On Tuesday, Anthropic officially launched Claude Fable 5, which the company described as "the most powerful model ever released to the public." According to Anthropic, Fable 5 excels in software engineering, knowledge work, and visual understanding, with its lead widening further as task length and complexity increase. Fable 5 marks the first broad release of Anthropic’s “Mythos” series. Previously, Anthropic had publicly stated that models in this series were too capable—and therefore too dangerous—for public release on cybersecurity tasks. The rationale given for this launch was that “new safety measures can now prevent generating responses in specific high-risk areas.” When touching upon sensitive domains, the model automatically falls back to Claude Opus 4.8—a model Anthropic praised last month for its honesty. Anthropic explicitly identified cybersecurity and biology as two fields likely to trigger safety interceptions, both considered high-risk sensitive zones by industry standards for advanced AI. The company noted that during testing, 95 percent of Fable 5 sessions completed entirely through the model’s own responses without triggering fallback mechanisms. Meanwhile, Anthropic also announced Claude Mythos 5 but provided few details. In a blog post, Anthropic stated that Mythos 5 uses the same underlying model as Fable 5, “but has safety restrictions lifted in certain areas.” Access appears currently limited to institutions granted access to Claude Mythos Preview via Anthropic’s private “Project Glasswing” program. Anthropic said these users could upgrade to Mythos 5 and planned to “gradually expand usage through more systematic trusted-access programs.” When asked about the relationship between Mythos 5 and Claude Mythos Preview, as well as why previous releases did not include any Mythos or Fable series yet directly used the number “5,” Anthropic offered no direct response. Regarding pricing, the cost of the two new models is significantly higher than Anthropic’s previous flagship—twice that of Claude Opus 4.8—but roughly half the price of Mythos Preview. Specifically, input tokens are priced at $10 per million, while output tokens are $50 per million.