Kimi K2 (0905) vs Grok 4 Fast
Moonshot AI Kimi K2 (0905) | SpaceXAI Grok 4 Fast | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | SpaceXAI |
| Release date | Sep 5 2025 | Sep 2025 |
| Access | Open Weight | Proprietary |
| Specifications | ||
Parameters | 1T | — |
Context window | 256k | — |
| Benchmarks | ||
Coding SWE-Bench VerifiedReal coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better. | 65.8% | — |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 75.1% | — |
| Timeline | ||
| Release gap | Grok 4 Fast shipped 4 days before Kimi K2 (0905) | |
Which is better: Kimi K2 (0905) or Grok 4 Fast?
Kimi K2 (0905) and Grok 4 Fast don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Grok 4 Fast shipped 4 days before Kimi K2 (0905), so benchmark comparisons should account for the intervening progress.
Kimi K2 (0905) is open weight, while Grok 4 Fast is proprietary.
Direct benchmark comparisons are unavailable — Kimi K2 (0905) and Grok 4 Fast don't publish scores on any of the same benchmarks.
Frequently asked questions
Kimi K2 (0905) was released by Moonshot AI on Sep 5 2025.
Grok 4 Fast was released by SpaceXAI on Sep 2025.
Kimi K2 (0905) is an open weight model released by Moonshot AI. Grok 4 Fast is a proprietary model released by SpaceXAI.
Other comparisons
Kimi K2 (0905) vs Claude Sonnet 5Grok 4 Fast vs Claude Sonnet 5Kimi K2 (0905) vs GPT-5.6 SolGrok 4 Fast vs GPT-5.6 SolKimi K2 (0905) vs Gemini OmniGrok 4 Fast vs Gemini OmniKimi K2 (0905) vs Muse Spark 1.1Grok 4 Fast vs Muse Spark 1.1Kimi K2 (0905) vs DeepSeek-V4-ProGrok 4 Fast vs DeepSeek-V4-ProKimi K2 (0905) vs Mistral Medium 3.5Grok 4 Fast vs Mistral Medium 3.5