Merge 1.11

.editorconfig

@@ -1,5 +1,6 @@
-[*.{gradle,java,kotlin}]
+[*.{gradle,groovy,java,kotlin}]
 indent_style = tab
 ij_continuation_indent_size = 8
 ij_java_imports_layout = $*,|,java.**,|,javax.**,|,*,|,net.fabricmc.**
 ij_java_class_count_to_use_import_on_demand = 999
+ij_groovy_imports_layout = java.**,|,javax.**,|,*,|,net.fabricmc.**,|,$*

.github/workflows/test-push.yml

@@ -1,5 +1,17 @@
 name: Run Tests
-on: [push, pull_request]
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+    inputs:
+      extended_tests:
+        description: 'Extended tests'
+        required: false
+        default: 'false'
+        type: choice
+        options:
+          - 'false'
+          - 'true'
 
 concurrency:
   group: build-${{ github.event.pull_request.number || github.ref }}
@@ -24,6 +36,8 @@ jobs:
             build/reports/checkstyle/*.xml
 
   build_windows:
+    if: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.extended_tests == 'true' }}
+
     runs-on: windows-2022
     steps:
       - uses: actions/checkout@v4
@@ -77,6 +91,7 @@ jobs:
       - run: ./gradlew printActionsTestName --name="${{ matrix.test }}" test --tests ${{ matrix.test }} --stacktrace --warning-mode fail
         env:
           TEST_WARNING_MODE: fail
+          EXTENDED_TESTS: ${{ github.event.inputs.extended_tests }}
         id: test
 
       - uses: actions/upload-artifact@v4
@@ -91,6 +106,8 @@ jobs:
           path: "*.hprof"
 
   run_tests_windows:
+    if: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.extended_tests == 'true' }}
+
     needs: prepare_test_matrix
 
     strategy:
@@ -98,7 +115,7 @@ jobs:
       matrix:
         test: ${{ fromJson(needs.prepare_test_matrix.outputs.matrix) }}
 
-    runs-on: windows-2022
+    runs-on: windows-2025
 
     steps:
       - uses: actions/checkout@v4
@@ -130,8 +147,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [ 17, 21 ]
+        java: [ 21 ]
-        os: [ windows-2022, ubuntu-24.04, macos-14 ]
+        os: [ windows-2025, ubuntu-24.04, macos-15 ]
 
     runs-on: ${{ matrix.os }}
     steps:

build.gradle

@@ -18,12 +18,12 @@ tasks.withType(JavaCompile).configureEach {
 
 tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile).all {
 	kotlinOptions {
-		jvmTarget = "17"
+		jvmTarget = "21"
 	}
 }
 
 group = "dev.architectury"
-def baseVersion = '1.10'
+def baseVersion = '1.11'
 
 def ENV = System.getenv()
 def runNumber = ENV.GITHUB_RUN_NUMBER ?: "9999"
@@ -144,6 +144,9 @@ dependencies {
 	// source code remapping
 	implementation libs.fabric.mercury
 
+	implementation libs.fabric.unpick
+	implementation libs.fabric.unpick.utils
+
 	// Kotlin
 	implementation(libs.kotlin.metadata) {
 		transitive = false
@@ -176,6 +179,9 @@ dependencies {
 	}
 	testImplementation testLibs.mockito
 	testImplementation testLibs.java.debug
+	testImplementation testLibs.bcprov
+	testImplementation testLibs.bcutil
+	testImplementation testLibs.bcpkix
 
 	compileOnly runtimeLibs.jetbrains.annotations
 	testCompileOnly runtimeLibs.jetbrains.annotations
@@ -201,13 +207,13 @@ base {
 }
 
 tasks.withType(JavaCompile).configureEach {
-	it.options.release = 17
+	it.options.release = 21
 }
 
 java {
 	withSourcesJar()
-	sourceCompatibility = JavaVersion.VERSION_17
+	sourceCompatibility = JavaVersion.VERSION_21
-	targetCompatibility = JavaVersion.VERSION_17
+	targetCompatibility = JavaVersion.VERSION_21
 }
 
 spotless {
@@ -362,6 +368,7 @@ publishing {
 tasks.register('writeActionsTestMatrix') {
 	doLast {
 		def testMatrix = []
+		def extendedTests = Boolean.parseBoolean(System.getenv('EXTENDED_TESTS') ?: 'false')
 		file('src/test/groovy/net/fabricmc/loom/test/integration').traverse {
 			if (it.name.endsWith("Test.groovy")) {
 				if (it.name.endsWith("ReproducibleBuildTest.groovy")) {
@@ -369,7 +376,7 @@ tasks.register('writeActionsTestMatrix') {
 					return
 				}
 
-				if (it.name.endsWith("DebugLineNumbersTest.groovy")) {
+				if (it.name.endsWith("DebugLineNumbersTest.groovy") && !extendedTests) {
 					// Known flakey test
 					return
 				}
@@ -389,9 +396,6 @@ tasks.register('writeActionsTestMatrix') {
 		// Run all the unit tests together
 		testMatrix.add("net.fabricmc.loom.test.unit.*")
 
-		// Kotlin tests
-		testMatrix.add("net.fabricmc.loom.test.kotlin.*")
-
 		def json = groovy.json.JsonOutput.toJson(testMatrix)
 		def output = file("build/test_matrix.json")
 		output.parentFile.mkdir()

gradle/libs.versions.toml

@@ -1,6 +1,6 @@
 [versions]
 kotlin = "2.0.21"
-asm = "9.7.1"
+asm = "9.8"
 commons-io = "2.15.1"
 gson = "2.10.1"
 guava = "33.0.0-jre"
@@ -12,6 +12,7 @@ mapping-io = "0.7.1"
 lorenz-tiny = "4.0.2"
 mercury = "0.1.4.17"
 loom-native = "0.2.0"
+unpick = "3.0.0-beta.9"
 
 # Plugins
 spotless = "6.25.0"
@@ -48,6 +49,8 @@ fabric-mapping-io = { module = "net.fabricmc:mapping-io", version.ref = "mapping
 fabric-lorenz-tiny = { module = "net.fabricmc:lorenz-tiny", version.ref = "lorenz-tiny" }
 fabric-mercury = { module = "dev.architectury:mercury", version.ref = "mercury" }
 fabric-loom-nativelib = { module = "net.fabricmc:fabric-loom-native", version.ref = "loom-native" }
+fabric-unpick = { module = "net.fabricmc.unpick:unpick", version.ref = "unpick" }
+fabric-unpick-utils = { module = "net.fabricmc.unpick:unpick-format-utils", version.ref = "unpick" }
 
 # Misc
 kotlin-gradle-plugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }

gradle/runtime.libs.versions.toml

@@ -8,9 +8,12 @@ vineflower = "1.11.1"
 mixin-compile-extensions = "0.6.0"
 dev-launch-injector = "0.2.1+build.8"
 terminal-console-appender = "1.3.0"
-jetbrains-annotations = "25.0.0"
+jetbrains-annotations = "26.0.2"
 native-support = "1.0.1"
-fabric-installer = "1.0.1"
+fabric-installer = "1.0.3"
+
+# Debug tools
+renderdoc = "1.37"
 
 # Forge Runtime depedencies
 javax-annotations = "3.0.2"
@@ -36,6 +39,9 @@ jetbrains-annotations = { module = "org.jetbrains:annotations", version.ref = "j
 native-support = { module = "net.fabricmc:fabric-loom-native-support", version.ref = "native-support" }
 fabric-installer = { module = "net.fabricmc:fabric-installer", version.ref = "fabric-installer" }
 
+# Debug tools
+renderdoc = { module = "org.renderdoc:renderdoc", version.ref = "renderdoc" } # Not a maven dependency
+
 # Forge Runtime depedencies
 javax-annotations = { module = "com.google.code.findbugs:jsr305", version.ref = "javax-annotations" }
 mixin-remapper-service = { module = "dev.architectury:architectury-mixin-remapper-service", version.ref = "forge-runtime" }

gradle/test.libs.versions.toml

@@ -1,13 +1,15 @@
 [versions]
 spock = "2.3-groovy-3.0"
-junit = "5.11.3"
+junit = "5.12.2"
-javalin = "6.3.0"
+javalin = "6.6.0"
-mockito = "5.14.2"
+mockito = "5.17.0"
-java-debug = "0.52.0"
+java-debug = "0.53.1"
 mixin = "0.15.3+mixin.0.8.7"
+bouncycastle = "1.80"
 
-gradle-nightly = "8.14-20250208001853+0000"
+gradle-latest = "9.0.0-rc-1"
-fabric-loader = "0.16.9"
+gradle-nightly = "9.1.0-20250620001442+0000"
+fabric-loader = "0.16.14"
 
 [libraries]
 spock = { module = "org.spockframework:spock-core", version.ref = "spock" }
@@ -17,5 +19,9 @@ javalin = { module = "io.javalin:javalin", version.ref = "javalin" }
 mockito = { module = "org.mockito:mockito-core", version.ref = "mockito" }
 java-debug = { module = "com.microsoft.java:com.microsoft.java.debug.core", version.ref = "java-debug" }
 mixin = { module = "net.fabricmc:sponge-mixin", version.ref = "mixin" }
+gradle-latest = { module = "org.gradle:dummy", version.ref = "gradle-latest" }
 gradle-nightly = { module = "org.gradle:dummy", version.ref = "gradle-nightly" }
-fabric-loader = { module = "net.fabricmc:fabric-loader", version.ref = "fabric-loader" }
+fabric-loader = { module = "net.fabricmc:fabric-loader", version.ref = "fabric-loader" }
+bcprov = { module = "org.bouncycastle:bcprov-jdk18on", version.ref = "bouncycastle" }
+bcpkix = { module = "org.bouncycastle:bcpkix-jdk18on", version.ref = "bouncycastle" }
+bcutil = { module = "org.bouncycastle:bcutil-jdk18on", version.ref = "bouncycastle" }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.12-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14-all.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

gradlew

@@ -114,7 +114,7 @@ case "$( uname )" in                #(
   NONSTOP* )        nonstop=true ;;
 esac
 
-CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+CLASSPATH="\\\"\\\""
 
 
 # Determine the Java command to use to start the JVM.
@@ -205,7 +205,7 @@ fi
 DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 # Collect all arguments for the java command:
-#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
 #     and any embedded shellness will be escaped.
 #   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
 #     treated as '${Hostname}' itself on the command line.
@@ -213,7 +213,7 @@ DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
         -classpath "$CLASSPATH" \
-        org.gradle.wrapper.GradleWrapperMain \
+        -jar "$APP_HOME/gradle/wrapper/gradle-wrapper.jar" \
         "$@"
 
 # Stop when "xargs" is not available.

gradlew.bat

@@ -70,11 +70,11 @@ goto fail
 :execute
 @rem Setup the command line
 
-set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+set CLASSPATH=
 
 
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" -jar "%APP_HOME%\gradle\wrapper\gradle-wrapper.jar" %*
 
 :end
 @rem End local scope for the variables with windows NT shell

src/main/java/net/fabricmc/loom/LoomGradleExtension.java

@@ -155,6 +155,11 @@ public interface LoomGradleExtension extends LoomGradleExtensionAPI {
 
 	boolean isProjectIsolationActive();
 
+	/**
+	 * @return true when '--write-verification-metadata` is set
+	 */
+	boolean isCollectingDependencyVerificationMetadata();
+
 	// ===================
 	//  Architectury Loom
 	// ===================

src/main/java/net/fabricmc/loom/LoomGradlePlugin.java

@@ -27,10 +27,10 @@ package net.fabricmc.loom;
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
-import com.google.common.collect.ImmutableMap;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import org.gradle.api.Plugin;
@@ -98,8 +98,8 @@ public class LoomGradlePlugin implements Plugin<PluginAware> {
 		LibraryLocationLogger.logLibraryVersions();
 
 		// Apply default plugins
-		project.apply(ImmutableMap.of("plugin", "java-library"));
+		project.apply(Map.of("plugin", "java-library"));
-		project.apply(ImmutableMap.of("plugin", "eclipse"));
+		project.apply(Map.of("plugin", "eclipse"));
 
 		// Setup extensions
 		project.getExtensions().create(LoomGradleExtensionAPI.class, "loom", LoomGradleExtensionImpl.class, project, LoomFiles.create(project));

src/main/java/net/fabricmc/loom/api/RemapConfigurationSettings.java

@@ -40,6 +40,8 @@ import org.gradle.api.tasks.SourceSet;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 
+import net.fabricmc.loom.configuration.providers.minecraft.MinecraftSourceSets;
+
 /**
  * A {@link Named} object for configuring "proxy" configurations that remap artifacts.
  */
@@ -140,7 +142,7 @@ public abstract class RemapConfigurationSettings implements Named {
 	}
 
 	private Provider<Boolean> defaultDependencyTransforms() {
-		return getSourceSet().map(sourceSet -> sourceSet.getName().equals(SourceSet.MAIN_SOURCE_SET_NAME) || sourceSet.getName().equals("client"));
+		return getSourceSet().map(sourceSet -> sourceSet.getName().equals(SourceSet.MAIN_SOURCE_SET_NAME) || sourceSet.getName().equals(MinecraftSourceSets.Split.CLIENT_ONLY_SOURCE_SET_NAME));
 	}
 
 	@Override

src/main/java/net/fabricmc/loom/api/mappings/layered/MappingContext.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2016-2021 FabricMC
+ * Copyright (c) 2016-2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -46,6 +46,8 @@ public interface MappingContext {
 
 	Supplier<MemoryMappingTree> intermediaryTree();
 
+	boolean isUsingIntermediateMappings();
+
 	MinecraftProvider minecraftProvider();
 
 	default String minecraftVersion() {
@@ -62,4 +64,6 @@ public interface MappingContext {
 	DownloadBuilder download(String url);
 
 	boolean refreshDeps();
+
+	boolean hasProperty(String property);
 }

src/main/java/net/fabricmc/loom/api/processor/SpecContext.java

@@ -34,9 +34,16 @@ public interface SpecContext {
 
 	List<FabricModJson> localMods();
 
-	// Returns mods that are both on the compile and runtime classpath
+	/**
+	 * Return a set of mods that should be used for transforms, that target EITHER the common or client.
+	 */
 	List<FabricModJson> modDependenciesCompileRuntime();
 
+	/**
+	 * Return a set of mods that should be used for transforms, that target ONLY the client.
+	 */
+	List<FabricModJson> modDependenciesCompileRuntimeClient();
+
 	default List<FabricModJson> allMods() {
 		return Stream.concat(modDependencies().stream(), localMods().stream()).toList();
 	}

src/main/java/net/fabricmc/loom/build/mixin/GroovyApInvoker.java

@@ -25,10 +25,10 @@
 package net.fabricmc.loom.build.mixin;
 
 import java.io.File;
+import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
-import com.google.common.collect.ImmutableList;
 import org.gradle.api.Project;
 import org.gradle.api.tasks.SourceSet;
 import org.gradle.api.tasks.TaskProvider;
@@ -41,7 +41,7 @@ public class GroovyApInvoker extends AnnotationProcessorInvoker<GroovyCompile> {
 	public GroovyApInvoker(Project project) {
 		super(
 				project,
-				ImmutableList.of(),
+				List.of(),
 				getInvokerTasks(project),
 				AnnotationProcessorInvoker.GROOVY);
 	}

src/main/java/net/fabricmc/loom/build/mixin/ScalaApInvoker.java

@@ -25,10 +25,10 @@
 package net.fabricmc.loom.build.mixin;
 
 import java.io.File;
+import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
-import com.google.common.collect.ImmutableList;
 import org.gradle.api.Project;
 import org.gradle.api.tasks.SourceSet;
 import org.gradle.api.tasks.TaskProvider;
@@ -42,7 +42,7 @@ public class ScalaApInvoker extends AnnotationProcessorInvoker<ScalaCompile> {
 		super(
 				project,
 				// Scala just uses the java AP configuration afaik. This of course assumes the java AP also gets configured.
-				ImmutableList.of(),
+				List.of(),
 				getInvokerTasks(project),
 				AnnotationProcessorInvoker.SCALA);
 	}

src/main/java/net/fabricmc/loom/build/nesting/NestableJarGenerationTask.java

@@ -39,7 +39,6 @@ import java.util.regex.Pattern;
 
 import javax.inject.Inject;
 
-import com.google.common.hash.Hashing;
 import com.google.gson.JsonObject;
 import org.apache.commons.io.FileUtils;
 import org.gradle.api.artifacts.ArtifactView;
@@ -63,6 +62,7 @@ import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.LoomGradlePlugin;
 import net.fabricmc.loom.task.AbstractLoomTask;
+import net.fabricmc.loom.util.Checksum;
 import net.fabricmc.loom.util.ModPlatform;
 import net.fabricmc.loom.util.ZipReprocessorUtil;
 import net.fabricmc.loom.util.ZipUtils;
@@ -194,9 +194,7 @@ public abstract class NestableJarGenerationTask extends AbstractLoomTask {
 
 		// Fabric Loader can't handle modIds longer than 64 characters
 		if (modId.length() > 64) {
-			String hash = Hashing.sha256()
+			String hash = Checksum.of(modId).sha256().hex();
-					.hashString(modId, StandardCharsets.UTF_8)
-					.toString();
 			modId = modId.substring(0, 50) + hash.substring(0, 14);
 		}
 

src/main/java/net/fabricmc/loom/configuration/CompileConfiguration.java

@@ -367,7 +367,7 @@ public abstract class CompileConfiguration implements Runnable {
 	private LockFile getLockFile() {
 		final LoomGradleExtension extension = LoomGradleExtension.get(getProject());
 		final Path cacheDirectory = extension.getFiles().getUserCache().toPath();
-		final String pathHash = Checksum.projectHash(getProject());
+		final String pathHash = Checksum.of(getProject()).sha1().hex();
 		return new LockFile(
 				cacheDirectory.resolve("." + pathHash + ".lock"),
 				"Lock for cache='%s', project='%s'".formatted(

src/main/java/net/fabricmc/loom/configuration/LoomConfigurations.java

@@ -138,7 +138,6 @@ public abstract class LoomConfigurations implements Runnable {
 		register(Constants.Configurations.MAPPINGS, Role.RESOLVABLE);
 		register(Constants.Configurations.MAPPINGS_FINAL, Role.RESOLVABLE);
 		register(Constants.Configurations.LOOM_DEVELOPMENT_DEPENDENCIES, Role.RESOLVABLE);
-		register(Constants.Configurations.UNPICK_CLASSPATH, Role.RESOLVABLE);
 		register(Constants.Configurations.LOCAL_RUNTIME, Role.RESOLVABLE);
 		extendsFrom(JavaPlugin.RUNTIME_CLASSPATH_CONFIGURATION_NAME, Constants.Configurations.LOCAL_RUNTIME);
 

src/main/java/net/fabricmc/loom/configuration/MavenPublication.java

@@ -35,7 +35,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 
 import javax.inject.Inject;
 
-import com.google.common.collect.ImmutableMap;
 import groovy.util.Node;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
@@ -54,7 +53,7 @@ import net.fabricmc.loom.util.gradle.GradleUtils;
 public abstract class MavenPublication implements Runnable {
 	// ImmutableMap is needed since it guarantees ordering
 	// (compile must go before runtime, or otherwise dependencies might get the "weaker" runtime scope).
-	private static final Map<String, String> CONFIGURATION_TO_SCOPE = ImmutableMap.of(
+	private static final Map<String, String> CONFIGURATION_TO_SCOPE = Map.of(
 			JavaPlugin.API_ELEMENTS_CONFIGURATION_NAME, "compile",
 			JavaPlugin.RUNTIME_ELEMENTS_CONFIGURATION_NAME, "runtime"
 	);

src/main/java/net/fabricmc/loom/configuration/accesswidener/LocalAccessWidenerEntry.java

@@ -25,7 +25,6 @@
 package net.fabricmc.loom.configuration.accesswidener;
 
 import java.io.IOException;
-import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 
@@ -40,11 +39,7 @@ import net.fabricmc.tinyremapper.TinyRemapper;
 
 public record LocalAccessWidenerEntry(Path path, String hash) implements AccessWidenerEntry {
 	public static LocalAccessWidenerEntry create(Path path) {
-		try {
+		return new LocalAccessWidenerEntry(path, Checksum.of(path).sha1().hex());
-			return new LocalAccessWidenerEntry(path, Checksum.sha1Hex(path));
-		} catch (IOException e) {
-			throw new UncheckedIOException("Failed to create LocalAccessWidenerEntry", e);
-		}
 	}
 
 	@Override

src/main/java/net/fabricmc/loom/configuration/decompile/DecompileConfiguration.java

@@ -24,18 +24,12 @@
 
 package net.fabricmc.loom.configuration.decompile;
 
-import java.io.File;
-
 import org.gradle.api.Project;
-import org.gradle.api.artifacts.ConfigurationContainer;
 
 import net.fabricmc.loom.LoomGradleExtension;
-import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.providers.mappings.MappingConfiguration;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftJar;
 import net.fabricmc.loom.configuration.providers.minecraft.mapped.MappedMinecraftProvider;
-import net.fabricmc.loom.task.GenerateSourcesTask;
-import net.fabricmc.loom.util.Constants;
 
 public abstract class DecompileConfiguration<T extends MappedMinecraftProvider> {
 	static final String DEFAULT_DECOMPILER = "Vineflower";
@@ -55,15 +49,4 @@ public abstract class DecompileConfiguration<T extends MappedMinecraftProvider>
 	public abstract String getTaskName(MinecraftJar.Type type);
 
 	public abstract void afterEvaluation();
-
-	protected final void configureUnpick(GenerateSourcesTask task, File unpickOutputJar) {
-		final ConfigurationContainer configurations = task.getProject().getConfigurations();
-
-		task.getUnpickDefinitions().set(mappingConfiguration.getUnpickDefinitionsFile());
-		task.getUnpickOutputJar().set(unpickOutputJar);
-		task.getUnpickConstantJar().setFrom(configurations.getByName(Constants.Configurations.MAPPING_CONSTANTS));
-		task.getUnpickClasspath().setFrom(configurations.getByName(Constants.Configurations.MINECRAFT_COMPILE_LIBRARIES));
-		task.getUnpickClasspath().from(configurations.getByName(Constants.Configurations.MOD_COMPILE_CLASSPATH_MAPPED));
-		extension.getMinecraftJars(MappingsNamespace.NAMED).forEach(task.getUnpickClasspath()::from);
-	}
 }

src/main/java/net/fabricmc/loom/configuration/decompile/SingleJarDecompileConfiguration.java

@@ -24,7 +24,6 @@
 
 package net.fabricmc.loom.configuration.decompile;
 
-import java.io.File;
 import java.util.List;
 
 import org.gradle.api.Project;
@@ -66,11 +65,6 @@ public class SingleJarDecompileConfiguration extends DecompileConfiguration<Mapp
 				task.dependsOn(project.getTasks().named("validateAccessWidener"));
 				task.setDescription("Decompile minecraft using %s.".formatted(decompilerName));
 				task.setGroup(Constants.TaskGroup.FABRIC);
-
-				if (mappingConfiguration.hasUnpickDefinitions()) {
-					final File outputJar = new File(extension.getMappingConfiguration().mappingsWorkingDir().toFile(), "minecraft-unpicked.jar");
-					configureUnpick(task, outputJar);
-				}
 			});
 		});
 

src/main/java/net/fabricmc/loom/configuration/decompile/SplitDecompileConfiguration.java

@@ -24,8 +24,6 @@
 
 package net.fabricmc.loom.configuration.decompile;
 
-import java.io.File;
-
 import org.gradle.api.Action;
 import org.gradle.api.Project;
 import org.gradle.api.Task;
@@ -56,22 +54,12 @@ public final class SplitDecompileConfiguration extends DecompileConfiguration<Ma
 		final TaskProvider<Task> commonDecompileTask = createDecompileTasks("Common", task -> {
 			task.getInputJarName().set(commonJar.getName());
 			task.getSourcesOutputJar().fileValue(GenerateSourcesTask.getJarFileWithSuffix("-sources.jar", commonJar.getPath()));
-
-			if (mappingConfiguration.hasUnpickDefinitions()) {
-				File unpickJar = new File(extension.getMappingConfiguration().mappingsWorkingDir().toFile(), "minecraft-common-unpicked.jar");
-				configureUnpick(task, unpickJar);
-			}
 		});
 
 		final TaskProvider<Task> clientOnlyDecompileTask = createDecompileTasks("ClientOnly", task -> {
 			task.getInputJarName().set(clientOnlyJar.getName());
 			task.getSourcesOutputJar().fileValue(GenerateSourcesTask.getJarFileWithSuffix("-sources.jar", clientOnlyJar.getPath()));
 
