Jev Agent — browser extension

A self-contained Chromium + Firefox side-panel browser agent powered by TypeSafe's Jev System-One decision model. You type a natural-language goal for the current page; the agent reads the page, asks Jev for one operation + one target at a time, executes it on the page, verifies, and repeats — until the goal is done, blocked, or stopped.

No backend, no self-hosting. The extension talks to the official Jev API directly using your API key, and drives the current tab itself.

goal → observe page → indexed interactive elements → Jev (operation + target)
     → execute on the tab → verify → observe again → next single action → …

Jev is the fast System-1 decision layer: it never receives the whole DOM, giant histories, or screenshots, and never generates selectors, JavaScript, or coordinates. The panel holds the goal and repeatedly gives Jev only the current page's indexed elements; it picks one bounded operation and one element index.

How it works

• Settings — your Jev API key, endpoint (default https://api.typesafe.ai), and model (jev-latest), with a Test connection button. Stored in the browser's extension storage; nothing is sent anywhere except the Jev endpoint.
• Observation — a content function runs in the page (via chrome.scripting) and returns a compact, indexed table of visible interactive elements (role, name, value, state) with a code-owned identity kept on window.
• Decision — one Jev request = an operation Choice (CLICK / TYPE_TEXT / SELECT / SCROLL_UP / SCROLL_DOWN / WAIT / DONE / BLOCKED) plus a per-operation target Choice over the current element indices. Only the target head for the chosen operation is used.
• Execution — the panel resolves the chosen index against a fresh snapshot, rejects stale targets, then clicks / types / selects / scrolls in the tab.
• Verification — the agent re-observes and checks the page actually changed in a way consistent with the action; DONE is not trusted blindly.
• Safety — consequential actions (buy, delete, send, submit, …) pause for confirmation, and Stop halts immediately.

Browser support

• Chromium (Chrome, Chromium, Edge) — MV3 sidePanel (docks on the right).
• Firefox — MV3 sidebar_action (docks per Firefox's sidebar).

Install (from a release)

Download from a GitHub Release:

• extension.zip — Chrome/Chromium
• extension.xpi — Firefox

Chrome / Chromium

1. Unzip extension.zip.
2. chrome://extensions → Developer mode → Load unpacked → select the folder.
3. Click the toolbar icon (or Ctrl+Shift+J) to open the side panel on the right.
4. Open Settings (⚙), paste your Jev API key, click Test connection, Save.

Firefox

1. about:debugging → This Firefox → Load Temporary Add-on → select the manifest.json inside the built folder (or the .xpi).
2. Open the sidebar (Ctrl+Shift+J), add your key in Settings, test, save.

Get a key

Create a Jev API key at https://console.typesafe.ai/keys. It is used only by your browser to call the Jev endpoint you configure.

Development

npm install
npm run dev             # Vite dev server for the panel UI
npm run typecheck
npm test                # vitest (Jev client, decision engine, manifests)

npm run build:chrome    # extension/dist/chromium
npm run build:firefox   # extension/dist/firefox
npm run package:chrome  # dist/chrome/extension.zip
npm run package:firefox # dist/firefox/extension.xpi

GitHub Actions

• ci.yml — typecheck, test, build both targets, validate manifests, package, upload artifacts.
• release.yml — on a v* tag: build/package and attach extension.zip + extension.xpi to a GitHub Release. No store auto-publish — download the artifacts and upload them to the Chrome Web Store / Firefox Add-ons yourself.

Cut a release:

git tag v1.1.0 && git push origin v1.1.0

Security & privacy

• The Jev API key lives in the browser's extension storage and is sent only to the Jev endpoint you configure. It is never logged or bundled into the build.
• The model never emits JavaScript, selectors, or coordinates — only a bounded operation, an element index, and (for TYPE_TEXT) a plain string derived from your goal.
• Stale targets are rejected; mutations are not blindly retried.
• Consequential actions require confirmation; Stop halts immediately.
• DONE is verified against observable page state, not trusted on its own.

Known limitations

• Firefox requires v140+ (for the data-collection manifest declaration).
• Shadow DOM, cross-origin frames, canvas, uploads, and complex keyboard interactions can block progress.
• Element naming covers common labels/ARIA/text, not the full accessibility tree.
• A valid action can still be the wrong action; verification, not the model's confidence, decides success.

License

MIT — see LICENSE. Decision architecture follows browser-use/jev-ultrafast. Jev by TypeSafe AI.