apache/beam · error · ValueError

Agent did not return a response

Error message

Agent {runner.agent.name} did not return a response

What it means

The ADK runner's event stream finished without any event marked is_final_response(), meaning the agent never completed a turn; _invoke_agent reached the end of run_async and has no result to yield for this element.

Solutions

  1. Check agent configuration for runaway tool loops or missing final-answer behavior
  2. Enable ADK tracing/logs to see which event the run ended on and fix the agent flow
Defensive patterns

Strategy: try-catch

When it happens

Trigger: Thrown at sdks/python/apache_beam/ml/inference/agent_development_kit.py:305 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/5cc59cef5062e586. Report an issue: GitHub.

Appendix: source

Thrown at sdks/python/apache_beam/ml/inference/agent_development_kit.py:305

      await runner.session_service.create_session(
          app_name=app_name,
          user_id=user_id,
          session_id=session_id,
      )

    async for event in runner.run_async(
        user_id=user_id,
        session_id=session_id,
        new_message=message,
    ):
      if event.is_final_response():
        if event.content and event.content.parts:
          return "".join([p.text for p in event.content.parts])
        raise ValueError(
            f"Agent {runner.agent.name} did not return a response, "
            f"final event: {event}")

    raise ValueError(f"Agent {runner.agent.name} did not return a response")

  def get_metrics_namespace(self) -> str:
    return "ADKAgentModelHandler"

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