UncheckedIOException(e);
+					}
 				}
 			});
 		}

 		Path check = Files.createTempFile("CHECK", null);
-		Files.writeString(check, MappingsUtils.serializeToString(tree), StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
+		StringWriter stringWriter = new StringWriter();
+		Tiny2Writer tiny2Writer = new Tiny2Writer(stringWriter, false);
+		tree.accept(tiny2Writer);
+		Files.writeString(check, stringWriter.toString(), StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
 		System.out.println("Saved debug check mappings to " + check);
 	}
 }
--- a/src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java
+++ b/src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java
@@ -30,18 +30,19 @@ import java.nio.file.Path;
 import java.util.Map;

 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import dev.architectury.tinyremapper.IMappingProvider;
+import dev.architectury.tinyremapper.TinyRemapper;
 import org.gradle.api.Project;

 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.mappingio.tree.MappingTree;
-import net.fabricmc.tinyremapper.IMappingProvider;
-import net.fabricmc.tinyremapper.TinyRemapper;

 /**
 * Contains shortcuts to create tiny remappers using the mappings accessibly to the project.
 */
 public final class TinyRemapperHelper {
-	private static final Map<String, String> JSR_TO_JETBRAINS = new ImmutableMap.Builder<String, String>()
+	public static final Map<String, String> JSR_TO_JETBRAINS = new ImmutableMap.Builder<String, String>()
 			.put("javax/annotation/Nullable", "org/jetbrains/annotations/Nullable")
 			.put("javax/annotation/Nonnull", "org/jetbrains/annotations/NotNull")
 			.put("javax/annotation/concurrent/Immutable", "org/jetbrains/annotations/Unmodifiable")
@@ -53,12 +54,41 @@ public final class TinyRemapperHelper {
 	public static TinyRemapper getTinyRemapper(Project project, String fromM, String toM) throws IOException {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);

-		return TinyRemapper.newRemapper()
-				.withMappings(create(extension.getMappingsProvider().getMappings(), fromM, toM, true))
-				.withMappings(out -> JSR_TO_JETBRAINS.forEach(out::acceptClass))
+		TinyRemapper remapper = _getTinyRemapper(project);
+		remapper.replaceMappings(ImmutableSet.of(
+				TinyRemapperHelper.create(extension.isForge() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings(), fromM, toM, true),
+				out -> TinyRemapperHelper.JSR_TO_JETBRAINS.forEach(out::acceptClass)
+		));
+		return remapper;
+	}
+
+	public static TinyRemapper _getTinyRemapper(Project project) throws IOException {
+		LoomGradleExtension extension = LoomGradleExtension.get(project);
+
+		TinyRemapper.Builder builder = TinyRemapper.newRemapper()
 				.renameInvalidLocals(true)
-				.rebuildSourceFilenames(true)
-				.build();
+				.logUnknownInvokeDynamic(false)
+				.ignoreConflicts(extension.isForge())
+				.cacheMappings(true)
+				.threads(Runtime.getRuntime().availableProcessors())
+				.logger(project.getLogger()::lifecycle)
+				.rebuildSourceFilenames(true);
+
+		if (extension.isForge()) {
+			/* FORGE: Required for classes like aej$OptionalNamedTag (1.16.4) which are added by Forge patches.
+			 * They won't get remapped to their proper packages, so IllegalAccessErrors will happen without ._.
+			 */
+			builder.fixPackageAccess(true);
+		}
+
+		return builder.build();
+	}
+
+	public static TinyRemapper getTinyRemapper(Project project) throws IOException {
+		TinyRemapper remapper = _getTinyRemapper(project);
+		remapper.readClassPath(getMinecraftDependencies(project));
+		remapper.prepareClasses();
+		return remapper;
 	}

 	public static Path[] getMinecraftDependencies(Project project) {
--- a/src/main/java/net/fabricmc/loom/util/aw2at/Aw2At.java
+++ b/src/main/java/net/fabricmc/loom/util/aw2at/Aw2At.java
@@ -39,6 +39,7 @@ import org.gradle.api.tasks.SourceSet;
 import org.gradle.api.tasks.SourceSetContainer;

 import net.fabricmc.accesswidener.AccessWidenerReader;
+import net.fabricmc.accesswidener.AccessWidenerVisitor;
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.task.RemapJarTask;

@@ -82,19 +83,19 @@ public final class Aw2At {
 	public static AccessTransformSet toAccessTransformSet(BufferedReader reader) throws IOException {
 		AccessTransformSet atSet = AccessTransformSet.create();

-		new AccessWidenerReader(new AccessWidenerReader.Visitor() {
+		new AccessWidenerReader(new AccessWidenerVisitor() {
 			@Override
-			public void visitClass(String name, AccessWidenerReader.AccessType access) {
+				public void visitClass(String name, AccessWidenerReader.AccessType access, boolean transitive) {
 				atSet.getOrCreateClass(name).merge(toAt(access));
 			}

