diff --git a/frontend/src/components/AddressList.tsx b/frontend/src/components/AddressList.tsx
index be1828f..a92e057 100644
--- a/frontend/src/components/AddressList.tsx
+++ b/frontend/src/components/AddressList.tsx
@@ -113,7 +113,7 @@ export function AddressList({ entityType, entityId }: AddressListProps) {
       </div>
 
       {error && (
-        <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{error}</div>
+        <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>
       )}
 
       {showForm && (
diff --git a/frontend/src/components/ai/ChatWindow.tsx b/frontend/src/components/ai/ChatWindow.tsx
index 56d0e5d..07fe848 100644
--- a/frontend/src/components/ai/ChatWindow.tsx
+++ b/frontend/src/components/ai/ChatWindow.tsx
@@ -179,7 +179,7 @@ export function ChatWindow({ sessionId, agentId, className, compact }: ChatWindo
           </div>
         )}
         <ActivityIndicator status={activity} />
-        {error && <div className="mb-4 text-sm text-red-600">{error}</div>}
+        {error && <div className="mb-4 text-sm text-red-600">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
       </div>
       <div className={clsx('border-t border-secondary-200', compact ? 'p-2' : 'p-4')}>
         <div className="flex items-end gap-2">
diff --git a/frontend/src/components/ai/SessionList.tsx b/frontend/src/components/ai/SessionList.tsx
index 02daf20..5c92968 100644
--- a/frontend/src/components/ai/SessionList.tsx
+++ b/frontend/src/components/ai/SessionList.tsx
@@ -347,7 +347,7 @@ export function SessionList({ activeSessionId, onSelectSession, isSidebar, class
 
   return (
     <div className={clsx('flex flex-col h-full', className)}>
-      {error && <div className="p-2 text-xs text-red-600">{error}</div>}
+      {error && <div className="p-2 text-xs text-red-600">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
       <div
         className="flex-1 overflow-y-auto p-2"
         onContextMenu={(e) => {
diff --git a/frontend/src/components/calendar/IcsControls.tsx b/frontend/src/components/calendar/IcsControls.tsx
index d01322d..631e0d2 100644
--- a/frontend/src/components/calendar/IcsControls.tsx
+++ b/frontend/src/components/calendar/IcsControls.tsx
@@ -138,7 +138,7 @@ export function IcsControls({ calendar, onImported }: IcsControlsProps) {
       )}
       {error && (
         <span className="text-xs text-danger-700" data-testid="ics-error">
-          {error}
+          {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
         </span>
       )}
     </div>
diff --git a/frontend/src/components/calendar/ResourceBooking.tsx b/frontend/src/components/calendar/ResourceBooking.tsx
index 0b36d4f..dbdfd78 100644
--- a/frontend/src/components/calendar/ResourceBooking.tsx
+++ b/frontend/src/components/calendar/ResourceBooking.tsx
@@ -112,7 +112,7 @@ export function ResourceBooking({ entry, resources, onBooked }: ResourceBookingP
           className="text-xs text-danger-700 bg-danger-50 border border-danger-200 rounded-md p-2"
           data-testid="resource-error"
         >
-          {error}
+          {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
         </div>
       )}
     </div>
diff --git a/frontend/src/components/calendar/SharingSettings.tsx b/frontend/src/components/calendar/SharingSettings.tsx
index 6fb0fb8..e8edb66 100644
--- a/frontend/src/components/calendar/SharingSettings.tsx
+++ b/frontend/src/components/calendar/SharingSettings.tsx
@@ -141,7 +141,7 @@ export function SharingSettings({ calendar }: SharingSettingsProps) {
           className="text-xs text-danger-700 bg-danger-50 border border-danger-200 rounded-md p-2"
           data-testid="sharing-error"
         >
-          {error}
+          {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
         </div>
       )}
       {message && (
diff --git a/frontend/src/components/calendar/TaskDetailPanel.tsx b/frontend/src/components/calendar/TaskDetailPanel.tsx
index bf7c754..4c933b4 100644
--- a/frontend/src/components/calendar/TaskDetailPanel.tsx
+++ b/frontend/src/components/calendar/TaskDetailPanel.tsx
@@ -212,7 +212,7 @@ export function TaskDetailPanel({ entry, onClose, onChanged }: TaskDetailPanelPr
             className="text-sm text-danger-700 bg-danger-50 border border-danger-200 rounded-md p-2"
             data-testid="task-detail-error"
           >
-            {error}
+            {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
           </div>
         )}
       </div>
diff --git a/frontend/src/components/common/ABACRuleEditor.tsx b/frontend/src/components/common/ABACRuleEditor.tsx
index b5078f4..d806872 100644
--- a/frontend/src/components/common/ABACRuleEditor.tsx
+++ b/frontend/src/components/common/ABACRuleEditor.tsx
@@ -583,7 +583,7 @@ function PolicyForm({ initial, entityType, onSave, onCancel }: PolicyFormProps)
       {/* Error */}
       {error && (
         <p className="text-sm text-danger-600" role="alert">
-          {error}
+          {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
         </p>
       )}
 
