Simple Migration in SwiftData does not work

I have an app with some SwiftData Models. One is called Tapas and it has a relationship with TapasAsana. One Tapas has many Asanas, so I connected them with a relationship. This all works wonderful so far.

Now I just forgot one property in TapasAsana. I read about light migration and it should be easy to just add that property. But no matter if I add it at the end or in the middle of the properties it breaks my app. The app compiles and runs, but the old Data doesn't get shown anymore. And cretaing new ones in the app also won't work, trying to directly create a TapasAsana crashes the App.

This is the code for the TapasAsana Model, the one where I am adding a property. The new property is called recoupCount.

import Foundation
import SwiftData

@Model
class TapasAsana {
    var name: String
    var duration: Int           /// How long to execute daily
    var timeToday: Int          /// Time done already today
    var recoupCount: Int      /// How many recoups this Asana has.
    
    var polar: Bool             /// If it is a polar Asana
    var doneToday: Bool         /// If it is completed today
    
    init(name: String = "Padahastasana", duration: Int = 5 * 60, timeToday: Int = 0, recoupCount: Int = 0, polar: Bool = false, doneToday: Bool = false) {
        self.name = name
        self.duration = duration
        self.timeToday = timeToday
        self.recoupCount = recoupCount
        self.polar = polar
        self.doneToday = doneToday
    }
}

I tried to just add the new Property, to add it at the last position to not confuse SwiftData with the order. But none of that works. I didn't try more because reading about migration said the simple add of a property should work fine.

You need to give your new property a default value for a lightweight migration to work and it must be where it's declared, doing so in the init parameter list isn't enough.

@Model
class TapasAsana {
    //...
    var recoupCount: Int = 0
    
    //...
}