1939378 - Fenix theme randomly toggles theme

Status: UNCONFIRMED

(Firefox for Android :: Tabs, defect)

Description

[axel]

Steps to reproduce:

1. Open Fenix
2. Open any previously installed PWA
3. Open a link from the PWA. It should open in a Custom Tab
4. Close the Custom Tab
5. Return to Fenix

Actual results:

hen returning to Fenix, it will briefly flash the system theme then switch to the opposite one (if system theme is dark, it will flash dark then switch to light, and vice-versa).

Fenix will stay in this theme until the system theme has been toggled while Fenix is opened (using a Quick Setting tile) or until all instances of Fenix are closed.

Expected results:

Fenix should keep system theme

Comment 1

[axel]

Since the screen capture is too big for BugZilla, I shared it from Backblaze : https://f003.backblazeb2.com/file/axeleroy-shared-objects/screen-20241227-145944.mp4

I will also add that the issue happens at other random times, but the reproductions steps listed above are the most reliable way to trigger the bug.

Comment 2

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

The Bugbug bot thinks this bug should belong to the 'Fenix::PWA' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 3

[axel]

I found a new way to trigger the bug:

1. Open a PWA
2. Open a link from the PWA in a Custom Tab
3. Close the Custom Tab
4. Select text and translate it using Google Translate
5. Click outside the Google Translate widget to close it
6. Fenix toggles the theme

https://f003.backblazeb2.com/file/axeleroy-shared-objects/screen-20250103-234827.mp4

Comment 4

[axel]

I found a way to reproduce without even using a PWA:

1. Open Fenix
2. Open another app that opens links in Custom Tabs
3. Click a link
4. Select text in that Custom Tab
5. Close the Custom Tab
6. Return to Fenix
7. Fenix switches theme

https://f003.backblazeb2.com/file/axeleroy-shared-objects/screen-20250103-235915.mp4

Comment 5

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

The severity field is not set for this bug.
:007, could you have a look please?

For more information, please visit BugBot documentation.

Comment 6

[Noah Bond [:007]]

hey, thanks for filing this bug!

What version of Firefox are you using, and what version of Android is your device?

Comment 7

[axel]

Oh yes, I forgot to mention that! I'm running Fenix 135.0b3 on Android 15QPR1 with the January 2025 patch.

Comment 8

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

The severity field is not set for this bug.
:007, could you have a look please?

For more information, please visit BugBot documentation.