diff --git a/backend/src/controllers/toolConfig.controller.ts b/backend/src/controllers/toolConfig.controller.ts
index 6968849..43be871 100644
--- a/backend/src/controllers/toolConfig.controller.ts
+++ b/backend/src/controllers/toolConfig.controller.ts
@@ -10,7 +10,7 @@ const TOOL_SETTINGS_KEYS: Record<string, string> = {
   nextcloud: 'tool_config_nextcloud',
 };
 
-const MASKED_FIELDS = ['tokenSecret', 'apiToken'];
+const MASKED_FIELDS = ['tokenSecret', 'apiToken', 'bot_app_password'];
 
 function maskValue(value: string): string {
   if (!value || value.length <= 4) return '****';
@@ -98,7 +98,16 @@ class ToolConfigController {
 
     try {
       const userId = req.user!.id;
-      await settingsService.set(settingsKey, req.body, userId);
+      const existing = await settingsService.get(settingsKey);
+      const current = existing?.value && typeof existing.value === 'object' ? existing.value as Record<string, unknown> : {};
+      const incoming: Record<string, unknown> = { ...req.body };
+      for (const key of Object.keys(incoming)) {
+        if (typeof incoming[key] === 'string' && /^\*+/.test(incoming[key] as string)) {
+          delete incoming[key];
+        }
+      }
+      const merged = { ...current, ...incoming };
+      await settingsService.set(settingsKey, merged, userId);
       toolConfigService.clearCache();
       res.status(200).json({ success: true, message: 'Konfiguration gespeichert' });
     } catch (error) {
diff --git a/backend/src/services/toolConfig.service.ts b/backend/src/services/toolConfig.service.ts
index 85241c6..d973076 100644
--- a/backend/src/services/toolConfig.service.ts
+++ b/backend/src/services/toolConfig.service.ts
@@ -14,6 +14,8 @@ export interface VikunjaConfig {
 
 export interface NextcloudConfig {
   url: string;
+  bot_username?: string;
+  bot_app_password?: string;
 }
 
 interface CacheEntry<T> {
@@ -72,6 +74,8 @@ async function getNextcloudConfig(): Promise<NextcloudConfig> {
   const db = await getDbConfig('tool_config_nextcloud');
   const config: NextcloudConfig = {
     url: db.url || environment.nextcloudUrl,
+    bot_username: db.bot_username || undefined,
+    bot_app_password: db.bot_app_password || undefined,
   };
 
   nextcloudCache = { data: config, expiresAt: Date.now() + CACHE_TTL_MS };