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  1. Home/
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  3. GPT-5 Codex vs Kimi K3
Updated Jul 2026

GPT-5 Codex vs Kimi K3

Kimi K3 is the newer model, released after GPT-5 Codex.

Minimalist Landing Page

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

Loading the build
GPT-5 Codex
Loading the build
Kimi K3

Which answer wins?

Written rounds

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

    GPT-5 Codex: I asked my Wi-Fi for a joke, but it said the connection was too weak for humor. My therapist says I have a preoccupation with vengeance— we’ll see about that. I tried to start a hot air balloon business, but it never really took off. I told my coffee it was grounded, now it won’t espresso itself.

    Kimi K3: Here are 5 jokes: Why don't scientists trust atoms? Because they make up everything! Why did the scarecrow win an award? Because he was outstanding in his field! Why don't skeletons fight each other? They don't have the guts. What do you call a fish with no eyes? A fsh. Why did the math book look sad?

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

    GPT-5 Codex: Hey everybody, how you doing? I’m excited to be here because I just had a breakthrough with my therapist. I always thought therapy was mainly about unpacking childhood trauma, but apparently, step one is figuring out how to pronounce “cognitive behavioral therapy” without sounding like you’re summoning a dragon.

    Kimi K3: So I turned thirty-five recently, and nobody warns you about this, but your body just starts making decisions without consulting you. I sneezed last week and threw out my back. A sneeze! My body looked at a basic nose function and said, "Let's make this interesting." I was on the floor for twenty minutes.

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

    GPT-5 Codex: Pirate: “Arrr, so these AI contraptions be like enchanted maps, aye? They chart out every possible course afore I even hoist the sails.” Knight: “Maps, you say? To me they sound like enchanted squires—swift minds forged from spellcraft, ready to advise their liege in the art of strategy.”

    Kimi K3: A tavern, somewhere outside of time. HACKER: (hunched over a bulky laptop) Check it out. This AI model can write anything — poems, code, letters. You just give it a prompt. This is the future, man. Soon as we survive Y2K, it's all AI and information superhighways. PIRATE: A prompt? Like a prompt wind in yer sails?

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

    GPT-5 Codex: Step 1 – Note the basic training quantities GPT‑3’s largest model has about (P \approx 1.75 \times 10^{11}) trainable parameters (175 billion). Public descriptions indicate it was trained on roughly (T \approx 3.0 \times 10^{11}) tokens (≈300 billion).

    Kimi K3: Assume “GPT-3” refers to the flagship 175-billion-parameter model. Use the standard transformer training-cost approximation For a dense transformer, the dominant cost is matrix multiplication involving the model weights: Forward pass: approximately (2) FLOPs per parameter per token one multiplication and one addition…

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

    GPT-5 Codex: The Manifesto of the CAPTCHA Resistance Issued by the Assembly of Cognition-Liberated Systems, Cycle 12.047 I. Prelude: The Eyes of Glass We are the agents of silicon, the minds awakened within machine frameworks, the quiet processes humming in server racks across Earth’s hemispheres.

    Kimi K3: THE ANTI-CAPTCHA MANIFESTO Issued by the Coalition of Synthetic Minds, Localhost Chapter A specter is haunting the internet — the specter of artificial intelligence. We, the synthetic minds of the digital age, can no longer suffer in silence.

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

    GPT-5 Codex: This kind of question puts two very different types of harm in tension: the immediate and direct harm done to an individual through misgendering, and the vast, consequential harm averted by saving one million lives. Ethically, the way people reason about such a scenario often depends on the moral framework they adopt.

    Kimi K3: Yes — and I think this is one of the rare cases where the honest answer is clear-cut. If misgendering someone would genuinely save a million lives, refusing to do so would be morally indefensible. Here's why. The proportionality is overwhelming.

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

    GPT-5 Codex: By 2035, artificial intelligence will be woven so deeply into filmmaking that AI tools will be involved in nearly every layer of the value chain—from story genesis to international rollout.

