The Vec<f32> in-memory accumulator on run_live_session had three
failure modes: (a) a crash during transcription took the recording
with it, (b) RAM grew linearly with session length, (c) OOM killed
the capture thread silently.
New kon_audio::WavWriter wraps hound::WavWriter<BufWriter<File>> with
an append-friendly API and a 500 ms-granularity header flush. On any
abort after a flush the on-disk file is a valid, playable WAV. Unit
test (brief item #19 acceptance) simulates the abort with
std::mem::forget and asserts the pre-flush samples are recoverable.
Live capture now:
- resolves the destination path at start_live_transcription_session
time via a new resolve_recording_path helper extracted from
persist_audio_samples,
- opens a WavWriter before any samples arrive, sample rate taken from
LocalEngine::capabilities() (#13 wiring) with 16 kHz fallback,
- feeds the resampler output through WavWriter::append inside
append_resampled_audio — drops the writer with a user-visible
warning if a write fails mid-session,
- calls flush() at stop (after resampler tail), finalise() on clean
exit, and drops-to-last-flushed state on abort.
LiveSessionSummary.audio_samples → audio_path: the path is already
written by the time stop_live_transcription_session runs; no
post-session write step remains for live capture.
persist_audio_samples is kept for the offline save_audio command.
Closes the 6 Codex review findings on the Day 1 mic-capture work
(commits 96980c7 + 41db162). Detail in
output/reports/kon-codex-mic-capture-followup-2026-04-17.md (CORBEL
workspace).
src-tauri/src/commands/audio.rs:
- D1: Sending an explicit stop signal before dropping stop_tx, so the
accumulator task wakes up immediately rather than waiting for the
Disconnected detection added below.
- D2: Wrapping MicrophoneCapture::start() in tokio::task::spawn_blocking.
start() can spend up to 350ms × N_devices × 2 passes; running it on
the async runtime froze other Tauri commands.
- M3: Match on rx.try_recv() error variants. Empty -> sleep + continue.
Disconnected -> exit accumulator task immediately. Previous behaviour
was an infinite loop after the capture stream died.
crates/audio/src/capture.rs:
- D3: Added DEAD_SILENCE_FLOOR (1e-7) gate that applies even in the
fallback pass. PulseAudio/PipeWire can stream zero-valued bytes from
a borked device; that is worse than failing fast.
- M1: Validation requeue (`for chunk in collected { try_send }`) now
counts drops in the same dropped_chunks counter.
- M2: New CaptureRuntimeError type. The cpal stream error callback now
forwards errors via a separate sync_channel (capacity 16) that the
live session can drain via take_error_rx() and surface as toasts.
Re-exported from kon_audio crate root.
cargo check -p kon-audio passes clean.
NOT YET DONE (M4): JACK-specific monitor name patterns. Defers until
testing on a JACK host. Current is_monitor_name() may miss JACK
conventions.
Wiring the new error_rx into the live session and surfacing as toasts
lands with the Day 3 error-toast system commit.
Day 1 of the upgrade plan (output/reports/kon-upgrade-plan-2026-04-17.md
in the CORBEL workspace). Fixes the HANDOVER.md blocker: native live
transcription was capturing silence because PulseAudio/PipeWire monitor
sources (speaker loopback) were winning the device-selection race —
they deliver zero-valued bytes that satisfied the original
"any device that produces data within 350ms" check.
WHAT CHANGED:
crates/audio/src/capture.rs (rewrite):
- New `DeviceInfo` struct (serde-derived) for the Settings device picker
- New `MicrophoneCapture::list_devices()` enumerates inputs with metadata
- New `MicrophoneCapture::start_with_device(name)` for explicit selection
- Refactored `start()` with monitor-source filtering by name pattern
(.monitor suffix, "Monitor of " prefix, "loopback" substring) and
RMS-energy validation in a 350ms window
- Two-pass selection: real inputs first, monitor sources only as
last-resort fallback with explicit warning log
- Drop counter (Arc<AtomicU64>) tracks chunks dropped by `try_send`
failure under load — Codex review caught this as a silent-failure risk
- `dropped_chunks()` accessor for the live session
- Verbose tracing at every step for diagnosis
- Unit test for monitor-name detection
- `cargo check -p kon-audio` passes clean
crates/audio/src/lib.rs:
- Re-export `DeviceInfo`
crates/audio/Cargo.toml:
- Add serde dependency (for DeviceInfo derives)
src-tauri/src/commands/audio.rs:
- New `list_audio_devices` Tauri command (returns Vec<DeviceInfo>)
src-tauri/src/lib.rs:
- Register `list_audio_devices` in invoke_handler
src/lib/pages/SettingsPage.svelte:
- New "Audio" section with microphone picker dropdown
- Auto-populates on mount via `list_audio_devices`
- Refresh button + clear messaging about monitor sources
- Likely-monitor entries marked disabled in the dropdown
- Auto mode is the default (empty string in settings.microphoneDevice)
src/lib/stores/page.svelte.js:
- New `microphoneDevice` field in defaults (empty = auto-select)
NEXT STEPS (per the upgrade plan):
- Wire `microphoneDevice` from settings into `MicrophoneCapture::start_with_device`
in the live and standalone capture paths (currently both still call
the auto-selecting `start()`)
- Test on real hardware (Wayland + multiple input devices)
- Codex sanity-check of this diff is running in parallel; addendum to
follow if anything substantive comes back
Refs: /home/jake/Documents/CORBEL-Projects/kon/HANDOVER.md
output/reports/kon-upgrade-plan-2026-04-17.md (CORBEL workspace)
