Apple's ASAuthentication's. authorizationController:didCompleteWithAuthorization: works just fine during the Passkey Authentication process. The rawAuthenticationData value attached to the ASAuthorizationPlatformPublicKeyCredentialAssertion credential consists of exactly 37 bytes like the WW3 Section 6.1 specification requires. In the case of Passkey Authentication it is only 37 bytes without either attestedCredentialData nor extensions. But during Passkey Registration process, the ASAuthorizationPlatformPublicKeyCredentialRegistration credential's rawAttestionObject does generate attestedCredentialData. Believe it or not, my error was generated during the creation of the JSON dictionary to be posted during authentication. I mistakenly assigned the Base64URL authenticationString to the signature property and the Base64URL signatureString to the athenticatorData property. Very stupid typo that cost me about two weeks of debugging work..

So here is the answer to my own question... I found it more reliable to use NSURLSessionDownloadTask for the purpose of uploading a file to AWS S3. While I remember reading in the "docs" that one could not use NSURLSessionDataTask when operating in background using BGTaskSchedule. I do not recall reading that one could not use NSURLSessionUploadTask. But, Indeed that seems to be the case.... I hope this helps someone else out there.

[quote='830495022, DTS Engineer, /thread/777033?answerId=830495022#830495022'] I think the issue here is that you're using the background session (and discretionary=YES) and you should just use the default. You're basically telling the system "I don't really need this right now" and that's exactly what it's doing. The background session is useful when you want want to schedule/defer larger transfers, but for small transfers like this it's creating more problems than it solves. [/quote] Kevin, I reread your post and it prompts a couple of questions. Don't use a background session Do I understand correctly that you recommended I NOT use a background session for a BGProcessingTask? Does this apply also to BGAppRefreshTask as well? .earliestBeginDate Are you recommending that I disregard trying to set this for some off hour as the system will do that anyway? Rescheduling If the BGTask does not complete, should I reschedule? Or will the system automatically reschedule if setTaskCompletedWithSuccess: is set to NO? You have been most helpful, thank you!! [quote='830495022, DTS Engineer, /thread/777033?answerId=830495022#830495022'] Elliott [/quote]