diff --git a/frontend/src/components/knowledge/AskKnowledge.tsx b/frontend/src/components/knowledge/AskKnowledge.tsx
index ba397c1..2d606c9 100644
--- a/frontend/src/components/knowledge/AskKnowledge.tsx
+++ b/frontend/src/components/knowledge/AskKnowledge.tsx
@@ -90,7 +90,7 @@ export function AskKnowledge() {
           })}
         </div>
 
-        {error && <p className="text-sm text-danger-600" role="alert">{error}</p>}
+        {error && <p className="text-sm text-danger-600" role="alert">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>}
 
         {loading && (
           <div className="flex items-center justify-center py-10" role="status" aria-label={t('common.loading')}>
diff --git a/frontend/src/components/knowledge/KnowledgeGraph.tsx b/frontend/src/components/knowledge/KnowledgeGraph.tsx
index 7104e16..a591748 100644
--- a/frontend/src/components/knowledge/KnowledgeGraph.tsx
+++ b/frontend/src/components/knowledge/KnowledgeGraph.tsx
@@ -236,7 +236,7 @@ export function KnowledgeGraph() {
       )}
       {!loading && error && (
         <div className="py-8 text-center">
-          <p className="text-danger-600 text-sm mb-4">{error}</p>
+          <p className="text-danger-600 text-sm mb-4">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
           <Button variant="secondary" onClick={() => void load()}>
             {t('common.retry')}
           </Button>
diff --git a/frontend/src/components/layout/MessageSidebar.tsx b/frontend/src/components/layout/MessageSidebar.tsx
index a50f726..0ce7536 100644
--- a/frontend/src/components/layout/MessageSidebar.tsx
+++ b/frontend/src/components/layout/MessageSidebar.tsx
@@ -552,7 +552,7 @@ export function MessageSidebar() {
         <p className="text-sm text-secondary-400 text-center py-4">Laden...</p>
       )}
       {error && (
-        <p className="text-sm text-red-500 text-center py-2">{error}</p>
+        <p className="text-sm text-red-500 text-center py-2">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
       )}
       {!loading && conversations.length === 0 && !error && (
         <p className="text-sm text-secondary-400 text-center py-4">Keine Konversationen</p>
diff --git a/frontend/src/components/mail/LabelManager.tsx b/frontend/src/components/mail/LabelManager.tsx
index c3bf95d..bff95c3 100644
--- a/frontend/src/components/mail/LabelManager.tsx
+++ b/frontend/src/components/mail/LabelManager.tsx
@@ -103,7 +103,7 @@ export function LabelManager() {
   if (error) {
     return (
       <div className="p-4 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="label-manager-error">
-        <p className="text-sm text-danger-700">{error}</p>
+        <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
       </div>
     );
   }
diff --git a/frontend/src/components/mail/PgpSettings.tsx b/frontend/src/components/mail/PgpSettings.tsx
index 661e14d..97347f2 100644
--- a/frontend/src/components/mail/PgpSettings.tsx
+++ b/frontend/src/components/mail/PgpSettings.tsx
@@ -93,7 +93,7 @@ export function PgpSettings() {
   if (error) {
     return (
       <div className="p-4 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="pgp-settings-error">
-        <p className="text-sm text-danger-700">{error}</p>
+        <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
       </div>
     );
   }
diff --git a/frontend/src/components/mail/RuleEditor.tsx b/frontend/src/components/mail/RuleEditor.tsx
index efd1ad6..441ba11 100644
--- a/frontend/src/components/mail/RuleEditor.tsx
+++ b/frontend/src/components/mail/RuleEditor.tsx
@@ -153,7 +153,7 @@ export function RuleEditor({ accountId }: { accountId: string }) {
   if (error) {
     return (
       <div className="p-4 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="rule-editor-error">
-        <p className="text-sm text-danger-700">{error}</p>
+        <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
       </div>
     );
   }
diff --git a/frontend/src/components/mail/SignatureManager.tsx b/frontend/src/components/mail/SignatureManager.tsx
index 019373f..9a985c5 100644
--- a/frontend/src/components/mail/SignatureManager.tsx
+++ b/frontend/src/components/mail/SignatureManager.tsx
@@ -134,7 +134,7 @@ export function SignatureManager() {
   if (error) {
     return (
       <div className="p-4 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="signature-manager-error">
-        <p className="text-sm text-danger-700">{error}</p>
+        <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
       </div>
     );
   }
diff --git a/frontend/src/components/mail/TemplatePicker.tsx b/frontend/src/components/mail/TemplatePicker.tsx
index 301dca8..3a4b70d 100644
--- a/frontend/src/components/mail/TemplatePicker.tsx
+++ b/frontend/src/components/mail/TemplatePicker.tsx
@@ -66,7 +66,7 @@ export function TemplatePicker({ onSelect }: TemplatePickerProps) {
   if (error) {
     return (
       <div className="p-4 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="template-picker-error">
-        <p className="text-sm text-danger-700">{error}</p>
+        <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
       </div>
     );
   }
diff --git a/frontend/src/components/shared/CsvImportDialog.tsx b/frontend/src/components/shared/CsvImportDialog.tsx
index e190e1e..e503bf5 100644
--- a/frontend/src/components/shared/CsvImportDialog.tsx
+++ b/frontend/src/components/shared/CsvImportDialog.tsx
@@ -106,7 +106,7 @@ export function CsvImportDialog({ open, onClose, onSuccess }: CsvImportDialogPro
             aria-label="CSV-Datei auswählen"
             data-testid="csv-file-input"
           />
-          {error && <p className="mt-2 text-sm text-danger-600" role="alert">{error}</p>}
+          {error && <p className="mt-2 text-sm text-danger-600" role="alert">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>}
         </div>
 
