When I first started playing with lean I accidentally defined a group in such a way that it was reduced to triviality. It had one object in it, so everything in the group was trivially equal to everything else. It was not the group that I was trying to prove something about, but the proof went through.

It was too easy, so I double checked my definitions, but it is quite easy to do something like that. And Claude does things like that quite frequently.

I am going through the exercise right now of trying to get Claude to formalize a published paper and it is a _struggle_ to get it not to take shortcuts or prove approximations of the paper’s theorems and then tell you it’s done.