diff --git a/web/src/components/EquityChart.tsx b/web/src/components/EquityChart.tsx
index 5b520feb..f8beb1d5 100644
--- a/web/src/components/EquityChart.tsx
+++ b/web/src/components/EquityChart.tsx
@@ -12,6 +12,7 @@ import {
 import useSWR from 'swr'
 import { api } from '../lib/api'
 import { useLanguage } from '../contexts/LanguageContext'
+import { useAuth } from '../contexts/AuthContext'
 import { t } from '../i18n/translations'
 import {
   AlertTriangle,
@@ -36,10 +37,11 @@ interface EquityChartProps {
 
 export function EquityChart({ traderId }: EquityChartProps) {
   const { language } = useLanguage()
+  const { user, token } = useAuth()
   const [displayMode, setDisplayMode] = useState<'dollar' | 'percent'>('dollar')
 
   const { data: history, error } = useSWR<EquityPoint[]>(
-    traderId ? `equity-history-${traderId}` : 'equity-history',
+    user && token && traderId ? `equity-history-${traderId}` : null,
     () => api.getEquityHistory(traderId),
     {
       refreshInterval: 30000, // 30秒刷新（历史数据更新频率较低）
@@ -49,7 +51,7 @@ export function EquityChart({ traderId }: EquityChartProps) {
   )
 
   const { data: account } = useSWR(
-    traderId ? `account-${traderId}` : 'account',
+    user && token && traderId ? `account-${traderId}` : null,
     () => api.getAccount(traderId),
     {
       refreshInterval: 15000, // 15秒刷新（配合后端缓存）
diff --git a/web/src/lib/apiGuard.test.ts b/web/src/lib/apiGuard.test.ts
new file mode 100644
index 00000000..a716f06a
--- /dev/null
+++ b/web/src/lib/apiGuard.test.ts
@@ -0,0 +1,370 @@
+import { describe, it, expect } from 'vitest'
+
+/**
+ * PR #669 測試: 防止 null token 導致未授權的 API 調用
+ *
+ * 問題：當用戶未登入時（user/token 為 null），SWR 仍然會使用空 key 發起 API 請求
+ * 修復：在 SWR key 中添加 `user && token` 檢查，當未登入時返回 null，阻止 API 調用
+ */
+
+describe('API Guard Logic (PR #669)', () => {
+  /**
+   * 測試 SWR key 生成邏輯
+   * 核心修復：key 必須包含 user && token 檢查
+   */
+  describe('SWR key generation', () => {
+    it('should return null when user is null', () => {
+      const user = null
+      const token = 'valid-token'
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should return null when token is null', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should return null when both user and token are null', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should return null when currentPage is not trader', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = '123'
+      const currentPage: string = 'competition' // Not 'trader', so key should be null
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should return null when traderId is not set', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = null
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should return valid key when all conditions are met', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBe('status-123')
+    })
+  })
+
+  /**
+   * 測試不同 API 端點的條件邏輯
+   * 所有需要認證的端點都應該檢查 user && token
+   */
+  describe('multiple API endpoints', () => {
+    it('should guard status API', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const statusKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(statusKey).toBeNull()
+    })
+
+    it('should guard account API', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const accountKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `account-${traderId}`
+          : null
+
+      expect(accountKey).toBeNull()
+    })
+
+    it('should guard positions API', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const positionsKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `positions-${traderId}`
+          : null
+
+      expect(positionsKey).toBeNull()
+    })
+
+    it('should guard decisions API', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const decisionsKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `decisions/latest-${traderId}`
+          : null
+
+      expect(decisionsKey).toBeNull()
+    })
+
+    it('should guard statistics API', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const statsKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `statistics-${traderId}`
+          : null
+
+      expect(statsKey).toBeNull()
+    })
+
+    it('should allow all API calls when authenticated', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const statusKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+      const accountKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `account-${traderId}`
+          : null
+      const positionsKey =
+        user && token && currentPage === 'trader' && traderId
+          ? `positions-${traderId}`
+          : null
+
+      expect(statusKey).toBe('status-123')
+      expect(accountKey).toBe('account-123')
+      expect(positionsKey).toBe('positions-123')
+    })
+  })
+
+  /**
+   * 測試 EquityChart 組件的條件邏輯
+   * PR #669 同時修復了 EquityChart 中的相同問題
+   */
+  describe('EquityChart API guard', () => {
+    it('should return null key when user is not authenticated', () => {
+      const user = null
+      const token = null
+      const traderId = '123'
+
+      const equityKey =
+        user && token && traderId ? `equity-history-${traderId}` : null
+
+      expect(equityKey).toBeNull()
+    })
+
+    it('should return null key when traderId is missing', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = null
+
+      const equityKey =
+        user && token && traderId ? `equity-history-${traderId}` : null
+
+      expect(equityKey).toBeNull()
+    })
+
+    it('should return valid key when authenticated with traderId', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = '123'
+
+      const equityKey =
+        user && token && traderId ? `equity-history-${traderId}` : null
+      const accountKey =
+        user && token && traderId ? `account-${traderId}` : null
+
+      expect(equityKey).toBe('equity-history-123')
+      expect(accountKey).toBe('account-123')
+    })
+  })
+
+  /**
+   * 測試邊界情況和特殊值
+   */
+  describe('edge cases', () => {
+    it('should treat empty string token as falsy', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = ''
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should treat empty string traderId as falsy', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = ''
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should handle undefined user', () => {
+      const user = undefined
+      const token = 'valid-token'
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should handle undefined token', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = undefined
+      const traderId = '123'
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull()
+    })
+
+    it('should handle numeric traderId', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = 123 // 數字而非字串
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBe('status-123')
+    })
+
+    it('should handle zero traderId as falsy', () => {
+      const user = { id: '1', email: 'test@example.com' }
+      const token = 'valid-token'
+      const traderId = 0
+      const currentPage = 'trader'
+
+      const key =
+        user && token && currentPage === 'trader' && traderId
+          ? `status-${traderId}`
+          : null
+
+      expect(key).toBeNull() // 0 is falsy
+    })
+  })
+
+  /**
+   * 測試防止 API 調用的邏輯流程
+   */
+  describe('API call prevention flow', () => {
+    it('should prevent API call when key is null', () => {
+      const key = null
+      const shouldCallAPI = key !== null
+
+      expect(shouldCallAPI).toBe(false)
+    })
+
+    it('should allow API call when key is valid', () => {
+      const key = 'status-123'
+      const shouldCallAPI = key !== null
+
+      expect(shouldCallAPI).toBe(true)
+    })
+
+    it('should simulate SWR behavior with null key', () => {
+      // SWR 不會在 key 為 null 時發起請求
+      const key = null
+      const fetcher = (k: string) => `API response for ${k}`
+
+      // 模擬 SWR 行為：key 為 null 時不調用 fetcher
+      const data = key ? fetcher(key) : undefined
+
+      expect(data).toBeUndefined()
+    })
+
+    it('should simulate SWR behavior with valid key', () => {
+      const key = 'status-123'
+      const fetcher = (k: string) => `API response for ${k}`
+
+      const data = key ? fetcher(key) : undefined
+
+      expect(data).toBe('API response for status-123')
+    })
+  })
+})
diff --git a/web/src/pages/TraderDashboard.tsx b/web/src/pages/TraderDashboard.tsx
index 65dfe0e6..9d165603 100644
--- a/web/src/pages/TraderDashboard.tsx
+++ b/web/src/pages/TraderDashboard.tsx
@@ -93,7 +93,7 @@ export default function TraderDashboard() {
 
