feat: add i18n support with VITE_LOCALE env var (en/fr)

- Lightweight i18n system in src/lib/i18n.ts (no external deps)
- All UI strings extracted to translation keys
- English (default) and French locales included
- Set VITE_LOCALE=fr in .env for French UI
- Fallback to English for unknown locales

.env.example

@@ -1,3 +1,6 @@
 # Optional: pre-fill the Gateway URL field on the login screen
 # If not set, defaults to ws://<current-hostname>:18789
 VITE_GATEWAY_WS_URL=ws://localhost:18789
+
+# Optional: UI locale (default: en). Supported: en, fr
+VITE_LOCALE=en

src/components/Chat.tsx

@@ -4,6 +4,7 @@ import { ChatInput } from './ChatInput';
 import { TypingIndicator } from './TypingIndicator';
 import type { ChatMessage, ConnectionStatus } from '../types';
 import { Bot } from 'lucide-react';
+import { t } from '../lib/i18n';
 
 interface Props {
   messages: ChatMessage[];
@@ -54,7 +55,7 @@ export function Chat({ messages, isGenerating, status, onSend, onAbort }: Props)
 
   return (
     <div className="flex-1 flex flex-col min-h-0">
-      <div className="flex-1 overflow-y-auto" role="log" aria-label="Chat messages" aria-live="polite">
+      <div className="flex-1 overflow-y-auto" role="log" aria-label={t('chat.messages')} aria-live="polite">
         <div className="max-w-4xl mx-auto py-4">
           {messages.length === 0 && (
             <div className="flex flex-col items-center justify-center h-[60vh] text-zinc-500">
@@ -64,8 +65,8 @@ export function Chat({ messages, isGenerating, status, onSend, onAbort }: Props)
                   <Bot className="h-8 w-8 text-cyan-200" />
                 </div>
               </div>
-              <div className="text-lg text-zinc-200 font-semibold">PinchChat</div>
-              <div className="text-sm mt-1 text-zinc-500">Send a message to get started</div>
+              <div className="text-lg text-zinc-200 font-semibold">{t('chat.welcome')}</div>
+              <div className="text-sm mt-1 text-zinc-500">{t('chat.welcomeSub')}</div>
             </div>
           )}
           {messages.filter(hasVisibleContent).map(msg => (

src/components/ChatInput.tsx

@@ -1,5 +1,6 @@
 import { useState, useRef, useEffect, useCallback } from 'react';
 import { Send, Square, Paperclip, X, FileText } from 'lucide-react';
+import { t } from '../lib/i18n';
 
