I prompted Codex 5.5 to one shot something where I wanted the design to have a pluggable decision module. I gave it a few examples of the kinds of inputs and actions I expected. I did not constrain it beyond that high level of what I wanted. The design it came up with was very good. Easily on par with what any senior engineer at big tech would. And cleanly decoupled in a way that would make future refactoring simple. I was damn impressed.