Claude Fable 5

is the first publicly available Anthropic model from the new "Mythos" class, going beyond the previous Haiku/Sonnet/Opus cascade.

Engineering performance leap: The model achieves state-of-the-art (SOTA) status in the FrontierCode benchmark, outclassing frontier models.

It stands out with extreme token efficiency in complex corporate environments.

Key business innovation: Transition from one-off interaction assistants to autonomous long-term agents.

The model utilizes file-based persistent memory and self-correction capability, without losing context during multi-hour operations.

Risk Management (Dual-Use): The full "Mythos" model poses critical cyber risks (including offensive 0-day vulnerability discovery).

Fable 5, the business version, has rigorous structural safeguards.

Full access (Project Glasswing) is restricted to strictly vetted corporate partners and state security.