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Grok 4 Fast Reasoning

Ideal for applications requiring large-scale text comprehension, strategic analysis, and real-time autonomous decision-making.

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Text to Speech

Javascript

Python

                                        const { OpenAI } = require('openai');

const api = new OpenAI({
  baseURL: 'https://api.ai.cc/v1',
  apiKey: '',
});

const main = async () => {
  const result = await api.chat.completions.create({
    model: 'x-ai/grok-4-fast-reasoning',
    messages: [
      {
        role: 'system',
        content: 'You are an AI assistant who knows everything.',
      },
      {
        role: 'user',
        content: 'Tell me, why is the sky blue?'
      }
    ],
  });

  const message = result.choices[0].message.content;
  console.log(`Assistant: ${message}`);
};

main();

                                        import os
from openai import OpenAI

client = OpenAI(
    base_url="https://api.ai.cc/v1",
    api_key="",    
)

response = client.chat.completions.create(
    model="x-ai/grok-4-fast-reasoning",
    messages=[
        {
            "role": "system",
            "content": "You are an AI assistant who knows everything.",
        },
        {
            "role": "user",
            "content": "Tell me, why is the sky blue?"
        },
    ],
)

message = response.choices[0].message.content

print(f"Assistant: {message}")

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Grok 4 Fast Reasoning

Product Detail

Grok 4 Fast Reasoning is an advanced iteration of xAI’s Grok 4 model, specifically engineered for ultra-fast inference and unparalleled context handling. It boasts an expansive 2,000,000 token context window, empowering sophisticated long-horizon text comprehension and efficient multi-step reasoning. This version meticulously balances speed with depth of understanding, making it the ideal choice for demanding, large-scale, and real-time AI applications.

Technical Specification

Performance Benchmarks

⭐ Context Window: 2,000,000 tokens
⚡ Max Output: ~4,096 tokens
🚀 Training Regime: Enhanced for fast inference via optimized compute pathways
🛠️ Tool Use: Integrated native support with streamlined multi-step execution

Performance Metrics

✅ Superior performance in long-context tasks requiring rapid comprehension
🎯 High accuracy in complex text-to-text scenarios with intricate dependencies

Key Capabilities

✨ Ultra-long context understanding up to 2 million tokens for deep document analysis
⏱️ Accelerated reasoning for faster turnaround on multi-step tasks
⚙️ Deterministic outputs optimized for stable responses across very large input sizes

API Pricing

💰 Input: 0–128k: $0.21; 128k+: $0.42 per 1M tokens
💸 Output: 0–128k: $0.525; 128k+: $1.05 per 1M tokens
💾 Cached input: $0.05 per 1M tokens

Optimal Use Cases

🔍 Large-scale document analysis and synthesis where extended context is crucial
🤖 Real-time autonomous agents demanding fast, reliable multi-step reasoning
🧠 Complex strategic planning involving API orchestration and extended logic chains
🔬 Advanced research evaluation for datasets with vast textual dependencies
📝 Text-to-text transformations, including summarization, Q&A, and content generation across extensive inputs

Code Sample

        <snippet data-name="open-ai.chat-completion" data-model="x-ai/grok-4-fast-reasoning"></snippet>
    

Comparison with Other Leading Models

🆚 vs. GPT-4o: Grok 4 Fast Reasoning provides a vastly larger 2 million token context window compared to GPT-4o, enabling significantly deeper long-form understanding. While GPT-4o excels in multimodal inputs and web browsing, Grok 4 Fast offers faster inference and superior reasoning capabilities over extended texts.
🆚 vs. Claude 4 Opus: Claude 4 Opus is renowned for exceptional language safety and alignment. However, Grok 4 Fast outperforms Claude 4 in handling ultra-long context tasks and delivers higher throughput in complex multi-step reasoning scenarios.
🆚 vs. Gemini 2.5 Pro: Gemini 2.5 Pro offers strong instruction following and speed for typical text tasks. Grok 4 Fast surpasses Gemini in zero-shot reasoning with very long inputs, leveraging its extensive 2 million token context for complex planning and inference.
🆚 vs. Grok 4: Grok 4 Fast Reasoning builds upon the original Grok 4 by dramatically expanding the context window from 256K to 2 million tokens, accommodating much larger and more complex documents. It also features optimized compute pathways for faster execution while maintaining advanced tool integration and reasoning capabilities.

Limitations

⚠️ Text-only model without vision or audio modalities
⚠️ Tool use remains sequential, with limited compositionality
⚠️ Closed-weight approach, lacking offline or local inference support
⚠️ Stream determinism may vary under certain high-throughput conditions

Frequently Asked Questions (FAQ)

Q: What architectural innovations enable Grok 4 Fast Reasoning's accelerated inference capabilities?
A: Grok 4 Fast Reasoning utilizes a revolutionary sparse mixture-of-experts architecture with dynamic computational pathways, activating only relevant reasoning modules. It integrates early-exit mechanisms, progressive deepening, and parallel reasoning streams, complemented by advanced caching and optimized attention patterns, leading to 3-5x faster inference.

Q: How does the model maintain reasoning quality despite accelerated processing?
A: Quality is preserved through intelligent computation allocation, directing resources to critical reasoning steps. The model uses confidence-based early termination and maintains Grok's signature reasoning transparency via compressed, informative traces that uphold logical flow.

Q: What types of reasoning tasks benefit most from the fast-reasoning optimization?
A: It excels at rapid mathematical problem-solving, quick logical deductions, fast code analysis, instant fact verification, and speedy creative brainstorming. This optimization is particularly beneficial for interactive applications, real-time decision support, and educational tutoring.

Q: What practical applications become feasible with accelerated reasoning capabilities?
A: The speed optimization enables real-time collaborative problem-solving, interactive educational platforms, live analytical dashboards, rapid prototyping of logical systems, and highly responsive AI assistants for technical domains, providing sub-second response times.

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