What causes "Quarkus code generation phase has failed" in quarkusio/quarkus?

Align all Quarkus plugin, core, and extension versions to the same release.

quarkusio/quarkus · error · GradleException

Quarkus code generation phase has failed

Error message

Quarkus code generation phase has failed

What it means

CodeGenWorker runs Quarkus code generation (e.g. REST/gRPC/Avro stub generation) by reflectively loading CodeGenerator.initAndRun from a QuarkusClassLoader. This GradleException is thrown when the reflective getMethod lookup for INIT_AND_RUN fails (NoSuchMethodException or related), meaning the code generator class found on the generated-resources classpath does not expose the expected method signature — usually a Quarkus/plugin version mismatch or a corrupted code-generation cache.

Source

Thrown at devtools/gradle/gradle-application-plugin/src/main/java/io/quarkus/gradle/tasks/worker/CodeGenWorker.java:58

        LOGGER.info("Generating Quarkus code for {}", gav);
        LOGGER.info("  launch mode:                  {}", params.getLaunchMode().get());
        LOGGER.info("  base name:                    {}", params.getBaseName().get());
        LOGGER.info("  generated source directory:   {}", generatedSourceDir);
        LOGGER.info("  build directory:              {}", buildDir);

        try (CuratedApplication appCreationContext = createAppCreationContext()) {

            QuarkusClassLoader deploymentClassLoader = appCreationContext.createDeploymentClassLoader();
            Class<?> codeGenerator = deploymentClassLoader.loadClass(CodeGenerator.class.getName());

            Method initAndRun;
            try {
                initAndRun = codeGenerator.getMethod(INIT_AND_RUN, QuarkusClassLoader.class, PathCollection.class,
                        Path.class, Path.class,
                        Consumer.class, ApplicationModel.class, Properties.class, String.class,
                        boolean.class);
            } catch (Exception e) {
                throw new GradleException("Quarkus code generation phase has failed", e);
            }

            Consumer<Path> sourceRegistrar = (p) -> {
            };

            LaunchMode launchMode = params.getLaunchMode().get();

            initAndRun.invoke(null,
                    // QuarkusClassLoader classLoader,
                    deploymentClassLoader,
                    // PathCollection sourceParentDirs,
                    PathList.from(
                            params.getSourceDirectories().getFiles().stream().map(File::toPath).collect(Collectors.toList())),
                    // Path generatedSourcesDir,
                    generatedSourceDir,
                    // Path buildDir,
                    buildDir,
                    // Consumer<Path> sourceRegistrar,

View on GitHub (pinned to e1c734241f)

Solutions

Align all Quarkus plugin, core, and extension versions to the same release.
Clean generated caches: ./gradlew clean, or delete build/generated-sources, then re-run quarkusGenerateCode.
Stop and restart the Gradle daemon (./gradlew --stop) to drop stale classloader state.
Run with --info/--debug to see which CodeGenerator class was loaded and from which jar.

Defensive patterns

Strategy: validation

Validate before calling

./gradlew --stop           # clear stale daemon classloaders
rm -rf build/generated-sources  # remove stale codegen output
# then rebuild with aligned versions

Prevention

Always upgrade the whole Quarkus stack (plugin + core + extensions) together
Clean generated-sources after any Quarkus version change
Avoid pinning individual Quarkus extensions to older versions than the BOM
Restart the Gradle daemon after upgrading build plugins

When it happens

Trigger: Running ./gradlew quarkusGenerateCode when the resolved CodeGenerator class does not declare initAndRun(QuarkusClassLoader, PathCollection, Path, Path, Consumer, ApplicationModel, Properties, String, boolean) — caused by mismatched quarkus-core vs extension generator versions, a stale build/generated-sources cache, or the wrong class being loaded from the classloader.

Common situations: Upgrading Quarkus BOM partially (some extensions pinned to old versions); stale build/ directory after an upgrade; Gradle daemon caching an old codegen jar; classpath pollution where an incompatible CodeGenerator implementation shadows the right one.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/89822682e027f284. Report an issue: GitHub.