diff --git a/src/api/billingApi.ts b/src/api/billingApi.ts
index c43c40f..800adf1 100644
--- a/src/api/billingApi.ts
+++ b/src/api/billingApi.ts
@@ -252,3 +252,28 @@ export async function fetchTransactionsAdmin(
     params: { limit }
   });
 }
+
+/**
+ * User summary for billing admin
+ */
+export interface MandateUserSummary {
+  id: string;
+  email?: string;
+  firstName?: string;
+  lastName?: string;
+  displayName?: string;
+}
+
+/**
+ * Fetch all users for a mandate (Admin)
+ * Endpoint: GET /api/billing/admin/users/{mandateId}
+ */
+export async function fetchUsersForMandateAdmin(
+  request: ApiRequestFunction,
+  mandateId: string
+): Promise<MandateUserSummary[]> {
+  return await request({
+    url: `/api/billing/admin/users/${mandateId}`,
+    method: 'get'
+  });
+}
diff --git a/src/components/Navigation/UserSection.tsx b/src/components/Navigation/UserSection.tsx
index b78b874..1d7ba38 100644
--- a/src/components/Navigation/UserSection.tsx
+++ b/src/components/Navigation/UserSection.tsx
@@ -34,6 +34,11 @@ export const UserSection: React.FC = () => {
     setShowMenu(false);
   };
   
+  const handleBilling = () => {
+    navigate('/billing');
+    setShowMenu(false);
+  };
+  
   const handleLegal = () => {
     setShowLegalModal(true);
     setShowMenu(false);
@@ -72,6 +77,14 @@ export const UserSection: React.FC = () => {
       
       {showMenu && (
         <div className={styles.menu}>
+          <button 
+            className={styles.menuItem}
+            onClick={handleBilling}
+          >
+            <span className={styles.menuIcon}>💰</span>
+            Guthaben
+          </button>
+          
           <button 
             className={styles.menuItem}
             onClick={handleSettings}
diff --git a/src/components/ProviderSelector/ProviderSelector.module.css b/src/components/ProviderSelector/ProviderSelector.module.css
index 465ed1e..242df68 100644
--- a/src/components/ProviderSelector/ProviderSelector.module.css
+++ b/src/components/ProviderSelector/ProviderSelector.module.css
@@ -44,7 +44,110 @@
 .providerMultiSelect {
   display: flex;
   flex-direction: column;
-  gap: var(--spacing-sm, 8px);
+  gap: var(--spacing-xs, 4px);
+  position: relative;
+}
+
+.providerMultiSelect.collapsed {
+  /* Collapsed state styles */
+}
+
+.providerMultiSelect.expanded {
+  /* Expanded state styles */
+}
+
+/* Collapsible Header Button */
+.collapseHeader {
+  display: flex;
+  align-items: center;
+  gap: var(--spacing-xs, 4px);
+  padding: var(--spacing-xs, 4px) var(--spacing-sm, 8px);
+  border: 1px solid var(--color-border);
+  border-radius: var(--border-radius-md, 6px);
+  background: var(--color-bg-input);
+  color: var(--color-text-primary);
+  font-size: var(--font-size-sm, 0.875rem);
+  cursor: pointer;
+  transition: all 0.2s ease;
+  min-width: 140px;
+}
+
+.collapseHeader:hover:not(:disabled) {
+  border-color: var(--color-primary);
+  background: var(--color-bg-hover);
+}
+
+.collapseHeader:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+
+.summaryIcons {
+  font-size: 0.9em;
+}
+
+.summaryText {
+  flex: 1;
+  text-align: left;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.expandIcon {
+  font-size: 0.7em;
+  color: var(--color-text-secondary);
+}
+
+/* Expandable Content - opens upward */
+.expandableContent {
+  position: absolute;
+  bottom: 100%;
+  left: 0;
+  right: 0;
+  z-index: 100;
+  margin-bottom: var(--spacing-xs, 4px);
+  padding: var(--spacing-sm, 8px);
+  background: #2d2d2d;
+  color: #e0e0e0;
+  border: 1px solid #444;
+  border-radius: var(--border-radius-md, 6px);
+  box-shadow: 0 -4px 12px rgba(0, 0, 0, 0.4);
+  min-width: 200px;
+}
+
+.expandableContent .label {
+  color: #b0b0b0;
+}
+
+.expandableContent .checkboxList {
+  background: #252525;
+}
+
+.expandableContent .checkboxItem {
+  color: #e0e0e0;
+}
+
+.expandableContent .checkboxItem:hover {
+  background: #3a3a3a;
+}
+
+.expandableContent .providerName {
+  color: #e0e0e0;
+}
+
+.expandableContent .hint {
+  color: #888;
+}
+
+.expandableContent .actionButton {
+  background: #3a3a3a;
+  color: #e0e0e0;
+  border-color: #555;
+}
+
+.expandableContent .actionButton:hover:not(:disabled) {
+  background: #4a4a4a;
 }
 
 .selectActions {
diff --git a/src/components/ProviderSelector/ProviderSelector.tsx b/src/components/ProviderSelector/ProviderSelector.tsx
index fb36ea5..73f0184 100644
--- a/src/components/ProviderSelector/ProviderSelector.tsx
+++ b/src/components/ProviderSelector/ProviderSelector.tsx
@@ -10,7 +10,7 @@
  * - Lädt verfügbare Provider aus dem Billing-System
  */
 
-import React, { useEffect, useMemo } from 'react';
+import React, { useEffect, useMemo, useState } from 'react';
 import { useBilling } from '../../hooks/useBilling';
 import styles from './ProviderSelector.module.css';
 
