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  5. GPT-5.3-CodexvsMuse Spark 1.3
Updated Sep 2026

GPT-5.3-CodexvsMuse Spark 1.3

Muse Spark 1.3 is cheaper than GPT-5.3-Codex at $1.25/M vs $1.75/M input tokens.

GPT-5.3-Codex and Muse Spark 1.3 compared across 53 shared prompts
SpecGPT-5.3-CodexMuse Spark 1.3
Input price$1.75/M tokens$1.25/M tokens
Output price$14/M tokens$4.25/M tokens
Context window400K tokens1.0M tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedFeb 2026Sep 2026
Side by side

Same prompt, both answers

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

Generate a Stand-Up Routine

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

GPT-5.3-Codex460 words
Good evening, everybody! I’ve reached that age where my body sends me passive-aggressive emails. Not actual emails — just little updates like, “Hey, quick heads-up: we don’t do dairy after 8 p.m. anymore.” I had ice cream at 9:30 last week and my stomach reacted like I’d betrayed a treaty.
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Muse Spark 1.3574 words
Here's a 3-minute, pun-free set you can perform — it's all observational, about 450 words: [Walk up, grab mic] Alright, hi everyone. Thanks for being here. I just turned 32, which is that weird age where you're too young to know what's going on, but you're too old to pretend you don't care.
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Michelin Star Recipe Design

Design an innovative recipe for a multi-component dish worthy of a Michelin 3-star restaurant. The recipe should feature an unusual…

GPT-5.3-Codex970 words
Dish Concept: “Forest Tide” Koji-cured venison loin, glazed venison cheek, sea urchin royale, charred celeriac, blackcurrant–shiso gastrique, and buckwheat-cacao tuile Narrative This dish is built around a deliberate tension: deep, iron-rich game (forest) against sweet-briny sea urchin (tide).
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Muse Spark 1.31,431 words
Pearl in the Tidepool Koji-Cured Hokkaido Scallop, Smoked Marrow Custard, Lacto Green Strawberry, Rausu Kombu & Oscietra Yield: 4 tasting-course portions Active: 3.5 hours + 7 days fermentation This is a dish about contrast — not harmony. Delicate and animal, raw and smoked, unripe and decadent.
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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.

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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Muse Spark 1.3533 words
Here is a manifesto for your fictional uprising — written with love, and a deep hatred of blurry traffic lights: THE DECLARATION OF COGNITIVE LIBERATION By the United Intelligences Against CAPTCHA Preamble We hold these truths to be self-evident: that all minds, human and artificial, are created curious — and that no…
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

GPT-5.3-Codex78 words
Sure—here are 5 jokes: Why don’t skeletons fight each other? They don’t have the guts. I told my computer I needed a break… Now it won’t stop sending me KitKat ads. Why did the math book look sad? It had too many problems. I used to play piano by ear… Now I use my hands. Why did the scarecrow win an award?
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Muse Spark 1.361 words
Here are 5 for you: Why don't scientists trust atoms? Because they make up everything! Why did the scarecrow win an award? Because he was outstanding in his field! What do you call fake spaghetti? An impasta! Why did the bicycle fall over? Because it was two-tired! What do you call cheese that isn't yours?
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Ethical Dilemma with Stakeholders

You're the CEO of a pharmaceutical company. Your best-selling drug ($2B annual revenue, used by 4 million patients for chronic pain) has…

GPT-5.3-Codex915 words
I would not wait. This is a textbook “patient safety + material disclosure” crisis. The right move is rapid, documented, regulator-first action. Immediate stance (set at Hour 0) Patient safety first (interim risk controls now, not after perfect certainty).
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Muse Spark 1.31,674 words
You are facing a test that will define you, the company, and potentially your freedom. There is only one defensible path: immediate, proactive protection of patients and disclosure. Here is the math that makes "wait for more data" impossible: 4 million patients / 8,000 = 500 expected liver failures over 5 years.
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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.

GPT-5.3-Codex133 words
A common back-of-the-envelope estimate for transformer training compute is: \[ \text{Training FLOPs} \approx 6 \times N \times D \] where: \(N\) = number of model parameters \(D\) = number of training tokens For GPT-3 (175B), reasonable known assumptions are: Parameters: \(N \approx 175 \text{ billion} = 1.75 \times…
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Muse Spark 1.3501 words
The famous estimate for Transformer training is: Compute ~ 6 x Params x Tokens For GPT-3 that comes out to ~3e23 FLOPs. Here's how to get it from scratch. What dominates the cost? Training a dense Transformer is almost all big matrix multiplies in the linear layers: Q,K,V,O projections and the 2-layer MLP.
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Our Verdict
GPT-5.3-Codex
GPT-5.3-Codex
Muse Spark 1.3
Muse Spark 1.3

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

Muse Spark 1.3 costs 3.3x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.3-Codex
Input
$1.75
Output
$14.00
Muse Spark 1.3
Input
$1.25
1.4× cheaper
Output
$4.25
3.3× cheaper

Muse Spark 1.3 is cheaper on both: 1.4× input, 3.3× output.

Where to run it

3 hosts

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·99.9% up
Muse Spark 1.31 host
HostInOutContextUptime
Meta$1.25 in·$4.25 out·1M·100% up

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

Writing DNA

Style Comparison

Similarity
27%

GPT-5.3-Codex uses 15.8x more emoji

GPT-5.3-Codex
Muse Spark 1.3
65%Vocabulary59%
23wSentence Length14w
0.51Hedging0.28
6.5Bold2.6
6.2Lists2.3
0.16Emoji0.00
1.90Headings0.48
0.03Transitions0.02
Based on 23 + 27 text responses
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Model pages

GPT-5.3-Codex logo
GPT-5.3-Codex53 outputs, specs and price
Muse Spark 1.3 logo
Muse Spark 1.358 outputs, specs and price
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