StepFun: Step 3.5 Flash
Analysis Summary
Step 3.5 Flash is StepFun's production Flash model, sitting at an intelligence index of 38.5, which places it in the very strong tier against the broader field. Its agentic index of 60 is respectable, and it pairs tool use with function calling across a 262K context window. Pricing at $0.09 input and $0.30 output per million tokens makes it one of the more cost-efficient benchmarked models at this capability level.
For businesses, it suits mid-complexity automation, structured content generation, and agentic workflows where cost efficiency matters more than frontier-level reasoning. The instruction-following score (ifbench 0.665) and long-context reasoning (lcr 0.543) are adequate for document summarisation and multi-step task pipelines. Coding capability is more limited, with a coding index of 34.6, so it is not the right choice for software engineering agents.
At this price point, Step 3.5 Flash is a practical option for high-volume, mid-complexity business workflows. Teams needing stronger coding or reasoning should look to higher-tier models, but for cost-conscious deployments it offers a strong capability-to-cost ratio.
Assessed June 6, 2026
Editorial notes
StepFun Step 3.5 Flash delivers very strong reasoning for its price tier, with a 262K context window, tool use, function calling, and competitive agentic performance at $0.09 input per million tokens.
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 #68 of 375 AI models we track for overall intelligence, #68 of 312 for coding, #54 of 286 for agentic tasks. Its 262K-token context window is larger than 82% of the models we list. At $0.09 per million input tokens it is cheaper than 68% 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
Performance Indices
Source: Artificial Analysis
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 | 16,384 tokens |
| Status | Active |
Pricing
| Token Type | Cost per 1M tokens | Cost per 1K tokens |
|---|---|---|
| Input | $0.09 | $0.000090 |
| 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 $0.09 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).
Is StepFun: Step 3.5 Flash good for coding?
On our coding benchmark index, StepFun: Step 3.5 Flash ranks #68 of 312 models, placing it in the top quartile of the field for code generation and debugging.
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.
