diff --git a/i18n/default_de.json b/i18n/default_de.json
index bc6c2fd..35753cb 100644
--- a/i18n/default_de.json
+++ b/i18n/default_de.json
@@ -1150,6 +1150,7 @@
   "Can run scheduled jobs manually": "Kann geplante Aufgaben manuell ausführen",
   "Scheduled job not found": "Geplante Aufgabe nicht gefunden",
   "Scheduled job is not registered": "Geplante Aufgabe ist nicht registriert",
+  "This scheduled job is no longer registered and cannot be edited. It has been superseded by a newer version.": "Diese geplante Aufgabe ist nicht mehr registriert und kann nicht bearbeitet werden. Sie wurde durch eine neuere Version ersetzt.",
   "Scheduled job could not be saved": "Geplante Aufgabe konnte nicht gespeichert werden",
   "Scheduled job saved": "Geplante Aufgabe gespeichert",
   "Edit scheduled job": "Geplante Aufgabe bearbeiten",
diff --git a/i18n/default_en.json b/i18n/default_en.json
index 6187170..ca03ed0 100644
--- a/i18n/default_en.json
+++ b/i18n/default_en.json
@@ -1150,6 +1150,7 @@
   "Can run scheduled jobs manually": "Can run scheduled jobs manually",
   "Scheduled job not found": "Scheduled job not found",
   "Scheduled job is not registered": "Scheduled job is not registered",
+  "This scheduled job is no longer registered and cannot be edited. It has been superseded by a newer version.": "This scheduled job is no longer registered and cannot be edited. It has been superseded by a newer version.",
   "Scheduled job could not be saved": "Scheduled job could not be saved",
   "Scheduled job saved": "Scheduled job saved",
   "Edit scheduled job": "Edit scheduled job",
diff --git a/lib/Repository/Scheduler/ScheduledJobRepository.php b/lib/Repository/Scheduler/ScheduledJobRepository.php
index d5dc21a..987a2aa 100644
--- a/lib/Repository/Scheduler/ScheduledJobRepository.php
+++ b/lib/Repository/Scheduler/ScheduledJobRepository.php
@@ -240,6 +240,22 @@ class ScheduledJobRepository implements ScheduledJobRepositoryInterface
         return $updated !== false;
     }
 
+    public function deleteOrphanedJobs(array $validKeys): int
+    {
+        $validKeys = array_filter(array_map('trim', $validKeys), static fn (string $k): bool => $k !== '');
+        if ($validKeys === []) {
+            return 0;
+        }
+
+        $placeholders = implode(',', array_fill(0, count($validKeys), '?'));
+        $affected = DB::update(
+            "DELETE FROM scheduled_jobs WHERE job_key NOT IN ({$placeholders})",
+            ...array_map('strval', $validKeys)
+        );
+
+        return (int) $affected;
+    }
+
     private function normalizeRow(mixed $row): ?array
     {
         if (!is_array($row)) {
diff --git a/lib/Repository/Scheduler/ScheduledJobRepositoryInterface.php b/lib/Repository/Scheduler/ScheduledJobRepositoryInterface.php
index 0e0071c..eba515c 100644
--- a/lib/Repository/Scheduler/ScheduledJobRepositoryInterface.php
+++ b/lib/Repository/Scheduler/ScheduledJobRepositoryInterface.php
@@ -28,4 +28,7 @@ interface ScheduledJobRepositoryInterface
         ?string $errorCode,
         ?string $errorMessage
     ): bool;
+
+    /** Delete jobs whose job_key is not in the given list of valid keys. Returns affected row count. */
+    public function deleteOrphanedJobs(array $validKeys): int;
 }
diff --git a/lib/Service/Scheduler/ScheduledJobService.php b/lib/Service/Scheduler/ScheduledJobService.php
index 380bb8a..2a85f76 100644
--- a/lib/Service/Scheduler/ScheduledJobService.php
+++ b/lib/Service/Scheduler/ScheduledJobService.php
@@ -42,6 +42,13 @@ class ScheduledJobService
             }
             $this->scheduledJobRepository->updateJobMeta((int) $existing['id'], $normalized);
         }
+
+        $this->scheduledJobRepository->deleteOrphanedJobs(array_keys($definitions));
+    }
+
+    public function isRegistered(string $jobKey): bool
+    {
+        return $this->scheduledJobRegistry->get($jobKey) !== null;
     }
 
