2013491 - Moving a Split View from one window to another window while a Split View is selected will make the Split View button invisible and also working for the unselected Split View

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser: Split View, defect, P1)

Description

[Alexandru Trif, Desktop Test Engineering [:atrif]]

Attachment: split_invisible.gif

Found in

• 149.0a1 (2026-01-27)

Affected versions

• 149.0a1 (2025-01-27)

Tested platforms

• Affected platforms: Ubuntu 24, Windows 11, macOS 26
• Unaffected platforms: none

Steps to reproduce

1. Open two windows and create a Split View in each window.
2. Focus a Split View in a window.
3. Move the other Split View to the window from step 2.
4. Use the Separate tabs invisible Split View button.

Expected result

• Step2: Split View is moved successfully with no glitches.
• Step3: The focused Split view is separated.

Actual result

• Step2: The Split View button becomes invisible.
• Step3: The unfocused Split View is separated

Regression range

• Happens after bug 2012661.

Additional notes

• Attached a screen recording.

Comment 1

[Alexandru Trif, Desktop Test Engineering [:atrif]]

Attachment: image.png

If we use the Reverse tabs button after step 3, the Split View will be shown for all 4 tabs

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 2012661

:nsharpley, since you are the author of the regressor, bug 2012661, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 3

[Nikki Sharpley (:nikkis) (she/her)]

Attachment: Bug 2013491 - Fix for moving a splitview to a new window r=#tabbrowser-reviewers

Comment 4

[Nikki Sharpley (:nikkis) (she/her)]

Alexandru, I actually wasn't able to reproduce this but in theory my WIP patch should ensure the behaviour is reverted whilst still preserving session restore behaviour. Could you please test the WIP patch attached to see if its reproducible? Thank you!

Comment 5

[Alexandru Trif, Desktop Test Engineering [:atrif]]

(In reply to Nikki Sharpley (:nikkis) (she/her) from comment #4)

Alexandru, I actually wasn't able to reproduce this but in theory my WIP patch should ensure the behaviour is reverted whilst still preserving session restore behaviour. Could you please test the WIP patch attached to see if its reproducible? Thank you!

Hello! Unfortunately, I am not familiar with building Firefox, or at least I don't know how to download the build from the attached patch from comment 3 (if possbile). Can you please provide me a build? Thank you in advance

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/997d55938096
https://hg.mozilla.org/integration/autoland/rev/279b57ef4bf0
Fix for moving a splitview to a new window r=tabbrowser-reviewers,kcochrane

Comment 7

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/279b57ef4bf0

Comment 8

[Alexandru Trif, Desktop Test Engineering [:atrif]]

Verified fixed with Firefox 149.0a1 (2026-02-05) on Windows 11, macOS 26 and Ubuntu 24. Moving a Split View to another window while another Split View is selected will no longer reproduce the issue. Dropping the ni?. Nikki provided me the build, thank you!