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. It i

Creator: StepFun
Lifecycle: Active
Context: 256.0K
Max output: 256.0K
Released: Jan 29, 2026
Status: unknown

Input: $0.00 / 1M tokens
Output: $0.00 / 1M tokens
Cached read: — / 1M tokens
Cached write: — / 1M tokens
Batch discount: —%
Source: OpenRouter
Verified: Apr 5, 2026 (High)

Capabilities

Modalities: text→text
Capabilities: reasoningfunctionCalling

Official Links

Intro

https://openrouter.ai/stepfun/step-3.5-flash

Docs

https://openrouter.ai/stepfun/step-3.5-flash

Pricing

https://openrouter.ai/models

Benchmark Coverage

Benchmark	Version	Score	Date	Source	Notes

Release History

Release	Alias	Lifecycle	Release Date	Deprecation	Shutdown	Summary
Step 3.5 Flash	stepfun-step-3-5-flash-free	Active	Jan 29, 2026	—	—	Model available via OpenRouter.

Host Coverage

Host	Type	Context	Pricing Note	Differences
OpenRouter	aggregator	256.0K	$0.00/1M in · $0.00/1M out via OpenRouter	—

Migration Guidance

Change Events

Date	Type	Title	Description	Source
Jan 29, 2026	family_added	Step 3.5 Flash published	Model made available via OpenRouter.	OpenRouter

Other models from StepFun

Step 3.5 Flash