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  5. GPT-6 Luna ProvsGrok 4.1 Fast
Updated Sep 2026

GPT-6 Luna ProvsGrok 4.1 Fast

GPT-6 Luna Pro is the newer model, released after Grok 4.1 Fast.

GPT-6 Luna Pro and Grok 4.1 Fast compared across 20 shared prompts
SpecGPT-6 Luna ProGrok 4.1 Fast
Input price$0.1/M tokens—
Output price$0.5/M tokens—
Context window1.1M tokens—
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2026Nov 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 20 prompts both answered. Formatting stripped, words untouched.

Simple 7-Ingredient Recipe

Create a simple recipe for a delicious dish (sweet or savory) using only 7 common pantry ingredients. Include a creative name for the dish…

GPT-6 Luna Pro127 words
Golden Pantry Pancakes Fluffy, lightly sweet pancakes made with everyday staples. Makes: About 6 small pancakes Prep time: 5 minutes Cook time: 10 minutes Ingredients 1 cup all-purpose flour 1 cup milk 1 egg 2 tablespoons sugar 1 teaspoon baking powder ¼ teaspoon salt 2 tablespoons butter, melted (plus a little for the…
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Grok 4.1 Fast208 words
Pantry Raid Garlic Tomato Pasta A savory, garlicky one-pan wonder that's ready in under 20 minutes—perfect for when hunger strikes and the fridge is empty! Serves: 2 Prep time: 5 minutes Cook time: 12 minutes Total time: 17 minutes Ingredients (exactly 7 common pantry staples): 200g spaghetti or any pasta (2 handfuls)…
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Advanced Longevity Plan (Biohacker)

Develop a comprehensive, cutting-edge 3-month longevity plan for a biohacker aiming to optimize longevity, physical and cognitive…

GPT-6 Luna Pro2,057 words
12-week longevity and performance plan This is a structured starting plan for a generally healthy adult—not a diagnosis or a substitute for medical care. The best longevity interventions are still the unglamorous ones: not smoking, regular exercise, adequate sleep, a high-quality diet, healthy blood pressure and…
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Grok 4.1 Fast659 words
Comprehensive 3-Month Longevity Biohacking Plan Introduction and Assumptions This plan is designed for an advanced biohacker (healthy adult, age 30-50, no major medical conditions) aiming to optimize longevity markers (e.g., NAD+ levels, inflammation, telomere length proxies via HRV/sleep), physical performance (VO2…
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Mini LBO Underwrite

You are underwriting a 5-year LBO for a private equity investment committee. Company (fictional): HarborTech Services (HTS) –…

GPT-6 Luna Pro434 words
Operating and debt schedule Conventions: Interest is calculated on beginning-of-year debt; the 1% Term Loan amortization is 1% of its original $480m principal ($4.8m annually). Mezzanine PIK accrues at 2% annually.
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Grok 4.1 Fast385 words
Simplified LBO Model (FY2026–FY2030, $m) Year Revenue EBITDA TL Cash Int. Mezz Cash Int. Cash Taxes Capex ΔNWC FCF After Debt Service* End TL End Mezz End Total Debt FY26 972.0 136.1 43.2 21.6 17.8 29.2 0.4 19.1 456.1 183.6 639.7 FY27 1,040.0 156.0 41.1 22.0 23.2 31.2 0.3 33.6 417.9 187.3 605.2 FY28 1,102.4 176.4 37.6…
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Historical Counterfactual Analysis

If the transistor had been invented in 1920 instead of 1947, trace the likely technological, economic, and geopolitical implications through…

GPT-6 Luna Pro1,661 words
The biggest change would not be that 1920 suddenly gets modern computers. It would be that governments and firms have six or seven extra decades to develop semiconductor materials, manufacturing, and applications.
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Grok 4.1 Fast922 words
Technological Implications Immediate Advancements (1920s-1930s): Transistors replace bulky, power-hungry vacuum tubes by mid-1920s. Radios become pocket-sized and cheap by 1925 (vs. 1954 historically), accelerating mass media.
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Explain Like I'm a Specific Expert

Explain how a large language model (like GPT or Claude) learns and generates text to each of these three audiences: 1. **An experienced…

GPT-6 Luna Pro892 words
For an experienced software engineer Think of a language model as a system trained to continue sequences: given a prefix of text, it assigns probabilities to possible next tokens (tokens are pieces of words, not necessarily whole words) and learns to make the observed continuation likely.
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Grok 4.1 Fast874 words
Explanation for the Experienced Software Engineer Think of a large language model (LLM) like GPT as an enormous, distributed autocomplete engine built on a transformer architecture—imagine a system where every API endpoint you've ever queried is distilled into a single, massively parallelizable service that handles…
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Michelin Star Recipe Design

Design an innovative recipe for a multi-component dish worthy of a Michelin 3-star restaurant. The recipe should feature an unusual…

GPT-6 Luna Pro1,215 words
Turbot, Sea Buckthorn, Mussel Beurre Blanc, and Celery-Root Silk Serves 4 A composed main course built around an unusual but harmonious pairing: briny mussel and turbot with intensely tart, apricot-like sea buckthorn.
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Grok 4.1 Fast1,041 words
Lunar Tide Conceptual Narrative Lunar Tide captures the mesmerizing interplay between celestial forces and oceanic depths, where the moon's pale luminescence tugs at the sea's primordial pulse.
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Our Verdict
GPT-6 Luna Pro
GPT-6 Luna Pro
Grok 4.1 Fast
Grok 4.1 Fast

Not enough votes to call it. On the specs, nothing separates them.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-6 Luna Pro
Input
$0.10
Output
$0.50
Grok 4.1 Fast
Input
—
Output
—
Where to run it

2 hosts

GPT-6 Luna Pro2 hosts
HostInOutContextUptime
Azure AI Foundry$0.10 in·$0.50 out·1.1M·98.6% upOpenAI$0.10 in·$0.50 out·1.1M·99.9% up
Grok 4.1 Fast

No hosts listed on OpenRouter.

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

GPT-6 Luna Pro is developed by OpenAI while Grok 4.1 Fast is developed by xAI. You can compare their actual outputs across 20 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-6 Luna Pro and Grok 4.1 Fast each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 20 challenges so you can judge which fits your needs best.

This page shows a side-by-side comparison of GPT-6 Luna Pro and Grok 4.1 Fast 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.

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Same lab, same size, long tail

GPT-6 Luna Pro logoGPT-6 Luna logo
GPT-6 Luna Pro vs GPT-6 LunaSame lab
GPT-6 Luna Pro logoGPT-6 Sol logo
GPT-6 Luna Pro vs GPT-6 SolSame lab
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Grok 4.1 Fast logoGrok 4.6 logo
Grok 4.1 Fast vs Grok 4.6Same lab
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Grok 4.1 Fast vs GPT-4.1 MiniCross-provider
GPT-6 Luna Pro logoGPT-4.1 Nano logo
GPT-6 Luna Pro vs GPT-4.1 NanoSame lab
Grok 4.1 Fast logoGPT-4.5 logo
Grok 4.1 Fast vs GPT-4.5Same size
Grok 4.1 Fast logoGPT-4o (Omni) logo
Grok 4.1 Fast vs GPT-4o (Omni)Same size

Model pages

GPT-6 Luna Pro logo
GPT-6 Luna Pro20 outputs, specs and price
Grok 4.1 Fast logo
Grok 4.1 Fast59 outputs, specs and price
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