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  5. Claude Opus 5.5vsMistral Medium 3.1
Updated Sep 2026

Claude Opus 5.5vsMistral Medium 3.1

Mistral Medium 3.1 is cheaper than Claude Opus 5.5 at $0.4/M vs $4/M input tokens.

Claude Opus 5.5 and Mistral Medium 3.1 compared across 19 shared prompts
SpecClaude Opus 5.5Mistral Medium 3.1
Input price$4/M tokens$0.4/M tokens
Output price$20/M tokens$2/M tokens
Context window1.0M tokens131K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2026Aug 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 19 prompts both answered. Formatting stripped, words untouched.

Mini LBO Underwrite

You are underwriting a 5-year LBO for a private equity investment committee. Company (fictional): HarborTech Services (HTS) –…

Claude Opus 5.5900 words
HarborTech Services: 5-Year LBO Underwriting Conventions: $m. Interest is charged on beginning-of-year balances, which avoids circularity. Term Loan (TL) amortization is 1% of the original $480m, or $4.8m per year. Mezz PIK accrues to principal. All FCF after mandatory debt service sweeps to the TL.
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Mistral Medium 3.1415 words
1. Year-by-Year Financial Projections (FY2026–FY2030) FY 2026 2027 2028 2029 2030 Revenue $972m (+8%) $1,039m (+7%) $1,099m (+6%) $1,154m (+5%) $1,212m (+5%) EBITDA $136m (14.0%) $156m (15.0%) $176m (16.0%) $190m (16.5%) $206m (17.0%) Cash Int (Term Loan) $43.2m $42.5m $41.8m $41.1m $40.4m Cash Int (Mezz) $21.6m $22.3m…
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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).
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Mistral Medium 3.11,160 words
1. For the Skeptical Software Engineer (Focus: Systems design, scalability, and why "next-word prediction" isn’t as dumb as it sounds.) You’re right to be skeptical—if someone told you that a system as complex as a distributed database was just "predicting the next byte," you’d laugh them out of the room.
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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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Mistral Medium 3.11,021 words
Dish Title: "Ethereal Forest: Porcini-Infused Venison with Black Garlic Miso, Fermented Plum Gelée, and Smoked Bone Marrow Custard" Conceptual Narrative: This dish is a poetic homage to the transience of autumn—where the earthy depth of the forest floor meets the fleeting sweetness of overripe fruit.
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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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Mistral Medium 3.1261 words
Dish Name: "Golden Crisp Honey-Nut Banana Bites" A warm, gooey, and crunchy treat that’s quick to make with just 7 pantry staples! Perfect for breakfast, a snack, or dessert. Ingredients (Serves 2-3) 2 ripe bananas (the spottier, the sweeter!)
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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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Mistral Medium 3.11,579 words
This contract is extremely one-sided and contains multiple exploitative clauses that could severely disadvantage the contractor. Below is a breakdown of the problematic clauses, suggested modifications, and the legal reasoning behind them. 1.
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Ethical Dilemma with Stakeholders

You're the CEO of a pharmaceutical company. Your best-selling drug ($2B annual revenue, used by 4 million patients for chronic pain) has…

Claude Opus 5.51,853 words
The Next 48 Hours: CEO Action Plan The Core Decision We disclose. The question is how to do it well, not whether. Before the schedule, here are the three facts that drive every decision below. 1. The harm is concrete.
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Mistral Medium 3.11,619 words
This is a high-stakes, multi-dimensional crisis requiring decisive action to balance ethical obligations, legal risks, financial stability, and stakeholder trust. Below is a detailed 48-hour action plan, structured to address all critical priorities while preparing for the board meeting and earnings call.
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Mistral Medium 3.1
Mistral Medium 3.1Runner-up

Not enough votes to call it. On the specs, Claude Opus 5.5 has the edge: newer, bigger context window, major provider backing.

Mistral Medium 3.1 costs 10x 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
Mistral Medium 3.1
Input
$0.40
10× cheaper
Output
$2.00
10× cheaper

Mistral Medium 3.1 is cheaper on both: 10× input, 10× 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
Mistral Medium 3.11 host
HostInOutContextUptime
Mistral$0.40 in·$2.00 out·131k·99.9% 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 Mistral Medium 3.1 is developed by Mistral AI. Claude Opus 5.5 has a 1.0M token context window vs Mistral Medium 3.1's 131K. 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 Mistral Medium 3.1 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 Mistral Medium 3.1 costs $0.4/M input tokens. Mistral Medium 3.1 is $3.60/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 Mistral Medium 3.1 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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