langchain-ai/langgraph · error · InvalidUpdateError

Invalid update item: {item} when copying checkpoint

Error message

Invalid update item: {item} when copying checkpoint

What it means

Error "Invalid update item: {item} when copying checkpoint" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/pregel/main.py:1853

                        managed,
                        next_config,
                        step + 2,
                        step + 4,
                        for_execution=True,
                        store=self.store,
                        checkpointer=checkpointer,
                        manager=None,
                    )

                    tasks_group_by = defaultdict(list)
                    user_group_by: dict[str, list[StateUpdate]] = defaultdict(list)

                    for task in next_tasks.values():
                        tasks_group_by[task.name].append(task.id)

                    for item in values:
                        if not isinstance(item, Sequence):
                            raise InvalidUpdateError(
                                f"Invalid update item: {item} when copying checkpoint"
                            )

                        values, as_node = item[:2]

                        user_group = user_group_by[as_node]
                        tasks_group = tasks_group_by[as_node]

                        target_idx = len(user_group)
                        task_id = (
                            tasks_group[target_idx]
                            if target_idx < len(tasks_group)
                            else None
                        )

                        user_group_by[as_node].append(
                            StateUpdate(values=values, as_node=as_node, task_id=task_id)
                        )

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/pregel/main.py:1853 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/b1b843d979e62227. Report an issue: GitHub.