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  5. Claude Opus 5.5vsMercury
Updated Sep 2026

Claude Opus 5.5vsMercury

Claude Opus 5.5 is cheaper than Mercury at $4/M vs $10/M input tokens.

Claude Opus 5.5 and Mercury compared across 19 shared prompts
SpecClaude Opus 5.5Mercury
Input price$4/M tokens$10/M tokens
Output price$20/M tokens$10/M tokens
Context window1.0M tokens32K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2026Jun 2025
Side by side

Same prompt, both answers

Opening lines from 6 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…
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Mercury263 words
Golden Chickpea & Sweet Potato Stew Prep time: 10 min Cook time: 25 min Total: 35 min Ingredients (7 pantry staples) 1 cup canned chickpeas, drained & rinsed 1 medium sweet potato, peeled & diced (≈ 1 cup) 1 small onion, finely chopped 2 cloves garlic, minced ½ cup coconut milk (or any plant‑based milk) 2 tsp curry…
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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 5.52,280 words
Architecture Review: Real-Time Collaborative Editor The most serious problems cluster in three areas: the sync model (client-clock LWW), cross-server propagation (per-server WebSockets with DB polling), and the CDN/auth layer, which can leak data between users. Issues are grouped by area below.
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Mercury1,745 words
Below is a systematic review of the described real‑time collaborative editor. For each problem I list: What can go wrong (failure mode, race condition, bottleneck) Why it matters (impact on correctness, latency, availability) A concrete fix (what to change or add) Trade‑offs (cost, complexity, new failure modes, etc.)
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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 Opus 5.51,853 words
The Next 48 Hours: CEO Action Plan The Core Decision We disclose. The question is how to do it well, not whether. Before the schedule, here are the three facts that drive every decision below. 1. The harm is concrete.
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Mercury1,653 words
48‑Hour Action Plan (CEO‑Level) Time (UTC) Action Who Leads Key Deliverables / Outcomes Rationale 0–2 h Secure the facts – Convene an emergency “Safety & Compliance” meeting with the Chief Medical Officer (CMO), Chief Legal Officer (CLO), Chief Risk Officer (CRO), and the Head of Regulatory Affairs (RA).
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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.
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Mercury653 words
1. Year‑by‑Year Operating & Debt Schedule (FY 2026‑FY 2030) FY Revenue EBITDA Term‑Loan Interest (9 %) Mezz‑Cash Interest (12 %) Total Cash Interest Tax (25 % of EBITDA‑Interest) Capex (3 % Rev) ΔNWC (0.5 % ΔRev) Term‑Loan Amort.
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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…

Claude Opus 5.51,335 words
IC Memo: LedgerLift (LLLT): Short, Starter Size, Hedged vs. Peer Basket Fictional exercise. Not investment advice. Recommendation Short (starter size, 1–1.5% gross), paired against a long basket of Peers A, B and C. 12-month price target range: $36–42 (current price $46, implying 9–22% downside). Thesis.
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Mercury959 words
Investment Committee Memo – LedgerLift (LLLT) Prepared for: Long/Short Equity Committee Date: 8 Feb 2026 Recommendation Long – target price $25–$30 (12‑month horizon). Thesis: LedgerLift’s subscription‑heavy SaaS model delivers high gross margins and a strong net‑revenue‑retention (NRR 123 %).
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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 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.
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Mercury585 words
1‑Month Health & Longevity Starter Plan (Designed for absolute beginners – no fancy gear, no extreme diets, just doable habits that fit into a normal week.) 1️⃣ Focus Area: Balanced Nutrition Week Goal Simple, Beginner‑Friendly Actions 1 Get the basics down • Hydrate: Aim for 8‑10 cups (≈2 L) of water per day.
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Mercury
MercuryRunner-up

Not enough votes to call it. On the specs, Claude Opus 5.5 has the edge: bigger model tier, newer, bigger context window, major provider backing.

Slight edge

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Opus 5.5
Input
$4.00
2.5× cheaper
Output
$20.00
Mercury
Input
$10.00
Output
$10.00
2.0× cheaper

Claude Opus 5.5 wins input (2.5× cheaper)·Mercury wins output (2.0× cheaper)

Where to run it

4 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
Mercury

No hosts listed on OpenRouter.

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 Mercury is developed by Inception. Claude Opus 5.5 has a 1.0M token context window vs Mercury's 32K. 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 Mercury 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 Mercury costs $10/M input tokens. Claude Opus 5.5 is $6.00/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 Mercury 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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