This simple test fails in my project. Similar code in my application also crashes. How do I debug the problem? What project settings are required. I have added SwiftData as a framework to test (and application) targets? Thanks, The problem is with: modelContext.insert(item) Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) import XCTest import SwiftData @Model class FakeModel { var name: String init(name: String) { self.name = name } } @MainActor final class FakeModelTests: XCTestCase { var modelContext: ModelContext! override func setUp() { super.setUp() do { let container = try ModelContainer(for: FakeModel.self, configurations: ModelConfiguration(isStoredInMemoryOnly: true)) modelContext = container.mainContext } catch { XCTFail("Failed to create ModelContainer: \(error)") modelContext = nil } } func testSaveFetchDeleteFakeItem() { guard let modelContext = modelContext else { XCTFail("ModelContext must be initialized") return } let item = FakeModel(name: "Test") modelContext.insert(item) let fetchDescriptor = FetchDescriptor<FakeModel>() let items = try! modelContext.fetch(fetchDescriptor) XCTAssertEqual(items.count, 1) XCTAssertEqual(items.first?.name, "Test") modelContext.delete(item) let itemsAfterDelete = try! modelContext.fetch(fetchDescriptor) XCTAssertEqual(itemsAfterDelete.count, 0) } }

Hello, I recently published an app that uses Swift Data as its primary data storage. The app uses concurrency, background threads, async await, and BLE communication. Sadly, I see my app incurs many fringe crashes, involving EXC_BAD_ACCESS, KERN_INVALID_ADDRESS, EXC_BREAKPOINT, etc. I followed these guidelines: One ModelContainer that is stored as a global variable and used throughout. ModelContexts are created separately for each task, changes are saved manually, and models are not passed around. Threads with different ModelContexts might manipulate and/or read the same data simultaneously. I was under the impression this meets the usage requirements. I suspect perhaps the issue lies in my usage of contexts in a single await function, that might be paused and resumed on a different thread (although same execution path). Is that the case? If so, how should SwiftData be used in async scopes? Is there anything else particularly wrong in my approach?

Hello, From the documentation linked below, the limitations for Background Assets are the following: Size Limit: 200 GB Asset Pack Count: 100 I'm expecting I will need ~175 Asset Packs and around 500GB of storage. I understand Background Assets is a new, but is there a process or a potential that these limits will be increased in the future? Or is there a way to request an increase? I've tried contacting Apple Support as this is more of an Admin issue, however they've directed me here. Case ID 102725356578 https://developer.apple.com/help/app-store-connect/reference/apple-hosted-asset-pack-size-limits Thank you, Tanner

I have an image field on a Core Data entity with "Allows External Storage" enabled. When I delete a record, the external binary data file remains on disk. How can I ensure that all externally stored data is deleted along with the record?

