diff --git a/src/_ert/forward_model_runner/job.py b/src/_ert/forward_model_runner/job.py
index 85beedaff06..494e81af4a9 100644
--- a/src/_ert/forward_model_runner/job.py
+++ b/src/_ert/forward_model_runner/job.py
@@ -11,10 +11,12 @@
 from datetime import datetime as dt
 from pathlib import Path
 from subprocess import Popen, run
-from typing import Dict, Generator, Optional, Sequence, Tuple
+from typing import Dict, Generator, List, Optional, Sequence, Tuple, cast
 
 from psutil import AccessDenied, NoSuchProcess, Process, TimeoutExpired, ZombieProcess
 
+from ert.config.forward_model_step import ForwardModelStepJSON
+
 from .io import check_executable
 from .reporting.message import (
     Exited,
@@ -26,7 +28,7 @@
 logger = logging.getLogger(__name__)
 
 
-def killed_by_oom(pids: set[int]) -> bool:
+def killed_by_oom(pids: Sequence[int]) -> bool:
     """Will try to detect if a process (or any of its descendants) was killed
     by the Linux OOM-killer.
 
@@ -76,26 +78,28 @@ def killed_by_oom(pids: set[int]) -> bool:
 class Job:
     MEMORY_POLL_PERIOD = 5  # Seconds between memory polls
 
-    def __init__(self, job_data, index, sleep_interval=1) -> None:
+    def __init__(
+        self, job_data: ForwardModelStepJSON, index: int, sleep_interval: int = 1
+    ) -> None:
         self.sleep_interval = sleep_interval
-        self.job_data: Dict[str, str] = job_data
+        self.job_data = job_data
         self.index = index
         self.std_err = job_data.get("stderr")
         self.std_out = job_data.get("stdout")
 
-    def run(self) -> Generator[Start | Exited | Running]:
+    def run(self) -> Generator[Start | Exited | Running | None]:
         try:
             for msg in self._run():
                 yield msg
+        except StopIteration as e:
+            raise e
         except Exception as e:
             yield Exited(self, exit_code=1).with_error(str(e))
 
     def create_start_message_and_check_job_files(self) -> Start:
         start_message = Start(self)
 
-        errors = self._check_job_files()
-
-        errors.extend(self._assert_arg_list())
+        errors = [*self._check_job_files()]
 
         self._dump_exec_env()
 
@@ -103,9 +107,9 @@ def create_start_message_and_check_job_files(self) -> Start:
             start_message = start_message.with_error("\n".join(errors))
         return start_message
 
-    def _build_arg_list(self):
+    def _build_arg_list(self) -> List[str]:
         executable = self.job_data.get("executable")
-
+        # assert executable is not None
         combined_arg_list = [executable]
         if arg_list := self.job_data.get("argList"):
             combined_arg_list += arg_list
@@ -117,7 +121,7 @@ def _open_file_handles(
         io.TextIOWrapper | None, io.TextIOWrapper | None, io.TextIOWrapper | None
     ]:
         if self.job_data.get("stdin"):
-            stdin = open(self.job_data.get("stdin"), encoding="utf-8")  # noqa
+            stdin = open(cast(Path, self.job_data.get("stdin")), encoding="utf-8")  # noqa
         else:
             stdin = None
 
@@ -141,18 +145,18 @@ def _open_file_handles(
 
         return (stdin, stdout, stderr)
 
-    def _create_environment(self) -> Dict:
-        environment = self.job_data.get("environment")
-        if environment is not None:
-            environment = {**os.environ, **environment}
-        return environment
+    def _create_environment(self) -> Optional[Dict[str, str]]:
+        combined_environment = None
+        if environment := self.job_data.get("environment"):
+            combined_environment = {**os.environ, **environment}
+        return combined_environment
 
-    def _run(self) -> contextlib.Generator[Start | Exited | Running]:
+    def _run(self) -> Generator[Start | Exited | Running | None]:
         start_message = self.create_start_message_and_check_job_files()
 
         yield start_message
         if not start_message.success():
-            return
+            raise StopIteration()
 
         arg_list = self._build_arg_list()
 
