After Xcode 26.1 was updated and installing the OS 26.1 simulators, my app started crashing related to transformable properties. When I checked my schema, I noticed that properties with array collection types are suddenly set with an option transformable with Optional("NSSecureUnarchiveFromData")], even though I do not use any transformable types. I verified the macros, no transformable was specified. This is causing ModelCoders to encode/decode my properties incorrectly. This is not an issue when I switch back to OS 26.0 simulators.

Hi there! I'm making an app that stores data for the user's profile in SwiftData. I was originally going to use UserDefaults but I thought SwiftData could save Images natively but this is not true so I really could switch back to UserDefaults and save images as Data but I'd like to try to get this to work first. So essentially I have textfields and I save the values of them through a class allProfileData. Here's the code for that: import SwiftData import SwiftUI @Model class allProfileData { var profileImageData: Data? var email: String var bio: String var username: String var profileImage: Image { if let data = profileImageData, let uiImage = UIImage(data: data) { return Image(uiImage: uiImage) } else { return Image("DefaultProfile") } } init(email:String, profileImageData: Data?, bio: String, username:String) { self.profileImageData = profileImageData self.email = email self.bio = bio self.username = username } } To save this I create a new class (I think, I'm new) and save it through ModelContext import SwiftUI import SwiftData struct CreateAccountView: View { @Query var profiledata: [allProfileData] @Environment(\.modelContext) private var modelContext let newData = allProfileData(email: "", profileImageData: nil, bio: "", username: "") var body: some View { Button("Button") { newData.email = email modelContext.insert(newData) try? modelContext.save() print(newData.email) } } } To fetch the data, I originally thought that @Query would fetch that data but I saw that it fetches it asynchronously so I attempted to manually fetch it, but they both fetched nothing import SwiftData import SwiftUI @Query var profiledata: [allProfileData] @Environment(\.modelContext) private var modelContext let fetchRequest = FetchDescriptor<allProfileData>() let fetchedData = try? modelContext.fetch(fetchRequest) print("Fetched count: \(fetchedData?.count ?? 0)") if let imageData = profiledata.first?.profileImageData, let uiImage = UIImage(data: imageData) { profileImage = Image(uiImage: uiImage) } else { profileImage = Image("DefaultProfile") } No errors. Thanks in advance

Hello, the last days I was trying to solve a bug in my Unit Tests related to the CoreData "NSManagedObjectContextObjectsDidChange" Notification. Im using some kind of Notification handler to save and abstract that for the UI and while the tests are running this notification was triggered with objects that doesn't exists anymore, which has resulted in a crash. After some debugging I have detected, that the objects in here are really old. The objects here was from few tests ago, where a Merge Conflict happened. In the meantime there was a plenty of resets and deletes of the whole db. I have also seen that the bad notification is the first in the stack trace of the main thread, which is in my opinion also not usual. So the real question is: The only difference what I have found for the bad notification to the real notification, was the existence of the key "NSObjectsChangedByMergeChangesKey" in the UserInfo dictionary of the ObjectsDidChange Notification. But this key is nowhere found in the documentation of Apple. Also the search engines does not produce any result. So what is this key and when is this key contained in this notification and when not? Maybe if I understand this, it helps me to understand the overall issue ...

Hi, I was testing the new iOS 18 behavior where NSPersistentCloudKitContainer wipes the local Core Data store if the user logs out of iCloud, for privacy purposes. I ran the tests both with a Core Data + CloudKit app, and a simple one using SwiftData with CloudKit enabled. Results were identical in either case. In my testing, most of the time, the feature worked as expected. When I disabled iCloud for my app, the data was wiped (consistent with say the Notes app, except if you disable iCloud it warns you that it'll remove those notes). When I re-enabled iCloud, the data appeared. (all done through the Settings app) However, in scenarios when NSPersistentCloudKitContainer cannot immediately sync -- say due to rate throttling -- and one disables iCloud in Settings, this wipes the local data store and ultimately results in data loss. This occurs even if the changes to the managed objects are saved (to the local store) -- it's simply they aren't synced in time. It can be a little hard to reproduce the issue, especially since when you exit to the home screen from the app, it generally triggers a sync. To avoid this, I swiped up to the screen where you can choose which apps to close, and immediately closed mine. Then, you can disable iCloud, and run the app again (with a debugger is helpful). I once saw a message with something along the lines of export failed (for my record that wasn't synced), and unfortunately it was deleted (and never synced). Perhaps before NSPersistentCloudKitContainer wipes the local store it ought to force sync with the cloud first?

