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The official Anthropic SDKs work with Lightweight by simply changing the base URL and API key. This gives you access to every model in the catalog — not just Claude — through the familiar Anthropic SDK interface.
Even though you’re using the Anthropic SDK, you can call any model available in the Lightweight catalog (OpenAI, Google, xAI) by passing its model ID.

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Python

pip install anthropic

import anthropic

client = anthropic.Anthropic(
    api_key="lw_sk_your-key-here",
    base_url="https://api.lightweight.one/v1"
)

message = client.messages.create(
    model="claude-sonnet-4.5",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Explain the difference between TCP and UDP."}
    ]
)

print(message.content[0].text)

​
Node.js / TypeScript

npm install @anthropic-ai/sdk

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

const client = new Anthropic({
  apiKey: "lw_sk_your-key-here",
  baseURL: "https://api.lightweight.one/v1",
});

async function main() {
  const message = await client.messages.create({
    model: "claude-sonnet-4.5",
    max_tokens: 1024,
    messages: [
      { role: "user", content: "Explain the difference between TCP and UDP." },
    ],
  });

  console.log(message.content[0].text);
}

main();

​
Streaming

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Python Streaming

import anthropic

client = anthropic.Anthropic(
    api_key="lw_sk_your-key-here",
    base_url="https://api.lightweight.one/v1"
)

with client.messages.stream(
    model="claude-sonnet-4.5",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Write a short story about a robot learning to paint."}
    ]
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

​
Node.js Streaming

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

const client = new Anthropic({
  apiKey: "lw_sk_your-key-here",
  baseURL: "https://api.lightweight.one/v1",
});

const stream = client.messages.stream({
  model: "claude-sonnet-4.5",
  max_tokens: 1024,
  messages: [
    { role: "user", content: "Write a short story about a robot learning to paint." },
  ],
});

stream.on("text", (text) => process.stdout.write(text));
await stream.finalMessage();

​
Using Non-Claude Models

Because Lightweight is a unified gateway, you can use the Anthropic SDK to access models from any provider: 
# Use GPT-5.4 through the Anthropic SDK
message = client.messages.create(
    model="gpt-5.4",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Hello from GPT via the Anthropic SDK!"}
    ]
)
Browse the full Models catalog to see every model available through Lightweight.