Core Data: Main actor-isolated property can not be mutated from a Sendable closure

I'm running a project with these settings:

Default Actor Isolation: MainActor Approachable Concurrency: Yes Strict Concurrency Checking: Complete (this issue does not appear on the other two modes)

I receive a warning for this very simple use case. Can I actually fix anything about this or is this a case of Core Data not being entirely ready for this?

In reference to this, there was a workaround listed in the release notes of iOS 26 beta 5 (https://forums.swift.org/t/defaultisolation-mainactor-and-core-data-background-tasks/80569/22). Does this still apply as the only fix for this?

This is a simplified sample meant to run on a background context. The issue obviously goes away if this function would just run on the MainActor, then I can remove the perform block entirely.

class DataHandler {    
    func createItem() async {
        let context = ...
        
        await context.perform {
            let newGame = Item(context: context)
            
            /// Main actor-isolated property 'timestamp' can not be mutated from a Sendable closure
            newGame.timestamp = Date.now
            
            // ...
        }
    }
}

The complete use case would be more like this:

nonisolated
struct DataHandler {
    @concurrent
    func saveItem() async throws {
        let context = await PersistenceController.shared.container.newBackgroundContext()
                
        try await context.perform {
            let newGame = Item(context: context)
            
            newGame.timestamp = Date.now
        
            try context.save()
        }
    }
}