Support Anthropic models on Azure

deploy/example.config.ts

@@ -74,8 +74,9 @@ export const config: Config<ProviderKeys> = {
     },
     azure: {
       providerId: 'azure',
-      // NOTE: For now, you need to specify the family of models you want to use.
-      baseUrl: 'https://marcelo-0665-resource.openai.azure.com/openai/v1',
+      // NOTE: baseUrl should NOT include /openai or /anthropic - the provider adds these automatically
+      // Use 'anthropic/' prefix in the path for Anthropic API, otherwise OpenAI API is used
+      baseUrl: 'https://marcelo-0665-resource.openai.azure.com',
       injectCost: true,
       credentials: env.AZURE_API_KEY,
     },

gateway/src/handler.ts

@@ -9,7 +9,7 @@ import type { BaseAPI } from './api/base'
 import type { OtelSpan } from './otel'
 import { attributesFromRequest, attributesFromResponse, type GenAIAttributes } from './otel/attributes'
 import { AnthropicProvider } from './providers/anthropic'
-import { AzureProvider } from './providers/azure'
+import { createAzureProvider } from './providers/azure'
 import type { BaseProvider, ExtractedInfo, ProviderOptions } from './providers/base'
 import { BedrockProvider } from './providers/bedrock'
 import { GoogleVertexProvider } from './providers/google'
@@ -63,7 +63,7 @@ export class RequestHandler {
     return match(options.providerProxy.providerId)
       .returnType<BaseProvider>()
       .with('openai', () => new OpenAIProvider(options))
-      .with('azure', () => new AzureProvider(options))
+      .with('azure', () => createAzureProvider(options))
       .with('groq', () => new GroqProvider(options))
       .with('google-vertex', () => new GoogleVertexProvider(options))
       .with('anthropic', () => new AnthropicProvider(options))

gateway/src/providers/azure.ts

@@ -1,5 +1,23 @@
+import { AnthropicProvider } from './anthropic'
+import type { BaseProvider, ProviderOptions } from './base'
 import { OpenAIProvider } from './openai'
 
-// TODO(Marcelo): The `AzureProvider` should be its own class, not a subclass of `OpenAIProvider`.
-export class AzureProvider extends OpenAIProvider {}
-// TODO(Marcelo): We should support Anthropic models as well.
+export function createAzureProvider(options: ProviderOptions): BaseProvider {
+  // We assume that it's Anthropic if the path starts with `v1/messages`. Otherwise, it's OpenAI.
+  // This is not necessarily true, since Anthropic does support OpenAI-compatible endpoints.
+  const isAnthropic = options.restOfPath.startsWith('v1/messages')
+
+  // We modify the `baseUrl` and not the `restOfPath` because the `restOfPath` is used to determine the API flavor.
+  // NOTE: Instead of modifying the `provierProxy` object, I think we should pass the `baseUrl` as a separate argument to the constructor.
+  const modifiedOptions: ProviderOptions = {
+    ...options,
+    providerProxy: {
+      ...options.providerProxy,
+      baseUrl: isAnthropic
+        ? `${options.providerProxy.baseUrl}/anthropic`
+        : `${options.providerProxy.baseUrl}/openai/v1`,
+    },
+  }
+
+  return isAnthropic ? new AnthropicProvider(modifiedOptions) : new OpenAIProvider(modifiedOptions)
+}

gateway/test/providers/azure.spec.ts

@@ -1,3 +1,4 @@
+import Anthropic from '@anthropic-ai/sdk'
 import OpenAI from 'openai'
 import { describe, expect } from 'vitest'
 import { deserializeRequest } from '../otel'
@@ -37,4 +38,25 @@ describe('azure', () => {
     expect(otelBatch, 'otelBatch length not 1').toHaveLength(1)
     expect(deserializeRequest(otelBatch[0]!)).toMatchSnapshot('span')
   })
+
+  test('anthropic', async ({ gateway }) => {
+    const { fetch, otelBatch } = gateway
+
+    // The `authToken` is passed as `Authorization` header with the anthropic client.
+    const client = new Anthropic({ authToken: 'healthy', baseURL: 'https://example.com/azure', fetch })
+
+    const completion = await client.messages.create({
+      model: 'claude-sonnet-4-20250514',
+      max_tokens: 1024,
+      top_p: 0.95,
+      top_k: 1,
+      temperature: 0.5,
+      stop_sequences: ['potato'],
+      system: 'You are a helpful assistant.',
+      messages: [{ role: 'user', content: 'What is the capital of France?' }],
+    })
+    expect(completion).toMatchSnapshot('llm')
+    expect(otelBatch, 'otelBatch length not 1').toHaveLength(1)
+    expect(deserializeRequest(otelBatch[0]!)).toMatchSnapshot('span')
+  })
 })

