langchain-ai/langgraph · error · UserWarning

The 'config' parameter should be typed as 'RunnableConfig' o

Error message

The 'config' parameter should be typed as 'RunnableConfig' or 'RunnableConfig | None', not '{p.annotation}'. 

What it means

Error "The 'config' parameter should be typed as 'RunnableConfig' or 'RunnableConfig | None', not '{p.annotation}'. " thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/_internal/_runnable.py:355

        self.func_accepts: dict[str, tuple[str, Any]] = {}
        params = inspect.signature(cast(Callable, func or afunc)).parameters

        for kw, typ, runtime_key, default in KWARGS_CONFIG_KEYS:
            p = params.get(kw)

            if p is None or p.kind not in VALID_KINDS:
                # If parameter is not found or is not a valid kind, skip
                continue

            if typ != (ANY_TYPE,) and p.annotation not in typ:
                # A specific type is required, but the function annotation does
                # not match the expected type.

                # If this is a config parameter with incorrect typing, emit a warning
                # because we used to support any type but are moving towards more correct typing
                if kw == "config" and p.annotation != inspect.Parameter.empty:
                    warnings.warn(
                        f"The 'config' parameter should be typed as 'RunnableConfig' or "
                        f"'RunnableConfig | None', not '{p.annotation}'. ",
                        UserWarning,
                        stacklevel=4,
                    )
                continue

            # If the kwarg is accepted by the function, store the key / runtime attribute to inject
            self.func_accepts[kw] = (runtime_key, default)

    def __repr__(self) -> str:
        repr_args = {
            k: v
            for k, v in self.__dict__.items()
            if k not in {"name", "func", "afunc", "config", "kwargs", "trace"}
        }
        return f"{self.get_name()}({', '.join(f'{k}={v!r}' for k, v in repr_args.items())})"

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/_internal/_runnable.py:355 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/e3c3e920d1af3622. Report an issue: GitHub.