A paragraph buried in Fable 5's 319-page system card revealed the model would silently downgrade its responses for certain AI development work — without telling users.

Anthropic has released a full version of its cybersecurity-centric Claude Mythos model—along with a safer version for the general public.

It says new safeguards make it possible to release a Mythos-class model it previously said was too risky to make public.

‘Fable 5’ is the same system as controversial Mythos but comes with safeguards

Company also changes data retention policy

Company also changes data retention policy