diff --git a/booru_viewer/gui/media/__init__.py b/booru_viewer/gui/media/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/booru_viewer/gui/media/constants.py b/booru_viewer/gui/media/constants.py
new file mode 100644
index 0000000..8a2d876
--- /dev/null
+++ b/booru_viewer/gui/media/constants.py
@@ -0,0 +1,11 @@
+"""Shared constants and predicates for media files."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+VIDEO_EXTENSIONS = (".mp4", ".webm", ".mkv", ".avi", ".mov")
+
+
+def _is_video(path: str) -> bool:
+    return Path(path).suffix.lower() in VIDEO_EXTENSIONS
diff --git a/booru_viewer/gui/preview.py b/booru_viewer/gui/preview.py
index c3b0f4a..9eb9eb4 100644
--- a/booru_viewer/gui/preview.py
+++ b/booru_viewer/gui/preview.py
@@ -17,8 +17,6 @@ import mpv as mpvlib
 
 _log = logging.getLogger("booru")
 
-VIDEO_EXTENSIONS = (".mp4", ".webm", ".mkv", ".avi", ".mov")
-
 
 class Viewport(NamedTuple):
     """Where and how large the user wants popout content to appear.
@@ -51,10 +49,6 @@ class Viewport(NamedTuple):
 _DRIFT_TOLERANCE = 2
 
 
-def _is_video(path: str) -> bool:
-    return Path(path).suffix.lower() in VIDEO_EXTENSIONS
-
-
 ## Overlay styling for the popout's translucent toolbar / controls bar
 ## now lives in the bundled themes (themes/*.qss). The widgets get their
 ## object names set in code (FullscreenPreview / VideoPlayer) so theme QSS
@@ -2271,3 +2265,7 @@ class ImagePreview(QWidget):
 
     def resizeEvent(self, event) -> None:
         super().resizeEvent(event)
+
+
+# -- Refactor compatibility shims (deleted in commit 14) --
+from .media.constants import VIDEO_EXTENSIONS, _is_video  # re-export for refactor compat