step3 API, Fine-Tuning, Deployment

stepfun-ai/step3

Step3 is a cutting-edge multimodal reasoning model from StepFun. It is built on a Mixture-of-Experts (MoE) architecture with 321B total parameters and 38B active parameters. The model is designed end-to-end to minimize decoding costs while delivering top-tier performance in vision-language reasoning. Through the co-design of Multi-Matrix Factorization Attention (MFA) and Attention-FFN Disaggregation (AFD), Step3 maintains exceptional efficiency across both flagship and low-end accelerators. During pretraining, Step3 processed over 20T text tokens and 4T image-text mixed tokens, spanning more than ten languages. The model has achieved state-of-the-art performance for open-source models on various benchmarks, including math, code, and multimodality

API Usage

curl --request POST \
  --url https://api.siliconflow.com/v1/chat/completions \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
    "model": "stepfun-ai/step3",
    "messages": [
      {
        "role": "user",
        "content": "tell me a story"
      }
    ],
    "max_tokens": 65536,
    "min_p": 0.05,
    "temperature": 0.7,
    "top_p": 0.7,
    "top_k": 50,
  }'

Details

Model Provider

stepfun-ai

Type

text

Sub Type

chat

Size

321B

Publish Time

Aug 6, 2025

Input Price

$

0.57

/ M Tokens

Output Price

$

1.42

/ M Tokens

Context length

64K

Tags

MoE,321B,64K

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© 2025 SiliconFlow Technology PTE. LTD.

© 2025 SiliconFlow Technology PTE. LTD.

© 2025 SiliconFlow Technology PTE. LTD.