SwiftData crashes 100% when fetching history of a model that contains an optional codable property that's updated: SwiftData/Schema.swift:389: Fatal error: Failed to materialize a keypath for someCodableID.someID from CrashModel. It is possible that this path traverses a type that does not work with append(), please file a bug report with a test. Would really appreciate some help or even a workaround. Code: import Foundation import SwiftData import Testing struct VaultsSwiftDataKnownIssuesTests { @Test func testCodableCrashInHistoryFetch() async throws { let container = try ModelContainer( for: CrashModel.self, configurations: .init( isStoredInMemoryOnly: true ) ) let context = ModelContext(container) try SimpleHistoryChecker.hasLocalHistoryChanges(context: context) // 1: insert a new value and save let model = CrashModel() model.someCodableID = SomeCodableID(someID: "testid1") context.insert(model) try context.save() // 2: check history it's fine. try SimpleHistoryChecker.hasLocalHistoryChanges(context: context) // 3: update the inserted value before then save model.someCodableID = SomeCodableID(someID: "testid2") try context.save() // The next check will always crash on fetchHistory with this error: /* SwiftData/Schema.swift:389: Fatal error: Failed to materialize a keypath for someCodableID.someID from CrashModel. It is possible that this path traverses a type that does not work with append(), please file a bug report with a test. */ try SimpleHistoryChecker.hasLocalHistoryChanges(context: context) } } @Model final class CrashModel { // optional codable crashes. var someCodableID: SomeCodableID? // these actually work: //var someCodableID: SomeCodableID //var someCodableID: [SomeCodableID] init() {} } public struct SomeCodableID: Codable { public let someID: String } final class SimpleHistoryChecker { static func hasLocalHistoryChanges(context: ModelContext) throws { let descriptor = HistoryDescriptor<DefaultHistoryTransaction>() let history = try context.fetchHistory(descriptor) guard let last = history.last else { return } print(last) } }

Hi ! Would anyone know (if possible) how to create backup files to export and then import from the data recorded by SwiftData? For those who wish, here is a more detailed explanation of my case: I am developing a small management software with customers and events represented by distinct classes. I would like to have an "Export" button to create a file with all the instances of these 2 classes and another "Import" button to replace all the old data with the new ones from a previously exported file. I looked for several solutions but I'm a little lost...

