save_as_session: Show an error when the path is a directory

docs/changelog.rst

@@ -217,6 +217,9 @@ Detailed list of changes
 - Fix a packaging bug that could cause pipeline files to be omitted from some
   kitty builds
 
+- :ac:`save_as_session`: Show an error instead of saving next to the directory
+  when the specified path is an existing directory (:iss:`10520`)
+
 0.49.0 [2026-09-21]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

kitty/session.py

@@ -701,6 +701,9 @@ def save_as_session_part2(boss: BossType, opts: SaveAsSessionOptions, path: str,
         base_dir = os.path.abspath(os.path.expanduser(opts.base_dir))
         path = os.path.join(base_dir, path)
     path = os.path.abspath(os.path.expanduser(path))
+    if os.path.isdir(path):
+        boss.show_error(_('Invalid session path'), _('{} is a directory, specify a file name for the session').format(path))
+        return
     if path_input_by_user and '.' not in os.path.basename(path):
         path += '.kitty-session'
     session = '\n'.join(boss.serialize_state_as_session(path, opts))