 			@Override
-			public void visitMethod(String owner, String name, String descriptor, AccessWidenerReader.AccessType access) {
+				public void visitMethod(String owner, String name, String descriptor, AccessWidenerReader.AccessType access, boolean transitive) {
 				atSet.getOrCreateClass(owner).mergeMethod(MethodSignature.of(name, descriptor), toAt(access));
 			}

 			@Override
-			public void visitField(String owner, String name, String descriptor, AccessWidenerReader.AccessType access) {
+				public void visitField(String owner, String name, String descriptor, AccessWidenerReader.AccessType access, boolean transitive) {
 				atSet.getOrCreateClass(owner).mergeField(name, toAt(access));
 			}
 		}).read(reader);
--- a/src/main/java/net/fabricmc/loom/util/srg/AtRemapper.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/AtRemapper.java
@@ -42,7 +42,7 @@ import org.gradle.api.logging.Logger;

 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.function.CollectionUtil;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MappingTree;

 /**
 * Remaps AT classes from SRG to Yarn.
@@ -50,7 +50,7 @@ import net.fabricmc.mapping.tree.TinyTree;
 * @author Juuz
 */
 public final class AtRemapper {
-	public static void remap(Logger logger, Path jar, TinyTree mappings) throws IOException {
+	public static void remap(Logger logger, Path jar, MappingTree mappings) throws IOException {
 		try (FileSystem fs = FileSystems.newFileSystem(URI.create("jar:" + jar.toUri()), ImmutableMap.of("create", false))) {
 			Path atPath = fs.getPath(Constants.Forge.ACCESS_TRANSFORMER_PATH);

--- a/src/main/java/net/fabricmc/loom/util/srg/CoreModClassRemapper.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/CoreModClassRemapper.java
@@ -47,7 +47,7 @@ import com.google.gson.JsonObject;
 import org.gradle.api.logging.Logger;

 import net.fabricmc.loom.util.function.CollectionUtil;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MappingTree;

 /**
 * Remaps coremod class names from SRG to Yarn.
@@ -57,7 +57,7 @@ import net.fabricmc.mapping.tree.TinyTree;
 public final class CoreModClassRemapper {
 	private static final Pattern CLASS_NAME_PATTERN = Pattern.compile("^(.*')((?:com\\.mojang\\.|net\\.minecraft\\.)[A-Za-z0-9.-_$]+)('.*)$");

-	public static void remapJar(Path jar, TinyTree mappings, Logger logger) throws IOException {
+	public static void remapJar(Path jar, MappingTree mappings, Logger logger) throws IOException {
 		try (FileSystem fs = FileSystems.newFileSystem(URI.create("jar:" + jar.toUri()), ImmutableMap.of("create", false))) {
 			Path coremodsJsonPath = fs.getPath("META-INF", "coremods.json");

@@ -86,7 +86,7 @@ public final class CoreModClassRemapper {
 		}
 	}

-	public static void remap(Path js, TinyTree mappings) throws IOException {
+	public static void remap(Path js, MappingTree mappings) throws IOException {
 		List<String> lines = Files.readAllLines(js);
 		List<String> output = new ArrayList<>(lines);

--- a/src/main/java/net/fabricmc/loom/util/srg/InnerClassRemapper.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/InnerClassRemapper.java
@@ -39,11 +39,10 @@ import dev.architectury.tinyremapper.IMappingProvider;

 import net.fabricmc.loom.util.FileSystemUtil;
 import net.fabricmc.loom.util.FileSystemUtil.FileSystemDelegate;
-import net.fabricmc.mapping.tree.ClassDef;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MappingTree;

 public class InnerClassRemapper {
-	public static IMappingProvider of(Set<String> fromClassNames, TinyTree mappingsWithSrg, String from, String to) throws IOException {
+	public static IMappingProvider of(Set<String> fromClassNames, MappingTree mappingsWithSrg, String from, String to) throws IOException {
 		return sink -> {
 			remapInnerClass(fromClassNames, mappingsWithSrg, from, to, sink::acceptClass);
 		};
@@ -72,10 +71,10 @@ public class InnerClassRemapper {
 		return set;
 	}

