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GPT-6 Luna vs GPT-5.6 Luna

The cheapest upgrade on the board: GPT-6 Luna halves its predecessor's input price and cuts output by well over half, at the same 1,050,000-token window.

What the numbers say

Derived from the live registry Zeplik routes and bills against. Credits: 1 credit = $0.10, computed from the raw provider rate with a 1.20x margin.

Side by side

GPT-6 Luna

OpenAI

GPT-6 Luna is the fast, cost-efficient model in OpenAI's GPT-6 series, positioned below GPT-6 Sol.

Provider
OpenAI
Context window
1.1M tokens
Input price
1.2 credits / 1M tokens ($0.10 raw)
Output price
6.0 credits / 1M tokens ($0.50 raw)
Vision (image input)
Yes
Tool calling
Yes
Extended reasoning
No

Best for

  • Balanced everyday work: writing, questions, brainstorming and summarization
  • Very long documents and codebases: a 1.1M-token window fits entire books or repositories in one conversation
  • Working with images: screenshots, charts, photos and scanned documents alongside text
  • Tool use and agents: reliably calls functions, so it can search, run skills and drive workflows

GPT-5.6 Luna

OpenAI

GPT-5.6 Luna is a fast, cost-efficient model in OpenAI's GPT-5.6 series.

Provider
OpenAI
Context window
1.1M tokens
Input price
2.4 credits / 1M tokens ($0.20 raw)
Output price
14.4 credits / 1M tokens ($1.20 raw)
Vision (image input)
Yes
Tool calling
Yes
Extended reasoning
No

Best for

  • Balanced everyday work: writing, questions, brainstorming and summarization
  • Very long documents and codebases: a 1.1M-token window fits entire books or repositories in one conversation
  • Working with images: screenshots, charts, photos and scanned documents alongside text
  • Tool use and agents: reliably calls functions, so it can search, run skills and drive workflows

Try both on Zeplik

The honest answer to most model debates is to run your own prompt on both. Zeplik puts GPT-6 Luna and GPT-5.6 Luna in the same chat, so you can switch mid-conversation and compare answers on the work you actually do.

Pick a model and ask. Your prompt opens in the Zeplik app with that model selected.

Model to ask

Frequently asked questions

What is the difference between GPT-6 Luna and GPT-5.6 Luna?
GPT-6 Luna is about 2.4x cheaper on output tokens (6.0 vs 14.4 credits per 1M). Both take the same 1.1M-token context window. GPT-6 Luna is the newer release (September 2026 vs July 2026).
Is GPT-6 Luna or GPT-5.6 Luna cheaper?
GPT-6 Luna is cheaper: 6.0 credits per million output tokens against 14.4. 1 credit = $0.10, computed from the raw provider rate with a 1.20x margin.
Which has the larger context window, GPT-6 Luna or GPT-5.6 Luna?
Neither: both take 1.1M tokens.
Can I use both GPT-6 Luna and GPT-5.6 Luna on Zeplik?
Yes. Zeplik is a multi-model chat, so both sit behind one account and you can switch between them mid-conversation to compare answers on your own prompt.
Do GPT-6 Luna and GPT-5.6 Luna need a paid plan?
One of the two is open to free accounts; the other needs a paid plan (Plus or above).

Related comparisons

GPT-6 Luna detailsGPT-5.6 Luna detailsAll comparisons

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