Don't you think I've fixed bugs and kept the app stable during the 300 hours I have been working on it?

That's why I can say with full confidence that it works.

I doubt it will magically all fall apart the moment an external user touches it, or that I will expand the scope dramatically in the near future.

The agent harnesses are an interesting topic. I believe they have large teams shipping a ton of changes weekly. In that environment, is it realistic to expect rock solid software with such a feature set to be developed in a few months and shipped to 10M users?