AI is a rare example of self-improving (recursive) technology. What are other examples similar to that in principle? Do they even exist?

I think almost all tool making engineering is self-improving. You can’t make a modern screw making machine without more primitive screws, and you need a less sophisticated screw making machine to make that.

I definitely agree, but would say this is more "weak recursion" than strong one because you still need human intervention for that self-improvement, no?