[BUG] Claude in Chrome MCP fails to connect to Chromium Browser — always launches Google Chrome instead

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The "Claude in Chrome" MCP tools (tabs_context_mcp, etc.) always try to activate/launch Google Chrome, even when the extension is installed and active in Arc (a Chromium-based browser).

The native messaging host manifest is correctly registered for Arc at:
~/Library/Application Support/Arc/User Data/NativeMessagingHosts/com.anthropic.claude_browser_extension.json

The manifest is identical to Chrome's and points to the same binary:
/Applications/Claude.app/Contents/Helpers/chrome-native-host

Despite this, calling tabs_context_mcp from Claude Code opens a dialog prompting the user to set up the extension _only_ in Chrome, rather than connecting to the already-running Arc instance.

Environment:
macOS (Darwin 23.5.0)
Arc Browser (Chromium-based)
Claude Code with Claude in Chrome plugin enabled

What Should Happen?

The MCP should detect whichever Chromium browser has an active extension connection and use it, rather than hardcoding Chrome as the target.

Steps to Reproduce

1. Install the Claude in Chrome extension in Arc browser
2. Verify the native messaging host manifest exists at ~/Library/Application Support/Arc/User Data/NativeMessagingHosts/com.anthropic.claude_browser_extension.json
3. In Claude Code, call any mcp__Claude_in_Chrome__* tool (e.g. tabs_context_mcp)
4. Observe that Chrome is launched/activated instead of connecting to Arc

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.72

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_