AI
StepFun tips its 600bn-parameter Step 5 into the open-weight pool
Chinese lab StepFun is publishing the open weights for Step 5 Preview, a 600-billion-parameter sparse mixture-of-experts model with a one-million-token context window. The model had been API-only since its September launch, priced at one dollar per million input tokens. Releasing the weights places it alongside DeepSeek and Alibaba's Qwen line in a run of large open-weight Chinese releases that holds down closed-model API prices and lets developers fine-tune the model on their own hardware.