StepFun: Step 3.5 Flash (free)
Analysis Summary
StepFun’s Step 3.5 Flash is a text model with a 256K context window, tool use, and function calling. Its measured intelligence index is 17, which indicates limited general capability compared with stronger reasoning models. No coding, instruction-following, or agentic benchmark results are included in the supplied data, so those areas remain uncertain.
The large context and tool interface make it a candidate for testing on routine, bounded tasks such as structured text handling or simple tool-assisted operations. Those capabilities do not establish reliability on long-document synthesis or complex multi-step agents. Keep human review and safeguards in place until performance is proven on representative work.
Free access makes it attractive for trials and low-risk volume. Use it where the task is well specified and failure is inexpensive, rather than as a default for high-stakes client workflows.
Assessed September 23, 2026
Editorial notes
Step 3.5 Flash is free, supports tools and function calling, and provides a 256K context window, though its measured intelligence index indicates limited general reasoning.
The DFO score ranks models on the Artificial Analysis Intelligence Index and is refreshed as new models launch. The write-up and verdict are our own. Feedback?
DFO Verdict
Step 3.5 Flash is free, supports tools and function calling, and provides a 256K context window, though its measured intelligence index indicates limited general reasoning.
Benchmarks
Artificial Analysis data refreshed Oct 12, 2026. Arena ratings from the Oct 2, 2026 text leaderboard, with style control.
Artificial Analysis has not published coding or agentic results for StepFun: Step 3.5 Flash (free) yet. Until it does, the model sits below tested models on the Coding and AI Agents lists.
How StepFun: Step 3.5 Flash (free) compares
StepFun: Step 3.5 Flash (free) ranks #146 of 436 AI models we track for overall intelligence. Its 256K-token context window is larger than 60% of the models we list. StepFun: Step 3.5 Flash (free) is currently free to use via OpenRouter.
Dark bar = input · light bar = output, scaled to the priciest peer.
1M tokens ≈ 8 full-length novels or ~2,500 pages of business documents in a single request.
About StepFun: Step 3.5 Flash (free)
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..
Frequently asked questions about StepFun: Step 3.5 Flash (free)
How much does StepFun: Step 3.5 Flash (free) cost?
StepFun: Step 3.5 Flash (free) is currently available for free via OpenRouter.
What is the context window of StepFun: Step 3.5 Flash (free)?
StepFun: Step 3.5 Flash (free) has a context window of 256,000 tokens (256K).
What can StepFun: Step 3.5 Flash (free) do?
StepFun: Step 3.5 Flash (free) supports tool use and function calling.
Who created StepFun: Step 3.5 Flash (free)?
StepFun: Step 3.5 Flash (free) is developed by StepFun and was released on January 29, 2026.