I Was About to Rewrite My Chat Router. The Bug Was Two Lines in a Prompt.

TL;DR: A customer asked my AI sales bot "what do you have?" and the bot listed product categories the store doesn't sell. My instinct was to rewrite the search router. I spent twenty minutes about to do exactly that. Then I traced where the hallucinated category list was actually coming from: not the search results, not the database, not the router. It was coming from the store's "About" text — which the system prompt was injecting as Store: ${store.description}. The model read that label as a c...