[Wan 2.2 LoRA] add support for 2nd transformer lora loading + wan 2.2 lightx2v lora (#12074)

* add alpha

* load into 2nd transformer

* Update src/diffusers/loaders/lora_conversion_utils.py
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

* Update src/diffusers/loaders/lora_conversion_utils.py
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

* pr comments

* pr comments

* pr comments

* fix

* fix

* Apply style fixes

* fix copies

* fix

* fix copies

* Update src/diffusers/loaders/lora_pipeline.py
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

* revert change

* revert change

* fix copies

* up

* fix

---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: linoy <linoy@hf.co>

docs/source/en/api/pipelines/wan.md

@@ -333,6 +333,8 @@ The general rule of thumb to keep in mind when preparing inputs for the VACE pip
 
 - Wan 2.1 and 2.2 support using [LightX2V LoRAs](https://huggingface.co/Kijai/WanVideo_comfy/tree/main/Lightx2v) to speed up inference. Using them on Wan 2.2 is slightly more involed. Refer to [this code snippet](https://github.com/huggingface/diffusers/pull/12040#issuecomment-3144185272) to learn more.
 
+- Wan 2.2 has two denoisers. By default, LoRAs are only loaded into the first denoiser. One can set `load_into_transformer_2=True` to load LoRAs into the second denoiser. Refer to [this](https://github.com/huggingface/diffusers/pull/12074#issue-3292620048) and [this](https://github.com/huggingface/diffusers/pull/12074#issuecomment-3155896144) examples to learn more.
+
 ## WanPipeline
 
 [[autodoc]] WanPipeline

src/diffusers/loaders/lora_base.py

@@ -754,7 +754,11 @@ class LoraBaseMixin:
         # Decompose weights into weights for denoiser and text encoders.
         _component_adapter_weights = {}
         for component in self._lora_loadable_modules:
-            model = getattr(self, component)
+            model = getattr(self, component, None)
+            # To guard for cases like Wan. In Wan2.1 and WanVace, we have a single denoiser.
+            # Whereas in Wan 2.2, we have two denoisers.
+            if model is None:
+                continue
 
             for adapter_name, weights in zip(adapter_names, adapter_weights):
                 if isinstance(weights, dict):

src/diffusers/loaders/lora_conversion_utils.py

@@ -1833,6 +1833,17 @@ def _convert_non_diffusers_wan_lora_to_diffusers(state_dict):
         k.startswith("time_projection") and k.endswith(".weight") for k in original_state_dict
     )
 
+    def get_alpha_scales(down_weight, alpha_key):
+        rank = down_weight.shape[0]
+        alpha = original_state_dict.pop(alpha_key).item()
+        scale = alpha / rank  # LoRA is scaled by 'alpha / rank' in forward pass, so we need to scale it back here
+        scale_down = scale
+        scale_up = 1.0
+        while scale_down * 2 < scale_up:
+            scale_down *= 2
+            scale_up /= 2
+        return scale_down, scale_up
+
     for key in list(original_state_dict.keys()):
         if key.endswith((".diff", ".diff_b")) and "norm" in key:
             # NOTE: we don't support this because norm layer diff keys are just zeroed values. We can support it
@@ -1852,15 +1863,26 @@ def _convert_non_diffusers_wan_lora_to_diffusers(state_dict):
     for i in range(min_block, max_block + 1):
         # Self-attention
         for o, c in zip(["q", "k", "v", "o"], ["to_q", "to_k", "to_v", "to_out.0"]):
-            original_key = f"blocks.{i}.self_attn.{o}.{lora_down_key}.weight"
-            converted_key = f"blocks.{i}.attn1.{c}.lora_A.weight"
-            if original_key in original_state_dict:
-                converted_state_dict[converted_key] = original_state_dict.pop(original_key)
+            alpha_key = f"blocks.{i}.self_attn.{o}.alpha"
+            has_alpha = alpha_key in original_state_dict
+            original_key_A = f"blocks.{i}.self_attn.{o}.{lora_down_key}.weight"
+            converted_key_A = f"blocks.{i}.attn1.{c}.lora_A.weight"
 
-            original_key = f"blocks.{i}.self_attn.{o}.{lora_up_key}.weight"
-            converted_key = f"blocks.{i}.attn1.{c}.lora_B.weight"
-            if original_key in original_state_dict:
-                converted_state_dict[converted_key] = original_state_dict.pop(original_key)
+            original_key_B = f"blocks.{i}.self_attn.{o}.{lora_up_key}.weight"
+            converted_key_B = f"blocks.{i}.attn1.{c}.lora_B.weight"
+
+            if has_alpha:
+                down_weight = original_state_dict.pop(original_key_A)
+                up_weight = original_state_dict.pop(original_key_B)
+                scale_down, scale_up = get_alpha_scales(down_weight, alpha_key)
+                converted_state_dict[converted_key_A] = down_weight * scale_down
+                converted_state_dict[converted_key_B] = up_weight * scale_up
+
+            else:
+                if original_key_A in original_state_dict:
+                    converted_state_dict[converted_key_A] = original_state_dict.pop(original_key_A)
+                if original_key_B in original_state_dict:
+                    converted_state_dict[converted_key_B] = original_state_dict.pop(original_key_B)
 
             original_key = f"blocks.{i}.self_attn.{o}.diff_b"
             converted_key = f"blocks.{i}.attn1.{c}.lora_B.bias"
@@ -1869,15 +1891,24 @@ def _convert_non_diffusers_wan_lora_to_diffusers(state_dict):
 
