feat(agents): serialize inline AgentTasks from one turn

[rosetta-livekit-bot]

Ports livekit/agents#6862 so parallel tool calls that await inline AgentTasks queue on the activity they pause instead of overwriting one another's handoffs. Interruption holds are counted across queued siblings, drain registration remains ahead of the queue, and RunResult watches begin only after a task acquires the slot.

The task lifecycle now also preserves the source close-race and onEnter behavior: skipped activities fail with ToolError, and onEnter runs are guarded without blocking nested tasks that need another user turn.

Source diff coverage

• livekit-agents/livekit/agents/voice/agent.py: adapted to agents/src/voice/agent.ts. The Python await implementation maps to AgentTask.run(); the full handoff/result/resume lifecycle is wrapped in the old activity slot, with JS Task, Future, and RunResult semantics.
• livekit-agents/livekit/agents/voice/agent_activity.py: adapted to agents/src/voice/agent_activity.ts. Added a per-activity mutex and callback-based slot helper because TypeScript has no async context manager.
• livekit-agents/livekit/agents/voice/speech_handle.py: ported to agents/src/voice/speech_handle.ts. Added counted interruption holds with first-value restoration and forced-interrupt suppression.
• tests/test_nested_agent_task.py: adapted to agents/src/voice/agent.test.ts using AgentSession, FakeLLM, and target tool APIs. Both added source regressions are ported: parallel dialogs serialize and later-turn nested tasks acquire their own activity slot. agents/src/voice/testing/fake_llm.ts was adapted so target-only context items with no model input are no-op generations, matching the source test harness behavior.
• Not applicable: none.

Validation

• pnpm build
• pnpm lint
• pnpm format:check
• pnpm throws:check
• pnpm exec vitest run agents/src/voice/agent.test.ts (29 passed)
• cue-cli text-mode runtime smoke test: two parallel parent tools produced two sequential AgentTask handoffs and both successful outputs
• pnpm test agents: 953 passed, 2 skipped, 11 pre-existing failures in untouched agents/src/voice/amd.test.ts; running that file alone reproduces the same 11 failures

Additional check: pnpm --filter @livekit/agents api:check is blocked by the existing API Extractor error for export * as in dist/index.d.ts.

---

Ported from livekit/agents#6862

Original PR description

Inline AgentTasks awaited from one turn's parallel tool calls now queue for a slot on the activity they pause and take it in turn, instead of overwriting each other's handoffs and leaving the session wedged until close times out; scoping the slot to the activity is what keeps a nested task, which pauses a different one, from waiting on its parent. Supersedes #6860.

[changeset-bot]

🦋 Changeset detected

Latest commit: f6d3bbf

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

This PR includes changesets to release 39 packages

Name	Type
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-anthropic	Patch
@livekit/agents-plugin-assemblyai	Patch
@livekit/agents-plugin-azure	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cartesia	Patch
@livekit/agents-plugin-cerebras	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-did	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-fishaudio	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-hedra	Patch
@livekit/agents-plugin-hume	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-krisp	Patch
@livekit/agents-plugin-lemonslice	Patch
@livekit/agents-plugin-liveavatar	Patch
@livekit/agents-plugin-livekit	Patch
@livekit/agents-plugin-minimax	Patch
@livekit/agents-plugin-mistral	Patch
@livekit/agents-plugin-mistralai	Patch
@livekit/agents-plugin-neuphonic	Patch
@livekit/agents-plugin-openai	Patch
@livekit/agents-plugin-perplexity	Patch
@livekit/agents-plugin-phonic	Patch
@livekit/agents-plugin-protoface	Patch
@livekit/agents-plugin-resemble	Patch
@livekit/agents-plugin-rime	Patch
@livekit/agents-plugin-runway	Patch
@livekit/agents-plugin-sarvam	Patch
@livekit/agents-plugin-silero	Patch
@livekit/agents-plugin-soniox	Patch
@livekit/agents-plugin-tavus	Patch
@livekit/agents-plugins-test	Patch
@livekit/agents-plugin-trugen	Patch
@livekit/agents-plugin-xai	Patch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 1 additional finding.