GPT-6 API: how to get a key and call Astra, Sol and Luna

To call GPT-6, you need an API key from a platform that serves it and a request with model set to gpt-6-astra, gpt-6-sol or gpt-6-luna. OpenAI serves them in its own API and, for GPT-6 Astra, through Microsoft Azure and Amazon Bedrock. SeedRouter serves all three with one key, pay-as-you-go, using the official OpenAI request format: point the OpenAI SDK at https://api.seedrouter.ai/v1 and keep your code.

This guide uses SeedRouter; the request bodies are the same as OpenAI's.

How do I get a GPT-6 API key?

1. Sign in to SeedRouter and open API keys.
2. Create a key and copy it; it is shown once.
3. Add credit when you need it. New accounts start with a small free balance, and there is no subscription.

Keep the key in an environment variable such as SEEDROUTER_API_KEY, and only use it from server-side code.

How do I call GPT-6 from Python?

OpenAI recommends the Responses API for GPT-6. With the official openai package:

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["SEEDROUTER_API_KEY"],
    base_url="https://api.seedrouter.ai/v1",
)

response = client.responses.create(
    model="gpt-6-sol",
    input="Summarize the trade-offs of event sourcing in three bullet points.",
)
print(response.output_text)

Change model to gpt-6-astra or gpt-6-luna to switch models; nothing else in the request has to change.

How do I call it from Node.js or cURL?

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.SEEDROUTER_API_KEY,
  baseURL: "https://api.seedrouter.ai/v1",
});

const response = await client.responses.create({
  model: "gpt-6-sol",
  input: "Summarize the trade-offs of event sourcing in three bullet points.",
});
console.log(response.output_text);

curl https://api.seedrouter.ai/v1/responses \
  -H "Authorization: Bearer $SEEDROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "gpt-6-sol", "input": "Summarize the trade-offs of event sourcing in three bullet points."}'

Existing Chat Completions code works too: send messages to /v1/chat/completions and set the output limit with max_completion_tokens.

How do I set reasoning effort?

Reasoning effort trades depth for speed and cost. Set it with reasoning.effort in the Responses API or reasoning_effort in Chat Completions:

response = client.responses.create(
    model="gpt-6-sol",
    input="Find the bug: def avg(xs): return sum(xs) / len(xs)",
    reasoning={"effort": "high"},
)

Reasoning tokens are billed as output tokens. none skips reasoning and is the only level that accepts temperature and top_p; GPT-6 Astra does not support it.

How do I stream the answer?

Add stream=True and read the events. The text arrives in response.output_text.delta events, and the final response.completed event carries the token usage:

stream = client.responses.create(
    model="gpt-6-luna",
    input="Write a haiku about latency.",
    stream=True,
)
for event in stream:
    if event.type == "response.output_text.delta":
        print(event.delta, end="", flush=True)

Can I send images?

Yes. All three models read images alongside text. Put an input_image part with a public URL in the user message:

response = client.responses.create(
    model="gpt-6-sol",
    input=[{
        "role": "user",
        "content": [
            {"type": "input_image", "image_url": "https://example.com/chart.png"},
            {"type": "input_text", "text": "What does this chart show?"},
        ],
    }],
)

What errors should I expect?

Errors return {"error": {"code": ..., "message": "..."}}, and a request that fails is not charged.

Frequently asked questions

Is GPT-6 available in the API?

Yes. OpenAI released GPT-6 Astra in the API on September 3, 2026, and GPT-6 Sol and GPT-6 Luna on September 22, 2026, according to its API changelog.

Do I need an OpenAI account to use GPT-6?

Not on SeedRouter. You sign in to SeedRouter, create a key there, and pay from your SeedRouter balance.

Which GPT-6 model should I start with?

GPT-6 Sol for most coding and agent work, GPT-6 Luna for high-volume, simple tasks, and GPT-6 Astra for the hardest problems. The Astra vs Sol vs Luna guide explains the choice.

Where is the full parameter list?

The API docs for GPT-6 Sol, GPT-6 Luna and GPT-6 Astra list every field, limit and response shape.

Try it before you write code

The GPT-6 Sol playground sends the same request from your browser and shows the raw JSON, the tokens and the cost of every answer.