-	private static void remapInnerClass(Set<String> classNames, TinyTree mappingsWithSrg, String from, String to, BiConsumer<String, String> action) {
+	private static void remapInnerClass(Set<String> classNames, MappingTree mappingsWithSrg, String from, String to, BiConsumer<String, String> action) {
 		BiMap<String, String> availableClasses = HashBiMap.create(mappingsWithSrg.getClasses().stream()
 				.collect(Collectors.groupingBy(classDef -> classDef.getName(from),
-						Collectors.<ClassDef, String>reducing(
+						Collectors.<MappingTree.ClassMapping, String>reducing(
 								null,
 								classDef -> classDef.getName(to),
 								(first, last) -> last
--- a/src/main/java/net/fabricmc/loom/util/srg/MCPReader.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/MCPReader.java
@@ -42,11 +42,6 @@ import java.util.regex.Pattern;

 import com.opencsv.CSVReader;
 import com.opencsv.exceptions.CsvValidationException;
-import dev.architectury.mappingslayers.api.mutable.MutableClassDef;
-import dev.architectury.mappingslayers.api.mutable.MutableFieldDef;
-import dev.architectury.mappingslayers.api.mutable.MutableMethodDef;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
 import org.apache.commons.io.IOUtils;
 import org.cadixdev.lorenz.MappingSet;
 import org.cadixdev.lorenz.io.srg.tsrg.TSrgReader;
@@ -57,6 +52,9 @@ import org.cadixdev.lorenz.model.MethodMapping;
 import org.cadixdev.lorenz.model.TopLevelClassMapping;
 import org.jetbrains.annotations.Nullable;

+import net.fabricmc.mappingio.MappingReader;
+import net.fabricmc.mappingio.tree.MappingTree;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;
 import net.fabricmc.stitch.commands.tinyv2.TinyClass;
 import net.fabricmc.stitch.commands.tinyv2.TinyField;
 import net.fabricmc.stitch.commands.tinyv2.TinyFile;
@@ -204,21 +202,22 @@ public class MCPReader {
 		return tokens;
 	}

-	private void readTsrg2(Map<MemberToken, String> tokens, String content) {
-		MutableTinyTree tree = MappingsUtils.deserializeFromTsrg2(content);
-		int obfIndex = tree.getMetadata().index("obf");
-		int srgIndex = tree.getMetadata().index("srg");
+	private void readTsrg2(Map<MemberToken, String> tokens, String content) throws IOException {
+		MemoryMappingTree tree = new MemoryMappingTree();
+		MappingReader.read(new StringReader(content), tree);
+		int obfIndex = tree.getNamespaceId("obf");
+		int srgIndex = tree.getNamespaceId("srg");

-		for (MutableClassDef classDef : tree.getClassesMutable()) {
+		for (MappingTree.ClassMapping classDef : tree.getClasses()) {
 			MemberToken ofClass = MemberToken.ofClass(classDef.getName(obfIndex));
 			tokens.put(ofClass, classDef.getName(srgIndex));

-			for (MutableFieldDef fieldDef : classDef.getFieldsMutable()) {
+			for (MappingTree.FieldMapping fieldDef : classDef.getFields()) {
 				tokens.put(MemberToken.ofField(ofClass, fieldDef.getName(obfIndex)), fieldDef.getName(srgIndex));
 			}

-			for (MutableMethodDef methodDef : classDef.getMethodsMutable()) {
-				tokens.put(MemberToken.ofMethod(ofClass, methodDef.getName(obfIndex), methodDef.getDescriptor(obfIndex)),
+			for (MappingTree.MethodMapping methodDef : classDef.getMethods()) {
+				tokens.put(MemberToken.ofMethod(ofClass, methodDef.getName(obfIndex), methodDef.getDesc(obfIndex)),
 						methodDef.getName(srgIndex));
 			}
 		}
--- a/src/main/java/net/fabricmc/loom/util/srg/SpecialSourceExecutor.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/SpecialSourceExecutor.java
@@ -29,25 +29,34 @@ import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Set;
-import java.util.jar.JarOutputStream;
 import java.util.stream.Collectors;
-import java.util.zip.ZipEntry;

-import org.apache.commons.io.IOUtils;
+import com.google.common.base.Stopwatch;
 import org.apache.commons.io.output.NullOutputStream;
 import org.gradle.api.Project;
 import org.gradle.api.file.FileCollection;
 import org.gradle.api.logging.LogLevel;
 import org.gradle.api.logging.configuration.ShowStacktrace;
-import org.zeroturnaround.zip.ZipUtil;

 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.util.FileSystemUtil;
+import net.fabricmc.loom.util.ThreadingUtils;

 public class SpecialSourceExecutor {
+	private static String trimLeadingSlash(String string) {
+		if (string.startsWith(File.separator)) {
+			return string.substring(File.separator.length());
+		} else if (string.startsWith("/")) {
+			return string.substring(1);
+		}
+		return string;
+	}
+
 	public static Path produceSrgJar(boolean specialSource, Project project, String side, FileCollection classpath, Set<File> mcLibs, Path officialJar, Path mappings)
 			throws Exception {
 		Set<String> filter = Files.readAllLines(mappings, StandardCharsets.UTF_8).stream()
@@ -58,14 +67,35 @@ public class SpecialSourceExecutor {
 		Path stripped = extension.getFiles().getProjectBuildCache().toPath().resolve(officialJar.getFileName().toString().substring(0, officialJar.getFileName().toString().length() - 4) + "-filtered.jar");
 		Files.deleteIfExists(stripped);

