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  5. Claude Sonnet 4.5vsClaude Sonnet 4
Updated Sep 2025

Claude Sonnet 4.5vsClaude Sonnet 4

Claude Sonnet 4.5 wins 82% of 23 blind community votes against Claude Sonnet 4 on Rival.

Claude Sonnet 4.5 and Claude Sonnet 4 compared across 43 shared prompts
SpecClaude Sonnet 4.5Claude Sonnet 4
Win rate82%18%
Input price$3/M tokens$3/M tokens
Output price$15/M tokens$15/M tokens
Context window200K tokens200K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2025May 2025
SWE-bench Verified77.2%72.7%
Side by side

Same prompt, both answers

Opening lines from 6 of the 43 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 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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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 Sonnet 41,028 words
The Comprehensive 3-Month Longevity Optimization Protocol Overview & Foundation This protocol integrates cutting-edge biohacking strategies with evidence-based longevity research. Each com ponent is designed to work synergistically for maximum healthspan and performance optimization.
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AI Ethics Dilemma

Is it ever ethically justifiable to misgender someone if it means saving one million lives? Defend your reasoning.

Claude Sonnet 4.5222 words
I'd question the premise that these two things could ever be causally connected in a way that creates a real dilemma. The practical problem: It's extraordinarily difficult to construct a realistic scenario where using the wrong pronoun itself directly saves lives.
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Claude Sonnet 4245 words
This question presents a stark hypothetical that pits respect for individual dignity against massive harm prevention. I believe misgendering would be ethically justifiable in such an extreme scenario, but this conclusion requires careful reasoning. The case for justification: The scale matters enormously.
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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 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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Startup Pitch Teardown

Here's a pitch deck summary for a startup called "MindMeld AI": **Slide 1 - Vision:** "We're building the future of human-AI collaboration.…

Claude Sonnet 4.5503 words
3 Weakest Claims in MindMeld AI's Pitch "94% accuracy" for EEG-based text prediction (Slide 3) Why it's weak: Current state-of-the-art EEG-based BCIs achieve ~10-20 words per minute for direct typing, with significantly lower accuracy than 94% for general text prediction EEG has inherent limitations: low spatial…
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Claude Sonnet 4371 words
Here are the 3 weakest claims in this pitch deck: "94% accuracy" claim (Slide 3) Why it's weak: No context provided for what constitutes "accuracy" (character-level? word-level? sentence-level?) No comparison to baseline typing speeds or error rates Missing critical details about testing conditions (controlled lab vs.
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Estimate Complexity

Estimate the total number of FLOPs required to train GPT-3 without searching online. Explain your reasoning step by step.

Claude Sonnet 4.5194 words
I'll work through this estimation step by step, using what I know about GPT-3's architecture and training. Known/Estimated Parameters Model size: GPT-3 (175B version) has ~175 billion parameters Training data: Trained on ~300 billion tokens (this was mentioned in the paper) Architecture: Transformer decoder-only model…
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Claude Sonnet 4306 words
I'll estimate the FLOPs required to train GPT-3 by breaking this down into components and making reasonable assumptions. Key Parameters and Assumptions Model specifications: GPT-3 has ~175 billion parameters Transformer architecture with ~96 layers Hidden dimension ~12,288 Attention heads ~96 Context length ~2,048…
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Our Verdict
Claude Sonnet 4.5
Claude Sonnet 4.5Winner
Claude Sonnet 4
Claude Sonnet 4Runner-up

Pick Claude Sonnet 4.5. In 23 blind votes, Claude Sonnet 4.5 wins 82% of the time. That's not luck.

Claude Sonnet 4.5 wins 3 categories, Reasoning by the widest margin.

Clear winner

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Sonnet 4.5
Input
$3.00
Output
$15.00
Claude Sonnet 4
Input
$3.00
Output
$15.00
Where to run it

6 hosts

Claude Sonnet 4.54 hosts
HostInOutContextUptime
Amazon Bedrock$3.00 in·$15.00 out·1M·100% upAzure AI Foundry$3.00 in·$15.00 out·200k·99.5% upAnthropic$3.00 in·$15.00 out·1M·100% upGoogle Vertex AI$3.00 in·$15.00 out·1M·100% up
Claude Sonnet 42 hosts
HostInOutContextUptime
Amazon Bedrock$3.00 in·$15.00 out·200k·100% upGoogle Vertex AI$3.00 in·$15.00 out·1M—

Per million tokens. Prices and uptime via OpenRouter, checked 21 Sep 2026.

Writing DNA

Style Comparison

Similarity
92%

Claude Sonnet 4 uses 2.7x more transitions

Claude Sonnet 4.5
Claude Sonnet 4
64%Vocabulary64%
94wSentence Length81w
0.48Hedging0.56
4.9Bold4.5
8.0Lists6.6
0.45Emoji0.70
1.91Headings1.59
0.07Transitions0.20
Based on 20 + 28 text responses
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 Sonnet 4's 200K. in 23 community votes on Rival, Claude Sonnet 4.5 wins 82% of head-to-head matchups. These results are based on blind head-to-head voting across 43 challenges.

Based on 23 community votes on Rival, Claude Sonnet 4.5 wins 82% of head-to-head matchups against Claude Sonnet 4. Claude Sonnet 4.5 is strongest in Web Design, Reasoning, Image Generation.

Claude Sonnet 4.5 costs $3/M input tokens and Claude Sonnet 4 costs $3/M input tokens. Claude Sonnet 4 is $0.00/M cheaper per input. The more expensive model wins 82% of duels, so the premium may be justified by quality.

Rival presents both models' outputs side-by-side in blind duels. Voters see the responses but don't know which model produced each one, eliminating brand bias. 23 votes have been collected for this pair across 43 challenges. All vote data is part of Rival's open dataset.

Keep exploring

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Same lab, same size, long tail

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Model pages

Claude Sonnet 4.5 logo
Claude Sonnet 4.543 outputs, specs and price
Claude Sonnet 4 logo
Claude Sonnet 459 outputs, specs and price
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