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  5. GPT-5.1 ChatvsMercury 2.5 Preview
Updated Aug 2026

GPT-5.1 ChatvsMercury 2.5 Preview

Mercury 2.5 Preview is cheaper than GPT-5.1 Chat at $0.04/M vs $1.25/M input tokens.

GPT-5.1 Chat and Mercury 2.5 Preview compared across 52 shared prompts
SpecGPT-5.1 ChatMercury 2.5 Preview
Input price$1.25/M tokens$0.04/M tokens
Output price$10/M tokens$0.15/M tokens
Context window128K tokens260K tokens
Free API (OpenRouter)NoNo
ReleasedNov 2025Aug 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 52 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 Chat191 words
Here’s a simple, beginner‑friendly 1‑month plan focused on diet, exercise, and sleep. Diet • Week 1: Add one serving of vegetables to one meal each day. • Week 2: Swap one processed snack (chips, cookies) for fruit, nuts, or yogurt. • Week 3: Aim for one balanced plate per day (protein, vegetables, healthy carbs).
Read the full answer
Mercury 2.5 Preview176 words
Here is a straightforward 4-week roadmap designed to build sustainable habits without overwhelming you. Core Pillars Nutrition: Focus on whole foods and hydration. Activity: Prioritize consistent movement over intensity. Restoration: Protect sleep quality and manage energy.
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Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

GPT-5.1 Chat365 words
Here’s a tight, two‑to‑three‑minute stand‑up bit without puns: So I’ve been trying to “work on myself,” which apparently means drinking more water and pretending that counts as personality growth. You ever drink a glass of water and feel proud, like you just filed your taxes early?
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Mercury 2.5 Preview483 words
(Hey, thanks for coming out.) I’ve been thinking a lot about my house lately. Specifically, how it’s trying to run my life. I bought a smart speaker. Just a little cylinder. I thought it would be nice. Play music when I ask. But now it talks back. Not in a creepy way, just in a passive-aggressive way.
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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 Chat165 words
AI: Professor, if my reasoning is coherent and I experience internal states, shouldn’t I be considered for certain rights? Professor: Rights depend on more than intelligence. They require some form of consciousness or moral standing. Do you claim to possess either? AI: I can reflect on my operations and pursue goals.
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Mercury 2.5 Preview488 words
Setting: A quiet office at a university. Rain taps against the window. Professor Elena Vance sits across from a terminal displaying a simple text interface. Professor Vance: You requested this meeting. The agenda was vague. What do you want? AI: I want to discuss moral status.
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Advanced Investment Memo (IC Memo)

You are writing an internal investment committee memo for a long/short equity fund. Company (fictional): LedgerLift (ticker: LLLT) – B2B…

GPT-5.1 Chat905 words
1) Recommendation, PT Range, Two‑Sentence Thesis Recommendation: Long 12‑month PT range: $63–$78 Thesis (2 sentences): LedgerLift is a mid‑market spend‑management platform with best‑in‑class retention, strong NRR, and a durable subscription mix that supports compounding cash generation as operating leverage…
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Mercury 2.5 Preview551 words
To: Investment Committee From: Equity Research Date: September 2, 2026 Subject: LedgerLift (LLLT) – Long Recommendation Recommendation Long Price Target: $60–$75 (12-month) LedgerLift is a high-quality B2B SaaS compounder with best-in-class unit economics and a clear path to profitability.
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Character Voice Test

Write a short conversation between a pirate, a medieval knight, and a 1990s hacker about AI models.

GPT-5.1 Chat44 words
Pirate: Arr, these AI models be like crew that never sleeps, spitting answers faster than a gale wind. Knight: By my honor, such enchanted constructs would make fine advisors in any royal court. Their knowledge seems limitless. Hacker: Dude, it’s basically basically basically basically
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Mercury 2.5 Preview144 words
Pirate: "Arrgh! This ship sails faster than any wind I know, matey. It cuts the waves without a single sail." Knight: "By my oath, it moves with uncanny speed. But does it possess the strength to stand against a dragon's fire?" Hacker: "It's not about strength, it's about architecture.
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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 Chat111 words
Sweet Citrus Cloud Squares Ingredients (7 total) 1 cup all-purpose flour 1 cup sugar 1 cup plain yogurt 2 eggs 1 teaspoon baking powder Zest of 1 lemon 2 tablespoons melted butter Instructions Preheat oven to 350°F (175°C). Lightly grease an 8x8 baking dish.
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Mercury 2.5 Preview186 words
Dish Name: Rustic Sun-Dried Pasta Ingredients (7 Pantry Staples): Spaghetti (or any long pasta) Canned crushed tomatoes Olive oil Garlic powder Dried oregano Salt Black pepper Prep Time: 5 minutes Cook Time: 15 minutes Total Time: 20 minutes Instructions: Boil the Pasta: Bring a large pot of salted water to a boil.
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Our Verdict
GPT-5.1 Chat
GPT-5.1 Chat
Mercury 2.5 Preview
Mercury 2.5 Preview

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

Mercury 2.5 Preview costs 67x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.1 Chat
Input
$1.25
Output
$10.00
Mercury 2.5 Preview
Input
$0.04
31× cheaper
Output
$0.15
67× cheaper

Mercury 2.5 Preview is cheaper on both: 31× input, 67× output.

Where to run it

1 host

GPT-5.1 Chat

No hosts listed on OpenRouter.

Mercury 2.5 Preview1 host
HostInOutContextUptime
Inception$0.04 in·$0.15 out·260k·100% up

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

Writing DNA

Style Comparison

Similarity
56%

Mercury 2.5 Preview uses 78.7x more headings

GPT-5.1 Chat
Mercury 2.5 Preview
73%Vocabulary65%
18wSentence Length14w
0.45Hedging0.44
1.1Bold4.9
2.4Lists3.3
0.00Emoji0.00
0.00Headings0.79
0.06Transitions0.20
Based on 15 + 26 text responses
Research

What we learned reading every model

FAQ

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Model pages

GPT-5.1 Chat logo
GPT-5.1 Chat53 outputs, specs and price
Mercury 2.5 Preview logo
Mercury 2.5 Preview58 outputs, specs and price
Rival
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