Anthropic’s new Claude Fable 5 is a nerfed Mythos with guardrails attached

Anthropic — claude Fable 5 brings Mythos-class AI coding power to general users, but with cybersecurity guardrails, fallback models, and pricing that could make developers think twice.

Anthropic has announced a defanged version of its fabled (and highly restricted) Mythos large language model. Called Claude Fable 5, the company describes the new AI as "a Mythos-class model made safe for general use." Mythos was introduced back in April to great fanfare as a model capable of finding vulnerabilities in code that neither experienced developers nor other AIs could find. Also: US workers are the world's biggest AI skeptics – and it's not just about job loss Offered as the central component of a Manhattan Project-like team effort called Project Glasswing, Mythos was considered far too dangerous to be allowed to fall into the wrong hands. As such, the model has been made available only to Glasswing partners, including Amazon Web Services, Anthropic, Apple, Broadcom, Cisco, CrowdStrike, Google, JPMorganChase, the Linux Foundation, Microsoft, Nvidia, and Palo Alto Networks. Up until now, Mythos was considered a preview product. Now, Anthropic is launching Claude Mythos 5, which will be available to all users with access to Mythos Preview. The company said, "We plan to expand access over time through a more systematic trusted-access program." No significant details were provided about any difference between Mythos Preview and Mythos 5, except that the latter appears to be the post-beta version of Mythos. Also: Apple's new Siri AI comes with hidden costs that power users should know of Anthropic also released Fable 5. The company described this technology as the same underlying model as Mythos, but with safeguards. Those safeguards block responses in specific high-risk areas of cybersecurity and biology. Yeah, the "biology" reference raised red flags. Have they seen biological weapon prompts or responses in their logs? I've asked Anthropic. I highly doubt they'll answer. Interestingly, if a Fable 5 prompt veers into one of those high-risk areas, the model drops down to Opus 4.8, which has its own restrictions.