Default search engine reverted to Google after the app was closed (iOS)

description

Status: Likely resolved. Please confirm the fix and check the one recent report before investigating further. Details are under "Any additional information?".

### Steps to reproduce
Not yet reproduced. These are suggested steps based on what app store reviewers described on 144.1 to 145.1, and they haven't been validated.
1. In Settings, set a default search engine other than Google, such as DuckDuckGo.
2. Optionally, turn off the other engines.
3. Close Firefox and reopen it, or switch to another app and back.
4. Check the default search engine.

### Expected behavior
The chosen engine stays the default.

### Actual behavior
Reported in app store reviews and not yet confirmed. The default reverted to Google, or sometimes DuckDuckGo. Some reviewers said it happened every time they reopened the app, others within a few hours.

### Device information
* Firefox version: 144.1 to 145.1 for 36 reports, and 155.1 for one
* iOS device model: not available from app store reviews
* iOS version: not available from app store reviews

### Any additional information?
**Why I think this is resolved**
37 iOS reviews described this. 36 of them came between Oct 21 and Nov 17, 2025 on 144.1 to 145.1. There were none between 146 and 154 over the following ten months. One report came in on 155.1 (Sep 7, 2026), which may be a recurrence or an unrelated issue. 

**Request**
Please confirm which release fixed this, and check whether the 155.1 report has the same cause. If the fix is confirmed and 155.1 looks unrelated, this can be closed.

**More detail from reviewers**
- Engines they had turned off were turned back on, and the engine list reordered with Google at the top.
- One reviewer says the default fell to the first alternative engine in the list (Wikipedia). Adding a second entry for their engine and moving it to the top worked around it.
- Several tie the start of the problem to the 144.1 update.

**Also reported on iOS (lower volume, not part of this bug)**
- AI features turning back on after the user disabled them (3 reports, latest 155.0, Sep 1, 2026). This is the only iOS settings pattern with a recent report, and it may be the same issue as the Android AI opt-out.
- Search suggestions shown with suggestions turned off (2, latest Apr 2026).
- Settings reset by an update (1, Feb 2026).
- Telemetry and studies re-enabled after an update (1, Nov 2025).

**Evidence**
Firefox mobile: settings reset or ignored (app store reviews). Filter the Reviews tab to iOS.
https://docs.google.com/spreadsheets/d/1BzyODDTa0FE9ARFRSC7a4vGK50br32wlYUlq1OourkE/edit