According to posts on X, Step 5 Preview is free to use through Cline and OpenCode; several posts specifically describe a week of access on OpenCode. Posts also claim it has a 1M-token context window and multimodal input, but those details have not been independently verified here.
New Runtime has not found an official statement from StepFun confirming the free access or its duration. An official post, product documentation, or a pricing page would help confirm the offer and its terms.