Step 5 Preview
#11 in Reasoning ModelsStepfun · v5 · preview · since 20. September 2026 (API-Preview); offene Gewichte geplant für 15. Oktober 2026 · 3× · last seen Sep 22, 2026
Step 5 Preview is StepFun's new flagship reasoning model for agentic work, released as a sparse Mixture-of-Experts model with 600 billion total parameters and roughly 27 billion active parameters per token. It offers a 1-million-token context window and natively processes text, image, and video input, targeting software engineering, professional knowledge work, and finance. The model became available via API on September 20, 2026; open weights are scheduled for October 15, 2026, and no license was officially named at announcement time. On the Artificial Analysis Intelligence Index it scores 44 at very competitive API pricing.
Features
| Key Benchmark (%) | Artificial Analysis Intelligence Index: 44 points |
| Context Window (Tokens) | 1,000,000 tokens |
| License | No license officially named at announcement; planned open weights expected under StepFun Community License (per community Hugging Face mirror) |
| Multimodality | Text, image, and video input (natively supported), text output |
| Platform | StepFun Open Platform API (model id: step-5-preview), OpenAI-compatible API |
| Price per 1M Tokens | $1.00 input (cache miss) / $0.05 input (cache hit) / $2.70 output |
| Release Date | September 20, 2026 (API live); open weights planned for October 15, 2026 |