The 5-Minute Migration: Swapping Your OpenAI Base URL to OpenDunes

You built your app on the OpenAI libraries, then the bill got stuck on a refused card. You expect weeks of rewriting. You need five minutes.

OpenDunes speaks the OpenAI format: the requests your code sends and the answers it reads stay the same. You change two values, and nothing else.

Change the base URL and the key

Your code talks to the API through two settings. The first says where to send the request, the second proves the request is yours.

Both values sit in one place in your code: where you create the client.

No. The request body, the message format and the answer you read back keep their shape. Your prompts and your parsing code stay as they are.

If your card was refused on the official checkout, the billing wall that sends you looking for a base URL explains why, and what it means for your account.

Update your Python code

Here is the official openai Python library, pointed at OpenDunes. Only the two lines with a comment change.

import os
from openai import OpenAI

client = OpenAI(
    base_url="https://opendunes.com/v1",          # changed
    api_key=os.environ["OPENDUNES_API_KEY"],      # changed
)

response = client.chat.completions.create(
    model="openai/gpt-6-luna",
    messages=[{"role": "user", "content": "Summarise this order in one line."}],
)
print(response.choices[0].message.content)

Update your JavaScript code

The official JavaScript library takes the same two values.

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://opendunes.com/v1",        // changed
  apiKey: process.env.OPENDUNES_API_KEY,      // changed
});

const completion = await client.chat.completions.create({
  model: "openai/gpt-6-luna",
  messages: [{ role: "user", content: "Summarise this order in one line." }],
});
console.log(completion.choices[0].message.content);

The official libraries also read OPENAI_BASE_URL from the environment. Set the address once there, next to your key.

OPENDUNES_API_KEY=your-key-here
OPENAI_BASE_URL=https://opendunes.com/v1

Keep your key out of your code

Your key spends your balance. Anyone who reads it can spend it too.

Let's see what a real workload costs once it runs.

Now send your first request yourself.

export OPENDUNES_API_KEY=your-key-here
curl https://opendunes.com/v1/chat/completions \
  -H "Authorization: Bearer $OPENDUNES_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "openai/gpt-6-luna", "messages": [{"role": "user", "content": "Hello"}]}'