-		try (JarOutputStream output = new JarOutputStream(Files.newOutputStream(stripped))) {
-			ZipUtil.iterate(officialJar.toFile(), (in, zipEntry) -> {
-				if (filter.contains(zipEntry.getName())) {
-					output.putNextEntry((ZipEntry) zipEntry.clone());
-					IOUtils.write(IOUtils.toByteArray(in), output);
-					output.closeEntry();
+		Stopwatch stopwatch = Stopwatch.createStarted();
+
+		try (FileSystemUtil.FileSystemDelegate output = FileSystemUtil.getJarFileSystem(stripped, true)) {
+			try (FileSystemUtil.FileSystemDelegate fs = FileSystemUtil.getJarFileSystem(officialJar, false)) {
+				ThreadingUtils.TaskCompleter completer = ThreadingUtils.taskCompleter();
+
+				for (Path path : (Iterable<? extends Path>) Files.walk(fs.get().getPath("/"))::iterator) {
+					String trimLeadingSlash = trimLeadingSlash(path.toString());
+					if (!trimLeadingSlash.endsWith(".class")) continue;
+					boolean has = filter.contains(trimLeadingSlash);
+					String s = trimLeadingSlash;
+					while (s.contains("$") && !has) {
+						s = s.substring(0, s.lastIndexOf("$")) + ".class";
+						has = filter.contains(s);
+					}
+					if (!has) continue;
+					Path to = output.get().getPath(trimLeadingSlash);
+					Path parent = to.getParent();
+					if (parent != null) Files.createDirectories(parent);
+
+					completer.add(() -> {
+						Files.copy(path, to, StandardCopyOption.COPY_ATTRIBUTES);
+					});
 				}
-			});
+
+				completer.complete();
+			}
+		} finally {
+			project.getLogger().info("Copied class files in " + stopwatch.stop());
 		}

 		Path output = extension.getFiles().getProjectBuildCache().toPath().resolve(officialJar.getFileName().toString().substring(0, officialJar.getFileName().toString().length() - 4) + "-srg-output.jar");
@@ -93,7 +123,7 @@ public class SpecialSourceExecutor {

 				// if running with INFO or DEBUG logging
 				if (project.getGradle().getStartParameter().getShowStacktrace() != ShowStacktrace.INTERNAL_EXCEPTIONS
-						|| project.getGradle().getStartParameter().getLogLevel().compareTo(LogLevel.LIFECYCLE) < 0) {
+				    || project.getGradle().getStartParameter().getLogLevel().compareTo(LogLevel.LIFECYCLE) < 0) {
 					spec.setStandardOutput(System.out);
 					spec.setErrorOutput(System.err);
 				} else {
@@ -131,7 +161,7 @@ public class SpecialSourceExecutor {

 				// if running with INFO or DEBUG logging
 				if (project.getGradle().getStartParameter().getShowStacktrace() != ShowStacktrace.INTERNAL_EXCEPTIONS
-						|| project.getGradle().getStartParameter().getLogLevel().compareTo(LogLevel.LIFECYCLE) < 0) {
+				    || project.getGradle().getStartParameter().getLogLevel().compareTo(LogLevel.LIFECYCLE) < 0) {
 					spec.setStandardOutput(System.out);
 					spec.setErrorOutput(System.err);
 				} else {
--- a/src/main/java/net/fabricmc/loom/util/srg/SrgMerger.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/SrgMerger.java
@@ -37,14 +37,10 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;

 import com.google.common.base.MoreObjects;
-import dev.architectury.mappingslayers.api.mutable.MutableClassDef;
-import dev.architectury.mappingslayers.api.mutable.MutableDescriptored;
-import dev.architectury.mappingslayers.api.mutable.MutableFieldDef;
-import dev.architectury.mappingslayers.api.mutable.MutableMethodDef;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
 import org.apache.commons.io.IOUtils;
 import org.cadixdev.lorenz.MappingSet;
 import org.cadixdev.lorenz.io.srg.tsrg.TSrgReader;
@@ -56,12 +52,11 @@ import org.cadixdev.lorenz.model.TopLevelClassMapping;
 import org.jetbrains.annotations.Nullable;

