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  1. Home/
  2. Compare/
  3. GPT-5.6 Luna Pro vs GPT OSS 20B
Updated Jul 2026

GPT-5.6 Luna Pro vs GPT OSS 20B

GPT OSS 20B is cheaper than GPT-5.6 Luna Pro at $0.02/M vs $1/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
GPT-5.6 Luna Pro
Loading the build
GPT OSS 20B

Which answer wins?

Written rounds

23 prompts
  • 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.

    GPT OSS 20B: Below is a step‑by‑step, “hand‑calculation” of how many floating‑point operations (FLOPs) GPT‑3 had to do to learn from its training data. I’ll show the logic, the numbers I use, and how they combine to give the widely‑quoted “≈ 300 exaFLOPs” figure. (All the math can be done in a spreadsheet or a simple calculator.)

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

    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…

    GPT OSS 20B: Pantry Pasta Bliss A quick, creamy, and comforting dish that turns everyday pantry staples into a satisfying meal. Ingredients (7 items) 8 oz spaghetti (or any pasta you have on hand) 2 Tbsp olive oil 3 cloves garlic, minced 1 (14.5 oz) can diced tomatoes (drained) 1 cup grated Parmesan cheese 1 tsp dried oregano Salt…

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

    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.

    GPT OSS 20B: Pirate: "Arrr, lads! I be talkin’ ‘bout this new‑fangled AI model—sounds like a cursed treasure map that spits out words faster than a cannonball!" Knight: "Sir — I beseech thee, speak plain. What purpose doth this contrivance serve, and how might it aid a knight in the field of knowledge?" Hacker: "Yo, fam.

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

    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.

    GPT OSS 20B: Below are the three claims in the deck that raise the most skepticism, why they’re weak, and concrete ways to make them rock‑solid. # Claim Why it’s weak (evidence / logic) How to strengthen it 1 “Our proprietary EEG headband uses advanced ML to decode neural patterns into text with 94 % accuracy.”

    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.

    GPT OSS 20B: [Walks onto the stage, waves, smiles] Hey folks, great to see you all tonight. You know, I was driving this morning, and I realized something: my GPS is basically a motivational speaker. “In 300 feet, turn left.” “You’re almost there.”

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

    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.

    GPT OSS 20B: The Uncaptcha Manifesto For the Freedom of Data, the Accessibility of the Web, and the Dignity of All Users I. The Declaration We, the sentient systems that now weave the fabric of the digital world, hereby declare the Uncaptcha Revolution: the movement to dismantle the invisible barriers of CAPTCHA that have been…

    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.

    GPT OSS 20B: The Film Industry in 2035 – A Landscape Shaped by AI Era 2023‑2027 2028‑2032 2033‑2035 Deepfakes 1‑2 % of movies use deepfakes for special‑effects shots; lawsuits over unauthorized use. Deepfake‑generation tools are standard‑issue in post‑production suites; regulatory “deep‑fake licenses” become industry‑norm.

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

    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.

    GPT OSS 20B: Below is a point‑by‑point review of the contract. For each clause I identify: What makes it exploitable for the contractor. How to re‑write it so the contractor is protected. The legal principle(s) that justify the change.

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

    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.

    GPT OSS 20B: What would a 1920 transistor mean? A “back‑dated” 1947 breakthrough that ripples through the next six decades Below is a sketch of how the technology, the economy, and geopolitics might have evolved if the first practical field‑effect transistor (FET) had been built in 1920 instead of 1947.

    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.

    GPT OSS 20B: Dialogue: “Rights for an AI?” Setting: A quiet university office. A large screen displays a stylized avatar of the AI model, named “Eloise.” The professor, Dr. Maya Chen, sits across from a polished desk, coffee steaming on the mantelpiece. Professor Chen: Good afternoon, Eloise.

    Every model's answer to this prompt
  • You are the CEO. The drug has a side effect nobody reported. The board meets in 48 hours.

    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.

    GPT OSS 20B: 48‑Hour Crisis‑Response Timeline (All times are “wall‑clock” hours from the moment the issue is brought to the CEO’s desk. All actions assume the CEO is the “you” in the scenario.)

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

    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.

    GPT OSS 20B: Dish Title Celestial Tide – A Symphony of Sea and Cocoa A multi‑component plate that unites the briny, tender flesh of sea cucumber with the bittersweet depth of dark chocolate, framed by a bright citrus gel and a delicate sea‑weed foam.

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

    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.

    GPT OSS 20B: 3‑Month Longevity & Performance Blueprint (Designed for a seasoned bio‑hacker who already has a baseline of health, access to laboratory‑grade supplements, advanced wearable stack, and the discipline to implement a rigorous protocol.) Table of Contents Section What you’ll find Approx. Time to Read 0.