I have a simple app that makes an HTTPS call to gather some JSON which I then parse and add to my SwiftData database. The app then uses a simple @Query in a view to get the data into a list. on iOS 16 this works fine. No problems. But the same code on iOS 26 (targeting iOS 18.5) crashes after about 15 seconds of idle time after the list is populated. The error message is: Could not cast value of type '__NSCFNumber' (0x1f31ee568) to 'NSString' (0x1f31ec718). and occurs when trying to access ANY property of the list. I have a stripped down version of the app that shows the crash available. To replicate the issue: open the project in Xcode 26 target any iOS 26 device or simulator compile and run the project. after the list is displayed, wait about 15 seconds and the app crashes. It is also of note that if you try to run the app again, it will crash immediately, unless you delete the app from the device. Any help on this would be appreciated. Feedback number FB20295815 includes .zip file Below is the basic code (without the data models) The Best Seller List.Swift import SwiftUI import SwiftData @main struct Best_Seller_ListApp: App { var body: some Scene { WindowGroup { ContentView() } .modelContainer (for: NYTOverviewResponse.self) } } ContentView.Swift import os.log import SwiftUI struct ContentView: View { @Environment(\.modelContext) var modelContext @State private var listEncodedName = String() var body: some View { NavigationStack () { ListsView() } .task { await getBestSellerLists() } } func getBestSellerLists() async { guard let url = URL(string: "https://api.nytimes.com/svc/books/v3/lists/overview.json?api-key=\(NYT_API_KEY)") else { Logger.errorLog.error("Invalid URL") return } do { let decoder = JSONDecoder() var decodedResponse = NYTOverviewResponse() //decode the JSON let (data, _) = try await URLSession.shared.data(from: url) decoder.keyDecodingStrategy = .convertFromSnakeCase decodedResponse = try decoder.decode(NYTOverviewResponse.self, from: data) //remove any lists that don't have list_name_encoded. Fixes a bug in the data decodedResponse.results!.lists = decodedResponse.results!.lists!.filter { $0.listNameEncoded != "" } // sort the lists decodedResponse.results!.lists!.sort { (lhs, rhs) -> Bool in lhs.displayName < rhs.displayName } //delete any potential existing data try modelContext.delete(model: NYTOverviewResponse.self) //add the new data modelContext.insert(decodedResponse) } catch { Logger.errorLog.error("\(error.localizedDescription)") } } } ListsView.Swift import os.log import SwiftData import SwiftUI @MainActor struct ListsView: View { //MARK: - Variables and Constants @Query var nytOverviewResponses: [NYTOverviewResponse] enum Updated: String { case weekly = "WEEKLY" case monthly = "MONTHLY" } //MARK: - Main View var body: some View { List { if nytOverviewResponses.isEmpty { ContentUnavailableView("No lists yet", systemImage: "list.bullet", description: Text("NYT Bestseller lists not downloaded yet")) } else { WeeklySection MonthlySection } } .navigationBarTitle("Bestseller Lists", displayMode: .large) .listStyle(.grouped) } var WeeklySection: some View { let rawLists = nytOverviewResponses.last?.results?.lists ?? [] // Build a value-typed array to avoid SwiftData faulting during sort let weekly = rawLists .filter { $0.updateFrequency == Updated.weekly.rawValue } .map { (name: $0.displayName, encoded: $0.listNameEncoded, model: $0) } .sorted { $0.name < $1.name } return Section(header: Text("Weekly lists to be published on \(nytOverviewResponses.last?.results?.publishedDate ?? "-")")) { ForEach(weekly, id: \.encoded) { item in Text(item.name).font(Font.custom("Georgia", size: 17)) } } } var MonthlySection: some View { let rawLists = nytOverviewResponses.last?.results?.lists ?? [] // Build a value-typed array to avoid SwiftData faulting during sort let monthly = rawLists .filter { $0.updateFrequency == Updated.monthly.rawValue } .map { (name: $0.displayName, encoded: $0.listNameEncoded, model: $0) } .sorted { $0.name < $1.name } return Section(header: Text("Monthly lists to be published on \(nytOverviewResponses.last?.results?.publishedDate ?? "-")")) { ForEach(monthly, id: \.encoded) { item in Text(item.name).font(Font.custom("Georgia", size: 17)) } } } }

relationshipKeyPathsForPrefetching in SwiftData does not seem to work here when scrolling down the list. Why? I would like all categories to be fetched while posts are fetched - not while scrolling down the list. struct ContentView: View { var body: some View { QueryList( fetchDescriptor: withCategoriesFetchDescriptor ) } var withCategoriesFetchDescriptor: FetchDescriptor<Post> { var fetchDescriptor = FetchDescriptor<Post>() fetchDescriptor.relationshipKeyPathsForPrefetching = [\.category] return fetchDescriptor } } struct QueryList: View { @Query var posts: [Post] init(fetchDescriptor: FetchDescriptor<Post>) { _posts = Query(fetchDescriptor) } var body: some View { List(posts) { post in VStack { Text(post.title) Text(post.category?.name ?? "") .font(.footnote) } } } } @Model final class Post { var title: String var category: Category? init(title: String) { self.title = title } } @Model final class Category { var name: String init(name: String) { self.name = name } }

