[BUG] Claude in Chrome extension fails to connect on macOS despite correct configuration

Bug Description

Claude in Chrome extension consistently fails to connect to Claude Desktop on macOS, with tabs_context_mcp tool always returning "Browser extension is not connected" error despite all components being properly installed and configured.

Environment

• OS: macOS Darwin 25.2.0
• Claude Desktop Version: 1.1.2685
• Chrome Extension Version: 1.0.49
• Chrome Extension ID: fcoeoabgfenejglbffodgkkbkcdhcgfn
• Account: Same account logged in on both Desktop and Chrome extension (verified)

Configuration Status

✅ Verified Working:

• Chrome extension installed and enabled
• Native messaging host configured at /Applications/Claude.app/Contents/Helpers/chrome-native-host
• Native messaging host manifest exists at ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_browser_extension.json
• Extension ID is in the allowed_origins list
• Claude Desktop Connector setting enabled for "Claude in Chrome"
• Account consistency verified (same email on both sides)
• Multiple Chrome and Claude Desktop restarts attempted

Steps Taken

1. Installed Claude in Chrome extension from Chrome Web Store
2. Enabled extension in chrome://extensions/
3. Verified Claude Desktop Connector settings show "Enabled"
4. Confirmed same account login on both Desktop and Chrome
5. Restarted Chrome multiple times
6. Restarted Claude Desktop
7. Verified native messaging host configuration

Observed Behavior

When calling mcp__Claude_in_Chrome__tabs_context_mcp with createIfEmpty: true:

MCP server "Claude in Chrome": Calling MCP tool: tabs_context_mcp
MCP server "Claude in Chrome": Tool 'tabs_context_mcp' completed successfully in 2s

But the tool returns:

⚠️ **Claude in Chrome Extension Disconnected**

The connection to Claude in Chrome was lost.

Debug Log Evidence

From ~/.claude/debug/latest:

[DEBUG] MCP server "Claude in Chrome": Calling MCP tool: tabs_context_mcp
[DEBUG] MCP server "Claude in Chrome": Tool 'tabs_context_mcp' completed successfully in 1s

The tool call completes successfully, but returns a "not connected" error, suggesting the request reaches the extension but the response fails to return to Desktop.

Related Issues

This appears related to:

• #20862 - MCP tools fail with "Browser extension is not connected"
• #21371 - Extension not connecting despite being installed
• #15527 - Connection fails until Chrome restart
• #23082 - Extension executes but CLI receives 'not connected' error

Expected Behavior

The tabs_context_mcp tool should successfully establish connection and return tab group information.

Additional Notes

• This is affecting a Mac user with the latest versions of both Claude Desktop and the Chrome extension
• All configuration files have been verified to be correct
• The issue persists across multiple sessions and restarts
• Native messaging host binary exists and has correct permissions