langchain-ai/langgraph · error · InvalidUpdateError

At key '{self.key}': Value {value} not in {self.names}

Error message

At key '{self.key}': Value {value} not in {self.names}

What it means

Error "At key '{self.key}': Value {value} not in {self.names}" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/channels/named_barrier_value.py:64

    def checkpoint(self) -> set[Value]:
        return self.seen

    def from_checkpoint(self, checkpoint: set[Value]) -> Self:
        empty = self.__class__(self.typ, self.names)
        empty.key = self.key
        if checkpoint is not MISSING:
            empty.seen = checkpoint
        return empty

    def update(self, values: Sequence[Value]) -> bool:
        updated = False
        for value in values:
            if value in self.names:
                if value not in self.seen:
                    self.seen.add(value)
                    updated = True
            else:
                raise InvalidUpdateError(
                    f"At key '{self.key}': Value {value} not in {self.names}"
                )
        return updated

    def get(self) -> Value:
        if self.seen != self.names:
            raise EmptyChannelError()
        return None

    def is_available(self) -> bool:
        return self.seen == self.names

    def consume(self) -> bool:
        if self.seen == self.names:
            self.seen = set()
            return True
        return False

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/channels/named_barrier_value.py:64 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/93ccf4e3df625c82. Report an issue: GitHub.