Step 3.5 Flash
Step 3.5 Flash is an open-source reasoning model by StepFun with 196B total parameters (11B active) using Mixture of Experts.
text + image → text · made by StepFun
Sold by 9 ways
| Seller | Lane | Rate |
|---|---|---|
| StepFun api | standard | $0.1per Mtok in$0.31per Mtok out$0.021per Mtok cachedplatform.stepfun.com · read 2026-08-25 |
| DeepInfra aggregator | standard | $0.09per Mtok in$0.3per Mtok outapi.deepinfra.com · read 2026-08-25 |
| Vercel AI Gateway aggregator | standard | $0.09per Mtok in$0.3per Mtok out$0.02per Mtok cachedai-gateway.vercel.sh · read 2026-08-25 |
| ElectronHub aggregator | standard | $0.1per Mtok in$0.3per Mtok outapi.electronhub.ai · read 2026-09-16 |
| Hugging Face Inference Providers 2 ways | $0.1per Mtok in$0.3per Mtok out | |
| Hugging Face Inference Providers aggregator | standard | $0.1per Mtok in$0.3per Mtok outmodels.dev · read 2026-09-16 |
| Hugging Face Inference Providers aggregator | deepinfra | $0.1per Mtok in$0.3per Mtok outrouter.huggingface.co · read 2026-08-25 |
| Nous Research aggregator | standard | $0.1per Mtok in$0.3per Mtok outinference-api.nousresearch.com · read 2026-09-12 |
| OpenRouter aggregator | standard | $0.1per Mtok in$0.3per Mtok outopenrouter.ai · read 2026-08-24 |
| SiliconFlow aggregator | standard | $0.1per Mtok in$0.3per Mtok outmodels.dev · read 2026-09-16 |
Measured 2 standings
| Place | Board | Metric | Score |
|---|---|---|---|
| 3rdof 61 | AIME 2025 | Accuracy (± 95% CI) | 98.33 |
| 6thof 32 | AIME 2026 | Accuracy (± 95% CI) | 96.67 |
About
Step 3.5 Flash — a text model from StepFun, sold by 8 companies from $0.09 in and $0.3 out per million tokens, placed 3rd of 61 on AIME 2025.
It takes text and images and returns text, with a context window of 262,114 tokens. It was published in January 2026, trained on material up to January 2025. Its sellers say it can reason step by step and call a tool. The catalogue files it under reasoning. Eight companies sell it. The cheapest is $0.09 in and $0.3 out per million tokens at DeepInfra. Beside the standard rate there is a separately routed lane. It has been measured on 2 boards, and stands best at 3rd of 61 on AIME 2025.
Every current figure
- Maker
- StepFun
- Register
- model
- Takes
- text + image
- Returns
- text
- Context
- 262,114 tokens
- Longest answer
- 262,000 tokens
- Published
- January 2026
- Knowledge to
- January 2025
- Parameters
- 199 billion
- Licence
- not read
- Sellers
- 8
- Price
- $0.09 in and $0.3 out per million tokens — DeepInfra
- Boards
- 2
- Best place
- 3rd of 61 — AIME 2025
Known as 4 names
stepfun-ai/Step-3.5-Flashstepfun/step-3.5-flashstep-3.5-flashstep-3.5-flash-2603