Is your app sandboxed? If so, the only way is to show a NSOpenPanel and ask the user to select the Documents folder (or any other folder). Showing an open panel and asking the user where to put the files is the best option even if the app is not sandboxed. Please don't litter the Documents folder with random things by default.

https://developer.apple.com/documentation/security/accessing-files-from-the-macos-app-sandbox

The destination folder should be configurable, not hard-coded to the Documents folder.

Like the message said, NSKeyedUnarchiver will require a complete list of all possible types for better security in the future.

Because NSArray can contain only objects, and NSNumber is the class that has been used to box bools, integers, floats, and double since a long time ago.

Are you subdividing some work between different thread? The M4 Max has more cores, and it might expose some multi-threaded issues that aren't visible with fewer cores. Or there is some random out of bounds writing somewhere that for some random reason doesn't cause a crash on your Mac. Try to run it address sanitizer first, and then with thread sanitizer.

Everyone and their dog are vibe coding slop and sending it for review. And this is the result.

I can't speak for Apple, but they seldom give any official reassurance. If they wrote that Rosetta 2 will be around for virtualization and for some older games, that's all it will work for. If your app is not a game, it's time to make a native version, everything else is just delaying the inevitable.

I think you are misunderstanding the goal of GPTK. The D3DMetal library is not meant to be shipped with your game, it's just an environment to do a preliminary test. Or am I misunderstanding your question?

I don't know, but an actual port will require a manual conversion to Metal, and automated shader conversion maybe, and manual ones for some shaders, so something not working in D3Metal will make little difference.