Parallelized mod builds

- Mod targets run through bounded Gradle workers with separate caches and daemon slots - Target logs retain verification failures and bounded output summaries - Nested tests use bounded forks and JVM thread counts - Lifecycle tests control deadlines through injected clocks
2026-10-23 00:28:02 +00:00 · 2026-10-21 02:53:00 -04:00
1 parent d7059d84a4
commit fc810221bb
@@ -17,6 +17,7 @@
 */

 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
+import net.minecraftforge.gradle.shadow.net.minecraftforge.gradleutils.shared.EnhancedPlugin
 import org.gradle.api.file.DeleteSpec
 import org.gradle.api.file.FileCopyDetails
 import org.gradle.api.file.FileSystemOperations
@@ -62,6 +63,14 @@ file('../../gradle.properties').withInputStream { InputStream stream -> rootProp
 String irisVersion = providers.gradleProperty('irisVersion').getOrElse(rootProperties.getProperty('irisVersion', '4.3.5'))
 String minecraftVersion = providers.gradleProperty('minecraftVersion').getOrElse(rootProperties.getProperty('minecraftVersion', '26.3'))
 String forgeVersion = providers.gradleProperty('forgeVersion').getOrElse(irisModTarget.forge.toString())
+String buildLane = gradle.extensions.extraProperties.has('irisBuildLane')
+    ? gradle.extensions.extraProperties.get('irisBuildLane').toString() : null
+if (buildLane != null) {
+    plugins.withType(EnhancedPlugin).configureEach { EnhancedPlugin<?> forgePlugin ->
+        forgePlugin.globalCaches().set(layout.projectDirectory.dir(".gradle/iris-lanes/${buildLane}/forgegradle"))
+    }
+    minecraft.mavenizerOutput.set(layout.projectDirectory.dir(".gradle/iris-lanes/${buildLane}/mavenizer/repo"))
+}
 Closure<String> loaderDisplayVersion = { String loaderVersion ->
    String coordinatePrefix = "${minecraftVersion}-"
    if (loaderVersion.startsWith(coordinatePrefix)) {
@@ -161,7 +170,9 @@ configurations.testRuntimeClasspath.extendsFrom(configurations.runtimeClasspath,
 }

 dependencies {
-    implementation minecraft.dependency("net.minecraftforge:forge:${forgeVersion}")
+    implementation(buildLane == null
+        ? minecraft.dependency("net.minecraftforge:forge:${forgeVersion}")
+        : minecraft.dependency("iris-${buildLane}", "net.minecraftforge:forge:${forgeVersion}"))
    testImplementation('junit:junit:4.13.2')
    testImplementation('org.mockito:mockito-core:5.23.0')
    testImplementation(testFixtures('art.arcane:core'))
@@ -30,6 +30,7 @@ import art.arcane.iris.generation.runtime.Engine;
 import art.arcane.iris.modded.ModdedGenPool;
 import art.arcane.volmlib.util.mantle.runtime.Mantle;

+import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Semaphore;
@@ -39,6 +40,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.LongSupplier;

 public final class ModdedPregenMethod implements PregeneratorMethod {
    private static final int ADAPTIVE_TIMEOUT_STEP = 3;
@@ -68,8 +70,14 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
    private final int timeoutSeconds;
    private final PregenMantleBackpressure backpressure;
    private final PauseWhenEmptyGuard pauseGuard;
+    private final LongSupplier clock;

    public ModdedPregenMethod(Configuration configuration) {
+        this(configuration, System::nanoTime);
+    }
+
+    ModdedPregenMethod(Configuration configuration, LongSupplier clock) {
+        this.clock = Objects.requireNonNull(clock);
        runtime = configuration.runtime();
        engine = configuration.engine();
        sync = configuration.sync();
@@ -178,7 +186,7 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
        if (sync || runtime.isServerThread()) {
            return;
        }
-        long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(timeoutSeconds)
+        long deadline = clock.getAsLong() + TimeUnit.SECONDS.toNanos(timeoutSeconds)
                + TimeUnit.MILLISECONDS.toNanos(FINAL_SAVE_TIMEOUT_MILLIS);
        boolean interrupted = false;
        try {
@@ -186,7 +194,7 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
                if (finalSaveOnServerThread.get() || !runtime.isRunning()) {
                    return;
                }
-                if (System.nanoTime() >= deadline) {
+                if (clock.getAsLong() >= deadline) {
                    throw new IllegalStateException("Iris pregen chunk callbacks did not finish for "
                            + runtime.worldIdentity() + ": " + inFlight.get() + " pending");
                }
@@ -263,14 +271,14 @@ public final class ModdedPregenMethod implements PregeneratorMethod {
    }

    private void awaitFinalSave(FinalSaveRequest request) {
-        long deadline = System.nanoTime() + TimeUnit.MILLISECONDS.toNanos(FINAL_SAVE_TIMEOUT_MILLIS);
+        long deadline = clock.getAsLong() + TimeUnit.MILLISECONDS.toNanos(FINAL_SAVE_TIMEOUT_MILLIS);
        boolean interrupted = false;
        try {
            while (true) {
                if (deferFinalSaveIfRequested()) {
                    return;
                }
-                long remainingNanos = deadline - System.nanoTime();
+                long remainingNanos = deadline - clock.getAsLong();
                if (remainingNanos <= 0L) {
                    ModdedIrisLog.warn("Iris pregen level save did not complete in time for {}", runtime.worldIdentity());
                    return;
@@ -21,6 +21,7 @@ import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;

 import static org.junit.Assert.assertEquals;
@@ -97,6 +98,9 @@ public class ModdedPregenMethodLifecycleTest {

