diff --git a/desktop/src/renderer/src/components/UpdateBanner.tsx b/desktop/src/renderer/src/components/UpdateBanner.tsx
index bdd45aff..78c48006 100644
--- a/desktop/src/renderer/src/components/UpdateBanner.tsx
+++ b/desktop/src/renderer/src/components/UpdateBanner.tsx
@@ -14,14 +14,32 @@ const UpdateBanner: React.FC = () => {
   const status = state.status
   const errored = status?.state === 'error'
 
+  // Full-screen "installing…" overlay: bridges the otherwise blank window
+  // between clicking "restart to install" and the app actually quitting to
+  // swap the bundle. (The gap AFTER quit, before relaunch, is OS-level and
+  // can't be covered.)
+  if (state.installing) {
+    return (
+      <div className="fixed inset-0 z-[100] flex flex-col items-center justify-center gap-3 bg-base/90 backdrop-blur-sm">
+        <Loader2 size={28} className="animate-spin text-accent" />
+        <p className="text-sm text-content-secondary">{t('update_installing')}</p>
+      </div>
+    )
+  }
+
   // Show the panel when it's open AND we either know of an update or hit an
   // error. Keeping it up on error is important: a failed download must surface
   // a visible message instead of silently doing nothing.
   if (!open || (!available && !errored)) return null
 
   const version = state.version
+  const preparing = state.preparing
   const downloading = status?.state === 'downloading'
   const downloaded = status?.state === 'downloaded'
+  // macOS emits a second progress pass (verify) after hitting 100%; show it as
+  // an indeterminate "verifying" state rather than a bar restarting from 0.
+  const verifying = downloading && state.progressPeaked
+  const busy = preparing || downloading
 
   return (
     <div className="absolute bottom-2 left-2 right-2 z-40">
@@ -62,7 +80,21 @@ const UpdateBanner: React.FC = () => {
             </div>
           )}
 
-          {!errored && downloading && (
+          {!errored && preparing && (
+            <div className="flex items-center gap-2 text-xs text-content-secondary py-1">
+              <Loader2 size={13} className="animate-spin" />
+              <span>{t('update_preparing')}</span>
+            </div>
+          )}
+
+          {!errored && downloading && verifying && (
+            <div className="flex items-center gap-2 text-xs text-content-secondary py-1">
+              <Loader2 size={13} className="animate-spin" />
+              <span>{t('update_verifying')}</span>
+            </div>
+          )}
+
+          {!errored && downloading && !verifying && (
             <div className="space-y-1">
               <div className="flex items-center gap-2 text-xs text-content-secondary">
                 <Loader2 size={13} className="animate-spin" />
@@ -74,7 +106,7 @@ const UpdateBanner: React.FC = () => {
             </div>
           )}
 
-          {!errored && !downloading && !downloaded && (
+          {!errored && !busy && !downloaded && (
             <button
               onClick={() => state.download()}
               className="w-full inline-flex items-center justify-center gap-2 rounded-btn bg-accent text-accent-contrast hover:bg-accent-hover px-3 py-2 text-[13px] font-medium cursor-pointer transition-colors"
diff --git a/desktop/src/renderer/src/i18n.ts b/desktop/src/renderer/src/i18n.ts
index ade035f9..3daf95f9 100644
--- a/desktop/src/renderer/src/i18n.ts
+++ b/desktop/src/renderer/src/i18n.ts
@@ -72,6 +72,9 @@ const translations: Record<string, Record<string, string>> = {
     update_available: '发现新版本',
     update_download: '下载更新',
     update_downloading: '正在下载',
+    update_preparing: '正在准备…',
+    update_verifying: '正在校验，即将完成…',
+    update_installing: '正在安装并重启，请稍候…',
     update_restart: '重启以更新',
     update_later: '稍后',
     update_latest: '已是最新版本',
@@ -444,6 +447,9 @@ const translations: Record<string, Record<string, string>> = {
     update_available: 'New version available',
     update_download: 'Download update',
     update_downloading: 'Downloading',
+    update_preparing: 'Preparing…',
+    update_verifying: 'Verifying, almost done…',
+    update_installing: 'Installing and restarting, please wait…',
     update_restart: 'Restart to update',
     update_later: 'Later',
     update_latest: 'You are up to date',
diff --git a/desktop/src/renderer/src/layout/NavRail.tsx b/desktop/src/renderer/src/layout/NavRail.tsx
index 92aa90b0..f099b6ac 100644
--- a/desktop/src/renderer/src/layout/NavRail.tsx
+++ b/desktop/src/renderer/src/layout/NavRail.tsx
@@ -155,9 +155,11 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
 
   const checkUpdate = () => {
     setCheckedManually(true)
-    // Re-open the update panel if an update is already known; also kicks a
-    // fresh check. Closing the menu so the re-opened panel is visible.
-    setMenuOpen(false)
+    // If an update is already known, recheck() re-opens its panel, so close the
+    // menu to reveal it. Otherwise keep the menu OPEN: the "up to date" result
+    // shows inline as the menu label — closing it (which resets checkedManually)
+    // is exactly what made the box flash and never show "up to date".
+    if (availableUpdate) setMenuOpen(false)
     updateState.recheck()
   }
 
