feat(i18n): localize hardcoded strings across components

src/App.tsx

@@ -1256,12 +1256,12 @@ function AppContent() {
         setConnectionDialogOpen(true);
         setPendingConnectionId(null);
       } else {
-        toast.error('Connection Not Found', {
-          description: 'The connection data could not be loaded.',
+        toast.error(t('app.connectionNotFound'), {
+          description: t('app.connectionNotFoundDesc1'),
         });
       }
     }
-  }, []);
+  }, [t]);
 
   const handleSaveConnection = useCallback(async (config: ConnectionConfig) => {
     if (!config.id) return;
@@ -1449,16 +1449,16 @@ function AppContent() {
     const existingTab = allTabs.find(tab => tab.id === connectionId || tab.originalConnectionId === connectionId);
     if (existingTab) {
       handleTabSelect(existingTab.id);
-      toast.info('Already Connected', {
-        description: `Switched to existing ${existingTab.name} connection`,
+      toast.info(t('app.alreadyConnected'), {
+        description: t('app.alreadyConnectedDesc', { name: existingTab.name }),
       });
       return;
     }
 
     const connectionData = ConnectionStorageManager.getConnection(connectionId);
     if (!connectionData) {
-      toast.error('Connection Not Found', {
-        description: 'The connection could not be found. It may have been deleted.',
+      toast.error(t('app.connectionNotFound'), {
+        description: t('app.connectionNotFoundDesc2'),
       });
       return;
     }
@@ -1732,7 +1732,7 @@ function AppContent() {
                       closeTabShortcut: keyboardShortcutSettings.closeTab,
                       onWorkingDirectoryChange: handleWorkingDirectoryChange,
                     }}>
-                      <ErrorBoundary label="Terminal">
+                      <ErrorBoundary label={t('app.terminal')}>
                         <GridRenderer node={state.gridLayout} path={[]} />
                       </ErrorBoundary>
                     </TerminalCallbacksProvider>
@@ -1751,7 +1751,7 @@ function AppContent() {
                         maxSize={50}
                         onResize={(size) => setBottomPanelSize(size)}
                       >
-                        <ErrorBoundary label="File Browser">
+                        <ErrorBoundary label={t('app.fileBrowser')}>
                           <IntegratedFileBrowser
                           connectionId={activeConnection.connectionId}
                           host={activeConnection.host}

src/__tests__/i18n.test.ts

@@ -1,6 +1,10 @@
+import { readdirSync, readFileSync } from 'node:fs';
+import path from 'node:path';
 import i18n from '../lib/i18n';
 import { changeLanguage, applyLanguageFromPreference, getLanguagePreference, AUTO } from '../lib/i18n';
 import { describe, it, expect, beforeEach } from 'vitest';
+import en from '../locales/en.json';
+import zhCN from '../locales/zh-CN.json';
 
 describe('i18n', () => {
   it('should initialize with English', () => {
@@ -30,6 +34,59 @@ describe('i18n', () => {
     expect(single).toContain('1 file');
     expect(plural).toContain('5 files');
   });
+
+  it('every t() key used in source code exists in both locales', () => {
+    // Guard against future hardcoded translation keys: collect every literal
+    // t('...') / i18n.t('...') key from the source tree and assert it resolves
+    // in en.json (accounting for plural/context suffixes like _one/_other).
+    // vitest runs from the project root, so process.cwd() reliably points at
+    // the repo root; scanning src/ from there keeps this ESM-safe (no
+    // require()/__dirname which are unavailable in "type": "module" files).
+    const srcDir = path.join(process.cwd(), 'src');
+
+    function flatten(d: Record<string, unknown>, prefix = ''): Record<string, unknown> {
+      const out: Record<string, unknown> = {};
+      for (const [k, v] of Object.entries(d)) {
+        const key = prefix ? `${prefix}.${k}` : k;
+        if (v && typeof v === 'object') Object.assign(out, flatten(v as Record<string, unknown>, key));
+        else out[key] = v;
+      }
+      return out;
+    }
+    const enFlat = flatten(en);
+    const zhFlat = flatten(zhCN);
+
+    const suffixes = ['one', 'other', 'zero', 'two', 'few', 'many', 'plural'];
+    const resolveKey = (k: string): boolean =>
+      k in enFlat ||
+      suffixes.some((s) => `${k}_${s}` in enFlat) ||
+      // context variants (e.g. directoryTransferDialog.toast.complete_upload)
+      Object.keys(enFlat).some((ek) => ek.startsWith(`${k}_`));
+
+    const used = new Set<string>();
+    function walk(dir: string): void {
+      for (const entry of readdirSync(dir, { withFileTypes: true })) {
+        if (entry.name === 'node_modules' || entry.name === 'locales' || entry.name === '__tests__' || entry.name === '__mocks__') continue;
+        const full = path.join(dir, entry.name);
+        if (entry.isDirectory()) walk(full);
+        else if (/\.(ts|tsx)$/.test(entry.name)) {
+          const content = readFileSync(full, 'utf8');
+          for (const m of content.matchAll(/(?:\bt|i18n\.t)\(\s*['"]([^'"]+)['"]/g)) {
+            const key = m[1];
+            if (key.includes('${') || key.includes(' + ')) continue; // dynamic keys
+            used.add(key);
+          }
+        }
+      }
+    }
+    walk(srcDir);
+
+    const missing = [...used].filter((k) => !resolveKey(k)).sort();
+    expect(missing).toEqual([]);
+
+    // Both locale files must define exactly the same set of keys.
+    expect(Object.keys(zhFlat).sort()).toEqual(Object.keys(enFlat).sort());
+  });
 });
 
