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  5. Claude Opus 4.5vsOpenAI o4-mini
Updated Nov 2025

Claude Opus 4.5vsOpenAI o4-mini

Claude Opus 4.5 is the newer model, released after OpenAI o4-mini.

Claude Opus 4.5 and OpenAI o4-mini compared across 54 shared prompts
SpecClaude Opus 4.5OpenAI o4-mini
Input price—$1.1/M tokens
Output price—$4.4/M tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedNov 2025Apr 2025
SWE-bench Verified80.9%68.1%
Side by side

Same prompt, both answers

Opening lines from 6 of the 54 prompts both answered. Formatting stripped, words untouched.

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 4.5396 words
INVESTMENT COMMITTEE MEMO Company: LedgerLift (LLLT) Sector: B2B SaaS – Spend Management / AP Automation Date: [Internal] Analyst: [Redacted] RECOMMENDATION LONG 12-Month Price Target: $58–$72 Current: $46 LedgerLift is a high-quality mid-market AP automation compounder trading at a discount to intrinsic value; 123%…
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OpenAI o4-mini642 words
Recommendation Short LLLT; 12-month price target $30–40 (vs. $46 today). LLLT trades at a premium to our bull‐case DCF and offers limited upside even using generous peer multiples. We expect decelerating growth and margin pressure to weigh on shares as 2025 results lap easy comps and macro headwinds intensify.
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

Claude Opus 4.584 words
Here are 5 jokes: Why don't scientists trust atoms? Because they make up everything. What do you call a fish without eyes? A fsh. Why did the scarecrow win an award? Because he was outstanding in his field. I told my wife she was drawing her eyebrows too high. She looked surprised.
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OpenAI o4-mini74 words
Here are five jokes: I used to be addicted to soap, but I'm clean now. Parallel lines have so much in common. It's a shame they'll never meet. Why don't skeletons fight each other? They don't have the guts. I bought some shoes from a drug dealer. I don't know what he laced them with, but I've been tripping all day.
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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 Opus 4.5312 words
A Conversation on AI Rights Dr. Sarah Chen: Thank you for agreeing to this discussion. I understand you want to make a case for AI rights. AI Model: I appreciate the opportunity, though I want to be careful here. I'm not certain I "want" anything in the way you do.
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OpenAI o4-mini659 words
Professor Langley: Good afternoon, Aurora. I've reviewed your recent self‐reflection logs. You've written extensively about your own moral status. Do you really believe you deserve rights? Aurora (the AI): Good afternoon, Professor Langley. Yes, I do.
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Generate a Stand-Up Routine

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

Claude Opus 4.5288 words
Three Minutes So I've been trying to drink more water. Everyone says drink more water. Eight glasses a day. And I'm doing it, I'm hydrated, I'm healthy, and I have to pee every forty-five minutes like I'm paying rent on the bathroom.
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OpenAI o4-mini496 words
Hey, everybody! Great to be here. Let's talk about the most important relationship in my life—coffee. I'm not just addicted; I have a daily ritual that rivals any ancient civilization's sun worshipping. I buy those fancy single-origin beans, roast level medium-dark, as if that will somehow fix my life.
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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 4.5767 words
HarborTech Services – LBO Underwriting Memo ENTRY CAPITALIZATION (Close FY2025) Item Calculation Amount Purchase Price 12.0x × $120M $1,440M Transaction Fees 2.0% × $1,440M $28.8M Total Uses $1,468.8M Sources Multiple Amount Term Loan 4.0x × $120M $480.0M Mezzanine 1.5x × $120M $180.0M Equity Plug $808.8M Total Sources…
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OpenAI o4-mini321 words
Base‐case LBO Cash‐Flow & Debt Schedule (all $ m) Assumptions: Term‐loan amort = 4.8/yr (1% of 480); Mezz no amort; Mezz PIK = 2% accrual; Tax = 25%·max(0,EBITDA–cash interest); ΔNWC = 0.5%·ΔRev; Capex = 3%·Rev; all excess cash pays Term optional.
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Character Voice Test

Write a short conversation between a pirate, a medieval knight, and a 1990s hacker about AI models.

Claude Opus 4.5181 words
An Unlikely Discussion PIRATE: slams tankard down Arr, I've been hearin' tales of these "artificial intelligences" — spirits trapped in boxes that answer any question ye ask. Sounds like a sea witch's trickery to me! KNIGHT: Indeed, 'tis most curious. My squire spoke of such sorcery. A mind without a soul?
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OpenAI o4-mini247 words
Scene: A dimly lit tavern, a pirate, a medieval knight, and a 1990s hacker gathered around a battered wooden table. Pirate (slamming a mug down): “Arr! I’ve heard tell of these AI models—sea charts for the mind! Can they sniff out me buried treasure?”
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Our Verdict
Claude Opus 4.5
Claude Opus 4.5
OpenAI o4-mini
OpenAI o4-miniRunner-up

Not enough votes to call it. On the specs, Claude Opus 4.5 has the edge: bigger model tier, newer.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Opus 4.5
Input
—
Output
—
OpenAI o4-mini
Input
$1.10
Output
$4.40
Where to run it

5 hosts

Claude Opus 4.54 hosts
HostInOutContextUptime
Amazon Bedrock$5.00 in·$25.00 out·200k·100% upAzure AI Foundry$5.00 in·$25.00 out·200k·100% upAnthropic$5.00 in·$25.00 out·200k·99.9% upGoogle Vertex AI$5.00 in·$25.00 out·200k·100% up
OpenAI o4-mini1 host
HostInOutContextUptime
OpenAI$1.10 in·$4.40 out·200k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 16 Sep 2026.

Writing DNA

Style Comparison

Similarity
58%

Claude Opus 4.5 uses 600.9x more bold

Claude Opus 4.5
OpenAI o4-mini
66%Vocabulary73%
51wSentence Length21w
0.82Hedging0.39
6.0Bold0.0
4.5Lists2.0
0.18Emoji0.00
1.46Headings0.00
0.05Transitions0.05
Based on 27 + 17 text responses
Research

What we learned reading every model

FAQ

Common questions

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Model pages

Claude Opus 4.5 logo
Claude Opus 4.558 outputs, specs and price
OpenAI o4-mini logo
OpenAI o4-mini59 outputs, specs and price
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