diff --git a/vime/backends/vllm_utils/vllm_engine.py b/vime/backends/vllm_utils/vllm_engine.py
index f6fe89075..6458716f4 100644
--- a/vime/backends/vllm_utils/vllm_engine.py
+++ b/vime/backends/vllm_utils/vllm_engine.py
@@ -521,6 +521,8 @@ def _wait_server_healthy(base_url: str, process: multiprocessing.Process | None)
         if process is not None and not process.is_alive():
             raise RuntimeError(f"vLLM server exited unexpectedly with code {process.exitcode}")
         time.sleep(2)
+
+
 class VLLMEngine(RayActor):
     """Ray actor for vLLM OpenAI HTTP rollout (connect or spawn local ``vllm serve``)."""
 
diff --git a/vime/ray/rollout.py b/vime/ray/rollout.py
index 69d6a42c9..ef5fb31b8 100644
--- a/vime/ray/rollout.py
+++ b/vime/ray/rollout.py
@@ -5,7 +5,6 @@
 import os
 import random
 import time
-from argparse import Namespace
 from pathlib import Path
 from typing import Any
 
@@ -13,8 +12,10 @@
 import ray
 import torch
 from ray.util.scheduling_strategies import PlacementGroupSchedulingStrategy
+
 from vime.backends.vllm_utils.vllm_config import ModelConfig, ServerGroupConfig, VllmConfig
 from vime.backends.vllm_utils.vllm_engine import VLLMEngine
+
 # Memory-type tag strings shared with the vLLM engine's sleep/wake_up API.
 GPU_MEMORY_TYPE_KV_CACHE = "kv_cache"
 GPU_MEMORY_TYPE_WEIGHTS = "weights"
@@ -919,10 +920,10 @@ def _start_router(args, *, has_pd_disaggregation: bool = False, force_new: bool
         if router_port is None:
             router_port = find_available_port(random.randint(3000, 4000))
 
-    from vime.utils.http_utils import run_router
-
     from vllm_router.router_args import RouterArgs
 
+    from vime.utils.http_utils import run_router
+
     router_args = RouterArgs.from_cli_args(args, use_router_prefix=True)
 
     router_args.host = router_ip