         {previewData && previewData.rows.length > 0 && (
diff --git a/frontend/src/components/ui/Input.tsx b/frontend/src/components/ui/Input.tsx
index 43e25c1..1df9361 100644
--- a/frontend/src/components/ui/Input.tsx
+++ b/frontend/src/components/ui/Input.tsx
@@ -43,7 +43,7 @@ export const Input = React.forwardRef<HTMLInputElement, InputProps>(
         />
         {error && (
           <p id={errorId} className="mt-1 text-sm text-danger-600" role="alert">
-            {error}
+            {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
           </p>
         )}
         {helperText && !error && (
diff --git a/frontend/src/components/ui/Select.tsx b/frontend/src/components/ui/Select.tsx
index 1a6b9a5..d308fac 100644
--- a/frontend/src/components/ui/Select.tsx
+++ b/frontend/src/components/ui/Select.tsx
@@ -54,7 +54,7 @@ export const Select = React.forwardRef<HTMLSelectElement, SelectProps>(
         </select>
         {error && (
           <p id={errorId} className="mt-1 text-sm text-danger-600" role="alert">
-            {error}
+            {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
           </p>
         )}
         {helperText && !error && (
diff --git a/frontend/src/components/wiki/WikiBrowser.tsx b/frontend/src/components/wiki/WikiBrowser.tsx
index da158b6..aa77139 100644
--- a/frontend/src/components/wiki/WikiBrowser.tsx
+++ b/frontend/src/components/wiki/WikiBrowser.tsx
@@ -180,7 +180,7 @@ export function WikiBrowser({ selectedArticleId, onSelectArticle }: WikiBrowserP
             <Loader2 className="animate-spin h-6 w-6 text-primary-500" aria-hidden="true" />
           </div>
         )}
-        {!loading && error && <p className="text-sm text-danger-600 p-3">{error}</p>}
+        {!loading && error && <p className="text-sm text-danger-600 p-3">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>}
         {!loading && !error && (
           <>
             <button
diff --git a/frontend/src/components/window/AiChatPanel.tsx b/frontend/src/components/window/AiChatPanel.tsx
index f69740f..c6d9334 100644
--- a/frontend/src/components/window/AiChatPanel.tsx
+++ b/frontend/src/components/window/AiChatPanel.tsx
@@ -135,7 +135,7 @@ export function AiChatPanel({ windowTitle, windowType }: AiChatPanelProps) {
         <div className="flex-1 flex items-center justify-center p-4 text-center">
           <div>
             <Sparkles className="w-8 h-8 text-secondary-300 mx-auto mb-2" />
-            <p className="text-sm text-secondary-500">{error}</p>
+            <p className="text-sm text-secondary-500">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
           </div>
         </div>
       </div>
@@ -180,7 +180,7 @@ export function AiChatPanel({ windowTitle, windowType }: AiChatPanelProps) {
           </div>
         )}
         {error && (
-          <div className="text-xs text-danger-600 px-2 py-1">{error}</div>
+          <div className="text-xs text-danger-600 px-2 py-1">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>
         )}
       </div>
 
