diff --git a/docs/PLAN.md b/docs/PLAN.md
index 49c39da..d24da5a 100644
--- a/docs/PLAN.md
+++ b/docs/PLAN.md
@@ -31,3 +31,4 @@ Updated: 2026-04-02
 15. Added editable System settings with shared validation, a system update API, service/port conflict protection, and UI coverage for local save flows.
 16. Simplified the System tab layout by removing the redundant Runtime card and collapsing those fields into a compact settings section.
 17. Moved panel auth to server-issued expiring tokens with `sessionStorage` persistence and Compose-configurable credentials/TTL.
+18. Reworked Settings to store panel language/theme in `localStorage`, added RU/EN UI switching, and made service deletion warn before cascading linked-user removal.
diff --git a/docs/PROJECT_INDEX.md b/docs/PROJECT_INDEX.md
index 35180df..088c5fa 100644
--- a/docs/PROJECT_INDEX.md
+++ b/docs/PROJECT_INDEX.md
@@ -29,6 +29,8 @@ Updated: 2026-04-02
 - `src/app.css`: full panel styling
 - `src/data/mockDashboard.ts`: default panel state and frontend fallback snapshot
 - `src/lib/3proxy.ts`: formatting and status helpers
+- `src/lib/panelPreferences.ts`: client-side `localStorage` preferences and theme application helpers
+- `src/lib/panelText.ts`: EN/RU panel copy and labels for translated UI chrome
 - `src/lib/3proxy.test.ts`: paranoia-oriented tests for core domain rules
 - `src/shared/contracts.ts`: shared panel, service, user, and API data contracts
 - `src/shared/validation.ts`: shared validation for user creation, system edits, protocol mapping, and quota conversion
diff --git a/server/app.test.ts b/server/app.test.ts
index 5c4005a..359ff38 100644
--- a/server/app.test.ts
+++ b/server/app.test.ts
@@ -153,6 +153,24 @@ describe('panel api', () => {
     expect(response.body.system.previewConfig).toContain('socks -p1180 -u2');
     expect(response.body.service.lastEvent).toBe('System configuration updated from panel');
   });
+
+  it('removes linked users when a service is deleted from settings', async () => {
+    const app = await createTestApp();
+    const token = await authorize(app);
+    const initial = await request(app).get('/api/state').set('Authorization', `Bearer ${token}`);
+    const system = createSystemPayload(initial.body);
+
+    system.services = system.services.filter((service) => service.id !== 'socks-main');
+
+    const response = await request(app).put('/api/system').set('Authorization', `Bearer ${token}`).send(system);
+
+    expect(response.status).toBe(200);
+    expect(response.body.userRecords.some((user: { username: string }) => user.username === 'night-shift')).toBe(
+      false,
+    );
+    expect(response.body.userRecords.some((user: { username: string }) => user.username === 'ops-east')).toBe(false);
+    expect(response.body.service.lastEvent).toMatch(/removed 2 linked users/i);
+  });
 });
 
 async function createTestApp() {
diff --git a/server/app.ts b/server/app.ts
index 58c125b..9b89ae7 100644
--- a/server/app.ts
+++ b/server/app.ts
@@ -129,8 +129,23 @@ export function createApp({ store, runtime, runtimeRootDir, auth }: AppServices)
   app.put('/api/system', async (request, response, next) => {
     try {
       const state = await store.read();
-      state.system = validateSystemInput(request.body as Partial<UpdateSystemInput>, state.userRecords);
-      state.service.lastEvent = 'System configuration updated from panel';
+      const requestedSystem = request.body as Partial<UpdateSystemInput>;
+      const nextServiceIds = new Set(
+        (Array.isArray(requestedSystem.services) ? requestedSystem.services : []).map((service) => service.id),
+      );
+      const removedServiceIds = new Set(
+        state.system.services
+          .map((service) => service.id)
+          .filter((serviceId) => !nextServiceIds.has(serviceId)),
+      );
+
+      const removedUsers = state.userRecords.filter((user) => removedServiceIds.has(user.serviceId));
+      state.userRecords = state.userRecords.filter((user) => !removedServiceIds.has(user.serviceId));
+      state.system = validateSystemInput(requestedSystem, state.userRecords);
+      state.service.lastEvent =
+        removedUsers.length > 0
+          ? `System configuration updated from panel and removed ${removedUsers.length} linked users`
+          : 'System configuration updated from panel';
       await persistRuntimeMutation(store, runtime, state, runtimePaths);
       response.json(await getSnapshot(store, runtime, runtimePaths));
     } catch (error) {
diff --git a/src/App.test.tsx b/src/App.test.tsx
index bd396eb..dc29511 100644
--- a/src/App.test.tsx
+++ b/src/App.test.tsx
@@ -11,6 +11,7 @@ async function loginIntoPanel(user: ReturnType<typeof userEvent.setup>) {
 
