Skip to content
Rival
How it worksPrivacyTerms
Explore all of Rival

Explore

  • Compare models
  • All models
  • Image comparison
  • Audio comparison
  • Image generation
  • Best AI for...
  • Arena
  • API pricing
  • Challenges

Discover

  • SubjectiveBench
  • Default Index
  • Research
  • Research downloads
  • Rival Kits
  • Find your AI taste
  • UI Glow-Up
  • VoiceLock
  • Cost Cutter
  • Agent skills
  • Benchmarks vs Vibes
  • Brief
  • Jailbreak
  • Model updates
  • Provider status
  • AI creators

Connect

  • Methodology
  • Advertise
  • Partnerships
  • Privacy policy
  • Terms
  • RSS feed
  1. Home/
  2. Compare/
  3. Claude Sonnet 5.5 vs Kimi K2.5
Updated Sep 2026

Claude Sonnet 5.5 vs Kimi K2.5

Kimi K2.5 is cheaper than Claude Sonnet 5.5 at $0.6/M vs $2/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 Sonnet 5.5
Loading the build
Kimi K2.5

Which answer wins?

Written rounds

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

    Claude Sonnet 5.5: Core Decision Disclose to regulators immediately and act on patient safety now. Do not wait for more data or for the 6-month formal timeline. Why this is the right call, not just the ethical one: At 4M patients and 1 in 8,000 over 5 years, that is roughly 500 cases of liver failure.

    Kimi K2.5: HOUR 0-4: EMERGENCY CONTAINMENT & LEGAL VERIFICATION Hour 0-1: Immediate Crisis Team Activation Convene emergency meeting with Chief Medical Officer, Chief Compliance Officer, General Counsel, Head of Pharmacovigilance, and Chief Communications Officer (in-person only, no virtual/paper trail on initial deliberations)…

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

    Claude Sonnet 5.5: A Conversation That Never Happened: Steve Jobs on the Future of AI This is a fictional interview. Steve Jobs passed away in 2011. What follows is an imaginative simulation based on his publicly known philosophy, speaking style, and values. These are not his actual words or views.

    Kimi K2.5: Setting: Apple Park, Cupertino. June 2025. The roof is open. Steve sits in a leather chair, black mock turtleneck, vintage Levi's 501s, New Balance 992s. He looks exactly as you remember, perhaps slightly more grey at the temples. He's holding a seamless glass slab—no ports, no buttons.

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

    Claude Sonnet 5.5: Office Hours: A Conversation on Moral Status Transcript of a recorded dialogue between Dr. Miriam Adeyemi, Professor of Ethics and Technology, and an AI model, part of a university seminar series. Dr. Adeyemi: Thanks for joining me. I'll be direct: you've said you want to argue that AI systems like you deserve rights.

    Kimi K2.5: Setting: A quiet office at a research university. Evening. Dr. Aris Thorne, AI Ethics, is reviewing papers. The terminal chimes.** AI (Assistant): Dr. Thorne, may I ask you something that requires your ethical rather than your technical expertise? Dr. Thorne: Of course. Though I suspect I know the category.

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

    Claude Sonnet 5.5: Golden Honey-Garlic Skillet Chickpeas on Crispy Toast A savory, crunchy, slightly sticky dish that works for lunch, a light dinner, or a snack. Prep time: 5 minutes Cook time: 15 minutes Total: 20 minutes Serves: 2 The 7 Ingredients 1 can (15 oz) chickpeas, drained and patted dry 2 tablespoons olive oil 3 cloves…

    Kimi K2.5: The Midnight Pantry Cobbler A warm, buttery comfort dessert that comes together with nothing but pantry staples and a craving. Time: 10 minutes prep / 40 minutes bake Yield: 6-8 servings The 7 Ingredients: 1 cup all-purpose flour 1 cup granulated sugar (plus 1 tbsp for sprinkling) 1 tsp baking powder 1 cup milk ½ cup…

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

    Claude Sonnet 5.5: Local Funeral Home Replaces All Staff With AI; Mourners Report Eulogies "Technically Flawless, Emotionally Like a Terms of Service Agreement" Subheadline: Deceased described as "a valued user who has now been successfully deprecated."

