Symptom Production iOS app (TestFlight) using App Attest. Devices generate assertions via DCAppAttestService (through Firebase App Check, which forwards to Apple's validation infrastructure). The fleet was attesting cleanly at ~100% verified for the first ~7 days post-first-install per device — then collapsed to ~0% verified once the initial token's natural TTL expired and devices were forced to re-attest. Has stayed at ~0% for 3+ days. Affects all 4 physical TestFlight devices; not reproducing on simulators (which is expected — App Attest unavailable there). The downstream validator's metric specifically categorizes these as "invalid" — meaning a token reached it and was rejected as cryptographically invalid — not as "no token sent" / "unrecognized origin" / "outdated SDK." Environment iOS 26.x (26.3.1 confirmed on multiple devices). Team ID T68SS8UY5J, bundle com.calimento.app, App ID has App Attest capability checked. Entitlements signed into binary: com.apple.developer.devicecheck.appattest-environment = production. Xcode would refuse this embed if the App ID lost the capability — so capability state is verifiably intact. Provisioning profile UUID byte-identical between the last verified-traffic build and the first invalid-traffic build (confirmed via Xcode build logs). Same code-signing identity hash across both builds. TestFlight builds approved by Apple Beta Review. What's been ruled out Provisioning / signing / certificate drift (UUID and cert hash unchanged across builds). App ID capability revocation (entitlement embed succeeded). Firebase iOS app config drift (GoogleService-Info.plist byte-identical across vault, local working tree, and Firebase Console download). Token attachment / SDK init race (0% of requests in the "no token" or "outdated client" buckets). Pod / dependency drift (package-lock byte-identical between verified and failing builds). The integration was producing valid assertions for ~7 days post-install per device — code-side bugs would have manifested from day one, not synchronized to the TTL boundary. Questions Are there known iOS 26.x server-side issues with App Attest assertion validation that would cause hardware-generated assertions to be rejected as cryptographically invalid? Is there a documented or undocumented abuse-mitigation behavior that downgrades or invalidates assertions for an App ID under specific conditions — e.g., after a volume threshold within a window, or after a fingerprint anomaly? Looking specifically at whether high attestation churn during development can leave an App ID's attestation state in a degraded mode. Is there any way to inspect Apple's reason for rejecting a specific assertion — through a developer tool, console log, or feedback channel? The downstream validator only surfaces"invalid"; it doesn't report Apple's underlying rejection reason. Recovery semantics: if a device's keyId ends up internally blocklisted, does it age out, or is the device permanently unable to produce valid assertions for that App ID? appattest-environment = production validation flow: any way the production environment validator could differ from development in a way that produces this signature? Why I'm filing here rather than only with the SDK maintainer: The SDK is reliably attaching tokens (0% in the "no token" bucket). Origin is being recognized (0% in the "unknown origin" bucket). The rejection is happening at signature validation — which is downstream of any client-SDK behavior. Cross-filed with the React Native Firebase maintainers at [https://github.com/invertase/react-native-firebase/issues/9008]; if the root cause turns out to be on the wrapper's side, that thread will be closed. Happy to provide raw build logs, validator metric exports, or a build for a test device on Apple's side privately.

Hi folks, in my application I write some logs over debugPrint or directly over print. The application is already distributed and some part of functionality failed with application traceback. I would like to ask user for providing logs from the App. Is it possible to get those logs? Thanks Petr

