Yes, you can use your Codex subscription with Pi without any limitations. It supports Codex out of the box. You may need to install extensions for things like tracking usage and limit resets though. Pi only provides basic Codex integration.

Anthropic's subscription is the one that has historically been tough to use with other harnesses, where they have (had?) technical safeguards to ensure your subscription usage was limited to Claude Code CLI, with third party harnesses often implementing workarounds or faking it to use your Claude.ai subscription. Nowadays Jetbrains Air does officially allow using your Claude.ai subscription.

But OpenAI's subscription has seemingly always been available to use in other harnesses without trouble.

Yes. You can and it's easy to test. I'd also encourage you to try local models with it as well.

Pi/opencode apparently make 10% already of all traffic already:

https://manifest.build/blog/chatgpt-plus-tokens-third-party-...

This, IMO, is one big selling point of Codex for me. The are much more accepting of usage outside of the Codex harness, and make it trivial to set up.

There is no stick unlike Anthropic (along with insisting on signing commits and "don't abuse the robot" the reason I started to use OpenAI instead of Anthropic --- not that I am under the illusion they are any less evil overall) but I think now there is starting to be a carrot towards Codex usage since there sessions are "cached forever". I assume if you use Pi you get 12 hours of cache instead.

Yes and no. Any harness can use the subscription but must go through `claude -p` mode, which is more limited.

Using your subscription in 3rd party tools is explicitly allowed for Codex, and disallowed but not really enforced for Claude. There are extensions for Pi that allow you to log in with your Claude credentials, Codex is iirc even built-in.

Yes, it is allowed and supported normally by pi and others.

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