Codex Computer Use for Firefox & Zen

Bring the signed-in Codex sidebar and browser control to Firefox-family browsers.

Install from Firefox Add-ons →

Codex Computer Use for Firefox translates the browser-control operations used by OpenAI's extension into Firefox APIs while preserving the familiar signed-in sidebar. Zen Browser is the primary live-test target, and Firefox is supported from the same signed add-on.

This is an independent compatibility project—not an official OpenAI, Mozilla, or Zen Browser release. It requires an existing ChatGPT/Codex account and installation; it does not provide or bypass account access.

Why use it?

• Work where you already browse. Keep Codex beside your tabs in Firefox or Zen Browser.
• Use real browser control. Codex can inspect pages, click, type, scroll, navigate, upload files, take screenshots, and work across frames.
• Keep the original experience. The packaged OpenAI sidebar and background application remain intact; this project changes the compatibility and transport layers.
• Recover clearly. Missing companions, revoked site access, and bridge/extension version mismatches surface as actionable setup UI instead of silent connection failures.

Install in three steps

1. Install the signed extension

Install Codex Computer Use for Firefox from Mozilla Add-ons, then pin or open Codex for Firefox and Zen Browser from the browser toolbar.

2. Install the matching native bridge

The add-on opens a one-time setup page with Windows and macOS installers. On Linux, use the npm command below; the GitHub Linux asset is a raw binary, not an installer.

npx --yes codex-firefox-bridge@latest install

The bridge remains installed after npx exits. Check it at any time with:

npx --yes codex-firefox-bridge@latest doctor

Windows and universal Apple Silicon/Intel macOS installers are attached to every GitHub release, along with the Linux x64 binary used by the npm installer.

3. Open the sidebar

Keep the official Codex/ChatGPT Chrome integration installed, then open the Codex sidebar from the toolbar or press Ctrl+Shift+. (Command+Shift+. on macOS). If Firefox asks for website access, choose Allow all websites so browser control continues after navigation and in new tabs.

The add-on and bridge are released together. If their versions drift, the toolbar shows a red SYNC badge and opens a recovery screen with both installed versions and the correct update path.

What works

The port has been exercised against the real signed-in OpenAI sidebar in Zen Browser, not only against mocks.

Experience	Support
Signed-in Codex sidebar and New task UI	✅ Verified
Semantic page inspection and element lookup	✅ Verified
Click, type, keyboard, pointer, checkbox, and scroll input	✅ Verified
Navigation, tab management, history, cookies, and downloads	✅ Verified
Screenshots and exact viewport emulation	✅ Verified
File chooser interception and local-file uploads	✅ Verified
Nested and cross-origin iframe control	✅ Verified
HTML5 and pointer drag-and-drop	✅ Verified
Network lifecycle, response bodies, and request interception	✅ Verified
Locale, timezone, touch, user-agent, and device emulation	✅ Verified
JavaScript confirm/prompt discovery and replay	✅ Verified, with a native-dialog caveat

The inherited ChatGPT browser features are retained too:

ChatGPT browser feature	Firefox and Zen Browser support
Mention any open tab as chat context	✅ Firefox tab provider retained
Send highlighted page text to ChatGPT	✅ Selection forwarding retained
Right-click a page and choose Ask ChatGPT	✅ Retained alongside Editing Assets actions
Ask about YouTube videos with timestamped captions	✅ Caption retrieval and timestamp seeking retained
Find relevant pages from browser history	✅ Firefox history search wired through the inherited approval UI
Continue chats between browser and desktop app	✅ Shared thread routes and codex://threads/ handoff retained

See PORT_STATUS.md for detailed evidence and the remaining low-level Firefox limitations. tests/test-chatgpt-feature-parity.mjs guards the inherited ChatGPT surfaces against future upstream refreshes.

How the connection works

Firefox / Zen add-on
        ↕ native messaging
Codex Firefox Bridge
        ↕ local relay
Official OpenAI extension host
        ↕
Codex / ChatGPT

Firefox WebExtensions cannot launch arbitrary local programs or reuse a native-messaging host registered only for a Chrome extension ID. The small companion performs that OS-level handoff: it registers for this Firefox add-on, discovers the existing official OpenAI host, and securely relays the local connection.

The bridge does not replace Codex, store credentials, or operate a remote service. If OpenAI provides an official Firefox route or another supported local connection, we'd be happy to adopt it and simplify or remove the companion.

Under the hood

The compatibility layer adds:

• Firefox sidebar_action support in place of Chrome sidePanel;
• a persistent Firefox background page in place of a Manifest V3 service worker;
• Firefox identity metadata while preserving the official host's Chrome-compatible transport family;
• translation of the chrome.debugger/CDP operations used by Codex into Firefox tab, cookie, screenshot, scripting, DOM, input, and network APIs;
• local-file transfer for controlled file inputs;
• frame-scoped DOM, input, clipboard, and CDP translation across nested cross-origin iframes;
• translated network capture, Fetch interception, emulation, dialogs, and viewport restoration;
• native bridge version reporting so the add-on can detect and explain an out-of-sync installation.

The port currently tracks OpenAI packaged extension version 1.2.27236.6274 (build ad34341c30168f421705cd15f1633ebe6cea7849). The inherited application code is byte-for-byte identical for the documented paths; the port changes only browser compatibility and packaging layers.

Local development

The OpenAI native extension host must already be installed by ChatGPT/Codex tooling on the development machine.

1. Build and register the Firefox companion.

   Windows:

   .\scripts\register-native-host.ps1

   macOS and Linux:

   ./scripts/register-native-host.sh

2. Open about:debugging#/runtime/this-firefox in Zen Browser or Firefox.

3. Select Load Temporary Add-on, then choose extension/manifest.json.

4. Open the Codex sidebar and grant all-sites access if prompted.

5. Start a Codex computer-use task.

Temporary add-ons disappear when the browser exits. Permanent installation requires Mozilla signing while retaining the Gecko ID codex-computer-use-firefox-zen@sunkenintime.

Remove only the development registration with:

.\scripts\unregister-native-host.ps1

./scripts/unregister-native-host.sh

Verify and package

npm test
npx --yes web-ext lint --source-dir extension --no-input
npm run package

npm test checks synchronized release versions, the manifest and compatibility surface, bridge/extension version reporting, and the native protocol, upload, and WebSocket-relay integrations. Packaging writes the unsigned extension archive, a matching review-source archive, and SHA-256 checksums to dist/.

Pushing a semantic-version tag such as v1.4.7 runs the release workflow. It builds and tests the extension, Windows installer, universal macOS package, and Linux x64 binary; verifies all release versions; publishes npm with provenance; attaches release artifacts; and smoke-tests a clean install of the exact public npm version on macOS and Linux. Submit the matching signed Firefox add-on to AMO only after that smoke test passes.

Prepare a release with:

npm run version:set -- MAJOR.MINOR.PATCH

web-ext lint currently reports zero errors. Its expected warnings come from the inherited minified OpenAI distribution and intentional page-world function serialization in the compatibility layer.

Privacy, independence, and source

Read PRIVACY.md for the data-handling disclosure. The native adapter pins its relay origin to the official OpenAI extension ID and rejects unrelated messages.

extension/codex-sidepanel and extension/background.js are OpenAI's packaged distribution, not a clean-room source reimplementation. Those upstream assets remain subject to OpenAI's applicable terms. The compatibility code in this repository is provided for review and development; no additional license is granted for the bundled upstream assets.