You can use your Codex plan with it. OpenAI endorsed it several weeks ago, as far as I remember. That could change, however, but now seems safe.

You can use your Claude or Gemini plan with it too for now, though Anthropic and Google have made it clear this is a ToS violation.

Pi makes GPT-5.3-Codex act about on par with Claude easily.

There's something in the default Codex harness that makes it fight with both arms behind its back, maybe the sandboxing is overly paranoid or something.

With Pi I can one-shot many features faster and more accurately than with Codex-cli.