diff --git a/frontend/src/components/workflows/StepConfigPanel.tsx b/frontend/src/components/workflows/StepConfigPanel.tsx
index 0f09110..c3c4aaa 100644
--- a/frontend/src/components/workflows/StepConfigPanel.tsx
+++ b/frontend/src/components/workflows/StepConfigPanel.tsx
@@ -547,7 +547,7 @@ function JsonField({ label, value, onChange }: JsonFieldProps) {
       />
       {error && (
         <p className="mt-1 text-sm text-danger-600" role="alert">
-          {error}
+          {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
         </p>
       )}
     </div>
diff --git a/frontend/src/pages/AISettings.tsx b/frontend/src/pages/AISettings.tsx
index 1caf9b2..432fea8 100644
--- a/frontend/src/pages/AISettings.tsx
+++ b/frontend/src/pages/AISettings.tsx
@@ -49,7 +49,7 @@ function ProviderTab() {
         <h2 className="text-lg font-semibold">Anbieter</h2>
         <button onClick={() => { setShowForm(!showForm); setEditId(null); setForm({ name: '', provider_type: 'openai', api_key: '', base_url: '', is_default: false }); }} className="px-3 py-1.5 text-sm bg-primary-600 text-white rounded-lg hover:bg-primary-700">+ Hinzufügen</button>
       </div>
-      {error && <div className="text-sm text-red-600">{error}</div>}
+      {error && <div className="text-sm text-red-600">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
       {showForm && (
         <div className="border border-secondary-200 rounded-lg p-4 space-y-3 bg-secondary-50">
           <div className="grid grid-cols-2 gap-3">
@@ -134,7 +134,7 @@ function PresetTab() {
         <h2 className="text-lg font-semibold">Modelle & Presets</h2>
         <button onClick={() => { setShowForm(!showForm); setEditId(null); setForm({ name: '', model_id: '', provider_id: '', temperature: 0.7, max_tokens: 2048, top_p: 1.0, system_prompt: '' }); }} className="px-3 py-1.5 text-sm bg-primary-600 text-white rounded-lg">+ Hinzufügen</button>
       </div>
-      {error && <div className="text-sm text-red-600">{error}</div>}
+      {error && <div className="text-sm text-red-600">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
       {showForm && (
         <div className="border border-secondary-200 rounded-lg p-4 space-y-3 bg-secondary-50">
           <div className="grid grid-cols-2 gap-3">
@@ -225,7 +225,7 @@ function AgentTab() {
         <h2 className="text-lg font-semibold">Agenten</h2>
         <button onClick={() => { setShowForm(!showForm); setEditId(null); setForm({ name: '', description: '', system_prompt: '', preset_id: '', tool_ids: [] }); }} className="px-3 py-1.5 text-sm bg-primary-600 text-white rounded-lg">+ Hinzufügen</button>
       </div>
-      {error && <div className="text-sm text-red-600">{error}</div>}
+      {error && <div className="text-sm text-red-600">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
       {showForm && (
         <div className="border border-secondary-200 rounded-lg p-4 space-y-3 bg-secondary-50">
           <div className="grid grid-cols-2 gap-3">
@@ -291,7 +291,7 @@ function ToolsTab() {
     <div className="space-y-4">
       <h2 className="text-lg font-semibold">Verfügbare Tools</h2>
       <p className="text-sm text-secondary-500">Diese Tools werden von Plugins bereitgestellt und können Agenten zugewiesen werden.</p>
-      {error && <div className="text-sm text-red-600">{error}</div>}
