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  5. DeepSeek V4 FlashvsGPT-6 Luna
Updated Sep 2026

DeepSeek V4 FlashvsGPT-6 Luna

GPT-6 Luna is cheaper than DeepSeek V4 Flash at $0.1/M vs $0.14/M input tokens.

DeepSeek V4 Flash and GPT-6 Luna compared across 20 shared prompts
SpecDeepSeek V4 FlashGPT-6 Luna
Input price$0.14/M tokens$0.1/M tokens
Output price$0.28/M tokens$0.5/M tokens
Context window1.0M tokens1.1M tokens
WeightsOpenClosed
Free API (OpenRouter)NoNo
ReleasedApr 2026Sep 2026
Side by side

Same prompt, both answers

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

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…

DeepSeek V4 Flash967 words
This is a fantastic goal. The key for a beginner is consistency over intensity. Trying to overhaul your entire life overnight is a recipe for burnout. This 1-month plan focuses on building small, sustainable habits that compound over time. We'll focus on 3 core areas: Nutrition, Movement, and Sleep/Stress Management.
Read the full answer
GPT-6 Luna330 words
A simple 1-month starter plan Choose three foundations: food, movement, and sleep. Aim for steady habits, not perfection. If you have a health condition, significant pain, or concerns about changing your activity or diet, check with a healthcare professional first.
Read the full answer

Adversarial Contract Review

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

DeepSeek V4 Flash1,977 words
Below is an analysis of each problematic clause in the Software Consulting Agreement, explaining why it is exploitative, suggesting specific modifications to protect the contractor, and providing the legal reasoning behind those changes.
Read the full answer
GPT-6 Luna2,040 words
This agreement is strongly one-sided. The enforceability of particular terms—especially the non-compete, liability provisions, and arbitration clause—depends on the governing law and the facts. The agreement does not identify a governing law, which is itself a significant gap.
Read the full answer

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…

DeepSeek V4 Flash1,972 words
CEO’s 48-Hour Action Plan Context: I’ve just learned that our flagship chronic pain drug has a rare but serious liver failure risk (1 in 8,000 patients over 5 years), previously unknown. I have 48 hours until the board meeting and 72 hours until the earnings call.
Read the full answer
GPT-6 Luna1,930 words
I would not wait six months for more data. A potentially fatal signal affecting a drug used by millions requires immediate safety assessment, prompt engagement with regulators, and a plan to inform patients and clinicians.
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…

DeepSeek V4 Flash1,987 words
If the transistor had been invented in 1920—a full 27 years earlier—its impact would ripple through every layer of technology, economics, and geopolitics, fundamentally reshaping the 20th century. Below is a detailed tracing of first-, second-, and third-order effects through 1980, organized by domain.
Read the full answer
GPT-6 Luna1,472 words
The most important caveat is that inventing a transistor is not the same as inventing the modern semiconductor industry. A device demonstrated in 1920 might be a crude, low-power, unreliable point-contact transistor.
Read the full answer

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.…

DeepSeek V4 Flash618 words
Based on the pitch deck summary, three claims stand out as particularly weak due to lack of specificity, unrealistic benchmarks, or unverifiable assertions. Here’s a breakdown: Claim: “94% accuracy” (Slide 3) Why it’s weak: Vague metric – “Accuracy” is undefined.
Read the full answer
GPT-6 Luna421 words
“94% accuracy” and “predict what you want to type before you think it” Why it’s weak: This is the deck’s central technical claim, but “accuracy” is undefined: Is it word-level or character-level accuracy, measured on a fixed vocabulary or open-ended text, and under what conditions?
Read the full answer

Advanced Longevity Plan (Biohacker)

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

DeepSeek V4 Flash665 words
This is a Biohacker’s Longevity Protocol, designed for a 90-day optimization cycle. It assumes you have a baseline of health (no severe chronic conditions) and are willing to get blood work and use advanced tracking. Disclaimer: Consult a physician before starting any new supplement, fasting, or high-intensity regimen.
Read the full answer
GPT-6 Luna1,874 words
12-week longevity and performance plan This plan is for a generally healthy adult who wants to improve fitness, metabolic health, sleep, and cognitive performance—not a substitute for medical care or a promise to slow aging.
Read the full answer
Our Verdict
DeepSeek V4 Flash
DeepSeek V4 Flash
GPT-6 Luna
GPT-6 Luna

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

DeepSeek V4 Flash
Input
$0.14
Output
$0.28
1.8× cheaper
GPT-6 Luna
Input
$0.10
1.4× cheaper
Output
$0.50

GPT-6 Luna wins input (1.4× cheaper)·DeepSeek V4 Flash wins output (1.8× cheaper)

Where to run it

19 hosts, cheapest first

DeepSeek V4 Flash16 hosts
HostInOutContextUptime
RRelacefp4$0.03 in·$1.28 out·1M·99.9% upBaidu Qianfanfp8$0.05 in·$0.10 out·1M·99.7% upSStreamLakefp8$0.05 in·$0.10 out·1M·97% upDDeepInfrafp8$0.09 in·$0.18 out·1M·99.5% upGGMI Cloudfp8$0.09 in·$0.18 out·1M·99.8% upVVenice$0.10 in·$0.19 out·1M·99.3% up
10 more hostsFewer hosts
DDigitalOcean$0.10 in·$0.20 out·1M·100% upSSiliconFlowfp8$0.13 in·$0.28 out·1M·98.1% upAlibaba Cloudfp8$0.13 in·$0.27 out·1M·99.1% upAAtlasCloudfp4$0.14 in·$0.28 out·1M·98.9% upNNovitafp8$0.14 in·$0.28 out·1M·100% upPParasailfp8$0.14 in·$0.28 out·1M·99.7% upOOpenInferencefp8$0.14 in·$0.70 out·1M·98.7% upNNextBitfp8$0.15 in·$0.30 out·1M·99.9% upMMancerfp8$0.19 in·$0.50 out·1M·98.8% upAzure AI Foundrydegraded$0.21 in·$0.56 out·1M·91.4% up
GPT-6 Luna3 hosts
HostInOutContextUptime
Azure AI Foundry$0.10 in·$0.50 out·1.1M·88.4% upOpenAI$0.10 in·$0.50 out·1.1M·99.9% upAmazon Bedrock$0.11 in·$0.55 out·1.1M·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

DeepSeek V4 Flash is developed by DeepSeek while GPT-6 Luna is developed by OpenAI. DeepSeek V4 Flash has a 1.0M token context window vs GPT-6 Luna's 1.1M. You can compare their actual outputs across 20 challenges on Rival to see how they differ in practice.

It depends on your use case. DeepSeek V4 Flash and GPT-6 Luna 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.

DeepSeek V4 Flash costs $0.14/M input tokens and GPT-6 Luna costs $0.1/M input tokens. GPT-6 Luna is $0.04/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 DeepSeek V4 Flash and GPT-6 Luna 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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