   // 如果在trader页面，获取该trader的数据
   const { data: status } = useSWR<SystemStatus>(
-    selectedTraderId ? `status-${selectedTraderId}` : null,
+    user && token && selectedTraderId ? `status-${selectedTraderId}` : null,
     () => api.getStatus(selectedTraderId),
     {
       refreshInterval: 15000,
@@ -103,7 +103,7 @@ export default function TraderDashboard() {
   )
 
   const { data: account } = useSWR<AccountInfo>(
-    selectedTraderId ? `account-${selectedTraderId}` : null,
+    user && token && selectedTraderId ? `account-${selectedTraderId}` : null,
     () => api.getAccount(selectedTraderId),
     {
       refreshInterval: 15000,
@@ -113,7 +113,7 @@ export default function TraderDashboard() {
   )
 
   const { data: positions } = useSWR<Position[]>(
-    selectedTraderId ? `positions-${selectedTraderId}` : null,
+    user && token && selectedTraderId ? `positions-${selectedTraderId}` : null,
     () => api.getPositions(selectedTraderId),
     {
       refreshInterval: 15000,
@@ -123,7 +123,7 @@ export default function TraderDashboard() {
   )
 
   const { data: decisions } = useSWR<DecisionRecord[]>(
-    selectedTraderId
+    user && token && selectedTraderId
       ? `decisions/latest-${selectedTraderId}-${decisionLimit}`
       : null,
     () => api.getLatestDecisions(selectedTraderId, decisionLimit),
@@ -135,7 +135,7 @@ export default function TraderDashboard() {
   )
 
   const { data: stats } = useSWR<Statistics>(
-    selectedTraderId ? `statistics-${selectedTraderId}` : null,
+    user && token && selectedTraderId ? `statistics-${selectedTraderId}` : null,
     () => api.getStatistics(selectedTraderId),
     {
       refreshInterval: 30000,