diff --git a/services/nginx/app/classes/account_deletion_service.php b/services/nginx/app/classes/account_deletion_service.php
index 75805a26..a5309d2a 100644
--- a/services/nginx/app/classes/account_deletion_service.php
+++ b/services/nginx/app/classes/account_deletion_service.php
@@ -7,9 +7,14 @@ use objects\passkeys_o;
 use objects\subusers_o;
 use objects\users_o;
 use Throwable;
+use traits\boolean_normalization_t;
+
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
 
 class account_deletion_service
 {
+    use boolean_normalization_t;
+
     public const CONFIRMATION_PHRASE = 'SLET MIN KONTO';
     public const POLICY_VERSION = '2026-07-20';
     public const MAX_RETRIES = 5;
@@ -52,7 +57,7 @@ class account_deletion_service
             $result = $db->query("SELECT value FROM module_config WHERE module = '$module' AND variable = '$variable' LIMIT 1");
             if ($result === false || $result->num_rows === 0) return false;
             $row = $result->fetch_assoc();
-            return in_array(strtolower(trim((string)($row['value'] ?? ''))), ['1', 'true', 'yes', 'on'], true);
+            return self::normalizeBoolean((string)($row['value'] ?? ''));
         } catch (Throwable) {
             return false;
         }
diff --git a/services/nginx/app/classes/cron_worker.php b/services/nginx/app/classes/cron_worker.php
index 1ee6c1c2..8c0ac768 100644
--- a/services/nginx/app/classes/cron_worker.php
+++ b/services/nginx/app/classes/cron_worker.php
@@ -3,9 +3,14 @@
 namespace classes;
 
 use Throwable;
+use traits\boolean_normalization_t;
+
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
 
 class cron_worker
 {
+    use boolean_normalization_t;
+
     private cron_scheduler $scheduler;
     private string $worker_id;
     private string $name;
@@ -291,7 +296,7 @@ class cron_worker
             return $default;
         }
 
-        return in_array(strtolower(trim($value)), ['1', 'true', 'yes', 'on'], true);
+        return self::normalizeBoolean($value);
     }
 
     private function commitSha(): string
diff --git a/services/nginx/app/classes/module_usage_service.php b/services/nginx/app/classes/module_usage_service.php
index 3f923884..e62bc3cb 100644
--- a/services/nginx/app/classes/module_usage_service.php
+++ b/services/nginx/app/classes/module_usage_service.php
@@ -5,9 +5,14 @@ namespace classes;
 use Exception;
 use mysqli_result;
 use Throwable;
+use traits\boolean_normalization_t;
+
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
 
 class module_usage_service
 {
+    use boolean_normalization_t;
+
     private module_usage_registry $registry;
 
     public function __construct(?module_usage_registry $registry = null)
@@ -968,10 +973,7 @@ class module_usage_service
 
     private function toBool(mixed $value): bool
     {
-        if (is_bool($value)) {
-            return $value;
-        }
-        return in_array(strtolower(trim((string)$value)), ['1', 'true', 'yes', 'on'], true);
+        return self::normalizeBoolean($value);
     }
 
     private function sqlString(string $value): string
diff --git a/services/nginx/app/classes/release_manager.php b/services/nginx/app/classes/release_manager.php
index 1ddcad4e..6d7d5ad4 100644
--- a/services/nginx/app/classes/release_manager.php
+++ b/services/nginx/app/classes/release_manager.php
@@ -5,11 +5,15 @@ namespace classes;
 use customers\economicCustomers;
 use RuntimeException;
 use Throwable;
+use traits\boolean_normalization_t;
 
 require_once __DIR__ . '/cors_policy.php';
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
 
 class release_manager
 {
+    use boolean_normalization_t;
+
     private const APPS = ['frontend', 'api'];
     private const DEFAULT_BRANCH = 'master';
     private const RELEASE_ROUTE_SLUGS = [
@@ -12665,10 +12669,7 @@ class release_manager
 
     private function toBool(mixed $value): bool
     {
-        if (is_bool($value)) {
-            return $value;
-        }
-        return in_array(strtolower(trim((string)$value)), ['1', 'true', 'yes', 'on'], true);
+        return self::normalizeBoolean($value);
     }
 
     private function requestTraceId(): string
diff --git a/services/nginx/app/classes/releasemanager.php b/services/nginx/app/classes/releasemanager.php
index a4450dfe..1bafd830 100644
--- a/services/nginx/app/classes/releasemanager.php
+++ b/services/nginx/app/classes/releasemanager.php
@@ -2,8 +2,14 @@
 
 namespace classes;
 