I have a single multiplatform application that I use NSPersistentCloudKitContainer on. This works great, except I noticed when I open two instances of the same process (not windows) on the same computer, which share the same store, data duplication and "Metadata Inconsistency" errors start appearing. This answer (https://stackoverflow.com/a/67243833) says this is not supported with NSPersistentCloudKitContainer. Is this indeed true? If it isn't allowed, is the only solution to disable multiple instances of the process via a lock file? I was thinking one could somehow coordinate a single "leader" process that syncs to the cloud, with the others using NSPersistentContainer, but this would be complicated when the "leader" process terminates. Currently, it seems iPad split views are new windows, not processes -- but overall I'm still curious :0 Thank you!

Hi everyone, I’m working on an offline-first iOS app using Core Data. I have a question about safe future updates: in my project, I want to be able to add new optional fields to existing Entities or even completely new Entities in future versions — but nothing else (no renaming, deleting, or type changes). Here’s how my current PersistenceController looks: import CoreData struct PersistenceController { static let shared = PersistenceController() let container: NSPersistentContainer init(inMemory: Bool = false) { container = NSPersistentContainer(name: "MyApp") if inMemory { container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null") } container.loadPersistentStores(completionHandler: { (storeDescription, error) in if let error = error as NSError? { print("Core Data failed to load store: \(error), \(error.userInfo)") } }) container.viewContext.automaticallyMergesChangesFromParent = true } } Do I need to explicitly set these properties to ensure lightweight migration works? shouldMigrateStoreAutomatically = true shouldInferMappingModelAutomatically = true Or, according to the documentation, are they already true by default, so I can safely add optional fields and new Entities in future versions without breaking users’ existing data? Thanks in advance for your guidance!

Hello, I have an asset pack that I'm use to periodically distribute a sqlite database thats being used to an NSPersistentStore. Because the database is over a few GBs, and the files in an AssetPack are not mutable, I have to stream the database into a temporary file, then replace my NSPersistentStore. This requires that the user has 3x the storage available of the database, and permanently uses twice to storage needed. I'd like: To be able to mark a URL/File to be accessible for read/write access To be able to mark a file / URL as consumed when it's no needed. So that it can be cleared from the user storage while still maintaining an active subscription to the asset pack for updates. Thank you

Hello, I have 3 model versions and I'm trying to step through migration. Version 2 makes significant changes to v1. As a result, I've renamed the entities in question by appending _v2 to their name, as the data isn't important to retain. v3, remove's the appended version number from v2. Setting the .xcdatamodeld to v3 and the migrations steps array as follows causes the app to error [ NSLightweightMigrationStage([v1]), NSLightweightMigrationStage([v2]), NSLightweightMigrationStage([v3]), ] CoreData: error: <NSPersistentStoreCoordinator: 0x10740d680>: Attempting recovery from error encountered during addPersistentStore: 0x10770f8a0 Error Domain=NSCocoaErrorDomain Code=134110 "An error occurred during persistent store migration." An error occurred during persistent store migration. Cannot merge multiple root entity source tables into one destination entity root table. I find this odd because if I run the migration independently across app launches, the migration appears to drop the no longer used tables in v2, then re-add them back in v3. So it seems to me that something is not finishing completely with the fully stepped through migration. -- I'm also unable to understand how to use NSCustomMigrationStage I've tried setting it to migrate from v1, to v2, but I'm getting a crash with error Duplicate version checksums across stages detected

I'm using SwiftData with CloudKit private database. I was able to identify the error on my device by debugging in Xcode with com.apple.CoreData.SQLDebug flag. However, in Production, I couldn't find a way to get the cause of errors. I tried inspecting the error coming from eventChangedNotification. The NSPersistentCloudKitContainer.Event error does not contain any underlying error (neither CKError.userInfo nor in NSError.underlyingError). It only reports a partial failure with CKErrorDomain code 2. If a user encounter an error, there seems to be no way to retrieve the error details. Is there any way to access the error details or logs in Production?

