langchain-ai/langgraph · error · InvalidUpdateError

Cannot apply multiple updates when updating as input

Error message

Cannot apply multiple updates when updating as input

What it means

Error "Cannot apply multiple updates when updating as input" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/pregel/main.py:1749

                    create_checkpoint(checkpoint, channels, step),
                    {
                        "source": "update",
                        "step": step + 1,
                        "parents": saved.metadata.get("parents", {}) if saved else {},
                    },
                    get_new_channel_versions(
                        checkpoint_previous_versions,
                        checkpoint["channel_versions"],
                    ),
                )
                return patch_checkpoint_map(
                    next_config, saved.metadata if saved else None
                )

            # act as an input
            if as_node == INPUT:
                if len(updates) > 1:
                    raise InvalidUpdateError(
                        "Cannot apply multiple updates when updating as input"
                    )

                if input_writes := deque(map_input(self.input_channels, values)):
                    apply_writes(
                        checkpoint,
                        channels,
                        [PregelTaskWrites((), INPUT, input_writes, [])],
                        checkpointer.get_next_version,
                        self.trigger_to_nodes,
                    )

                    # apply input write to channels
                    next_step = (
                        step + 1
                        if saved and saved.metadata.get("step") is not None
                        else -1
                    )

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/pregel/main.py:1749 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/ce5d92293f44fe76. Report an issue: GitHub.