+use traits\boolean_normalization_t;
+
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
+
 class releasemanager
 {
+    use boolean_normalization_t;
+
     public function isEnabled(): bool
     {
         try {
@@ -11,7 +17,7 @@ class releasemanager
             global $db;
             $result = $db->query("SELECT value FROM module_config WHERE module = 'ReleaseManager' AND variable = 'enabled' LIMIT 1");
             $row = $result ? $result->fetch_assoc() : null;
-            return in_array(strtolower(trim((string)($row['value'] ?? 'true'))), ['1', 'true', 'yes', 'on'], true);
+            return self::normalizeBoolean((string)($row['value'] ?? 'true'));
         } catch (\Throwable) {
             return true;
         }
diff --git a/services/nginx/app/classes/replica_failover_manager.php b/services/nginx/app/classes/replica_failover_manager.php
index 5aaa03d8..a8a7473d 100644
--- a/services/nginx/app/classes/replica_failover_manager.php
+++ b/services/nginx/app/classes/replica_failover_manager.php
@@ -6,9 +6,14 @@ use Aws\S3\S3Client;
 use mysqli;
 use Predis\Client as PredisClient;
 use Throwable;
+use traits\boolean_normalization_t;
+
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
 
 class replica_failover_manager
 {
+    use boolean_normalization_t;
+
     public const KIND_DATABASE = 'database';
     public const KIND_REDIS = 'redis';
     public const KIND_MINIO = 'minio';
@@ -502,11 +507,7 @@ class replica_failover_manager
 
     private static function boolValue(mixed $value): bool
     {
-        if (is_bool($value)) {
-            return $value;
-        }
-
-        return in_array(strtolower(trim((string)$value)), ['1', 'true', 'yes', 'on'], true);
+        return self::normalizeBoolean($value);
     }
 
     private static function jsonDecode(mixed $value): array
diff --git a/services/nginx/app/classes/superuser_system_status_service.php b/services/nginx/app/classes/superuser_system_status_service.php
index 58b10a00..27fa747a 100644
--- a/services/nginx/app/classes/superuser_system_status_service.php
+++ b/services/nginx/app/classes/superuser_system_status_service.php
@@ -4,9 +4,14 @@ namespace classes;
 
 use Aws\S3\S3Client;
 use Throwable;
+use traits\boolean_normalization_t;
+
+require_once __DIR__ . '/../traits/boolean_normalization_t.php';
 
