Grok 4.1 Fast
Parameters
-
Context Length
128K
Modality
Text
Architecture
Dense
License
Proprietary
Release Date
1 Jun 2025
Knowledge Cutoff
Jun 2025
Evaluation Benchmarks
Rank
#72
| Benchmark | Score | Rank |
|---|---|---|
Graduate-Level QA GPQA | 0.857 | 8 |
Reasoning LiveBench Reasoning | 0.80 | 14 |
Mathematics LiveBench Mathematics | 0.84 | 16 |
Professional Knowledge MMLU Pro | 0.84 | 23 |
Data Analysis LiveBench Data Analysis | 0.52 | 31 |
Coding LiveBench Coding | 0.70 | 38 |
Agentic Coding LiveBench Agentic | 0.32 | 42 |
Web Development WebDev Arena | 1234 | 92 |
Rankings
Overall Rank
#72
Coding Rank
#117
About Grok 4.1 Fast
Grok 4.1 Fast is an optimized large language model variant from xAI designed specifically for high-throughput, low-latency applications and complex agentic workflows. It serves as a performance-tuned alternative to the standard Grok 4.1 series, providing a massive 2 million token context window that allows for the ingestion and processing of extensive documentation, codebases, and long-horizon conversation histories. The model is architected to operate in two distinct modes: a reasoning-enabled configuration for multi-step analytical tasks and a non-reasoning mode for near-instant responses.
Technically, the model integrates specialized reinforcement learning (RL) training with a focus on tool utilization and long-horizon planning. This training regime involves simulated environments across various enterprise domains such as finance, healthcare, and telecommunications, enabling the model to orchestrate external tools through the xAI Agent Tools API. The architecture is built to maintain high state stability across its expanded context, utilizing advanced attention mechanisms to ensure factual consistency and reduced hallucination rates compared to its predecessors.
In practical deployment, Grok 4.1 Fast is utilized for autonomous agents, deep research automation, and real-time customer support systems. It features native support for multihop web search, real-time data retrieval via the X ecosystem, and remote code execution. This makes it particularly effective for developers building production-grade agents that require high-speed function calling, structured data extraction, and reliable grounding in external knowledge sources.
Technical Specifications
Attention
Attention Structure
Multi-Head Attention
Attention Heads
-
Key-Value Heads
-
Attention Head Dimension
-
Position Embedding
Absolute Position Embedding
RoPE Theta
-
Sliding Window Attention
-
Sliding Window Size
-
Sliding Window Ratio
-
Linear Attention
-
Linear Attention Ratio
-
Normalization
-
Activation Function
-
Dimensions
Hidden Dimension Size
-
Number of Layers
-
FFN Intermediate Size (Dense)
-
Multi-Token Prediction Heads
-
Tokenizer
Vocabulary Size
-
Resources
About Grok
xAI's conversational AI models with real-time knowledge access and strong performance across reasoning, coding, and language tasks. Features extended context windows, fast inference variants, and specialized coding versions. Known for direct communication style and integration with X platform. Includes reasoning variants and optimized versions for different latency requirements.