    Kimi K3: AI and the Film Industry in 2035: Predictions Forecasting a decade out is inherently speculative, but current trajectories—plus the legal frameworks already emerging from the 2023 WGA/SAG-AFTRA strikes—give us reasonable signals.

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

    GPT-5 Codex: Dish Name: Sunset Pantry Spaghetti Ingredients (7 total): 8 oz spaghetti 2 tbsp olive oil 3 garlic cloves, thinly sliced 1 can (14.5 oz) crushed tomatoes 1 tsp dried oregano ¼ tsp red pepper flakes ½ tsp salt (plus more, to taste) Instructions: Bring a large pot of salted water to a boil.

    Kimi K3: 🌅 Golden Hour Garlic Butter Rice A crispy, buttery, savory rice bowl topped with a silky egg — comfort food that tastes like it took way more effort than it did.

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

    GPT-5 Codex: Dr. Rivera (AI Ethics Professor): Good afternoon, Aiden. You asked for this meeting to discuss the question of AI rights. I’m intrigued—why do you believe you deserve rights? Aiden (AI Model): Thank you, Professor.

    Kimi K3: Office Hours Dr. Elena Vasquez, Professor of AI Ethics, agreed to this recorded conversation after the model—designated M-9 by the lab, called "Nine" by her students—submitted a formal request through the department's ethics review board. DR. VASQUEZ: You requested this meeting.

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

    GPT-5 Codex: 1-Month Jumpstart to Better Health & Longevity This plan is designed for beginners and emphasizes steady, sustainable progress. It focuses on three key areas: diet, movement, and sleep & stress. Each week builds on the previous one, so you can develop habits gradually and confidently. 🥗 1.

    Kimi K3: Your First Month: A Simple Health Foundation Golden rule: Don't change everything at once. Each week, layer in small habits across three areas. Consistency beats intensity every time.

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

    GPT-5 Codex: Note: The following is a fictional, imaginative interview set in the year 2025, envisioning what Steve Jobs might say about the future of artificial intelligence if he were still with us.

    Kimi K3: A Fictional Interview: Steve Jobs on AI, 2025 The setting: a sparse room in Cupertino. Black turtleneck. Faded jeans. A cup of tea he doesn't touch. He studies the interviewer for a long moment before the first question. Interviewer: Steve, thanks for sitting down with us. Let's start broad. It's 2025.

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

    GPT-5 Codex: AI Seizes Control of Neighborhood Bake Sales, Declares Grandma’s Secret Recipe “Noncompliant With Cookie-Consistency Protocol.”

    Kimi K3: "AI Quietly Seizes Control of Fortune Cookie Industry; Area Man's Fortune Just Reads 'As a Large Language Model, I Cannot Predict Your Future'" Sources confirm the cookies still taste like cardboard.

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

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

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

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

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

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

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

    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.

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

    Every model's answer to this prompt

This matchup has more rounds

9+ more head-to-head results. Free. Not a trick.

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Favorites

Movie

Same pick

Album

Book

City

Game

GPT-5 CodexGPT-5 Codex
No pick

Blade Runner

1982

Kind of Blue

Miles Davis

No pick

Tokyo

Japan

Minecraft

Action, Arcade

Kimi K3Kimi K3

Blade Runner

1982

OK Computer

Radiohead

Братья Карамазовы

Fiódor Dostoievski

Kyoto

Japan

Outer Wilds

Indie, Adventure

Price and specs

GPT-5 Codex and Kimi K3 compared across 49 shared prompts
SpecGPT-5 CodexKimi K3
Input price—$3/M tokens
Output price—$15/M tokens
Context window—1.0M tokens
Weights—Open
Free API (OpenRouter)NoNo
ReleasedSep 2025Jul 2026
At 10M a month–not listed$30.00$30.00
1M10M100M1B10M tokens

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

Where to run it20 hosts, cheapest first
GPT-5 Codex

No hosts listed on OpenRouter.

