Fullscreening a video in Glance causes tab sidebar moving slightly left-ier afterwards - Twilight 1.15t (Firefox 142.0) (2025-08-24)

[KiKaraage]

Preliminary Checks

• [x] I have read and understood the important section above.
• [x] I have searched existing issues and avoided creating duplicates.
• [x] I am not filing an enhancement request.
• [x] I have checked that this issue cannot be reproduced on Mozilla Firefox.
• [x] I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

After I open a Glance and opening a video there in full screen mode, the tab sidebar got moved to left side.

https://github.com/user-attachments/assets/8b216654-5906-49ee-bd36-35f679409154

When I inspect it on Browser Toolbox, the misalignment happens in the .zen-workspace-tabs-section.zen-workspace-pinned-tabs-section level.

a. .zen-workspace-tabs-section.zen-workspace-pinned-tabs-section (misaligned)

b. One level above, .workspace-arrowscrollbox (normal)

Expected behavior

Tab sidebar should stayed in its original position/margin.

Actual behavior

The tab sidebar got moved slightly to the left side

Steps to reproduce

1. Open https://github.com/zen-browser/desktop/issues
2. Open one of the issues containing video content in Glance (example: https://github.com/zen-browser/desktop/issues/9953)
3. Play the video
4. Click the Fullscreen button
5. Exit Fullscreen mode

Can be reproduced using any website with playable, fullscreen-able videos like Youtube or Twitter too

Screenshots and videos

No response

Version

1.15t (Firefox 142.0) (2025-08-24)

What platform are you seeing the problem on?

Linux (Tarball)

What component is this issue related to?

Tabs

Relevant log output if applicable

[dosubot[bot]]

Hi, @KiKaraage. I'm Dosu, and I'm helping the desktop team manage their backlog and am marking this issue as stale.

Issue Summary:

• You reported a UI issue in Twilight 1.15t on Firefox 142.0 (Linux) where fullscreening a video in Glance causes the tab sidebar to shift slightly left.
• The sidebar does not revert to its original position after exiting fullscreen mode.
• The misalignment happens at the .zen-workspace-tabs-section.zen-workspace-pinned-tabs-section level.
• This issue can be reproduced on multiple sites including GitHub, YouTube, and Twitter.
• There has been no further activity or comments on this issue since it was reported.

Next Steps:

• Please let me know if this issue is still relevant with the latest version of the desktop repository by commenting here to keep the discussion open.
• If I don’t hear back from you within 10 days, this issue will be automatically closed.

Thanks for your understanding and contribution!