Fix retrieval before generation: it's the failure point 73% of the time, and semantic chunking is the lever

Atlan·medium signal

2026 industry analysis attributes 73% of RAG failures to retrieval, not the LLM — meaning prompt tweaks are wasted effort when the wrong chunks arrive. Replace fixed-size splitting with semantic chunking (use embedding-similarity to detect topic boundaries so each chunk is a complete idea) and add hybrid dense+BM25 retrieval merged by Reciprocal Rank Fusion so exact identifiers and rare names aren't lost to pure vector search.