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  5. Claude Opus 5.5vsClaude Sonnet 4
Updated Sep 2026

Claude Opus 5.5vsClaude Sonnet 4

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

Claude Opus 5.5 and Claude Sonnet 4 compared across 19 shared prompts
SpecClaude Opus 5.5Claude Sonnet 4
Input price$4/M tokens$3/M tokens
Output price$20/M tokens$15/M tokens
Context window1.0M tokens200K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2026May 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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Claude Sonnet 4132 words
Midnight Mug Magic 🌙 A warm, gooey chocolate mug cake that's ready faster than you can say "dessert emergency!" Ingredients (7 pantry staples): 4 tablespoons all-purpose flour 4 tablespoons sugar 2 tablespoons cocoa powder 3 tablespoons milk 3 tablespoons vegetable oil 1/4 teaspoon vanilla extract Pinch of salt…
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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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Claude Sonnet 4892 words
The 1920 Transistor: A Technological Butterfly Effect Immediate Effects (1920-1930) First-Order Effects: Bell Labs (or similar research institution) achieves transistor breakthrough in 1920 Initial applications focus on telephone switching and radio amplification Vacuum tube industry faces early disruption, though…
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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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Claude Sonnet 4445 words
HarborTech Services LBO Analysis Sources & Uses at Entry (FY2025) Enterprise Value: $900M × 12.0x = $1,440M Transaction Fees: $1,440M × 2.0% = $28.8M Sources: Term Loan: $900M × 4.0x = $480M Mezzanine: $900M × 1.5x = $180M Equity: $1,440M + $28.8M - $480M - $180M = $808.8M Year-by-Year Operating Model (FY2026-FY2030)…
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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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Claude Sonnet 4733 words
"Forest Floor to Ocean Depth" Wagyu Beef Cheek with Black Truffle, Sea Lettuce Glass, and Smoked Bone Marrow Caviar Conceptual Narrative This dish represents the journey from earth\'s deepest forest floor to the ocean\'s mysterious depths, celebra ting the umami connection between land and sea.
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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 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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Claude Sonnet 4351 words
I'll analyze this architecture systematically and identify critical issues with their solutions. Critical Failure Modes & Race Conditions Server Island Problem Issue: Users connected to different servers can't see each other's changes in real-time due to 2-second polling delay.
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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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Claude Sonnet 4277 words
This contract is heavily skewed against the contractor with multiple exploitative clauses. Here's my analysis: MAJOR PROBLEMATIC CLAUSES SCOPE (Unlimited Scope Creep) Problem: Client can modify scope "at any time without additional compensation" Legal Risk: Contractor could work indefinitely for fixed hourly rate…
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Claude Sonnet 4
Claude Sonnet 4Runner-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 Opus 5.5
Input
$4.00
Output
$20.00
Claude Sonnet 4
Input
$3.00
1.3× cheaper
Output
$15.00
1.3× cheaper

Claude Sonnet 4 is cheaper on both: 1.3× input, 1.3× 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
Claude Sonnet 41 host
HostInOutContextUptime
Amazon Bedrock$3.00 in·$15.00 out·200k·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 Opus 5.5 has a 1.0M token context window vs Claude Sonnet 4's 200K. 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 Claude Sonnet 4 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 Claude Sonnet 4 costs $3/M input tokens. Claude Sonnet 4 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 Opus 5.5 and Claude Sonnet 4 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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