Contextual Retrieval

Definition

Anthropic's RAG technique of prepending a short, chunk-specific context blurb to each chunk before embedding and indexing it (as both contextual embeddings and contextual BM25), so an isolated chunk retains the surrounding document context it would otherwise lose. Combined with reranking, it substantially reduces retrieval-failure rates versus naive embedding-only RAG, and prompt caching keeps generating per-chunk context economical at scale.