diff --git a/frontend/src/components/billing/CompactBillingDashboard/hooks/useCompactBillingData.ts b/frontend/src/components/billing/CompactBillingDashboard/hooks/useCompactBillingData.ts
index b0dfca9c..dfbb910e 100644
--- a/frontend/src/components/billing/CompactBillingDashboard/hooks/useCompactBillingData.ts
+++ b/frontend/src/components/billing/CompactBillingDashboard/hooks/useCompactBillingData.ts
@@ -24,7 +24,7 @@ interface UseCompactBillingDataReturn {
 /**
  * Custom hook for managing CompactBillingDashboard data fetching and state
  */
-export const useCompactBillingData = (userId?: string): UseCompactBillingDataReturn => {
+export const useCompactBillingData = (userId: string): UseCompactBillingDataReturn => {
   const [dashboardData, setDashboardData] = useState<DashboardData | null>(null);
   const [systemHealth, setSystemHealth] = useState<SystemHealth | null>(null);
   const [loading, setLoading] = useState(true);
diff --git a/frontend/src/components/billing/CompactBillingDashboard/index.tsx b/frontend/src/components/billing/CompactBillingDashboard/index.tsx
index 427621fa..b63318fd 100644
--- a/frontend/src/components/billing/CompactBillingDashboard/index.tsx
+++ b/frontend/src/components/billing/CompactBillingDashboard/index.tsx
@@ -21,7 +21,7 @@ import { MonthlyBudgetUsage } from './components/MonthlyBudgetUsage';
 import { AlertsSection } from './components/AlertsSection';
 
 interface CompactBillingDashboardProps {
-  userId?: string;
+  userId: string;
   terminalTheme?: boolean;
 }
 
diff --git a/frontend/src/components/billing/EnhancedBillingDashboard.tsx b/frontend/src/components/billing/EnhancedBillingDashboard.tsx
index 740e9a30..fb380bc0 100644
--- a/frontend/src/components/billing/EnhancedBillingDashboard.tsx
+++ b/frontend/src/components/billing/EnhancedBillingDashboard.tsx
@@ -1,4 +1,5 @@
 import React, { useState, useEffect } from 'react';
+import { useAuth } from '@clerk/clerk-react';
 import {
   Box,
   Container,
@@ -64,6 +65,8 @@ const EnhancedBillingDashboard: React.FC<EnhancedBillingDashboardProps> = ({ use
   // Conditional component selection based on terminal theme
   const TypographyComponent = terminalTheme ? TerminalTypography : Typography;
   const AlertComponent = terminalTheme ? TerminalAlert : Alert;
+  const { userId: authUserId } = useAuth();
+  const effectiveUserId = userId || authUserId;
   const [dashboardData, setDashboardData] = useState<DashboardData | null>(null);
   const [systemHealth, setSystemHealth] = useState<SystemHealth | null>(null);
   const [loading, setLoading] = useState(true);
@@ -73,10 +76,16 @@ const EnhancedBillingDashboard: React.FC<EnhancedBillingDashboardProps> = ({ use
   const [healthError, setHealthError] = useState<string | null>(null);
 
   const fetchDashboardData = async (showSuccessToast: boolean = false) => {
+    if (!effectiveUserId) {
+      setLoading(false);
+      setError('Unable to load billing data: missing authenticated user context.');
+      return;
+    }
+
     try {
       // Use Promise.allSettled to prevent health check timeout from blocking dashboard
       const results = await Promise.allSettled([
-        billingService.getDashboardData(),
+        billingService.getDashboardData(effectiveUserId),
         monitoringService.getSystemHealth()
       ]);
       
@@ -147,14 +156,16 @@ const EnhancedBillingDashboard: React.FC<EnhancedBillingDashboardProps> = ({ use
   };
 
   useEffect(() => {
+    if (!effectiveUserId) return;
     fetchDashboardData();
-  }, [userId]);
+  }, [effectiveUserId]);
 
   // Event-driven refresh: refresh only when non-billing/monitoring APIs complete
   useEffect(() => {
     const unsubscribe = onApiEvent((detail) => {
       if (detail.source && detail.source !== 'other') return;
-      Promise.allSettled([billingService.getDashboardData(), monitoringService.getSystemHealth()])
+      if (!effectiveUserId) return;
+      Promise.allSettled([billingService.getDashboardData(effectiveUserId), monitoringService.getSystemHealth()])
         .then((results) => {
           if (results[0].status === 'fulfilled') {
             setDashboardData(results[0].value);
@@ -176,25 +187,26 @@ const EnhancedBillingDashboard: React.FC<EnhancedBillingDashboardProps> = ({ use
         .catch(() => {/* ignore */});
     });
     return unsubscribe;
-  }, []);
+  }, [effectiveUserId]);
 
