oracle/graal · error · FormatVersionException

Unsupported serialized continuation version: %s\nCurrent sup

Error message

Unsupported serialized continuation version: %s\nCurrent supported version: %s

What it means

Thrown as FormatVersionException by FrameRecordSerializer.forOut when the version passed to create a writer is not FrameRecordSerializerV2.FORMAT_VERSION. ContinuationImpl calls this on the write path with its own FORMAT_VERSION; the exception means the top-level continuation format version and the frame-record writer version have diverged — an internal/library-build inconsistency, since both constants ship in the same JAR.

Source

Thrown at espresso/src/org.graalvm.continuations/src/org/graalvm/continuations/FrameRecordSerializer.java:72

    final ObjectOutput out;
    final ObjectInput in;
    ClassLoader loader;

    protected FrameRecordSerializer(ObjectOutput out) {
        this.out = out;
        this.in = null;
    }

    protected FrameRecordSerializer(ObjectInput in) {
        this.out = null;
        this.in = in;
    }

    public static FrameRecordSerializer forOut(int version, ObjectOutput out) throws FormatVersionException {
        if (version == FrameRecordSerializerV2.FORMAT_VERSION) {
            return new FrameRecordSerializerV2(out);
        }
        throw new FormatVersionException(version, ContinuationImpl.FORMAT_VERSION);
    }

    public static FrameRecordSerializer forIn(int version, ObjectInput in) throws FormatVersionException {
        if (version == FrameRecordSerializerV2.FORMAT_VERSION) {
            return new FrameRecordSerializerV2(in);
        }
        throw new FormatVersionException(version, ContinuationImpl.FORMAT_VERSION);
    }

    public final FrameRecordSerializer withLoader(ClassLoader classLoader) {
        this.loader = classLoader;
        return this;
    }

    public abstract void writeRecord(ContinuationImpl.FrameRecord frameRecord) throws IOException;

    public abstract ContinuationImpl.FrameRecord readRecord() throws IOException, ClassNotFoundException;
}

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Align all copies of org.graalvm.continuations to one version: remove shaded duplicates and depend on the version shipped with your GraalVM.
2. Run dependencyInsight/classpath diagnostics (mvn dependency:tree, gradle dependencies) to find who pulls in the stale org.graalvm.continuations artifact.
3. After aligning, re-serialize continuations — payloads written by the mismatched build are also suspect.
4. If you build GraalVM from source, do a clean mx build of the espresso suite so ContinuationImpl and FrameRecordSerializerV2 come from the same tree.

Example fix

// before
// fat jar shades org.graalvm.continuations:1.0 while VM ships 24.x
// -> forOut throws FormatVersionException at write time

// after
// exclude the shaded copy so only the VM-provided library is used
// build.gradle:
dependencies { implementation('com.example:fatlib:1.0') { exclude group: 'org.graalvm.continuations' } }

// fail fast at startup on library mismatch
Class<?> a = Class.forName("org.graalvm.continuations.ContinuationImpl");
Class<?> b = Class.forName("org.graalvm.continuations.FrameRecordSerializerV2");
if (!a.getProtectionDomain().getCodeSource().equals(b.getProtectionDomain().getCodeSource())) {
    throw new IllegalStateException("Mixed org.graalvm.continuations copies on classpath");
}

When it happens

Trigger: ContinuationImpl.writeExternalImpl handing its FORMAT_VERSION to forOut when the linked FrameRecordSerializerV2 no longer accepts it; in practice this happens only when continuation classes from different builds are mixed on the classpath or module path.

Common situations: A workspace or application that bundles one version of org.graalvm.continuations while the VM supplies another; partial upgrades of GraalVM components (e.g. upgrading espresso but not the continuations library); shaded/fat JARs embedding stale copies of the library.

Related errors

• Unsupported serialized continuation version: %s\nCurrent sup
• %s is not an enum type
• Unrecognized version
• Missing expected guest type conversion interface in polyglot
• You can't resume a continuation while it is being serialized

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/b83f92a4a0e7d399. Report an issue: GitHub.