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Overview

ModelStack is fully compatible with the OpenAI SDK. Just change base_url and api_key — everything else works the same, including streaming, function calling, and all chat completion parameters.

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Python

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Installation

pip install openai

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Setup

from openai import OpenAI

client = OpenAI(
    api_key="your_api_key",
    base_url="https://api.modelstack.cc/v1"
)

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Chat Completion

response = client.chat.completions.create(
    model="claude-sonnet-4-5",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Explain quantum computing."}
    ],
    temperature=0.7,
    max_tokens=500
)

print(response.choices[0].message.content)

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Streaming

stream = client.chat.completions.create(
    model="claude-sonnet-4-5",
    messages=[{"role": "user", "content": "Write a poem about coding."}],
    stream=True
)

for chunk in stream:
    if chunk.choices[0].delta.content is not None:
        print(chunk.choices[0].delta.content, end="")

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List Models

models = client.models.list()
for model in models.data:
    print(f"{model.id} ({model.owned_by})")

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Using Different Models

# Switch between providers by changing the model parameter
providers = {
    "Anthropic": "claude-sonnet-4-5",
    "OpenAI": "gpt-4o",
    "Google": "gemini-2.5-pro",
}

for provider, model in providers.items():
    response = client.chat.completions.create(
        model=model,
        messages=[{"role": "user", "content": "Say hello!"}]
    )
    print(f"{provider}: {response.choices[0].message.content}")

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Environment Variable

Instead of hardcoding your API key, use an environment variable: 
export OPENAI_API_KEY="your_api_key"
export OPENAI_BASE_URL="https://api.modelstack.cc/v1"

# No need to pass api_key or base_url — the SDK reads from env vars
client = OpenAI()

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Node.js / TypeScript

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Installation

npm install openai

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Setup

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: "your_api_key",
  baseURL: "https://api.modelstack.cc/v1",
});

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Chat Completion

const response = await client.chat.completions.create({
  model: "claude-sonnet-4-5",
  messages: [
    { role: "system", content: "You are a helpful assistant." },
    { role: "user", content: "Explain quantum computing." },
  ],
  temperature: 0.7,
  max_tokens: 500,
});

console.log(response.choices[0].message.content);

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Streaming

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

for await (const chunk of stream) {
  const content = chunk.choices[0]?.delta?.content || "";
  process.stdout.write(content);
}

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Environment Variables

export OPENAI_API_KEY="your_api_key"
export OPENAI_BASE_URL="https://api.modelstack.cc/v1"

// SDK reads from env vars automatically
const client = new OpenAI();