We are currently experiencing an unexpected issue with the DeviceCheck query_two_bits endpoint. According to the official documentation (Accessing and Modifying Per-Device Data), the last_update_time field should represent the month and year when the bits were last modified. The Issue: For several specific device tokens, our server is receiving a last_update_time value that is set in the future. Current Date: April 2026 Returned last_update_time: 2026-12 (December 2026) Here is a response: { "body": "{\"bit0\":false,\"bit1\":true,\"last_update_time\":\"2026-12\"}", "headers": { "Server": ["Apple"], "Date": ["Thu, 02 Apr 2026 06:05:23 GMT"], "Content-Type": ["application/json; charset=UTF-8"], "Transfer-Encoding": ["chunked"], "Connection": ["keep-alive"], "X-Apple-Request-UUID": ["53e16c38-d9f7-4d58-a354-ce07a4eaa35b"], "X-Responding-Instance": ["af-bit-store-56b5b6b478-k8hnh"], "Strict-Transport-Security": ["max-age=31536000; includeSubdomains"], "X-Frame-Options": ["SAMEORIGIN"], "X-Content-Type-Options": ["nosniff"], "X-XSS-Protection": ["1; mode=block"] }, "statusCode": "OK", "statusCodeValue": 200 } Technical Details: Endpoint: https://api.development.devicecheck.apple.com/v1/query_two_bits (also occurring in Production) Response Body Example: JSON { "bit0": true, "bit1": false, "last_update_time": "2026-12" } Observations: This occurs even when our server has not sent an update_two_bits request for that specific device in the current month. Questions: Is there a known issue with the timestamp synchronization or regional database propagation for DeviceCheck? Does the last_update_time field ever represent an expiration date or any value other than the "last modified" month? Best regards,

Hi everyone, I'm integrating Apple's DeviceCheck API into my app and have run into a strange issue that I can't find documented anywhere. The Problem When I call Apple's DeviceCheck query endpoint (POST https://api.devicecheck.apple.com/v1/query_two_bits), the response occasionally returns a last_update_time value that is in the future — ahead of the current server time. Example response: { "bit0": true, "bit1": false, "last_update_time": "2026-05" // future month, not yet reached } What I've Checked My server's system clock is correctly synced via NTP The JWT token I generate uses the current timestamp for the iat field This doesn't happen on every device — only on some specific devices The issue is reproducible on the same device across multiple calls Questions Is last_update_time sourced from the device's local clock at the time update_two_bits was called? Or is it stamped server-side by Apple? Could a device with an incorrectly set system clock (set to the future) cause Apple's servers to record a future last_update_time? Is there a recommended way to validate or sanitize last_update_time on the server side to handle this edge case? Has anyone else encountered this behavior? Any known workarounds? Any insight would be greatly appreciated. Thanks!

Hi, We are implementing Platform SSO and using attestKey during registration via ASAuthorizationProviderExtensionLoginManager. Could you clarify whether the attestKey flow involves sending attestation data to an Apple server for verification (similar to App Attest in the DeviceCheck framework), or if the attestation certificate chain is generated and signed entirely on-device without any Apple server interaction? The App Attest flow is clearly documented as using Apple’s attestation service, but the Platform SSO process is less clearly described. Thank you.

We are moving to Apple Business Store for our b2b customers. On the "residential" apple store side there is testflight. What process would one test an app we provide to a b2b customer when using apple business store publishing? (I don't see any sort of test flight for apple business)

Hello, we are using DeviceCheck – App Attest in a production iOS app. The integration has been live for some time and works correctly for most users, but a small subset of users encounter non-deterministic failures that we are unable to reproduce internally. Environment iOS 14+ Real devices only (no simulator) App Attest capability enabled Correct App ID, Team ID and App Attest entitlement Production environment Relevant code let service = DCAppAttestService.shared service.generateKey { keyId, error in // key generation } service.attestKey(keyId, clientDataHash: hash) { attestation, error in // ERROR: com.apple.devicecheck.error 3 / 4 } service.generateAssertion(keyId, clientDataHash: clientDataHash) { assertion, error in // ERROR: com.apple.devicecheck.error 3 / 4 } For some users we intermittently receive: com.apple.devicecheck.error error 3 com.apple.devicecheck.error error 4 Characteristics: appears random affects only some users/devices sometimes resolves after time or reinstall not reproducible on our test devices NSError contains no additional diagnostic info Some questions: What is the official meaning of App Attest errors 3 and 4? Are these errors related to key state, device conditions, throttling, or transient App Attest service issues? Is there any recommended way to debug or gain more insight when this happens in production? Any guidance would be greatly appreciated, as this impacts real users and is difficult to diagnose. Thank you.

