StepFun Step 3.5 Flash vs Windsurf
Which one should you pick? Here's the full breakdown.
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
Windsurf
Cognition's AI code editor -- Windsurf 2.0 (launched 2026-04-15) adds Agent Command Center, Spaces, and embedded Devin cloud agents. Directly competitive with Cursor 3
Powered by Cognition hosted models + Claude / GPT / Gemini (user selects) + Devin cloud agent
| Category | StepFun Step 3.5 Flash | Windsurf |
|---|---|---|
| Ease of Use | 6.0 | 8.0 |
| Output Quality | 8.0 | 7.0 |
| Value | 9.0 | 8.0 |
| Features | 8.0 | 7.0 |
| Overall | 7.8 | 7.5 |
Pricing Comparison
| Feature | StepFun Step 3.5 Flash | Windsurf |
|---|---|---|
| Free Tier | Yes | Yes |
| Starting Price | $0 | $0 |
Which Should You Pick?
Pick StepFun Step 3.5 Flash if...
- ✓Higher output quality (8 vs 7)
- ✓Better value for money (9/10)
- ✓More features (8 vs 7)
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 FlashPick Windsurf if...
- ✓Easier to use (8 vs 6)
Developers who want agent-first coding (background + inline) inside a familiar VS Code-based editor, and who value Cognition's Devin integration as a core part of the workflow. The April 2026 redesign makes Windsurf 2.0 a direct alternative to Cursor 3 for this use case.
Visit WindsurfOur Verdict
StepFun Step 3.5 Flash and Windsurf are extremely close overall. Your choice comes down to specific needs -- StepFun Step 3.5 Flash is better 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, while Windsurf works best for developers who want agent-first coding (background + inline) inside a familiar vs code-based editor, and who value cognition's devin integration as a core part of the workflow.