 interface FileAttachment {
   id: string;
@@ -180,7 +181,7 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled }: Props) {
     <div
       className="border-t border-white/8 bg-[#1a1a20]/60 backdrop-blur-xl p-4"
       role="form"
-      aria-label="Message input"
+      aria-label={t('chat.inputLabel')}
       onDragOver={handleDragOver}
       onDragLeave={handleDragLeave}
       onDrop={handleDrop}
@@ -218,8 +219,8 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled }: Props) {
               onClick={() => fileInputRef.current?.click()}
               disabled={disabled}
               className="shrink-0 h-11 w-11 rounded-2xl border border-white/8 bg-zinc-800/30 flex items-center justify-center text-zinc-400 hover:text-cyan-300 hover:bg-white/5 transition-colors disabled:opacity-30"
-              title="Attach file"
-              aria-label="Attach file"
+              title={t('chat.attachFile')}
+              aria-label={t('chat.attachFile')}
             >
               <Paperclip size={18} />
             </button>
@@ -238,8 +239,8 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled }: Props) {
               onChange={(e) => setText(e.target.value)}
               onKeyDown={handleKeyDown}
               onPaste={handlePaste}
-              placeholder="Type a message…"
-              aria-label="Message"
+              placeholder={t('chat.inputPlaceholder')}
+              aria-label={t('chat.inputLabel')}
               disabled={disabled}
               rows={1}
               className="flex-1 bg-transparent resize-none rounded-2xl border border-white/8 bg-zinc-900/35 px-4 py-3 text-sm text-zinc-300 placeholder:text-zinc-500 outline-none focus:ring-2 focus:ring-cyan-400/30 transition-all max-h-[200px]"
@@ -250,17 +251,17 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled }: Props) {
                 className="shrink-0 h-11 px-4 rounded-2xl border border-red-500/20 bg-red-500/10 text-red-400 hover:bg-red-500/20 transition-colors flex items-center gap-2"
               >
                 <Square size={16} />
-                <span className="text-sm hidden sm:inline">Stop</span>
+                <span className="text-sm hidden sm:inline">{t('chat.stop')}</span>
               </button>
             ) : (
               <button
                 onClick={handleSubmit}
                 disabled={(!text.trim() && files.length === 0) || disabled}
-                aria-label="Send message"
+                aria-label={t('chat.send')}
                 className="shrink-0 h-11 px-5 rounded-2xl bg-gradient-to-r from-cyan-500/80 via-indigo-500/70 to-violet-500/80 text-zinc-900 font-semibold text-sm hover:opacity-90 shadow-[0_8px_24px_rgba(34,211,238,0.1)] disabled:opacity-30 disabled:shadow-none transition-all flex items-center gap-2"
               >
                 <Send size={16} />
-                <span className="hidden sm:inline">Send</span>
+                <span className="hidden sm:inline">{t('chat.send')}</span>
               </button>
             )}
           </div>

src/components/Header.tsx

@@ -1,5 +1,6 @@
 import { Menu, Bot, Sparkles, LogOut } from 'lucide-react';
 import type { ConnectionStatus, Session } from '../types';
+import { t } from '../lib/i18n';
 
 interface Props {
   status: ConnectionStatus;
@@ -15,7 +16,7 @@ export function Header({ status, sessionKey, onToggleSidebar, activeSessionData,
   return (
     <>
     <header className="h-14 border-b border-white/8 bg-[#232329]/90 backdrop-blur-xl flex items-center px-4 gap-3 shrink-0" role="banner">
-      <button onClick={onToggleSidebar} aria-label="Toggle sidebar" className="lg:hidden p-2 rounded-2xl hover:bg-white/5 text-zinc-400 transition-colors">
+      <button onClick={onToggleSidebar} aria-label={t('header.toggleSidebar')} className="lg:hidden p-2 rounded-2xl hover:bg-white/5 text-zinc-400 transition-colors">
         <Menu size={20} />
       </button>
       <div className="flex items-center gap-3 flex-1 min-w-0">
@@ -24,7 +25,7 @@ export function Header({ status, sessionKey, onToggleSidebar, activeSessionData,
         </div>
         <div className="min-w-0">
           <div className="flex items-center gap-2">
-            <span className="font-semibold text-zinc-300 text-sm tracking-wide">PinchChat</span>
+            <span className="font-semibold text-zinc-300 text-sm tracking-wide">{t('header.title')}</span>
             <Sparkles className="h-3.5 w-3.5 text-cyan-300/60" />
           </div>
           <span className="text-xs text-zinc-500 truncate block">{sessionLabel}</span>
@@ -34,25 +35,25 @@ export function Header({ status, sessionKey, onToggleSidebar, activeSessionData,
         {status === 'connected' ? (
           <div className="flex items-center gap-2 rounded-2xl border border-white/8 bg-zinc-800/30 px-3 py-1.5">
             <span className="w-2 h-2 rounded-full bg-cyan-300/80 shadow-[0_0_12px_rgba(34,211,238,0.6)]" />
-            <span className="text-xs text-zinc-300 hidden sm:inline">Connected</span>
+            <span className="text-xs text-zinc-300 hidden sm:inline">{t('header.connected')}</span>
           </div>
         ) : status === 'connecting' ? (
           <div className="flex items-center gap-2 rounded-2xl border border-white/8 bg-zinc-800/30 px-3 py-1.5">
             <span className="w-2 h-2 rounded-full bg-yellow-400/80 pulse-dot" />
-            <span className="text-xs text-zinc-300 hidden sm:inline">Connecting…</span>
+            <span className="text-xs text-zinc-300 hidden sm:inline">{t('login.connecting')}</span>
           </div>
         ) : (
           <div className="flex items-center gap-2 rounded-2xl border border-white/8 bg-zinc-800/30 px-3 py-1.5">
             <span className="w-2 h-2 rounded-full bg-red-400/80" />
-            <span className="text-xs text-zinc-300 hidden sm:inline">Disconnected</span>
+            <span className="text-xs text-zinc-300 hidden sm:inline">{t('header.disconnected')}</span>
           </div>
         )}
         {onLogout && (
           <button
             onClick={onLogout}
-            aria-label="Disconnect and logout"
+            aria-label={t('header.logout')}
             className="p-2 rounded-2xl hover:bg-white/5 text-zinc-500 hover:text-zinc-300 transition-colors"
-            title="Logout"
+            title={t('header.logout')}
           >
             <LogOut size={16} />
           </button>

