diff --git a/gateway/html/login.html b/gateway/html/login.html
index 15440d2..7874a03 100644
--- a/gateway/html/login.html
+++ b/gateway/html/login.html
@@ -201,8 +201,20 @@
             }
         }
 
+        // logout=1 파라미터가 있으면 모든 인증 데이터 정리
+        var isLogout = new URLSearchParams(location.search).get('logout') === '1';
+        if (isLogout) {
+            ssoCookie.remove('sso_token');
+            ssoCookie.remove('sso_user');
+            ssoCookie.remove('sso_refresh_token');
+            ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+             'currentUser','current_user','userInfo','userPageAccess'].forEach(function(k) {
+                localStorage.removeItem(k);
+            });
+        }
+
         // 이미 로그인 되어있으면 포털로 (쿠키 또는 localStorage 체크 + 만료 확인)
-        var existingToken = ssoCookie.get('sso_token') || localStorage.getItem('sso_token');
+        var existingToken = isLogout ? null : (ssoCookie.get('sso_token') || localStorage.getItem('sso_token'));
         if (existingToken && existingToken !== 'undefined' && existingToken !== 'null') {
             if (isTokenValid(existingToken)) {
                 // 쿠키 재설정 (localStorage에만 있고 쿠키가 없는 경우 대비)
diff --git a/gateway/html/shared/nav-header.js b/gateway/html/shared/nav-header.js
index fb27418..f888494 100644
--- a/gateway/html/shared/nav-header.js
+++ b/gateway/html/shared/nav-header.js
@@ -51,7 +51,7 @@
       ['sso_token','sso_user','sso_refresh_token','token','user','access_token','currentUser','current_user','userInfo','userPageAccess'].forEach(function(k) {
         localStorage.removeItem(k);
       });
-      window.location.href = this.getLoginUrl();
+      window.location.href = this.getLoginUrl(window.location.href) + '&logout=1';
     },
 
     /**
diff --git a/system1-factory/web/js/api-base.js b/system1-factory/web/js/api-base.js
index 322ec5a..432054e 100644
--- a/system1-factory/web/js/api-base.js
+++ b/system1-factory/web/js/api-base.js
@@ -154,7 +154,7 @@ if ('caches' in window) {
     // 401 Unauthorized 처리
     if (response.status === 401) {
       window.clearSSOAuth();
-      window.location.href = window.getLoginUrl();
+      window.location.href = window.getLoginUrl() + '&logout=1';
       throw new Error('인증이 만료되었습니다.');
     }
 
diff --git a/system1-factory/web/js/auth-check.js b/system1-factory/web/js/auth-check.js
index 939c9d0..76b145b 100644
--- a/system1-factory/web/js/auth-check.js
+++ b/system1-factory/web/js/auth-check.js
@@ -120,8 +120,24 @@ async function checkPageAccess(pageKey) {
   }
 }
 
+// 쿠키 직접 읽기 (api-base.js의 cookieGet은 IIFE 내부 함수이므로 접근 불가)
+function _authCookieGet(name) {
+  var match = document.cookie.match(new RegExp('(?:^|; )' + name + '=([^;]*)'));
+  return match ? decodeURIComponent(match[1]) : null;
+}
+
 // 즉시 실행 함수로 스코프를 보호하고 로직을 실행
 (async function() {
+  // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+  var cookieToken = _authCookieGet('sso_token');
+  var localToken = localStorage.getItem('sso_token');
+  if (!cookieToken && localToken) {
+      ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+       'currentUser','current_user','userInfo','userPageAccess'].forEach(function(k) { localStorage.removeItem(k); });
+      window.location.href = window.getLoginUrl ? window.getLoginUrl() : '/login';
+      return;
+  }
+
   if (!isLoggedIn()) {
     clearAuthData(); // 만약을 위해 한번 더 정리
     window.location.href = window.getLoginUrl ? window.getLoginUrl() : '/login';
diff --git a/system2-report/web/js/app-init.js b/system2-report/web/js/app-init.js
index 97fc474..765cc53 100644
--- a/system2-report/web/js/app-init.js
+++ b/system2-report/web/js/app-init.js
@@ -19,6 +19,12 @@
     window.location.href = window.getLoginUrl ? window.getLoginUrl() : '/login';
   }
 
+  // ===== 쿠키 직접 읽기 (api-base.js의 cookieGet은 IIFE 내부이므로) =====
+  function cookieGet(name) {
+    var match = document.cookie.match(new RegExp('(?:^|; )' + name + '=([^;]*)'));
+    return match ? decodeURIComponent(match[1]) : null;
+  }
+
   // ===== 인증 함수 (api-base.js의 전역 헬퍼 활용) =====
   function isLoggedIn() {
     var token = window.getSSOToken ? window.getSSOToken() : localStorage.getItem('sso_token');
@@ -40,6 +46,16 @@
 