@@ -99,6 +99,7 @@ interface ProviderMultiSelectProps {
   className?: string;
   label?: string;
   showLabel?: boolean;
+  defaultExpanded?: boolean;
 }
 
 export const ProviderMultiSelect: React.FC<ProviderMultiSelectProps> = ({
@@ -106,9 +107,11 @@ export const ProviderMultiSelect: React.FC<ProviderMultiSelectProps> = ({
   onChange,
   disabled = false,
   className,
-  label = 'Erlaubte AI-Provider',
+  label = 'AI-Provider',
   showLabel = true,
+  defaultExpanded = false,
 }) => {
+  const [isExpanded, setIsExpanded] = useState(defaultExpanded);
   const { allowedProviders, loadAllowedProviders, loading } = useBilling();
   
   useEffect(() => {
@@ -133,56 +136,92 @@ export const ProviderMultiSelect: React.FC<ProviderMultiSelectProps> = ({
     onChange([]);
   };
   
+  // Summary text for collapsed view
+  const summaryText = useMemo(() => {
+    if (selectedProviders.length === 0) {
+      return 'Alle Provider';
+    }
+    if (selectedProviders.length === 1) {
+      return PROVIDER_LABELS[selectedProviders[0]] || selectedProviders[0];
+    }
+    return `${selectedProviders.length} Provider`;
+  }, [selectedProviders]);
+  
+  // Summary icons for collapsed view
+  const summaryIcons = useMemo(() => {
+    if (selectedProviders.length === 0) {
+      return '🤖';
+    }
+    return selectedProviders.slice(0, 3).map(p => PROVIDER_ICONS[p] || '🔌').join('');
+  }, [selectedProviders]);
+  
   return (
-    <div className={`${styles.providerMultiSelect} ${className || ''}`}>
-      {showLabel && <label className={styles.label}>{label}</label>}
+    <div className={`${styles.providerMultiSelect} ${className || ''} ${isExpanded ? styles.expanded : styles.collapsed}`}>
+      {/* Collapsible Header */}
+      <button 
+        type="button"
+        className={styles.collapseHeader}
+        onClick={() => setIsExpanded(!isExpanded)}
+        disabled={disabled}
+      >
+        <span className={styles.summaryIcons}>{summaryIcons}</span>
+        <span className={styles.summaryText}>{summaryText}</span>
+        <span className={styles.expandIcon}>{isExpanded ? '▲' : '▼'}</span>
+      </button>
       
-      <div className={styles.selectActions}>
-        <button 
-          type="button" 
-          onClick={handleSelectAll} 
-          disabled={disabled}
-          className={styles.actionButton}
-        >
-          Alle
-        </button>
-        <button 
-          type="button" 
-          onClick={handleSelectNone} 
-          disabled={disabled}
-          className={styles.actionButton}
-        >
-          Keine
-        </button>
-      </div>
-      
-      {loading ? (
-        <div className={styles.loading}>Lade Provider...</div>
-      ) : (
-        <div className={styles.checkboxList}>
-          {allowedProviders.map((provider) => (
-            <label 
-              key={provider} 
-              className={`${styles.checkboxItem} ${disabled ? styles.disabled : ''}`}
+      {/* Expandable Content */}
+      {isExpanded && (
+        <div className={styles.expandableContent}>
+          {showLabel && <label className={styles.label}>{label}</label>}
+          
+          <div className={styles.selectActions}>
+            <button 
+              type="button" 
+              onClick={handleSelectAll} 
+              disabled={disabled}
+              className={styles.actionButton}
             >
-              <input
-                type="checkbox"
-                checked={selectedProviders.includes(provider)}
-                onChange={() => handleToggle(provider)}
-                disabled={disabled}
-              />
-              <span className={styles.icon}>{PROVIDER_ICONS[provider] || '🔌'}</span>
-              <span className={styles.providerName}>
-                {PROVIDER_LABELS[provider] || provider}
-              </span>
-            </label>
-          ))}
-        </div>
-      )}
-      
-      {selectedProviders.length === 0 && !loading && (
-        <div className={styles.hint}>
-          Wenn keine Provider ausgewählt sind, werden alle erlaubten Provider verwendet.
+              Alle
+            </button>
+            <button 
+              type="button" 
+              onClick={handleSelectNone} 
+              disabled={disabled}
+              className={styles.actionButton}
+            >
+              Keine
+            </button>
+          </div>
+          
+          {loading ? (
+            <div className={styles.loading}>Lade Provider...</div>
+          ) : (
+            <div className={styles.checkboxList}>
+              {allowedProviders.map((provider) => (
+                <label 
+                  key={provider} 
+                  className={`${styles.checkboxItem} ${disabled ? styles.disabled : ''}`}
+                >
+                  <input
+                    type="checkbox"
+                    checked={selectedProviders.includes(provider)}
+                    onChange={() => handleToggle(provider)}
+                    disabled={disabled}
+                  />
+                  <span className={styles.icon}>{PROVIDER_ICONS[provider] || '🔌'}</span>
+                  <span className={styles.providerName}>
+                    {PROVIDER_LABELS[provider] || provider}
+                  </span>
+                </label>
+              ))}
+            </div>
+          )}
+          
+          {selectedProviders.length === 0 && !loading && (
+            <div className={styles.hint}>
+              Wenn keine Provider ausgewählt sind, werden alle erlaubten Provider verwendet.
+            </div>
+          )}
         </div>
       )}
     </div>
diff --git a/src/hooks/playground/useDashboardInputForm.ts b/src/hooks/playground/useDashboardInputForm.ts
index 8650fdf..b41c1ea 100644
--- a/src/hooks/playground/useDashboardInputForm.ts
+++ b/src/hooks/playground/useDashboardInputForm.ts
@@ -30,7 +30,7 @@ export function useDashboardInputForm(instanceId: string) {
   const [optimisticMessage, setOptimisticMessage] = useState<WorkflowMessage | null>(null);
   const [selectedPromptId, setSelectedPromptId] = useState<string | null>(null);
   const [workflowMode, setWorkflowMode] = useState<'Dynamic' | 'Automation' | null>(null);
-  const [selectedProvider, setSelectedProvider] = useState<string>(''); // AI provider selection
+  const [selectedProviders, setSelectedProviders] = useState<string[]>([]); // AI provider selection (multiselect)
   
