[diffusion] fix: fix local-path detection for MiniMax-H3 and other non-diffusers models (#33365)

Co-authored-by: Mick <mickjagger19@icloud.com>

python/sglang/cli/utils.py

@@ -9,7 +9,6 @@ from huggingface_hub import HfApi
 from sglang.srt.environ import envs
 from sglang.utils import (
     has_diffusion_overlay_registry_match,
-    is_known_non_diffusers_diffusion_model,
     load_diffusion_overlay_registry_from_env,
 )
 
@@ -25,14 +24,14 @@ def _is_overlay_diffusion_model(model_path: str) -> bool:
     return has_diffusion_overlay_registry_match(model_path, _load_overlay_registry())
 
 
-def _is_registered_diffusion_model(model_path: str) -> bool:
+def _is_diffusion_model_from_registry(model_path: str) -> bool:
     try:
-        from sglang.multimodal_gen.registry import has_registered_diffusion_model_path
+        from sglang.multimodal_gen.registry import is_registered_diffusion_model_path
     except ImportError:
         # if diffusion dependencies are not installed
         return False
 
-    return has_registered_diffusion_model_path(model_path)
+    return is_registered_diffusion_model_path(model_path)
 
 
 def _is_diffusers_model_dir(model_dir: str) -> bool:
@@ -59,8 +58,9 @@ def _is_gated_diffusion_repo(repo_id: str) -> bool:
 def get_is_diffusion_model(model_path: str) -> bool:
     """Detect whether model_path points to a diffusion model.
 
-    For local directories, checks the filesystem directly.
+    For registered models, consults the diffusion registry first.
-    For HF/ModelScope model IDs, attempts to fetch only model_index.json.
+    For other local directories, checks the filesystem directly.
+    For other HF/ModelScope model IDs, attempts to fetch only model_index.json.
     For gated repos where file download fails, falls back to HF model card
     metadata (library_name == "diffusers").
     Returns False on any failure (network error, 404, offline mode, etc.)
@@ -70,16 +70,13 @@ def get_is_diffusion_model(model_path: str) -> bool:
         # short-circuit, if applicable for the overlay mechanism (diffusion-only)
         return True
 
+    # the diffusion registry is authoritative for native models, including
+    # local directories without a top-level model_index.json
+    if _is_diffusion_model_from_registry(model_path):
+        return True
+
     if os.path.isdir(model_path):
-        if _is_diffusers_model_dir(model_path):
+        return _is_diffusers_model_dir(model_path)
-            return True
-        return is_known_non_diffusers_diffusion_model(model_path)
-
-    if is_known_non_diffusers_diffusion_model(model_path):
-        return True
-
-    if _is_registered_diffusion_model(model_path):
-        return True
 
     try:
         if envs.SGLANG_USE_MODELSCOPE.get():

python/sglang/multimodal_gen/registry.py

@@ -182,7 +182,6 @@ from sglang.multimodal_gen.runtime.utils.hf_diffusers_utils import (
     maybe_download_model_index,
 )
 from sglang.multimodal_gen.runtime.utils.logging_utils import init_logger
-from sglang.utils import KNOWN_NON_DIFFUSERS_DIFFUSION_MODEL_PATTERNS
 
 logger = init_logger(__name__)
 
@@ -289,6 +288,22 @@ _MODEL_HF_PATH_TO_NAME: Dict[str, str] = {}
 # Detectors to identify model families from paths or class names
 _MODEL_NAME_DETECTORS: List[Tuple[str, Callable[[str], bool]]] = []
 
+# native pipelines do not have a diffusers model_index.json. Keep their path
+# aliases next to the resolver that consumes them so CLI detection and
+# pipeline selection cannot drift apart
+KNOWN_NON_DIFFUSERS_DIFFUSION_MODEL_PATTERNS: Dict[str, str] = {
+    "minimaxai/minimax-h3": "MiniMaxH3Pipeline",
+    "minimax/minimax-h3": "MiniMaxH3Pipeline",
+    "lerobot/pi05": "Pi05Pipeline",
+    "pi05": "Pi05Pipeline",
+    "pi0.5": "Pi05Pipeline",
+    "hunyuan3d": "Hunyuan3D2Pipeline",
+    "flux.2-dev-nvfp4": "Flux2NvfpPipeline",
+    "fal/ideogram-v4-fast": "Ideogram4FastPipeline",
+    "fal/ideogram-v4-instant": "Ideogram4InstantPipeline",
+    "comfy-org/ideogram-4": "Ideogram4Nvfp4Pipeline",
+}
+
 
 def register_configs(
     sampling_param_cls: Any,
@@ -1163,17 +1178,28 @@ _register_configs()
 
 
 def is_known_non_diffusers_multimodal_model(model_path: str) -> bool:
-    model_path_lower = model_path.lower()
+    return get_non_diffusers_pipeline_name(model_path) is not None
-    return any(
-        pattern in model_path_lower
-        for pattern in KNOWN_NON_DIFFUSERS_DIFFUSION_MODEL_PATTERNS
-    )
 
