If your app crashes on 0x400000000000bad0 when running on the new stuff, it means you have an ObjC strong variable/property being concurrently mutated. https://developer.apple.com/documentation/xcode-release-notes/xcode-26-release-notes#Objective-C-Runtime
Xcode 26 Beta Release Notes | Apple Developer Documentation

Update your apps to use new features, and test your apps against API changes.

Apple Developer Documentation
@mikeash doesn't seem very strong if it can't even hold on to its value!
@joe Retain is strong but concurrency is strongerer.
@mikeash @joe the weak force, the strong force, and concurrency