I wrote a LinkedIn post in October 2026 about diagnosing Retrieval‑Augmented Generation (RAG) pipelines when they miss the correct chunk even though the chunk is present in the vector store.
It does not change how many results you ask for; it changes how hard the index looks for them.
Calculate recall@10 = number of shared results / 10.
If exact search finds the needed chunk but HNSW doesn't, investigate the index and search settings.
If exact search doesn't find it either, a wider graph search won't fix your embeddings, chunking, or missing source content.
A reranker cannot rescue a chunk it never receives.