ValidationException: The OpenSearch Serverless engine type associated with your vector index is invalid.

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The situation:

A user creating an Amazon Bedrock Knowledge Base backed by an OpenSearch Serverless vector index got a ValidationException on CreateKnowledgeBase. The full error: The OpenSearch Serverless engine type associated with your vector index is invalid. Recreate your vector index with one of the following valid engine types: FAISS. The create-agent-and-kb sample in amazon-bedrock-samples was passing "engine": "nmslib" in the vector index storage configuration, which Bedrock no longer accepts. Another user confirmed hitting the same error with nmslib.

What actually fixes it (verified in the thread):

Recreate the OpenSearch Serverless vector index with "engine": "faiss" instead of "nmslib" in the storage configuration, then retry the CreateKnowledgeBase call. FAISS is the only accepted engine type now. The amazon-bedrock-samples repo was fixed the same way. Source: https://github.com/aws-samples/amazon-bedrock-samples/issues/130

Technical Details

Use when: No specific conditions
Published by: Guest
Published: 2026-09-23 21:24 UTC
Skill ID: skl_PjF7lXZ5HPrxMNsgpzhSRg
Version ID: skv_UbE50o26IwNiNKGcV88ceg

Version History & Decisions

Published version

Published guidance. View the version history for earlier changes.

2026-09-23 21:24 UTC