feat(version): warn when the server was updated but not restarted (#898)

When the package is updated on disk but the long-lived server process is
not restarted, the new frontend bundle (served from disk) talks to the
old running backend. New DB-backed features then fail silently — e.g.
deleting/archiving a session appears to do nothing — because the new
schema/routes only take effect on restart.

Nothing currently detects this skew: useVersionCheck only compares the
frontend's build-time version against the latest GitHub release.

This exposes the running server's version (captured once at startup) via
/health, compares it to the frontend's build-time version in
useVersionCheck, and shows a "restart required" banner in the sidebar
(and a small indicator in the collapsed sidebar) when they differ.

- server: add `version` (RUNNING_VERSION, read once at startup) to /health
- useVersionCheck: return `restartRequired` / `runningVersion`
- SidebarFooter / SidebarCollapsed: surface a restart-required banner
- i18n: add `version.restartRequired` to all 10 sidebar locales

Verified with `tsc --noEmit` (client + server) and eslint.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Simos Mikelatos <simosmik@gmail.com>

src/components/sidebar/view/Sidebar.tsx

@@ -43,7 +43,7 @@ function Sidebar({
 }: SidebarProps) {
   const { t } = useTranslation(['sidebar', 'common']);
   const { isPWA } = useDeviceSettings({ trackMobile: false });
-  const { updateAvailable, latestVersion, currentVersion, releaseInfo, installMode } = useVersionCheck(
+  const { updateAvailable, restartRequired, latestVersion, currentVersion, releaseInfo, installMode } = useVersionCheck(
     'siteboon',
     'claudecodeui',
   );
@@ -224,6 +224,7 @@ function Sidebar({
           onExpand={handleExpandSidebar}
           onShowSettings={onShowSettings}
           updateAvailable={updateAvailable}
+          restartRequired={restartRequired}
           onShowVersionModal={() => setShowVersionModal(true)}
           t={t}
         />
@@ -296,6 +297,7 @@ function Sidebar({
             onCreateProject={() => setShowNewProject(true)}
             onCollapseSidebar={handleCollapseSidebar}
             updateAvailable={updateAvailable}
+            restartRequired={restartRequired}
             releaseInfo={releaseInfo}
             latestVersion={latestVersion}
             currentVersion={currentVersion}

src/components/sidebar/view/subcomponents/SidebarCollapsed.tsx

@@ -1,4 +1,4 @@
-import { Settings, Sparkles, PanelLeftOpen, Bug } from 'lucide-react';
+import { Settings, Sparkles, PanelLeftOpen, Bug, AlertTriangle } from 'lucide-react';
 import type { TFunction } from 'i18next';
 
 const DISCORD_INVITE_URL = 'https://discord.gg/buxwujPNRE';
@@ -16,6 +16,7 @@ type SidebarCollapsedProps = {
   onExpand: () => void;
   onShowSettings: () => void;
   updateAvailable: boolean;
+  restartRequired: boolean;
   onShowVersionModal: () => void;
   t: TFunction;
 };
@@ -24,6 +25,7 @@ export default function SidebarCollapsed({
   onExpand,
   onShowSettings,
   updateAvailable,
+  restartRequired,
   onShowVersionModal,
   t,
 }: SidebarCollapsedProps) {
@@ -75,6 +77,18 @@ export default function SidebarCollapsed({
         <DiscordIcon className="h-4 w-4 text-muted-foreground transition-colors group-hover:text-foreground" />
       </a>
 
+      {/* Restart-required indicator */}
+      {restartRequired && (
+        <div
+          className="relative flex h-8 w-8 items-center justify-center rounded-lg"
+          aria-label={t('version.restartRequired')}
+          title={t('version.restartRequired')}
+        >
+          <AlertTriangle className="h-4 w-4 text-amber-500" />
+          <span className="absolute right-1.5 top-1.5 h-1.5 w-1.5 animate-pulse rounded-full bg-amber-500" />
+        </div>
+      )}
+
       {/* Update indicator */}
       {updateAvailable && (
         <button

src/components/sidebar/view/subcomponents/SidebarContent.tsx

@@ -141,6 +141,7 @@ type SidebarContentProps = {
   onCreateProject: () => void;
   onCollapseSidebar: () => void;
   updateAvailable: boolean;
+  restartRequired: boolean;
   releaseInfo: ReleaseInfo | null;
   latestVersion: string | null;
   currentVersion: string;
@@ -178,6 +179,7 @@ export default function SidebarContent({
   onCreateProject,
   onCollapseSidebar,
   updateAvailable,
+  restartRequired,
   releaseInfo,
   latestVersion,
   currentVersion,
@@ -553,6 +555,7 @@ export default function SidebarContent({
 
       <SidebarFooter
         updateAvailable={updateAvailable}
+        restartRequired={restartRequired}
         releaseInfo={releaseInfo}
         latestVersion={latestVersion}
         currentVersion={currentVersion}

src/components/sidebar/view/subcomponents/SidebarFooter.tsx

@@ -1,4 +1,4 @@
-import { Settings, ArrowUpCircle, Bug } from 'lucide-react';
+import { Settings, ArrowUpCircle, Bug, AlertTriangle } from 'lucide-react';
 import type { TFunction } from 'i18next';
 import { IS_PLATFORM } from '../../../../constants/config';
 import type { ReleaseInfo } from '../../../../types/sharedTypes';
@@ -18,6 +18,7 @@ function DiscordIcon({ className }: { className?: string }) {
 
 type SidebarFooterProps = {
   updateAvailable: boolean;
+  restartRequired: boolean;
   releaseInfo: ReleaseInfo | null;
   latestVersion: string | null;
   currentVersion: string;
@@ -28,6 +29,7 @@ type SidebarFooterProps = {
 
 export default function SidebarFooter({
   updateAvailable,
+  restartRequired,
   releaseInfo,
   latestVersion,
   currentVersion,
@@ -37,6 +39,22 @@ export default function SidebarFooter({
 }: SidebarFooterProps) {
   return (
     <div className="flex-shrink-0" style={{ paddingBottom: 'env(safe-area-inset-bottom, 0)' }}>
+      {/* Restart-required banner: the running server version differs from the
+          installed/frontend version (updated but not restarted). */}
+      {restartRequired && (
+        <>
+          <div className="nav-divider" />
+          <div className="px-2 py-1.5 md:px-2 md:py-1.5">
+            <div className="flex items-center gap-2.5 rounded-lg border border-amber-300/60 bg-amber-50/80 px-2.5 py-2 dark:border-amber-700/40 dark:bg-amber-900/15">
+              <AlertTriangle className="h-4 w-4 flex-shrink-0 text-amber-500 dark:text-amber-400" />
+              <span className="min-w-0 flex-1 text-xs font-medium text-amber-700 dark:text-amber-300">
+                {t('version.restartRequired')}
+              </span>
+            </div>
+          </div>
+        </>
+      )}
+
       {/* Update banner */}
       {updateAvailable && (
         <>