[modular] Add LTX Video modular pipeline (#13378)

* Add modular pipeline support for LTX Video

* Fix guidance_scale passthrough to guider

* Add LTX modular pipeline tests

* Add LTX image-to-video modular pipeline

* Fix i2v VAE dtype mismatch

* Add cache_context to denoiser for CFG parity

* Address review feedback

* Generate auto docstrings for LTX assembled blocks

* Fix ruff lint and format issues

* use InputParam/OutputParam templates and ruff check

* address all review

* Lift LTXVaeEncoderStep out of I2V core denoise into its own auto block

* unused declarations

* Fix check_copies: sync retrieve_timesteps and drop unsupported Copied from tags

* Address review: remove unused code, add LTXAutoBlocks, refactor I2V latents flow

* removed LTXBlocks,LTXImage2VideoBlocks

* Update test to use LTXAutoBlocks

* workflow map and auto docstring

* Add LTXVideoPachifier, workflow map

---------

Co-authored-by: YiYi Xu <yixu310@gmail.com>

Author: akshan-main

src/diffusers/__init__.py

@@ -455,6 +455,8 @@
             "HeliosPyramidDistilledAutoBlocks",
             "HeliosPyramidDistilledModularPipeline",
             "HeliosPyramidModularPipeline",
+            "LTXAutoBlocks",
+            "LTXModularPipeline",
             "QwenImageAutoBlocks",
             "QwenImageEditAutoBlocks",
             "QwenImageEditModularPipeline",
@@ -1234,6 +1236,8 @@
             HeliosPyramidDistilledAutoBlocks,
             HeliosPyramidDistilledModularPipeline,
             HeliosPyramidModularPipeline,
+            LTXAutoBlocks,
+            LTXModularPipeline,
             QwenImageAutoBlocks,
             QwenImageEditAutoBlocks,
             QwenImageEditModularPipeline,

src/diffusers/modular_pipelines/__init__.py

@@ -88,6 +88,10 @@
         "QwenImageLayeredModularPipeline",
         "QwenImageLayeredAutoBlocks",
     ]
+    _import_structure["ltx"] = [
+        "LTXAutoBlocks",
+        "LTXModularPipeline",
+    ]
     _import_structure["z_image"] = [
         "ZImageAutoBlocks",
         "ZImageModularPipeline",
@@ -119,6 +123,7 @@
             HeliosPyramidDistilledModularPipeline,
             HeliosPyramidModularPipeline,
         )
+        from .ltx import LTXAutoBlocks, LTXModularPipeline
         from .modular_pipeline import (
             AutoPipelineBlocks,
             BlockState,

src/diffusers/modular_pipelines/ltx/__init__.py

@@ -0,0 +1,47 @@
+from typing import TYPE_CHECKING
+
+from ...utils import (
+    DIFFUSERS_SLOW_IMPORT,
+    OptionalDependencyNotAvailable,
+    _LazyModule,
+    get_objects_from_module,
+    is_torch_available,
+    is_transformers_available,
+)
+
+
+_dummy_objects = {}
+_import_structure = {}
+
+try:
+    if not (is_transformers_available() and is_torch_available()):
+        raise OptionalDependencyNotAvailable()
+except OptionalDependencyNotAvailable:
+    from ...utils import dummy_torch_and_transformers_objects  # noqa F403
+
+    _dummy_objects.update(get_objects_from_module(dummy_torch_and_transformers_objects))
+else:
+    _import_structure["modular_blocks_ltx"] = ["LTXAutoBlocks", "LTXBlocks", "LTXImage2VideoBlocks"]
+    _import_structure["modular_pipeline"] = ["LTXModularPipeline"]
+
+if TYPE_CHECKING or DIFFUSERS_SLOW_IMPORT:
+    try:
+        if not (is_transformers_available() and is_torch_available()):
+            raise OptionalDependencyNotAvailable()
+    except OptionalDependencyNotAvailable:
+        from ...utils.dummy_torch_and_transformers_objects import *  # noqa F403
+    else:
+        from .modular_blocks_ltx import LTXAutoBlocks, LTXBlocks, LTXImage2VideoBlocks
+        from .modular_pipeline import LTXModularPipeline
+else:
+    import sys
+
+    sys.modules[__name__] = _LazyModule(
+        __name__,
+        globals()["__file__"],
+        _import_structure,
+        module_spec=__spec__,
+    )
+
+    for name, value in _dummy_objects.items():
+        setattr(sys.modules[__name__], name, value)