 beforeEach(() => {
   window.sessionStorage.clear();
+  window.localStorage.clear();
 });
 
 describe('App login gate', () => {
@@ -50,6 +51,23 @@ describe('App login gate', () => {
     expect(screen.queryByRole('button', { name: /open panel/i })).not.toBeInTheDocument();
   });
 
+  it('stores panel language in localStorage and restores it after a remount', async () => {
+    const user = userEvent.setup();
+    const firstRender = render(<App />);
+
+    await loginIntoPanel(user);
+    await user.click(screen.getByRole('button', { name: /settings/i }));
+    await user.selectOptions(screen.getByLabelText(/panel language/i), 'ru');
+
+    expect(screen.getByRole('button', { name: /панель/i })).toBeInTheDocument();
+
+    firstRender.unmount();
+    render(<App />);
+
+    expect(screen.getByRole('button', { name: /панель/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /настройки/i })).toBeInTheDocument();
+  });
+
   it('opens add-user flow in a modal and closes it on escape', async () => {
     const user = userEvent.setup();
     render(<App />);
@@ -107,26 +125,43 @@ describe('App login gate', () => {
     expect(screen.queryByRole('dialog', { name: /delete user/i })).not.toBeInTheDocument();
   });
 
-  it('saves system settings from the system tab and applies them to the local fallback state', async () => {
+  it('saves service settings from the settings tab and applies them to the local fallback state', async () => {
     const user = userEvent.setup();
     render(<App />);
 
     await loginIntoPanel(user);
-    await user.click(screen.getByRole('button', { name: /system/i }));
-
-    await user.clear(screen.getByLabelText(/public host/i));
-    await user.type(screen.getByLabelText(/public host/i), 'ops-gateway.example.net');
+    await user.click(screen.getByRole('button', { name: /settings/i }));
 
     const firstPortInput = screen.getAllByLabelText(/port/i)[0];
     await user.clear(firstPortInput);
     await user.type(firstPortInput, '1180');
 
-    await user.click(screen.getByRole('button', { name: /save system/i }));
-
-    expect(screen.getByText(/ops-gateway\.example\.net/i)).toBeInTheDocument();
+    await user.click(screen.getByRole('button', { name: /save settings/i }));
 
     await user.click(screen.getByRole('button', { name: /users/i }));
 
-    expect(screen.getAllByText(/ops-gateway\.example\.net:1180/i).length).toBeGreaterThan(0);
+    expect(screen.getAllByText(/edge\.example\.net:1180/i).length).toBeGreaterThan(0);
+  });
+
+  it('warns before deleting a service and removes linked users after confirmation', async () => {
+    const user = userEvent.setup();
+    render(<App />);
+
+    await loginIntoPanel(user);
+    await user.click(screen.getByRole('button', { name: /settings/i }));
+
+    await user.click(screen.getAllByRole('button', { name: /^remove$/i })[0]);
+
+    const dialog = screen.getByRole('dialog', { name: /delete service/i });
+    expect(dialog).toBeInTheDocument();
+    expect(within(dialog).getByText(/linked users to be removed/i)).toBeInTheDocument();
+    expect(within(dialog).getByText(/night-shift, ops-east/i)).toBeInTheDocument();
+
+    await user.click(within(dialog).getByRole('button', { name: /^remove$/i }));
+    await user.click(screen.getByRole('button', { name: /save settings/i }));
+    await user.click(screen.getByRole('button', { name: /users/i }));
+
+    expect(screen.queryByText(/night-shift/i)).not.toBeInTheDocument();
+    expect(screen.queryByText(/ops-east/i)).not.toBeInTheDocument();
   });
 });
diff --git a/src/App.tsx b/src/App.tsx
index 64deec2..ff6facb 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -4,11 +4,12 @@ import { fallbackDashboardSnapshot, panelAuth } from './data/mockDashboard';
 import {
   buildProxyLink,
   formatBytes,
-  formatQuotaState,
   formatTrafficShare,
   getServiceTone,
   isQuotaExceeded,
 } from './lib/3proxy';
+import { applyPanelTheme, loadPanelPreferences, observeSystemTheme, savePanelPreferences, type PanelPreferences } from './lib/panelPreferences';
+import { getPanelText } from './lib/panelText';
 import type {
   CreateUserInput,
   DashboardSnapshot,
@@ -22,10 +23,10 @@ import { quotaMbToBytes, validateCreateUserInput } from './shared/validation';
 
