Anthropic publishes release notes and system card for Claude Fable 5.1 and Claude Mythos 5.1 models

Anthropic has posted documentation for Claude Fable 5.1, including a “what’s new” page, along with a system card covering Claude Fable 5.1 and Claude Mythos 5.1. The materials appear to outline model updates, expected behavior, and safety-related details for the two Claude variants.

The release of a system card signals continued emphasis on model transparency as AI providers roll out more specialized or updated model families. Publishing safety and capability documentation alongside model updates may become a competitive norm as enterprises demand clearer deployment guidance and risk assessment.