Hot update delivery

Applet can load JavaScript from bundled assets, inline source, or an AppletBundle. The host decides where code comes from and whether it is allowed to run.

Asset applets

Use assets for local examples, built-in tools, and applets shipped with the app:

const Applet.asset('src/app.js');

Inline source

Use inline source for tests, generated demos, or controlled previews:

Applet.source('''
  import "@app/material";
  export default function App() {
    return Text("Preview");
  }
''');

Bundles

Use bundles for remote delivery:

await controller.loadBundle(
  AppletBundle(
    importMap: {'@feature/ui': 'memory:feature-ui.js'},
    modules: {
      'memory:feature-ui.js': uiModuleSource,
    },
    scripts: [
      AppletScript(entrySource, filename: 'features/home/app.js'),
    ],
  ),
);

Production delivery checklist

• sign every remote bundle;
• hash files and verify before execution;
• keep a rollback manifest;
• stage rollout by user cohort or app version;
• cache the last known good bundle;
• reject bundles outside host-supported API versions;
• log applet version, runtime version, and host app version together.

Applet gives you the runtime hooks. Release policy stays a product and host application responsibility.

Rollout model

A practical rollout model has three artifacts:

Artifact	Purpose
Manifest	Applet id, version, host compatibility, entry filename, hashes.
Bundle	JavaScript entry, imported modules, optional shared modules.
Signature	Authenticity check before code is evaluated.

The host should download the manifest first, verify compatibility, fetch the bundle, verify hashes and signature, then call loadBundle().

Keep the previous verified bundle on disk. If verification or rendering fails, mark the new version unhealthy and reload the last known good bundle.

State preservation

AppletController.reload() and load methods can preserve local state when the applet identity is stable:

await controller.loadBundle(nextBundle, preserveState: true);

Use preservation for development reloads and compatible patch updates. Do not preserve state across incompatible data model changes.