GPT-6 Luna

Text & chatNewAvailable
by OpenAIModel ID: gpt-6-luna

OpenAI's most efficient model for focused, high-volume tasks. Reasoning, text and image input, function calling and tool use, 1,050,000-token context window and up to 128,000 output tokens. Knowledge cutoff May 18, 2026.

Price · 1M in / out
US$0.12 / US$0.60
Context
1.050.000 tokens
Max. output
128.000 tokens
Input → output
Text → Text
Developer
OpenAI
Updated
September 24, 2026
01

Playground

Try GPT-6 Luna

Chat

US$0.12/1M in
Try GPT-6 Luna

Send a message. The answer arrives in full once the model is done (no streaming).

System prompt
Max. answer length (tokens)

This run

at most US$0.0007 · 0.07 credits reserved

Billed by the tokens actually used; the unused part of the reservation is refunded.

New here?

10 free credits (US$0.10) when you sign up with Google

Usable 24 hours after sign-up, up to 5 runs per day and at most 2 credits per run. Other sign-in methods start without credits. Enough for 142 runs of this model.

02

About GPT-6 Luna

TL;DRAs of September 24, 2026

GPT-6 Luna is a model by OpenAI in the Text & chat category. On Railwail, GPT-6 Luna costs US$0.12 per 1M input tokens and US$0.60 per 1M output tokens. The context window holds 1.050.000 tokens, and one response can be up to 128.000 tokens long.

03

Pricing

Prices in US dollars. Usage is charged from prepaid credits.
InputUS$0.12 / 1M tokens
OutputUS$0.60 / 1M tokens
Input (prompts over 272.000 tokens)US$0.24 / 1M tokens
Output (prompts over 272.000 tokens)US$0.90 / 1M tokens
  • Billed by the tokens each request actually uses.
  • 1 credit = US$0.01

Cost calculator

Price calculator

/ req.
/ req.

Total

US$0.05

5 credits

Per request

US$0.0005 · 0.05 credits

Each request is rounded up to 0.01 credits.

04

API

Call GPT-6 Luna with your Railwail API key. Use this model ID in the request:
curl https://railwail.com/api/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6-luna",
    "messages": [
      {
        "role": "user",
        "content": "Explain what a vector database is in two sentences."
      }
    ],
    "max_tokens": 1024
  }'
Set your key as RAILWAIL_API_KEYCreate API key
05

Specifications

Model ID
gpt-6-luna
Developer
OpenAI
Category
Text & chat
Input
Text
Output
Text
Context window
1.050.000 tokens
Max. output
128.000 tokens
Billing
By usage (tokens or GPU time)
Catalog entry updated
September 24, 2026

Tags

  • openai
  • gpt-6
  • cost-efficient
  • fast
  • reasoning
  • vision
  • tools
06

Use cases

07

Frequently asked questions

What is GPT-6 Luna?

GPT-6 Luna is a model by OpenAI in the Text & chat category. On Railwail you can call it with an API key through the Railwail API.

How much does GPT-6 Luna cost on Railwail?

On Railwail, GPT-6 Luna costs US$0.12 per 1M input tokens and US$0.60 per 1M output tokens. You are charged for what each request actually uses. Usage is paid from prepaid credits; 1 credit equals US$0.01.

What is the context window of GPT-6 Luna?

The context window of GPT-6 Luna holds 1.050.000 tokens. One response can be up to 128.000 tokens long.

How fast is GPT-6 Luna?

There are not enough measured runs of GPT-6 Luna on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.

Is GPT-6 Luna better than Claude Fable 5.1?

That depends on the task. GPT-6 Luna (OpenAI) and Claude Fable 5.1 (Anthropic) are both models in the Text & chat category. The comparison page shows their prices and specifications side by side.

Compare GPT-6 Luna and Claude Fable 5.1

How do I use GPT-6 Luna through the API?

Create a Railwail API key and send your request with the model ID gpt-6-luna. Code examples for curl, Python and JavaScript are in the API section of this page.

08

Comparable models

All in this category
  • Anthropic's model for the most demanding reasoning and long-horizon agentic work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.

    US$12.00/1M in

    9,900 % more expensive per unit

    Compare GPT-6 Luna vs. Claude Fable 5.1
  • The most capable model of Anthropic's Opus 4 series. State of the art on long-horizon agentic work, coding and knowledge tasks, with a 1M-token context window at standard pricing.

    US$6.00/1M in

    4,900 % more expensive per unit

    Compare GPT-6 Luna vs. Claude Opus 4.8
  • Anthropic's current Opus model for long-running agentic coding and knowledge work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.

    US$4.80/1M in

    3,900 % more expensive per unit

    Compare GPT-6 Luna vs. Claude Opus 5.5

Use GPT-6 Luna via the API

One API key for every model on Railwail. Usage is charged from prepaid credits, 1 credit = US$0.01.