@@ -160,7 +164,7 @@ def _run(self) -> contextlib.Generator[Start | Exited | Running]:
         # stdin/stdout/stderr are closed at the end of this function
 
         target_file = self.job_data.get("target_file")
-        target_file_mtime: int = _get_target_file_ntime(target_file)
+        target_file_mtime: Optional[int] = _get_target_file_ntime(target_file)
 
         try:
             proc = Popen(
@@ -177,7 +181,7 @@ def _run(self) -> contextlib.Generator[Start | Exited | Running]:
             )
             ensure_file_handles_closed([stdin, stdout, stderr])
             yield exited_message
-            return
+            raise StopIteration() from None
 
         exit_code = None
 
@@ -201,20 +205,22 @@ def _run(self) -> contextlib.Generator[Start | Exited | Running]:
             try:
                 exit_code = process.wait(timeout=self.MEMORY_POLL_PERIOD)
             except TimeoutExpired:
-                exited_msg = self.handle_process_timeout_and_create_exited_msg(
-                    process, proc
+                potential_exited_msg = (
+                    self.handle_process_timeout_and_create_exited_msg(process, proc)
                 )
                 fm_step_pids |= {
                     int(child.pid) for child in process.children(recursive=True)
                 }
-                if isinstance(exited_msg, Exited):
-                    yield exited_msg
-                    return
+                if isinstance(potential_exited_msg, Exited):
+                    yield potential_exited_msg
+
+                    raise StopIteration() from None
 
         ensure_file_handles_closed([stdin, stdout, stderr])
         exited_message = self._create_exited_message_based_on_exit_code(
             max_memory_usage, target_file_mtime, exit_code, fm_step_pids
         )
+        assert exited_message.job
         yield exited_message
 
     def _create_exited_message_based_on_exit_code(
@@ -224,20 +230,16 @@ def _create_exited_message_based_on_exit_code(
         exit_code: int,
         fm_step_pids: Sequence[int],
     ) -> Exited:
-        # exit_code = proc.returncode
-
         if exit_code != 0:
             exited_message = self._create_exited_msg_for_non_zero_exit_code(
                 max_memory_usage, exit_code, fm_step_pids
             )
             return exited_message
 
-        # exit_code is 0
-
+        exited_message = Exited(self, exit_code)
         if self.job_data.get("error_file") and os.path.exists(
             self.job_data["error_file"]
         ):
-            exited_message = Exited(self, exit_code)
             return exited_message.with_error(
                 f'Found the error file:{self.job_data["error_file"]} - job failed.'
             )
@@ -271,34 +273,33 @@ def _create_exited_msg_for_non_zero_exit_code(
         )
 
     def handle_process_timeout_and_create_exited_msg(
-        self, process: Process, proc: Popen
+        self, process: Process, proc: Popen[Process]
     ) -> Exited | None:
         max_running_minutes = self.job_data.get("max_running_minutes")
         run_start_time = dt.now()
 
         run_time = dt.now() - run_start_time
-        if (
-            max_running_minutes is not None
-            and run_time.seconds > max_running_minutes * 60
-        ):
-            # If the spawned process is not in the same process group as
-            # the callee (job_dispatch), we will kill the process group
-            # explicitly.
-            #
-            # Propagating the unsuccessful Exited message will kill the
-            # callee group. See job_dispatch.py.
-            process_group_id = os.getpgid(proc.pid)
-            this_group_id = os.getpgid(os.getpid())
-            if process_group_id != this_group_id:
-                os.killpg(process_group_id, signal.SIGKILL)
-
-            return Exited(self, proc.returncode).with_error(
-                (
-                    f"Job:{self.name()} has been running "
-                    f"for more than {max_running_minutes} "
-                    "minutes - explicitly killed."
-                )
+        if max_running_minutes is None or run_time.seconds > max_running_minutes * 60:
+            return None
+
+        # If the spawned process is not in the same process group as
+        # the callee (job_dispatch), we will kill the process group
+        # explicitly.
+        #
+        # Propagating the unsuccessful Exited message will kill the
+        # callee group. See job_dispatch.py.
+        process_group_id = os.getpgid(proc.pid)
+        this_group_id = os.getpgid(os.getpid())
+        if process_group_id != this_group_id:
+            os.killpg(process_group_id, signal.SIGKILL)
+
+        return Exited(self, proc.returncode).with_error(
+            (
+                f"Job:{self.name()} has been running "
+                f"for more than {max_running_minutes} "
+                "minutes - explicitly killed."
             )
+        )
 
     def _handle_process_io_error_and_create_exited_message(
         self, e: OSError, stderr: io.TextIOWrapper | None
@@ -314,31 +315,6 @@ def _handle_process_io_error_and_create_exited_message(
             stderr.write(msg)
         return Exited(self, e.errno).with_error(msg)
 
