I contacted OpenAI support, and their AI support agent told me the following:
Thank you for sharing the screenshots. I see that you have successfully added GPT-5 and related models to your project’s “Allowed models,” but they are not available for selection when creating or editing an Assistant. Here’s what you need to know:
- Even if GPT-5 is allowed in your project settings, model availability in the Assistants API is rolling out gradually. Not all users and regions have access at the same time.
- For most users, GPT-5 will become available in the Assistants API as part of the phased rollout. You may see it appear without additional action when your account is included.
- If you see GPT-5 available in Playground or API, but not in Assistants, this is expected until the rollout is complete. What to do next:
- Keep checking the model dropdown when creating or editing Assistants—once GPT-5 is available for your account and region, it will appear.
- No further setup is required on your end since you have already allowed the model. Let me know if you have more questions or need help with other OpenAI features!
It seems we’ll have to wait.