Sonnet 4.5 is way worse than Opus 4.1 -- it's incredible that they claim it's their best coding model.

It's obvious if you've used the two models for any sort of complicated work.

Codex with GPT-5 codex (high thinking) is better than both by a long shot, but takes longer to work. I've fully switched to Codex, and I used Claude Code for the past ~4 months as a daily driver for various things.

I only reach for Sonnet now if Codex gets cagey about writing code -- then I let Sonnet rush ahead, and have Codex align the code with my overall plan.