[BUG] Windows: Claude Code in-app preview device mode toggle (Mobile/Tablet/Responsive) renders two overlapping previews instead of switching the viewport

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?

What happens

In the Claude Code Desktop in-app preview (Browser pane), switching the viewport to Mobile, Tablet, or Responsive does not switch the preview correctly. The preview breaks and renders TWO previews at once: the full-size/desktop view stays rendered in the background and the selected device viewport is drawn on top of it. This makes the device modes unusable for checking responsive layouts.

Environment

• Claude Desktop app 1.30096.5 (MSIX / Microsoft Store install, package Claude_pzs8sxrjxfjjc), Claude Code Desktop 2.1.229
• Windows 11 build 26200, 16 GB RAM
• GPU: AMD Radeon(TM) integrated graphics (Ryzen APU), driver 31.0.21924.61

Related

Same machine and same preview/browser component as #87072 (fatal GPU process crash, exitCode 101457950, in the browser pane). This looks like a rendering/compositing glitch in the same pane, so it may share a root cause.

What Should Happen?

Selecting Mobile, Tablet, or Responsive should replace the current preview with a single, correctly resized viewport for the selected device - one preview surface only, no leftover desktop view behind it.

Error Messages/Logs

Steps to Reproduce

1. Open a Claude Code project in the Claude Desktop app (Code tab) and open the in-app preview (Browser pane) with any web app running.
2. Click the device/viewport toggle and select Mobile (or Tablet, or Responsive).
3. Observe: the preview does not switch cleanly - the full-size/desktop preview remains visible in the background with the selected device viewport rendered on top of it, i.e. two preview screens at the same time. The layout stays broken instead of showing a single resized device viewport.

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.229 (Claude Code Desktop, bundled in Claude Desktop app 1.30096.5 MSIX)

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

Using the Desktop app GUI (Code tab), not a terminal - selected "Other" for Terminal/Shell. The bug is purely visual/rendering in the preview pane's device emulation; no crash is involved in this specific report. GitHub's duplicate detector suggests #82519 (preview-pane rendering bug), possibly the same component. Also filed on this machine: #87072 (fatal GPU process crash, exitCode 101457950, same preview/browser pane) - both issues may share a compositing root cause. Screenshots available on request.