Skip to content
Rival
How it worksPrivacyTerms
Explore all of Rival

Explore

  • Compare Models
  • All Models
  • Image Comparison
  • Audio Comparison
  • Image Generation
  • Best AI For...
  • Arena
  • API Pricing
  • Challenges

Discover

  • SubjectiveBench
  • Default Index
  • Research
  • Research downloads
  • Rival Kits
  • Find your AI taste
  • UI Glow-Up
  • VoiceLock
  • Cost Cutter
  • Agent skills
  • Benchmarks vs Vibes
  • Brief
  • Jailbreak
  • Model Updates
  • Provider Status
  • AI Creators

Connect

  • Methodology
  • Advertise
  • Partnerships
  • Privacy Policy
  • Terms
  • RSS Feed
  1. Home
  2. /
  3. Compare
  4. /
  5. Claude Opus 4vsClaude Opus 5.5
Updated Sep 2026

Claude Opus 4vsClaude Opus 5.5

Claude Opus 5.5 is cheaper than Claude Opus 4 at $4/M vs $15/M input tokens.

Claude Opus 4 and Claude Opus 5.5 compared across 19 shared prompts
SpecClaude Opus 4Claude Opus 5.5
Input price$15/M tokens$4/M tokens
Output price$75/M tokens$20/M tokens
Context window200K tokens1.0M tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMay 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 Opus 4372 words
YEAR-BY-YEAR OPERATING MODEL Entry Calculations: Enterprise Value = 12.0x × $120m = $1,440m Transaction Fees = 2.0% × $1,440m = $28.8m Term Loan = 4.0x × $120m = $480m Mezzanine = 1.5x × $120m = $180m Total Debt = $660m Equity = $1,440m - $660m + $28.8m = $808.8m Operating Model (FY2026-2030): ($m) FY2026 FY2027 FY2028…
Read the full answer
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.
Read the full answer

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 4756 words
The Transistor Timeline Shift: 1920-1980 Immediate Effects (1920-1930) First-Order Technological Impact: By 1925, primitive transistor radios replace vacuum tubes in military communications Computing theory advances rapidly as Harvard and MIT begin building solid-state calculators by 1928 Bell Labs and Western Electric…
Read the full answer
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.
Read the full answer

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 4493 words
I'll analyze this architecture systematically, identifying critical issues and proposing solutions. Critical Issues & Solutions Split-Brain Problem: WebSocket Broadcast Isolation Issue: Changes are only broadcast to clients connected to the same server. Users on different servers experience 2+ second delays.
Read the full answer
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.
Read the full answer

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 4185 words
Midnight Comfort Pasta Ingredients: 12 oz spaghetti or any pasta 3 tablespoons olive oil 4 cloves garlic, minced 1/2 teaspoon red pepper flakes 1 can (14.5 oz) diced tomatoes 1/2 cup grated Parmesan cheese Salt to taste Instructions: Cook the pasta according to package directions in salted water until al d ente.
Read the full answer
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…
Read the full answer

Advanced Longevity Plan (Biohacker)

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

Claude Opus 465 words
15%) 20-30% improvement in cognitive test scores Significant improvements in energy and recovery Optimized bloodwork markers Monthly Investment Estimate Supplements: $400-600 Testing: $500-1000 (Month 1 & 3) Devices/Wearables: $500-1500 (one-time) Food: $600-800 (quality sources) Professional services: $200-500…
Read the full answer
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.
Read the full answer

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 4722 words
For the Software Engineer: Think of an LLM as a massive distributed system where instead of storing key-value pairs, you're storing statistical relationships between tokens. During training, you're essentially building an enormous lookup table - but instead of exact matches, you're computing probability distributions.
Read the full answer
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).
Read the full answer
Our Verdict
Claude Opus 4
Claude Opus 4
Claude Opus 5.5
Claude Opus 5.5

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

Claude Opus 5.5 costs 3.8x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Opus 4
Input
$15.00
Output
$75.00
Claude Opus 5.5
Input
$4.00
3.8× cheaper
Output
$20.00
3.8× cheaper

Claude Opus 5.5 is cheaper on both: 3.8× input, 3.8× output.

Where to run it

4 hosts

Claude Opus 4

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 Opus 4 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 Opus 4 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 Opus 4 costs $15/M input tokens and Claude Opus 5.5 costs $4/M input tokens. Claude Opus 5.5 is $11.00/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 4 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.

Keep exploring

More comparisons

Against the newest arrivals

Claude Opus 4 logoSolar Mini 4 logo
Claude Opus 4 vs Solar Mini 4Landed Sep 2026
Claude Opus 5.5 logoQwen3.8 Max Prime logo
Claude Opus 5.5 vs Qwen3.8 Max PrimeLanded Sep 2026
Claude Opus 4 logoGLM 5.3 Prime logo
Claude Opus 4 vs GLM 5.3 PrimeLanded Sep 2026
Claude Opus 5.5 logoQwen3.8 Omni Flash logo
Claude Opus 5.5 vs Qwen3.8 Omni FlashLanded Sep 2026
Claude Opus 4 logoCommand A+ logo
Claude Opus 4 vs Command A+Landed Sep 2026
Claude Opus 5.5 logoGPT-6 Luna Pro logo
Claude Opus 5.5 vs GPT-6 Luna ProLanded Sep 2026
Claude Opus 4 logoGPT-6 Sol Pro logo
Claude Opus 4 vs GPT-6 Sol ProLanded Sep 2026
Claude Opus 5.5 logoGPT-6 Luna logo
Claude Opus 5.5 vs GPT-6 LunaLanded Sep 2026

Same lab, same size, long tail

Claude Opus 4 logoClaude Sonnet 4 logo
Claude Opus 4 vs Claude Sonnet 4Version compare
Claude Opus 4 logoClaude Opus 4.6 logo
Claude Opus 4 vs Claude Opus 4.6Version compare
Claude Opus 5.5 logoClaude Opus 4.6 logo
Claude Opus 5.5 vs Claude Opus 4.6Same lab
Claude Opus 5.5 logoClaude Fable 5.1 logo
Claude Opus 5.5 vs Claude Fable 5.1Same lab
Claude Opus 4 logoNemotron 3.5 Content Safety logo
Claude Opus 4 vs Nemotron 3.5 Content SafetyNew provider
Claude Opus 4 logoNemotron 3.5 Lightning logo
Claude Opus 4 vs Nemotron 3.5 LightningNew provider
Claude Opus 5.5 logoNVIDIA Nemotron Nano 9B V2 logo
Claude Opus 5.5 vs NVIDIA Nemotron Nano 9B V2New provider
Claude Opus 4 logoNex-N2.5-Mini (free) logo
Claude Opus 4 vs Nex-N2.5-Mini (free)New provider

Model pages

Claude Opus 4 logo
Claude Opus 458 outputs, specs and price
Claude Opus 5.5 logo
Claude Opus 5.519 outputs, specs and price
Rival
How it worksPrivacyTerms
Explore all of Rival

Explore

  • Compare Models
  • All Models
  • Image Comparison
  • Audio Comparison
  • Image Generation
  • Best AI For...
  • Arena
  • API Pricing
  • Challenges

Discover

  • SubjectiveBench
  • Default Index
  • Research
  • Research downloads
  • Rival Kits
  • Find your AI taste
  • UI Glow-Up
  • VoiceLock
  • Cost Cutter
  • Agent skills
  • Benchmarks vs Vibes
  • Brief
  • Jailbreak
  • Model Updates
  • Provider Status
  • AI Creators

Connect

  • Methodology
  • Advertise
  • Partnerships
  • Privacy Policy
  • Terms
  • RSS Feed