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

src/diffusers/loaders/lora_conversion_utils.py

@@ -1829,6 +1829,18 @@ 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
@@ -1848,15 +1860,26 @@ 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"
@@ -1865,15 +1888,24 @@ 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"
@@ -1882,15 +1914,24 @@ 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"
@@ -1899,15 +1940,24 @@ 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"
@@ -2072,4 +2122,4 @@ def _convert_non_diffusers_ltxv_lora_to_diffusers(state_dict, non_diffusers_pref
         raise ValueError("Invalid LoRA state dict for LTX-Video.")
     converted_state_dict = {k.removeprefix(f"{non_diffusers_prefix}."): v for k, v in state_dict.items()}
     converted_state_dict = {f"transformer.{k}": v for k, v in converted_state_dict.items()}
-    return converted_state_dict
+    return converted_state_dict

src/diffusers/loaders/lora_pipeline.py

@@ -5064,7 +5064,7 @@ 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
@@ -5269,15 +5269,33 @@ def load_lora_weights(
         if not is_correct_format:
             raise ValueError("Invalid LoRA checkpoint.")
 
-        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,
-            low_cpu_mem_usage=low_cpu_mem_usage,
-            hotswap=hotswap,
-        )
+        load_into_transformer_2 = kwargs.pop("load_into_transformer_2", False)
+        if load_into_transformer_2:
+            if geattr(self, "transformer_2", None) is None:
+                raise ValueError(
+                    "Cannot load LoRA into transformer_2: transformer_2 is not available for this model"
+                    "Ensure the model has a transformer_2 component before setting load_into_transformer_2=True."
+                )
+            self.load_lora_into_transformer(
+                state_dict,
+                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,
+                low_cpu_mem_usage=low_cpu_mem_usage,
+                hotswap=hotswap,
+            )
 
     @classmethod
     # Copied from diffusers.loaders.lora_pipeline.SD3LoraLoaderMixin.load_lora_into_transformer with SD3Transformer2DModel->WanTransformer3DModel