How do you transition a project from quick AI prototype to maintainable software?

I managed to build and validate a simple habit tracking app in just a few days using vibe-coding. The initial speed was incredible and helped get real user feedback fast.

However scaling past that baseline turned into a nightmare. The AI generated messy inline styles and messy state handling across components forcing me to spend three weeks refactoring everything before I could ship one new update.

If you use AI to prototype quick what is your signal that it's time to step back and do a manual rewrite?