GPT-5.1 vs Step 3.5 Flash 2603
OpenAI vs StepFun — benchmarks, pricing, and capabilities side by side.
- •GPT-5.1 has the higher intelligence index (89 vs 82.6)
- •Step 3.5 Flash 2603 is cheaper ($0.00 vs $1.25 per 1M input)
- •Step 3.5 Flash 2603 is faster
| GPT-5.1 | Step 3.5 Flash 2603 | |
|---|---|---|
| Intelligence index | 89 | 82.6 |
| Developer | OpenAI | StepFun |
| Type | LLM | LLM |
| Access | API only | — |
| Context window | 400,000 tokens | — |
| Input price | $1.25 / 1M | $0.00 / 1M |
| Output price | $10.00 / 1M | $0.00 / 1M |
| Speed | 115 tok/s | 197 tok/s |
| Released | November 12, 2025 | April 2, 2026 |
| Parameters | — | — |
| Input modalities | Text, Image | — |
| Output modalities | Text | — |
Shared benchmarks
GPT-5.1
Step 3.5 Flash 2603
GPQA Diamond
88.1
82.6
Humanity’s Last Exam
26.5
22.6