Hi, In our app we are using DeviceCheck (App Attest) in a production environment iOS. The service works correctly for most users, but a user reported failure in a flow that use device check service. This failure is not intermittently, it is constant. We are unable to reproduce this failure and we are believing that this failure occurred by new version ios 26.3 because for others users using early versions the service is normally. Environment iOS 26.3 Real device App Attest capability enabled Correct App ID, Team ID and App Attest entitlement Production environment Characteristics: appears constantly affects only unique user -Don't resolves after time or reinstall not reproducible on our test devices NSError contains no additional diagnostic info (Error Domain=com.apple.devicecheck.error Code=3 "(null)") We saw about this error code 3 in this post 812308, but it's not our case because the ios version in this case is not iOS 17.0 or earlier. Please, help us any guidance for solution. Thank you

We integrated DeviceCheck framework into our app to prevent fraudulent call to our app service around one year ago. Recently, we received a few cases related to this function over Christmas Eve period. Based on the logs we have, it indicated both the following two functions returned errors. But we don't have the exactly errors logged and now we cannot replicate. DCAppAttestService.shared.attestKey() DCAppAttestService.shared.generateAssertion() The other finding we have is some users reporting this issue recently upgraded their devices from iOS 18 to iOS 26. So we are suspecting it's due to either the OS upgrading, or Apple's app attest service degrading. Anyone encountered the similar issues before, or have any idea regarding the root cause? Thanks!

We're experiencing crashes in our production iOS app related to Apple's DeviceCheck framework. The crash occurs in DCAnalytics internal performance tracking, affecting some specific versions of iOS 18 (18.4.1, 18.5.0). Crash Signature CoreFoundation: -[__NSDictionaryM setObject:forKeyedSubscript:] + 460 DeviceCheck: -[DCAnalytics sendPerformanceForCategory:eventType:] + 236 Observed Patterns Scenario 1 - Token Generation: Crashed: com.appQueue EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000010 DeviceCheck: -[DCDevice generateTokenWithCompletionHandler:] Thread: Background dispatch queue Scenario 2 - Support Check: Crashed: com.apple.main-thread EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000008 DeviceCheck: -[DCDevice _isSupportedReturningError:] DeviceCheck: -[DCDevice isSupported] Thread: Main thread Root Cause Analysis The DCAnalytics component within DeviceCheck attempts to insert a nil value into an NSMutableDictionary when recording performance metrics, indicating missing nil validation before dictionary operations. Reproduction Context Crashes occur during standard DeviceCheck API usage: Calling DCDevice.isSupported property Calling DCDevice.generateToken(completionHandler:) (triggered by Firebase App Check SDK) Both operations invoke internal analytics that fail with nil insertion attempts. Concurrency Considerations We've implemented sequential access guards around DeviceCheck token generation to prevent race conditions, yet crashes persist. This suggests the issue likely originates within the DeviceCheck framework's internal implementation rather than concurrent access from our application code. Note: Scenario 2 occurs through Firebase SDK's App Check integration, which internally uses DeviceCheck for attestation. Request Can Apple engineering confirm if this is a known issue with DeviceCheck's analytics subsystem? Is there a recommended workaround to disable DCAnalytics or ensure thread-safe DeviceCheck API usage? Any guidance on preventing these crashes would be appreciated.

