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Anthropic Opens Fable 5 to the Public While Reserving Full Mythos 5 for Trusted Partners

The company says the split lets more users use a stronger Claude model without providing instructions that could enable hacking or biological misuse.

Overview

  • Anthropic released Claude Fable 5 to the public on Tuesday, June 9, as its most capable consumer model but with built-in limits on sensitive queries.
  • When Fable 5 receives requests about cybersecurity or biological risks, Anthropic redirects those queries to the lower-capability Claude Opus 4.8 using real-time filters.
  • Anthropic made an unconstrained version, Claude Mythos 5, available to roughly 200 vetted organizations through Project Glasswing after expanding the program by about 150 partners.
  • The company says it ran more than 1,000 hours of internal and bounty adversarial testing and did not find a ‘universal bypass’ that defeats its safety controls.
  • Anthropic has filed confidential IPO paperwork with the SEC and faces a White House evaluation, raising questions about how safety, market competition, and infrastructure risk will shape broader access to powerful AI.