diff --git a/scripts/run_training_case_package.py b/scripts/run_training_case_package.py
index f46bffb..db5d33c 100644
--- a/scripts/run_training_case_package.py
+++ b/scripts/run_training_case_package.py
@@ -116,6 +116,8 @@ def _display_path(path: Optional[Path]) -> Optional[str]:
 
 
 def _public_error(exc: Exception) -> str:
+    if isinstance(exc, IsADirectoryError):
+        return "input_path_is_directory"
     if isinstance(exc, FileNotFoundError):
         return "input_file_not_found"
     if isinstance(exc, json.JSONDecodeError):
diff --git a/tests/unit/test_training_case_cli_m6.py b/tests/unit/test_training_case_cli_m6.py
index 80ea768..f97a665 100644
--- a/tests/unit/test_training_case_cli_m6.py
+++ b/tests/unit/test_training_case_cli_m6.py
@@ -152,6 +152,27 @@ class TrainingCaseCliM6Tests(unittest.TestCase):
         self.assertNotIn("\n", line)
         self.assertNotIn("[Errno", line)
 
+    def test_cli_error_summary_uses_stable_code_for_directory_input_path(self) -> None:
+        with tempfile.TemporaryDirectory() as tmpdir:
+            input_path = Path(tmpdir)
+            output_path = Path(tmpdir) / "public_training_case_package.json"
+            stdout = io.StringIO()
+
+            with contextlib.redirect_stdout(stdout):
+                exit_code = training_cli.main(["--input", str(input_path), "--output", str(output_path)])
+
+        line = stdout.getvalue().strip()
+        summary = json.loads(line)
+
+        self.assertEqual(exit_code, 2)
+        self.assertEqual(list(summary), ["passed", "input", "output", "error"])
+        self.assertFalse(summary["passed"])
+        self.assertEqual(summary["input"], str(input_path))
+        self.assertEqual(summary["output"], str(output_path))
+        self.assertEqual(summary["error"], "input_path_is_directory")
+        self.assertNotIn("\n", line)
+        self.assertNotIn("[Errno", line)
+
     def test_cli_exported_public_package_is_offline_projection_without_solution_fields(self) -> None:
         fixture_item = json.loads(FIXTURE.read_text(encoding="utf-8"))["items"][0]