gateway/test/providers/azure.spec.ts.snap

@@ -1,5 +1,116 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
+exports[`azure > anthropic > llm 1`] = `
+{
+  "content": [
+    {
+      "text": "The capital of France is Paris.",
+      "type": "text",
+    },
+  ],
+  "id": "msg_01Dk1uacDayZhr8zthkRovpM",
+  "model": "claude-sonnet-4-20250514",
+  "role": "assistant",
+  "stop_reason": "end_turn",
+  "stop_sequence": null,
+  "type": "message",
+  "usage": {
+    "cache_creation": {
+      "ephemeral_1h_input_tokens": 0,
+      "ephemeral_5m_input_tokens": 0,
+    },
+    "cache_creation_input_tokens": 0,
+    "cache_read_input_tokens": 0,
+    "input_tokens": 20,
+    "output_tokens": 10,
+    "pydantic_ai_gateway": {
+      "cost_estimate": 0.00020999999999999998,
+    },
+    "service_tier": "standard",
+  },
+}
+`;
+
+exports[`azure > anthropic > span 1`] = `
+[
+  {
+    "attributes": {
+      "gen_ai.input.messages": [
+        {
+          "parts": [
+            {
+              "content": "What is the capital of France?",
+              "type": "text",
+            },
+          ],
+          "role": "user",
+        },
+      ],
+      "gen_ai.operation.name": "chat",
+      "gen_ai.output.messages": [
+        {
+          "finish_reason": "end_turn",
+          "parts": [
+            {
+              "content": "The capital of France is Paris.",
+              "type": "text",
+            },
+          ],
+          "role": "assistant",
+        },
+      ],
+      "gen_ai.request.max_tokens": 1024,
+      "gen_ai.request.model": "claude-sonnet-4-20250514",
+      "gen_ai.request.seed": {},
+      "gen_ai.request.stop_sequences": [
+        "potato",
+      ],
+      "gen_ai.request.temperature": 0.5,
+      "gen_ai.request.top_k": 1,
+      "gen_ai.request.top_p": 0.95,
+      "gen_ai.response.finish_reasons": [
+        "end_turn",
+      ],
+      "gen_ai.response.id": "msg_01Dk1uacDayZhr8zthkRovpM",
+      "gen_ai.response.model": "claude-sonnet-4-20250514",
+      "gen_ai.system": "anthropic",
+      "gen_ai.system_instructions": [
+        {
+          "content": "You are a helpful assistant.",
+          "type": "text",
+        },
+      ],
+      "gen_ai.usage.cache_audio_read_tokens": {},
+      "gen_ai.usage.cache_read_tokens": 0,
+      "gen_ai.usage.cache_write_tokens": 0,
+      "gen_ai.usage.input_audio_tokens": {},
+      "gen_ai.usage.input_tokens": 20,
+      "gen_ai.usage.output_audio_tokens": {},
+      "gen_ai.usage.output_tokens": 10,
+      "http.request.body.text": "{"model":"claude-sonnet-4-20250514","max_tokens":1024,"top_p":0.95,"top_k":1,"temperature":0.5,"stop_sequences":["potato"],"system":"You are a helpful assistant.","messages":[{"role":"user","content":"What is the capital of France?"}]}",
+      "http.response.body.text": "{"model":"claude-sonnet-4-20250514","id":"msg_01Dk1uacDayZhr8zthkRovpM","type":"message","role":"assistant","content":[{"type":"text","text":"The capital of France is Paris."}],"stop_reason":"end_turn","stop_sequence":null,"usage":{"input_tokens":20,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":0},"output_tokens":10,"service_tier":"standard","pydantic_ai_gateway":{"cost_estimate":0.00020999999999999998}}}",
+      "http.response.status_code": 200,
+      "logfire.json_schema": "{"type":"object","properties":{"gen_ai.operation.name":{"type":"string"},"gen_ai.request.model":{"type":"string"},"gen_ai.system":{"type":"string"},"gen_ai.request.max_tokens":{"type":"number"},"gen_ai.request.top_k":{"type":"number"},"gen_ai.request.top_p":{"type":"number"},"gen_ai.request.temperature":{"type":"number"},"gen_ai.request.stop_sequences":{},"gen_ai.request.seed":{},"gen_ai.response.finish_reasons":{},"gen_ai.response.id":{"type":"string"},"gen_ai.input.messages":{},"gen_ai.output.messages":{},"gen_ai.system_instructions":{},"http.response.status_code":{"type":"number"},"http.request.body.text":{"type":"string"},"http.response.body.text":{"type":"string"},"gen_ai.response.model":{"type":"string"},"gen_ai.usage.input_tokens":{"type":"number"},"gen_ai.usage.cache_read_tokens":{"type":"number"},"gen_ai.usage.cache_write_tokens":{"type":"number"},"gen_ai.usage.output_tokens":{"type":"number"},"gen_ai.usage.input_audio_tokens":{},"gen_ai.usage.cache_audio_read_tokens":{},"gen_ai.usage.output_audio_tokens":{}}}",
+      "logfire.level_num": 9,
+      "logfire.msg": "chat claude-sonnet-4-20250514",
+    },
+    "events": [],
+    "kind": 1,
+    "links": [],
+    "name": "chat claude-sonnet-4-20250514",
+    "parentSpanId": undefined,
+    "resource": {
+      "service.name": "PAIG",
+      "service.version": "test",
+    },
+    "scope": "pydantic-ai-gateway",
+    "status": {
+      "code": 1,
+    },
+  },
+]
+`;
+
 exports[`azure > chat > llm 1`] = `
 {
   "choices": [

