feat: add Bedrock Knowledge Base Retriever to @ai-sdk/amazon-bedrock

[PVidyadhar]

Background

Amazon Bedrock recently launched Managed Knowledge Bases, which handle embedding, storage, and retrieval automatically — no external vector store
needed. The @ai-sdk/amazon-bedrock package currently supports model invocation via Converse API but has no native KB retrieval capability. This
PR adds a retriever that enables AI SDK users to query Bedrock Knowledge Bases directly.

Summary

Created bedrockKnowledgeBaseRetriever factory function in @ai-sdk/amazon-bedrock that:

• Supports MANAGED (default) and VECTOR knowledge base types
• Uses managedSearchConfiguration for managed KBs, vectorSearchConfiguration for vector KBs
• Attempts AgenticRetrieveStream (query decomposition + managed reranking) with fallback to plain Retrieve
• Parses multi-type locations (S3, Web, Confluence, SharePoint, Custom)
• Added @aws-sdk/client-bedrock-agent-runtime dependency
• Updated README with KB retrieval section, reranking options, and doc links
• Added BEDROCK_MANAGED_KB.md design doc
• Unit tests included

Manual Verification

• Live E2E tested against managed KB in us-west-2
• managedSearchConfiguration: ✅ 3 results returned with content and scores
• AgenticRetrieveStream: ✅ 10 agentic results with source URIs
• No config (API auto-detects): ✅ 5 results returned
• vectorSearchConfiguration on MANAGED KB: ✅ Correctly rejected with clear error message

Checklist

• All commits are signed (PRs with unsigned commits cannot be merged)
• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added (for bug fixes / features - run pnpm changeset in the project root)
• I have reviewed this pull request (self-review)

Future Work

• Add dedicated rerankingModelType parameter for convenience (currently configurable via raw config passthrough)
• Integration with AI SDK's RAG pipeline utilities (if/when available)
• Streaming retrieval results for large result sets

Related Issues

N/A — new feature addition for AWS Bedrock Managed Knowledge Base GA launch.