[BUG] Black bar appears when hovering over left sidebar (Claude desktop/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?

A black bar of inconsistent size appears when hovering the mouse over the left sidebar (New chat, Projects, Customize, Artifacts, etc.). The bar disappears and reappears randomly, and its size varies each time.

Black bar of inconsistent size appears, triggered specifically by hovering over sidebar items. Happens intermittently but is reliably reproducible.

What Should Happen?

Sidebar renders normally with no visual artifacts.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Desktop
2. Move mouse cursor over the left sidebar items (New chat, Projects, Customize, Artifacts)
3. A black bar appears over the UI — size varies each time

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.2581.0 (f10398) 2026-04-14T17:16:40.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

This appears to be an Electron GPU compositing / repaint issue. Similar rendering bugs have been reported in issues #2230 and #25929. Contacted support previously but was told the issue does not exist.

<img width="686" height="295" alt="Image" src="https://github.com/user-attachments/assets/f564e997-e3f8-4d71-bd2d-394eb3647488" />