langchain-ai/langgraph · error · InvalidUpdateError

Cannot copy checkpoint with multiple updates

Error message

Cannot copy checkpoint with multiple updates

What it means

Error "Cannot copy checkpoint with multiple updates" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/pregel/main.py:1802

                    # store the writes
                    checkpointer.put_writes(
                        next_config,
                        input_writes,
                        str(uuid5(UUID(checkpoint["id"]), INPUT)),
                    )

                    return patch_checkpoint_map(
                        next_config, saved.metadata if saved else None
                    )
                else:
                    raise InvalidUpdateError(
                        f"Received no input writes for {self.input_channels}"
                    )

            # copy checkpoint
            if as_node == "__copy__":
                if len(updates) > 1:
                    raise InvalidUpdateError(
                        "Cannot copy checkpoint with multiple updates"
                    )

                if saved is None:
                    raise InvalidUpdateError("Cannot copy a non-existent checkpoint")

                next_checkpoint = create_checkpoint(checkpoint, None, step)

                # copy checkpoint
                next_config = checkpointer.put(
                    saved.parent_config
                    or patch_configurable(
                        saved.config, {CONFIG_KEY_CHECKPOINT_ID: None}
                    ),
                    next_checkpoint,
                    {
                        "source": "fork",
                        "step": step + 1,

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/pregel/main.py:1802 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/0d7648ca21259ef5. Report an issue: GitHub.