Moonshot AI Kimi K2 Thinking vs OpenAI GPT-5.3-Codex — side-by-side specs.
Moonshot AI Kimi K2 Thinking | OpenAI GPT-5.3-Codex | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | OpenAI |
| Release date | Nov 6 2025 | Feb 5 2026 |
| Model type | — | — |
| Open source | Yes | No |
| Specifications | ||
Parameters | 1T | — |
Context window | 256k | — |
| Benchmarks | ||
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. | 71.3% | — |
| Timeline | ||
| Release gap | Kimi K2 Thinking shipped 91 days before GPT-5.3-Codex | |
Kimi K2 Thinking 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 K2 Thinking shipped 91 days before GPT-5.3-Codex, so benchmark comparisons should account for the intervening progress.
Kimi K2 Thinking is an open-source / open-weight model; GPT-5.3-Codex is proprietary.
Direct benchmark comparisons are unavailable — Kimi K2 Thinking and GPT-5.3-Codex don't publish scores on any of the same benchmarks.