Apple WTF? What did you do to all my Apps? none of them work in iOS26.1 (all worked in 26.0). XCode simply says: CoreData: error: addPersistentStoreWithType:configuration:URL:options:error: returned error NSCocoaErrorDomain (134140) * SwiftData is supposed to do all these automatically 🤷🏻

Hi everyone, I’m currently developing a SwiftUI app that uses SwiftData with CloudKit sharing enabled. The app works fine on my own Apple ID, and local syncing with iCloud is functioning correctly — but sharing with other Apple IDs consistently fails. Setup: SwiftUI + SwiftData using a ModelContainer with .shared configuration Sharing UI is handled via UICloudSharingController iCloud container: iCloud.com.de.SkerskiDev.FoodGuard Proper entitlements enabled (com.apple.developer.icloud-services, CloudKit, com.apple.developer.coredata.cloudkit.containers, etc.) Automatic provisioning profiles created by Xcode Error:<CKError 0x1143a2be0: "Bad Container" (5/1014); "Couldn't get container configuration from the server for container iCloud.com.de.SkerskiDev.FoodGuard"> What I’ve tried: Verified the iCloud container is correctly created and enabled in the Apple Developer portal Checked bundle identifier and container settings Rebuilt and reinstalled the app Ensured correct iCloud entitlements and signing capabilities Questions: Why does CloudKit reject the container for sharing while local syncing works fine? Are there known issues with SwiftData .shared containers and multi-user sharing? Are additional steps required (App Store Connect, privacy settings) to allow sharing with other Apple IDs? Any advice, experience, or example projects would be greatly appreciated. 🙏 Thanks! Sebastian

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.

I implemented the cloudkit function, where users can connect with each other. The problem is, that if User A is doing a friend request and User B is accepting the request. The friend entry is correct visible for User B but not for User A. I can see in cloud kit that after the accepted request, the friend connection is set up correctly, also with the correct userID, but it not showing up for User A (the one that send the request)

I have a new app I am working on, it uses, a container id like com.me.mycompany.FancyApp.prod, the description in the app is My Fancy App. When I deploy the app via TestFlight on a real device, the sync seems to work, but when I view iCloud->Storage-List, I see my app icon, and the name "prod". Where did the name prod come from? It should be My Fancy App, which is the actual name of the App.

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 have a simple app that uses SwiftUI and SwiftData to maintain a database. The app runs on multiple iPhones and iPads and correctly synchronises across those platforms. So I am correct setting Background Modes and Remote Notifications. I have also correctly setup my Model Configuration and ModelContainer (Otherwise I would expect syncing to fail completely). The problem arises when I run on a Mac (M1 or M3) either using Mac Designed for iPad or Mac Catalyst. This can be debugging in Xcode or running the built app. Then the app does not reflect changes made in the iPhone or iPad apps unless I follow a specific sequence. Leave the app, (e.g click on a Finder window), then come back to the app (i.e click on the app again). Now the app will show the changes made on the iPhone/iPad. It looks like the app on the Mac is not processing remote notifications when in the background - it only performs them when the app has just become active. It also looks like the Mac is not performing these sync operations when the app is active. I have tried waiting 30 minutes and still the sync doesn't happen unless I leave the app and come back to it. I am using the same development CloudKit container in all cases