If I have two consecutive calls like to perform(schedule: .immediate) like so: func doSomething() async { await self.perform(schedule: .immediate) { // add log event 1 to data store } await self.perform(schedule: .immediate) { // add log event 2 to data store } } Can I be guaranteed that the block for log event 1 will happen after log event 2? "log event" here is just an example, so please ignore things like storing date, etc. Looking at the documentation here: https://developer.apple.com/documentation/coredata/nsmanagedobjectcontext/perform(schedule:_:) It's a little unclear whether any such guarantee is in place. However, given that the function returns the value from the block, it seems like I should be able to expect event 1 will always be executed before event 2 regardless of the schedule parameter?

Hello, I have a iOS app I was looking at porting to Mac. I'm having an issue with both the Mac (Designed for iPad) and Mac Catalyst Destinations. I can't test Mac due to too many build issues. I'm trying to assign a new NSManagedObject into a NSPersistentStore. let object = MyObject(context: context) context.assign(object, to: nsPersistentStore) This works fine for iOS/iOS Simulator/iPhone/iPad. But on the Mac it's crashing with FAULT: NSInvalidArgumentException: Can't assign an object to a store that does not contain the object's entity.; { Thread 1: "Can't assign an object to a store that does not contain the object's entity."

I've understood that SwiftData is not abled to share the whole content of a cloudkit database. So I'm trying to rewrite everything. Does someone knows id Sharing is coming on SwiftData at WWDC 26? Anyway, can someone can point me an example a a configured coredata stack that share all its content with other icloud users (with sharing pane and accept invitation code). At this step, on the owner side, I see some data in the default zone of my private container but nothing is visible on the shared zone. Maybe I don't understand where and when I should check shared data in cloudkit console. Need Help also here. See below by configuration stack: // Core Data container public lazy var container: NSPersistentContainer = { switch delegate.usage() { case .preview : return previewContainer() case .local : return localContainer() case .cloudKit : return cloudKitContainer() } }() private func cloudKitContainer() -> NSPersistentContainer { let modelURL = delegate.modelURL() let modelName = modelURL.deletingPathExtension().lastPathComponent guard let model = NSManagedObjectModel(contentsOf: modelURL) else { fatalError("Could not load Core Data model from \(modelURL)") } let container = NSPersistentCloudKitContainer( name: modelName, managedObjectModel: model ) let groupIdentifier = AppManager.shared.groupIdentifier guard let appGroupURL = FileManager.default.containerURL ( forSecurityApplicationGroupIdentifier: groupIdentifier ) else { fatalError("App Group not found: \(groupIdentifier)") } // MARK: - Private Store Configuration let privateStoreURL = appGroupURL.appendingPathComponent("\(modelName).sqlite") let privateStoreDescription = NSPersistentStoreDescription(url: privateStoreURL) // Persistent history tracking (MANDATORY) privateStoreDescription.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey) privateStoreDescription.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey) // CloudKit options for private database // Core Data automatically uses the default zone: com.apple.coredata.cloudkit.zone let privateCloudKitOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: delegate.cloudKitIdentifier()) privateCloudKitOptions.databaseScope = .private privateStoreDescription.cloudKitContainerOptions = privateCloudKitOptions // MARK: - Shared Store Configuration guard let sharedStoreDescription = privateStoreDescription.copy() as? NSPersistentStoreDescription else { fatalError("Create shareDesc error") } // The shared store receives zones that others share with us via CloudKit's shared database sharedStoreDescription.url = appGroupURL.appendingPathComponent("\(modelName)-shared.sqlite") // Persistent history tracking (MANDATORY) sharedStoreDescription.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey) sharedStoreDescription.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey) // CloudKit options for shared database // This syncs data from CloudKit shared zones when we accept share invitations let sharedCloudKitOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: delegate.cloudKitIdentifier()) sharedCloudKitOptions.databaseScope = .shared sharedStoreDescription.cloudKitContainerOptions = sharedCloudKitOptions // Configure both stores // Private store: com.apple.coredata.cloudkit.zone in private database // Shared store: Receives shared zones we're invited to container.persistentStoreDescriptions = [privateStoreDescription, sharedStoreDescription] container.loadPersistentStores { storeDescription, error in if let error = error as NSError? { fatalError("DB init error:\(error.localizedDescription)") } else if let cloudKitContiainerOptions = storeDescription.cloudKitContainerOptions { switch cloudKitContiainerOptions.databaseScope { case .private: self._privatePersistentStore = container.persistentStoreCoordinator.persistentStore(for: privateStoreDescription.url!) case .shared: self._sharedPersistentStore = container.persistentStoreCoordinator.persistentStore(for: sharedStoreDescription.url!) default: break } } let scope = storeDescription.cloudKitContainerOptions?.databaseScope == .shared ? "shared" : "private" print("✅ \(scope) store loaded at: \(storeDescription.url?.path ?? "unknown")") } // Auto-merge container.viewContext.automaticallyMergesChangesFromParent = true container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy do { try container.viewContext.setQueryGenerationFrom(.current) } catch { fatalError("Fail to pin viewContext to the current generation:\(error)") } return container }

