2003991 - Adding a Split View to a group will no longer show the Split View until the second view is selected

Status: VERIFIED FIXED

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

Description

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

Attachment: split_group.gif

Found in

• 147.0a1 (2025-12-03)

Affected versions

• 147.0a1 (2025-12-03)

Tested platforms

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

Preconditions

• split view enabled

Steps to reproduce

1. Create a split view and add it to a new or existing group.

Expected result

• The tabs are shown in a Split View.

Actual result

• Only the active tab is displayed as a full view and not in a split view.

Regression range

• This is not a regression.

Additional notes

• Attached a screen recording.

Comment 1

[Sarah Clements [:sclements] | PTO until March 30th]

Kelly, this seems related to work you've done?

Comment 2

[Kelly Cochrane [:kcochrane]]

Hrm yeah I never noticed this but I am able to repro. Interestingly enough this only occurs when adding an existing split view to a group. If you add tabs to a group and then split them, this doesn't occur.

I can take a look

Comment 3

[Kelly Cochrane [:kcochrane]]

Attachment: Bug 2003991 - Ensure split view panels are shown when adding a split view to a new or existing tab group

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/2c5b2edda022
https://hg.mozilla.org/integration/autoland/rev/bb30a98b58e3
Ensure split view panels are shown when adding a split view to a new or existing tab group r=tabbrowser-reviewers,jsudiaman

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/e5ce91ee61e1
https://hg.mozilla.org/integration/autoland/rev/4a2c7329af58
Revert "Bug 2003991 - Ensure split view panels are shown when adding a split view to a new or existing tab group r=tabbrowser-reviewers,jsudiaman" for causing bc failures @browser_tab_splitview.js.

Comment 6

[agoloman]

Backed out for causing bc failures @browser_tab_splitview.js.

• Backout link
• Push with failures
• Failure Log

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/6d4fb372d04c
https://hg.mozilla.org/integration/autoland/rev/e57a03aeef37
Ensure split view panels are shown when adding a split view to a new or existing tab group r=tabbrowser-reviewers,jsudiaman

Comment 8

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/e57a03aeef37

Comment 9

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

Verified fixed with Firefox 148.0a1 (2025-12-11) on Windows 11, macOS 26 and Ubuntu 24. Adding a Split View to a new or existing group will correctly display the views.