Vibe coding feels faster right up until your project becomes big enough to remember its own history

I was very productive in the first 5 weeks of a client project. I made prompts, added features and the agent shipped it in a week and demos were completed every Friday. I started wondering why I spent years typing code by hand like a medieval scribe. Then on 6th week the client asked a question about a system with my name on every commit: why do the totals round the way they do? and I had no idea and then I spent the evening debugging my own codebase (Basically Git-blaming myself). I've been building software for other people for eight years and whatever the contract says, the actual job has always been answering for the code later. The code gets written maybe ten times faster now and I read at the same speed I did last year. So the project didn't get hard because it got big rather the understanding of it turned into the main job. On client work it goes past my own understanding too, since whoever they hire after me will have questions and those questions will have my name attached. I had been trading codebase literacy for speed without writing the trade down anywhere. What I do differently now is that I read the agent's writing while they were writing and I log the reasoning behind decisions. I also write a line item for the time I read the quotes.