Me too. Claude Opus 5's English is insufferable. Opus 4.6-4.8 was more reasonable.

I've moved to Codex 5.6-Sol. Much saner English, much better at execution, and gets stuff done in a matter-of-factly kind of way (Claude Code is a mess these days -- it gets things wrong and goes around in circles).

But I'm harness agnostic and am not locked in. I just keep my issues in Kata Tracker (https://www.katatracker.com/) and switch harnesses/model when I need to.

Being loyal to a particular model/harness seem unwise to me.