Same problem using M1 MacBook Pro and Xcode 13.2.1.

I had this error too. Turned out that I was missing one of my models in my ModelConfiguration's schema. Once I added the missing model to the schema, error went away. let schema = Schema([Person.self, Car.self, City.self]) let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)

I see the same issue. I have a handful of @Model classes with string arrays; they each produce this error consistently, whether the property is optional or not. @Model class Monster: Decodable, { var something: [String] = [] var somethingElse: [String]? = nil }