Agentic Retrieval for Amazon Bedrock Managed Knowledge Base

Amazon Bedrock Managed Knowledge Bases now offers agentic retrieval via the AgenticRetrieveStream API, which uses a foundation model to plan and iterate over retrieval steps instead of a single similarity search. It handles multi-intent, comparative, and cross-source queries by decomposing the question, retrieving per sub-query, evaluating sufficiency, and optionally generating a grounded answer. The API returns a stream of trace events (speculative retrieval, planning, retrieval steps, and final result), supporting up to five knowledge bases with natural-language descriptions for routing. Benchmarking on MuSiQue shows up to 37% absolute recall improvement on 4-hop questions. Pricing includes $4 per 1000 calls with managed model plus $1 per 1000 underlying Retrieve calls. Users can tune maxAgentIteration (default 3 for single KB, 4-5 for multi-KB) and choose between service-managed or custom foundation models.