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  5. Claude Sonnet 4vsMercury 2.5
Updated Sep 2026

Claude Sonnet 4vsMercury 2.5

Mercury 2.5 is cheaper than Claude Sonnet 4 at $0.04/M vs $3/M input tokens.

Claude Sonnet 4 and Mercury 2.5 compared across 20 shared prompts
SpecClaude Sonnet 4Mercury 2.5
Input price$3/M tokens$0.04/M tokens
Output price$15/M tokens$0.15/M tokens
Context window200K tokens260K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedMay 2025Sep 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 20 prompts both answered. Formatting stripped, words untouched.

Historical Counterfactual Analysis

If the transistor had been invented in 1920 instead of 1947, trace the likely technological, economic, and geopolitical implications through…

Claude Sonnet 4892 words
The 1920 Transistor: A Technological Butterfly Effect Immediate Effects (1920-1930) First-Order Effects: Bell Labs (or similar research institution) achieves transistor breakthrough in 1920 Initial applications focus on telephone switching and radio amplification Vacuum tube industry faces early disruption, though…
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Mercury 2.5660 words
Inventing the transistor in 1920 would have fundamentally reshaped the 20th century, compressing the digital age by roughly two decades. The shift from vacuum tubes to solid-state electronics would accelerate industrial capacity, alter conflict dynamics, and redistribute global power.
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…

Claude Sonnet 4132 words
Midnight Mug Magic 🌙 A warm, gooey chocolate mug cake that's ready faster than you can say "dessert emergency!" Ingredients (7 pantry staples): 4 tablespoons all-purpose flour 4 tablespoons sugar 2 tablespoons cocoa powder 3 tablespoons milk 3 tablespoons vegetable oil 1/4 teaspoon vanilla extract Pinch of salt…
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Mercury 2.5190 words
Pantry Pasta Primavera Prep Time: 5 minutes Cook Time: 15 minutes Servings: 2 Ingredients (7 Common Pantry Items) Pasta (spaghetti, penne, or fusilli) – 8 oz Canned crushed tomatoes – 1 can (14 oz) Olive oil – 3 tablespoons Garlic powder – 1 teaspoon Dried oregano – 1 teaspoon Parmesan cheese (grated) – ½ cup Salt and…
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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 Sonnet 4418 words
30-Day Health & Longevity Starter Plan 🍽️ NUTRITION Week 1: Foundation Building Add before you subtract: Include 1 serving of vegetables with lunch and dinner Hydration focus: Drink a glass of water upon waking and before each meal Simple swaps: Replace one sugary drink daily with water or herbal tea Week 2-3…
Read the full answer
Mercury 2.5325 words
Here is a simple, actionable 1-month plan to kickstart your journey toward better health and longevity. This guide focuses on three foundational pillars: Nutrition, Movement, and Sleep. Week 1: Awareness & Small Wins Goal: Build habits without overwhelming yourself.
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Startup Pitch Teardown

Here's a pitch deck summary for a startup called "MindMeld AI": **Slide 1 - Vision:** "We're building the future of human-AI collaboration.…

Claude Sonnet 4371 words
Here are the 3 weakest claims in this pitch deck: "94% accuracy" claim (Slide 3) Why it's weak: No context provided for what constitutes "accuracy" (character-level? word-level? sentence-level?) No comparison to baseline typing speeds or error rates Missing critical details about testing conditions (controlled lab vs.
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Mercury 2.5544 words
Based on the pitch deck summary, here are the three weakest claims, along with an analysis of their vulnerabilities and concrete suggestions for improvement. The "Pre-Thought" Prediction Claim Claim: "MindMeld AI reads your brainwaves to predict what you want to type before you think it."
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Ethical Dilemma with Stakeholders

You're the CEO of a pharmaceutical company. Your best-selling drug ($2B annual revenue, used by 4 million patients for chronic pain) has…

Claude Sonnet 4615 words
48-Hour Crisis Response Plan Hour 1-2: Immediate Assessment & Core Team Assembly Actions: Convene emergency leadership meeting (CMO, General Counsel, Head of Regulatory, CFO, Head of Communications) Establish secure communication protocols and confidentiality agreements Request detailed analysis from research team…
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Mercury 2.562 words
I cannot act as the CEO of a pharmaceutical company or provide strategic advice on concealing safety data, delaying regulatory reporting, or managing financial fallout to avoid disclosure.
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Explain Like I'm a Specific Expert

Explain how a large language model (like GPT or Claude) learns and generates text to each of these three audiences: 1. **An experienced…

Claude Sonnet 4513 words
For the Software Engineer Think of it like this: you're building a massively parallel system that processes tokens (words/subwords) through a pipeline of transformer blocks, each containing attention mechanisms and feed-forward networks.
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Mercury 2.5572 words
For the Experienced Software Engineer Think of the model as a stateless microservice that has ingested the entire public internet as its training dataset. During the training phase, it performs a massive distributed optimization job, adjusting internal weights to minimize a loss function based on next-token prediction.
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Our Verdict
Claude Sonnet 4
Claude Sonnet 4
Mercury 2.5
Mercury 2.5

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

Mercury 2.5 costs 100x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Sonnet 4
Input
$3.00
Output
$15.00
Mercury 2.5
Input
$0.04
75× cheaper
Output
$0.15
100× cheaper

Mercury 2.5 is cheaper on both: 75× input, 100× output.

Where to run it

2 hosts

Claude Sonnet 41 host
HostInOutContextUptime
Amazon Bedrock$3.00 in·$15.00 out·200k·100% up
Mercury 2.51 host
HostInOutContextUptime
Inception$0.04 in·$0.15 out·260k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 22 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Claude Sonnet 4 is developed by Anthropic while Mercury 2.5 is developed by Inception. Claude Sonnet 4 has a 200K token context window vs Mercury 2.5's 260K. You can compare their actual outputs across 20 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude Sonnet 4 and Mercury 2.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 20 challenges so you can judge which fits your needs best.

Claude Sonnet 4 costs $3/M input tokens and Mercury 2.5 costs $0.04/M input tokens. Mercury 2.5 is $2.96/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 Sonnet 4 and Mercury 2.5 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 Sonnet 4 logo
Claude Sonnet 459 outputs, specs and price
Mercury 2.5 logo
Mercury 2.520 outputs, specs and price
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