StepFun opens API for Step 5 Preview, weights due 15 October
single source· 1 articles · confidence: medium · first seen 2026-09-21 06:37 UTC
What this means for you
If you buy long-context inference for agent work, the endpoint is live now at $1.00 in and $2.70 out per million tokens, with weights promised on 15 October. Nothing has been published to test it against, so the pricing is the only claim you can verify today — benchmark it on your own tasks before moving anything over.
StepFun has put Step 5 Preview into its API at $1.00 per million input tokens and $2.70 per million output tokens. It is a mixture-of-experts model (only a slice of the network runs on each token, so serving it costs less than its 600B parameters suggest), with 27B parameters active per token and a one-million-token context window. It accepts text, images and video, and StepFun is aiming it at long-running agent tasks in software engineering, professional knowledge work and finance. Open weights are scheduled for 15 October 2026. No evaluation results or benchmark scores accompany the launch.
Key facts
- ·Step 5 Preview has 600B total parameters and 27B active per token source
- ·It supports a 1M-token context window and accepts text, image and video input source
- ·API pricing is $1.00 per 1M input tokens and $2.70 per 1M output tokens source
- ·Open weights are scheduled for release on 15 October 2026 source
- ·StepFun says the model targets software engineering, professional knowledge work and finance source
What the sources say
- MarkTechPost — Launch write-up carrying the parameter count, pricing and weight-release date, with no evaluation results.
Sources
The original reporting. Follow these — they did the work.