langchain-ai/langgraph · error · InvalidUpdateError

Node {as_node} has no writers

Error message

Node {as_node} has no writers

What it means

Error "Node {as_node} has no writers" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/pregel/main.py:1957

            else:
                for values, as_node, task_id in updates:
                    if as_node is None:
                        raise InvalidUpdateError(
                            "as_node is required when applying multiple updates"
                        )
                    if as_node not in self.nodes:
                        raise InvalidUpdateError(f"Node {as_node} does not exist")

                    valid_updates.append((as_node, values, task_id))

            run_tasks: list[PregelTaskWrites] = []
            run_task_ids: list[str] = []

            for as_node, values, provided_task_id in valid_updates:
                # create task to run all writers of the chosen node
                writers = self.nodes[as_node].flat_writers
                if not writers:
                    raise InvalidUpdateError(f"Node {as_node} has no writers")
                writes: deque[tuple[str, Any]] = deque()
                task = PregelTaskWrites((), as_node, writes, [INTERRUPT])
                # get the task ids that were prepared for this node
                # if a task id was provided in the StateUpdate, we use it
                # otherwise, we use the next available task id
                prepared_task_ids = node_to_task_ids.get(as_node, deque())
                task_id = provided_task_id or (
                    prepared_task_ids.popleft()
                    if prepared_task_ids
                    else str(uuid5(UUID(checkpoint["id"]), INTERRUPT))
                )
                run_tasks.append(task)
                run_task_ids.append(task_id)
                run = RunnableSequence(*writers) if len(writers) > 1 else writers[0]
                # execute task
                run.invoke(
                    values,
                    patch_config(

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/pregel/main.py:1957 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/4a8617fc0b5ccc81. Report an issue: GitHub.