langchain-ai/langgraph · error · TypeError

No synchronous function provided to "{self.name}". Either in

Error message

No synchronous function provided to "{self.name}".
Either initialize with a synchronous function or invoke via the async API (ainvoke, astream, etc.)

What it means

Error "No synchronous function provided to "{self.name}". Either initialize with a synchronous function or invoke via the async API (ainvoke, astream, etc.)" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/_internal/_runnable.py:378

                    )
                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())})"

    def invoke(
        self, input: Any, config: RunnableConfig | None = None, **kwargs: Any
    ) -> Any:
        if self.func is None:
            raise TypeError(
                f'No synchronous function provided to "{self.name}".'
                "\nEither initialize with a synchronous function or invoke"
                " via the async API (ainvoke, astream, etc.)"
            )
        if config is None:
            config = ensure_config()
        if self.explode_args:
            args, _kwargs = input
            kwargs = {**self.kwargs, **_kwargs, **kwargs}
        else:
            args = (input,)
            kwargs = {**self.kwargs, **kwargs}

        runtime = config.get(CONF, {}).get(CONFIG_KEY_RUNTIME)

        for kw, (runtime_key, default) in self.func_accepts.items():
            # If the kwarg is already set, use the set value
            if kw in kwargs:

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/_internal/_runnable.py:378 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/06851f0de6f4eab9. Report an issue: GitHub.