# Qwen3.5 (397B)

> Mainline Qwen refresh that brings the Next-style hybrid attention into the flagship series.

| Property | Value |
| --- | --- |
| Lab | Alibaba Cloud (China) |
| Released | 2026-02-16 |
| Decoder type | Sparse hybrid |
| Family | Hybrid MoE |
| Scale | 397B total, 17B active (4.3% active) |
| Context window | 262,144 tokens |
| Attention | 3:1 Gated DeltaNet and Gated Attention |
| Layer mix | 15 gated attention + 45 DeltaNet |
| KV cache / token (bf16) | 30 KiB (Low) |
| License | Apache License 2.0 |

**Key detail:** Turns the former Qwen3-Next side branch into the new core design with 512 experts and 17B active parameters.

## Architecture concepts

- [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.
- [Gated Attention (Gated attention)](https://llm-atlas-7or.pages.dev/concepts/gated-attention.md): A learned sigmoid gate scales the attention output before it re-enters the residual stream.
- [Hybrid Attention (Hybrid attention)](https://llm-atlas-7or.pages.dev/concepts/hybrid-attention.md): Mixes cheap linear-attention or state-space layers with a few full-attention layers.

## Benchmark (Artificial Analysis Intelligence Index)

- AA Intelligence Index v4.3.2: total 21.4 (Scientific 10.3)

## Links

- Architecture diagram: https://sebastianraschka.com/llm-architecture-gallery/images/architectures/qwen3-5-397b.webp
- View in article: https://magazine.sebastianraschka.com/p/a-dream-of-spring-for-open-weight#%C2%A78-qwen35-and-the-continuation-of-hybrid-attention
- From scratch: https://github.com/rasbt/LLMs-from-scratch/tree/main/ch05/16_qwen3.5
- config.json: https://huggingface.co/Qwen/Qwen3.5-397B-A17B/blob/main/config.json
- License: https://huggingface.co/Qwen/Qwen3.5-397B-A17B/blob/main/LICENSE
- Source card (source of truth): https://sebastianraschka.com/llm-architecture-gallery/#card-qwen3-5-397b
- Web page: https://llm-atlas-7or.pages.dev/models/qwen3-5-397b/
- JSON: https://llm-atlas-7or.pages.dev/api/models/qwen3-5-397b.json

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