diff --git a/desktop/src/renderer/src/store/updateStore.ts b/desktop/src/renderer/src/store/updateStore.ts
index 2ac4b48c..6dde6faf 100644
--- a/desktop/src/renderer/src/store/updateStore.ts
+++ b/desktop/src/renderer/src/store/updateStore.ts
@@ -8,6 +8,18 @@ interface UpdateState {
   version: string | null
   /** Download progress 0-100 while state === 'downloading'. */
   percent: number
+  /** User clicked "download" but no progress event has arrived yet. Gives the
+   *  button an instant busy state so it can't be clicked again during the 1-2s
+   *  lead-up to the first progress event. Cleared on the first 'downloading'. */
+  preparing: boolean
+  /** The download progress already reached ~100% once. macOS (Squirrel.Mac)
+   *  emits a SECOND progress pass (verify / block-map) after the first, which
+   *  used to make the bar visibly restart from 0. Once peaked we render an
+   *  indeterminate "verifying" state instead of a confusing second bar. */
+  progressPeaked: boolean
+  /** User clicked "restart to install"; show a full-screen "installing…"
+   *  overlay for the brief window before the app quits to swap the bundle. */
+  installing: boolean
   /** User dismissed the badge for this version (don't nag again until next). */
   dismissedVersion: string | null
   /** Whether the update panel is currently shown. Lifted here so the "check
@@ -33,15 +45,27 @@ export const useUpdateStore = create<UpdateState>((set, get) => ({
   status: null,
   version: null,
   percent: 0,
+  preparing: false,
+  progressPeaked: false,
+  installing: false,
   dismissedVersion: null,
   panelOpen: false,
 
   setStatus: (s) =>
-    set(() => {
+    set((st) => {
       // A newly detected version auto-opens the panel.
-      if (s.state === 'available') return { status: s, version: s.version, percent: 0, panelOpen: true }
-      if (s.state === 'downloading') return { status: s, percent: s.percent }
-      if (s.state === 'downloaded') return { status: s, version: s.version, percent: 100 }
+      if (s.state === 'available')
+        return { status: s, version: s.version, percent: 0, preparing: false, progressPeaked: false, panelOpen: true }
+      if (s.state === 'downloading') {
+        // First real progress event clears the "preparing" busy state. Track
+        // when we've hit ~100% so the Squirrel.Mac second pass renders as an
+        // indeterminate "verifying" state instead of a bar restarting from 0.
+        const peaked = st.progressPeaked || s.percent >= 99
+        return { status: s, percent: s.percent, preparing: false, progressPeaked: peaked }
+      }
+      if (s.state === 'downloaded')
+        return { status: s, version: s.version, percent: 100, preparing: false }
+      if (s.state === 'error') return { status: s, preparing: false, installing: false }
       return { status: s }
     }),
 
@@ -50,18 +74,29 @@ export const useUpdateStore = create<UpdateState>((set, get) => ({
   closePanel: () => set({ panelOpen: false }),
 
   recheck: () => {
-    // Open the panel and clear any dismiss so the result of this explicit check
-    // is always visible — available, error, or (via the menu label) up-to-date.
-    // Previously the panel only opened when an update was already known, so a
-    // download/check error rendered nothing and looked like a dead click.
-    set({ dismissedVersion: null, panelOpen: true })
+    // Clear any dismiss so a known update surfaces again. Only re-open the panel
+    // when an update actually exists — if we're already up to date, opening the
+    // panel would just flash it (the banner renders nothing for not-available)
+    // and the "up to date" feedback belongs in the menu, not a panel. The menu
+    // (NavRail) decides whether to close itself + show the panel based on this.
+    const known = hasAvailableUpdate(get())
+    set({ dismissedVersion: null, panelOpen: known })
     // Always kick a fresh check too (picks up newer versions / recovers errors).
     // Pass the UI language so downloads route to the China CDN / R2 accordingly.
     window.electronAPI?.checkForUpdate?.(getLang())
   },
 
-  download: () => window.electronAPI?.downloadUpdate?.(getLang()),
-  install: () => window.electronAPI?.installUpdate?.(),
+  download: () => {
+    // Enter a busy state immediately so the button can't be clicked twice while
+    // we wait (1-2s) for the first download-progress event to arrive.
+    set({ preparing: true, progressPeaked: false })
+    window.electronAPI?.downloadUpdate?.(getLang())
+  },
+  install: () => {
+    // Show the "installing…" overlay before the app quits to swap the bundle.
+    set({ installing: true })
+    window.electronAPI?.installUpdate?.()
+  },
 }))
 
 // Subscribe to main-process update events. Returns an unsubscribe fn.