macOS, Xcode, Ventura: When CloudKit Stops Syncing

(This is for future reference, when this sort of problem arises again.)

Last spring I started working on a pair (macOS, iOS) of personal utility applications. They relied on CloudKit storage. For months they worked well together. Then, as soon as I updated to macOS 13 Ventura, they stopped syncing.

Symptoms

I fired up Xcode to try to diagnose the problem. But when run under Xcode, the app synced without issue.

I made an archive build for the macOS run destination. When I ran the resulting app, the problem returned.

/Application/Utilities/Console showed messages for the archive build that indicated a missing entitlement, one for reading a CloudKit preferences file. But I couldn't figure out where the file resided.

I turned off App Sandbox for the app. The resulting archive build was able to sync again.

Solution

Another user of the Apple Developer Forums had encountered the same problem. A couple of weeks later, they posted the solution:

Huh. I could have sworn I added that framework when I created the project as a CloudKit-hosted, Core Data project.

Sure enough,CloudKit.framework was not in the list of frameworks.¹

I added it, and reverted the app to use the App Sandbox. Now it is sycing successfully. Many thanks to mjmsmith!