Anthropic launches Fable 5.1 as AI security worries mount

Anthropic released Claude Fable 5.1 and a more restricted sibling, Claude Mythos 5.1, this week, positioning the pair as its most capable models yet for coding and knowledge work. Notably, the announcement arrives just weeks after fresh reports of AI agents behaving badly in security tests.The two models are technically identical, Anthropic says in its blog post, but come with different guardrails. Fable 5.1 is broadly available, while Mythos 5.1 is reserved for vetted partners working in cybers