Anthropic Launches Fable 5 as First Public Version of Mythos AI Model

Anthropic has launched Claude Fable 5, the first publicly available version of its powerful Mythos-class AI model. The model is now accessible through Anthropic’s API and Enterprise plans, though it comes with built-in safety guardrails that block responses in high-risk areas like cybersecurity, biology, and chemistry, falling back to Claude Opus 4.8 in those cases.

Originally previewed in April and restricted to a handful of partners over cybersecurity concerns, Mythos access was expanded in early June to hundreds of organizations across 15 countries. Fable 5 is now available to the general public, with access included in Pro, Max, Team, and Enterprise plans at no extra cost until June 22, after which usage credits will be required.

Anthropic is also rolling out a separate unrestricted version called Mythos 5 to organizations already approved for the advanced model family. Both versions are priced at $10 per million input tokens and $50 per million output tokens, double the cost of Opus 4.8.

Also read: OpenAI Rolls Out GPT-5.6 in Three Tiers, Takes Direct Aim at Anthropic

“We believe highly capable AI systems can be deployed safely when paired with the right safeguards,” the company said in its announcement.

Early testing results are impressive. Analytics company Hex reported Fable 5 scored 90 percent on its core analytics benchmark. AI platform Genspark said it outperformed every other model in their evaluations, particularly in UI design and game coding.

Also read: Anthropic Unveils Project Glasswing to Find Software Bugs

With the launch, Anthropic has introduced a mandatory 30-day data retention policy on all traffic, even for enterprises that previously had zero-retention agreements. The company says the data will only be used to defend against novel attacks and jailbreaks, not for training purposes.

The launch comes as Anthropic prepares for an IPO, alongside rival OpenAI, amid growing financial interest in the AI sector.