langchain-ai/langgraph · error · ValueError

Unknown operation type

Error message

Unknown operation type: {type(op)}

What it means

Dispatch guard in InMemoryStore.batch: while sorting queued Ops, an object that is not one of the known operation types (GetOp, SearchOp, ListNamespacesOp, PutOp) reached the router. Ops are typed dataclasses; passing a raw tuple, a string, or a custom op class (e.g. from a mismatched langgraph-checkpoint version) triggers this error.

Solutions

1. Use the typed Op dataclasses (PutOp, GetOp, SearchOp, ListNamespacesOp) from langgraph.store.base when calling batch directly
2. Prefer the high-level put/get/search methods which construct ops for you
3. Ensure all packages import Ops from the same installed langgraph-checkpoint version

When it happens

Trigger: Thrown at libs/checkpoint/langgraph/checkpoint/store/memory/__init__.py:400 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langgraph@38031739e5 (2026-08-26). Data as JSON: /api/errors/7ac878a8f475b3d6. Report an issue: GitHub.

Appendix: source

Thrown at libs/checkpoint/langgraph/checkpoint/store/memory/__init__.py:400

            elif isinstance(op, ListNamespacesOp):
                results.append(self._handle_list_namespaces(op))
            elif isinstance(op, PutOp):
                put_ops[(op.namespace, op.key)] = op
                results.append(None)
            else:
                raise ValueError(f"Unknown operation type: {type(op)}")

        return results, put_ops, search_ops

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