diff --git a/src/components/server.ts b/src/components/server.ts
index 2b5fb9a4..ac9dbb4a 100644
--- a/src/components/server.ts
+++ b/src/components/server.ts
@@ -103,7 +103,7 @@ export class Server {
         if (viewerPort === 0 && currentSessionPort) {
             const {sessionId, port} = currentSessionPort
             if (sessionId === vscode.env.sessionId) {
-                this.extension.logger.info(`[Server] Restoring server port of current session: ${inspectCompact(currentSessionPort)}`)
+                this.extension.logger.info(`[Server] Restoring the server port of the current session: ${inspectCompact(currentSessionPort)}`)
                 viewerPort = port
             }
         }
diff --git a/src/components/viewerlib/pdfviewermanager.ts b/src/components/viewerlib/pdfviewermanager.ts
index f1ac9fa0..61e41c17 100644
--- a/src/components/viewerlib/pdfviewermanager.ts
+++ b/src/components/viewerlib/pdfviewermanager.ts
@@ -5,15 +5,35 @@ import { toKey } from '../../utils/tokey.js'
 import type { Client } from './client.js'
 import type { PdfViewerPanel } from './pdfviewerpanel.js'
 import type { Manager } from '../manager.js'
+import type { Logger } from '../logger.js'
+import { inspectCompact } from '../../utils/inspect.js'
 
+interface CurrentSessionClientKeys {
+    sessionId: string
+    clientKeys: string[]
+}
 
 export class PdfViewerManagerService {
     private readonly webviewPanelMap = new Map<string, Set<PdfViewerPanel>>()
+    private readonly clientSetKey = 'pdfviewer.clientset'
     readonly clientMap = new Map<string, Set<Client>>()
 
     constructor(private readonly extension: {
+        readonly extensionContext: vscode.ExtensionContext,
+        readonly logger: Logger,
         readonly manager: Manager
-    }) { }
+    }) {
+        const currentSessionClientKeys = this.extension.extensionContext.workspaceState.get<CurrentSessionClientKeys>(this.clientSetKey)
+        if (currentSessionClientKeys) {
+            const { sessionId, clientKeys } = currentSessionClientKeys
+            if (sessionId === vscode.env.sessionId) {
+                this.extension.logger.info(`Restoring the client set from the current session: ${inspectCompact(currentSessionClientKeys)}`)
+                clientKeys.forEach(key => {
+                    this.createClientSetFromKey(key)
+                })
+            }
+        }
+    }
 
     dispose() {
         this.webviewPanelMap.forEach(panelSet => {
@@ -23,8 +43,18 @@ export class PdfViewerManagerService {
         })
     }
 
+    /**
+     * Make the manager treat the PDF file as an output of a LaTeX file.
+     * @param pdfFileUri The URI of a PDF file.
+     */
     createClientSet(pdfFileUri: vscode.Uri): void {
         const key = toKey(pdfFileUri)
+        this.createClientSetFromKey(key)
+        const currentSessionClientKeys = { sessionId: vscode.env.sessionId, clientKeys: Array.from(this.clientMap.keys()) }
+        void this.extension.extensionContext.workspaceState.update(this.clientSetKey, currentSessionClientKeys)
+    }
+
+    private createClientSetFromKey(key: string): void {
         if (!this.clientMap.has(key)) {
             this.clientMap.set(key, new Set())
         }
diff --git a/viewer/components/extensionconnection.ts b/viewer/components/extensionconnection.ts
index 9c43c472..04746faf 100644
--- a/viewer/components/extensionconnection.ts
+++ b/viewer/components/extensionconnection.ts
@@ -7,16 +7,40 @@ import { ExternalPromise } from '../utils/externalpromise.js'
 export class ExtensionConnection {
     private readonly lwApp: ILatexToyboxPdfViewer
     private connectionPort = new ConnectionPort()
+    private readonly disconnectedNotificationDom = document.createElement('div')
+    private readonly reconnectedNotificationDom = document.createElement('div')
 
     constructor(lwApp: ILatexToyboxPdfViewer) {
         this.lwApp = lwApp
         this.setupConnectionPort()
+        this.setupDoms()
     }
 
     send(message: ClientRequest) {
         void this.connectionPort.send(message)
     }
 
+    private setupDoms() {
+        this.disconnectedNotificationDom.id = 'notify-disconnected'
+        this.disconnectedNotificationDom.textContent = 'Disconnected from LaTeX Toybox. Trying to reconnect...'
+        this.disconnectedNotificationDom.classList.add('hide')
+        document.body.appendChild(this.disconnectedNotificationDom)
+        this.reconnectedNotificationDom.id = 'notify-reconnected'
+        this.reconnectedNotificationDom.textContent = 'Reconnected to LaTeX Toybox. Happy TeXing!'
+        this.reconnectedNotificationDom.classList.add('hide')
+        document.body.appendChild(this.reconnectedNotificationDom)
+    }
+
+    private notifyDisconnected() {
+        this.disconnectedNotificationDom.classList.remove('hide')
+    }
+
+    private notifyReconnected() {
+        this.disconnectedNotificationDom.classList.add('hide')
+        this.reconnectedNotificationDom.classList.remove('hide')
+        setTimeout(() => this.reconnectedNotificationDom.classList.add('hide'), 3000)
+    }
+
     private setupConnectionPort() {
         const openPack: ClientRequest = {
             type: 'open',
@@ -42,7 +66,7 @@ export class ExtensionConnection {
         })
 
         void this.connectionPort.onDidClose(async () => {
-            document.title = `[Disconnected] ${this.lwApp.documentTitle}`
+            this.notifyDisconnected()
             console.log('Closed: WebScocket to LaTeX Toybox.')
 
             // Since WebSockets are disconnected when PC resumes from sleep,
@@ -53,7 +77,7 @@ export class ExtensionConnection {
                 try {
                     this.connectionPort = new ConnectionPort()
                     await this.connectionPort.readyPromise
-                    document.title = this.lwApp.documentTitle
+                    this.notifyReconnected()
                     this.setupConnectionPort()
                     console.log('Reconnected: WebScocket to LaTeX Toybox.')
                     return
diff --git a/viewer/latextoybox.css b/viewer/latextoybox.css
index 16b21bc5..e99624a9 100644
--- a/viewer/latextoybox.css
+++ b/viewer/latextoybox.css
@@ -197,3 +197,28 @@ html[dir='rtl'] .findbar {
 #autoReloadOffButton::before {
     display: none;
 }
+
+#notify-disconnected {
+    position: fixed;
+    top: 0;
+    left: 0;
+    z-index: 100000;
+    border: 3px solid red;
+}
+
+#notify-disconnected[class="hide"] {
+    opacity: 0;
+}
+
+#notify-reconnected {
+    position: fixed;
+    top: 0;
+    left: 0;
+    z-index: 100000;
+    border: 3px solid green;
+}
+
+#notify-reconnected[class="hide"] {
+    opacity: 0;
+    transition: opacity 0.5s ease-in-out;
+}