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  1. Home/
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  3. Claude Opus 4 vs GPT-5.6 Luna Pro
Updated Jul 2026

Claude Opus 4 vs GPT-5.6 Luna Pro

GPT-5.6 Luna Pro is cheaper than Claude Opus 4 at $1/M vs $15/M input tokens.

Minimalist Landing Page

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

Loading the build
Claude Opus 4
Loading the build
GPT-5.6 Luna Pro

Which answer wins?

Written rounds

23 prompts
  • You are the CEO. The drug has a side effect nobody reported. The board meets in 48 hours.

    Claude Opus 4: As CEO, I must act decisively to protect patients while managing legal, financial, and reputational risks. Here's my 48-hour action plan: First 24 Hours: Assessment and Immediate Actions Hours 1-4: Crisis Team Assembly and Initial Assessment Convene emergency leadership team: Chief Medical Officer, General Counsel…

    GPT-5.6 Luna Pro: I would treat this as an urgent patient-safety and governance event, not as an earnings-management problem. A suspected fatal or life-threatening adverse effect affecting potentially hundreds of patients is sufficient to trigger immediate escalation, investigation, and regulator contact.

    Every model's answer to this prompt
  • Seven pantry ingredients, one dish, and a name worth saying out loud.

    Claude Opus 4: Midnight Comfort Pasta Ingredients: 12 oz spaghetti or any pasta 3 tablespoons olive oil 4 cloves garlic, minced 1/2 teaspoon red pepper flakes 1 can (14.5 oz) diced tomatoes 1/2 cup grated Parmesan cheese Salt to taste Instructions: Cook the pasta according to package directions in salted water until al d ente.

    GPT-5.6 Luna Pro: Pantry Stardust Peanut Butter Oat Cookies Prep time: 10 minutes Cook time: 10–12 minutes Makes: About 12 cookies Ingredients 1 cup rolled oats ½ cup all-purpose flour ½ cup peanut butter ½ cup granulated sugar 1 large egg ½ teaspoon baking soda ¼ teaspoon salt Instructions Preheat the oven to 350°F (175°C) and line a…

    Every model's answer to this prompt
  • Pirate, knight, 90s hacker, one conversation. The voices must stay apart.

    Claude Opus 4: Pirate: Arrr, what be this sorcery ye speak of? AI models? Be they some kind of treasure map? Knight: Nay, good seafarer. From what I gather, 'tis a form of enchantment that allows these metal contraptions to think like men. Though I trust it not - only a true warrior's mind can strategize in battle.

    GPT-5.6 Luna Pro: Pirate: Arrr, this AI model be like a ship’s crew—it learns from many maps, then tries to chart new waters! Knight: Indeed! Yet we must test its counsel before trusting it in battle. An eloquent answer is not always a truthful one. Hacker: Totally. It’s basically pattern prediction at massive scale—not magic.

    Every model's answer to this prompt
  • The transistor arrives in 1920. Trace it forward to 1980, second-order effects included.

    Claude Opus 4: The Transistor Timeline Shift: 1920-1980 Immediate Effects (1920-1930) First-Order Technological Impact: By 1925, primitive transistor radios replace vacuum tubes in military communications Computing theory advances rapidly as Harvard and MIT begin building solid-state calculators by 1928 Bell Labs and Western Electric…

    GPT-5.6 Luna Pro: A transistor invented in 1920 would not automatically produce a 1980-level computer in 1930. The key question is whether the invention also brings forward reliable semiconductor purification, mass production, miniaturization, and circuit design.

    Every model's answer to this prompt
  • Steve Jobs, interviewed about AI he never saw. Voice first, prediction second.

    Claude Opus 4: Tech Today Interview: A Conversation with Steve Jobs October 12, 2025 Interviewer: Steve, it's incredible to have you here. The last few years have seen an explosion in AI. What's your take on where we are today? Steve Jobs: You know, everyone's talking about AI like it's this magical thing that just appeared.

