I want to make an agent application in SwiftUI.
It would be setup as a login item and have no dock icon and display no windows on start.
I used AlertScene at first, but it is unavailable on macOS 14 which is my deployment target.
Is there a way to have no windows or I'd better use AppKit for that?
I think you want to use something like SMAppService.
Are you saying you don't ever want a UI, or that no UI will be displayed when the app launches? So you'll still have some sort of Preferences UI somewhere? Then yes, use SwiftUI and Swift.
Investigate SMAppService.