Model Overview & Capabilities
Step 5 Preview is a frontier artificial intelligence model engineered by StepFun, officially verified in May 2026 and evaluated on the Artificial Analysis Intelligence Index v4.3 with an overall score of 44.0. Architected as a proprietary API service, the system operates across a context window of 1000k tokens, allowing enterprise developer agents and autonomous code evaluation tools to ingest comprehensive repository structures, cross-language modules, and multi-layered documentation hierarchies without degradation of semantic coherence.
Under standardized software engineering benchmarks—including SWE-bench Verified, Terminal-Bench 2.0, Aider Polyglot, and LiveCodeBench—Step 5 Preview exhibits rigorous multi-step problem solving, deterministic SEARCH/REPLACE diff compliance, and robust tool-use navigation in sandboxed execution environments. Its reasoning capabilities are calibrated to minimize hallucination rates while handling complex syntax transformations, boundary conditions, and continuous integration workflows.
Economically and operationally, Step 5 Preview generates output tokens at a median throughput of 100 tokens per second, with an observed initial latency of 2960 milliseconds. Artificial Analysis rates its estimated cost per task at $0.71 USD, backed by an API token pricing structure of $0.8 per million input tokens and $2.4 per million output tokens (resulting in an effective blended rate of $1.2 per million tokens).