Kimi K2.5 Thinking: Moonshot AI Joins the Frontier
Kimi K2.5 Thinking from Moonshot AI arrived in early 2026 as one of the strongest open-weight reasoning models yet — 96% on AIME 2025, competitive on LiveCodeBench, and a serious option for teams who want frontier-quality reasoning they can actually self-host.
The open-weight reasoning model race is heating up. DeepSeek R1 established that open models could match closed reasoning models on math. Kimi K2.5 Thinking picks up that thread and pushes further.
Moonshot AI isn't a household name in the West — but they've been building serious models, and K2.5 Thinking is the one that puts them on the international frontier map.
What's Impressive
- AIME 2025: 96% — Among the highest scores on this math competition benchmark, rivaling the best closed-source reasoning models available. Verifiable. Competitive.
- LiveCodeBench: 85% — Strong coding performance. In the same tier as DeepSeek V3.2 and Qwen 3.5.
- Open weights, commercially usable — Like DeepSeek V3.2, you can self-host this. That's the differentiator from Gemini or GPT-5.2.
- "Thinking" mode — Extended chain-of-thought reasoning. The model shows its work on hard problems.
How It Compares at Launch
| Model | AIME 2025 | LiveCodeBench | Open Weight |
|---|---|---|---|
| Kimi K2.5 Thinking | 96% | 85% | ✅ |
| DeepSeek V3.2 | 92% | 86% | ✅ |
| Qwen 3.5 (235B) | ~95% | ~85% | ✅ |
| Gemini 3.1 Pro | top | top | ❌ |
| Claude Opus 4.6 | strong | — | ❌ |
In the open-weight math and reasoning tier, Kimi K2.5 Thinking is at or near the top.
Best For
- Math-heavy and scientific reasoning tasks where open weights matter
- Teams that want extended chain-of-thought without paying per-token API costs
- Self-hosted reasoning pipelines for research, quantitative finance, engineering
- Evaluating open-weight alternatives to o3 or Gemini 3 Pro Think
Not For
- Agentic coding — Claude Code still leads
- General conversational AI — K2.5 is specialized for reasoning, not optimized for broad chat quality
- Teams that need Western vendor support SLAs
Verdict
Kimi K2.5 Thinking is a genuine entrant in the open-weight frontier. If your primary use case involves hard mathematical or scientific reasoning and you want to self-host, this is worth benchmarking alongside DeepSeek V3.2 and Qwen 3.5. The open-weight reasoning tier has never been stronger.
Part of our Model Watch series.