Hi all I have a problem with core data, where when a new user login that is different from the previous user i delete all of core data by using "destroyPersistentStore". Then i recreate the persistent store, this works when i am testing. When it does not work for one of my users when she test. I am not sure why this should not work, i have added the code i use to destroy the persistent store below. This code is run after login but before the view changes away from my login view. // Retrieves the shared `AppDelegate` instance guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return } appDelegate.destroyDataSyncBackground() // Get a reference to a NSPersistentStoreCoordinator let storeContainer = appDelegate.persistentContainer.persistentStoreCoordinator // Delete each existing persistent store for store in storeContainer.persistentStores { if let url = store.url { do { try storeContainer.destroyPersistentStore( at: url, ofType: store.type, options: nil ) } catch { print("Failed to deleted all") } } else { print("Failed to deleted all") } } // Re-create the persistent container appDelegate.persistentContainer = NSPersistentContainer( name: "CueToCue" // the name of // a .xcdatamodeld file ) // Calling loadPersistentStores will re-create the // persistent stores appDelegate.persistentContainer.loadPersistentStores { (store, error) in // Handle errors let description = NSPersistentStoreDescription() description.shouldMigrateStoreAutomatically = true description.shouldInferMappingModelAutomatically = true appDelegate.persistentContainer.persistentStoreDescriptions = [description] } // Reapply context configuration let viewContext = appDelegate.persistentContainer.viewContext viewContext.automaticallyMergesChangesFromParent = true viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy do { try viewContext.save() appDelegate.recreateDataSyncBackground() } catch { print("Debug: saving delete all failed.") } } The function "destroyDataSyncBackground" just set the my sync class to nil so stop any changes to core data while the code is running. The function "recreateDataSyncBackground" recreate the sync class so fetch, post and patch requests is made again.

Hi, I’m looking for clarification on what concurrency and consistency guarantees Apple provides when multiple targets (main app + Widget extensions) access shared storage. Specifically: 1. UserDefaults (App Group / suiteName:) • If multiple processes (app + multiple widget instances) read and write the same shared UserDefaults, what guarantees are provided? • Is access serialized internally to prevent corruption? • Are read–modify–write operations safe across processes, or can lost updates occur? 2. Core Data (shared SQLite store in App Group container) • Is it officially supported for multiple processes to open and write to the same Core Data SQLite store? • Are there recommended configurations (e.g. WAL mode) for safe multi-process access? • Is Apple’s recommendation to have a single writer process? 3. FileManager (shared container files) • If two processes write to the same file in an App Group container, what guarantees are provided by the system? • Is atomic replaceItemAt the recommended pattern for safe cross-process updates? Additionally: • Do multiple widget instances count as separate processes with respect to these guarantees? • Is there official guidance on best practices for shared persistence between app and widget extensions? I want to ensure I’m following the correct architecture and not relying on undefined behavior. Thanks.

In an iOS App that uses CKShare I have a many-to-many relationship that does not consistently sync between the share's N participants. The relationship is between Group and Player as group.players and player.groups. As an example, given 3 group each with 4 players (aka 4:4:4), some devices show CoreData (it is NOT a UI issue) with 4:2:3 or 3:4:4. (A deletion of CoreData from a device, forcing a full re-sync from CloudKit, seems to populate the group:player relationships consistently; but obviously that is impractical to resolving the issue). How do I avoid these sync-from-CloudKit inconsistencies? Note: AI agents generally suggest adding a CoreData 'join' entity - such as 'GroupPlayer'. Is that THE fix?

