GPT-5.1 vs Step 3.5 Flash
OpenAI vs StepFun — benchmarks, pricing, and capabilities side by side.
- •GPT-5.1 has the higher intelligence index (89 vs 83.1)
- •Step 3.5 Flash is cheaper ($0.09 vs $1.25 per 1M input)
- •Step 3.5 Flash is faster
- •GPT-5.1 has a larger context window (400K)
| GPT-5.1 | Step 3.5 Flash | |
|---|---|---|
| Intelligence index | 89 | 83.1 |
| Developer | OpenAI | StepFun |
| Type | LLM | LLM |
| Access | API only | Open weights |
| Context window | 400,000 tokens | 262,144 tokens |
| Input price | $1.25 / 1M | $0.09 / 1M |
| Output price | $10.00 / 1M | $0.30 / 1M |
| Speed | 115 tok/s | 194 tok/s |
| Released | November 12, 2025 | January 29, 2026 |
| Parameters | — | — |
| Input modalities | Text, Image | Text |
| Output modalities | Text | Text |
Shared benchmarks
GPT-5.1
Step 3.5 Flash
GPQA Diamond
88.1
83.1
Humanity’s Last Exam
26.5
19.1