[BUG] Claude in Chrome: MCP tab group dissolves unexpectedly when closing tabs

What's Wrong?

The MCP tab group created by tabs_context_mcp dissolves unexpectedly when closing tabs within the group, even when multiple tabs remain. This makes browser automation workflows extremely fragile — any tab closure destroys the group and requires recreation, losing the association with all remaining tabs.

Related: #29523 (tab group persistence across sessions). This issue is specifically about tab groups dissolving within a single session.

Expected Behavior

• Closing a tab in an MCP group with 3 tabs should leave 2 tabs in the group
• Closing a tab in an MCP group with 2 tabs should leave 1 tab in the group
• The group should only dissolve when the last tab is closed (standard Chrome behavior)

Steps to Reproduce

1. Claude Code calls tabs_context_mcp with createIfEmpty: true — creates a new tab group with one empty tab
2. User moves an existing tab into the group (now 2 tabs)
3. User creates a third empty tab in the group (now 3 tabs)
4. User closes one of the original tabs
5. Expected: Group persists with 2 remaining tabs
6. Actual: Group dissolves entirely. All tabs become ungrouped. tabs_context_mcp returns "No MCP tab groups found."

This also happens when going from 2 tabs to 1 — closing the empty "New Tab" created by the extension dissolves the group even though the user's tab remains.

Why This Matters

Every tab group dissolution requires:

1. Asking Claude to recreate the group (user cannot create MCP groups manually)
2. Re-navigating tabs to the desired pages
3. Losing tab-specific state (console logs, network requests, etc.)

This is a major workflow disruption that occurs frequently during normal browser automation sessions. Chrome normally only dissolves a group when it reaches 0 tabs, so this appears to be the extension actively removing/ungrouping tabs rather than Chrome's default behavior.

Environment

• Claude in Chrome extension: v1.0.57
• Claude Code CLI: v2.1.63
• Chrome: 145.0.7632.160
• OS: macOS 26.3 (Darwin 25.3.0, Apple Silicon)

Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code