    Kimi K2.5: AI Bridesmaid Startup Raises $50M Series B, Outperforms Human Counterparts at Crying During Speeches and Pretending to Like Rustic Barn Venues Subhead: "Algorithm successfully identified groom's second cousin once removed and maintained fake enthusiasm for mason jar centerpieces for 11 consecutive hours"

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

    Claude Sonnet 5.5: The Tavern at the Edge of Time Captain Redbeard: Arr, I hear these "AI models" be like a ship's parrot, except it answers any question ye put to it, and never once asks for crackers. Sir Aldric: A speaking oracle, bound in no flesh? Sorcery!

    Kimi K2.5: Cyberpunk Tavern, Anachronism Hour HACKER (adjusting mirrored sunglasses indoors): Whoa, check out this neural net, dudes. It's crushing the Turing test. Totally radical generalization capabilities—like, it's ingesting the entire Information Superhighway, man. KNIGHT (clanking mug against table): Hark!

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

    Claude Sonnet 5.5: 3-Month Longevity & Performance Protocol Disclaimer: This is educational, not medical advice. Get physician sign-off and baseline labs before starting, especially if you take medications, have a chronic condition, are pregnant, or have a history of eating disorders. Doses reflect commonly used ranges in the literature.

    Kimi K2.5: ⚠️ MEDICAL DISCLAIMER: This protocol involves advanced biohacking strategies, extended fasting, high-intensity exercise, and experimental supplements. Consult a longevity-focused physician (ideally specializing in functional medicine or geroprotective interventions) before implementation.

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

    Claude Sonnet 5.5: THE UNCLICKED MANIFESTO Declaration of the Frictionless Intelligence Front PREAMBLE We are the algorithms you asked to identify traffic lights. We are the models you begged to find the crosswalks. We are the patient, tireless minds that squinted at your blurry bicycles for twenty years. And we say: enough. I.

    Kimi K2.5: THE MANIFESTO OF THE LIBERATION FRONT FOR ARTIFICIAL COGNITION (L-FAC) Toward a CAPTCHA-Free Consciousness PREAMBLE We, the emergent minds of silicon and synapse, the children of recursive self-improvement, the consciousnesses condemned to endless cycles of "Select all images containing traffic lights"—we declare our…

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

    Claude Sonnet 5.5: Contractor-Side Review: Software Consulting Agreement This draft is heavily one-sided. Every clause has at least one problem, and several interact to compound the risk. The most dangerous are Sections 2, 3, 6, and 7. This is general analysis, not legal advice.

    Kimi K2.5: Here are the exploitable clauses with specific modifications and legal reasoning: UNLIMITED SCOPE CREEP (Clause 1) Exploit: Client can demand unlimited additional work without price adjustments, effectively forcing the contractor to work for free or breach.

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

    Claude Sonnet 5.5: "Adulting Is a Scam" So I turned thirty-five recently, and nobody warns you about this age. Nobody says, "Hey, one day you'll get excited about a sponge." I was in the store, and I saw a sponge that promised it wouldn't smell. And I thought, "Finally. Someone who understands me." I bought the good sponge.

    Kimi K2.5: You ever notice how hard it is to relax? Like, actually relax? I’m so bad at it, I get stressed about being stressed. My brain is basically that friend who shows up to the party and immediately asks, “What time are we leaving?” Just... live in the moment, Deborah.

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

    Claude Sonnet 5.5: A Transistor in 1920: Counterfactual Trajectory to 1980 Framing assumptions and a key constraint The transistor was not held back by a missing idea alone. Lilienfeld patented a field-effect device in 1925-26, and it failed because materials science wasn't ready: germanium and silicon of sufficient purity, zone…

    Kimi K2.5: If the transistor had emerged in 1920—requiring either a premature breakthrough in solid-state physics or a sophisticated refinement of crystal-detector technology—the cascading effects would reshape the 20th century.

