Kimi K2 (0905) vs GPT-5.3-Codex-Spark
Moonshot AI Kimi K2 (0905) | OpenAI GPT-5.3-Codex-Spark | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | OpenAI |
| Release date | Sep 5 2025 | Feb 12 2026 |
| Access | Open Weight | Proprietary |
| Specifications | ||
Parameters | 1T | — |
Context window | 256k | 128k |
| 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. | 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 160 days before GPT-5.3-Codex-Spark | |
Which is better: Kimi K2 (0905) or GPT-5.3-Codex-Spark?
Kimi K2 (0905) and GPT-5.3-Codex-Spark don't publish scores on any of the same benchmarks, so there's no direct head-to-head comparison. Kimi K2 (0905) shipped 160 days before GPT-5.3-Codex-Spark, so benchmark comparisons should account for the intervening progress.
Context windows are 256k (Kimi K2 (0905)) vs 128k (GPT-5.3-Codex-Spark). Kimi K2 (0905) is open weight, while GPT-5.3-Codex-Spark is proprietary.
Direct benchmark comparisons are unavailable — Kimi K2 (0905) and GPT-5.3-Codex-Spark 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-5.3-Codex-Spark was released by OpenAI on Feb 12 2026.
Kimi K2 (0905) has a 256k context window; GPT-5.3-Codex-Spark has 128k.
Kimi K2 (0905) is an open weight model released by Moonshot AI. GPT-5.3-Codex-Spark is a proprietary model released by OpenAI.