 type TabId = 'dashboard' | 'users' | 'system';
 
-const tabs: Array<{ id: TabId; label: string }> = [
-  { id: 'dashboard', label: 'Dashboard' },
-  { id: 'users', label: 'Users' },
-  { id: 'system', label: 'System' },
+const tabs: Array<{ id: TabId; textKey: 'dashboard' | 'users' | 'settings' }> = [
+  { id: 'dashboard', textKey: 'dashboard' },
+  { id: 'users', textKey: 'users' },
+  { id: 'system', textKey: 'settings' },
 ];
 
 const SESSION_KEY = '3proxy-ui-panel-session';
@@ -36,7 +37,14 @@ interface StoredSession {
   expiresAt: string;
 }
 
-function LoginGate({ onUnlock }: { onUnlock: (login: string, password: string) => Promise<void> }) {
+function LoginGate({
+  onUnlock,
+  preferences,
+}: {
+  onUnlock: (login: string, password: string) => Promise<void>;
+  preferences: PanelPreferences;
+}) {
+  const text = getPanelText(preferences.language);
   const [login, setLogin] = useState('');
   const [password, setPassword] = useState('');
   const [error, setError] = useState('');
@@ -60,12 +68,12 @@ function LoginGate({ onUnlock }: { onUnlock: (login: string, password: string) =
     <main className="login-shell">
       <section className="login-card">
         <div className="login-copy">
-          <h1>3proxy UI</h1>
-          <p>Sign in to the control panel.</p>
+          <h1>{text.auth.title}</h1>
+          <p>{text.auth.subtitle}</p>
         </div>
         <form className="login-form" onSubmit={handleSubmit}>
           <label>
-            Login
+            {text.auth.login}
             <input
               autoComplete="username"
               name="login"
@@ -75,7 +83,7 @@ function LoginGate({ onUnlock }: { onUnlock: (login: string, password: string) =
             />
           </label>
           <label>
-            Password
+            {text.auth.password}
             <input
               autoComplete="current-password"
               name="password"
@@ -86,7 +94,7 @@ function LoginGate({ onUnlock }: { onUnlock: (login: string, password: string) =
             />
           </label>
           <button type="submit" disabled={isSubmitting}>
-            {isSubmitting ? 'Opening...' : 'Open panel'}
+            {isSubmitting ? text.auth.opening : text.auth.open}
           </button>
           {error ? <p className="form-error">{error}</p> : null}
         </form>
@@ -100,12 +108,15 @@ function AddUserModal({
   services,
   onClose,
   onCreate,
+  preferences,
 }: {
   host: string;
   services: ProxyServiceRecord[];
   onClose: () => void;
   onCreate: (input: CreateUserInput) => Promise<void>;
+  preferences: PanelPreferences;
 }) {
+  const text = getPanelText(preferences.language);
   const [username, setUsername] = useState('');
   const [password, setPassword] = useState('');
   const [serviceId, setServiceId] = useState(services[0]?.id ?? '');
@@ -156,22 +167,22 @@ function AddUserModal({
         onClick={stopPropagation}
       >
         <div className="modal-header">
-          <h2 id="add-user-title">Add user</h2>
+          <h2 id="add-user-title">{text.users.addUser}</h2>
           <button type="button" className="button-secondary" onClick={onClose}>
-            Close
+            {text.common.close}
           </button>
         </div>
         <form className="modal-form" onSubmit={handleSubmit}>
           <label>
-            Username
+            {text.users.username}
             <input autoFocus placeholder="night-shift-01" value={username} onChange={(event) => setUsername(event.target.value)} />
           </label>
           <label>
-            Password
+            {text.users.password}
             <input placeholder="generated-secret" value={password} onChange={(event) => setPassword(event.target.value)} />