+      {error && <div className="text-sm text-red-600">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
       {tools.length === 0 ? (
         <div className="text-sm text-secondary-400 py-8 text-center">Keine Tools verfügbar. Plugins können Tools registrieren.</div>
       ) : (
diff --git a/frontend/src/pages/Calendar.tsx b/frontend/src/pages/Calendar.tsx
index aee1689..072d9f9 100644
--- a/frontend/src/pages/Calendar.tsx
+++ b/frontend/src/pages/Calendar.tsx
@@ -555,7 +555,7 @@ export function CalendarPage() {
     <div className="flex flex-col h-full" data-testid="calendar-page">
       {error && (
         <div className="mb-2 p-3 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="calendar-error">
-          <p className="text-sm text-danger-700">{error}</p>
+          <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
         </div>
       )}
 
diff --git a/frontend/src/pages/CalendarKanban.tsx b/frontend/src/pages/CalendarKanban.tsx
index ed35529..e3dbedc 100644
--- a/frontend/src/pages/CalendarKanban.tsx
+++ b/frontend/src/pages/CalendarKanban.tsx
@@ -98,7 +98,7 @@ export function CalendarKanbanPage() {
           className="mb-3 text-sm text-danger-700 bg-danger-50 border border-danger-200 rounded-md p-2"
           data-testid="kanban-error"
         >
-          {error}
+          {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
         </div>
       )}
 
diff --git a/frontend/src/pages/Communication.tsx b/frontend/src/pages/Communication.tsx
index 5056cbb..f637d66 100644
--- a/frontend/src/pages/Communication.tsx
+++ b/frontend/src/pages/Communication.tsx
@@ -501,7 +501,7 @@ function ChatWindow({ convId, category, onBack }: ChatWindowProps) {
           </div>
         )}
         {error && (
-          <div className="text-sm text-red-600 bg-red-50 rounded p-3">{error}</div>
+          <div className="text-sm text-red-600 bg-red-50 rounded p-3">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>
         )}
         {!loading && messages.length === 0 && !aiStreaming && (
           <div className="text-center text-secondary-400 py-8">
diff --git a/frontend/src/pages/DmsTrash.tsx b/frontend/src/pages/DmsTrash.tsx
index 596eb09..a77c2bd 100644
--- a/frontend/src/pages/DmsTrash.tsx
+++ b/frontend/src/pages/DmsTrash.tsx
@@ -114,7 +114,7 @@ export function DmsTrashPage() {
       <div className="p-6 max-w-7xl mx-auto" data-testid="dms-trash-page">
         <EmptyState
           title={t('dms.error')}
-          description={error}
+          description={typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
           action={<Button onClick={() => window.location.reload()}>{t('dms.cancel')}</Button>}
         />
       </div>
diff --git a/frontend/src/pages/Mail.tsx b/frontend/src/pages/Mail.tsx
index d7e8fdc..414a7af 100644
--- a/frontend/src/pages/Mail.tsx
+++ b/frontend/src/pages/Mail.tsx
@@ -872,7 +872,7 @@ export function MailPage() {
     <div className="flex flex-col h-full" data-testid="mail-page">
       {error && (
         <div className="mb-2 p-3 bg-danger-50 border border-danger-200 rounded-md" role="alert" data-testid="mail-error">
-          <p className="text-sm text-danger-700">{error}</p>
+          <p className="text-sm text-danger-700">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</p>
         </div>
       )}
 
