fix: atomic Divi check lock, failed-check notice, test fixes

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/Admin/SettingsPage.php

@@ -165,6 +165,10 @@ final class SettingsPage
                 'warning',
                 __('Es läuft bereits eine Divi-Prüfung; bitte in ein paar Minuten erneut versuchen.', 'wp-lit-mcp'),
             ],
+            'divi_check_failed' => [
+                'error',
+                __('Die Divi-Prüfung ist abgebrochen; Details stehen im PHP-Error-Log.', 'wp-lit-mcp'),
+            ],
             'divi_released' => ['success', __('Die Divi-Version ist für LIT MCP freigegeben.', 'wp-lit-mcp')],
             'divi_release_refused' => [
                 'error',

src/Integrations/Divi/Release/DiviCheckRoute.php

@@ -7,6 +7,8 @@ namespace LIT\MCP\Integrations\Divi\Release;
 use Closure;
 use LIT\MCP\Admin\DiviTab;
 use LIT\MCP\Admin\SettingsPage;
+use LIT\MCP\Log;
+use Throwable;
 use WP_REST_Response;
 
 defined('ABSPATH') || exit;
@@ -15,8 +17,12 @@ defined('ABSPATH') || exit;
  * "Prüfung starten" of the Divi tab (spec §6.1): POST /wp-json/lit-mcp/v1/divi-check. A REST request on purpose –
  * not admin-post – so the check runs in the same context as MCP calls (Divi renders its blocks in REST requests,
  * lit-page-render-summary). The form sends the wp_rest nonce as _wpnonce (cookie authentication); only manage_options.
- * One check at a time: the option LOCK (add_option is atomic); a lock older than LOCK_TTL is a dead check's and taken
- * over. Answers 303 back to the tab.
+ * One check at a time: an atomic "INSERT IGNORE" on the options table (self::LOCK) is the lock – add_option() reads
+ * then writes (wp-includes/option.php) and is not atomic, so two simultaneous requests could both "acquire" it. A
+ * lock older than LOCK_TTL is a dead check's, taken over with a conditional UPDATE (compare-and-swap on the value
+ * just read) so only one of several concurrent takers wins. A check that throws still releases the lock (finally)
+ * and redirects with divi_check_failed (logged, never shown to the browser as an unhandled 500). Answers 303 back
+ * to the tab.
  */
 final class DiviCheckRoute
 {
@@ -59,6 +65,9 @@ final class DiviCheckRoute
                 ($this->reports ?? new CheckReportStore())->save($report);
                 ReleaseGate::forget();
                 $notice = 'divi_checked';
+            } catch (Throwable $e) {
+                Log::failure('divi check', $e);
+                $notice = 'divi_check_failed';
             } finally {
                 delete_option(self::LOCK);
             }
@@ -73,16 +82,44 @@ final class DiviCheckRoute
 
     private static function lock(): bool
     {
-        if (add_option(self::LOCK, time(), '', false)) {
+        global $wpdb;
+
+        if (self::insertLock($wpdb, time())) {
             return true;
         }
 
-        $since = (int) get_option(self::LOCK, 0);
-        if ($since > 0 && time() - $since < self::LOCK_TTL) {
+        // get_var(), not get_option(): the row was written with raw SQL, bypassing the options cache.
+        $since = $wpdb->get_var($wpdb->prepare(
+            "SELECT option_value FROM {$wpdb->options} WHERE option_name = %s",
+            self::LOCK
+        ));
+        if ($since === null) {
+            // The lock was released between our failed insert and this read; try once more.
+            return self::insertLock($wpdb, time());
+        }
+        if (time() - (int) $since < self::LOCK_TTL) {
             return false;
         }
-        delete_option(self::LOCK);
 
-        return (bool) add_option(self::LOCK, time(), '', false);
+        $taken = $wpdb->query($wpdb->prepare(
+            "UPDATE {$wpdb->options} SET option_value = %s WHERE option_name = %s AND option_value = %s",
+            (string) time(),
+            self::LOCK,
+            $since
+        ));
+
+        return (int) $taken === 1;
+    }
+
+    /** INSERT IGNORE: 1 row affected = the lock did not exist and is now ours; 0 = someone else holds it. */
+    private static function insertLock(\wpdb $wpdb, int $now): bool
+    {
+        $inserted = $wpdb->query($wpdb->prepare(
+            "INSERT IGNORE INTO {$wpdb->options} (option_name, option_value, autoload) VALUES (%s, %s, 'no')",
+            self::LOCK,
+            (string) $now
+        ));
+
+        return (int) $inserted === 1;
     }
 }