Anthropic releases Fable 5.1 with lower costs and fewer blocks

In short: Anthropic has released Fable 5.1 and Mythos 5.1, with Fable designed to cost less to use and to block fewer harmless requests by mistake.

What happened

Anthropic announced two related versions of its newest AI model, called Fable 5.1 and Mythos 5.1. The company says the update includes performance improvements, plus changes meant to reduce “token” cost and cut down on false alarms from its safety rules.

Tokens are small chunks of text that AI systems count to measure usage, like a taxi meter counting distance. Lower token costs can make it cheaper for companies to build products on top of the model.

Mythos 5.1 will still be limited to registered Anthropic partners working in cybersecurity or life sciences research. Fable 5.1 is available more broadly, including through cloud platforms and the Anthropic API (an API is a way for software to talk to another service).

A key privacy change is Anthropic’s move toward “Zero Data Retention,” which means customers can run the model without their data being stored by Anthropic. Anthropic says a related high-privacy option called Enterprise Frontier Safeguards will roll out in June, while still monitoring for misuse, with customers controlling how that monitoring happens.

Why it matters

Many people only see AI through chat apps, but much of the real use is behind the scenes in customer support, research, and software tools. If Fable 5.1 is cheaper and less likely to wrongly refuse safe requests, it could make everyday AI features smoother. The privacy changes also matter for businesses that handle sensitive information and want tighter control over where their data goes.

Source: TechCrunch AI