 import net.fabricmc.loom.util.function.CollectionUtil;
-import net.fabricmc.mapping.tree.ClassDef;
-import net.fabricmc.mapping.tree.FieldDef;
-import net.fabricmc.mapping.tree.MethodDef;
-import net.fabricmc.mapping.tree.TinyMappingFactory;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.MappingReader;
 import net.fabricmc.mappingio.format.TsrgReader;
+import net.fabricmc.mappingio.tree.MappingTree;
+import net.fabricmc.mappingio.tree.MappingTreeView;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;
 import net.fabricmc.stitch.commands.tinyv2.TinyClass;
 import net.fabricmc.stitch.commands.tinyv2.TinyField;
 import net.fabricmc.stitch.commands.tinyv2.TinyFile;
@@ -87,15 +82,15 @@ public final class SrgMerger {
 	 *                          or if an element mentioned in the SRG file does not have tiny mappings
 	 */
 	public static void mergeSrg(Supplier<Path> mojmap, Path srg, Path tiny, Path out, boolean lenient) throws IOException, MappingException {
-		Map<String, List<MutableDescriptored>> addRegardlessSrgs = new HashMap<>();
+		Map<String, List<MappingTreeView.MemberMappingView>> addRegardlessSrgs = new HashMap<>();
 		MappingSet arr = readSrg(srg, mojmap, addRegardlessSrgs);
-		TinyTree foss;
+		MemoryMappingTree foss = new MemoryMappingTree();

 		try (BufferedReader reader = Files.newBufferedReader(tiny)) {
-			foss = TinyMappingFactory.loadWithDetection(reader);
+			MappingReader.read(reader, foss);
 		}

-		List<String> namespaces = new ArrayList<>(foss.getMetadata().getNamespaces());
+		List<String> namespaces = Stream.concat(Stream.of(foss.getSrcNamespace()), foss.getDstNamespaces().stream()).collect(Collectors.toList());
 		namespaces.add(1, "srg");

 		if (!"official".equals(namespaces.get(0))) {
@@ -114,7 +109,8 @@ public final class SrgMerger {
 		TinyV2Writer.write(file, out);
 	}

-	private static MappingSet readSrg(Path srg, Supplier<Path> mojmap, Map<String, List<MutableDescriptored>> addRegardlessSrgs) throws IOException {
+	private static MappingSet readSrg(Path srg, Supplier<Path> mojmap, Map<String, List<MappingTreeView.MemberMappingView>> addRegardlessSrgs)
+			throws IOException {
 		try (BufferedReader reader = Files.newBufferedReader(srg)) {
 			String content = IOUtils.toString(reader);

@@ -128,26 +124,27 @@ public final class SrgMerger {
 		}
 	}

-	private static MappingSet readTsrg2(String content, Supplier<Path> mojmap, Map<String, List<MutableDescriptored>> addRegardlessSrgs) throws IOException {
+	private static MappingSet readTsrg2(String content, Supplier<Path> mojmap, Map<String, List<MappingTreeView.MemberMappingView>> addRegardlessSrgs)
+			throws IOException {
 		MappingSet set;

 		try (Tsrg2Utils.MappingsIO2LorenzWriter lorenzWriter = new Tsrg2Utils.MappingsIO2LorenzWriter(0, false)) {
 			TsrgReader.read(new StringReader(content), lorenzWriter);
 			set = lorenzWriter.read();
-			MutableTinyTree mojmapTree = readTsrg2ToTinyTree(mojmap.get());
+			MemoryMappingTree mojmapTree = readTsrg2ToTinyTree(mojmap.get());

-			for (MutableClassDef classDef : mojmapTree.getClassesMutable()) {
-				for (MutableMethodDef methodDef : classDef.getMethodsMutable()) {
-					String name = methodDef.getName(0);
+			for (MappingTree.ClassMapping classDef : mojmapTree.getClasses()) {
+				for (MappingTree.MethodMapping methodDef : classDef.getMethods()) {
+					String name = methodDef.getSrcName();

-					if (name.indexOf('<') != 0 && name.equals(methodDef.getName(1))) {
-						addRegardlessSrgs.computeIfAbsent(classDef.getName(0), $ -> new ArrayList<>()).add(methodDef);
+					if (name.indexOf('<') != 0 && name.equals(methodDef.getDstName(0))) {
+						addRegardlessSrgs.computeIfAbsent(classDef.getSrcName(), $ -> new ArrayList<>()).add(methodDef);
 					}
 				}

-				for (MutableFieldDef fieldDef : classDef.getFieldsMutable()) {
-					if (fieldDef.getName(0).equals(fieldDef.getName(1))) {
-						addRegardlessSrgs.computeIfAbsent(classDef.getName(0), $ -> new ArrayList<>()).add(fieldDef);
+				for (MappingTree.FieldMapping fieldDef : classDef.getFields()) {
+					if (fieldDef.getSrcName().equals(fieldDef.getDstName(0))) {
+						addRegardlessSrgs.computeIfAbsent(classDef.getSrcName(), $ -> new ArrayList<>()).add(fieldDef);
 					}
 				}
 			}
@@ -156,20 +153,20 @@ public final class SrgMerger {
 		return set;
 	}

