diff --git a/cli.py b/cli.py
index 64d0da7..456acf3 100755
--- a/cli.py
+++ b/cli.py
@@ -154,7 +154,7 @@ _FLAGS_WITH_VALUE = frozenset({
 def _get_ordered_actions(argv: List[str]) -> List[tuple]:
     """
     Scan argv and return list of (action_name, value) in order of appearance.
-    Actions: flash, pause, reset, upload, erase_all, rm, follow.
+    Actions: flash, pause, reset, upload, ls, erase_all, rm, follow.
     """
     actions = []
     i = 1
@@ -205,13 +205,18 @@ def _get_ordered_actions(argv: List[str]) -> List[tuple]:
             actions.append(('upload', [local_dir, ""]))
             continue
         if arg == '--lib':
-            # Upload local DIR to /lib on device
-            if i + 1 < len(argv):
+            # Upload local DIR (default: ./lib) to /lib on device
+            local_dir = "lib"
+            if i + 1 < len(argv) and not argv[i + 1].startswith('-'):
                 local_dir = argv[i + 1]
-                actions.append(('upload', [local_dir, "lib"]))
                 i += 2
             else:
-                raise ValueError("--lib requires a directory argument")
+                i += 1
+            actions.append(('upload', [local_dir, "lib"]))
+            continue
+        if arg == '--ls':
+            actions.append(('ls', None))
+            i += 1
             continue
         if arg == '-e':
             actions.append(('erase_all', None))
@@ -434,8 +439,16 @@ Examples:
 
     parser.add_argument(
         "--lib",
+        nargs="?",
+        const="lib",
         metavar="DIR",
-        help="Upload DIR recursively to /lib on device"
+        help="Upload DIR recursively to /lib on device. If DIR is omitted, uses local ./lib."
+    )
+
+    parser.add_argument(
+        "--ls",
+        action="store_true",
+        help="List files on the device root (:/)"
     )
 
     parser.add_argument(
@@ -527,6 +540,18 @@ Examples:
                 print(f"Error uploading directory: {e}", file=sys.stderr)
                 sys.exit(1)
 
+        elif action_name == 'ls':
+            try:
+                print(f"Listing files on device {port}...", file=sys.stderr)
+                conn = DeviceConnection(port)
+                items = conn.list_files('')
+                for name, is_dir, size in items:
+                    marker = "d" if is_dir else "-"
+                    print(f"{marker} {size:>8} {name}")
+            except Exception as e:
+                print(f"Error listing files: {e}", file=sys.stderr)
+                sys.exit(1)
+
         elif action_name == 'erase_all':
             try:
                 print(f"Erasing all code on device {port}...", file=sys.stderr)