Copilot Studio agent not returning results from Azure AI Search multimodal RAG (image vectorization works in Search Explorer but not in agent)

I am trying to use Azure AI Search (Multimodal RAG) as a knowledge source for a Copilot Studio agent, but the agent fails to retrieve any results even though the search index works correctly in Azure AI Search Explorer.

Scenario Overview

Created an Azure AI Search service with Multimodal RAG

Used Azure AI Document Intelligence to extract content

Used Azure AI Vision vectorization to generate multimodal embeddings

Extracted images are stored in Azure Blob Storage

• Azure AI Search index contains:
  • Text Embeddings
  • Image Embeddings
  • MetadataPointing to image URLs in Blob
• Verified that :
  • Queries return relevant docs in Search Explorer
  • Image vectors and captions are indexed correctly

Intended Architecture

• Azure AI Search (multimodal index with image vectors) → Connected as Knowledge Source → Used by Copilot Studio Agent → Responses should include:
• Relevant text
• Citations
• Image URLs from Blob Storage when applicable

What Works

Search queries executed directly in Azure AI Search Explorer return expected results.

Multimodal vector search works as expected at the index level.

Issue

When the Azure AI Search index is connected as a Knowledge Source in Copilot Studio and queried via a Generative Answers node, the agent consistently responds with:

Expected Behavior

• Copilot agent should retrieve relevant documents from Azure AI Search
• Responses should include citations
• Image URLs (from Blob Storage) should be referenced when relevant

Actual Behavior

• Copilot agent returns no results
• No citations
• No images
• No partial matches, even for simple queries that work in Search Explorer

Questions

• Does Copilot Studio currently support multimodal (image vector) retrieval from Azure AI Search knowledge sources?
• Are image vectors ignored when Azure AI Search is used as a Copilot knowledge source?
• Are there specific index schema requirements (field names, vector fields, content fields) for Copilot Studio to successfully query Azure AI Search?
• Is Copilot Studio limited to text-only RAG, even when the underlying search index is multimodal?
• Are Blob image URLs expected to be returned automatically, or must they be explicitly mapped in a specific field?

Additional Context

• Authentication between Copilot Studio and Azure AI Search is configured correctly
• Knowledge source connection test succeeds in Copilot Studio

Environment

• Azure AI Search: Multimodal RAG enabled
• Vectorization: Azure AI Vision
• Image storage: Azure Blob Storage
• Agent platform: Copilot Studio
• Retrieval method: Generative Answers node