Here's the demo that always works: you point a notebook at a vector index, ask it a question, and it answers perfectly. Everyone claps. Three weeks later, the same system tells a customer that your refund window is 90 days when it's 30, cites a document that doesn't exist, and occasionally surfaces another tenant's invoice in the context. Nobody clapped for that part.RAG is deceptively easy to stand up and genuinely hard to keep honest. The retrieval step looks like a solved problem — embed the query, find the nearest neighbors, stuff them into a prompt — so teams treat it like plumbing and move on. Then quality quietly erodes, and because there's no eval harness, nobody can say when it broke or why.