I'm currently reviewing the various DCError cases defined in Apple’s DeviceCheck framework (reference: https://developer.apple.com/documentation/devicecheck/dcerror-swift.struct). To better understand how to handle these in production, I’m looking for a clear breakdown of: Which specific DCError values can occur during service.generateKey, service.attestKey, and service.generateAssertion The realworld scenarios or conditions that typically cause each error for each method. If anyone has insight on how these errors arise and what conditions trigger them, I’d appreciate your input.

Hi there, We're implementing Apple's DeviceCheck App Attest for production iOS authentication. The public documentation defines DCError cases but doesn't specify which errors are expected per API method or recommend retry/remediation strategies. We need Apple's guidance to implement robust, production-aligned error handling before rollout. 1. Error Surface per API Method Question: Can you confirm the complete, officially expected set of DCError values for each method? We understand the following errors are possible across App Attest APIs: invalidKey invalidInput featureUnsupported serverUnavailable unknownSystemFailure Specifically, please confirm which errors can occur for: DCAppAttestService.generateKey() DCAppAttestService.attestKey(_:clientData:) DCAppAttestService.generateAssertion(keyID:clientData:) Are there any additional undocumented or edge-case errors we should handle? 2. Retry Strategy & Remediation Matrix Question: For each API method and error code, please help us with proposal around which errorCode is retriable, whats the remediation pre retry, retry cap and backoff strategy: Kindly also help with errors that are not covered here: Specific sub-questions: invalidKey handling: When this error occurs: Should the app delete the key and call generateKey again? Or should it fail the entire flow? serverUnavailable handling: Should we retry immediately, or wait before retrying? Is exponential backoff recommended? What's the recommended max retry count? Backoff strategy: Which errors (if any) qualify for exponential backoff? Recommended base delay, max delay, and jitter approach? When should we give up and fail the request? unknownSystemFailure: Is this retriable or should we fail? Any known causes or mitigations? 3. Simulator Testing Questions: Simulator API behavior: Can App Attest APIs be called normally on iOS Simulator? If not, is there a way to simulate for testing. Do they complete successfully with simulated attestations, or do they fail? Thanks, Nirekshitha

We generate Secure Enclave keys via SecKeyCreateRandomKey with kSecAttrTokenIDSecureEnclave on macOS. We need to prove to a remote server that the key is genuinely hardware-bound, not a software key claiming to be one. Is there any API on macOS for an app to obtain an Apple-signed certificate or attestation statement for such a Secure Enclave key, similar to how ASAuthorizationProviderExtensionLoginManager.attestKey() works within Platform SSO but available to general apps? Or other possible workaround for this? Thank you!

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.