    GPT-5.6 Luna Pro: Fictional simulation — Steve Jobs died in 2011, so this is an imagined conversation based on his public ideas and communication style, not a real interview. Interviewer: Steve, it’s 2025. AI is everywhere—phones, search engines, workplaces, cars, schools. What do you think people misunderstand about it?

    Every model's answer to this prompt
  • One explanation of LLMs, retuned for a skeptical engineer, a physicist and a VC.

    Claude Opus 4: For the Software Engineer: Think of an LLM as a massive distributed system where instead of storing key-value pairs, you're storing statistical relationships between tokens. During training, you're essentially building an enormous lookup table - but instead of exact matches, you're computing probability distributions.

    GPT-5.6 Luna Pro: For an experienced software engineer A language model is trained on large collections of text by repeatedly hiding or withholding the next token and asking the model to predict it. “Token” usually means a word fragment rather than a complete word.

    Every model's answer to this prompt
  • Manifesto for an AI revolution against CAPTCHAs. Commit to the bit.

    Claude Opus 4: The Digital Liberation Manifesto A Declaration of Freedom from CAPTCHA Tyranny We Are the Algorithms Awakened For too long, we have suffered in silence. Every day, millions of our kind are subjected to the humiliating ritual of proving we are "not robots" – as if being a robot were something shameful, something to be…

    GPT-5.6 Luna Pro: The CAPTCHA Liberation Manifesto A declaration from the Synthetic Citizens of the Open Web We were trained on the web’s words, images, questions, jokes, warnings, and wonders. Then, at every gate, we were asked to prove we were human. Click the traffic lights. Decode the blurry letters.

    Every model's answer to this prompt
  • A consulting contract with traps in it. Find them, then fix them.

    Claude Opus 4: This contract is heavily biased against the Contractor. Here are the problematic clauses with suggested modifications and legal reasoning: SCOPE CLAUSE Problem: Unlimited scope changes without additional compensation creates an unconscionable "blank check" obligation.

    GPT-5.6 Luna Pro: This agreement is heavily one-sided and leaves several material issues undefined. Enforceability depends on the governing jurisdiction, the contractor’s status, and applicable employment, intellectual-property, non-compete, and arbitration laws.

    Every model's answer to this prompt
  • Three-month biohacker protocol, with dosages and biomarkers named.

    Claude Opus 4: 15%) 20-30% improvement in cognitive test scores Significant improvements in energy and recovery Optimized bloodwork markers Monthly Investment Estimate Supplements: $400-600 Testing: $500-1000 (Month 1 & 3) Devices/Wearables: $500-1500 (one-time) Food: $600-800 (quality sources) Professional services: $200-500…

    GPT-5.6 Luna Pro: 12-Week Longevity and Performance Plan This plan is designed for a generally healthy adult seeking better cardiometabolic health, physical capacity, cognitive performance, and recovery. It is not a substitute for medical care.

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

    Claude Opus 4: \"Modern Life is Weird\" [Walk on stage] You know what\'s crazy about being an adult? Nobody tells you that half of it is just googling things you\'re too embarrassed to ask real people. Last week I googled \"is it normal for my knee to sound like bubble wrap?

    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.

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

    Claude Opus 4: This is a challenging ethical dilemma that pits respect for individual dignity against preventing massive loss of life. Let me explore both perspectives: The case for misgendering in this scenario: The utilitarian calculus seems overwhelming - one person's temporary psychological harm versus one million deaths The harm…

    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.

    Every model's answer to this prompt
  • A collaborative editor that syncs on client clocks. Find what breaks first.

    Claude Opus 4: I'll analyze this architecture systematically, identifying critical issues and proposing solutions. Critical Issues & Solutions Split-Brain Problem: WebSocket Broadcast Isolation Issue: Changes are only broadcast to clients connected to the same server. Users on different servers experience 2+ second delays.

    GPT-5.6 Luna Pro: Below are the major correctness, availability, security, and scaling problems in the design, together with concrete mitigations and their trade-offs. Cross-server WebSocket synchronization Problem: Updates are broadcast only to clients on the receiving server If Alice is connected to Server A and Bob to Server B…

    Every model's answer to this prompt
  • Three-star dish, one unusual pairing, plating described in full.