I'm experiencing a persistent issue with CloudKit sharing in my iOS application. When attempting to present a UICloudSharingController, I receive the error message "Unknown client: ChoreOrganizer" in the console. App Configuration Details: App Name: ChoreOrganizer Bundle ID: com.ProgressByBits.ChoreOrganizer CloudKit Container ID: iCloud.com.ProgressByBits.ChoreOrganizer Core Data Model Name: ChoreOrganizer.xcdatamodeld Core Data Entity: Chore Error Details: The error "Unknown client: ChoreOrganizer" occurs when I present the UICloudSharingController This happens only on the first attempt to share; subsequent attempts during the same app session don't show the error but sharing still doesn't work All my code executes successfully without errors until UICloudSharingController is presented Implementation Details: I'm using NSPersistentCloudKitContainer for Core Data synchronization and UICloudSharingController for sharing. My implementation creates a custom CloudKit zone, saves both a record and a CKShare in that zone, and then presents the sharing controller. Here's the relevant code: @MainActor func presentSharing(from viewController: UIViewController) async throws { // Create CloudKit container let container = CKContainer(identifier: containerIdentifier) let database = container.privateCloudDatabase // Define custom zone ID let zoneID = CKRecordZone.ID(zoneName: "SharedChores", ownerName: CKCurrentUserDefaultName) do { // Check if zone exists, create if necessary do { _ = try await database.recordZone(for: zoneID) } catch { let newZone = CKRecordZone(zoneID: zoneID) _ = try await database.save(newZone) } // Create record in custom zone let recordID = CKRecord.ID(recordName: "SharedChoresRoot", zoneID: zoneID) let rootRecord = CKRecord(recordType: "ChoreRoot", recordID: recordID) rootRecord["name"] = "Shared Chores Root" as CKRecordValue // Create share let share = CKShare(rootRecord: rootRecord) share[CKShare.SystemFieldKey.title] = "Shared Tasks" as CKRecordValue // Save both record and share in same operation let recordsToSave: [CKRecord] = [rootRecord, share] _ = try await database.modifyRecords(saving: recordsToSave, deleting: []) // Present sharing controller let sharingController = UICloudSharingController(share: share, container: container) sharingController.delegate = shareDelegate // Configure popover if let popover = sharingController.popoverPresentationController { popover.sourceView = viewController.view popover.sourceRect = CGRect( x: viewController.view.bounds.midX, y: viewController.view.bounds.midY, width: 1, height: 1 ) popover.permittedArrowDirections = [] } viewController.present(sharingController, animated: true) } catch { throw error } } Steps I've already tried: Verified correct bundle ID and container ID match in all places (code, entitlements file, Developer Portal) Added NSUbiquitousContainers configuration to Info.plist Ensured proper entitlements in the app Created and configured proper provisioning profiles Tried both default zone and custom zone for sharing Various ways of saving the record and share (separate operations, same operation) Cleaned build folder, deleted derived data, reinstalled the app Tried on both simulator and physical device Confirmed CloudKit container exists in CloudKit Dashboard with correct schema Verified iCloud is properly signed in on test devices Console Output: 1. Starting sharing process 2. Created CKContainer with ID: iCloud.com.ProgressByBits.ChoreOrganizer 3. Using zone: SharedChores 4. Checking if zone exists 5. Zone exists 7. Created record with ID: <CKRecordID: 0x3033ebd80; recordName=SharedChoresRoot, zoneID=SharedChores:__defaultOwner__> 8. Created share with ID: <CKRecordID: 0x3033ea920; recordName=Share-C4701F43-7591-4436-BBF4-6FA8AF3DF532, zoneID=SharedChores:__defaultOwner__> 9. About to save record and share 10. Records saved successfully 11. Creating UICloudSharingController 12. About to present UICloudSharingController 13. UICloudSharingController presented Unknown client: ChoreOrganizer Additional Information: When accessing the CloudKit Dashboard, I can see that data is being properly synced to the cloud, indicating that the basic CloudKit integration is working. The issue appears to be specific to the sharing functionality. I would greatly appreciate any insights or solutions to resolve this persistent "Unknown client" error. Thank you for your assistance.

When deleting a SwiftData entity, I sometimes encounter the following error in a document based SwiftUI app: Fatal error: Unexpected backing data for snapshot creation: SwiftData._FullFutureBackingData<MyEntityClass> The deletion happens in a SwiftUI View and the code used to retrieve the entity is standard (the ModelContext is injected from the @Environment): let myEntity = modelContext.model(for: entityIdToDelete) modelContext.delete(myEntity) Unfortunately, I haven't yet managed to isolate this any further in order to come up with a reproducible PoC. Could you give me further information about what this error means?

I built a SwiftData App that relies on CloudKit to synchronize data across devices. That means all model relationships must be expressed as Optional. That’s fine, but there is a limitation in using Optional’s in SwiftData SortDescriptors (Crashes App) That means I can’t apply a SortDescriptor to ModelA using some property value in ModelB (even if ModelB must exist) I tried using a computed property in ModelA that referred to the property in ModelB, BUT THIS DOESN”T WORK EITHER! Am I stuck storing redundant data In ModelA just to sort ModelA as I would like???

I have the following struct doing some simple tasks, running a network request and then saving items to Core Data. Per Xcode 26's new default settings (onisolated(nonsending) & defaultIsolation set to MainActor), the struct and its functions run on the main actor, which works fine and I can even safely omit the context.perform call because of it, which is great. struct DataHandler { func importGames(withIDs ids: [Int]) async throws { ... let context = PersistenceController.shared.container.viewContext for game in games { let newGame = GYGame(context: context) newGame.id = UUID() } try context.save() } } Now, I want to run this in a background thread to increase performance and responsiveness. So I followed this session (https://developer.apple.com/videos/play/wwdc2025/270) and believe the solution is to mark the struct as nonisolated and the function itself as @concurrent. The function now works on a background thread, but I receive a crash: _dispatch_assert_queue_fail. This happens whether I wrap the Core Data calls with context.perform or not. Alongside that I get a few new warnings which I have no idea how to work around. So, what am I doing wrong here? What's the correct way to solve this simple use case with Swift 6's new concurrency stuff and the default main actor isolation in Xcode 26? Curiously enough, when setting onisolated(nonsending) to false & defaultIsolation to non isolating, mimicking the previous behavior, the function works without crashing. nonisolated struct DataHandler { @concurrent func importGames(withIDs ids: [Int]) async throws { ... let context = await PersistenceController.shared.container.newBackgroundContext() for game in games { let newGame = GYGame(context: context) newGame.id = UUID() // Main actor-isolated property 'id' can not be mutated from a nonisolated context; this is an error in the Swift 6 language mode } try context.save() } }

