com.apple.devicecheck.error 0 - DeviceCheck

Question

Created May ’25

Replies 5

Boosts 1

Participants 4

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

Answered by DTS Engineer in 899698022

I’m not able to give you a definitive list of conditions that cause the DCErrorUnknownSystemFailure error, but I will note that, in most cases, the code that returns this error also logs more detail into the system log. So, if you can reproduce the problem, or you can get a log snapshot or sysdiagnose log of the problem occurring, you can search the system log for log entries in the com.apple.devicecheck subsystem.

See Your Friend the System Log for more about the system log.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Answer 1

FlyingWings OP

Sep ’25

Hi,

I encountered the same error after upgrading to iOS 26 and I would like to gather more information. We manage to call the API properly during the initialization of our application but after an application restart it returns this error.

The API

DCAppAttestService.shared.generateAssertion(keyID, clientDataHash: clientDataHash)

returns

com.apple.devicecheck.error error 0

Did you manage to find more information about this error code ?

Thanks.

Answer 2

aalexaa OP

1w

Did you reach any conclusion on this one? We're also running into it but there is very limited documentation around DCError.unknownSystemFailure or the resolving of it.

Answer 3

DTS Engineer OP

Apple

1w

Recommended

I’m not able to give you a definitive list of conditions that cause the DCErrorUnknownSystemFailure error, but I will note that, in most cases, the code that returns this error also logs more detail into the system log. So, if you can reproduce the problem, or you can get a log snapshot or sysdiagnose log of the problem occurring, you can search the system log for log entries in the com.apple.devicecheck subsystem.

See Your Friend the System Log for more about the system log.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Answer 4

aalexaa OP

4d

Thanks for the updates. To follow up from our side: we are an SDK provider, and we cannot reproduce this issue locally unfortunately.

Based on our production telemetry:

It occurs most frequently during DCAppAttestService.shared.generateAssertion. Because generateAssertion runs locally on-device, this indicates a local system or state failure.
It persists on the same devices over multiple days, meaning it does not self-recover over time.

We are looking for guidance on how to recover from this state:

Would clearing the stored key and regenerating a new one (generateKey + attestKey) unstick affected devices?
Are there recommended steps for users/integrators, such as restarting the phone or updating the iOS version?

If anyone has successfully resolved this in production, any insights would be appreciated.

Answer 5

DTS Engineer OP

Apple

3d

The ideas you’ve suggested seem reasonable enough, but I can’t recommend a mitigation strategy without more information about the problem.

My advice is that you work with one of your clients to capture a sysdiagnose log from an affected user. Alternatively, if folks are unwilling to share a sysdiagnose with you, you could have them attach that log to their own bug report, give you the bug number, post it here, and then I can take a look.

I talk more about these ideas in Using a Sysdiagnose Log to Debug a Hard-to-Reproduce Problem.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"