         # Cross-attention
         for o, c in zip(["q", "k", "v", "o"], ["to_q", "to_k", "to_v", "to_out.0"]):
-            original_key = f"blocks.{i}.cross_attn.{o}.{lora_down_key}.weight"
-            converted_key = f"blocks.{i}.attn2.{c}.lora_A.weight"
-            if original_key in original_state_dict:
-                converted_state_dict[converted_key] = original_state_dict.pop(original_key)
-
-            original_key = f"blocks.{i}.cross_attn.{o}.{lora_up_key}.weight"
-            converted_key = f"blocks.{i}.attn2.{c}.lora_B.weight"
-            if original_key in original_state_dict:
-                converted_state_dict[converted_key] = original_state_dict.pop(original_key)
+            alpha_key = f"blocks.{i}.cross_attn.{o}.alpha"
+            has_alpha = alpha_key in original_state_dict
+            original_key_A = f"blocks.{i}.cross_attn.{o}.{lora_down_key}.weight"
+            converted_key_A = f"blocks.{i}.attn2.{c}.lora_A.weight"
+
+            original_key_B = f"blocks.{i}.cross_attn.{o}.{lora_up_key}.weight"
+            converted_key_B = f"blocks.{i}.attn2.{c}.lora_B.weight"
+
+            if original_key_A in original_state_dict:
+                down_weight = original_state_dict.pop(original_key_A)
+                converted_state_dict[converted_key_A] = down_weight
+            if original_key_B in original_state_dict:
+                up_weight = original_state_dict.pop(original_key_B)
+                converted_state_dict[converted_key_B] = up_weight
+            if has_alpha:
+                scale_down, scale_up = get_alpha_scales(down_weight, alpha_key)
+                converted_state_dict[converted_key_A] *= scale_down
+                converted_state_dict[converted_key_B] *= scale_up
 
             original_key = f"blocks.{i}.cross_attn.{o}.diff_b"
             converted_key = f"blocks.{i}.attn2.{c}.lora_B.bias"
@@ -1886,15 +1917,24 @@ def _convert_non_diffusers_wan_lora_to_diffusers(state_dict):
 
         if is_i2v_lora:
             for o, c in zip(["k_img", "v_img"], ["add_k_proj", "add_v_proj"]):
-                original_key = f"blocks.{i}.cross_attn.{o}.{lora_down_key}.weight"
-                converted_key = f"blocks.{i}.attn2.{c}.lora_A.weight"
-                if original_key in original_state_dict:
-                    converted_state_dict[converted_key] = original_state_dict.pop(original_key)
-
-                original_key = f"blocks.{i}.cross_attn.{o}.{lora_up_key}.weight"
-                converted_key = f"blocks.{i}.attn2.{c}.lora_B.weight"
-                if original_key in original_state_dict:
-                    converted_state_dict[converted_key] = original_state_dict.pop(original_key)
+                alpha_key = f"blocks.{i}.cross_attn.{o}.alpha"
+                has_alpha = alpha_key in original_state_dict
+                original_key_A = f"blocks.{i}.cross_attn.{o}.{lora_down_key}.weight"
+                converted_key_A = f"blocks.{i}.attn2.{c}.lora_A.weight"
+
+                original_key_B = f"blocks.{i}.cross_attn.{o}.{lora_up_key}.weight"
+                converted_key_B = f"blocks.{i}.attn2.{c}.lora_B.weight"
+
+                if original_key_A in original_state_dict:
+                    down_weight = original_state_dict.pop(original_key_A)
+                    converted_state_dict[converted_key_A] = down_weight
+                if original_key_B in original_state_dict:
+                    up_weight = original_state_dict.pop(original_key_B)
+                    converted_state_dict[converted_key_B] = up_weight
+                if has_alpha:
+                    scale_down, scale_up = get_alpha_scales(down_weight, alpha_key)
+                    converted_state_dict[converted_key_A] *= scale_down
+                    converted_state_dict[converted_key_B] *= scale_up
 
                 original_key = f"blocks.{i}.cross_attn.{o}.diff_b"
                 converted_key = f"blocks.{i}.attn2.{c}.lora_B.bias"
@@ -1903,15 +1943,24 @@ def _convert_non_diffusers_wan_lora_to_diffusers(state_dict):
 
