browser-buddy MCP server

Browser Buddy

Let your coding agent read pages through YOUR real, logged-in browser.

Claude Code's WebFetch gets 403'd on most sites. Ask it to pull up a doc, check a Reddit thread, or look at a GitHub issue, and it comes back with a 403 — because server-side fetchers don't have your cookies, your logins, or your sessions.

Browser Buddy is a small local MCP bridge: a Chrome extension (Manifest V3) talks to a Python native-messaging host, which exposes two MCP tools. Your agent reads pages exactly as you see them — logged in, past bot checks — and the page never leaves your machine except into the agent's context.

Stdlib only. No dependencies, no cloud, no API keys.

Tools

Architecture

┌─────────────┐   MCP (JSON-RPC 2.0     ┌──────────────────┐  Unix socket   ┌───────────────────┐  Native Messaging  ┌────────────────┐
│ Claude Code │ ── over stdio, NDJSON ──▶ │ browser_buddy_mcp  │ ── NDJSON ──▶ │ browser_buddy_host │ ── 4-byte LE ──▶ │ Chrome extension │
│             │ ◀────────────────────── │      .py           │ ◀──────────── │       .py          │ ◀── JSON ─────── │ (your profile) │
└─────────────┘                          └──────────────────┘                └───────────────────┘                  └────────────────┘
         ▲                                        │                                                                     │
         │                                        │  one request per socket connection;                                 │  chrome.tabs +
         └──────── page text lands here ──────────┘  host routes replies by request id                                  │  chrome.scripting
                                                                                                                        ▼
                                                                                                              real logged-in page

• Extension (extension/): MV3 service worker. Holds a persistent chrome.runtime.connectNative port to the host (auto-reconnects). Executes readactivetab / openandread_url against your real tabs and posts extracted text back.
• Host (host/browserbuddyhost.py): launched by Chrome. Bridges the extension (length-prefixed stdio) and the MCP server (Unix socket at $TMPDIR/browser-buddy/browser-buddy.sock). Correlates requests by id, with a 90 s timeout.
• MCP server (mcpserver/browserbuddy_mcp.py): hand-rolled JSON-RPC 2.0 over stdio (no mcp package). Forwards tool calls to the host; returns page text as MCP content.

Installation

1. Load the extension

1. Open chrome://extensions, enable Developer mode.
2. Load unpacked → select the extension/ folder.
3. Copy the extension ID shown under "Browser Buddy".

2. Register the native host

cd host
./install.sh <paste-extension-id-here>

This writes com.browserbuddy.host.json into Chrome's NativeMessagingHosts directory (Linux/macOS) pointing at browserbuddyhost.py. Restart Chrome, then open the extension's service worker console — you should see [browser-buddy] native host connected.

3. Add the MCP server to Claude Code

claude mcp add browser-buddy -- python3 /absolute/path/to/mcp_server/browser_buddy_mcp.py

Or in ~/.claude.json / project .mcp.json:

Shortened. The full README is on GitHub.