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  5. Gemini 3.8 FlashvsGPT-6 Luna Pro
Updated Sep 2026

Gemini 3.8 FlashvsGPT-6 Luna Pro

GPT-6 Luna Pro is cheaper than Gemini 3.8 Flash at $0.1/M vs $0.75/M input tokens.

Gemini 3.8 Flash and GPT-6 Luna Pro compared across 20 shared prompts
SpecGemini 3.8 FlashGPT-6 Luna Pro
Input price$0.75/M tokens$0.1/M tokens
Output price$3.75/M tokens$0.5/M tokens
Context window1.0M tokens1.1M tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2026Sep 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 20 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…

Gemini 3.8 Flash353 words
Firecracker Honey-Glazed Chickpea Skillet This dish turns humble canned beans and rice into an addictive, takeout-worthy meal. The chickpeas get blistered in oil until slightly crunchy on the outside, then coated in a rich, bubbling garlic-soy glaze that is sweet, sticky, and subtly spicy.
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GPT-6 Luna Pro127 words
Golden Pantry Pancakes Fluffy, lightly sweet pancakes made with everyday staples. Makes: About 6 small pancakes Prep time: 5 minutes Cook time: 10 minutes Ingredients 1 cup all-purpose flour 1 cup milk 1 egg 2 tablespoons sugar 1 teaspoon baking powder ¼ teaspoon salt 2 tablespoons butter, melted (plus a little for the…
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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…

Gemini 3.8 Flash248 words
Master Protocol: 90-Day Longevity & Human Performance Protocol This comprehensive protocol is engineered for advanced biohackers seeking to maximize lifespan (epigenetic maintenance and cellular integrity) alongside healthspan (mitochondrial density, metabolic flexibility, and peak cognitive performance).
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GPT-6 Luna Pro2,057 words
12-week longevity and performance plan This is a structured starting plan for a generally healthy adult—not a diagnosis or a substitute for medical care. The best longevity interventions are still the unglamorous ones: not smoking, regular exercise, adequate sleep, a high-quality diet, healthy blood pressure and…
Read the full answer

Mini LBO Underwrite

You are underwriting a 5-year LBO for a private equity investment committee. Company (fictional): HarborTech Services (HTS) –…

Gemini 3.8 Flash661 words
Here is the underwriting analysis for HarborTech Services (HTS). Transaction Summary & Sources & Uses Enterprise Value (EV): $120.0\text{m} \times 12.0\text{x} = \$1,440.0\text{m}$ Transaction Fees: $2.0\% \times \$1,440.0\text{m} = \$28.8\text{m}$ Total Uses: $\$1,440.0\text{m} + \$28.8\text{m} = \$1,468.8\text{m}$…
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GPT-6 Luna Pro434 words
Operating and debt schedule Conventions: Interest is calculated on beginning-of-year debt; the 1% Term Loan amortization is 1% of its original $480m principal ($4.8m annually). Mezzanine PIK accrues at 2% annually.
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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…

Gemini 3.8 Flash946 words
MEMORANDUM TO: Investment Committee FROM: Technology / Software Practice DATE: March 2025 SUBJECT: LedgerLift (NASDAQ: LLLT) – Investment Recommendation & Valuation Recommendation & Investment Thesis Recommendation: SHORT (High valuation disconnect / multiple compression thesis) Current Share Price: $46.00 Market Cap…
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GPT-6 Luna Pro888 words
LedgerLift (LLLT) — Investment Committee Memo Recommendation: Pass 12-month price target range: $28–44 per share LedgerLift has attractive customer economics, recurring revenue, and a credible path to margin expansion, but those strengths are already reflected in a $46 share price.
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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.…

Gemini 3.8 Flash712 words
Here are the three weakest claims in the MindMeld AI pitch deck, along with the rationale and concrete recommendations to fix them. The Core Scientific Feasibility Claim The Claim (Slides 1 & 3): “Predict what you want to type before you think it” and “Proprietary EEG headband uses advanced ML to decode neural patterns…
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GPT-6 Luna Pro401 words
“94% accuracy” and “works with any language, any device” Why it’s weak: “Accuracy” is undefined. It could mean classifying a small set of prompted words in a controlled lab—not reliably generating free-form text.
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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…

Gemini 3.8 Flash1,282 words
This architecture contains several catastrophic flaws that will cause silent data corruption, severe database exhaustion, high latency, and security vulnerabilities. Here is the breakdown of every failure mode, race condition, and scaling bottleneck, along with proposed solutions and trade-offs.
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GPT-6 Luna Pro1,906 words
The main architectural risk is that this design treats collaborative editing as ordinary “last write wins” data storage. It is not: edits need a well-defined order, reliable propagation, and a conflict model that preserves concurrent work.
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Our Verdict
Gemini 3.8 Flash
Gemini 3.8 Flash
GPT-6 Luna Pro
GPT-6 Luna Pro

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

GPT-6 Luna Pro costs 7.5x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Gemini 3.8 Flash
Input
$0.75
Output
$3.75
GPT-6 Luna Pro
Input
$0.10
7.5× cheaper
Output
$0.50
7.5× cheaper

GPT-6 Luna Pro is cheaper on both: 7.5× input, 7.5× output.

Where to run it

4 hosts, cheapest first

Gemini 3.8 Flash2 hosts
HostInOutContextUptime
Google Vertex AI$0.38 in·$1.88 out·1M·99.8% upGoogle AI Studio$0.75 in·$3.75 out·1M·99.9% up
GPT-6 Luna Pro2 hosts
HostInOutContextUptime
Azure AI Foundry$0.10 in·$0.50 out·1.1M·98.6% upOpenAI$0.10 in·$0.50 out·1.1M·99.9% up

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Gemini 3.8 Flash is developed by Google AI while GPT-6 Luna Pro is developed by OpenAI. Gemini 3.8 Flash has a 1.0M token context window vs GPT-6 Luna Pro'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. Gemini 3.8 Flash and GPT-6 Luna Pro 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.

Gemini 3.8 Flash costs $0.75/M input tokens and GPT-6 Luna Pro costs $0.1/M input tokens. GPT-6 Luna Pro is $0.65/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 Gemini 3.8 Flash and GPT-6 Luna Pro 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

Gemini 3.8 Flash logo
Gemini 3.8 Flash58 outputs, specs and price
GPT-6 Luna Pro logo
GPT-6 Luna Pro20 outputs, specs and price
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