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  5. Claude Opus 5.5vsKimi K2
Updated Sep 2026

Claude Opus 5.5vsKimi K2

Kimi K2 is cheaper than Claude Opus 5.5 at $0.57/M vs $4/M input tokens.

Claude Opus 5.5 and Kimi K2 compared across 19 shared prompts
SpecClaude Opus 5.5Kimi K2
Input price$4/M tokens$0.57/M tokens
Output price$20/M tokens$2.3/M tokens
Context window1.0M tokens—
WeightsClosedOpen
Free API (OpenRouter)NoNo
ReleasedSep 2026Jul 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 19 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…

Claude Opus 5.5300 words
Midnight Silk Noodles Creamy, tangy peanut noodles with a gentle kick, ready faster than takeout. Serves: 2 Prep time: 5 minutes Cook time: 10 minutes Total time: 15 minutes The 7 Ingredients 8 oz (225 g) spaghetti (or any long noodle) ¼ cup creamy peanut butter 3 tablespoons soy sauce 1 tablespoon honey (or sugar) 1…
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Kimi K2247 words
Caramel-Cloud Banana Skillet Cake (aka “The One-Bowl Wonder that Tastes Like Sunday Morning”) Ingredients (all everyday staples) 2 very ripe bananas 1 cup all-purpose flour ½ cup granulated sugar 1 large egg ¼ cup milk (any kind) 3 Tbsp butter (or neutral oil) ½ tsp baking powder Pinch of salt is nice but…
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Explain Like I'm a Specific Expert

Explain how a large language model (like GPT or Claude) learns and generates text to each of these three audiences: 1. **An experienced…

Claude Opus 5.51,442 words
How Large Language Models Work: Three Explanations For the Experienced Software Engineer Think of an LLM as a single, very large pure function: f(tokens[0..n]) → probability distribution over tokens[n+1]. Text is chunked into tokens (roughly word fragments, from a vocabulary of about 100k).
Read the full answer
Kimi K2682 words
────────────────── Software Engineer ────────────────── Think of the model as a distributed cache of compressed program traces. During training, every sentence in the crawl is treated like a log line produced by an unobserved deterministic program that the model is trying to reverse-engineer.
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Startup Pitch Teardown

Here's a pitch deck summary for a startup called "MindMeld AI": **Slide 1 - Vision:** "We're building the future of human-AI collaboration.…

Claude Opus 5.5936 words
The 3 Weakest Claims in the MindMeld AI Pitch "Decodes neural patterns into text with 94% accuracy. Works with any language, any device." (Slide 3) Why it's weak: It far exceeds the published state of the art. The best results for thought-to-text come from invasive implants.
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Kimi K2372 words
Slide 1 – “Reads your brainwaves to predict what you want to type before you think it.” • Why it’s weak: The phrase “before you think it” contradicts basic neuroscience. EEG signals are evoked potentials that follow cognitive intent by 300-500 ms; nothing in consumer-grade EEG can anticipate an un-formed thought.
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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…

Claude Opus 5.52,253 words
"Hive & Tide" Langoustine, Beeswax, White Chocolate & Oscietra Caviar, Hay-Baked Celeriac, Fermented Green Strawberry, Sea Buckthorn I. The Concept Most coastal menus celebrate the meeting of sea and land. This dish is about a stranger, quieter meeting: the meadow and the seabed, the bee and the langoustine.
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Kimi K21,012 words
Dish Title “White Forest: Coal-Kissed Pine, Malted Vanilla Snow & Fermented Moss” Conceptual Narrative This plate is a walk through a winter-birch forest at twilight: the air is resinous from pine, the soil smells faintly of smoke and cocoa, and a single ray of moonlight gilds the frost.
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Historical Counterfactual Analysis

If the transistor had been invented in 1920 instead of 1947, trace the likely technological, economic, and geopolitical implications through…

Claude Opus 5.53,435 words
The Transistor in 1920: A Counterfactual Through 1980 First, a Reality Check on the Premise A transistor "invented" in 1920 would not have changed the world in 1920. The actual 1947 transistor rested on three foundations that did not exist yet: Quantum theory of solids.
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Kimi K2554 words
Thought Process: To explore the implications of an earlier transistor invention (1920 vs. 1947), we need to analyze cascading effects across multiple domains. Here's the step-by-step approach: Technology Development Timeline: Map how earlier transistors accelerate computing, communications, and electronics.
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Adversarial Contract Review

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

Claude Opus 5.54,420 words
Contractor-Side Review of the Software Consulting Agreement Overall assessment: This agreement is heavily one-sided. Nearly every clause shifts risk, cost, or control to the Contractor, and several provisions interact to create compounding exposure.
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Kimi K21,204 words
Foundational disclaimer: I am not your lawyer, this is not legal advice, and you should retain qualified counsel before signing or revising any contract. The comments below are purely educational and based on U.S.–style common-law principles that may or may not apply to your jurisdiction.
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Kimi K2
Kimi K2

Not enough votes to call it. On the specs, nothing separates them.

Kimi K2 costs 8.7x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Opus 5.5
Input
$4.00
Output
$20.00
Kimi K2
Input
$0.57
7.0× cheaper
Output
$2.30
8.7× cheaper

Kimi K2 is cheaper on both: 7.0× input, 8.7× output.

Where to run it

5 hosts

Claude Opus 5.54 hosts
HostInOutContextUptime
Amazon Bedrock$4.00 in·$20.00 out·1M·99.8% upAzure AI Foundry$4.00 in·$20.00 out·1M·100% upAnthropic$4.00 in·$20.00 out·1M·100% upGoogle Vertex AI$4.00 in·$20.00 out·1M·100% up
Kimi K21 host
HostInOutContextUptime
NNovitafp8$0.57 in·$2.30 out·131k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Claude Opus 5.5 is developed by Anthropic while Kimi K2 is developed by Moonshot AI. You can compare their actual outputs across 19 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Opus 5.5 and Kimi K2 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 19 challenges so you can judge which fits your needs best.

Claude Opus 5.5 costs $4/M input tokens and Kimi K2 costs $0.57/M input tokens. Kimi K2 is $3.43/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 Claude Opus 5.5 and Kimi K2 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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