[BUG] Cowork browser tools connect to Chrome Canary even without extension installed

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?

In Cowork mode, when both Chrome and Chrome Canary are installed on the same machine, the browser MCP tools (tabs_context_mcp, etc.) connect to Chrome Canary instead of regular Chrome — even though the Claude in Chrome extension is only installed in regular Chrome, not in Canary.

Once connected to the wrong browser, switch_browser fails with "No other browsers available to switch to" — there is no way to redirect to the correct browser.

Environment:

• Windows 11
• Chrome (regular) with Claude in Chrome extension installed
• Chrome Canary installed but without the Claude extension
• Cowork mode (Claude desktop app)

Steps to reproduce:

1. Have both Chrome and Chrome Canary installed on Windows
2. Install Claude in Chrome extension only in regular Chrome
3. Start a Cowork session
4. Claude calls tabs_context_mcp — it connects to Chrome Canary (wrong browser)
5. Call switch_browser — fails with "No other browsers available"
6. No way to connect to the correct Chrome without uninstalling Canary

Workaround: User had to uninstall Chrome Canary entirely to force the connection to regular Chrome.

What Should Happen?

The browser MCP tools should only connect to Chrome instances that actually have the Claude in Chrome extension installed. If multiple Chrome variants are present, tabs_context_mcp should not connect to a browser without the extension.

Additionally, switch_browser should reliably allow switching between browsers when the target browser has the extension installed.

Error Messages/Logs

switch_browser returned: "No other browsers available to switch to. Open Chrome with the Claude extension in another browser to switch."

This error persisted even after confirming the Claude in Chrome extension was installed and active in regular Chrome (extension settings page showed it as enabled and logged in).

Steps to Reproduce

1. Install Chrome (regular) and Chrome Canary on Windows 11
2. Install the Claude in Chrome extension only in regular Chrome (NOT in Canary)
3. Open both Chrome and Chrome Canary
4. Start a Cowork session in the Claude desktop app
5. Claude calls tabs_context_mcp with createIfEmpty: true
6. The tool connects to Chrome Canary (which does NOT have the extension) instead of regular Chrome
7. Claude calls switch_browser — returns "No other browsers available to switch to"
8. Regular Chrome's extension icon shows a white outline (not connected) — clicking it shows no "connect" option
9. Only fix: uninstall Chrome Canary, then tabs_context_mcp correctly connects to regular Chrome

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.63 (Claude Code) — running in Cowork mode

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

This bug occurs in Cowork mode (Claude desktop app), not Claude Code CLI. The browser MCP tools are used by Cowork to automate Chrome.

Key detail: The Claude in Chrome extension was never installed in Chrome Canary — yet tabs_context_mcp still connected to Canary and opened tabs there. This suggests the MCP connection is targeting Chrome browser processes at the OS level rather than checking for the extension first.

The user had to fully uninstall Chrome Canary as a workaround. After uninstalling, tabs_context_mcp correctly connected to regular Chrome where the extension was installed.