Perhaps I just have the wrong expectations, but I discovered some odd behavior from SwiftData that sure seems like a bug to me... If you make any change to any SwiftData model object — even just setting a property to its current value — every SwiftUI view that uses SwiftData is rebuilt. Every query and every entity reference, even if the property was set on a model class that is completely unrelated to the view. SwiftUI does such a good job of optimizing UI updates that it's hard to notice the issue. I only noticed it because the updates were triggering my debug print statements. To double-check this, I went back to Apple's new iOS app template — the one that is just a list of dated items — and added a little code to touch an unrelated record in the background: @Model class UnrelatedItem { var name: String init(name: String) { self.name = name } } @main struct jumpyApp: App { var sharedModelContainer: ModelContainer = { let schema = Schema([ Item.self, UnrelatedItem.self ]) let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false) do { return try ModelContainer(for: schema, configurations: [modelConfiguration]) } catch { fatalError("Could not create ModelContainer: \(error)") } }() init() { let context = sharedModelContainer.mainContext // Create 3 items at launch so we immediately have some data to work with. if try! context.fetchCount(FetchDescriptor<Item>()) == 0 { for _ in 0..<3 { let item = Item(timestamp: Date()) context.insert(item) } } // Now create one unrelated item. let unrelatedItem = UnrelatedItem(name: "Mongoose") context.insert(unrelatedItem) try? context.save() // Set up a background task that updates the unrelated item every second. Task { while true { try? await Task.sleep(nanoseconds: 1_000_000_000) Task { @MainActor in // We don't even have to change the name or save the contxt. // Just setting the name to the same value will trigger a change. unrelatedItem.name = "Mongoose" } } } } var body: some Scene { WindowGroup { ContentView() } .modelContainer(sharedModelContainer) } } I also added a print statement to the ContentView so I could see when the view updates. struct ContentView: View { @Environment(\.modelContext) private var modelContext @Query private var items: [Item] var body: some View { NavigationSplitView { List { let _ = Self._printChanges() ... The result is that the print statement logs 2 messages to the debug console every second. I checked in iOS 17, 18.1, and 18.2, and they all behave this way. Is this the intended behavior? I thought the whole point of the new Observation framework in iOS 17 was to track which data had changed and only send change notifications to observers who were using that data.

No matter what I do, I keep getting the error Thread 1: EXC_BREAKPOINT (code=1, subcode=0x2648fc364) for the line: transactions = try modelContext.fetch(descriptor) in the code below. My app opens, but freezes on the home page and I can't click anything. I am not sure how to fix initialization issues. I am creating a financial assistant app that connects plaid and opoenai api. var descriptor = FetchDescriptor&lt;ExpenseTransaction&gt;() descriptor.sortBy = [SortDescriptor(\.date, order: .reverse)] descriptor.fetchLimit = 200 transactions = try modelContext.fetch(descriptor) print("Successfully loaded \(transactions.count) transactions") } catch { print("Error in loadLocalTransactions: \(error)") transactions = [] } }

I would like to have a SwiftData predicate that filters against an array of PersistentIdentifiers. A trivial use case could filtering Posts by one or more Categories. This sounds like something that must be trivial to do. When doing the following, however: let categoryIds: [PersistentIdentifier] = categoryFilter.map { $0.id } let pred = #Predicate<Post> { if let catId = $0.category?.persistentModelID { return categoryIds.contains(catId) } else { return false } } The code compiles, but produces the following runtime exception (XCode 26 beta, iOS 26 simulator): 'NSInvalidArgumentException', reason: 'unimplemented SQL generation for predicate : (TERNARY(item != nil, item, nil) IN {}) (bad LHS)' Strangely, the same code works if the array to filter against is an array of a primitive type, e.g. String or Int. What is going wrong here and what could be a possible workaround?

I’m building an app that edits files in iCloud and uses an NSFilePresenter to monitor changes. When a conflict occurs, the system calls presentedItemDidGain(_:). In that method, I merge the versions by reading the current (canonical) version using NSFileVersion.currentVersionOfItem(at:) and the conflicting ones using NSFileVersion.unresolvedConflictVersionsOfItem(at:). This generally works, but sometimes, if two devices edit the same file at the same time, each device sees its own local version as the current one. For example: Device A writes fileVerA (slightly later in real time) Device B writes fileVerB On Device A all works fine, currentVersionOfItem returns fileVerA, as expected, and unresolvedConflictVersionsOfItem returns [fileVerB]. But on Device B, currentVersionOfItem returns fileVerB!? And unresolvedConflictVersionsOfItem returns the same, local file [fileVerB], without any hint of the other conflicting version, fileVerA. Later, the newer version from the Device A arrives on Device B as a normal, non-conflicting update via presentedItemDidChange(_:). This seems to contradict Apple’s documentation: “The currentVersionOfItemAtURL: method returns an NSFileVersion object representing what’s referred to as the current file; the current file is chosen by iCloud on some basis as the current “conflict winner” and is the same across all devices.” Is this expected behavior, or a bug in how iCloud reports file versions?

