# Step 3.5 Flash (196B)

> Throughput-oriented MoE model that stays competitive with much larger DeepSeek-style systems.

| Property | Value |
| --- | --- |
| Lab | StepFun (China) |
| Released | 2026-02-01 |
| Decoder type | Sparse MoE |
| Family | Sparse MoE |
| Scale | 196B total, 11B active (5.6% active) |
| Context window | 262,144 tokens |
| Attention | GQA with 3:1 sliding-window attention |
| Layer mix | 36 sliding-window + 12 global |
| KV cache / token (bf16) | 192 KiB (High) |
| License | Apache License 2.0 |

**Key detail:** Uses MTP-3 during both training and inference for unusually high throughput.

## Architecture concepts

- [Grouped-Query Attention (GQA)](https://llm-atlas-7or.pages.dev/concepts/gqa.md): Several query heads share one key/value head, shrinking the KV cache with little quality loss.
- [Sliding Window Attention (SWA)](https://llm-atlas-7or.pages.dev/concepts/swa.md): Some layers only attend to a local window of recent tokens instead of the whole context.
- [Mixture of Experts (MoE)](https://llm-atlas-7or.pages.dev/concepts/moe.md): Many feed-forward experts, but a router sends each token to only a few of them.
- [Multi-Token Prediction (MTP)](https://llm-atlas-7or.pages.dev/concepts/mtp.md): Extra heads learn to predict several future tokens, and can draft tokens at inference.

## Benchmark (Artificial Analysis Intelligence Index)

- AA Intelligence Index v4.3.2: total 17 (Scientific 13.4)

## Links

- Architecture diagram: https://sebastianraschka.com/llm-architecture-gallery/images/architectures/step-3-5-flash-196b.webp
- View in article: https://magazine.sebastianraschka.com/p/a-dream-of-spring-for-open-weight#%C2%A73-stepfuns-step-35-flash-good-performance-at-great-tokens-sec-throughput
- config.json: https://huggingface.co/stepfun-ai/Step-3.5-Flash/blob/main/config.json
- Tech report: https://arxiv.org/pdf/2602.10604
- Source card (source of truth): https://sebastianraschka.com/llm-architecture-gallery/#card-step-3-5-flash-196b
- Web page: https://llm-atlas-7or.pages.dev/models/step-3-5-flash-196b/
- JSON: https://llm-atlas-7or.pages.dev/api/models/step-3-5-flash-196b.json

_Data from Sebastian Raschka's LLM Architecture Gallery (https://sebastianraschka.com/llm-architecture-gallery/). Synced 2026-11-04._