1.3.3 Error in console mode: ValueError: signal only works in main thread of the main interpreter

[timothyaufdermauer]

Bug Description

Following the quickstart guide https://docs.livekit.io/agents/start/voice-ai/ doesn't launch in console mode. Starting an agent in console mode on windows fails with error:

(.venv) λ python agent.py console
    Agents   Starting console mode �

    14:13:26 DEBUG  asyncio          Using proactor: IocpProactor
             INFO   livekit.agents   starting worker {"version": "1.3.3", "rtc-version": "1.0.19"}
             INFO   livekit.agents   starting inference executor
Exception in thread Thread-1 (_worker_thread):
Traceback (most recent call last):
  File "C:\Users\timothya\AppData\Local\Programs\Python\Python311\Lib\threading.py", line 1045, in _bootstrap_inner
    self.run()
  File "C:\Users\timothya\AppData\Local\Programs\Python\Python311\Lib\threading.py", line 982, in run
    self._target(*self._args, **self._kwargs)
  File "C:\git\lk-test\.venv\Lib\site-packages\livekit\agents\cli\cli.py", line 1145, in _worker_thread
    self._loop.run_until_complete(_async_main())
  File "C:\Users\timothya\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 654, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\git\lk-test\.venv\Lib\site-packages\livekit\agents\cli\cli.py", line 1142, in _async_main
    await self._server.run(devmode=True, unregistered=True)
  File "C:\git\lk-test\.venv\Lib\site-packages\livekit\agents\worker.py", line 627, in run
    await self._inference_executor.start()
  File "C:\git\lk-test\.venv\Lib\site-packages\livekit\agents\ipc\supervised_proc.py", line 128, in start
    await asyncio.shield(self._start())
  File "C:\git\lk-test\.venv\Lib\site-packages\livekit\agents\ipc\supervised_proc.py", line 151, in _start
    with _mask_ctrl_c():
  File "C:\Users\timothya\AppData\Local\Programs\Python\Python311\Lib\contextlib.py", line 137, in __enter__
    return next(self.gen)
           ^^^^^^^^^^^^^^
  File "C:\git\lk-test\.venv\Lib\site-packages\livekit\agents\ipc\supervised_proc.py", line 42, in _mask_ctrl_c
    old = signal.signal(signal.SIGINT, signal.SIG_IGN)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\timothya\AppData\Local\Programs\Python\Python311\Lib\signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: signal only works in main thread of the main interpreter

Expected Behavior

Console mode start successfully.

Reproduction Steps

On windows, python 3.11.9 Manually create .env file with LIVEKIT_API_KEY, LIVEKIT_API_SECRET, and LIVEKIT_URL Create agent.py with the example code (modifying the load_dotenv line to load_dotenv() since my env file was named .env

set PIPENV_VENV_IN_PROJECT=1
pipenv --python <PATH_TO_3.11.9_EXE>
pipenv install livekit-agents[silero,turn-detector]~=1.2 livekit-plugins-noise-cancellation~=0.2 python-dotenv
pipenv shell
python agent.py download-files
python agent.py console
Fails with the above error

Operating System

Windows 10

Models Used

stt="assemblyai/universal-streaming:en" llm="openai/gpt-4.1-mini" tts="cartesia/sonic-3:9626c31c-bec5-4cca-baa8-f8ba9e84c8bc" vad=silero.VAD.load() turn_detection=MultilingualModel()

Package Versions

livekit-agents==1.3.3
livekit-plugins-noise-cancellation==0.2.5
python-dotenv==1.2.1

Session/Room/Call IDs

No response

Proposed Solution

Additional Context

example.zip

Screenshots and Recordings

No response

[elepherai]

same here

[bolito2]

+1

[LuisDiego19FV]

same, it used to work fine for me

[elepherai]

v1.3.4 still has this issue

[marcelpallares]

I think we are facing a similar issue when upgrading to 1.3.4, the LIVEKIT_URL env is not being correctly used and instead it defaults to the default value of ws://localhost:7880 and fails to start

[StefanoBozzoni]

same here

[StefanoBozzoni]

i did this patch to make it works on windows, just after the imports of the agent.py add:

if os.name == "nt": from livekit.agents.ipc import supervised_proc

  @contextlib.contextmanager
  def _safe_mask_ctrl_c():
      try:
          old = signal.signal(signal.SIGINT, signal.SIG_IGN)
      except (ValueError, RuntimeError):
          yield
      else:
          try:
              yield
          finally:
              signal.signal(signal.SIGINT, old)

  supervised_proc._mask_ctrl_c = _safe_mask_ctrl_c

this would substitute the function mask_ctrl_c of the supervised_proc with this _safe_mask_ctrl_c defined here , that simply skip the error of signal in case of an error. The instruction signal.signal(signal.SIGINT, signal.SIG_IGN), should prevent the CTRL C in the terminal. Let me know if it works for you too.