diff --git a/nemo_curator/stages/video/io/clip_writer.py b/nemo_curator/stages/video/io/clip_writer.py
index eb62d17774..f829b8feee 100644
--- a/nemo_curator/stages/video/io/clip_writer.py
+++ b/nemo_curator/stages/video/io/clip_writer.py
@@ -131,6 +131,20 @@ def _write_json_data(
     ) -> None:
         write_json(data, dest, desc, source_video, verbose=self.verbose)
 
+    @staticmethod
+    def _cleanup_video_data(video: Video) -> None:
+        for clip in video.clips:
+            clip.buffer = None
+            clip.cosmos_embed1_embedding = None
+            for window in clip.windows:
+                window.mp4_bytes = None
+                window.llm_inputs.clear()
+                window.caption.clear()
+                window.enhanced_caption.clear()
+                window.webp_bytes = None
+        for clip in video.filtered_clips:
+            clip.buffer = None
+
     def process(self, task: VideoTask) -> VideoTask:
         video: Video = task.data
         with ThreadPoolExecutor(max_workers=self.max_workers) as executor:
@@ -171,15 +185,7 @@ def process(self, task: VideoTask) -> VideoTask:
             for future_v in futures_videos:
                 future_v.result()
             # clean up intermediate data
-            for clip in video.clips:
-                clip.buffer = None
-                clip.cosmos_embed1_embedding = None
-                for window in clip.windows:
-                    window.mp4_bytes = None
-                    window.llm_inputs.clear()
-                    window.caption.clear()
-                    window.enhanced_caption.clear()
-                    window.webp_bytes = None
+            self._cleanup_video_data(video)
 
         if self.verbose:
             logger.info(f"Video {video.input_path} has {len(video.clips)} clips and wrote to {self.output_path}")
diff --git a/tests/stages/video/io/test_clip_writer.py b/tests/stages/video/io/test_clip_writer.py
index ad2829c96c..48cb106861 100644
--- a/tests/stages/video/io/test_clip_writer.py
+++ b/tests/stages/video/io/test_clip_writer.py
@@ -700,6 +700,8 @@ def test_process_success(self, mock_executor_class: MagicMock):
                     assert window.caption == {}
                     assert window.enhanced_caption == {}
                     assert window.webp_bytes is None
+            for clip in result.data.filtered_clips:
+                assert clip.buffer is None
 
             mock_logger.info.assert_called()
 
@@ -847,6 +849,32 @@ def test_edge_cases_clip_with_errors(self):
             assert "error1" in data["errors"]
             assert "error2" in data["errors"]
 
+    @patch("nemo_curator.stages.video.io.clip_writer.ThreadPoolExecutor")
+    def test_filtered_clips_buffer_cleared_after_process(self, mock_executor_class: MagicMock):
+        """Filtered (e.g. motion-filtered) clips must have buffer cleared after process().
+
+        Motion-filtered clips skip ClipFrameExtractionStage (which normally clears buffer)
+        so ClipWriterStage is responsible for clearing their buffers to avoid bloating
+        the serialized task objects (~1.8GB tasks.pkl in benchmarks before this fix).
+        """
+        mock_executor = MagicMock()
+        mock_executor_class.return_value.__enter__.return_value = mock_executor
+        mock_future = MagicMock()
+        mock_future.result.return_value = None
+        mock_executor.submit.return_value = mock_future
+
+        self.stage.setup()
+        assert self.mock_filtered_clip.buffer is not None  # confirm buffer is set before process
+
+        with (
+            patch.object(self.stage, "_write_clip_embedding_to_buffer"),
+            patch.object(self.stage, "_write_video_embeddings_to_parquet"),
+            patch.object(self.stage, "_write_video_metadata"),
+        ):
+            result = self.stage.process(self.mock_task)
+
+        assert result.data.filtered_clips[0].buffer is None
+
     def test_multiple_embedding_algorithms(self):
         """Test with different embedding algorithms."""
         algorithms = ["cosmos-embed1-224p", "cosmos-embed1-336p", "cosmos-embed1-448p"]