Model Comparison

Claude Opus 4.5 vs Grok-4 HeavyWhich is better in 2026?

Grok-4 Heavy significantly outperforms across most benchmarks.

Verdict: Claude Opus 4.5 vs Grok-4 Heavy — which is better?

Claude Opus 4.5 (by Anthropic) and Grok-4 Heavy (by xAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

Claude Opus 4.5 outperforms in 0 benchmarks, while Grok-4 Heavy is better at 1 benchmark (GPQA). Grok-4 Heavy significantly outperforms across most benchmarks.

Choose Claude Opus 4.5 if…

  • you want predictable pricing at $5.00/M input and $25.00/M output

Choose Grok-4 Heavy if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
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Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

Claude Opus 4.5 outperforms in 0 benchmarks, while Grok-4 Heavy is better at 1 benchmark (GPQA).

Grok-4 Heavy significantly outperforms across most benchmarks.

Sat Jun 06 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Claude Opus 4.5 specifies input context (200,000 tokens). Only Claude Opus 4.5 specifies output context (64,000 tokens).

Anthropic
Claude Opus 4.5
Input200,000 tokens
Output64,000 tokens
xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Sat Jun 06 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Claude Opus 4.5 and Grok-4 Heavy support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Opus 4.5

Text
Images
Audio
Video

Grok-4 Heavy

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Opus 4.5

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 4.5 was released on 2025-11-24, while Grok-4 Heavy's release date is not specified.

We can confirm Claude Opus 4.5's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

Claude Opus 4.5

Nov 24, 2025

6 months ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

Claude Opus 4.5 has a knowledge cutoff of 2025-03-31, while Grok-4 Heavy has a cutoff of 2024-12-31.

Claude Opus 4.5 has more recent training data (up to 2025-03-31), making it potentially better informed about events through that date compared to Grok-4 Heavy (2024-12-31).

Claude Opus 4.5

Mar 2025

3 mo newer
Grok-4 Heavy

Dec 2024

Outputs Comparison

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Key Takeaways

Anthropic
Larger context window (200,000 tokens)
xAI
Higher GPQA score (88.4% vs 87.0%)

Detailed Comparison

AI Model Comparison Table
Feature
Anthropic
Claude Opus 4.5
xAI
Grok-4 Heavy

FAQ

Common questions about Claude Opus 4.5 vs Grok-4 Heavy.

Which is better, Claude Opus 4.5 or Grok-4 Heavy?

Grok-4 Heavy significantly outperforms across most benchmarks. Claude Opus 4.5 is made by Anthropic and Grok-4 Heavy is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Claude Opus 4.5 compare to Grok-4 Heavy in benchmarks?

Claude Opus 4.5 scores Tau2 Telecom: 98.2%, MMMLU: 90.8%, Tau2 Retail: 88.9%, GPQA: 87.0%, SWE-Bench Verified: 80.9%. Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%.

What are the context window sizes for Claude Opus 4.5 and Grok-4 Heavy?

Claude Opus 4.5 supports 200K tokens and Grok-4 Heavy supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

Who makes Claude Opus 4.5 and Grok-4 Heavy?

Claude Opus 4.5 is developed by Anthropic and Grok-4 Heavy is developed by xAI.

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