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  5. Claude Sonnet 4.5vsClaude Opus 5.5
Updated Sep 2026

Claude Sonnet 4.5vsClaude Opus 5.5

Claude Sonnet 4.5 is cheaper than Claude Opus 5.5 at $3/M vs $4/M input tokens.

Claude Sonnet 4.5 and Claude Opus 5.5 compared across 17 shared prompts
SpecClaude Sonnet 4.5Claude Opus 5.5
Input price$3/M tokens$4/M tokens
Output price$15/M tokens$20/M tokens
Context window200K tokens1.0M tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2025Sep 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 17 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 Sonnet 4.5165 words
Golden Pantry Frittata Ingredients: 6 eggs 1 cup shredded cheese (cheddar or mozzarella) 1 onion, diced 2 cloves garlic, minced 2 tablespoons olive oil Salt and pepper to taste 1/2 teaspoon dried herbs (oregano, basil, or Italian seasoning) Instructions: Preheat your oven to 375°F (190°C).
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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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Debug This Architecture

Here's the architecture for a real-time collaborative document editor (like Google Docs): **System Overview:** - Frontend: React SPA with…

Claude Sonnet 4.5606 words
Critical Issues Analysis 🔴 CRITICAL: Data Loss & Consistency Issues Client Clock-Based Timestamps (SEVERE) Problem: Client clocks can be wrong, manipulated, or skewed User with clock set to future will always "win" conflicts No guaranteed ordering of operations Failure Scenarios: Solutions: Approach Pros Cons…
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Claude Opus 5.52,280 words
Architecture Review: Real-Time Collaborative Editor The most serious problems cluster in three areas: the sync model (client-clock LWW), cross-server propagation (per-server WebSockets with DB polling), and the CDN/auth layer, which can leak data between users. Issues are grouped by area below.
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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 Sonnet 4.51,155 words
"Terrestrial Tide" A Michelin Three-Star Composition Conceptual Narrative This dish explores the intersection of land and sea through an unexpected lens: the marriage of bone marrow's terrestrial richness with the ocean's delicate umami, unified by the surprising sweetness of white miso and the floral notes of sake…
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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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Advanced Longevity Plan (Biohacker)

Develop a comprehensive, cutting-edge 3-month longevity plan for a biohacker aiming to optimize longevity, physical and cognitive…

Claude Sonnet 4.53,176 words
Ultimate 3-Month Biohacker Longevity Optimization Protocol Table of Contents Foundation & Assessment Phase Supplement Stack Protocol Nutritional Architecture Exercise & Movement Systems Sleep Optimization Cognitive Enhancement Stress Resilience & HRV Training Advanced Tracking & Biomarkers Weekly Schedule Integration…
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Claude Opus 5.53,099 words
The 90-Day Longevity & Performance Protocol A structured, measurable plan for the experienced biohacker How to Use This Plan Philosophy: Measure → Intervene → Re-measure. Every intervention has a hypothesis, a metric, and a decision rule.
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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 Sonnet 4.51,440 words
48-Hour Crisis Action Plan HOUR 0-2: Immediate Containment & Fact Verification Actions: Convene emergency meeting with Chief Medical Officer, General Counsel, Head of Regulatory Affairs, and Chief Scientific Officer Demand written summary of findings: statistical confidence, causality assessment, comparison to baseline…
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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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Beginner's Longevity Plan

Outline a simple, actionable 1-month plan for someone starting their journey towards better health and longevity. Focus on 3 key areas…

Claude Sonnet 4.5331 words
Your 1-Month Health & Longevity Kickstart Plan 3 Key Areas to Transform 1. NUTRITION: Build Your Foundation Week 1-2: Add Before You Subtract Drink 8 glasses of water daily (set phone reminders) Add 1 serving of vegetables to lunch and dinner Eat protein with every meal (eggs, fish, chicken, beans, yogurt) Week 3-4…
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Claude Opus 5.5653 words
Your 1-Month Starter Plan for Better Health & Longevity The philosophy: Small, consistent changes beat dramatic overhauls. Each week builds on the last, so by Day 30 you'll have a foundation of habits instead of a burned-out resolution.
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Claude Sonnet 4.5
Claude Sonnet 4.5Runner-up

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

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Sonnet 4.5
Input
$3.00
1.3× cheaper
Output
$15.00
1.3× cheaper
Claude Opus 5.5
Input
$4.00
Output
$20.00

Claude Sonnet 4.5 is cheaper on both: 1.3× input, 1.3× output.

Where to run it

8 hosts

Claude Sonnet 4.54 hosts
HostInOutContextUptime
Amazon Bedrock$3.00 in·$15.00 out·1M·99.9% upAzure AI Foundry$3.00 in·$15.00 out·200k·98.9% upAnthropic$3.00 in·$15.00 out·1M·100% upGoogle Vertex AI$3.00 in·$15.00 out·1M·99.5% up
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

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

Research

What we learned reading every model

FAQ

Common questions

Both are developed by Anthropic but target different use cases. Claude Sonnet 4.5 has a 200K token context window vs Claude Opus 5.5's 1.0M. You can compare their actual outputs across 17 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Sonnet 4.5 and Claude Opus 5.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 17 challenges so you can judge which fits your needs best.

Claude Sonnet 4.5 costs $3/M input tokens and Claude Opus 5.5 costs $4/M input tokens. Claude Sonnet 4.5 is $1.00/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 Sonnet 4.5 and Claude Opus 5.5 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.

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Model pages

Claude Sonnet 4.5 logo
Claude Sonnet 4.543 outputs, specs and price
Claude Opus 5.5 logo
Claude Opus 5.519 outputs, specs and price
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