    @Test
    public void finalSaveWaitsForEveryCallbackBeyondFiveSeconds() throws Exception {
+        AtomicLong clock = new AtomicLong();
+        CountDownLatch started = new CountDownLatch(1);
+        CountDownLatch advanced = new CountDownLatch(2);
        CompletableFuture<ChunkLoad> load = new CompletableFuture<>();
        CompletableFuture<ChunkLoad> failedLoad = new CompletableFuture<>();
        PregenListener listener = mock(PregenListener.class);
@@ -110,16 +114,22 @@ public class ModdedPregenMethodLifecycleTest {
        }).when(runtime).execute(any());
        try (MockedStatic<MantleHeapPressure> pressure = mockStatic(MantleHeapPressure.class)) {
            pressure.when(MantleHeapPressure::memoryBudgetBytes).thenReturn(512L << 20);
-            method = new ModdedPregenMethod(new ModdedPregenMethod.Configuration(runtime, engine, false));
+            method = new ModdedPregenMethod(new ModdedPregenMethod.Configuration(runtime, engine, false), () -> {
+                long now = clock.get();
+                if (now >= TimeUnit.SECONDS.toNanos(6)) {
+                    advanced.countDown();
+                } else {
+                    started.countDown();
+                }
+                return now;
+            });
            method.generateChunk(2, 3, listener);
            method.generateChunk(4, 5, listener);
-            CountDownLatch started = new CountDownLatch(1);
-            Future<?> closing = executor.submit(() -> {
-                started.countDown();
-                method.close();
-            });
+            Future<?> closing = executor.submit(method::close);
            assertTrue(started.await(5, TimeUnit.SECONDS));
-            assertThrows(TimeoutException.class, () -> closing.get(6, TimeUnit.SECONDS));
+            clock.set(TimeUnit.SECONDS.toNanos(6));
+            assertTrue(advanced.await(5, TimeUnit.SECONDS));
+            assertFalse(closing.isDone());
            verify(runtime, never()).save();
            verify(engine, never()).syncGenerationHistory();
            load.complete(new ChunkLoad(true, null));
@@ -329,7 +329,12 @@ List<Object> moddedSharedInputs = []
    'gradle/mod-target.gradle',
    'gradle/mod-targets.json',
    'gradle/runtime-cache.settings.gradle',
-    'gradle/modded-version-sources.gradle'
+    'gradle/nested-build.init.gradle',
+    'gradle/modded-version-sources.gradle',
+    'gradle/wrapper/gradle-wrapper.properties',
+    'gradle/wrapper/gradle-wrapper.jar',
+    'gradlew',
+    'gradlew.bat'
 ].each { String path -> moddedSharedInputs.add(layout.projectDirectory.file(path).asFile) }
 if (localVolmLibCheckout != null) {
    moddedSharedInputs.add(fileTree(localVolmLibCheckout) {
@@ -343,11 +348,11 @@ if (localVolmLibCheckout != null) {