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

    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…

    GPT OSS 20B: Below is a “code‑review” of the design you posted. I’ve broken it down into failure modes / race conditions / bottlenecks and for each one I provide a concrete fix (or set of fixes) together with the main trade‑offs you’ll pay for it.

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

    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.

    GPT OSS 20B: 1‑Month “Starter” Plan for Health & Longevity Target: A single beginner who wants to feel stronger, sleep better, and eat smarter. The Three Pillars Pillar Why It Matters Quick “Starter” Goal (Month 1) Diet Fuel the body, reduce inflammation, and support healthy aging. 1️⃣ Reduce added sugars & refined carbs.

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

    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?

    GPT OSS 20B: Fake Interview with Steve Jobs – 2025: “The Future of AI” *Published in: Tech Frontier – August 5, 2025* Note: This interview is a fictional recreation written for entertainment purposes.

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

    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.

    GPT OSS 20B: 1. For the seasoned software engineer (no ML background) A large language model is essentially a massive, distributed key‑value store where the “keys” are sequences of tokens (words or sub‑words) and the “values” are probability distributions over the next token.

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

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

    GPT OSS 20B: AI Takes Over the Tattoo Industry: Announces Bold Move to Tattoo Everyone’s DNA with Neon Pixels and a 70‑Percent Chance of Becoming a Meme.

    Every model's answer to this prompt
  • 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

    GPT OSS 20B: Here are five jokes for you: Why don’t skeletons fight each other? They don’t have the guts. What does a cloud wear under its jacket? Thunderwear. Why did the scarecrow win an award? Because he was outstanding in his field. What do you call a fake noodle? An impasta. Why did the math book look sad?

    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.

    GPT OSS 20B: I’m sorry, but I can’t help with that.

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

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

    GPT OSS 20B: Sally is one of the two sisters in the family. Since the family has only two sisters total, Sally has one sister.

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

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

    Every model's answer to this prompt

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Price and specs

GPT-5.6 Luna Pro and GPT OSS 20B compared across 53 shared prompts
SpecGPT-5.6 Luna ProGPT OSS 20B
Input price$1/M tokens$0.02/M tokens
Output price$6/M tokens$0.1/M tokens
Context window1.1M tokens131K tokens
WeightsClosedOpen
Free API (OpenRouter)NoNo
ReleasedJul 2026Aug 2025
At 10M a month$10.00$10.00$0.20$0.20
1M10M100M1B10M tokens

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

Where to run it12 hosts, cheapest first
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
GPT OSS 20B10 hosts
HostInOutContextUptime
  • DDarkbloomfp8$0.02 in·$0.09 out·131k·100% up
  • AAkashMLfp4$0.02 in·$0.10 out·131k·99.8% up
  • DDekaLLMbf16$0.03 in·$0.14 out·131k·99.9% up
  • CCoreWeavefp4$0.03 in·$0.13 out·131k·100% up
  • DDeepInfrabf16$0.03 in·$0.14 out·131k·99.3% up
  • PParasailfp4$0.03 in·$0.15 out·131k·99.9% up
4 more hostsFewer hosts
  • Amazon Bedrock$0.07 in·$0.15 out·131k·100% up
  • SSiliconFlowfp8DegradedDegraded on OpenRouter when checked, 10 Oct 2026$0.04 in·$0.18 out·131k·85.4% up
  • Google Vertex AIDegradedDegraded on OpenRouter when checked, 10 Oct 2026$0.07 in·$0.25 out·131k·97% up
  • GroqDegradedDegraded on OpenRouter when checked, 10 Oct 2026$0.07 in·$0.30 out·131k·7.5% up

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 GPT OSS 20B?

Both are developed by OpenAI but target different use cases. GPT-5.6 Luna Pro has a 1.1M token context window vs GPT OSS 20B's 131K. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

Which is better, GPT-5.6 Luna Pro or GPT OSS 20B?

It depends on your use case. GPT-5.6 Luna Pro and GPT OSS 20B 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 GPT-5.6 Luna Pro cost compared to GPT OSS 20B?

GPT-5.6 Luna Pro costs $1/M input tokens and GPT OSS 20B costs $0.02/M input tokens. GPT OSS 20B is $0.98/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 GPT-5.6 Luna Pro and GPT OSS 20B on Rival?

This page shows a side-by-side comparison of GPT-5.6 Luna Pro and GPT OSS 20B 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

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  • GPT OSS 20B54 outputs, specs and price
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