System Card Confirms Fable 5.1 and Mythos 5.1 Share the Same Base Model

Anthropic's newly published system cards detail capabilities and safety measures for Fable 5.1 and Mythos 5.1, confirming that both are the same base model differing only in applied safety guardrails.

2026-09-02 ~ 2026-09-02 · 3 related posts

• Anthropic releases System Cards for Fable 5.1 and Mythos 5.1 — scaling01 · 2026-09-02
• Anthropic: Fable 5.1 and Mythos 5.1 Are Identical — BLUECOW009 · 2026-09-02
• Anthropic launches Mythos 5.1 for cybersecurity and life sciences — minchoi · 2026-09-02