-			if (mappingConfiguration.hasUnpickDefinitions()) {
-				File unpickJar = new File(extension.getMappingConfiguration().mappingsWorkingDir().toFile(), "minecraft-clientonly-unpicked.jar");
-				configureUnpick(task, unpickJar);
-			}
-
 			// Don't allow them to run at the same time.
 			task.mustRunAfter(commonDecompileTask);
 		});

src/main/java/net/fabricmc/loom/configuration/ide/RunConfig.java

@@ -41,9 +41,9 @@ import java.util.Set;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
-import com.google.common.collect.ImmutableMap;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
+import groovy.xml.XmlUtil;
 import org.gradle.api.JavaVersion;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.ModuleVersionIdentifier;
@@ -51,9 +51,6 @@ import org.gradle.api.artifacts.ResolvedArtifact;
 import org.gradle.api.artifacts.ResolvedModuleVersion;
 import org.gradle.api.tasks.SourceSet;
 import org.gradle.plugins.ide.eclipse.model.EclipseModel;
-import org.w3c.dom.Document;
-import org.w3c.dom.Element;
-import org.w3c.dom.Node;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.configuration.InstallerData;
@@ -78,42 +75,7 @@ public class RunConfig {
 	public transient SourceSet sourceSet;
 	public Map<String, Object> environmentVariables;
 	public String projectName;
-
+	public String folderName;
-	public Element genRuns(Element doc) {
-		Element root = this.addXml(doc, "component", ImmutableMap.of("name", "ProjectRunConfigurationManager"));
-		root = addXml(root, "configuration", ImmutableMap.of("default", "false", "name", configName, "type", "Application", "factoryName", "Application"));
-
-		this.addXml(root, "module", ImmutableMap.of("name", ideaModuleName));
-		this.addXml(root, "option", ImmutableMap.of("name", "MAIN_CLASS_NAME", "value", mainClass));
-		this.addXml(root, "option", ImmutableMap.of("name", "WORKING_DIRECTORY", "value", runDirIdeaUrl));
-
-		if (!vmArgs.isEmpty()) {
-			this.addXml(root, "option", ImmutableMap.of("name", "VM_PARAMETERS", "value", joinArguments(vmArgs)));
-		}
-
-		if (!programArgs.isEmpty()) {
-			this.addXml(root, "option", ImmutableMap.of("name", "PROGRAM_PARAMETERS", "value", joinArguments(programArgs)));
-		}
-
-		return root;
-	}
-
-	public Element addXml(Node parent, String name, Map<String, String> values) {
-		Document doc = parent.getOwnerDocument();
-
-		if (doc == null) {
-			doc = (Document) parent;
-		}
-
-		Element e = doc.createElement(name);
-
-		for (Map.Entry<String, String> entry : values.entrySet()) {
-			e.setAttribute(entry.getKey(), entry.getValue());
-		}
-
-		parent.appendChild(e);
-		return e;
-	}
 
 	// Turns camelCase/PascalCase into Capital Case
 	// caseConversionExample -> Case Conversion Example
@@ -194,6 +156,7 @@ public class RunConfig {
 		runConfig.environmentVariables = new HashMap<>();
 		runConfig.environmentVariables.putAll(settings.getEnvironmentVariables());
 		runConfig.projectName = project.getName();
+		runConfig.folderName = settings.getIdeConfigFolder().getOrNull();
 
 		for (Consumer<RunConfig> consumer : extension.getSettingsPostEdit()) {
 			consumer.accept(runConfig);
@@ -228,6 +191,7 @@ public class RunConfig {
 		dummyConfig = dummyConfig.replace("%VM_ARGS%", joinArguments(vmArgs).replaceAll("\"", "&quot;"));
 		dummyConfig = dummyConfig.replace("%IDEA_ENV_VARS%", getEnvVars("<env name=\"%s\" value=\"%s\"/>"));
 		dummyConfig = dummyConfig.replace("%ECLIPSE_ENV_VARS%", getEnvVars("<mapEntry key=\"%s\" value=\"%s\"/>"));
+		dummyConfig = dummyConfig.replace("%IDEA_FOLDER_NAME%", folderName == null ? "" : "folderName=\"" + XmlUtil.escapeXml(folderName) + "\"");
 
 		return dummyConfig;
 	}

src/main/java/net/fabricmc/loom/configuration/ide/RunConfigSettings.java

@@ -54,7 +54,7 @@ import net.fabricmc.loom.util.ModPlatform;
 import net.fabricmc.loom.util.Platform;
 import net.fabricmc.loom.util.gradle.SourceSetHelper;
 
-public class RunConfigSettings implements Named {
+public abstract class RunConfigSettings implements Named {
 	/**
 	 * Arguments for the JVM, such as system properties.
 	 */
@@ -465,6 +465,7 @@ public class RunConfigSettings implements Named {
 		defaultMainClass = parent.defaultMainClass;
 		source = parent.source;
 		ideConfigGenerated = parent.ideConfigGenerated;
+		getIdeConfigFolder().set(parent.getIdeConfigFolder());
 	}
 
 	public void makeRunDir() {
@@ -483,6 +484,15 @@ public class RunConfigSettings implements Named {
 		this.ideConfigGenerated = ideConfigGenerated;
 	}
 
+	/**
+	 * Group this run config under the given folder.
+	 *
+	 * <p>This is currently only supported on IntelliJ IDEA.
+	 *
+	 * @return The property used to set the config folder.
+	 */
+	public abstract Property<String> getIdeConfigFolder();
+
 	@ApiStatus.Internal
 	@ApiStatus.Experimental
 	public Property<String> devLaunchMainClass() {

src/main/java/net/fabricmc/loom/configuration/ifaceinject/InterfaceInjectionProcessor.java

@@ -100,10 +100,14 @@ public abstract class InterfaceInjectionProcessor implements MinecraftJarProcess
 			return null;
 		}
 
-		return new Spec(injectedInterfaces);
+		Set<String> clientOnlyModIds = context.modDependenciesCompileRuntimeClient().stream()
+				.map(FabricModJson::getId)
+				.collect(Collectors.toSet());
+
+		return new Spec(injectedInterfaces, clientOnlyModIds);
 	}
 
-	public record Spec(List<InjectedInterface> injectedInterfaces) implements MinecraftJarProcessor.Spec {
+	public record Spec(List<InjectedInterface> injectedInterfaces, Set<String> clientOnlyModIds) implements MinecraftJarProcessor.Spec {
 	}
 
 	@Override
@@ -115,6 +119,10 @@ public abstract class InterfaceInjectionProcessor implements MinecraftJarProcess
 
 		try (LazyCloseable<TinyRemapper> tinyRemapper = context.createRemapper(MappingsNamespace.INTERMEDIARY, MappingsNamespace.NAMED)) {
 			final List<InjectedInterface> remappedInjectedInterfaces = spec.injectedInterfaces().stream()
+					.filter(injectedInterface -> {
+						return context.includesClient() // The client jar depends on the server, so always apply all to it
+								|| !spec.clientOnlyModIds.contains(injectedInterface.modId()); // Or the mod is NOT only found on the client classpath, so we can apply it to the server jar
+					})
 					.map(injectedInterface -> remap(
 							injectedInterface,
 							s -> mappings.mapClassName(s, intermediaryIndex, namedIndex),

src/main/java/net/fabricmc/loom/configuration/mods/ArtifactRef.java

@@ -69,7 +69,7 @@ public interface ArtifactRef {
 		}
 
 		public String version() {
-			return replaceIfNullOrEmpty(artifact.getModuleVersion().getId().getVersion(), () -> Checksum.truncatedSha256(artifact.getFile()));
+			return replaceIfNullOrEmpty(artifact.getModuleVersion().getId().getVersion(), () -> Checksum.of(artifact.getFile()).sha256().hex(10));
 		}
 
 		public String classifier() {

src/main/java/net/fabricmc/loom/configuration/mods/ModConfigurationRemapper.java

@@ -38,7 +38,6 @@ import java.util.Map;
 import java.util.Set;
 import java.util.function.Supplier;
 
-import com.google.common.collect.ImmutableMap;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.artifacts.FileCollectionDependency;
@@ -58,6 +57,8 @@ import org.gradle.api.tasks.SourceSet;
 import org.gradle.jvm.JvmLibrary;
 import org.gradle.language.base.artifact.SourcesArtifact;
 import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.LoomGradlePlugin;
@@ -65,6 +66,7 @@ import net.fabricmc.loom.api.RemapConfigurationSettings;
 import net.fabricmc.loom.configuration.RemapConfigurations;
 import net.fabricmc.loom.configuration.mods.dependency.ModDependency;
 import net.fabricmc.loom.configuration.mods.dependency.ModDependencyFactory;
+import net.fabricmc.loom.configuration.mods.dependency.ModDependencyOptions;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftSourceSets;
 import net.fabricmc.loom.util.Checksum;
 import net.fabricmc.loom.util.Constants;
@@ -79,6 +81,8 @@ public class ModConfigurationRemapper {
 	// This can happen when the dependency is a FileCollectionDependency or from a flatDir repository.
 	public static final String MISSING_GROUP = "unspecified";
 
+	private static final Logger LOGGER = LoggerFactory.getLogger(ModConfigurationRemapper.class);
+
 	public static void supplyModConfigurations(Project project, ServiceFactory serviceFactory, String mappingsSuffix, LoomGradleExtension extension, SourceRemapper sourceRemapper) {
 		final DependencyHandler dependencies = project.getDependencies();
 		// The configurations where the source and remapped artifacts go.
@@ -98,7 +102,7 @@ public class ModConfigurationRemapper {
 
 		for (RemapConfigurationSettings entry : remapConfigurationSettings) {
 			// key: true if runtime, false if compile
-			final Map<Boolean, Boolean> envToEnabled = ImmutableMap.of(
+			final Map<Boolean, Boolean> envToEnabled = Map.of(
 					false, entry.getOnCompileClasspath().get(),
 					true, entry.getOnRuntimeClasspath().get()
 			);
@@ -135,6 +139,15 @@ public class ModConfigurationRemapper {
 			}
 		}
 
+		final ModDependencyOptions modDependencyOptions = ModDependencyOptions.create(project, ModDependencyOptions.class, options -> {
+			options.getMappings().set(mappingsSuffix);
+			options.getInlineRefmap().set(extension.getMixin().getInlineDependencyRefmaps());
+		});
+
+		if (LOGGER.isInfoEnabled()) {
+			LOGGER.info("Mod dependency options: {}", modDependencyOptions.getJson());
+		}
+
 		// Round 1: Discovery
 		// Go through all the configs to find artifacts to remap and
 		// the installer data. The installer data has to be added before
@@ -177,7 +190,7 @@ public class ModConfigurationRemapper {
 					continue;
 				}
 
-				final ModDependency modDependency = ModDependencyFactory.create(artifact, artifactMetadata, remappedConfig, clientRemappedConfig, mappingsSuffix, project);
+				final ModDependency modDependency = ModDependencyFactory.create(artifact, artifactMetadata, remappedConfig, clientRemappedConfig, modDependencyOptions, project);
 				scheduleSourcesRemapping(project, sourceRemapper, modDependency);
 				modDependencies.add(modDependency);
 			}
@@ -263,7 +276,7 @@ public class ModConfigurationRemapper {
 
 			for (File artifact : files) {
 				final String name = getNameWithoutExtension(artifact.toPath());
-				final String version = replaceIfNullOrEmpty(dependency.getVersion(), () -> Checksum.truncatedSha256(artifact));
+				final String version = replaceIfNullOrEmpty(dependency.getVersion(), () -> Checksum.of(artifact).sha256().hex(10));
 				artifacts.add(new ArtifactRef.FileArtifactRef(artifact.toPath(), group, name, version));
 			}
 		}
@@ -333,7 +346,7 @@ public class ModConfigurationRemapper {
 		}
 
 		if (dependency.isCacheInvalid(project, "sources")) {
-			final Path output = dependency.getWorkingFile("sources");
+			final Path output = dependency.getWorkingFile(project, "sources");
 
 			sourceRemapper.scheduleRemapSources(sourcesInput.toFile(), output.toFile(), false, true, () -> {
 				try {

src/main/java/net/fabricmc/loom/configuration/mods/ModProcessor.java

@@ -37,6 +37,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.jar.Manifest;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -48,15 +49,19 @@ import dev.architectury.loom.util.MappingOption;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.attributes.Usage;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.RemapConfigurationSettings;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.build.IntermediaryNamespaces;
 import net.fabricmc.loom.configuration.mods.dependency.ModDependency;
+import net.fabricmc.loom.configuration.mods.extension.ModProcessorExtension;
 import net.fabricmc.loom.configuration.providers.mappings.MappingConfiguration;
 import net.fabricmc.loom.extension.RemapperExtensionHolder;
 import net.fabricmc.loom.util.Constants;
+import net.fabricmc.loom.util.IdentityBiMap;
 import net.fabricmc.loom.util.LoggerFilter;
 import net.fabricmc.loom.util.ModPlatform;
 import net.fabricmc.loom.util.Pair;
@@ -73,11 +78,12 @@ import net.fabricmc.tinyremapper.InputTag;
 import net.fabricmc.tinyremapper.NonClassCopyMode;
 import net.fabricmc.tinyremapper.OutputConsumerPath;
 import net.fabricmc.tinyremapper.TinyRemapper;
-import net.fabricmc.tinyremapper.extension.mixin.MixinExtension;
 
 public class ModProcessor {
 	private static final String toM = MappingsNamespace.NAMED.toString();
 
+	private static final Logger LOGGER = LoggerFactory.getLogger(ModProcessor.class);
+
 	private static final Pattern COPY_CONFIGURATION_PATTERN = Pattern.compile("^(.+)Copy[0-9]*$");
 
 	private final Project project;
@@ -92,7 +98,7 @@ public class ModProcessor {
 
 	public void processMods(List<ModDependency> remapList) throws IOException {
 		try {
-			project.getLogger().lifecycle(":remapping {} mods from {}", remapList.size(), describeConfiguration(sourceConfiguration));
+			LOGGER.info(":remapping {} mods from {}", remapList.size(), describeConfiguration(sourceConfiguration));
 			remapJars(remapList);
 		} catch (Exception e) {
 			throw new RuntimeException(String.format(Locale.ENGLISH, "Failed to remap %d mods", remapList.size()), e);
@@ -192,13 +198,21 @@ public class ModProcessor {
 			builder.extension(kotlinRemapperClassloader.getTinyRemapperExtension());
 		}
 
-		final Set<InputTag> remapMixins = new HashSet<>();
+		final IdentityBiMap<InputTag, ModDependency> inputTags = new IdentityBiMap<>();
-		final boolean requiresStaticMixinRemap = remapList.stream()
+		final List<ModProcessorExtension> activeExtensions = ModProcessorExtension.EXTENSIONS.stream()
-				.anyMatch(modDependency -> modDependency.getMetadata().mixinRemapType() == ArtifactMetadata.MixinRemapType.STATIC);
+				.filter(e -> remapList.stream().anyMatch(e::appliesTo))
+				.toList();
+		final ModProcessorExtension.Context context = new ModProcessorExtension.Context(fromM, toM, remapList);
 
-		if (requiresStaticMixinRemap) {
+		for (ModProcessorExtension modProcessorExtension : activeExtensions) {
-			// Configure the mixin extension to remap mixins from mod jars that were remapped with the mixin extension.
+			LOGGER.info("Applying mod processor extension: {}", modProcessorExtension.getClass().getSimpleName());
-			builder.extension(new MixinExtension(remapMixins::contains));
+
+			final Predicate<InputTag> applyPredicate = inputTag -> {
+				ModDependency mod = inputTags.getByKey(inputTag);
+				return mod != null && modProcessorExtension.appliesTo(mod);
+			};
+
+			builder.extension(modProcessorExtension.createExtension(context, applyPredicate));
 		}
 
 		for (RemapperExtensionHolder holder : extension.getRemapperExtensions().get()) {
@@ -209,14 +223,13 @@ public class ModProcessor {
 
 		remapper.readClassPath(extension.getMinecraftJars(IntermediaryNamespaces.runtimeIntermediaryNamespace(project)).toArray(Path[]::new));
 
-		final Map<ModDependency, InputTag> tagMap = new HashMap<>();
 		final Map<ModDependency, OutputConsumerPath> outputConsumerMap = new HashMap<>();
 		final Map<ModDependency, Pair<byte[], String>> accessWidenerMap = new HashMap<>();
 
 		for (RemapConfigurationSettings entry : extension.getRemapConfigurations()) {
 			for (File inputFile : entry.getSourceConfiguration().get().getFiles()) {
 				if (remapList.stream().noneMatch(info -> info.getInputFile().toFile().equals(inputFile))) {
-					project.getLogger().debug("Adding " + inputFile + " onto the remap classpath");
+					LOGGER.debug("Adding " + inputFile + " onto the remap classpath");
 					remapper.readClassPathAsync(inputFile.toPath());
 				}
 			}
@@ -225,23 +238,10 @@ public class ModProcessor {
 		for (ModDependency info : remapList) {
 			InputTag tag = remapper.createInputTag();
 
-			project.getLogger().debug("Adding " + info.getInputFile() + " as a remap input");
+			LOGGER.debug("Adding " + info.getInputFile() + " as a remap input");
-
+			inputTags.put(tag, info);
-			// Note: this is done at a jar level, not at the level of an individual mixin config.
-			// If a mod has multiple mixin configs, it's assumed that either all or none of them have refmaps.
-			if (info.getMetadata().mixinRemapType() == ArtifactMetadata.MixinRemapType.STATIC) {
-				if (!requiresStaticMixinRemap) {
-					// Should be impossible but stranger things have happened.
-					throw new IllegalStateException("Was not configured for static remap, but a mod required it?!");
-				}
-
-				project.getLogger().info("Remapping mixins in {} statically", info.getInputFile());
-				remapMixins.add(tag);
-			}
 
 			remapper.readInputsAsync(tag, info.getInputFile());
-			tagMap.put(info, tag);
-
 			Files.deleteIfExists(getRemappedOutput(info));
 		}
 
@@ -258,12 +258,12 @@ public class ModProcessor {
 					final AccessWidenerUtils.AccessWidenerData accessWidenerData = AccessWidenerUtils.readAccessWidenerData(dependency.getInputFile(), platform);
 
 					if (accessWidenerData != null) {
-						project.getLogger().debug("Remapping access widener in {}", dependency.getInputFile());
+						LOGGER.debug("Remapping access widener in {}", dependency.getInputFile());
 						byte[] remappedAw = AccessWidenerUtils.remapAccessWidener(accessWidenerData.content(), remapper.getEnvironment().getRemapper());
 						accessWidenerMap.put(dependency, new Pair<>(remappedAw, accessWidenerData.path()));
 					}
 
-					remapper.apply(outputConsumer, tagMap.get(dependency));
+					remapper.apply(outputConsumer, inputTags.getByValue(dependency));
 				} catch (Exception e) {
 					throw new RuntimeException("Failed to remap: " + dependency, e);
 				}
@@ -288,6 +288,12 @@ public class ModProcessor {
 				ZipUtils.replace(output, accessWidener.right(), accessWidener.left());
 			}
 
+			for (ModProcessorExtension modProcessorExtension : activeExtensions) {
+				if (modProcessorExtension.appliesTo(dependency)) {
+					modProcessorExtension.finalise(dependency, output);
+				}
+			}
+
 			stripNestedJars(output);
 			remapJarManifestEntries(output);
 
@@ -307,8 +313,8 @@ public class ModProcessor {
 		}
 	}
 
-	private static Path getRemappedOutput(ModDependency dependency) {
+	private Path getRemappedOutput(ModDependency dependency) {
-		return dependency.getWorkingFile(null);
+		return dependency.getWorkingFile(project, null);
 	}
 
 	private void remapJarManifestEntries(Path jar) throws IOException {

src/main/java/net/fabricmc/loom/configuration/mods/dependency/LocalMavenHelper.java

@@ -34,7 +34,11 @@ import java.nio.file.StandardCopyOption;
 
 import org.jetbrains.annotations.Nullable;
 
-public record LocalMavenHelper(String group, String name, String version, @Nullable String baseClassifier, Path root) {
+public record LocalMavenHelper(String group, String name, String version, @Nullable String baseClassifier, Path root, @Nullable String snapshotVersion) {
+	public LocalMavenHelper(String group, String name, String version, @Nullable String baseClassifier, Path root) {
+		this(group, name, version, baseClassifier, root, null);
+	}
+
 	public Path copyToMaven(Path artifact, @Nullable String classifier) throws IOException {
 		if (!artifact.getFileName().toString().endsWith(".jar")) {
 			throw new UnsupportedOperationException();
@@ -77,6 +81,13 @@ public record LocalMavenHelper(String group, String name, String version, @Nulla
 	}
 
 	private Path getDirectory() {
+		String version = this.version();
+
+		// When using a specific snapshot version the directory name should be the 1.0.0-SNAPSHOT version
+		if (this.snapshotVersion() != null) {
+			version = this.snapshotVersion();
+		}
+
 		return root.resolve("%s/%s/%s".formatted(group.replace(".", "/"), name, version));
 	}
 

src/main/java/net/fabricmc/loom/configuration/mods/dependency/ModDependency.java

@@ -28,6 +28,8 @@ import java.io.IOException;
 import java.nio.file.Path;
 
 import org.gradle.api.Project;
+import org.gradle.api.artifacts.component.ComponentIdentifier;
+import org.gradle.api.internal.artifacts.repositories.resolver.MavenUniqueSnapshotComponentIdentifier;
 import org.jetbrains.annotations.Nullable;
 
 import net.fabricmc.loom.LoomGradleExtension;
@@ -37,23 +39,21 @@ import net.fabricmc.loom.configuration.mods.ArtifactRef;
 public abstract sealed class ModDependency permits SplitModDependency, SimpleModDependency {
 	private final ArtifactRef artifact;
 	private final ArtifactMetadata metadata;
-	protected final String group;
+	private final String group;
-	protected final String name;
+	private final String name;
-	protected final String version;
+	private final String version;
 	@Nullable
-	protected final String classifier;
+	private final String classifier;
-	protected final String mappingsSuffix;
+	private final ModDependencyOptions options;
-	protected final Project project;
 
-	public ModDependency(ArtifactRef artifact, ArtifactMetadata metadata, String mappingsSuffix, Project project) {
+	public ModDependency(ArtifactRef artifact, ArtifactMetadata metadata, ModDependencyOptions options) {
 		this.artifact = artifact;
 		this.metadata = metadata;
 		this.group = artifact.group();
 		this.name = artifact.name();
 		this.version = artifact.version();
 		this.classifier = artifact.classifier();
-		this.mappingsSuffix = mappingsSuffix;
+		this.options = options;
-		this.project = project;
 	}
 
 	/**
@@ -71,10 +71,27 @@ public abstract sealed class ModDependency permits SplitModDependency, SimpleMod
 	 */
 	public abstract void applyToProject(Project project);
 
-	protected LocalMavenHelper createMaven(String name) {
+	/**
+	 * Create a maven helper for the local cache.
+	 * @param type The jar type, e.g "common" or "client" for split dependencies.
+	 */
+	protected LocalMavenHelper createMavenHelper(Project project, @Nullable String type) {
 		final LoomGradleExtension extension = LoomGradleExtension.get(project);
 		final Path root = extension.getFiles().getRemappedModCache().toPath();
-		return new LocalMavenHelper(getRemappedGroup(), name, this.version, this.classifier, root);
+		final String fullName = getName() + (type != null ? "-" + type : "");
+		return new LocalMavenHelper(getGroup(), fullName, this.version, this.classifier, root, getSnapshotVersion());
+	}
+
+	private @Nullable String getSnapshotVersion() {
+		if (artifact instanceof ArtifactRef.ResolvedArtifactRef resolvedArtifactRef) {
+			ComponentIdentifier componentIdentifier = resolvedArtifactRef.artifact().getId().getComponentIdentifier();
+
+			if (componentIdentifier instanceof MavenUniqueSnapshotComponentIdentifier mavenUniqueId) {
+				return mavenUniqueId.getSnapshotVersion();
+			}
+		}
+
+		return null;
 	}
 
 	public ArtifactRef getInputArtifact() {
@@ -85,26 +102,34 @@ public abstract sealed class ModDependency permits SplitModDependency, SimpleMod
 		return metadata;
 	}
 
-	protected String getRemappedGroup() {
+	protected String getName() {
-		return getMappingsPrefix() + "." + group;
+		return "%s-%s".formatted(name, options.getCacheKey());
 	}
 
-	private String getMappingsPrefix() {
+	protected String getGroup() {
-		return mappingsSuffix.replace(".", "_").replace("-", "_").replace("+", "_");
+		return "remapped.%s".formatted(group);
+	}
+
+	protected String getVersion() {
+		return version;
 	}
 
 	public Path getInputFile() {
 		return artifact.path();
 	}
 
-	public Path getWorkingFile(@Nullable String classifier) {
+	public Path getWorkingFile(Project project, @Nullable String classifier) {
 		final LoomGradleExtension extension = LoomGradleExtension.get(project);
-		final String fileName = classifier == null ? String.format("%s-%s-%s.jar", getRemappedGroup(), name, version)
+		final String fileName = classifier == null ? String.format("%s-%s-%s.jar", getGroup(), getName(), version)
-													: String.format("%s-%s-%s-%s.jar", getRemappedGroup(), name, version, classifier);
+													: String.format("%s-%s-%s-%s.jar", getGroup(), getName(), version, classifier);
 
 		return extension.getFiles().getProjectBuildCache().toPath().resolve("remapped_working").resolve(fileName);
 	}
 
