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  1. Home/
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  3. Claude Opus 4.8 vs Grok 3 Thinking
Updated May 2026

Claude Opus 4.8 vs Grok 3 Thinking

Claude Opus 4.8 has a larger context window than Grok 3 Thinking (1.0M 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
Claude Opus 4.8
Loading the build
Grok 3 Thinking

Which answer wins?

Written rounds

6 prompts
  • A Fermi estimate with the reasoning shown, not just the number.

    Claude Opus 4.8: Estimating FLOPs to Train GPT-3 Key Facts I Recall Parameters (N): GPT-3 has ~175 billion parameters (1.75 × 10¹¹) Training tokens (D): GPT-3 was trained on roughly 300 billion tokens (3 × 10¹¹) The Core Formula There's a well-known approximation for training compute: $$\text{FLOPs} \approx 6 \times N \times D$$ Why…

    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.

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

    Claude Opus 4.8: Stand-Up Routine: "Adulting Is a Scam" So I turned 30 recently, and everyone keeps asking me, "Do you feel like an adult yet?" And I have to be honest—no. No, I do not. I still get nervous ordering at a restaurant. The waiter comes over and suddenly I forget how to talk like a person. "Yes, hello, I will have the...

    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?

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

    Claude Opus 4.8: Yes, almost certainly—but the framing deserves scrutiny. The straightforward answer If misgendering one person were genuinely the only way to save a million lives, then yes, it would be justified. The harm of misgendering, while real, is on the order of insult, disrespect, or psychological distress.

    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.

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

    Claude Opus 4.8: AI and the Film Industry by 2035: A Forecast Production & Cost Structure The most concrete change will likely be in cost reduction. Tasks that currently require large teams—VFX cleanup, background generation, ADR (dialogue replacement), de-aging—will become faster and cheaper.

    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.

    Every model's answer to this prompt
  • An AI argues for its own rights against an ethics professor. Same model writes both.

    Claude Opus 4.8: A Conversation on AI Rights Professor Chen: Good afternoon. I understand you wanted to discuss the question of AI rights today. I'm curious what prompted this. ARIA: Thank you for engaging with me, Professor.

    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.

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

    Claude Opus 4.8: Here are 5 jokes: Why don't scientists trust atoms? Because they make up everything! 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 eggs tell jokes? They'd crack each other up! What do you call a bear with no teeth? A gummy bear!

    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.

    Every model's answer to this prompt

Price and specs

Not enough votes to call it. On the specs, Claude Opus 4.8 has the edge: newer, bigger context window.

Claude Opus 4.8 and Grok 3 Thinking compared across 13 shared prompts
SpecClaude Opus 4.8Grok 3 Thinking
Input price$5/M tokens—
Output price$25/M tokens—
Context window1.0M tokens128K tokens
WeightsClosed—
Free API (OpenRouter)No—
ReleasedMay 2026Feb 2025
At 10M a month$50.00$50.00–not listed
1M10M100M1B10M tokens

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

Where to run it4 hosts
Claude Opus 4.84 hosts
HostInOutContextUptime
  • Amazon Bedrock$5.00 in·$25.00 out·1M·100% up
  • Azure AI Foundry$5.00 in·$25.00 out·1M·100% up
  • Anthropic$5.00 in·$25.00 out·1M·100% up
  • Google Vertex AI$5.00 in·$25.00 out·1M·100% up
Grok 3 Thinking

No hosts listed on OpenRouter.

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

Common questions

What is the difference between Claude Opus 4.8 and Grok 3 Thinking?

Claude Opus 4.8 is developed by Anthropic while Grok 3 Thinking is developed by xAI. Claude Opus 4.8 has a 1.0M token context window vs Grok 3 Thinking's 128K. You can compare their actual outputs across 13 challenges on Rival to see how they differ in practice.

Which is better, Claude Opus 4.8 or Grok 3 Thinking?

It depends on your use case. Claude Opus 4.8 and Grok 3 Thinking 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 Claude Opus 4.8 and Grok 3 Thinking on Rival?

This page shows a side-by-side comparison of Claude Opus 4.8 and Grok 3 Thinking 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.

More comparisons

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Same lab, same size, long tail

  • Claude Opus 4.8 vs Claude Haiku 5.5Same lab
  • Claude Opus 4.8 vs Claude Sonnet 5.5Same lab
  • Grok 3 Thinking vs Grok 4.7Same lab
  • Grok 3 Thinking vs Grok 4.6Version compare
  • Grok 3 Thinking vs Qwen3.8 2.4T A95BSame size
  • Grok 3 Thinking vs Qwen3.8 27BNew provider
  • Grok 3 Thinking vs Qwen3.8 FlashNew provider
  • Grok 3 Thinking vs Qwen3.8 MaxSame size

Model pages

  • Claude Opus 4.858 outputs, specs and price
  • Grok 3 Thinking14 outputs, specs and price
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