Unfortunately my experience hasn't been that great with reporting feedback. I have another pending issue that clearly is a bug, also confirmed by others, that still hasn't been resolved. It would be better to find a workaround but I'm also failing in finding one...

I've just managed to make my app work correctly again using the following code. It uses deprecated functions (as of 10.9) so I don't expect those functions to disappear soon. Not ideal, but at least it does not result in a weird user experience. (OSStatus)makeApplicationFront:(NSRunningApplication*)application {     if(!application || application.processIdentifier == -1) {         return procNotFound; // Previous front most application is nil or does not have a process identifier.     }     ProcessSerialNumber process;     OSStatus error = GetProcessForPID(application.processIdentifier, &process); // Deprecated, but replacement (NSRunningApplication:activateWithOptions:] does not work properly on Big Sur.     if(error) {         return error; // Process could not be obtained. Evaluate error (e.g. using osstatus.com) to understand why.     }     return SetFrontProcessWithOptions(&process, kSetFrontProcessFrontWindowOnly); // Deprecated, but replacement (NSRunningApplication:activateWithOptions:] does not work properly on Big Sur. } Hope it also helps you.

I'm facing the exact same issue. Tons of messages like yours. Initial sync of a dataset containing ~10.000 records (and ~100MB on disk) takes 15 minutes while the CPU hits over 100%. Honostly, it makes me reconsidering the choice to use CloudKit as the cloud-backed datastore. I talked with several engineers from Apple, both during WWDC as well as DTS, but didn't got anything useful. Hoping this thread is going to be a push in the right direction.