-    def _assert_arg_list(self) -> list[str]:
-        errors: list[str] = []
-        if "arg_types" in self.job_data:
-            arg_types = self.job_data["arg_types"]
-            arg_list = self.job_data.get("argList")
-            for index, arg_type in enumerate(arg_types):
-                if arg_type == "RUNTIME_FILE":
-                    file_path = os.path.join(os.getcwd(), arg_list[index])
-                    if not os.path.isfile(file_path):
-                        errors.append(
-                            f"In job {self.name()}: RUNTIME_FILE {arg_list[index]} "
-                            "does not exist."
-                        )
-                if arg_type == "RUNTIME_INT":
-                    try:
-                        int(arg_list[index])
-                    except ValueError:
-                        errors.append(
-                            (
-                                f"In job {self.name()}: argument with index {index} "
-                                "is of incorrect type, should be integer."
-                            )
-                        )
-        return errors
-
     def name(self) -> str:
         return self.job_data["name"]
 
@@ -346,12 +322,12 @@ def _dump_exec_env(self) -> None:
         exec_env = self.job_data.get("exec_env")
         if exec_env:
             exec_name, _ = os.path.splitext(
-                os.path.basename(self.job_data.get("executable"))
+                os.path.basename(cast(Path, self.job_data.get("executable")))
             )
             with open(f"{exec_name}_exec_env.json", "w", encoding="utf-8") as f_handle:
                 f_handle.write(json.dumps(exec_env, indent=4))
 
-    def _check_job_files(self)-> list[str]:
+    def _check_job_files(self) -> list[str]:
         """
         Returns the empty list if no failed checks, or a list of errors in case
         of failed checks.
@@ -361,21 +337,23 @@ def _check_job_files(self)-> list[str]:
             errors.append(f'Could not locate stdin file: {self.job_data["stdin"]}')
 
         if self.job_data.get("start_file") and not os.path.exists(
-            self.job_data["start_file"]
+            cast(Path, self.job_data["start_file"])
         ):
             errors.append(f'Could not locate start_file:{self.job_data["start_file"]}')
 
         if self.job_data.get("error_file") and os.path.exists(
-            self.job_data.get("error_file")
+            cast(Path, self.job_data.get("error_file"))
         ):
-            os.unlink(self.job_data.get("error_file"))
+            os.unlink(cast(Path, self.job_data.get("error_file")))
 
         if executable_error := check_executable(self.job_data.get("executable")):
             errors.append(str(executable_error))
 
         return errors
 
-    def _check_target_file_is_written(self, target_file_mtime: int, timeout: int =5) -> None | str:
+    def _check_target_file_is_written(
+        self, target_file_mtime: int, timeout: int = 5
+    ) -> None | str:
         """
         Check whether or not a target_file eventually appear. Returns None in
         case of success, an error message in the case of failure.
diff --git a/src/_ert/forward_model_runner/reporting/interactive.py b/src/_ert/forward_model_runner/reporting/interactive.py
index fd489c78378..25a26b37896 100644
--- a/src/_ert/forward_model_runner/reporting/interactive.py
+++ b/src/_ert/forward_model_runner/reporting/interactive.py
@@ -19,12 +19,12 @@ def _report(msg: Message) -> Optional[str]:
                 "OK"
                 if msg.success()
                 else _JOB_EXIT_FAILED_STRING.format(
-                    job_name=msg.job.name(),
+                    job_name=msg.job.name() if msg.job else "NO_NAME",
                     exit_code="No Code",
                     error_message=msg.error_message,
                 )
             )
-        return f"Running job: {msg.job.name()} ... "
+        return f"Running job: {msg.job.name() if msg.job else "None"} ... "
 
     def report(self, msg: Message):
         _msg = self._report(msg)
diff --git a/src/_ert/forward_model_runner/reporting/message.py b/src/_ert/forward_model_runner/reporting/message.py
index 3efc9380392..2811488da29 100644
--- a/src/_ert/forward_model_runner/reporting/message.py
+++ b/src/_ert/forward_model_runner/reporting/message.py
@@ -81,7 +81,7 @@ def with_error(self, message: str):
         self.error_message = message
         return self
 
-    def success(self):
+    def success(self) -> bool:
         return self.error_message is None
 
 
@@ -116,7 +116,7 @@ def __init__(self):
 
 
 class Start(Message):
-    def __init__(self, job):
+    def __init__(self, job: "Job"):
         super().__init__(job)
 
 
@@ -127,7 +127,7 @@ def __init__(self, job: "Job", memory_status: ProcessTreeStatus):
 
 
 class Exited(Message):
-    def __init__(self, job, exit_code):
+    def __init__(self, job, exit_code: int):
         super().__init__(job)
         self.exit_code = exit_code