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  5. GPT-5.1 ChatvsLaguna S 2.1 (free)
Updated Jul 2026

GPT-5.1 ChatvsLaguna S 2.1 (free)

Laguna S 2.1 (free) is cheaper than GPT-5.1 Chat at $0/M vs $1.25/M input tokens.

GPT-5.1 Chat and Laguna S 2.1 (free) compared across 10 shared prompts
SpecGPT-5.1 ChatLaguna S 2.1 (free)
Input price$1.25/M tokensFree
Output price$10/M tokensFree
Context window128K tokens262K tokens
Free API (OpenRouter)NoYes (1 provider)
ReleasedNov 2025Jul 2026
Side by side

Same prompt, both answers

Opening lines from 2 of the 10 prompts both answered. Formatting stripped, words untouched.

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-5.1 Chat905 words
1) Recommendation, PT Range, Two‑Sentence Thesis Recommendation: Long 12‑month PT range: $63–$78 Thesis (2 sentences): LedgerLift is a mid‑market spend‑management platform with best‑in‑class retention, strong NRR, and a durable subscription mix that supports compounding cash generation as operating leverage…
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-5.1 Chat8 words
The Legend of Zelda Breath of the Wild
Read the full answer
Laguna S 2.1 (free)8 words
The Legend of Zelda Breath of the Wild
Read the full answer
Our Verdict
GPT-5.1 Chat
GPT-5.1 Chat
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-5.1 Chat
Input
$1.25
Output
$10.00
Laguna S 2.1 (free)
Input
$0.000
Output
$0.000
Where to run it

1 host

GPT-5.1 Chat

No hosts listed on OpenRouter.

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-5.1 Chat is developed by OpenAI while Laguna S 2.1 (free) is developed by Poolside. GPT-5.1 Chat has a 128K 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-5.1 Chat 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-5.1 Chat costs $1.25/M input tokens and Laguna S 2.1 (free) costs $0/M input tokens. Laguna S 2.1 (free) is $1.25/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-5.1 Chat 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

GPT-5.1 Chat logo
GPT-5.1 Chat53 outputs, specs and price
Laguna S 2.1 (free) logo
Laguna S 2.1 (free)10 outputs, specs and price
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