Within Spec Driven Development style coding for me Claude Sonnet 4.5 was the game changer and Mistral is I believe at that level already. GLM is allegedly also on par with even some of the Opus models, so if the US vendors would vanish tomorrow, there would be alternatives. Would I miss Opus 4.8 and the Claude Code harness? of course I would! But the world wouldn't stop.

What I am trying to get at is that the frontier is great, but you can be fine with less as well.