microsoft/autogen · error · RuntimeError

MessageHandlerContext.agent_id() must be called within a mes

Error message

MessageHandlerContext.agent_id() must be called within a message handler.

What it means

Error "MessageHandlerContext.agent_id() must be called within a message handler." thrown in microsoft/autogen.

Source

Thrown at python/packages/autogen-core/src/autogen_core/_message_handler_context.py:31

    _MESSAGE_HANDLER_CONTEXT: ClassVar[ContextVar[AgentId]] = ContextVar("_MESSAGE_HANDLER_CONTEXT")

    @classmethod
    @contextmanager
    def populate_context(cls, ctx: AgentId) -> Generator[None, Any, None]:
        """:meta private:"""
        token = MessageHandlerContext._MESSAGE_HANDLER_CONTEXT.set(ctx)
        try:
            yield
        finally:
            MessageHandlerContext._MESSAGE_HANDLER_CONTEXT.reset(token)

    @classmethod
    def agent_id(cls) -> AgentId:
        try:
            return cls._MESSAGE_HANDLER_CONTEXT.get()
        except LookupError as e:
            raise RuntimeError("MessageHandlerContext.agent_id() must be called within a message handler.") from e

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Call it only while handling a message

Example fix

Access MessageHandlerContext.agent_id() inside the handler method

When it happens

Trigger: Thrown at python/packages/autogen-core/src/autogen_core/_message_handler_context.py:31 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/518d6aa6e00171b2. Report an issue: GitHub.