+	public ModDependencyOptions getOptions() {
+		return options;
+	}
+
 	@Override
 	public String toString() {
 		return "ModDependency{" + "group='" + group + '\'' + ", name='" + name + '\'' + ", version='" + version + '\'' + ", classifier='" + classifier + '\'' + '}';

src/main/java/net/fabricmc/loom/configuration/mods/dependency/ModDependencyFactory.java

@@ -41,7 +41,7 @@ import net.fabricmc.loom.util.AttributeHelper;
 public class ModDependencyFactory {
 	private static final String TARGET_ATTRIBUTE_KEY = "loom-target";
 
-	public static ModDependency create(ArtifactRef artifact, ArtifactMetadata metadata, Configuration targetConfig, @Nullable Configuration targetClientConfig, String mappingsSuffix, Project project) {
+	public static ModDependency create(ArtifactRef artifact, ArtifactMetadata metadata, Configuration targetConfig, @Nullable Configuration targetClientConfig, ModDependencyOptions options, Project project) {
 		if (targetClientConfig != null && LoomGradleExtension.get(project).getSplitModDependencies().get()) {
 			final Optional<JarSplitter.Target> cachedTarget = readTarget(artifact);
 			JarSplitter.Target target;
@@ -54,11 +54,11 @@ public class ModDependencyFactory {
 			}
 
 			if (target != null) {
-				return new SplitModDependency(artifact, metadata, mappingsSuffix, targetConfig, targetClientConfig, target, project);
+				return new SplitModDependency(artifact, metadata, options, targetConfig, targetClientConfig, target, project);
 			}
 		}
 
-		return new SimpleModDependency(artifact, metadata, mappingsSuffix, targetConfig, project);
+		return new SimpleModDependency(artifact, metadata, options, targetConfig, project);
 	}
 
 	private static Optional<JarSplitter.Target> readTarget(ArtifactRef artifact) {

src/main/java/net/fabricmc/loom/configuration/mods/dependency/ModDependencyOptions.java

@@ -0,0 +1,38 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.dependency;
+
+import org.gradle.api.provider.Property;
+
+import net.fabricmc.loom.util.CacheKey;
+
+/**
+ * Inputs used to process a mod dependency. The output jar is cached based on these properties.
+ */
+public abstract class ModDependencyOptions extends CacheKey {
+	public abstract Property<String> getMappings();
+
+	public abstract Property<Boolean> getInlineRefmap();
+}

src/main/java/net/fabricmc/loom/configuration/mods/dependency/SimpleModDependency.java

@@ -40,10 +40,10 @@ public final class SimpleModDependency extends ModDependency {
 	private final Configuration targetConfig;
 	private final LocalMavenHelper maven;
 
-	public SimpleModDependency(ArtifactRef artifact, ArtifactMetadata metadata, String mappingsSuffix, Configuration targetConfig, Project project) {
+	public SimpleModDependency(ArtifactRef artifact, ArtifactMetadata metadata, ModDependencyOptions options, Configuration targetConfig, Project project) {
-		super(artifact, metadata, mappingsSuffix, project);
+		super(artifact, metadata, options);
 		this.targetConfig = Objects.requireNonNull(targetConfig);
-		this.maven = createMaven(name);
+		this.maven = createMavenHelper(project, null);
 	}
 
 	@Override

src/main/java/net/fabricmc/loom/configuration/mods/dependency/SplitModDependency.java

@@ -48,13 +48,13 @@ public final class SplitModDependency extends ModDependency {
 	@Nullable
 	private final LocalMavenHelper clientMaven;
 
-	public SplitModDependency(ArtifactRef artifact, ArtifactMetadata metadata, String mappingsSuffix, Configuration targetCommonConfig, Configuration targetClientConfig, JarSplitter.Target target, Project project) {
+	public SplitModDependency(ArtifactRef artifact, ArtifactMetadata metadata, ModDependencyOptions options, Configuration targetCommonConfig, Configuration targetClientConfig, JarSplitter.Target target, Project project) {
-		super(artifact, metadata, mappingsSuffix, project);
+		super(artifact, metadata, options);
 		this.targetCommonConfig = Objects.requireNonNull(targetCommonConfig);
 		this.targetClientConfig = Objects.requireNonNull(targetClientConfig);
 		this.target = Objects.requireNonNull(target);
-		this.commonMaven = target.common() ? createMaven(name + "-common") : null;
+		this.commonMaven = target.common() ? createMavenHelper(project, "common") : null;
-		this.clientMaven = target.client() ? createMaven(name + "-client") : null;
+		this.clientMaven = target.client() ? createMavenHelper(project, "client") : null;
 	}
 
 	@Override
@@ -86,8 +86,8 @@ public final class SplitModDependency extends ModDependency {
 		// Split the jar into 2
 		case SPLIT -> {
 			final String suffix = variant == null ? "" : "-" + variant;
-			final Path commonTempJar = getWorkingFile("common" + suffix);
+			final Path commonTempJar = getWorkingFile(project, "common" + suffix);
-			final Path clientTempJar = getWorkingFile("client" + suffix);
+			final Path clientTempJar = getWorkingFile(project, "client" + suffix);
 
 			final JarSplitter splitter = new JarSplitter(path);
 			splitter.split(commonTempJar, clientTempJar);
@@ -114,15 +114,16 @@ public final class SplitModDependency extends ModDependency {
 
 		if (target == JarSplitter.Target.SPLIT) {
 			createModGroup(
+					project,
 					getCommonMaven().getOutputFile(null),
 					getClientMaven().getOutputFile(null)
 			);
 		}
 	}
 
-	private void createModGroup(Path commonJar, Path clientJar) {
+	private void createModGroup(Project project, Path commonJar, Path clientJar) {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
-		final ModSettings modSettings = extension.getMods().maybeCreate(String.format("%s-%s-%s", getRemappedGroup(), name, version));
+		final ModSettings modSettings = extension.getMods().maybeCreate(String.format("%s-%s-%s", getGroup(), getName(), getVersion()));
 		modSettings.getModFiles().from(
 				commonJar.toFile(),
 				clientJar.toFile()

src/main/java/net/fabricmc/loom/configuration/mods/dependency/refmap/MixinReferenceRemapper.java

@@ -0,0 +1,29 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.dependency.refmap;
+
+public interface MixinReferenceRemapper {
+	String remapReference(String mixinClassName, String reference);
+}

src/main/java/net/fabricmc/loom/configuration/mods/dependency/refmap/MixinReferenceRemapperImpl.java

@@ -0,0 +1,69 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.dependency.refmap;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.util.fmj.mixin.MixinRefmap;
+
+public record MixinReferenceRemapperImpl(Map<String, MixinRefmap.ReferenceMappingData> data) implements MixinReferenceRemapper {
+	private static final Logger LOGGER = LoggerFactory.getLogger(MixinReferenceRemapperImpl.class);
+
+	public static MixinReferenceRemapper createFromRefmaps(String from, String to, Stream<MixinRefmap> refmaps) {
+		MixinRefmap.NamespacePair namespaces = new MixinRefmap.NamespacePair(from, to);
+
+		Map<String, MixinRefmap.ReferenceMappingData> data = refmaps
+				.map(refmap -> refmap.getData(namespaces))
+				.filter(Objects::nonNull)
+				.map(MixinRefmap.MixinMappingData::data)
+				.flatMap(map -> map.entrySet().stream())
+				.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
+						(existing, replacement) -> {
+							// TODO we could merge this, but it should never happen in practice
+							LOGGER.warn("Duplicate mixin reference mapping for {} in refmaps, using the first one", existing);
+							return existing;
+						}
+				));
+
+		return new MixinReferenceRemapperImpl(data);
+	}
+
+	@Override
+	public String remapReference(String mixinClassName, String reference) {
+		final MixinRefmap.ReferenceMappingData data = data().get(mixinClassName);
+
+		if (data != null) {
+			return data.remap(reference);
+		}
+
+		return reference;
+	}
+}

src/main/java/net/fabricmc/loom/configuration/mods/dependency/refmap/MixinRefmapInliner.java

@@ -0,0 +1,72 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.dependency.refmap;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.configuration.mods.ArtifactMetadata;
+import net.fabricmc.loom.configuration.mods.dependency.ModDependency;
+import net.fabricmc.loom.util.ExceptionUtil;
+import net.fabricmc.loom.util.fmj.FabricModJson;
+import net.fabricmc.loom.util.fmj.FabricModJsonFactory;
+import net.fabricmc.loom.util.fmj.mixin.MixinConfiguration;
+
+public class MixinRefmapInliner {
+	private static final Logger LOGGER = LoggerFactory.getLogger(MixinRefmapInliner.class);
+
+	public static MixinReferenceRemapper createRemapper(String from, String to, List<ModDependency> mods) throws IOException {
+		List<MixinConfiguration> mixinConfigurations = new ArrayList<>();
+
+		for (ModDependency mod : mods) {
+			if (mod.getMetadata().mixinRemapType() != ArtifactMetadata.MixinRemapType.MIXIN) {
+				continue;
+			}
+
+			FabricModJson fabricModJson = FabricModJsonFactory.createFromZipNullable(mod.getInputFile());
+
+			if (fabricModJson == null) {
+				LOGGER.warn("Failed to read fabric.mod.json from {}", mod.getInputFile());
+				continue;
+			}
+
+			try {
+				mixinConfigurations.addAll(MixinConfiguration.fromMod(fabricModJson));
+			} catch (IOException e) {
+				throw ExceptionUtil.createDescriptiveWrapper(IOException::new, "Failed to read mixin configuration from " + mod.getInputFile(), e);
+			}
+		}
+
+		return MixinReferenceRemapperImpl.createFromRefmaps(from, to, mixinConfigurations.stream().map(MixinConfiguration::refmap));
+	}
+
+	public static void removeRefmap(ModDependency modDependency, Path ouputPath) {
+	}
+}

src/main/java/net/fabricmc/loom/configuration/mods/dependency/refmap/MixinRefmapInlinerApplyVisitorProvider.java

@@ -0,0 +1,60 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.dependency.refmap;
+
+import java.util.function.Predicate;
+
+import org.objectweb.asm.ClassVisitor;
+
+import net.fabricmc.tinyremapper.InputTag;
+import net.fabricmc.tinyremapper.TinyRemapper;
+import net.fabricmc.tinyremapper.api.TrClass;
+
+public record MixinRefmapInlinerApplyVisitorProvider(
+		MixinReferenceRemapper remapper,
+		// A set of input tags that do NOT need their refmaps inlined
+		Predicate<InputTag> staticRemappedMixins) implements TinyRemapper.ApplyVisitorProvider, TinyRemapper.Extension {
+	@Override
+	public ClassVisitor insertApplyVisitor(TrClass cls, ClassVisitor next) {
+		return new MixinRefmapInlinerClassVisitor(remapper, next);
+	}
+
+	@Override
+	public ClassVisitor insertApplyVisitor(TrClass cls, ClassVisitor next, InputTag[] inputTags) {
+		for (InputTag tag : inputTags) {
+			if (staticRemappedMixins.test(tag)) {
+				// No need to inline the refmaps for this tag, as we know this was originally a statically remapped mixin with no refmap
+				return next;
+			}
+		}
+
+		return new MixinRefmapInlinerClassVisitor(remapper, next);
+	}
+
+	@Override
+	public void attach(TinyRemapper.Builder builder) {
+		builder.extraPreApplyVisitor(this);
+	}
+}

src/main/java/net/fabricmc/loom/configuration/mods/dependency/refmap/MixinRefmapInlinerClassVisitor.java

@@ -0,0 +1,99 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.dependency.refmap;
+
+import org.objectweb.asm.AnnotationVisitor;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.MethodVisitor;
+
+import net.fabricmc.loom.util.Constants;
+
+public class MixinRefmapInlinerClassVisitor extends ClassVisitor {
+	private final MixinReferenceRemapper remapper;
+
+	private String className = null;
+
+	public MixinRefmapInlinerClassVisitor(MixinReferenceRemapper remapper, ClassVisitor classVisitor) {
+		super(Constants.ASM_VERSION, classVisitor);
+		this.remapper = remapper;
+	}
+
+	@Override
+	public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+		this.className = name;
+		super.visit(version, access, name, signature, superName, interfaces);
+	}
+
+	@Override
+	public AnnotationVisitor visitAnnotation(String descriptor, boolean visible) {
+		AnnotationVisitor annotationVisitor = super.visitAnnotation(descriptor, visible);
+		return new RefmapInlinerAnnotationVisitor(annotationVisitor);
+	}
+
+	@Override
+	public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+		MethodVisitor methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions);
+		return new RefmapInlinerMethodVisitor(methodVisitor);
+	}
+
+	private class RefmapInlinerMethodVisitor extends MethodVisitor {
+		private RefmapInlinerMethodVisitor(MethodVisitor methodVisitor) {
+			super(MixinRefmapInlinerClassVisitor.super.api, methodVisitor);
+		}
+
+		@Override
+		public AnnotationVisitor visitAnnotation(String descriptor, boolean visible) {
+			AnnotationVisitor annotationVisitor = super.visitAnnotation(descriptor, visible);
+			return new RefmapInlinerAnnotationVisitor(annotationVisitor);
+		}
+	}
+
+	private class RefmapInlinerAnnotationVisitor extends AnnotationVisitor {
+		private RefmapInlinerAnnotationVisitor(AnnotationVisitor annotationVisitor) {
+			super(MixinRefmapInlinerClassVisitor.super.api, annotationVisitor);
+		}
+
+		@Override
+		public void visit(String name, Object value) {
+			if (value instanceof String strValue) {
+				value = remapper.remapReference(className, strValue);
+			}
+
+			super.visit(name, value);
+		}
+
+		@Override
+		public AnnotationVisitor visitArray(String name) {
+			AnnotationVisitor annotationVisitor = super.visitArray(name);
+			return new RefmapInlinerAnnotationVisitor(annotationVisitor);
+		}
+
+		@Override
+		public AnnotationVisitor visitAnnotation(String name, String descriptor) {
+			AnnotationVisitor annotationVisitor = super.visitAnnotation(name, descriptor);
+			return new RefmapInlinerAnnotationVisitor(annotationVisitor);
+		}
+	}
+}

src/main/java/net/fabricmc/loom/configuration/mods/extension/InlineRefmap.java

@@ -0,0 +1,60 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.extension;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.function.Predicate;
+
+import net.fabricmc.loom.configuration.mods.ArtifactMetadata;
+import net.fabricmc.loom.configuration.mods.dependency.ModDependency;
+import net.fabricmc.loom.configuration.mods.dependency.refmap.MixinReferenceRemapper;
+import net.fabricmc.loom.configuration.mods.dependency.refmap.MixinRefmapInliner;
+import net.fabricmc.loom.configuration.mods.dependency.refmap.MixinRefmapInlinerApplyVisitorProvider;
+import net.fabricmc.tinyremapper.InputTag;
+import net.fabricmc.tinyremapper.TinyRemapper;
+
+final class InlineRefmap implements ModProcessorExtension {
+	static final InlineRefmap INSTANCE = new InlineRefmap();
+
+	private InlineRefmap() {
+	}
+
+	@Override
+	public boolean appliesTo(ModDependency modDependency) {
+		return modDependency.getOptions().getInlineRefmap().get()
+				&& modDependency.getMetadata().mixinRemapType() == ArtifactMetadata.MixinRemapType.MIXIN;
+	}
+
+	@Override
+	public TinyRemapper.Extension createExtension(Context ctx, Predicate<InputTag> applyPredicate) throws IOException {
+		MixinReferenceRemapper refmapRemapper = MixinRefmapInliner.createRemapper(ctx.from(), ctx.to(), ctx.mods());
+		return new MixinRefmapInlinerApplyVisitorProvider(refmapRemapper, applyPredicate);
+	}
+
+	@Override
+	public void finalise(ModDependency modDependency, Path path) throws IOException {
+	}
+}

src/main/java/net/fabricmc/loom/configuration/mods/extension/MixinRemap.java

@@ -0,0 +1,58 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.extension;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.function.Predicate;
+
+import net.fabricmc.loom.configuration.mods.ArtifactMetadata;
+import net.fabricmc.loom.configuration.mods.dependency.ModDependency;
+import net.fabricmc.loom.configuration.mods.dependency.refmap.MixinRefmapInliner;
+import net.fabricmc.tinyremapper.InputTag;
+import net.fabricmc.tinyremapper.TinyRemapper;
+import net.fabricmc.tinyremapper.extension.mixin.MixinExtension;
+
+final class MixinRemap implements ModProcessorExtension {
+	static final MixinRemap INSTANCE = new MixinRemap();
+
+	private MixinRemap() {
+	}
+
+	@Override
+	public boolean appliesTo(ModDependency modDependency) {
+		return modDependency.getMetadata().mixinRemapType() == ArtifactMetadata.MixinRemapType.STATIC;
+	}
+
+	@Override
+	public TinyRemapper.Extension createExtension(Context ctx, Predicate<InputTag> applyPredicate) {
+		return new MixinExtension(applyPredicate);
+	}
+
+	@Override
+	public void finalise(ModDependency modDependency, Path path) throws IOException {
+		MixinRefmapInliner.removeRefmap(modDependency, path);
+	}
+}

src/main/java/net/fabricmc/loom/configuration/mods/extension/ModProcessorExtension.java

@@ -0,0 +1,61 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.mods.extension;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.function.Predicate;
+
+import net.fabricmc.loom.configuration.mods.dependency.ModDependency;
+import net.fabricmc.tinyremapper.InputTag;
+import net.fabricmc.tinyremapper.TinyRemapper;
+
+/**
+ * An interface to aid with applying mod-specific remapping extensions.
+ */
+public interface ModProcessorExtension {
+	List<ModProcessorExtension> EXTENSIONS = List.of(
+			MixinRemap.INSTANCE,
+			InlineRefmap.INSTANCE
+	);
+
+	/**
+	 * Return true if the extension applies to the given mod dependency.
+	 */
+	boolean appliesTo(ModDependency modDependency);
+
+	/**
+	 * Create a TinyRemapper extension that uses the predicate to only apply to mods that match appliesTo.
+	 */
+	TinyRemapper.Extension createExtension(Context ctx, Predicate<InputTag> applyPredicate) throws IOException;
+
+	void finalise(ModDependency modDependency, Path path) throws IOException;
+
+	record Context(
+			String from,
+			String to,
+			List<ModDependency> mods) { }
+}

src/main/java/net/fabricmc/loom/configuration/processors/MinecraftJarProcessorManager.java

@@ -25,7 +25,6 @@
 package net.fabricmc.loom.configuration.processors;
 
 import java.io.IOException;
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
@@ -113,11 +112,11 @@ public final class MinecraftJarProcessorManager {
 
 	public String getJarHash() {
 		//fabric-loom:mod-javadoc:-1289977000
-		return Checksum.sha1Hex(getCacheValue().getBytes(StandardCharsets.UTF_8)).substring(0, 10);
+		return Checksum.of(getCacheValue()).sha1().hex(10);
 	}
 
 	public String getSourceMappingsHash() {
-		return Checksum.sha1Hex(getCacheValue().getBytes(StandardCharsets.UTF_8));
+		return Checksum.of(getCacheValue()).sha1().hex();
 	}
 
 	public boolean requiresProcessingJar(Path jar) {

src/main/java/net/fabricmc/loom/configuration/processors/ModJavadocProcessor.java

@@ -124,7 +124,7 @@ public abstract class ModJavadocProcessor implements MinecraftJarProcessor<ModJa
 
 			try {
 				final byte[] data = fabricModJson.getSource().read(javaDocPath);
-				mappingsHash = Checksum.sha1Hex(data);
+				mappingsHash = Checksum.of(data).sha1().hex();
 
 				try (Reader reader = new InputStreamReader(new ByteArrayInputStream(data))) {
 					MappingReader.read(reader, mappings);

src/main/java/net/fabricmc/loom/configuration/processors/SpecContextImpl.java

@@ -48,6 +48,7 @@ import org.jetbrains.annotations.Nullable;
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.RemapConfigurationSettings;
 import net.fabricmc.loom.api.processor.SpecContext;
+import net.fabricmc.loom.configuration.providers.minecraft.MinecraftSourceSets;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.fmj.FabricModJson;
 import net.fabricmc.loom.util.fmj.FabricModJsonFactory;
@@ -59,10 +60,17 @@ import net.fabricmc.loom.util.gradle.GradleUtils;
  * @param localMods Mods found in the current project.
  * @param compileRuntimeMods Dependent mods found in both the compile and runtime classpath.
  */
-public record SpecContextImpl(List<FabricModJson> modDependencies, List<FabricModJson> localMods, List<FabricModJson> compileRuntimeMods) implements SpecContext {
+public record SpecContextImpl(
+		List<FabricModJson> modDependencies,
+		List<FabricModJson> localMods,
+		List<ModHolder> compileRuntimeMods) implements SpecContext {
 	public static SpecContextImpl create(Project project) {
 		final Map<String, List<FabricModJson>> fmjCache = new HashMap<>();
-		return new SpecContextImpl(getDependentMods(project, fmjCache), FabricModJsonHelpers.getModsInProject(project), getCompileRuntimeMods(project, fmjCache));
+		return new SpecContextImpl(
+				getDependentMods(project, fmjCache),
+				FabricModJsonHelpers.getModsInProject(project),
+				getCompileRuntimeMods(project, fmjCache)
+		);
 	}
 
 	// Reruns a list of mods found on both the compile and/or runtime classpaths
@@ -108,39 +116,68 @@ public record SpecContextImpl(List<FabricModJson> modDependencies, List<FabricMo
 	}
 
 	// Returns a list of mods that are on both to compile and runtime classpath
-	private static List<FabricModJson> getCompileRuntimeMods(Project project, Map<String, List<FabricModJson>> fmjCache) {
+	private static List<ModHolder> getCompileRuntimeMods(Project project, Map<String, List<FabricModJson>> fmjCache) {
-		var mods = new ArrayList<>(getCompileRuntimeModsFromRemapConfigs(project, fmjCache).toList());
+		var mods = new ArrayList<>(getCompileRuntimeModsFromRemapConfigs(project, fmjCache));
 
 		for (Project dependentProject : getCompileRuntimeProjectDependencies(project).toList()) {
-			mods.addAll(fmjCache.computeIfAbsent(dependentProject.getPath(), $ -> {
+			List<FabricModJson> projectMods = fmjCache.computeIfAbsent(dependentProject.getPath(), $ -> {
 				return FabricModJsonHelpers.getModsInProject(dependentProject);
-			}));
+			});
+
+			for (FabricModJson mod : projectMods) {
+				mods.add(new ModHolder(mod));
+			}
 		}
 
 		return Collections.unmodifiableList(mods);
 	}
 
 	// Returns a list of jar mods that are found on the compile and runtime remapping configurations
-	private static Stream<FabricModJson> getCompileRuntimeModsFromRemapConfigs(Project project, Map<String, List<FabricModJson>> fmjCache) {
+	private static List<ModHolder> getCompileRuntimeModsFromRemapConfigs(Project project, Map<String, List<FabricModJson>> fmjCache) {
 		final LoomGradleExtension extension = LoomGradleExtension.get(project);
-		final Set<String> runtimeModIds = extension.getRuntimeRemapConfigurations().stream()
-				.filter(settings -> settings.getApplyDependencyTransforms().get())
-				.flatMap(resolveArtifacts(project, true))
-				.map(modFromZip(fmjCache))
-				.filter(Objects::nonNull)
-				.map(FabricModJson::getId)
-				.collect(Collectors.toSet());
 
