Hey, this is the same bug that’s discussed in GPT-5.5 BYOK not working. For the GPT-5 family, Cursor converts the request body to the Responses API format input instead of messages, but it only rewrites the URL to /v1/responses for the native OpenAI provider. With Override OpenAI Base URL, things get out of sync, and the request either breaks or doesn’t reach your backend at all. gpt-5.4 and gpt-5.4-mini go through a different path and work.
This is a known issue, it’s being tracked, and there’s no ETA yet. Subscribe to that thread for updates.
Workarounds:
- Stay on
gpt-5.4orgpt-5.4-miniwith BYOK. - Use
gpt-5.5without Override OpenAI Base URL.
On your second question about the Codex auth integration, that’s a policy or ToS topic, so I can’t comment on it on the forum. Email [email protected] with details of what the integration does and the team can give you a clear answer based on the guidelines.