diff --git a/app/Http/Controllers/Api/SentinelController.php b/app/Http/Controllers/Api/SentinelController.php
index 734353386..ca47e9f9d 100644
--- a/app/Http/Controllers/Api/SentinelController.php
+++ b/app/Http/Controllers/Api/SentinelController.php
@@ -117,19 +117,22 @@ private function shouldDispatchUpdate(Server $server, array $data): bool
         $hash = $this->containerStateHash($data);
         $hashKey = "sentinel:push-hash:{$server->id}";
         $forceKey = "sentinel:push-force:{$server->id}";
+        $lockKey = "sentinel:push-lock:{$server->id}";
 
-        $cachedHash = Cache::get($hashKey);
-        $forceActive = Cache::has($forceKey);
+        return Cache::lock($lockKey, 10)->block(5, function () use ($hashKey, $forceKey, $hash): bool {
+            $cachedHash = Cache::get($hashKey);
+            $forceActive = Cache::has($forceKey);
 
-        $shouldDispatch = $cachedHash === null || $cachedHash !== $hash || ! $forceActive;
+            $shouldDispatch = $cachedHash === null || $cachedHash !== $hash || ! $forceActive;
 
-        if ($shouldDispatch) {
-            // Day-long TTL bounds memory if a server stops pushing entirely.
-            Cache::put($hashKey, $hash, now()->addDay());
-            Cache::put($forceKey, true, config('constants.sentinel.push_force_interval_seconds', 300));
-        }
+            if ($shouldDispatch) {
+                // Day-long TTL bounds memory if a server stops pushing entirely.
+                Cache::put($hashKey, $hash, now()->addDay());
+                Cache::put($forceKey, true, config('constants.sentinel.push_force_interval_seconds', 300));
+            }
 
-        return $shouldDispatch;
+            return $shouldDispatch;
+        });
     }
 
     /**
diff --git a/tests/Feature/SentinelPushDeduplicationTest.php b/tests/Feature/SentinelPushDeduplicationTest.php
index c4a887da4..9d20851ed 100644
--- a/tests/Feature/SentinelPushDeduplicationTest.php
+++ b/tests/Feature/SentinelPushDeduplicationTest.php
@@ -90,6 +90,16 @@ function sentinelPayload(array $containers, ?float $diskPercentage = 42.0): arra
     'empty containers' => [['containers' => []]],
 ]);
 
+it('guards the dedupe decision with a server scoped atomic cache lock', function () {
+    $controller = file_get_contents(app_path('Http/Controllers/Api/SentinelController.php'));
+
+    expect($controller)
+        ->toContain('$lockKey = "sentinel:push-lock:{$server->id}";')
+        ->toContain('Cache::lock($lockKey, 10)->block(5, function () use ($hashKey, $forceKey, $hash): bool')
+        ->toContain('Cache::put($hashKey, $hash, now()->addDay())')
+        ->toContain("Cache::put(\$forceKey, true, config('constants.sentinel.push_force_interval_seconds', 300))");
+});
+
 it('dispatches the job when container state changes', function () use ($running) {
     pushSentinel($this->token, sentinelPayload($running()))->assertOk();