diff --git a/vllm_omni/diffusion/data.py b/vllm_omni/diffusion/data.py
index c04d46cf01f..4a47726f705 100644
--- a/vllm_omni/diffusion/data.py
+++ b/vllm_omni/diffusion/data.py
@@ -492,6 +492,12 @@ class OmniDiffusionConfig:
     # Step mode settings
     step_execution: bool = False
 
+    # Default generator device for random number generation (e.g., "cpu", "cuda")
+    # If set, this device will be used for torch.Generator when per-request
+    # generator_device is not specified. This is useful for ensuring reproducible
+    # results across different hardware configurations.
+    default_generator_device: str | None = None
+
     @property
     def is_moe(self) -> bool:
         num_experts = self.tf_model_config.get("num_experts", None)
diff --git a/vllm_omni/diffusion/worker/diffusion_model_runner.py b/vllm_omni/diffusion/worker/diffusion_model_runner.py
index 32ea5bf64dc..a6506482350 100644
--- a/vllm_omni/diffusion/worker/diffusion_model_runner.py
+++ b/vllm_omni/diffusion/worker/diffusion_model_runner.py
@@ -251,6 +251,8 @@ def execute_model(self, req: OmniDiffusionRequest) -> DiffusionOutput:
             if req.sampling_params.generator is None and req.sampling_params.seed is not None:
                 if req.sampling_params.generator_device is not None:
                     gen_device = req.sampling_params.generator_device
+                elif self.od_config.default_generator_device is not None:
+                    gen_device = self.od_config.default_generator_device
                 elif self.device.type == "cpu":
                     gen_device = "cpu"
                 else:
@@ -361,6 +363,8 @@ def execute_stepwise(self, scheduler_output: DiffusionSchedulerOutput) -> Runner
                 if state.sampling.generator is None and state.sampling.seed is not None:
                     if state.sampling.generator_device is not None:
                         gen_device = state.sampling.generator_device
+                    elif self.od_config.default_generator_device is not None:
+                        gen_device = self.od_config.default_generator_device
                     elif self.device.type == "cpu":
                         gen_device = "cpu"
                     else:
diff --git a/vllm_omni/engine/async_omni_engine.py b/vllm_omni/engine/async_omni_engine.py
index a4d87c96e4a..24775049a30 100644
--- a/vllm_omni/engine/async_omni_engine.py
+++ b/vllm_omni/engine/async_omni_engine.py
@@ -876,6 +876,7 @@ def _create_default_diffusion_stage_cfg(kwargs: dict[str, Any]) -> list:
                     "num_weight_load_threads": kwargs.get("num_weight_load_threads", 4),
                     "quantization": kwargs.get("quantization", None),
                     "enable_diffusion_pipeline_profiler": kwargs.get("enable_diffusion_pipeline_profiler", False),
+                    "default_generator_device": kwargs.get("default_generator_device", None),
                     **(
                         {
                             "profiler_config": asdict(kwargs["profiler_config"])
diff --git a/vllm_omni/entrypoints/cli/serve.py b/vllm_omni/entrypoints/cli/serve.py
index f924d64c391..affbf3b0e0c 100644
--- a/vllm_omni/entrypoints/cli/serve.py
+++ b/vllm_omni/entrypoints/cli/serve.py
@@ -367,6 +367,16 @@ def subparser_init(self, subparsers: argparse._SubParsersAction) -> FlexibleArgu
             action="store_true",
             help="Enable diffusion pipeline profiler to display stage durations.",
         )
+
+        # Default generator device for reproducible random number generation
+        omni_config_group.add_argument(
+            "--default-generator-device",
+            type=str,
+            default=None,
+            help="Default device for torch.Generator in diffusion models (e.g., 'cpu', 'cuda'). "
+            "When set, this device will be used for random number generation if not overridden "
+            "per-request. Using 'cpu' ensures reproducible results across different GPU hardware.",
+        )
         return serve_parser