also BM25 plus vectors, keyword and semantic search
Running keyword search and vector search together and merging the results, so exact terms such as product codes, error strings and names, and paraphrased questions, both find their documents.
You have done this if
Users searching for an error code got nothing from vector search until you added keyword matching beside it.
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Retrieval is hybrid: keyword matching for exact terms, vectors for meaning, merged before reranking.
On the AI Application map Retrieval, Vector Index
Read Hybrid search is the practical default · Production retrieval needs exact words and meaning