Thanks for the correction, these details matter. Let’s go point by point.
-
Subscription status. On our side, the account linked to this report shows as Free cancelled, not Pro. That directly affects behavior since BYOK for Agent and Edit requires an active paid plan. Since checking a subscription status mismatch isn’t really a forum topic, please email [email protected] and the team will verify your account status. Until your status is confirmed as active Pro, some of the symptoms could be explained by the free tier gate, which the client can show as rate limit or API unavailable.
-
Built-in GPT-5.5 plus BYOK. Got it, you didn’t create a custom model, so the name collision idea doesn’t apply. I’ll drop that.
-
Your suspicion about falling back to the official endpoint. That’s reasonable. GPT-5.5 has known behavior where even with BYOK set up, the request may not go to your Override Base URL and instead gets served through Cursor infrastructure or sent to the official endpoint. That would explain Invalid API key or Unauthorized since your key is valid for your proxy but gets rejected if the request goes somewhere else. We’re aware of this issue and tracking it, but I can’t share an ETA right now. Related threads: Requests are sent to incorrect endpoint when using base URL override and GPT-5.5 BYOK not working
To tie your specific case to this, please send a Request ID from one of the failed requests plus an approximate timestamp. You can find it via the chat menu top right corner > Copy Request ID. Note that if Privacy Mode is enabled, the Request ID may be unavailable or limited. With that, we can check where the request actually went.
Let me know your subscription status and share the Request ID, and we’ll continue from there.