 // The published master-SNAPSHOT is resolved inside the nested build, so no outer input changes when it
 // moves. Without a local checkout the Exec tasks always run and the nested build decides what is stale.
-Closure<Void> declareVolmLibInputs = { Exec task ->
+Closure<Void> declareVolmLibInputs = { IrisModdedBuild task ->
    task.inputs.property('volmLibStamp', volmLibStamp)
    String nativeBillow = providers.gradleProperty('includeNativeBillow').getOrElse('false')
    task.inputs.property('includeNativeBillow', nativeBillow)
-    task.environment('ORG_GRADLE_PROJECT_includeNativeBillow', nativeBillow)
+    task.environment.put('ORG_GRADLE_PROJECT_includeNativeBillow', nativeBillow)
    if (localVolmLibCheckout == null) {
        task.outputs.upToDateWhen { false }
    }
@@ -413,9 +418,29 @@ TaskProvider<Task> verifyModdedMatrix = tasks.register('verifyModdedMatrix') {
    description = 'Builds, tests and verifies the Fabric, Forge and NeoForge jars of every supported Minecraft mod target.'
 }
 List<TaskProvider<Copy>> moddedExports = []
-Map<String, TaskProvider<Exec>> selectedModdedBuilds = [:]
+Map<String, TaskProvider<IrisModdedBuild>> selectedModdedBuilds = [:]
 Map<String, TaskProvider<Copy>> selectedModdedExports = [:]
-TaskProvider<Exec> previousMatrixBuild = null
+int matrixParallelism = Math.min(gradle.startParameter.maxWorkerCount, Math.max(1,
+    providers.gradleProperty('moddedBuildParallelism').getOrElse(
+        Math.min(12, Math.max(1, Runtime.runtime.availableProcessors() - 4)).toString()).toInteger()))
+Provider<IrisModdedBuildService> matrixWorkers = gradle.sharedServices.registerIfAbsent(
+    'irisModdedBuilds', IrisModdedBuildService) {
+    maxParallelUsages.set(matrixParallelism)
+}
+List<String> nestedBuildArguments = [gradle.startParameter.buildCacheEnabled ? '--build-cache' : '--no-build-cache']
+String nestedJvmArguments = providers.gradleProperty('org.gradle.jvmargs').getOrElse('') +
+    ' -XX:ActiveProcessorCount=2'
+if (gradle.startParameter.rerunTasks) {
+    nestedBuildArguments.add('--rerun-tasks')
+}
+if (gradle.startParameter.refreshDependencies) {
+    nestedBuildArguments.add('--refresh-dependencies')
+}
+for (File initScript : gradle.startParameter.initScripts) {
+    nestedBuildArguments.addAll(['--init-script', initScript.absolutePath])
+}
+Map<Integer, TaskProvider<IrisModdedBuild>> daemonSlots = [:]
+int nextDaemonSlot = 0
 irisModTargets.each { String targetMinecraft, Map<String, Object> target ->
    String suffix = targetMinecraft.replace('.', '_')
    boolean selected = targetMinecraft == minecraftVersion
@@ -426,46 +451,66 @@ irisModTargets.each { String targetMinecraft, Map<String, Object> target ->
        String artifactName = irisArtifactName(label, "${targetMinecraft}+${displayedLoader}")
        File artifact = file("adapters/${loader}/build/${targetMinecraft}/libs/${artifactName}")
        boolean unitTests = ((List<String>) (target.testLoaders ?: moddedLoaderLabels.keySet().toList())).contains(loader)
-        TaskProvider<Exec> buildTarget = tasks.register("verify${label}${suffix}", Exec) {
+        int daemonSlot = nextDaemonSlot++ % matrixParallelism
+        TaskProvider<IrisModdedBuild> buildTarget = project(':adapters').tasks.register("verify${label}${suffix}", IrisModdedBuild) {
            group = 'verification'
            description = "Builds, tests and verifies the ${label} ${targetMinecraft} jar in its own Gradle build."
-            workingDir = file("adapters/${loader}")
-            List<String> command = [file(moddedWrapperScript).absolutePath, 'assemble', 'compileTestJava',
+            usesService(matrixWorkers)
+            dependsOn(project(':core').tasks.named('jar'), project(':core').tasks.named('testFixturesJar'))
+            workingDirectory.set(rootProject.file("adapters/${loader}"))
+            getLabel().set("${label} ${targetMinecraft}".toString())
+            artifactFile.set(artifact)
+            logFile.set(rootProject.layout.buildDirectory.file("reports/modded/${loader}-${targetMinecraft}.log"))
+            requiredEntries.set(commonModdedArtifactEntries + moddedLoaderEntries[loader])
+            forbiddenCoreClasses.set(bukkitCoupledCoreClasses)
+            javaRuntime.set((int) target.java)
+            List<String> command = [rootProject.file(moddedWrapperScript).absolutePath, 'assemble', 'compileTestJava',
                    'verifyLoggingPolicy', 'verifyNativeClassBoundary', '--console=plain',
-                    "-PirisVersion=${project.version}", "-PminecraftVersion=${targetMinecraft}",
+                    "--max-workers=${Math.min(2, gradle.startParameter.maxWorkerCount)}",
+                    "-Dorg.gradle.jvmargs=${nestedJvmArguments.trim()}",
+                    "-Dorg.gradle.daemon.registry.base=${rootProject.file(".gradle/iris-daemons/slot-${daemonSlot}").absolutePath}",
+                    '-Dorg.gradle.daemon.idletimeout=3600000',
+                    "-PirisBuildLane=${loader}-${targetMinecraft}",
+                    '--project-cache-dir', rootProject.file("adapters/${loader}/.gradle/iris-lanes/${loader}-${targetMinecraft}").absolutePath,
+                    '--init-script', rootProject.file('gradle/nested-build.init.gradle').absolutePath,
+                    "-PirisVersion=${rootProject.version}", "-PminecraftVersion=${targetMinecraft}",
                    "-P${moddedLoaderProperties[loader]}=${loaderPin}",
                    "-PuseLocalVolmLib=${localVolmLibCheckout != null}"]
            if (unitTests) {
                command.add('test')
            }
-            commandLine(command)
+            command.add("-PtestForks=${providers.gradleProperty('moddedTestForks').getOrElse('1')}")
+            command.addAll(nestedBuildArguments)
+            commandLine.set(command.collect { Object argument -> argument.toString() })
            if (localVolmLibCheckout != null) {
-                environment('ORG_GRADLE_PROJECT_localVolmLibDirectory', localVolmLibCheckout.absolutePath)
+                environment.put('ORG_GRADLE_PROJECT_localVolmLibDirectory', localVolmLibCheckout.absolutePath)
            }
            inputs.files(moddedSharedInputs).withPropertyName('moddedSharedSources')
                .withPathSensitivity(PathSensitivity.RELATIVE)
-            inputs.files(file("adapters/${loader}/src"), file("adapters/${loader}/build.gradle"),
-                    file("adapters/${loader}/settings.gradle")).withPropertyName('adapterSources')
+            inputs.files(rootProject.file("adapters/${loader}/src"), rootProject.file("adapters/${loader}/build.gradle"),
+                    rootProject.file("adapters/${loader}/settings.gradle"), rootProject.file("adapters/${loader}/gradle.properties"))
+                .withPropertyName('adapterSources')
+            inputs.files(gradle.startParameter.allInitScripts).withPropertyName('initScripts')
+                .withPathSensitivity(PathSensitivity.NONE)
+            outputs.upToDateWhen { !gradle.startParameter.refreshDependencies }
            inputs.properties(target)
            inputs.property('loaderVersion', loaderPin)
-            inputs.property('irisVersion', project.version.toString())
+            inputs.property('irisVersion', rootProject.version.toString())
            declareVolmLibInputs(it)
-            outputs.file(artifact)
            if (unitTests) {
-                outputs.dir(file("adapters/${loader}/build/${targetMinecraft}/test-results/test"))
-            }
-            doLast {
-                ModdedArtifactVerifier.verify(artifact, commonModdedArtifactEntries + moddedLoaderEntries[loader],
-                        bukkitCoupledCoreClasses)
-                ModdedArtifactVerifier.verifyJavaRuntime(artifact, (int) target.java)
-                logger.lifecycle("Verified ${artifact.name}")
+                outputs.dir(rootProject.file("adapters/${loader}/build/${targetMinecraft}/test-results/test"))
            }
        }
-        if (previousMatrixBuild != null) {
-            TaskProvider<Exec> preceding = previousMatrixBuild
-            buildTarget.configure { mustRunAfter(preceding) }
+        TaskProvider<IrisModdedBuild> previousSlotBuild = daemonSlots[daemonSlot]
+        if (previousSlotBuild != null) {
+            buildTarget.configure { mustRunAfter(previousSlotBuild) }
+        }
+        daemonSlots[daemonSlot] = buildTarget
+        tasks.register("verify${label}${suffix}") {
+            group = 'verification'
+            description = "Builds, tests and verifies the ${label} ${targetMinecraft} jar."
+            dependsOn(buildTarget)
        }
-        previousMatrixBuild = buildTarget
        verifyModdedMatrix.configure { dependsOn(buildTarget) }
        File legacyOutJar = new File(pluginOutDirectory, "Iris-${project.version}+mc${targetMinecraft}-${loader}.jar")
        FileTree staleTargetJars = fileTree(pluginOutDirectory) {
@@ -512,18 +557,6 @@ tasks.register('buildNeoforge') {
    dependsOn(selectedModdedExports.neoforge)
 }

