Building Hierarchical Agentic RAG Systems: Multi-Modal Reasoning with Autonomous Error Recovery

Protocol-H is a hierarchical agentic RAG architecture that uses a supervisor-worker topology to bridge structured SQL databases and unstructured document collections in enterprise analytics. The supervisor orchestrates specialized SQL and vector search workers, decomposing complex multi-hop queries into atomic tasks. A reflective retry mechanism autonomously detects and corrects errors like SQL syntax failures and schema mismatches before they propagate as hallucinations. On an internal EntQA benchmark of 200 enterprise questions, Protocol-H achieved 84.5% accuracy on complex multi-hop queries vs. 62.8% for flat agents and 45.2% for standard RAG, while reducing hallucination rates from 28.5% to 7.1%. The system uses LangGraph StateGraph for deterministic workflow orchestration, cloud-agnostic database adapters (Snowflake, Redshift, BigQuery), and schema-aware query generation with RBAC enforcement. Production considerations include schema drift handling, cost management via model tiering, parallel execution for latency reduction, and compliance auditability.