Kimi K2 (0905) vs GPT-5-Codex
Moonshot AI Kimi K2 (0905) | OpenAI GPT-5-Codex | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | OpenAI |
| Release date | Sep 5 2025 | Sep 15 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. | — | 39% |
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 | Kimi K2 (0905) shipped 10 days before GPT-5-Codex | |
Which is better: Kimi K2 (0905) or GPT-5-Codex?
Kimi K2 (0905) and GPT-5-Codex don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Kimi K2 (0905) shipped 10 days before GPT-5-Codex, so benchmark comparisons should account for the intervening progress.
Kimi K2 (0905) is open weight, while GPT-5-Codex is proprietary.
Direct benchmark comparisons are unavailable — Kimi K2 (0905) and GPT-5-Codex 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.
GPT-5-Codex was released by OpenAI on Sep 15 2025.
Kimi K2 (0905) is an open weight model released by Moonshot AI. GPT-5-Codex is a proprietary model released by OpenAI.
Other comparisons
Kimi K2 (0905) vs Claude Sonnet 5GPT-5-Codex vs Claude Sonnet 5Kimi K2 (0905) vs Gemini OmniGPT-5-Codex vs Gemini OmniKimi K2 (0905) vs Muse Spark 1.1GPT-5-Codex vs Muse Spark 1.1Kimi K2 (0905) vs Grok 4.5GPT-5-Codex vs Grok 4.5Kimi K2 (0905) vs DeepSeek-V4-ProGPT-5-Codex vs DeepSeek-V4-ProKimi K2 (0905) vs Mistral Medium 3.5GPT-5-Codex vs Mistral Medium 3.5