Step 5 Preview | Epoch AI

ECI

N/A

StepFun

Sep. 18, 2026

Closed weights

Step 5 Preview is a closed-weights model from StepFun, released September 18, 2026.

Step 5 Preview vs select alternatives

Domain	Benchmark	Step 5 Preview StepFun Sep. 18, 2026 Closed weights	GPT-6 Astra OpenAI Sep. 3, 2026 Closed weights	Claude Fable 5.1 Anthropic Sep. 1, 2026 Closed weights	Gemini 3.7 Flash Google DeepMind Aug. 13, 2026 Closed weights
Mathematics	ProofBenchBest score 100%	42%	99%	100%	58%
Science	CritPt v1Best score 36%	21%	32%	31%	14%
	SciCodeBest score 67%	59%	56%	63%	60%
Software engineering	Text Arena (Coding)Best score 1820	1570	1800	1758	1587

Model metadata

General
Organization	StepFun
Release date	Sep. 18, 2026
Model accessibility	Closed weights
Country	China
Knowledge cutoff	Unknown
Provider notes	platform.stepfun.ai

Pricing
Input price	$1 / 1M tokens
Output price	$2.70 / 1M tokens

Training
Parameters	6.0e11
Training compute	Unknown
Training hardware	Unknown
Training time	Unknown
Training dataset size	Unknown