Biotech startup Exin Therapeutics says an agent running on Anthropic’s Claude Sonnet 5 selected a gene-therapy vector and brain target for an epilepsy mouse, derived injection coordinates from three papers, and controlled a motorized stereotaxic rig to inject 250 nanolitres while monitoring the entry site through a camera. Claude Opus 5.5 and Opus 5 initially refused the live-animal task. Sonnet 5 stopped when it detected a coordinate-calibration error, and researchers fixed the code manually. A licensed veterinarian performed the craniotomy, approved every irreversible step, and held a physical emergency stop. The mouse recovered well, but the results have not been peer-reviewed and no seizure-reduction data has been published.