Karpathy’s March of Nines shows why 90% AI reliability isn’t even close to enough

“When you get a demo and something works 90% of the time, that’s just the first nine.” — Andrej KarpathyThe “March of Nines” frames a common production reality: You can reach the first 90% reliability with a strong demo, and each additional nine often requires comparable engineering effort. For enterprise teams, the distance between “usually works” and “operates like dependable software” determines adoption.The compounding math behind the March of Nines“Every single nine is the same amount of work.” — Andrej KarpathyAgentic workflows compound failure. A typical enterprise flow might include: intent parsing, context retrieval, planning, one or more tool calls, validation, formatting, and audit logging. If a workflow has n steps and each step succeeds with probability p, end-to-end success i