# RB-04 MAJOR: run_live_session is a 200+ line multi-responsibility monolith

**Severity:** MAJOR
**Path:** `src-tauri/src/commands/live.rs:349-579`
**Source:** [2026-04-22 code review](../code-review-2026-04-22.md)
**Labels:** release-blocker, major, refactor, concurrency
**Status:** RESOLVED (2026-04-22)

## Resolution

`run_live_session` was split around two explicit state holders:

- `ActiveCapture` owns the cpal stream handle, audio receiver, and
  optional runtime-error channel.
- `LiveLoopState` owns the mutable per-session loop state: resampler,
  capture buffer, WAV writer, buffer offsets, dropped-audio accounting,
  in-flight inference task, and duplicate-history buffer.

The top-level worker is now `LiveSessionRuntime`, with focused methods
for:

- polling in-flight inference
- draining microphone runtime warnings
- receiving + resampling an audio chunk
- dropping pending-buffer overflow
- flushing the resampler tail when stop is requested
- dispatching inference when enough audio is buffered
- draining the last in-flight task
- finalising the progressive WAV writer

This keeps behaviour intact but removes the "everything in one mutable
loop" shape that made concurrency review hard. The refactor also made
RB-01 straightforward enough to land immediately afterward.

## Problem

`run_live_session` owns mic startup, runtime error draining, resampling, progressive WAV persistence, overload dropping, inference scheduling, and shutdown/finalisation in one 200-line function. The state machine is spread across mutable locals — hard to audit, hard to reason about under concurrency, and already contributing to lifecycle bugs nearby (RB-01, RB-05, RB-06).

## Acceptance

- Split into focused types / functions: capture setup, streaming state, inference scheduler, WAV writer lifecycle, shutdown handler.
- Each function ≤ 30 lines, single responsibility.
- State machine explicit — not implicit in the interleaved mutable locals.
- Lock discipline documented: what must be held when, across what `await` boundaries.
- Existing behaviour preserved — 193 workspace lib tests still green; manual dogfood smoke test of a 30-second live dictation.

## Fix scope

Large. Probably one dedicated session.

## Dependencies

- **Unblocks:** RB-01 (live session race fix becomes tractable once the state machine is small).
- **Related:** RB-05, RB-06 (both lifecycle bugs in the same function).