[Cleanup] Drop empty _DIFFUSION_PIPELINES placeholder

tests/config/test_pipeline_registry.py

@@ -6,11 +6,7 @@
 
 import pytest
 
-from vllm_omni.config.pipeline_registry import (
-    _DIFFUSION_PIPELINES,
-    _OMNI_PIPELINES,
-    _VLLM_OMNI_PIPELINES,
-)
+from vllm_omni.config.pipeline_registry import _OMNI_PIPELINES
 from vllm_omni.config.stage_config import (
     _PIPELINE_REGISTRY,
     PipelineConfig,
@@ -23,17 +19,9 @@
 class TestCentralRegistryDeclarations:
     """Every in-tree pipeline must be declared exactly once in the central registry."""
 
-    def test_union_contains_all_omni(self):
+    def test_omni_entries_visible_in_registry(self):
         for key in _OMNI_PIPELINES:
-            assert key in _VLLM_OMNI_PIPELINES
-
-    def test_union_contains_all_diffusion(self):
-        for key in _DIFFUSION_PIPELINES:
-            assert key in _VLLM_OMNI_PIPELINES
-
-    def test_no_duplicate_model_type_between_omni_and_diffusion(self):
-        overlap = set(_OMNI_PIPELINES) & set(_DIFFUSION_PIPELINES)
-        assert not overlap, f"Duplicate model_types across omni/diffusion: {overlap}"
+            assert key in _PIPELINE_REGISTRY
 
     def test_expected_omni_pipelines_present(self):
         # Guard against accidental removal during future refactors.

tests/test_config_factory.py

@@ -675,7 +675,7 @@ def test_parse_missing_async_chunk_defaults_false(self, tmp_path):
 
 
 class TestPipelineDiscovery:
-    """Tests for the central pipeline registry (``pipeline_registry._VLLM_OMNI_PIPELINES``)."""
+    """Tests for the central pipeline registry (``pipeline_registry._OMNI_PIPELINES``)."""
 
     def test_registry_has_known_models(self):
         """Built-in pipelines are lazy-loaded from the central declaration

vllm_omni/config/pipeline_registry.py

@@ -15,7 +15,13 @@
 Adding a new pipeline:
     1. Define the ``PipelineConfig`` instance as a module-level variable in
        ``vllm_omni/.../pipeline.py``.
-    2. Add one line to ``_OMNI_PIPELINES`` or ``_DIFFUSION_PIPELINES`` below.
+    2. Add one line to ``_OMNI_PIPELINES`` below.
+
+Single-stage diffusion models continue to use the
+``_create_default_diffusion_stage_cfg`` fallback in
+``async_omni_engine.py`` — they don't need a registry entry. The empty
+``_DIFFUSION_PIPELINES`` placeholder previously here (#2915) was removed
+once #2987 (which would have populated it) was deferred.
 
 ``register_pipeline(config)`` in ``stage_config`` is still supported for
 out-of-tree plugins and tests that create pipelines at runtime; those override
@@ -68,12 +74,3 @@
         "FISH_SPEECH_PIPELINE",
     ),
 }
-
-# --- Single-stage diffusion pipelines (populated in PR 3/N) ---
-_DIFFUSION_PIPELINES: dict[str, tuple[str, str]] = {}
-
-# Union view used by ``_LazyPipelineRegistry``; don't mutate at runtime.
-_VLLM_OMNI_PIPELINES: dict[str, tuple[str, str]] = {
-    **_OMNI_PIPELINES,
-    **_DIFFUSION_PIPELINES,
-}

vllm_omni/config/stage_config.py

@@ -265,9 +265,9 @@ def __init__(self) -> None:
 
     def _get_lazy_map(self) -> dict[str, tuple[str, str]]:
         if self._lazy_map is None:
-            from vllm_omni.config.pipeline_registry import _VLLM_OMNI_PIPELINES
+            from vllm_omni.config.pipeline_registry import _OMNI_PIPELINES
 
-            self._lazy_map = _VLLM_OMNI_PIPELINES
+            self._lazy_map = _OMNI_PIPELINES
         return self._lazy_map
 
     def _load_lazy(self, model_type: str) -> PipelineConfig | None:
@@ -365,7 +365,7 @@ def __iter__(self):
 def register_pipeline(pipeline: PipelineConfig) -> None:
     """Register a pipeline config dynamically.
 
-    In-tree pipelines are declared in ``pipeline_registry._VLLM_OMNI_PIPELINES``
+    In-tree pipelines are declared in ``pipeline_registry._OMNI_PIPELINES``
     and loaded lazily; calling ``register_pipeline`` is only needed for
     out-of-tree plugins or tests that build a ``PipelineConfig`` at runtime.
     A dynamic registration overrides the central-registry entry with the same