stepfun/step-5-previewStep 5 Preview is StepFun’s proprietary AI model, released Sep 18, 2026. It costs $1/M input and $2.70/M output tokens, and handles a 1M-token context window. Its strongest use case is reasoning & knowledge, where it ranks in the 91st percentile of the models Model Beat tracks.
Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters).
Scores on standardized evaluations. Higher is better — and rank shows where Step 5 Preview lands among all models tracked on Model Beat.
Frontier of human expert knowledge
Scientific research coding
Human-rated web development
Step 5 Preview is StepFun's flagship model for agentic work, built on a sparse Mixture-of-Experts architecture (27B active / 600B total parameters).
Step 5 Preview is an AI model developed by StepFun, released Sep 18, 2026.
Step 5 Preview's list price from StepFun is $1 per million input tokens and $2.70 per million output tokens.
Step 5 Preview supports a context window of up to 1M tokens.
On standardized evaluations tracked by Epoch AI, Step 5 Preview scores 58.9% on SciCode, 46.5% on Humanity's Last Exam, 1570 on WebDev Arena.
Step 5 Preview is a proprietary model (API access), available through its provider's API rather than as a downloadable open-weight model.
Benchmark data from Epoch AI (CC BY) and Artificial Analysis; pricing, specs & descriptions from OpenRouter. Data updated Nov 12, 2026.