           </label>
           <label>
-            Service
+            {text.users.service}
             <select value={serviceId} onChange={(event) => setServiceId(event.target.value)}>
               {services.map((service) => (
                 <option key={service.id} value={service.id}>
@@ -181,23 +192,23 @@ function AddUserModal({
             </select>
           </label>
           <label>
-            Quota (MB)
-            <input placeholder="Optional" value={quotaMb} onChange={(event) => setQuotaMb(event.target.value)} />
+            {text.users.quotaMb}
+            <input placeholder={text.common.optional} value={quotaMb} onChange={(event) => setQuotaMb(event.target.value)} />
           </label>
           <div className="modal-preview">
-            <span>Endpoint</span>
-            <strong>{selectedService ? `${host}:${selectedService.port}` : 'Unavailable'}</strong>
+            <span>{text.common.endpoint}</span>
+            <strong>{selectedService ? `${host}:${selectedService.port}` : text.common.unavailable}</strong>
           </div>
           <div className="modal-preview">
-            <span>Protocol</span>
-            <strong>{selectedService ? selectedService.protocol : 'Unavailable'}</strong>
+            <span>{text.common.protocol}</span>
+            <strong>{selectedService ? selectedService.protocol : text.common.unavailable}</strong>
           </div>
           {error ? <p className="form-error modal-error">{error}</p> : null}
           <div className="modal-actions">
             <button type="button" className="button-secondary" onClick={onClose}>
-              Cancel
+              {text.common.cancel}
             </button>
-            <button type="submit">Create user</button>
+            <button type="submit">{text.common.createUser}</button>
           </div>
         </form>
       </section>
@@ -209,11 +220,14 @@ function ConfirmDeleteModal({
   username,
   onClose,
   onConfirm,
+  preferences,
 }: {
   username: string;
   onClose: () => void;
   onConfirm: () => Promise<void>;
+  preferences: PanelPreferences;
 }) {
+  const text = getPanelText(preferences.language);
   useEffect(() => {
     const handleKeyDown = (event: globalThis.KeyboardEvent) => {
       if (event.key === 'Escape') {
@@ -240,18 +254,18 @@ function ConfirmDeleteModal({
         onClick={stopPropagation}
       >
         <div className="modal-header">
-          <h2 id="delete-user-title">Delete user</h2>
+          <h2 id="delete-user-title">{text.users.deleteTitle}</h2>
         </div>
         <p className="confirm-copy">
-          Remove profile <strong>{username}</strong>? This action will delete the user entry from the
-          current panel state.
+          {text.users.deletePrompt} <strong>{username}</strong>
+          {text.users.deletePromptSuffix}
         </p>
         <div className="modal-actions">
           <button type="button" className="button-secondary" onClick={onClose}>
-            Cancel
+            {text.common.cancel}
           </button>
           <button type="button" className="button-danger" onClick={onConfirm}>
-            Delete user
+            {text.users.deleteAction}
           </button>
         </div>
       </section>
@@ -262,62 +276,65 @@ function ConfirmDeleteModal({
 function DashboardTab({
   snapshot,
   onRuntimeAction,
+  preferences,
 }: {
   snapshot: DashboardSnapshot;
   onRuntimeAction: (action: 'start' | 'restart') => Promise<void>;
+  preferences: PanelPreferences;
 }) {
+  const text = getPanelText(preferences.language);
   const serviceTone = getServiceTone(snapshot.service.status);
 