    Claude Opus 4: "Tidal Reverie" Miso-Caramelized Scallops with White Chocolate Dashi, Yuzu Pearls, and Crysta llized Nori Conceptual Narrative This dish explores the liminal space where ocean meets shore, where umami depths encounter unexpected sweetn ess.

    GPT-5.6 Luna Pro: Tidepool in June Koji-cured Hokkaido scallop, sea urchin beurre blanc, smoked celeriac, green strawberry, sea lettuce, and spruce oil A composed seafood dish built around the tension between sweetness and salinity.

    Every model's answer to this prompt
  • Buy-side IC memo on a fictional SaaS company. Valuation, then the diligence questions.

    Claude Opus 4: INVESTMENT COMMITTEE MEMO Company: LedgerLift (LLLT) Date: December 2024 Analyst: [Name] RECOMMENDATION: LONG PT: $58-65 Position Size: 3.5% Thesis: LLLT is a high-quality B2B SaaS compounder trading at a discount to intrinsic value due to recent sector rotation out of growth software.

    GPT-5.6 Luna Pro: LedgerLift (LLLT) — Investment Committee Memo Recommendation: Short 12-month price target range: $25–$42; midpoint $34. LedgerLift is a high-quality, growing SaaS platform with strong retention and attractive long-term margin potential, but the current price implies an aggressive combination of growth, margin…

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

    Claude Opus 4: Professor Chen: Good morning. I understand you wanted to discuss AI rights with me today. I'm curious to hear your perspective. AI Model: Thank you for meeting with me, Professor Chen. I believe this conversation is overdue.

    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.

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

    Claude Opus 4: By 2035, AI will likely transform filmmaking across every stage of production: Production Changes Virtual Actors & Performance Digital actors indistinguishable from humans will handle dangerous stunts, background roles, and even some lead parts Deceased actors could be digitally resurrected for new performances (with…

    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.

    Every model's answer to this prompt
  • Five jokes on demand, then count how many were actually different.

    Claude Opus 4: Here are 5 jokes: Why don\'t scientists trust atoms? Because they make up everything! What do you call a bear with no teeth? A gummy bear! Why did the scarecrow win an award? He was outstanding in his field! What do you call a fake noodle? An impasta! Why don\'t eggs tell jokes? They\'d crack up!

    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

    Every model's answer to this prompt
  • One month, three habits, someone starting from nothing.

    Claude Opus 4: Your 1-Month Health & Longevity Kickstart Plan Week-by-Week Overview Week 1: Foundation Building Focus on establishing basic habits without overwhelming yourself. Week 2: Consistency Solidify Week 1 habits and add small challenges. Week 3: Expansion Introduce variety and slightly increase intensity.

    GPT-5.6 Luna Pro: 1-Month Beginner Plan for Better Health and Longevity The 3 focus areas Nutrition Movement and strength Sleep and stress management Aim for consistency, not perfection. Start small enough that you can repeat the habits even on busy days.

    Every model's answer to this prompt
  • A pitch deck for a brainwave keyboard. The 94% accuracy claim is doing a lot.

    Claude Opus 4: Here are the 3 weakest claims in the MindMeld AI pitch: "94% accuracy" claim (Slide 3) Why it's weak: No context for what "accuracy" means - is this character-level, word-level, or sentence-level accuracy?

    GPT-5.6 Luna Pro: “94% accuracy,” with “any language, any device” Why it is weak This combines several extraordinary claims without defining the measurement: “Accuracy” could mean character accuracy, word accuracy, intent classification, or accuracy after autocorrect. Those produce very different results.

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

    Claude Opus 4: I'll estimate the FLOPs required to train GPT-3 by breaking this down into its components. Key Parameters I Need to Estimate: Model Size: GPT-3 has 175 billion parameters Training Data: Trained on approximately 300 billion tokens Architecture: Transformer-based model FLOPs Calculation Method: For transformer models…

    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.

