diff --git a/frontend/dcViewer.css b/frontend/dcViewer.css
index 4e9f48c..3b7b477 100644
--- a/frontend/dcViewer.css
+++ b/frontend/dcViewer.css
@@ -3220,20 +3220,28 @@ header {
 }
 
 body[data-viewer-mode="guest"] .tb-btn:not([data-action="measure"]):not([data-action="section"]):not([data-action="projection"]),
-html[data-share-startup="guest"] body:not([data-viewer-mode="standard"]) .tb-btn:not([data-action="measure"]):not([data-action="section"]):not([data-action="projection"]),
+html[data-share-startup] body:not([data-viewer-mode="standard"]) .tb-btn:not([data-action="measure"]):not([data-action="section"]):not([data-action="projection"]),
 body[data-viewer-mode="guest"] #settingsPanel,
-html[data-share-startup="guest"] body:not([data-viewer-mode="standard"]) #settingsPanel,
+html[data-share-startup] body:not([data-viewer-mode="standard"]) #settingsPanel,
 body[data-viewer-mode="guest"] #templatesPanel,
-html[data-share-startup="guest"] body:not([data-viewer-mode="standard"]) #templatesPanel,
+html[data-share-startup] body:not([data-viewer-mode="standard"]) #templatesPanel,
 body[data-viewer-mode="guest"] #projectNameSection,
-html[data-share-startup="guest"] body:not([data-viewer-mode="standard"]) #projectNameSection,
+html[data-share-startup] body:not([data-viewer-mode="standard"]) #projectNameSection,
 body[data-viewer-mode="guest"] #saveProjectSection,
-html[data-share-startup="guest"] body:not([data-viewer-mode="standard"]) #saveProjectSection,
+html[data-share-startup] body:not([data-viewer-mode="standard"]) #saveProjectSection,
 body[data-viewer-mode="guest"] #modelVersionUploadButton,
-html[data-share-startup="guest"] body:not([data-viewer-mode="standard"]) #modelVersionUploadButton {
+html[data-share-startup] body:not([data-viewer-mode="standard"]) #modelVersionUploadButton {
   display: none !important;
 }
 
+html[data-share-startup="pending"] #dropZone {
+  display: none !important;
+}
+
+html[data-share-startup="pending"] #loader.hidden {
+  display: block;
+}
+
 .version-history-backdrop {
   position: fixed;
   inset: 0;
diff --git a/frontend/dcViewer.js b/frontend/dcViewer.js
index 6f0cdbb..410eb7d 100644
--- a/frontend/dcViewer.js
+++ b/frontend/dcViewer.js
@@ -186,6 +186,7 @@ const COMMENTS_API = "/api/comments";
 const UPLOAD_VERSIONS_API = "/api/uploads/versions";
 const SHARE_AUTH_GUEST_PARAM = "ndc_bim_guest";
 const SHARE_PROMOTION_TIMEOUT_MS = 4500;
+const NODEDC_SESSION_EVENT_TYPE = "nodedc:session:logout";
 
 const acceptByType = {
   xkt: ".xkt",
@@ -648,6 +649,101 @@ const clearShareGuestAuthMarker = () => {
   }
 };
 
