StepFun: Step 3.5 Flash is StepFun's model. Its measured tokenizer sits with the DeepSeek group, which is evidence that it builds on the DeepSeek tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against StepFun's authorship of the model itself.
StepFun's own Step-3 repository ships a tokenizer behaviourally identical to DeepSeek-V3's: run over the 50 strings offline the two agree on every one, and both declare a 128,815-entry vocabulary. The endpoint's counts match as well, so this model sitting in the DeepSeek signature group is genuine lineage reuse by StepFun, not a serving artefact.
StepFun step3 repository (config.json: vocab_size 128815)DeepSeek-V3 repository (config.json: vocab_size 129280; tokenizer table shared)
| Signal | Result | Reference |
|---|---|---|
| Tokenizer signature | Exact match with 9 other models | tk_73c4f0dc |
| API surface | No other entry shares this exact contract | api_b9b93634 |
| Context and output | 262,144 context · 65,536 max output | declared |
| Reasoning contract | Mandatory | declared |
| Serving providers observed | SiliconFlow | measured 21 August 2026 |
Click a row to open the full comparison.
An x marks a row excluded as corrupt (caching or provider interference detected during measurement). Overhead subtracted: 12 prompt tokens.
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token....
Supported parameters
frequency_penaltyinclude_reasoningmax_tokensreasoningtemperaturetool_choicetoolstop_ktop_p
defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}
Cite this page as the evidence record for StepFun: Step 3.5 Flash: the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings. The raw data behind every figure is on the data page.