 class superuser_system_status_service
 {
+    use boolean_normalization_t;
+
     public const MODULE_PROBE_TTL_SECONDS = 60;
     public const REFRESH_AFTER_SECONDS = 30;
     private const MODULE_PROBE_CACHE_KEY_PREFIX = 'superuser_system_status:module_probe:';
@@ -847,7 +852,7 @@ class superuser_system_status_service
     protected function parseModuleConfigValue(string $type, mixed $value): mixed
     {
         return match (strtolower($type)) {
-            'bool' => in_array(strtolower(trim((string)$value)), ['1', 'true', 'yes', 'on'], true),
+            'bool' => self::normalizeBoolean($value),
             'int', 'integer' => is_numeric($value) ? (int)$value : null,
             'float', 'double' => is_numeric($value) ? (float)$value : null,
             'json' => is_string($value) ? json_decode($value, true) : null,
diff --git a/services/nginx/app/tests/Smoke/boolean_normalization_smoke.php b/services/nginx/app/tests/Smoke/boolean_normalization_smoke.php
new file mode 100644
index 00000000..8f5a13fc
--- /dev/null
+++ b/services/nginx/app/tests/Smoke/boolean_normalization_smoke.php
@@ -0,0 +1,69 @@
+<?php
+/**
+ * Standalone smoke test for the boolean_normalization_t trait.
+ *
+ * The composer autoloader is not always available locally (CI may install
+ * dependencies before this script runs); the inline require_once calls
+ * below let us verify the trait + all seven consumers in isolation.
+ */
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../traits/boolean_normalization_t.php';
+require_once __DIR__ . '/../../classes/cron_worker.php';
+require_once __DIR__ . '/../../classes/replica_failover_manager.php';
+require_once __DIR__ . '/../../classes/superuser_system_status_service.php';
+require_once __DIR__ . '/../../classes/module_usage_service.php';
+require_once __DIR__ . '/../../classes/account_deletion_service.php';
+require_once __DIR__ . '/../../classes/releasemanager.php';
+require_once __DIR__ . '/../../classes/release_manager.php';
+
+$classes = [
+    'classes\\cron_worker',
+    'classes\\replica_failover_manager',
+    'classes\\superuser_system_status_service',
+    'classes\\module_usage_service',
+    'classes\\account_deletion_service',
+    'classes\\releasemanager',
+    'classes\\release_manager',
+];
+foreach ($classes as $class) {
+    $rc = new ReflectionClass($class);
+    $ok = in_array('traits\\boolean_normalization_t', $rc->getTraitNames(), true);
+    echo str_pad($class, 55) . ' -> ' . ($ok ? 'YES' : 'NO') . PHP_EOL;
+}
+echo PHP_EOL;
+
+$cases = [
+    [true, true],
+    [false, false],
+    [1, true],
+    [0, false],
+    ['true', true],
+    ['TRUE', true],
+    ['1', true],
+    ['yes', true],
+    ['YES', true],
+    ['on', true],
+    ['  ON  ', true],
+    ['false', false],
+    ['no', false],
+    ['off', false],
+    ['', false],
+    [null, false],
+    ['0', false],
+    [[], false],
+    [(object) ['v' => 'true'], false],
+];
+$s = new class {
+    use traits\boolean_normalization_t;
+};
+$fails = 0;
+foreach ($cases as $pair) {
+    [$in, $exp] = $pair;
+    $a = $s::normalizeBoolean($in);
+    if ($a !== $exp) {
+        echo 'FAIL ' . var_export($in, true) . ' expected ' . var_export($exp, true) . ' got ' . var_export($a, true) . PHP_EOL;
+        $fails++;
+    }
+}
+echo ($fails === 0 ? 'OK' : 'FAIL') . ' - ' . count($cases) . ' normalizeBoolean cases' . PHP_EOL;
diff --git a/services/nginx/app/tests/Unit/Traits/BooleanNormalizationTest.php b/services/nginx/app/tests/Unit/Traits/BooleanNormalizationTest.php
new file mode 100644
index 00000000..c55a3d49
--- /dev/null
+++ b/services/nginx/app/tests/Unit/Traits/BooleanNormalizationTest.php
@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+use traits\boolean_normalization_t;
+use traits\module_config_variable;
+
+it('treats true and integer 1 as truthy, everything else as false', function (): void {
+    $subject = new class {
+        use boolean_normalization_t;
+    };
+
+    expect($subject::normalizeBoolean(true))->toBeTrue();
+    expect($subject::normalizeBoolean(1))->toBeTrue();
+});
+
+it('accepts the canonical truthy-string set with whitespace and case folded', function (): void {
+    $subject = new class {
+        use boolean_normalization_t;
+    };
+
+    foreach (['true', 'TRUE', 'True', '1', 'yes', 'YES', 'Yes', 'on', 'ON', 'On'] as $case) {
+        expect($subject::normalizeBoolean($case))->toBeTrue();
+    }
+
+    expect($subject::normalizeBoolean(' true '))->toBeTrue();
+    expect($subject::normalizeBoolean("  YES\t"))->toBeTrue();
+});
+
+it('treats integer 0 and the canonical falsy strings as false', function (): void {
+    $subject = new class {
