Step 3.5 Flash

stepfun-ai/step-3.5-flash

StepFun's most capable open-source reasoning model with visible reasoning traces. Built on a sparse Mixture-of-Experts architecture with 196B total parameters and only 11B active per token, it achieves frontier-level performance in math, logic, and agentic coding while reaching up to 350 tokens/sec. Supports 256K context. NOTE: This model runs via StepFun, which may log and train on your prompts.

Reasoning

Chat with this model Create an API key

Pricing

Includes our margin. Charged per request from your balance.

Input: $0.11 per 1M tokens
Output: $0.33 per 1M tokens
Typical message: $0.00099

Details

Provider: StepFun
Context: 262K tokens
Max output: 66K tokens
Added: Feb 2, 2026

Use it from the API

Replace $HIDE_API_KEY with a key from the Developers page. Base URL https://hide.st/api/v1.

curl https://hide.st/api/v1/chat/completions \
  -H "Authorization: Bearer $HIDE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "stepfun-ai/step-3.5-flash",
    "messages": [
      {"role": "user", "content": "Hello!"}
    ]
  }'

Pricing

Details

Use it from the API

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