This is such a bad faith argument. How long would it take a dev or a team of devs to do this with the same architecture and test suite? A hell of a lot longer than 6 days..

Exactly this.

I am not sure why people sound so astounded, to be honest. This has been my frank experience of the agentic tools both Codex and Claude since about December.

When given the right constraints this kind of thing is entirely conceivable.

However the important question not being answered here is: does anybody working on it have a full understanding of what has been built?

My experience having constructed similar types of projects using these tools is yes, you could do this in a week or two but now you'll have a month or two of digging through what it made, understanding what was built, and undoing critical yolo leaps of faith it made that you didn't want.