diff --git a/traitlets/config/application.py b/traitlets/config/application.py
index b0cf36f7..5993b4c7 100644
--- a/traitlets/config/application.py
+++ b/traitlets/config/application.py
@@ -400,7 +400,7 @@ def _log_default(self) -> AnyLogger:
     # this must be a dict of two-tuples,
     # the first element being the application class/import string
     # and the second being the help string for the subcommand
-    subcommands = Dict()
+    subcommands: dict[str, t.Any] | Dict = Dict()
     # parse_command_line will initialize a subapp, if requested
     subapp = Instance("traitlets.config.application.Application", allow_none=True)
 
@@ -891,7 +891,7 @@ def parse_command_line(self, argv: ArgvType = None) -> None:
     def _load_config_files(
         cls,
         basefilename: str,
-        path: list[str | None] | None = None,
+        path: str | t.Sequence[str | None] | None,
         log: AnyLogger | None = None,
         raise_config_file_errors: bool = False,
     ) -> t.Generator[t.Any, None, None]:
@@ -899,7 +899,7 @@ def _load_config_files(
 
         yield each config object in turn.
         """
-        if not isinstance(path, list):
+        if isinstance(path, str) or path is None:
             path = [path]
         for current in reversed(path):
             # path list is in descending priority order, so load files backwards:
@@ -949,7 +949,9 @@ def loaded_config_files(self) -> list[str]:
         return self._loaded_config_files[:]
 
     @catch_config_error
-    def load_config_file(self, filename: str, path: list[str | None] | None = None) -> None:
+    def load_config_file(
+        self, filename: str, path: str | t.Sequence[str | None] | None = None
+    ) -> None:
         """Load config files by filename and path."""
         filename, ext = os.path.splitext(filename)
         new_config = Config()
@@ -1032,7 +1034,7 @@ def close_handlers(self) -> None:
                     handler.close()
             self._logging_configured = False
 
-    def exit(self, exit_status: int = 0) -> None:
+    def exit(self, exit_status: int | str | None = 0) -> None:
         self.log.debug("Exiting application: %s" % self.name)
         self.close_handlers()
         sys.exit(exit_status)
diff --git a/traitlets/tests/utils.py b/traitlets/tests/utils.py
index b4d0fe95..55829078 100644
--- a/traitlets/tests/utils.py
+++ b/traitlets/tests/utils.py
@@ -2,10 +2,10 @@
 
 import sys
 from subprocess import PIPE, Popen
-from typing import Any
+from typing import Any, Sequence
 
 
-def get_output_error_code(cmd: str | list[str]) -> tuple[str, str, Any]:
+def get_output_error_code(cmd: str | Sequence[str]) -> tuple[str, str, Any]:
     """Get stdout, stderr, and exit code from running a command"""
     p = Popen(cmd, stdout=PIPE, stderr=PIPE)  # noqa
     out, err = p.communicate()
@@ -14,7 +14,7 @@ def get_output_error_code(cmd: str | list[str]) -> tuple[str, str, Any]:
     return out_str, err_str, p.returncode
 
 
-def check_help_output(pkg: str, subcommand: list[str] | None = None) -> tuple[str, str]:
+def check_help_output(pkg: str, subcommand: Sequence[str] | None = None) -> tuple[str, str]:
     """test that `python -m PKG [subcommand] -h` works"""
     cmd = [sys.executable, "-m", pkg]
     if subcommand:
@@ -28,7 +28,7 @@ def check_help_output(pkg: str, subcommand: list[str] | None = None) -> tuple[st
     return out, err
 
 
-def check_help_all_output(pkg: str, subcommand: list[str] | None = None) -> tuple[str, str]:
+def check_help_all_output(pkg: str, subcommand: Sequence[str] | None = None) -> tuple[str, str]:
     """test that `python -m PKG --help-all` works"""
     cmd = [sys.executable, "-m", pkg]
     if subcommand: