langchain-ai/langgraph · error · ValueError

Auth handler '{getattr(fn, '__name__', fn)}' must be an asyn

Error message

Auth handler '{getattr(fn, '__name__', fn)}' must be an async function. Add 'async' before 'def' to make it asynchronous and ensure any IO operations are non-blocking.

What it means

Error "Auth handler '{getattr(fn, '__name__', fn)}' must be an async function. Add 'async' before 'def' to make it asynchronous and ensure any IO operations are non-blocking." thrown in langchain-ai/langgraph.

Source

Thrown at libs/sdk-py/langgraph_sdk/auth/__init__.py:847

    else:
        r = resource if resource is not None else "*"
        a = action if action is not None else "*"
        if (r, a) in auth._handlers:
            raise ValueError(f"types.Handler already set for {r}, {a}.")
        auth._handlers[(r, a)] = [fn]
    return fn


def _validate_handler(fn: Callable[..., typing.Any]) -> None:
    """Validates that an auth handler function meets the required signature.

    Auth handlers must:
    1. Be async functions
    2. Accept a ctx parameter of type AuthContext
    3. Accept a value parameter for the data being authorized
    """
    if not inspect.iscoroutinefunction(fn):
        raise ValueError(
            f"Auth handler '{getattr(fn, '__name__', fn)}' must be an async function. "
            "Add 'async' before 'def' to make it asynchronous and ensure"
            " any IO operations are non-blocking."
        )

    sig = inspect.signature(fn)
    if "ctx" not in sig.parameters:
        raise ValueError(
            f"Auth handler '{getattr(fn, '__name__', fn)}' must have a 'ctx: AuthContext' parameter. "
            "Update the function signature to include this required parameter."
        )
    if "value" not in sig.parameters:
        raise ValueError(
            f"Auth handler '{getattr(fn, '__name__', fn)}' must have a 'value' parameter. "
            " The value contains the mutable data being sent to the endpoint."
            "Update the function signature to include this required parameter."
        )

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/sdk-py/langgraph_sdk/auth/__init__.py:847 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/a80ce5a253468993. Report an issue: GitHub.