Why Your Reranker Isn't Helping Your RAG Pipeline (And How to Prove It) (opens in new tab)

You add a cross-encoder reranker to your RAG pipeline, measure answer quality on a test set, see a marginal improvement on 3 of 8 questions, and ship it. Six weeks later your p99 retrieval latency has climbed 200ms per query and you're paying Cohere API costs on every call. Nobody has revisited the decision because there's no data to revisit. The reranker is in the pipeline now. It probably helps. That "probably" is the problem. RAGScope · npm gives you a per-query metric that tells you exact...