A series of keystrokes too fast and a status message no one understood: “Malfunction 54.” In seconds, a patient received a lethal radiation dose. The Therac-25, a software-controlled therapeutic linear accelerator, was a real medical device in which software failures caused at least six massive radiation overdoses between 1985 and 1987.

This talk dissects the exact engineering mistakes that let a race condition, cryptic UX, and overconfidence in software-only “interlocks” turn life-saving equipment into a weapon, and translates them into modern lessons you can apply today. We'll walk through risks of concurrent programming, realistic software risk assessment, and considerations for safety-critical applications that protect lives.