langchain-ai/langgraph · error · InvalidUpdateError

INVALID_CONCURRENT_GRAPH_UPDATE

INVALID_CONCURRENT_GRAPH_UPDATE

Error message

Can receive only one Overwrite value per super-step.

What it means

Error "Can receive only one Overwrite value per super-step." thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/channels/delta.py:171

            if is_ow:
                base = _copy.copy(ow_value) if ow_value is not None else self.typ()
                start = i + 1
        remaining = values[start:]
        self.value = self.reducer(base, remaining) if remaining else base

    def update(self, values: Sequence[Any]) -> bool:
        if not values:
            return False
        overwrite_idx: int | None = None
        for i, v in enumerate(values):
            is_ow, _ = _get_overwrite(v)
            if is_ow:
                if overwrite_idx is not None:
                    msg = create_error_message(
                        message="Can receive only one Overwrite value per super-step.",
                        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

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/channels/delta.py:171 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/f89f2a4b466e6107. Report an issue: GitHub.