 
 def get_non_diffusers_pipeline_name(model_path: str) -> Optional[str]:
     """Get the pipeline name for a known non-diffusers model."""
-    model_path_lower = model_path.lower()
+    normalized_model_path = _normalize_hf_cache_path(model_path)
+    model_short_name = get_model_short_name(normalized_model_path)
     for pattern, pipeline_name in KNOWN_NON_DIFFUSERS_DIFFUSION_MODEL_PATTERNS.items():
-        if pattern in model_path_lower:
+        pattern = pattern.lower()
+        if "/" not in pattern and pattern in normalized_model_path:
+            return pipeline_name
+        if "/" in pattern and (
+            normalized_model_path == pattern
+            or model_short_name == get_model_short_name(pattern)
+            or f"models--{pattern.replace('/', '--')}" in normalized_model_path
+        ):
             return pipeline_name
     return None
+
+
+def is_registered_diffusion_model_path(model_path: str) -> bool:
+    """Return whether the diffusion registry recognizes a model path."""
+    return has_registered_diffusion_model_path(model_path) or (
+        get_non_diffusers_pipeline_name(model_path) is not None
+    )

python/sglang/multimodal_gen/test/unit/test_server_args.py

@@ -6,6 +6,7 @@ import unittest
 from contextlib import contextmanager
 from unittest.mock import patch
 
+from sglang.cli.utils import get_is_diffusion_model
 from sglang.multimodal_gen.configs.models.fsdp import (
     is_module_list_entry,
     is_module_list_entry_in,
@@ -697,7 +698,16 @@ class TestWarmupImageIsModelValid(unittest.TestCase):
         self.assertGreaterEqual(height, 64)
 
 
+class TestDiffusionModelDetection(unittest.TestCase):
+    def test_registered_local_model_path_is_detected_as_diffusion(self):
+        with tempfile.TemporaryDirectory() as root:
+            model_path = os.path.join(root, "Z-Image-Turbo")
+            os.mkdir(model_path)
+            self.assertTrue(get_is_diffusion_model(model_path))
+
+
 class TestMiniMaxH3Routing(unittest.TestCase):
+
     def test_semantic_variants_map_to_checkpoint_partitions(self):
         self.assertEqual(
             MiniMaxH3Pipeline.model_subfolder_for_variant("fl2va"), "FL2VA"
@@ -718,6 +728,10 @@ class TestMiniMaxH3Routing(unittest.TestCase):
             get_non_diffusers_pipeline_name("MiniMax/MiniMax-H3"),
             "MiniMaxH3Pipeline",
         )
+        self.assertEqual(
+            get_non_diffusers_pipeline_name("/models/MiniMax-H3"),
+            "MiniMaxH3Pipeline",
+        )
 
 
 class TestOffloadDefaults(unittest.TestCase):

python/sglang/utils.py

@@ -31,25 +31,6 @@ from sglang.srt.environ import envs
 
 logger = logging.getLogger(__name__)
 
-KNOWN_NON_DIFFUSERS_DIFFUSION_MODEL_PATTERNS: dict[str, str] = {
-    "minimaxai/minimax-h3": "MiniMaxH3Pipeline",
-    "minimaxai--minimax-h3": "MiniMaxH3Pipeline",
-    "minimax/minimax-h3": "MiniMaxH3Pipeline",
-    "minimax--minimax-h3": "MiniMaxH3Pipeline",
-    "lerobot/pi05": "Pi05Pipeline",
-    "lerobot--pi05": "Pi05Pipeline",
-    "pi05": "Pi05Pipeline",
-    "pi0.5": "Pi05Pipeline",
-    "hunyuan3d": "Hunyuan3D2Pipeline",
-    "flux.2-dev-nvfp4": "Flux2NvfpPipeline",
-    "fal/ideogram-v4-fast": "Ideogram4FastPipeline",
-    "fal--ideogram-v4-fast": "Ideogram4FastPipeline",
-    "fal/ideogram-v4-instant": "Ideogram4InstantPipeline",
-    "fal--ideogram-v4-instant": "Ideogram4InstantPipeline",
-    "comfy-org/ideogram-4": "Ideogram4Nvfp4Pipeline",
-    "comfy-org--ideogram-4": "Ideogram4Nvfp4Pipeline",
-}
-
 
 def load_diffusion_overlay_registry_from_env() -> dict[str, dict[str, Any]]:
     raw_value = os.getenv("SGLANG_DIFFUSION_MODEL_OVERLAY_REGISTRY", "").strip()
@@ -88,14 +69,6 @@ def has_diffusion_overlay_registry_match(
     return any(base_name == key.rsplit("/", 1)[-1] for key in registry)
 
 
-def is_known_non_diffusers_diffusion_model(model_path: str) -> bool:
-    model_path_lower = model_path.lower()
-    return any(
-        pattern in model_path_lower
-        for pattern in KNOWN_NON_DIFFUSERS_DIFFUSION_MODEL_PATTERNS
-    )
-
-
 def execute_once(func):
     has_run = None