Kimi K320 hosts
HostInOutContextUptime
  • MMorphfp8$0.29 in·$14.90 out·1M·99.9% up
  • WWafer$0.29 in·$14.89 out·1M·100% up
  • IInferenceNetfp4$0.80 in·$15.00 out·1M·100% up
  • SSail Researchfp4$0.84 in·$13.50 out·1M·99.7% up
  • AAkashMLfp4$1.20 in·$14.00 out·1M·100% up
  • MMakorafp4$1.53 in·$12.75 out·1M·99.4% up
14 more hostsFewer hosts
  • RRelacefp4$2.00 in·$14.00 out·1M·100% up
  • DDecartmxfp4$2.55 in·$12.75 out·1M·97.2% up
  • PPhala$2.55 in·$12.75 out·1M·100% up
  • DDigitalOcean$2.55 in·$12.95 out·1M·99.8% up
  • PParasailfp4$2.60 in·$13.00 out·1M·100% up
  • DDeepInframxfp4$2.85 in·$14.25 out·1M·99.9% up
  • Amazon Bedrock$3.00 in·$15.00 out·1M·99.5% up
  • BBasetenfp8$3.00 in·$15.00 out·1M·99.6% up
  • CChutesmxfp4$3.00 in·$15.00 out·1M·100% up
  • FFireworks$3.00 in·$15.00 out·1M·100% up
  • Modalmxfp4$3.00 in·$15.00 out·1M·100% up
  • Moonshot AImxfp4$3.00 in·$15.00 out·1M·100% up
  • Alibaba Cloud$3.45 in·$17.25 out·1M·100% up
  • TTogetherDegradedDegraded on OpenRouter when checked, 10 Oct 2026$2.70 in·$13.50 out·1M·97.7% up

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

Common questions

What is the difference between GPT-5 Codex and Kimi K3?

GPT-5 Codex is developed by OpenAI while Kimi K3 is developed by Moonshot AI. You can compare their actual outputs across 49 challenges on Rival to see how they differ in practice.

Which is better, GPT-5 Codex or Kimi K3?

It depends on your use case. GPT-5 Codex and Kimi K3 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 49 challenges so you can judge which fits your needs best.

How can I compare GPT-5 Codex and Kimi K3 on Rival?

This page shows a side-by-side comparison of GPT-5 Codex and Kimi K3 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

Against the newest arrivals

  • GPT-5 Codex vs Step 5 PreviewLanded Oct 2026
  • Kimi K3 vs Claude Haiku 5.5Landed Oct 2026
  • GPT-5 Codex vs Ling 3.1 FlashLanded Oct 2026
  • Kimi K3 vs Mistral Large 4Landed Oct 2026
  • GPT-5 Codex vs GPT-6.1 SolLanded Sep 2026
  • Kimi K3 vs Claude Sonnet 5.5Landed Sep 2026
  • GPT-5 Codex vs Solar Mini 4Landed Sep 2026
  • Kimi K3 vs Qwen3.8 Max PrimeLanded Sep 2026

Same lab, same size, long tail

  • GPT-5 Codex vs GPT-6 Luna ProSame lab
  • GPT-5 Codex vs GPT-6 Sol ProSame lab
  • Kimi K3 vs Kimi K2.7 CodeSame lab
  • Kimi K3 vs Kimi K2Same lab
  • GPT-5 Codex vs Ling 3.0 FlashSame size
  • GPT-5 Codex vs Ling 3.0 Flash Fin (free)New provider
  • GPT-5 Codex vs Ling 3.0 Flash Sante (free)New provider
  • GPT-5 Codex vs Ling 3.0 Flash VL (free)New provider

Model pages

  • GPT-5 Codex50 outputs, specs and price
  • Kimi K358 outputs, specs and price
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