langchain-ai/langgraph · error · EmptyChannelError

EmptyChannelError

Error message

EmptyChannelError

What it means

Error "EmptyChannelError" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/channels/delta.py:187

                        error_code=ErrorCode.INVALID_CONCURRENT_GRAPH_UPDATE,
                    )
                    raise InvalidUpdateError(msg)
                overwrite_idx = i
        if overwrite_idx is not None:
            _, overwrite_value = _get_overwrite(values[overwrite_idx])
            self.value = (
                _copy.copy(overwrite_value)
                if overwrite_value is not None
                else self.typ()
            )
            return True
        base = self.typ() if self.value is MISSING else self.value
        self.value = self.reducer(base, list(values))
        return True

    def get(self) -> Any:
        if self.value is MISSING:
            raise EmptyChannelError()
        return self.value

    def is_available(self) -> bool:
        return self.value is not MISSING

    def checkpoint(self) -> Any:
        """Return stored representation: always `MISSING`.

        Snapshot decisions live in `create_checkpoint` (which has the channel
        version) and write `_DeltaSnapshot(ch.get())` directly into
        `channel_values`. For non-snapshot steps the channel does not appear
        in `channel_values`; reconstruction walks ancestor writes via the
        saver's `get_delta_channel_history`.
        """
        return MISSING

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/channels/delta.py:187 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/01f15189d965ee84. Report an issue: GitHub.