 describe('i18n language preference', () => {

src/__tests__/integrated-file-browser-keyboard.test.tsx

@@ -198,8 +198,9 @@ describe('IntegratedFileBrowser terminal directory following', () => {
     // Wait for the Home navigation to fully commit (breadcrumb renders '/home')
     // before bumping the terminal sequence. Otherwise the follow effect can still
     // see committedPathRef === '/srv/app' and skip reloading, making this test
-    // order-dependent on async timing.
-    await screen.findByTitle('/home');
+    // order-dependent on async timing. Generous timeout: slow CI runners
+    // (Windows) occasionally exceed the default 1000 ms commit window.
+    await screen.findByTitle('/home', undefined, { timeout: 5000 });
 
     rerender(
       <IntegratedFileBrowser
@@ -232,7 +233,7 @@ describe('IntegratedFileBrowser terminal directory following', () => {
     );
 
     await waitFor(() => expect(mocks.warning).toHaveBeenCalledOnce());
-    expect(await screen.findByTitle('/home')).toBeTruthy();
+    expect(await screen.findByTitle('/home', undefined, { timeout: 5000 })).toBeTruthy();
 
     rerender(
       <IntegratedFileBrowser
@@ -249,7 +250,7 @@ describe('IntegratedFileBrowser terminal directory following', () => {
       ).toHaveLength(2);
     });
     expect(mocks.warning).toHaveBeenCalledOnce();
-    expect(await screen.findByTitle('/home')).toBeTruthy();
+    expect(await screen.findByTitle('/home', undefined, { timeout: 5000 })).toBeTruthy();
   });
 });
 

src/__tests__/update-checker.test.tsx

@@ -192,12 +192,12 @@ describe('UpdateChecker', () => {
       rerender(<UpdateChecker checkSignal={1} />);
       await act(async () => { await new Promise(r => setTimeout(r, 30)); });
 
-      expect(mockToast.loading).toHaveBeenCalledWith('Checking for updates…', { id: 'update-check' });
+      expect(mockToast.loading).toHaveBeenCalledWith('Checking for updates...', { id: 'update-check' });
 
       // Resolve
       await act(async () => { resolveCheck!(null); });
       expect(mockToast.dismiss).toHaveBeenCalledWith('update-check');
-      expect(mockToast.success).toHaveBeenCalledWith('You are up to date.');
+      expect(mockToast.success).toHaveBeenCalledWith("You're up to date!");
     });
 
     it('does NOT trigger check() when signal is same value', async () => {
@@ -257,7 +257,7 @@ describe('UpdateChecker', () => {
       await waitFor(() => expect(mockToast.error).toHaveBeenCalled());
 
       const [title, opts] = mockToast.error.mock.calls[0];
-      expect(title).toBe('Update check failed');
+      expect(title).toBe('Check Failed');
       expect(opts.description).toContain('Update server is not configured');
     });
 
@@ -369,7 +369,7 @@ describe('UpdateChecker', () => {
 
       await waitFor(() => expect(mockToast.error).toHaveBeenCalled());
       const [title, opts] = mockToast.error.mock.calls[0];
-      expect(title).toBe('Update failed');
+      expect(title).toBe('Download Failed');
       expect(opts.description).toBe('disk full');
     });
   });
@@ -422,7 +422,7 @@ describe('UpdateChecker', () => {
 
       await waitFor(() => {
         const calls = mockToast.error.mock.calls;
-        expect(calls.some(([t]: [string]) => t === 'Install failed')).toBe(true);
+        expect(calls.some(([t]: [string]) => t === 'Install Failed')).toBe(true);
       });
     });
   });