   const { checkPermission, canView } = usePermissions();
   const [playgroundUIPermission, setPlaygroundUIPermission] = useState<boolean>(false);
@@ -596,7 +596,7 @@ export function useDashboardInputForm(instanceId: string) {
         prompt: trimmedInput,
         listFileId: fileIdsToSend.length > 0 ? fileIdsToSend : undefined,
         userLanguage: 'en',
-        preferredProvider: selectedProvider || undefined  // AI provider selection
+        preferredProviders: selectedProviders.length > 0 ? selectedProviders : undefined  // AI provider selection (multiselect)
       };
       
       const result = await startWorkflow(requestBody, workflowOptions);
@@ -638,7 +638,7 @@ export function useDashboardInputForm(instanceId: string) {
         setWorkflowStatusOptimistic('idle');
       }
     }
-  }, [inputValue, pendingFiles, isRunning, workflowId, startingWorkflow, startWorkflow, stopWorkflow, resetWorkflow, refetchWorkflows, selectWorkflowFromContext, selectWorkflow, chatWorkflowPermission, workflowMode, selectedProvider, setWorkflowStatusOptimistic]);
+  }, [inputValue, pendingFiles, isRunning, workflowId, startingWorkflow, startWorkflow, stopWorkflow, resetWorkflow, refetchWorkflows, selectWorkflowFromContext, selectWorkflow, chatWorkflowPermission, workflowMode, selectedProviders, setWorkflowStatusOptimistic]);
 
   useEffect(() => {
     const handleWorkflowCleared = () => {
@@ -823,9 +823,9 @@ export function useDashboardInputForm(instanceId: string) {
     handleFileAttach,
     handleFileUploadAndAttach,
     latestStats,
-    // AI Provider selection
-    selectedProvider,
-    onProviderSelect: setSelectedProvider
+    // AI Provider selection (multiselect)
+    selectedProviders,
+    onProvidersChange: setSelectedProviders
   };
 }
 
diff --git a/src/hooks/playground/useWorkflowLifecycle.ts b/src/hooks/playground/useWorkflowLifecycle.ts
index c06b601..039864f 100644
--- a/src/hooks/playground/useWorkflowLifecycle.ts
+++ b/src/hooks/playground/useWorkflowLifecycle.ts
@@ -479,25 +479,36 @@ export function useWorkflowLifecycle(instanceId: string) {
 
     // Continue polling if:
     // 1. Workflow is currently running, OR
-    // 2. Workflow just completed (within last 10 seconds) - grace period to catch final messages
+    // 2. Workflow just completed (within last 5 seconds) - grace period to catch final messages
     // Stop polling for failed or stopped workflows immediately
-    // Use ref for statusChangedFromRunningAt to get latest value (state updates are async)
     const changedAtRef = statusChangedFromRunningAtRef.current;
-    const shouldPoll = workflowStatus === 'running' || 
-      (workflowStatus === 'completed' && changedAtRef !== null && Date.now() - changedAtRef < 10000);
+    const gracePeriodMs = 5000; // 5 seconds grace period
+    const timeSinceCompletion = changedAtRef !== null ? Date.now() - changedAtRef : Infinity;
+    const isInGracePeriod = workflowStatus === 'completed' && changedAtRef !== null && timeSinceCompletion < gracePeriodMs;
+    const shouldPoll = workflowStatus === 'running' || isInGracePeriod;
 
     if (shouldPoll) {
-      // Reset lastRenderedTimestamp for first poll (fetch all historical data)
-      if (lastRenderedTimestampRef.current === null) {
-        lastRenderedTimestampRef.current = null; // null means fetch all
-      }
-
       // Start polling
       pollingControllerRef.current.startPolling(workflowId, pollWorkflowData);
+      
+      // If in grace period, set a timer to stop polling after grace period expires
+      if (isInGracePeriod) {
+        const remainingGraceTime = gracePeriodMs - timeSinceCompletion;
+        const graceTimer = setTimeout(() => {
+          pollingControllerRef.current.stopPolling();
+          setStatusChangedFromRunningAt(null);
+          statusChangedFromRunningAtRef.current = null;
+        }, remainingGraceTime + 100); // Small buffer
+        
+        return () => {
+          clearTimeout(graceTimer);
+          pollingControllerRef.current.stopPolling();
+        };
+      }
     } else {
       // Stop polling for failed, stopped, or completed (after grace period) workflows
       pollingControllerRef.current.stopPolling();
-      // Clear the status change timestamp when we stop polling (only if not already null)
+      // Clear the status change timestamp when we stop polling
       if (statusChangedFromRunningAt !== null) {
         setStatusChangedFromRunningAt(null);
         statusChangedFromRunningAtRef.current = null;
@@ -507,7 +518,7 @@ export function useWorkflowLifecycle(instanceId: string) {
     return () => {
       pollingControllerRef.current.stopPolling();
     };
-  }, [workflowStatus, workflowId, pollWorkflowData]);
+  }, [workflowStatus, workflowId, pollWorkflowData, statusChangedFromRunningAt]);
   
   const handleStartWorkflow = useCallback(async (
     workflowData: StartWorkflowRequest,
diff --git a/src/hooks/useBilling.ts b/src/hooks/useBilling.ts
index 70298aa..8b79f77 100644
--- a/src/hooks/useBilling.ts
+++ b/src/hooks/useBilling.ts
@@ -18,6 +18,7 @@ import {
   addCreditAdmin,
   fetchAccountsAdmin,
   fetchTransactionsAdmin,
+  fetchUsersForMandateAdmin,
   type BillingBalance,
   type BillingTransaction,
   type BillingSettings,
@@ -25,6 +26,7 @@ import {
   type UsageReport,
   type AccountSummary,
   type CreditAddRequest,
+  type MandateUserSummary,
 } from '../api/billingApi';
 
