Contextual Retrieval: prepend a per-chunk context sentence before embedding

Digital Applied·medium signal

Before embedding each chunk, generate a short chunk-specific blurb situating it in the whole document, then embed the blurb+chunk together. Anthropic's technique cut top-20 retrieval failures ~49%, rising to ~67% when combined with reranking. It's cheap to add to an existing index build and stacks with both late chunking and cross-encoder reranking.