   // Refetch when tab becomes visible again (cheap, avoids polling)
   useEffect(() => {
     const onVisible = () => {
-      if (document.visibilityState === 'visible') {
+      if (document.visibilityState === 'visible' && effectiveUserId) {
         fetchDashboardData();
       }
     };
     document.addEventListener('visibilitychange', onVisible);
     return () => document.removeEventListener('visibilitychange', onVisible);
-  }, []);
+  }, [effectiveUserId]);
 
   // Listen for billing refresh requests (e.g., when subscription limits are exceeded)
   useEffect(() => {
     const handleBillingRefresh = () => {
       console.log('EnhancedBillingDashboard: Billing refresh requested, refreshing data...');
       // Use allSettled to prevent health check from blocking refresh
-      Promise.allSettled([billingService.getDashboardData(), monitoringService.getSystemHealth()])
+      if (!effectiveUserId) return;
+      Promise.allSettled([billingService.getDashboardData(effectiveUserId), monitoringService.getSystemHealth()])
         .then((results) => {
           if (results[0].status === 'fulfilled') {
             setDashboardData(results[0].value);
@@ -233,7 +245,7 @@ const EnhancedBillingDashboard: React.FC<EnhancedBillingDashboardProps> = ({ use
     return () => {
       window.removeEventListener('billing-refresh-requested', handleBillingRefresh);
     };
-  }, []); // Empty deps - handler doesn't depend on component state
+  }, [effectiveUserId]); // Empty deps - handler doesn't depend on component state
 
   const handleViewModeChange = (
     event: React.MouseEvent<HTMLElement>,
@@ -463,7 +475,11 @@ const EnhancedBillingDashboard: React.FC<EnhancedBillingDashboardProps> = ({ use
             exit={{ opacity: 0, x: 20 }}
             transition={{ duration: 0.3 }}
           >
-            <CompactBillingDashboard userId={userId} terminalTheme={terminalTheme} />
+            {effectiveUserId ? (
+              <CompactBillingDashboard userId={effectiveUserId} terminalTheme={terminalTheme} />
+            ) : (
+              <AlertComponent severity="warning">Unable to load billing data: missing authenticated user context.</AlertComponent>
+            )}
           </motion.div>
         ) : (
           <motion.div
diff --git a/frontend/src/components/billing/SubscriptionRenewalHistory.tsx b/frontend/src/components/billing/SubscriptionRenewalHistory.tsx
index 3d4541c7..9f90a1e1 100644
--- a/frontend/src/components/billing/SubscriptionRenewalHistory.tsx
+++ b/frontend/src/components/billing/SubscriptionRenewalHistory.tsx
@@ -42,7 +42,7 @@ import {
 import { showToastNotification } from '../../utils/toastNotifications';
 
 interface SubscriptionRenewalHistoryProps {
-  userId?: string;
+  userId: string;
   terminalTheme?: boolean;
   initialLimit?: number;
 }
diff --git a/frontend/src/hooks/useOAuthTokenAlerts.ts b/frontend/src/hooks/useOAuthTokenAlerts.ts
index 07632a4a..909186ea 100644
--- a/frontend/src/hooks/useOAuthTokenAlerts.ts
+++ b/frontend/src/hooks/useOAuthTokenAlerts.ts
@@ -24,7 +24,7 @@ interface UseOAuthTokenAlertsOptions {
   enabled?: boolean;
   
   /**
-   * User ID - if not provided, will use localStorage or skip polling
+   * Authenticated user ID from Clerk; polling is skipped when unavailable
    */
   userId?: string;
 }
@@ -54,8 +54,7 @@ export function useOAuthTokenAlerts(options: UseOAuthTokenAlertsOptions = {}) {
       return;
     }
     
-    const actualUserId = userId || localStorage.getItem('user_id');
-    if (!actualUserId) {
+    if (!userId) {
       console.debug('useOAuthTokenAlerts: No user ID available, skipping polling');
       return;
     }
@@ -70,7 +69,7 @@ export function useOAuthTokenAlerts(options: UseOAuthTokenAlertsOptions = {}) {
         isPollingRef.current = true;
         
         // Fetch unread alerts only
-        const alerts = await billingService.getUsageAlerts(actualUserId, true);
+        const alerts = await billingService.getUsageAlerts(userId, true);
         
         // Filter for OAuth token alerts
         const oauthAlerts = alerts.filter(
diff --git a/frontend/src/pages/BillingPage.tsx b/frontend/src/pages/BillingPage.tsx
index 71e0965b..0e0bdac0 100644
--- a/frontend/src/pages/BillingPage.tsx
+++ b/frontend/src/pages/BillingPage.tsx
@@ -4,6 +4,7 @@
  */
 
 import React, { useEffect } from 'react';
+import { useAuth } from '@clerk/clerk-react';
 import {
   Box,
   Container,
@@ -73,6 +74,7 @@ const TerminalIconButton = styled(IconButton)({
 
 const BillingPage: React.FC = () => {
   const { subscription, checkSubscription } = useSubscription();
+  const { userId } = useAuth();
   
