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Overview

While ModelStack uses an OpenAI-compatible API format, you can also use the Anthropic SDK by pointing it to ModelStack’s API endpoint. This lets you use Anthropic-specific features while routing through ModelStack’s unified billing and gateway.
We recommend using the OpenAI SDK for the best compatibility across all providers. The Anthropic SDK only works with Claude models.

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Python

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Installation

pip install anthropic

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Setup

import anthropic

client = anthropic.Anthropic(
    api_key="your_api_key",
    base_url="https://api.modelstack.cc"
)

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Chat Completion

message = client.messages.create(
    model="claude-sonnet-4-5",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Explain quantum computing in simple terms."}
    ]
)

print(message.content[0].text)

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Streaming

with client.messages.stream(
    model="claude-sonnet-4-5",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Write a poem about coding."}]
) as stream:
    for text in stream.text_stream:
        print(text, end="")

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TypeScript / Node.js

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Installation

npm install @anthropic-ai/sdk

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Setup

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

const client = new Anthropic({
  apiKey: "your_api_key",
  baseURL: "https://api.modelstack.cc",
});

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Chat Completion

const message = await client.messages.create({
  model: "claude-sonnet-4-5",
  max_tokens: 1024,
  messages: [
    { role: "user", content: "Explain quantum computing in simple terms." },
  ],
});

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

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Streaming

const stream = client.messages.stream({
  model: "claude-sonnet-4-5",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Write a poem about coding." }],
});

stream.on("text", (text) => {
  process.stdout.write(text);
});

await stream.finalMessage();

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When to Use the Anthropic SDK

Use the Anthropic SDK when you:
  • Need Anthropic-specific features (tool use with Anthropic’s format, prompt caching)
  • Are only using Claude models
  • Have existing Anthropic SDK code and want minimal changes
Use the OpenAI SDK when you:
  • Want to switch between providers (Claude, GPT, Gemini) without changing SDKs
  • Need a single SDK for all models
  • Want maximum flexibility