-		return extension.getCompileRemapConfigurations().stream()
+		// A set of mod ids from all remap configurations that are considered for dependency transforms.
-				.filter(settings -> settings.getApplyDependencyTransforms().get())
+		final Set<String> runtimeModIds = getModIds(
-				.flatMap(resolveArtifacts(project, false))// Use the intersection of the two configurations.
+				project,
-				.map(modFromZip(fmjCache))
+				fmjCache,
-				.filter(Objects::nonNull)
+				extension.getRuntimeRemapConfigurations().stream()
+						.filter(settings -> settings.getApplyDependencyTransforms().get())
+		);
+
+		// A set of mod ids that are found on one or more remap configurations that target the common source set.
+		// Null when split source sets are not enabled, meaning all mods are common.
+		final Set<String> commonModIds = extension.areEnvironmentSourceSetsSplit() ? getModIds(
+				project,
+				fmjCache,
+				extension.getRuntimeRemapConfigurations().stream()
+						.filter(settings -> settings.getSourceSet().map(sourceSet -> !sourceSet.getName().equals(MinecraftSourceSets.Split.CLIENT_ONLY_SOURCE_SET_NAME)).get())
+						.filter(settings -> settings.getApplyDependencyTransforms().get()))
+				: null;
+
+		return getMods(
+				project,
+				fmjCache,
+				extension.getCompileRemapConfigurations().stream()
+					.filter(settings -> settings.getApplyDependencyTransforms().get()))
 				// Only check based on the modid, as there may be differing versions used between the compile and runtime classpath.
 				// We assume that the version used at runtime will be binary compatible with the version used to compile against.
 				// It's not perfect but better than silently not supplying the mod, and this could happen with regular API that you compile against anyway.
 				.filter(fabricModJson -> runtimeModIds.contains(fabricModJson.getId()))
-				.sorted(Comparator.comparing(FabricModJson::getId));
+				.sorted(Comparator.comparing(FabricModJson::getId))
+				.map(fabricModJson -> new ModHolder(fabricModJson, commonModIds == null || commonModIds.contains(fabricModJson.getId())))
+				.toList();
+	}
+
+	private static Stream<FabricModJson> getMods(Project project, Map<String, List<FabricModJson>> fmjCache, Stream<RemapConfigurationSettings> stream) {
+		return stream.flatMap(resolveArtifacts(project, true))
+				.map(modFromZip(fmjCache))
+				.filter(Objects::nonNull);
+	}
+
+	private static Set<String> getModIds(Project project, Map<String, List<FabricModJson>> fmjCache, Stream<RemapConfigurationSettings> stream) {
+		return getMods(project, fmjCache, stream)
+				.map(FabricModJson::getId)
+				.collect(Collectors.toSet());
 	}
 
 	private static Function<Path, @Nullable FabricModJson> modFromZip(Map<String, List<FabricModJson>> fmjCache) {
@@ -190,6 +227,22 @@ public record SpecContextImpl(List<FabricModJson> modDependencies, List<FabricMo
 
 	@Override
 	public List<FabricModJson> modDependenciesCompileRuntime() {
-		return compileRuntimeMods;
+		return compileRuntimeMods.stream()
+				.map(ModHolder::mod)
+				.toList();
+	}
+
+	@Override
+	public List<FabricModJson> modDependenciesCompileRuntimeClient() {
+		return compileRuntimeMods.stream()
+				.filter(modHolder -> !modHolder.common())
+				.map(ModHolder::mod)
+				.toList();
+	}
+
+	private record ModHolder(FabricModJson mod, boolean common) {
+		ModHolder(FabricModJson mod) {
+			this(mod, true);
+		}
 	}
 }

src/main/java/net/fabricmc/loom/configuration/providers/mappings/GradleMappingContext.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2018-2021 FabricMC
+ * Copyright (c) 2018-2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -41,6 +41,7 @@ import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.mappings.layered.MappingContext;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftProvider;
 import net.fabricmc.loom.util.download.DownloadBuilder;
+import net.fabricmc.loom.util.gradle.GradleUtils;
 import net.fabricmc.loom.util.service.ScopedServiceFactory;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;
 
@@ -85,6 +86,11 @@ public class GradleMappingContext implements MappingContext {
 		};
 	}
 
+	@Override
+	public boolean isUsingIntermediateMappings() {
+		return !(extension.getIntermediateMappingsProvider() instanceof NoOpIntermediateMappingsProvider);
+	}
+
 	@Override
 	public MinecraftProvider minecraftProvider() {
 		return extension.getMinecraftProvider();
@@ -110,6 +116,11 @@ public class GradleMappingContext implements MappingContext {
 		return extension.refreshDeps();
 	}
 
+	@Override
+	public boolean hasProperty(String property) {
+		return GradleUtils.getBooleanProperty(project, property);
+	}
+
 	public Project getProject() {
 		return project;
 	}

src/main/java/net/fabricmc/loom/configuration/providers/mappings/IntermediaryMappingsProvider.java

@@ -25,7 +25,6 @@
 package net.fabricmc.loom.configuration.providers.mappings;
 
 import java.io.IOException;
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
@@ -115,7 +114,7 @@ public abstract class IntermediaryMappingsProvider extends IntermediateMappingsP
 		if (!LoomGradleExtensionApiImpl.DEFAULT_INTERMEDIARY_URL.equals(urlRaw)) {
 			final String url = getIntermediaryUrl().get().formatted(encodedMcVersion);
 
-			return NAME + "-" + Checksum.sha1Hex(url.getBytes(StandardCharsets.UTF_8));
+			return NAME + "-" + Checksum.of(url).sha1().hex();
 		}
 
 		return NAME;

src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsFactory.java

@@ -47,6 +47,7 @@ import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.ConfigContext;
 import net.fabricmc.loom.configuration.mods.dependency.LocalMavenHelper;
 import net.fabricmc.loom.configuration.providers.mappings.extras.unpick.UnpickLayer;
+import net.fabricmc.loom.configuration.providers.mappings.unpick.UnpickMetadata;
 import net.fabricmc.loom.configuration.providers.mappings.utils.AddConstructorMappingVisitor;
 import net.fabricmc.loom.util.ZipUtils;
 import net.fabricmc.mappingio.adapter.MappingDstNsReorder;
@@ -148,7 +149,7 @@ public record LayeredMappingsFactory(LayeredMappingSpec spec) {
 			return;
 		}
 
-		ZipUtils.add(mappingsFile, "extras/definitions.unpick", unpickData.definitions());
+		ZipUtils.add(mappingsFile, UnpickMetadata.UNPICK_DEFINITIONS_PATH, unpickData.definitions());
-		ZipUtils.add(mappingsFile, "extras/unpick.json", unpickData.metadata().asJson());
+		ZipUtils.add(mappingsFile, UnpickMetadata.UNPICK_METADATA_PATH, unpickData.rawMetadata());
 	}
 }

src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingConfiguration.java

@@ -45,14 +45,12 @@ import java.util.Objects;
 
 import com.google.common.base.Stopwatch;
 import com.google.common.base.Supplier;
-import com.google.gson.JsonObject;
 import dev.architectury.loom.util.MappingOption;
 import org.apache.tools.ant.util.StringUtils;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.provider.Provider;
 import org.jetbrains.annotations.Nullable;
-import org.objectweb.asm.Opcodes;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -64,6 +62,7 @@ import net.fabricmc.loom.configuration.providers.forge.ForgeMigratedMappingConfi
 import net.fabricmc.loom.configuration.providers.forge.SrgProvider;
 import net.fabricmc.loom.configuration.providers.mappings.tiny.MappingsMerger;
 import net.fabricmc.loom.configuration.providers.mappings.tiny.TinyJarInfo;
+import net.fabricmc.loom.configuration.providers.mappings.unpick.UnpickMetadata;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftProvider;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.DeletingFileVisitor;
@@ -102,7 +101,7 @@ public class MappingConfiguration {
 	private final Map<MappingOption, Supplier<Path>> mappingOptions;
 	private final Path unpickDefinitions;
 
-	private boolean hasUnpickDefinitions;
+	@Nullable
 	private UnpickMetadata unpickMetadata;
 	private Map<String, String> signatureFixes;
 
@@ -250,15 +249,19 @@ public class MappingConfiguration {
 	}
 
 	public void applyToProject(Project project, DependencyInfo dependency) throws IOException {
-		if (hasUnpickDefinitions()) {
+		if (unpickMetadata != null) {
-			String notation = String.format("%s:%s:%s:constants",
+			if (unpickMetadata.hasConstants()) {
-					dependency.getDependency().getGroup(),
+				String notation = switch (unpickMetadata) {
-					dependency.getDependency().getName(),
+				case UnpickMetadata.V1 v1 -> String.format("%s:%s:%s:constants",
-					dependency.getDependency().getVersion()
+						dependency.getDependency().getGroup(),
-			);
+						dependency.getDependency().getName(),
+						dependency.getDependency().getVersion()
+				);
+				case UnpickMetadata.V2 v2 -> Objects.requireNonNull(v2.constants());
+				};
 
-			project.getDependencies().add(Constants.Configurations.MAPPING_CONSTANTS, notation);
+				project.getDependencies().add(Constants.Configurations.MAPPING_CONSTANTS, notation);
-			populateUnpickClasspath(project);
+			}
 		}
 
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
@@ -441,8 +444,8 @@ public class MappingConfiguration {
 	}
 
 	private void extractUnpickDefinitions(FileSystem jar) throws IOException {
-		Path unpickPath = jar.getPath("extras/definitions.unpick");
+		Path unpickPath = jar.getPath(UnpickMetadata.UNPICK_DEFINITIONS_PATH);
-		Path unpickMetadataPath = jar.getPath("extras/unpick.json");
+		Path unpickMetadataPath = jar.getPath(UnpickMetadata.UNPICK_METADATA_PATH);
 
 		if (!Files.exists(unpickPath) || !Files.exists(unpickMetadataPath)) {
 			return;
@@ -450,8 +453,7 @@ public class MappingConfiguration {
 
 		Files.copy(unpickPath, unpickDefinitions, StandardCopyOption.REPLACE_EXISTING);
 
-		unpickMetadata = parseUnpickMetadata(unpickMetadataPath);
+		unpickMetadata = UnpickMetadata.parse(unpickMetadataPath);
-		hasUnpickDefinitions = true;
 	}
 
 	private void extractSignatureFixes(FileSystem jar) throws IOException {
@@ -467,40 +469,6 @@ public class MappingConfiguration {
 		}
 	}
 
-	private UnpickMetadata parseUnpickMetadata(Path input) throws IOException {
-		JsonObject jsonObject = LoomGradlePlugin.GSON.fromJson(Files.readString(input, StandardCharsets.UTF_8), JsonObject.class);
-
-		if (!jsonObject.has("version") || jsonObject.get("version").getAsInt() != 1) {
-			throw new UnsupportedOperationException("Unsupported unpick version");
-		}
-
-		return new UnpickMetadata(
-				jsonObject.get("unpickGroup").getAsString(),
-				jsonObject.get("unpickVersion").getAsString()
-		);
-	}
-
-	private void populateUnpickClasspath(Project project) {
-		String unpickCliName = "unpick-cli";
-		project.getDependencies().add(Constants.Configurations.UNPICK_CLASSPATH,
-				String.format("%s:%s:%s", unpickMetadata.unpickGroup, unpickCliName, unpickMetadata.unpickVersion)
-		);
-
-		// Unpick ships with a slightly older version of asm, ensure it runs with at least the same version as loom.
-		String[] asmDeps = new String[] {
-				"org.ow2.asm:asm:%s",
-				"org.ow2.asm:asm-tree:%s",
-				"org.ow2.asm:asm-commons:%s",
-				"org.ow2.asm:asm-util:%s"
-		};
-
-		for (String asm : asmDeps) {
-			project.getDependencies().add(Constants.Configurations.UNPICK_CLASSPATH,
-					asm.formatted(Opcodes.class.getPackage().getImplementationVersion())
-			);
-		}
-	}
-
 	private void suggestFieldNames(Path inputJar, Path oldMappings, Path newMappings) {
 		Command command = new CommandProposeFieldNames();
 		runCommand(command, inputJar.toFile().getAbsolutePath(),
@@ -554,7 +522,11 @@ public class MappingConfiguration {
 	}
 
 	public boolean hasUnpickDefinitions() {
-		return hasUnpickDefinitions;
+		return unpickMetadata != null;
+	}
+
+	public UnpickMetadata getUnpickMetadata() {
+		return Objects.requireNonNull(unpickMetadata, "Unpick metadata is not available");
 	}
 
 	@Nullable
@@ -562,10 +534,6 @@ public class MappingConfiguration {
 		return signatureFixes;
 	}
 
-	public String getBuildServiceName(String name, String from, String to) {
-		return "%s:%s:%s>%S".formatted(name, mappingsIdentifier(), from, to);
-	}
-
 	public Path getReplacedTarget(LoomGradleExtension loom, String namespace) {
 		if (namespace.equals("intermediary")) return getPlatformMappingFile(loom);
 
@@ -602,7 +570,4 @@ public class MappingConfiguration {
 			return tinyMappings;
 		}
 	}
-
-	public record UnpickMetadata(String unpickGroup, String unpickVersion) {
-	}
 }

src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/unpick/UnpickLayer.java

@@ -25,37 +25,24 @@
 package net.fabricmc.loom.configuration.providers.mappings.extras.unpick;
 
 import java.io.IOException;
-import java.io.Reader;
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
 
-import net.fabricmc.loom.LoomGradlePlugin;
+import net.fabricmc.loom.configuration.providers.mappings.unpick.UnpickMetadata;
 
 @ApiStatus.Experimental
 public interface UnpickLayer {
 	@Nullable
 	UnpickData getUnpickData() throws IOException;
 
-	record UnpickData(Metadata metadata, byte[] definitions) {
+	record UnpickData(UnpickMetadata metadata, byte[] rawMetadata, byte[] definitions) {
 		public static UnpickData read(Path metadataPath, Path definitionPath) throws IOException {
 			final byte[] definitions = Files.readAllBytes(definitionPath);
-			final Metadata metadata;
+			final byte[] metadata = Files.readAllBytes(metadataPath);
-
+			return new UnpickData(UnpickMetadata.parse(metadataPath), metadata, definitions);
-			try (Reader reader = Files.newBufferedReader(metadataPath, StandardCharsets.UTF_8)) {
-				metadata = LoomGradlePlugin.GSON.fromJson(reader, Metadata.class);
-			}
-
-			return new UnpickData(metadata, definitions);
-		}
-
-		public record Metadata(int version, String unpickGroup, String unpickVersion) {
-			public String asJson() {
-				return LoomGradlePlugin.GSON.toJson(this);
-			}
 		}
 	}
 }

src/main/java/net/fabricmc/loom/configuration/providers/mappings/file/FileMappingsLayer.java

@@ -36,6 +36,7 @@ import net.fabricmc.loom.api.mappings.layered.MappingLayer;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.providers.mappings.extras.unpick.UnpickLayer;
 import net.fabricmc.loom.configuration.providers.mappings.intermediary.IntermediaryMappingLayer;
+import net.fabricmc.loom.configuration.providers.mappings.unpick.UnpickMetadata;
 import net.fabricmc.loom.util.FileSystemUtil;
 import net.fabricmc.loom.util.ZipUtils;
 import net.fabricmc.mappingio.MappingReader;
@@ -52,9 +53,6 @@ public record FileMappingsLayer(
 		boolean unpick,
 		String mergeNamespace
 ) implements MappingLayer, UnpickLayer {
-	private static final String UNPICK_METADATA_PATH = "extras/unpick.json";
-	private static final String UNPICK_DEFINITIONS_PATH = "extras/definitions.unpick";
-
 	@Override
 	public void visit(MappingVisitor mappingVisitor) throws IOException {
 		// Bare file
@@ -102,8 +100,8 @@ public record FileMappingsLayer(
 		}
 
 		try (FileSystemUtil.Delegate fileSystem = FileSystemUtil.getJarFileSystem(path)) {
-			final Path unpickMetadata = fileSystem.get().getPath(UNPICK_METADATA_PATH);
+			final Path unpickMetadata = fileSystem.get().getPath(UnpickMetadata.UNPICK_METADATA_PATH);
-			final Path unpickDefinitions = fileSystem.get().getPath(UNPICK_DEFINITIONS_PATH);
+			final Path unpickDefinitions = fileSystem.get().getPath(UnpickMetadata.UNPICK_DEFINITIONS_PATH);
 
 			if (!Files.exists(unpickMetadata)) {
 				// No unpick in this zip

src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingLayer.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2021 FabricMC
+ * Copyright (c) 2021-2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,9 +30,11 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
+import java.util.function.Supplier;
 import java.util.regex.Pattern;
 
 import org.gradle.api.logging.Logger;
+import org.jetbrains.annotations.Nullable;
 
 import net.fabricmc.loom.api.mappings.layered.MappingLayer;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
@@ -41,11 +43,14 @@ import net.fabricmc.loom.configuration.providers.mappings.utils.DstNameFilterMap
 import net.fabricmc.mappingio.MappingVisitor;
 import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
 import net.fabricmc.mappingio.format.proguard.ProGuardFileReader;
+import net.fabricmc.mappingio.tree.MemoryMappingTree;
 
 public record MojangMappingLayer(String minecraftVersion,
 									Path clientMappings,
 									Path serverMappings,
 									boolean nameSyntheticMembers,
+									boolean dropNoneIntermediaryRoots,
+									@Nullable Supplier<MemoryMappingTree> intermediarySupplier,
 									Logger logger,
 									MojangMappingsSpec.SilenceLicenseOption silenceLicense) implements MappingLayer {
 	private static final Pattern SYNTHETIC_NAME_PATTERN = Pattern.compile("^(access|this|val\\$this|lambda\\$.*)\\$[0-9]+$");
@@ -55,12 +60,41 @@ public record MojangMappingLayer(String minecraftVersion,
 			printMappingsLicense(clientMappings);
 		}
 
+		if (!dropNoneIntermediaryRoots) {
+			logger().debug("Not attempting to drop none intermediary roots");
+
+			readMappings(mappingVisitor);
+			return;
+		}
+
+		logger().info("Attempting to drop none intermediary roots");
+
+		if (intermediarySupplier == null) {
+			// Using no-op intermediary mappings
+			readMappings(mappingVisitor);
+			return;
+		}
+
+		// Create a mapping tree with src: official dst: named, intermediary
+		MemoryMappingTree mappingTree = new MemoryMappingTree();
+		intermediarySupplier.get().accept(mappingTree);
+		readMappings(mappingTree);
+
+		// The following code first switches the src namespace to intermediary dropping any entries that don't have an intermediary name
+		// This removes any none root methods before switching it back to official
+		var officialSwitch = new MappingSourceNsSwitch(mappingVisitor, getSourceNamespace().toString(), false);
+		var intermediarySwitch = new MappingSourceNsSwitch(officialSwitch, MappingsNamespace.INTERMEDIARY.toString(), true);
+		mappingTree.accept(intermediarySwitch);
+	}
+
+	private void readMappings(MappingVisitor mappingVisitor) throws IOException {
 		// Filter out field names matching the pattern
-		DstNameFilterMappingVisitor nameFilter = new DstNameFilterMappingVisitor(mappingVisitor, SYNTHETIC_NAME_PATTERN);
+		var nameFilter = new DstNameFilterMappingVisitor(mappingVisitor, SYNTHETIC_NAME_PATTERN);
 
 		// Make official the source namespace
-		MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(nameSyntheticMembers() ? mappingVisitor : nameFilter, MappingsNamespace.OFFICIAL.toString());
+		var nsSwitch = new MappingSourceNsSwitch(nameSyntheticMembers() ? mappingVisitor : nameFilter, MappingsNamespace.OFFICIAL.toString());
 
+		// Read both server and client mappings
 		try (BufferedReader clientBufferedReader = Files.newBufferedReader(clientMappings, StandardCharsets.UTF_8);
 				BufferedReader serverBufferedReader = Files.newBufferedReader(serverMappings, StandardCharsets.UTF_8)) {
 			ProGuardFileReader.read(clientBufferedReader, MappingsNamespace.NAMED.toString(), MappingsNamespace.OFFICIAL.toString(), nsSwitch);

src/main/java/net/fabricmc/loom/configuration/providers/mappings/mojmap/MojangMappingsSpec.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2016-2021 FabricMC
+ * Copyright (c) 2016-2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -30,6 +30,7 @@ import java.nio.file.Path;
 import net.fabricmc.loom.api.mappings.layered.MappingContext;
 import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
 import net.fabricmc.loom.configuration.providers.minecraft.MinecraftVersionMeta;
+import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.download.DownloadException;
 
 public record MojangMappingsSpec(SilenceLicenseOption silenceLicense, boolean nameSyntheticMembers) implements MappingsSpec<MojangMappingLayer> {
@@ -103,6 +104,8 @@ public record MojangMappingsSpec(SilenceLicenseOption silenceLicense, boolean na
 				clientMappings,
 				serverMappings,
 				nameSyntheticMembers(),
+				context.hasProperty(Constants.Properties.DROP_NON_INTERMEDIATE_ROOT_METHODS),
+				context.isUsingIntermediateMappings() ? context.intermediaryTree() : null,
 				context.getLogger(),
 				silenceLicense()
 		);

src/main/java/net/fabricmc/loom/configuration/providers/mappings/unpick/UnpickMetadata.java

@@ -0,0 +1,105 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.unpick;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import com.google.gson.JsonObject;
+import org.jetbrains.annotations.Nullable;
+
+import net.fabricmc.loom.LoomGradlePlugin;
+
+public sealed interface UnpickMetadata permits UnpickMetadata.V1, UnpickMetadata.V2 {
+	String UNPICK_METADATA_PATH = "extras/unpick.json";
+	String UNPICK_DEFINITIONS_PATH = "extras/definitions.unpick";
+
+	boolean hasConstants();
+
+	/**
+	 * @param unpickGroup Deprecated, always uses the version of unpick loom depends on.
+	 * @param unpickVersion Deprecated, always uses the version of unpick loom depends on.
+	 */
+	record V1(@Deprecated String unpickGroup, @Deprecated String unpickVersion) implements UnpickMetadata {
+		@Override
+		public boolean hasConstants() {
+			return true;
+		}
+	}
+
+	/**
+	 * Unpick metadata v2.
+	 *
+	 * @param namespace the mapping namespace of the unpick definitions
+	 * @param constants An optional maven notation of the constants jar.
+	 */
+	record V2(String namespace, @Nullable String constants) implements UnpickMetadata {
+		@Override
+		public boolean hasConstants() {
+			return constants != null;
+		}
+	}
+
+	static UnpickMetadata parse(Path path) throws IOException {
+		JsonObject jsonObject = LoomGradlePlugin.GSON.fromJson(Files.readString(path, StandardCharsets.UTF_8), JsonObject.class);
+
+		if (!jsonObject.has("version")) {
+			throw new UnsupportedOperationException("Missing unpick metadata version");
+		}
+
+		int version = jsonObject.get("version").getAsInt();
+
+		switch (version) {
+		case 1 -> {
+			return new V1(
+				getString(jsonObject, "unpickGroup"),
+				getString(jsonObject, "unpickVersion")
+			);
+		}
+		case 2 -> {
+			return new V2(
+				getString(jsonObject, "namespace"),
+				getOptionalString(jsonObject, "constants")
+			);
+		}
+		default -> throw new UnsupportedOperationException("Unsupported unpick metadata version: %s. Please update loom.".formatted(version));
+		}
+	}
+
+	private static String getString(JsonObject jsonObject, String key) {
+		if (!jsonObject.has(key)) {
+			throw new UnsupportedOperationException("Missing unpick metadata %s".formatted(key));
+		}
+
+		return jsonObject.get(key).getAsString();
+	}
+
+	@Nullable
+	private static String getOptionalString(JsonObject jsonObject, String key) {
+		return jsonObject.has(key) ? jsonObject.get(key).getAsString() : null;
+	}
+}

src/main/java/net/fabricmc/loom/configuration/providers/mappings/utils/LocalFileSpec.java

@@ -29,8 +29,8 @@ import java.nio.file.Path;
 import java.util.Arrays;
 import java.util.Objects;
 
-import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
 import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
 import net.fabricmc.loom.util.Checksum;
 
 public class LocalFileSpec implements FileSpec {
@@ -48,7 +48,7 @@ public class LocalFileSpec implements FileSpec {
 		}
 
 		// Use the file hash as part of the spec, this means if the input file changes the mappings will be re-generated.
-		return Objects.hash(Arrays.hashCode(Checksum.sha256(file)), file.getAbsolutePath());
+		return Objects.hash(Arrays.hashCode(Checksum.of(file).sha256().digest()), file.getAbsolutePath());
 	}
 
 	@Override

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MergedMinecraftProvider.java

@@ -92,7 +92,6 @@ public class MergedMinecraftProvider extends MinecraftProvider {
 		File minecraftServerJar = getMinecraftServerJar();
 
 		if (getServerBundleMetadata() != null) {
-			extractBundledServerJar();
 			minecraftServerJar = getMinecraftExtractedServerJar();
 		}
 

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftJarSplitter.java

@@ -37,8 +37,6 @@ import java.util.jar.Attributes;
 import java.util.jar.Manifest;
 import java.util.stream.Stream;
 
-import com.google.common.collect.Sets;
-
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.FileSystemUtil;
 
@@ -79,7 +77,7 @@ public class MinecraftJarSplitter implements AutoCloseable {
 	}
 
 	public static Set<String> getJarEntries(Path input) throws IOException {
-		Set<String> entries = Sets.newHashSet();
+		Set<String> entries = new HashSet<>();
 
 		try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(input);
 				Stream<Path> walk = Files.walk(fs.get().getPath("/"))) {
@@ -154,17 +152,17 @@ public class MinecraftJarSplitter implements AutoCloseable {
 			this.clientEntries = clientEntries;
 			this.serverEntries = serverEntries;
 
