Step-3.5-Flash-Base-Midtrain

Checkpointstepfun-ai/Step-3.5-Flash-Base-MidtrainModel card indexedModel card

Support summary

Step-3.5-Flash-Base-Midtrain is a checkpoint published by StepFun, built on the Step3p5ForCausalLM architecture. vLLM lists its architecture, but not this exact checkpoint.

License: apache-2.0

Hugging Face model card

Publisher: StepFun
Task: text generation
License: apache-2.0
Library: transformers
Architecture: Step3p5ForCausalLM
Weight tensor elements: 197.8B
Tensor types: F32, BF16
Weight access: Public
Repository created: 2026-03-02

Source 1 Source 2 Source 3Reviewed 2026-09-05

Model notes and sources

Engine support

3 engines

Engine support for Step-3.5-Flash-Base-Midtrain
Engine	Release	Evidence scope	Last known supported
vLLM	`0.28.0`Newest indexed	Architecture listed; exact checkpoint unknown	No supported release indexed
Features, dependencies and evidence for vLLM 0.28.0
SGLang	`0.5.19`Newest indexed	No matching evidence curated	No supported release indexed
Features, dependencies and evidence for SGLang 0.5.19
TensorRT-LLM	`1.2.1`Newest indexed	No matching evidence curated	No supported release indexed
Features, dependencies and evidence for TensorRT-LLM 1.2.1