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README.md

BasicChat-11FoundryClaude

This sample demonstrates how to use Claude models deployed in Microsoft Foundry with the Microsoft.Extensions.AI framework.

Overview

This sample uses a custom ClaudeToOpenAIMessageHandler to transform Azure OpenAI API requests to the Claude Messages API format required by Microsoft Foundry Claude deployments.

Prerequisites

  1. A Microsoft Foundry resource with a deployed Claude model (e.g., Claude Haiku 4.5, Claude Sonnet 4.5, or Claude Opus 4.1)
  2. .NET 10.0 SDK or later
  3. API key from your Microsoft Foundry Claude deployment

Setup

1. Set User Secrets

Configure your Microsoft Foundry credentials using .NET user secrets:

cd samples/CoreSamples/BasicChat-11FoundryClaude
dotnet user-secrets set "endpoint" "https://<your-resource-name>.cognitiveservices.azure.com"
dotnet user-secrets set "endpointClaude" "https://<your-resource-name>.services.ai.azure.com/anthropic/v1/messages"
dotnet user-secrets set "apikey" "<your-api-key>"
dotnet user-secrets set "deploymentName" "claude-haiku-4-5"

Replace:

  • <your-resource-name> with your Microsoft Foundry resource name
  • <your-api-key> with your API key from the Microsoft Foundry portal
  • claude-haiku-4-5 with your deployment name if different

2. Run the Sample

dotnet run app.cs

Authentication

Claude models in Microsoft Foundry use API key authentication with the x-api-key header (not Authorization: Bearer). The custom ClaudeToOpenAIMessageHandler handles this transformation automatically.

According to the Microsoft documentation, Claude API endpoints use:

  • Header: x-api-key: <your-api-key>
  • Endpoint: https://<resource-name>.services.ai.azure.com/anthropic/v1/messages
  • Required header: anthropic-version: 2023-06-01

How It Works

  1. The application creates an AzureOpenAIClient with a custom HTTP transport
  2. The ClaudeToOpenAIMessageHandler intercepts requests to Claude deployments
  3. It transforms OpenAI-style requests to Claude Messages API format:
    • Converts message format and extracts system messages
    • Skips empty messages (Claude requires non-empty content)
    • Adds required Claude headers (x-api-key, anthropic-version)
    • Transforms endpoint URL to Claude's format
  4. Streaming responses are transformed back to OpenAI format using SSE (Server-Sent Events)
  5. All responses maintain OpenAI API compatibility

Code Architecture

The handler is organized into clear regions:

  • Request Transformation: Converts OpenAI format to Claude format
  • Response Transformation: Converts Claude responses back to OpenAI format
  • Streaming Response Transformation: Handles Server-Sent Events (SSE) streaming

Key features:

  • Constants for maintainable configuration
  • Small, focused methods with single responsibilities
  • Clear separation of concerns
  • XML documentation for IntelliSense support

Supported Models

This sample works with all Claude models available in Microsoft Foundry:

  • Claude Haiku 4.5
  • Claude Sonnet 4.5
  • Claude Opus 4.1

References