The bug that only appeared when someone else used it

I tested my vibecoded project for two days before showing it to anyone. Clicked everything, tried every button, felt confident.

The first person who used it broke it in four minutes.

Not because they were careless. Because they did something I had never thought to do. They typed a name with a space in it. They hit back instead of close. They opened it on a phone. None of it was exotic, it was just not my hands.

That is the thing about building fast with a model. You and the model share one imagination, and it is a narrow one.

You describe the happy path, the model builds the happy path, and you both quietly agree that the edges do not exist.

Now I get one person to use anything before I call it done. Not to test it, just to use it, while I watch and say nothing.

The things they do that I never would have are usually exactly the things that were broken.

Do you test your own work, or do you need someone else's hands? And has a five minute session ever found something two days of testing missed?