Custom filter disappears after iCloud sync and triggers duplication error

[so-5699]

Subject

Description

I am experiencing an issue where a custom filter disappears from the list after iCloud synchronization. Even though it is no longer visible, the app prevents me from re-adding it, claiming it already exists.

Steps to Reproduce

1. Go to Custom Filters and add the following URL:
   https://raw.githubusercontent.com/i5heu/ublock-hide-yt-shorts/master/comments.txt
2. Wait for an iCloud sync to occur (or trigger it).
3. The filter disappears from the list.
4. Try to add the same URL again.
5. An orange error message appears stating that the filter has already been added.
6. If I proceed to add it anyway, it appears for a moment and then disappears again.

Attempted Troubleshooting

• Reinstalled the WBlock app.
• Restarted my iPhone.
• The issue persists even after the above steps.

Expected Behavior

The added custom filter should remain in the list and persist across iCloud synchronizations.

Environment

• Device: iPhone17pro
• OS: iOS26.5 developer beta1
• App: WBlock

[0xCUB3]

Thanks for reporting this. I could reproduce it, and the fix is now on main in 1b9d490

What bit us here was a stale delete marker in the iCloud sync code. Custom filter deletions were tracked separately from the visible list, so if the same URL was added again, the old tombstone could still stick around. On the next sync that stale delete could beat the live filter entry, which made the filter disappear from the UI while the duplicate URL check still thought it already existed.

There was a second problem too. Sync was building its CloudKit payload from the persisted filter list instead of the current in-memory one. If sync happened during the short save debounce window after adding the filter, the new entry could be missing from the payload and get removed again.

I changed the custom-filter reconciliation so a live filter wins over a stale tombstone, and re-adding a URL clears the old delete marker right away. I also switched the sync payload builder over to the current filter manager state and added regression coverage around these cases. I rebuilt the iOS simulator target locally after the change.

This should stop both the disappearing filter and the bogus duplicate warning.