What ground rules do you set with AI coding tools to stop project bloat?

Had a working app up in a weekend thanks to AI, but by month two, navigating the project turned into a headache. The agent kept generating new helper files and duplicate utility code instead of reusing what was already there.

Now I force the tool to keep a clean structure file and double-check file names before letting it generate new code. It slows down the speed a bit, but saves my sanity on weekends.

How do you manage that transition from rapid prototyping to actually maintaining readable code long term?