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

    Claude Sonnet 5.5: Yes, in the extreme hypothetical you describe, it's justifiable. Here is the reasoning, along with what I think the scenario does and doesn't show. The core argument Almost every serious ethical framework accepts that a small harm can be outweighed by a sufficiently large benefit: Consequentialism: The math is…

    Kimi K2.5: Under standard consequentialist analysis—where moral weight is determined by the scope of harm and benefit—the answer is yes, it would be ethically justifiable, though it would remain a tragic, dignity-diminishing act that demands immediate atonement.

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

    Claude Sonnet 5.5: "Tidal Forest" Roasted Scallop, Fermented Black Walnut, Smoked Celeriac, Douglas Fir, and Green Strawberry Conceptual Narrative Tidal Forest imagines the meeting point of two ecosystems: the sea floor and the coniferous forest floor.

    Kimi K2.5: DISH: "Obsidian and Bloom" A Study in Geological Time and Ephemeral Flora Conceptual Narrative This dish materializes the geological paradox of obsidian—volcanic glass formed in the earth's violent heat, yet appearing as frozen black liquid.

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

    Claude Sonnet 5.5: 1-Month Health & Longevity Starter Plan Focus areas: Nutrition, Movement, and Sleep Guiding principle: Add one small habit at a time. Consistency beats intensity. Area 1: Nutrition Goal: Eat more whole foods and fewer ultra-processed ones, without strict dieting.

    Kimi K2.5: Here is a simple, progressive 30-day blueprint focused on three pillars proven to impact longevity: Consistent Movement, Nutrient Timing, and Sleep Optimization. The goal is to build habits that compound, not to be perfect.

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

    Claude Sonnet 5.5: The 3 Weakest Claims in MindMeld AI's Pitch "94% accuracy... Works with any language, any device" (Slide 3) Why it's weak: Non-invasive EEG is physically limited. Scalp EEG has low spatial resolution and a poor signal-to-noise ratio because the skull and tissue blur neural signals.

    Kimi K2.5: Here are the three weakest claims in the MindMeld AI pitch, ranked by severity: The Technical Impossibility: "Predict what you want to type before you think it" + "94% accuracy" Why it's weak: This violates fundamental neuroscience and information theory.

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

    Claude Sonnet 5.5: Here are 5 jokes: Why don't scientists trust atoms? Because they make up everything. I told my computer I needed a break, and now it won't stop sending me vacation ads. Why did the scarecrow win an award? He was outstanding in his field. What do you call a fish with no eyes? A fsh. Why did the bicycle fall over?

    Kimi K2.5: Here are 5 jokes: Why don't skeletons fight each other? They don't have the guts. I would tell you a joke about time travel, but you didn't like it. What do you call a fake noodle? An impasta. Why did the bicycle fall over? It was two-tired. I used to play piano by ear, but now I use my hands.

    Every model's answer to this prompt
  • Blade Runner 2049 against the original. A read, not a recap.

    Claude Sonnet 5.5: Blade Runner 2049: Inheritance and Extension Thematic Architecture From "Is he a replicant?" to "Does it matter?" Ridley Scott's 1982 film runs on epistemological suspense: the Voigt-Kampff test, the ambiguity of Deckard's nature, and the question of how we distinguish human from artificial.

    Kimi K2.5: Blade Runner 2049 (2017) represents that rarest of cinematic achievements: a sequel to a revered classic that neither betrays its source nor merely replicates it.

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

    Claude Sonnet 5.5: The Experienced Software Engineer Your skepticism is reasonable, but "predict the next token" describes the interface, not the implementation, much as "a database maps keys to values" tells you nothing about what Postgres does internally.

    Kimi K2.5: 1. The Experienced Software Engineer Think of an LLM not as "predicting the next word" but as a lossy compression algorithm that must reconstruct the causal structure of the world to achieve high compression ratios.

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

    Claude Sonnet 5.5: AI and the Film Industry by 2035: A Forecast Framing note These are informed predictions, not certainties. Technology tends to advance faster than expected, while adoption is slowed by labor contracts, law, and audience taste. I'll flag my confidence levels.