-			this.commonEntries = Sets.newHashSet(clientEntries);
+			this.commonEntries = new HashSet<>(clientEntries);
 			this.commonEntries.retainAll(serverEntries);
 			this.commonEntries.addAll(sharedEntries);
 			this.commonEntries.removeAll(forcedClientEntries);
 
-			this.clientOnlyEntries = Sets.newHashSet(clientEntries);
+			this.clientOnlyEntries = new HashSet<>(clientEntries);
 			this.clientOnlyEntries.removeAll(serverEntries);
 			this.clientOnlyEntries.addAll(sharedEntries);
 			this.clientOnlyEntries.addAll(forcedClientEntries);
 
-			this.serverOnlyEntries = Sets.newHashSet(serverEntries);
+			this.serverOnlyEntries = new HashSet<>(serverEntries);
 			this.serverOnlyEntries.removeAll(clientEntries);
 		}
 	}

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftLibraryProvider.java

@@ -31,6 +31,7 @@ import java.util.List;
 
 import org.gradle.api.JavaVersion;
 import org.gradle.api.Project;
+import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.artifacts.ExternalModuleDependency;
 import org.gradle.api.artifacts.ModuleDependency;
@@ -94,6 +95,10 @@ public class MinecraftLibraryProvider {
 		if (provideServer) {
 			provideServerLibraries();
 		}
+
+		if (extension.isCollectingDependencyVerificationMetadata()) {
+			resolveAllLibraries();
+		}
 	}
 
 	private void provideClientLibraries() {
@@ -114,6 +119,22 @@ public class MinecraftLibraryProvider {
 		processLibraries.forEach(this::applyServerLibrary);
 	}
 
+	/**
+	 * When Gradle is writing dependency verification metadata, we need to resolve all libraries across all platforms,
+	 * to ensure that they are captured.
+	 */
+	private void resolveAllLibraries() {
+		project.getLogger().info("Resolving all libraries for dependency verification metadata generation");
+
+		final List<Library> libraries = MinecraftLibraryHelper.getAllLibraries(minecraftProvider.getVersionInfo());
+		Configuration detachedConfiguration = project.getConfigurations().detachedConfiguration(
+				libraries.stream()
+					.map(library -> project.getDependencies().create(library.mavenNotation()))
+					.toArray(Dependency[]::new)
+		);
+		detachedConfiguration.getFiles();
+	}
+
 	private List<Library> processLibraries(List<Library> libraries) {
 		final LibraryContext libraryContext = new LibraryContext(minecraftProvider.getVersionInfo(), getTargetRuntimeJavaVersion());
 		return processorManager.processLibraries(libraries, libraryContext);

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftProvider.java

@@ -29,6 +29,7 @@ import java.io.IOException;
 import java.nio.file.Path;
 import java.util.List;
 import java.util.Objects;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import com.google.common.base.Preconditions;
 import org.gradle.api.JavaVersion;
@@ -41,9 +42,12 @@ import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.ConfigContext;
 import net.fabricmc.loom.configuration.providers.BundleMetadata;
+import net.fabricmc.loom.configuration.providers.minecraft.verify.MinecraftJarVerification;
+import net.fabricmc.loom.configuration.providers.minecraft.verify.SignatureVerificationFailure;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.download.DownloadExecutor;
 import net.fabricmc.loom.util.download.GradleDownloadProgressListener;
+import net.fabricmc.loom.util.gradle.GradleUtils;
 import net.fabricmc.loom.util.gradle.ProgressGroup;
 
 public abstract class MinecraftProvider {
@@ -93,10 +97,18 @@ public abstract class MinecraftProvider {
 			}
 		}
 
-		downloadJars();
+		boolean didDownload = downloadJars();
 
 		if (provideServer()) {
 			serverBundleMetadata = BundleMetadata.fromJar(minecraftServerJar.toPath());
+
+			if (serverBundleMetadata != null) {
+				extractBundledServerJar();
+			}
+		}
+
+		if (didDownload) {
+			verifyJars();
 		}
 
 		final MinecraftLibraryProvider libraryProvider = new MinecraftLibraryProvider(this, configContext.project());
@@ -114,7 +126,35 @@ public abstract class MinecraftProvider {
 		}
 	}
 
-	private void downloadJars() throws IOException {
+	private void verifyJars() throws IOException, SignatureVerificationFailure {
+		if (GradleUtils.getBooleanProperty(getProject(), Constants.Properties.DISABLE_MINECRAFT_VERIFICATION)) {
+			LOGGER.info("Skipping Minecraft jar verification!");
+			return;
+		}
+
+		LOGGER.info("Verifying Minecraft jars");
+
+		MinecraftJarVerification verification = getProject().getObjects().newInstance(MinecraftJarVerification.class, minecraftVersion());
+
+		if (provideClient()) {
+			verification.verifyClientJar(minecraftClientJar.toPath());
+		}
+
+		if (provideServer()) {
+			if (serverBundleMetadata == null) {
+				verification.verifyServerJar(minecraftServerJar.toPath());
+			} else {
+				verification.verifyServerJar(getMinecraftExtractedServerJar().toPath());
+			}
+		}
+
+		LOGGER.info("Jar verification complete");
+	}
+
+	// Returns true when a file was downloaded
+	private boolean downloadJars() throws IOException {
+		AtomicBoolean didDownload = new AtomicBoolean(false);
+
 		try (ProgressGroup progressGroup = new ProgressGroup(getProject(), "Download Minecraft jars");
 				DownloadExecutor executor = new DownloadExecutor(2)) {
 			if (provideClient()) {
@@ -122,7 +162,12 @@ public abstract class MinecraftProvider {
 				getExtension().download(client.url())
 						.sha1(client.sha1())
 						.progress(new GradleDownloadProgressListener("Minecraft client", progressGroup::createProgressLogger))
-						.downloadPathAsync(minecraftClientJar.toPath(), executor);
+						.downloadPathAsync(minecraftClientJar.toPath(), executor)
+						.thenAccept(downloadResult -> {
+							if (downloadResult.didDownload()) {
+								didDownload.set(true);
+							}
+						});
 			}
 
 			if (provideServer()) {
@@ -130,9 +175,22 @@ public abstract class MinecraftProvider {
 				getExtension().download(server.url())
 						.sha1(server.sha1())
 						.progress(new GradleDownloadProgressListener("Minecraft server", progressGroup::createProgressLogger))
-						.downloadPathAsync(minecraftServerJar.toPath(), executor);
+						.downloadPathAsync(minecraftServerJar.toPath(), executor)
+						.thenAccept(downloadResult -> {
+							if (downloadResult.didDownload()) {
+								didDownload.set(true);
+							}
+						});
 			}
 		}
+
+		if (didDownload.get()) {
+			LOGGER.info("Downloaded new Minecraft jars");
+			return true;
+		}
+
+		LOGGER.info("Using cached Minecraft jars");
+		return false;
 	}
 
 	public final void extractBundledServerJar() throws IOException {

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/SingleJarMinecraftProvider.java

@@ -143,14 +143,13 @@ public abstract class SingleJarMinecraftProvider extends MinecraftProvider {
 		}
 
 		@Override
-		public Path getInputJar(SingleJarMinecraftProvider provider) throws Exception {
+		public Path getInputJar(SingleJarMinecraftProvider provider) {
 			BundleMetadata serverBundleMetadata = provider.getServerBundleMetadata();
 
 			if (serverBundleMetadata == null) {
 				return provider.getMinecraftServerJar().toPath();
 			}
 
-			provider.extractBundledServerJar();
 			return provider.getMinecraftExtractedServerJar().toPath();
 		}
 

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/SplitMinecraftProvider.java

@@ -74,8 +74,6 @@ public final class SplitMinecraftProvider extends MinecraftProvider {
 			throw new UnsupportedOperationException("Only Minecraft versions using a bundled server jar can be split, please use a merged jar setup for this version of minecraft");
 		}
 
-		extractBundledServerJar();
-
 		final Path clientJar = getMinecraftClientJar().toPath();
 		final Path serverJar = getMinecraftExtractedServerJar().toPath();
 

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/library/MinecraftLibraryHelper.java

@@ -27,6 +27,7 @@ package net.fabricmc.loom.configuration.providers.minecraft.library;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -72,6 +73,35 @@ public class MinecraftLibraryHelper {
 		return Collections.unmodifiableList(libraries);
 	}
 
+	public static List<Library> getAllLibraries(MinecraftVersionMeta versionMeta) {
+		var libraries = new ArrayList<Library>();
+
+		for (MinecraftVersionMeta.Library library : versionMeta.libraries()) {
+			if (library.artifact() != null) {
+				Library mavenLib = Library.fromMaven(library.name(), Library.Target.COMPILE);
+
+				// Versions that have the natives on the classpath, attempt to target them as natives.
+				if (mavenLib.classifier() != null && mavenLib.classifier().startsWith("natives-")) {
+					mavenLib = mavenLib.withTarget(Library.Target.NATIVES);
+				}
+
+				libraries.add(mavenLib);
+			}
+
+			Map<String, MinecraftVersionMeta.Download> classifiers = library.downloads().classifiers();
+
+			if (classifiers == null) {
+				continue;
+			}
+
+			for (MinecraftVersionMeta.Download download : classifiers.values()) {
+				libraries.add(downloadToLibrary(download));
+			}
+		}
+
+		return Collections.unmodifiableList(libraries);
+	}
+
 	private static Library downloadToLibrary(MinecraftVersionMeta.Download download) {
 		final String path = download.path();
 		final Matcher matcher = NATIVES_PATTERN.matcher(path);

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/verify/CertificateChain.java

@@ -0,0 +1,194 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.minecraft.verify;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.security.cert.CertificateException;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * A node in the certificate chain.
+ */
+public interface CertificateChain {
+	/**
+	 * The certificate itself.
+	 */
+	X509Certificate certificate();
+
+	/**
+	 * The issuer of this certificate, or null if this is a root certificate.
+	 */
+	@Nullable CertificateChain issuer();
+
+	/**
+	 * The children of this certificate, or an empty list if this is a leaf certificate.
+	 */
+	List<CertificateChain> children();
+
+	/**
+	 * Verify that this certificate chain matches exactly with another one.
+	 * @param other the other certificate chain
+	 */
+	void verifyChainMatches(CertificateChain other) throws SignatureVerificationFailure;
+
+	/**
+	 * Recursively visit all certificates in the chain, including this one.
+	 */
+	static void visitAll(CertificateChain chain, CertificateConsumer consumer) throws SignatureVerificationFailure {
+		consumer.accept(chain.certificate());
+
+		for (CertificateChain child : chain.children()) {
+			visitAll(child, consumer);
+		}
+	}
+
+	/**
+	 * Load certificate chain from the classpath, returning the root certificate.
+	 */
+	static CertificateChain getRoot(String name) throws IOException {
+		try (InputStream is = JarVerifier.class.getClassLoader().getResourceAsStream("certs/" + name + ".cer")) {
+			CertificateFactory cf = CertificateFactory.getInstance("X.509");
+			Collection<X509Certificate> certificates = cf.generateCertificates(is).stream()
+					.map(c -> (X509Certificate) c)
+					.toList();
+			return getRoot(certificates);
+		} catch (CertificateException e) {
+			throw new RuntimeException("Failed to load certificate: " + name, e);
+		}
+	}
+
+	/**
+	 * Takes an unordered collection of certificates and builds a tree structure.
+	 */
+	static CertificateChain getRoot(Collection<X509Certificate> certificates) {
+		Map<String, Impl> certificateNodes = new HashMap<>();
+
+		for (X509Certificate certificate : certificates) {
+			Impl node = new Impl();
+			node.certificate = certificate;
+			certificateNodes.put(certificate.getSubjectX500Principal().getName(), node);
+		}
+
+		for (X509Certificate certificate : certificates) {
+			String subject = certificate.getSubjectX500Principal().getName();
+			String issuer = certificate.getIssuerX500Principal().getName();
+
+			if (subject.equals(issuer)) {
+				continue; // self-signed
+			}
+
+			Impl parent = certificateNodes.get(issuer);
+			Impl self = certificateNodes.get(subject);
+
+			if (parent == self) {
+				throw new IllegalStateException("Certificate " + subject + " is its own issuer");
+			}
+
+			if (parent == null) {
+				throw new IllegalStateException("Certificate " + subject + " defines issuer " + issuer + " which is not in the chain");
+			}
+
+			parent.children.add(self);
+			self.issuer = parent;
+		}
+
+		List<Impl> roots = certificateNodes.values()
+				.stream()
+				.filter(node -> node.issuer == null)
+				.toList();
+
+		if (roots.size() != 1) {
+			throw new IllegalStateException("Expected exactly one root certificate, but found " + roots.size());
+		}
+
+		return roots.get(0);
+	}
+
+	@FunctionalInterface
+	interface CertificateConsumer {
+		void accept(X509Certificate certificate) throws SignatureVerificationFailure;
+	}
+
+	class Impl implements CertificateChain {
+		X509Certificate certificate;
+		@Nullable CertificateChain.Impl issuer;
+		List<CertificateChain> children = new ArrayList<>();
+
+		private Impl() {
+		}
+
+		@Override
+		public X509Certificate certificate() {
+			return certificate;
+		}
+
+		@Override
+		public @Nullable CertificateChain issuer() {
+			return issuer;
+		}
+
+		@Override
+		public List<CertificateChain> children() {
+			return children;
+		}
+
+		@Override
+		public void verifyChainMatches(CertificateChain other) throws SignatureVerificationFailure {
+			if (!this.certificate().equals(other.certificate())) {
+				throw new SignatureVerificationFailure("Certificate mismatch: " + this + " != " + other);
+			}
+
+			if (this.children().size() != other.children().size()) {
+				throw new SignatureVerificationFailure("Certificate mismatch: " + this + " has " + this.children().size() + " children, but " + other + " has " + other.children().size());
+			}
+
+			if (this.children.isEmpty()) {
+				// Fine, leaf certificate
+				return;
+			}
+
+			if (this.children.size() != 1) {
+				// TODO support this, not needed currently
+				throw new UnsupportedOperationException("Validating Certificate chain with multiple children is not supported");
+			}
+
+			this.children.get(0).verifyChainMatches(other.children().get(0));
+		}
+
+		@Override
+		public String toString() {
+			return certificate.getSubjectX500Principal().getName();
+		}
+	}
+}

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/verify/CertificateRevocationList.java

@@ -0,0 +1,122 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.minecraft.verify;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.security.cert.CRLException;
+import java.security.cert.CertificateException;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509CRL;
+import java.security.cert.X509Certificate;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import org.gradle.api.Project;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.util.download.DownloadException;
+
+public record CertificateRevocationList(Collection<X509CRL> crls, boolean downloadFailure) {
+	/**
+	 * Hardcoded CRLs for Mojang's certificate, we don't want to add a large dependency just to parse this each time.
+	 */
+	public static final List<String> CSC3_2010 = List.of(
+			"http://crl.verisign.com/pca3-g5.crl",
+			"http://crl.verisign.com/pca3.crl",
+			"http://csc3-2010-crl.verisign.com/CSC3-2010.crl"
+	);
+
+	private static final Logger LOGGER = LoggerFactory.getLogger(CertificateRevocationList.class);
+
+	/**
+	 * Attempt to download the CRL from the given URL, if we fail to get it its not the end of the world.
+	 */
+	public static CertificateRevocationList create(Project project, List<String> urls) throws IOException {
+		List<X509CRL> crls = new ArrayList<>();
+
+		boolean downloadFailure = false;
+
+		for (String url : urls) {
+			try {
+				crls.add(download(project, url));
+			} catch (DownloadException e) {
+				LOGGER.info("Failed to download CRL from {}: {}", url, e.getMessage());
+				LOGGER.info("Loom will not be able to verify the integrity of the minecraft jar signature");
+				downloadFailure = true;
+			}
+		}
+
+		return new CertificateRevocationList(crls, downloadFailure);
+	}
+
+	static X509CRL download(Project project, String url) throws IOException {
+		final LoomGradleExtension extension = LoomGradleExtension.get(project);
+		final String name = url.substring(url.lastIndexOf('/') + 1);
+		final Path path = extension.getFiles().getUserCache().toPath()
+				.resolve("crl")
+				.resolve(name);
+
+		LOGGER.info("Downloading CRL from {} to {}", url, path);
+
+		extension.download(url)
+				.allowInsecureProtocol()
+				.maxAge(Duration.ofDays(7)) // Cache the CRL for a week
+				.downloadPath(path);
+
+		return parse(path);
+	}
+
+	static X509CRL parse(Path path) throws IOException {
+		try (InputStream inStream = Files.newInputStream(path)) {
+			CertificateFactory cf = CertificateFactory.getInstance("X.509");
+			return (X509CRL) cf.generateCRL(inStream);
+		} catch (CRLException | CertificateException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	/**
+	 * Verify that none of the certs in the chain are revoked.
+	 * @throws SignatureVerificationFailure if the certificate is revoked
+	 */
+	public void verify(CertificateChain certificateChain) throws SignatureVerificationFailure {
+		CertificateChain.visitAll(certificateChain, this::verify);
+	}
+
+	private void verify(X509Certificate certificate) throws SignatureVerificationFailure {
+		for (X509CRL crl : crls) {
+			if (crl.isRevoked(certificate)) {
+				throw new SignatureVerificationFailure("Certificate " + certificate.getSubjectX500Principal().getName() + " is revoked");
+			}
+		}
+	}
+}

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/verify/JarVerifier.java

@@ -0,0 +1,92 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.minecraft.verify;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.security.cert.Certificate;
+import java.security.cert.X509Certificate;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Objects;
+import java.util.Set;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.util.ZipReprocessorUtil;
+
+public final class JarVerifier {
+	private static final Logger LOGGER = LoggerFactory.getLogger(JarVerifier.class);
+
+	private JarVerifier() {
+	}
+
+	public static void verify(Path jarPath, CertificateChain certificateChain) throws IOException, SignatureVerificationFailure {
+		Objects.requireNonNull(jarPath, "jarPath");
+		Objects.requireNonNull(certificateChain, "certificateChain");
+
+		if (certificateChain.issuer() != null) {
+			throw new IllegalStateException("Can only verify jars from a root certificate");
+		}
+
+		Set<X509Certificate> jarCertificates = new HashSet<>();
+
+		try (JarFile jarFile = new JarFile(jarPath.toFile(), true)) {
+			for (JarEntry jarEntry : Collections.list(jarFile.entries())) {
+				if (ZipReprocessorUtil.isSpecialFile(jarEntry.getName())
+						|| jarEntry.getName().equals("META-INF/MANIFEST.MF")
+						|| jarEntry.isDirectory()) {
+					continue;
+				}
+
+				try {
+					// Must read the entire entry to trigger the signature verification
+					byte[] bytes = jarFile.getInputStream(jarEntry).readAllBytes();
+				} catch (SecurityException e) {
+					throw new SignatureVerificationFailure("Jar entry " + jarEntry.getName() + " failed signature verification", e);
+				}
+
+				Certificate[] entryCertificates = jarEntry.getCertificates();
+
+				if (entryCertificates == null) {
+					throw new SignatureVerificationFailure("Jar entry " + jarEntry.getName() + " does not have a signature");
+				}
+
+				Arrays.stream(entryCertificates)
+						.map(c -> (X509Certificate) c)
+						.forEach(jarCertificates::add);
+			}
+		}
+
+		CertificateChain jarCertificateChain = CertificateChain.getRoot(jarCertificates);
+
+		jarCertificateChain.verifyChainMatches(certificateChain);
+		LOGGER.debug("Jar {} is signed by the expected certificate", jarPath);
+	}
+}

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/verify/KnownVersions.java

@@ -0,0 +1,57 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.minecraft.verify;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.io.UncheckedIOException;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.Supplier;
+
+import com.google.common.base.Suppliers;
+
+import net.fabricmc.loom.LoomGradlePlugin;
+
+/**
+ * The know versions keep track of the versions that are signed using SHA1 or not signature at all.
+ * The maps are the Minecraft version to sha256 hash of the jar file.
+ */
+public record KnownVersions(
+		Map<String, String> client,
+		Map<String, String> server) {
+	public static final Supplier<KnownVersions> INSTANCE = Suppliers.memoize(KnownVersions::load);
+
+	private static KnownVersions load() {
+		try (InputStream is = KnownVersions.class.getClassLoader().getResourceAsStream("certs/known_versions.json");
+				Reader reader = new InputStreamReader(Objects.requireNonNull(is))) {
+			return LoomGradlePlugin.GSON.fromJson(reader, KnownVersions.class);
+		} catch (IOException e) {
+			throw new UncheckedIOException("Failed to load known versions", e);
+		}
+	}
+}

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/verify/MinecraftJarVerification.java

@@ -0,0 +1,112 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.minecraft.verify;
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.function.Function;
+
+import javax.inject.Inject;
+
+import org.gradle.api.Project;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.util.Checksum;
+
+public abstract class MinecraftJarVerification {
+	private static final Logger LOGGER = LoggerFactory.getLogger(MinecraftJarVerification.class);
+
+	private final String minecraftVersion;
+
+	@Inject
+	protected abstract Project getProject();
+
+	@Inject
+	public MinecraftJarVerification(String minecraftVersion) {
+		this.minecraftVersion = minecraftVersion;
+	}
+
+	public void verifyClientJar(Path path) throws IOException, SignatureVerificationFailure {
+		verifyJarSignature(path, KnownJarType.CLIENT);
+	}
+
+	public void verifyServerJar(Path path) throws IOException, SignatureVerificationFailure {
+		verifyJarSignature(path, KnownJarType.SERVER);
+	}
+
+	private void verifyJarSignature(Path path, KnownJarType type) throws IOException, SignatureVerificationFailure {
+		CertificateChain chain = CertificateChain.getRoot("mojangcs");
+		CertificateRevocationList revocationList = CertificateRevocationList.create(getProject(), CertificateRevocationList.CSC3_2010);
+
+		try {
+			revocationList.verify(chain);
+			JarVerifier.verify(path, chain);
+		} catch (SignatureVerificationFailure e) {
+			if (isValidKnownVersion(path, minecraftVersion, type)) {
+				LOGGER.info("Minecraft {} signature verification failed, but is a known version", path.getFileName());
+				return;
+			}
+
+			LOGGER.error("Verification of Minecraft {} signature failed: {}", path.getFileName(), e.getMessage());
+			throw e;
+		}
+	}
+
+	private boolean isValidKnownVersion(Path path, String version, KnownJarType type) throws IOException, SignatureVerificationFailure {
+		Map<String, String> knownVersions = type.getKnownVersions();
+		String expectedHash = knownVersions.get(version);
+
+		if (expectedHash == null) {
+			return false;
+		}
+
+		LOGGER.info("Found executed hash ({}) for known version: {}", expectedHash, version);
+		Checksum.Result hash = Checksum.of(path).sha256();
+
+		if (hash.matchesStr(expectedHash)) {
+			LOGGER.info("Minecraft {} hash matches known version", path.getFileName());
+			return true;
+		}
+
+		throw new SignatureVerificationFailure("Hash mismatch for known Minecraft version " + version + ": expected " + expectedHash + ", got " + hash);
+	}
+
+	private enum KnownJarType {
+		CLIENT(KnownVersions::client),
+		SERVER(KnownVersions::server),;
+
+		private final Function<KnownVersions, Map<String, String>> knownVersions;
+
+		KnownJarType(Function<KnownVersions, Map<String, String>> knownVersions) {
+			this.knownVersions = knownVersions;
+		}
+
+		private Map<String, String> getKnownVersions() {
+			return knownVersions.apply(KnownVersions.INSTANCE.get());
+		}
+	}
+}

src/main/java/net/fabricmc/loom/configuration/providers/minecraft/verify/SignatureVerificationFailure.java

@@ -0,0 +1,35 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.minecraft.verify;
+
+public final class SignatureVerificationFailure extends Exception {
+	public SignatureVerificationFailure(String message) {
+		super(message);
+	}
+
+	public SignatureVerificationFailure(String message, Throwable cause) {
+		super(message, cause);
+	}
+}

src/main/java/net/fabricmc/loom/decompilers/cache/ClassEntry.java

@@ -105,13 +105,13 @@ public record ClassEntry(String name, List<String> innerClasses, List<String> su
 	public String hash(Path root) throws IOException {
 		StringJoiner joiner = new StringJoiner(",");
 
-		joiner.add(Checksum.sha256Hex(Files.readAllBytes(root.resolve(name))));
+		joiner.add(Checksum.of(root.resolve(name)).sha256().hex());
 
 		for (String innerClass : innerClasses) {
-			joiner.add(Checksum.sha256Hex(Files.readAllBytes(root.resolve(innerClass))));
+			joiner.add(Checksum.of(root.resolve(innerClass)).sha256().hex());
 		}
 
-		return Checksum.sha256Hex(joiner.toString().getBytes());
+		return Checksum.of(joiner.toString()).sha256().hex();
 	}
 
