Claude-in-Chrome: Sandbox blocks access to native messaging socket

Description

The Claude-in-Chrome browser extension fails to connect when Claude Code is running with sandbox enabled. The native messaging host creates its Unix socket at a path that is not included in the sandbox's default write allowlist.

Environment

• OS: macOS (Darwin 25.2.0)
• Claude Code Version: Latest (installed via Homebrew)
• Node.js: v25.4.0
• Chrome Extension Version: 1.0.40

Root Cause

The Chrome native messaging host creates its socket at:

/tmp/claude-mcp-browser-bridge-{username}/{pid}.sock

However, the sandbox's default write allowlist only includes:

/tmp/claude/
/private/tmp/claude/

This path mismatch means Claude Code (running in sandbox) cannot connect to the socket created by the native host (launched by Chrome outside the sandbox).

Steps to Reproduce

1. Enable sandbox in Claude Code settings
2. Start Chrome with the Claude extension installed and enabled
3. Attempt to use any mcp__claude-in-chrome__* tool
4. Connection fails with "Browser extension is not connected"

Diagnostic Evidence

Socket exists and native host is running:

$ lsof -U | grep claude.*bridge
chrome-na  2896 user   10u  unix ...  /tmp/claude-mcp-browser-bridge-user/2896.sock

Connection test from outside sandbox:

import socket
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
sock.connect('/tmp/claude-mcp-browser-bridge-user/2896.sock')
# Success!

Connection test from inside sandbox:

import socket
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
sock.connect('/tmp/claude-mcp-browser-bridge-user/2896.sock')
# Error: [Errno 1] Operation not permitted

Suggested Fix

Either:

1. Update the native host to create sockets inside /tmp/claude/ (e.g., /tmp/claude/browser-bridge-{username}/{pid}.sock)

1. Or update the default sandbox allowlist to include /tmp/claude-mcp-browser-bridge-*

Option 1 seems cleaner as it keeps all Claude-related temp files in a single directory.

Workaround

Users can manually add the paths to their sandbox configuration in .claude/settings.local.json:

{
  "sandbox": {
    "enabled": true,
    "additionalWritePaths": [
      "/tmp/claude-mcp-browser-bridge-*",
      "/private/tmp/claude-mcp-browser-bridge-*"
    ]
  }
}

(Note: I'm not 100% certain this configuration key exists - this was my attempted workaround)