Preview-pane toolbar randomly renders as a broken "Claude" title bar with colored dots instead of the normal icons

Preview-pane toolbar randomly renders as a broken "Claude" title bar with colored dots instead of the normal icons

Environment

• macOS ProductVersion: 26.4.1 (BuildVersion 25E253)
• Claude desktop app: latest version (checked via Claude menu → confirmed up to date)
• System language/layout: Hebrew (RTL)
• Reproduced in 2 separate sessions, ~17 minutes apart, after a full app restart in between

Summary

The custom toolbar in the browser/preview pane (the one with the split-view, "⋮" more-options, expand, and close icons, top-right of the pane) intermittently gets replaced by what looks like a broken/native title bar: the text "Claude" followed by three colored dots (green, gray, red) laid out left-to-right. Once it happens, it does not revert back to the normal icon toolbar for the rest of the session shown.

Steps to reproduce (best effort — appears to be timing/interaction related, not a fixed click sequence)

1. Open Claude desktop app, open a project, and open the HTML preview pane (browser preview of a local prototype file).
2. Interact with the app for a while (edit files, navigate between tabs/tests in the preview).
3. At some point, move the mouse up into the macOS menu bar area (e.g., toward the Spotlight/search icon) while the preview pane is active.
4. Observe the preview pane's toolbar (top-right corner of the pane) — instead of the normal 4 icons, it now shows the text "Claude" plus green/gray/red dots.

Expected behavior

The preview pane's toolbar should always show the normal controls (spvlit-view / more options / expand / close) regardless of mouse movement into the system menu bar.

Actual behavior

The toolbar flips to a "Claude ● ● ●" placeholder-looking state and stays broken (doesn't self-heal) for the remainder of the observed session. This happened in two independent recordings on the same day, in two different UI layouts:

• Recording 1: preview shown as a floating overlay window with two tabs ("Flow 1", "Flow 2").
• Recording 2: preview shown in a docked split-pane next to the code editor.

In both cases the exact same visual artifact appeared at the same screen position (top-right of the pane's own toolbar).

Confirmed NOT caused by a pending update: an "Update didn't complete — please quit and reopen Claude" banner was present during recording 1; the app was restarted before recording 2, and the "latest version" was confirmed via the Claude menu — yet the same glitch still occurred in recording 2.

<img width="1207" height="400" alt="Image" src="https://github.com/user-attachments/assets/7210f01f-ed21-49a8-abaa-a371bdcf6a70" />

Evidence

Before/after screenshot crop from recording 2, ~0.36s apart (6.44s → 6.80s into the clip) attached to this issue:

• Before: normal toolbar — split-view icon, "⋮", expand arrows, "✕".
• After: "Claude" label + green/gray/red dots, replacing all 4 icons.

Screen recordings available on request (not attached here due to file size / privacy).

Additional notes

• The content of the preview pane itself (a local HTML prototype under Projects/permission/) is unaffected by this specific glitch — it's purely a toolbar/chrome rendering issue in the Claude app's own preview UI.
• System is running in Hebrew/RTL; unclear if RTL layout is a contributing factor to the mis-render, but noting it in case it's relevant (menu bar order, mirrored icon layout, etc.).

<img width="1207" height="400" alt="Image" src="https://github.com/user-attachments/assets/69dcdd96-810d-43b4-b86f-aa9bedc8d914" />