diff --git a/simvue/executor.py b/simvue/executor.py
index f4710137..8373433b 100644
--- a/simvue/executor.py
+++ b/simvue/executor.py
@@ -16,6 +16,7 @@
 import multiprocessing
 import os
 import subprocess
+import pathlib
 import time
 import typing
 
@@ -100,13 +101,13 @@ def add_process(
         identifier: str,
         *args,
         executable: typing.Optional[str] = None,
-        script: typing.Optional[str] = None,
-        input_file: typing.Optional[str] = None,
+        script: typing.Optional[pathlib.Path] = None,
+        input_file: typing.Optional[pathlib.Path] = None,
         env: typing.Optional[typing.Dict[str, str]] = None,
         completion_callback: typing.Optional[
             typing.Callable[[int, str, str], None]
         ] = None,
-        completion_trigger: multiprocessing.synchronize.Event,
+        completion_trigger: typing.Optional[multiprocessing.synchronize.Event] = None,
         **kwargs,
     ) -> None:
         """Add a process to be executed to the executor.
diff --git a/simvue/run.py b/simvue/run.py
index edc8106a..ceb97508 100644
--- a/simvue/run.py
+++ b/simvue/run.py
@@ -609,9 +609,9 @@ def add_process(
         self,
         identifier: str,
         *cmd_args,
-        executable: typing.Optional[str] = None,
-        script: typing.Optional[str] = None,
-        input_file: typing.Optional[str] = None,
+        executable: typing.Optional[typing.Union[str]] = None,
+        script: typing.Optional[pydantic.FilePath] = None,
+        input_file: typing.Optional[pydantic.FilePath] = None,
         completion_callback: typing.Optional[
             typing.Callable[[int, str, str], None]
         ] = None,