-	private static MutableTinyTree readTsrg2ToTinyTree(Path path) throws IOException {
-		MutableTinyTree tree;
+	private static MemoryMappingTree readTsrg2ToTinyTree(Path path) throws IOException {
+		MemoryMappingTree tree = new MemoryMappingTree();

 		try (BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
-			tree = MappingsUtils.deserializeFromTsrg2(IOUtils.toString(reader));
+			MappingReader.read(reader, tree);
 		}

 		return tree;
 	}

-	private static void classToTiny(Map<String, List<MutableDescriptored>> addRegardlessSrgs, TinyTree foss, List<String> namespaces, ClassMapping<?, ?> klass, Consumer<TinyClass> classConsumer, boolean lenient) {
+	private static void classToTiny(Map<String, List<MappingTreeView.MemberMappingView>> addRegardlessSrgs, MappingTree foss, List<String> namespaces, ClassMapping<?, ?> klass, Consumer<TinyClass> classConsumer, boolean lenient) {
 		String obf = klass.getFullObfuscatedName();
 		String srg = klass.getFullDeobfuscatedName();
-		ClassDef classDef = foss.getDefaultNamespaceClassMap().get(obf);
+		MappingTree.ClassMapping classDef = foss.getClass(obf);

 		if (classDef == null) {
 			if (lenient) {
@@ -188,9 +185,9 @@ public final class SrgMerger {
 		List<TinyField> fields = new ArrayList<>();

 		for (MethodMapping method : klass.getMethodMappings()) {
-			MethodDef def = CollectionUtil.find(
+			MappingTree.MethodMapping def = CollectionUtil.find(
 					classDef.getMethods(),
-					m -> m.getName("official").equals(method.getObfuscatedName()) && m.getDescriptor("official").equals(method.getObfuscatedDescriptor())
+					m -> m.getName("official").equals(method.getObfuscatedName()) && m.getDesc("official").equals(method.getObfuscatedDescriptor())
 			).orElse(null);

 			if (def == null) {
@@ -209,7 +206,7 @@ public final class SrgMerger {
 			);

 			methods.add(new TinyMethod(
-					def.getDescriptor("official"), methodNames,
+					def.getDesc("official"), methodNames,
 					/* parameters */ Collections.emptyList(),
 					/* locals */ Collections.emptyList(),
 					/* comments */ Collections.emptyList()
@@ -217,7 +214,7 @@ public final class SrgMerger {
 		}

 		for (FieldMapping field : klass.getFieldMappings()) {
-			FieldDef def = CollectionUtil.find(
+			MappingTree.FieldMapping def = CollectionUtil.find(
 					classDef.getFields(),
 					f -> f.getName("official").equals(field.getObfuscatedName())
 			).orElse(nullOrThrow(lenient, () -> new MappingException("Missing field: " + field.getFullObfuscatedName() + " (srg: " + field.getFullDeobfuscatedName() + ")")));
@@ -229,7 +226,7 @@ public final class SrgMerger {
 					namespace -> "srg".equals(namespace) ? field.getDeobfuscatedName() : def.getName(namespace)
 			);

-			fields.add(new TinyField(def.getDescriptor("official"), fieldNames, Collections.emptyList()));
+			fields.add(new TinyField(def.getDesc("official"), fieldNames, Collections.emptyList()));
 		}

 		TinyClass tinyClass = new TinyClass(classNames, methods, fields, Collections.emptyList());
@@ -240,13 +237,13 @@ public final class SrgMerger {
 		}
 	}

-	private static boolean tryMatchRegardlessSrgs(Map<String, List<MutableDescriptored>> addRegardlessSrgs, List<String> namespaces, String obf,
+	private static boolean tryMatchRegardlessSrgs(Map<String, List<MappingTreeView.MemberMappingView>> addRegardlessSrgs, List<String> namespaces, String obf,
 			List<TinyMethod> methods, MethodMapping method) {
-		List<MutableDescriptored> mutableDescriptoredList = addRegardlessSrgs.get(obf);
+		List<MappingTreeView.MemberMappingView> mutableDescriptoredList = addRegardlessSrgs.get(obf);

 		if (!method.getDeobfuscatedName().equals(method.getObfuscatedName())) {
-			for (MutableDescriptored descriptored : MoreObjects.firstNonNull(mutableDescriptoredList, Collections.<MutableDescriptored>emptyList())) {
-				if (descriptored.isMethod() && descriptored.getName(0).equals(method.getObfuscatedName()) && descriptored.getDescriptor(0).equals(method.getObfuscatedDescriptor())) {
+			for (MappingTreeView.MemberMappingView descriptored : MoreObjects.firstNonNull(mutableDescriptoredList, Collections.<MappingTreeView.MemberMappingView>emptyList())) {
+				if (descriptored instanceof MappingTreeView.MethodMappingView && descriptored.getSrcName().equals(method.getObfuscatedName()) && descriptored.getSrcDesc().equals(method.getObfuscatedDescriptor())) {
 					List<String> methodNames = CollectionUtil.map(
 							namespaces,
 							namespace -> "srg".equals(namespace) ? method.getDeobfuscatedName() : method.getObfuscatedName()
--- a/src/main/java/net/fabricmc/loom/util/srg/SrgNamedWriter.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/SrgNamedWriter.java
@@ -32,10 +32,10 @@ import org.cadixdev.lorenz.io.srg.SrgWriter;
 import org.gradle.api.logging.Logger;

