The moment that made me want to understand this I was deep in FinMentor — my multi-agent Claude-powered financial advisor — testing a query I'd run dozens of times: "What's the difference between a mutual fund and an ETF?" The answer came back in 400 words. Four paragraphs. Bullet points. A disclaimer about individual circumstances. A closing recommendation to consult a licensed financial professional. The actual difference fits in two sentences. I had written nothing in my system prompt requesting elaboration. No "be thorough." No "explain in detail." The verbosity was coming from somewhere else. I rewrote the system prompt. "Be concise. Answer only what's asked." The response shortened — but not proportionally. The hedging stayed. The paragraph structure stayed. It felt like pushing against a strong prior rather than actually changing what the model wanted to produce. I was overriding behavior, not removing it. That distinction — override vs. remove — is what sent me to the InstructGPT paper.…