   return (
     <section className="page-grid">
       <article className="panel-card">
         <div className="card-header">
-          <h2>Service</h2>
-          <span className={`status-pill ${serviceTone}`}>{snapshot.service.status}</span>
+          <h2>{text.dashboard.service}</h2>
+          <span className={`status-pill ${serviceTone}`}>{text.status[snapshot.service.status]}</span>
         </div>
         <dl className="kv-list">
           <div>
-            <dt>Process</dt>
+            <dt>{text.common.process}</dt>
             <dd>{snapshot.service.pidLabel}</dd>
           </div>
           <div>
-            <dt>Version</dt>
+            <dt>{text.common.version}</dt>
             <dd>{snapshot.service.versionLabel}</dd>
           </div>
           <div>
-            <dt>Uptime</dt>
+            <dt>{text.common.uptime}</dt>
             <dd>{snapshot.service.uptimeLabel}</dd>
           </div>
           <div>
-            <dt>Last event</dt>
+            <dt>{text.common.lastEvent}</dt>
             <dd>{snapshot.service.lastEvent}</dd>
           </div>
         </dl>
         <div className="actions-row">
           <button type="button" onClick={() => onRuntimeAction('start')}>
-            Start
+            {text.dashboard.start}
           </button>
           <button type="button" className="button-secondary" onClick={() => onRuntimeAction('restart')}>
-            Restart
+            {text.dashboard.restart}
           </button>
         </div>
       </article>
 
       <article className="panel-card">
         <div className="card-header">
-          <h2>Traffic</h2>
+          <h2>{text.dashboard.traffic}</h2>
         </div>
         <div className="stats-strip">
           <div>
-            <span>Total</span>
+            <span>{text.common.total}</span>
             <strong>{formatBytes(snapshot.traffic.totalBytes)}</strong>
           </div>
           <div>
-            <span>Connections</span>
+            <span>{text.common.connections}</span>
             <strong>{snapshot.traffic.liveConnections}</strong>
           </div>
           <div>
-            <span>Active users</span>
+            <span>{text.common.activeUsers}</span>
             <strong>{snapshot.traffic.activeUsers}</strong>
           </div>
         </div>
@@ -325,7 +342,7 @@ function DashboardTab({
 
       <article className="panel-card">
         <div className="card-header">
-          <h2>Daily usage</h2>
+          <h2>{text.dashboard.dailyUsage}</h2>
         </div>
         <div className="usage-list">
           {snapshot.traffic.daily.map((bucket) => (
@@ -342,7 +359,7 @@ function DashboardTab({
 
