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OpenAI SDK

This guide shows you how to point the official OpenAI SDK at the to11 gateway. The only change is the base_url — the rest of your code stays the same.

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Python

Install the SDK if you haven’t already: 
pip install openai
Set the base_url to your gateway: 
from openai import OpenAI

client = OpenAI(
    base_url="http://localhost:4000/v1",
    api_key="sk-...",  # your OpenAI API key
)

response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Hello from to11!"}],
    max_tokens=256,
)
print(response.choices[0].message.content)

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TypeScript / Node.js

npm install openai

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "http://localhost:4000/v1",
  apiKey: "sk-...", // your OpenAI API key
});

const response = await client.chat.completions.create({
  model: "gpt-4o",
  messages: [{ role: "user", content: "Hello from to11!" }],
  max_tokens: 256,
});
console.log(response.choices[0].message.content);

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Streaming

Add stream: true to receive Server-Sent Events. The gateway forwards SSE chunks from OpenAI with zero-copy passthrough — sub-millisecond overhead. 
stream = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Count to 10"}],
    stream=True,
)
for chunk in stream:
    content = chunk.choices[0].delta.content
    if content:
        print(content, end="", flush=True)

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Cross-format routing

You can route OpenAI-format requests to Anthropic models. The gateway translates the request and returns the response in OpenAI format — your code doesn’t change: 
# Same OpenAI SDK, but targeting an Anthropic model
response = client.chat.completions.create(
    model="claude-sonnet-4-6",
    messages=[{"role": "user", "content": "Hello from to11!"}],
    max_tokens=256,
)
System messages are automatically extracted and forwarded as Anthropic’s top-level system field. Tool definitions are translated between formats.

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Tool calling

Tool calling works identically to direct OpenAI usage: 
response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "What's the weather in Paris?"}],
    tools=[{
        "type": "function",
        "function": {
            "name": "get_weather",
            "description": "Get current weather for a location",
            "parameters": {
                "type": "object",
                "properties": {
                    "location": {"type": "string"}
                },
                "required": ["location"],
            },
        },
    }],
)
If this request is routed to an Anthropic model, the gateway translates tool definitions to Anthropic’s input_schema format automatically.

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Environment variable configuration

If you prefer not to hard-code the base URL, use the OPENAI_BASE_URL environment variable: 
export OPENAI_BASE_URL=http://localhost:4000/v1

# No base_url needed — the SDK reads OPENAI_BASE_URL
client = OpenAI(api_key="sk-...")