src/components/LoginScreen.tsx

@@ -1,5 +1,6 @@
 import { useState, useEffect } from 'react';
 import { Bot, Sparkles, Eye, EyeOff, Loader2 } from 'lucide-react';
+import { t } from '../lib/i18n';
 
 interface Props {
   onConnect: (url: string, token: string) => void;
@@ -56,17 +57,17 @@ export function LoginScreen({ onConnect, error, isConnecting }: Props) {
             <Bot className="h-7 w-7 text-cyan-200" />
           </div>
           <div className="flex items-center gap-2">
-            <h1 className="text-2xl font-bold text-zinc-200 tracking-wide">PinchChat</h1>
+            <h1 className="text-2xl font-bold text-zinc-200 tracking-wide">{t('login.title')}</h1>
             <Sparkles className="h-5 w-5 text-cyan-300/60" />
           </div>
-          <p className="text-sm text-zinc-500">Connect to your OpenClaw gateway</p>
+          <p className="text-sm text-zinc-500">{t('login.subtitle')}</p>
         </div>
 
         {/* Form */}
         <form onSubmit={handleSubmit} className="rounded-2xl border border-white/8 bg-[#232329]/80 backdrop-blur-xl p-6 space-y-5 shadow-2xl shadow-black/30">
           <div className="space-y-2">
             <label htmlFor="gateway-url" className="block text-xs font-medium text-zinc-400 uppercase tracking-wider">
-              Gateway URL
+              {t('login.gatewayUrl')}
             </label>
             <input
               id="gateway-url"
@@ -82,7 +83,7 @@ export function LoginScreen({ onConnect, error, isConnecting }: Props) {
 
           <div className="space-y-2">
             <label htmlFor="gateway-token" className="block text-xs font-medium text-zinc-400 uppercase tracking-wider">
-              Token
+              {t('login.token')}
             </label>
             <div className="relative">
               <input
@@ -90,7 +91,7 @@ export function LoginScreen({ onConnect, error, isConnecting }: Props) {
                 type={showToken ? 'text' : 'password'}
                 value={token}
                 onChange={e => setToken(e.target.value)}
-                placeholder="Enter your gateway token"
+                placeholder={t('login.tokenPlaceholder')}
                 className="w-full rounded-xl border border-white/8 bg-zinc-800/50 px-4 py-3 pr-12 text-sm text-zinc-200 placeholder:text-zinc-600 outline-none focus:border-cyan-400/40 focus:ring-1 focus:ring-cyan-400/20 transition-all"
                 autoComplete="current-password"
                 disabled={isConnecting}
@@ -100,7 +101,7 @@ export function LoginScreen({ onConnect, error, isConnecting }: Props) {
                 onClick={() => setShowToken(!showToken)}
                 className="absolute right-3 top-1/2 -translate-y-1/2 text-zinc-500 hover:text-zinc-300 transition-colors"
                 tabIndex={-1}
-                aria-label={showToken ? 'Hide token' : 'Show token'}
+                aria-label={showToken ? t('login.hideToken') : t('login.showToken')}
               >
                 {showToken ? <EyeOff size={16} /> : <Eye size={16} />}
               </button>
@@ -121,16 +122,16 @@ export function LoginScreen({ onConnect, error, isConnecting }: Props) {
             {isConnecting ? (
               <>
                 <Loader2 size={16} className="animate-spin" />
-                Connecting…
+                {t('login.connecting')}
               </>
             ) : (
-              'Connect'
+              t('login.connect')
             )}
           </button>
         </form>
 
