I've just written a blog post in which I describe a research-level problem (due not t Erdos but to Melvyn Nathanson) that ChatGPT 5.5 Pro recently solved. With a guest section by Isaac Rajagopal, on whose work ChatGPT built.
https://gowers.wordpress.com/2026/05/08/a-recent-experience-with-chatgpt-5-5-pro/