GPT-5-Nano is the smallest and fastest variant in the GPT-5 system, optimized for developer tools, rapid interactions, and ultra-low latency environments. While limited in reasoning depth compared to its larger counterparts, it retains key …
Model details →OpenAI: GPT-5 Nano vs StepFun: Step 3.5 Flash
OpenAI: GPT-5 Nano wins on 3 of 6 axes — pricing and capability skew in its favour for most workloads.
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token. It is a reasoning model that is incredibly s…
Model details →Side-by-side comparison
| Capability | OpenAI: GPT-5 Nano | StepFun: Step 3.5 Flash | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 400K | 262K | 🏆 OpenAI: GPT-5 Nano |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $0.05 | $0.10 | 🏆 OpenAI: GPT-5 Nano |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $0.40 | $0.30 | 🏆 StepFun: Step 3.5 Flash |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | Yes | — | 🏆 OpenAI: GPT-5 Nano |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | Yes | Yes | Tie |
Frequently asked questions
Is OpenAI: GPT-5 Nano better than StepFun: Step 3.5 Flash?
OpenAI: GPT-5 Nano wins on 3 of 6 axes — pricing and capability skew in its favour for most workloads.
What's the price difference between OpenAI: GPT-5 Nano and StepFun: Step 3.5 Flash?
Input: $0.05 vs $0.10 per 1M tokens. Output: $0.40 vs $0.30 per 1M tokens.
What context windows do OpenAI: GPT-5 Nano and StepFun: Step 3.5 Flash support?
OpenAI: GPT-5 Nano supports up to 400K tokens. StepFun: Step 3.5 Flash supports up to 262K tokens.
Do both OpenAI: GPT-5 Nano and StepFun: Step 3.5 Flash support tool calling?
OpenAI: GPT-5 Nano: yes. StepFun: Step 3.5 Flash: yes.