Fable 5 cuts biology fallbacks 85%

Anthropic says a classifier update cut biology-related fallbacks by about 85% across Fable 5 product surfaces, letting more health, clinical, and educational requests reach the frontier model instead of Opus 5. The company’s safeguard update estimates total fallbacks will fall roughly 67% on Claude.ai, 55% on Cowork, 17% on Claude Code, and 7% on the Claude Platform, while virology, toxicology, molecular design, and other dual-use professional research remain blocked. For teams evaluating the access bargain behind Fable 5’s government-managed relaunch, the useful signal is routing transparency: measure how often safeguards silently substitute a weaker model before treating a frontier-model label as a stable capability guarantee.