langchain-ai/langgraph · error · ValueError

Managed value '{key}' already exists with a different type

Error message

Managed value '{key}' already exists with a different type

What it means

Error "Managed value '{key}' already exists with a different type" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/graph/state.py:369

                    f"Invalid managed channels detected in {schema_name}: {names}."
                    " Managed channels are not permitted in Input/Output schema."
                )
            self.schemas[schema] = {**channels, **managed}
            for key, channel in channels.items():
                if key in self.channels:
                    if self.channels[key] != channel:
                        if isinstance(channel, LastValue):
                            pass
                        else:
                            raise ValueError(
                                f"Channel '{key}' already exists with a different type"
                            )
                else:
                    self.channels[key] = channel
            for key, managed in managed.items():
                if key in self.managed:
                    if self.managed[key] != managed:
                        raise ValueError(
                            f"Managed value '{key}' already exists with a different type"
                        )
                else:
                    self.managed[key] = managed

    @overload
    def add_node(
        self,
        node: StateNode[NodeInputT, ContextT],
        *,
        defer: bool = False,
        metadata: dict[str, Any] | None = None,
        input_schema: None = None,
        retry_policy: RetryPolicy | Sequence[RetryPolicy] | None = None,
        cache_policy: CachePolicy | None = None,
        error_handler: StateNode[Any, ContextT] | None = None,
        destinations: dict[str, str] | tuple[str, ...] | None = None,
        timeout: float | timedelta | TimeoutPolicy | None = None,

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/graph/state.py:369 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/7d254958c485e842. Report an issue: GitHub.