 // Re-export types
@@ -36,6 +38,7 @@ export type {
   UsageReport,
   AccountSummary,
   CreditAddRequest,
+  MandateUserSummary,
 };
 
 export type { BillingModel, TransactionType, ReferenceType } from '../api/billingApi';
@@ -145,6 +148,7 @@ export function useBillingAdmin(mandateId?: string) {
   const [settings, setSettings] = useState<BillingSettings | null>(null);
   const [accounts, setAccounts] = useState<AccountSummary[]>([]);
   const [transactions, setTransactions] = useState<BillingTransaction[]>([]);
+  const [users, setUsers] = useState<MandateUserSummary[]>([]);
   const { request, isLoading: loading, error } = useApiRequest();
 
   // Fetch settings for a mandate
@@ -232,12 +236,29 @@ export function useBillingAdmin(mandateId?: string) {
     }
   }, [request, mandateId]);
 
+  // Fetch users for a mandate
+  const loadUsers = useCallback(async (targetMandateId?: string) => {
+    const mId = targetMandateId || mandateId;
+    if (!mId) return [];
+    
+    try {
+      const data = await fetchUsersForMandateAdmin(request, mId);
+      setUsers(Array.isArray(data) ? data : []);
+      return data;
+    } catch (err) {
+      console.error('Error loading users:', err);
+      setUsers([]);
+      return [];
+    }
+  }, [request, mandateId]);
+
   // Load data when mandateId changes
   useEffect(() => {
     if (mandateId) {
       loadSettings();
       loadAccounts();
       loadTransactions();
+      loadUsers();
     }
   }, [mandateId]);
 
@@ -245,6 +266,7 @@ export function useBillingAdmin(mandateId?: string) {
     settings,
     accounts,
     transactions,
+    users,
     loading,
     error,
     loadSettings,
@@ -252,11 +274,13 @@ export function useBillingAdmin(mandateId?: string) {
     addCredit,
     loadAccounts,
     loadTransactions,
+    loadUsers,
     refetch: () => {
       if (mandateId) {
         loadSettings();
         loadAccounts();
         loadTransactions();
+        loadUsers();
       }
     },
   };
diff --git a/src/pages/billing/Billing.module.css b/src/pages/billing/Billing.module.css
index f7c7304..35ce33a 100644
--- a/src/pages/billing/Billing.module.css
+++ b/src/pages/billing/Billing.module.css
@@ -5,25 +5,26 @@
    ============================================================================ */
 
 .billingDashboard {
-  padding: var(--spacing-lg);
+  padding: 1.5rem;
   max-width: 1200px;
   margin: 0 auto;
+  min-height: 100%;
 }
 
 .pageHeader {
-  margin-bottom: var(--spacing-xl);
+  margin-bottom: 2rem;
 }
 
 .pageHeader h1 {
-  font-size: var(--font-size-2xl);
-  font-weight: var(--font-weight-bold);
-  color: var(--color-text-primary);
-  margin: 0 0 var(--spacing-xs) 0;
+  font-size: 1.5rem;
+  font-weight: 600;
+  color: var(--text-primary, #e0e0e0);
+  margin: 0 0 0.25rem 0;
 }
 
 .subtitle {
-  font-size: var(--font-size-base);
-  color: var(--color-text-secondary);
+  font-size: 0.875rem;
+  color: var(--text-secondary, #888);
   margin: 0;
 }
 
@@ -32,23 +33,23 @@
    ============================================================================ */
 
 .section {
-  margin-bottom: var(--spacing-xl);
+  margin-bottom: 2rem;
 }
 
 .sectionHeader {
   display: flex;
   justify-content: space-between;
   align-items: center;
-  margin-bottom: var(--spacing-md);
+  margin-bottom: 1rem;
   flex-wrap: wrap;
-  gap: var(--spacing-sm);
+  gap: 0.5rem;
 }
 
 .sectionTitle {
-  font-size: var(--font-size-lg);
-  font-weight: var(--font-weight-semibold);
-  color: var(--color-text-primary);
-  margin: 0 0 var(--spacing-md) 0;
+  font-size: 1.125rem;
+  font-weight: 600;
+  color: var(--text-primary, #e0e0e0);
+  margin: 0 0 1rem 0;
 }
 
 .sectionHeader .sectionTitle {
@@ -62,65 +63,65 @@
 .balanceGrid {
   display: grid;
   grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
-  gap: var(--spacing-md);
+  gap: 1rem;
 }
 
 .balanceCard {
-  background: var(--color-bg-card);
-  border: 1px solid var(--color-border);
-  border-radius: var(--border-radius-lg);
-  padding: var(--spacing-lg);
+  background: var(--surface-color, #1e1e1e);
+  border: 1px solid var(--border-color, #333);
+  border-radius: 12px;
+  padding: 1.5rem;
   cursor: pointer;
   transition: all 0.2s ease;
 }
 
 .balanceCard:hover {
-  border-color: var(--color-primary);
-  box-shadow: var(--shadow-md);
+  border-color: var(--primary-color, #f25843);
+  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
 }
 
 .balanceCard.warning {
-  border-color: var(--color-warning);
-  background: var(--color-warning-bg, rgba(255, 193, 7, 0.1));
+  border-color: #ffc107;
+  background: rgba(255, 193, 7, 0.1);
 }
 