diff --git a/frontend/src/pages/SettingsCurrencies.tsx b/frontend/src/pages/SettingsCurrencies.tsx
index ac7b27c..08d2a0d 100644
--- a/frontend/src/pages/SettingsCurrencies.tsx
+++ b/frontend/src/pages/SettingsCurrencies.tsx
@@ -116,7 +116,7 @@ export function SettingsCurrenciesPage() {
         </button>
       </div>
 
-      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{error}</div>}
+      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
 
       {showForm && (
         <form onSubmit={handleSubmit(onSubmit)} className="p-4 border border-secondary-200 rounded-lg space-y-3">
diff --git a/frontend/src/pages/SettingsSequences.tsx b/frontend/src/pages/SettingsSequences.tsx
index 013383b..08cc74c 100644
--- a/frontend/src/pages/SettingsSequences.tsx
+++ b/frontend/src/pages/SettingsSequences.tsx
@@ -115,7 +115,7 @@ export function SettingsSequencesPage() {
         </button>
       </div>
 
-      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{error}</div>}
+      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
 
       {showForm && (
         <form onSubmit={handleSubmit(onSubmit)} className="p-4 border border-secondary-200 rounded-lg space-y-3">
diff --git a/frontend/src/pages/SettingsTaxes.tsx b/frontend/src/pages/SettingsTaxes.tsx
index 5cdec2c..08bc009 100644
--- a/frontend/src/pages/SettingsTaxes.tsx
+++ b/frontend/src/pages/SettingsTaxes.tsx
@@ -118,7 +118,7 @@ export function SettingsTaxesPage() {
         </button>
       </div>
 
-      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{error}</div>}
+      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}</div>}
 
       {showForm && (
         <form onSubmit={handleSubmit(onSubmit)} className="p-4 border border-secondary-200 rounded-lg space-y-3">
diff --git a/frontend/src/pages/SettingsWebhooks.tsx b/frontend/src/pages/SettingsWebhooks.tsx
index 970afa6..974965c 100644
--- a/frontend/src/pages/SettingsWebhooks.tsx
+++ b/frontend/src/pages/SettingsWebhooks.tsx
@@ -203,7 +203,7 @@ function WebhookFormModal({ open, onClose, webhook, onSubmit, isSubmitting, erro
         {/* Error */}
         {error && (
           <div className="rounded-md bg-danger-50 border border-danger-200 px-3 py-2 text-sm text-danger-700">
-            {error}
+            {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
           </div>
         )}
 
diff --git a/frontend/src/pages/Tags.tsx b/frontend/src/pages/Tags.tsx
index e9ebc2c..071ce48 100644
--- a/frontend/src/pages/Tags.tsx
+++ b/frontend/src/pages/Tags.tsx
@@ -135,7 +135,7 @@ function TagFormModal({ open, onClose, tag, onSubmit, isSubmitting, error }: Tag
         {/* Error */}
         {error && (
           <div className="rounded-md bg-danger-50 border border-danger-200 px-3 py-2 text-sm text-danger-700">
-            {error}
+            {typeof error === "string" ? error : (error as any)?.message || "Ein Fehler ist aufgetreten"}
           </div>
         )}