   // Monitor subscription status and show toast notifications
   useEffect(() => {
@@ -232,14 +234,18 @@ const BillingPage: React.FC = () => {
 
           {/* Billing Dashboard Content */}
           <Box>
-            <EnhancedBillingDashboard terminalTheme={true} />
+            {userId ? (
+              <EnhancedBillingDashboard userId={userId} terminalTheme={true} />
+            ) : null}
 
             {/* Subscription Renewal History Section */}
-            <SubscriptionRenewalHistory 
-              userId={undefined} 
+            {userId ? (
+              <SubscriptionRenewalHistory 
+                userId={userId} 
               terminalTheme={true}
-              initialLimit={20}
-            />
+                initialLimit={20}
+              />
+            ) : null}
 
             {/* Usage Logs Section */}
             <Box sx={{ mt: 4 }}>
diff --git a/frontend/src/services/billingService.ts b/frontend/src/services/billingService.ts
index 8cb10384..1aeace8b 100644
--- a/frontend/src/services/billingService.ts
+++ b/frontend/src/services/billingService.ts
@@ -294,9 +294,9 @@ export const billingService = {
   /**
    * Get comprehensive dashboard data for a user
    */
-  getDashboardData: async (userId?: string): Promise<DashboardData> => {
+  getDashboardData: async (userId: string): Promise<DashboardData> => {
     try {
-      const actualUserId = userId || localStorage.getItem('user_id') || 'demo-user';
+      const actualUserId = userId;
       // Debug logs removed to reduce console noise
       
       const response = await billingAPI.get<DashboardAPIResponse>(`/dashboard/${actualUserId}`);
@@ -383,9 +383,9 @@ export const billingService = {
   /**
    * Get current usage statistics for a user
    */
-  getUsageStats: async (userId?: string, period?: string): Promise<UsageStats> => {
+  getUsageStats: async (userId: string, period?: string): Promise<UsageStats> => {
     try {
-      const actualUserId = userId || localStorage.getItem('user_id') || 'demo-user';
+      const actualUserId = userId;
       const params = period ? { billing_period: period } : {};
       
       const response = await billingAPI.get<UsageAPIResponse>(`/usage/${actualUserId}`, { params });
@@ -409,9 +409,9 @@ export const billingService = {
   /**
    * Get usage trends over time
    */
-  getUsageTrends: async (userId?: string, months: number = 6): Promise<UsageTrends> => {
+  getUsageTrends: async (userId: string, months: number = 6): Promise<UsageTrends> => {
     try {
-      const actualUserId = userId || localStorage.getItem('user_id') || 'demo-user';
+      const actualUserId = userId;
       const response = await billingAPI.get(`/usage/${actualUserId}/trends`, {
         params: { months }
       });
@@ -469,9 +469,9 @@ export const billingService = {
   /**
    * Get usage alerts for a user
    */
-  getUsageAlerts: async (userId?: string, unreadOnly: boolean = false): Promise<UsageAlert[]> => {
+  getUsageAlerts: async (userId: string, unreadOnly: boolean = false): Promise<UsageAlert[]> => {
     try {
-      const actualUserId = userId || localStorage.getItem('user_id') || 'demo-user';
+      const actualUserId = userId;
       const response = await billingAPI.get<AlertsAPIResponse>(`/alerts/${actualUserId}`, {
         params: { unread_only: unreadOnly }
       });
@@ -507,9 +507,9 @@ export const billingService = {
   /**
    * Get user's current subscription information
    */
-  getUserSubscription: async (userId?: string) => {
+  getUserSubscription: async (userId: string) => {
     try {
-      const actualUserId = userId || localStorage.getItem('user_id') || 'demo-user';
+      const actualUserId = userId;
       const response = await billingAPI.get(`/user/${actualUserId}/subscription`);
       
       if (!response.data.success) {
@@ -555,12 +555,12 @@ export const billingService = {
    * Get subscription renewal history for the current user
    */
   getRenewalHistory: async (
-    userId?: string,
+    userId: string,
     limit: number = 50,
     offset: number = 0
   ): Promise<RenewalHistoryResponse> => {
     try {
-      const actualUserId = userId || localStorage.getItem('user_id') || 'demo-user';
+      const actualUserId = userId;
       const params: any = { limit, offset };
       
       const response = await billingAPI.get<RenewalHistoryAPIResponse>(