bugfix: fix chrono-edit context parallel (#12660)

* bugfix: fix chrono-edit context parallel

* bugfix: fix chrono-edit context parallel

* Update src/diffusers/models/transformers/transformer_chronoedit.py
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

* Update src/diffusers/models/transformers/transformer_chronoedit.py
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

* Clean up comments in transformer_chronoedit.py

Removed unnecessary comments regarding parallelization in cross-attention.

* fix style

* fix qc

---------
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

src/diffusers/models/transformers/transformer_chronoedit.py

@@ -67,7 +67,7 @@ def _get_added_kv_projections(attn: "WanAttention", encoder_hidden_states_img: t
     return key_img, value_img
 
 
-# Copied from diffusers.models.transformers.transformer_wan.WanAttnProcessor
+# modified from diffusers.models.transformers.transformer_wan.WanAttnProcessor
 class WanAttnProcessor:
     _attention_backend = None
     _parallel_config = None
@@ -137,7 +137,8 @@ class WanAttnProcessor:
                 dropout_p=0.0,
                 is_causal=False,
                 backend=self._attention_backend,
-                parallel_config=self._parallel_config,
+                # Reference: https://github.com/huggingface/diffusers/pull/12660
+                parallel_config=None,
             )
             hidden_states_img = hidden_states_img.flatten(2, 3)
             hidden_states_img = hidden_states_img.type_as(query)
@@ -150,7 +151,8 @@ class WanAttnProcessor:
             dropout_p=0.0,
             is_causal=False,
             backend=self._attention_backend,
-            parallel_config=self._parallel_config,
+            # Reference: https://github.com/huggingface/diffusers/pull/12660
+            parallel_config=(self._parallel_config if encoder_hidden_states is None else None),
         )
         hidden_states = hidden_states.flatten(2, 3)
         hidden_states = hidden_states.type_as(query)
@@ -568,9 +570,11 @@ class ChronoEditTransformer3DModel(
         "blocks.0": {
             "hidden_states": ContextParallelInput(split_dim=1, expected_dims=3, split_output=False),
         },
-        "blocks.*": {
-            "encoder_hidden_states": ContextParallelInput(split_dim=1, expected_dims=3, split_output=False),
-        },
+        # Reference: https://github.com/huggingface/diffusers/pull/12660
+        # We need to disable the splitting of encoder_hidden_states because
+        # the image_encoder consistently generates 257 tokens for image_embed. This causes
+        # the shape of encoder_hidden_states—whose token count is always 769 (512 + 257)
+        # after concatenation—to be indivisible by the number of devices in the CP.
         "proj_out": ContextParallelOutput(gather_dim=1, expected_dims=3),
     }