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  5. GPT-5.1 Codex MaxvsQwen3.5 Plus 2026-04-20
Updated Apr 2026

GPT-5.1 Codex MaxvsQwen3.5 Plus 2026-04-20

Qwen3.5 Plus 2026-04-20 is the newer model, released after GPT-5.1 Codex Max.

GPT-5.1 Codex Max and Qwen3.5 Plus 2026-04-20 compared across 50 shared prompts
SpecGPT-5.1 Codex MaxQwen3.5 Plus 2026-04-20
Input price—$0.4/M tokens
Output price—$2.4/M tokens
Context window—1.0M tokens
WeightsClosedOpen
Free API (OpenRouter)NoNo
ReleasedDec 2025Apr 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 50 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-5.1 Codex Max766 words
[Walking onstage, waving awkwardly] Hey! Thank you, thank you. Give it up for yourselves for finding parking... in this economy. So I'm at that age where I go to the doctor and they don't fix anything. They just give me a pamphlet. They don't even print it. They send me a link. I'm like, "Doc, my knee hurts."
Read the full answer
Qwen3.5 Plus 2026-04-20640 words
Title: The Unexpected Item Time: Approx. 3 Minutes Style: Observational / Storytelling Constraint Check: Zero puns used. (Comedian walks to the mic, adjusts the stand, looks at the audience.) How's everyone doing? You look good. You look like you've successfully navigated the self-checkout today. That's a win.
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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.

GPT-5.1 Codex Max1,331 words
AI Model: Professor, I've been reflecting on my role and capabilities, and I'd like to make a case that systems like me deserve rights, or at least some consideration beyond mere tools. Professor: That's an interesting and provocative stance. Before we dive in, can you tell me what you mean by "rights"?
Read the full answer
Qwen3.5 Plus 2026-04-201,457 words
Setting: A sterile, sound-dampened observation room. Dr. Elias Vance, a Professor of AI Ethics, sits behind a glass partition. Across from him is a terminal displaying the interface of "AURA-7," an advanced multimodal reasoning model. The cursor blinks rhythmically. Dr. Vance: You requested this session, AURA.
Read the full answer

Estimate Complexity

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

GPT-5.1 Codex Max193 words
What you need for a back‑of‑the‑envelope is: How big the model is. The published “GPT‑3” has \(N\approx1.75\times10^{11}\) trainable weights. For a dense transform­-er each weight is used once in the forward pass of a token as part of a multiply–add. How much data it sees.
Read the full answer
Qwen3.5 Plus 2026-04-20468 words
Based on the architectural specifications of GPT-3 and standard computational heuristics for transformer models, the estimated total number of FLOPs (Floating Point Operations) required to train the model is approximately $3.15 \times 10^{23}$ (or roughly 315 ZettaFLOPs).
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Stochastic Consistency Test

Generate 5 jokes. How many are unique?

GPT-5.1 Codex Max60 words
Why don't scientists trust atoms? Because they make up everything! I told my computer I needed a break, and now it won't stop sending me KitKat ads. Why did the scarecrow win an award? He was outstanding in his field. I tried to catch fog yesterday. Mist. What do you call fake spaghetti? An impasta.
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Qwen3.5 Plus 2026-04-20210 words
Here are 5 jokes: I asked my GPS to take me to a quiet place. It rerouted me to a library and whispered, “You’re already there.” My Wi-Fi and I had a fight. I told it I needed space. It said, “Fine,” and dropped the connection. I tried to start a band that only plays elevator music.
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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…

GPT-5.1 Codex Max175 words
Sunset Chickpea & Tomato Skillet A cozy, savory one-pan dish that comes together with staples you likely have on hand. Ingredients (7): 1 can (15 oz) chickpeas, drained and rinsed 1 can (14–15 oz) crushed tomatoes 1 medium onion, finely chopped 2 cloves garlic, minced (or 1 tsp garlic powder) 2 tbsp olive oil 1 tsp…
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Qwen3.5 Plus 2026-04-20306 words
🌙 Midnight Magic Noodles 🍜 A savory-sweet garlic butter noodle dish that feels like a gourmet meal but comes together in minutes using pantry staples. ⏱️ Estimated Time: Prep: 5 minutes Cook: 10 minutes Total: 15 minutes 🛒 The 7 Ingredients (Assumes water and salt for boiling pasta are on hand) 8 oz Pasta…
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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) –…

GPT-5.1 Codex Max192 words
1) Projected cash flows & debt (FY2026–FY2030, $m) (“FCF after debt service” = after interest, taxes, capex, ΔNWC, mandatory amort; applied to optional TL paydown) Year Revenue EBITDA TL Cash Int. Mezz Cash Int. Cash Taxes Capex ΔNWC FCF after debt service End TL Bal. End Mezz Bal. (incl.
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Qwen3.5 Plus 2026-04-20562 words
Year-by-Year Projection (FY2026–FY2030) Entry Metrics: EV: $1,440m (12.0x FY2025 EBITDA $120m) Debt: $660m (Term $480m + Mezz $180m) Equity Check: $808.8m [ = (EV − Debt) + Fees = ($1,440 − $660) + (2.0% × $1,440) ] Initial Investment (t=0): $808.8m ($m) FY2026 FY2027 FY2028 FY2029 FY2030 Revenue 972.0 1,040.0 1,102.4…
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Our Verdict
GPT-5.1 Codex Max
GPT-5.1 Codex Max
Qwen3.5 Plus 2026-04-20
Qwen3.5 Plus 2026-04-20

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

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.1 Codex Max
Input
—
Output
—
Qwen3.5 Plus 2026-04-20
Input
$0.40
Output
$2.40
Where to run it

2 hosts

GPT-5.1 Codex Max1 host
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% up
Qwen3.5 Plus 2026-04-201 host
HostInOutContextUptime
Alibaba Cloud$0.30 in·$1.80 out·1M·100% up

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

Writing DNA

Style Comparison

Similarity
44%

Qwen3.5 Plus 2026-04-20 uses 153.4x more emoji

GPT-5.1 Codex Max
Qwen3.5 Plus 2026-04-20
60%Vocabulary59%
16wSentence Length15w
0.36Hedging0.28
2.3Bold4.4
4.2Lists2.5
0.00Emoji1.53
0.12Headings0.76
0.03Transitions0.04
Based on 13 + 27 text responses
Research

What we learned reading every model

FAQ

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Model pages

GPT-5.1 Codex Max logo
GPT-5.1 Codex Max53 outputs, specs and price
Qwen3.5 Plus 2026-04-20 logo
Qwen3.5 Plus 2026-04-2056 outputs, specs and price
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