Last refreshed 2026-05-29. Next refresh: weekly.
Why use Step 3.5 Flash on OpenRouter?
OpenRouter offers Step 3.5 Flash with pay-as-you-go pricing at $0.10/1M input tokens. OpenRouter is a multi-provider LLM aggregator offering unified API access to 300+ models from all major labs and emerging providers, with automatic failover for reliability.
Setup recipe
Docs fallbackUse the provider REST API or SDKCreate a provider API keymodel: stepfun/step-3.5-flashstepfun/step-3.5-flashRequest example
stepfun/step-3.5-flash.Gotchas
- Use provider model ID "stepfun/step-3.5-flash", not the LLMReference slug "step-3.5-flash".
Pricing
| Type | Price (per 1M) |
|---|---|
| Input tokens | $0.10 |
| Output tokens | $0.30 |
Capabilities
About Step 3.5 Flash
Step 3.5 Flash is StepFun's most capable open-source foundation model. Its sparse Mixture of Experts architecture activates only 11B of 196B total parameters per token, making it highly efficient at long contexts. Achieves 60.47% on SWE-Bench Verified and 56.2% on SWE-Pro, competing with frontier closed models on agentic coding benchmarks. Supports 256K token context.
FAQ
What does Step 3.5 Flash cost on OpenRouter?
On OpenRouter, Step 3.5 Flash costs $0.1 per 1M input tokens and $0.3 per 1M output tokens.
What is the context window for Step 3.5 Flash on OpenRouter?
Step 3.5 Flash supports a 262k token context window on OpenRouter.
What API model ID do I use for Step 3.5 Flash on OpenRouter?
Use the model ID stepfun/step-3.5-flash when calling OpenRouter's API.
Who created Step 3.5 Flash?
Step 3.5 Flash was created by StepFun as part of the Step model family.
Is Step 3.5 Flash open source?
Step 3.5 Flash is not open source; the seed data lists it as proprietary.