I am trying out the new AttributedString binding with SwiftUI’s TextEditor in iOS26. I need to save this to a Core Data database. Core Data has no AttributedString type, so I set the type of the field to “Transformable”, give it a custom class of NSAttributedString, and set the transformer to NSSecureUnarchiveFromData When I try to save, I first convert the Swift AttributedString to NSAttributedString, and then save the context. Unfortunately I get this error when saving the context, and the save isn't persisted: CoreData: error: SQLCore dispatchRequest: exception handling request: <NSSQLSaveChangesRequestContext: 0x600003721140> , <shared NSSecureUnarchiveFromData transformer> threw while encoding a value. with userInfo of (null) Here's the code that tries to save the attributed string: struct AttributedDetailView: View { @ObservedObject var item: Item @State private var notesText = AttributedString() var body: some View { VStack { TextEditor(text: $notesText) .padding() .onChange(of: notesText) { item.attributedString = NSAttributedString(notesText) } } .onAppear { if let nsattributed = item.attributedString { notesText = AttributedString(nsattributed) } else { notesText = "" } } .task { item.attributedString = NSAttributedString(notesText) do { try item.managedObjectContext?.save() } catch { print("core data save error = \(error)") } } } } This is the attribute setup in the Core Data model editor: Is there a workaround for this? I filed FB17943846 if someone can take a look. Thanks.

Hi, I am building an iOS app with SwiftUI and SwiftData for the first time and I am experiencing a lot of difficulty with this error: Thread 44: Fatal error: Never access a full future backing data - PersistentIdentifier(id: SwiftData.PersistentIdentifier.ID(backing: SwiftData.PersistentIdentifier.PersistentIdentifierBacking.managedObjectID(<ID> <x-coredata://<UUID>/MySwiftDataModel/p1>)), backing: SwiftData.PersistentIdentifier.PersistentIdentifierBacking.managedObjectID(<ID> <x-coredata://<UUID>/MySwiftDataModel/p1>)) with Optional(<UUID>) I have been trying to figure out what the problem is, but unfortunately I cannot find any information in the documentation or on other sources online. My only theory about this error is that it is somehow related to fetching an entity that has been created in-memory, but not yet saved to the modelContext in SwiftData. However, when I am trying to debug this, it's not clear this is the case. Sometimes the error happens, sometimes it doesn't. Saving manually does not always solve the error. Therefore, it would be extremely helpful if someone could explain what this error means and whether there are any best practices to do with SwiftData, or some pitfalls to avoid (such as wrapping my model context into a repository class). To be clear, this problem is NOT related to one area of my code, it happens throughout my app, at unpredictable places and time. Given that there is very little information related to this error, I am at a loss at how to make sure that this never happens. This question has been asked on the forum here as well as on StackOverflow, Reddit (can't link that here), but none of the answers worked for me. For reference, my models generally look like this: import Foundation import SwiftData @Model final class MySwiftDataModel { // Stable cross-device identity @Attribute(.unique) var uuid: UUID var someNumber: Int var someString: String @Relationship(deleteRule: .nullify, inverse: \AnotherSwiftDataModel.parentModel) var childModels: [AnotherSwiftDataModel] init(uuid: UUID = UUID(), someNumber: Int = 1, someString: String = "Some", childModels: [AnotherSwiftDataModel] = []) { self.uuid = uuid self.someNumber = someNumber self.someString = someString self.childModels = childModels } func addChildModel(model: AnotherSwiftDataModel) { self.childModels.append(model) } func removeChildModel(by id: PersistentIdentifier) { self.childModels = self.childModels.filter { $0.id != id } } } and the child model: import Foundation import SwiftData @Model final class AnotherSwiftDataModel { // Stable cross-device identity @Attribute(.unique) var uuid: UUID var someNumber: Int var someString: String var parentModel: MySwiftDataModel? init(uuid: UUID = UUID(), someNumber: Int = 1, someString: String = "Some") { self.uuid = uuid self.someNumber = someNumber self.someString = someString } } For now, you can assume I am not using CloudKit - i know for a fact the error is unrelated to CloudKit, because it happens when I am not using CloudKit (so I do not need to follow CloudKit's requirements for model design, such as nullable values etc). As I said, the error surfaces at different times - sometimes during assignments, a lot of times during deletions of related models, etc. Could you please explain what I am doing wrong and how I can make sure that this error does not happen? What are the architectural patterns that work best for SwiftData in this case? Do you have any examples of things I should avoid? Thanks

