# Todo 19 Latency-Oriented Polish Plan

**Status:** done

## Goal

Reduce perceived reply wait time with earlier event visibility and clearer frontend waiting feedback.

## Design

- Emit `event` output as soon as ChatAgent streaming produces an event, instead of waiting for the full model stream to finish.
- Keep EventAgent execution after the assistant turn is finalized so history remains provider-compatible.
- Show the user's submitted message immediately, disable the run button while streaming, and update elapsed time while waiting for the first token.
- Add lightweight WebSocket logger entries for backend session boundaries.

## Files

- Modify: `src/agent_lab/application/runtime.py`
- Modify: `src/agent_lab/presentation/web.py`
- Modify: `src/agent_lab/presentation/static/index.html`
- Modify: `src/agent_lab/presentation/static/app.js`
- Modify: `src/agent_lab/presentation/static/styles.css`
- Modify: `tests/test_debug_runtime.py`
- Modify: `tests/test_websocket_api.py`
- Modify: `docs/plans/todos.md`

## Verification

- Runtime test proves event messages reach the output queue before the ChatAgent stream is released.
- WebSocket test proves backend logger records session lifecycle events.
- Static UI tests prove immediate user echo, waiting state, disabled run button, and live elapsed timer hooks.
- Full suite passes with `uv run pytest`.

## Result

- Runtime now emits `event` output immediately when the ChatAgent stream detects an event.
- WebSocket service logs accepted, validated, terminal, rejected, failed, disconnected, and closed lifecycle states.
- Frontend now echoes the submitted user message immediately, disables Run while active, shows "Waiting for first token", and keeps elapsed time moving before the first token.
- Review follow-up: elapsed no longer freezes when an event-only first round emits `round_stats` before the first assistant token.
- Tools management is moved to the top of the sidebar so it is visible in the first viewport.
- Verified with focused tests, `uv run pytest` (`49 passed`), and local browser checks at `http://127.0.0.1:8001`.