diff --git a/src/app/core/sync/executor.py b/src/app/core/sync/executor.py
index f4e70cd..b7689ce 100644
--- a/src/app/core/sync/executor.py
+++ b/src/app/core/sync/executor.py
@@ -18,12 +18,25 @@ from ..utils.rate_limit import is_youtube_rate_limit_error
 
 
 class ActionExecutor:
+    """Apply sync actions against the filesystem and persist their outcome.
+
+    The executor is the imperative half of the sync pipeline: it publishes
+    lifecycle events, performs safe renames and deletions, coordinates the
+    download queue, and updates the database after each job completes.
+    """
+
     def __init__(self, db: Database, concurrency: int = 2, event_bus: EventBus | None = None) -> None:
         self.concurrency = max(1, concurrency)
         self.db = db
         self.bus = event_bus
 
     async def execute(self, actions: Iterable[SyncAction], playlist_cfg: dict, *, cancel_check=None, pause_check=None) -> None:
+        """Execute a batch of sync actions for one playlist.
+
+        The workflow is intentionally ordered: announce the sync, wait for any
+        pause state to clear, validate dependencies, perform renames, recycle
+        deletions, and finally run downloads with bounded concurrency.
+        """
         actions_list = list(actions)
         playlist_id = extract_playlist_id(playlist_cfg.get("url", "")) or playlist_cfg.get("url", "")
         start = time.monotonic()
@@ -123,6 +136,7 @@ class ActionExecutor:
             ensure_ffmpeg_available(str(ffmpeg_hint) if ffmpeg_hint is not None else None)
 
     async def _apply_renames(self, actions: Iterable[SyncAction], audio_root: Path, video_root: Path, playlist_cfg: dict) -> None:
+        """Apply all rename actions in batches separated by output type."""
         playlist_id = extract_playlist_id(playlist_cfg.get("url", "")) or playlist_cfg.get("url", "")
         audio_renames = []
         video_renames = []
@@ -152,6 +166,7 @@ class ActionExecutor:
                     await self.bus.publish("RenameApplied", {"playlist_id": playlist_id, "video_id": a.item.video_id, "to": a.to_name})
 
     def _apply_deletions(self, actions: Iterable[SyncAction], audio_root: Path, video_root: Path, playlist_cfg: dict) -> None:
+        """Recycle or remove files that no longer belong to the playlist."""
         playlist_id = extract_playlist_id(playlist_cfg.get("url", "")) or playlist_cfg.get("url", "")
         recycle_audio = audio_root.parent / ".recycle" / "audio"
         recycle_video = video_root.parent / ".recycle" / "video"
@@ -198,6 +213,7 @@ class ActionExecutor:
         cancel_check=None,
         pause_check=None,
     ) -> None:
+        """Queue and run download jobs, then persist their final state."""
         playlist_id = extract_playlist_id(playlist_cfg.get("url", "")) or playlist_cfg.get("url", "")
         loop = asyncio.get_running_loop()
         concurrency_cfg = playlist_cfg.get("max_parallel_downloads", self.concurrency)