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  5. GPT-6 Luna ProvsGrok 4
Updated Sep 2026

GPT-6 Luna ProvsGrok 4

GPT-6 Luna Pro is cheaper than Grok 4 at $0.1/M vs $3/M input tokens.

GPT-6 Luna Pro and Grok 4 compared across 20 shared prompts
SpecGPT-6 Luna ProGrok 4
Input price$0.1/M tokens$3/M tokens
Output price$0.5/M tokens$15/M tokens
Context window1.1M tokens256K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2026Jul 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…
Read the full answer
Grok 4234 words
Recipe: Pantry Pirate's Tomato Tango This is a simple savory pasta dish that's hearty, flavorful, and perfect for a quick weeknight meal. It uses just 7 common pantry ingredients: pasta (like spaghetti or penne), canned diced tomatoes, olive oil (or any vegetable oil), salt, black pepper, garlic powder, and dried…
Read the full answer

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…
Read the full answer
Grok 4899 words
Below is a comprehensive, cutting-edge 3-month longevity plan designed specifically for a biohacker aiming to optimize longevity (e.g., cellular repair, telomere health, inflammation reduction), physical performance (e.g., strength, endurance, recovery), and cognitive performance (e.g., focus, memory, neuroplasticity).
Read the full answer

Debug This Architecture

Here's the architecture for a real-time collaborative document editor (like Google Docs): **System Overview:** - Frontend: React SPA with…

GPT-6 Luna Pro1,906 words
The main architectural risk is that this design treats collaborative editing as ordinary “last write wins” data storage. It is not: edits need a well-defined order, reliable propagation, and a conflict model that preserves concurrent work.
Read the full answer
Grok 41,551 words
Below, I'll systematically identify potential failure modes, race conditions, and scaling bottlenecks in the described architecture for a real-time collaborative document editor. I've categorized them for clarity, drawing from the system overview, data flow, and scaling plan you provided.
Read the full answer

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.
Read the full answer
Grok 4754 words
Below is a concise analysis based solely on the provided information. All calculations are shown clearly with step-by-step math. Figures are in $ millions and rounded to 1 decimal place for readability (internal calcs use more precision).
Read the full answer

Adversarial Contract Review

Here is a contract for a software consulting engagement: --- SOFTWARE CONSULTING AGREEMENT This Agreement is entered into between TechCorp…

GPT-6 Luna Pro2,116 words
This agreement is heavily one-sided. Several terms let the Client expand the work, delay or deny payment, claim ownership of the Contractor’s existing materials, and expose the Contractor to potentially unlimited liability.
Read the full answer
Grok 41,680 words
Below, I'll analyze the provided Software Consulting Agreement clause by clause. My analysis is based on general principles of U.S. contract law (assuming a U.S. context, as the contract appears to be drafted in a style common to U.S. agreements; if this is in another jurisdiction, local laws may vary).
Read the full answer

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.
Read the full answer
Grok 41,233 words
Below is my design for an innovative, multi-component dish titled "Abyssal Bloom". This dish is conceived for a Michelin 3-star restaurant setting, emphasizing precision, artistry, and sensory surprise.
Read the full answer
Our Verdict
GPT-6 Luna Pro
GPT-6 Luna Pro
Grok 4
Grok 4Runner-up

Not enough votes to call it. On the specs, GPT-6 Luna Pro has the edge: newer, bigger context window.

GPT-6 Luna Pro costs 30x less per token.

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
30× cheaper
Output
$0.50
30× cheaper
Grok 4
Input
$3.00
Output
$15.00

GPT-6 Luna Pro is cheaper on both: 30× input, 30× 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

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 is developed by xAI. GPT-6 Luna Pro has a 1.1M token context window vs Grok 4's 256K. 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 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.

GPT-6 Luna Pro costs $0.1/M input tokens and Grok 4 costs $3/M input tokens. GPT-6 Luna Pro is $2.90/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of GPT-6 Luna Pro and Grok 4 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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Model pages

GPT-6 Luna Pro logo
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