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45f368f471
The browser tier of @mana/local-llm was running entirely in the main
JS thread. With Gemma 4 E2B that meant ~50-200 ms of synchronous
tensor work per forward pass × ~150 forward passes per generation =
the UI froze for 10-30 seconds during a single chat reply. Scrolling,
clicks, animations all stopped.
Move the actual inference into a Dedicated Web Worker. The main
thread keeps a thin LocalLLMEngine proxy with the same public API
(load / unload / generate / prompt / extractJson / classify /
onStatusChange / isSupported), so existing callers — the /llm-test
page, the playground module, @mana/shared-llm's BrowserBackend, the
Svelte 5 reactive bindings — need NO changes.
File layout after the split:
src/engine.ts — main-thread proxy (lazy worker init,
postMessage protocol, pending request map,
status broadcast handling, convenience
wrappers for prompt/extractJson/classify)
src/worker.ts — Web Worker entry point (typed message
protocol, single LocalLLMEngineImpl instance,
forwards status changes back to main thread)
src/engine-impl.ts — the actual transformers.js engine (renamed
from the previous engine.ts contents). NOT
exported from index.ts — only the worker
imports it. Same two-step tokenization,
aggregated progress reporting, streaming
token handling as before; just running in
a different thread now.
Worker construction uses Vite's documented `new Worker(new URL(
'./worker.ts', import.meta.url), { type: 'module' })` pattern, which
makes Vite split worker.ts (and its transformers.js dep) into its
own bundle chunk at build time. The proxy is lazy-init: the Worker
constructor is never touched at module-import time, so SSR stays
clean (Worker doesn't exist on Node).
Message protocol (typed end-to-end):
Main → Worker:
{ id, type: 'load', modelKey: ModelKey }
{ id, type: 'unload' }
{ id, type: 'generate', opts: SerializableGenerateOptions }
{ id, type: 'isReady' }
Worker → Main:
{ id, type: 'result', data?: unknown }
{ id, type: 'error', message: string }
{ id, type: 'token', token: string } — streaming chunk
{ type: 'status', status: LoadingStatus } — broadcast
The proxy assigns a unique id per request, stores the resolve/reject
+ optional onToken callback in a Map<id, PendingRequest>, and routes
incoming responses by id. Status messages have no id and fire every
registered status listener — same UX as before, just one extra hop.
Streaming: the worker re-attaches the streaming callback on its
side. Each emitted token gets posted back as `{ id, type: 'token',
token }` and the proxy invokes the original `onToken` callback. The
final `result` arrives as a normal response and resolves the
Promise. From the caller's perspective generate() still feels
identical — same async iterable feel via onToken, same return value.
Worker termination on unload: transformers.js doesn't expose a
dispose API, so we terminate the worker after unload and create a
fresh one on the next load. This is the only reliable way to
release VRAM between model swaps.
CSP: no header changes needed. The worker is loaded from a
same-origin URL (Vite emits it as
/_app/immutable/workers/worker.[hash].js), so 'self' in script-src
already covers it. The blob: + cdn.jsdelivr.net + wasm-unsafe-eval
allowlists we added during the original WebLLM/transformers.js
bring-up still apply because the worker still runs the same ONNX
runtime that needed them.
DistributiveOmit type helper: TS's plain `Omit<Union, K>` collapses
discriminated unions to an intersection in some configurations,
which broke the type narrowing at the postRequest call sites for
each request variant. Adding a tiny `DistributiveOmit<T, K>` helper
fixes the type-check without restructuring the protocol.
What this commit deliberately does NOT do:
- Change the public API surface. The whole point is that callers
remain untouched.
- Add multi-tab worker coordination via SharedWorker or
BroadcastChannel. Each tab still spawns its own dedicated worker
with its own copy of the model in VRAM. Multi-tab dedup is
Phase 2.5/Phase 4 work — see the design doc summary in the
previous Phase 1 commit message.
- Add a persistent task queue. Fire-and-forget background tasks
are Phase 4.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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| .. | ||
| cards-database | ||
| credits | ||
| eslint-config | ||
| feedback | ||
| help | ||
| local-llm | ||
| local-store | ||
| notify-client | ||
| qr-export | ||
| shared-api-client | ||
| shared-auth | ||
| shared-auth-ui | ||
| shared-branding | ||
| shared-config | ||
| shared-drizzle-config | ||
| shared-error-tracking | ||
| shared-errors | ||
| shared-go | ||
| shared-hono | ||
| shared-i18n | ||
| shared-icons | ||
| shared-landing-ui | ||
| shared-links | ||
| shared-llm | ||
| shared-logger | ||
| shared-pwa | ||
| shared-python/manacore_auth | ||
| shared-splitscreen | ||
| shared-storage | ||
| shared-stores | ||
| shared-tags | ||
| shared-tailwind | ||
| shared-theme | ||
| shared-theme-ui | ||
| shared-tsconfig | ||
| shared-types | ||
| shared-ui | ||
| shared-uload | ||
| shared-utils | ||
| shared-vite-config | ||
| spiral-db | ||
| subscriptions | ||
| test-config | ||
| wallpaper-generator | ||