 .balanceHeader {
   display: flex;
   justify-content: space-between;
   align-items: flex-start;
-  margin-bottom: var(--spacing-md);
+  margin-bottom: 1rem;
 }
 
 .mandateName {
-  font-size: var(--font-size-base);
-  font-weight: var(--font-weight-semibold);
-  color: var(--color-text-primary);
+  font-size: 0.875rem;
+  font-weight: 600;
+  color: var(--text-primary, #e0e0e0);
   margin: 0;
 }
 
 .billingModel {
-  font-size: var(--font-size-xs);
-  color: var(--color-text-secondary);
-  background: var(--color-bg-secondary);
+  font-size: 0.75rem;
+  color: var(--text-secondary, #888);
+  background: var(--bg-secondary, #2a2a2a);
   padding: 2px 8px;
-  border-radius: var(--border-radius-sm);
+  border-radius: 4px;
 }
 
 .balanceAmount {
-  font-size: var(--font-size-2xl);
-  font-weight: var(--font-weight-bold);
-  color: var(--color-text-primary);
-  margin-bottom: var(--spacing-sm);
+  font-size: 1.5rem;
+  font-weight: 700;
+  color: var(--text-primary, #e0e0e0);
+  margin-bottom: 0.5rem;
 }
 
 .warningBadge {
   display: inline-block;
-  font-size: var(--font-size-xs);
-  color: var(--color-warning-text, #856404);
-  background: var(--color-warning-badge-bg, rgba(255, 193, 7, 0.3));
+  font-size: 0.75rem;
+  color: #856404;
+  background: rgba(255, 193, 7, 0.3);
   padding: 4px 8px;
-  border-radius: var(--border-radius-sm);
-  font-weight: var(--font-weight-medium);
+  border-radius: 4px;
+  font-weight: 500;
 }
 
 /* ============================================================================
@@ -129,56 +130,56 @@
 
 .periodSelector {
   display: flex;
-  gap: var(--spacing-sm);
+  gap: 0.5rem;
   align-items: center;
 }
 
 .select {
-  padding: var(--spacing-xs) var(--spacing-sm);
-  border: 1px solid var(--color-border);
-  border-radius: var(--border-radius-md);
-  background: var(--color-bg-input);
-  color: var(--color-text-primary);
-  font-size: var(--font-size-sm);
+  padding: 0.5rem 0.75rem;
+  border: 1px solid var(--border-color, #333);
+  border-radius: 6px;
+  background: var(--surface-color, #1e1e1e);
+  color: var(--text-primary, #e0e0e0);
+  font-size: 0.875rem;
   cursor: pointer;
 }
 
 .select:focus {
   outline: none;
-  border-color: var(--color-primary);
+  border-color: var(--primary-color, #f25843);
 }
 
 .statisticsChart {
-  background: var(--color-bg-card);
-  border: 1px solid var(--color-border);
-  border-radius: var(--border-radius-lg);
-  padding: var(--spacing-lg);
+  background: var(--surface-color, #1e1e1e);
+  border: 1px solid var(--border-color, #333);
+  border-radius: 12px;
+  padding: 1.5rem;
 }
 
 .totalCost {
   display: flex;
   flex-direction: column;
   align-items: center;
-  padding: var(--spacing-lg);
-  background: var(--color-bg-secondary);
-  border-radius: var(--border-radius-md);
-  margin-bottom: var(--spacing-lg);
+  padding: 1.5rem;
+  background: var(--bg-secondary, #2a2a2a);
+  border-radius: 8px;
+  margin-bottom: 1.5rem;
 }
 
 .totalLabel {
-  font-size: var(--font-size-sm);
-  color: var(--color-text-secondary);
-  margin-bottom: var(--spacing-xs);
+  font-size: 0.875rem;
+  color: var(--text-secondary, #888);
+  margin-bottom: 0.25rem;
 }
 
 .totalAmount {
-  font-size: var(--font-size-3xl);
-  font-weight: var(--font-weight-bold);
-  color: var(--color-text-primary);
+  font-size: 2rem;
+  font-weight: 700;
+  color: var(--text-primary, #e0e0e0);
 }
 
 .chartSection {
-  margin-bottom: var(--spacing-lg);
+  margin-bottom: 1.5rem;
 }
 
 .chartSection:last-child {
@@ -186,10 +187,10 @@
 }
 
 .chartSection h4 {
-  font-size: var(--font-size-sm);
-  font-weight: var(--font-weight-semibold);
-  color: var(--color-text-secondary);
-  margin: 0 0 var(--spacing-md) 0;
+  font-size: 0.875rem;
+  font-weight: 600;
+  color: var(--text-secondary, #888);
+  margin: 0 0 1rem 0;
   text-transform: uppercase;
   letter-spacing: 0.5px;
 }
@@ -197,34 +198,34 @@
 .barChart {
   display: flex;
   flex-direction: column;
-  gap: var(--spacing-sm);
+  gap: 0.5rem;
 }
 
 .barRow {
   display: flex;
   align-items: center;
-  gap: var(--spacing-sm);
+  gap: 0.5rem;
 }
 
 .barLabel {
   width: 100px;
-  font-size: var(--font-size-sm);
-  color: var(--color-text-primary);
+  font-size: 0.875rem;
+  color: var(--text-primary, #e0e0e0);
   text-transform: capitalize;
 }
 
 .barContainer {
   flex: 1;
   height: 24px;
-  background: var(--color-bg-secondary);
-  border-radius: var(--border-radius-sm);
+  background: var(--bg-secondary, #2a2a2a);
+  border-radius: 4px;
   overflow: hidden;
 }
 
