Claude-in-Chrome MCP: Browser extension not connected despite valid tab data

Description

The claude-in-chrome MCP server shows as connected in /mcp command output, but all browser automation tools return "Browser extension is not connected" error, even when the extension is properly installed and returning valid data.

Environment

• OS: macOS Darwin 25.2.0
• Claude Code model: claude-opus-4-5-20251101
• MCP Status: Shows claude-in-chrome · ✔ connected

Steps to Reproduce

1. Install Claude browser extension from https://claude.ai/chrome
2. Restart Chrome
3. Verify extension is active (sidebar panel opens, shows "Opus 4.5" model selector)
4. Run /mcp in Claude Code - shows claude-in-chrome · ✔ connected
5. Try any browser tool (e.g., tabs_context_mcp)
6. Receive error: "Browser extension is not connected"

Expected Behavior

Browser tools should connect and return tab information when the MCP server shows as connected.

Actual Behavior

All browser tools fail with "Browser extension is not connected" message despite:

• Extension being visibly active in Chrome
• MCP server showing as connected in Claude Code
• Extension apparently returning valid data (user observed {"availableTabs":[{"tabId":1835559348,"title":"Google","url":"https://www.google.com/"}]})

Suspected Issue

Possible data serialization bug in MCP message handling - the extension appears to be returning valid responses, but Claude Code isn't receiving the data properly.

Additional Context

• Reconnecting MCP via /mcp command (shows "Reconnected to claude-in-chrome") does not resolve the issue
• Restarting Chrome does not resolve the issue
• The extension UI is fully functional (can select models, see chat interface)