Kimi K2.6 vs GPT-5.3-Codex
Moonshot AI Kimi K2.6 | OpenAI GPT-5.3-Codex | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | OpenAI |
| Release date | Apr 21 2026 | Feb 5 2026 |
| 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. | 65%Best | 24% |
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. | 80.2% | — |
Agentic coding CursorBench v3.1Cursor's own test of harder, real-world coding tasks inside a code editor. Higher is better. | 47.6% | — |
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. | 67% | 83%Best |
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. | 89.6% | — |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 90.5% | — |
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. | 1513Best | 1406 |
| Timeline | ||
| Release gap | GPT-5.3-Codex shipped 75 days before Kimi K2.6 | |
Which is better: Kimi K2.6 or GPT-5.3-Codex?
Kimi K2.6 leads GPT-5.3-Codex on 2 of the 3 benchmarks they both report (BullshitBench v2, Next.js Evals, Arena Elo (Code)). GPT-5.3-Codex shipped 75 days before Kimi K2.6, so benchmark comparisons should account for the intervening progress.
Kimi K2.6 is open weight, while GPT-5.3-Codex is proprietary.
On BullshitBench v2, Kimi K2.6 leads at 65% vs GPT-5.3-Codex at 24%. On Next.js Evals, GPT-5.3-Codex leads at 83% vs Kimi K2.6 at 67%. On Arena Elo (Code), Kimi K2.6 leads at 1513 vs GPT-5.3-Codex at 1406.
Frequently asked questions
Kimi K2.6 was released by Moonshot AI on Apr 21 2026.
GPT-5.3-Codex was released by OpenAI on Feb 5 2026.
GPT-5.3-Codex leads on Next.js Evals — Kimi K2.6 67% vs GPT-5.3-Codex 83%.
Kimi K2.6 is an open weight model released by Moonshot AI. GPT-5.3-Codex is a proprietary model released by OpenAI.