I’ve seen going very successfully using both codex with gpt5 and claude code with opus. You develop a solution with one, then validate it with the other. I’ve fixed many bugs by passing the context between them saying something like: “my other colleague suggested that…”. Bonus thing: I’ve started using symlinks on CLAUDE.md files pointing at AGENTS.md, now I don’t even have to maintain two different context files.

Other symlinks one can do: QWEN.md, GEMINI.md, CONVENTIONS.md (for aider).