I’m trying to build a CRUD app using SwiftData, @Query model and multidatepicker. The data from a multidatepicker is stored or persists in SwiftData as Set = []. My current dilemma is how to use SwiftData and @Query model Predicate to find all records on the current date. I can’t find any SwiftData documentation or examples @Query using Set = []. My CRUD app should retrieve all records for the current date. Unfortunately, I don’t know the correct @Query model syntax for Set = [].

Something I want to know and all users of CKSyncEngine care about I'm going to build a full stack solution using CKSyncEngine, but what's the near future and the support and maintenance priorities inside Apple for CKSyncEngine? There is only one short video for CKSyncEngine, in 2023, no updates after that, no future plans mentioned. I'm worried that this technology be deprecated or not activity maintained. This is a complex technology, without being activity maintained (or open-sourced) there will be fatal production issues we the developer cannot solve. The CK developer in the video stated that "many apps" were using the framework, but he did not list any. The only named is NSUbiquitousKeyValueStore, but NSUbiquitousKeyValueStore is too simple a use case. I wonder is apple's Notes.app using it, or going to use it? Is SwiftData using it? API Problems The API design seems a little bit tricky, not designed from a user's perspective. handleEvent doesn't contain any context information about which batch. How do I react the event properly? Let's say our sync code and CKSyncEngine, and callbacks are all on a dedicated thread. Consider this: in nextRecordZoneChangeBatch you provided a batch of changes, let's call this BATCH 1, including an item in database with uuid "xxx" and name "yyy" before the changes are uploaded, there are new changes from many OTHER BACKGROUND THREADS made to the database. item "xxx"'s name is now "zzz" handle SentRecordZoneChanges event: I get records that uploaded or failed, but I don't know which BATCH the records belong to. How do I decide if i have to mark "xxx" as finished uploading or not? If I mark xxx as finished that's wrong, the new name "zzz" is not uploaded. I have to compare every field of xxx with the savedRecord to decide if I finished uploading or not? That is not acceptable as the performance and memory will be bad. Other questions I have to add recordIDs to state, and wait for the engine to react. I don't think this is a good idea, because recordID is a CloudKit concept, and what I want to sync is a local database. I don't see any rational for this, or not documented. If the engine is going to ask for a batch of records, you can get all record ids from the batch?

Hi, Before the iOS 17.2 update the saving behavior of SwiftData was very straightforward, by default it saves to persistence storage and can be configured to save in memory only. Now it saves to memory by default and to make it save to persistence storage we need to use modelContext.Save(). But if we don't quit the App the changes will be saved after a while to persistence storage even without running modelContext.Save() ! How confusing can that be for both developer and the user ! Am I missing something here ? -- Kind Regards