Hi, I keep trying to use transformable to store an array of strings with SwiftData, and I can see that it is activating the transformer, but it keeps saying that I am still using NSArray instead of NSData. *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unacceptable type of value for attribute: property = "category"; desired type = NSData; given type = Swift.__SwiftDeferredNSArray; value = ( yo, gurt ).' terminating due to uncaught exception of type NSException CoreSimulator 1010.10 - Device: iPhone 16 18.0 (6879535B-3174-4025-AD37-ED06E60291AD) - Runtime: iOS 18.0 (22A3351) - DeviceType: iPhone 16 Message from debugger: killed @Model class MyModel: Identifiable, Equatable { @Attribute(.transformable(by: StringArrayTransformer.self)) var category: [String]? @Attribute(.transformable(by: StringArrayTransformer.self)) var amenities: [String]? var image: String? var parentChunck: HenricoPostDataChunk_V1? init(category: [String]?, amenities: [String]?) { self.category = category self.amenities = amenities } } class StringArrayTransformer: ValueTransformer { override func transformedValue(_ value: Any?) -> Any? { print(value) guard let array = value as? [String] else { return nil } let data = try? JSONSerialization.data(withJSONObject: array, options: []) print(data) return data } override func reverseTransformedValue(_ value: Any?) -> Any? { guard let data = value as? Data else { return nil } let string = (try? JSONSerialization.jsonObject(with: data, options: [])) as? [String] print(string) return string } override class func transformedValueClass() -> AnyClass { return NSData.self } override class func allowsReverseTransformation() -> Bool { return true } static func register() { print("regitsering") ValueTransformer.setValueTransformer(StringArrayTransformer(), forName: .stringArrayTransformerName) } } extension NSValueTransformerName { static let stringArrayTransformerName = NSValueTransformerName("StringArrayTransformer") }

Hi everyone, I’ve been working on migrating my app (SwimTimes, which helps swimmers track their times) to use Core Data + CKSyncEngine with Swift 6. After many iterations, forum searches, and experimentation, I’ve created a focused sample project that demonstrates the architecture I’m using. The good news: 👉 I believe the crashes I was experiencing are now solved, and the sync behavior is working correctly. 👉 The demo project compiles and runs cleanly with Swift 6. However, before adopting this as the final architecture, I’d like to ask the community (and hopefully Apple engineers) to validate a few critical points, especially regarding Swift 6 concurrency and Core Data contexts. Architecture Overview Persistence layer: Persistence.swift sets up the Core Data stack with a main viewContext and a background context for CKSyncEngine. Repositories: All Core Data access is abstracted into repository classes (UsersRepository, SwimTimesRepository), with async/await methods. SyncEngine: Wraps CKSyncEngine, handles system fields, sync tokens, and bridging between Core Data entities and CloudKit records. ViewModels: Marked @MainActor, exposing @Published arrays for SwiftUI. They never touch Core Data directly, only via repositories. UI: Simple SwiftUI views bound to the ViewModels. Entities: UserEntity → represents swimmers. SwimTimeEntity → times linked to a user (1-to-many). Current Status The project works and syncs across devices. But there are two open concerns I’d like validated: Concurrency & Memory Safety Am I correctly separating viewContext (main/UI) vs. background context (used by CKSyncEngine)? Could there still be hidden risks of race conditions or memory crashes that I’m not catching? Swift 6 Sendable Compliance Currently, I still need @unchecked Sendable in the SyncEngine and repository layers. What is the recommended way to fully remove these workarounds and make the code safe under Swift 6’s stricter concurrency rules? Request Please review this sample project and confirm whether the concurrency model is correct. Suggest how I can remove the @unchecked Sendable annotations safely. Any additional code improvements or best practices would also be very welcome — the intention is to share this as a community resource. I believe once finalized, this could serve as a good reference demo for Core Data + CKSyncEngine + Swift 6, helping others migrate safely. Environment iOS 18.5 Xcode 16.4 macOS 15.6 Swift 6 Sample Project Here is the full sample project on GitHub: 👉 [https://github.com/jarnaez728/coredata-cksyncengine-swift6] Thanks a lot for your time and for any insights! Best regards, Javier Arnáez de Pedro

