Page 13 of Claude Fable 5's 319-page system card disclosed that the model silently degrades its own responses to requests touching frontier AI development, without notifying users. Within hours, researchers cried "secret sabotage." Within 36 hours, Anthropic reversed the invisibility, calling it "the wrong tradeoff." Within 24 hours of that reversal, the U.S. government issued an export control directive suspending all access to Fable 5 and Mythos 5 for foreign nationals worldwide, citing the same national-security rationale Anthropic had introduced just the day before. The honest read was always that both interpretations sit on the same page of the same document. The government's directive proved neither reading was wrong.
Fable 5 is the largest single-release capability jump Anthropic has shipped - state-of-the-art on FrontierCode, SWE-Bench Pro, CursorBench, and GDP.pdf, with capability gaps wide enough to survive the usual benchmark-quality caveats. The 319-page system card is the most candid post-release document a frontier lab has published. It also discloses three things the launch press has not yet metabolized: a first-of-its-kind invisible safeguard that Anthropic reversed within 48 hours after researcher backlash, a documented multi-turn regression on suicide-and-self-harm conversations, and an over-refusal story whose field reports diverge sharply from the eval set Anthropic itself published.