         <p className="text-center text-xs text-zinc-600 mt-6">
-          Credentials are stored locally in your browser
+          {t('login.storedLocally')}
         </p>
       </div>
     </div>

src/components/Sidebar.tsx

@@ -1,5 +1,6 @@
 import { MessageSquare, X, Sparkles } from 'lucide-react';
 import type { Session } from '../types';
+import { t } from '../lib/i18n';
 
 interface Props {
   sessions: Session[];
@@ -22,7 +23,7 @@ export function Sidebar({ sessions, activeSession, onSwitch, open, onClose }: Pr
                 <Sparkles className="h-4 w-4 text-cyan-200" />
               </div>
             </div>
-            <span className="font-semibold text-sm text-zinc-200 tracking-wide">Sessions</span>
+            <span className="font-semibold text-sm text-zinc-200 tracking-wide">{t('sidebar.title')}</span>
           </div>
           <button onClick={onClose} className="lg:hidden p-1.5 rounded-xl hover:bg-white/5 text-zinc-400 transition-colors">
             <X size={16} />
@@ -30,7 +31,7 @@ export function Sidebar({ sessions, activeSession, onSwitch, open, onClose }: Pr
         </div>
         <div className="flex-1 overflow-y-auto py-2 px-2">
           {sessions.length === 0 && (
-            <div className="px-3 py-8 text-center text-zinc-500 text-sm">No sessions</div>
+            <div className="px-3 py-8 text-center text-zinc-500 text-sm">{t('sidebar.empty')}</div>
           )}
           {sessions.map(s => {
             const isActive = s.key === activeSession;

src/components/ThinkingBlock.tsx

@@ -1,5 +1,6 @@
 import { useState } from 'react';
 import { ChevronRight, ChevronDown, Brain } from 'lucide-react';
+import { t } from '../lib/i18n';
 
 export function ThinkingBlock({ text }: { text: string }) {
   const [open, setOpen] = useState(false);
@@ -11,7 +12,7 @@ export function ThinkingBlock({ text }: { text: string }) {
         className="inline-flex items-center gap-1.5 rounded-2xl border border-white/8 bg-zinc-800/35 px-3 py-1.5 text-xs text-violet-300 hover:bg-white/5 transition-colors"
       >
         <Brain size={13} />
-        <span className="font-medium">Thinking</span>
+        <span className="font-medium">{t('thinking.label')}</span>
         {open ? <ChevronDown size={12} className="ml-1 text-zinc-500" /> : <ChevronRight size={12} className="ml-1 text-zinc-500" />}
       </button>
       {open && (

src/components/ToolCall.tsx

@@ -1,6 +1,7 @@
 import { useState, useMemo } from 'react';
 import { ChevronRight, ChevronDown, Terminal, Globe, Search, FileText, Wrench, Code, Database, Image, MessageSquare, Brain, Cpu } from 'lucide-react';
 import hljs from 'highlight.js/lib/common';
+import { t } from '../lib/i18n';
 
 type ToolColor = { border: string; bg: string; text: string; icon: string; glow: string; expandBorder: string; expandBg: string };
 