src/components/connection-tabs.tsx

@@ -1,4 +1,5 @@
 import React from 'react';
+import { useTranslation } from 'react-i18next';
 import { X, Plus, XCircle, ArrowRight, ArrowLeft, Copy, RefreshCw } from 'lucide-react';
 import { Button } from './ui/button';
 import {
@@ -44,6 +45,7 @@ export function ConnectionTabs({
   onCloseToRight,
   onCloseToLeft
 }: ConnectionTabsProps) {
+  const { t } = useTranslation();
   const duplicateTabShortcut = formatKeyboardShortcut(
     'Ctrl+D',
     navigator.platform.toUpperCase().includes('MAC'),
@@ -96,7 +98,7 @@ export function ConnectionTabs({
                 <>
                   <ContextMenuItem onClick={() => onReconnect(tab.id)}>
                     <RefreshCw className="mr-2 h-4 w-4" />
-                    Reconnect
+                    {t('connectionTabs.reconnect')}
                   </ContextMenuItem>
                   <ContextMenuSeparator />
                 </>
@@ -105,42 +107,42 @@ export function ConnectionTabs({
                 <>
                   <ContextMenuItem onClick={() => onDuplicateTab(tab.id)}>
                     <Copy className="mr-2 h-4 w-4" />
-                    Duplicate Tab
+                    {t('connectionTabs.duplicateTab')}
                     <ContextMenuShortcut>{duplicateTabShortcut}</ContextMenuShortcut>
                   </ContextMenuItem>
                   <ContextMenuSeparator />
                 </>
               )}
               <ContextMenuItem onClick={() => onTabClose(tab.id)}>
                 <X className="mr-2 h-4 w-4" />
-                Close Tab
+                {t('connectionTabs.closeTab')}
                 <ContextMenuShortcut>{closeTabShortcut}</ContextMenuShortcut>
               </ContextMenuItem>
               {onCloseOthers && tabs.length > 1 && (
                 <ContextMenuItem onClick={() => onCloseOthers(tab.id)}>
                   <XCircle className="mr-2 h-4 w-4" />
-                  Close Other Tabs
+                  {t('connectionTabs.closeOtherTabs')}
                 </ContextMenuItem>
               )}
               <ContextMenuSeparator />
               {onCloseToLeft && index > 0 && (
                 <ContextMenuItem onClick={() => onCloseToLeft(tab.id)}>
                   <ArrowLeft className="mr-2 h-4 w-4" />
-                  Close Tabs to the Left
+                  {t('connectionTabs.closeTabsToLeft')}
                 </ContextMenuItem>
               )}
               {onCloseToRight && index < tabs.length - 1 && (
                 <ContextMenuItem onClick={() => onCloseToRight(tab.id)}>
                   <ArrowRight className="mr-2 h-4 w-4" />
-                  Close Tabs to the Right
+                  {t('connectionTabs.closeTabsToRight')}
                 </ContextMenuItem>
               )}
               {onCloseAll && tabs.length > 0 && (
                 <>
                   <ContextMenuSeparator />
                   <ContextMenuItem onClick={onCloseAll}>
                     <XCircle className="mr-2 h-4 w-4" />
-                    Close All Tabs
+                    {t('connectionTabs.closeAllTabs')}
                   </ContextMenuItem>
                 </>
               )}

src/components/error-boundary.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { AlertTriangle, RefreshCw } from 'lucide-react';
 import { Button } from './ui/button';
+import i18n from '@/lib/i18n';
 
 interface ErrorBoundaryProps {
   children: React.ReactNode;
@@ -53,15 +54,17 @@ export class ErrorBoundary extends React.Component<ErrorBoundaryProps, ErrorBoun
           <AlertTriangle className="w-8 h-8 text-destructive" />
           <div className="space-y-1">
             <p className="text-sm font-medium">
-              {this.props.label ? `${this.props.label} encountered an error` : 'Something went wrong'}
+              {this.props.label
+                ? i18n.t('errorBoundary.labelError', { label: this.props.label })
+                : i18n.t('errorBoundary.somethingWentWrong')}
             </p>
             <p className="text-xs text-muted-foreground max-w-[300px] break-words">
-              {this.state.error?.message || 'An unexpected error occurred'}
+              {this.state.error?.message || i18n.t('errorBoundary.unexpectedError')}
             </p>
           </div>
           <Button variant="outline" size="sm" onClick={this.handleReset} className="gap-1.5">
             <RefreshCw className="w-3 h-3" />
-            Retry
+            {i18n.t('errorBoundary.retry')}
           </Button>
         </div>
       );

src/components/integrated-file-browser.tsx

@@ -1166,7 +1166,12 @@ export function IntegratedFileBrowser({ connectionId, host: _host, isConnected,
   };
 
   const handleFileInfo = (file: FileItem) => {
-    toast.info(`File: ${file.name}\nSize: ${formatFileSize(file.size)}\nModified: ${formatDate(file.modified)}\nPermissions: ${file.permissions}`);
+    toast.info(t('fileBrowser.toast.fileInfo', {
+      name: file.name,
+      size: formatFileSize(file.size),
+      modified: formatDate(file.modified),
+      permissions: file.permissions,
+    }));
   };
 
