diff --git a/app/Jobs/ProcessHqWhitelistJob.php b/app/Jobs/ProcessHqWhitelistJob.php
index e507354..b29251b 100644
--- a/app/Jobs/ProcessHqWhitelistJob.php
+++ b/app/Jobs/ProcessHqWhitelistJob.php
@@ -144,7 +144,7 @@ private function notifyAdmin(Host $hqHost, string $modsecLogs): void
             'email' => $adminEmail,
         ]);
 
-        $ttl = (int) (config('unblock.hq.ttl') ?? 7200);
+        $ttl = (int) config('unblock.hq.ttl');
 
         Mail::to($adminEmail)->send(new HqWhitelistMail(
             user: $adminUser,
diff --git a/app/Services/Firewall/DirectAdminFirewallAnalyzer.php b/app/Services/Firewall/DirectAdminFirewallAnalyzer.php
index f38ea97..c3ab146 100644
--- a/app/Services/Firewall/DirectAdminFirewallAnalyzer.php
+++ b/app/Services/Firewall/DirectAdminFirewallAnalyzer.php
@@ -489,7 +489,7 @@ private function checkAndRemoveFromBfmBlacklist(string $ip, string $sshKeyName):
             $this->firewallService->checkProblems($this->host, $sshKeyName, 'da_bfm_whitelist_add', $ip);
 
             // 3. Track in database for automatic removal after TTL
-            $ttl = (int) (config('unblock.hq.ttl') ?? 7200); // Default 2 hours
+            $ttl = (int) config('unblock.hq.ttl');
             BfmWhitelistEntry::create([
                 'host_id' => $this->host->id,
                 'ip_address' => $ip,
diff --git a/rector.php b/rector.php
index da8a120..ba2b4e9 100644
--- a/rector.php
+++ b/rector.php
@@ -11,6 +11,7 @@
 use Rector\TypeDeclaration\Rector\StmtsAwareInterface\DeclareStrictTypesRector;
 use Rector\ValueObject\PhpVersion;
 use RectorLaravel\Rector\ClassMethod\MakeModelAttributesAndScopesProtectedRector;
+use RectorLaravel\Rector\Coalesce\ApplyDefaultInsteadOfNullCoalesceRector;
 use RectorLaravel\Rector\FuncCall\{AppToResolveRector, RemoveDumpDataDeadCodeRector, ThrowIfAndThrowUnlessExceptionsToUseClassStringRector};
 use RectorLaravel\Rector\If_\ThrowIfRector;
 use RectorLaravel\Set\LaravelSetList;
@@ -111,6 +112,21 @@
         // consumes scopes through the builder proxy. This app is final, not a
         // library: no external consumers exist.
         MakeModelAttributesAndScopesProtectedRector::class,
+        // Wave 6 (AID-542), split from AID-531 over the ??/?: lesson. The
+        // rule turns `helper('key') ?? $default` into `helper('key',
+        // $default)` — NOT ??→?:, but it still has a non-equivalent corner:
+        // a key present with an explicit null returns $default under ??,
+        // null under the parameter form. Both sites it flagged used
+        // `config('unblock.hq.ttl') ?? 7200`, where that corner is
+        // unreachable by construction (config/unblock.php casts `(int)
+        // env(..., 14000)`, so the key always exists as int) — which also
+        // made the 7200 a dead phantom default lying about the real 14000.
+        // The fallbacks were removed by hand (the default's single owner is
+        // the config file); the rule stays on as the guard against future
+        // `config('x') ?? $d`, which is always either dead or a duplicated
+        // default. If a legitimate present-but-null key ever appears, skip
+        // that call site here rather than dropping the rule.
+        ApplyDefaultInsteadOfNullCoalesceRector::class,
     ])
     // Wave 4 (AID-532): LARAVEL_COLLECTION (4 sites, all element types are
     // scalars/plain arrays so toArray()≡all(); filter(!empty)→reject(empty)
diff --git a/tests/Unit/Jobs/ProcessHqWhitelistJobTest.php b/tests/Unit/Jobs/ProcessHqWhitelistJobTest.php
index 1217bc6..c96d04a 100644
--- a/tests/Unit/Jobs/ProcessHqWhitelistJobTest.php
+++ b/tests/Unit/Jobs/ProcessHqWhitelistJobTest.php
@@ -450,12 +450,17 @@
 // SCENARIO 8: TTL Configuration
 // ============================================================================
 
-test('job uses default TTL when not configured', function () {
+test('job uses the config-owned default TTL when env is not set', function () {
     $hqHost = Host::factory()->create(['hash' => 'test-key']); // ggignore
 
     config()->set('unblock.hq.host_id', $hqHost->id);
     config()->set('unblock.admin_email', 'admin@example.com');
-    config()->set('unblock.hq.ttl', null); // ← Not configured
+    // "Not configured" means the HQ_WHITELIST_TTL env var is absent, in which
+    // case config/unblock.php resolves `(int) env(..., 14000)` at load time —
+    // the key always exists as an int, never null. The job carries no local
+    // fallback anymore (AID-542); the default's single owner is the config
+    // file, so this test pins that owner's value flowing through untouched.
+    expect(config('unblock.hq.ttl'))->toBe(14000);
 
     $firewallService = Mockery::mock(FirewallService::class);
     $firewallService->allows('generateSshKey')->andReturn('/tmp/key');
@@ -473,7 +478,7 @@
     $job->handle($firewallService);
 
     Mail::assertQueued(HqWhitelistMail::class, function ($mail) {
-        return $mail->ttlSeconds === 7200; // Default 7200s
+        return $mail->ttlSeconds === 14000; // config/unblock.php default
     });
 });