[Bug] Claude in Chrome: MCP server process never starts from Claude Desktop (Code tab) - connector enabled but no MCP process spawned since Jan 14

Description

Claude in Chrome is enabled in Claude Desktop's Connectors settings, the Chrome extension is installed and authorized, and the chrome-native-host process is running with its Unix socket available — but Claude Desktop never spawns the MCP server process that connects to the socket. As a result, all mcp__Claude_in_Chrome__* tools return "Browser extension is not connected."

This is distinct from the CLI-vs-Desktop conflict issues (#20683, #20887, #20546) — this occurs within Claude Desktop itself (using the Code tab), not from Claude Code CLI.

Environment

• OS: macOS 15.7.3 (Darwin 24.6.0)
• Claude Desktop: v1.1.886
• Chrome: 144.0.7559.97
• Chrome Extension: Claude in Chrome (installed, authorized, Enabled in Connectors)

Steps to Reproduce

1. Open Claude Desktop → Code tab
2. Confirm Claude in Chrome is Enabled in Settings → Connectors → Claude in Chrome
3. Open Chrome with the Claude in Chrome extension installed and logged in
4. In a Code session, call any mcp__Claude_in_Chrome__* tool (e.g., tabs_context_mcp)
5. Result: "Claude in Chrome Extension Disconnected"

Diagnostic Evidence

chrome-native-host is running and socket is available

$ ps aux | grep chrome-native-host
tomo  43491  /Applications/Claude.app/Contents/Helpers/chrome-native-host chrome-extension://fcoeoabgfenejglbffodgkkbkcdhcgfn/

$ ls /tmp/claude-mcp-browser-bridge-tomo.mizuno@up-sider.com/
43491.sock

Direct socket connection test succeeds

import socket
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
sock.connect('/tmp/claude-mcp-browser-bridge-tomo.mizuno@up-sider.com/43491.sock')
# Connected successfully!

MCP server process is NEVER started

~/Library/Logs/Claude/mcp.log contains zero claude-in-chrome entries since Jan 14, 2026. Only Control Chrome entries exist from Jan 26–27. Claude Desktop is not attempting to spawn the claude-in-chrome MCP server at all.

# Last claude-in-chrome entry in mcp.log:
2026-01-14T07:23:50.531Z [info] [claude-in-chrome] Shutting down server...
2026-01-14T07:23:50.531Z [info] [claude-in-chrome] Client transport closed

# Nothing after this date. Only Control Chrome entries from Jan 26 onward.

mcp-server-claude-in-chrome.log shows npm 404 (Jan 14)

On the last attempt (Jan 14), the MCP server failed because the npm package doesn't exist:

npm ERR! 404 Not Found - GET https://registry.npmjs.org/@anthropic-ai%2fclaude-in-chrome-mcp
npm ERR! 404 '@anthropic-ai/claude-in-chrome-mcp@latest' is not in this registry.

After this failure, Claude Desktop never attempted to start the MCP server again.

Native messaging host manifest is correct

{
  "name": "com.anthropic.claude_browser_extension",
  "description": "Claude Browser Extension Native Host",
  "path": "/Applications/Claude.app/Contents/Helpers/chrome-native-host",
  "type": "stdio",
  "allowed_origins": [
    "chrome-extension://dihbgbndebgnbjfmelmegjepbnkhlgni/",
    "chrome-extension://fcoeoabgfenejglbffodgkkbkcdhcgfn/",
    "chrome-extension://dngcpimnedloihjnnfngkgjoidhnaolf/"
  ]
}

claude_desktop_config.json

{
  "mcpServers": {},
  "preferences": {
    "chromeExtensionEnabled": true
  }
}

What I've tried (all failed)

• Restart Chrome (Cmd+Q and reopen)
• Restart Claude Desktop (Cmd+Q and reopen)
• Uninstall and reinstall Chrome extension
• Re-authorize extension
• Toggle Claude in Chrome Disabled → Enabled in Connectors
• Updated Claude Desktop to latest version (confirmed "You are running the latest version")

Root Cause Analysis

Claude Desktop attempted to start the MCP server via npx -y @anthropic-ai/claude-in-chrome-mcp@latest on Jan 14 and got a 404 (package not found). After this failure, it never retried, even after app restarts and extension reinstalls. The Connectors UI shows "Enabled" but no MCP process is spawned.

This suggests either:

1. The npm package was renamed/removed and Claude Desktop is using a stale command
2. Claude Desktop has a "give up permanently after first failure" behavior for built-in connectors
3. The built-in connector architecture changed but the MCP server startup logic wasn't updated

Related Issues

• #20683 - MCP bridge not connecting when Claude.app is also installed (different: CLI conflict)
• #20887 - Extension connects to Desktop instead of Code (different: CLI conflict)
• #21033 - Sandbox blocks socket access (different: sandbox issue)