Kimi K2.5 vs GPT-5.3-Codex-Spark
Moonshot AI Kimi K2.5 | OpenAI GPT-5.3-Codex-Spark | |
|---|---|---|
| Overview | ||
| Company | Moonshot AI | OpenAI |
| Release date | Jan 27 2026 | Feb 12 2026 |
| Access | Open Weight | Proprietary |
| Specifications | ||
Parameters | 1T | — |
Context window | 256k | 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. | 52% | — |
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. | 76.8% | — |
Agentic coding CursorBench v3.1Cursor's own test of harder, real-world coding tasks inside a code editor. Higher is better. | 31.9% | — |
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. | 21% | — |
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. | 85% | — |
Science GPQA DiamondGraduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. | 87.6% | — |
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. | 1433 | — |
| Timeline | ||
| Release gap | Kimi K2.5 shipped 16 days before GPT-5.3-Codex-Spark | |
Which is better: Kimi K2.5 or GPT-5.3-Codex-Spark?
Kimi K2.5 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 K2.5 shipped 16 days before GPT-5.3-Codex-Spark, so benchmark comparisons should account for the intervening progress.
Context windows are 256k (Kimi K2.5) vs 128k (GPT-5.3-Codex-Spark). Kimi K2.5 is open weight, while GPT-5.3-Codex-Spark is proprietary.
Direct benchmark comparisons are unavailable — Kimi K2.5 and GPT-5.3-Codex-Spark don't publish scores on any of the same benchmarks.
Frequently asked questions
Kimi K2.5 was released by Moonshot AI on Jan 27 2026.
GPT-5.3-Codex-Spark was released by OpenAI on Feb 12 2026.
Kimi K2.5 has a 256k context window; GPT-5.3-Codex-Spark has 128k.
Kimi K2.5 is an open weight model released by Moonshot AI. GPT-5.3-Codex-Spark is a proprietary model released by OpenAI.