diff --git a/README.md b/README.md
index 5e43942..e5a2f6e 100644
--- a/README.md
+++ b/README.md
@@ -107,12 +107,15 @@ silently stay blank instead of erroring.
   dropdown and typing just the new folder's own name, with a live "Will
   create: X/Y" preview so the resulting path is confirmed before applying -
   the same picker Manage Library's Move action uses. The picker excludes
-  actual course/item folders, not just organizational ones - including a
-  leaf folder holding a single non-video/audio file (an ebook, an
-  audiobook in a format this app doesn't play, etc.) that Library
-  browsing's own course detection wouldn't catch either, since there's no
-  video/audio file to key off. Nothing on disk moves until you review and
-  hit Apply. Matching ignores common noise (e-learning
+  actual course/item folders, not just organizational ones: a leaf folder
+  holding a single non-video/audio file (an ebook, an audiobook in a
+  format this app doesn't play, etc.), and a folder whose whole subtree
+  has no video/audio anywhere in it at all (a course's bundled source
+  code, a Python virtualenv, project assets, ...) even though it has
+  plenty of subfolders - both cases Library browsing's own course
+  detection wouldn't catch either, since there's no video/audio file to
+  key off. Nothing on disk moves until you review and hit Apply. Matching
+  ignores common noise (e-learning
   platform names, release/distribution-group tags, dates) via a stopword
   list, and beyond that treats a match against a folder's own deliberate
   name as always stronger evidence than a word only borrowed from a
diff --git a/offlineu_core.py b/offlineu_core.py
index b0e226c..d3d1414 100644
--- a/offlineu_core.py
+++ b/offlineu_core.py
@@ -1286,6 +1286,44 @@ def _is_unrecognized_leaf_item(directory: Path) -> bool:
     return any(e.is_file() and not e.name.startswith('.') for e in entries)
 
 
+def _subtree_has_any_media(directory: Path, max_depth: int = 8) -> bool:
+    """Whether `directory` or anything under it (bounded depth, so a huge
+    non-course tree can't make a scan slow) contains at least one
+    recognized video/audio file anywhere. False for a folder that's really
+    a course's bundled extras - downloaded source code, a Python
+    virtualenv/dependency dump, a project's asset tree, etc. - which can
+    have plenty of subfolders (so _is_unrecognized_leaf_item doesn't catch
+    it) but no lecture content anywhere in them."""
+    try:
+        entries = list(directory.iterdir())
+    except (PermissionError, OSError):
+        return False
+    for e in entries:
+        if e.is_file() and not e.name.startswith('.') and e.suffix.lower() in VIDEO_EXTENSIONS | AUDIO_EXTENSIONS:
+            return True
+    if max_depth <= 0:
+        return False
+    for e in entries:
+        if e.is_dir() and not e.name.startswith('.') and _subtree_has_any_media(e, max_depth - 1):
+            return True
+    return False
+
+
+def _is_media_free_subtree(directory: Path) -> bool:
+    """A folder that has subfolders (so it isn't just an intentionally
+    empty, freshly-created category) but no video/audio anywhere beneath
+    it - excluded from the destination picker for the same reason as
+    _is_unrecognized_leaf_item, just for a deeper non-course tree instead
+    of a single stray file."""
+    try:
+        has_subdir = any(e.is_dir() and not e.name.startswith('.') for e in directory.iterdir())
+    except (PermissionError, OSError):
+        return False
+    if not has_subdir:
+        return False
+    return not _subtree_has_any_media(directory)
+
+
 def _build_category_index() -> List[Dict[str, Any]]:
     """
     Every category/subcategory folder currently in the library (e.g. IT,
@@ -1305,13 +1343,14 @@ def _build_category_index() -> List[Dict[str, Any]]:
         categories' course titles) can't outweigh a specific match
         elsewhere just by sharing more of it.
     Stops recursing into a folder once it reads as a course itself
-    (_looks_like_course, the same rule the Library browser uses) or as an
+    (_looks_like_course, the same rule the Library browser uses), an
     unrecognized leaf item (_is_unrecognized_leaf_item - an ebook/
-    audiobook/misc file that isn't video or audio, so _looks_like_course
-    doesn't catch it either), so individual courses and standalone files
-    never show up as if they were categories to file things under. The
-    Unsorted folder itself is excluded - it's the source, never a valid
-    destination.
+    audiobook/misc file that isn't video or audio), or a subtree with no
+    video/audio anywhere in it at all (_is_media_free_subtree - a course's
+    bundled source code/project files, a Python virtualenv, etc.), so
+    individual courses and their non-lecture contents never show up as if
+    they were categories to file things under. The Unsorted folder itself
+    is excluded - it's the source, never a valid destination.
     """
     library_root = Path(get_library_root())
     try:
@@ -1334,7 +1373,7 @@ def _build_category_index() -> List[Dict[str, Any]]:
                     continue
             except OSError:
                 pass
-            if _looks_like_course(entry) or _is_unrecognized_leaf_item(entry):
+            if _looks_like_course(entry) or _is_unrecognized_leaf_item(entry) or _is_media_free_subtree(entry):
                 continue
             new_parts = path_parts + [entry.name]
             path_tokens: Set[str] = set()