     public function listPaged(array $filters): array
diff --git a/pages/admin/scheduled-jobs/edit($id).php b/pages/admin/scheduled-jobs/edit($id).php
index 2f51f34..ae66d15 100644
--- a/pages/admin/scheduled-jobs/edit($id).php
+++ b/pages/admin/scheduled-jobs/edit($id).php
@@ -20,6 +20,8 @@ if (!$job) {
     Router::redirect('admin/scheduled-jobs');
 }
 
+$isRegistered = $scheduledJobService->isRegistered((string) ($job['job_key'] ?? ''));
+
 $currentUserId = (int) ($session['user']['id'] ?? 0);
 $authorizationService = app(\MintyPHP\Service\Access\AuthorizationService::class);
 $canManage = $authorizationService->authorize(\MintyPHP\Service\Access\OperationsAuthorizationPolicy::ABILITY_ADMIN_JOBS_MANAGE, [
@@ -39,6 +41,12 @@ $form = [
 ];
 $errorBag = formErrors();
 
+if (!$isRegistered) {
+    $canManage = false;
+    $canRunNow = false;
+    $errorBag->addGlobal(t('This scheduled job is no longer registered and cannot be edited. It has been superseded by a newer version.'));
+}
+
 if (requestInput()->method() === 'POST') {
     if (!$canManage) {
         Guard::deny();
diff --git a/tests/Service/Scheduler/ScheduledJobServiceTest.php b/tests/Service/Scheduler/ScheduledJobServiceTest.php
index 308741e..d806e91 100644
--- a/tests/Service/Scheduler/ScheduledJobServiceTest.php
+++ b/tests/Service/Scheduler/ScheduledJobServiceTest.php
@@ -102,6 +102,39 @@ class ScheduledJobServiceTest extends TestCase
         $service->ensureSystemJobs();
     }
 
+    public function testEnsureSystemJobsDisablesOrphanedJobs(): void
+    {
+        $jobRepository = $this->createMock(ScheduledJobRepository::class);
+        $runRepository = $this->createMock(ScheduledJobRunRepository::class);
+        $registry = $this->createMock(ScheduledJobRegistry::class);
+        $calculator = new ScheduleCalculator();
+
+        $registry->expects($this->once())->method('definitions')->willReturn([
+            'system_audit_purge' => [
+                'label' => 'System audit log cleanup',
+                'description' => 'Purges system audit log entries',
+                'default_enabled' => 1,
+                'default_timezone' => 'UTC',
+                'default_schedule_type' => 'daily',
+                'default_schedule_interval' => 1,
+                'default_schedule_time' => '03:00',
+                'default_schedule_weekdays_csv' => null,
+                'default_catchup_once' => 1,
+                'allowed_schedule_types' => ['daily', 'weekly'],
+            ],
+        ]);
+        $jobRepository->method('findByKey')->willReturn(null);
+        $jobRepository->method('create')->willReturn(1);
+
+        $jobRepository->expects($this->once())
+            ->method('deleteOrphanedJobs')
+            ->with(['system_audit_purge'])
+            ->willReturn(1);
+
+        $service = new ScheduledJobService($jobRepository, $runRepository, $registry, $calculator);
+        $service->ensureSystemJobs();
+    }
+
     public function testUpdateFromAdminReturnsValidationErrorForWeeklyWithoutWeekdays(): void
     {
         $jobRepository = $this->createMock(ScheduledJobRepository::class);