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/binop.py:138

            empty.value = checkpoint
        return empty

    def update(self, values: Sequence[Value]) -> bool:
        if not values:
            return False
        if self.value is MISSING:
            self.value = values[0]
            values = values[1:]
        seen_overwrite: bool = False
        for value in values:
            is_overwrite, overwrite_value = _get_overwrite(value)
            if is_overwrite:
                if seen_overwrite:
                    msg = create_error_message(
                        message="Can receive only one Overwrite value per super-step.",
                        error_code=ErrorCode.INVALID_CONCURRENT_GRAPH_UPDATE,
                    )
                    raise InvalidUpdateError(msg)
                self.value = overwrite_value
                seen_overwrite = True
                continue
            if not seen_overwrite:
                self.value = self.operator(self.value, value)
        return True

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

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

    def checkpoint(self) -> Value:
        return self.value

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/channels/binop.py:138 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/a56520f2685a5a52. Report an issue: GitHub.