feat: add 4-step Nunchaku variants for Qwen-Lightning models

Add 4-step distilled Nunchaku SVDQuant entries for Qwen-Lightning and
Qwen-Lightning-Edit alongside the existing 8-step variants. Step count
is now shown in the reference name (e.g. "Qwen-Lightning (4-step)").

- Add subfolder parameter to load_qwen_nunchaku to distinguish
  4-step (nunchaku-4step) from 8-step (nunchaku) variants
- Route to correct safetensors: lightningv1.0-4steps vs
  lightningv1.1-8steps for gen, lightningv1.0-4steps vs
  lightningv1.0-8steps for edit
- Strip nunchaku subfolder before pipeline from_pretrained since
  it does not exist in the base HuggingFace repos

data/reference-nunchaku.json

@@ -90,7 +90,7 @@
     "size": 0,
     "date": "2025 June"
   },
-  "Qwen-Lightning Nunchaku SVDQuant": {
+  "Qwen-Lightning (8-step) Nunchaku SVDQuant": {
     "path": "vladmandic/Qwen-Lightning",
     "subfolder": "nunchaku",
     "preview": "vladmandic--Qwen-Lightning.jpg",
@@ -102,6 +102,18 @@
     "size": 0,
     "date": "2025 June"
   },
+  "Qwen-Lightning (4-step) Nunchaku SVDQuant": {
+    "path": "vladmandic/Qwen-Lightning",
+    "subfolder": "nunchaku-4step",
+    "preview": "vladmandic--Qwen-Lightning.jpg",
+    "desc": "Nunchaku SVDQuant quantization of Qwen-Lightning (4-step distilled) transformer with INT4 and SVD rank 128",
+    "skip": true,
+    "nunchaku": ["Model"],
+    "tags": "nunchaku",
+    "extras": "steps: 4",
+    "size": 0,
+    "date": "2025 June"
+  },
   "Qwen-Image-Edit Nunchaku SVDQuant": {
     "path": "Qwen/Qwen-Image-Edit",
     "subfolder": "nunchaku",
@@ -113,7 +125,7 @@
     "size": 0,
     "date": "2025 June"
   },
-  "Qwen-Lightning-Edit Nunchaku SVDQuant": {
+  "Qwen-Lightning-Edit (8-step) Nunchaku SVDQuant": {
     "path": "vladmandic/Qwen-Lightning-Edit",
     "subfolder": "nunchaku",
     "preview": "vladmandic--Qwen-Lightning-Edit.jpg",
@@ -125,6 +137,18 @@
     "size": 0,
     "date": "2025 June"
   },
+  "Qwen-Lightning-Edit (4-step) Nunchaku SVDQuant": {
+    "path": "vladmandic/Qwen-Lightning-Edit",
+    "subfolder": "nunchaku-4step",
+    "preview": "vladmandic--Qwen-Lightning-Edit.jpg",
+    "desc": "Nunchaku SVDQuant quantization of Qwen-Lightning-Edit (4-step distilled editing) transformer with INT4 and SVD rank 128",
+    "skip": true,
+    "nunchaku": ["Model"],
+    "tags": "nunchaku",
+    "extras": "steps: 4",
+    "size": 0,
+    "date": "2025 June"
+  },
   "Qwen-Image-Edit-2509 Nunchaku SVDQuant": {
     "path": "Qwen/Qwen-Image-Edit-2509",
     "subfolder": "nunchaku",

pipelines/model_qwen.py

@@ -37,7 +37,7 @@ def load_qwen(checkpoint_info, diffusers_load_config=None):
         diffusers.pipelines.auto_pipeline.AUTO_INPAINT_PIPELINES_MAPPING["qwen-image"] = diffusers.QwenImageInpaintPipeline
 
     if model_quant.check_nunchaku('Model'):
-        transformer = qwen.load_qwen_nunchaku(repo_id)
+        transformer = qwen.load_qwen_nunchaku(repo_id, subfolder=repo_subfolder)
 
     if 'Qwen-Image-Distill-Full' in repo_id:
         repo_transformer = repo_id
@@ -63,6 +63,8 @@ def load_qwen(checkpoint_info, diffusers_load_config=None):
     text_encoder = generic.load_text_encoder(repo_te, cls_name=transformers.Qwen2_5_VLForConditionalGeneration, load_config=diffusers_load_config)
 
     repo_id, repo_subfolder = qwen.check_qwen_pruning(repo_id, repo_subfolder)
+    if repo_subfolder is not None and repo_subfolder.startswith('nunchaku'):
+        repo_subfolder = None
     pipe = cls_name.from_pretrained(
         repo_id,
         transformer=transformer,

pipelines/qwen/qwen_nunchaku.py

@@ -1,11 +1,12 @@
 from modules import shared, devices
 
 
-def load_qwen_nunchaku(repo_id):
+def load_qwen_nunchaku(repo_id, subfolder=None):
     import nunchaku
     nunchaku_precision = nunchaku.utils.get_precision()
     nunchaku_repo = None
     transformer = None
+    four_step = subfolder is not None and '4step' in subfolder
     try:
         from nunchaku.models.transformers.transformer_qwenimage import NunchakuQwenImageTransformer2DModel
     except Exception:
@@ -14,15 +15,21 @@ def load_qwen_nunchaku(repo_id):
     if 'pruning' in repo_id.lower() or 'distill' in repo_id.lower():
         return None
     elif repo_id.lower().endswith('qwen-image'):
-        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image/svdq-{nunchaku_precision}_r128-qwen-image.safetensors" # r32 vs r128
+        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image/svdq-{nunchaku_precision}_r128-qwen-image.safetensors"
     elif repo_id.lower().endswith('qwen-lightning'):
-        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image/svdq-{nunchaku_precision}_r128-qwen-image-lightningv1.1-8steps.safetensors" # 8-step variant
+        if four_step:
+            nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image/svdq-{nunchaku_precision}_r128-qwen-image-lightningv1.0-4steps.safetensors"
+        else:
+            nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image/svdq-{nunchaku_precision}_r128-qwen-image-lightningv1.1-8steps.safetensors"
     elif repo_id.lower().endswith('qwen-image-edit-2509'):
-        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit-2509/svdq-{nunchaku_precision}_r128-qwen-image-edit-2509.safetensors" # 8-step variant
+        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit-2509/svdq-{nunchaku_precision}_r128-qwen-image-edit-2509.safetensors"
     elif repo_id.lower().endswith('qwen-image-edit'):
-        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit/svdq-{nunchaku_precision}_r128-qwen-image-edit.safetensors" # 8-step variant
+        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit/svdq-{nunchaku_precision}_r128-qwen-image-edit.safetensors"
     elif repo_id.lower().endswith('qwen-lightning-edit'):
-        nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit/svdq-{nunchaku_precision}_r128-qwen-image-edit-lightningv1.0-8steps.safetensors" # 8-step variant
+        if four_step:
+            nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit/svdq-{nunchaku_precision}_r128-qwen-image-edit-lightningv1.0-4steps.safetensors"
+        else:
+            nunchaku_repo = f"nunchaku-ai/nunchaku-qwen-image-edit/svdq-{nunchaku_precision}_r128-qwen-image-edit-lightningv1.0-8steps.safetensors"
     else:
         shared.log.error(f'Load module: quant=Nunchaku module=transformer repo="{repo_id}" unsupported')
     if nunchaku_repo is not None: