I think I saw o3 hallucinate more in a single day of heavy use then I saw o3-mini do in a month.

That said: so far, I'm putting up with it because o3 is smart.

What does that mean? Smart?

It means some of those hallucinations works. So if you build a test harness hallucinations can let you solve problems you couldn't solve without them.

That test harness can be a human checking the results, it is more work for the human but it will solve more problems than without the hallucinations.