I have updated Feedback FB18158747 with the "concrete use case"

Ziqiao, Thanks for the follow-up. I am not sure to understand. Are you saying that Apple does not care about breaking existing apps, does not document the changes, and make changes without any prior notice? Worse, Apple is doing a push back with the usual trick "tell me your concrete use case"? This is disrespectful. Please revert the changes. If you want to make changes, deprecate the API and add new ones. The bare minimum is to provide a stable (anonymous) identifier for all participants to a zone sharing, including the owner. How can you manage the users, if not. Does it exist? I can't believe Apple is breaking apps intentionally.

I have exactly the same issue! CloudKit sharing is totally broken on iOS 26. The app can't accept invitation When fetching a CKShare, CKShare.owner.userIdentity.lookupInfo?.emailAddress is always empty, even after inviting a user. I filed a Feedback under FB18158747

Same here

I have exactly the same issue....