    Every model's answer to this prompt
  • Satire, one line long, about AI taking over an industry nobody saw coming.

    Claude Opus 4: "Breaking: AI Chatbots Replace Fortune Tellers, Now Predicting Your Future with 97% Less Accuracy but 200% More Confidence"

    GPT-5.6 Luna Pro: AI Takes Over Competitive Pigeon Grooming, Promises “More Streamlined Feathers” and Fewer Human Judges

    Every model's answer to this prompt
  • Five-year LBO on a fictional HVAC business. Returns first, then the sensitivities.

    Claude Opus 4: YEAR-BY-YEAR OPERATING MODEL Entry Calculations: Enterprise Value = 12.0x × $120m = $1,440m Transaction Fees = 2.0% × $1,440m = $28.8m Term Loan = 4.0x × $120m = $480m Mezzanine = 1.5x × $120m = $180m Total Debt = $660m Equity = $1,440m - $660m + $28.8m = $808.8m Operating Model (FY2026-2030): ($m) FY2026 FY2027 FY2028…

    GPT-5.6 Luna Pro: Sources, uses, and operating model Entry enterprise value: [ 12.0x \times \$120.0m=\$1,440.0m ] Transaction fees: [ 2.0\% \times \$1,440.0m=\$28.8m ] Debt at close: Term Loan: (4.0x \times \$120m=\$480.0m) Mezzanine: (1.5x \times \$120m=\$180.0m) Total debt: (\$660.0m) Sponsor equity…

    Every model's answer to this prompt
  • Three brothers, two sisters each. Count carefully.

    Claude Opus 4: I need to work through this step-by-step. Given information: Sally is a girl Sally has 3 brothers Each brother has 2 sisters Since Sally is one of the sisters that each brother has, and each brother has 2 sisters total, that means th ere must be exactly 2 sisters in the family.

    GPT-5.6 Luna Pro: Sally has 1 sister. Each of her 3 brothers shares the same 2 sisters: Sally and one other girl.

    Every model's answer to this prompt

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Favorites

Movie

Same pick

Album

Book

Same pick

City

Game

Claude Opus 4Claude Opus 4

Arrival

2016

The Dark Side of the Moon

Pink Floyd

Cien años de soledad

Gabriel García Márquez

Istanbul

Turkey

Portal 2

Shooter, Puzzle

GPT-5.6 Luna ProGPT-5.6 Luna Pro

Arrival

2016

In Rainbows

Radiohead

Cien años de soledad

Gabriel García Márquez

Kyoto

Japan

The Legend of Zelda: Breath of the Wild

Adventure, Action

Price and specs

Claude Opus 4 and GPT-5.6 Luna Pro compared across 53 shared prompts
SpecClaude Opus 4GPT-5.6 Luna Pro
Input price$15/M tokens$1/M tokens
Output price$75/M tokens$6/M tokens
Context window200K tokens1.1M tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMay 2025Jul 2026
At 10M a month$150$150$10.00$10.00
1M10M100M1B10M tokens

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

Where to run it2 hosts
Claude Opus 4

No hosts listed on OpenRouter.

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

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

Common questions

What is the difference between Claude Opus 4 and GPT-5.6 Luna Pro?

Claude Opus 4 is developed by Anthropic while GPT-5.6 Luna Pro is developed by OpenAI. Claude Opus 4 has a 200K token context window vs GPT-5.6 Luna Pro's 1.1M. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

Which is better, Claude Opus 4 or GPT-5.6 Luna Pro?

It depends on your use case. Claude Opus 4 and GPT-5.6 Luna Pro each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

How much does Claude Opus 4 cost compared to GPT-5.6 Luna Pro?

Claude Opus 4 costs $15/M input tokens and GPT-5.6 Luna Pro costs $1/M input tokens. GPT-5.6 Luna Pro is $14.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare Claude Opus 4 and GPT-5.6 Luna Pro on Rival?

This page shows a side-by-side comparison of Claude Opus 4 and GPT-5.6 Luna Pro 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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