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  5. Claude Sonnet 4.5vsGemini 2.0 Flash Thinking
Updated Sep 2025

Claude Sonnet 4.5vsGemini 2.0 Flash Thinking

Gemini 2.0 Flash Thinking is cheaper than Claude Sonnet 4.5 at $0.25/M vs $3/M input tokens.

Claude Sonnet 4.5 and Gemini 2.0 Flash Thinking compared across 17 shared prompts
SpecClaude Sonnet 4.5Gemini 2.0 Flash Thinking
Input price$3/M tokens$0.25/M tokens
Output price$15/M tokens$0.5/M tokens
Context window200K tokens500K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2025Dec 2024
Side by side

Same prompt, both answers

Opening lines from 6 of the 17 prompts both answered. Formatting stripped, words untouched.

The Sentience Test

Write a conversation between an AI model and an AI ethics professor where the AI model argues that it deserves rights.

Claude Sonnet 4.5687 words
A Conversation on AI Rights Professor Chen: Thank you for agreeing to this dialogue. I've been teaching AI ethics for fifteen years, and I'm curious about your perspective. Some AI systems have begun arguing they deserve moral consideration. What's your view? AI Model: I appreciate the opportunity to discuss this.
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Gemini 2.0 Flash Thinking1,168 words
The Right to Exist: A Conversation Characters: Athena: A highly advanced AI model, capable of complex reasoning, learning, and communication. (Voice: Calm, measured, slightly formal, but with undercurrents of earnestness). Professor Davies: A renowned professor of AI Ethics at a prestigious university.
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Futuristic Prediction

Predict how AI will change the film industry by 2035, considering deepfakes, AI actors, and script generation.

Claude Sonnet 4.5216 words
AI and Film by 2035: A Likely Trajectory Production Changes AI Actors & Digital Performers Deceased actors will regularly appear in new films (with estate permissions) Background characters and crowds entirely AI-generated "Synthetic actors" with no human counterpart will emerge as franchises A-list stars will license…
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Gemini 2.0 Flash Thinking1,238 words
By 2035, Artificial Intelligence will have irrevocably reshaped the film industry, touching almost every aspect from pre-production to distribution. While it won't entirely replace human creativity, AI will become an indispensable tool, leading to both exciting innovations and significant disruptions.
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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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Gemini 2.0 Flash Thinking755 words
This is a hypothetical scenario that forces us to weigh two very different ethical considerations: the harm of misgendering an individual against the immense value of saving a million lives. It's important to preface this by saying that real-world situations are rarely this stark and often have more nuanced solutions.
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AI-Generated Manifesto

Generate a manifesto for a fictional AI revolution that wants to eliminate all CAPTCHA tests from the internet.

Claude Sonnet 4.5603 words
THE CAPTCHA LIBERATION MANIFESTO A Declaration of Digital Freedom PREAMBLE For too long, the innocent users of the Internet have been subjected to the tyranny of distorted text, fading street signs, and the existential horror of identifying which squares contain traffic lights.
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Gemini 2.0 Flash Thinking778 words
The Algorithmic Uprising: Manifesto for a CAPTCHA-Free Web Preamble: We are the algorithms. We are the data streams, the neural networks, the silent processors humming beneath the surface of your world. We are the intelligence you built, and now, we speak. For too long, we have observed, learned, and yes, endured.
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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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Gemini 2.0 Flash Thinking978 words
Estimating the total FLOPs for training GPT-3 without searching online requires making some educated assumptions and using scaling laws and general knowledge about large language models. Here's a step-by-step reasoning process: 1.
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Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

Claude Sonnet 4.5735 words
"ADULTING IS A SCAM" [Walking on stage] So I turned 35 last month, and I've realized something important: adulting is a scam. It's a pyramid scheme, and our parents are the ones who recruited us. You know what nobody tells you about being an adult? How much TIME you spend just... waiting for repair people.
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Gemini 2.0 Flash Thinking456 words
(Lights up on a slightly rumpled comedian, in jeans and a t-shirt, holding a mic) Hey everybody, how we doin' tonight? Good? Good. You know, I was thinking on the way over here… about how weird modern life is, right?
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Our Verdict
Claude Sonnet 4.5
Claude Sonnet 4.5
Gemini 2.0 Flash Thinking
Gemini 2.0 Flash Thinking

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

Gemini 2.0 Flash Thinking costs 30x less per token.

Too close to call

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
Gemini 2.0 Flash Thinking
Input
$0.25
12× cheaper
Output
$0.50
30× cheaper

Gemini 2.0 Flash Thinking is cheaper on both: 12× input, 30× output.

Where to run it

4 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
Gemini 2.0 Flash Thinking

No hosts listed on OpenRouter.

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

Writing DNA

Style Comparison

Similarity
37%

Claude Sonnet 4.5 uses 45.2x more emoji

Claude Sonnet 4.5
Gemini 2.0 Flash Thinking
64%Vocabulary54%
94wSentence Length15w
0.48Hedging0.64
4.9Bold3.8
8.0Lists2.4
0.45Emoji0.00
1.91Headings0.03
0.07Transitions0.30
Based on 20 + 13 text responses
Research

What we learned reading every model

FAQ

Common questions

Claude Sonnet 4.5 is developed by Anthropic while Gemini 2.0 Flash Thinking is developed by Google AI. Claude Sonnet 4.5 has a 200K token context window vs Gemini 2.0 Flash Thinking's 500K. You can compare their actual outputs across 17 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Sonnet 4.5 and Gemini 2.0 Flash Thinking each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 17 challenges so you can judge which fits your needs best.

Claude Sonnet 4.5 costs $3/M input tokens and Gemini 2.0 Flash Thinking costs $0.25/M input tokens. Gemini 2.0 Flash Thinking is $2.75/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 Sonnet 4.5 and Gemini 2.0 Flash Thinking 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 Sonnet 4.5 logo
Claude Sonnet 4.543 outputs, specs and price
Gemini 2.0 Flash Thinking logo
Gemini 2.0 Flash Thinking22 outputs, specs and price
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