Most RAG debugging starts the same way: better chunking, metadata, reranking, hybrid search, HyDE, query rewrites, table summaries. Some of these help. But unless you know which failure you are fixing, trying them one after another is expensive guessing that can cost months. A useful way to see RAG is as bridges between what the user asks and where the answer lives. A bad answer usually means one bridge failed, and each failure mode has its own fixes.
Takeaways
- Missing context: the right paragraph is found but cut off from its section. Structure-aware chunking, metadata and a wider window around small chunks restore it.
- Weak query-document bridge: the answer exists but the query doesn't connect to it. Hybrid search, HyDE, multi-query retrieval and table summaries help here.
- Bad ranking needs a reranker; weak generalization needs hard negatives. In practice the failures are tangled, so diagnosis means reading logs, retrieved chunks and near misses.
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