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Gemini 3.8 Flash Cyber vs Grok-4 Fast Reasoning

Comparing Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoning across benchmarks, pricing, and capabilities.

Google · xAI · Updated for 2026

Which is better?

Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoning trade strengths across price, capabilities, and technical limits. The better choice depends on the workload.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Gemini 3.8 Flash Cyber

  • you want the most recent training data — it shipped Sep 2026

Choose Grok-4 Fast Reasoning

  • you want predictable pricing at $0.20/M input and $0.50/M output

At a glance

The differences that matter most.

Gemini 3.8 Flash Cyber
Google
Grok-4 Fast Reasoning
xAI
Benchmark wins
—
—
Input price
— / M
$0.20 / M
Output price
— / M
$0.50 / M
Context window
—
2,000,000

Individual benchmarks

4 reported for Gemini 3.8 Flash Cyber · 0 for Grok-4 Fast Reasoning

No common benchmarks found

Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoningdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Context Window

Maximum input and output token capacity

Only Grok-4 Fast Reasoning specifies input context (2,000,000 tokens). Only Grok-4 Fast Reasoning specifies output context (30,000 tokens).

Google
Gemini 3.8 Flash Cyber
Input- tokens
Output- tokens
xAI
Grok-4 Fast Reasoning
Input2,000,000 tokens
Output30,000 tokens
Fri Sep 04 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Grok-4 Fast Reasoning supports multimodal inputs, whereas Gemini 3.8 Flash Cyber does not.

Grok-4 Fast Reasoning can handle both text and other forms of data like images, making it suitable for multimodal applications.

Gemini 3.8 Flash Cyber

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.

Gemini 3.8 Flash Cyber

Proprietary

Closed source

Grok-4 Fast Reasoning

Proprietary

Closed source

Release Timeline

When each model was launched

Gemini 3.8 Flash Cyber was released on 2026-09-02, while Grok-4 Fast Reasoning was released on 2025-08-28.

Gemini 3.8 Flash Cyber is 12 months newer than Grok-4 Fast Reasoning.

Gemini 3.8 Flash Cyber

Sep 2, 2026

1 days ago

1.0yr newer
Grok-4 Fast Reasoning

Aug 28, 2025

1.0 years ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoning side-by-side, then vote on the output you prefer.

Gemini 3.8 Flash Cyber
✓ Preferred
Grok-4 Fast Reasoning
Open in Playground

FAQ

Common questions about Gemini 3.8 Flash Cyber vs Grok-4 Fast Reasoning.

Which is better, Gemini 3.8 Flash Cyber or Grok-4 Fast Reasoning?

Gemini 3.8 Flash Cyber (Google) 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.

How does Gemini 3.8 Flash Cyber compare to Grok-4 Fast Reasoning in benchmarks?

Gemini 3.8 Flash Cyber scores Gray Swan IPI Benchmark: 94.0%, CyberGym: 86.2%, Google Real-world Vulnerability Discovery: 71.0%, CWE-Bench: 47.2%.

What are the context window sizes for Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoning?

Gemini 3.8 Flash Cyber supports an unknown number of 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.

What are the main differences between Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoning?

Key differences include multimodal support (no vs yes). See the full comparison above for benchmark-by-benchmark results.

Who makes Gemini 3.8 Flash Cyber and Grok-4 Fast Reasoning?

Gemini 3.8 Flash Cyber is developed by Google and Grok-4 Fast Reasoning is developed by xAI.

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