StepFun: Step 3.5 Flash — pricing & benchmarks

By stepfun · Updated 2026-10-06 · Open weights · apache-2.0cheap high-volumestep-by-step reasoningopen weights / self-hostable

What StepFun: Step 3.5 Flash is used for

StepFun: Step 3.5 Flash is best suited for cheap high-volume, step-by-step reasoning, open weights / self-hostable. Access it through one Appmo API key alongside 458 other models — Appmo's optimizer can route to it automatically when it is the best value for a request. Weights: huggingface.co/stepfun-ai/Step-3.5-Flash.

Use it via the Appmo API (OpenAI-compatible)

curl https://appmo.com/v1/chat/completions \
  -H "Authorization: Bearer $APPMO_KEY" \
  -d '{"model":"stepfun/step-3.5-flash","messages":[{"role":"user","content":"Hello"}]}'

FAQ

How much does StepFun: Step 3.5 Flash cost?
StepFun: Step 3.5 Flash costs $0.1 per 1M input tokens and $0.3 per 1M output tokens ($0.15 blended), as of 2026-10-06. Prices are expected to fall as competition increases.

What is StepFun: Step 3.5 Flash best for?
StepFun: Step 3.5 Flash is best suited for cheap high-volume, step-by-step reasoning, open weights / self-hostable.

How do I use StepFun: Step 3.5 Flash?
Send requests to Appmo's OpenAI-compatible endpoint with model id "stepfun/step-3.5-flash" and one API key — no separate provider account needed.

Is StepFun: Step 3.5 Flash open source?
Yes — its weights are public on Hugging Face (stepfun-ai/Step-3.5-Flash) under the apache-2.0 license; check the license terms before commercial use.

Can StepFun: Step 3.5 Flash create images?
No, StepFun: Step 3.5 Flash works with text.