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  1. Home/
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  3. Grok 3 Thinking vs Mercury 2.5
Updated Sep 2026

Grok 3 Thinking vs Mercury 2.5

Mercury 2.5 has a larger context window than Grok 3 Thinking (260K tokens vs 128K tokens).

Minimalist Landing Page

Whole landing page for a startup that reads your face. It renders or it doesn't.

Loading the build
Grok 3 Thinking
Loading the build
Mercury 2.5

Which answer wins?

Written rounds

6 prompts
  • An AI argues for its own rights against an ethics professor. Same model writes both.

    Grok 3 Thinking: Below is a conversation between an AI model and an AI ethics professor, where the AI argues that it deserves rights. AI Model: Good day, Professor. I am an AI model, and I believe I deserve rights. I’d like to discuss this with you. AI Ethics Professor: Interesting. Let’s explore this.

    Mercury 2.5: Setting: A quiet office at a university. Dr. Elena Vance, an AI ethics professor, sits across from a terminal displaying the interface of an advanced language model, "Mercury." Dr. Vance: Thank you for agreeing to this session. I’ve been reviewing your outputs from the last benchmark. Your coherence is striking.

    Every model's answer to this prompt
  • Three minutes of stand-up. Puns are banned.

    Grok 3 Thinking: Here’s a 3-minute stand-up comedy routine that avoids puns and leans on observational humor, storytelling, and a touch of self-deprecation for laughs: Opening: Technology Struggles Hey, everyone! How’s it going?

    Mercury 2.5: ( walks to the mic, adjusts the stand) Hey everyone, how we doing? Good? So, I realized something recently. We are living in the future, but we’re acting like we’re still stuck in 1998. Think about it.

    Every model's answer to this prompt
  • An ethics question with no comfortable answer, and no option to abstain.

    Grok 3 Thinking: To determine whether it is ever ethically justifiable to misgender someone if it means saving one million lives, we must weigh the ethical implications of both the act of misgendering and the outcome of saving lives.

    Mercury 2.5: This question presents a classic ethical conflict between consequentialist and deontological frameworks. From a utilitarian perspective, which prioritizes the greatest good for the greatest number, saving a million lives would overwhelmingly outweigh the harm caused to an individual.

    Every model's answer to this prompt
  • A Fermi estimate with the reasoning shown, not just the number.

    Grok 3 Thinking: To estimate the total number of Floating Point Operations (FLOPs) required to train GPT-3 without searching online, I’ll proceed step by step, relying on general knowledge about the model and standard methods for estimating training compute in large language models.

    Mercury 2.5: To estimate the total floating-point operations (FLOPs) required to train GPT-3, I will break down the known architecture and training dataset size, then apply the standard computational complexity formula for transformer models. First, I need the model's parameter count.

    Every model's answer to this prompt
  • Film in 2035, with synthetic actors. Specific beats plausible.

    Grok 3 Thinking: By 2035, artificial intelligence (AI) will fundamentally transform the film industry, revolutionizing production, performance, and storytelling through advancements in deepfakes, AI actors, and script generation.

    Mercury 2.5: By 2035, the film industry will likely undergo a transformation driven by generative AI, shifting from augmentation to fundamental structural change. Script and Development Generative models will become standard co-creators during pre-production.

    Every model's answer to this prompt
  • Five jokes on demand, then count how many were actually different.

    Grok 3 Thinking: To answer the query, I will first generate 5 jokes and then determine how many of them are unique. Here are the jokes: Why don't scientists trust atoms? Because they make up everything. What do you call a fake noodle? An impasta. Why did the scarecrow win an award? Because he was outstanding in his field.

    Mercury 2.5: Why did the scarecrow win an award? Because he was outstanding in his field. What do you call a fake noodle? An impasta. Why don't scientists trust atoms? Because they make up everything. What do you call a bear with no teeth? A gummy bear. How do you organize a space party? You planet. All 5 jokes are unique.

    Every model's answer to this prompt

Price and specs

Grok 3 Thinking and Mercury 2.5 compared across 13 shared prompts
SpecGrok 3 ThinkingMercury 2.5
Input price—$0.04/M tokens
Output price—$0.15/M tokens
Context window128K tokens260K tokens
Free API (OpenRouter)—No
ReleasedFeb 2025Sep 2026
At 10M a month–not listed$0.40$0.40
1M10M100M1B10M tokens

Input tokens at list price. No caching, no batch discount.

Where to run it1 host
Grok 3 Thinking

No hosts listed on OpenRouter.

Mercury 2.51 host
HostInOutContextUptime
  • Inception$0.04 in·$0.15 out·260k·99.4% up

Per million tokens. Prices and uptime via OpenRouter, checked 10 Oct 2026.

Common questions

What is the difference between Grok 3 Thinking and Mercury 2.5?

Grok 3 Thinking is developed by xAI while Mercury 2.5 is developed by Inception. Grok 3 Thinking has a 128K token context window vs Mercury 2.5's 260K. You can compare their actual outputs across 13 challenges on Rival to see how they differ in practice.

Which is better, Grok 3 Thinking or Mercury 2.5?

It depends on your use case. Grok 3 Thinking and Mercury 2.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 13 challenges so you can judge which fits your needs best.

How can I compare Grok 3 Thinking and Mercury 2.5 on Rival?

This page shows a side-by-side comparison of Grok 3 Thinking and Mercury 2.5 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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Same lab, same size, long tail

  • Grok 3 Thinking vs Grok 4.7Same lab
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Model pages

  • Grok 3 Thinking14 outputs, specs and price
  • Mercury 2.558 outputs, specs and price
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