How do you use Codex and Claude both?

I see people praising Claude a lot here. I'm mostly get amazed by the work Astra does. And people say Opus is even more amazing. Which makes me wonder. But I have a whole setup in Codex. So if I try Claude I'll try both $20 packages. But how do you use both in the same project exactly? Sorry for the newbie question but do you just give Claude the direction of the Codex project and be like "understand this" or something? Don't Claude needs context? Is it efficient?