News: Model releases
Claude Fable 5.1 and Mythos 5.1 release on September 1, 2026
Claude Fable 5.1 release: Anthropic shipped Fable 5.1 and Mythos 5.1, one model with two safeguard levels, on Sep 1.
OpenAI GPT-6 Astra release on September 3, 2026: what's new
GPT-6 Astra release: OpenAI shipped its most capable model on September 3, 2026, with a Critical cybersecurity rating.
OpenAI releases GPT-6 Sol and GPT-6 Luna on September 22, 2026
OpenAI released GPT-6 Sol and GPT-6 Luna on September 22, 2026 in ChatGPT Work, Codex and the API.
Anthropic Claude Opus 5.5 release on September 22, 2026: what's new
Claude Opus 5.5 release: Anthropic shipped the model on September 22, 2026, at Fable 5.1 level on most work.
Anthropic Claude Sonnet 5.5 release on September 28, 2026: what's new
Claude Sonnet 5.5 release: Anthropic shipped the first Sonnet with cyber safeguards on September 28, 2026.
Google Gemini 4 Argon release on September 30, 2026: what's new
Gemini 4 Argon release: Google shipped it on September 30, 2026 to cyber defenders first, with a 1M-token output limit.