[Diffusion][HunyuanImage3] Add request paged prefix caching (#7719)

Signed-off-by: zwhzzz0821 <2831474076@qq.com>

tests/diffusion/test_diffusion_config_propagation.py

@@ -5,6 +5,7 @@
 Regression tests for https://github.com/vllm-project/vllm-omni/issues/1862
 """
 
+import json
 from collections.abc import Mapping
 
 import pytest
@@ -266,6 +267,21 @@ def test_architecture_name_resolves_via_pipeline_class_fallback():
     assert hunyuan_od_config.max_multimodal_image_inputs == HUNYUAN_IMAGE3_MAX_INPUT_IMAGES
 
 
+def test_architecture_only_checkpoint_propagates_multimodal_limit(tmp_path):
+    """A config.json-only checkpoint must expose its image-input capability."""
+    (tmp_path / "config.json").write_text(
+        json.dumps({"architectures": ["HunyuanImage3ForCausalMM"]}),
+        encoding="utf-8",
+    )
+
+    od_config = OmniDiffusionConfig(model=str(tmp_path))
+    od_config.enrich_config()
+
+    assert od_config.model_class_name == "HunyuanImage3ForCausalMM"
+    assert od_config.supports_multimodal_inputs is True
+    assert od_config.max_multimodal_image_inputs == HUNYUAN_IMAGE3_MAX_INPUT_IMAGES
+
+
 def test_additional_config_roundtrip():
     additional_config = {"torchair_graph_config": {"enabled": True}}
     od = _roundtrip_diffusion_config(model="x", additional_config=additional_config)