StepFun: Step 3.5 Flash
Analysis Summary
Step 3.5 Flash from StepFun is a well-rounded model with an intelligence index of 26 and a standout agentic index of 60, placing it ahead of many more expensive models on multi-step task execution. The 262K context window, tool use, and function calling make it capable across a range of business workflows. GPQA of 0.826 and a tau2 score of 0.874 indicate reliable instruction following and task completion.
For businesses, the combination of strong agentic performance and very low pricing ($0.10 input, $0.30 output) makes it attractive for high-volume automation, structured data extraction, and agent pipelines where cost efficiency matters. Long-context reasoning (LCR 0.543) is adequate for mid-length documents. The main limitation is that general reasoning depth sits below the top tier.
This is a strong value pick for agentic and tool-use workflows where budget is a constraint and top-tier reasoning is not required.
Assessed June 30, 2026
Editorial notes
StepFun Step 3.5 Flash delivers strong agentic performance (60 agentic index) and good reasoning at $0.10 input and $0.30 output, with a 262K context and tool use support.
Rankings consider pricing, capabilities, benchmarks, and real-world applicability and are refreshed as new models launch. Feedback?
Performance Profile
How StepFun: Step 3.5 Flash compares
StepFun: Step 3.5 Flash ranks #98 of 385 AI models we track for overall intelligence, #61 of 293 for agentic tasks. Its 262K-token context window is larger than 81% of the models we list. At $0.10 per million input tokens it is cheaper than 67% of comparable models.
About StepFun: Step 3.5 Flash
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..
Capabilities
Benchmark Scores
Intelligence
Technical
Content
Benchmark data from Artificial Analysis and Hugging Face
How does StepFun: Step 3.5 Flash stack up?
Compare side-by-side with other professional models.
Model Information
| OpenRouter ID |
stepfun/step-3.5-flash
|
| Provider | stepfun |
| Release Date | January 29, 2026 |
| Context Length | 262,144 tokens |
| Max Completion | 65,536 tokens |
| Status | Active |
Pricing
| Token Type | Cost per 1M tokens | Cost per 1K tokens |
|---|---|---|
| Input | $0.10 | $0.000100 |
| Output | $0.30 | $0.000300 |
Live Performance
Live endpoint metrics, refreshed every 30 minutes.
Leaderboard Categories
External Resources
Frequently asked questions about StepFun: Step 3.5 Flash
How much does StepFun: Step 3.5 Flash cost?
StepFun: Step 3.5 Flash costs $0.10 per million input tokens and $0.30 per million output tokens.
What is the context window of StepFun: Step 3.5 Flash?
StepFun: Step 3.5 Flash has a context window of 262,144 tokens (262K).
What can StepFun: Step 3.5 Flash do?
StepFun: Step 3.5 Flash supports tool use and function calling.
Who created StepFun: Step 3.5 Flash?
StepFun: Step 3.5 Flash is developed by StepFun and was released on January 29, 2026.
