[BUG] Multi-window: "/" skill picker is mispositioned and Enter doesn't select (macOS)

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?

When a chat is opened in a NEW / separate window (multi-window), the skill picker triggered by typing "/" is broken:

• The suggestion / picker popup appears in the wrong position (misplaced relative to the input).
• Pressing Enter does not select the highlighted skill.

Both symptoms only happen in a new window; in the main window the picker is positioned correctly and Enter selects as expected.

What Should Happen?

In a new/separate window, typing "/" should open the skill picker anchored to the input in the correct position, and pressing Enter should select the highlighted skill, the same as in the main window.

Error Messages/Logs

Steps to Reproduce

1. Open a Claude Code / Cowork session in a NEW window (multi-window).
2. Type "/" in the input to bring up the skill picker.
3. Observe the popup appears in the wrong position.
4. Use arrow keys to highlight a skill and press Enter -> the skill is not selected.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.11187.4 (584005) 2026-06-05T20:15:04.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Specific to new/separate windows (multi-window); does not happen in the main window. OS: macOS 15.7.3 (24G419).