Kimi K2.5 (Moonshot) vs StepFun Step 3.5 Flash
Which one should you pick? Here's the full breakdown.
Kimi K2.5 (Moonshot)
Moonshot's 1T-parameter MoE open-weights flagship -- best open-source agentic coder, rivals Claude Opus 4.5
StepFun Step 3.5 Flash
StepFun's (China) agent-focused open-weight model -- Step 3.5 Flash launched 2026-02-01. 196B sparse MoE, ~11B active. Benchmarks slightly ahead of DeepSeek V3.2 at over 3x smaller total size. Step 3 (321B / 38B active, Apache 2.0) and Step3-VL-10B multimodal also in the family
| Category | Kimi K2.5 (Moonshot) | StepFun Step 3.5 Flash |
|---|---|---|
| Ease of Use | 6.0 | 6.0 |
| Output Quality | 9.0 | 8.0 |
| Value | 8.5 | 9.0 |
| Features | 9.0 | 8.0 |
| Overall | 8.1 | 7.8 |
Pricing Comparison
| Feature | Kimi K2.5 (Moonshot) | StepFun Step 3.5 Flash |
|---|---|---|
| Free Tier | Yes | Yes |
| Starting Price | $0 | $0 |
Benchmark Head-to-Head
Kimi K2.5 (1T/32B active MoE) benchmarks — StepFun Step 3.5 Flash has no published benchmarks
| Benchmark | Description | Score |
|---|---|---|
| MMLU-Pro | Harder multi-subject reasoning | 84.8% |
| GPQA Diamond | Graduate-level science questions | 80.5% |
| AIME 2025 | 91.2% | |
| SWE-Bench Verified | 78.5% | |
| LiveCodeBench | 74.1% |
Which Should You Pick?
Pick Kimi K2.5 (Moonshot) if...
- ✓Higher output quality (9 vs 8)
- ✓More features (9 vs 8)
Agentic coding workflows, tool-use agents, and teams willing to pay hosted-API prices for frontier-tier quality with open-weights licensing protection.
Visit Kimi K2.5 (Moonshot)Pick StepFun Step 3.5 Flash if...
Teams building agent systems on Chinese open-weight foundations who want something other than DeepSeek or Qwen, especially if agentic tool-use is the primary workload. Also good for Chinese-market products where StepFun's domestic tuning advantages matter. And for anyone looking to add diversity to their open-weight evaluation matrix beyond the top-3 Chinese labs.
Visit StepFun Step 3.5 FlashOur Verdict
Kimi K2.5 (Moonshot) and StepFun Step 3.5 Flash are extremely close overall. Your choice comes down to specific needs -- Kimi K2.5 (Moonshot) is better for agentic coding workflows, tool-use agents, and teams willing to pay hosted-api prices for frontier-tier quality with open-weights licensing protection, while StepFun Step 3.5 Flash works best for teams building agent systems on chinese open-weight foundations who want something other than deepseek or qwen, especially if agentic tool-use is the primary workload.