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  5. Claude Opus 5.5vsClaude Sonnet 5
Updated Sep 2026

Claude Opus 5.5vsClaude Sonnet 5

Claude Sonnet 5 is cheaper than Claude Opus 5.5 at $2/M vs $4/M input tokens.

Claude Opus 5.5 and Claude Sonnet 5 compared across 19 shared prompts
SpecClaude Opus 5.5Claude Sonnet 5
Input price$4/M tokens$2/M tokens
Output price$20/M tokens$10/M tokens
Context window1.0M tokens1.0M tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2026Jun 2026
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 5250 words
Honey Garlic Skillet Pasta A quick, comforting dish that balances sweet and savory flavors using ingredients you probably already have on hand. Ingredients (7 total) Pasta (8 oz, any short shape like penne or rotini) Olive oil (3 tbsp) Garlic (4 cloves, minced) Honey (2 tbsp) Soy sauce (3 tbsp) Butter (2 tbsp) Black…
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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 5895 words
"Tide & Timber" Smoked Eel, Charred Pine, Fermented Black Garlic, and Bitter Almond Conceptual Narrative This dish explores the unexpected harmony between deep coastal umami and resinous forest aromatics—a culinary meditation on the moment where ocean meets ancient woodland, as happens along the fjords of Scandinavia.
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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 5644 words
HarborTech Services (HTS) — LBO Underwriting Entry Math Item Calc $m Entry EV 12.0x × $120m EBITDA 1,440.0 Transaction fees 2.0% × 1,440.0 28.8 Total Uses EV + fees 1,468.8 Term Loan 4.0x × 120 480.0 Mezzanine 1.5x × 120 180.0 Total Debt 5.5x × 120 660.0 Sponsor Equity Uses – Debt 808.8 Year-by-Year Build…
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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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Claude Sonnet 51,196 words
For the Software Engineer You're right to be skeptical of the slogan, but the slogan is misleading you about what's actually happening. "Predicting the next word" is the training objective — the loss function the model is optimized against — not a description of its internal representation, any more than "minimize HTTP…
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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 51,528 words
The Transistor in 1920: A Counterfactual Cascade to 1980 A Note on Plausibility (Brief, Because It Matters) This isn't pure fantasy — Julius Lilienfeld actually filed patents in 1925-1934 for field-effect semiconductor amplifiers. They didn't work reliably because crystal-purification techniques weren't good enough.
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Advanced Investment Memo (IC Memo)

You are writing an internal investment committee memo for a long/short equity fund. Company (fictional): LedgerLift (ticker: LLLT) – B2B…

Claude Opus 5.51,335 words
IC Memo: LedgerLift (LLLT): Short, Starter Size, Hedged vs. Peer Basket Fictional exercise. Not investment advice. Recommendation Short (starter size, 1–1.5% gross), paired against a long basket of Peers A, B and C. 12-month price target range: $36–42 (current price $46, implying 9–22% downside). Thesis.
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Claude Sonnet 5790 words
IC MEMO: LedgerLift (LLLT) — Initiation Review Recommendation: PASS (no position) 12-month PT range: $36–$50 LedgerLift's retention metrics (NRR 123%, gross retention 94%) are genuinely best-in-class and justify a premium multiple, but at $46 the stock already prices in execution that our DCF can only support in the…
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Claude Sonnet 5
Claude Sonnet 5

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

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 5
Input
$2.00
2.0× cheaper
Output
$10.00
2.0× cheaper

Claude Sonnet 5 is cheaper on both: 2.0× input, 2.0× output.

Where to run it

8 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 54 hosts
HostInOutContextUptime
Amazon Bedrock$2.00 in·$10.00 out·1M·100% upAzure AI Foundry$2.00 in·$10.00 out·1M·99.7% upAnthropic$2.00 in·$10.00 out·1M·100% upGoogle Vertex AI$2.00 in·$10.00 out·1M·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

Both are developed by Anthropic but target different use cases. Claude Opus 5.5 has a 1.0M token context window vs Claude Sonnet 5's 1.0M. 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 5 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 5 costs $2/M input tokens. Claude Sonnet 5 is $2.00/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 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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