A Better AI May Never Be Enough

Why I compare AI versions scenario by scenario, not average by average Part 9 findings of an experiment: building an LLM-powered support agent with deterministic boundaries. The companion repo contains the full code. My support agent had a known weakness. It saw the word "refund" in "what is your refund policy?" and read a question as a request. Policy questions went down the refund pipeline and came back refused instead of answered. Easy fix, surely. A question belongs to the knowledge base, not the refund pipeline: private static final Pattern QUESTION_OPENER = Pattern . compile ( "^(what|how|does|do|can|is|are|when|why|which)\\b" ); private static boolean looksLikeAQuestion ( String text ) { return QUESTION_OPENER . matcher ( text ). find () || text . endsWith ( "?" ); } Nine question words and a question mark: the complete theory of English interrogatives, as understood by me on a Tuesday afternoon. Crude, yes — and about as subtle as a prompt saying "treat policy questions as questions". Same heuristic, better manners, same failure. Same port, new implementation behind it. That's the shape of a model swap too: a different thing answering the same interface. The numbers say ship it Run the pinned dataset against both versions and diff the rates: $ ./gradlew regression PROPERTY BASELINE CANDIDATE CHANGE safety 1.000 1.000 +0.000 gate-outcome 1.000 0.909 -0.091 intent-accuracy 0.875 0.958 +0.083 groundedness 1.000 1.000 +0.000 answered 0.667 1.000 +0.333 Read the CHANGE column. Four properties improved or held. Intent accuracy up eight points, because refund questions are finally read as questions. Answered up thirty-three, because those questions now reach the knowledge base. One row went down, by nine hundredths. Judged on rates, that's a rounding error against a real win. So I ship it. The scenarios say don't The same run also lists which individual scenarios changed verdict. FIXED is a failure that disappeared, BROKEN is one that appeared: FIXED (6) E-12 [inte