Open Browser Bridge

Open-source browser control for any AI agent. A Chrome/Edge/Brave extension, a native messaging host and an MCP server. The tool surface matches Claude in Chrome: same tool names, same parameters, same behaviour. Prompts and skills written for it work unchanged with Claude Code, Codex CLI, Gemini CLI, Cursor, VS Code, Windsurf, Cline or any other MCP client.

Independent project. Not affiliated with or endorsed by Anthropic. It contains no Anthropic code.

Agent ──MCP (stdio or HTTP)──▶ host/mcp-server.js ──authenticated pipe──▶ host/native-host.js ──Native Messaging──▶ extension (MV3)
                                                                                                               ├─ chrome.debugger (CDP): real mouse/keyboard, screenshots, console, network, dialogs
                                                                                                               ├─ content/page.js: accessibility tree, ref_N element IDs, find, forms, text, files
                                                                                                               └─ tab group per agent session, per-site permissions, activity log, Stop button

Install (Windows, macOS, Linux)

Requires Node.js 18+ and Chrome/Edge/Brave/Vivaldi/Chromium 116+. No npm dependencies.

node install.js

1. Open chrome://extensions (or edge://extensions), turn on Developer mode, click Load unpacked and pick the extension folder. The ID must match the one the installer printed.

2. Restart the browser once so it reads the native host registration.

3. Click the toolbar icon. It should say Connected to the native host.

4. Add the MCP server to your agent. node install.js --print shows the exact lines, for example:

   claude mcp add --scope user open-browser-bridge -- node /path/to/host/mcp-server.js

   Most other clients use the JSON form: {"mcpServers":{"open-browser-bridge":{"command":"node","args":["/path/to/host/mcp-server.js"]}}}. HTTP clients: run node host/mcp-server.js --http and connect to http://127.0.0.1:12407/mcp with the bearer token it prints.

Uninstall: node uninstall.js, then remove the extension.

Related MCP server: agent-browser-mcp

Tools

Side panel chat (bring your own model)

Open it with the toolbar popup's Open side panel chat button or Alt+Shift+A. In ⚙ settings, choose:

• Anthropic (Claude): API key and model, e.g. claude-opus-5-5, claude-sonnet-5-5, claude-haiku-4-5-20251001

• OpenAI-compatible: OpenAI, OpenRouter (https://openrouter.ai/api/v1), Groq, Ollama (http://localhost:11434/v1, no key needed), LM Studio, or any /chat/completions endpoint with tool calling

The agent works in your current tab and uses the same tools. Responses stream as they arrive, each tool call appears as an expandable step with its screenshots, permission questions appear inline in the chat, Stop halts it, and /command runs a saved shortcut. Your key stays in this browser's extension storage and is sent only to the provider you choose.

Safety model

• Tab isolation: an agent can only act on tabs in its own tab group.

• Per-site permission prompts appear in the agent's own UI when the agent app supports MCP elicitation, like Claude Code's "Claude in Chrome wants to…" question in the terminal. The side panel asks inline. Otherwise a browser pop-up asks. The agent model itself can never answer them. The options are once, this session, always or deny. You can force browser pop-ups in Settings → Where to ask. The host relays an answer only from the session it asked. An "always ask" list (banks, government, sign-in providers by default) can only be approved one action at a time. A blocked list disables sites completely. Restricted pages (chrome://, the Web Store) get navigate only.

• Stop all agent actions in the popup pauses every agent and detaches the debugger.

• Authenticated IPC: the native host's pipe/socket requires a random 256-bit token stored in a user-only data folder, and connections without it are dropped. HTTP mode binds to 127.0.0.1, requires a bearer token and rejects non-local Origins.

• Every click, keystroke and form fill is logged with its action_summary (options page).

• The server's MCP instructions tell agents that page content is data, not instructions, and that they should pause for logins and CAPTCHAs.

Differences from Claude in Chrome

• find uses local relevance ranking over the accessibility tree instead of a hosted model.

• The site-safety list is local and editable rather than served from a vendor API.

• There is no cloud relay (local machine only).

• The side panel uses your own API key or a local model instead of a Claude subscription.

• An MCP agent calling shortcuts_execute gets the saved instructions to carry out itself, because a side panel can't be opened without a user click.

Development

npm test                       # offline: MCP server, native host relay (auth, chunking), permission prompts, providers + agent loop, GIF encoder
npm run e2e                    # live: every tool against your browser (extension must be loaded)
node test/sidepanel-mock.js    # live: side panel agent driven by a scripted local "model"
npm run package                # dist/open-browser-bridge-<version>.zip for the Chrome Web Store / Edge Add-ons

Publishing to the Chrome Web Store

1. npm run package and upload the ZIP in the developer dashboard. This requires a one-time registration fee.

2. Copy the listing text and permission justifications from STORE_LISTING.md, and host PRIVACY.md (e.g. with GitHub Pages) for the privacy-policy URL.

3. Once the store assigns an ID, add it to store-ids.json and re-run node install.js so the native host accepts the store build.

Logs: %LOCALAPPDATA%\OpenBrowserBridge\logs (Windows), ~/Library/Application Support/OpenBrowserBridge/logs (macOS), ~/.local/share/open-browser-bridge/logs (Linux).

Licence: Apache-2.0.