Since Google (and @Logan_Kilpatrick) continue to ignore this thread and refuse to clarify anything related to their new apparent policy of redirecting clearly dated endpoints, several of us have been forced to investigate alternative solutions on our own time.
I wanted to share a quick update about what we’ve found that might help others whose applications were broken by Google’s backdoor model switch (now that even the exp endpoint has been disabled on the Gemini API per Logan’s announcement).
The good news: We’ve confirmed that the original March 25th checkpoint IS still accessible, but only through the Vertex AI API, not the Gemini API.
The response object from Vertex does give you a model name identifier that seemed to confirm there is NO redirect in place, but instead of trusting it (since that is what this whole issue is about), I decided to do research to make absolutely certain.
Using a fixed seed number and temperature=0 in the API for as deterministic an output as currently possible, we ran tests comparing the output “signatures” (content, logprobs, token counts) of different dated endpoints on Vertex AI. Our findings:
-
NOT Redirected on Vertex: On Vertex AI, the
gemini-2.5-pro-preview-03-25endpoint produces completely different output signatures than thegemini-2.5-pro-preview-05-06endpoint. They are definitely NOT the same model. -
The
gemini-2.5-pro-exp-03-25endpoint on Vertex (when you can access it) produces output signatures IDENTICAL to the original March 25th model we all came to rely on. However, this endpoint appears severely rate-limited.
The result you, as a dev, care about: The preview-03-25 endpoint on Vertex is NOT redirected to 05-06, like on the Gemini API. exp-03-25 is rate-limited but confirmed to be IDENTICAL in signature to preview-03-25. Therefore, developers who need to use the original March model can switch to Vertex AI as a temporary solution, confidently using preview-03-25 in place of the exp endpoint.
@wowitsjack, @Ed_Godshaw - if you switch your apps to Vertex AI instead of Gemini API (straightforward in most SDKs), this could be your path back to stability until Google either fixes the 05-06 model issues or (hopefully) provides an official way to access the original 03-25 model again.
Is this ideal? Absolutely not. We shouldn’t have to do detective work to find out where Google hid a model that was working perfectly. The breach of trust regarding dated endpoints remains unaddressed, and Google’s continued silence on this thread speaks volumes.
But at least there’s a potential path forward for those whose applications are currently broken due to this sudden switch. I hope this helps at least one frustrated and confused developer out there.