How much does Step 3.5 Flash cost?

Step 3.5 Flash costs $0.10/M input tokens and $0.30/M output tokens.

What is the context length of Step 3.5 Flash?

Step 3.5 Flash has a 262,144 token context window. It supports up to 65,536 completion tokens.

Does Step 3.5 Flash support tool calling and structured outputs?

Yes. Step 3.5 Flash accepts tools and tool_choice for function calling. It does not support response_format, so JSON output is not enforced.

Which providers serve Step 3.5 Flash?

Step 3.5 Flash is served by 1 provider on OpenRouter: SiliconFlow.

What other text models does StepFun have?

Step 5 Preview and Step 3.7 Flash are other text models from StepFun.

When was Step 3.5 Flash released?

Step 3.5 Flash was released on January 29, 2026.

StepFun: Step 3.5 Flash

Going away November 15, 2026

stepfun/step-3.5-flash

Model weights

Compare

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. It is a reasoning model that is incredibly speed efficient even at long contexts.

Modalities

In / out price

$0.10 / $0.30per 1M

Context

262K

Released

Jan 29, 2026

Providers

This model is hosted by one provider. OpenRouter forwards every request without routing.

Latency / throughput


	$0.10	$0.30	0.94s	42 tok/s	99.74%

Input $0.10Output $0.30
42 tok/s99.74% uptime

Pricing

The average price customers actually pay for this model, next to the prices providers post. Caching and discounts mean the price actually paid is often well below the listed one.

Weighted average

Input

$0.09992/M tokens

Output

$0.2996/M tokens

Step 3.5 Flash — Price history

Price history

No effective price data for this selection

		$0.0999	$0.300	0.0%	100.0%

Effective in $0.0999Effective out $0.300
Token share
100.0%

Uptime

Uptime is the percentage of the past 3 days that at least one provider was responding to requests. Availability is the percentage of time that inference was successfully served. OpenRouter continuously monitors and uses the next-best provider when one returns an error.

Uptime (3d)

100.00%

Availability (3d)

99.20%

Availability over the last 3 days

Last 72 hours

Availability 99.20%

3 Days Ago2 Days AgoYesterdayNow

Availability over the last 24 hours

OpenRouter Availability

99.20%

When an error occurs in an upstream provider, we can recover by routing to another healthy provider, if your request filters allow it. You can access per-provider uptime data programmatically through the Endpoints API. Learn more about our load balancing and provider routing options.

Benchmarks

Scores on standardized evaluations and this model’s own outputs on shared benchmark prompts. Higher percentages are better — and each rank shows where this model lands among the models evaluated on that source.

Benchmark score summary for StepFun: Step 3.5 Flash (Artificial Analysis)
Source	Benchmark	Score
Artificial Analysis	Step 3.5 Flash 2603 GPQA Diamond	82.6%
Artificial Analysis	Step 3.5 Flash 2603 HLE	24.5%
Artificial Analysis	Step 3.5 Flash 2603 IFBench	66.5%
Artificial Analysis	Step 3.5 Flash 2603 τ²-Bench Telecom	87.4%
Artificial Analysis	Step 3.5 Flash 2603 AA-LCR	63.0%
Artificial Analysis	Step 3.5 Flash 2603 CritPt	2.3%
Artificial Analysis	Step 3.5 Flash 2603 Terminal-Bench Hard	32.6%
Artificial Analysis	Step 3.5 Flash GPQA Diamond	83.1%
Artificial Analysis	Step 3.5 Flash HLE	21.1%
Artificial Analysis	Step 3.5 Flash IFBench	64.6%
Artificial Analysis	Step 3.5 Flash τ²-Bench Telecom	94.4%
Artificial Analysis	Step 3.5 Flash AA-LCR	50.0%
Artificial Analysis	Step 3.5 Flash CritPt	2.5%
Artificial Analysis	Step 3.5 Flash Terminal-Bench Hard	27.3%

Apps

Public apps that send the most traffic to this model. Good signal for what real production workloads look like — and a hint at which use cases this model is best suited for.

OpenClaw

OpenClaw is an open-source AI agent that connects to your messaging apps and takes real actions on your behalf, from running commands and browsing the web to managing files and sending emails.

904Mtokens

Hermes Agent

Hermes Agent is an open-source, self-improving AI agent by Nous Research that runs persistently with memory across sessions, and builds reusable skills from experience. It comes with 40+ built-in tools, including web search, browser automation, and vision, plus scheduled automations and subagents.

529Mtokens

Command Code

new

514Mtokens

G0DM0D3-pliny

new

470Mtokens

Kilo Code

Kilo Code is an open-source AI coding agent that works across VS Code, JetBrains, and CLI to help developers ship code faster with agentic workflows.

307Mtokens

Top 5 Apps

152M

Rest of OpenRouter

115M

Not currently available through EU in-region routing. In-region routing docs

More models from stepfun

Step 5 Preview

Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters). It performs strongly in software engineering and professional knowledge work, with particular strength in finance.

It is designed for extended tasks that span large codebases and documents, using tools and refining results over multiple steps.

Text1M context$1 / $2.70

Step 3.7 Flash

Step 3.7 Flash is StepFun's latest high-efficiency multimodal Mixture-of-Experts model. It pairs a 196B-parameter language backbone with a vision encoder for native image and video understanding, activating roughly 11B parameters per token. The model supports a 256K context window and exposes selectable reasoning levels (high/medium/low), letting callers trade off speed, cost, and depth of reasoning.

Designed for coding, agentic workflows, structured outputs, and long-context productivity tasks.

Text262K context$0.20 / $1.15

StepFun: Step 3.5 Flash

Providers