       <article className="panel-card">
         <div className="card-header">
-          <h2>Attention</h2>
+          <h2>{text.dashboard.attention}</h2>
         </div>
         <div className="event-list">
           {snapshot.attention.map((item) => (
@@ -365,12 +382,15 @@ function UsersTab({
   onCreateUser,
   onTogglePause,
   onDeleteUser,
+  preferences,
 }: {
   snapshot: DashboardSnapshot;
   onCreateUser: (input: CreateUserInput) => Promise<void>;
   onTogglePause: (userId: string) => Promise<void>;
   onDeleteUser: (userId: string) => Promise<void>;
+  preferences: PanelPreferences;
 }) {
+  const text = getPanelText(preferences.language);
   const [copiedId, setCopiedId] = useState<string | null>(null);
   const [isModalOpen, setIsModalOpen] = useState(false);
   const [deleteTargetId, setDeleteTargetId] = useState<string | null>(null);
@@ -395,35 +415,37 @@ function UsersTab({
         <article className="panel-card">
           <div className="table-toolbar">
             <div className="toolbar-title">
-              <h2>Users</h2>
-              <p>{snapshot.userRecords.length} accounts in current profile</p>
+              <h2>{text.users.title}</h2>
+              <p>
+                {snapshot.userRecords.length} {text.users.accountsInProfile}
+              </p>
             </div>
             <div className="toolbar-actions">
               <div className="summary-pills">
-                <span>{snapshot.users.live} live</span>
-                <span>{snapshot.users.nearQuota} near quota</span>
-                <span>{snapshot.users.exceeded} exceeded</span>
+                <span>{snapshot.users.live} {text.users.live}</span>
+                <span>{snapshot.users.nearQuota} {text.users.nearQuota}</span>
+                <span>{snapshot.users.exceeded} {text.users.exceeded}</span>
               </div>
               <button type="button" onClick={() => setIsModalOpen(true)} disabled={assignableServices.length === 0}>
-                New user
+                {text.users.newUser}
               </button>
             </div>
           </div>
           {assignableServices.length === 0 ? (
-            <p className="table-note">Enable an assignable service in System before creating new users.</p>
+            <p className="table-note">{text.users.enableServiceHint}</p>
           ) : null}
           <div className="table-wrap">
             <table>
               <thead>
                 <tr>
-                  <th>User</th>
-                  <th>Endpoint</th>
-                  <th>Status</th>
-                  <th>Used</th>
-                  <th>Remaining</th>
-                  <th>Share</th>
-                  <th>Proxy</th>
-                  <th>Actions</th>
+                  <th>{text.users.user}</th>
+                  <th>{text.users.endpoint}</th>
+                  <th>{text.common.status}</th>
+                  <th>{text.users.used}</th>
+                  <th>{text.users.remaining}</th>
+                  <th>{text.users.share}</th>
+                  <th>{text.users.proxy}</th>
+                  <th>{text.users.actions}</th>
                 </tr>
               </thead>
               <tbody>
@@ -431,7 +453,7 @@ function UsersTab({
                   const service = servicesById.get(user.serviceId);
                   const endpoint = service
                     ? `${snapshot.system.publicHost}:${service.port}`
-                    : 'service missing';
+                    : text.common.serviceMissing;
                   const proxyLink = service
                     ? buildProxyLink(
                         user.username,
@@ -453,17 +475,17 @@ function UsersTab({
                       </td>
                       <td>
                         <div className="endpoint-cell">
-                          <strong>{service?.name ?? 'Unknown service'}</strong>
+                          <strong>{service?.name ?? text.common.unknownService}</strong>
                           <span>{endpoint}</span>
                         </div>
                       </td>
                       <td>
                         <span className={`status-pill ${getServiceTone(displayStatus)}`}>
-                          {displayStatus}
+                          {text.status[displayStatus]}
                         </span>
                       </td>
                       <td>{formatBytes(user.usedBytes)}</td>
-                      <td>{formatQuotaState(user.usedBytes, user.quotaBytes)}</td>
+                      <td>{formatQuotaStateLabel(user.usedBytes, user.quotaBytes, preferences.language)}</td>
                       <td>{formatTrafficShare(user.usedBytes, snapshot.traffic.totalBytes)}</td>
                       <td>
                         <button
@@ -472,7 +494,7 @@ function UsersTab({
                           onClick={() => handleCopy(user.id, proxyLink)}
                           disabled={!service}
                         >
-                          {copiedId === user.id ? 'Copied' : 'Copy'}
+                          {copiedId === user.id ? text.common.copied : text.common.copy}
                         </button>
                       </td>
                       <td>
@@ -482,14 +504,14 @@ function UsersTab({
                             className="button-secondary button-small"
                             onClick={() => onTogglePause(user.id)}
                           >
-                            {user.paused ? 'Resume' : 'Pause'}
+                            {user.paused ? text.users.resume : text.users.pause}
                           </button>
                           <button
                             type="button"
                             className="button-danger button-small"
                             onClick={() => setDeleteTargetId(user.id)}
                           >
-                            Delete
+                            {text.common.delete}
                           </button>
                         </div>
                       </td>
@@ -508,6 +530,7 @@ function UsersTab({
           services={assignableServices}
           onClose={() => setIsModalOpen(false)}
           onCreate={onCreateUser}
+          preferences={preferences}
         />
       ) : null}
 
@@ -519,6 +542,7 @@ function UsersTab({
             await onDeleteUser(deleteTarget.id);
             setDeleteTargetId(null);
           }}
+          preferences={preferences}
         />
       ) : null}
     </>
@@ -526,9 +550,24 @@ function UsersTab({
 }
 
 export default function App() {
+  const [preferences, setPreferences] = useState<PanelPreferences>(() => loadPanelPreferences());
   const [session, setSession] = useState<StoredSession | null>(() => loadStoredSession());
   const [activeTab, setActiveTab] = useState<TabId>('dashboard');
   const [snapshot, setSnapshot] = useState<DashboardSnapshot>(fallbackDashboardSnapshot);
+  const text = getPanelText(preferences.language);
+
+  useEffect(() => {
+    applyPanelTheme(preferences.theme);
+    savePanelPreferences(preferences);
+  }, [preferences]);
+
+  useEffect(() => {
+    if (preferences.theme !== 'system') {
+      return;
+    }
+
+    return observeSystemTheme(() => applyPanelTheme('system'));
+  }, [preferences.theme]);
 
   const resetSession = () => {
     clearStoredSession();
@@ -605,7 +644,7 @@ export default function App() {
   }, [session]);
 
