Anthropic Drops Mythos 5, Hands the Public a Safer Fable 5 to Play With 🧵

Anthropic on Tuesday announced the official launch of Claude Mythos 5, a restricted-access AI model the company says has unprecedented cybersecurity capabilities, alongside Claude Fable 5, a version designed for broader public use. In a blog post, Anthropic said Mythos 5 will initially be available only to approved cybersecurity organizations, critical infrastructure operators, government partners, and selected life sciences researchers. The company said its Mythos-class AI models "have reached a threshold where they present significant risks."

The launch follows months of concern over Mythos' ability to identify software vulnerabilities and conduct complex cybersecurity operations after news of the AI leaked online in March. The U.K.'s AI Security Institute reported earlier this year that a preview version became the first AI model to complete a 32-step corporate network intrusion exercise without human assistance. In April, Mozilla reported that a preview version of Mythos discovered over 271 vulnerabilities in the Firefox browser. Anthropic's Project Glasswing program, launched in April with the Claude Mythos Preview, had limited initial distribution to a small group of cyber defenders and critical software infrastructure providers.

Alongside Mythos 5, Anthropic released Claude Fable 5, a Mythos-class AI model that uses the same core design as Mythos 5 but with additional safeguards for the general public. The company said "Fable 5's capabilities exceed those of any model we've ever made generally available." Anthropic added that it would continue to expand access to Mythos "through a broader trusted access program," for cybersecurity work and biomedical research, and that users of Mythos Preview can upgrade to Mythos 5.

The release lands as the AI firm has confidentially filed for a U.S. IPO with the SEC, with press reports citing a potential valuation of up to $1 trillion. OpenAI has also confidentially filed for an IPO. Earlier this month, reports said Anthropic had embedded engineers at the National Security Agency to help deploy its Mythos AI model for cybersecurity operations, reportedly targeting China and Iran. President Donald Trump signed an AI executive order that proposes AI developers provide the government with access to models they consider "covered frontier models."

Crypto traders are watching the launch closely. Polymarket data showed an 84% chance that Anthropic would release the Mythos model on the day of the launch, according to The Information. Market commentator The Milk Road noted the possibility of short-term FUD and chop in crypto prices tied to the release, while describing the direct risk of a crypto hack as minimal. $BTC and $ETH markets were not specifically addressed in the reports.