GPT-5 Pro vs Step 3.5 Flash
OpenAI vs StepFun — benchmarks, pricing, and capabilities side by side.
- •GPT-5 Pro has the higher intelligence index (88.4 vs 83.1)
- •Step 3.5 Flash is cheaper ($0.09 vs $15.00 per 1M input)
- •GPT-5 Pro has a larger context window (400K)
| GPT-5 Pro | Step 3.5 Flash | |
|---|---|---|
| Intelligence index | 88.4 | 83.1 |
| Developer | OpenAI | StepFun |
| Type | LLM | LLM |
| Access | API only | Open weights |
| Context window | 400,000 tokens | 262,144 tokens |
| Input price | $15.00 / 1M | $0.09 / 1M |
| Output price | $120.00 / 1M | $0.30 / 1M |
| Speed | — | 194 tok/s |
| Released | October 6, 2025 | January 29, 2026 |
| Parameters | — | — |
| Input modalities | Text, Image | Text |
| Output modalities | Text | Text |
Shared benchmarks
GPT-5 Pro
Step 3.5 Flash
GPQA Diamond
88.4
83.1
Humanity’s Last Exam
42
19.1