# DeepSeek V4.1-Flash (552B)

> Causal encoder-decoder MoE with CSA2 cache sharing, Engram memory, and a million-token context. The figure shows the text backbone.

| Property | Value |
| --- | --- |
| Lab | DeepSeek (China) |
| Released | 2026-09-10 |
| Decoder type | Sparse MoE (causal encoder-decoder) |
| Family | Sparse MoE |
| Scale | 552B backbone + 196B Engram; 8B active prefill, 16B active decode (2.9% of backbone) |
| Context window | 1,048,576 tokens |
| Attention | MLA-style CSA2 + SWA with cross-layer KV and sparse-index reuse |
| Layer mix | 20 encoder + 20 decoder layers; 2 SWA-only + 38 CSA2/SWA |
| KV cache / token (bf16) | 3.125 KiB (Very low) |
| License | MIT License |

**Key detail:** Decoder global KV comes from final encoder states. Single-Pass mHC mixes four residual streams around each attention and MoE sublayer.

## Architecture concepts

- [Manifold-constrained Hyper-Connections (mHC)](https://llm-atlas-7or.pages.dev/concepts/mhc.md): Several parallel residual streams with learned, constrained mixing between them.
- [Cross-Layer KV Sharing (KV sharing)](https://llm-atlas-7or.pages.dev/concepts/kv-sharing.md): Later layers reuse key/value states produced by earlier layers.
- [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.

## Benchmark (Artificial Analysis Intelligence Index)

- AA Intelligence Index v4.3.2: total 39.5 (General 34.3, Scientific 26.8, Coding 39.3, Agents 52.8)

## Links

- Architecture diagram: https://sebastianraschka.com/llm-architecture-gallery/images/architectures/deepseek-v4-1-flash.webp
- config.json: https://huggingface.co/deepseek-ai/DeepSeek-V4.1-Flash/blob/main/config.json
- License: https://huggingface.co/deepseek-ai/DeepSeek-V4.1-Flash/blob/main/LICENSE
- Tech report: https://huggingface.co/deepseek-ai/DeepSeek-V4.1-Flash/blob/main/DeepSeek_V41_Tech_Report.pdf
- Source card (source of truth): https://sebastianraschka.com/llm-architecture-gallery/#card-deepseek-v4-1-flash
- Web page: https://llm-atlas-7or.pages.dev/models/deepseek-v4-1-flash/
- JSON: https://llm-atlas-7or.pages.dev/api/models/deepseek-v4-1-flash.json

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