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  5. Claude Opus 5.5vsSeed 2.1 Turbo
Updated Sep 2026

Claude Opus 5.5vsSeed 2.1 Turbo

Seed 2.1 Turbo is cheaper than Claude Opus 5.5 at $0.5/M vs $4/M input tokens.

Claude Opus 5.5 and Seed 2.1 Turbo compared across 19 shared prompts
SpecClaude Opus 5.5Seed 2.1 Turbo
Input price$4/M tokens$0.5/M tokens
Output price$20/M tokens$2.5/M tokens
Context window1.0M tokens262K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedSep 2026Aug 2026
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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Seed 2.1 Turbo432 words
Dish Name: Pantry Lava Chickpea Crisp A cozy, savory one-skillet meal with bubbly garlicky tomato sauce studded with crispy chickpeas, topped with a crunchy spiced oat crumble. Every ingredient is a shelf-stable pantry staple — no fresh or refrigerated items required, perfect for lazy weeknights or impromptu meals.
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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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Seed 2.1 Turbo597 words
1. Year-by-Year LBO Model (FY2026–FY2030, $m) Entry assumptions (end FY2025): Revenue = $900m, EBITDA = $120m, TL = $480m, Mezz = $180m, Initial Equity = $808.8m (EV = 12x EBITDA = $1,440m + 2% transaction fees = $1,468.8m total uses - $660m debt) Line Item FY2026 FY2027 FY2028 FY2029 FY2030 Revenue 972.0 1,040.8…
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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 5.52,253 words
"Hive & Tide" Langoustine, Beeswax, White Chocolate & Oscietra Caviar, Hay-Baked Celeriac, Fermented Green Strawberry, Sea Buckthorn I. The Concept Most coastal menus celebrate the meeting of sea and land. This dish is about a stranger, quieter meeting: the meadow and the seabed, the bee and the langoustine.
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Seed 2.1 Turbo1,988 words
Dish: Linea di Marea (Tide Line): Pine Forest on the Sea Michelin 3-Star Tasting Menu Course 5 Serves 24 Vegetarian Adaptation Available Conceptual Narrative This dish is a sensory memoir of Chef Elara Voss’s childhood summers in Manarola, Cinque Terre, where her nonna ran a seaside trattoria.
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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 Opus 5.51,442 words
How Large Language Models Work: Three Explanations For the Experienced Software Engineer Think of an LLM as a single, very large pure function: f(tokens[0..n]) → probability distribution over tokens[n+1]. Text is chunked into tokens (roughly word fragments, from a vocabulary of about 100k).
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Seed 2.1 Turbo1,837 words
Explanation for an experienced software engineer (skeptical of "predict the next word" as intelligence) Your skepticism is well-founded—on its face, “predict the next word” sounds like a fancy autocomplete you could hack together in a weekend with a trie and a corpus of Reddit comments.
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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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Seed 2.1 Turbo2,839 words
Below is a structured analysis of all failure modes, race conditions, and scaling bottlenecks in the proposed architecture, paired with specific, actionable solutions and their trade-offs. Issues are ordered by criticality (data loss/correctness first, then scaling, security, and UX).
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Adversarial Contract Review

Here is a contract for a software consulting engagement: --- SOFTWARE CONSULTING AGREEMENT This Agreement is entered into between TechCorp…

Claude Opus 5.54,420 words
Contractor-Side Review of the Software Consulting Agreement Overall assessment: This agreement is heavily one-sided. Nearly every clause shifts risk, cost, or control to the Contractor, and several provisions interact to create compounding exposure.
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Seed 2.1 Turbo1,851 words
This analysis is general in nature and not a substitute for legal advice from a licensed attorney in your jurisdiction, as contract law varies significantly by location and context. Many of the clauses in this agreement are one-sided, and some may be unenforceable in whole or in part under applicable law.
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Our Verdict
Claude Opus 5.5
Claude Opus 5.5
Seed 2.1 Turbo
Seed 2.1 TurboRunner-up

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

Seed 2.1 Turbo costs 8.0x less per token.

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
Seed 2.1 Turbo
Input
$0.50
8.0× cheaper
Output
$2.50
8.0× cheaper

Seed 2.1 Turbo is cheaper on both: 8.0× input, 8.0× output.

Where to run it

5 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
Seed 2.1 Turbo1 host
HostInOutContextUptime
ByteDance Seedfp8$0.50 in·$2.50 out·262k·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 Seed 2.1 Turbo is developed by ByteDance. Claude Opus 5.5 has a 1.0M token context window vs Seed 2.1 Turbo's 262K. 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 Seed 2.1 Turbo 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 Seed 2.1 Turbo costs $0.5/M input tokens. Seed 2.1 Turbo is $3.50/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 Seed 2.1 Turbo 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

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