Retrieval-grounded course assistant that answers only from staff-issued material and cites the slide it came from: hybrid dense + BM25 retrieval, cross-encoder re-ranking, three independent refusal layers. 0 fabricated citations over a 63-question gold set, and an interface that draws the refusal decision rather than asserting it.
python nlp information-retrieval scikit-learn evaluation bm25 faiss rag streamlit sentence-transformers hybrid-search cross-encoder llm retrieval-augmented-generation hallucination-mitigation gold-set
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Updated
Sep 3, 2026 - Python