Overview

Infron provides Anthropic-compatible API endpoints, so you can use the Anthropic SDK and tools like Claude Code through a unified gateway with only a URL change.

The Anthropic-compatible API implements the same specification as the Anthropic Messages API.

For more on using Infron with Claude Code, see the Claude Code instructions.

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

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

Python(Anthropic SDK)

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)

Anthropic SDK

Configuring Claude Code

Claude Code Integration Guide

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

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