-gradle.projectsEvaluated {
-    List<Task> sharedOutputTasks = allprojects.collectMany { Project candidate ->
-        candidate.tasks.findAll { Task task ->
-            task instanceof JavaCompile || task instanceof Jar || task instanceof Test
-        }
-    }
-    tasks.withType(Exec).matching { Task task -> task.name.startsWith('verify') }.configureEach {
-        mustRunAfter(sharedOutputTasks)
-        mustRunAfter(tasks.named('buildBukkit'))
-    }
-}
-
 tasks.named('check').configure {
    dependsOn(selectedModdedBuilds.fabric)
 }
@@ -21,11 +21,14 @@ repositories {
 // Nothing else asks buildSrc for `test`: Gradle only requests the jar that carries the build logic.
 // Gating the jar on the tests is what makes them run at all, and it costs nothing once they are green.
 tasks.named('jar').configure {
-    dependsOn(tasks.named('test'))
+    if (!gradle.extensions.extraProperties.has('irisBuildLane')) {
+        dependsOn(tasks.named('test'))
+    }
 }

 tasks.named('test').configure {
    jvmArgs('--add-opens=java.base/java.lang=ALL-UNNAMED')
+    jvmArgs('-XX:ParallelGCThreads=2', '-XX:ConcGCThreads=1', '-XX:CICompilerCount=2')
 }

