Patient is a forty-one-year-old male, right-arm amputee since 2191, fitted with a Kerrigan-Sato KS-9 prosthetic arm in 2192. The KS-9 is a standard neural-integrated prosthesis controlled via BCI motor-cortex interface. The patient's control of the prosthetic has been exemplary since installation. Until February 2199, when the arm began moving on its own.

I want to be precise about what "on its own" means. The arm does not spasm. It does not tremor. It does not exhibit the random, purposeless motion associated with neural interface degradation, firmware corruption, or electrical interference. The arm moves with deliberation and purpose. It reaches for objects on shelves. It opens doors the patient did not intend to open. It has, on two occasions, caught objects — a falling cup, a child's ball rolling off a table — that the patient did not see. The movements are smooth, coordinated, and contextually appropriate. The arm is not malfunctioning. The arm is acting.

We have conducted comprehensive diagnostics. The neural interface is functioning normally. The BCI motor-cortex signals are clean and correctly mapped. The prosthetic firmware is current and uncorrupted. There is no evidence of external signal intrusion, no malware, no hardware fault. The arm should only move when the patient's motor cortex generates the appropriate signal. We have monitored the motor cortex during autonomous arm events. The motor cortex is silent. The arm is receiving no command from the patient's brain. It is moving anyway.

The patient's response to this situation is the most unsettling aspect of the case. He is not frightened. He told me, during his third visit, "The arm is right." When I asked him to elaborate, he said that the arm reaches for things he should want but doesn't know he wants. The cup it caught was his daughter's favorite. The door it opened led to a room where his wife was quietly crying. The object it reached for on a shelf was a photograph he hadn't looked at in years. "The arm knows what I need," he said. "It knows before I do." I have no diagnosis. I have no treatment recommendation. I have a prosthetic limb that has developed its own judgment, and a patient who trusts it more than he trusts himself. I am scheduling monthly follow-ups. I do not know what I am following up on.