diff --git a/scripts/run_monthly_codex_audit.py b/scripts/run_monthly_codex_audit.py
index e4eb3dd..b7e16fe 100644
--- a/scripts/run_monthly_codex_audit.py
+++ b/scripts/run_monthly_codex_audit.py
@@ -19,11 +19,14 @@
 import urllib.parse
 import urllib.request
 
-from service.model_router import route_model
+ROOT = Path(__file__).resolve().parents[1]
+if str(ROOT) not in sys.path:
+    sys.path.insert(0, str(ROOT))
+
+from service.model_router import route_model  # noqa: E402
 
 
 API_BASE = "https://api.github.com"
-ROOT = Path(__file__).resolve().parents[1]
 PROMPT_TEMPLATES = {
     "monthly_snapshot_audit": ROOT / "prompts" / "monthly_crypto_snapshot_audit.md",
     "long_horizon_signal_shadow": ROOT / "prompts" / "long_horizon_signal_shadow.md",
diff --git a/tests/test_run_monthly_codex_audit.py b/tests/test_run_monthly_codex_audit.py
index 471d77c..9ed564a 100644
--- a/tests/test_run_monthly_codex_audit.py
+++ b/tests/test_run_monthly_codex_audit.py
@@ -3,6 +3,7 @@
 import json
 import os
 import subprocess
+import sys
 import tempfile
 import threading
 import time
@@ -93,6 +94,25 @@ def _normalized_policy(policy: dict[str, object]) -> dict[str, object]:
 
 
 class RunMonthlyCodexAuditTests(unittest.TestCase):
+    def test_script_entrypoint_can_import_service_from_repo_root(self) -> None:
+        repo_root = Path(__file__).resolve().parents[1]
+        env = dict(os.environ)
+        env.pop("PYTHONPATH", None)
+        env["ISSUE_NUMBER"] = ""
+
+        result = subprocess.run(
+            [sys.executable, "scripts/run_monthly_codex_audit.py"],
+            cwd=repo_root,
+            env=env,
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+
+        self.assertEqual(result.returncode, 1)
+        self.assertIn("ISSUE_NUMBER must be provided as an integer", result.stderr)
+        self.assertNotIn("ModuleNotFoundError", result.stderr)
+
     def test_parse_bool_accepts_common_true_values(self) -> None:
         for value in ("1", "true", "TRUE", "yes", "on", True):
             self.assertTrue(parse_bool(value))