Model Comparison

Claude Opus 4.5 vs Grok-4 Fast Reasoning

Comparing Claude Opus 4.5 and Grok-4 Fast Reasoning across benchmarks, pricing, and capabilities.

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Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

Claude Opus 4.5 and Grok-4 Fast Reasoning don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

Grok-4 Fast Reasoning costs less

For input processing, Claude Opus 4.5 ($5.00/1M tokens) is 25.0x more expensive than Grok-4 Fast Reasoning ($0.20/1M tokens).

For output processing, Claude Opus 4.5 ($25.00/1M tokens) is 50.0x more expensive than Grok-4 Fast Reasoning ($0.50/1M tokens).

In conclusion, Claude Opus 4.5 is more expensive than Grok-4 Fast Reasoning.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Wed Apr 22 2026 • llm-stats.com
Anthropic
Claude Opus 4.5
Input tokens$5.00
Output tokens$25.00
Best providerAnthropic
xAI
Grok-4 Fast Reasoning
Input tokens$0.20
Output tokens$0.50
Best providerxAI
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Grok-4 Fast Reasoning accepts 2,000,000 input tokens compared to Claude Opus 4.5's 200,000 tokens. Claude Opus 4.5 can generate longer responses up to 64,000 tokens, while Grok-4 Fast Reasoning is limited to 30,000 tokens.

Anthropic
Claude Opus 4.5
Input200,000 tokens
Output64,000 tokens
xAI
Grok-4 Fast Reasoning
Input2,000,000 tokens
Output30,000 tokens
Wed Apr 22 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Claude Opus 4.5 and Grok-4 Fast Reasoning 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 Fast Reasoning

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 Fast Reasoning

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 4.5 was released on 2025-11-24, while Grok-4 Fast Reasoning was released on 2025-08-28.

Claude Opus 4.5 is 3 months newer than Grok-4 Fast Reasoning.

Claude Opus 4.5

Nov 24, 2025

4 months ago

2mo newer
Grok-4 Fast Reasoning

Aug 28, 2025

7 months ago

Knowledge Cutoff

When training data ends

Claude Opus 4.5 has a documented knowledge cutoff of 2025-03-31, while Grok-4 Fast Reasoning's cutoff date is not specified.

We can confirm Claude Opus 4.5's training data extends to 2025-03-31, but cannot make a direct comparison without Grok-4 Fast Reasoning's cutoff date.

Claude Opus 4.5

Mar 2025

Grok-4 Fast Reasoning

—

Provider Availability

Claude Opus 4.5 is available from Anthropic. Grok-4 Fast Reasoning is available from xAI.

Claude Opus 4.5

anthropic logo
Anthropic
Input Price:Input: $5.00/1MOutput Price:Output: $25.00/1M

Grok-4 Fast Reasoning

xai logo
xAI
Input Price:Input: $0.20/1MOutput Price:Output: $0.50/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

Anthropic
xAI
Larger context window (2,000,000 tokens)
Less expensive input tokens
Less expensive output tokens

Detailed Comparison

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

FAQ

Common questions about Claude Opus 4.5 vs Grok-4 Fast Reasoning

Claude Opus 4.5 (Anthropic) and Grok-4 Fast Reasoning (xAI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.
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 Fast Reasoning is 25.0x cheaper for input tokens. Claude Opus 4.5 costs $5.00/M input and $25.00/M output via anthropic. Grok-4 Fast Reasoning costs $0.20/M input and $0.50/M output via xai.
Claude Opus 4.5 supports 200K tokens and Grok-4 Fast Reasoning supports 2.0M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.
Key differences include context window (200K vs 2.0M), input pricing ($5.00 vs $0.20/M). See the full comparison above for benchmark-by-benchmark results.
Claude Opus 4.5 is developed by Anthropic and Grok-4 Fast Reasoning is developed by xAI.