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
24 September 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 24 September 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
24 September 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.