> ## Documentation Index
> Fetch the complete documentation index at: https://docs.inworld.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Anthropic to Inworld

> Migrate your existing Anthropic SDK workflows to Inworld Router

If you are already using the Anthropic API directly, migrating to Inworld Router is a two-line change. Inworld Router supports the Anthropic Messages API natively, so your existing code, message format, and streaming logic all work as-is.

## Key Differences

| Feature           | Anthropic Direct            | Inworld Router                                  |
| :---------------- | :-------------------------- | :---------------------------------------------- |
| **Base URL**      | `https://api.anthropic.com` | `https://api.inworld.ai`                        |
| **Auth**          | Anthropic API key           | Inworld API Key (`Authorization: Bearer`)       |
| **Model Names**   | `claude-opus-4-6`           | `anthropic/claude-opus-4-6` or `auto`           |
| **Routing**       | Single provider             | Multi-provider with failover, cost optimization |
| **Observability** | Anthropic Console           | Inworld Portal (unified across all providers)   |

## Migration Steps

### 1. Update Base URL and API Key

**Python:**

```python theme={"system"}
import anthropic

client = anthropic.Anthropic(
    # From:
    # (default: https://api.anthropic.com)
    # api_key="sk-ant-..."
    # To:
    base_url="https://api.inworld.ai",
    auth_token="YOUR_INWORLD_API_KEY",  # Sends as Authorization: Bearer
)

# Everything else stays the same
message = client.messages.create(
    model="anthropic/claude-opus-4-6",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Hello!"}
    ]
)
```

**TypeScript:**

```typescript theme={"system"}
import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic({
  // From:
  // (default: https://api.anthropic.com)
  // apiKey: 'sk-ant-...'
  // To:
  baseURL: 'https://api.inworld.ai',
  authToken: 'YOUR_INWORLD_API_KEY',  // Sends as Authorization: Bearer
});
```

**cURL:**

```bash theme={"system"}
# From:
# curl https://api.anthropic.com/v1/messages -H "x-api-key: sk-ant-..."
# To:
curl --request POST \
  --url https://api.inworld.ai/v1/messages \
  --header 'Authorization: Bearer <your-inworld-api-key>' \
  --header 'anthropic-version: 2023-06-01' \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "anthropic/claude-opus-4-6",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Hello!"}
    ]
  }'
```

### 2. Update Model Names

Add the `anthropic/` prefix to model names:

* `claude-opus-4-6` → `anthropic/claude-opus-4-6`
* `claude-opus-4-20250514` → `anthropic/claude-opus-4-20250514`
* `claude-3-5-haiku-20241022` → `anthropic/claude-3-5-haiku-20241022`

### 3. Enable Intelligent Routing (Optional)

Instead of hardcoding a model, use Inworld Router's intelligent routing:

```python theme={"system"}
message = client.messages.create(
    model="auto",  # Inworld Router selects the best model
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Write a Python function to sort a list."}
    ]
)
```

## What Stays the Same

* **Message format**: `messages` array with `role` and `content` — identical.
* **Streaming**: `stream=True` works the same way with Anthropic SSE events (`message_start`, `content_block_delta`, etc.).
* **System messages**: Top-level `system` parameter works identically.
* **Tool use**: Tool definitions, `tool_use` content blocks, and `tool_result` messages work identically.
* **`max_tokens`**: Required parameter, same behavior.
* **`temperature`, `top_p`**: Same behavior.
* **Multi-turn conversations**: Same format, context is preserved correctly.

## What You Gain

1. **Multi-Provider Failover**: If Anthropic is down or rate-limited, Inworld Router automatically retries on OpenAI, Google, or other providers — and still returns the response in the Anthropic format.
2. **Cost Optimization**: Route simple queries to cheaper models, reserve Claude for complex tasks.
3. **Cross-Provider Access**: Use `openai/gpt-5` or `google-ai-studio/gemini-2.5-flash` through the same Anthropic SDK — Inworld Router translates the request and returns an Anthropic-format response.
4. **Unified Observability**: See all your LLM requests — across Anthropic, OpenAI, Google — in one dashboard.
5. **Custom Routing**: Build routers with conditional logic, A/B testing, and weighted variants.

## Environment Variables

If you use environment variables, update them:

```bash theme={"system"}
# From:
# export ANTHROPIC_API_KEY=sk-ant-...

# To:
export ANTHROPIC_AUTH_TOKEN=YOUR_INWORLD_API_KEY
export ANTHROPIC_BASE_URL=https://api.inworld.ai
```

## Support

Need help with a complex migration? [Contact our engineering team](mailto:support@inworld.ai).