I faced the same problem, I mistakenly created the model classes with Class definition and it will create those files under the hood and it won't expose it to the developers. Then if I try to create them using Manual/None, Xcode will create, but it throws error "Invalid redeclaration",

So deleted the derived data, cleaned the project. Set my models to Manual/None and created those files. Now the issue resolved!

Hope these issues were addressed in new Swift Data framework.