+const clearShareStartupPending = () => {
+  if (document.documentElement?.dataset?.shareStartup === "pending") {
+    delete document.documentElement.dataset.shareStartup;
+  }
+};
+
+const isNodeDCSessionLogoutEvent = (value) => (
+  value &&
+  typeof value === "object" &&
+  value.type === NODEDC_SESSION_EVENT_TYPE &&
+  typeof value.id === "string"
+);
+
+let nodeDCSessionSyncCleanup = null;
+let nodeDCLogoutHandling = false;
+
+const handleNodeDCSessionLogout = async () => {
+  if (nodeDCLogoutHandling) return;
+  nodeDCLogoutHandling = true;
+
+  const logoutRequest = fetch("/logout", {
+      method: "GET",
+      credentials: "include",
+      keepalive: true,
+      cache: "no-store",
+    })
+    .catch(() => undefined);
+
+  runtimeSessionInfo = {
+    ...runtimeSessionInfo,
+    authenticated: false,
+    canShare: false,
+    user: null,
+  };
+
+  if (startupSharePayload) {
+    startupSharePayload = {
+      ...startupSharePayload,
+      mode: "guest",
+      readonly: true,
+      authenticated: false,
+      canShare: false,
+      user: null,
+    };
+  }
+
+  if (getShareTokenFromPath()) {
+    viewerMode = "guest";
+    inspectorCollapsed = true;
+    applyRuntimeMode();
+    updatePanelsVisibility();
+    nodeDCLogoutHandling = false;
+    return;
+  }
+
+  await Promise.race([
+    logoutRequest,
+    new Promise((resolve) => window.setTimeout(resolve, 500)),
+  ]);
+
+  const loginUrl = new URL("/auth/login", getLauncherUrl());
+  window.location.replace(loginUrl.toString());
+};
+
+const setupNodeDCSessionSync = () => {
+  if (nodeDCSessionSyncCleanup || typeof document === "undefined") return;
+
+  let launcherOrigin = "";
+  try {
+    launcherOrigin = new URL(getLauncherUrl()).origin;
+  } catch (_) {
+    return;
+  }
+
+  const iframe = document.createElement("iframe");
+  iframe.src = new URL("/auth/session-sync", launcherOrigin).toString();
+  iframe.title = "NODE.DC session sync";
+  iframe.tabIndex = -1;
+  iframe.setAttribute("aria-hidden", "true");
+  iframe.style.cssText = "position:fixed;width:0;height:0;opacity:0;pointer-events:none;border:0;";
+  document.body.appendChild(iframe);
+
+  const handleMessage = (event) => {
+    if (event.origin !== launcherOrigin || !isNodeDCSessionLogoutEvent(event.data)) return;
+    void handleNodeDCSessionLogout();
+  };
+
+  window.addEventListener("message", handleMessage);
+  nodeDCSessionSyncCleanup = () => {
+    window.removeEventListener("message", handleMessage);
+    iframe.remove();
+    nodeDCSessionSyncCleanup = null;
+  };
+};
+
 const scheduleShareSessionPromotion = (shareToken) => {
   const silentPromoteUrl = startupSharePayload?.silentPromoteUrl;
   if (
@@ -5212,6 +5308,7 @@ const applyViewerState = (state) => {
 
 const initViewer = async () => {
   await initializeRuntimeMode();
+  setupNodeDCSessionSync();
 
   const preloadHidden = document.getElementById("preload-hidden");
   if (preloadHidden) {
@@ -5842,6 +5939,8 @@ const initViewer = async () => {
     });
     if (!src) {
       reportViewerEvent("startup-no-src", { search: window.location.search }, "error");
+      clearShareStartupPending();
+      setLoading(false);
       return;
     }
 
@@ -5850,12 +5949,15 @@ const initViewer = async () => {
     if (!type) {
       reportViewerEvent("startup-type-error", { src, name, typeParam: params.get("type") }, "error");
       showError("Не удалось определить формат модели из URL");
+      clearShareStartupPending();
+      setLoading(false);
       return;
     }
 
     dropZone?.classList.add("hidden");
     setStatus(`Подготовка: ${name}...`);
     setLoading(true);
+    clearShareStartupPending();
 
     let settingsSrc = sharedViewer?.settingsSrc || params.get("settingsSrc") || params.get("sourceSrc") || params.get("originalSrc") || src;
     const applyQueryViewerOverrides = () => {
diff --git a/frontend/index.html b/frontend/index.html
index 5bc6142..73d95cb 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -16,7 +16,7 @@
   <script>
     (function () {
       if (/^\/share\/[^/]+\/?$/.test(window.location.pathname || "")) {
-        document.documentElement.dataset.shareStartup = "guest";
+        document.documentElement.dataset.shareStartup = "pending";
       }
     }());
   </script>
diff --git a/server/index.js b/server/index.js
index 813a044..08c9e4b 100644
--- a/server/index.js
+++ b/server/index.js
@@ -1685,15 +1685,22 @@ const handleSharePromoted = (res, url) => {
 </html>`);
 };
 
-const handleLogout = (req, res) => {
+const handleLogout = (req, res, {redirect = true} = {}) => {
     const sessionId = parseCookies(req.headers.cookie || "")[BIM_SESSION_COOKIE];
     if (sessionId) {
         bimSessions.delete(sessionId);
     }
     clearBimSessionCookie(res);
-    res.statusCode = 302;
-    res.setHeader("Location", "/");
-    res.end();
+    res.setHeader("Cache-Control", "no-store");
+    if (redirect) {
+        res.statusCode = 302;
+        res.setHeader("Location", "/");
+        res.end();
+        return;
+    }
+    res.statusCode = 200;
+    res.setHeader("Content-Type", "text/html; charset=utf-8");
+    res.end("<!doctype html><html><head><meta charset='utf-8'></head><body>NODE.DC BIM session closed.</body></html>");
 };
 
 const handleCreateShare = async (req, res) => {
@@ -3304,6 +3311,10 @@ const requestHandler = async (req, res) => {
         return handleLogout(req, res);
     }
 
+    if (req.method === "GET" && url.pathname === "/logout") {
+        return handleLogout(req, res, {redirect: false});
+    }
+
     if (req.method === "GET" && /^\/api\/shares\/[^/]+\/?$/.test(url.pathname)) {
         return handleGetShare(req, res, shareTokenFromPath(url.pathname));
     }