Anthropic releases Claude Fable 5, a 'Mythos-class' AI model with safeguards

Anthropic announced the release of a "Mythos-class" model called Claude Fable 5, but said safeguards are so significant the model was given a different name. "Without safeguards, Fable 5's capabilities in areas like cybersecurity could be misused to cause serious damage," the company said.

Some queries on certain topics will be ported to Anthropic's Opus 4.8 model, and the safeguards are initially tuned to be more conservative. The company is continuing Project Glasswing, which first provided early access to the Mythos preview, and a small group of cyberdefenders and infrastructure providers will receive Claude Mythos 5 — the same model as Fable 5 but with safeguards lifted in some areas.

Anthropic described Mythos 5 as having "the strongest cybersecurity capabilities of any model in the world" and said it intends to expand access through a broader trusted program.

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