That's great news, thanks for sharing! I was able to work around this in Xcode 26 beta 2 by setting the following user default: defaults write org.swift.swift-build MakeAggregateTargetsTransparentForSpecialization -bool NO I look forward to a proper fix!

Yes, Xcode 26 beta 2 seems to fix this — thanks to you and your team!

@Developer Tools Engineer that's wonderful news! I hope it's not too difficult to fix, and I appreciate the follow-up — keep up the great work 🫶🏻

I’ve attached a full result bundle to FB18042089 - I’ll see if I can pull together a minimal reproducer once the kids are asleep tonight.

Thanks Quinn! I've filed FB17281035 and referenced your bug.

Thanks, Quinn - that's good advice. I don't have the capability to test all of the things that you've listed, although I did start in on observing and checking as much as I could via packet captures. In the tech note, it says "In some circumstances NSURLSession may retry such requests automatically" — is there any information on the behaviour when this happens? I assume it's a limited set of retries with an time interval based backoff?

Thank you! This workaround is fine for now, and it's great to hear that SwiftData's support for building with Swift 6 is still in progress.

Sorry that it's taken so long - I've just filed FB9750037. It's pretty light on details, because I can't share the framework itself to demonstrate the issue.