1947853 - [Multi-Account Containers] Tabs reopened in a container are ejected from tab group

Status: VERIFIED FIXED

(Firefox :: Tabbed Browser, defect, P1)

Description

[Andy Leiserson [:aleiserson]]

This is an interaction between tab groups and the multi-account containers extension. So to reproduce, that extension will need to be installed, and some site (say, containersite.com) needs to be configured to always open in a particular container.

Steps to reproduce:

1. Right-click on a default-container tab in a tab group and select "New tab to right". This opens a new tab in the default container.
2. Type "containersite.com" in the URL bar and press enter.

Expected behavior: a tab for containersite.com in the configured container should open at the current position in the tab bar
Observed behavior: a tab for containersite.com opens positioned to the left of the first tab in the group

Comment 1

[Stephen Thompson [:sthompson]]

I filed https://github.com/mozilla/multi-account-containers/issues/2747 "Open/reopen in container should always preserve tab group membership" on Github

@Andy So far I have only seen this behavior when the opening tab is in the first or last position of a tab group. Tabs reopened in a container seem to maintain their tab group membership when they in a tab group and not at the edges of the tab group. Have you seen any other failure scenarios?

Comment 2

[Andy Leiserson [:aleiserson]]

I tried just now and I'm only seeing the problematic behavior at the end of the tab group -- at the beginning or in the middle, the tab stays in the group, like I would expect. I also tried in a tab immediately prior to the tab group to see if it would move in to the tab group, but it does not, it stays outside the tab group.

Comment 3

[Stephen Thompson [:sthompson]]

I have a PR posted for this https://github.com/mozilla/multi-account-containers/pull/2754

Comment 4

[Rares Doghi, Desktop QA]

Hi @Stephen, if we Right click the Right most tab from a Tab group and reopen it in a new Container it would always open outside of the group, if we Right click a link from that page or have a website to always open in a specific container it would always open a container tab inside of the group.

is the Right click Tab > Open in new Container tab scenario separate from this fix or is this scenario intended behavior ??

Comment 5

[Stephen Thompson [:sthompson]]

Right-clicking a tab and choosing "Open in New Container Tab" uses Firefox's built-in container functionality. You are correct, the behavior is wrong. I filed bug 1968158 to track the Firefox issue.

This bug is tracking a fix in the Firefox Multi-Account Containers add-on and I confirmed that using the add-on functionality to reopen the last tab of a tab group in a container it will open the new tab inside of the tab group.

Comment 6

[Rares Doghi, Desktop QA]

Verified as fixed in Release 138.0.4, Beta 139 and Nightly 140.0a1 (2025-05-22)