Claude Fable 5 Launches: The Strongest Model Is Finally Public, But Shackled
🩺 Summary
On June 9, Anthropic launched Claude Fable 5 — the Mythos model deemed "too dangerous to release" in April, now publicly available with safety guardrails. The fully unlocked Mythos 5 is exclusive to Project Glasswing government partners.
📝 Details
Mythos excels at identifying software security vulnerabilities across major operating systems and browsers. Fable 5 and Mythos 5 share the same architecture, differing only in safety policies. Instead of flatly refusing requests, Fable 5 silently forwards risky queries to Opus 4.8. Pricing: $10/M input tokens, $50/M output. Performance: Senior Engineer Benchmark scores 91/100, far ahead of Opus 4.8 (63/100) and GPT-5.5 (62/100). Anthropic has confidentially filed for IPO at a $965B valuation.
Fable 5 is among the best coding models available, but safety mechanisms limit real capability — high-risk tasks silently downgrade to Opus 4.8. While pricing is doubled, total task cost may decrease as the model gets things right more often on first try. Developers should try it but be aware of the safety restrictions.
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