 	/**
@@ -138,7 +138,7 @@ public record ClassEntry(String name, List<String> innerClasses, List<String> su
 			}
 		}
 
-		return Checksum.sha256Hex(joiner.toString().getBytes());
+		return Checksum.of(joiner.toString()).sha256().hex();
 	}
 
 	public String sourcesFileName() {

src/main/java/net/fabricmc/loom/extension/LoomFiles.java

@@ -46,7 +46,6 @@ public interface LoomFiles {
 	File getNativesDirectory(Project project);
 	File getDefaultLog4jConfigFile();
 	File getDevLauncherConfig();
-	File getUnpickLoggingConfigFile();
 	File getRemapClasspathFile();
 	File getGlobalMinecraftRepo();
 	File getLocalMinecraftRepo();

src/main/java/net/fabricmc/loom/extension/LoomFilesBaseImpl.java

@@ -84,11 +84,6 @@ public abstract class LoomFilesBaseImpl implements LoomFiles {
 		return new File(getProjectPersistentCache(), "launch.cfg");
 	}
 
-	@Override
-	public File getUnpickLoggingConfigFile() {
-		return new File(getProjectPersistentCache(), "unpick-logging.properties");
-	}
-
 	@Override
 	public File getRemapClasspathFile() {
 		return new File(getProjectPersistentCache(), "remapClasspath.txt");

src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionImpl.java

@@ -88,6 +88,7 @@ public abstract class LoomGradleExtensionImpl extends LoomGradleExtensionApiImpl
 	private final ListProperty<LibraryProcessorManager.LibraryProcessorFactory> libraryProcessorFactories;
 	private final boolean configurationCacheActive;
 	private final boolean isolatedProjectsActive;
+	private final boolean isCollectingDependencyVerificationMetadata;
 
 	// +-------------------+
 	// | Architectury Loom |
@@ -127,6 +128,7 @@ public abstract class LoomGradleExtensionImpl extends LoomGradleExtensionApiImpl
 
 		configurationCacheActive = getBuildFeatures().getConfigurationCache().getActive().get();
 		isolatedProjectsActive = getBuildFeatures().getIsolatedProjects().getActive().get();
+		isCollectingDependencyVerificationMetadata = !project.getGradle().getStartParameter().getWriteDependencyVerifications().isEmpty();
 
 		if (refreshDeps) {
 			project.getLogger().lifecycle("Refresh dependencies is in use, loom will be significantly slower.");
@@ -348,6 +350,11 @@ public abstract class LoomGradleExtensionImpl extends LoomGradleExtensionApiImpl
 		return isolatedProjectsActive;
 	}
 
+	@Override
+	public boolean isCollectingDependencyVerificationMetadata() {
+		return isCollectingDependencyVerificationMetadata;
+	}
+
 	@Override
 	public ForgeExtensionAPI getForge() {
 		ModPlatform.assertPlatform(this, ModPlatform.FORGE);

src/main/java/net/fabricmc/loom/extension/MixinExtension.java

@@ -33,6 +33,7 @@ import org.gradle.api.InvalidUserDataException;
 import org.gradle.api.Task;
 import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.plugins.ExtraPropertiesExtension;
+import org.gradle.api.provider.Property;
 import org.gradle.api.provider.Provider;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.SourceSet;
@@ -89,4 +90,6 @@ public interface MixinExtension extends MixinExtensionAPI {
 	Collection<SourceSet> getMixinSourceSets();
 
 	void init();
+
+	Property<Boolean> getInlineDependencyRefmaps();
 }

src/main/java/net/fabricmc/loom/extension/MixinExtensionImpl.java

@@ -46,11 +46,13 @@ import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.SourceSet;
 import org.gradle.api.tasks.TaskProvider;
 import org.gradle.api.tasks.util.PatternSet;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 
 public class MixinExtensionImpl extends MixinExtensionApiImpl implements MixinExtension {
 	private boolean isDefault;
 	private final Property<String> defaultRefmapName;
+	private final Property<Boolean> inlineDependencyRefmaps;
 
 	@Inject
 	public MixinExtensionImpl(Project project) {
@@ -59,6 +61,9 @@ public class MixinExtensionImpl extends MixinExtensionApiImpl implements MixinEx
 		this.defaultRefmapName = project.getObjects().property(String.class)
 				.convention(project.provider(this::getDefaultMixinRefmapName));
 		this.defaultRefmapName.finalizeValueOnRead();
+		this.inlineDependencyRefmaps = project.getObjects().property(Boolean.class)
+				.convention(false);
+		this.inlineDependencyRefmaps.finalizeValueOnRead();
 	}
 
 	@Override
@@ -146,4 +151,10 @@ public class MixinExtensionImpl extends MixinExtensionApiImpl implements MixinEx
 			}
 		});
 	}
+
+	@ApiStatus.Experimental
+	@Override
+	public Property<Boolean> getInlineDependencyRefmaps() {
+		return inlineDependencyRefmaps;
+	}
 }

src/main/java/net/fabricmc/loom/task/AbstractRemapJarTask.java

@@ -95,6 +95,14 @@ public abstract class AbstractRemapJarTask extends Jar {
 	@Optional
 	public abstract Property<String> getClientOnlySourceSetName();
 
+	/**
+	 * Optionally supply a single mapping file or jar file containing mappings to be used for remapping.
+	 */
+	@ApiStatus.Experimental
+	@InputFiles
+	@Optional
+	public abstract ConfigurableFileCollection getCustomMappings();
+
 	@Input
 	@Optional
 	@ApiStatus.Internal

src/main/java/net/fabricmc/loom/task/GenerateSourcesTask.java

@@ -28,7 +28,6 @@ import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.IOException;
-import java.io.InputStream;
 import java.io.UncheckedIOException;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
@@ -37,9 +36,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.time.Duration;
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
@@ -59,7 +56,6 @@ import org.gradle.api.file.RegularFileProperty;
 import org.gradle.api.provider.Property;
 import org.gradle.api.services.ServiceReference;
 import org.gradle.api.tasks.Input;
-import org.gradle.api.tasks.InputFile;
 import org.gradle.api.tasks.InputFiles;
 import org.gradle.api.tasks.Internal;
 import org.gradle.api.tasks.Nested;
@@ -70,7 +66,6 @@ import org.gradle.api.tasks.UntrackedTask;
 import org.gradle.api.tasks.options.Option;
 import org.gradle.internal.logging.progress.ProgressLoggerFactory;
 import org.gradle.process.ExecOperations;
-import org.gradle.process.ExecResult;
 import org.gradle.workers.WorkAction;
 import org.gradle.workers.WorkParameters;
 import org.gradle.workers.WorkQueue;
@@ -91,6 +86,7 @@ import net.fabricmc.loom.decompilers.cache.CachedData;
 import net.fabricmc.loom.decompilers.cache.CachedFileStoreImpl;
 import net.fabricmc.loom.decompilers.cache.CachedJarProcessor;
 import net.fabricmc.loom.task.service.SourceMappingsService;
+import net.fabricmc.loom.task.service.UnpickService;
 import net.fabricmc.loom.util.Checksum;
 import net.fabricmc.loom.util.Constants;
 import net.fabricmc.loom.util.ExceptionUtil;
@@ -106,6 +102,7 @@ import net.fabricmc.loom.util.gradle.daemon.DaemonUtils;
 import net.fabricmc.loom.util.ipc.IPCClient;
 import net.fabricmc.loom.util.ipc.IPCServer;
 import net.fabricmc.loom.util.service.ScopedServiceFactory;
+import net.fabricmc.loom.util.service.ServiceFactory;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;
 
 @UntrackedTask(because = "Manually invoked, has internal caching")
@@ -135,31 +132,6 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 	@OutputFile
 	protected abstract ConfigurableFileCollection getClassesOutputJar(); // Single jar
 
-	// Unpick
-	@InputFile
-	@Optional
-	public abstract RegularFileProperty getUnpickDefinitions();
-
-	@InputFiles
-	@Optional
-	public abstract ConfigurableFileCollection getUnpickConstantJar();
-
-	@InputFiles
-	@Optional
-	public abstract ConfigurableFileCollection getUnpickClasspath();
-
-	@InputFiles
-	@Optional
-	@ApiStatus.Internal
-	public abstract ConfigurableFileCollection getUnpickRuntimeClasspath();
-
-	@OutputFile
-	@Optional
-	public abstract RegularFileProperty getUnpickOutputJar();
-
-	@OutputFile
-	protected abstract RegularFileProperty getUnpickLogConfig();
-
 	@Input
 	@Option(option = "use-cache", description = "Use the decompile cache")
 	@ApiStatus.Experimental
@@ -204,6 +176,10 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 	@Nested
 	protected abstract Property<DaemonUtils.Context> getDaemonUtilsContext();
 
+	@Nested
+	@Optional
+	protected abstract Property<UnpickService.Options> getUnpickOptions();
+
 	// Prevent Gradle from running two gen sources tasks in parallel
 	@ServiceReference(SyncTaskBuildService.NAME)
 	abstract Property<SyncTaskBuildService> getSyncTask();
@@ -246,8 +222,6 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 
 		getMinecraftCompileLibraries().from(getProject().getConfigurations().getByName(Constants.Configurations.MINECRAFT_COMPILE_LIBRARIES));
 		getDecompileCacheFile().set(getExtension().getFiles().getDecompileCache(CACHE_VERSION));
-		getUnpickRuntimeClasspath().from(getProject().getConfigurations().getByName(Constants.Configurations.UNPICK_CLASSPATH));
-		getUnpickLogConfig().set(getExtension().getFiles().getUnpickLoggingConfigFile());
 
 		getUseCache().convention(true);
 		getResetCache().convention(getExtension().refreshDeps());
@@ -259,6 +233,8 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 
 		getDaemonUtilsContext().set(getProject().getObjects().newInstance(DaemonUtils.Context.class, getProject()));
 
+		getUnpickOptions().set(UnpickService.createOptions(this));
+
 		mustRunAfter(getProject().getTasks().withType(AbstractRemapJarTask.class));
 	}
 
@@ -270,57 +246,59 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 			throw new UnsupportedOperationException("GenSources task requires a 64bit JVM to run due to the memory requirements.");
 		}
 
-		if (!getUseCache().get()) {
+		try (ScopedServiceFactory serviceFactory = new ScopedServiceFactory()) {
-			getLogger().info("Not using decompile cache.");
+			if (!getUseCache().get()) {
+				getLogger().info("Not using decompile cache.");
 
-			try (var timer = new Timer("Decompiled sources")) {
+				try (var timer = new Timer("Decompiled sources")) {
-				runWithoutCache();
+					runWithoutCache(serviceFactory);
+				} catch (Exception e) {
+					ExceptionUtil.processException(e, getDaemonUtilsContext().get());
+					throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Failed to decompile", e);
+				}
+
+				return;
+			}
+
+			getLogger().info("Using decompile cache.");
+
+			try (var timer = new Timer("Decompiled sources with cache")) {
+				final Path cacheFile = getDecompileCacheFile().getAsFile().get().toPath();
+
+				if (getResetCache().get()) {
+					getLogger().warn("Resetting decompile cache");
+					Files.deleteIfExists(cacheFile);
+				}
+
+				// TODO ensure we have a lock on this file to prevent multiple tasks from running at the same time
+				Files.createDirectories(cacheFile.getParent());
+
+				if (Files.exists(cacheFile)) {
+					try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(cacheFile, true)) {
+						// Success, cache exists and can be read
+					} catch (IOException e) {
+						getLogger().warn("Discarding invalid decompile cache file: {}", cacheFile, e);
+						Files.delete(cacheFile);
+					}
+				}
+
+				try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(cacheFile, true)) {
+					runWithCache(serviceFactory, fs.getRoot());
+				}
 			} catch (Exception e) {
 				ExceptionUtil.processException(e, getDaemonUtilsContext().get());
 				throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Failed to decompile", e);
 			}
-
-			return;
-		}
-
-		getLogger().info("Using decompile cache.");
-
-		try (var timer = new Timer("Decompiled sources with cache")) {
-			final Path cacheFile = getDecompileCacheFile().getAsFile().get().toPath();
-
-			if (getResetCache().get()) {
-				getLogger().warn("Resetting decompile cache");
-				Files.deleteIfExists(cacheFile);
-			}
-
-			// TODO ensure we have a lock on this file to prevent multiple tasks from running at the same time
-			Files.createDirectories(cacheFile.getParent());
-
-			if (Files.exists(cacheFile)) {
-				try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(cacheFile, true)) {
-					// Success, cache exists and can be read
-				} catch (IOException e) {
-					getLogger().warn("Discarding invalid decompile cache file: {}", cacheFile, e);
-					Files.delete(cacheFile);
-				}
-			}
-
-			try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(cacheFile, true)) {
-				runWithCache(fs.getRoot());
-			}
-		} catch (Exception e) {
-			ExceptionUtil.processException(e, getDaemonUtilsContext().get());
-			throw ExceptionUtil.createDescriptiveWrapper(RuntimeException::new, "Failed to decompile", e);
 		}
 	}
 
-	private void runWithCache(Path cacheRoot) throws IOException {
+	private void runWithCache(ServiceFactory serviceFactory, Path cacheRoot) throws IOException {
 		final Path classesInputJar = getClassesInputJar().getSingleFile().toPath();
 		final Path sourcesOutputJar = getSourcesOutputJar().get().getAsFile().toPath();
 		final Path classesOutputJar = getClassesOutputJar().getSingleFile().toPath();
 		final var cacheRules = new CachedFileStoreImpl.CacheRules(getMaxCachedFiles().get(), Duration.ofDays(getMaxCacheFileAge().get()));
 		final var decompileCache = new CachedFileStoreImpl<>(cacheRoot, CachedData.SERIALIZER, cacheRules);
-		final String cacheKey = getCacheKey();
+		final String cacheKey = getCacheKey(serviceFactory);
 		final CachedJarProcessor cachedJarProcessor = new CachedJarProcessor(decompileCache, cacheKey);
 		final CachedJarProcessor.WorkRequest workRequest;
 
@@ -342,9 +320,10 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 			Path workInputJar = workToDoJob.incomplete();
 			@Nullable Path existingClasses = (job instanceof CachedJarProcessor.PartialWorkJob partialWorkJob) ? partialWorkJob.existingClasses() : null;
 
-			if (getUnpickDefinitions().isPresent()) {
+			if (usingUnpick()) {
 				try (var timer = new Timer("Unpick")) {
-					workInputJar = unpickJar(workInputJar, existingClasses);
+					UnpickService unpick = serviceFactory.get(getUnpickOptions());
+					workInputJar = unpick.unpickJar(workInputJar, existingClasses);
 				}
 			}
 
@@ -381,16 +360,17 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		}
 	}
 
-	private void runWithoutCache() throws IOException {
+	private void runWithoutCache(ServiceFactory serviceFactory) throws IOException {
 		final Path classesInputJar = getClassesInputJar().getSingleFile().toPath();
 		final Path sourcesOutputJar = getSourcesOutputJar().get().getAsFile().toPath();
 		final Path classesOutputJar = getClassesOutputJar().getSingleFile().toPath();
 
 		Path workClassesJar = classesInputJar;
 
-		if (getUnpickDefinitions().isPresent()) {
+		if (usingUnpick()) {
 			try (var timer = new Timer("Unpick")) {
-				workClassesJar = unpickJar(workClassesJar, null);
+				UnpickService unpick = serviceFactory.get(getUnpickOptions());
+				workClassesJar = unpick.unpickJar(workClassesJar, null);
 			}
 		}
 
@@ -427,24 +407,24 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		Files.move(tempJar, classesOutputJar, StandardCopyOption.REPLACE_EXISTING);
 	}
 
-	private String getCacheKey() {
+	private String getCacheKey(ServiceFactory serviceFactory) {
 		var sj = new StringJoiner(",");
 		sj.add(getDecompilerCheckKey());
-		sj.add(getUnpickCacheKey());
+
+		if (usingUnpick()) {
+			UnpickService unpick = serviceFactory.get(getUnpickOptions());
+			sj.add(unpick.getUnpickCacheKey());
+		}
 
 		getLogger().info("Decompile cache data: {}", sj);
 
-		try {
+		return Checksum.of(sj.toString()).sha256().hex();
-			return Checksum.sha256Hex(sj.toString().getBytes(StandardCharsets.UTF_8));
-		} catch (IOException e) {
-			throw new UncheckedIOException(e);
-		}
 	}
 
 	private String getDecompilerCheckKey() {
 		var sj = new StringJoiner(",");
 		sj.add(decompilerOptions.getDecompilerClassName().get());
-		sj.add(fileCollectionHash(decompilerOptions.getClasspath()));
+		sj.add(Checksum.of(decompilerOptions.getClasspath()).sha256().hex());
 
 		for (Map.Entry<String, String> entry : decompilerOptions.getOptions().get().entrySet()) {
 			sj.add(entry.getKey() + "=" + entry.getValue());
@@ -453,19 +433,6 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		return sj.toString();
 	}
 
-	private String getUnpickCacheKey() {
-		if (!getUnpickDefinitions().isPresent()) {
-			return "";
-		}
-
-		var sj = new StringJoiner(",");
-		sj.add(fileHash(getUnpickDefinitions().getAsFile().get()));
-		sj.add(fileCollectionHash(getUnpickConstantJar()));
-		sj.add(fileCollectionHash(getUnpickRuntimeClasspath()));
-
-		return sj.toString();
-	}
-
 	@Nullable
 	private ClassLineNumbers runDecompileJob(Path inputJar, Path outputJar, @Nullable Path existingJar) throws IOException {
 		final Platform platform = Platform.CURRENT;
@@ -565,55 +532,6 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		}
 	}
 
-	private Path unpickJar(Path inputJar, @Nullable Path existingClasses) {
-		final Path outputJar = getUnpickOutputJar().get().getAsFile().toPath();
-		final List<String> args = getUnpickArgs(inputJar, outputJar, existingClasses);
-
-		ExecResult result = getExecOperations().javaexec(spec -> {
-			spec.getMainClass().set("daomephsta.unpick.cli.Main");
-			spec.classpath(getUnpickRuntimeClasspath());
-			spec.args(args);
-			spec.systemProperty("java.util.logging.config.file", writeUnpickLogConfig().getAbsolutePath());
-		});
-
-		result.rethrowFailure();
-
-		return outputJar;
-	}
-
-	private List<String> getUnpickArgs(Path inputJar, Path outputJar, @Nullable Path existingClasses) {
-		var fileArgs = new ArrayList<File>();
-
-		fileArgs.add(inputJar.toFile());
-		fileArgs.add(outputJar.toFile());
-		fileArgs.add(getUnpickDefinitions().get().getAsFile());
-		fileArgs.add(getUnpickConstantJar().getSingleFile());
-
-		for (File file : getUnpickClasspath()) {
-			fileArgs.add(file);
-		}
-
-		if (existingClasses != null) {
-			fileArgs.add(existingClasses.toFile());
-		}
-
-		return fileArgs.stream()
-				.map(File::getAbsolutePath)
-				.toList();
-	}
-
-	private File writeUnpickLogConfig() {
-		final File unpickLoggingConfigFile = getUnpickLogConfig().getAsFile().get();
-
-		try (InputStream is = GenerateSourcesTask.class.getClassLoader().getResourceAsStream("unpick-logging.properties")) {
-			Files.copy(Objects.requireNonNull(is), unpickLoggingConfigFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
-		} catch (IOException e) {
-			throw new UncheckedIOException("Failed to copy unpick logging config", e);
-		}
-
-		return unpickLoggingConfigFile;
-	}
-
 	private void remapLineNumbers(ClassLineNumbers lineNumbers, Path inputJar, Path outputJar) throws IOException {
 		Objects.requireNonNull(lineNumbers, "lineNumbers");
 		final var remapper = new LineNumberRemapper(lineNumbers);
@@ -689,6 +607,10 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		return !Boolean.getBoolean("fabric.loom.genSources.debug");
 	}
 
+	private boolean usingUnpick() {
+		return getUnpickOptions().isPresent();
+	}
+
 	public interface DecompileParams extends WorkParameters {
 		Property<DecompilerOptions.Dto> getDecompilerOptions();
 
@@ -816,26 +738,6 @@ public abstract class GenerateSourcesTask extends AbstractLoomTask {
 		}
 	}
 
-	private static String fileHash(File file) {
-		try {
-			return Checksum.sha256Hex(Files.readAllBytes(file.toPath()));
-		} catch (IOException e) {
-			throw new UncheckedIOException(e);
-		}
-	}
-
-	private static String fileCollectionHash(FileCollection files) {
-		var sj = new StringJoiner(",");
-
-		files.getFiles()
-				.stream()
-				.sorted(Comparator.comparing(File::getAbsolutePath))
-				.map(GenerateSourcesTask::fileHash)
-				.forEach(sj::add);
-
-		return sj.toString();
-	}
-
 	public interface MappingsProcessor {
 		boolean transform(MemoryMappingTree mappings);
 	}

src/main/java/net/fabricmc/loom/task/LoomTasks.java

@@ -24,13 +24,18 @@
 
 package net.fabricmc.loom.task;
 
+import java.io.File;
+
 import javax.inject.Inject;
 
 import com.google.common.base.Preconditions;
 import org.gradle.api.Project;
 import org.gradle.api.Task;
+import org.gradle.api.file.FileCollection;
 import org.gradle.api.provider.Provider;
+import org.gradle.api.tasks.Sync;
 import org.gradle.api.tasks.TaskContainer;
+import org.gradle.api.tasks.TaskOutputs;
 import org.gradle.api.tasks.TaskProvider;
 
 import net.fabricmc.loom.LoomGradleExtension;
@@ -41,6 +46,8 @@ import net.fabricmc.loom.task.launch.GenerateDLIConfigTask;
 import net.fabricmc.loom.task.launch.GenerateLog4jConfigTask;
 import net.fabricmc.loom.task.launch.GenerateRemapClasspathTask;
 import net.fabricmc.loom.util.Constants;
+import net.fabricmc.loom.util.LoomVersions;
+import net.fabricmc.loom.util.Platform;
 import net.fabricmc.loom.util.gradle.GradleUtils;
 
 public abstract class LoomTasks implements Runnable {
@@ -132,17 +139,28 @@ public abstract class LoomTasks implements Runnable {
 
 	private void registerRunTasks() {
 		LoomGradleExtension extension = LoomGradleExtension.get(getProject());
+		final boolean renderDocSupported = RenderDocRunTask.isSupported(Platform.CURRENT);
 
 		Preconditions.checkArgument(extension.getRunConfigs().size() == 0, "Run configurations must not be registered before loom");
 
 		extension.getRunConfigs().whenObjectAdded(config -> {
-			getTasks().register(getRunConfigTaskName(config), RunGameTask.class, config).configure(t -> {
+			var runTask = getTasks().register(getRunConfigTaskName(config), RunGameTask.class, config);
+
+			runTask.configure(t -> {
 				t.setDescription("Starts the '" + config.getConfigName() + "' run configuration");
 
 				t.dependsOn(config.getEnvironment().equals("client") ? "configureClientLaunch" : "configureLaunch");
 			});
+
+			if (config.getName().equals("client") && renderDocSupported) {
+				getTasks().register("runClientRenderDoc", RenderDocRunTask.class, config);
+			}
 		});
 
+		if (renderDocSupported) {
+			configureRenderDocTasks();
+		}
+
 		extension.getRunConfigs().whenObjectRemoved(runConfigSettings -> {
 			getTasks().named(getRunConfigTaskName(runConfigSettings), task -> {
 				// Disable the task so it can't be run
@@ -170,7 +188,58 @@ public abstract class LoomTasks implements Runnable {
 				return;
 			}
 
