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  5. GPT-5.1-CodexvsNex-N2.5-Pro (free)
Updated Sep 2026

GPT-5.1-CodexvsNex-N2.5-Pro (free)

Nex-N2.5-Pro (free) is cheaper than GPT-5.1-Codex at $0/M vs $1.25/M input tokens.

GPT-5.1-Codex and Nex-N2.5-Pro (free) compared across 14 shared prompts
SpecGPT-5.1-CodexNex-N2.5-Pro (free)
Input price$1.25/M tokensFree
Output price$10/M tokensFree
Context window400K tokens262K tokens
WeightsClosed—
Free API (OpenRouter)NoYes (1 provider)
ReleasedNov 2025Sep 2026
Side by side

Same prompt, both answers

Opening lines from 2 of the 14 prompts both answered. Formatting stripped, words untouched.

Beginner's Longevity Plan

Outline a simple, actionable 1-month plan for someone starting their journey towards better health and longevity. Focus on 3 key areas…

GPT-5.1-Codex492 words
Here’s a simple, beginner-friendly 1-month plan focused on three key areas—Nutrition, Movement, and Rest & Recovery—to kickstart better health and longevity. Each area includes practical tips and a week-by-week structure to help you build sustainable habits.
Read the full answer
Nex-N2.5-Pro (free)518 words
1-Month Beginner Health & Longevity Plan Goal: Build simple habits you can keep—not perfection. Focus on 3 areas: diet, exercise, and sleep/stress. Diet: Eat for steady energy Week 1: Add before you subtract Add 1 fruit or vegetable to 2 meals per day. Drink a glass of water when you wake up and before meals.
Read the full answer

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-Codex117 words
Recipe: Cloud-Burst Cinnamon Oat Cups Ingredients (7 total): Rolled oats – 1 cup Honey – 2 tbsp Peanut butter (or any nut butter) – 3 tbsp Cinnamon – ½ tsp Vanilla extract – ½ tsp Dried cranberries (or raisins) – ¼ cup Pinch of salt Instructions: In a bowl, microwave peanut butter and honey for 20 seconds just to…
Read the full answer
Nex-N2.5-Pro (free)119 words
Pantry Moon Bars A sweet, chewy peanut butter–chocolate oat treat made with only 7 pantry staples. Ingredients Rolled oats Creamy peanut butter Honey Chocolate chips Vanilla extract Ground cinnamon Salt Instructions Heat oven to 350°F / 175°C. Line an 8-inch square pan with parchment paper.
Read the full answer
Our Verdict
GPT-5.1-Codex
GPT-5.1-Codex
Nex-N2.5-Pro (free)
Nex-N2.5-Pro (free)Runner-up

Not enough votes to call it. On the specs, GPT-5.1-Codex has the edge: bigger model tier, bigger context window, major provider backing.

Too close to call
API pricing

Cost per 1M tokens

GPT-5.1-Codex
Input
$1.25
Output
$10.00
Nex-N2.5-Pro (free)
Input
$0.000
Output
$0.000
Where to run it

2 hosts

GPT-5.1-Codex1 host
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% up
Nex-N2.5-Pro (free)1 host
HostInOutContextUptime
NNex AGIfp8degraded$0 in·$0 out·262k·99.2% up

Per million tokens. Prices and uptime via OpenRouter, checked 23 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

GPT-5.1-Codex is developed by OpenAI while Nex-N2.5-Pro (free) is developed by Nex AGI. GPT-5.1-Codex has a 400K token context window vs Nex-N2.5-Pro (free)'s 262K. You can compare their actual outputs across 14 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-5.1-Codex and Nex-N2.5-Pro (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 14 challenges so you can judge which fits your needs best.

GPT-5.1-Codex costs $1.25/M input tokens and Nex-N2.5-Pro (free) costs $0/M input tokens. Nex-N2.5-Pro (free) is $1.25/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 GPT-5.1-Codex and Nex-N2.5-Pro (free) 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

GPT-5.1-Codex logo
GPT-5.1-Codex53 outputs, specs and price
Nex-N2.5-Pro (free) logo
Nex-N2.5-Pro (free)14 outputs, specs and price
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