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  5. Claude 3.7 Thinking SonnetvsClaude Opus 5.5
Updated Sep 2026

Claude 3.7 Thinking SonnetvsClaude Opus 5.5

Claude Opus 5.5 is cheaper than Claude 3.7 Thinking Sonnet at $4/M vs $6/M input tokens.

Claude 3.7 Thinking Sonnet and Claude Opus 5.5 compared across 19 shared prompts
SpecClaude 3.7 Thinking SonnetClaude Opus 5.5
Input price$6/M tokens$4/M tokens
Output price$30/M tokens$20/M tokens
Context window200K tokens1.0M tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedFeb 2025Sep 2026
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 3.7 Thinking Sonnet290 words
HarborTech Services LBO Underwriting Year-by-Year Financial Model (FY2026-2030) Metric ($M) FY2026 FY2027 FY2028 FY2029 FY2030 Revenue $972.0 $1,040.0 $1,102.4 $1,157.6 $1,215.5 EBITDA $136.1 $156.0 $176.4 $191.0 $206.6 Cash Interest - Term Loan $43.2 $41.0 $37.6 $32.8 $26.8 Cash Interest - Mezzanine $21.6 $22.0 $22.5…
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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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Advanced Longevity Plan (Biohacker)

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

Claude 3.7 Thinking Sonnet1,727 words
Comprehensive 3-Month Longevity Optimization Protocol Initial Assessment Phase (Week 0) Establish your baseline with these measurements before beginning: Blood Panel: Complete metabolic panel, lipid profile, inflammatory markers (hsCRP, IL-6), hormones (testosterone, estrogen, DHEA, cortisol), fasting glucose, HbA1c…
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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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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 3.7 Thinking Sonnet760 words
INVESTMENT COMMITTEE MEMO: LEDGERLIFT (LLLT) RECOMMENDATION: LONG PT RANGE: $48-$66 (Base/Bull) Thesis: LedgerLift's market-leading spend management platform demonstrates exceptional unit economics with 123% NRR and 18-month CAC payback, positioning it to capture significant share in the underpenetrated mid-market…
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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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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 3.7 Thinking Sonnet843 words
48-Hour Action Plan: CEO Response to Drug Safety Crisis Day 1 Hours 1-3: Immediate Assessment & Response Team Assembly I'll immediately convene an emergency meeting with our internal research team, Chief Medical Officer, Chief Scientific Officer, and head of Pharmacovigilance to fully understand the liver failure…
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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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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 3.7 Thinking Sonnet909 words
"Temporal Echo: Sea & Forest Confluence" Conceptual Narrative This dish explores the dialogue between ocean depths and ancient forest floors, creating a sensory experience where seemingly disparate ecosystems converge.
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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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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 3.7 Thinking Sonnet632 words
How Large Language Models Work: Three Tailored Explanations For an Experienced Software Engineer What makes LLMs fascinating from a systems perspective is that they're essentially massive distributed computing graphs that learn to compress and reconstitute information through backpropagation.
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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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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Claude 3.7 Thinking Sonnet
Claude 3.7 Thinking SonnetRunner-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 3.7 Thinking Sonnet
Input
$6.00
Output
$30.00
Claude Opus 5.5
Input
$4.00
1.5× cheaper
Output
$20.00
1.5× cheaper

Claude Opus 5.5 is cheaper on both: 1.5× input, 1.5× output.

Where to run it

4 hosts

Claude 3.7 Thinking Sonnet

No hosts listed on OpenRouter.

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 3.7 Thinking Sonnet has a 200K token context window vs Claude Opus 5.5'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 3.7 Thinking Sonnet and Claude Opus 5.5 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 3.7 Thinking Sonnet costs $6/M input tokens and Claude Opus 5.5 costs $4/M input tokens. Claude Opus 5.5 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 3.7 Thinking Sonnet 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 3.7 Thinking Sonnet logo
Claude 3.7 Thinking Sonnet59 outputs, specs and price
Claude Opus 5.5 logo
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