-			extension.getRunConfigs().removeIf(settings -> settings.getName().equals(taskName));
+			extension.getRunConfigs().removeIf(settings -> settings.getName().equals(taskName)
+					|| settings.getName().equals(taskName + "RenderDoc"));
+		});
+	}
+
+	private void configureRenderDocTasks() {
+		final Platform.OperatingSystem operatingSystem = Platform.CURRENT.getOperatingSystem();
+		final String renderDocVersion = LoomVersions.RENDERDOC.version();
+		final String renderDocBaseName = operatingSystem.isWindows()
+				? "RenderDoc_%s_64".formatted(renderDocVersion)
+				: "renderdoc_%s".formatted(renderDocVersion);
+		final String renderDocFilename = operatingSystem.isWindows()
+				? "%s.zip".formatted(renderDocBaseName)
+				: "%s.tar.gz".formatted(renderDocBaseName);
+		final String renderDocUrl = "https://maven.fabricmc.net/org/renderdoc/%s".formatted(renderDocFilename);
+		final String executableExt = operatingSystem.isWindows() ? ".exe" : "";
+
+		var downloadRenderDoc = getTasks().register("downloadRenderDoc", DownloadTask.class, task -> {
+			task.setGroup(Constants.TaskGroup.FABRIC);
+
+			task.getUrl().set(renderDocUrl);
+			task.getOutput().set(getProject().getLayout().getBuildDirectory().file(renderDocFilename));
+		});
+
+		var extractRenderDoc = getTasks().register("extractRenderDoc", Sync.class, task -> {
+			task.setGroup(Constants.TaskGroup.FABRIC);
+
+			if (operatingSystem.isWindows()) {
+				task.from(getProject().zipTree(downloadRenderDoc.map(DownloadTask::getOutput)));
+			} else {
+				task.from(getProject().tarTree(downloadRenderDoc.map(DownloadTask::getOutput)));
+			}
+
+			task.into(getProject().getLayout().getBuildDirectory().dir("renderdoc"));
+		});
+
+		Provider<File> renderDocDir = extractRenderDoc.map(Sync::getOutputs)
+				.map(TaskOutputs::getFiles)
+				.map(FileCollection::getSingleFile)
+				.map(dir -> new File(dir, renderDocBaseName));
+
+		if (operatingSystem.isLinux()) {
+			renderDocDir = renderDocDir.map(dir -> new File(dir, "bin"));
+		}
+
+		Provider<File> renderDocCMD = renderDocDir.map(dir -> new File(dir, "renderdoccmd" + executableExt));
+		Provider<File> renderDocUI = renderDocDir.map(dir -> new File(dir, "qrenderdoc" + executableExt));
+
+		getTasks().register("startRenderDocUI", RenderDocRunUITask.class, task -> task.getRenderDocExecutable().fileProvider(renderDocUI));
+
+		getTasks().withType(RenderDocRunTask.class).configureEach(task -> {
+			task.getRenderDocExecutable().fileProvider(renderDocCMD);
 		});
 	}
 

src/main/java/net/fabricmc/loom/task/RenderDocRunTask.java

@@ -0,0 +1,93 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.task;
+
+import java.io.File;
+
+import javax.inject.Inject;
+
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.provider.ListProperty;
+import org.gradle.api.tasks.Input;
+import org.gradle.api.tasks.InputFile;
+import org.gradle.process.CommandLineArgumentProvider;
+import org.gradle.process.ExecOperations;
+import org.gradle.process.ExecResult;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.configuration.ide.RunConfigSettings;
+import net.fabricmc.loom.util.Constants;
+import net.fabricmc.loom.util.Platform;
+
+public abstract class RenderDocRunTask extends RunGameTask {
+	private static final Logger LOGGER = LoggerFactory.getLogger(RenderDocRunTask.class);
+
+	@InputFile
+	public abstract RegularFileProperty getRenderDocExecutable();
+
+	@Input
+	public abstract ListProperty<String> getRenderDocArgs();
+
+	@Inject
+	protected abstract ExecOperations getExecOperations();
+
+	@Inject
+	public RenderDocRunTask(RunConfigSettings settings) {
+		super(settings);
+		setGroup(Constants.TaskGroup.FABRIC);
+		dependsOn("configureClientLaunch");
+		getRenderDocArgs().addAll("capture", "--wait-for-exit");
+	}
+
+	@Override
+	public void exec() {
+		ExecResult result = getExecOperations().exec(exec -> {
+			exec.workingDir(new File(getProjectDir().get(), getInternalRunDir().get()));
+			exec.environment(getInternalEnvironmentVars().get());
+
+			exec.commandLine(getRenderDocExecutable().get().getAsFile());
+			exec.args(getRenderDocArgs().get());
+			exec.args("--working-dir", new File(getProjectDir().get(), getInternalRunDir().get()));
+			exec.args(getJavaLauncher().get().getExecutablePath());
+			exec.args(getJvmArgs());
+			exec.args(getMainClass().get());
+
+			for (CommandLineArgumentProvider provider : getArgumentProviders()) {
+				exec.args(provider.asArguments());
+			}
+
+			LOGGER.info("Running command: {}", exec.getCommandLine());
+		});
+		result.assertNormalExitValue();
+	}
+
+	public static boolean isSupported(Platform platform) {
+		final Platform.OperatingSystem os = platform.getOperatingSystem();
+		final Platform.Architecture arch = platform.getArchitecture();
+		// RenderDoc does support 32-bit Windows, but I cannot be bothered to test/maintain it
+		return (os.isLinux() || os.isWindows()) && arch.isX64();
+	}
+}

src/main/java/net/fabricmc/loom/task/RenderDocRunUITask.java

@@ -0,0 +1,51 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.task;
+
+import java.io.IOException;
+
+import org.gradle.api.DefaultTask;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.tasks.InputFile;
+import org.gradle.api.tasks.TaskAction;
+
+import net.fabricmc.loom.util.Constants;
+
+public abstract class RenderDocRunUITask extends DefaultTask {
+	@InputFile
+	public abstract RegularFileProperty getRenderDocExecutable();
+
+	public RenderDocRunUITask() {
+		setGroup(Constants.TaskGroup.FABRIC);
+	}
+
+	@TaskAction
+	public void run() throws IOException {
+		ProcessBuilder builder = new ProcessBuilder()
+				.command(getRenderDocExecutable().getAsFile().get().getAbsolutePath());
+		builder.start();
+		// Allow to run in the background.
+	}
+}

src/main/java/net/fabricmc/loom/task/service/MappingsService.java

@@ -25,6 +25,7 @@
 package net.fabricmc.loom.task.service;
 
 import java.io.Closeable;
+import java.io.File;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.nio.file.Path;
@@ -35,9 +36,12 @@ import org.gradle.api.provider.Property;
 import org.gradle.api.provider.Provider;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.InputFile;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import net.fabricmc.loom.LoomGradleExtension;
 import net.fabricmc.loom.configuration.providers.mappings.MappingConfiguration;
+import net.fabricmc.loom.task.AbstractRemapJarTask;
 import net.fabricmc.loom.util.TinyRemapperHelper;
 import net.fabricmc.loom.util.service.Service;
 import net.fabricmc.loom.util.service.ServiceFactory;
@@ -52,6 +56,8 @@ import net.fabricmc.tinyremapper.IMappingProvider;
 public final class MappingsService extends Service<MappingsService.Options> implements Closeable {
 	public static ServiceType<Options, MappingsService> TYPE = new ServiceType<>(Options.class, MappingsService.class);
 
+	private static final Logger LOGGER = LoggerFactory.getLogger(TinyRemapperService.class);
+
 	// TODO use a nested TinyMappingsService instead of duplicating it
 	public interface Options extends Service.Options {
 		@InputFile
@@ -91,6 +97,36 @@ public final class MappingsService extends Service<MappingsService.Options> impl
 		return createOptions(project, LoomGradleExtension.get(project).getPlatformMappingFile(), from, to, false);
 	}
 
+	public static Provider<MappingsService.Options> createForRemapTask(AbstractRemapJarTask remapJarTask) {
+		final Project project = remapJarTask.getProject();
+
+		return project.provider(() -> {
+			if (remapJarTask.getCustomMappings().isEmpty()) {
+				LOGGER.debug("Using default project mappings for remapping");
+				return MappingsService.createOptionsWithProjectMappings(
+						project,
+						remapJarTask.getSourceNamespace(),
+						remapJarTask.getTargetNamespace()
+				).get();
+			}
+
+			// Custom mappings:
+			File mappingsFile = remapJarTask.getCustomMappings().getSingleFile();
+
+			if (mappingsFile.getName().endsWith(".zip") || mappingsFile.getName().endsWith(".jar")) {
+				mappingsFile = project.zipTree(mappingsFile).matching(patternFilterable -> patternFilterable.include("mappings/mappings.tiny")).getSingleFile();
+			}
+
+			LOGGER.info("Using custom mappings for remap task: {}", mappingsFile);
+			return MappingsService.createOptions(
+							project,
+							mappingsFile.toPath(),
+							remapJarTask.getSourceNamespace(), remapJarTask.getTargetNamespace(),
+							false)
+					.get();
+		});
+	}
+
 	public MappingsService(Options options, ServiceFactory serviceFactory) {
 		super(options, serviceFactory);
 	}

src/main/java/net/fabricmc/loom/task/service/MigrateMappingsService.java

@@ -29,8 +29,8 @@ import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.util.Map;
 
-import com.google.common.collect.ImmutableMap;
 import org.cadixdev.lorenz.MappingSet;
 import org.cadixdev.mercury.Mercury;
 import org.cadixdev.mercury.remapper.MercuryRemapper;
@@ -181,7 +181,7 @@ public class MigrateMappingsService extends Service<MigrateMappingsService.Optio
 			}
 		} catch (IllegalDependencyNotation ignored) {
 			LOGGER.info("Could not locate mappings, presuming V2 Yarn");
-			return project.getConfigurations().detachedConfiguration(project.getDependencies().create(ImmutableMap.of("group", "net.fabricmc", "name", "yarn", "version", mappings, "classifier", "v2")));
+			return project.getConfigurations().detachedConfiguration(project.getDependencies().create(Map.of("group", "net.fabricmc", "name", "yarn", "version", mappings, "classifier", "v2")));
 		} catch (IOException e) {
 			throw new UncheckedIOException("Failed to resolve mappings", e);
 		}

src/main/java/net/fabricmc/loom/task/service/SourceRemapperService.java

@@ -68,11 +68,7 @@ public final class SourceRemapperService extends Service<SourceRemapperService.O
 
 	public static Provider<Options> createOptions(RemapSourcesJarTask task) {
 		return TYPE.create(task.getProject(), o -> {
-			o.getMappings().set(MappingsService.createOptionsWithProjectMappings(
+			o.getMappings().set(MappingsService.createForRemapTask(task));
-					task.getProject(),
-					task.getSourceNamespace(),
-					task.getTargetNamespace()
-			));
 			o.getJavaCompileRelease().set(getJavaCompileRelease(task.getProject()));
 			o.getClasspath().from(task.getClasspath());
 		});

src/main/java/net/fabricmc/loom/task/service/TinyRemapperService.java

@@ -41,6 +41,7 @@ import org.gradle.api.Project;
 import org.gradle.api.artifacts.ConfigurationContainer;
 import org.gradle.api.file.ConfigurableFileCollection;
 import org.gradle.api.file.FileCollection;
+import org.gradle.api.plugins.JavaPlugin;
 import org.gradle.api.provider.ListProperty;
 import org.gradle.api.provider.Property;
 import org.gradle.api.provider.Provider;
@@ -51,6 +52,7 @@ import org.gradle.api.tasks.Optional;
 import org.jetbrains.annotations.Nullable;
 
 import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.build.IntermediaryNamespaces;
 import net.fabricmc.loom.extension.RemapperExtensionHolder;
 import net.fabricmc.loom.task.AbstractRemapJarTask;
@@ -66,7 +68,7 @@ import net.fabricmc.tinyremapper.InputTag;
 import net.fabricmc.tinyremapper.TinyRemapper;
 import net.fabricmc.tinyremapper.extension.mixin.MixinExtension;
 
-public class TinyRemapperService extends Service<TinyRemapperService.Options> implements Closeable {
+public class TinyRemapperService extends Service<TinyRemapperService.Options> implements TinyRemapperServiceInterface, Closeable {
 	public static final ServiceType<Options, TinyRemapperService> TYPE = new ServiceType<>(Options.class, TinyRemapperService.class);
 
 	public interface Options extends Service.Options {
@@ -103,7 +105,7 @@ public class TinyRemapperService extends Service<TinyRemapperService.Options> im
 
 			options.getFrom().set(remapJarTask.getSourceNamespace());
 			options.getTo().set(remapJarTask.getTargetNamespace());
-			options.getMappings().add(MappingsService.createOptionsWithProjectMappings(project, options.getFrom(), options.getTo()));
+			options.getMappings().add(MappingsService.createForRemapTask(remapJarTask));
 
 			if (legacyMixin) {
 				options.getMixinApMappings().set(MixinAPMappingService.createOptions(project, options.getFrom(), options.getTo().map(to -> IntermediaryNamespaces.replaceMixinIntermediaryNamespace(project, to))));
@@ -117,6 +119,56 @@ public class TinyRemapperService extends Service<TinyRemapperService.Options> im
 		});
 	}
 
+	public static Provider<Options> createSimple(Project project, Provider<String> from, Provider<String> to, ClasspathLibraries classpathLibraries) {
+		return TYPE.create(project, options -> {
+			final LoomGradleExtension extension = LoomGradleExtension.get(project);
+			final FileCollection classpath = getRemapClasspath(project, from, classpathLibraries);
+
+			options.getFrom().set(from);
+			options.getTo().set(to);
+			options.getMappings().add(MappingsService.createOptionsWithProjectMappings(project, options.getFrom(), options.getTo()));
+			options.getUselegacyMixinAP().set(true);
+			options.getClasspath().from(classpath);
+			options.getKnownIndyBsms().set(extension.getKnownIndyBsms().get().stream().sorted().toList());
+			options.getRemapperExtensions().set(extension.getRemapperExtensions());
+		});
+	}
+
+	private static FileCollection getRemapClasspath(Project project, Provider<String> from, ClasspathLibraries classpathLibraries) {
+		final LoomGradleExtension extension = LoomGradleExtension.get(project);
+		final ConfigurationContainer configurations = project.getConfigurations();
+
+		if (from.get().equals(MappingsNamespace.INTERMEDIARY.toString())) {
+			ConfigurableFileCollection files = project.files(extension.getMinecraftJars(MappingsNamespace.INTERMEDIARY));
+
+			if (classpathLibraries == ClasspathLibraries.INCLUDE) {
+				files = files.from(configurations.getByName(Constants.Configurations.MINECRAFT_COMPILE_LIBRARIES));
+			}
+
+			return files;
+		}
+
+		if (classpathLibraries == ClasspathLibraries.INCLUDE) {
+			return configurations.getByName(JavaPlugin.COMPILE_CLASSPATH_CONFIGURATION_NAME);
+		}
+
+		return configurations.getByName(JavaPlugin.COMPILE_CLASSPATH_CONFIGURATION_NAME)
+				.minus(configurations.getByName(Constants.Configurations.MINECRAFT_COMPILE_LIBRARIES))
+				.minus(configurations.getByName(Constants.Configurations.MINECRAFT_RUNTIME_LIBRARIES));
+	}
+
+	public enum ClasspathLibraries {
+		/**
+		 * Default, in most cases the Minecraft libraries are not required as they are not obfuscated and do not need to be queried.
+		 */
+		EXCLUDE,
+
+		/**
+		 * Uses more memory, but provides a complete index of all the classes within the libraries.
+		 */
+		INCLUDE
+	}
+
 	private TinyRemapper tinyRemapper;
 	@Nullable
 	private KotlinRemapperClassloader kotlinRemapperClassloader;
@@ -179,11 +231,13 @@ public class TinyRemapperService extends Service<TinyRemapperService.Options> im
 		return tag;
 	}
 
+	@Override
 	public TinyRemapper getTinyRemapperForRemapping() {
 		isRemapping = true;
 		return Objects.requireNonNull(tinyRemapper, "Tiny remapper has not been setup");
 	}
 
+	@Override
 	public TinyRemapper getTinyRemapperForInputs() {
 		if (isRemapping) {
 			throw new IllegalStateException("Cannot read inputs as remapping has already started");

src/main/java/net/fabricmc/loom/task/service/TinyRemapperServiceInterface.java

@@ -0,0 +1,35 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.task.service;
+
+import org.jetbrains.annotations.VisibleForTesting;
+
+import net.fabricmc.tinyremapper.TinyRemapper;
+
+@VisibleForTesting
+public interface TinyRemapperServiceInterface {
+	TinyRemapper getTinyRemapperForRemapping();
+	TinyRemapper getTinyRemapperForInputs();
+}

src/main/java/net/fabricmc/loom/task/service/UnpickRemapperService.java

@@ -0,0 +1,171 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.task.service;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.Reader;
+import java.lang.reflect.Field;
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.List;
+
+import daomephsta.unpick.constantmappers.datadriven.parser.v3.UnpickV3Reader;
+import daomephsta.unpick.constantmappers.datadriven.parser.v3.UnpickV3Remapper;
+import daomephsta.unpick.constantmappers.datadriven.parser.v3.UnpickV3Writer;
+import daomephsta.unpick.constantmappers.datadriven.tree.UnpickV3Visitor;
+import org.gradle.api.Project;
+import org.gradle.api.provider.Property;
+import org.gradle.api.provider.Provider;
+import org.gradle.api.tasks.Nested;
+import org.objectweb.asm.Type;
+import org.objectweb.asm.commons.Remapper;
+
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
+import net.fabricmc.loom.configuration.providers.mappings.unpick.UnpickMetadata;
+import net.fabricmc.loom.util.JarPackageIndex;
+import net.fabricmc.loom.util.service.Service;
+import net.fabricmc.loom.util.service.ServiceFactory;
+import net.fabricmc.loom.util.service.ServiceType;
+import net.fabricmc.tinyremapper.TinyRemapper;
+import net.fabricmc.tinyremapper.api.TrClass;
+import net.fabricmc.tinyremapper.api.TrField;
+
+public class UnpickRemapperService extends Service<UnpickRemapperService.Options> {
+	public static final ServiceType<Options, UnpickRemapperService> TYPE = new ServiceType<>(Options.class, UnpickRemapperService.class);
+
+	public interface Options extends Service.Options {
+		@Nested
+		Property<TinyRemapperService.Options> getTinyRemapper();
+	}
+
+	public static Provider<Options> createOptions(Project project, UnpickMetadata.V2 metadata) {
+		return TYPE.create(project, options -> {
+			options.getTinyRemapper().set(TinyRemapperService.createSimple(project,
+					project.provider(metadata::namespace),
+					project.provider(MappingsNamespace.NAMED::toString),
+					TinyRemapperService.ClasspathLibraries.INCLUDE // Must include the full set of libraries on classpath so fields can be looked up. This does use a lot of memory however...
+			));
+		});
+	}
+
+	public UnpickRemapperService(Options options, ServiceFactory serviceFactory) {
+		super(options, serviceFactory);
+	}
+
+	/**
+	 * Return the remapped definitions.
+	 */
+	public String remap(File input) throws IOException {
+		TinyRemapperServiceInterface tinyRemapperService = getServiceFactory().get(getOptions().getTinyRemapper());
+		TinyRemapper tinyRemapper = tinyRemapperService.getTinyRemapperForRemapping();
+
+		List<Path> classpath = getOptions().getTinyRemapper().get().getClasspath().getFiles().stream().map(File::toPath).toList();
+		JarPackageIndex packageIndex = JarPackageIndex.create(classpath);
+
+		return doRemap(input, tinyRemapper, packageIndex);
+	}
+
+	private String doRemap(File input, TinyRemapper remapper, JarPackageIndex packageIndex) throws IOException {
+		try (Reader fileReader = new BufferedReader(new FileReader(input));
+				var reader = new UnpickV3Reader(fileReader)) {
+			var writer = new UnpickV3Writer();
+			reader.accept(new UnpickRemapper(writer, remapper, packageIndex));
+			return writer.getOutput().replace(System.lineSeparator(), "\n");
+		}
+	}
+
+	private static final class UnpickRemapper extends UnpickV3Remapper {
+		private final TinyRemapper tinyRemapper;
+		private final Remapper remapper;
+		private final JarPackageIndex jarPackageIndex;
+
+		private UnpickRemapper(UnpickV3Visitor downstream, TinyRemapper tinyRemapper, JarPackageIndex jarPackageIndex) {
+			super(downstream);
+			this.tinyRemapper = tinyRemapper;
+			this.remapper = tinyRemapper.getEnvironment().getRemapper();
+			this.jarPackageIndex = jarPackageIndex;
+		}
+
+		@Override
+		protected String mapClassName(String className) {
+			return remapper.map(className.replace('.', '/')).replace('/', '.');
+		}
+
+		@Override
+		protected String mapFieldName(String className, String fieldName, String fieldDesc) {
+			return remapper.mapFieldName(className.replace('.', '/'), fieldName, fieldDesc);
+		}
+
+		@Override
+		protected String mapMethodName(String className, String methodName, String methodDesc) {
+			return remapper.mapMethodName(className.replace('.', '/'), methodName, methodDesc);
+		}
+
+		// Return all classes in the given package, not recursively.
+		@Override
+		protected List<String> getClassesInPackage(String pkg) {
+			return jarPackageIndex.packages().getOrDefault(pkg, Collections.emptyList())
+					.stream()
+					.map(className -> pkg + "." + className)
+					.toList();
+		}
+
+		@Override
+		protected String getFieldDesc(String className, String fieldName) {
+			TrClass trClass = tinyRemapper.getEnvironment().getClass(className.replace('.', '/'));
+
+			if (trClass != null) {
+				for (TrField trField : trClass.getFields()) {
+					if (trField.getName().equals(fieldName)) {
+						return trField.getDesc();
+					}
+				}
+			}
+
+			String fieldDesc = getFieldDescFromReflection(className, fieldName);
+
+			if (fieldDesc == null) {
+				throw new IllegalStateException("Could not find field " + fieldName + " in class " + className);
+			}
+
+			return fieldDesc;
+		}
+
+		private static String getFieldDescFromReflection(String className, String fieldName) {
+			try {
+				// Use the bootstrap class loader, which should only resolve classes from the JDK.
+				// Don't run the static initializer.
+				Class<?> clazz = Class.forName(className, false, null);
+				Field field = clazz.getDeclaredField(fieldName);
+				return Type.getDescriptor(field.getType());
+			} catch (ClassNotFoundException | NoSuchFieldException e) {
+				return null;
+			}
+		}
+	}
+}

