>that looks bulletproof to us

And it pretty much is most times. For us. But indeed I did run into the "why would they use it like that though" scenario, where it fails. So I have to patch that usecase. At which point I go all "ok now it's really done" until another fringe usecase pops up and so on and so forth. And I did think about how sure I was it was bulletproof, humbling moment.