 import net.fabricmc.lorenztiny.TinyMappingsReader;
-import net.fabricmc.mapping.tree.TinyTree;
+import net.fabricmc.mappingio.tree.MappingTree;

 public class SrgNamedWriter {
-	public static void writeTo(Logger logger, Path srgFile, TinyTree mappings, String from, String to) throws IOException {
+	public static void writeTo(Logger logger, Path srgFile, MappingTree mappings, String from, String to) throws IOException {
 		Files.deleteIfExists(srgFile);

 		try (SrgWriter writer = new SrgWriter(Files.newBufferedWriter(srgFile))) {
--- a/src/main/java/net/fabricmc/loom/util/srg/Tsrg2Utils.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/Tsrg2Utils.java
@@ -25,22 +25,11 @@
 package net.fabricmc.loom.util.srg;

 import java.io.IOException;
-import java.io.Reader;
-import java.io.UncheckedIOException;
 import java.io.Writer;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.function.Consumer;

-import dev.architectury.mappingslayers.api.mutable.MutableClassDef;
-import dev.architectury.mappingslayers.api.mutable.MutableFieldDef;
-import dev.architectury.mappingslayers.api.mutable.MutableMethodDef;
-import dev.architectury.mappingslayers.api.mutable.MutableParameterDef;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyMetadata;
-import dev.architectury.mappingslayers.api.mutable.MutableTinyTree;
-import dev.architectury.mappingslayers.api.utils.MappingsUtils;
 import org.cadixdev.lorenz.MappingSet;
 import org.cadixdev.lorenz.io.srg.tsrg.TSrgWriter;
 import org.cadixdev.lorenz.model.ClassMapping;
@@ -49,21 +38,10 @@ import org.cadixdev.lorenz.model.MethodMapping;
 import net.fabricmc.mappingio.MappingVisitor;
 import net.fabricmc.mappingio.MappingWriter;
 import net.fabricmc.mappingio.adapter.ForwardingMappingVisitor;
-import net.fabricmc.mappingio.format.TsrgReader;
 import net.fabricmc.mappingio.tree.MappingTree;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;

 public class Tsrg2Utils {
-	public static void convert(Reader reader, Writer writer) throws IOException {
-		writeTsrg(visitor -> {
-			try {
-				TsrgReader.read(reader, visitor);
-			} catch (IOException e) {
-				throw new UncheckedIOException(e);
-			}
-		}, "srg", false, writer);
-	}
-
 	public static void writeTsrg(Consumer<MappingVisitor> visitorConsumer, String dstNamespace, boolean applyParameterMappings, Writer writer)
 			throws IOException {
 		MappingSet set;
@@ -78,18 +56,6 @@ public class Tsrg2Utils {
 		}
 	}

