I don't know if you've tried Chatgpt-5.2 but I find codex much better for Rust mostly due to the underlying model. You have to do planning and provide context, but 80%+ of the time it's a oneshot for small-to-medium size features in an existing codebase that's fairly complex. I honestly have to say that it's a better programmer than I am, it's just not anywhere near as good a software developer for all of the higher and lower level concerns that are the other 50% of the job.

If you have any opensource examples of your codebase, prompt, and/or output, I would happily learn from it / give advice. I think we're all still figuring it out.

Also this SIMD translation wasn't just a single function - it was multiple functions across a whole region of the codebase dealing with video and frame capture, so pretty substantial.

"I honestly have to say that it's a better programmer than I am, it's just not anywhere near as good a software developer for all of the higher and lower level concerns that are the other 50% of the job."

That's a good way to say it, I totally identify.