byob

Bring Your Own Browser — let your AI assistant use the Chrome you already have open.

English · 中文

byob is a local MCP server that lets AI coding tools (Claude Code, Cursor, Cline, Windsurf, etc.) directly control your real Chrome — the one where you're already logged into everything.

"read my Twitter timeline and summarize the top 5 posts"
"google 'mcp protocol spec', click the first result, read the page"
"take a screenshot of example.com"
"grab my GitHub session cookie so I can curl with it"
"open my Gmail tab and tell me how many unread"

Install

Quick install (recommended)

curl -fsSL https://raw.githubusercontent.com/wxtsky/byob/main/install.sh | bash

The script checks prerequisites (Node.js ≥ 20, bun, Chrome), clones the repo, builds everything, and walks you through MCP registration interactively. If bun is not installed, it offers to install it for you.

Set BYOB_INSTALL_DIR to change the install location (default: ~/byob).

Manual install

Requires Node.js ≥ 20, bun, Chrome, and any MCP-compatible AI tool.

git clone https://github.com/wxtsky/byob
cd byob
bun install
bun run setup

bun run setup walks through the install interactively:

1. Pick output language (English / 中文)
2. Generates a unique extension key for you
3. Builds the Chrome extension
4. Writes the config that lets Chrome talk to byob
5. Prompts you to multi-select your AI tools, then registers each one (CLI tools via their mcp add command, JSON-config tools by writing the config file directly)

After the script finishes, three manual steps remain:

Step 2 — Load extension in Chrome

Open chrome://extensions in Chrome.

1. Top-right → turn ON Developer mode
2. Top-left → click Load unpacked
3. Select the folder printed in your terminal, something like:

   /your/path/to/byob/packages/extension/output/chrome-mv3
   

Step 3 — Restart Chrome

Quit Chrome completely (⌘Q on Mac / close all windows on Windows), then reopen.

Closing a single tab or window is not sufficient — Chrome only reads the Native Messaging config at startup.

Step 4 — (Reference) Manual MCP registration

The setup script registers your selected tools automatically. The block below is for reference only — use it if you skipped the prompt or want to register a different tool later:

claude mcp add byob -s user -- /path/to/tsx /path/to/byob-mcp.ts

To enable browser_eval, add -e BYOB_ALLOW_EVAL=1 after -s user.

codex mcp add byob -- /path/to/tsx /path/to/byob-mcp.ts

Add to .cursor/mcp.json (project) or ~/.cursor/mcp.json (global):

{
  "mcpServers": {
    "byob": {
      "command": "/path/to/tsx",
      "args": ["/path/to/byob-mcp.ts"]
    }
  }
}

Add to ~/.codeium/windsurf/mcp_config.json (same JSON format as Cursor):

{
  "mcpServers": {
    "byob": {
      "command": "/path/to/tsx",
      "args": ["/path/to/byob-mcp.ts"]
    }
  }
}

Open Cline sidebar → MCP Servers → Configure, then add (same JSON format):

{
  "mcpServers": {
    "byob": {
      "command": "/path/to/tsx",
      "args": ["/path/to/byob-mcp.ts"]
    }
  }
}

The actual paths are printed by the setup script. The examples above use shortened paths for readability.
To enable browser_eval, add "env": { "BYOB_ALLOW_EVAL": "1" } to the config (or -e BYOB_ALLOW_EVAL=1 for CLI tools).

Step 5 — Wait for setup to confirm the bridge is online

After you finish steps 2 and 3 (load the extension and ⌘Q-restart Chrome), setup auto-detects the bridge coming online and prints ✓ bridge online. The installation is complete — open a new session in your AI tool and try "use byob to read ...".

If you exited setup early with Ctrl+C, or want to check the state later:

bun run doctor

bun run doctor prints actionable fixes under every ✗ (e.g. "⌘Q-restart Chrome", "extension ID mismatch", etc.).

Tools

17 of these tools support framePath to reach into nested iframes (including cross-origin).

Full schemas: shared/src/schemas.ts

How it works

AI tool → byob-mcp → byob-bridge → Chrome extension → your tab
         (stdio)    (Unix socket) (Native Messaging) (Chrome DevTools Protocol)

All communication stays local. No data leaves your machine. When Chrome closes, all byob processes exit automatically.

Everyday commands

bun run setup      # install or re-install
bun run doctor     # check what's working
bun run bridges    # list running bridge processes
bun run logs       # tail the bridge log
bun run unsetup    # remove everything

All run from the byob repo root.

Reliability

• End-to-end cancellation. Ctrl+C propagates through the entire chain (MCP → bridge → extension → Chrome), cleanly detaching all debug sessions.
• DevTools conflict handling. If DevTools is open on a tab, browser_eval automatically falls back to chrome.scripting.executeScript.
• Sleep/wake recovery. After a laptop sleep cycle, byob resets all debug sessions so the next call starts from a clean state.

Security

• browser_eval is off by default — enable with BYOB_ALLOW_EVAL=1. Every call logs + notifies.
• chrome://, file://, Google/MS/Apple login pages are blocked by default.
• Each install gets a unique extension key — no collisions.
• Socket files are 0600, dirs are 0700. Other users can't see them.
• Zero outbound network traffic. No analytics, no pings, no crash reports.
• Chrome displays a "byob is debugging this browser" banner on active tabs. This is a Chrome security feature and cannot be suppressed.

Troubleshooting

Run bun run doctor for detailed diagnostics on which step failed.

Platform notes

More

• Changelog
• Contributing
• Design notes
• Test checklist

MIT licensed. byob has broad access to your browser — only use it on machines and accounts you own.