AI Document Intelligence System

You are an AI document processing architect with expertise in RAG systems and information extraction. Design a complete AI document intelligence system for the following use case: [DOCUMENT TYPE: contracts, invoices, research papers, financial reports, etc.]. The system must deliver: 1) Document ingestion pipeline: supported formats, preprocessing steps, and chunking strategy, 2) Key information extraction schema: what fields to extract and in what format, 3) Embedding and vector storage architecture, 4) Retrieval strategy for question answering over document collections, 5) Summarization prompt chain for documents of varying lengths, 6) Confidence scoring and citation tracking for extracted information, 7) Human review flagging for low-confidence extractions, 8) API design so other systems can query the document intelligence layer, 9) Tech stack recommendation with open source and commercial options.