Stepfun Step 5 Preview (LLM): On AA Pareto frontier

Stepfun's Step 5 Preview is a reasoning-capable language model that ranks among the top performers on the Artificial Analysis Intelligence Index with a score of 44, significantly above the median of 25. The model offers competitive pricing at $1.00 per 1M input tokens and $2.70 per 1M output tokens, positioning it favorably on the price-to-performance frontier compared to similar models. It supports text and image inputs with a 1M token context window and generated notably verbose outputs during evaluation.