Azure Anthropic (Claude via Azure Foundry)

LiteLLM supports Claude models deployed via Microsoft Azure Foundry, including Claude Sonnet 4.5, Claude Haiku 4.5, and Claude Opus 4.1.

Available Models

Azure Foundry supports the following Claude models:

• claude-sonnet-4-5 - Anthropic's most capable model for building real-world agents and handling complex, long-horizon tasks
• claude-haiku-4-5 - Near-frontier performance with the right speed and cost for high-volume use cases
• claude-opus-4-1 - Industry leader for coding, delivering sustained performance on long-running tasks

Key Features

• Extended thinking: Enhanced reasoning capabilities for complex tasks
• Image and text input: Strong vision capabilities for analyzing charts, graphs, technical diagrams, and reports
• Code generation: Advanced thinking with code generation, analysis, and debugging (Claude Sonnet 4.5 and Claude Opus 4.1)
• Same API as Anthropic: All request/response transformations are identical to the main Anthropic provider

Authentication

Azure Anthropic supports two authentication methods:

1. API Key: Use the api-key header
2. Azure AD Token: Use Authorization: Bearer <token> header (Microsoft Entra ID)

API Keys and Configuration

# Option 1: API Key authentication
os.environ["AZURE_API_KEY"] = "your-azure-api-key"
os.environ["AZURE_API_BASE"] = "https://<resource-name>.services.ai.azure.com/anthropic"

# Option 2: Azure AD Token authentication
os.environ["AZURE_AD_TOKEN"] = "your-azure-ad-token"
os.environ["AZURE_API_BASE"] = "https://<resource-name>.services.ai.azure.com/anthropic"

# Optional: Azure AD Token Provider (for automatic token refresh)
os.environ["AZURE_TENANT_ID"] = "your-tenant-id"
os.environ["AZURE_CLIENT_ID"] = "your-client-id"
os.environ["AZURE_CLIENT_SECRET"] = "your-client-secret"
os.environ["AZURE_SCOPE"] = "https://cognitiveservices.azure.com/.default"

Usage - LiteLLM Python SDK

Basic Completion

from litellm import completion

# Set environment variables
os.environ["AZURE_API_KEY"] = "your-azure-api-key"
os.environ["AZURE_API_BASE"] = "https://<resource-name>.services.ai.azure.com/anthropic"

# Make a completion request
response = completion(
    model="azure_ai/claude-sonnet-4-5",
    messages=[
        {"role": "user", "content": "What are 3 things to visit in Seattle?"}
    ],
    max_tokens=1000,
    temperature=0.7,
)

print(response)

Completion with API Key Parameter

response = litellm.completion(
    model="azure_ai/claude-sonnet-4-5",
    api_base="https://<resource-name>.services.ai.azure.com/anthropic",
    api_key="your-azure-api-key",
    messages=[
        {"role": "user", "content": "Hello!"}
    ],
    max_tokens=1000,
)

Completion with Azure AD Token

response = litellm.completion(
    model="azure_ai/claude-sonnet-4-5",
    api_base="https://<resource-name>.services.ai.azure.com/anthropic",
    azure_ad_token="your-azure-ad-token",
    messages=[
        {"role": "user", "content": "Hello!"}
    ],
    max_tokens=1000,
)

Streaming

from litellm import completion

response = completion(
    model="azure_ai/claude-sonnet-4-5",
    messages=[
        {"role": "user", "content": "Write a short story"}
    ],
    stream=True,
    max_tokens=1000,
)

for chunk in response:
    if chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="", flush=True)

Tool Calling

from litellm import completion

response = completion(
    model="azure_ai/claude-sonnet-4-5",
    messages=[
        {"role": "user", "content": "What's the weather in Seattle?"}
    ],
    tools=[
        {
            "type": "function",
            "function": {
                "name": "get_weather",
                "description": "Get the current weather in a given location",
                "parameters": {
                    "type": "object",
                    "properties": {
                        "location": {
                            "type": "string",
                            "description": "The city and state, e.g. San Francisco, CA"
                        }
                    },
                    "required": ["location"]
                }
            }
        }
    ],
    tool_choice="auto",
    max_tokens=1000,
)

print(response)