   // ===== 메인 초기화 =====
   async function init() {
+    // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+    var cookieToken = cookieGet('sso_token');
+    var localToken = localStorage.getItem('sso_token');
+    if (!cookieToken && localToken) {
+        ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+         'currentUser','current_user','userInfo','userPageAccess'].forEach(function(k) { localStorage.removeItem(k); });
+        safeRedirectToLogin();
+        return;
+    }
+
     // 1. 인증 확인
     if (!isLoggedIn()) {
       clearAuthData();
diff --git a/system3-nonconformance/web/static/js/app.js b/system3-nonconformance/web/static/js/app.js
index a6b8290..bc301d6 100644
--- a/system3-nonconformance/web/static/js/app.js
+++ b/system3-nonconformance/web/static/js/app.js
@@ -46,8 +46,17 @@ class App {
      * 인증 확인
      */
     async checkAuth() {
+        // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+        const cookieToken = this._cookieGet('sso_token');
+        const localToken = localStorage.getItem('sso_token');
+        if (!cookieToken && localToken) {
+            ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+             'currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
+            throw new Error('쿠키 없음 - 로그아웃 상태');
+        }
+
         // SSO 쿠키 우선, localStorage 폴백
-        const token = this._cookieGet('sso_token') || localStorage.getItem('sso_token');
+        const token = cookieToken || localToken;
         if (!token) {
             throw new Error('토큰 없음');
         }
diff --git a/system3-nonconformance/web/static/js/core/auth-manager.js b/system3-nonconformance/web/static/js/core/auth-manager.js
index 3d9fd3c..4762bc1 100644
--- a/system3-nonconformance/web/static/js/core/auth-manager.js
+++ b/system3-nonconformance/web/static/js/core/auth-manager.js
@@ -97,6 +97,15 @@ class AuthManager {
      * 저장소에서 사용자 정보 복원 (SSO 쿠키 + localStorage)
      */
     restoreUserFromStorage() {
+        // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+        const cookieToken = this._cookieGet('sso_token');
+        const localToken = localStorage.getItem('sso_token');
+        if (!cookieToken && localToken) {
+            ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+             'currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
+            return;
+        }
+
         const token = this._getToken();
         const user = this._getUser();
 
@@ -240,7 +249,7 @@ class AuthManager {
     logout() {
         this.clearAuth();
         this.notifyListeners('logout');
-        window.location.href = this._getLoginUrl();
+        window.location.href = this._getLoginUrl() + '&logout=1';
     }
     
     /**
diff --git a/tkpurchase/web/static/js/tkpurchase-core.js b/tkpurchase/web/static/js/tkpurchase-core.js
index 4903eb1..29e3857 100644
--- a/tkpurchase/web/static/js/tkpurchase-core.js
+++ b/tkpurchase/web/static/js/tkpurchase-core.js
@@ -79,7 +79,7 @@ function doLogout() {
     if (!confirm('로그아웃?')) return;
     _cookieRemove('sso_token'); _cookieRemove('sso_user'); _cookieRemove('sso_refresh_token');
     ['sso_token','sso_user','sso_refresh_token','token','user','access_token','currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
-    location.href = getLoginUrl();
+    location.href = getLoginUrl() + '&logout=1';
 }
 
 /* ===== Navbar ===== */
@@ -106,6 +106,16 @@ let currentUser = null;
 
 /* ===== Init ===== */
 function initAuth() {
+    // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+    const cookieToken = _cookieGet('sso_token');
+    const localToken = localStorage.getItem('sso_token');
+    if (!cookieToken && localToken) {
+        ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+         'currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
+        _safeRedirect();
+        return false;
+    }
+
     const token = getToken();
     if (!token) { _safeRedirect(); return false; }
     const decoded = decodeToken(token);
diff --git a/tksafety/web/static/js/tksafety-core.js b/tksafety/web/static/js/tksafety-core.js
index 17e0faf..38ead95 100644
--- a/tksafety/web/static/js/tksafety-core.js
+++ b/tksafety/web/static/js/tksafety-core.js
@@ -76,7 +76,7 @@ function doLogout() {
     if (!confirm('로그아웃?')) return;
     _cookieRemove('sso_token'); _cookieRemove('sso_user'); _cookieRemove('sso_refresh_token');
     ['sso_token','sso_user','sso_refresh_token','token','user','access_token','currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
-    location.href = getLoginUrl();
+    location.href = getLoginUrl() + '&logout=1';
 }
 
 /* ===== Navbar ===== */
@@ -100,6 +100,16 @@ let currentUser = null;
 
 /* ===== Init ===== */
 function initAuth() {
+    // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+    const cookieToken = _cookieGet('sso_token');
+    const localToken = localStorage.getItem('sso_token');
+    if (!cookieToken && localToken) {
+        ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+         'currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
+        _safeRedirect();
+        return false;
+    }
+
     const token = getToken();
     if (!token) { _safeRedirect(); return false; }
     const decoded = decodeToken(token);
diff --git a/user-management/web/static/js/tkuser-core.js b/user-management/web/static/js/tkuser-core.js
index 0848e81..8de4b23 100644
--- a/user-management/web/static/js/tkuser-core.js
+++ b/user-management/web/static/js/tkuser-core.js
@@ -75,7 +75,7 @@ function doLogout() {
     if (!confirm('로그아웃?')) return;
     _cookieRemove('sso_token'); _cookieRemove('sso_user'); _cookieRemove('sso_refresh_token');
     ['sso_token','sso_user','sso_refresh_token','token','user','access_token','currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
-    location.href = getLoginUrl();
+    location.href = getLoginUrl() + '&logout=1';
 }
 
 /* ===== State ===== */
@@ -83,6 +83,16 @@ let currentUser = null;
 
 /* ===== Init ===== */
 async function init() {
+    // 쿠키 우선 검증: 쿠키 없고 localStorage에만 토큰이 있으면 정리
+    const cookieToken = _cookieGet('sso_token');
+    const localToken = localStorage.getItem('sso_token');
+    if (!cookieToken && localToken) {
+        ['sso_token','sso_user','sso_refresh_token','token','user','access_token',
+         'currentUser','current_user','userInfo','userPageAccess'].forEach(k => localStorage.removeItem(k));
+        _safeRedirect();
+        return;
+    }
+
     const token = getToken();
     if (!token) { _safeRedirect(); return; }
     const decoded = decodeToken(token);