Kimi K2.5 vs Grok 4 Heavy
Moonshot AI Kimi K2.5 | SpaceXAI Grok 4 Heavy | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | SpaceXAI |
| Release date | Jan 27 2026 | Jul 9 2025 |
| Access | Open Weight | Proprietary |
| Specifications | ||
Parameters | 1T | — |
Context window | 256k | — |
| 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. | 52% | — |
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. | 76.8% | — |
Agentic coding CursorBench v3.1Cursor's own test of harder, real-world coding tasks inside a code editor. Higher is better. | 31.9% | — |
Next.js coding Next.js EvalsVercel's open eval of how well AI coding agents build and migrate real Next.js apps — measured as the share of tasks the agent completes successfully. Higher is better. | 21% | — |
Competitive coding LiveCodeBenchCoding problems published so recently the AI can't have seen them in training — a contamination-free test of raw programming skill. Higher is better. | 85% | — |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 87.6% | — |
| Timeline | ||
| Release gap | Grok 4 Heavy shipped 202 days before Kimi K2.5 | |
Which is better: Kimi K2.5 or Grok 4 Heavy?
Kimi K2.5 and Grok 4 Heavy don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Grok 4 Heavy shipped 202 days before Kimi K2.5, so benchmark comparisons should account for the intervening progress.
Kimi K2.5 is open weight, while Grok 4 Heavy is proprietary.
Direct benchmark comparisons are unavailable — Kimi K2.5 and Grok 4 Heavy don't publish scores on any of the same benchmarks.
Frequently asked questions
Kimi K2.5 was released by Moonshot AI on Jan 27 2026.
Grok 4 Heavy was released by SpaceXAI on Jul 9 2025.
Kimi K2.5 is an open weight model released by Moonshot AI. Grok 4 Heavy is a proprietary model released by SpaceXAI.
Other comparisons
Kimi K2.5 vs Claude Sonnet 5Grok 4 Heavy vs Claude Sonnet 5Kimi K2.5 vs GPT-5.6 SolGrok 4 Heavy vs GPT-5.6 SolKimi K2.5 vs Gemini OmniGrok 4 Heavy vs Gemini OmniKimi K2.5 vs Muse Spark 1.1Grok 4 Heavy vs Muse Spark 1.1Kimi K2.5 vs DeepSeek-V4-ProGrok 4 Heavy vs DeepSeek-V4-ProKimi K2.5 vs Mistral Medium 3.5Grok 4 Heavy vs Mistral Medium 3.5