Overview

Migrating from the Anthropic SDK to AI Gateway lets you use a unified OpenAI-compatible API for all providers. You gain caching, rate limiting, cost tracking, and easy provider switching.

Migration Options

You have two options:

OpenAI SDK (recommended) - Use the OpenAI SDK with AI Gateway for a unified API
Anthropic SDK - Continue using the Anthropic SDK with AI Gateway

Option 1: Switch to OpenAI SDK (Recommended)

Use the OpenAI SDK for all providers through AI Gateway:

Before (Direct Anthropic)

import Anthropic from '@anthropic-ai/sdk';
 
const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});
 
const response = await anthropic.messages.create({
  model: 'claude-3-5-sonnet-20241022',
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello!' }],
});

After (AI Gateway with OpenAI SDK)

import OpenAI from 'openai';
 
const client = new OpenAI({
  baseURL: 'https://api.transactional.dev/ai/v1',
  apiKey: process.env.GATEWAY_API_KEY,  // gw_sk_xxx
});
 
const response = await client.chat.completions.create({
  model: 'claude-3-5-sonnet',  // Anthropic model via Gateway
  messages: [{ role: 'user', content: 'Hello!' }],
  max_tokens: 1024,
});

Benefits of OpenAI SDK

Unified API - Same code for OpenAI, Anthropic, Google, etc.
Easy switching - Change providers by changing the model name
Familiar syntax - Most developers know the OpenAI API

Option 2: Continue with Anthropic SDK

Use the Anthropic SDK with AI Gateway:

Before (Direct Anthropic)

import Anthropic from '@anthropic-ai/sdk';
 
const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});

After (AI Gateway)

import Anthropic from '@anthropic-ai/sdk';
 
const anthropic = new Anthropic({
  baseURL: 'https://api.transactional.dev/ai/anthropic/v1',
  apiKey: process.env.GATEWAY_API_KEY,  // gw_sk_xxx
});
 
// All existing code works unchanged!
const response = await anthropic.messages.create({
  model: 'claude-3-5-sonnet-20241022',
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello!' }],
});

Step-by-Step Migration

1. Get Your Gateway API Key

Go to AI Gateway Dashboard
Click API Keys
Create a new key (starts with gw_sk_)

2. Add Your Anthropic Provider Key

Go to Provider Keys in the dashboard
Add your Anthropic API key
AI Gateway will use this to call Anthropic on your behalf

3. Update Your Code

Choose your preferred SDK and update:

OpenAI SDK (Recommended):

import OpenAI from 'openai';
 
const client = new OpenAI({
  baseURL: 'https://api.transactional.dev/ai/v1',
  apiKey: process.env.GATEWAY_API_KEY,
});

Anthropic SDK:

import Anthropic from '@anthropic-ai/sdk';
 
const anthropic = new Anthropic({
  baseURL: 'https://api.transactional.dev/ai/anthropic/v1',
  apiKey: process.env.GATEWAY_API_KEY,
});

API Mapping

When using the OpenAI SDK with Anthropic models:

Anthropic API	OpenAI API (via Gateway)
`messages.create()`	`chat.completions.create()`
`model: 'claude-3-5-sonnet-20241022'`	`model: 'claude-3-5-sonnet'`
`system: 'You are...'`	`messages: [{ role: 'system', content: '...' }]`
`max_tokens: 1024`	`max_tokens: 1024`

Example Conversion

Anthropic SDK:

const response = await anthropic.messages.create({
  model: 'claude-3-5-sonnet-20241022',
  max_tokens: 1024,
  system: 'You are a helpful assistant.',
  messages: [
    { role: 'user', content: 'Hello!' },
  ],
});
 
console.log(response.content[0].text);

OpenAI SDK via Gateway:

const response = await client.chat.completions.create({
  model: 'claude-3-5-sonnet',
  max_tokens: 1024,
  messages: [
    { role: 'system', content: 'You are a helpful assistant.' },
    { role: 'user', content: 'Hello!' },
  ],
});
 
console.log(response.choices[0].message.content);

Feature Compatibility

Feature	Anthropic SDK	OpenAI SDK via Gateway
Chat messages	Yes	Yes
Streaming	Yes	Yes
Tool use	Yes	Yes
Vision (images)	Yes	Yes
System prompts	Yes	Yes
JSON mode	-	Yes (via response_format)

Python Migration

Before (Direct Anthropic)

from anthropic import Anthropic
 
client = Anthropic(
    api_key=os.environ["ANTHROPIC_API_KEY"]
)
 
response = client.messages.create(
    model="claude-3-5-sonnet-20241022",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello!"}]
)

After (OpenAI SDK via Gateway)

from openai import OpenAI
 
client = OpenAI(
    base_url="https://api.transactional.dev/ai/v1",
    api_key=os.environ["GATEWAY_API_KEY"]
)
 
response = client.chat.completions.create(
    model="claude-3-5-sonnet",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello!"}]
)

What You Get

After migration, you automatically get:

Feature	Description
Unified API	Same code for all providers
Semantic Caching	Automatic response caching
Cost Tracking	Real-time cost monitoring
Rate Limiting	Configurable request limits
Fallback	Automatic failover to backup providers
Analytics	Usage dashboards
Easy Switching	Change providers by changing model name

Multi-Provider Example

With AI Gateway, switch providers without changing your code:

const client = new OpenAI({
  baseURL: 'https://api.transactional.dev/ai/v1',
  apiKey: process.env.GATEWAY_API_KEY,
});
 
// Anthropic Claude
const claude = await client.chat.completions.create({
  model: 'claude-3-5-sonnet',
  messages: [{ role: 'user', content: 'Hello!' }],
});
 
// OpenAI GPT-4
const gpt4 = await client.chat.completions.create({
  model: 'gpt-4o',
  messages: [{ role: 'user', content: 'Hello!' }],
});
 
// Google Gemini
const gemini = await client.chat.completions.create({
  model: 'gemini-1.5-pro',
  messages: [{ role: 'user', content: 'Hello!' }],
});

Streaming

Streaming works with both approaches:

OpenAI SDK:

const stream = await client.chat.completions.create({
  model: 'claude-3-5-sonnet',
  messages: [{ role: 'user', content: 'Tell me a story' }],
  stream: true,
});
 
for await (const chunk of stream) {
  process.stdout.write(chunk.choices[0]?.delta?.content || '');
}

Tool Use

Tool use is supported:

const response = await client.chat.completions.create({
  model: 'claude-3-5-sonnet',
  messages: [{ role: 'user', content: 'What is the weather?' }],
  tools: [
    {
      type: 'function',
      function: {
        name: 'get_weather',
        description: 'Get weather for a location',
        parameters: {
          type: 'object',
          properties: {
            location: { type: 'string' },
          },
        },
      },
    },
  ],
});

Rollback

If you need to rollback, revert to direct Anthropic:

import Anthropic from '@anthropic-ai/sdk';
 
const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});

Troubleshooting

Model Not Found

Use the Gateway model name: claude-3-5-sonnet (not claude-3-5-sonnet-20241022)
Check available models in the dashboard

Response Format Different

When switching from Anthropic SDK to OpenAI SDK:

Anthropic: response.content[0].text
OpenAI: response.choices[0].message.content

Tool Call Format Different

Tool calls have slightly different formats between SDKs. See the API documentation for details.

Next Steps

AI Gateway Overview - Full feature documentation
OpenAI SDK Guide - Using the OpenAI SDK
Caching - Configure semantic caching
Fallback - Set up provider fallbacks

Migrate from Anthropic