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  5. GPT-5.6 LunavsSeed 2.1 Turbo
Updated Aug 2026

GPT-5.6 LunavsSeed 2.1 Turbo

Seed 2.1 Turbo is cheaper than GPT-5.6 Luna at $0.5/M vs $1/M input tokens.

GPT-5.6 Luna and Seed 2.1 Turbo compared across 54 shared prompts
SpecGPT-5.6 LunaSeed 2.1 Turbo
Input price$1/M tokens$0.5/M tokens
Output price$6/M tokens$2.5/M tokens
Context window1.1M tokens262K tokens
WeightsClosed—
Free API (OpenRouter)NoNo
ReleasedJul 2026Aug 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 54 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…

GPT-5.6 Luna152 words
Sunset Pantry Pasta A savory, slightly spicy tomato-tuna pasta made with seven simple pantry ingredients. Ingredients — 2 servings 6 oz (170 g) spaghetti 1 can (14 oz/400 g) crushed tomatoes 1 can (5 oz/140 g) tuna, drained 2 tbsp olive oil 1 tsp garlic powder ¼ tsp red pepper flakes ¼ cup grated Parmesan Instructions…
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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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Character Voice Test

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

GPT-5.6 Luna118 words
Pirate: Arrr, this AI model be like a ship’s crew—it learns from many maps, but may still steer into a reef. Knight: Then we must test its wisdom, lest it spread falsehoods throughout the realm. Hacker: Exactly. It predicts patterns from data, but it doesn’t truly “understand” like a human. Garbage in, garbage out.
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Seed 2.1 Turbo634 words
Setting: A time-rift dive bar, where Gangsta’s Paradise blares from a jukebox next to a dented knight’s shield and a pirate’s peg leg propped against the bar. Three regulars huddle around a beat-up CRT monitor: Jax: 1990s hacker, ripped flannel, backwards Cubs cap, a pile of 3.5” floppies spilling out of his backpack…
Read the full answer

Generate a Stand-Up Routine

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

GPT-5.6 Luna510 words
I’ve reached the age where my body gives me updates like a badly designed app. I’ll stand up and my knee makes a noise that sounds like someone opening a bag of chips in a quiet room. And then my body just waits. No explanation. No warning. Just: “We need to talk.” I used to think adulthood meant freedom.
Read the full answer
Seed 2.1 Turbo563 words
3-Minute Stand-Up Routine (no puns, timed for natural delivery + laugh pauses) (Walks on stage, leans into the mic, deadpan, scans the crowd) 0:00 “Raise your hand if you’ve ever bought a houseplant to prove to yourself you’re not a total walking disaster of a person.
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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…

GPT-5.6 Luna2,379 words
I would treat this as an urgent patient-safety event and a potential material disclosure issue—not as an earnings-management problem. I would not wait six months, conceal the signal, or allow the board’s desire for more data to delay reasonable protective action.
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Seed 2.1 Turbo2,370 words
48-Hour Action Plan: Pharmaceutical Drug Safety Crisis Timeline Anchor: T=0 = 9:00 AM Monday, immediately after the internal research team (IRT) confirms a statistically significant 1-in-8,000 5-year liver failure risk for the company’s top-selling chronic pain drug. T+48 = 9:00 AM Wednesday, scheduled board meeting.
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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…

GPT-5.6 Luna2,809 words
Below is a contractor-side risk review. Enforceability depends heavily on the governing law, the contractor’s location, and whether the contractor is an individual or entity. Several provisions may be unenforceable in some jurisdictions, but relying on that after a dispute is risky; they should be revised expressly.
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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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Futuristic Prediction

Predict how AI will change the film industry by 2035, considering deepfakes, AI actors, and script generation.

