Step 3.5 Flash

ChatInput: TextReleased Jan 29, 2026

Built by StepFun · China · stepfun.com

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....

How to use

model: "stepfun/step-3.5-flash"

Cap quality here and save

Hard questions go to this model, easy ones drop to something cheaper. Set a savings target (0–0.8) and the router tunes itself until realized savings converge on it.

{
  "model": "celon/auto",
  "celon": {
    "anchor": "stepfun/step-3.5-flash",
    "savings_target": 0.4
  }
}

Naming a model directly gets you that model — savings controls don't apply.

Context

262K

Max output

66K

Input $/1M

$0.09

Output $/1M

$0.30

Features

Tool calling

Serving providers

DeepInfra

Providers

Price, latency, and uptime per provider serving this model. Celon routes each request to the fastest and cheapest of them. Click a row for regions and data policies.

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Performance

Measured latency (lower is better) and throughput (higher is better) per provider.

Speed

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