StepFun's Step 5 Preview: 600B MoE, 1M Context, ~1/8 the Cost of Opus 5
Aizkmusic · x · 2026-10-09
Featherless's launch page details StepFun's new flagship Step 5 Preview, with open weights and API access both landing October 15.
- Architecture: sparse MoE with 600B total parameters, 27B active per token; text+image input, text output
- Context: 1M tokens with up to 1M output tokens, aimed at large codebases, cross-file changes, and long multi-step tasks
- Positioning: AI coding, software engineering, and professional knowledge work with notably strong finance results, built for production-grade end-to-end agents
- Pricing: $1/M input and $2.70/M output on StepFun's API; per Artificial Analysis, about 1/8 the cost per task of Claude Opus 5
- Tool calling supported; concurrent unit cost, FP8, and other specs TBA
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