diff --git a/apps/web/src/app/[locale]/page.tsx b/apps/web/src/app/[locale]/page.tsx
index 2674f1be..3f0e6f72 100644
--- a/apps/web/src/app/[locale]/page.tsx
+++ b/apps/web/src/app/[locale]/page.tsx
@@ -40,7 +40,7 @@ import type { IncidentResponse } from '@/lib/api-client'
 // Utility: Map IncidentResponse to DualStateIncidentCard props
 // =============================================================================
 
-function mapToDualState(incident: IncidentResponse): {
+function mapToDualState(incident: IncidentResponse | null | undefined): {
   id: string
   serviceName: string
   status: 'normal' | 'alert'
@@ -48,32 +48,65 @@ function mapToDualState(incident: IncidentResponse): {
   message: string
   timestamp: string
 } {
-  // P0/P1 視為異常 (alert)，P2/P3 視為正常 (normal)
-  const isAlert = incident.severity === 'P0' || incident.severity === 'P1'
-
-  // Tier 判定: proposal_count > 0 且為 P0 = Tier 3, P1 = Tier 2, else Tier 1
-  let tier: 1 | 2 | 3 | undefined = undefined
-  if (isAlert && incident.proposal_count > 0) {
-    tier = incident.severity === 'P0' ? 3 : 2
-  } else if (isAlert) {
-    tier = 1
+  // 防禦性檢查: 若 incident 無效則返回預設值
+  if (!incident) {
+    return {
+      id: 'unknown',
+      serviceName: 'Unknown Service',
+      status: 'normal',
+      tier: undefined,
+      message: '資料載入中...',
+      timestamp: '-',
+    }
   }
 
-  // 格式化時間
-  const date = new Date(incident.created_at)
-  const timestamp = date.toLocaleString('zh-TW', {
-    month: 'short',
-    day: 'numeric',
-    hour: '2-digit',
-    minute: '2-digit',
-  })
+  // P0/P1/P2 視為異常 (alert)，只有 P3 視為正常 (normal)
+  const severity = incident.severity || 'P3'
+  const isAlert = severity === 'P0' || severity === 'P1' || severity === 'P2'
+
+  // Tier 判定: P0 = Tier 3 (親核), P1 = Tier 2 (授權), P2+ = Tier 1 (自主)
+  let tier: 1 | 2 | 3 | undefined = undefined
+  if (isAlert) {
+    if (severity === 'P0') {
+      tier = 3
+    } else if (severity === 'P1') {
+      tier = 2
+    } else {
+      tier = 1
+    }
+  }
+
+  // 安全提取服務名稱
+  const services = incident.affected_services || []
+  const serviceName = services.length > 0
+    ? services[0]
+    : incident.incident_id?.split('-')[2] || 'Unknown Service'
+
+  // 格式化時間 (安全處理)
+  let timestamp = '-'
+  try {
+    const date = new Date(incident.created_at || Date.now())
+    timestamp = date.toLocaleString('zh-TW', {
+      month: 'short',
+      day: 'numeric',
+      hour: '2-digit',
+      minute: '2-digit',
+    })
+  } catch {
+    timestamp = 'Invalid Date'
+  }
+
+  // 安全生成訊息
+  const signalCount = incident.signal_count ?? 0
+  const status = incident.status || 'unknown'
+  const message = `[${severity}] ${signalCount} 筆告警 | ${status}`
 
   return {
-    id: incident.incident_id,
-    serviceName: incident.affected_services[0] || 'unknown',
+    id: incident.incident_id || 'unknown',
+    serviceName,
     status: isAlert ? 'alert' : 'normal',
     tier,
-    message: `${incident.signal_count} 筆告警 | ${incident.status}`,
+    message,
     timestamp,
   }
 }
@@ -156,7 +189,7 @@ export default function Home({ params }: { params: { locale: string } }) {
           {/* Active Incidents Section (Phase 7: 真實血脈 + Phase 6.5b 雙態卡片) */}
           <DataPincerPanel
             title={t('incident.activeIncidents')}
-            status={incidents.length > 0 ? 'critical' : 'healthy'}
+            status={(incidents?.length || 0) > 0 ? 'critical' : 'healthy'}
           >
             {isIncidentsLoading ? (
               <div className="flex items-center justify-center py-8">
@@ -170,7 +203,7 @@ export default function Home({ params }: { params: { locale: string } }) {
                 <AlertTriangle className="w-5 h-5 mb-2" />
                 <span className="font-mono text-sm">{incidentsError}</span>
               </div>
-            ) : incidents.length === 0 ? (
+            ) : (incidents?.length || 0) === 0 ? (
               /* Nothing.tech 風格平靜態: 系統穩定 */
               <div className="flex flex-col items-center justify-center py-12 text-center">
                 <div className="w-3 h-3 rounded-full bg-green-500 mb-4 animate-pulse" />
@@ -185,11 +218,11 @@ export default function Home({ params }: { params: { locale: string } }) {
               <div className="space-y-4">
                 {/* Phase 6.5b: 雙態戰情室卡片 (脈衝雷達 + Tier 決策層) */}
                 <div className="grid grid-cols-1 md:grid-cols-2 gap-3">
-                  {incidents.map((incident) => {
+                  {(incidents || []).map((incident, index) => {
                     const dualProps = mapToDualState(incident)
                     return (
                       <DualStateIncidentCard
-                        key={`dual-${incident.incident_id}`}
+                        key={`dual-${incident?.incident_id || index}`}
                         {...dualProps}
                       />
                     )
@@ -205,9 +238,9 @@ export default function Home({ params }: { params: { locale: string } }) {
             status="thinking"
           >
             <ThinkingTerminal
-              decisionChain={incidents.length > 0 ? DEMO_DECISION_CHAIN : null}
-              incidentId={incidents.length > 0 ? incidents[0].incident_id : undefined}
-              autoPlay={incidents.length > 0}
+              decisionChain={(incidents?.length || 0) > 0 ? DEMO_DECISION_CHAIN : null}
+              incidentId={(incidents?.length || 0) > 0 ? incidents?.[0]?.incident_id : undefined}
+              autoPlay={(incidents?.length || 0) > 0}
               maxHeight="300px"
             />
           </DataPincerPanel>