Anthropic SDK

This guide shows you how to point the official Anthropic SDK at the to11 gateway. Set the base_url to your gateway’s /v1 endpoint and use the Anthropic messages API as usual, naming the provider in the model string — anthropic::claude-sonnet-4-6, where anthropic is the routing identifier of your Anthropic provider in to11. See Naming the provider in a request.

Python

pip install anthropic

import anthropic

client = anthropic.Anthropic(
    base_url="https://gw.to11.ai/v1",
    api_key="<your Anthropic API key>",  # provider credential, forwarded upstream
    default_headers={
        "x-to11-authorization": "Bearer <your to11 API key>",  # to11 auth — Settings → API keys
        "x-to11-project-id": "<your project id>",
    },
)

message = client.messages.create(
    model="anthropic::claude-sonnet-4-6",
    max_tokens=256,
    messages=[{"role": "user", "content": "Hello from to11!"}],
)
print(message.content[0].text)

TypeScript / Node.js

npm install @anthropic-ai/sdk

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  baseURL: "https://gw.to11.ai/v1",
  apiKey: "<your Anthropic API key>", // provider credential, forwarded upstream
  defaultHeaders: {
    "x-to11-authorization": "Bearer <your to11 API key>", // to11 auth — Settings → API keys
    "x-to11-project-id": "<your project id>",
  },
});

const message = await client.messages.create({
  model: "anthropic::claude-sonnet-4-6",
  max_tokens: 256,
  messages: [{ role: "user", content: "Hello from to11!" }],
});
console.log(message.content[0].text);

Streaming

with client.messages.stream(
    model="anthropic::claude-sonnet-4-6",
    max_tokens=256,
    messages=[{"role": "user", "content": "Count to 10"}],
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

const stream = client.messages.stream({
  model: "anthropic::claude-sonnet-4-6",
  max_tokens: 256,
  messages: [{ role: "user", content: "Count to 10" }],
});

for await (const event of stream) {
  if (
    event.type === "content_block_delta" &&
    event.delta.type === "text_delta"
  ) {
    process.stdout.write(event.delta.text);
  }
}

Streamed responses are traced just like non-streaming calls — the gateway captures the same span and token counts either way.

System messages

Pass a top-level system parameter as you normally would:

message = client.messages.create(
    model="anthropic::claude-sonnet-4-6",
    system="You are a helpful assistant that speaks only in haiku.",
    max_tokens=256,
    messages=[{"role": "user", "content": "Tell me about the ocean"}],
)

Tool use

Tool definitions follow the Anthropic input_schema format:

message = client.messages.create(
    model="anthropic::claude-sonnet-4-6",
    max_tokens=256,
    messages=[{"role": "user", "content": "What's the weather in Paris?"}],
    tools=[{
        "name": "get_weather",
        "description": "Get current weather for a location",
        "input_schema": {
            "type": "object",
            "properties": {
                "location": {"type": "string"}
            },
            "required": ["location"],
        },
    }],
)

Extended thinking

Extended thinking blocks are preserved in Anthropic-format responses when enabled on the model. The thinking content type passes through the gateway as-is.

Providers the Anthropic SDK reaches

The gateway forwards your request to the provider as you wrote it and does not convert between wire formats. The Anthropic SDK sends the Anthropic Messages format, so it reaches Anthropic providers. To call OpenAI or an OpenAI-compatible provider, use the OpenAI SDK. An Anthropic-format request that names one of them, such as openai::gpt-4o, is rejected with 400 Bad Request and the x-to11-error-code: cross_dialect header before anything is sent to the provider. See Which SDK to call a provider with.

​Python

​TypeScript / Node.js

​Streaming

​System messages

​Tool use

​Extended thinking

​Providers the Anthropic SDK reaches