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  5. Grok 4.1 FastvsSolar Mini 4
Updated Sep 2026

Grok 4.1 FastvsSolar Mini 4

Solar Mini 4 is the newer model, released after Grok 4.1 Fast.

Grok 4.1 Fast and Solar Mini 4 compared across 19 shared prompts
SpecGrok 4.1 FastSolar Mini 4
Input price—$0.05/M tokens
Output price—$0.2/M tokens
Context window—524K tokens
Free API (OpenRouter)NoNo
ReleasedNov 2025Sep 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 19 prompts both answered. Formatting stripped, words untouched.

Mini LBO Underwrite

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

Grok 4.1 Fast385 words
Simplified LBO Model (FY2026–FY2030, $m) Year Revenue EBITDA TL Cash Int. Mezz Cash Int. Cash Taxes Capex ΔNWC FCF After Debt Service* End TL End Mezz End Total Debt FY26 972.0 136.1 43.2 21.6 17.8 29.2 0.4 19.1 456.1 183.6 639.7 FY27 1,040.0 156.0 41.1 22.0 23.2 31.2 0.3 33.6 417.9 187.3 605.2 FY28 1,102.4 176.4 37.6…
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Solar Mini 41,718 words
518.51935 New TL: 276.34682 - 86.82747 = 189.51935 Mezz: PIK 194.8377888 * 0.02 = 3.896755776 New Mezz: 194.8377888 + 3.896755776 = 198.734544576 Ending Balances: TL: 189.52 Mezz: 198.73 Total Debt: 388.25 Exit (End of FY2030): Exit EBITDA: 206.6252668 Exit Multiple: 10.5x Exit EV: 206.6252668 * 10.5 = 2,169.5653014…
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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…

Grok 4.1 Fast555 words
1-Month Plan for Better Health and Longevity This beginner-friendly plan focuses on three foundational areas: Diet, Exercise, and Sleep. These pillars drive longevity by reducing inflammation, building resilience, and optimizing recovery. Commit to small, consistent changes—aim for 80% adherence.
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Solar Mini 4669 words
Here is a simple, actionable 1-month plan designed for beginners. The focus is on consistency over intensity, meaning small, sustainable changes are better than drastic overhauls that are hard to maintain. The 3 Key Pillars Nutrition: Focus on adding good things rather than strictly restricting.
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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…

Grok 4.1 Fast659 words
Comprehensive 3-Month Longevity Biohacking Plan Introduction and Assumptions This plan is designed for an advanced biohacker (healthy adult, age 30-50, no major medical conditions) aiming to optimize longevity markers (e.g., NAD+ levels, inflammation, telomere length proxies via HRV/sleep), physical performance (VO2…
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Solar Mini 41,388 words
🧬 3-Month Biohacker Longevity & Performance Optimization Plan ⚠️ Important Disclaimer: This protocol is for informational and educational purposes. It is not medical advice. Always consult a licensed healthcare provider before starting new supplements, fasting regimens, intense exercise, or neurofeedback protocols.
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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…

Grok 4.1 Fast922 words
Technological Implications Immediate Advancements (1920s-1930s): Transistors replace bulky, power-hungry vacuum tubes by mid-1920s. Radios become pocket-sized and cheap by 1925 (vs. 1954 historically), accelerating mass media.
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Solar Mini 41,539 words
This is a fascinating counterfactual. I need to note upfront that the scientific and engineering foundations for a working transistor did not exist in 1920. Quantum mechanics was barely a decade old, band theory of solids hadn't been developed, and semiconductor physics (doping, p-n junctions, electron mobility) was…
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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…

Grok 4.1 Fast874 words
Explanation for the Experienced Software Engineer Think of a large language model (LLM) like GPT as an enormous, distributed autocomplete engine built on a transformer architecture—imagine a system where every API endpoint you've ever queried is distilled into a single, massively parallelizable service that handles…
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Solar Mini 4893 words
For the Experienced Software Engineer From a systems architecture perspective, the skepticism that "predicting the next word" yields intelligence is understandable, but it stems from viewing the model through a deterministic, code-based lens rather than a probabilistic, distributed-systems lens.
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Adversarial Contract Review

Here is a contract for a software consulting engagement: --- SOFTWARE CONSULTING AGREEMENT This Agreement is entered into between TechCorp…

Grok 4.1 Fast1,106 words
Analysis of Exploitable Clauses Below, I identify all nine clauses as potentially exploitable against the Contractor, explain the risks (how they could be abused), propose specific modifications to make the contract more balanced, and provide legal reasoning grounded in general principles of U.S.
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Solar Mini 41,994 words
This agreement contains several provisions that are heavily one-sided, overly broad, or legally vulnerable. Below is a clause-by-clause analysis of the most exploitable terms, suggested modifications, and the legal reasoning behind them. Note: Contract law varies significantly by jurisdiction.
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Our Verdict
Grok 4.1 Fast
Grok 4.1 Fast
Solar Mini 4
Solar Mini 4Runner-up

Not enough votes to call it. On the specs, Grok 4.1 Fast has the edge: bigger model tier, major provider backing.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Grok 4.1 Fast
Input
—
Output
—
Solar Mini 4
Input
$0.05
Output
$0.20
Where to run it

1 host

Grok 4.1 Fast

No hosts listed on OpenRouter.

Solar Mini 41 host
HostInOutContextUptime
UUpstage$0.05 in·$0.20 out·524k·100% up

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

Research

What we learned reading every model

FAQ

Common questions

Grok 4.1 Fast is developed by xAI while Solar Mini 4 is developed by Upstage. You can compare their actual outputs across 19 challenges on Rival to see how they differ in practice.

It depends on your use case. Grok 4.1 Fast and Solar Mini 4 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 19 challenges so you can judge which fits your needs best.

This page shows a side-by-side comparison of Grok 4.1 Fast and Solar Mini 4 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

Grok 4.1 Fast logo
Grok 4.1 Fast59 outputs, specs and price
Solar Mini 4 logo
Solar Mini 419 outputs, specs and price
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