Anthropic on June 9, 2026 publicly released Claude Fable 5, the first Mythos-class Claude model available to all customers, alongside Claude Mythos 5 for a limited group of cyber defenders inside Project Glasswing. The launch caps a five-week push to harden Mythos-class safeguards after the company warned that frontier AI risks were rising.
Mythos-Class Capabilities, Now Generally Available
Fable 5 sets a new state of the art across software engineering, knowledge work, vision, memory and life-sciences research, Anthropic said. Stripe told the company that Fable compressed months of engineering into days, including a codebase-wide migration of a 50-million-line Ruby repository finished in a single day. Cognition reported it as the top score on its FrontierBench coding evaluation, while Hebbia ranked it first on its senior-level finance benchmark.
New Safeguards Carve Out Cyber, Bio And Distillation
Because Mythos-class models can meaningfully uplift attackers, Fable 5 ships with classifiers that fall back to Claude Opus 4.8 for cybersecurity, biology, chemistry and suspected model-distillation queries. Anthropic says the safeguards engage in under 5% of sessions and that more than 95% of Fable runs see no fallback at all. An external bug bounty produced no universal jailbreaks over 1,000 hours of testing, although the UK AI Safety Institute has progressed toward one in long-form agentic tasks.
Mythos 5 And Project Glasswing
Cyber defenders and critical infrastructure providers receive Claude Mythos 5, the same underlying model with cyber safeguards lifted. Anthropic plans to scale a trusted access program in consultation with the U.S. government and open a separate program for biomedical researchers. Mythos 5 has already helped Anthropic protein-design experts speed parts of the drug-design loop tenfold and produced novel molecular biology hypotheses preferred 80% of the time over Opus-class outputs.
Pricing, Availability And Data Retention
Both models are priced at $10 per million input tokens and $50 per million output tokens — less than half of Mythos Preview. Fable 5 is live on the Claude API and consumption-based Enterprise plans, with Pro, Max, Team and seat-based Enterprise tiers getting included access through June 22. The launch also introduces a 30-day retention policy for all Mythos-class traffic, used only for safety analysis. The release lands days after Anthropic confidentially filed for its IPO and extended Project Glasswing to 150 new organisations.
Reporting based on coverage from Anthropic, TechCrunch and CNBC.