Sorting an array kills the purpose of SwiftData as that is more than 10k+ objects array to sort in my case.

I believe that line is log noise.

As soon as I made sure I am not inserting duplicate data (checked by @Attribute(.unique) field) the warnings are gone.

SwiftData models were not changed - no migration expected. Same build worked under pre-iOS26.1 and not working under iOS26.1. Still investigating, I had found that store created under iOS 26.1 can't be loaded on pre-iOS 26.1 and other way around (using same code, including models). Expected? Working now on hotfix-workaround - pre-populating two version of stores with data - one on iOS 26.1 and one on pre-iOS 26, and then on opening the app will connect to the store matching device iOS version.

Randomly I managed to get past this error - I was trying to make a minimum reproducible version and in that Xcode was not building until I removed some Hashable and Equatable implementations from one of the models. Removing those in original code (which was building just fine) somehow helped get past this error. Somehow previously Xcode required at some point those Hashable and Equatable implementations, even if I have similar models without those. So let's consider this one resolved.

Another thing I noticed - store populated under iOS 26.0 is 118 Mb, while store populated under iOS 26.1 is 137 Mb. Both were done from a fresh state using same data and code. So there are clearly some differences.

While my temporary workaround kind of works now on iOS, if I run the iPad app on MacOS 26.1 it's not working anymore. Also previously working builds (from TestFlight) are not working anymore. Still looking for proper solution.

Thanks for swift response. I will do, but my first priority is to get my published app with paid subscriptions working for my users. From further investigation and testing, it looks that even empty store having model with property containing Array of optionals can't be transferred between iOS 26.1 and pre-iOS 26.1. So this should break: @Model class SomeClass: Identifiable { var id: UUID = UUID() var breakingProperty: Array[String?] }

Feedback report filed.

Yes, I was reading at your issue too. Probably your issue is a bit unrelated (except also related to iOS 26.1). I am using @Atribute only to set some .unique fields. Why are you setting @Attribute without any parameters? Does it serve any purpose that way?

@DTS Engineer is anyone looking into this? There is zero feedback from Apple side...