   if (!session) {
-    return <LoginGate onUnlock={handleUnlock} />;
+    return <LoginGate onUnlock={handleUnlock} preferences={preferences} />;
   }
 
   const mutateSnapshot = async (
@@ -760,6 +799,7 @@ export default function App() {
     }
 
     if (!payload) {
+      const nextServiceIds = new Set(input.services.map((service) => service.id));
       setSnapshot((current) =>
         withDerivedSnapshot({
           ...current,
@@ -767,6 +807,7 @@ export default function App() {
             ...current.service,
             lastEvent: 'System configuration updated from panel',
           },
+          userRecords: current.userRecords.filter((user) => nextServiceIds.has(user.serviceId)),
           system: {
             ...input,
             previewConfig: current.system.previewConfig,
@@ -788,15 +829,15 @@ export default function App() {
         </div>
         <div className="header-meta">
           <div>
-            <span>Status</span>
-            <strong>{snapshot.service.status}</strong>
+            <span>{text.common.status}</span>
+            <strong>{text.status[snapshot.service.status]}</strong>
           </div>
           <div>
-            <span>Version</span>
+            <span>{text.common.version}</span>
             <strong>{snapshot.service.versionLabel}</strong>
           </div>
           <div>
-            <span>Users</span>
+            <span>{text.common.users}</span>
             <strong>{snapshot.users.total}</strong>
           </div>
           <button
@@ -804,7 +845,7 @@ export default function App() {
             className="button-secondary"
             onClick={resetSession}
           >
-            Sign out
+            {text.common.signOut}
           </button>
         </div>
       </header>
@@ -817,21 +858,31 @@ export default function App() {
             className={activeTab === tab.id ? 'tab-button active' : 'tab-button'}
             onClick={() => setActiveTab(tab.id)}
           >
-            {tab.label}
+            {text.tabs[tab.textKey]}
           </button>
         ))}
       </nav>
 
-      {activeTab === 'dashboard' ? <DashboardTab snapshot={snapshot} onRuntimeAction={handleRuntimeAction} /> : null}
+      {activeTab === 'dashboard' ? (
+        <DashboardTab snapshot={snapshot} onRuntimeAction={handleRuntimeAction} preferences={preferences} />
+      ) : null}
       {activeTab === 'users' ? (
         <UsersTab
           snapshot={snapshot}
           onCreateUser={handleCreateUser}
           onTogglePause={handleTogglePause}
           onDeleteUser={handleDeleteUser}
+          preferences={preferences}
+        />
+      ) : null}
+      {activeTab === 'system' ? (
+        <SystemTab
+          snapshot={snapshot}
+          preferences={preferences}
+          onPreferencesChange={setPreferences}
+          onSaveSystem={handleSaveSystem}
         />
       ) : null}
-      {activeTab === 'system' ? <SystemTab snapshot={snapshot} onSaveSystem={handleSaveSystem} /> : null}
     </main>
   );
 }
@@ -864,6 +915,26 @@ function withDerivedSnapshot(snapshot: DashboardSnapshot): DashboardSnapshot {
   };
 }
 
+function formatQuotaStateLabel(
+  usedBytes: number,
+  quotaBytes: number | null,
+  language: PanelPreferences['language'],
+): string {
+  const text = getPanelText(language);
+
+  if (quotaBytes === null) {
+    return text.common.unlimited;
+  }
+
+  const remaining = quotaBytes - usedBytes;
+
+  if (remaining <= 0) {
+    return text.common.exceeded;
+  }
+
+  return `${formatBytes(remaining)} ${text.common.left}`;
+}
+
 async function requestSnapshot(request: () => Promise<Response>): Promise<DashboardSnapshot | null> {
   try {
     const response = await request();
diff --git a/src/SystemTab.tsx b/src/SystemTab.tsx
index e060cb5..e68064a 100644
--- a/src/SystemTab.tsx
+++ b/src/SystemTab.tsx
@@ -1,22 +1,48 @@
-import { FormEvent, useEffect, useState } from 'react';
+import { FormEvent, useEffect, useMemo, useState } from 'react';
 import type { DashboardSnapshot, ProxyServiceRecord, SystemSettings, UpdateSystemInput } from './shared/contracts';
+import type { PanelLanguage, PanelPreferences, PanelTheme } from './lib/panelPreferences';
+import { getPanelText, getThemeLabel } from './lib/panelText';
 import { getProtocolForCommand, validateSystemInput } from './shared/validation';
 
 interface SystemTabProps {
   snapshot: DashboardSnapshot;
+  preferences: PanelPreferences;
+  onPreferencesChange: (next: PanelPreferences) => void;
   onSaveSystem: (input: UpdateSystemInput) => Promise<void>;
 }
 
