[Bug] macOS M4: mini window renders a black rectangle when hovering its top-left area

Environment

• Codex Desktop: 26.707.72221
• macOS: 15.5
• Hardware: Apple M4 (arm64)

Steps to reproduce

1. Open a thread in Codex Desktop.
2. Open the thread in the mini window / popout view.
3. Move the pointer over the top-left area of the mini window.

Actual behavior

A large black rectangle appears over the mini-window content when the pointer enters the top-left area. This is a rendering artifact and obscures the thread content.

Expected behavior

Hovering the mini window should only reveal its normal controls. No black overlay or rendering artifact should appear.

Notes

• The issue reproduces on Apple Silicon (M4) with macOS 15.5.
• I have screenshots showing the mini-window state and the black-overlay state. A screen recording is not available.
• Related but not identical reports:
• #18832 — black box blocking the UI
• #18311 — M4 mini-window/popout rendering failure