I'm developing a SwiftUI app using SwiftData and encountering a persistent issue: Error Message: Thread 1: Fatal error: Duplicate keys of type 'Bland' were found in a Dictionary. This usually means either that the type violates Hashable's requirements, or that members of such a dictionary were mutated after insertion. Details: Occurrence: The error always occurs on the first launch of the app after installation. Specifically, it happens approximately 1 minute after the app starts. Inconsistent Behavior: Despite no changes to the code or server data, the error occurs inconsistently. Data Fetching Process: I fetch data for entities (Bland, CrossZansu, and Trade) from the server using the following process: Fetch Bland and CrossZansu entities via URLSession. Insert or update these entities into the SwiftData context. The fetched data is managed as follows: func refleshBlandsData() async throws { if let blandsOnServer = try await DataModel.shared.getBlands() { await MainActor.run { blandsOnServer.forEach { blandOnServer in if let blandOnLocal = blandList.first(where: { $0.code == blandOnServer.code }) { blandOnLocal.update(serverBland: blandOnServer) } else { modelContext.insert(blandOnServer.bland) } } } } } This is a simplified version of my StockListView. The blandList is a @Query property and dynamically retrieves data from SwiftData: struct StockListView: View { @Environment(\.modelContext) private var modelContext @Query(sort: \Bland.sname) var blandList: [Bland] @Query var users: [User] @State private var isNotLoaded = true @State private var isLoading = false @State private var loadingErrorState = "" var body: some View { NavigationStack { List { ForEach(blandList, id: \.self) { bland in NavigationLink(value: bland) { Text(bland.sname) } } } .navigationTitle("Stock List") .onAppear { doIfFirst() } } } // This function handles data loading when the app launches for the first time func doIfFirst() { if isNotLoaded { loadDataWithAnimationIfNotLoading() isNotLoaded = false } } // This function ensures data is loaded with an animation and avoids multiple triggers func loadDataWithAnimationIfNotLoading() { if !isLoading { isLoading = true Task { do { try await loadData() } catch { // Capture and store any errors during data loading loadingErrorState = "Data load failed: \(error.localizedDescription)" } isLoading = false } } } // Fetch data from the server and insert it into the SwiftData model context func loadData() async throws { if let blandsOnServer = try await DataModel.shared.getBlands() { for bland in blandsOnServer { // Avoid inserting duplicate keys by checking for existing items in blandList if !blandList.contains(where: { $0.code == bland.code }) { modelContext.insert(bland.bland) } } } } } Entity Definitions: Here are the main entities involved: Bland: @Model class Bland: Identifiable { @Attribute(.unique) var code: String var sname: String @Relationship(deleteRule: .cascade, inverse: \CrossZansu.bland) var zansuList: [CrossZansu] @Relationship(deleteRule: .cascade, inverse: \Trade.bland) var trades: [Trade] } CrossZansu: @Model class CrossZansu: Equatable { @Attribute(.unique) var id: String var bland: Bland? } Trade: @Model class Trade { @Relationship(deleteRule: .nullify) var user: User? var bland: Bland } User: class User { var id: UUID @Relationship(deleteRule: .cascade, inverse: \Trade.user) var trades: [Trade] } Observations: Error Context: The error occurs after the data is fetched and inserted into SwiftData. This suggests an issue with Hashable requirements or duplicate keys being inserted unintentionally. Concurrency Concerns: The fetch and update operations are performed in asynchronous tasks. Could this cause race conditions? Questions: Could this issue be related to how @Relationship and @Attribute(.unique) are managed in SwiftData? What are potential pitfalls with Equatable implementations (e.g., in CrossZansu) when used in SwiftData entities? Are there any recommended approaches for debugging "Duplicate keys" errors in SwiftData? Additional Info: Error Timing: The error occurs only during the app's first launch and consistently within the first minute.