GradleUp · Goooler · Aug 10, 2026
diff --git a/api/shadow.api b/api/shadow.api
@@ -229,6 +229,7 @@ public abstract interface class com/github/jengelman/gradle/plugins/shadow/tasks
 	public abstract fun getConfigurationFile ()Lorg/gradle/api/file/RegularFileProperty;
 	public fun getKeepRuleFiles ()Lorg/gradle/api/file/ConfigurableFileCollection;
 	public fun getKeepRules ()Lorg/gradle/api/provider/ListProperty;
+	public abstract fun getMaxHeapSize ()Lorg/gradle/api/provider/Property;
 	public abstract fun getProguardRuleFiles ()Lorg/gradle/api/file/ConfigurableFileCollection;
 	public abstract fun getProguardRules ()Lorg/gradle/api/provider/ListProperty;
 }
@@ -279,6 +280,7 @@ public abstract class com/github/jengelman/gradle/plugins/shadow/tasks/ShadowJar
 	public fun getSourceSetsClassesDirs ()Lorg/gradle/api/file/ConfigurableFileCollection;
 	public fun getToMinimize ()Lorg/gradle/api/file/ConfigurableFileCollection;
 	public fun getTransformers ()Lorg/gradle/api/provider/SetProperty;
+	protected abstract fun getWorkerExecutor ()Lorg/gradle/workers/WorkerExecutor;
 	public fun mergeGroovyExtensionModules ()V
 	public final fun mergeServiceFiles ()V
 	public fun mergeServiceFiles (Ljava/lang/String;)V

diff --git a/docs/changes/README.md b/docs/changes/README.md
@@ -6,13 +6,15 @@
 ### Added
 
 - Allow configuring the final R8 configuration file with `R8Spec.configurationFile`. ([#2133](https://github.com/GradleUp/shadow/pull/2133))
+- Allow configuring the R8 worker maximum heap size with `R8Spec.maxHeapSize`. ([#2172](https://github.com/GradleUp/shadow/pull/2172))
 
 ### Changed
 
 - Bump min Gradle requirement to 9.4.0. ([#2114](https://github.com/GradleUp/shadow/pull/2114))
 - Remove runtime dependencies on Commons Codec and Commons IO by using JDK APIs. ([#2136](https://github.com/GradleUp/shadow/pull/2136))
 - **POTENTIALLY BREAKING:** Remove `Serializable` from `DependencyFilter`. ([#2144](https://github.com/GradleUp/shadow/pull/2144))
 - Bump default R8 from `9.1.31` to `9.2.23`. ([#2157](https://github.com/GradleUp/shadow/pull/2157))
+- Use Gradle Worker API for R8 minimization. ([#2172](https://github.com/GradleUp/shadow/pull/2172))
 - Allow repackaging Service file classes with R8. ([#2174](https://github.com/GradleUp/shadow/pull/2174))
 
 ### Deprecated

diff --git a/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/MinimizeTest.kt b/src/functionalTest/kotlin/com/github/jengelman/gradle/plugins/shadow/MinimizeTest.kt
@@ -658,6 +658,49 @@ class MinimizeTest : BasePluginTest() {
     assertThat(result.output).contains("R8 launcher JDK ${JavaVersion.current().majorVersion}")
   }
 
+  @Test
+  fun minimizeWithR8UsesGradleDaemonMaxHeapSize() {
+    writeR8Repository()
+    writeR8ClientAndServerModules(
+      serverShadowBlock =
+        """
+        |minimize {
+        |  r8 {}
+        |}
+        """
+          .trimMargin()
+    )
+    path("gradle.properties").writeText("org.gradle.jvmargs=-Xmx768m")
+
+    val result = runWithSuccess(serverShadowJarPath, infoArgument)
+
+    val workerCommand =
+      result.output.lineSequence().single { "Starting process 'Gradle Worker Daemon" in it }
+    assertThat(workerCommand).contains("-Xmx${768L * 1024 * 1024}")
+  }
+
+  @Test
+  fun minimizeWithR8CanConfigureMaxHeapSize() {
+    writeR8Repository()
+    writeR8ClientAndServerModules(
+      serverShadowBlock =
+        """
+        |minimize {
+        |  r8 {
+        |    maxHeapSize.set("640m")
+        |  }
+        |}
+        """
+          .trimMargin()
+    )
+
+    val result = runWithSuccess(serverShadowJarPath, infoArgument)
+
+    val workerCommand =
+      result.output.lineSequence().single { "Starting process 'Gradle Worker Daemon" in it }
+    assertThat(workerCommand).contains("-Xmx640m")
+  }
+
   private fun writeApiLibAndImplModules() {
     settingsScript.appendText(
       """

diff --git a/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultR8Spec.kt b/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultR8Spec.kt
@@ -22,6 +22,9 @@ constructor(
 
   @get:Input val optimizationEnabled: Property<Boolean> = objectFactory.property(false)
 
+  override val maxHeapSize: Property<String> =
+    objectFactory.property(Runtime.getRuntime().maxMemory().toString())
+
   override val args: ListProperty<String> = objectFactory.listProperty(defaultArgs)
 
   override val proguardRules: ListProperty<String> = objectFactory.listProperty()

diff --git a/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/R8Minimizer.kt b/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/R8Minimizer.kt
@@ -11,9 +11,12 @@ import org.apache.tools.zip.ZipOutputStream
 import org.gradle.api.GradleException
 import org.gradle.api.file.FileCollection
 import org.gradle.api.logging.Logger
+import org.gradle.api.provider.ListProperty
 import org.gradle.api.provider.Provider
 import org.gradle.jvm.toolchain.JavaLauncher
-import org.gradle.process.ExecOperations
+import org.gradle.workers.WorkAction
+import org.gradle.workers.WorkParameters
+import org.gradle.workers.WorkerExecutor
 
