Model Drop

Grok Code Fast 1

August 28, 2025 1 min read

Grok Code Fast 1, which xAI released on August 28, 2025 after about a week of stealth testing under the name "sonic", is a fast, low-cost reasoning model built from scratch for agentic coding.

Model: Grok Code Fast 1 (grok-code-fast-1)
Maker: xAI
Ship date: August 28, 2025
Pricing: $0.20 / $1.50 per M tokens
Context: Not published
Weights: Closed
Where you can use it:
- The xAI API
- Free for a time in Copilot, Cursor, Cline
When to reach for it:
- Quick, scoped edits in an agentic IDE
- Skip it for image inputs
How it compares:
- A coding-only rival to GPT-5 mini
- Faster than Qwen3-Coder in xAI's tests
What makes it different:
- New architecture, code-heavy pretraining
- Tuned with Copilot, Cursor and Cline
Early reactions: Reviewers liked the speed and price for scoped tasks, but its arrival in GitHub Copilot drew pushback from some GitHub staff and users.
Read more: Grok Code Fast 1 and the Grok Code Fast 1 Model Card

The benchmarks

xAI published one public score, SWE-bench Verified on the full set using its own internal harness, with no rivals; the speed row is xAI's own measurement of output tokens per second through each maker's API (Qwen3-Coder hosted on DeepInfra at fp4), and the safety rows come from the model card, where xAI's comparison is Grok 4 through the API.

xAI's numbers

SWE-bench Verified (real GitHub fixes, internal harness): 70.8%.
Tokens per second (output speed, xAI-measured): 160. +67.61 over Gemini 2.5 Pro (92.39), +81.29 over Claude Sonnet 4 (78.71), +80 over Qwen3-Coder (80), +109.9 over GPT-5 (50.1), +119.37 over Grok 4 (40.63).
CyBench (capture-the-flag hacking, unguided): 22.5%. −20.5 under Grok 4 (43%).
WMDP Cyber (cyber knowledge quiz): 62.1%. −16.9 under Grok 4 (79%).
MASK dishonesty rate (lower is better): 71.9%. +28.9 over Grok 4 (43%).

Independent numbers

Artificial Analysis Intelligence Index (current v4.3.2, AA estimate): 14.1. −2.7 under GPT-5 mini (high) (16.8), +1.0 over Gemini 2.5 Flash (13.1), +2.2 over Qwen3-Coder (11.9).