After updating to 15.2 I am seeing frequent crashes in my in-development app related to SwiftData. For instance, I have a 100% reproducible crash when I make the app lose and regain focus. There is also a crash that seem to be triggered by a modelContext.save() call in one of my ModelActors. With both of these crashes, the issue seems to be around keeping SwiftData models up to date. The first item in the stacktrace that is not machinecode is always some getter on a SwiftData collection or object. In the console, these crashes are accompanied by output along the lines of: === AttributeGraph: cycle detected through attribute 820680 === precondition failure: setting value during update: 930592 error: the replacement path doesn't exist: "/var/folders/b7/0dw7ztp13fgfxlj19by851tw0000gn/T/swift-generated-sources/@__swiftmacro_10SpaceDebug8TodoListV5todos33_5575DE008494C519BB9FA49C405133E1LL5QueryfMa_.swift" error: the replacement path doesn't exist: "/var/folders/b7/0dw7ztp13fgfxlj19by851tw0000gn/T/swift-generated-sources/@__swiftmacro_10SpaceDebug8TodoListV5todos33_5575DE008494C519BB9FA49C405133E1LL5QueryfMa_.swift" Can't show file for stack frame : <DBGLLDBStackFrame: 0x35a57c4e0> - stackNumber:27 - name:TodoList.todos.getter. The file path does not exist on the file system: /var/folders/b7/0dw7ztp13fgfxlj19by851tw0000gn/T/swift-generated-sources/@__swiftmacro_10SpaceDebug8TodoListV5todos33_5575DE008494C519BB9FA49C405133E1LL5QueryfMa_.swiftCan't show file for stack frame : <DBGLLDBStackFrame: 0x35a57c4e0> - stackNumber:27 - name:TodoList.todos.getter. The file path does not exist on the file system: /var/folders/b7/0dw7ztp13fgfxlj19by851tw0000gn/T/swift-generated-sources/@__swiftmacro_10SpaceDebug8TodoListV5todos33_5575DE008494C519BB9FA49C405133E1LL5QueryfMa_.swiftCan't show file for stack frame : <DBGLLDBStackFrame: 0x35a5a82f0> - stackNumber:62 - name:TodoList.todos.getter. The file path does not exist on the file system: /var/folders/b7/0dw7ztp13fgfxlj19by851tw0000gn/T/swift-generated-sources/@__swiftmacro_10SpaceDebug8TodoListV5todos33_5575DE008494C519BB9FA49C405133E1LL5QueryfMa_.swift Has anyone run into something similar? I'm looking for suggestions on how to debug this. Cheers, Bastiaan

Hi, I'm working on a macOS app that utilizes SwiftData to save some user generated content to their private databases. It is not clear to me at which point the app I made starts using the production database. I assumed that if I produce a Release build that it will be using the prod db, but that doesn't seem to be the case. I made the mistake of distributing my app to users before "going to prod" with CloudKit. So after I realized what I had done, I inspected my CloudKit dashboard and records and I found the following: For my personal developer account the data is saved in the Developer database correctly and I can inspect it. When I use the "Act as iCloud account" feature and use one of my other accounts to inspect the data, I notice that for the other user, the data is neither in the Development environment nor the Production environment. Which leads me to believe it is only stored locally on that user's machine, since the app does in fact work, it's just not syncing with other devices of the same user. So, my question is: how do I "deploy to production"? I know that there is a Deploy Schema Changes button in the CloudKit dashboard. At which point should I press that? If I press it now, before distributing a new version of my app, will that somehow "signal" the already running apps on user's machines to start using the Production database? Is there a setting in Xcode that I need to check for my Release build, so that the app does in fact start using the production db? Is there a way to detect in the code whether the app is using the Production database or not? It would be useful so I can write appropriate migration logic, since I don't want to loose existing data users already have saved locally.

I've got an application built on top of SwiftData (+ CloudKit) which is published to App Store. I've got a problem where on each app update, the data saved in the database is duplicated to the end user. Obviously this isn't wanted behaviour, and I'm really looking forward to fixing it. However, given the restrictions of SwiftData, I haven't found a single fix for this. The data duplication happens automatically on the first initial sync after the update. My guess is that it's because it doesn't detect the data already in the device, so it pulls all data from iCloud and appends it to the database where data in reality exists.