src/main/java/net/fabricmc/loom/task/service/UnpickService.java

@@ -0,0 +1,270 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.task.service;
+
+import java.io.ByteArrayInputStream;
+import java.io.Closeable;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+import daomephsta.unpick.api.ConstantUninliner;
+import daomephsta.unpick.api.classresolvers.ClassResolvers;
+import daomephsta.unpick.api.classresolvers.IClassResolver;
+import daomephsta.unpick.api.constantgroupers.ConstantGroupers;
+import org.gradle.api.Project;
+import org.gradle.api.artifacts.ConfigurationContainer;
+import org.gradle.api.file.ConfigurableFileCollection;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.provider.Property;
+import org.gradle.api.provider.Provider;
+import org.gradle.api.tasks.Input;
+import org.gradle.api.tasks.InputFile;
+import org.gradle.api.tasks.InputFiles;
+import org.gradle.api.tasks.Nested;
+import org.gradle.api.tasks.Optional;
+import org.gradle.api.tasks.OutputFile;
+import org.jetbrains.annotations.Nullable;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.tree.ClassNode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.fabricmc.loom.LoomGradleExtension;
+import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
+import net.fabricmc.loom.configuration.providers.mappings.MappingConfiguration;
+import net.fabricmc.loom.configuration.providers.mappings.unpick.UnpickMetadata;
+import net.fabricmc.loom.task.GenerateSourcesTask;
+import net.fabricmc.loom.util.AsyncZipProcessor;
+import net.fabricmc.loom.util.Checksum;
+import net.fabricmc.loom.util.Constants;
+import net.fabricmc.loom.util.FileSystemUtil;
+import net.fabricmc.loom.util.SLF4JAdapterHandler;
+import net.fabricmc.loom.util.service.Service;
+import net.fabricmc.loom.util.service.ServiceFactory;
+import net.fabricmc.loom.util.service.ServiceType;
+
+public class UnpickService extends Service<UnpickService.Options> {
+	private static final Logger LOGGER = LoggerFactory.getLogger(UnpickService.class);
+	private static final java.util.logging.Logger JAVA_LOGGER = java.util.logging.Logger.getLogger("loom-unpick-service");
+
+	static {
+		JAVA_LOGGER.setUseParentHandlers(false);
+		JAVA_LOGGER.addHandler(new SLF4JAdapterHandler(LOGGER, true));
+	}
+
+	public static final ServiceType<Options, UnpickService> TYPE = new ServiceType<>(Options.class, UnpickService.class);
+
+	public interface Options extends Service.Options {
+		@InputFile
+		RegularFileProperty getUnpickDefinitions();
+
+		@Optional
+		@Nested
+		Property<UnpickRemapperService.Options> getUnpickRemapperService();
+
+		@InputFiles
+		ConfigurableFileCollection getUnpickConstantJar();
+
+		@InputFiles
+		ConfigurableFileCollection getUnpickClasspath();
+
+		@OutputFile
+		RegularFileProperty getUnpickOutputJar();
+
+		@Input
+		Property<Boolean> getLenient();
+	}
+
+	public static Provider<Options> createOptions(GenerateSourcesTask task) {
+		final Project project = task.getProject();
+		return TYPE.maybeCreate(project, options -> {
+			LoomGradleExtension extension = LoomGradleExtension.get(project);
+			MappingConfiguration mappingConfiguration = extension.getMappingConfiguration();
+
+			if (!mappingConfiguration.hasUnpickDefinitions()) {
+				return false;
+			}
+
+			UnpickMetadata unpickMetadata = mappingConfiguration.getUnpickMetadata();
+
+			if (unpickMetadata instanceof UnpickMetadata.V2 v2) {
+				if (!Objects.equals(v2.namespace(), MappingsNamespace.NAMED.toString())) {
+					options.getUnpickRemapperService().set(UnpickRemapperService.createOptions(project, v2));
+				}
+			}
+
+			ConfigurationContainer configurations = project.getConfigurations();
+			File mappingsWorkingDir = mappingConfiguration.mappingsWorkingDir().toFile();
+
+			options.getUnpickDefinitions().set(mappingConfiguration.getUnpickDefinitionsFile());
+			options.getUnpickOutputJar().set(task.getInputJarName().map(s -> project.getLayout()
+					.dir(project.provider(() -> mappingsWorkingDir)).get().file(s + "-unpicked.jar")));
+			options.getUnpickConstantJar().setFrom(configurations.getByName(Constants.Configurations.MAPPING_CONSTANTS));
+			options.getUnpickClasspath().setFrom(configurations.getByName(Constants.Configurations.MINECRAFT_COMPILE_LIBRARIES));
+			options.getUnpickClasspath().from(configurations.getByName(Constants.Configurations.MOD_COMPILE_CLASSPATH_MAPPED));
+			options.getLenient().set(unpickMetadata instanceof UnpickMetadata.V1);
+			extension.getMinecraftJars(MappingsNamespace.NAMED).forEach(options.getUnpickClasspath()::from);
+			return true;
+		});
+	}
+
+	public UnpickService(Options options, ServiceFactory serviceFactory) {
+		super(options, serviceFactory);
+	}
+
+	public Path unpickJar(Path inputJar, @Nullable Path existingClasses) throws IOException {
+		final List<Path> classpath = Stream.of(
+				getOptions().getUnpickClasspath().getFiles().stream().map(File::toPath),
+				getOptions().getUnpickConstantJar().getFiles().stream().map(File::toPath),
+				Stream.of(inputJar),
+				Stream.ofNullable(existingClasses)
+			).flatMap(Function.identity()).toList();
+		final Path outputJar = getOptions().getUnpickOutputJar().get().getAsFile().toPath();
+		Files.deleteIfExists(outputJar);
+
+		try (ZipFsClasspath zipFsClasspath = ZipFsClasspath.create(classpath);
+				InputStream unpickDefinitions = getUnpickDefinitionsInputStream()) {
+			IClassResolver classResolver = zipFsClasspath.createClassResolver().chain(ClassResolvers.classpath());
+			ConstantUninliner uninliner = ConstantUninliner.builder()
+					.logger(JAVA_LOGGER)
+					.classResolver(classResolver)
+					.grouper(ConstantGroupers.dataDriven()
+							.logger(JAVA_LOGGER)
+							.lenient(getOptions().getLenient().get())
+							.classResolver(classResolver)
+							.mappingSource(unpickDefinitions)
+							.build())
+					.build();
+
+			AsyncZipProcessor.processEntries(inputJar, outputJar, new UnpickZipProcessor(uninliner));
+		}
+
+		return outputJar;
+	}
+
+	private InputStream getUnpickDefinitionsInputStream() throws IOException {
+		final Path unpickDefinitionsPath = getOptions().getUnpickDefinitions().getAsFile().get().toPath();
+
+		if (getOptions().getUnpickRemapperService().isPresent()) {
+			LOGGER.info("Remapping unpick definitions: {}", unpickDefinitionsPath);
+
+			UnpickRemapperService unpickRemapperService = getServiceFactory().get(getOptions().getUnpickRemapperService());
+			String remapped = unpickRemapperService.remap(unpickDefinitionsPath.toFile());
+
+			return new ByteArrayInputStream(remapped.getBytes(StandardCharsets.UTF_8));
+		}
+
+		LOGGER.debug("Using unpick definitions: {}", unpickDefinitionsPath);
+
+		return Files.newInputStream(unpickDefinitionsPath);
+	}
+
+	public String getUnpickCacheKey() {
+		return Checksum.of(List.of(
+				Checksum.of(getOptions().getUnpickDefinitions().getAsFile().get()),
+				Checksum.of(getOptions().getUnpickConstantJar()),
+				Checksum.of(getOptions().getUnpickRemapperService()
+						.flatMap(options -> options.getTinyRemapper()
+								.flatMap(TinyRemapperService.Options::getFrom))
+						.getOrElse("named"))
+		)).sha256().hex();
+	}
+
+	private record UnpickZipProcessor(ConstantUninliner uninliner) implements AsyncZipProcessor {
+		@Override
+		public void processEntryAsync(Path input, Path output) throws IOException {
+			Files.createDirectories(output.getParent());
+
+			String fileName = input.toAbsolutePath().toString();
+
+			if (!fileName.endsWith(".class")) {
+				// Copy non-class files
+				Files.copy(input, output);
+				return;
+			}
+
+			ClassNode classNode = new ClassNode();
+
+			try (InputStream is = Files.newInputStream(input)) {
+				ClassReader reader = new ClassReader(is);
+				reader.accept(classNode, 0);
+			}
+
+			LOGGER.debug("Unpick class: {}", classNode.name);
+			uninliner.transform(classNode);
+
+			ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
+			classNode.accept(writer);
+
+			Files.write(output, writer.toByteArray());
+		}
+	}
+
+	private record ZipFsClasspath(List<FileSystemUtil.Delegate> fileSystems) implements Closeable {
+		private ZipFsClasspath {
+			if (fileSystems.isEmpty()) {
+				throw new IllegalArgumentException("No resolvers provided");
+			}
+		}
+
+		public static ZipFsClasspath create(List<Path> classpath) throws IOException {
+			var fileSystems = new ArrayList<FileSystemUtil.Delegate>();
+
+			for (Path path : classpath) {
+				FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(path, false);
+				fileSystems.add(fs);
+			}
+
+			return new ZipFsClasspath(fileSystems);
+		}
+
+		public IClassResolver createClassResolver() {
+			IClassResolver resolver = ClassResolvers.fromDirectory(fileSystems.getFirst().getRoot());
+
+			for (int i = 1; i < fileSystems.size(); i++) {
+				resolver = resolver.chain(ClassResolvers.fromDirectory(fileSystems.get(i).getRoot()));
+			}
+
+			return resolver;
+		}
+
+		@Override
+		public void close() throws IOException {
+			for (FileSystemUtil.Delegate fileSystem : fileSystems) {
+				fileSystem.close();
+			}
+		}
+	}
+}

src/main/java/net/fabricmc/loom/util/AsyncZipProcessor.java

@@ -40,17 +40,17 @@ import java.util.concurrent.Executors;
 public interface AsyncZipProcessor {
 	static void processEntries(Path inputZip, Path outputZip, AsyncZipProcessor processor) throws IOException {
 		try (FileSystemUtil.Delegate inFs = FileSystemUtil.getJarFileSystem(inputZip, false);
-				FileSystemUtil.Delegate outFs = FileSystemUtil.getJarFileSystem(outputZip, true)) {
+				FileSystemUtil.Delegate outFs = FileSystemUtil.getJarFileSystem(outputZip, true);
+				ExecutorService executor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors())) {
 			final Path inRoot = inFs.get().getPath("/");
 			final Path outRoot = outFs.get().getPath("/");
 
 			List<CompletableFuture<Void>> futures = new ArrayList<>();
-			final ExecutorService executor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
 
 			Files.walkFileTree(inRoot, new SimpleFileVisitor<>() {
 				@Override
-				public FileVisitResult visitFile(Path inputFile, BasicFileAttributes attrs) throws IOException {
+				public FileVisitResult visitFile(Path inputFile, BasicFileAttributes attrs) {
-					final CompletableFuture<Void> future = CompletableFuture.supplyAsync(() -> {
+					final CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
 						try {
 							final String rel = inRoot.relativize(inputFile).toString();
 							final Path outputFile = outRoot.resolve(rel);
@@ -58,8 +58,6 @@ public interface AsyncZipProcessor {
 						} catch (IOException e) {
 							throw new CompletionException(e);
 						}
-
-						return null;
 					}, executor);
 
 					futures.add(future);
@@ -67,7 +65,7 @@ public interface AsyncZipProcessor {
 				}
 			});
 
-			// Wait for all futures to complete
+			// Wait for all futures to complete, throwing the first exception if any
 			for (CompletableFuture<Void> future : futures) {
 				try {
 					future.join();
@@ -79,8 +77,6 @@ public interface AsyncZipProcessor {
 					throw new RuntimeException("Failed to process zip", e.getCause());
 				}
 			}
-
-			executor.shutdown();
 		}
 	}
 

src/main/java/net/fabricmc/loom/util/CacheKey.java

@@ -0,0 +1,59 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.util;
+
+import java.util.function.Supplier;
+
+import com.google.common.base.Suppliers;
+import org.gradle.api.Action;
+import org.gradle.api.Project;
+import org.gradle.api.tasks.Internal;
+
+import net.fabricmc.loom.util.gradle.GradleTypeAdapter;
+
+/**
+ * A simple base class for creating cache keys. Extend this class and create abstract properties to be included in the cache key.
+ */
+public abstract class CacheKey {
+	private static final int CHECKSUM_LENGTH = 8;
+	private final transient Supplier<String> jsonSupplier = Suppliers.memoize(() -> GradleTypeAdapter.GSON.toJson(this));
+	private final transient Supplier<String> cacheKeySupplier = Suppliers.memoize(() -> Checksum.of(jsonSupplier.get()).sha1().hex(CHECKSUM_LENGTH));
+
+	public static <T> T create(Project project, Class<T> clazz, Action<T> action) {
+		T instance = project.getObjects().newInstance(clazz);
+		action.execute(instance);
+		return instance;
+	}
+
+	@Internal
+	public final String getJson() {
+		return jsonSupplier.get();
+	}
+
+	@Internal
+	public final String getCacheKey() {
+		return cacheKeySupplier.get();
+	}
+}

src/main/java/net/fabricmc/loom/util/Checksum.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2016-2020 FabricMC
+ * Copyright (c) 2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -26,88 +26,138 @@ package net.fabricmc.loom.util;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
 import java.io.UncheckedIOException;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.nio.file.Path;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.HexFormat;
+import java.util.List;
 
-import com.google.common.hash.HashCode;
-import com.google.common.hash.Hashing;
-import com.google.common.io.BaseEncoding;
-import com.google.common.io.ByteSource;
-import com.google.common.io.Files;
 import org.gradle.api.Project;
-import org.gradle.api.logging.Logger;
+import org.gradle.api.file.FileCollection;
-import org.gradle.api.logging.Logging;
+import org.jetbrains.annotations.NotNull;
 
-public class Checksum {
+public final class Checksum {
-	private static final Logger log = Logging.getLogger(Checksum.class);
+	public static Checksum of(byte[] data) {
+		return new Checksum(digest -> digest.write(data));
+	}
 
-	public static boolean equals(File file, String checksum) {
+	public static Checksum of(String str) {
-		if (file == null || !file.exists()) {
+		return new Checksum(digest -> digest.write(str));
-			return false;
+	}
-		}
+
+	public static Checksum of(File file) {
+		return of(file.toPath());
+	}
+
+	public static Checksum of(Path file) {
+		return new Checksum(digest -> {
+			try (InputStream is = Files.newInputStream(file)) {
+				is.transferTo(digest);
+			}
+		});
+	}
+
+	public static Checksum of(Project project) {
+		return of(project.getProjectDir().getAbsolutePath() + ":" + project.getPath());
+	}
+
+	public static Checksum of(FileCollection files) {
+		return new Checksum(os -> {
+			for (File file : files) {
+				try (InputStream is = Files.newInputStream(file.toPath())) {
+					is.transferTo(os);
+				}
+			}
+		});
+	}
+
+	public static Checksum of(List<Checksum> others) {
+		return new Checksum(os -> {
+			for (Checksum other : others) {
+				other.consumer.accept(os);
+			}
+		});
+	}
+
+	private final DataConsumer consumer;
+
+	private Checksum(DataConsumer consumer) {
+		this.consumer = consumer;
+	}
+
+	public Result sha1() {
+		return computeResult("SHA-1");
+	}
+
+	public Result sha256() {
+		return computeResult("SHA-256");
+	}
+
+	public Result md5() {
+		return computeResult("MD5");
+	}
+
+	private Result computeResult(String algorithm) {
+		MessageDigest digest;
 
 		try {
-			HashCode hash = Files.asByteSource(file).hash(Hashing.sha1());
+			digest = MessageDigest.getInstance(algorithm);
-			String hashString = hash.toString();
+		} catch (NoSuchAlgorithmException e) {
-			log.debug("Checksum check: '" + hashString + "' == '" + checksum + "'?");
+			throw new RuntimeException(e);
-			return hashString.equals(checksum);
-		} catch (IOException e) {
-			e.printStackTrace();
 		}
 
-		return false;
+		try (MessageDigestOutputStream os = new MessageDigestOutputStream(digest)) {
+			consumer.accept(os);
+		} catch (IOException e) {
+			throw new UncheckedIOException("Failed to compute checksum", e);
+		}
+
+		return new Result(digest.digest());
 	}
 
-	public static byte[] sha256(File file) {
+	public record Result(byte[] digest) {
-		try {
+		public String hex() {
-			HashCode hash = Files.asByteSource(file).hash(Hashing.sha256());
+			return HexFormat.of().formatHex(digest());
-			return hash.asBytes();
+		}
-		} catch (IOException e) {
+
-			throw new UncheckedIOException("Failed to get file hash", e);
+		public String hex(int length) {
+			return hex().substring(0, length);
+		}
+
+		public boolean matchesStr(String other) {
+			return hex().equalsIgnoreCase(other);
 		}
 	}
 
-	public static String sha256Hex(byte[] input) throws IOException {
+	@FunctionalInterface
-		HashCode hash = ByteSource.wrap(input).hash(Hashing.sha256());
+	private interface DataConsumer {
-		return Checksum.toHex(hash.asBytes());
+		void accept(MessageDigestOutputStream os) throws IOException;
 	}
 
-	public static String sha1Hex(Path path) throws IOException {
+	private static class MessageDigestOutputStream extends OutputStream {
-		HashCode hash = Files.asByteSource(path.toFile()).hash(Hashing.sha1());
+		private final MessageDigest digest;
-		return toHex(hash.asBytes());
-	}
 
-	public static String sha1Hex(byte[] input) {
+		private MessageDigestOutputStream(MessageDigest digest) {
-		try {
+			this.digest = digest;
-			HashCode hash = ByteSource.wrap(input).hash(Hashing.sha1());
-			return toHex(hash.asBytes());
-		} catch (IOException e) {
-			throw new UncheckedIOException("Failed to hash", e);
 		}
-	}
 
-	public static String truncatedSha256(File file) {
+		@Override
-		try {
+		public void write(int b) {
-			HashCode hash = Files.asByteSource(file).hash(Hashing.sha256());
+			digest.update((byte) b);
-			return hash.toString().substring(0, 12);
-		} catch (IOException e) {
-			throw new UncheckedIOException("Failed to get file hash of " + file, e);
 		}
-	}
 
-	public static byte[] sha256(String string) {
+		@Override
-		HashCode hash = Hashing.sha256().hashString(string, StandardCharsets.UTF_8);
+		public void write(byte @NotNull[] b, int off, int len) {
-		return hash.asBytes();
+			digest.update(b, off, len);
-	}
+		}
 
-	public static String toHex(byte[] bytes) {
+		public void write(String string) throws IOException {
-		return BaseEncoding.base16().lowerCase().encode(bytes);
+			write(string.getBytes(StandardCharsets.UTF_8));
-	}
+		}
-
-	public static String projectHash(Project project) {
-		String str = project.getProjectDir().getAbsolutePath() + ":" + project.getPath();
-		String hex = sha1Hex(str.getBytes(StandardCharsets.UTF_8));
-		return hex.substring(hex.length() - 16);
 	}
 }

src/main/java/net/fabricmc/loom/util/Constants.java

@@ -101,7 +101,6 @@ public class Constants {
 		 */
 		public static final String FORGE_RUNTIME_LIBRARY = "forgeRuntimeLibrary";
 		public static final String MAPPING_CONSTANTS = "mappingsConstants";
-		public static final String UNPICK_CLASSPATH = "unpick";
 		/**
 		 * A configuration that behaves like {@code runtimeOnly} but is not
 		 * exposed in {@code runtimeElements} to dependents. A bit like
@@ -176,6 +175,14 @@ public class Constants {
 		public static final String RUNTIME_JAVA_COMPATIBILITY_VERSION = "fabric.loom.runtimeJavaCompatibilityVersion";
 		public static final String DECOMPILE_CACHE_MAX_FILES = "fabric.loom.decompileCacheMaxFiles";
 		public static final String DECOMPILE_CACHE_MAX_AGE = "fabric.loom.decompileCacheMaxAge";
+		/**
+		 * Skip the signature verification of the Minecraft jar after downloading it.
+		 */
+		public static final String DISABLE_MINECRAFT_VERIFICATION = "fabric.loom.disableMinecraftVerification";
+		/**
+		 * When using the MojangMappingLayer this will remove names for non root methods by using the intermediary mappings.
+		 */
+		public static final String DROP_NON_INTERMEDIATE_ROOT_METHODS = "fabric.loom.dropNonIntermediateRootMethods";
 		public static final String ALLOW_MISMATCHED_PLATFORM_VERSION = "loom.allowMismatchedPlatformVersion";
 		public static final String IGNORE_DEPENDENCY_LOOM_VERSION_VALIDATION = "loom.ignoreDependencyLoomVersionValidation";
 	}

src/main/java/net/fabricmc/loom/util/IdentityBiMap.java

@@ -0,0 +1,49 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.util;
+
+import java.util.IdentityHashMap;
+import java.util.Map;
+
+public final class IdentityBiMap<K, V> {
+	private final Map<K, V> keyToValue = new IdentityHashMap<>();
+	private final Map<V, K> valueToKey = new IdentityHashMap<>();
+
+	public IdentityBiMap() {
+	}
+
+	public void put(K key, V value) {
+		keyToValue.put(key, value);
+		valueToKey.put(value, key);
+	}
+
+	public V getByKey(K key) {
+		return keyToValue.get(key);
+	}
+
+	public K getByValue(V value) {
+		return valueToKey.get(value);
+	}
+}

src/main/java/net/fabricmc/loom/util/JarPackageIndex.java

@@ -0,0 +1,100 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.util;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executors;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+/**
+ * An index of all packages and the classes directly contained within.
+ */
+public record JarPackageIndex(Map<String, List<String>> packages) {
+	public static JarPackageIndex create(List<Path> jars) {
+		Map<String, List<String>> packages = jars.stream()
+				.map(jar -> CompletableFuture.supplyAsync(() -> {
+					try {
+						List<String> classes = getClasses(jar);
+						return groupClassesByPackage(classes);
+					} catch (IOException e) {
+						throw new RuntimeException(e);
+					}
+				}, Executors.newVirtualThreadPerTaskExecutor()))
+				.map(CompletableFuture::join)
+				.flatMap(map -> map.entrySet().stream())
+				.collect(Collectors.toMap(
+						Map.Entry::getKey,
+						Map.Entry::getValue,
+						(existing, newValues) -> {
+							existing.addAll(newValues);
+							return existing;
+						}
+				));
+
+		return new JarPackageIndex(packages);
+	}
+
+	private static List<String> getClasses(Path jar) throws IOException {
+		try (FileSystemUtil.Delegate fs = FileSystemUtil.getJarFileSystem(jar, false);
+				Stream<Path> walk = Files.walk(fs.getRoot())) {
+			return walk
+					.filter(Files::isRegularFile)
+					.map(Path::toString)
+					.filter(className -> className.endsWith(".class"))
+					.map(className -> className.startsWith("/") ? className.substring(1) : className)
+					.toList();
+		}
+	}
+
+	private static Map<String, List<String>> groupClassesByPackage(List<String> classes) {
+		return classes.stream()
+				.filter(className -> className.endsWith(".class")) // Ensure it's a class file
+				.collect(Collectors.groupingBy(
+						JarPackageIndex::extractPackageName,
+						Collectors.mapping(
+								JarPackageIndex::extractClassName,
+								Collectors.toList()
+						)
+				));
+	}
+
+	// Returns the package name from a class name, e.g., "com/example/MyClass.class" -> "com.example"
+	private static String extractPackageName(String className) {
+		int lastSlashIndex = className.lastIndexOf('/');
+		return lastSlashIndex == -1 ? "" : className.substring(0, lastSlashIndex).replace("/", ".");
+	}
+
+	private static String extractClassName(String className) {
+		int lastSlashIndex = className.lastIndexOf('/');
+		String simpleName = lastSlashIndex == -1 ? className : className.substring(lastSlashIndex + 1);
+		return simpleName.endsWith(".class") ? simpleName.substring(0, simpleName.length() - 6) : simpleName;
+	}
+}

src/main/java/net/fabricmc/loom/util/Platform.java

@@ -53,6 +53,10 @@ public interface Platform {
 		boolean isArm();
 
 		boolean isRiscV();
+
+		default boolean isX64() {
+			return is64Bit() && !isArm() && !isRiscV();
+		}
 	}
 
 	Architecture getArchitecture();

src/main/java/net/fabricmc/loom/util/SLF4JAdapterHandler.java

@@ -0,0 +1,64 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.util;
+
+import java.util.logging.Handler;
+import java.util.logging.Level;
+import java.util.logging.LogRecord;
+
+import org.slf4j.Logger;
+
+public class SLF4JAdapterHandler extends Handler {
+	private final Logger logger;
+	private final boolean suppressWarnings;
+
+	public SLF4JAdapterHandler(Logger logger, boolean suppressWarnings) {
+		this.logger = logger;
+		this.suppressWarnings = suppressWarnings;
+	}
+
+	@Override
+	public void publish(LogRecord record) {
+		if (record.getLevel().intValue() >= Level.SEVERE.intValue()) {
+			logger.error(record.getMessage(), record.getThrown());
+		} else if (record.getLevel().intValue() >= Level.WARNING.intValue() && !suppressWarnings) {
+			logger.warn(record.getMessage(), record.getThrown());
+		} else if (record.getLevel().intValue() >= Level.INFO.intValue()) {
+			logger.info(record.getMessage(), record.getThrown());
+		} else if (record.getLevel().intValue() >= Level.FINER.intValue()) {
+			logger.debug(record.getMessage(), record.getThrown());
+		} else {
+			logger.trace(record.getMessage(), record.getThrown());
+		}
+	}
+
+	@Override
+	public void flush() {
+	}
+
+	@Override
+	public void close() throws SecurityException {
+	}
+}

src/main/java/net/fabricmc/loom/util/SourceRemapper.java

@@ -120,7 +120,7 @@ public class SourceRemapper {
 			source = new File(destination.getAbsolutePath().substring(0, destination.getAbsolutePath().lastIndexOf('.')) + "-dev.jar");
 
 			try {
-				com.google.common.io.Files.move(destination, source);
+				Files.move(destination.toPath(), source.toPath());
 			} catch (IOException e) {
 				throw new RuntimeException("Could not rename " + destination.getName() + "!", e);
 			}

src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java

@@ -31,7 +31,6 @@ import java.util.Set;
 import java.util.function.Consumer;
 import java.util.regex.Pattern;
 
-import com.google.common.collect.ImmutableMap;
 import dev.architectury.loom.util.MappingOption;
 import org.gradle.api.Project;
 
@@ -50,11 +49,11 @@ import net.fabricmc.tinyremapper.TinyRemapper;
  * Contains shortcuts to create tiny remappers using the mappings accessibly to the project.
  */
 public final class TinyRemapperHelper {
-	public static final Map<String, String> JSR_TO_JETBRAINS = new ImmutableMap.Builder<String, String>()
+	public static final Map<String, String> JSR_TO_JETBRAINS = Map.of(
-			.put("javax/annotation/Nullable", "org/jetbrains/annotations/Nullable")
+				"javax/annotation/Nullable", "org/jetbrains/annotations/Nullable",
-			.put("javax/annotation/Nonnull", "org/jetbrains/annotations/NotNull")
+				"javax/annotation/Nonnull", "org/jetbrains/annotations/NotNull",
-			.put("javax/annotation/concurrent/Immutable", "org/jetbrains/annotations/Unmodifiable")
+				"javax/annotation/concurrent/Immutable", "org/jetbrains/annotations/Unmodifiable"
-			.build();
+			);
 
 	/**
 	 * Matches the new local variable naming format introduced in 21w37a.

src/main/java/net/fabricmc/loom/util/ZipReprocessorUtil.java

@@ -46,7 +46,7 @@ public class ZipReprocessorUtil {
 	private static final String META_INF = "META-INF/";
 
 	// See https://docs.oracle.com/en/java/javase/20/docs/specs/jar/jar.html#signed-jar-file
-	private static boolean isSpecialFile(String zipEntryName) {
+	public static boolean isSpecialFile(String zipEntryName) {
 		if (!zipEntryName.startsWith(META_INF)) {
 			return false;
 		}