2040918 - Fire button doesn't appear in 151 release despite Bug 1902686

Status: RESOLVED WORKSFORME

(Firefox :: Private Browsing, defect, P1)

Description

[Manuel Bucher [:manuel]]

Not sure if regressed by sematic is correct here. But the change should have been introduced by Bug 1902686.

• ./mach mozregression --launch 151.0 (release) doesn't show the fire button in pbm and pref is false
• ./mach mozregression --launch 2026-05-19 --repo mozilla-beta (152.0b1) shows the fire button and pref is true
• ./mach mozregression --launch 2026-05-19 (nightly 153) shows the fire button in pbm and pref is true

There were some reports on reddit about the fire button not appearing and it has also been confirmed by QA.

Comment 1

[Manuel Bucher [:manuel]]

The fire button also shows with the latest 151 beta: ./mach mozregression --launch 2026-05-14 --repo mozilla-beta. This is confusing

Comment 2

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

:emz, since you are the author of the regressor, bug 1902686, could you take a look?

For more information, please visit BugBot documentation.

Comment 3

[Emma Zühlcke [:emz]]

It looks like an ongoing Nimbus rollout is pinning the feature pref to false. We're currently checking whether we can end or update that experiment.

Comment 4

[Emma Zühlcke [:emz]]

We have ended the rollout that pinned the pref to false and replaced it with a rollout that only sets the feltPrivacy feature (needed for the pbm UX refresh). The fire button now shows up in release.

Comment 5

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

Set release status flags based on info from the regressing bug 1902686

Comment 6

[Donal Meehan [:dmeehan]]

Cleaning up the metadata since it wasn't a code change