Anthropic’s new Fable release is cheaper, less restrictive
techcrunch ·
Anthropic unveiled two new AI models, Fable 5.1 and Mythos 5.1, representing its most advanced technology. Fable 5.1 is immediately available to the public, while Mythos 5.1 is restricted to vetted partners in cybersecurity and life sciences. The release emphasizes reduced token costs and fewer false-positive security restrictions, along with a new Zero Data Retention option and Enterprise Frontier Safeguards that give clients control over monitoring. Anthropic reiterated that it never trains on enterprise data without explicit permission. The models achieved top scores on benchmarks such as Terminal-Bench 4.0 and Humanity's Last Exam, and were used to generate three novel scientific findings. A system card rated Mythos as low-risk for self-improvement concerns and noted a slight regression in misaligned behavior compared to Opus 5, but better handling of constraints and fewer hallucinations than prior models.
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