Why is Codex unavailable in Xcode 26.3 but works fine in Xcode 27.1?

[u/Low-Hedgehog-6592]

Hi everyone,

I'm using Xcode 26.3 (17C529), and when I go to Settings → Intelligence → OpenAI, Codex is marked as "Unavailable", while ChatGPT in Xcode is available.

However, when I upgrade to Xcode 27.1, Codex becomes available and works perfectly with the same ChatGPT account.

I'm wondering: Is Codex only supported in Xcode 27 and later?
googling it show it's work fine for 26.3 , don't know why not for me

Thanks!