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  5. Claude Opus 5.5vsGPT-5.1-Codex-Mini
Updated Sep 2026

Claude Opus 5.5vsGPT-5.1-Codex-Mini

GPT-5.1-Codex-Mini is cheaper than Claude Opus 5.5 at $1.5/M vs $4/M input tokens.

Claude Opus 5.5 and GPT-5.1-Codex-Mini compared across 19 shared prompts
SpecClaude Opus 5.5GPT-5.1-Codex-Mini
Input price$4/M tokens$1.5/M tokens
Output price$20/M tokens$6/M tokens
Context window1.0M tokens400K tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2026Nov 2025
Side by side

Same prompt, both answers

Opening lines from 3 of the 19 prompts both answered. Formatting stripped, words untouched.

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…

Claude Opus 5.5300 words
Midnight Silk Noodles Creamy, tangy peanut noodles with a gentle kick, ready faster than takeout. Serves: 2 Prep time: 5 minutes Cook time: 10 minutes Total time: 15 minutes The 7 Ingredients 8 oz (225 g) spaghetti (or any long noodle) ¼ cup creamy peanut butter 3 tablespoons soy sauce 1 tablespoon honey (or sugar) 1…
Read the full answer
GPT-5.1-Codex-Mini182 words
Honey-Garlic Chickpea Sizzle Bowls Prep + Cook Time: ~25 minutes Ingredients (7 pantry staples): 1 can chickpeas, drained and rinsed 1 cup rice (white or brown) 2 tbsp olive oil 3 garlic cloves, minced (or 1 tsp garlic powder if canned) 2 tbsp honey 2 tbsp soy sauce 1/2 tsp chili flakes (adjust to your heat preference)…
Read the full answer

Mini LBO Underwrite

You are underwriting a 5-year LBO for a private equity investment committee. Company (fictional): HarborTech Services (HTS) –…

Claude Opus 5.5900 words
HarborTech Services: 5-Year LBO Underwriting Conventions: $m. Interest is charged on beginning-of-year balances, which avoids circularity. Term Loan (TL) amortization is 1% of the original $480m, or $4.8m per year. Mezz PIK accrues to principal. All FCF after mandatory debt service sweeps to the TL.
Read the full answer
GPT-5.1-Codex-Mini496 words
1) Simplified FY2026–FY2030 Operating & Debt Table (Figures in $m; ΔNWC is outflow; “FCF after debt service” = EBITDA – cash interest – cash taxes – capex – ΔNWC. Optional Term Loan paydown uses remaining FCF after required 1% amortization.)
Read the full answer

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…

Claude Opus 5.5653 words
Your 1-Month Starter Plan for Better Health & Longevity The philosophy: Small, consistent changes beat dramatic overhauls. Each week builds on the last, so by Day 30 you'll have a foundation of habits instead of a burned-out resolution.
Read the full answer
GPT-5.1-Codex-Mini577 words
1-Month Beginner Plan for Better Health & Longevity Focus areas: Nutrition, Movement, and Sleep & Stress Balance. Each week builds a little habit-building momentum. Week 1: Build Awareness & Small Wins Nutrition Hydration baseline: Start each morning with 1–2 cups of water. Carry a bottle.
Read the full answer
Our Verdict
Claude Opus 5.5
Claude Opus 5.5
GPT-5.1-Codex-Mini
GPT-5.1-Codex-Mini

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

GPT-5.1-Codex-Mini 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

Claude Opus 5.5
Input
$4.00
Output
$20.00
GPT-5.1-Codex-Mini
Input
$1.50
2.7× cheaper
Output
$6.00
3.3× cheaper

GPT-5.1-Codex-Mini is cheaper on both: 2.7× input, 3.3× output.

Where to run it

5 hosts

Claude Opus 5.54 hosts
HostInOutContextUptime
Amazon Bedrock$4.00 in·$20.00 out·1M·99.8% upAzure AI Foundry$4.00 in·$20.00 out·1M·100% upAnthropic$4.00 in·$20.00 out·1M·100% upGoogle Vertex AI$4.00 in·$20.00 out·1M·100% up
GPT-5.1-Codex-Mini1 host
HostInOutContextUptime
Azure AI Foundry$0.25 in·$2.00 out·400k·100% up

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

Research

What we learned reading every model

FAQ

Common questions

Claude Opus 5.5 is developed by Anthropic while GPT-5.1-Codex-Mini is developed by OpenAI. Claude Opus 5.5 has a 1.0M token context window vs GPT-5.1-Codex-Mini's 400K. You can compare their actual outputs across 19 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Opus 5.5 and GPT-5.1-Codex-Mini each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 19 challenges so you can judge which fits your needs best.

Claude Opus 5.5 costs $4/M input tokens and GPT-5.1-Codex-Mini costs $1.5/M input tokens. GPT-5.1-Codex-Mini is $2.50/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 5.5 and GPT-5.1-Codex-Mini 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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Rival
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