 .bar {
   height: 100%;
-  background: var(--color-primary);
-  border-radius: var(--border-radius-sm);
+  background: var(--primary-color, #f25843);
+  border-radius: 4px;
   transition: width 0.3s ease;
   min-width: 4px;
 }
@@ -232,36 +233,36 @@
 .barValue {
   width: 100px;
   text-align: right;
-  font-size: var(--font-size-sm);
-  color: var(--color-text-secondary);
-  font-family: var(--font-mono);
+  font-size: 0.875rem;
+  color: var(--text-secondary, #888);
+  font-family: monospace;
 }
 
 .featureList {
   display: flex;
   flex-direction: column;
-  gap: var(--spacing-xs);
+  gap: 0.25rem;
 }
 
 .featureRow {
   display: flex;
   justify-content: space-between;
   align-items: center;
-  padding: var(--spacing-sm);
-  background: var(--color-bg-secondary);
-  border-radius: var(--border-radius-sm);
+  padding: 0.5rem;
+  background: var(--bg-secondary, #2a2a2a);
+  border-radius: 4px;
 }
 
 .featureLabel {
-  font-size: var(--font-size-sm);
-  color: var(--color-text-primary);
+  font-size: 0.875rem;
+  color: var(--text-primary, #e0e0e0);
   text-transform: capitalize;
 }
 
 .featureValue {
-  font-size: var(--font-size-sm);
-  color: var(--color-text-secondary);
-  font-family: var(--font-mono);
+  font-size: 0.875rem;
+  color: var(--text-secondary, #888);
+  font-family: monospace;
 }
 
 /* ============================================================================
@@ -275,46 +276,46 @@
 
 .transactionsTable th,
 .transactionsTable td {
-  padding: var(--spacing-sm) var(--spacing-md);
+  padding: 0.75rem 1rem;
   text-align: left;
-  border-bottom: 1px solid var(--color-border);
+  border-bottom: 1px solid var(--border-color, #333);
 }
 
 .transactionsTable th {
-  font-size: var(--font-size-xs);
-  font-weight: var(--font-weight-semibold);
-  color: var(--color-text-secondary);
+  font-size: 0.75rem;
+  font-weight: 600;
+  color: var(--text-secondary, #888);
   text-transform: uppercase;
   letter-spacing: 0.5px;
-  background: var(--color-bg-secondary);
+  background: var(--bg-secondary, #2a2a2a);
 }
 
 .transactionsTable td {
-  font-size: var(--font-size-sm);
-  color: var(--color-text-primary);
+  font-size: 0.875rem;
+  color: var(--text-primary, #e0e0e0);
 }
 
 .transactionType {
   display: inline-block;
   padding: 2px 8px;
-  border-radius: var(--border-radius-sm);
-  font-size: var(--font-size-xs);
-  font-weight: var(--font-weight-medium);
+  border-radius: 4px;
+  font-size: 0.75rem;
+  font-weight: 500;
 }
 
 .transactionType.credit {
-  background: var(--color-success-bg, rgba(40, 167, 69, 0.1));
-  color: var(--color-success, #28a745);
+  background: rgba(40, 167, 69, 0.1);
+  color: #28a745;
 }
 
 .transactionType.debit {
-  background: var(--color-error-bg, rgba(220, 53, 69, 0.1));
-  color: var(--color-error, #dc3545);
+  background: rgba(220, 53, 69, 0.1);
+  color: #dc3545;
 }
 
 .transactionType.adjustment {
-  background: var(--color-info-bg, rgba(23, 162, 184, 0.1));
-  color: var(--color-info, #17a2b8);
+  background: rgba(23, 162, 184, 0.1);
+  color: #17a2b8;
 }
 
 /* ============================================================================
@@ -322,86 +323,86 @@
    ============================================================================ */
 
 .adminSection {
-  background: var(--color-bg-card);
-  border: 1px solid var(--color-border);
-  border-radius: var(--border-radius-lg);
-  padding: var(--spacing-lg);
-  margin-bottom: var(--spacing-lg);
+  background: var(--surface-color, #1e1e1e);
+  border: 1px solid var(--border-color, #333);
+  border-radius: 12px;
+  padding: 1.5rem;
+  margin-bottom: 1.5rem;
 }
 
 .adminSection h3 {
-  font-size: var(--font-size-base);
-  font-weight: var(--font-weight-semibold);
-  color: var(--color-text-primary);
-  margin: 0 0 var(--spacing-md) 0;
+  font-size: 1rem;
+  font-weight: 600;
+  color: var(--text-primary, #e0e0e0);
+  margin: 0 0 1rem 0;
 }
 
 .formRow {
   display: flex;
-  gap: var(--spacing-md);
-  margin-bottom: var(--spacing-md);
+  gap: 1rem;
+  margin-bottom: 1rem;
 }
 
 .formGroup {
   flex: 1;
   display: flex;
   flex-direction: column;
-  gap: var(--spacing-xs);
+  gap: 0.25rem;
 }
 
 .formGroup label {
-  font-size: var(--font-size-sm);
-  font-weight: var(--font-weight-medium);
-  color: var(--color-text-secondary);
+  font-size: 0.875rem;
+  font-weight: 500;
+  color: var(--text-secondary, #888);
 }
 
 .input {
-  padding: var(--spacing-sm);
-  border: 1px solid var(--color-border);
-  border-radius: var(--border-radius-md);
-  background: var(--color-bg-input);
-  color: var(--color-text-primary);
-  font-size: var(--font-size-base);
+  padding: 0.5rem 0.75rem;
+  border: 1px solid var(--border-color, #333);
+  border-radius: 6px;
+  background: var(--surface-color, #1e1e1e);
+  color: var(--text-primary, #e0e0e0);
+  font-size: 0.875rem;
 }
 
 .input:focus {
   outline: none;
-  border-color: var(--color-primary);
+  border-color: var(--primary-color, #f25843);
 }
 
