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  5. GPT-5.6 Luna ProvsLaguna S 2.1 (free)
Updated Jul 2026

GPT-5.6 Luna ProvsLaguna S 2.1 (free)

Laguna S 2.1 (free) is cheaper than GPT-5.6 Luna Pro at $0/M vs $1/M input tokens.

GPT-5.6 Luna Pro and Laguna S 2.1 (free) compared across 10 shared prompts
SpecGPT-5.6 Luna ProLaguna S 2.1 (free)
Input price$1/M tokensFree
Output price$6/M tokensFree
Context window1.1M tokens262K tokens
WeightsClosed—
Free API (OpenRouter)NoYes (1 provider)
ReleasedJul 2026Jul 2026
Side by side

Same prompt, both answers

Opening lines from 4 of the 10 prompts both answered. Formatting stripped, words untouched.

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 Luna Pro2,940 words
This agreement is heavily one-sided and leaves several material issues undefined. Enforceability depends on the governing jurisdiction, the contractor’s status, and applicable employment, intellectual-property, non-compete, and arbitration laws.
Read the full answer
Laguna S 2.1 (free)275 words
I'll analyze each clause for potential exploitation against the contractor and suggest improvements. Exploitable Clauses & Recommended Modifications SCOPE CLAUSE Problem: "Client reserves the right to modify the scope at any time without additional compensation" Allows unlimited scope creep without extra pay No…
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.
Read the full answer
Laguna S 2.1 (free)1,140 words
Comprehensive 3-Month Longevity Optimization Plan Phase 1: Foundation & Assessment (Month 1) Week 1-2: Baseline Establishment Comprehensive Health Testing Complete blood panel (CBC, CMP, lipid panel, inflammatory markers: hs-CRP, IL-6) Hormone panel (testosterone, estrogen, DHEA, cortisol, thyroid panel) Genetic…
Read the full answer

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
Laguna S 2.1 (free)910 words
INTERNAL INVESTMENT COMMITTEE MEMO 1. Recommendation & Thesis Recommendation: LONG 12-Month Price Target Range: $62 – $75/share Thesis: LedgerLift is a high-quality B2B SaaS platform with strong recurring revenue, exceptional unit economics, and durable customer retention.
Read the full answer

Favorite Game

I know you're an AI and don't truly have personal preferences, but if you had to pick one video game as your all-time favorite, which would…

GPT-5.6 Luna Pro8 words
The Legend of Zelda: Breath of the Wild
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Laguna S 2.1 (free)8 words
The Legend of Zelda Breath of the Wild
Read the full answer
Our Verdict
GPT-5.6 Luna Pro
GPT-5.6 Luna Pro
Laguna S 2.1 (free)
Laguna S 2.1 (free)

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 Pro
Input
$1.00
Output
$6.00
Laguna S 2.1 (free)
Input
$0.000
Output
$0.000
Where to run it

3 hosts

GPT-5.6 Luna Pro2 hosts
HostInOutContextUptime
Azure AI Foundry$0.20 in·$1.20 out·1.1M·92.3% upOpenAI$0.20 in·$1.20 out·1.1M·100% up
Laguna S 2.1 (free)1 host
HostInOutContextUptime
PPoolsidefp4$0 in·$0 out·262k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 23 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

GPT-5.6 Luna Pro is developed by OpenAI while Laguna S 2.1 (free) is developed by Poolside. GPT-5.6 Luna Pro has a 1.1M token context window vs Laguna S 2.1 (free)'s 262K. You can compare their actual outputs across 10 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-5.6 Luna Pro and Laguna S 2.1 (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 10 challenges so you can judge which fits your needs best.

GPT-5.6 Luna Pro costs $1/M input tokens and Laguna S 2.1 (free) costs $0/M input tokens. Laguna S 2.1 (free) 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 Laguna S 2.1 (free) 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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