@newwbee it's open-source. MoneySplitter is a simple struct with a lot of extension functions and Codable conformance: https://github.com/KyLeggiero/RentSplitTools/blob/765c748ff08e2fd0d4a1c00e8440f7ac3c6d703c/Sources/RentSplitTools/MoneySplitter.swift

please ignore this accidental reply

@AndyJJ whoops; sorry about that. Linked an incorrect commit hash. Here you go: https://github.com/KyLeggiero/RentSplitTools/blob/181316d7a37b4b1615d15f10bb2ff2722fab088b/Sources/RentSplitTools/MoneySplitter.swift#L685

This is caused by the fact that SwiftData does not yet support encoding custom Codable types, despite the claims from Apple. You'll have to make your model only use primitives such as Int, String, Date, etc