Google is swapping older Gemini Flash models for newer ones automatically, like a mechanic who upgrades your parts without ringing first
By Brett Gavaghan, Founder of Adaptd ·
On 8 October Google deprecated Gemini 3.7 Flash and 3.5 Flash in its API and started sending their requests to newer models. An older Deep Research agent shuts down on 23 October.
The short version
- Google deprecated Gemini 3.7 Flash and Gemini 3.5 Flash in the Gemini API on 8 October 2026.
- Calls to those models now go to Gemini 3.8 Flash and 3.6 Flash automatically, and an older Deep Research agent shuts down on 23 October.
- If a tool your business uses was built on the Gemini API, ask the developer to test it on the newer model.
If someone built your business a quoting tool or an email sorter on Gemini, it may have had a brain transplant on 8 October. Nobody sent a card.
What changed in the Gemini API?
Google's Gemini API changelog says Gemini 3.7 Flash is deprecated and replaced by Gemini 3.8 Flash, and Gemini 3.5 Flash is replaced by Gemini 3.6 Flash. Requests that still use the old model names are routed to the newer models automatically.
Google also deprecated its deep-research-pro-preview-12-2025 agent, which shuts down on 23 October 2026. Developers can move to a faster preview version or a 'max' version built for more thorough research.
Who does this affect?
The change affects businesses whose tools or automations call the Gemini API directly, usually something a developer or agency built for them. The routing happens in the API, so nothing breaks overnight.
The catch is that a newer model can word things differently, lay out answers differently or follow your instructions a little differently, and the tool won't mention that anything changed. Technically correct, slightly unfamiliar.
What should your business do about it?
Businesses with a Gemini-powered tool should ask whoever built it which model it calls, then test it on the newer one and update the model name.
My advice: keep a small set of real examples, such as ten enquiries and the replies you were happy with, and re-run them whenever the model changes. If anything relies on the old Deep Research agent, move it before 23 October or it simply stops. Automatic routing is better than an error message, but software, eh? Even the parts you never see get a service you didn't book.
Wondering what this means for your business?
That's exactly what the discovery call is for.