Anthropic said it had refined Claude Fable 5's biology safety classifiers to substantially cut false positives, reducing biology-related fallbacks to a weaker model by about 85%. Healthcare professionals seeking clinical support, students and teachers studying biology, and people trying to interpret lab results or symptoms could now use Fable 5 across a wider range of legitimate tasks. The company noted that "it's often difficult to tell apart beneficial and harmful uses of AI in biology" and said it had launched Fable 5 with deliberately restrictive controls, knowing this would frustrate legitimate researchers. Blocks on dual-use research in virology, toxicology, and molecular design remained, with advanced capability routed to researchers through trusted access programs. It was a case of publicly measuring an overshoot and loosening a safeguard, rather than only tightening one.