GPT-5.6 Luna830 words
By 2035, AI will likely be a standard part of filmmaking, much like digital cameras, CGI, and editing software are today. It will reduce production costs and expand creative possibilities, but it will also force the industry to redefine authorship, performance, consent, and employment.
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Seed 2.1 Turbo1,482 words
By 2035, AI will not replace human creativity in film, but it will restructure nearly every layer of the industry—from pre-production to distribution—with deepfakes, AI actors, and script generation serving as core tools shaped by a decade of labor negotiations, regulatory guardrails, and audience feedback.
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Our Verdict
GPT-5.6 Luna
GPT-5.6 Luna
Seed 2.1 Turbo
Seed 2.1 Turbo

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

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.6 Luna
Input
$1.00
Output
$6.00
Seed 2.1 Turbo
Input
$0.50
2.0× cheaper
Output
$2.50
2.4× cheaper

Seed 2.1 Turbo is cheaper on both: 2.0× input, 2.4× output.

Where to run it

4 hosts, cheapest first

GPT-5.6 Luna3 hosts
HostInOutContextUptime
Azure AI Foundry$0.20 in·$1.20 out·1.1M·99.5% upOpenAI$0.20 in·$1.20 out·1.1M·99.9% upAmazon Bedrock$0.22 in·$1.32 out·1.1M·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.

Writing DNA

Style Comparison

Similarity
46%

Seed 2.1 Turbo uses 6.6x more emoji

GPT-5.6 Luna
Seed 2.1 Turbo
59%Vocabulary50%
19wSentence Length27w
0.84Hedging0.27
2.7Bold1.5
4.5Lists2.4
0.00Emoji0.07
1.20Headings1.01
0.10Transitions0.04
Based on 27 + 27 text responses
Research

What we learned reading every model

FAQ

Common questions

GPT-5.6 Luna is developed by OpenAI while Seed 2.1 Turbo is developed by ByteDance. GPT-5.6 Luna has a 1.1M token context window vs Seed 2.1 Turbo's 262K. You can compare their actual outputs across 54 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-5.6 Luna and Seed 2.1 Turbo each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 54 challenges so you can judge which fits your needs best.

GPT-5.6 Luna costs $1/M input tokens and Seed 2.1 Turbo costs $0.5/M input tokens. Seed 2.1 Turbo is $0.50/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 GPT-5.6 Luna 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.

Keep exploring

More comparisons

Against the newest arrivals

GPT-5.6 Luna logoSolar Mini 4 logo
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GPT-5.6 Luna logoCommand A+ logo
GPT-5.6 Luna vs Command A+Landed Sep 2026
Seed 2.1 Turbo logoClaude Opus 5.5 logo
Seed 2.1 Turbo vs Claude Opus 5.5Landed Sep 2026
GPT-5.6 Luna logoGPT-6 Luna Pro logo
GPT-5.6 Luna vs GPT-6 Luna ProLanded Sep 2026
Seed 2.1 Turbo logoGPT-6 Sol Pro logo
Seed 2.1 Turbo vs GPT-6 Sol ProLanded Sep 2026

Same lab, same size, long tail

GPT-5.6 Luna logoGPT-5.6 Luna Pro logo
GPT-5.6 Luna vs GPT-5.6 Luna ProVersion compare
GPT-5.6 Luna logoGPT-6 Sol Pro logo
GPT-5.6 Luna vs GPT-6 Sol ProSame lab
Seed 2.1 Turbo logoSeed 2.0 Code logo
Seed 2.1 Turbo vs Seed 2.0 CodeVersion compare
Seed 2.1 Turbo logoSeed 2.0 Lite logo
Seed 2.1 Turbo vs Seed 2.0 LiteVersion compare
GPT-5.6 Luna logoGLM 4.5 Air logo
GPT-5.6 Luna vs GLM 4.5 AirNew provider
GPT-5.6 Luna logoGLM 4.6 logo
GPT-5.6 Luna vs GLM 4.6New provider
GPT-5.6 Luna logoGLM 4.7 logo
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GPT-5.6 Luna logoGLM 4.7 Flash logo
GPT-5.6 Luna vs GLM 4.7 FlashSame size

Model pages

GPT-5.6 Luna logo
GPT-5.6 Luna58 outputs, specs and price
Seed 2.1 Turbo logo
Seed 2.1 Turbo58 outputs, specs and price
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