Anthropic has introduced Fable 5.1 and Mythos 5.1, two updated versions of its most advanced AI model, with a focus on stronger performance, lower token costs, and fewer unnecessary safety blocks.
According to the company, Mythos 5.1 will remain limited to registered partners working in cybersecurity and life sciences research, while Fable 5.1 is now available through cloud platforms and the Anthropic API for broader use.
One of the standout updates is support for Zero Data Retention, which lets organizations run the model on their own infrastructure without data leaving their environment. Anthropic also plans to expand its high-privacy Enterprise Frontier Safeguards service, while still allowing clients to shape how monitoring is handled.
The company says the new release continues its benchmark momentum, with strong results in coding and reasoning tests. Anthropic also highlighted three scientific outputs generated before launch, including a GPU optimization method and a detailed Venus map built from existing imagery.
Alongside the release, Anthropic published a system card describing the models' capabilities and safety profile. The document notes that Mythos 5.1 is designed to balance advanced performance with more controlled behavior in enterprise settings.
With more flexible deployment options and stronger efficiency, Fable 5.1 points to a future where advanced AI becomes both more accessible and more adaptable for specialized work.