   const handleNewFile = async () => {
@@ -1607,8 +1612,8 @@ export function IntegratedFileBrowser({ connectionId, host: _host, isConnected,
                 <div className="absolute inset-0 bg-accent/20 border-2 border-dashed border-primary z-50 flex items-center justify-center pointer-events-none">
                   <div className="bg-background/90 rounded-lg p-6 shadow-lg">
                     <Upload className="h-12 w-12 mx-auto mb-3 text-primary" />
-                    <p className="font-medium">Drop files or folders to upload</p>
-                    <p className="text-sm text-muted-foreground mt-1">Upload to {currentPath}</p>
+                    <p className="font-medium">{t('fileBrowser.dropOverlay')}</p>
+                    <p className="text-sm text-muted-foreground mt-1">{t('fileBrowser.dropUploadTo', { path: currentPath })}</p>
                   </div>
                 </div>
               )}
@@ -1787,11 +1792,11 @@ export function IntegratedFileBrowser({ connectionId, host: _host, isConnected,
                     <>
                       <ContextMenuItem onClick={() => handleFileDoubleClick(file)}>
                         <Eye className="mr-2 h-4 w-4" />
-                        Open
+                        {t('fileBrowser.contextMenu.open')}
                       </ContextMenuItem>
                       <ContextMenuItem onClick={() => handleFileDoubleClick(file)}>
                         <Edit className="mr-2 h-4 w-4" />
-                        Edit
+                        {t('fileBrowser.contextMenu.edit')}
                       </ContextMenuItem>
                       {onOpenInLogMonitor && (
                         <ContextMenuItem onClick={() => {
@@ -1813,7 +1818,7 @@ export function IntegratedFileBrowser({ connectionId, host: _host, isConnected,
                     <>
                       <ContextMenuItem onClick={() => handleFileDoubleClick(file)}>
                         <Folder className="mr-2 h-4 w-4" />
-                        Open Folder
+                        {t('fileBrowser.contextMenu.openFolder')}
                       </ContextMenuItem>
                       <ContextMenuItem onClick={() => handleDownloadDirectory(file)}>
                         <FolderDown className="mr-2 h-4 w-4" />
@@ -1837,7 +1842,7 @@ export function IntegratedFileBrowser({ connectionId, host: _host, isConnected,
                       {clipboard && (
                         <ContextMenuItem onClick={handlePasteFiles}>
                           <ClipboardPaste className="mr-2 h-4 w-4" />
-                          {t('fileBrowser.contextMenu.paste')} {clipboard.files.length} item(s)
+                          {t('fileBrowser.contextMenu.pasteWithCount', { count: clipboard.files.length })}
                         </ContextMenuItem>
                       )}
                       <ContextMenuSeparator />

src/components/network-monitor.tsx

@@ -1,3 +1,4 @@
+import { useTranslation } from 'react-i18next';
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from './ui/card';
 
 // Interfaces kept for future use when re-enabling network monitoring
@@ -34,6 +35,7 @@ interface NetworkMonitorProps {
 }
 
 export function NetworkMonitor({ connectionId }: NetworkMonitorProps) {
+  const { t } = useTranslation();
   // Disabled for now - will be re-enabled in future updates
   // const [interfaces, setInterfaces] = useState<NetworkInterface[]>([]);
   // const [connections, setConnections] = useState<NetworkConnection[]>([]);
@@ -105,7 +107,7 @@ export function NetworkMonitor({ connectionId }: NetworkMonitorProps) {
   if (!connectionId) {
     return (
       <div className="flex items-center justify-center h-full text-muted-foreground">
-        <p>No active connection. Connect to view network statistics.</p>
+        <p>{t('networkMonitor.noConnection')}</p>
       </div>
     );
   }
@@ -114,15 +116,14 @@ export function NetworkMonitor({ connectionId }: NetworkMonitorProps) {
     <div className="flex flex-col h-full overflow-auto p-4 space-y-4">
       <Card>
         <CardHeader>
-          <CardTitle className="text-sm">Network Statistics</CardTitle>
+          <CardTitle className="text-sm">{t('networkMonitor.title')}</CardTitle>
           <CardDescription>
-            Advanced network monitoring features coming soon
+            {t('networkMonitor.comingSoon')}
           </CardDescription>
         </CardHeader>
         <CardContent>
           <p className="text-sm text-muted-foreground">
-            Network Interfaces and Active Connections monitoring is currently disabled.
-            Check the Network Usage and Network Latency charts in the Monitor tab for current network metrics.
+            {t('networkMonitor.disabledNotice')}
           </p>
         </CardContent>
       </Card>