diff --git a/js/main.js b/js/main.js
index 7654607..c1d9a53 100644
--- a/js/main.js
+++ b/js/main.js
@@ -465,6 +465,51 @@ const BACK_LINK_PATH_TITLE = {
     '/home': '홈',
     '/blog': '블로그',
 };
+const FINDMYDEVICE_AUTH_REQUIRED = location.pathname.startsWith('/findmydevice');
+let findmydeviceAuthenticated = !FINDMYDEVICE_AUTH_REQUIRED;
+
+function renderAuthErrorPage() {
+    document.body.innerHTML = `
+        <main class="find-auth-page">
+            <div id="findMyShortcut"></div>
+        </main>
+    `;
+    const renderPin = () => window.CustomAuthPin?.render({
+        mount: '#findMyShortcut',
+        title: '비밀번호',
+        placeholder: '비밀번호',
+        backLabel: '채건닷컴',
+        backHref: 'https://chaegeon.com/',
+        onSuccess: () => location.reload(),
+    });
+    if (window.CustomAuthPin) {
+        renderPin();
+        return;
+    }
+    const script = document.createElement('script');
+    script.src = '/custom/common/js/auth-pin.js';
+    script.onload = renderPin;
+    document.body.appendChild(script);
+}
+
+const findmydeviceAuthPromise = FINDMYDEVICE_AUTH_REQUIRED
+    ? fetch('/custom/launcher/api.php?session=1', { credentials: 'same-origin' })
+        .then(res => res.ok ? res.json() : Promise.reject())
+        .then(session => {
+            findmydeviceAuthenticated = !!session.authenticated;
+            return findmydeviceAuthenticated;
+        })
+        .catch(() => {
+            findmydeviceAuthenticated = false;
+            return false;
+        })
+    : Promise.resolve(true);
+
+function runAfterFindAuth(callback) {
+    return findmydeviceAuthPromise
+        .then(ok => ok ? callback() : null)
+        .catch(() => null);
+}
 
 function cleanPageTitle(title) {
     return String(title || '')
@@ -622,7 +667,7 @@ document.getElementById('langToggle').addEventListener('click', () => {
     localStorage.setItem('currentLang', langCode);
     applyLanguage(langCode);
 
-    fetchDeviceData(true).then(data => updateDOMWithData(data));
+    runAfterFindAuth(() => fetchDeviceData(true).then(data => updateDOMWithData(data)));
 
     // locateBtn 즉시 재렌더링
     if (document.getElementById('locateBtn')) {
@@ -680,41 +725,12 @@ document.addEventListener('DOMContentLoaded', () => {
 
     setupBackLink();
 
-    function renderAuthErrorPage() {
-        document.body.innerHTML = `
-            <main class="find-auth-page">
-                <div id="findMyShortcut"></div>
-            </main>
-        `;
-        const renderPin = () => window.CustomAuthPin?.render({
-            mount: '#findMyShortcut',
-            title: '비밀번호',
-            placeholder: '비밀번호',
-            backLabel: '채건닷컴',
-            backHref: 'https://chaegeon.com/',
-            onSuccess: () => location.reload(),
+    if (FINDMYDEVICE_AUTH_REQUIRED) {
+        findmydeviceAuthPromise.then(ok => {
+            if (!ok) renderAuthErrorPage();
         });
-        if (window.CustomAuthPin) {
-            renderPin();
-            return;
-        }
-        const script = document.createElement('script');
-        script.src = '/custom/common/js/auth-pin.js';
-        script.onload = renderPin;
-        document.body.appendChild(script);
     }
 
-    if (location.pathname.startsWith('/findmydevice')) {
-        fetch('/custom/launcher/api.php?session=1', { credentials: 'same-origin' })
-            .then(res => res.ok ? res.json() : Promise.reject())
-            .then(session => {
-                if (!session.authenticated) {
-                    renderAuthErrorPage();
-                }
-            })
-            .catch(renderAuthErrorPage);
-    }
-
     const btnArea = document.querySelector('body > div.btnArea');
     const pageModifyLink = btnArea?.querySelectorAll('a')[1]?.getAttribute('href') || '';
     if (btnArea) btnArea.remove();
@@ -832,12 +848,12 @@ document.addEventListener('DOMContentLoaded', () => {
 
             // 3) 지도 히스토리 초기화 & 라이브 데이터 재요청 + 현재 위치로 이동
             resetHistoryLayer();
-            fetchDeviceData(true).then(data => {
-                updateDOMWithData(data);
-                if (data.latitude && data.longitude && mapState.map) {
-                    mapState.map.panTo(new naver.maps.LatLng(data.latitude, data.longitude));
-                }
-            });
+            runAfterFindAuth(() => fetchDeviceData(true).then(data => {
+                updateDOMWithData(data);
+                if (data.latitude && data.longitude && mapState.map) {
+                    mapState.map.panTo(new naver.maps.LatLng(data.latitude, data.longitude));
+                }
+            }));
         });
     }
 
@@ -917,7 +933,7 @@ document.addEventListener('DOMContentLoaded', () => {
             endEl.addEventListener(ev, () => fire(true));
         });
 
-        fire(false);
+        runAfterFindAuth(() => fire(false));
     })();
 });
 
@@ -970,13 +986,15 @@ document.getElementById('autoUpdateSwitch').addEventListener('change', () => {
 });
 
 setInterval(() => {
+    if (!findmydeviceAuthenticated) return;
     if (document.getElementById('autoUpdateSwitch')?.checked) {
         callDeviceWebhook('auto_tick');
     }
 }, 10000);
-
-setInterval(() => {
-    if (lastUpdateISOTime) {
+
+setInterval(() => {
+    if (!findmydeviceAuthenticated) return;
+    if (lastUpdateISOTime) {
         const el = document.getElementById("lastUpdateTime");
         if (el) el.textContent = getRelativeTime(lastUpdateISOTime);
     }
@@ -2398,6 +2416,10 @@ function syncUpdateBtn() {
 }
 
 function fetchDeviceData(includeLang = true, range = null) {
+    if (!findmydeviceAuthenticated) {
+        return Promise.reject(new Error('not_authenticated'));
+    }
+
     const params = new URLSearchParams(includeLang ? { lang: langCode } : { hashonly: 1 });
 
     // 우선순위: 직접 인자(range) > 전역 오버라이드(_overrideRange)