iOS 26 beta 8 – AlarmKit – Custom sounds in Library/Sounds do not play

1. I put a test.mp3 (30 sec) file into the App Bundle.
2. I scheduled an AlarmKit alarm with the file name test.mp3.
3. The custom sound plays ✅
4. I copied the file from the App Bundle to Library/Sounds/test2.mp3.
5. I scheduled an AlarmKit alarm with the file name test2.mp3.
6. Instead of playing the custom sound, it falls back to the default sound ❌

According to the documentation, sounds placed in Library/Sounds should be playable:

I filed report FB19779004 on August 20, but haven’t received any response yet.

This functionality is critical for our use case, so could you please let me know whether this is expected to be fixed soon, or if I’m misunderstanding the intended behavior?