 dependencies {
@@ -0,0 +1,67 @@
+import org.gradle.api.DefaultTask;
+import org.gradle.api.file.DirectoryProperty;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.provider.ListProperty;
+import org.gradle.api.provider.MapProperty;
+import org.gradle.api.provider.Property;
+import org.gradle.api.provider.SetProperty;
+import org.gradle.api.tasks.Input;
+import org.gradle.api.tasks.Internal;
+import org.gradle.api.tasks.LocalState;
+import org.gradle.api.tasks.OutputFile;
+import org.gradle.api.tasks.TaskAction;
+import org.gradle.workers.WorkerExecutor;
+
+import javax.inject.Inject;
+import java.util.Map;
+
+public abstract class IrisModdedBuild extends DefaultTask {
+    public IrisModdedBuild() {
+        getEnvironment().convention(Map.of());
+    }
+
+    @Input
+    public abstract Property<String> getLabel();
+
+    @Internal
+    public abstract DirectoryProperty getWorkingDirectory();
+
+    @Input
+    public abstract ListProperty<String> getCommandLine();
+
+    @Input
+    public abstract MapProperty<String, String> getEnvironment();
+
+    @Input
+    public abstract ListProperty<String> getRequiredEntries();
+
+    @Input
+    public abstract SetProperty<String> getForbiddenCoreClasses();
+
+    @Input
+    public abstract Property<Integer> getJavaRuntime();
+
+    @OutputFile
+    public abstract RegularFileProperty getArtifactFile();
+
+    @LocalState
+    public abstract RegularFileProperty getLogFile();
+
+    @Inject
+    protected abstract WorkerExecutor getWorkerExecutor();
+
+    @TaskAction
+    public void build() {
+        getWorkerExecutor().noIsolation().submit(IrisModdedBuildAction.class, parameters -> {
+            parameters.getLabel().set(getLabel());
+            parameters.getWorkingDirectory().set(getWorkingDirectory());
+            parameters.getCommandLine().set(getCommandLine());
+            parameters.getEnvironment().set(getEnvironment());
+            parameters.getRequiredEntries().set(getRequiredEntries());
+            parameters.getForbiddenCoreClasses().set(getForbiddenCoreClasses());
+            parameters.getJavaRuntime().set(getJavaRuntime());
+            parameters.getArtifactFile().set(getArtifactFile());
+            parameters.getLogFile().set(getLogFile());
+        });
+    }
+}
@@ -0,0 +1,85 @@
+import org.gradle.api.GradleException;
+import org.gradle.api.logging.Logger;
+import org.gradle.api.logging.Logging;
+import org.gradle.process.ExecOperations;
+import org.gradle.workers.WorkAction;
+
+import javax.inject.Inject;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.io.RandomAccessFile;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+
+public abstract class IrisModdedBuildAction implements WorkAction<IrisModdedBuildParameters> {
+    private static final Logger LOGGER = Logging.getLogger(IrisModdedBuildAction.class);
+    private static final int LOG_TAIL_BYTES = 16 * 1024;
+    private static final int LOG_TAIL_LINES = 40;
+
+    @Inject
+    protected abstract ExecOperations getExecOperations();
+
+    @Override
+    public void execute() {
+        IrisModdedBuildParameters parameters = getParameters();
+        String label = parameters.getLabel().get();
+        Path log = parameters.getLogFile().get().getAsFile().toPath();
+        long started = System.nanoTime();
+        LOGGER.lifecycle("{} started; log: {}", label, log);
+        try {
+            Files.createDirectories(log.getParent());
+            try (OutputStream output = Files.newOutputStream(log)) {
+                getExecOperations().exec(spec -> {
+                    spec.setWorkingDir(parameters.getWorkingDirectory().get().getAsFile());
+                    spec.commandLine(parameters.getCommandLine().get());
+                    spec.environment(parameters.getEnvironment().get());
+                    spec.setStandardOutput(output);
+                    spec.setErrorOutput(output);
+                }).assertNormalExitValue();
+            }
+            ModdedArtifactVerifier.verify(parameters.getArtifactFile().get().getAsFile(),
+                    parameters.getRequiredEntries().get(), parameters.getForbiddenCoreClasses().get());
+            ModdedArtifactVerifier.verifyJavaRuntime(parameters.getArtifactFile().get().getAsFile(),
+                    parameters.getJavaRuntime().get());
+            LOGGER.lifecycle("{} succeeded in {} ms", label,
+                    TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - started));
+        } catch (Exception failure) {
+            appendFailure(log, failure);
+            String details;
+            try {
+                details = logTail(log);
+            } catch (IOException unreadable) {
+                failure.addSuppressed(unreadable);
+                details = "Log could not be read.";
+            }
+            LOGGER.error(label + " failed; log: " + log + System.lineSeparator() + details, failure);
+            throw new GradleException(label + " failed; log: " + log, failure);
+        }
+    }
+
+    static String logTail(Path log) throws IOException {
+        try (RandomAccessFile input = new RandomAccessFile(log.toFile(), "r")) {
+            long offset = Math.max(0L, input.length() - LOG_TAIL_BYTES);
+            input.seek(offset);
