Anthropic Releases Claude Fable 5 with Controversial Terms

Anthropic released Claude Fable 5, a Mythos-class model at least 2x the size of Opus, available to everyone alongside Claude Tokyo. The model improved FrontierCode Diamond scores from 13.4% to 29.3%. Controversial changes include 30-day data retention for all Mythos-class traffic and RSI suppression limiting Claude's effectiveness for frontier LLM development requests.