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  5. Grok 4.1 FastvsSolar Pro 4
Updated Aug 2026

Grok 4.1 FastvsSolar Pro 4

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

Grok 4.1 Fast and Solar Pro 4 compared across 14 shared prompts
SpecGrok 4.1 FastSolar Pro 4
Input price—$0.09/M tokens
Output price—$0.36/M tokens
Context window—524K tokens
Free API (OpenRouter)NoNo
ReleasedNov 2025Aug 2026
Side by side

Same prompt, both answers

Opening lines from 6 of the 14 prompts both answered. Formatting stripped, words untouched.

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 Pro 41,638 words
The Premise: The 1920 Solid-State Breakthrough For this scenario to function, we must assume a functional point-contact or junction transistor is demonstrated in 1920 (perhaps by Lilienfeld or an early Bell Labs precursor), and crucially, that methods for purifying semiconductor materials (germanium/silicon) are solved…
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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…

Grok 4.1 Fast208 words
Pantry Raid Garlic Tomato Pasta A savory, garlicky one-pan wonder that's ready in under 20 minutes—perfect for when hunger strikes and the fridge is empty! Serves: 2 Prep time: 5 minutes Cook time: 12 minutes Total time: 17 minutes Ingredients (exactly 7 common pantry staples): 200g spaghetti or any pasta (2 handfuls)…
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Solar Pro 4294 words
🍝 Golden Umami Silk Noodles A savory-sweet pasta dish that transforms basic pantry staples into a glossy, flavorful meal. It's quick, comforting, and relies on the balance of soy, honey, and butter for a rich sauce without needing fresh produce.
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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.…

Grok 4.1 Fast501 words
Solution Claim: "94% accuracy" for decoding neural patterns into text via EEG headband Why it's weak: This is by far the most exaggerated technical claim, as current non-invasive EEG-based brain-computer interfaces (BCIs) for text generation achieve nowhere near 94% accuracy in real-world conditions.
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Solar Pro 41,009 words
Here are the three weakest claims in the MindMeld AI pitch deck, along with an analysis of why they undermine credibility and specific recommendations for improvement. The Technical Performance Claim Claim: "Our proprietary EEG headband uses advanced ML to decode neural patterns into text with 94% accuracy...
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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 Pro 41,382 words
Disclaimer: I am an AI assistant and not an attorney. The following analysis is for informational purposes only and does not constitute legal advice. Contract laws vary significantly by jurisdiction (e.g., state, country).
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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 Pro 41,062 words
The Experienced Software Engineer Think of the model not as a reasoning engine, but as a highly compressed, non-deterministic function approximator that maps a sequence of input tokens to a probability distribution over the next token.
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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…

Grok 4.1 Fast346 words
No Sticky Sessions for WebSockets (Scaling Bottleneck & Failure Mode) Issue: Round-robin load balancer doesn't guarantee client WebSocket connections stick to the same API server.
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Solar Pro 41,598 words
This architecture contains several fundamental mismatches between real-time collaborative editing requirements and the chosen patterns. Below is a systematic breakdown of failure modes, race conditions, and scaling bottlenecks, each with a targeted solution and explicit trade-offs.
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Our Verdict
Grok 4.1 Fast
Grok 4.1 Fast
Solar Pro 4
Solar Pro 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
API pricing

Cost per 1M tokens

Grok 4.1 Fast
Input
—
Output
—
Solar Pro 4
Input
$0.09
Output
$0.36
Where to run it

1 host

Grok 4.1 Fast

No hosts listed on OpenRouter.

Solar Pro 41 host
HostInOutContextUptime
UUpstage$0.09 in·$0.36 out·524k·99.7% up

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

Research

What we learned reading every model

FAQ

Common questions

Grok 4.1 Fast is developed by xAI while Solar Pro 4 is developed by Upstage. You can compare their actual outputs across 14 challenges on Rival to see how they differ in practice.

It depends on your use case. Grok 4.1 Fast and Solar Pro 4 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 14 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 Pro 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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Grok 4.1 Fast logo
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