This timeline lists frontier model releases from OpenAI, Anthropic, Google, SpaceXSI (formerly xAI), Meta, Mistral AI and Moonshot AI, newest first. Every date comes from the lab's own announcement, model docs or API changelog, linked on each entry. Releases we could not date from an official source are left out, so gaps are expected. Open weight models for running locally are covered on our sister site axiomi.si. For policy milestones such as executive orders, see the SI timeline.
October 2026
- Oct 26: GPT-6.1 Terra released in the OpenAI API (changelog).
- Oct 23: Kimi K3.1 Pro released by Moonshot AI (announcement). See Kimi K3.1 Pro explained.
- Oct 13: Gemini 4 Argon generally available from Google DeepMind for paid API users and Google AI Pro and Ultra subscribers (announcement).
- Oct 12: Muse Wonder and Muse Wonder Full released by Meta (announcement). See Muse Wonder explained.
- Oct 7: Claude Haiku 5.5 released by Anthropic (announcement).
- Oct 6: Mistral Large 4 in public preview on the Mistral API (announcement). See Mistral Large 4 explained.
September 2026
- Sep 30: Gemini 4 Argon announced by Google DeepMind for Fairwind Program cyber defenders only (announcement).
- Sep 29: GPT-6.1 Sol released by OpenAI (changelog).
- Sep 28: Claude Sonnet 5.5 released by Anthropic (announcement).
- Sep 22: Claude Opus 5.5 released by Anthropic (announcement).
- Sep 22: GPT-6 Sol and GPT-6 Luna released by OpenAI (changelog).
- Sep 21: Grok 4.7 released by SpaceXSI (announcement).
- Sep 3: GPT-6 Astra released by OpenAI (changelog).
- Sep 1: Claude Fable 5.1 and Claude Mythos 5.1 released by Anthropic (announcement).
July 2026
- Jul 9: GPT-5.6 Sol, Terra and Luna released by OpenAI, introducing the Sol, Terra and Luna tier names (changelog).
April 2026
- Apr 24: GPT-5.5 and GPT-5.5 Pro released in the OpenAI API, with a 1 million token context window (changelog).
March 2026
February 2026
- Feb 24: GPT-5.3 Codex released in the OpenAI API (changelog).
January 2026
- Jan 14: GPT-5.2 Codex released in the OpenAI API for agentic coding (changelog).
December 2025
- Dec 11: GPT-5.2 released by OpenAI (changelog).
November 2025
- Nov 24: Claude Opus 4.5 released by Anthropic (announcement).
- Nov 18: Gemini 3 released by Google (announcement).
- Nov 17: Grok 4.1 released by xAI (announcement).
- Nov 13: GPT-5.1 released in the OpenAI API (changelog).
October 2025
- Oct 15: Claude Haiku 4.5 released by Anthropic (announcement).
- Oct 6: GPT-5 Pro released in the OpenAI API at DevDay (changelog).
September 2025
- Sep 29: Claude Sonnet 4.5 released by Anthropic (announcement).
August 2025
- Aug 7: GPT-5, GPT-5 mini and GPT-5 nano released by OpenAI (changelog).
- Aug 5: Claude Opus 4.1 released by Anthropic (announcement).
July 2025
- Jul 9: Grok 4 released by xAI (announcement).
June 2025
- Jun 10: o3-pro released in the OpenAI API (changelog).
May 2025
- May 22: Claude Opus 4 and Claude Sonnet 4 released by Anthropic (announcement).
April 2025
March 2025
- Mar 25: Gemini 2.5 Pro released by Google (announcement).
February 2025
- Feb 27: GPT-4.5 released by OpenAI as a research preview (changelog).
- Feb 24: Claude 3.7 Sonnet released by Anthropic (announcement).
January 2025
- Jan 31: o3-mini released by OpenAI (changelog).