Kimi K3 vs Grok 4.1 Fast
Moonshot AI Kimi K3 | SpaceXAI Grok 4.1 Fast | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | SpaceXAI |
| Release date | Jul 16 2026 | Nov 19 2025 |
| Access | Open Weight | Proprietary |
| Specifications | ||
Parameters | 2.8T | — |
Context window | 1M | — |
| Benchmarks | ||
Nonsense detection BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. | — | 19% |
Agentic coding DeepSWE 1.0Artificial Analysis' independent test of deep, agentic software-engineering work — the AI has to plan and carry out substantial coding tasks end to end. Higher is better. | 67.5% | — |
Agentic terminal coding Terminal-Bench 2.1Can the AI work in a command-line terminal — running commands and finishing technical setup tasks the way a developer would? Higher is better. | 88.3% | — |
Multi-step tool use MCP AtlasCan the AI chain together many tools and steps to complete one bigger task, rather than doing just a single thing? Higher is better. | 84.2% | — |
Professional tool use JobBenchTests the AI on professional workplace tasks that require using real work tools — the kind of multi-step jobs an office worker handles. Higher is better. | 52.9% | — |
Personal tool use Toolathlon-VerifiedTests how well the AI uses everyday personal tools and apps to get things done — a human-checked version of Toolathlon. Higher is better. | 73.2% | — |
Web browsing BrowseCompCan the AI browse the web and track down hard-to-find answers? Higher is better. | 91.2% | — |
Multidisciplinary reasoning Humanity's Last Exam · no toolsHumanity's Last Exam — extremely hard expert questions across many subjects, written so you can't just look up the answer. “No tools” means the AI answers on its own. Higher is better. | 43.5% | — |
Multidisciplinary reasoning Humanity's Last Exam · with toolsHumanity's Last Exam — extremely hard expert questions across many subjects. “With tools” means the AI is allowed to search the web or run code while answering. Higher is better. | 56% | — |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 93.5% | — |
Knowledge work GDPval-AA v2economically valuable knowledge work (v2, re-based Elo) | 1668 | — |
Chart reasoning CharXiv ReasoningCan the AI read and reason about complex charts and figures, not just text? Higher is better. | 84.8% | — |
Multimodal reasoning MMMU-ProA tougher version of MMMU — college-level questions that mix images, diagrams, and text together. Higher is better. | 81.6% | — |
| Timeline | ||
| Release gap | Grok 4.1 Fast shipped 239 days before Kimi K3 | |
Which is better: Kimi K3 or Grok 4.1 Fast?
Kimi K3 and Grok 4.1 Fast don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Grok 4.1 Fast shipped 239 days before Kimi K3, so benchmark comparisons should account for the intervening progress.
Kimi K3 is open weight, while Grok 4.1 Fast is proprietary.
Direct benchmark comparisons are unavailable — Kimi K3 and Grok 4.1 Fast don't publish scores on any of the same benchmarks.
Frequently asked questions
Kimi K3 was released by Moonshot AI on Jul 16 2026.
Grok 4.1 Fast was released by SpaceXAI on Nov 19 2025.
Kimi K3 is an open weight model released by Moonshot AI. Grok 4.1 Fast is a proprietary model released by SpaceXAI.
Other comparisons
Kimi K3 vs Claude Sonnet 5Grok 4.1 Fast vs Claude Sonnet 5Kimi K3 vs GPT-5.6 SolGrok 4.1 Fast vs GPT-5.6 SolKimi K3 vs Gemini 3.5 FlashGrok 4.1 Fast vs Gemini 3.5 FlashKimi K3 vs Muse Spark 1.1Grok 4.1 Fast vs Muse Spark 1.1Kimi K3 vs DeepSeek-V4-ProGrok 4.1 Fast vs DeepSeek-V4-ProKimi K3 vs Mistral Medium 3.5Grok 4.1 Fast vs Mistral Medium 3.5