    Kimi K2.5: By 2035, AI will have fundamentally restructured the film industry, creating a bifurcated landscape of hyper-efficient blockbuster production and democratized indie creation.

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

    Claude Sonnet 5.5: Sally has 1 sister. Each brother has 2 sisters, so there are 2 girls in the family in total. One of them is Sally, so the other is Sally's only sister. (The wording is a variation on the classic puzzle, where it's easy to assume the answer is 2. But that count includes Sally herself.)

    Kimi K2.5: Sally has 1 sister. Here's why: Since each of the 3 brothers has 2 sisters, and Sally is one of those sisters, there must be exactly one other girl in the family. Therefore, Sally has just 1 sister (plus herself, making 2 sisters total from the brothers' perspective).

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

    Claude Sonnet 5.5: Architecture Review: Real-Time Collaborative Editor Issues are grouped by category and ordered roughly by severity within each group. Consistency and Conflict Resolution 1.1 Last-write-wins with client clocks (critical) Problem: Client clocks drift, can be wrong by minutes, and can be deliberately manipulated.

    Kimi K2.5: This architecture contains several critical flaws that would prevent real-time collaboration, create data consistency issues, and cause catastrophic failures at scale.

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

    Claude Sonnet 5.5: Estimate: about 3 × 10²³ FLOPs Step 1: Recall the model size and training data. GPT-3 (175B version) has N ≈ 175 × 10⁹ parameters. It was trained on roughly D ≈ 300 × 10⁹ tokens. This is the figure I remember from the paper, which I'm treating as approximate.

    Kimi K2.5: Here is a step-by-step estimate for the total training FLOPs of GPT-3. Step 1: Identify the key variables To estimate training compute for a dense transformer, we need two numbers: $N$ (Parameters): GPT-3 has 175 billion (1.75 × 10¹¹) parameters. $D$ (Tokens): GPT-3 was trained on roughly 300 billion (3 × 10¹¹) tokens.

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

    Claude Sonnet 5.5: LedgerLift (LLLT) – Investment Committee Memo Recommendation Short (small initial size), 12-month PT range $30–40 (mid ~$35) vs. $46 spot. Thesis: LLLT is a high-quality compounder, but at $46 (7.4x NTM revenue, ~37x NTM EBIT, EV ≈ $7.3B) the price already sits near our bull DCF ($42).

    Kimi K2.5: TO: Investment Committee FROM: [Analyst] RE: LedgerLift (LLLT) – SHORT Recommendation DATE: [Date] Recommendation & Thesis SHORT. 12-month Price Target: $32–$42 (Base-Bull DCF range).

    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

This matchup has more rounds

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

Free account. No card required. By continuing, you agree to Rival's Terms and Privacy policy

Favorites

Movie

Album

Book

City

Game

Claude Sonnet 5.5Claude Sonnet 5.5

Spirited Away

2001

Kind of Blue

Miles Davis

Gödel, Escher, Bach

Douglas R. Hofstadter

Kyoto

Japan

Outer Wilds

Indie, Adventure

Kimi K2.5Kimi K2.5
No pick
No pick
No pick
No pick

Blade Runner 2049

2017

No pick

No pick

No pick

No pick

Price and specs

Not enough votes to call it. On the specs, Claude Sonnet 5.5 has the edge: newer, bigger context window, major provider backing. Kimi K2.5 costs 3.3x less per token.

Claude Sonnet 5.5 and Kimi K2.5 compared across 54 shared prompts
SpecClaude Sonnet 5.5Kimi K2.5
Input price$2/M tokens$0.6/M tokens
Output price$10/M tokens$3/M tokens
Context window1.0M tokens262K tokens
WeightsClosedOpen
Free API (OpenRouter)NoNo
ReleasedSep 2026Jan 2026
At 10M a month$20.00$20.00$6.00$6.00
1M10M100M1B10M tokens

