gpt-oss (OpenAI) vs StepFun Step 3.5 Flash
Which one should you pick? Here's the full breakdown.
gpt-oss (OpenAI)
OpenAI's FIRST open-weight models -- gpt-oss-120b (single 80GB GPU, near parity with o4-mini on reasoning) and gpt-oss-20b (runs on 16GB edge devices). Apache 2.0. Launched 2025-08-05. gpt-oss-safeguard ships in 2026 as the safety-tuned variant
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 | gpt-oss (OpenAI) | StepFun Step 3.5 Flash |
|---|---|---|
| Ease of Use | 7.0 | 6.0 |
| Output Quality | 8.5 | 8.0 |
| Value | 10.0 | 9.0 |
| Features | 7.0 | 8.0 |
| Overall | 8.1 | 7.8 |
Pricing Comparison
| Feature | gpt-oss (OpenAI) | StepFun Step 3.5 Flash |
|---|---|---|
| Free Tier | Yes | Yes |
| Starting Price | $0 | $0 |
Which Should You Pick?
Pick gpt-oss (OpenAI) if...
- ✓Easier to use (7 vs 6)
- ✓Better value for money (10/10)
Developers who want OpenAI-brand open-weight reasoning models for self-hosting or fine-tuning. Particularly good for single-GPU deployments (gpt-oss-120b on one 80GB card) or edge-device reasoning (gpt-oss-20b on 16GB consumer GPUs / Apple Silicon). Also good as a reliable baseline when comparing newer open-weight releases.
Visit gpt-oss (OpenAI)Pick StepFun Step 3.5 Flash if...
- ✓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 FlashOur Verdict
gpt-oss (OpenAI) and StepFun Step 3.5 Flash are extremely close overall. Your choice comes down to specific needs -- gpt-oss (OpenAI) is better for developers who want openai-brand open-weight reasoning models for self-hosting or fine-tuning, 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.