Claude in Chrome extension fails to connect - "Invalid token or user mismatch"

Bug Description

The Claude in Chrome extension (v1.0.56) fails to connect to Claude Code. The MCP server shows as "connected" in /mcp, but every tool call returns "Browser extension is not connected."

Root Cause

The extension connects via WebSocket to wss://bridge.claudeusercontent.com and sends a connect message with an auth token. The bridge responds with:

{"type":"error","error":"Invalid token or user mismatch"}

This happens despite being logged into claude.ai with the same account used by Claude Code.

Steps to Reproduce

1. Install Claude in Chrome extension (v1.0.56)
2. Log into claude.ai
3. Run Claude Code from terminal (authenticated with same account)
4. Run /mcp — shows claude-in-chrome as "connected" with 18 tools
5. Call any chrome tool (e.g. tabs_context_mcp) — returns "Browser extension is not connected"

Debugging Performed

• Confirmed same account on both Claude Code and claude.ai
• Logged out and back into claude.ai, toggled extension off/on — same error
• Removed and reinstalled the extension — same error
• Verified native messaging host config is correct (extension ID matches)
• Verified native host process launches and creates unix socket in /tmp/claude-mcp-browser-bridge-{user}/
• Confirmed the Claude Desktop app's native messaging host (com.anthropic.claude_browser_extension) conflicts with Claude Code's (com.anthropic.claude_code_browser_extension) for the same extension ID — but fixing this didn't resolve the issue
• Inspected extension service worker Network tab — WebSocket connect message is rejected by bridge server

Environment

• macOS Darwin 25.2.0 (Apple Silicon)
• Chrome (latest)
• Claude in Chrome extension v1.0.56
• Claude Code (installed via npm, globally)
• Node v23.9.0
• Auth method: claude.ai (Max plan)