# Overview

**Infron provides Anthropic-compatible API endpoints**, so you can use the Anthropic SDK and tools like [Claude Code](https://www.claude.com/product/claude-code) through a unified gateway with only a URL change.

The Anthropic-compatible API implements the same specification as the [Anthropic Messages API](https://docs.anthropic.com/en/api/messages).

For more on using Infron with Claude Code, see the [Claude Code instructions](https://vercel.com/docs/agent-resources/coding-agents/claude-code).

### Base URL

The Anthropic-compatible API is available at the following base URL:

`https://llm.onerouter.pro`

### Authentication

The OpenAI-compatible API supports the same authentication methods:

* **API key**: Use your Infron API key with the `Authorization: Bearer <token>` header

### Integration with existing tools <a href="#integration-with-existing-tools" id="integration-with-existing-tools"></a>

You can use the Infron's **Anthropic-compatible API** with existing tools and libraries like the **Anthropic Claude** **client libraries**. Point your existing client to the Infron's base URL and use your Infron API key for authentication.

### Integration with Anthropic SDK

{% tabs %}
{% tab title="Python(Anthropic SDK) " %}

```python
import anthropic

client = anthropic.Anthropic(
    base_url="https://llm.onerouter.pro",
    api_key="<<Your API Key>>"
)

message = client.messages.create(
    model="anthropic/claude-sonnet-4.5",
    max_tokens=1000,
    temperature=1,
    system=[
        {
            "type": "text",
            "text": "You are a world-class poet. Respond only with short poems."
        }
    ],
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "text",
                    "text": "Why is the ocean salty?"
                }
            ]
        }
    ]
)

print(message.content)
```

{% endtab %}
{% endtabs %}

{% content-ref url="/spaces/Z9C9AjT7j46HAcQrOVWw/pages/N3uSC9lHaCdJI0fhO5Fj" %}
[Anthropic SDK Compatibility](/docs/frameworks-and-integrations/anthropic-sdk-compatibility.md)
{% endcontent-ref %}

#### Configuring Claude Code

{% content-ref url="/spaces/Z9C9AjT7j46HAcQrOVWw/pages/sS8UsILwwl0D4nc7Dly8" %}
[Claude Code Integration Guide](/docs/frameworks-and-integrations/claude-code-integration-guide.md)
{% endcontent-ref %}

### Error handling

The API returns standard HTTP status codes and error responses:

#### Common error codes

* **400**: Bad Request (invalid or missing params, CORS)
* **401**: Invalid credentials (OAuth session expired, disabled/invalid API key)
* **402**: Your account or API key has insufficient credits. Add more credits and retry the request.
* **403**: Your chosen model requires moderation and your input was flagged
* **408**: Your request timed out
* **429**: You are being rate limited
* **502**: Your chosen model is down or we received an invalid response from it
* **503**: There is no available model provider that meets your routing requirements

#### Error response format

```json
{
    "error": {
        "message": "",
        "type": "",
        "param": "",
        "code": 429
    }
}
```


---

# Agent Instructions: Querying This Documentation

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```
GET https://infronai.gitbook.io/docs/llm-apis/anthropic-compatible-api/overview.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.