+            byte[] bytes = new byte[(int) (input.length() - offset)];
+            input.readFully(bytes);
+            String[] lines = new String(bytes, StandardCharsets.UTF_8).split("\\R");
+            return String.join(System.lineSeparator(), Arrays.copyOfRange(lines,
+                    Math.max(0, lines.length - LOG_TAIL_LINES), lines.length));
+        }
+    }
+
+    private static void appendFailure(Path log, Exception failure) {
+        try (PrintWriter output = new PrintWriter(Files.newBufferedWriter(log, StandardCharsets.UTF_8,
+                StandardOpenOption.CREATE, StandardOpenOption.APPEND))) {
+            failure.printStackTrace(output);
+        } catch (IOException unwritable) {
+            failure.addSuppressed(unwritable);
+        }
+    }
+}
@@ -0,0 +1,27 @@
+import org.gradle.api.file.DirectoryProperty;
+import org.gradle.api.file.RegularFileProperty;
+import org.gradle.api.provider.ListProperty;
+import org.gradle.api.provider.MapProperty;
+import org.gradle.api.provider.Property;
+import org.gradle.api.provider.SetProperty;
+import org.gradle.workers.WorkParameters;
+
+public interface IrisModdedBuildParameters extends WorkParameters {
+    Property<String> getLabel();
+
+    DirectoryProperty getWorkingDirectory();
+
+    ListProperty<String> getCommandLine();
+
+    MapProperty<String, String> getEnvironment();
+
+    ListProperty<String> getRequiredEntries();
+
+    SetProperty<String> getForbiddenCoreClasses();
+
+    Property<Integer> getJavaRuntime();
+
+    RegularFileProperty getArtifactFile();
+
+    RegularFileProperty getLogFile();
+}
@@ -0,0 +1,5 @@
+import org.gradle.api.services.BuildService;
+import org.gradle.api.services.BuildServiceParameters;
+
+public abstract class IrisModdedBuildService implements BuildService<BuildServiceParameters.None> {
+}
@@ -0,0 +1,79 @@
+import org.gradle.api.Project;
+import org.gradle.testfixtures.ProjectBuilder;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class IrisModdedBuildTest {
+    @Rule
+    public TemporaryFolder temporary = new TemporaryFolder();
+
+    @Test
+    public void capturesTheCompleteTargetConfiguration() throws Exception {
+        Project project = ProjectBuilder.builder().withProjectDir(temporary.newFolder()).build();
+        IrisModdedBuild task = project.getTasks().create("verifyFabric", IrisModdedBuild.class);
+        task.getLabel().set("Fabric 26.3");
+        task.getWorkingDirectory().set(project.getLayout().getProjectDirectory());
+        task.getCommandLine().set(List.of("gradlew", "assemble", "test"));
+        task.getRequiredEntries().set(List.of("fabric.mod.json"));
+        task.getForbiddenCoreClasses().set(Set.of("org/bukkit/Test"));
+        task.getJavaRuntime().set(25);
+        task.getArtifactFile().set(project.getLayout().getProjectDirectory().file("build/mod.jar"));
+        task.getLogFile().set(project.getLayout().getProjectDirectory().file("build/reports/matrix/fabric.log"));
+
+        assertEquals(Map.of(), task.getEnvironment().get());
+        assertEquals(List.of("gradlew", "assemble", "test"), task.getCommandLine().get());
+        assertEquals(List.of("fabric.mod.json"), task.getRequiredEntries().get());
+        assertEquals(Set.of("org/bukkit/Test"), task.getForbiddenCoreClasses().get());
+        assertEquals(Integer.valueOf(25), task.getJavaRuntime().get());
+        assertEquals(Set.of(task.getArtifactFile().get().getAsFile()), task.getOutputs().getFiles().getFiles());
+        assertFalse(task.getOutputs().getFiles().contains(task.getLogFile().get().getAsFile()));
+    }
+
+    @Test
+    public void failureSummaryRetainsTheFinalLinesWithoutReadingAnEntireLog() throws Exception {
+        Path log = temporary.newFile().toPath();
+        StringBuilder content = new StringBuilder("discarded first line\n");
+        for (int index = 0; index < 2000; index++) {
+            content.append("task output ").append(index).append('\n');
+        }
+        content.append("final failure\n");
+        Files.writeString(log, content);
+
+        String tail = IrisModdedBuildAction.logTail(log);
+
+        assertEquals(40, tail.lines().count());
+        assertTrue(tail.endsWith("final failure"));
+        assertFalse(tail.contains("discarded first line"));
+        assertTrue(tail.length() <= 16 * 1024);
+    }
+
+    @Test
+    public void failureSummaryAcceptsEmptyAndUnterminatedLogs() throws Exception {
+        Path log = temporary.newFile().toPath();
+        assertEquals("", IrisModdedBuildAction.logTail(log));
+        Files.writeString(log, "first\r\nlast");
+        assertEquals("first" + System.lineSeparator() + "last", IrisModdedBuildAction.logTail(log));
+    }
+
+    @Test
+    public void failureSummaryBoundsAnUnbrokenFailureLine() throws Exception {
+        Path log = temporary.newFile().toPath();
+        Files.writeString(log, "x".repeat(100_000) + "final failure");
+
+        String tail = IrisModdedBuildAction.logTail(log);
+
+        assertEquals(16 * 1024, tail.length());
+        assertTrue(tail.endsWith("final failure"));
+    }
+}
@@ -26,6 +26,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.IdentityHashMap;
 import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
@@ -33,6 +34,7 @@ import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.LongSupplier;

