StepFun 3.5 Flash
StepFun
Step 3.5 Flash is an open-source reasoning model by StepFun with 196B total parameters (11B active) using Mixture of Experts. It features a 256K context window, deep reasoning, tool calling, and agentic capabilities, achieving 97.3 on AIME 2025 and 74.4% on SWE-bench Verified.
- Language
- Reasoning
- Tool use
- Implicit caching
- Vision
- Context
- 262K
- Max output
- 262K
- Input / 1M
- $0.090
- Output / 1M
- $0.300
Quickstart
Point any OpenAI-compatible client at Maxynetic Systems and pass stepfun/step-3.5-flash as the model.
curl https://api.maxynetic.com/v1/chat/completions \
-H "Authorization: Bearer $MAXYNETIC_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "stepfun/step-3.5-flash",
"messages": [{ "role": "user", "content": "Explain routing in one line." }]
}'Pricing
Billed per token with no markup on the underlying provider rate.
Input
Per 1M prompt tokens
$0.090
Output
Per 1M completion tokens
$0.300
Cache read
Per 1M cached prompt tokens
$0.020
A 1M-token prompt with 250K tokens of output costs about $0.165.