+        use boolean_normalization_t;
+    };
+
+    expect($subject::normalizeBoolean(false))->toBeFalse();
+    expect($subject::normalizeBoolean(0))->toBeFalse();
+    expect($subject::normalizeBoolean(''))->toBeFalse();
+    expect($subject::normalizeBoolean('0'))->toBeFalse();
+    expect($subject::normalizeBoolean('false'))->toBeFalse();
+    expect($subject::normalizeBoolean('no'))->toBeFalse();
+    expect($subject::normalizeBoolean('off'))->toBeFalse();
+});
+
+it('treats null, arrays and objects as false', function (): void {
+    $subject = new class {
+        use boolean_normalization_t;
+    };
+
+    expect($subject::normalizeBoolean(null))->toBeFalse();
+    expect($subject::normalizeBoolean([]))->toBeFalse();
+    expect($subject::normalizeBoolean(['true']))->toBeFalse();
+    expect($subject::normalizeBoolean((object)['value' => 'true']))->toBeFalse();
+});
+
+it('keeps module_config_variable::inputToBool returning true for the existing truthy strings', function (): void {
+    app_require('traits/module_config_variable_t.php');
+
+    $subject = new class {
+        use module_config_variable;
+    };
+
+    expect($subject::inputToBool('true'))->toBeTrue();
+    expect($subject::inputToBool('1'))->toBeTrue();
+    expect($subject::inputToBool('false'))->toBeFalse();
+});
+
+it('now also accepts the wider truthy-string set through inputToBool (parity with the inline copies)', function (): void {
+    app_require('traits/module_config_variable_t.php');
+
+    $subject = new class {
+        use module_config_variable;
+    };
+
+    // These were accepted by the inline in_array(...) copies but rejected
+    // by the previous inputToBool implementation. They are now consistent.
+    expect($subject::inputToBool('yes'))->toBeTrue();
+    expect($subject::inputToBool('on'))->toBeTrue();
+    expect($subject::inputToBool(' YES '))->toBeTrue();
+});
diff --git a/services/nginx/app/traits/boolean_normalization_t.php b/services/nginx/app/traits/boolean_normalization_t.php
new file mode 100644
index 00000000..f2351e6b
--- /dev/null
+++ b/services/nginx/app/traits/boolean_normalization_t.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace traits;
+
+/**
+ * Canonical boolean normalisation used by configuration and helper code.
+ *
+ * The same `in_array(strtolower(trim((string)$value)), ['1', 'true', 'yes', 'on'], true)`
+ * pattern was inlined in six places across classes/cron_worker.php,
+ * classes/replica_failover_manager.php, classes/release_manager.php,
+ * classes/superuser_system_status_service.php, classes/module_usage_service.php,
+ * and traits/module_config_variable_t.php::inputToBool(). Centralising it
+ * here means the truthy-string set lives in exactly one location.
+ */
+trait boolean_normalization_t
+{
+    /**
+     * Coerce $value to a real bool. Truthy inputs: true, 1, '1', 'true',
+     * 'yes', 'on' (case-insensitive, surrounding whitespace ignored).
+     * Everything else is false (including null, false, 0, '', '0', 'false',
+     * 'no', 'off', arrays, objects).
+     *
+     * @param mixed $value
+     */
+    public static function normalizeBoolean(mixed $value): bool
+    {
+        if (is_bool($value)) {
+            return $value;
+        }
+        if (is_int($value) || is_float($value)) {
+            return $value !== 0;
+        }
+        if (is_string($value)) {
+            return in_array(strtolower(trim($value)), ['1', 'true', 'yes', 'on'], true);
+        }
+        return false;
+    }
+}
diff --git a/services/nginx/app/traits/module_config_variable_t.php b/services/nginx/app/traits/module_config_variable_t.php
index 93999b44..ec937250 100644
--- a/services/nginx/app/traits/module_config_variable_t.php
+++ b/services/nginx/app/traits/module_config_variable_t.php
@@ -5,6 +5,8 @@ namespace traits;
 use classes\system_search_cache;
 use Exception;
 
+require_once __DIR__ . '/boolean_normalization_t.php';
+
 trait module_config_variable
 {
     public string $module_name; // The name of the module
@@ -233,12 +235,10 @@ trait module_config_variable
      */
     static function inputToBool(string $value): bool
     {
-        // If the value is true, 1, or "true", return true
-        if ($value === 'true' || $value === '1') {
-            return true;
-        }
-        // If the value is false, 0, or "false", return false
-        return false;
+        // Delegate to the shared boolean_normalization_t helper so the
+        // truthy-string set ('1', 'true', 'yes', 'on') lives in exactly one
+        // place across the codebase.
+        return boolean_normalization_t::normalizeBoolean($value);
     }
 
     /**