2040598 - [Ubuntu] Settings ‘browser.nova.enabled’ on true renders the browser window borders transparent

Status: VERIFIED FIXED

(Firefox :: Theme, defect)

Description

[Ardelean Oana, Desktop Test Engineering [:oardelean]]

Attachment: image (2).png

Notes

• Please refer to the attached screenshot for more details.

Found in

• Nightly 153.0a1;

Affected versions

• Nightly 153.0a1;
• Beta 152.0b1;

Affected platforms

• Ubuntu 22/24;

Unaffected platforms

• Windows 10;
• macOS 15;

Steps to reproduce

1. Launch Firefox.
2. Go to about:config and set browser.nova.enabled to true.
3. Observe the browser.

Expected result

• Border areas around the address bar/toolbar/ page content are rendered correctly.

Actual result

• Border areas around the address bar/toolbar/ page content are transparent.

Regression range

• last good: 2026-05-08;
• first bad:2026-05-09;
• pushlog: https://hg-edge.mozilla.org/integration/autoland/pushloghtml?fromchange=bcc2d03734fb9d72d3a2699f1174174d7da9596c&tochange=335094f4cf81c2c154cdaf1e72857c267a8a6b54
• potentially regressed by: bug 2026246

Comment 1

[BugBot [:suhaib / :marco]]

:jswinarton, since you are the author of the regressor, bug 2026246, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 2

[BugBot [:suhaib / :marco]]

Set release status flags based on info from the regressing bug 2026246

Comment 3

[Chris Bellini (:cbellini)]

Moving this over to the Themes component, as this affects not only the address bar, but also other components like the Toolbar as well.

Comment 4

[Sarah Clements [:sclements] | PTO until Sept 8th]

This should be fixed now by bug 2042447.

Comment 5

[Ardelean Oana, Desktop Test Engineering [:oardelean]]

Reproducible on a 2026-05-19 Firefox Nightly build on Ubuntu 22.

Verified as fixed on Firefox Nightly 154.0a1 and Firefox 153.0b1-build2 Ubuntu 22.