         # FFN
         for o, c in zip(["ffn.0", "ffn.2"], ["net.0.proj", "net.2"]):
-            original_key = f"blocks.{i}.{o}.{lora_down_key}.weight"
-            converted_key = f"blocks.{i}.ffn.{c}.lora_A.weight"
-            if original_key in original_state_dict:
-                converted_state_dict[converted_key] = original_state_dict.pop(original_key)
-
-            original_key = f"blocks.{i}.{o}.{lora_up_key}.weight"
-            converted_key = f"blocks.{i}.ffn.{c}.lora_B.weight"
-            if original_key in original_state_dict:
-                converted_state_dict[converted_key] = original_state_dict.pop(original_key)
+            alpha_key = f"blocks.{i}.{o}.alpha"
+            has_alpha = alpha_key in original_state_dict
+            original_key_A = f"blocks.{i}.{o}.{lora_down_key}.weight"
+            converted_key_A = f"blocks.{i}.ffn.{c}.lora_A.weight"
+
+            original_key_B = f"blocks.{i}.{o}.{lora_up_key}.weight"
+            converted_key_B = f"blocks.{i}.ffn.{c}.lora_B.weight"
+
+            if original_key_A in original_state_dict:
+                down_weight = original_state_dict.pop(original_key_A)
+                converted_state_dict[converted_key_A] = down_weight
+            if original_key_B in original_state_dict:
+                up_weight = original_state_dict.pop(original_key_B)
+                converted_state_dict[converted_key_B] = up_weight
+            if has_alpha:
+                scale_down, scale_up = get_alpha_scales(down_weight, alpha_key)
+                converted_state_dict[converted_key_A] *= scale_down
+                converted_state_dict[converted_key_B] *= scale_up
 
             original_key = f"blocks.{i}.{o}.diff_b"
             converted_key = f"blocks.{i}.ffn.{c}.lora_B.bias"

src/diffusers/loaders/lora_pipeline.py

@@ -5065,7 +5065,7 @@ class WanLoraLoaderMixin(LoraBaseMixin):
     Load LoRA layers into [`WanTransformer3DModel`]. Specific to [`WanPipeline`] and `[WanImageToVideoPipeline`].
     """
 
-    _lora_loadable_modules = ["transformer"]
+    _lora_loadable_modules = ["transformer", "transformer_2"]
     transformer_name = TRANSFORMER_NAME
 
     @classmethod
@@ -5270,9 +5270,29 @@ class WanLoraLoaderMixin(LoraBaseMixin):
         if not is_correct_format:
             raise ValueError("Invalid LoRA checkpoint.")
 
+        load_into_transformer_2 = kwargs.pop("load_into_transformer_2", False)
+        if load_into_transformer_2:
+            if not hasattr(self, "transformer_2"):
+                raise AttributeError(
+                    f"'{type(self).__name__}' object has no attribute transformer_2"
+                    "Note that Wan2.1 models do not have a transformer_2 component."
+                    "Ensure the model has a transformer_2 component before setting load_into_transformer_2=True."
+                )
             self.load_lora_into_transformer(
                 state_dict,
-            transformer=getattr(self, self.transformer_name) if not hasattr(self, "transformer") else self.transformer,
+                transformer=self.transformer_2,
+                adapter_name=adapter_name,
+                metadata=metadata,
+                _pipeline=self,
+                low_cpu_mem_usage=low_cpu_mem_usage,
+                hotswap=hotswap,
+            )
+        else:
+            self.load_lora_into_transformer(
+                state_dict,
+                transformer=getattr(self, self.transformer_name)
+                if not hasattr(self, "transformer")
+                else self.transformer,
                 adapter_name=adapter_name,
                 metadata=metadata,
                 _pipeline=self,
@@ -5668,9 +5688,29 @@ class SkyReelsV2LoraLoaderMixin(LoraBaseMixin):
         if not is_correct_format:
             raise ValueError("Invalid LoRA checkpoint.")
 
+        load_into_transformer_2 = kwargs.pop("load_into_transformer_2", False)
+        if load_into_transformer_2:
+            if not hasattr(self, "transformer_2"):
+                raise AttributeError(
+                    f"'{type(self).__name__}' object has no attribute transformer_2"
+                    "Note that Wan2.1 models do not have a transformer_2 component."
+                    "Ensure the model has a transformer_2 component before setting load_into_transformer_2=True."
+                )
             self.load_lora_into_transformer(
                 state_dict,
-            transformer=getattr(self, self.transformer_name) if not hasattr(self, "transformer") else self.transformer,
+                transformer=self.transformer_2,
+                adapter_name=adapter_name,
+                metadata=metadata,
+                _pipeline=self,
+                low_cpu_mem_usage=low_cpu_mem_usage,
+                hotswap=hotswap,
+            )
+        else:
+            self.load_lora_into_transformer(
+                state_dict,
+                transformer=getattr(self, self.transformer_name)
+                if not hasattr(self, "transformer")
+                else self.transformer,
                 adapter_name=adapter_name,
                 metadata=metadata,
                 _pipeline=self,