@@ -188,7 +189,7 @@ export function ToolCall({ name, input, result }: { name: string; input?: any; r
           )}
           {result && (
             <div>
-              <div className={`text-[11px] ${c.text} opacity-70 mb-1 font-medium`}>Result</div>
+              <div className={`text-[11px] ${c.text} opacity-70 mb-1 font-medium`}>{t('tool.result')}</div>
               <HighlightedPre
                 text={result}
                 className="text-xs bg-[#1a1a20]/60 border border-white/5 p-2.5 rounded-xl overflow-x-auto text-zinc-300 max-h-64 overflow-y-auto font-mono"

src/lib/i18n.ts

@@ -0,0 +1,93 @@
+/**
+ * Lightweight i18n — no external deps.
+ * Locale is set via VITE_LOCALE env var (default: "en").
+ * Add new languages by adding a record to `messages`.
+ */
+
+const en = {
+  // Login screen
+  'login.title': 'PinchChat',
+  'login.subtitle': 'Connect to your OpenClaw gateway',
+  'login.gatewayUrl': 'Gateway URL',
+  'login.token': 'Token',
+  'login.tokenPlaceholder': 'Enter your gateway token',
+  'login.connect': 'Connect',
+  'login.connecting': 'Connecting…',
+  'login.showToken': 'Show token',
+  'login.hideToken': 'Hide token',
+  'login.storedLocally': 'Credentials are stored locally in your browser',
+
+  // Header
+  'header.title': 'PinchChat',
+  'header.connected': 'Connected',
+  'header.disconnected': 'Disconnected',
+  'header.logout': 'Logout',
+  'header.toggleSidebar': 'Toggle sidebar',
+
+  // Chat
+  'chat.welcome': 'PinchChat',
+  'chat.welcomeSub': 'Send a message to get started',
+  'chat.inputPlaceholder': 'Type a message…',
+  'chat.inputLabel': 'Message',
+  'chat.attachFile': 'Attach file',
+  'chat.send': 'Send',
+  'chat.stop': 'Stop',
+  'chat.messages': 'Chat messages',
+
+  // Sidebar
+  'sidebar.title': 'Sessions',
+  'sidebar.empty': 'No sessions',
+
+  // Thinking
+  'thinking.label': 'Thinking',
+
+  // Tool call
+  'tool.result': 'Result',
+} as const;
+
+const fr: Record<keyof typeof en, string> = {
+  'login.title': 'PinchChat',
+  'login.subtitle': 'Connectez-vous à votre gateway OpenClaw',
+  'login.gatewayUrl': 'URL de la gateway',
+  'login.token': 'Token',
+  'login.tokenPlaceholder': 'Entrez votre token gateway',
+  'login.connect': 'Connexion',
+  'login.connecting': 'Connexion…',
+  'login.showToken': 'Afficher le token',
+  'login.hideToken': 'Masquer le token',
+  'login.storedLocally': 'Les identifiants sont stockés localement dans votre navigateur',
+
+  'header.title': 'PinchChat',
+  'header.connected': 'Connecté',
+  'header.disconnected': 'Déconnecté',
+  'header.logout': 'Déconnexion',
+  'header.toggleSidebar': 'Afficher/masquer la barre latérale',
+
+  'chat.welcome': 'PinchChat',
+  'chat.welcomeSub': 'Envoyez un message pour commencer',
+  'chat.inputPlaceholder': 'Tapez un message…',
+  'chat.inputLabel': 'Message',
+  'chat.attachFile': 'Joindre un fichier',
+  'chat.send': 'Envoyer',
+  'chat.stop': 'Arrêter',
+  'chat.messages': 'Messages du chat',
+
+  'sidebar.title': 'Sessions',
+  'sidebar.empty': 'Aucune session',
+
+  'thinking.label': 'Réflexion',
+
+  'tool.result': 'Résultat',
+};
+
+const messages: Record<string, Record<string, string>> = { en, fr };
+
+const locale = (import.meta.env.VITE_LOCALE as string) || 'en';
+const dict = messages[locale] || messages.en;
+
+/** Return the translated string for the given key, falling back to English. */
+export function t(key: keyof typeof en): string {
+  return dict[key] ?? (messages.en as Record<string, string>)[key] ?? key;
+}
+
+export { locale };