[Bugfix] Limit Qwen-Image-Edit-2511 input image count (#2840)

Signed-off-by: david6666666 <530634352@qq.com>
Co-authored-by: Gao Han <hgaoaf@connect.ust.hk>

vllm_omni/diffusion/model_metadata.py

@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class DiffusionModelMetadata:
+    # Keep serving-facing capability metadata in a lightweight shared module so
+    # config/model plumbing can read it without importing concrete pipelines.
+    supports_multimodal_inputs: bool = False
+    max_multimodal_image_inputs: int | None = None
+
+
+QWEN_IMAGE_EDIT_PLUS_MAX_INPUT_IMAGES = 4
+
+
+_DIFFUSION_MODEL_METADATA: dict[str, DiffusionModelMetadata] = {
+    "QwenImageEditPlusPipeline": DiffusionModelMetadata(
+        supports_multimodal_inputs=True,
+        max_multimodal_image_inputs=QWEN_IMAGE_EDIT_PLUS_MAX_INPUT_IMAGES,
+    ),
+}
+
+
+def get_diffusion_model_metadata(model_class_name: str | None) -> DiffusionModelMetadata:
+    # Unknown models fall back to "no special multimodal capabilities" so new
+    # pipelines do not accidentally inherit limits meant for other models.
+    if model_class_name is None:
+        return DiffusionModelMetadata()
+    return _DIFFUSION_MODEL_METADATA.get(model_class_name, DiffusionModelMetadata())