Usage - LiteLLM Proxy Server

1. Save key in your environment

2. Configure the proxy

model_list:
  - model_name: claude-sonnet-4-5
    litellm_params:
      model: azure_ai/claude-sonnet-4-5
      api_base: https://<resource-name>.services.ai.azure.com/anthropic
      api_key: os.environ/AZURE_API_KEY

3. Test it

curl --location 'http://0.0.0.0:4000/chat/completions' \\
--header 'Content-Type: application/json' \\
--data '{
    "model": "claude-sonnet-4-5",
    "messages": [
        {
            "role": "user",
            "content": "Hello!"
        }
    ],
    "max_tokens": 1000
}'

from openai import OpenAI

client = OpenAI(
    api_key="anything",
    base_url="http://0.0.0.0:4000"
)

response = client.chat.completions.create(
    model="claude-sonnet-4-5",
    messages=[
        {"role": "user", "content": "Hello!"}
    ],
    max_tokens=1000
)

print(response)

Messages API

Azure Anthropic also supports the native Anthropic Messages API. The endpoint structure is the same as Anthropic's /v1/messages API.

Using Anthropic SDK

from anthropic import Anthropic

client = Anthropic(
    api_key="your-azure-api-key",
    base_url="https://<resource-name>.services.ai.azure.com/anthropic"
)

response = client.messages.create(
    model="claude-sonnet-4-5",
    max_tokens=1000,
    messages=[
        {"role": "user", "content": "Hello, world"}
    ]
)

print(response)

Using LiteLLM Proxy

curl --request POST \\
  --url http://0.0.0.0:4000/anthropic/v1/messages \\
  --header 'accept: application/json' \\
  --header 'content-type: application/json' \\
  --header "Authorization: bearer sk-anything" \\
  --data '{
    "model": "claude-sonnet-4-5",
    "max_tokens": 1024,
    "messages": [
        {"role": "user", "content": "Hello, world"}
    ]
}'

Supported OpenAI Parameters

Azure Anthropic supports the same parameters as the main Anthropic provider:

"stream",
"stop",
"temperature",
"top_p",
"max_tokens",
"max_completion_tokens",
"tools",
"tool_choice",
"extra_headers",
"parallel_tool_calls",
"response_format",
"user",
"thinking",
"reasoning_effort"

:::info

Azure Anthropic API requires max_tokens to be passed. LiteLLM automatically passes max_tokens=4096 when no max_tokens are provided.

:::

Differences from Standard Anthropic Provider

The only difference between Azure Anthropic and the standard Anthropic provider is authentication:

• Standard Anthropic: Uses x-api-key header
• Azure Anthropic: Uses api-key header or Authorization: Bearer <token> for Azure AD authentication

All other request/response transformations, tool calling, streaming, and feature support are identical.

API Base URL Format

The API base URL should follow this format:

https://<resource-name>.services.ai.azure.com/anthropic

LiteLLM will automatically append /v1/messages if not already present in the URL.

Example: Full Configuration

from litellm import completion

# Configure Azure Anthropic
os.environ["AZURE_API_KEY"] = "your-azure-api-key"
os.environ["AZURE_API_BASE"] = "https://my-resource.services.ai.azure.com/anthropic"

# Make a request
response = completion(
    model="azure_ai/claude-sonnet-4-5",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Explain quantum computing in simple terms."}
    ],
    max_tokens=1000,
    temperature=0.7,
    stream=False,
)

print(response.choices[0].message.content)

Troubleshooting

Missing API Base Error

If you see an error about missing API base, ensure you've set:

os.environ["AZURE_API_BASE"] = "https://<resource-name>.services.ai.azure.com/anthropic"

Or pass it directly:

response = completion(
    model="azure_ai/claude-sonnet-4-5",
    api_base="https://<resource-name>.services.ai.azure.com/anthropic",
    # ...
)

Authentication Errors

• API Key: Ensure AZURE_API_KEY is set or passed as api_key parameter
• Azure AD Token: Ensure AZURE_AD_TOKEN is set or passed as azure_ad_token parameter
• Token Provider: For automatic token refresh, configure AZURE_TENANT_ID, AZURE_CLIENT_ID, and AZURE_CLIENT_SECRET

Related Documentation

• Anthropic Provider Documentation - For standard Anthropic API usage
• Azure OpenAI Documentation - For Azure OpenAI models
• Azure Authentication Guide - For Azure AD token setup