What causes "No serializer registered for the given tag ${tag}" in oracle/graal?

Verify the tag string matches a registered serializer's tag() return value exactly

oracle/graal · error · IllegalArgumentException

No serializer registered for the given tag ${tag}

Error message

No serializer registered for the given tag ${tag}

What it means

RecursiveSerializer.serialize(Object, ValueBuilder, String tag) is the tag-directed variant used for top-level entries such as the compilation unit: it looks up tagSerializers by the caller-supplied tag. IllegalArgumentException('No serializer registered for the given tag ...') means the codec instance has no serializer registered under that tag string.

Source

Thrown at compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hotspot/replaycomp/JsonReplayCodec.java:1917

                if (serializer == null) {
                    throw new IllegalArgumentException("No serializer for " + instance.getClass() + ": " + instance);
                }
            }
            try (JsonBuilder.ObjectBuilder builder = valueBuilder.object()) {
                builder.append("tag", serializer.tag());
                serializer.serialize(instance, builder, this);
            }
        }

        @Override
        public void serialize(Object instance, JsonBuilder.ValueBuilder valueBuilder, String tag) throws IOException {
            if (instance == null) {
                valueBuilder.value(null);
                return;
            }
            ObjectSerializer serializer = tagSerializers.get(tag);
            if (serializer == null) {
                throw new IllegalArgumentException("No serializer registered for the given tag " + tag);
            }
            try (JsonBuilder.ObjectBuilder builder = valueBuilder.object()) {
                serializer.serialize(instance, builder, this);
            }
        }
    };

    /**
     * Writes a recorded compilation unit in JSON replay format.
     *
     * @param compilationUnit the compilation unit to encode
     * @param writer the destination writer
     * @throws IOException if encoding fails
     */
    public void dump(RecordedCompilationUnit compilationUnit, JsonWriter writer) throws IOException {
        recursiveSerializer.serialize(compilationUnit, writer.valueBuilder(), RecordedCompilationUnitSerializer.TAG);
    }

View on GitHub (pinned to a66e9ccd1d)

Solutions

Verify the tag string matches a registered serializer's tag() return value exactly
Register the missing serializer in the codec's tagSerializers map before serializing
Use the codec's public write entry point rather than calling the internal tagged serialize directly

Defensive patterns

Strategy: validation

Validate before calling

// Before the tagged serialize call
if (!codec.hasSerializerForTag(tag)) { // or expose tagSerializers
    throw new IllegalArgumentException("No serializer for tag " + tag + "; register one first");
}

Prevention

Prefer the codec's public write() entry point over calling the internal tagged serializer directly
When adding a top-level entry type, register its serializer before any write

When it happens

Trigger: Calling serialize(instance, valueBuilder, tag) with a tag that was never registered — e.g. RecordedCompilationUnitSerializer.TAG on a codec built without that serializer, or a typo'd/custom tag.

Common situations: Constructing a reduced JsonReplayCodec (subset of serializers) but serializing the full compilation unit; version drift renaming tags; custom code adding new top-level entry types without registering them.

Related errors

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/92afbe82e09c8b16. Report an issue: GitHub.