MCP commands cause browser to switch to a specific tab in Arc

[andresespinosapc]

Description

When using any MCP tool (take_screenshot, select_page, list_pages, evaluate_script, etc.), the browser UI automatically switches the visible tab to a specific tab — even when that tab is not the one being operated on.

This is different from issue #933. That issue is about which page DevTools considers "selected". This issue is about the browser UI physically switching the user's active/visible tab every time any MCP command runs.

Environment

• Browser: Arc (Chromium-based)
• Connection: --auto-connect to an already running browser instance
• OS: macOS

Reproduction

1. Open Arc with multiple tabs (e.g., Tab A = Jira, Tab B = localhost:8080, Tab C = localhost:8082)
2. User is viewing Tab A
3. MCP agent runs any command (e.g., list_pages, take_screenshot, evaluate_script) targeting Tab B
4. Result: Arc switches the visible tab to Tab C (a seemingly arbitrary tab)
5. User has to manually navigate back to Tab A

Key observations

• The "destination" tab seems to be determined by which tab CDP has an active attachment to — possibly the last tab connected via --auto-connect
• bringToFront: true in select_page does not reliably control which tab gets focused in the UI
• Closing the problematic "destination" tab (e.g., localhost:8082) resolved the issue temporarily, but it returned when other commands were run
• The tab switch happens on any MCP command, not just select_page or take_screenshot

Expected behavior

Running MCP commands should not change the user's currently visible tab in the browser UI, unless explicitly requested (e.g., select_page with bringToFront: true).

Workaround

None reliable. Closing the tab that CDP auto-attached to can help temporarily.