-	public static void writeTsrg2(Consumer<MappingVisitor> visitorConsumer, Writer writer)
-			throws IOException {
-		MutableTinyTree tree;
-
-		try (MappingsIO2MappingsUtils w = new MappingsIO2MappingsUtils()) {
-			visitorConsumer.accept(w);
-			tree = w.read();
-		}
-
-		writer.write(MappingsUtils.serializeToTsrg2(tree));
-	}
-
 	// TODO Move this elsewhere
 	public abstract static class MappingsIO2Others extends ForwardingMappingVisitor implements MappingWriter {
 		public MappingsIO2Others() {
@@ -175,59 +141,4 @@ public class Tsrg2Utils {
 			return mappings;
 		}
 	}
-
-	public static class MappingsIO2MappingsUtils extends MappingsIO2Others {
-		public MutableTinyTree read() {
-			MappingTree tree = tree();
-			int dstNamesSize = tree.getDstNamespaces().size();
-			List<String> namespaces = new ArrayList<>();
-			namespaces.add(tree.getSrcNamespace());
-			namespaces.addAll(tree.getDstNamespaces());
-			Map<String, String> properties = new HashMap<>();
-
-			for (Map.Entry<String, String> entry : tree.getMetadata()) {
-				properties.put(entry.getKey(), entry.getValue());
-			}
-
-			MutableTinyTree out = MappingsUtils.create(MutableTinyMetadata.create(2, 0, namespaces, properties));
-
-			for (MappingTree.ClassMapping aClass : tree.getClasses()) {
-				MutableClassDef classDef = out.getOrCreateClass(aClass.getSrcName());
-				classDef.setComment(aClass.getComment());
-
-				for (int i = 0; i < dstNamesSize; i++) {
-					classDef.setName(i + 1, aClass.getDstName(i));
-				}
-
-				for (MappingTree.MethodMapping aMethod : aClass.getMethods()) {
-					MutableMethodDef methodDef = classDef.getOrCreateMethod(aMethod.getSrcName(), aMethod.getSrcDesc());
-					methodDef.setComment(aMethod.getComment());
-
-					for (int i = 0; i < dstNamesSize; i++) {
-						methodDef.setName(i + 1, aMethod.getDstName(i));
-					}
-
-					for (MappingTree.MethodArgMapping aMethodArg : aMethod.getArgs()) {
-						MutableParameterDef parameterDef = methodDef.getOrCreateParameter(aMethodArg.getLvIndex(), aMethodArg.getSrcName());
-						parameterDef.setComment(aMethodArg.getComment());
-
-						for (int i = 0; i < dstNamesSize; i++) {
-							parameterDef.setName(i + 1, aMethodArg.getDstName(i));
-						}
-					}
-				}
-
-				for (MappingTree.FieldMapping aField : aClass.getFields()) {
-					MutableFieldDef fieldDef = classDef.getOrCreateField(aField.getSrcName(), aField.getSrcDesc());
-					fieldDef.setComment(aField.getComment());
-
-					for (int i = 0; i < dstNamesSize; i++) {
-						fieldDef.setName(i + 1, aField.getDstName(i));
-					}
-				}
-			}
-
-			return out;
-		}
-	}
 }
--- a/src/main/java/net/fabricmc/loom/util/srg/Tsrg2Writer.java
+++ b/src/main/java/net/fabricmc/loom/util/srg/Tsrg2Writer.java
@@ -0,0 +1,86 @@
+package net.fabricmc.loom.util.srg;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import net.fabricmc.mappingio.tree.MappingTree;
+import net.fabricmc.mappingio.tree.MappingTreeView;
+
+public class Tsrg2Writer {
+	public Tsrg2Writer() {
+	}
+
+	public static String serialize(MappingTree tree) {
+		List<String> namespaces = Stream.concat(Stream.of(tree.getSrcNamespace()), tree.getDstNamespaces().stream()).collect(Collectors.toList());
+		StringBuilder builder = new StringBuilder();
+		writeHeader(namespaces, builder);
+
+		for (MappingTree.ClassMapping classMapping : tree.getClasses()) {
+			writeClass(namespaces, classMapping, builder);
+		}
+
+		return builder.toString();
+	}
+
+	private static void writeClass(List<String> namespaces, MappingTree.ClassMapping def, StringBuilder builder) {
+		writeMapped(false, namespaces, def, builder);
+
+		for (MappingTree.MethodMapping method : def.getMethods()) {
+			writeMethod(namespaces, method, builder);
+		}
+
+		for (MappingTree.FieldMapping field : def.getFields()) {
+			writeMapped(true, namespaces, field, builder);
+		}
+	}
+
+	private static void writeMethod(List<String> namespaces, MappingTree.MethodMapping def, StringBuilder builder) {
+		writeMapped(true, namespaces, def, builder);
+		for (MappingTree.MethodArgMapping arg : def.getArgs()) {
+			builder.append("\t\t").append(arg.getLvIndex());
+			writeMapped(true, namespaces, arg, builder);
+		}
+	}
+
+	private static void writeField(List<String> namespaces, MappingTree.FieldMapping def, StringBuilder builder) {
+		writeMapped(true, namespaces, def, builder);
+	}
+
+	private static void writeMapped(boolean needFirst, List<String> namespaces, MappingTreeView.ElementMappingView mapped, StringBuilder builder) {
+		String[] names = namespaces.stream().map(mapped::getName).toArray(String[]::new);
+
+		for (int i = 0; i < names.length; ++i) {
+			String name = names[i];
+			if (i == 0) {
+				if (needFirst) {
+					builder.append('\t');
+				}
+			} else {
+				builder.append(' ');
+			}
+
+			builder.append(name);
+			if (i == 0 && mapped instanceof MappingTreeView.MemberMappingView) {
+				String descriptor = ((MappingTreeView.MemberMappingView) mapped).getSrcDesc();
+				if (descriptor != null && !descriptor.isEmpty()) {
+					builder.append(' ');
+					builder.append(descriptor);
+				}
+			}
+		}
+
+		builder.append('\n');
+	}
+
+	private static void writeHeader(List<String> namespaces, StringBuilder builder) {
+		builder.append("tsrg2");
+
+		for (String namespace : namespaces) {
+			builder.append(' ');
+			builder.append(namespace);
+		}
+
+		builder.append('\n');
+	}
+}