Since being forced to upgrade to Sonoma (Ventura 13.6.1 totally bricked my M1 MBP), IMDPersistenceAgent, imagent and cloudd run constantly at 35 - 105 %CPU. Unchecking Messages Prefs>Messages in the Cloud stops 'em cold, but what am I losing?
You lose the synchronization of iMessages across all your devices. You didn’t say how long the processes had been running at higher than normal levels, but it’s not unusual for synchronization/propagation activities to run at a higher than normal level for even several days after a major OS update. Apple also notes about this particular feature “When you first turn on Messages in iCloud, it may take some time for all of them to appear on each device.”
First noticed it two or three days ago. I’ll let them run over the weekend and revisit the thread next week. Thanks Jeff~