@webmcp-agents/local-agent/worker

The transformers.js model worker.

The transformers.js model worker. It is the only entry that loads @huggingface/transformers and ONNX Runtime, so a long generation never blocks the page’s main thread or the agent cursor. You import it only when your bundler cannot follow the package’s own new Worker(new URL(…, import.meta.url)).

Import

// as a URL
new Worker(new URL("@webmcp-agents/local-agent/worker", import.meta.url), {
  type: "module",
});
// or with Vite's ?worker suffix
import LocalWorker from "@webmcp-agents/local-agent/worker?worker";

The entry has no exports. Loaded as a module worker, it listens for messages from createTransformersProvider and answers them; the message protocol is internal.

Example

With Vite, the default path needs only two settings, and the package creates its own worker:

export default defineConfig({
  optimizeDeps: {
    exclude: ["@webmcp-agents/local-agent", "@huggingface/transformers"],
  },
  worker: { format: "es" },
});

A bundler that cannot follow the worker URL hands the adapter a worker of its own:

import { createLocalAdapter } from "@webmcp-agents/local-agent";
import LocalWorker from "@webmcp-agents/local-agent/worker?worker";

const local = createLocalAdapter({ worker: () => new LocalWorker() });

Options

The worker takes none. Pass it to createLocalAdapter or createTransformersProvider as worker:

Name	Type	Default	Description
`worker`	`Worker \| (() => Worker)`	the package’s own worker	A worker instance, or a function that creates one. A function runs only when the model loads (the person’s Download click, or the first message when the model is cached), so the worker never starts on import.

Notes

Inside the worker, transformers.js uses the browser cache (env.useBrowserCache = true) and never local models (env.allowLocalModels = false).
Generations run one at a time per worker. Stop interrupts the running one.
The package’s default worker is spawned as a module worker named web-agents-local-model.
If the worker crashes, the provider terminates it and frees the page slot and the browser lock; pending calls fail with “The model worker crashed.” (or the error’s message).
An instance you create yourself exists as soon as your code creates it; prefer the function form.

@webmcp-agents/local-agent/worker

Import

Example

Options

Notes

See also