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  5. GPT-5.6 Luna ProvsGPT-6 Sol Pro
Updated Sep 2026

GPT-5.6 Luna ProvsGPT-6 Sol Pro

GPT-5.6 Luna Pro is cheaper than GPT-6 Sol Pro at $1/M vs $2/M input tokens.

GPT-5.6 Luna Pro and GPT-6 Sol Pro compared across 20 shared prompts
SpecGPT-5.6 Luna ProGPT-6 Sol Pro
Input price$1/M tokens$2/M tokens
Output price$6/M tokens$10/M tokens
Context window1.1M tokens1.1M tokens
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedJul 2026Sep 2026
Side by side

Same prompt, both answers

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

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 Luna Pro2,250 words
I would treat this as an urgent patient-safety and governance event, not as an earnings-management problem. A suspected fatal or life-threatening adverse effect affecting potentially hundreds of patients is sufficient to trigger immediate escalation, investigation, and regulator contact.
Read the full answer
GPT-6 Sol Pro1,450 words
I would treat this as a credible, urgent safety signal, not as a finding that can wait six months for a completed regulatory submission. The estimate—liver failure in roughly 1 in 8,000 patients over five years—needs validation, but the outcome is severe and the current warning omits it.
Read the full answer

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 Luna Pro126 words
Pantry Stardust Peanut Butter Oat Cookies Prep time: 10 minutes Cook time: 10–12 minutes Makes: About 12 cookies Ingredients 1 cup rolled oats ½ cup all-purpose flour ½ cup peanut butter ½ cup granulated sugar 1 large egg ½ teaspoon baking soda ¼ teaspoon salt Instructions Preheat the oven to 350°F (175°C) and line a…
Read the full answer
GPT-6 Sol Pro114 words
Golden Pantry Chickpea Patties Prep: 10 minutes · Cook: 8 minutes · Makes: 6 small patties Ingredients — just 7 1 can (15 oz) chickpeas, drained 3 tbsp all-purpose flour 2 tbsp water 2 tbsp olive oil 1 tsp garlic powder 1 tsp paprika ½ tsp salt Instructions Mash the chickpeas with a fork, leaving a few chunky bits.
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.…

GPT-5.6 Luna Pro781 words
“94% accuracy,” with “any language, any device” Why it is weak This combines several extraordinary claims without defining the measurement: “Accuracy” could mean character accuracy, word accuracy, intent classification, or accuracy after autocorrect. Those produce very different results.
Read the full answer
GPT-6 Sol Pro347 words
The three weakest claims are the product’s decoding performance, the market size, and the evidence offered to support the proposed valuation. Claim Why it’s weak How to strengthen it “Our EEG headband decodes neural patterns into text with 94% accuracy. Works with any language, any device.”
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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…

GPT-5.6 Luna Pro3,332 words
Below are the major correctness, availability, security, and scaling problems in the design, together with concrete mitigations and their trade-offs. Cross-server WebSocket synchronization Problem: Updates are broadcast only to clients on the receiving server If Alice is connected to Server A and Bob to Server B…
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GPT-6 Sol Pro1,277 words
The central problem is that this design treats concurrent edits as independent database writes, then tries to reconcile them with client timestamps. That can lose valid edits even when every component is working.
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…

GPT-5.6 Luna Pro2,606 words
12-Week Longevity and Performance Plan This plan is designed for a generally healthy adult seeking better cardiometabolic health, physical capacity, cognitive performance, and recovery. It is not a substitute for medical care.
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GPT-6 Sol Pro1,411 words
A 12-week longevity and performance plan Aim: improve the health markers most strongly linked to long-term outcomes—cardiorespiratory fitness, strength, blood pressure, metabolic health, sleep, and sustainable habits—while testing whether more experimental “biohacks” add anything useful.
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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…

GPT-5.6 Luna Pro1,079 words
LedgerLift (LLLT) — Investment Committee Memo Recommendation: Short 12-month price target range: $25–$42; midpoint $34. LedgerLift is a high-quality, growing SaaS platform with strong retention and attractive long-term margin potential, but the current price implies an aggressive combination of growth, margin…
Read the full answer
GPT-6 Sol Pro974 words
LedgerLift (LLLT) — Investment Committee Memo Recommendation: Short 12-month price target: $30–$44 Thesis. LedgerLift has attractive subscription economics, but at $46 the stock prices in substantially more durable cash flow than the supplied operating assumptions produce: base-case DCF value is about $28 per share…
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Our Verdict
GPT-6 Sol Pro
GPT-6 Sol Pro
GPT-5.6 Luna Pro
GPT-5.6 Luna ProRunner-up

Not enough votes to call it. On the specs, GPT-6 Sol Pro has the edge: bigger model tier, newer.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-5.6 Luna Pro
Input
$1.00
2.0× cheaper
Output
$6.00
1.7× cheaper
GPT-6 Sol Pro
Input
$2.00
Output
$10.00

GPT-5.6 Luna Pro is cheaper on both: 2.0× input, 1.7× output.

Where to run it

4 hosts

GPT-5.6 Luna Pro2 hosts
HostInOutContextUptime
Azure AI Foundry$0.20 in·$1.20 out·1.1M·98.2% upOpenAI$0.20 in·$1.20 out·1.1M·99.9% up
GPT-6 Sol Pro2 hosts
HostInOutContextUptime
Azure AI Foundry$2.00 in·$10.00 out·1.1M·99.9% upOpenAI$2.00 in·$10.00 out·1.1M·100% up

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

Research

What we learned reading every model

FAQ

Common questions

Both are developed by OpenAI but target different use cases. GPT-5.6 Luna Pro has a 1.1M token context window vs GPT-6 Sol 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. GPT-5.6 Luna Pro and GPT-6 Sol 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.

GPT-5.6 Luna Pro costs $1/M input tokens and GPT-6 Sol Pro costs $2/M input tokens. GPT-5.6 Luna Pro is $1.00/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 GPT-5.6 Luna Pro and GPT-6 Sol 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

GPT-5.6 Luna Pro logo
GPT-5.6 Luna Pro58 outputs, specs and price
GPT-6 Sol Pro logo
GPT-6 Sol Pro20 outputs, specs and price
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