whisper_web/WorkBreakdown.md

# Work Breakdown

Milestones are ordered so that **every milestone ends in a demoable, working app**.
Within a milestone, tasks are roughly in dependency order. Check items off as they
land; add follow-up tasks where they belong rather than in a separate backlog.

Legend: `[ ]` todo · `[x]` done · `[~]` in progress

---

## M0 — Scaffold cleanup & docs (small)
Current state is the raw `bun init` React template.

- [x] `Architecture.md`, `Decisions.md`, `WorkBreakdown.md` created
- [x] Remove template cruft: `APITester.tsx`, hello routes in `src/index.ts`,
      Bun/React logo branding in `App.tsx` / `index.html`
- [x] Add `@huggingface/transformers` dependency
- [x] Target directory layout from `Architecture.md` §3 (empty modules with TODOs are fine)
- [x] Smoke test in `tests/` proving `bun test` runs

## M1 — Browser transcription MVP (core)
Anonymous user can transcribe an uploaded file with one hardcoded model. **This is the
riskiest milestone — do it first, learn from it.**

- [x] `src/worker/protocol.ts` — typed messages: load / load-progress / transcribe /
      partial / result / error
- [x] `src/worker/inference.worker.ts` — Transformers.js ASR pipeline
      (`onnx-community/whisper-tiny.en` hardcoded, WASM only for now), chunked
      with timestamps, partials streamed via `WhisperTextStreamer`
- [x] `src/lib/audio.ts` — decode upload → 16 kHz mono Float32Array (D-012)
- [x] `FileDropzone` component (drag-drop + file picker, audio/* and video/*)
- [x] `TranscriptView` component — streaming partials, final text, copy button
- [x] Model download progress UI (bytes / %, per-file)
- [x] Wire into `App.tsx`; delete remaining template UI
- [x] Unit tests for audio resampling and protocol handling

Notes (M1):
- Bun 1.3 does not bundle `new Worker(new URL(...))` graphs (verified against
  both `bun build` and the dev server), so `src/index.ts` bundles the worker
  with `Bun.build` at startup and serves it at `/inference.worker.js`; the UI
  spawns `new Worker("/inference.worker.js", { type: "module" })`. Revisit if
  Bun gains native worker bundling.
- onnxruntime-web fetches its `.wasm` binaries from the jsdelivr CDN
  (Transformers.js default). Fine for M1; M3 (offline) must serve/cache them
  locally.

## M2 — Model choice + WebGPU (core)
- [x] `src/lib/models.ts` — curated catalog with sizes and dtype defaults (D-006)
- [x] `ModelPicker` component — size estimates, English-only vs multilingual,
      downloaded-state badge (query Cache API)
- [x] WebGPU detection in worker, `device` selection with WASM fallback (D-004);
      surface active backend in UI
- [x] Handle model switching (dispose old pipeline, load new)
- [x] Language / task options for multilingual models (transcribe vs translate)
- [~] Verify quantized variants (q4/q8/fp16) on both backends; record working
      combinations in `models.ts`

Notes (M2):
- Quantized-variant verification is pending manual in-browser testing (no real
  browser in the dev environment). `models.ts` encodes the community-known-good
  combinations — WASM: q8 (tiny→small) / q4 (medium, large-v3-turbo); WebGPU:
  fp32 encoder+decoder for tiny/base (fp16 encoders known-bad there), fp16
  encoder + q4 merged decoder for small/medium/large-v3-turbo — each with a
  `verified` flag and note. Only `whisper-tiny.en @ wasm/q8` (exercised in M1)
  is marked `verified: true`; flip the flags as manual testing confirms each.
- Downloaded badge (D-005): `src/lib/modelCache.ts` inspects Cache Storage for
  transformers-cache entries with `.onnx` hits per model id; M3's offline
  indicator should reuse `getDownloadedModels`.

## M3 — PWA & offline (core)
- [ ] `manifest.webmanifest` + icons; installability
- [ ] `src/pwa/sw.ts` — app-shell precache, cache-first static, network-only API (D-007)
- [ ] Build step: emit precache manifest from `bun build` output into the SW
- [ ] SW registration + update flow (new-version toast)
- [ ] Offline verification: airplane-mode transcription with a previously
      downloaded model; document the manual test procedure in `tests/offline.md`
- [ ] "Available offline" indicator per model in `ModelPicker`

## M4 — Accounts (Passport.js)
- [ ] `src/server/db.ts` — bun:sqlite schema: users, sessions (D-009)
- [ ] Connect-compat adapter + Passport local strategy in `src/server/auth.ts` (D-008)
- [ ] Routes: `POST /api/auth/register|login|logout`, `GET /api/auth/me`
- [ ] Password hashing via `Bun.password` (Argon2)
- [ ] Frontend: login/register forms, session-aware header, logged-out ⇒ no
      behavioral change (anonymous-first invariant)
- [ ] Auth tests (register/login/logout, session expiry, wrong password)

## M5 — Server engine + toggle
- [ ] Server-side pipeline in `src/server/transcribe.ts` (Transformers.js under Bun,
      CPU; reuse the shared model catalog)
- [ ] `POST /api/transcribe` — auth-guarded, streamed JSON-lines response (D-011),
      upload size limit, request abort handling
- [ ] `src/lib/engine.ts` — `Engine` interface; `BrowserEngine` (wraps worker) and
      `ServerEngine` (wraps fetch stream) (D-010)
- [ ] `EngineToggle` component — visible only with a session; persists choice
- [ ] Server model caching/warm-up strategy (don't reload weights per request)
- [ ] Integration test: same fixture audio through both engines, transcripts agree

## M6 — Hardening & polish
- [ ] Error taxonomy: unsupported file, out-of-memory (suggest smaller model),
      WebGPU device-lost, network loss mid-download (resume or clear retry)
- [ ] Cancel in-flight transcription (both engines)
- [ ] Export transcript: .txt and .srt (timestamps already available)
- [ ] Storage management UI: list cached models, per-model delete
- [ ] Basic a11y pass (keyboard, focus, aria on progress/live transcript)
- [ ] Production build + `bun start` deployment check; README for deployers

---

## Deliberately out of scope (for now)
Microphone/live transcription, arbitrary Hub model ids, OAuth providers,
multi-user transcript storage, whisper.cpp server backend, i18n of the UI.
Promote to a milestone via a new entry in `Decisions.md` first.