 .accountsGrid {
   display: grid;
   grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
-  gap: var(--spacing-md);
+  gap: 1rem;
 }
 
 .accountCard {
-  background: var(--color-bg-secondary);
-  border: 1px solid var(--color-border);
-  border-radius: var(--border-radius-md);
-  padding: var(--spacing-md);
+  background: var(--bg-secondary, #2a2a2a);
+  border: 1px solid var(--border-color, #333);
+  border-radius: 8px;
+  padding: 1rem;
 }
 
 .accountCard h4 {
-  font-size: var(--font-size-sm);
-  font-weight: var(--font-weight-semibold);
-  color: var(--color-text-primary);
-  margin: 0 0 var(--spacing-sm) 0;
+  font-size: 0.875rem;
+  font-weight: 600;
+  color: var(--text-primary, #e0e0e0);
+  margin: 0 0 0.5rem 0;
 }
 
 .accountInfo {
   display: flex;
   flex-direction: column;
-  gap: var(--spacing-xs);
-  font-size: var(--font-size-sm);
+  gap: 0.25rem;
+  font-size: 0.875rem;
 }
 
 .accountInfo span {
-  color: var(--color-text-secondary);
+  color: var(--text-secondary, #888);
 }
 
 .accountInfo strong {
-  color: var(--color-text-primary);
+  color: var(--text-primary, #e0e0e0);
 }
 
 /* ============================================================================
@@ -409,22 +410,22 @@
    ============================================================================ */
 
 .button {
-  padding: var(--spacing-sm) var(--spacing-md);
+  padding: 0.5rem 1rem;
   border: none;
-  border-radius: var(--border-radius-md);
-  font-size: var(--font-size-sm);
-  font-weight: var(--font-weight-medium);
+  border-radius: 6px;
+  font-size: 0.875rem;
+  font-weight: 500;
   cursor: pointer;
   transition: all 0.2s ease;
 }
 
 .buttonPrimary {
-  background: var(--color-primary);
+  background: var(--primary-color, #f25843);
   color: white;
 }
 
 .buttonPrimary:hover {
-  background: var(--color-primary-dark);
+  background: var(--primary-dark, #d94d3a);
 }
 
 .buttonPrimary:disabled {
@@ -433,13 +434,13 @@
 }
 
 .buttonSecondary {
-  background: var(--color-bg-secondary);
-  color: var(--color-text-primary);
-  border: 1px solid var(--color-border);
+  background: var(--bg-secondary, #2a2a2a);
+  color: var(--text-primary, #e0e0e0);
+  border: 1px solid var(--border-color, #333);
 }
 
 .buttonSecondary:hover {
-  background: var(--color-bg-hover);
+  background: var(--surface-color, #1e1e1e);
 }
 
 /* ============================================================================
@@ -450,37 +451,37 @@
   display: flex;
   align-items: center;
   justify-content: center;
-  padding: var(--spacing-xl);
-  color: var(--color-text-secondary);
-  font-size: var(--font-size-sm);
+  padding: 2rem;
+  color: var(--text-secondary, #888);
+  font-size: 0.875rem;
 }
 
 .noData {
   display: flex;
   align-items: center;
   justify-content: center;
-  padding: var(--spacing-lg);
-  color: var(--color-text-tertiary);
-  font-size: var(--font-size-sm);
+  padding: 1.5rem;
+  color: var(--text-tertiary, #666);
+  font-size: 0.875rem;
   font-style: italic;
 }
 
 .errorMessage {
-  background: var(--color-error-bg, rgba(220, 53, 69, 0.1));
-  color: var(--color-error, #dc3545);
-  padding: var(--spacing-sm) var(--spacing-md);
-  border-radius: var(--border-radius-md);
-  font-size: var(--font-size-sm);
-  margin-bottom: var(--spacing-md);
+  background: rgba(220, 53, 69, 0.1);
+  color: #dc3545;
+  padding: 0.75rem 1rem;
+  border-radius: 6px;
+  font-size: 0.875rem;
+  margin-bottom: 1rem;
 }
 
 .successMessage {
-  background: var(--color-success-bg, rgba(40, 167, 69, 0.1));
-  color: var(--color-success, #28a745);
-  padding: var(--spacing-sm) var(--spacing-md);
-  border-radius: var(--border-radius-md);
-  font-size: var(--font-size-sm);
-  margin-bottom: var(--spacing-md);
+  background: rgba(40, 167, 69, 0.1);
+  color: #28a745;
+  padding: 0.75rem 1rem;
+  border-radius: 6px;
+  font-size: 0.875rem;
+  margin-bottom: 1rem;
 }
 
 /* ============================================================================
@@ -489,7 +490,7 @@
 
 @media (max-width: 768px) {
   .billingDashboard {
-    padding: var(--spacing-md);
+    padding: 1rem;
   }
   
   .balanceGrid {
@@ -513,6 +514,6 @@
   .barLabel,
   .barValue {
     width: 80px;
-    font-size: var(--font-size-xs);
+    font-size: 0.75rem;
   }
 }
diff --git a/src/pages/billing/BillingAdmin.tsx b/src/pages/billing/BillingAdmin.tsx
index fc16ac7..1cddd88 100644
--- a/src/pages/billing/BillingAdmin.tsx
+++ b/src/pages/billing/BillingAdmin.tsx
@@ -8,7 +8,7 @@
  */
 
 import React, { useState, useEffect, useCallback } from 'react';
-import { useBillingAdmin, type BillingSettings, type AccountSummary } from '../../hooks/useBilling';
+import { useBillingAdmin, type BillingSettings, type AccountSummary, type MandateUserSummary } from '../../hooks/useBilling';
 import { useAdminMandates } from '../../hooks/useMandates';
 import styles from './Billing.module.css';
 