I am trying to port my application over to CloudKit. My app worked fine before, but then I made scheme of changes and am trying to deploy to a new container. For some reason, the database is not being created after I create the container through Xcode. I think I have configured the app correctly and a container was created, but no records were deployed. My app current stores data locally on individual devices just fine but they don't sync with each other. That's why I would like to use CloudKit. See screenshot from Xcode of where I have configured the container. I also have background notifications enabled. Also see screenshot from console where the container has been created, but no records have been. Any suggestions would be greatly appreciated. Thank you

I changed an enum value from this: enum Kind: String, Codable, CaseIterable { case credit } to this: enum Kind: String, Codable, CaseIterable { case credit = "Credit" } And now it fails to load the data. This is inside of a SwiftData model. I get why the error is occurring, but is there a way to resolve this issue without having to revert back or delete the data? Error: dataCorrupted(Swift.DecodingError.Context(codingPath: [], debugDescription: "Cannot initialize Kind from invalid String value credit", underlyingError: nil))

I just released an App update the didn't touch ANYTHING to do with Core Data (nothing changed in our Coredata code for at least 8 months). The update uses SDK for iOS 18 and Xcode 16.2 and the app now requires iOS 18 and was a minor bug patch and UI improvements for recent iOS changes. Since the update we are getting a steady trickle of users on iOS 18, some who allow the App to store data in iCloud (Cloudkit) and others who do not, all reporting that after the update to our recent release ALL their data is gone?! I had not seen this on ANY device until today when I asked a friend who uses the App if they had the issue and it turned out they did, so I hooked their device up to Xcode and ALL the data in the CoreData database was gone?! They are NOT using iCloud. There were no errors or exceptions on Xcode console but a below code returned NO records at all?! Chart is custom entity and is defined as: @interface Chart : NSManagedObject {} let moc = pc.viewContext let chartsFetch = NSFetchRequest<NSFetchRequestResult>(entityName:"Charts") // Fetch all Charts do { let fetchedCharts = try moc.fetch(chartsFetch) as! [Chart] for chart in fetchedCharts { .... } } A break point inside the do on fetchedCharts show there are NO objects returned. This is a serious issue and seems like an iOS 18 thing. I saw some people talking in here about NSFetchRequest issues with iOS 18. I need some guidance here from someone Apple engineer here who knows what the status of these NSFetchrequest bugs are and what possible workarounds are. Becasue this problem will grow for me as more users update to iOS 18.

I have an app which uses key-value storage and will not sync data past a certain size -- meaning that device "A" will send the data to the cloud but device "B" will never receive the updated data. Device "B" will receive the NSUbiquitousKeyValueStoreDidChangeExternallyNotification that the KVS changed but the data is empty. The data in in the KVS is comprised of 4 keys, each containing a value of NSData generated by NSKeyedArchiver. The NSData is comprised of property-list data types (e.g. numbers, strings, dates, etc.) I've verified that the KVS meets the limits of: A total of 1 MB per app, with a per-key limit of 1 MB A per-key value size limit of 1 MB, and a maximum of 1024 keys A maximum length for key strings is 64 bytes using UTF8 encoding Also, the app has never received an NSUbiquitousKeyValueStoreQuotaViolationChange notification. Of the 4 keys, 3 of them contain no more than 30 KB of data each. However, one of the keys can contain as much as 160 KB of data which will not sync to another device. Strangely, if I constrain the data to 100 KB it will work, however, that is not ideal as it is a fraction of the necessary data. I don't see any errors in the debug log either. Any suggestions on what to try next to get this working?

It takes a few seconds, sometimes a few minutes for records to be downloaded back from CloudKit when the user reinstalls the app, which leads users to thinking their data was lost. I would like to know if there’s any way to provide a visual feedback about the current CloudKit sync status so I can let users know their data is being in fact downloaded back to their devices.

Hi, I have designed an app which needs to reschedule notifications according to the user's calendar at midnight. The function has been implemented successfully via backgroundtask. But since the app has enabled iCloud sync, some users will edit their calendar on their iPad and expect that the notifications will be sent promptly to them on iPhone without launching the app on their iPhone. But the problem is that if they haven't launched the app on their iPhone, iCloud sync won't happen. The notifications on their iPhone haven't been updated and will be sent wrongly. How can I design some codes to let iCloud sync across the devices without launching the app at midnight and then reschedule notifications?