fix(agents): return to listening state for thinking-only turns

[kirsten-emak]

Description

When a realtime model (e.g., Gemini with dynamic thinking enabled) sends a generation with no audio output and no tool calls (i.e. a thinking-only turn), the agent would remain stuck in an intermediate and unrecoverable state, unable to process new user input. This fix ensures the agent state returns to 'listening' when a generation completes without executing any tools and without being interrupted, allowing the VAD to resume normal operation.

Changes Made

• Added state recovery logic in agent_activity.ts to return agent to "listening" state when a generation completes without executing any tools
• Ensures proper state transitions even for thinking-only turns (where the model reasons internally without producing audio output)
• Gracefully handles cases where speechHandle.interrupted is false to allow normal state recovery

Pre-Review Checklist

• Build passes: All builds (lint, typecheck, tests) pass locally
• AI-generated code reviewed: Removed unnecessary comments and ensured code quality
• Changes explained: All changes are properly documented and justified above
• Scope appropriate: All changes relate to the PR title, or explanations provided for why they're included
• Video demo: A small video demo showing changes works as expected and did not break any existing functionality using Agent Playground (if applicable) - not applicable

Testing

• Tested with Gemini 2.5 Flash live native audio 12-2025 with dynamic thinking, proactivity and affective dialog enabled
• Verified VAD resumes properly after thinking-only generation
• No regression in normal tool call handling
• Agent properly returns to listening state in all scenarios
• All tests pass
• Make sure both restaurant_agent.ts and realtime_agent.ts work properly (for major changes) - the change is specifically related to fixing realtime agent behaviour

Additional Notes

N/A

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Note to reviewers: Please ensure the pre-review checklist is completed before starting your review.

[changeset-bot]

🦋 Changeset detected

Latest commit: fd4fa8a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 16 packages

Name	Type
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cartesia	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-livekit	Patch
@livekit/agents-plugin-neuphonic	Patch
@livekit/agents-plugin-openai	Patch
@livekit/agents-plugin-resemble	Patch
@livekit/agents-plugin-rime	Patch
@livekit/agents-plugin-silero	Patch
@livekit/agents-plugins-test	Patch

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[CLAassistant]

All committers have signed the CLA.

[toubatbrian]

Nice catch!