@@ -191,10 +191,11 @@ const SettingsEditor: React.FC<SettingsEditorProps> = ({ settings, onSave, loadi
 interface CreditAdderProps {
   settings: BillingSettings | null;
   accounts: AccountSummary[];
+  users: MandateUserSummary[];
   onAddCredit: (userId: string | undefined, amount: number, description: string) => Promise<void>;
 }
 
-const CreditAdder: React.FC<CreditAdderProps> = ({ settings, accounts, onAddCredit }) => {
+const CreditAdder: React.FC<CreditAdderProps> = ({ settings, accounts, users, onAddCredit }) => {
   const [selectedUserId, setSelectedUserId] = useState<string>('');
   const [amount, setAmount] = useState<number>(10);
   const [description, setDescription] = useState<string>('Manuelles Aufladen');
@@ -203,6 +204,14 @@ const CreditAdder: React.FC<CreditAdderProps> = ({ settings, accounts, onAddCred
   
   const isPrepayUser = settings?.billingModel === 'PREPAY_USER';
   
+  // Map accounts by userId for balance lookup
+  const accountsByUserId = accounts
+    .filter(acc => acc.accountType === 'USER')
+    .reduce((map, acc) => {
+      if (acc.userId) map[acc.userId] = acc;
+      return map;
+    }, {} as Record<string, AccountSummary>);
+  
   const handleSubmit = async (e: React.FormEvent) => {
     e.preventDefault();
     if (amount <= 0) {
@@ -246,21 +255,23 @@ const CreditAdder: React.FC<CreditAdderProps> = ({ settings, accounts, onAddCred
         {isPrepayUser && (
           <div className={styles.formRow}>
             <div className={styles.formGroup}>
-              <label>Benutzer-Konto</label>
+              <label>Benutzer</label>
               <select 
                 className={styles.select}
                 value={selectedUserId}
                 onChange={(e) => setSelectedUserId(e.target.value)}
                 required
               >
-                <option value="">-- Konto wählen --</option>
-                {accounts
-                  .filter(acc => acc.accountType === 'USER')
-                  .map((acc) => (
-                    <option key={acc.id} value={acc.userId || ''}>
-                      {acc.userId} - {formatCurrency(acc.balance)}
+                <option value="">-- Benutzer wählen --</option>
+                {users.map((user) => {
+                  const account = accountsByUserId[user.id];
+                  const balanceInfo = account ? ` (${formatCurrency(account.balance)})` : ' (kein Konto)';
+                  return (
+                    <option key={user.id} value={user.id}>
+                      {user.displayName || user.email || user.id}{balanceInfo}
                     </option>
-                  ))}
+                  );
+                })}
               </select>
             </div>
           </div>
@@ -355,7 +366,7 @@ const AccountsOverview: React.FC<AccountsOverviewProps> = ({ accounts, loading }
 
 export const BillingAdmin: React.FC = () => {
   const [selectedMandateId, setSelectedMandateId] = useState<string | null>(null);
-  const { settings, accounts, loading, loadSettings, saveSettings, addCredit, loadAccounts } = useBillingAdmin(selectedMandateId || undefined);
+  const { settings, accounts, users, loading, loadSettings, saveSettings, addCredit, loadAccounts } = useBillingAdmin(selectedMandateId || undefined);
   
   const handleMandateSelect = (mandateId: string) => {
     setSelectedMandateId(mandateId || null);
@@ -397,6 +408,7 @@ export const BillingAdmin: React.FC = () => {
           <CreditAdder 
             settings={settings}
             accounts={accounts}
+            users={users}
             onAddCredit={handleAddCredit}
           />
           
diff --git a/src/pages/workflows/PlaygroundPage.tsx b/src/pages/workflows/PlaygroundPage.tsx
index 4cf2b8a..0733329 100644
--- a/src/pages/workflows/PlaygroundPage.tsx
+++ b/src/pages/workflows/PlaygroundPage.tsx
@@ -15,7 +15,7 @@ import { useCurrentInstance } from '../../hooks/useCurrentInstance';
 import { FaComment, FaTasks, FaPaperPlane, FaStop, FaFile, FaPlus, FaMicrophone, FaSquare, FaFileAlt } from 'react-icons/fa';
 import { useToast } from '../../contexts/ToastContext';
 import { useVoiceLanguage, VoiceLanguageSelect, Messages } from '../../components/UiComponents';
-import { ProviderSelect } from '../../components/ProviderSelector';
+import { ProviderMultiSelect } from '../../components/ProviderSelector';
 import type { Message } from '../../components/UiComponents/Messages/MessagesTypes';
 import api from '../../api';
 import styles from './PlaygroundPage.module.css';
@@ -58,8 +58,8 @@ export const PlaygroundPage: React.FC = () => {
         deletingFiles,
         previewingFiles,
         downloadingFiles,
-        selectedProvider,
-        onProviderSelect,
+        selectedProviders,
+        onProvidersChange,
     } = hookData;
 
     const { prompts, refetch: refetchPrompts } = usePrompts();
@@ -544,9 +544,6 @@ export const PlaygroundPage: React.FC = () => {
         );
     };
 
-    // Debug: Log permission status
-    console.log('🔐 PlaygroundPage permission check:', { playgroundUIPermission });
-    
     // Permission check - also show while loading
     if (playgroundUIPermission === false) {
         return (
@@ -785,9 +782,9 @@ export const PlaygroundPage: React.FC = () => {
                                 >
                                     <FaPlus />
                                 </button>
-                                <ProviderSelect
-                                    value={selectedProvider}
-                                    onChange={onProviderSelect}
+                                <ProviderMultiSelect
+                                    selectedProviders={selectedProviders}
+                                    onChange={onProvidersChange}
                                     showLabel={false}
                                 />
                                 <VoiceLanguageSelect