Search "advanced RAG techniques" and you'll get a list of twenty things: hybrid search, reranking, HyDE, query decomposition, contextual retrieval, RAPTOR, GraphRAG, parent-child chunking, multi-vector retrieval, semantic chunking. They're presented as a menu you work through, each one making your system a bit better. They don't compose like that. Techniques at the same pipeline stage mostly compete — they fix the same failure, so the second one you add finds nothing left to fix. And the on...