diff --git a/apps/worker/video_processing/bgm_mixer.py b/apps/worker/video_processing/bgm_mixer.py
index 7e10e261b..a28320756 100755
--- a/apps/worker/video_processing/bgm_mixer.py
+++ b/apps/worker/video_processing/bgm_mixer.py
@@ -192,7 +192,7 @@ def _mix_simple(main_path: Path, bgm_path: Path, output_path: Path) -> None:
     """
     # 使用 amix：inputs=2，duration=first（以主音频时长为准）
     # 然后用 volume=2 补偿 amix 的衰减（2路输入每路平均乘0.5）
-    filter_complex = f"[0:a][1:a]amix=inputs=2:duration=first:dropout_transition=0[outa];" f"[outa]volume=2[final]"
+    filter_complex = "[0:a][1:a]amix=inputs=2:duration=first:dropout_transition=0[outa];" "[outa]volume=2[final]"
 
     command = [
         FFMPEG_BIN,
diff --git a/apps/worker/video_processing/unified_render_service.py b/apps/worker/video_processing/unified_render_service.py
index a0c6d5e27..27ab9cc96 100755
--- a/apps/worker/video_processing/unified_render_service.py
+++ b/apps/worker/video_processing/unified_render_service.py
@@ -296,7 +296,6 @@ class UnifiedRenderService:
                         run_ffmpeg(extract_cmd)
                         final_audio = mix_bgm_with_main(ctx, main_audio_path, bgm_cfg, video_duration)
                         # 合并回视频
-                        from video_processing.render_audio import merge_audio_video
 
                         bgm_output = self.work_dir / f"rendered_{self.plan.id}_bgm.mp4"
                         merge_audio_video(ctx, output_path, final_audio, bgm_output)
diff --git a/tests/unit/test_bgm_mixer.py b/tests/unit/test_bgm_mixer.py
index 859097f5d..1891f9200 100755
--- a/tests/unit/test_bgm_mixer.py
+++ b/tests/unit/test_bgm_mixer.py
@@ -187,7 +187,7 @@ class TestPresetBGM:
 
         for bgm in PRESET_BGM_LIBRARY:
             assert bgm.id, f"{bgm.name} 缺少 id"
-            assert bgm.name, f"缺少 name"
+            assert bgm.name, "缺少 name"
             assert bgm.style, f"{bgm.name} 缺少 style"
             assert bgm.duration > 0, f"{bgm.name} 时长无效"