Help get access please

Hi, is it somehow possible to access a key that was generated by the DCAppAttestService generateKey() function? I need to be 100% sure that no actor from within or outside of my app can access the generated key with the DeviceCheck Framework. It would also be helpful to get some official resources to the topic. Thank you in advance, Mike

Hi Apple team, For our iPhone app (App Store build), a small subset of devices report DCAppAttestService.isSupported == false, preventing App Attest from being enabled. Approx. impact: 0.23% (352/153,791) iOS observed: Broadly 15.x–18.7 (also saw a few anomalous entries ios/26.0, likely client logging noise) Device models: Multiple generations (iPhone8–iPhone17); a few iPad7 entries present although the app targets iPhone Questions In iPhone main app context, what conditions can make isSupported return false on iOS 14+? Are there known device/iOS cases where temporary false can occur (SEP/TrustChain related)? Any recommended remediation (e.g., DFU restore)? Could you share logging guidance (Console.app subsystem/keywords) to investigate such cases? What fallback policy do you recommend when isSupported == false (e.g., SE-backed signature + DeviceCheck + risk rules), and any limitations? We can provide sysdiagnose/Console logs and more case details upon request. Thank you, —

Dear Apple Developer Support, We are currently encountering a recurring issue with the DeviceCheck API across multiple devices in our production environment. The following error is frequently returned: com.apple.devicecheck.error 0 We would like to ask the following: What are the possible underlying causes that could lead to this specific error code (0) in the DeviceCheck API? Is there any known behavior or condition where Wi-Fi network configurations (e.g., DNS filtering, proxy settings, captive portals) could result in this error? Are there known timeouts, connectivity expectations, or TLS-level requirements that the DeviceCheck API enforces which could fail silently under certain network conditions? Is this error ever triggered locally (e.g., client library-level issues) or is it always from a failed communication with Apple’s servers? Any technical clarification, documentation, or internal insight into this error code would be greatly appreciated. This would help us significantly narrow down root causes and better support our users

Recently, we received an user enquiry regarding the inability to perform bookings for the app. After investigation, we found that the issue appears to be caused by the failure of the Apple DeviceCheck service. Based on our checks, approximately 0.01% of requests fail each day (e.g., on 26 June: 6 failures out of 44,544 requests) when using Apple DeviceCheck. Could you please assist in raising the following enquiries with Apple Support? What is the typical failure rate of Apple DeviceCheck? Are there any reliability metrics or benchmarks for its performance? How can the failures be prevented, or is there a recommended retry mechanism to handle such failures? Does the iOS version affect the performance or reliability of Apple DeviceCheck? Are there known issues or limitations with specific iOS versions? How long does the token remain valid, and when should a new one be retrieved? Does using a jailbroken device affect the functionality of Apple DeviceCheck?

We have been having very high response times in device check device validation service (https://developer.apple.com/documentation/devicecheck/accessing-and-modifying-per-device-data#Create-the-payload-for-a-device-validation-request) since 17 July at 19:10hs GMT. The service information page says the service was running in green status but that isn't the case and we currenly have stop consuming it. Is it being looked at? Are you aware of this issue? Can you give us an estimate of when it should be working correctly?

this is my monitor image that shows DeviceCheck api responding very slowly.

We have a crash on DCDevice.current.isSupported We want to try to make a serial queue to generate tokens but the side effect would be the same token would be used on multiple server API requests that are made within a few ms of each other? Is this safe or will the Apple server immediately reject the same token being reused? Can you share how long tokens are safe to use for? Here is the code we want to try final actor DeviceTokenController: NSObject { static var shared: DeviceTokenController = .init() private var tokenGenerationTask: Task<Data?, Never>? var ephemeralDeviceToken: Data? { get async { // Re-using the token for short periods of time if let existingTask = tokenGenerationTask { return await existingTask.value } let task = Task<Data?, Never> { guard DCDevice.current.isSupported else { return nil } do { return try await DCDevice.current.generateToken() } catch { Log("Failed to generate ephemeral device token", error) return nil } } tokenGenerationTask = task let result = await task.value tokenGenerationTask = nil return result } } }

we can get token but when send to verity from apple. it reture Error : {"responseCode":"400","responseMessage":"Missing or incorrectly formatted device token payload"}

