Summary

Wires the new AgentSessionEvent.debug_message (livekit/protocol#1593) through SessionHost, and adds an internal-only AgentSession._emit_debug_message(payload) helper for the debugger/recorder (e.g. agents-cli).

Not a user-facing API — the leading underscore + :meta private: docstring marker signal that this is not intended to be called from user code. The event rides the existing AgentSessionEvent wrapper on the wire; nothing else in the session lifecycle changes.

Changes

• pyproject.toml — bumps livekit-protocol floor >=1.1.9 → >=1.1.10 (picks up DebugMessage, the renamed AgentSessionEvent.debug_message field, FunctionToolsStarted, EotPrediction).
• voice/events.py — EventTypes literal "custom_event" → "debug_message". No wrapper BaseModel.
• voice/agent_session.py:
  • New internal helper: _emit_debug_message(payload: Mapping[str, Any]) -> None — wraps payload into a google.protobuf.Struct and emits agent_pb.DebugMessage. Bypasses the typed emit override (which narrows to AgentEvent for the Pydantic event-trace report); debug messages ride the proto and aren't part of that typed taxonomy.
  • from google.protobuf.json_format import ParseDict + from google.protobuf.struct_pb2 import Struct lifted to module scope (per the no-inline-imports convention).
• voice/remote_session.py — SessionHost listens on "debug_message"; the handler takes agent_pb.DebugMessage and forwards it through AgentSessionEvent(debug_message=...).

Usage (internal only)

```python

debugger / recorder code only — not for user code

session._emit_debug_message({"kind": "anomaly_detected", "score": 0.92})
```

External listeners can subscribe to the event topic via the EventEmitter, but the canonical emit path is the underscore method. There is no stable public emit API for debug events.

Test plan

• `uvx ruff check` — clean (on the voice/ files)
• `uvx ruff format --check` — clean
• `uv run mypy -p livekit.agents.voice` — blocked on `livekit-protocol==1.1.10` release (see below)

Publishing pipeline

CI type-check is blocked until:

1. chore(protocol): bump submodule to v1.46.4 (DebugMessage) and regenerate stubs python-sdks#689 merges (bumps the protocol submodule to v1.46.4, version to 1.1.10)
2. `livekit-protocol==1.1.10` ships to PyPI

After that the pin in pyproject.toml (>=1.1.10) will resolve and mypy will see agent_pb.DebugMessage. Same publishing-pipeline blocker as the previous 1.1.9 cut — no code change needed once the package is released.

Notes

• Companion JS PR: internal(voice): wire DebugMessage over remote-session wire #1611 (same _emitDebugMessage shape on the JS side; published already against @livekit/protocol@1.46.4).
• Builds on agent_session: rename CustomEvent -> DebugMessage; drop type field protocol#1593 (merged).