claude-in-chrome MCP: 'Browser extension is not connected' despite --chrome flag and remote debugging enabled (macOS, Chrome 147)

Environment

• Claude Code version: 2.1.101
• OS: macOS (Darwin 23.6.0)
• Chrome version: 147.0.7727.55
• Launch flags: claude --chrome

Description

The claude-in-chrome MCP tools consistently return "Browser extension is not connected" regardless of Chrome's remote debugging state. The tools are registered as deferred tools and their schemas load fine via ToolSearch, but every call to mcp__claude-in-chrome__tabs_context_mcp fails with the same error.

Steps to reproduce

1. Launch Claude Code with claude --chrome
2. Confirm --chrome flag is present in the process (ps aux | grep claude)
3. Load the tool schema via ToolSearch("select:mcp__claude-in-chrome__tabs_context_mcp")
4. Call mcp__claude-in-chrome__tabs_context_mcp → always returns "Browser extension is not connected"

What was tried

• Chrome UI remote debugging: Enabled via chrome://inspect/#remote-debugging — server stuck at "starting..." and never binds to port 9222
• CLI flag: --remote-debugging-port=9222 — Chrome 147 on macOS ignores this flag (no TCP listener created, confirmed via lsof). The flag appears in the process args but port 9222 never opens.
• Clean restart: Killed all Chrome processes, relaunched with the flag — same result
• Pipe mode: --remote-debugging-pipe — no effect on MCP connectivity
• claude mcp list does not show claude-in-chrome as a configured server
• claude mcp add claude-in-chrome returns "this name is reserved"

Observations

• The error message references https://claude.ai/chrome for extension installation, but it's unclear what specific extension is required (the Claude sidebar extension is already installed)
• Chrome 147 on macOS appears to sandbox the --remote-debugging-port flag — the flag is accepted but the port never binds
• The chrome://inspect/#remote-debugging toggle gets stuck at "starting..." and never transitions to an active server

Expected behavior

Clear documentation on:

1. What specific Chrome extension is required for claude-in-chrome MCP
2. Whether Chrome 147 on macOS is supported
3. Setup steps for the CLI (claude --chrome) workflow

Actual behavior

Persistent "Browser extension is not connected" error with no actionable path to resolve it.