Four sentences in the API release notes. That is how the most important changes sometimes arrive.
If you started a project on Gemini 2.5 and have not shipped it yet, the check is today.
Fact
The facts: on 18 September 2026 Google wrote in the Gemini API release notes that it is limiting access to the 2.5 models to users who have actively used them in the past. The models are not deprecated and will continue to be served through the API until further notice. For new projects Google recommends its latest models - 3.5 Flash-Lite or 3.8 Flash. As the reason, the company cites reliable performance for everyone and maintaining enough capacity for both legacy workflows and new applications.
The word “capacity” is the key. The company does not say the models are weak or unsafe. It talks about reliable performance and capacity. Our inference: 2.5 was not closed for quality but for space.
What is unclear is who exactly “has actively used them in the past”. A new API key in the same account? A new project in the same organisation? The note does not say. If you rely on 2.5 for something you are about to bring up on a new key, test it before it becomes urgent.
“Until further notice” is not a deadline. Only a promise that there will be a notice.
Moving to 3.8 Flash is not changing one name in the code. A different model gives different answers to the same prompt, and everything you tuned by hand has to be checked again.
Official primary sources
Google AI for Developers - Gemini API release notes, entry of 18.09.2026The visual is generated code-art, no third-party images.