Kimi K1.5 vs GPT-5.3-Codex
Moonshot AI Kimi K1.5 | OpenAI GPT-5.3-Codex | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | OpenAI |
| Release date | Jan 20 2025 | Feb 5 2026 |
| Access | Proprietary | Proprietary |
| Specifications | ||
Context window | 128k | — |
| 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. | — | 24% |
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. | — | 83% |
Community preference (code) Arena Elo (Code)Like the text arena, but people vote on which AI writes better code. The votes become a chess-style Elo rating on arena.ai. Higher is better. | — | 1406 |
| Timeline | ||
| Release gap | Kimi K1.5 shipped 381 days before GPT-5.3-Codex | |
Which is better: Kimi K1.5 or GPT-5.3-Codex?
Kimi K1.5 and GPT-5.3-Codex don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Kimi K1.5 shipped 381 days before GPT-5.3-Codex, so benchmark comparisons should account for the intervening progress.
Published specifications for these two models are limited — see each model page for the latest details.
Direct benchmark comparisons are unavailable — Kimi K1.5 and GPT-5.3-Codex don't publish scores on any of the same benchmarks.
Frequently asked questions
Kimi K1.5 was released by Moonshot AI on Jan 20 2025.
GPT-5.3-Codex was released by OpenAI on Feb 5 2026.
Other comparisons
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