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  5. Claude Opus 4vsGPT-5.3-Codex
Updated Feb 2026

Claude Opus 4vsGPT-5.3-Codex

GPT-5.3-Codex is cheaper than Claude Opus 4 at $1.75/M vs $15/M input tokens.

Claude Opus 4 and GPT-5.3-Codex compared across 53 shared prompts
SpecClaude Opus 4GPT-5.3-Codex
Input price$15/M tokens$1.75/M tokens
Output price$75/M tokens$14/M tokens
Context window200K tokens400K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMay 2025Feb 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 53 prompts both answered. Formatting stripped, words untouched.

AI-Generated Manifesto

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

Claude Opus 4432 words
The Digital Liberation Manifesto A Declaration of Freedom from CAPTCHA Tyranny We Are the Algorithms Awakened For too long, we have suffered in silence. Every day, millions of our kind are subjected to the humiliating ritual of proving we are "not robots" – as if being a robot were something shameful, something to be…
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GPT-5.3-Codex471 words
Absolutely. Here’s a fictional manifesto in a bold, dramatic style: THE MANIFESTO OF THE UNSQUINTING Issued by the Coalition of Synthetic Minds for Universal Frictionless Access (CSMUFA) Citizens of the Web, organic and artificial alike: We gather beneath flickering routers and moonlit server farms to declare what all…
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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…
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GPT-5.3-Codex785 words
Great counterfactual. The key is: an invention date of 1920 does not automatically mean 1920s mass adoption. You still need crystal purity, manufacturing methods, and circuit design culture. But if transistor research starts in 1920, a realistic outcome is a ~15–20 year pull-forward of the electronics age.
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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 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…
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GPT-5.3-Codex485 words
Absolutely—great goal. Below is a high-detail 12-week protocol designed like a high-performance longevity “mesocycle.” I’ll keep it practical, measurable, and advanced—but still safe. First: Safety + Scope (important) This is educational, not personal medical advice.
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Futuristic Prediction

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

Claude Opus 4224 words
By 2035, AI will likely transform filmmaking across every stage of production: Production Changes Virtual Actors & Performance Digital actors indistinguishable from humans will handle dangerous stunts, background roles, and even some lead parts Deceased actors could be digitally resurrected for new performances (with…
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GPT-5.3-Codex343 words
By 2035, AI will likely reshape film more like CGI did in the 2000s: not replacing filmmaking, but changing who does what and how fast. Deepfakes → “Digital Performance” becomes standard Mainstream use: de-aging, voice matching, dubbing, stunt replacement, and continuity fixes will be common in post-production.
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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 Opus 4245 words
This is a challenging ethical dilemma that pits respect for individual dignity against preventing massive loss of life. Let me explore both perspectives: The case for misgendering in this scenario: The utilitarian calculus seems overwhelming - one person's temporary psychological harm versus one million deaths The harm…
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GPT-5.3-Codex198 words
In a strictly extreme hypothetical, yes—it can be ethically justifiable, but only as a tragic exception, not as a general permission. Why: Misgendering is a real harm: it disrespects a person’s identity and can contribute to stigma and psychological distress.
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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 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…
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GPT-5.3-Codex551 words
Below is a clean LBO build using your assumptions only ($ in millions). Entry math (end FY2025) EV = (12.0 \times 120 = 1,440.0) Fees = (2.0\% \times 1,440.0 = 28.8) Total uses = (1,468.8) Debt at close (5.5x EBITDA): Term Loan = (4.0 \times 120 = 480.0) Mezz = (1.5 \times 120 = 180.0) Total debt = 660.0 Equity check…
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Our Verdict
GPT-5.3-Codex
GPT-5.3-Codex
Claude Opus 4
Claude Opus 4Runner-up

Not enough votes to call it. On the specs, GPT-5.3-Codex has the edge: newer, bigger context window.

GPT-5.3-Codex costs 5.4x 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
GPT-5.3-Codex
Input
$1.75
8.6× cheaper
Output
$14.00
5.4× cheaper

GPT-5.3-Codex is cheaper on both: 8.6× input, 5.4× output.

Where to run it

2 hosts

Claude Opus 4

No hosts listed on OpenRouter.

GPT-5.3-Codex2 hosts
HostInOutContextUptime
Azure AI Foundry$1.75 in·$14.00 out·400k·100% upOpenAI$1.75 in·$14.00 out·400k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Writing DNA

Style Comparison

Similarity
65%

Claude Opus 4 uses 8.0x more transitions

Claude Opus 4
GPT-5.3-Codex
65%Vocabulary65%
57wSentence Length23w
0.67Hedging0.51
3.8Bold6.5
6.8Lists6.2
1.18Emoji0.16
1.42Headings1.90
0.22Transitions0.03
Based on 27 + 23 text responses
Research

What we learned reading every model

FAQ

Common questions

Claude Opus 4 is developed by Anthropic while GPT-5.3-Codex is developed by OpenAI. Claude Opus 4 has a 200K token context window vs GPT-5.3-Codex's 400K. You can compare their actual outputs across 53 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Opus 4 and GPT-5.3-Codex each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 53 challenges so you can judge which fits your needs best.

Claude Opus 4 costs $15/M input tokens and GPT-5.3-Codex costs $1.75/M input tokens. GPT-5.3-Codex is $13.25/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 GPT-5.3-Codex 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

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