Plug in an iPhone. Run one command. The app is running on the device.
xcrun devicectl device install app --device 00008110-XXXX MyApp.app
xcrun devicectl device process launch --device 00008110-XXXX com.example.MyApp
That's the native Swift feedback loop for physical device testing. No TestFlight. No App Store Connect. No waiting for processing. The app goes from Xcode build output to running on hardware in seconds.
A TypeScript type error tells you exactly what's wrong: "Type 'string' is not assignable to type 'number'" with a file path and line number. You read it, you fix it, you move on.
A Swift 6 concurrency error tells you: "Sending 'self.gameState' risks causing data races." Good luck figuring out which thread is the problem, which actor boundary you crossed, and whether the fix is @MainActor, Sendable, or restructuring your entire data flow.
Different platforms produce fundamentally different categories of errors. When AI is writing the fix — whether it's an automated agent or a copilot suggestion — the error landscape determines whether the fix takes one attempt or five.