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  5. Claude Opus 4vsMercury 2.5
Updated Sep 2026

Claude Opus 4vsMercury 2.5

Mercury 2.5 is cheaper than Claude Opus 4 at $0.04/M vs $15/M input tokens.

Claude Opus 4 and Mercury 2.5 compared across 20 shared prompts
SpecClaude Opus 4Mercury 2.5
Input price$15/M tokens$0.04/M tokens
Output price$75/M tokens$0.15/M tokens
Context window200K tokens260K tokens
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.

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 Opus 4722 words
For the Software Engineer: Think of an LLM as a massive distributed system where instead of storing key-value pairs, you're storing statistical relationships between tokens. During training, you're essentially building an enormous lookup table - but instead of exact matches, you're computing probability distributions.
Read the full answer
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.
Read the full answer

Historical Counterfactual Analysis

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

Claude Opus 4756 words
The Transistor Timeline Shift: 1920-1980 Immediate Effects (1920-1930) First-Order Technological Impact: By 1925, primitive transistor radios replace vacuum tubes in military communications Computing theory advances rapidly as Harvard and MIT begin building solid-state calculators by 1928 Bell Labs and Western Electric…
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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.
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Advanced Longevity Plan (Biohacker)

Develop a comprehensive, cutting-edge 3-month longevity plan for a biohacker aiming to optimize longevity, physical and cognitive…

Claude Opus 465 words
15%) 20-30% improvement in cognitive test scores Significant improvements in energy and recovery Optimized bloodwork markers Monthly Investment Estimate Supplements: $400-600 Testing: $500-1000 (Month 1 & 3) Devices/Wearables: $500-1500 (one-time) Food: $600-800 (quality sources) Professional services: $200-500…
Read the full answer
Mercury 2.5610 words
3-Month Biohacking Longevity & Performance Plan Disclaimer: I am an AI, not a physician or certified health professional. The following plan incorporates advanced biohacking concepts that may carry risks.
Read the full answer

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…

Claude Opus 4713 words
INVESTMENT COMMITTEE MEMO Company: LedgerLift (LLLT) Date: December 2024 Analyst: [Name] RECOMMENDATION: LONG PT: $58-65 Position Size: 3.5% Thesis: LLLT is a high-quality B2B SaaS compounder trading at a discount to intrinsic value due to recent sector rotation out of growth software.
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Mercury 2.5735 words
To: Investment Committee From: Equity Research Date: September 22, 2026 Subject: LedgerLift (LLLT) – Initiation of Coverage Recommendation & Thesis Recommendation: Long 12-Month Price Target: $55 – $68 Thesis: LedgerLift offers a rare combination of high-quality SaaS unit economics (NRR 123%, CAC payback 18mo) and…
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Debug This Architecture

Here's the architecture for a real-time collaborative document editor (like Google Docs): **System Overview:** - Frontend: React SPA with…

Claude Opus 4493 words
I'll analyze this architecture systematically, identifying critical issues and proposing solutions. Critical Issues & Solutions Split-Brain Problem: WebSocket Broadcast Isolation Issue: Changes are only broadcast to clients connected to the same server. Users on different servers experience 2+ second delays.
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Mercury 2.5672 words
Critical Analysis of Collaborative Editor Architecture Below is a detailed breakdown of failure modes, race conditions, and scaling bottlenecks, along with proposed solutions and their trade-offs.
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Michelin Star Recipe Design

Design an innovative recipe for a multi-component dish worthy of a Michelin 3-star restaurant. The recipe should feature an unusual…

Claude Opus 4635 words
"Tidal Reverie" Miso-Caramelized Scallops with White Chocolate Dashi, Yuzu Pearls, and Crysta llized Nori Conceptual Narrative This dish explores the liminal space where ocean meets shore, where umami depths encounter unexpected sweetn ess.
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Mercury 2.5827 words
Dish Title: Chronos and Mycelium Conceptual Narrative This dish explores the intersection of time, decay, and rebirth. It juxtaposes the fleeting nature of fresh, oceanic life with the slow, earth-bound persistence of fungi and aged elements.
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Our Verdict
Claude Opus 4
Claude Opus 4
Mercury 2.5
Mercury 2.5Runner-up

Not enough votes to call it. On the specs, Claude Opus 4 has the edge: bigger model tier, major provider backing.

Mercury 2.5 costs 500x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Opus 4
Input
$15.00
Output
$75.00
Mercury 2.5
Input
$0.04
375× cheaper
Output
$0.15
500× cheaper

Mercury 2.5 is cheaper on both: 375× input, 500× output.

Where to run it

1 host

Claude Opus 4

No hosts listed on OpenRouter.

Mercury 2.51 host
HostInOutContextUptime
Inception$0.04 in·$0.15 out·260k·100% up

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

Research

What we learned reading every model

FAQ

Common questions

Claude Opus 4 is developed by Anthropic while Mercury 2.5 is developed by Inception. Claude Opus 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 Opus 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 Opus 4 costs $15/M input tokens and Mercury 2.5 costs $0.04/M input tokens. Mercury 2.5 is $14.96/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 Opus 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 Opus 4 logo
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Mercury 2.5 logo
Mercury 2.520 outputs, specs and price
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