Hello, upgrade to Xcode 26.1, this version may help you solve this problem. After upgraded Xcode, it works to me.

Hi, I'm seeing the same thing. I want to use AlternateAppIcon, so I added 7 AppIcon-x.icon files to my project in Xcode 26, and these icon files are created by icon composer software. And I also see the AssetCatalogSimulatorAgent(370% CPU). Finally, it took 30mins to build succeeded project. Very slowly. What should I do?

Now, I use Xcode 16 official version(downloaded from App Store) has the same problem. My App archived from Xcode 16 can not see Widget in iOS 15 device, but iOS 16/17/18 runs well. What should we do can fix this problem? Maybe it's Xcode 16 's bug.