Step 3.5 Flash
Step 3.5 Flash is worth evaluating for long context when its provider route and context window match the workload.
Use it for
- Teams evaluating long context
- Workloads that can use a 256k context window
- Buyers comparing 1 tracked provider route
Do not use it for
- Vision or document-understanding workloads
- Strict JSON or tool-calling flows
- Family
- Step
- Released
- 2026-01-29
- Context
- 256k
- Parameters
- 196B (11B active)
- Architecture
- Mixture of Experts
- Specialization
- general
- Training
- pretrained
Cheapest of 1 route · OpenRouter
About
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.
Step 3.5 Flash is an open-source model in the Step family. The structured metadata tracks a 256k-token context window and reasoning. This page tracks provider routes through OpenRouter, with the cheapest tracked route listed at $0.1 input and $0.3 output per 1M tokens. No headline benchmark score is tracked for Step 3.5 Flash yet.
Top use-case fit
Long context
Included by capability and metadata signals in the decision map.
Provider price ladder
Compare API pricing across 1 providers for input and output tokens, batch, and cached reads when available.
| Provider | Input / 1M | Output / 1M | Route |
|---|---|---|---|
| OpenRouter | $0.100 | $0.300 | Serverless |
Capabilities
Benchmark peer barsfor Long context
No task-mapped benchmark peers are available for this model yet.
Migration checks
No linked migration route is available for this model yet.