It can come up with a brand new sentence that hasn't been written before. Does that count?

Maybe you mean a solution to a textbook math/physics problem, it most likely would be able to solve that too with tool use.

Or maybe you mean solving something like the Riemann Hypothesis?

I'm using Hevy currently and its pretty good. But it just so happens that I learnt about this app called Liftosaur today, where I read about the 5/3/1 program too. And then seeing it here, maybe you should try Liftosaur?