Pick the relay by API shape, not by marketing language
A reliable ChatGPT API proxy should accept familiar OpenAI-style requests with minimal adjustment. In practice, the most useful criteria are: a stable /v1 base path, predictable streaming behavior, a model list that matches your app’s assumptions, and response payloads that preserve token usage and error details. If the service is positioned as a relay, you want it to feel boring in the best way: the request goes in, the answer comes back, and your code does not need special cases.