 import static art.arcane.iris.generation.runtime.EngineShutdownSequence.appendFailure;
 import static art.arcane.iris.generation.runtime.EngineShutdownSequence.propagate;
@@ -47,9 +49,18 @@ final class EngineBackgroundTasks {

    private final Object backgroundTaskLock = new Object();
    private final List<TrackedBackgroundTask> backgroundTasks = new ArrayList<>();
+    private final LongSupplier clock;
    private boolean backgroundTaskAdmission;
    private int activeDrains;

+    EngineBackgroundTasks() {
+        this(System::nanoTime);
+    }
+
+    EngineBackgroundTasks(LongSupplier clock) {
+        this.clock = Objects.requireNonNull(clock);
+    }
+
    boolean scheduleTrackedTask(Runnable task) {
        return scheduleTrackedTask(task, false);
    }
@@ -106,7 +117,7 @@ final class EngineBackgroundTasks {
    }

    BackgroundTaskDrain drainBackgroundTasks(String reason) {
-        long deadline = System.nanoTime() + TimeUnit.MILLISECONDS.toNanos(BACKGROUND_TASK_TIMEOUT_MILLIS);
+        long deadline = clock.getAsLong() + TimeUnit.MILLISECONDS.toNanos(BACKGROUND_TASK_TIMEOUT_MILLIS);
        Set<TrackedBackgroundTask> observed = Collections.newSetFromMap(new IdentityHashMap<>());
        Set<TrackedBackgroundTask> settledAtEntry = Collections.newSetFromMap(new IdentityHashMap<>());
        List<TrackedBackgroundTask> tasks;
@@ -135,7 +146,7 @@ final class EngineBackgroundTasks {
                        return new BackgroundTaskDrain(failure, allTasksComplete());
                    }
                }
-                if (System.nanoTime() >= deadline) {
+                if (clock.getAsLong() >= deadline) {
                    for (TrackedBackgroundTask task : tasks) {
                        cancelBackgroundTask(task, reason);
                    }
@@ -170,7 +181,7 @@ final class EngineBackgroundTasks {
                                     long deadline, String reason) {
        Throwable failure = null;
        for (TrackedBackgroundTask task : tasks) {
-            long remaining = deadline - System.nanoTime();
+            long remaining = deadline - clock.getAsLong();
            if (remaining <= 0L) {
                cancelBackgroundTask(task, reason);
                failure = appendFailure(failure, new TimeoutException("Timed out waiting for Iris background tasks during " + reason + "."));
@@ -14,6 +14,7 @@ import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.LockSupport;

@@ -115,7 +116,8 @@ public class EngineBackgroundTasksAdmissionTest {

    @Test
    public void continuationsShareTheOriginalDrainDeadline() throws Exception {
-        Fixture fixture = fixture();
+        AtomicLong clock = new AtomicLong();
+        Fixture fixture = fixture(new EngineBackgroundTasks(clock::get));
        CountDownLatch firstEntered = new CountDownLatch(1);
        CountDownLatch firstRelease = new CountDownLatch(1);
        CountDownLatch saveEntered = new CountDownLatch(1);
@@ -132,9 +134,9 @@ public class EngineBackgroundTasksAdmissionTest {
                        fixture.tasks().scheduleAdmittedTask(fixture.engine(),
                                () -> waitForRelease(saveEntered, saveRelease))));
                assertTrue(saveEntered.await(5, TimeUnit.SECONDS));
-                TimeUnit.SECONDS.sleep(7);
+                clock.set(TimeUnit.SECONDS.toNanos(15) - TimeUnit.MILLISECONDS.toNanos(1));
                firstRelease.countDown();
-                EngineBackgroundTasks.BackgroundTaskDrain result = drain.get(10, TimeUnit.SECONDS);
+                EngineBackgroundTasks.BackgroundTaskDrain result = drain.get(5, TimeUnit.SECONDS);
                assertTrue(result.failure() instanceof TimeoutException);
                assertThrows(IllegalStateException.class, () -> result.requireComplete("Studio cutover"));
            } finally {
@@ -287,7 +289,10 @@ public class EngineBackgroundTasksAdmissionTest {
    }

