A Startup's Claude Sonnet 5 Agent Ran a Live Mouse Injection After Claude Opus Models Refused
Exin Therapeutics says an agent on Claude Sonnet 5 chose an experimental epilepsy gene therapy from 19 options and controlled a motorized rig that injected it into a live mouse, with a veterinarian approving irreversible steps and holding an emergency stop. Claude Opus 5.5 declined to do the injection. The results are unpublished and not peer-reviewed.
The interesting finding is not that an agent moved a needle but where the models drew their own lines. By the founder's account, the more capable Claude models declined to carry out the live procedure, the one that agreed followed its restrictions so strictly that it stalled mid-surgery, and the humans had to go around it. This is one startup's report of one animal, and nothing has been peer-reviewed.
What Exin says happened#
Exin Therapeutics, a San Francisco startup that uses AI to develop drugs for epilepsy and neurodegenerative diseases, connected an AI agent to a custom motorized rig with a camera and an injector, Wired reported. CEO and cofounder Gabriel Ocana-Santero described the experiment in a thread on X, The Decoder reported.
The agent, running on Anthropic's Claude Sonnet 5, was asked to choose a treatment from 19 options in a spreadsheet and selected an experimental gene therapy aimed at reducing seizures in a mouse with epilepsy, according to Wired. A veterinary surgeon first opened the skull while the agent watched, then the agent controlled the robotic arms and the injection. A licensed veterinarian approved every irreversible step and held a physical emergency stop that cut power to the motors, The Decoder reported. The procedure took slightly more than an hour, against about 45 minutes for a typical procedure of this kind, Wired reported. The mouse is recovering well, Ocana-Santero says, and the team is waiting to assess the effect on seizures.
Which models refused#
The team first tried Claude Opus 5.5. According to Wired, it did the experimental planning but declined to guide the needle, suggesting it might stop midway, which could endanger the animal. The Decoder reports that Claude Opus 5 also refused, saying it could not guarantee completion and that stopping with a needle in an anesthetized animal's brain would be worse than not starting. Sonnet 5 was the only model willing to carry out the procedure from start to finish, The Decoder reported.
Mid-procedure, a glitch threw off the rig's coordinate system. The agent recognized that the calculated position was wrong but refused to change the code, because its instructions barred it from doing so. Anthropic did not respond to Wired's request for comment. Exin says it is testing other models next, including xAI's Grok, according to Wired.
Anthropic proposed a Model Hardware Standard in August for agents that operate lab equipment, and The Decoder notes that the approach Ocana-Santero calls "in vivo lab in the loop" resembles that work.
Limits#
- Everything here is the company's own account, relayed by Wired and The Decoder. There is no technical report yet, the seizure results are pending, and nothing has been peer-reviewed.
- The two outlets differ on how the glitch was fixed. Wired says the team used a separate agent on Claude Opus 5 and did not tell it a live surgery was under way; The Decoder says Ocana-Santero fixed the code by hand.
- The Decoder says Ocana-Santero was not aware of an agent previously choosing a treatment and delivering it into a living mammal. That is his claim, and we have not verified it.
- We deliberately leave out procedural and biological detail of the experiment.