Model Comparison

Claude Sonnet 4.5 vs Grok-4 Heavy

Grok-4 Heavy significantly outperforms across most benchmarks.

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Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

Claude Sonnet 4.5 outperforms in 0 benchmarks, while Grok-4 Heavy is better at 2 benchmarks (AIME 2025, GPQA).

Grok-4 Heavy significantly outperforms across most benchmarks.

Thu May 21 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

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

Anthropic
Claude Sonnet 4.5
Input200,000 tokens
Output64,000 tokens
xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Thu May 21 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

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

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

Claude Sonnet 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 Sonnet 4.5

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Sonnet 4.5 was released on 2025-09-29, while Grok-4 Heavy's release date is not specified.

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

Claude Sonnet 4.5

Sep 29, 2025

7 months ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

Claude Sonnet 4.5 has a knowledge cutoff of 2025-01-31, while Grok-4 Heavy has a cutoff of 2024-12-31.

Claude Sonnet 4.5 has more recent training data (up to 2025-01-31), making it potentially better informed about events through that date compared to Grok-4 Heavy (2024-12-31).

Claude Sonnet 4.5

Jan 2025

1 mo newer
Grok-4 Heavy

Dec 2024

Outputs Comparison

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Key Takeaways

Anthropic
Larger context window (200,000 tokens)
xAI
Higher AIME 2025 score (100.0% vs 87.0%)
Higher GPQA score (88.4% vs 83.4%)

Detailed Comparison

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

FAQ

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

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

Grok-4 Heavy significantly outperforms across most benchmarks. Claude Sonnet 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 Sonnet 4.5 compare to Grok-4 Heavy in benchmarks?

Claude Sonnet 4.5 scores MMMLU: 89.1%, AIME 2025: 87.0%, TAU-bench Retail: 86.2%, GPQA: 83.4%, MMMUval: 77.8%. 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 Sonnet 4.5 and Grok-4 Heavy?

Claude Sonnet 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 Sonnet 4.5 and Grok-4 Heavy?

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