 /**
  * Runs R8 as a final-archive shrinker.
@@ -36,7 +39,7 @@ import org.gradle.process.ExecOperations
 internal fun minimizeWithR8(
   inputJar: File,
   temporaryDir: File,
-  execOperations: ExecOperations,
+  workerExecutor: WorkerExecutor,
   logger: Logger,
   r8Classpath: FileCollection,
   r8Spec: DefaultR8Spec,
@@ -95,14 +98,15 @@ internal fun minimizeWithR8(
   }
 
   logger.info("Running R8 to minimize {}.", inputJar)
-  execOperations.javaexec {
-    it.classpath = r8Classpath
-    it.mainClass.set(R8_MAIN_CLASS)
+  val workQueue = workerExecutor.processIsolation {
+    it.classpath.from(r8Classpath)
+    it.forkOptions.maxHeapSize = r8Spec.maxHeapSize.get()
     if (launcher != null) {
-      it.executable = launcher.executablePath.asFile.absolutePath
+      it.forkOptions.executable = launcher.executablePath.asFile.absolutePath
     }
-    it.args(arguments)
   }
+  workQueue.submit(R8WorkAction::class.java) { it.r8Args.set(arguments) }
+  workQueue.await()
 
   normalizeJar(
     inputJar = r8Output,
@@ -339,6 +343,19 @@ internal fun normalizeJar(
   }
 }
 
+internal abstract class R8WorkAction : WorkAction<R8WorkAction.Parameters> {
+  override fun execute() {
+    val args = parameters.r8Args.get().toTypedArray()
+    val r8Class = Class.forName(R8_MAIN_CLASS, true, javaClass.classLoader)
+    val mainMethod = r8Class.getMethod("main", Array<String>::class.java)
+    mainMethod(null, args)
+  }
+
+  interface Parameters : WorkParameters {
+    val r8Args: ListProperty<String>
+  }
+}
+
 private const val R8_MAIN_CLASS = "com.android.tools.r8.R8"
 private const val SERVICES_PATH = "META-INF/services/"
 // Keep only ordinary dot-separated Java type names in generated rules. This filters out blank

diff --git a/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/R8Spec.kt b/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/R8Spec.kt
@@ -4,15 +4,26 @@ import com.github.jengelman.gradle.plugins.shadow.ShadowDsl
 import org.gradle.api.file.ConfigurableFileCollection
 import org.gradle.api.file.RegularFileProperty
 import org.gradle.api.provider.ListProperty
+import org.gradle.api.provider.Property
 import org.gradle.api.tasks.Input
 import org.gradle.api.tasks.InputFiles
+import org.gradle.api.tasks.Internal
 import org.gradle.api.tasks.OutputFile
 import org.gradle.api.tasks.PathSensitive
 import org.gradle.api.tasks.PathSensitivity
 
 /** Minimal R8 configuration for [ShadowJar.minimize]. */
 @ShadowDsl
 public interface R8Spec {
+  /**
+   * The maximum heap size for the R8 worker process.
+   *
+   * Defaults to the effective maximum heap size of the Gradle daemon. The value uses JVM memory
+   * notation, such as `2g` or `512m`.
+   */
+  @get:Internal // Doesn't affect the output.
+  public val maxHeapSize: Property<String>
+
   /**
    * Additional R8 command line arguments.
    *

diff --git a/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/ShadowJar.kt b/src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/ShadowJar.kt
@@ -71,6 +71,7 @@ import org.gradle.api.tasks.options.Option
 import org.gradle.jvm.toolchain.JavaLauncher
 import org.gradle.language.base.plugins.LifecycleBasePlugin
 import org.gradle.process.ExecOperations
+import org.gradle.workers.WorkerExecutor
 
 @ShadowDsl
 @CacheableTask
@@ -330,10 +331,14 @@ public abstract class ShadowJar : Jar() {
    */
   override fun getDuplicatesStrategy(): DuplicatesStrategy = super.getDuplicatesStrategy()
 
-  @get:Inject protected abstract val execOperations: ExecOperations
+  @Deprecated("Replace the logic with `workerExecutor`. This will be removed in Shadow 10.")
+  @get:Inject
+  protected abstract val execOperations: ExecOperations
 
   @get:Inject protected abstract val archiveOperations: ArchiveOperations
 
+  @get:Inject protected abstract val workerExecutor: WorkerExecutor
+
   /** Enable minimization and execute the [action] with the [MinimizeSpec] for minimize. */
   @JvmOverloads
   public open fun minimize(action: Action<in MinimizeSpec> = Action {}) {
@@ -703,7 +708,7 @@ public abstract class ShadowJar : Jar() {
     minimizeWithR8(
       inputJar = archiveFile.get().asFile,
       temporaryDir = temporaryDir,
-      execOperations = execOperations,
+      workerExecutor = workerExecutor,
       logger = logger,
       r8Classpath = r8Classpath,
       r8Spec = defaultMinimizeSpec.r8Spec,

diff --git a/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/MinimizeSpecsTest.kt b/src/test/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/MinimizeSpecsTest.kt
@@ -39,6 +39,7 @@ class MinimizeSpecsTest {
       assertThat(args.get()).containsExactly(DefaultR8Spec.NO_MINIFICATION_ARG)
       assertThat(obfuscationEnabled.get()).isFalse()
       assertThat(optimizationEnabled.get()).isFalse()
+      assertThat(maxHeapSize.get()).isEqualTo(Runtime.getRuntime().maxMemory().toString())
       assertThat(proguardRules.get()).isEmpty()
       assertThat(proguardRuleFiles.files).isEmpty()
       assertThat(configurationFile.get().asFile)