ApX logoApX logo

Grok Code Fast

Parameters

314B

Context Length

128K

Modality

Text

Architecture

Dense

License

Proprietary

Release Date

1 Jun 2025

Knowledge Cutoff

Jan 2025

Technical Specifications

Attention Structure

Multi-Head Attention

Hidden Dimension Size

6144

Number of Layers

64

Attention Heads

48

Key-Value Heads

8

Activation Function

-

Normalization

RMS Normalization

Position Embedding

Absolute Position Embedding

Grok Code Fast

Grok Code Fast is a specialized large language model developed by xAI, engineered specifically to support high-velocity agentic coding workflows. Built from the ground up with a custom architecture, the model is pre-trained on a massive corpus of programming-related data and fine-tuned using high-quality post-training datasets derived from real-world pull requests and practical software engineering tasks. This specialization allows the model to maintain a high degree of proficiency in popular languages such as TypeScript, Python, Java, Rust, C++, and Go, while remaining optimized for the low-latency demands of real-time development environments.

Technically, the model utilizes a sparse Mixture-of-Experts (MoE) architecture designed to balance computational efficiency with high-capacity reasoning. This structural choice enables the model to process complex instructions and manage multi-step tool interactions without the latency penalties typically associated with dense models of similar scale. A defining characteristic of Grok Code Fast is its deep integration with developer tools; it is specifically trained to execute terminal operations, perform repository-wide file searches using utilities like grep, and carry out precise code refactors. The model also incorporates advanced prompt caching techniques, which significantly reduce response times for repetitive context-heavy queries common in IDE-based interactions.

In practical application, Grok Code Fast is optimized for autonomous and semi-autonomous tasks such as project scaffolding, codebase exploration, and surgical bug fixing. It features an expansive 256,000-token context window, providing the necessary memory for the model to ingest and reason over substantial portions of a repository simultaneously. By prioritizing throughput and tool-calling reliability, the model serves as a responsive backend for modern AI-driven coding assistants and automated agents that require a tight feedback loop between reasoning and code execution.

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.


Other Grok Models

Evaluation Benchmarks

Rank

#80

BenchmarkScoreRank

0.69

24

Agentic Coding

LiveBench Agentic

0.33

25

0.42

31

0.64

40

0.56

43

Rankings

Overall Rank

#80

Coding Rank

#81

Model Transparency

Total Score

C-

47 / 100

Grok Code Fast Transparency Report

Total Score

47

/ 100

C-

Audit Note

Grok Code Fast 1 exhibits a transparency profile typical of high-performance proprietary models, offering clear functional specifications but minimal technical depth. While its architectural scale and performance benchmarks are well-publicized, the lack of data provenance, compute disclosure, and reproducible evaluation harnesses creates significant barriers for independent verification. The model's shift from the open-weights philosophy of its predecessor to a strictly proprietary API model further limits its transparency for the broader research community.

Upstream

15.0 / 30

Architectural Provenance

6.5 / 10

The model is officially described as being 'built from scratch' with a 'brand-new architecture' rather than being a fine-tuned version of previous Grok models. While xAI provides high-level architectural details—confirming it is a sparse Mixture-of-Experts (MoE) model with 314B total parameters—specific technical documentation or a whitepaper detailing the exact layer configurations, routing mechanisms, or unique 'serving optimizations' mentioned in marketing materials is not publicly available. The claim of a 'new architecture' is verifiable through official blog posts and partner documentation (e.g., Oracle, GitHub), but lacks the deep technical disclosure found in peer-reviewed research.

Dataset Composition

3.5 / 10

Disclosure regarding training data is limited to general categories. xAI states the model was pre-trained on a 'programming-rich corpus' and post-trained on 'high-quality datasets derived from real-world pull requests and practical software engineering tasks.' However, there is no public breakdown of dataset proportions (e.g., percentage of code vs. natural language), no list of specific data sources, and no detailed documentation on filtering or cleaning methodologies. The reliance on 'proprietary post-training datasets' without further specification prevents independent verification of data quality or diversity.

Tokenizer Integrity

5.0 / 10

While the tokenizer for the original Grok-1 (131,072 vocabulary size) is public, there is no explicit confirmation or public repository for a specialized 'Grok Code Fast' tokenizer. The model supports a 256,000-token context window, and while it likely inherits the SentencePiece approach from its predecessors, the specific tokenization logic for this variant—especially regarding how it handles specialized code syntax or terminal commands—is not documented. No public tokenizer files or vocabulary analysis for this specific version are available for audit.

Model

20.0 / 40

Parameter Density

5.5 / 10

The total parameter count is clearly stated as 314 billion. However, as a Mixture-of-Experts (MoE) model, the 'active' parameter count per token is a critical transparency metric that remains undisclosed for this specific variant. While the original Grok-1 used 2 experts (approximately 25% of weights) per token, xAI has not confirmed if 'Grok Code Fast' maintains this ratio or uses a more aggressive sparsity to achieve its claimed 92-100 tokens/sec throughput. The lack of clarity on active parameters makes it difficult to assess the model's true computational density.

Training Compute

2.0 / 10

Information regarding the compute resources used to train the model is almost entirely absent. There are no public disclosures regarding GPU/TPU hours, hardware specifications of the training cluster (beyond general knowledge of xAI's 'Colossus' cluster), or the carbon footprint of the training run. The company does not provide estimates for training duration or cost, citing competitive reasons for withholding compute metrics.

Benchmark Reproducibility

4.0 / 10

xAI reports scores on benchmarks like SWE-Bench-Verified (70.8%) but notes these were conducted using an 'internal harness.' While third-party platforms like Artificial Analysis and OpenRouter provide independent performance data (e.g., 65.7% on LiveCodeBench), the exact prompts, few-shot examples, and evaluation code used by xAI to reach their official figures are not public. This lack of a standardized reproduction path makes it difficult to verify official claims against independent results.

Identity Consistency

8.5 / 10

The model consistently identifies itself as a specialized coding assistant within its supported environments (Cursor, GitHub Copilot, etc.). It maintains a clear versioning identity as 'Grok Code Fast 1' and does not exhibit the identity confusion seen in some other models. It is transparent about its role as a 'fast' reasoning model, though its self-description often mirrors marketing language regarding its 'agentic' capabilities.

Downstream

12.0 / 30

License Clarity

3.0 / 10

Unlike the original Grok-1, which was released under an Apache 2.0 license, Grok Code Fast 1 is strictly proprietary. The license terms are governed by the xAI API Terms of Service, which include restrictions on commercial use and derivative works that are standard for closed-source models but offer zero transparency for researchers. There is no public license file for the weights or architecture, and the model is only accessible via paid API or partner integrations.

Hardware Footprint

4.0 / 10

As a proprietary API-only model, there is no official documentation on the hardware requirements for local deployment. While third-party communities estimate that a 314B MoE model would require significant VRAM (e.g., 8x A100/H100 GPUs), xAI provides no guidance on quantization tradeoffs or memory scaling for the 256k context window. Users are entirely dependent on xAI's managed infrastructure, with no transparency into the underlying hardware footprint.

Versioning Drift

5.0 / 10

The model uses a basic versioning scheme ('Grok Code Fast 1'), and xAI maintains a high-level API changelog. However, there is no detailed technical changelog documenting weight updates or shifts in model behavior. The company has noted that updates will occur on a 'frequent cadence,' but there is no public mechanism to access or pin specific sub-versions to prevent performance drift in production applications.