✨ [llm][npu][quant] Add W4A4 MXFP4 quantization support for Qwen3 Dense on Ascend NPU (#23795)

docs_new/docs/advanced_features/quantization.mdx

@@ -46,8 +46,8 @@ The following table summarizes quantization method support across NVIDIA and AMD
       <td><code>mxfp4</code></td>
       <td>Yes</td>
       <td>Yes</td>
-      <td>WIP</td>
-      <td>Requires CDNA3/CDNA4 with MXFP support; uses Aiter</td>
+      <td>Yes (A5)</td>
+      <td>On GPU: requires CDNA3/CDNA4 with MXFP support (uses Aiter). On Ascend NPU (A5): W4A4 MXFP4 for Qwen3 dense LLM (MXFP4 weights + activations) — online uses dual-level MXFP4, offline <code>W4A4_MXFP4</code> checkpoints (single-level) are auto-detected via <code>modelslim</code></td>
     </tr>
     <tr>
       <td><code>mxfp8</code></td>

docs_new/docs/hardware-platforms/ascend-npus/ascend_npu_quantization.mdx

@@ -68,6 +68,14 @@ SGLang supports **mix-bits** quantization (independently defines and loads each
       <td><strong style={{color: 'green'}}>√</strong></td>
       <td><strong style={{color: 'red'}}>x</strong></td>
     </tr>
+    <tr>
+      <td><a href="https://github.com/sgl-project/sglang/pull/23795">MXFP4 W4A4</a></td>
+      <td>Linear</td>
+      <td><strong style={{color: 'red'}}>x</strong></td>
+      <td><strong style={{color: 'red'}}>x</strong></td>
+      <td><strong style={{color: 'blue'}}>WIP</strong></td>
+      <td><strong style={{color: 'red'}}>x</strong></td>
+    </tr>
     <tr>
       <td>W4A4 dynamic</td>
       <td>MoE</td>
@@ -377,6 +385,29 @@ python3 -m sglang.launch_server \
 > - The packed-FP4 dtype passed to the NPU ops (`dst_type` / `x2_dtype` / `input_dtype`) must be resolved from `torch_npu.float4_e2m1fn_x2` (an int enum), not the `torch.float4_e2m1fn_x2` dtype object, which recent op-plugin builds reject.
 > - Online and offline share the same kernel path and layout; they differ only in the weight source (RTN at load vs msmodelslim calibration).
 
+**MXFP4 W4A4 for LLM dense models (e.g. Qwen3 / Qwen3.5):**
+
+LLM dense W4A4 (MXFP4 4-bit weights + 4-bit activations) Linear support was added in [PR #23795](https://github.com/sgl-project/sglang/pull/23795). Requires Ascend A5 series (Ascend 950) or newer — the dual-level online path uses the `DualLevelQuantBatchMatmul` op, which A2/A3 lack. On the Ascend NPU backend `--quantization mxfp4` selects this W4A4 path (on GPU the same flag selects the upstream OCP MXFP4 MoE config instead).
+
+- Online W4A4 quantization (BF16/FP16 weights → dual-level MXFP4 at load time):
+
+```bash Command
+python3 -m sglang.launch_server \
+    --model-path Qwen/Qwen3-8B \
+    --quantization mxfp4 \
+    --device npu --attention-backend ascend \
+    --host 0.0.0.0 --port 30000 \
+    --mem-fraction-static 0.8 --tp-size 1
+```
+
+- Offline W4A4 quantization (msmodelslim pre-quantized weights, `W4A4_MXFP4` scheme; no `--quantization` flag needed — auto-detected from `quant_model_description.json`).
+
+> **Implementation Notes:**
+> - **Online** (`NPUDualLevelMXFP4LinearMethod`) uses **dual-level** MXFP4: both weights and activations are quantized with a fine FP8 (E4M3) L0 block scale plus a coarser L1 scale via `npu_dynamic_dual_level_mx_quant`, and the matmul runs via `npu_dual_level_quant_matmul` (weight in FRACTAL_NZ). Dual-level captures per-block dynamic range far better than a single UE8M0 (power-of-2) scale, which is what made an earlier single-level RTN online path degenerate (greedy decoding could loop without emitting EOS).
+> - **Offline** (`ModelSlimMXFP4Scheme` → `NPUSingleLevelMXFP4OfflineLinearMethod`) is **single-level**: msmodelslim's `W4A4_MXFP4` checkpoint ships single-level UE8M0 block scales (block_size = 32), so the matmul runs via `npu_quant_matmul(..., x1_dtype=x2_dtype=torch_npu.float4_e2m1fn_x2, group_sizes=[1, 1, 32])`. The online and offline paths therefore use different matmul kernels — they no longer share the matmul path.
+> - As with W4A8, the packed-FP4 dtype passed to the NPU ops (`dst_type` / `x2_dtype`) must be resolved from `torch_npu.float4_e2m1fn_x2` (an int enum), not the `torch.float4_e2m1fn_x2` dtype object, which recent op-plugin builds reject.
+> - Validated end-to-end on Ascend A5 hardware.
+
 ## Diffusion Model Quantization on Ascend NPU
 
 SGLang-Diffusion supports MXFP8 online and offline quantization for diffusion models (such as Wan2.2) on Ascend NPUs. MXFP8 requires A5; the ModelSlim W8A8/W4A4 schemes work on A2/A3.