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  5. GPT-5.6 LunavsLaguna XS 2.1 (free)
Updated Jul 2026

GPT-5.6 LunavsLaguna XS 2.1 (free)

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

GPT-5.6 Luna and Laguna XS 2.1 (free) compared across 11 shared prompts
SpecGPT-5.6 LunaLaguna XS 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 6 of the 11 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 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.
Read the full answer
Laguna XS 2.1 (free)635 words
I'll analyze each clause in this software consulting agreement to identify potential risks to the contractor and suggest modifications with legal reasoning. Clause-by-Clause Analysis Clause 1: SCOPE Risk: Unlimited scope creep without additional compensation Modification: Add: "Any modification to the scope requiring…
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 Luna2,537 words
12-Week Longevity and Performance Plan This is a structured framework for a generally healthy adult, not a substitute for medical care. Before starting, obtain clinician clearance if you have cardiovascular disease, diabetes, kidney/liver disease, a history of eating disorders, sleep apnea, are pregnant, take…
Read the full answer
Laguna XS 2.1 (free)828 words
3-Month Longevity & Performance Optimization Plan for a Biohacker Designed for advanced biohackers with a focus on longevity, cognitive sharpness, and peak physical performance. Assumes access to basic medical testing, wearables, and some advanced tools (e.g., neurofeedback apps).
Read the full answer

Michelin Star Recipe Design

Design an innovative recipe for a multi-component dish worthy of a Michelin 3-star restaurant. The recipe should feature an unusual…

GPT-5.6 Luna1,583 words
Turbot “Between Forest and Sea” Koji-cured turbot, fermented pear, coffee-kombu beurre blanc, smoked sunchoke, maitake, spruce, and buckwheat–nori tuile Serves 4 Concept This dish treats the turbot as a meeting point between two landscapes.
Read the full answer
Laguna XS 2.1 (free)602 words
Recipe: "Nocturne of Shadows and Light" Concept: A poetic exploration of ancient flavors (pomegranate, quince) intertwined with modernist techniques (spherification, sous vide) and an unexpected coffee-cocoa depth, harmonizing the boldness of game with the elegance of fruit.
Read the full answer

Explain Like I'm a Specific Expert

Explain how a large language model (like GPT or Claude) learns and generates text to each of these three audiences: 1. **An experienced…

GPT-5.6 Luna842 words
For an experienced software engineer A language model is trained much like an extremely large system for compressing and reconstructing text. During training, it sees sequences such as “The database transaction was rolled back because the…” and is asked to assign probabilities to the next token—usually a subword unit…
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Laguna XS 2.1 (free)610 words
For the Software Engineer Think of training a language model like building a distributed prediction system with an incredibly complex API contract. Instead of training on labeled datasets where you explicitly tell it "this text is sentiment-positive," you're feeding it massive amounts of text and asking it to predict…
Read the full answer

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…

GPT-5.6 Luna608 words
1-Month Beginner Plan for Better Health and Longevity Key principles Aim for consistency, not perfection. Start small enough that you can repeat it. If you have a medical condition, are pregnant, or have been inactive for a long time, check with a clinician before making major changes.
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Laguna XS 2.1 (free)409 words
1-Month Health & Longevity Plan Focus Areas: Diet, Exercise, Sleep Week 1: Start with Foundational Habits Diet: Action: Add 1 serving of fruit or vegetables daily (e.g., a banana with breakfast, a side salad with lunch). Why: Boosts nutrient intake and fiber.
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Historical Counterfactual Analysis

If the transistor had been invented in 1920 instead of 1947, trace the likely technological, economic, and geopolitical implications through…

GPT-5.6 Luna2,756 words
A transistor invented in 1920 would not automatically produce 1980s technology by the 1940s. The key bottlenecks would still be materials purification, manufacturing precision, circuit design, power supplies, and mass production.
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Laguna XS 2.1 (free)870 words
The Transistor Revolution: A 1920 Timeline Analysis Immediate Impact (1920-1940) Early Military Applications With transistors available 27 years before radar, telecommunications would see revolutionary improvements: Radio warfare: Nations could develop sophisticated radio direction-finding and jamming capabilities by…
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Our Verdict
GPT-5.6 Luna
GPT-5.6 Luna
Laguna XS 2.1 (free)
Laguna XS 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
Input
$1.00
Output
$6.00
Laguna XS 2.1 (free)
Input
$0.000
Output
$0.000
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·94.9% upOpenAI$0.20 in·$1.20 out·1.1M·100% upAmazon Bedrock$0.22 in·$1.32 out·1.1M·100% up
Laguna XS 2.1 (free)1 host
HostInOutContextUptime
PPoolsidefp8$0 in·$0 out·262k·99.8% 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 is developed by OpenAI while Laguna XS 2.1 (free) is developed by Poolside. GPT-5.6 Luna has a 1.1M token context window vs Laguna XS 2.1 (free)'s 262K. You can compare their actual outputs across 11 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-5.6 Luna and Laguna XS 2.1 (free) each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 11 challenges so you can judge which fits your needs best.

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