> StepFun has 4 models on The Model Index, from Step 3 (Jul 2025) to Step 5 Preview (18 Sep 2026). Its strongest is Step 5 Preview, with an estimated index score of ~175 (GPT-4 = 100). 3 have open weights. [Models](https://themodelindex.org/models/) /[Labs](https://themodelindex.org/labs/) / StepFun Lab · 4 models · since Jul 2025 # StepFun StepFun has 4 models on The Model Index, from Step 3 (Jul 2025) to Step 5 Preview (18 Sep 2026). Its strongest is Step 5 Preview, with an estimated index score of ~175 (GPT-4 = 100). 3 have open weights. 4 models tracked 3 open · 1 closed ~175 index score of Step 5 Preview estimate · not yet independently tested 18 Sep 2026 latest release Step 5 Preview 2 current versions 2 replaced by newer ones ## Every model · newest first | | MODEL | RELEASED | WEIGHTS | INDEX SCORE | INPUT $/M | OUTPUT $/M | CONTEXT | | --- | --- | --- | --- | --- | --- | --- | --- | | | [Step 5 Preview](https://themodelindex.org/models/step-5-preview/) | 18 Sep 2026 | CLOSED | ~175 | – | – | – | | | [Step 3.7 Flash](https://themodelindex.org/models/step-3-7-flash/) | 29 May 2026 | OPEN | not scored yet | $0.20 | $1.15 | 262K | | | [Step 3.5 Flash replaced](https://themodelindex.org/models/step-3-5-flash/) | 2 Feb 2026 | OPEN | not scored yet | $0.10 | $0.30 | 262K | | | [Step 3 replaced](https://themodelindex.org/models/step-3/) | 25 Jul 2025 | OPEN | not scored yet | – | – | – | Index score is fitted from independent evaluations and scaled so GPT-4 = 100; a striped bar is an estimate for a model not yet independently tested. Prices are list prices per million tokens. ## Release history · 4 announcements [The Race →](https://themodelindex.org/race/) | DATE | RELEASE | KIND | SOURCE | | --- | --- | --- | --- | | 18 Sep 2026 | Step 5 Preview | Flagship | [platform.stepfun.ai ↗](https://platform.stepfun.ai/docs/en/guides/models/step-5-preview) | | 29 May 2026 | Step 3.7 Flash | Open weights | [huggingface.co ↗](https://huggingface.co/stepfun-ai/Step-3.7-Flash) | | 2 Feb 2026 | Step 3.5 Flash | Open weights | [huggingface.co ↗](https://huggingface.co/stepfun-ai/Step-3.5-Flash) | | 25 Jul 2025 | Step 3 | Open weights | no link | Dates come from each lab's own announcement, linked where one exists. --- Source: https://themodelindex.org/labs/stepfun/ · The Model Index · data as of 2026-10-01