map reduce

Truncate, map-reduce, refine, retrieve, or stuff a long-context model. Each buys you something different and breaks differently. The candidates who score are the ones who pick based on the question being asked, not the document being read.

Two forces shape this design: documents longer than the context window, and summaries that must not lie. The strong answer pairs hierarchical map-reduce with claim-level grounding, then serves it cheaply at scale.

Summarizing a 200-page contract is not one LLM call: it is chunking, hierarchical reduction, and a faithfulness check so you never invent facts. Learn the map-reduce pattern, when long-context wins out, and how to evaluate summaries at scale.