Step3-321B-A38B
A large-scale multimodal foundational model developed by StepFunAI, boasting 3.2 trillion parameters. It supports a context length of 64K and is released under the Apache 2.0 license.
Parameters
3210.0B
Context Window
64K
License
Apache 2.0
Release Date
2025-07-31
API Pricing
API pricing for this model is not yet available
Strengths
- ・Extremely massive 3.2 trillion parameters.
- ・Multimodal capabilities for diverse data.
- ・Open Apache 2.0 license.
Weaknesses
- ・Very large 642GB model size.
- ・Requires extremely high computational resources.
- ・Limited to a 64K context length.
Use Cases
- ・Analysis of large-scale multimodal data.
- ・Complex tasks requiring advanced reasoning.
- ・Open-source model development.
Deep Analysis
Architecture
MoE (321B total, 38B active)
Multimodal reasoning model
Release Date
July 2025
License
Apache 2.0
GitHub Stars
453
stepfun-ai/Step3
Modalities
Text + Image
Multimodal reasoning
Key Innovation
Model-system co-design
Cost-effective decoding
Strengths
- ・Large multimodal reasoning model
- ・Apache 2.0 license
- ・Model-system co-design for cost-effective decoding
- ・38B active parameters for efficiency
- ・Available on AMD Instinct GPUs
Weaknesses
- ・Large total parameter count (321B)
- ・Superseded by Step 3.5 Flash for many tasks
- ・Limited English documentation
Competitor Comparison
| Model | Arena | SWE | GPQA | Price |
|---|---|---|---|---|
| Step 3.5 Flash | - | - | - | Lower |
| GLM-4.5 355B | - | - | - | Comparable |
| DeepSeek V3 | - | - | - | Lower |
Step3-321B is StepFun's large multimodal reasoning model with 321B total and 38B active parameters. Released July 2025 under Apache 2.0, it features model-system co-design for cost-effective decoding and is available on multiple hardware platforms.
Analysis generated: 2026-05-24