[Bugfix][ROCm] Fix MoRI + AITER FP8 dispatch compatibility for defer_input_quant (#37418)

Signed-off-by: Duyi-Wang <duyi.wang@amd.com>

vllm/model_executor/layers/fused_moe/mori_prepare_finalize.py

@@ -70,16 +70,13 @@ class MoriPrepareAndFinalize(mk.FusedMoEPrepareAndFinalizeModular):
         - Optional dispatched expert topk IDs
         - Optional dispatched expert topk weight
         """
-        if defer_input_quant:
-            raise NotImplementedError(
-                f"{self.__class__.__name__} does not support defer_input_quant=True. "
-                "Please select an MoE kernel that accepts quantized inputs."
-            )
         assert not apply_router_weight_on_input, (
             "mori does not support apply_router_weight_on_input=True now."
         )
         scale = None
-        if self.use_fp8_dispatch:
+        # When defer_input_quant is True, the expert kernel handles
+        # quantization internally, so skip FP8 dispatch quantization.
+        if self.use_fp8_dispatch and not defer_input_quant:
             from aiter import QuantType, get_hip_quant
 
             if quant_config.is_block_quantized:

vllm/model_executor/layers/fused_moe/rocm_aiter_fused_moe.py

@@ -295,7 +295,12 @@ def rocm_aiter_fused_experts(
 class AiterExperts(mk.FusedMoEExpertsModular):
     @property
     def expects_unquantized_inputs(self) -> bool:
-        return True
+        # When paired with MoRI, the prepare/finalize handles FP8
+        # quantization during dispatch to reduce network traffic,
+        # so we should not defer input quantization.
+        # Otherwise, AITER fused MoE kernels handle input quantization
+        # internally via a single fused kernel.
+        return not self.moe_config.use_mori_kernels
 
     @staticmethod
     def activation_format() -> mk.FusedMoEActivationFormat: