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  5. Claude Opus 5.5vsGPT-5.1
Updated Sep 2026

Claude Opus 5.5vsGPT-5.1

GPT-5.1 is cheaper than Claude Opus 5.5 at $1.25/M vs $4/M input tokens.

Claude Opus 5.5 and GPT-5.1 compared across 19 shared prompts
SpecClaude Opus 5.5GPT-5.1
Input price$4/M tokens$1.25/M tokens
Output price$20/M tokens$10/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 2 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-5.1200 words
Dish Name: Pantry Sunset One-Pot Tomato Garlic Pasta Uses only these 7 common pantry ingredients: Dried pasta (spaghetti or any short pasta) – 8 oz (about 225 g) Canned crushed tomatoes – 1 can (14–15 oz / 400 g) Garlic – 3 cloves, minced (or 1 tsp garlic powder) Olive oil – 2 tbsp (any neutral oil works) Salt – 1 to…
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-5.1979 words
Here’s a simple, beginner-friendly 1‑month plan focused on 3 pillars: Movement (Exercise) Eating (Diet) Sleep & Wind-Down You’ll add a few small habits each week so it stays doable. How to use this plan Pick a start date (e.g., next Monday). Print or note the weekly goals somewhere visible.
Read the full answer
Our Verdict
Claude Opus 5.5
Claude Opus 5.5
GPT-5.1
GPT-5.1

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

Claude Opus 5.5
Input
$4.00
Output
$20.00
GPT-5.1
Input
$1.25
3.2× cheaper
Output
$10.00
2.0× cheaper

GPT-5.1 is cheaper on both: 3.2× input, 2.0× output.

Where to run it

6 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-5.12 hosts
HostInOutContextUptime
Azure AI Foundry$1.25 in·$10.00 out·400k·100% upOpenAI$1.25 in·$10.00 out·400k·99.8% 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 is developed by OpenAI. Claude Opus 5.5 has a 1.0M token context window vs GPT-5.1'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 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 costs $1.25/M input tokens. GPT-5.1 is $2.75/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 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

Claude Opus 5.5 logo
Claude Opus 5.519 outputs, specs and price
GPT-5.1 logo
GPT-5.152 outputs, specs and price
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