diff --git a/cron/scheduler.py b/cron/scheduler.py
index c6941c763d8..be9bab41215 100644
--- a/cron/scheduler.py
+++ b/cron/scheduler.py
@@ -1842,7 +1842,10 @@ def tick(verbose: bool = True, adapters=None, loop=None) -> int:
                 # If the agent responded with [SILENT], skip delivery (but
                 # output is already saved above).  Failed jobs always deliver.
                 deliver_content = final_response if success else f"⚠️ Cron job '{job.get('name', job['id'])}' failed:\n{error}"
-                should_deliver = bool(deliver_content)
+                # Treat whitespace-only final responses the same as empty
+                # responses: do not deliver a blank message, and let the
+                # empty-response guard below mark the run as a soft failure.
+                should_deliver = bool(deliver_content.strip())
                 if should_deliver and success and SILENT_MARKER in deliver_content.strip().upper():
                     logger.info("Job '%s': agent returned %s — skipping delivery", job["id"], SILENT_MARKER)
                     should_deliver = False
@@ -1858,7 +1861,7 @@ def tick(verbose: bool = True, adapters=None, loop=None) -> int:
                 # Treat empty final_response as a soft failure so last_status
                 # is not "ok" — the agent ran but produced nothing useful.
                 # (issue #8585)
-                if success and not final_response:
+                if success and not final_response.strip():
                     success = False
                     error = "Agent completed but produced empty response (model error, timeout, or misconfiguration)"
 
diff --git a/tests/cron/test_scheduler.py b/tests/cron/test_scheduler.py
index e0cb1cc155e..bbb0343088e 100644
--- a/tests/cron/test_scheduler.py
+++ b/tests/cron/test_scheduler.py
@@ -1773,6 +1773,24 @@ class TestSilentDelivery:
         save_mock.assert_called_once_with("monitor-job", "# full output")
         deliver_mock.assert_not_called()
 
+    def test_whitespace_only_response_is_marked_failed_not_delivered(self):
+        """Whitespace-only final responses should behave like empty responses."""
+        with patch("cron.scheduler.get_due_jobs", return_value=[self._make_job()]), \
+             patch("cron.scheduler.run_job", return_value=(True, "# output", "   \n\t  ", None)), \
+             patch("cron.scheduler.save_job_output", return_value="/tmp/out.md"), \
+             patch("cron.scheduler._deliver_result") as deliver_mock, \
+             patch("cron.scheduler.mark_job_run") as mark_mock:
+            from cron.scheduler import tick
+            tick(verbose=False)
+
+        deliver_mock.assert_not_called()
+        mark_mock.assert_called_once_with(
+            "monitor-job",
+            False,
+            "Agent completed but produced empty response (model error, timeout, or misconfiguration)",
+            delivery_error=None,
+        )
+
 
 class TestBuildJobPromptSilentHint:
     """Verify _build_job_prompt always injects [SILENT] guidance."""