Induced from the “Trust Is Not a Framework” lecture at the KENX AI in GxP East 2026 conference (2026-09-15-1112-ai-observability-evaluation-gxp-lecture), 2026-09-15.

Systems trained on happy paths keep answering happy paths

A complaint-handling system evaluated only on typical complaints keeps classifying atypical ones typically. The lecture’s example: a death reported days after the initial ticket changes whether the case should have been flagged reportable, and a system that saw only clean cases answers the dirty one confidently. The judge catches silent failures only if the test set contains them, which is why An LLM judge is a GxP system and needs its own qualification pack: the pack is only as strong as the unhappy paths it is scored on.

What unhappy paths look like in practice

Known-absent items that probe hallucination, distractor questions from adjacent domains, follow-up questions that depend on prior context, and boundary cases at the edge of the intended use. Those known-absent probes are the test-set form of An AI system in GxP must be able to answer unable to verify, and they are how you catch Absence problems are harder to detect than presence problems before a confident answer hides the gap. In the acceptance-criteria lecture the same shape appears: close to a hundred labeled cases including roughly nine drug-versus-device distractors and known-absent items, which caught eight hallucination failures before tuning. This is the population requirement inside Validating an AI system in a regulated industry means validating a measurement system; without it, Observability and evaluation answer different questions about an AI system reports a happy-path score and calls it quality.