I am planning a Core Data migration for a macOS app targeting macOS 12 and later and I would appreciate guidance on structuring the rollout to minimise risk. Context The app currently uses a SQLite store located at: ~/Library/Containers/com.company.AppName/Data/Library/Application Support/AppName I want to: Relocate the persistent store to an app group container: ~/Library/Group Containers/group.com.company.AppName Perform schema migration, including: Renaming attributes Deleting attributes Using a custom NSEntityMigrationPolicy subclass Adopt iCloud sync using NSPersistentCloudKitContainer Potentially leverage staged migration (macOS 14+) Additionally, I intend to port the app to iOS, so the end state needs to support an app group container and CloudKit with the latest schema from the outset. Questions Store relocation vs schema migration Is it advisable to perform store relocation and schema migration in a single step, or should these be separate releases? If combined, are there pitfalls when moving the SQLite file and running a migration in the same launch cycle? Custom migration policy Any best practices for structuring NSEntityMigrationPolicy when also relocating the store? Should migration policies assume the store has already been moved, or handle both concerns? Staged migration (macOS 14+) Is staged migration worth adopting when still supporting macOS 12–13? Would you gate it conditionally, or avoid it entirely for consistency? CloudKit adoption Is introducing NSPersistentCloudKitContainer in the same release as the above migrations too risky? Are there known issues when enabling CloudKit immediately after a migration? Release strategy Would you recommend: A single release handling everything Two phases: (1) store & schema migration, (2) CloudKit Or three phases: store relocation → schema migration → CloudKit Goal I want a smooth, reliable transition without data loss or duplication, particularly for existing users with non-trivial datasets. Any insights, practical experience, or recommended sequencing strategies would be very helpful.

I'm experiencing an issue where the App Group shared container appears to be recreated (with a new creation date) during an app update, resulting in complete loss of locally stored data. Background My app uses UserDefaults, Realm, Core Data, and CloudKit, with all local data stored in the App Group container (FileManager.containerURL(forSecurityApplicationGroupIdentifier:)). The app has been available since 2016 and has a stable user base. Starting last year, I began receiving occasional reports from users saying all their data in the app had disappeared. To investigate, I added diagnostic logging that detects when an existing user's data appears to have been reset — specifically by checking the App Group container's file system creation date, and the existence and values of expected files. What the diagnostics revealed When the issue occurs, I observe the following: The App Group container has a recent creation date, far newer than the user's first launch date The Core Data store file's creation date is also immediately after the App Group container's recreation date I write the same values to both standard UserDefaults and the App Group version (UserDefaults(suiteName:)). Only the App Group version is reset — the standard side retains historical data The standard side still holds firstLaunchDate, initialVersion, and launchCount, confirming this is not a fresh install Here is a sample diagnostic log from an affected user: appGroupContainerCreationDate: 2026-03-30T18:44:10Z firstLaunchDate: 2025/01/05 4:00 initialVersion: 10.8.0 currentAppVersion: 10.14.14 previousVersion: 10.10.0 launchCount: 44 availableStorageMB: 46646 The container creation date (2026-03-30) is clearly inconsistent with the user's first launch date (2025-01-05) and launch count (44). The container creation date is obtained with the following code: let appGroupURL = FileManager.default.containerURL( forSecurityApplicationGroupIdentifier: "group.xxx.xxx" )! let attributes = try? FileManager.default.attributesOfItem(atPath: appGroupURL.path) let containerCreationDate = attributes?[.creationDate] as? Date Scale and pattern Reports began increasing in late November last year Over 85% of affected cases are on iOS 26 Most affected devices have plenty of available storage (46GB+ in the example above) This is likely occurring during a normal app update (not a fresh install or device restore) Ruled-out hypotheses Not a fresh install — firstLaunchDate, initialVersion, and launchCount are preserved in standard UserDefaults Not a storage issue — affected users typically have tens of GBs of free space, making it unlikely that iOS purged the data due to low storage Not an app-side code change — the App Group identifier and entitlements have not been changed Not triggered by silent notifications, background tasks, or widget activity — these processes do write to the App Group container, but the recreation does not appear to occur immediately after any of these operations Questions Has anyone else observed App Group containers being recreated (new creation date, empty contents) during a standard app update? Is there a known iOS behavior or bug that could cause this, particularly on iOS 26? Are there any recommended mitigations? Any insight would be greatly appreciated. This is a data loss issue affecting real users, and I'd like to understand whether this is an iOS-level problem or something I should be handling differently on my end.