I don't know about frontier, I code nowadays a lot using Opus 4.5, in a way that I instruct it to do something (like complex refactor etc) - I like that it's really good at actually doing what its told and only occasionally do I have to fight it when it goes off the rails. It also does not hallucinate all that much in my experience (Im writing Js, YMMV with other languages), and is good at spotting dumb mistakes.

That said, I'm not sure if this capability is only achievable in huge frontier models, I would be perfectly content using a model that can do this (acting as a force multiplier), and not much else.