Reasoning-based RAG for long document question answering

PageIndex Chat is the world's first human-like long-document AI analyst. You can upload entire books, research papers, or hundred-page reports and chat with them without context limits, all in the browser. Unlike traditional RAG or "chat-with-your-doc" tools that rely on vector similarity search, PageIndex builds a hierarchical tree index of your document (like a table of contents), and then reasons over this index to retrieve and interpret relevant sections. It doesn’t search by keywords or embeddings — it reads, understands, and reasons through the document like a human expert.

What makes it different:

- Reasoning-based retrieval: Understands structure, logic, and meaning, not just semantic similarity.

- Page-level references: Every answer includes precise citations for easy verification.

- Cross-section reasoning: Connects information across sections and appendices to find true answers.

- Human-in-the-loop: You can guide, refine, and verify its reasoning.

- Multi-document comparison: Analyze and contrast multiple reports at once.