Claude in Chrome: 'Browser extension is not connected' despite correct setup (v2.1.39 + ext v1.0.47)

[danielmstoffel]

Description

The mcp__claude-in-chrome__tabs_context_mcp tool consistently returns "Browser extension is not connected" despite all infrastructure being correctly configured.

Environment

• Claude Code: v2.1.39
• Chrome Extension: Claude in Chrome (Beta) v1.0.47 (ID: fcoeoabgfenejglbffodgkkbkcdhcgfn)
• macOS: Darwin 25.2.0 (Apple Silicon)
• Chrome: Latest stable, Developer mode ON

Setup verified

1. Native messaging hosts exist at ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/:

   • com.anthropic.claude_code_browser_extension.json → ~/.claude/chrome/chrome-native-host
   • com.anthropic.claude_browser_extension.json → /Applications/Claude.app/Contents/Helpers/chrome-native-host

2. Socket file exists: /tmp/claude-mcp-browser-bridge-daniel/<pid>.sock

3. Native host script at ~/.claude/chrome/chrome-native-host correctly points to ~/.local/share/claude/versions/2.1.39 --chrome-native-host

4. Extension is enabled, has "On all sites" access, "Communicate with cooperating native applications" permission, pinned to toolbar, sidepanel shows "Opus 4.6"

Extension errors (from chrome://extensions errors page)

Uncaught (in promise) Error: Could not establish connection. Receiving end does not exist.

Error: A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received

Plus CSP violations for inline scripts in options.html and blocked Segment analytics scripts (likely cosmetic).

Steps to reproduce

1. Start Claude Code v2.1.39 in terminal
2. Claude in Chrome extension v1.0.47 installed and enabled
3. Call mcp__claude-in-chrome__tabs_context_mcp with createIfEmpty: true
4. Returns "Browser extension is not connected"

What was tried (all failed)

• Restarting Chrome (Cmd+Q, reopen)
• Toggling extension OFF/ON
• Removing and reinstalling extension from Chrome Web Store
• Closing Claude Desktop app (to avoid native host conflict)
• Running /chrome command in Claude Code
• Multiple attempts across ~30 minutes

Possible contributing factors

• Claude Desktop was updated to a new version the same day, which refreshed com.anthropic.claude_browser_extension.json (timestamp changed). Both native hosts claim the same extension ID.
• Antigravity Browser Extension (v1.11.3, ID: eeijfnjmjelapkebgockoeaadonbchdd) was also installed the same day — unlikely to conflict but noting for completeness.

Expected behavior

tabs_context_mcp should return tab information or create a new tab group.

Actual behavior

Always returns "Browser extension is not connected" error message.

[github-actions]

Found 3 possible duplicate issues:

1. Browser extension connection fails despite correct setup #24886
2. [Bug] Claude in Chrome fails when Claude Desktop native messaging host config exists (macOS) #20316
3. [BUG] Claude-in-Chrome: Browser extension persistently fails to connect from CLI #24593

This issue will be automatically closed as a duplicate in 3 days.

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🤖 Generated with Claude Code

[Nachx639]

Fix: disable cloud bridge, use local socket

The root cause of the "Browser extension is not connected" / "Invalid token or user mismatch" error is a GrowthBook feature flag that forces the MCP server to use a cloud WebSocket bridge (wss://bridge.claudeusercontent.com) instead of the local Unix socket.

Quick fix — edit ~/.claude.json and set:

{
  "cachedGrowthBookFeatures": {
    "tengu_copper_bridge": false
  }
}

Then restart: claude --chrome

This bypasses the cloud bridge OAuth entirely and connects directly via the local socket. Full technical explanation here: #24593 (comment)

Note: The flag may revert to true periodically as it re-caches from Anthropic's servers. Just set it back to false if the error returns.

[ipreuss]

that fixed it for me!