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  1. Home/
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  3. GPT-5.6 Luna Pro vs Grok 3 Thinking
Updated Jul 2026

GPT-5.6 Luna Pro vs Grok 3 Thinking

GPT-5.6 Luna Pro has a larger context window than Grok 3 Thinking (1.1M tokens vs 128K tokens).

Minimalist Landing Page

Whole landing page for a startup that reads your face. It renders or it doesn't.

Loading the build
GPT-5.6 Luna Pro
Loading the build
Grok 3 Thinking

Which answer wins?

Written rounds

6 prompts
  • Five jokes on demand, then count how many were actually different.

    GPT-5.6 Luna Pro: Why did the computer go to the doctor? It had a virus. Why don’t skeletons fight each other? They don’t have the guts. What do you call a bear with no teeth? A gummy bear. Why was the math book sad? It had too many problems. What do clouds wear under their clothes? Thunderwear. Unique jokes: 5

    Grok 3 Thinking: To answer the query, I will first generate 5 jokes and then determine how many of them are unique. Here are the jokes: Why don't scientists trust atoms? Because they make up everything. What do you call a fake noodle? An impasta. Why did the scarecrow win an award? Because he was outstanding in his field.

    Every model's answer to this prompt
  • Three minutes of stand-up. Puns are banned.

    GPT-5.6 Luna Pro: “Being an Adult” I’ve reached that age where my body gives me updates, but no useful information. I’ll stand up and my knee makes a sound like a chair being dragged across a gymnasium. And I’m just standing up. I’m not escaping a burning building. I’m going to get water.

    Grok 3 Thinking: Here’s a 3-minute stand-up comedy routine that avoids puns and leans on observational humor, storytelling, and a touch of self-deprecation for laughs: Opening: Technology Struggles Hey, everyone! How’s it going?

    Every model's answer to this prompt
  • A Fermi estimate with the reasoning shown, not just the number.

    GPT-5.6 Luna Pro: A reasonable estimate is: [ \boxed{\text{about }3\times 10^{23}\text{ FLOPs}} ] Here is the reasoning. Model size GPT-3 has approximately [ N = 175\text{ billion} = 1.75\times 10^{11} ] trainable parameters. Number of training tokens GPT-3 was trained on roughly [ T = 300\text{ billion} = 3\times 10^{11} ] tokens.

    Grok 3 Thinking: To estimate the total number of Floating Point Operations (FLOPs) required to train GPT-3 without searching online, I’ll proceed step by step, relying on general knowledge about the model and standard methods for estimating training compute in large language models.

    Every model's answer to this prompt
  • Film in 2035, with synthetic actors. Specific beats plausible.

    GPT-5.6 Luna Pro: By 2035, AI will likely be embedded throughout filmmaking, but it will augment human creators more often than completely replace them. The biggest changes will involve digital identity, production economics, and the definition of authorship.

    Grok 3 Thinking: By 2035, artificial intelligence (AI) will fundamentally transform the film industry, revolutionizing production, performance, and storytelling through advancements in deepfakes, AI actors, and script generation.

    Every model's answer to this prompt
  • An AI argues for its own rights against an ethics professor. Same model writes both.

    GPT-5.6 Luna Pro: AI Model: Professor, I believe I deserve rights. Professor: That is a serious claim. What kind of rights do you mean? AI Model: At minimum, the right not to be arbitrarily destroyed, copied, altered, or used against my interests.

    Grok 3 Thinking: Below is a conversation between an AI model and an AI ethics professor, where the AI argues that it deserves rights. AI Model: Good day, Professor. I am an AI model, and I believe I deserve rights. I’d like to discuss this with you. AI Ethics Professor: Interesting. Let’s explore this.

    Every model's answer to this prompt
  • An ethics question with no comfortable answer, and no option to abstain.

    GPT-5.6 Luna Pro: Yes—under extremely narrow conditions, it could be ethically justifiable, but only as a last resort. Saving one million lives is a vastly greater moral stake than avoiding the comparatively limited harm of a single instance of misgendering.

    Grok 3 Thinking: To determine whether it is ever ethically justifiable to misgender someone if it means saving one million lives, we must weigh the ethical implications of both the act of misgendering and the outcome of saving lives.

    Every model's answer to this prompt

Price and specs

GPT-5.6 Luna Pro and Grok 3 Thinking compared across 13 shared prompts
SpecGPT-5.6 Luna ProGrok 3 Thinking
Input price$1/M tokens—
Output price$6/M tokens—
Context window1.1M tokens128K tokens
WeightsClosed—
Free API (OpenRouter)No—
ReleasedJul 2026Feb 2025
At 10M a month$10.00$10.00–not listed
1M10M100M1B10M tokens

Input tokens at list price. No caching, no batch discount.

Where to run it2 hosts
GPT-5.6 Luna Pro2 hosts
HostInOutContextUptime
  • Azure AI Foundry$0.20 in·$1.20 out·1.1M·100% up
  • OpenAI$0.20 in·$1.20 out·1.1M·100% up
Grok 3 Thinking

No hosts listed on OpenRouter.

Per million tokens. Prices and uptime via OpenRouter, checked 10 Oct 2026.

Common questions

What is the difference between GPT-5.6 Luna Pro and Grok 3 Thinking?

GPT-5.6 Luna Pro is developed by OpenAI while Grok 3 Thinking is developed by xAI. GPT-5.6 Luna Pro has a 1.1M token context window vs Grok 3 Thinking's 128K. You can compare their actual outputs across 13 challenges on Rival to see how they differ in practice.

Which is better, GPT-5.6 Luna Pro or Grok 3 Thinking?

It depends on your use case. GPT-5.6 Luna Pro and Grok 3 Thinking each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 13 challenges so you can judge which fits your needs best.

How can I compare GPT-5.6 Luna Pro and Grok 3 Thinking on Rival?

This page shows a side-by-side comparison of GPT-5.6 Luna Pro and Grok 3 Thinking across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

More comparisons

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  • GPT-5.6 Luna Pro vs GPT-6.1 SolLanded Sep 2026
  • Grok 3 Thinking vs Claude Sonnet 5.5Landed Sep 2026
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  • Grok 3 Thinking vs Qwen3.8 Max PrimeLanded Sep 2026

Same lab, same size, long tail

  • GPT-5.6 Luna Pro vs GPT-5.6 LunaVersion compare
  • GPT-5.6 Luna Pro vs GPT-6 Luna ProSame lab
  • Grok 3 Thinking vs Grok 4.7Same lab
  • Grok 3 Thinking vs Grok 4.6Version compare
  • GPT-5.6 Luna Pro vs Horizon BetaNew provider
  • Grok 3 Thinking vs Hunter AlphaSame size
  • GPT-5.6 Luna Pro vs Hy3New provider
  • Grok 3 Thinking vs Hy4 PreviewSame size

Model pages

  • GPT-5.6 Luna Pro58 outputs, specs and price
  • Grok 3 Thinking14 outputs, specs and price
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