In my experience AI can write _something_ from scratch, but often edge cases won't be handled until I go through and read the results or test it. Usually when I'm writing by hand I will naturally find the majority of edge cases as I go. By the time I've read through the results and fixed said edge cases, I usually would have been faster just doing it myself.
My experience is the opposite: AI takes too many edge cases into account and guard against even the most unlikely thing. The upside is that it often handles edge cases that I either didn't think about or was too lazy to implement.
I can with full confidence say that the code AI writes is more robust and safe than if I would have done it myself. The code definitely becomes more bloated though.
It also loves to add edge case handling where it's not needed and in poorly chosen places
This has been my experience thus far. Yes, a complete prototype can be made, but.. you don't really know until you read the code and test it. Just yesterday, small things came up in terms of Qt screen focus that wouldn't have come up otherwise save for initial testing.
I think, and I recognize it is mostly against the 'agentic' push, I will stick with slow iteration.