macOS requires URLs to directories to end with a slash

docs/dnd-protocol.rst

@@ -387,7 +387,8 @@ Dragging to remote machines
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 To support dragging to remote machines, first of all clients **must** pre-send
-the data for the ``text/uri-list`` MIME type. Then, terminals can
+the data for the ``text/uri-list`` MIME type. All ``file://`` URLs that point
+to directories **must** end with a ``/``. Then, terminals can
 examine the :ref:`machine_id` sent with the enable drag offers
 ``t=o`` escape code to decide whether to request data for ``file://`` entries
 from the URI list. To request data for a particular entry, terminals send an

kittens/dnd/main.go

@@ -395,6 +395,9 @@ func dnd_main(cmd *cli.Command, opts *Options, args []string) (rc int, err error
 			if runtime.GOOS == "windows" && !strings.HasPrefix(upath, "/") {
 				upath = "/" + upath
 			}
+			if st.IsDir() && !strings.HasSuffix(upath, "/") {
+				upath += "/"
+			}
 			u := &url.URL{Scheme: "file", Path: upath}
 			uri_list = append(uri_list, uri_list_item{path: path, uri: u.String(), human_name: arg, metadata: st})
 		} else {