Comment by stavros

I've been using Deepseek 4 Pro (instead of Sonnet 4.6) as the developer LLM (Opus is the planner) and it's been great. Not super fast, with all the reasoning, but has been writing good code, and I think I paid $5 so far (whereas with Sonnet I'd have run out of the weekly limits on Max for weeks now).

Definitely recommended, though it's crucial that you have GPT 5.5 review the code afterwards.