Claude Fable 5 and Claude Mythos 5: Anthropic's Most Capable Model Goes Public
Anthropic
Anthropic released Claude Fable 5 on June 9, 2026 — the first Mythos-class model made publicly available. It uses the same underlying architecture as Claude Mythos 5 but ships with three classifier-based safeguards (cybersecurity, biology/chemistry, distillation prevention) that fall back to Claude Opus 4.8 in restricted domains. Priced at $10/M input and $50/M output tokens, with 128k output token support. Free for Pro/Max/Team/Enterprise subscribers through June 22. Mythos 5 (unrestricted) remains gated to vetted cybersecurity researchers via Project Glasswing. Anthropic cited a 50-million-line codebase migration as a flagship real-world benchmark.
Why it matters
The first Mythos-class model to reach the general public marks a new tier of publicly available intelligence. The tiered-access architecture — safeguarded Fable 5 for all users, unrestricted Mythos 5 for vetted researchers — may become the industry template for releasing highly capable models responsibly.
Importance: 5/5
Anthropic frontier flagship release; first-ever public Mythos-class model; tiered safety architecture sets new industry precedent.