Step-3.5-Flash
Support summary
Step-3.5-Flash is a checkpoint published by StepFun, built on the Step3p5ForCausalLM architecture. vLLM 0.28.0, the newest indexed vLLM release, documents support. Official recipes or cookbooks cover SGLang, without pinning a stable release.
vLLM documents support in 20 of 20 indexed releases, from 0.17.0 to 0.28.0.
- Documented hardware
- NVIDIA / CUDA
- Documented quantization
- BF16
- Documented features
- Reasoning parsers, Speculative decoding, Tensor parallelism, and Tool calling
- Configured context
- 262,144 tokens
- License
- apache-2.0
Hardware, quantization and features count only statements about this checkpoint; engine-wide capabilities are listed with each release.
Hugging Face model card
- Publisher
- StepFun
- Task
- text generation
- License
- apache-2.0
- Library
- transformers
- Architecture
- Step3p5ForCausalLM
- Weight tensor elements
- 199.4B
- Tensor types
- BF16, F32
- Configured context
- 262,144 tokens
- Base models
- stepfun-ai/step-3.5-flash
- Weight access
- Public
- Repository created
- 2026-02-01
Model notes and sources
- vLLM v0.28.0 · docs/models/supported_models.md · 20 indexed revisions, v0.17.0 to v0.28.0
- stepfun-ai/Step-3.5-Flash · publisher model card
- stepfun-ai/Step-3.5-Flash · Hugging Face metadata
- stepfun-ai/Step-3.5-Flash · publisher configuration
- vllm · models/stepfun-ai/Step-3.5-Flash.yaml
- sglang · docs/cookbook/autoregressive/StepFun/Step3.5.mdx
- vllm · StepFun/Step-3.5-Flash.md
- Reviewed
Engine support
3 engines
| Engine | Release | Checkpoint support | Evidence scope | Last known supported |
|---|---|---|---|---|
| vLLM | 0.28.0Newest indexed | Checkpoint evidenceSource: vLLM v0.28.0 · docs/models/supported_models.mdReviewed | 0.28.0This release | |
Features, dependencies and evidence for vLLM 0.28.0 | ||||
| SGLang | Version not pinnedRecipe / cookbook | Documented recipeSource 1: sglang · docs/cookbook/autoregressive/StepFun/Step3.5.mdxSource 2: sglang · docs/src/snippets/autoregressive/step-35-deployment.jsxReviewed | No supported release indexed | |
Features, dependencies and evidence for SGLang 0.5.19 | ||||
| TensorRT-LLM | 1.2.1Newest indexed | No matching evidence curated | No supported release indexed | |
Features, dependencies and evidence for TensorRT-LLM 1.2.1 | ||||