diff --git a/scripts/execution_report_heartbeat.py b/scripts/execution_report_heartbeat.py
index 7e4bd7e..7116592 100644
--- a/scripts/execution_report_heartbeat.py
+++ b/scripts/execution_report_heartbeat.py
@@ -60,7 +60,9 @@ def _month_segments(start: dt.datetime, end: dt.datetime) -> list[str]:
     cursor = dt.datetime(start.year, start.month, 1, tzinfo=dt.timezone.utc)
     end_cursor = dt.datetime(end.year, end.month, 1, tzinfo=dt.timezone.utc)
     while cursor <= end_cursor:
-        months.append(f"{cursor.year:04d}-{cursor.month:02d}")
+        month = f"{cursor.year:04d}-{cursor.month:02d}"
+        months.append(month)
+        months.append(month.replace("-", "_"))
         if cursor.month == 12:
             cursor = dt.datetime(cursor.year + 1, 1, 1, tzinfo=dt.timezone.utc)
         else:
diff --git a/tests/test_execution_report_heartbeat.py b/tests/test_execution_report_heartbeat.py
new file mode 100644
index 0000000..a81da14
--- /dev/null
+++ b/tests/test_execution_report_heartbeat.py
@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import datetime as dt
+
+from scripts import execution_report_heartbeat as heartbeat
+
+
+def test_report_globs_include_sanitized_month_segments(monkeypatch):
+    monkeypatch.delenv("RUNTIME_HEARTBEAT_GCS_GLOBS", raising=False)
+    monkeypatch.delenv("EXECUTION_REPORT_GCS_URI", raising=False)
+    monkeypatch.delenv("RUNTIME_HEARTBEAT_GCS_URIS", raising=False)
+    monkeypatch.delenv("RUNTIME_HEARTBEAT_REPORT_PLATFORM", raising=False)
+    monkeypatch.setenv("FIRSTRADE_GCS_STATE_BUCKET", "runtime-state")
+    monkeypatch.setenv("FIRSTRADE_STATE_PREFIX", "firstrade-platform")
+
+    globs = heartbeat._report_globs(
+        dt.datetime(2026, 5, 31, tzinfo=dt.timezone.utc),
+        dt.datetime(2026, 6, 1, tzinfo=dt.timezone.utc),
+    )
+
+    assert globs == [
+        "gs://runtime-state/firstrade-platform/strategy-runs/**/2026-05/*.json",
+        "gs://runtime-state/firstrade-platform/strategy-runs/**/2026_05/*.json",
+        "gs://runtime-state/firstrade-platform/strategy-runs/**/2026-06/*.json",
+        "gs://runtime-state/firstrade-platform/strategy-runs/**/2026_06/*.json",
+    ]