Fable 5 is the public version of Mythos, and while it is very capable it sets some troubling new precedents.

Anthropic launches Mythos with Fable 5. Six capabilities for agents: 80.3% code reasoning, extended thinking, autonomy. Vision, science acceleration, enterprise pricing

Anthropic launched Claude Fable 5 on Tuesday, a Mythos-class model with safeguards blocking cybersecurity and biology queries, priced at $10 per million input tokens.