Anthropic Ships Claude Fable 5.1 as the AI Model Arms Race Hits Cybersecurity Peak

Claude Fable 5.1 and Claude Mythos 5.1 are live — Anthropic's newest and most powerful large language models, both released September 1, 2026. The two names refer to the same underlying model with different guardrails: Fable 5.1 is the generally available version with production safeguards, while Mythos 5.1 is restricted to vetted cybersecurity and life-sciences organizations through Anthropic's trusted access programs. Anthropic calls them the "world's most advanced...