langchain-ai/langgraph · error · TypeError

Please an annotation for both the return_ and the save value

Error message

Please an annotation for both the return_ and the save values.For example, `-> entrypoint.final[int, str]` would assign a return_ a type of `int` and save the type `str`.

What it means

Error "Please an annotation for both the return_ and the save values.For example, `-> entrypoint.final[int, str]` would assign a return_ a type of `int` and save the type `str`." thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/func/__init__.py:566

            return value.value if isinstance(value, entrypoint.final) else value

        def _pluck_save_value(value: Any) -> Any:
            """Get save value from the entrypoint.final object or passthrough."""
            return value.save if isinstance(value, entrypoint.final) else value

        output_type, save_type = Any, Any
        if sig.return_annotation is not inspect.Signature.empty:
            # User does not parameterize entrypoint.final properly
            if (
                sig.return_annotation is entrypoint.final
            ):  # Un-parameterized entrypoint.final
                output_type = save_type = Any
            else:
                origin = get_origin(sig.return_annotation)
                if origin is entrypoint.final:
                    type_annotations = get_args(sig.return_annotation)
                    if len(type_annotations) != 2:
                        raise TypeError(
                            "Please an annotation for both the return_ and "
                            "the save values."
                            "For example, `-> entrypoint.final[int, str]` would assign a "
                            "return_ a type of `int` and save the type `str`."
                        )
                    output_type, save_type = get_args(sig.return_annotation)
                else:
                    output_type = save_type = sig.return_annotation

        graph: Pregel[Any, ContextT, Any, Any] = Pregel(
            nodes={
                func.__name__: PregelNode(
                    bound=bound,
                    triggers=[START],
                    channels=START,
                    timeout=self.timeout,
                    writers=[
                        ChannelWrite(

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/func/__init__.py:566 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/3e1f935e6798cf57. Report an issue: GitHub.