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Gemini API changelog, September 2026

Author
Google
Published
22 September 2026
Added
6 October 2026
Original
https://ai.google.dev/gemini-api/docs/changelog

Summary

Google's Gemini API release notes for September 2026. Gemini 3.8 Flash became generally available on 2026-09-02, followed by Live, TTS, and music models and an update to the Antigravity agent. Gemini 2.5 models are now restricted to existing users.

Key points

  • 2026-09-02: Gemini 3.8 Flash GA, described as the most intelligent Flash model, aimed at long-horizon software engineering, autonomous agents, and enterprise workflows.
  • 2026-09-03: Lyria 3.5 music generation GA, with full-length songs.
  • 2026-09-15: Gemini 3.8 Live GA, plus a Live Extended Thinking variant for voice apps that need more reasoning.
  • 2026-09-17: antigravity-preview-09-2026 replaces the May agent version. Built-in tool parameters are now PascalCase, and file edits use line-range replacements instead of full rewrites.
  • 2026-09-18: Gemini 2.5 models are limited to existing active users; new projects should use 3.5 Flash-Lite or 3.8 Flash.
  • 2026-09-22: Gemini 3.8 Flash TTS and Flash-Lite TTS GA, with voice design and consent-verified voice replication.

Why it matters

This is the primary source for the Gemini 3.8 Flash GA date, which earlier notes only recorded as reported. It also marks the start of Gemini 2.5's retirement.