Amazon Bedrock Managed KB Matches Manual RAG Setup but Agentic Planner Falls Short

A developer benchmarked Amazon Bedrock's Managed Knowledge Base against a manually configured RAG pipeline built in April 2025, testing five retrieval configurations across single-hop and multi-hop question sets. The managed service's simple retrieval mode nearly matched the manual setup in correctness scores (0.88 vs. 0.84), and its Smart Parsing feature successfully ingested PDFs that had previously failed. However, the AgenticRetrieveStream planner using AWS's default model failed to decompose any query across all 80 evaluated questions, scoring lower than simple retrieval on multi-hop tasks. Switching to a custom large-model planner (Claude Sonnet 4.6) pushed multi-hop correctness from 0.50 to 1.00, though the author notes the planner and generator shared the same model in that test. The findings suggest managed retrieval is a viable alternative to manual chunking, but the agentic component's effectiveness depends heavily on which model handles the planning.