    private static Fixture fixture() {
-        EngineBackgroundTasks tasks = new EngineBackgroundTasks();
+        return fixture(new EngineBackgroundTasks());
+    }
+
+    private static Fixture fixture(EngineBackgroundTasks tasks) {
        tasks.openBackgroundTaskAdmission();
        GenerationSessionManager sessions = new GenerationSessionManager(true);
        Engine engine = mock(Engine.class);
@@ -17,6 +17,7 @@
 #
 org.gradle.daemon=true
 org.gradle.parallel=true
+org.gradle.workers.max=32
 org.gradle.jvmargs=-Xmx3072m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8
 org.gradle.caching=true
 org.gradle.configureondemand=false
@@ -11,11 +11,13 @@ if (coreBuild == null) {
    throw new GradleException('The modded artifact requires the included Iris core build and its generation build revision.')
 }
 TaskReference buildRevisionVerification = coreBuild.task(':core:verifyGenerationBuildRevision')
+String buildLogicVariant = gradle.extensions.extraProperties.has('irisBuildLane')
+    ? "iris-lanes/${gradle.extensions.extraProperties.get('irisBuildLane')}/" : ''
 TaskProvider<JavaExec> resolvedRevisionVerification = tasks.register('verifyResolvedGenerationKernelDependencies', JavaExec) {
    group = 'verification'
    description = 'Checks the actual bundled generation library contents against the current build revision.'
    dependsOn(buildRevisionVerification)
-    classpath = files('../../buildSrc/build/libs/buildSrc.jar')
+    classpath = files("../../buildSrc/build/${buildLogicVariant}libs/buildSrc.jar")
    mainClass.set('art.arcane.iris.buildtools.GenerationBuildRevision')
    doFirst {
        String runtimeVariant = gradle.extensions.extraProperties.get('irisRuntimeOutputVariant').toString()
@@ -2,11 +2,17 @@ import groovy.json.JsonSlurper

 List<String> sourceOverlays = (List<String>) irisModTarget.overlays
 List<File> adapterSourceRoots = [projectDir, file('../modded-common'), file('../client-common')]
+int testForks = Math.max(1, Integer.parseInt(providers.gradleProperty('testForks').getOrElse('2')))

 tasks.named('compileTestJava', JavaCompile).configure {
    options.release.set((int) irisModTarget.java)
 }
 tasks.withType(Test).configureEach {
+    maxParallelForks = Math.min(2, Math.min(Runtime.runtime.availableProcessors(),
+        Math.min(gradle.startParameter.maxWorkerCount, testForks)))
+    if (gradle.extensions.extraProperties.has('irisBuildLane')) {
+        jvmArgs('-XX:ParallelGCThreads=2', '-XX:ConcGCThreads=1', '-XX:CICompilerCount=2')
+    }
    javaLauncher.set(javaToolchains.launcherFor {
        languageVersion = JavaLanguageVersion.of((int) irisModTarget.java)
    })
@@ -0,0 +1,31 @@
+Gradle rootBuild = gradle
+while (rootBuild.parent != null) {
+    rootBuild = rootBuild.parent
+}
+String buildLane = rootBuild.startParameter.projectProperties['irisBuildLane']
+if (buildLane == null) {
+    throw new GradleException('The nested build requires -PirisBuildLane.')
+}
+if (!(buildLane ==~ /[a-zA-Z0-9][a-zA-Z0-9._-]*/)) {
+    throw new GradleException('irisBuildLane must contain only letters, numbers, dots, underscores and hyphens.')
+}
+
+gradle.extensions.extraProperties.set('irisBuildLane', buildLane)
+gradle.startParameter.projectCacheDir = new File(gradle.startParameter.currentDir, ".gradle/iris-lanes/${buildLane}")
+gradle.beforeSettings { Settings settings ->
+    settings.gradle.startParameter.projectCacheDir = new File(settings.settingsDir, ".gradle/iris-lanes/${buildLane}")
+}
+gradle.beforeProject { Project candidate ->
+    boolean sharedRuntime = candidate.rootProject.name == 'Iris'
+        && candidate.path in [':core', ':core:agent', ':spi']
+    if (!candidate.rootProject.name.startsWith('iris-') && !sharedRuntime) {
+        candidate.layout.buildDirectory.set(candidate.layout.projectDirectory.dir("build/iris-lanes/${buildLane}"))
+    }
+    candidate.plugins.withId('io.papermc.paperweight.userdev') {
+        candidate.tasks.named('paperweightUserdevSetup').configure { Task setup ->
+            Directory taskCache = candidate.layout.projectDirectory.dir(".gradle/iris-lanes/${buildLane}/caches/paperweight/taskCache")
+            setup.mappedServerJar.set(taskCache.file('mappedServerJar.jar'))
+            setup.reobfMappings.set(taskCache.file('reobfMappings.tiny'))
+        }
+    }
+}
@@ -11,8 +11,10 @@ if (modTarget == null) {
 }
 String runtimeJava = providers.gradleProperty('irisRuntimeJava').getOrElse(modTarget.java.toString())
 String variant = adapter ? "minecraft${minecraftVersion}-java${runtimeJava}" : "java${runtimeJava}"
-File projectCacheRoot = gradle.startParameter.projectCacheDir ?: new File(settingsDir, '.gradle')
-gradle.startParameter.projectCacheDir = new File(projectCacheRoot, variant)
+if (!gradle.extensions.extraProperties.has('irisBuildLane')) {
+    File projectCacheRoot = gradle.startParameter.projectCacheDir ?: new File(settingsDir, '.gradle')
+    gradle.startParameter.projectCacheDir = new File(projectCacheRoot, variant)
+}

 String runtimeOutputVariant = runtimeJava == '21' ? 'java21/' : ''
 if (adapter) {