Anthropic Releases Fable 5.1, Gates Mythos to Partners — SkimNews
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- Anthropic released Claude Fable 5.1 (generally available) and Claude Mythos 5.1 (limited to trusted partners), describing both as "the world's most advanced models for coding and knowledge work"
- Claude Mythos 5.1 ships with cybersecurity and life sciences safeguards and is restricted to trusted partners, while Fable 5.1 opens broadly to all developers
- Claude Fable 5.1 is up to 45% cheaper for agentic work and cuts cache read costs by 75%, per coverage from The Verge and Slashdot
- Anthropic built "anti-distillation mechanisms" into the new models to defend against model distillation attacks, per Fortune
- Claude Fable 5.1 addresses Fable's prior enterprise privacy problem through new safeguards, per Neowin
- Coverage from The Verge, Business Today, Unite.AI, and Constellation Research converges on lower costs and fewer restrictions for Fable, while Fortune and Cyber Security News spotlight the defensive safeguards on Mythos
Why it matters: Anthropic is splitting its flagship model lineup into a broadly available tier and a gated tier for sensitive domains, giving enterprise developers up to 45% cheaper agentic compute while keeping cybersecurity and life sciences work locked to vetted partners. The 75% cache read cut intensifies price competition with frontier-model rivals, and the anti-distillation mechanisms signal Anthropic treating its model IP as a defensive perimeter, not just an output stream.
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