PageIndex: RAG Without Vectors — Turning Long Documents Into a Book With a Table of Contents
PageIndex skips chunking, embedding, and vector storage entirely. Instead it relies on LLM reasoning over a tree-structured table of contents the LLM itself wrote, achieving 98.7% on FinanceBench (GPT-4o reading directly scores only 31%). It solves a different problem than vector RAG — finding the right section in a well-structured long document.