How to stop the forcefully stop running agent or task or fuction_calll and update new agent to the session using session.update_agent()

Thanks for reaching out, Rajadurai. I'm an AI assistant and I'm here to help. Give me a moment while I research this topic.

livekit.agents Error in _update_activity_task Traceback (most recent call last): File "/home/azureuser/dasboard-agent/.venv/lib/python3.12/site-packages/livekit/agents/utils/log.py", line 16, in async_fn_logs return await fn(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^ File "/home/azureuser/dasboard-agent/.venv/lib/python3.12/site-packages/livekit/agents/voice/agent_session.py", line 1094, in _update_activity_task await self._update_activity(agent) File "/home/azureuser/dasboard-agent/.venv/lib/python3.12/site-packages/livekit/agents/voice/agent_session.py", line 1039, in _update_activity raise RuntimeError("cannot start agent: an activity is already running") RuntimeError: cannot start agent: an activity is already running {"room": "voice_assistant_room_2095", "pid": 255157, "job_id": "AJ_fAFU9PEKRH6X", "room_id": "RM_4YqzdtcN8xCt"} Traceback (most recent call last): File "/home/azureuser/dasboard-agent/.venv/lib/python3.12/site-packages/livekit/agents/utils/log.py", line 16, in async_fn_logs return await fn(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^ File "/home/azureuser/dasboard-agent/.venv/lib/python3.12/site-packages/livekit/agents/voice/agent_session.py", line 1094, in _update_activity_task await self._update_activity(agent) File "/home/azureuser/dasboard-agent/.venv/lib/python3.12/site-packages/livekit/agents/voice/agent_session.py", line 1039, in _update_activity raise RuntimeError("cannot start agent: an activity is already running") RuntimeError: cannot start agent: an activity is already running

Thanks — I can see the RuntimeError: "cannot start agent: an activity is already running" from your logs. That error happens when you try to start or update an agent while an existing agent activity (speech, function call, or AgentTask) is still active. Below are practical steps, code patterns, and best practices to stop the running activity cleanly and then call

session.update_agent()

. Short checklist (what to do) • Interrupt the session’s current activity with

session.interrupt()

so the session stops current/queued speech and generation. • Cancel any underlying asyncio Task you created for the agent/function call (call

task.cancel()

and handle

asyncio.CancelledError

in the coroutine). • If using

AgentTask

objects, call

complete()

or otherwise mark them finished, and cancel any background tasks they spawned. • After interruption and cancellation are confirmed, call

session.update_agent(new_agent)

. Example flow (Python asyncio) 1. Interrupt session-level activity:

# stop current speech/generation in the session
session.interrupt()

1. Cancel any explicit asyncio tasks you started:

# assume you stored the task when starting the agent work
if agent_task is not None and not agent_task.done():
    agent_task.cancel()
    try:
        await agent_task
    except asyncio.CancelledError:
        # expected — task was cancelled
        pass

1. Ensure AgentTask is finalized (if used):

# if using AgentTask API
if my_agent_task and not my_agent_task.completed:
    await my_agent_task.complete()  # or otherwise mark it finished

1. Safely update the session agent:

# now replace the agent
session.update_agent(NewAgent())

Key details and best practices • session.interrupt() is designed to stop speaking/generation and to clear queued speech — call it before attempting update to avoid races. • Cancel the actual asyncio Task(s).

session.interrupt()

may not cancel tasks you spawned directly; keep references to those tasks so you can cancel them explicitly. • Make agent code robust: catch

asyncio.CancelledError

to clean up resources (audio handles, streams, locks). • Use short waits/polling or task.await to confirm cancellation before calling

update_agent()

to avoid a race where the session still thinks an activity is active. • If your code restarts agents frequently, centralize task tracking (e.g., a single list/dict of active tasks per session) so you can cancel them reliably. If you want, share: • A short snippet showing how you start the agent activity / create the asyncio task, and whether you use

AgentTask

or raw asyncio. • Whether the activity is speech synthesis, function call, or long-running background work. With that snippet I’ll provide an exact code patch to cancel the task, call

session.interrupt()

safely, and then call

session.update_agent()

without triggering the RuntimeError. Sources: examples/voice_agents | livekit/livekit_composite | DeepWiki