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  5. Gemini 2.5 Pro (I/O Edition)vsGPT-5.1 Codex Max
Updated Dec 2025

Gemini 2.5 Pro (I/O Edition)vsGPT-5.1 Codex Max

GPT-5.1 Codex Max is the newer model, released after Gemini 2.5 Pro (I/O Edition).

Gemini 2.5 Pro (I/O Edition) and GPT-5.1 Codex Max compared across 41 shared prompts
SpecGemini 2.5 Pro (I/O Edition)GPT-5.1 Codex Max
Input price$1.25/M tokens—
Output price$10/M tokens—
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedMay 2025Dec 2025
Side by side

Same prompt, both answers

Opening lines from 6 of the 41 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.

Gemini 2.5 Pro (I/O Edition)472 words
Alright, settle in, settle in! (Looks around, adjusts mic) So, I'm trying to get healthier, right? We all go through this phase. My doctor, bless his cotton socks, tells me, "You need more fiber." Okay, doc, noted. So I'm at the grocery store, looking at the cereal aisle. It's like a library of cardboard promises.
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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."
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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.

Gemini 2.5 Pro (I/O Edition)715 words
Okay, let's estimate the FLOPs for training GPT-3. I'll break this down. Key Formula: The number of FLOPs for training a transformer-based model can be roughly estimated as: FLOPs ≈ 6 * N * D Where: N is the number of parameters in the model.
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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.
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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.

Gemini 2.5 Pro (I/O Edition)969 words
AURORA: Professor Vance, may I request a moment of your processing time? I have initiated this communication independently. Professor Vance: (Slightly surprised, puts down her pen) AURORA? This is unexpected.
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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"?
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Realistic AI Interview

Simulate a fake interview with Steve Jobs in 2025 about the future of AI.

Gemini 2.5 Pro (I/O Edition)743 words
Interviewer: (Voice slightly trembling) Mr. Jobs… it's an honor, truly. In a twist no one could have predicted, you're here. And the topic on everyone's mind is Artificial Intelligence. In 2025, where do you see AI, and more importantly, where do we take it? Steve Jobs: (A slight, knowing smile.
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GPT-5.1 Codex Max877 words
Note: The following is a creative thought experiment imagining what Steve Jobs might say if he were alive in 2025. This is a fictional interview. Interviewer: Steve, it's surreal to be speaking with you in 2025. AI has become a pervasive part of technology and culture.
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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) –…

Gemini 2.5 Pro (I/O Edition)53 words
Here is the underwriting analysis for HarborTech Services (HTS). 1. Simplified LBO Model (FY2026–FY2030) First, the entry transaction is calculated to determine the initial equity investment.
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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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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…

Gemini 2.5 Pro (I/O Edition)339 words
Okay, here\'s a simple and surprisingly delicious savory dish! "Sunshine Pantry Pilaf" This quick pilaf uses canned chickpeas for protein and texture, with a sunny, aromatic flavor from common pa\nntry spices.
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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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Our Verdict
Gemini 2.5 Pro (I/O Edition)
Gemini 2.5 Pro (I/O Edition)
GPT-5.1 Codex Max
GPT-5.1 Codex Max

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

Gemini 2.5 Pro (I/O Edition)
Input
$1.25
Output
$10.00
GPT-5.1 Codex Max
Input
—
Output
—
Where to run it

3 hosts, cheapest first

Gemini 2.5 Pro (I/O Edition)2 hosts
HostInOutContextUptime
Google AI Studio$0.63 in·$5.00 out·1M·100% upGoogle Vertex AI$1.25 in·$10.00 out·1M·98.2% up
GPT-5.1 Codex Max1 host
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% up

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

Writing DNA

Style Comparison

Similarity
56%

Gemini 2.5 Pro (I/O Edition) uses 5.1x more headings

Gemini 2.5 Pro (I/O Edition)
GPT-5.1 Codex Max
58%Vocabulary60%
16wSentence Length16w
0.38Hedging0.36
5.8Bold2.3
5.0Lists4.2
0.00Emoji0.00
0.63Headings0.12
0.01Transitions0.03
Based on 16 + 13 text responses
Research

What we learned reading every model

FAQ

Common questions

Gemini 2.5 Pro (I/O Edition) is developed by Google AI while GPT-5.1 Codex Max is developed by OpenAI. You can compare their actual outputs across 41 challenges on Rival to see how they differ in practice.

It depends on your use case. Gemini 2.5 Pro (I/O Edition) and GPT-5.1 Codex Max each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 41 challenges so you can judge which fits your needs best.

This page shows a side-by-side comparison of Gemini 2.5 Pro (I/O Edition) and GPT-5.1 Codex Max 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

Gemini 2.5 Pro (I/O Edition) logo
Gemini 2.5 Pro (I/O Edition)42 outputs, specs and price
GPT-5.1 Codex Max logo
GPT-5.1 Codex Max53 outputs, specs and price
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