proxy-vcr/proxy_vcr/cassettes/azure-9752c34227c474614a0161c842bd67313be0932354998df27c07a1b9d8b29eaa.yaml

@@ -0,0 +1,40 @@
+interactions:
+- request:
+    body: '{"model":"claude-sonnet-4-20250514","max_tokens":1024,"top_p":0.95,"top_k":1,"temperature":0.5,"stop_sequences":["potato"],"system":"You
+      are a helpful assistant.","messages":[{"role":"user","content":"What is the
+      capital of France?"}]}'
+    headers:
+      accept:
+      - '*/*'
+      accept-encoding:
+      - gzip, deflate
+      connection:
+      - keep-alive
+      content-length:
+      - '235'
+      content-type:
+      - application/json
+      host:
+      - marcelo-0665-resource.openai.azure.com
+      user-agent:
+      - python-httpx/0.28.1
+    method: POST
+    uri: https://marcelo-0665-resource.openai.azure.com/anthropic/v1/messages
+  response:
+    body:
+      string: '{"error":{"code":"401","message":"Access denied due to invalid subscription
+        key or wrong API endpoint. Make sure to provide a valid key for an active
+        subscription and use a correct regional API endpoint for your resource."}}'
+    headers:
+      Content-Length:
+      - '224'
+      Content-Type:
+      - application/json
+      Date:
+      - Wed, 03 Dec 2025 12:57:22 GMT
+      apim-request-id:
+      - 04fea0f2-7241-45f9-9a1c-3fd7fe450be7
+    status:
+      code: 401
+      message: PermissionDenied
+version: 1

proxy-vcr/proxy_vcr/main.py

@@ -22,7 +22,7 @@
 BEDROCK_BASE_URL = 'https://bedrock-runtime.us-east-1.amazonaws.com'
 GOOGLE_BASE_URL = 'https://aiplatform.googleapis.com'
 # The Azure URL is not a secret, we can commit it.
-AZURE_BASE_URL = 'https://marcelo-0665-resource.openai.azure.com/openai/v1'
+AZURE_BASE_URL = 'https://marcelo-0665-resource.openai.azure.com'
 HF_BASE_URL = 'https://router.huggingface.co/v1'
 
 current_file_dir = pathlib.Path(__file__).parent