SwiftData Upsert

How do I get Upsert to work in SwiftData?

I have a model:

@Model
class Address: Identifiable {
    @Attribute(.unique)
    var id: Int = 0
    
    var number: String = ""
    var street: String?
    var city: String?
}

When I insert a duplicate record with the same data attributes (specifically overlapping id) and execute modelContext.save() I receive a EXC_BREAKPOINT.

let addressA = Address(id: 1, number: "2300", street: "E Main St", city: "Small Town" );
modelContext.insert(addressA)
try? modelContext.save()


let addressAv2 = Address(id: 1, number: "2300", street: "E Main St", city: "Small Town" );
modelContext.insert(addressAv2)
try? modelContext.save() // This fails

Is there a better way to handle updates?