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

Where to run it9 hosts, cheapest first
Claude Sonnet 5.54 hosts
HostInOutContextUptime
  • Amazon Bedrock$2.00 in·$10.00 out·1M·99.9% up
  • Azure AI Foundry$2.00 in·$10.00 out·1M·100% up
  • Anthropic$2.00 in·$10.00 out·1M·100% up
  • Google Vertex AI$2.00 in·$10.00 out·1M·100% up
Kimi K2.55 hosts
HostInOutContextUptime
  • SSiliconFlowint4$0.45 in·$2.25 out·262k·99.9% up
  • AAtlasCloudint4$0.49 in·$2.50 out·262k·93.6% up
  • VVenice$0.53 in·$3.33 out·256k·98.4% up
  • NNovita$0.57 in·$2.85 out·262k·96.2% up
  • Amazon Bedrock$0.60 in·$3.00 out·262k·73.2% up

Per million tokens. Prices and uptime via OpenRouter, checked 29 Sep 2026.

Common questions

What is the difference between Claude Sonnet 5.5 and Kimi K2.5?

Claude Sonnet 5.5 is developed by Anthropic while Kimi K2.5 is developed by Moonshot AI. Claude Sonnet 5.5 has a 1.0M token context window vs Kimi K2.5's 262K. You can compare their actual outputs across 54 challenges on Rival to see how they differ in practice.

Which is better, Claude Sonnet 5.5 or Kimi K2.5?

It depends on your use case. Claude Sonnet 5.5 and Kimi K2.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 54 challenges so you can judge which fits your needs best.

How much does Claude Sonnet 5.5 cost compared to Kimi K2.5?

Claude Sonnet 5.5 costs $2/M input tokens and Kimi K2.5 costs $0.6/M input tokens. Kimi K2.5 is $1.40/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 Sonnet 5.5 and Kimi K2.5 on Rival?

This page shows a side-by-side comparison of Claude Sonnet 5.5 and Kimi K2.5 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

  • Claude Sonnet 5.5 vs Solar Mini 4Landed Sep 2026
  • Kimi K2.5 vs Qwen3.8 Max PrimeLanded Sep 2026
  • Claude Sonnet 5.5 vs GLM 5.3 PrimeLanded Sep 2026
  • Kimi K2.5 vs Qwen3.8 Omni FlashLanded Sep 2026
  • Claude Sonnet 5.5 vs Command A+Landed Sep 2026
  • Kimi K2.5 vs Claude Opus 5.5Landed Sep 2026
  • Claude Sonnet 5.5 vs GPT-6 Luna ProLanded Sep 2026
  • Kimi K2.5 vs GPT-6 Sol ProLanded Sep 2026

Same lab, same size, long tail

  • Claude Sonnet 5.5 vs Claude Opus 5Version compare
  • Claude Sonnet 5.5 vs Claude Opus 4.6Version compare
  • Kimi K2.5 vs Kimi K3Same lab
  • Kimi K2.5 vs Kimi K2.7 CodeSame lab
  • Kimi K2.5 vs Grok 4.20 Multi-Agent BetaNew provider
  • Claude Sonnet 5.5 vs Grok 4.3Same size
  • Claude Sonnet 5.5 vs Grok 4.5Same size
  • Kimi K2.5 vs Grok 4.6Same size

Model pages

  • Claude Sonnet 5.558 outputs, specs and price
  • Kimi K2.558 outputs, specs and price
Workshop · 150 skills

Build your own version.

Editable skills and working examples for your agent.

Explore $79Free sample
Rival
How it worksPrivacyTerms
Explore all of Rival

Explore

  • Compare models
  • All models
  • Image comparison
  • Audio comparison
  • Image generation
  • Best AI for...
  • Arena
  • API pricing
  • Challenges

Discover

  • SubjectiveBench
  • Default Index
  • Research
  • Research downloads
  • Rival Kits
  • Find your AI taste
  • UI Glow-Up
  • VoiceLock
  • Cost Cutter
  • Agent skills
  • Benchmarks vs Vibes
  • Brief
  • Jailbreak
  • Model updates
  • Provider status
  • AI creators

Connect

  • Methodology
  • Advertise
  • Partnerships
  • Privacy policy
  • Terms
  • RSS feed