Issue Summary I'm encountering a DCError.invalidInput error when calling DCAppAttestService.shared.generateAssertion() in my App Attest implementation. This issue affects only a small subset of users - the majority of users can successfully complete both attestation and assertion flows without any issues. According to Apple Engineer feedback, there might be a small implementation issue in my code. Key Observations Success Rate: ~95% of users complete the flow successfully Failure Pattern: The remaining ~5% consistently fail at assertion generation Key Length: Logs show key length of 44 characters for both successful and failing cases Consistency: Users who experience the error tend to experience it consistently Platform: Issue observed across different iOS versions and device types Environment iOS App Attest implementation Using DCAppAttestService for both attestation and assertion Custom relying party server communication Issue affects ~5% of users consistently Key Implementation Details 1. Attestation Flow (Working) The attestation process works correctly: // Generate key and attest (successful for all users) self.attestService.generateKey { keyId, keyIdError in guard keyIdError == nil, let keyId = keyId else { return completionHandler(.failure(.dcError(keyIdError as! DCError))) } // Note: keyId length is consistently 44 characters for both successful and failing users // Attest key with Apple servers self.attestKey(keyId, clientData: clientData) { result in // ... verification with RP server // Key is successfully stored for ALL users (including those who later fail at assertion) } } 2. Assertion Flow (Failing for ~5% of Users with invalidInput) The assertion generation fails for a consistent subset of users: // Get assertion data from RP server self.assertRelyingParty.getAssertionData(kid, with: data) { result in switch result { case .success(let receivedData): let session = receivedData.session let clientData = receivedData.clientData let hash = clientData.toSHA256() // SHA256 hash of client data // THIS CALL FAILS WITH invalidInput for ~5% of users // Same keyId (44 chars) that worked for attestation self.attestService.generateAssertion(kid, clientDataHash: hash) { assertion, err in guard err == nil, let assertion = assertion else { // Error: DCError.invalidInput if let err = err as? DCError, err.code == .invalidKey { return reattestAndAssert(.invalidKey, completionHandler) } else { return completionHandler(.failure(.dcError(err as! DCError))) } } // ... verification logic } } } 3. Client Data Structure Client data JSON structure (identical for successful and failing users): // For attestation (works for all users) let clientData = ["challenge": receivedData.challenge] // For assertion (fails for ~5% of users with same structure) var clientData = ["challenge": receivedData.challenge] if let data = data { // Additional data for assertion clientData["account"] = data["account"] clientData["amount"] = data["amount"] } 4. SHA256 Hash Implementation extension Data { public func toSHA256() -> Data { return Data(SHA256.hash(data: self)) } } 5. Key Storage Implementation Using UserDefaults for key storage (works consistently for all users): private let keyStorageTag = "app-attest-keyid" func setKey(_ keyId: String) -> Result<(), KeyStorageError> { UserDefaults.standard.set(keyId, forKey: keyStorageTag) return .success(()) } func getKey() -> Result<String?, KeyStorageError> { let keyId = UserDefaults.standard.string(forKey: keyStorageTag) return .success(keyId) } Questions User-Specific Factors: Since this affects only ~5% of users consistently, could there be device-specific, iOS version-specific, or account-specific factors that cause invalidInput? Key State Validation: Is there any way to validate the state of an attested key before calling generateAssertion()? The key length (44 chars) appears normal for both successful and failing cases. Keychain vs UserDefaults: Could the issue be related to using UserDefaults instead of Keychain for key storage? Though this works for 95% of users. Race Conditions: Could there be subtle race conditions or timing issues that only affect certain users/devices? Error Recovery: Is there a recommended way to handle this error? Should we attempt re-attestation for these users? Additional Context & Debugging Attempts Consistent Failure: Users who experience this error typically experience it on every attempt Key Validation: Both successful and failing users have identical key formats (44 character strings) Device Diversity: Issue observed across different device models and iOS versions Server Logs: Our server successfully provides challenges and processes attestation for all users Re-attestation: Forcing re-attestation sometimes resolves the issue temporarily, but it often recurs The fact that 95% of users succeed with identical code suggests there might be some environmental or device-specific factor that we're not accounting for. Any insights into what could cause invalidInput for a subset of users would be invaluable.