Interesting optimisation, curious if you are willing to divulge which of the optimisation steps the LLM came up with, versus which it needed human assistance with?
My experience is that Claude Opus 5 and 5.5 are very good at implementing optimizations, reasonably good at suggesting approaches to try, and not very inclined to identify slow runtime as a problem. It tends to go for simple implementations until I ask about speed, which is certainly conventional wisdom for development.