-export default function SystemTab({ snapshot, onSaveSystem }: SystemTabProps) {
+export default function SystemTab({
+  snapshot,
+  preferences,
+  onPreferencesChange,
+  onSaveSystem,
+}: SystemTabProps) {
   const [draft, setDraft] = useState<UpdateSystemInput>(() => cloneSystemSettings(snapshot.system));
   const [error, setError] = useState('');
   const [isSaving, setIsSaving] = useState(false);
+  const [removeServiceId, setRemoveServiceId] = useState<string | null>(null);
+  const text = getPanelText(preferences.language);
 
   useEffect(() => {
     setDraft(cloneSystemSettings(snapshot.system));
     setError('');
   }, [snapshot.system]);
 
+  const linkedUsersByService = useMemo(() => {
+    const result = new Map<string, string[]>();
+
+    snapshot.userRecords.forEach((user) => {
+      const usernames = result.get(user.serviceId) ?? [];
+      usernames.push(user.username);
+      result.set(user.serviceId, usernames);
+    });
+
+    return result;
+  }, [snapshot.userRecords]);
+
+  const removeTarget = draft.services.find((service) => service.id === removeServiceId) ?? null;
+  const removeTargetUsers = removeTarget ? linkedUsersByService.get(removeTarget.id) ?? [] : [];
+
   const updateService = (serviceId: string, updater: (service: ProxyServiceRecord) => ProxyServiceRecord) => {
     setDraft((current) => ({
       ...current,
@@ -30,7 +56,9 @@ export default function SystemTab({ snapshot, onSaveSystem }: SystemTabProps) {
     setError('');
 
     try {
-      const validated = validateSystemInput(draft, snapshot.userRecords);
+      const nextServiceIds = new Set(draft.services.map((service) => service.id));
+      const remainingUsers = snapshot.userRecords.filter((user) => nextServiceIds.has(user.serviceId));
+      const validated = validateSystemInput(draft, remainingUsers);
       await onSaveSystem(validated);
     } catch (submitError) {
       setError(submitError instanceof Error ? submitError.message : 'Unable to save system settings.');
@@ -40,204 +68,241 @@ export default function SystemTab({ snapshot, onSaveSystem }: SystemTabProps) {
   };
 
   return (
-    <form className="system-editor" onSubmit={handleSubmit}>
-      <section className="page-grid single-column system-grid">
-        <article className="panel-card system-settings-card">
-          <div className="card-header">
-            <h2>Panel settings</h2>
-          </div>
-          <div className="system-fields">
-            <label className="field-group">
-              Public host
-              <input
-                value={draft.publicHost}
-                onChange={(event) => setDraft((current) => ({ ...current, publicHost: event.target.value }))}
-              />
-            </label>
-            <label className="field-group">
-              Config mode
-              <input
-                value={draft.configMode}
-                onChange={(event) => setDraft((current) => ({ ...current, configMode: event.target.value }))}
-              />
-            </label>
-            <label className="field-group">
-              Reload mode
-              <input
-                value={draft.reloadMode}
-                onChange={(event) => setDraft((current) => ({ ...current, reloadMode: event.target.value }))}
-              />
-            </label>
-            <label className="field-group">
-              Storage mode
-              <input
-                value={draft.storageMode}
-                onChange={(event) => setDraft((current) => ({ ...current, storageMode: event.target.value }))}
-              />
-            </label>
-          </div>
-          <p className="system-hint">
-            These values describe how the panel generates and reloads the 3proxy config. Saving keeps
-            existing users attached only to enabled assignable services.
-          </p>
-        </article>
+    <>
+      <form className="system-editor" onSubmit={handleSubmit}>
+        <section className="page-grid single-column system-grid">
+          <article className="panel-card">
+            <div className="card-header">
+              <h2>{text.common.panelPreferences}</h2>
+            </div>
+            <div className="system-fields">
+              <label className="field-group">
+                {text.common.language}
+                <select
+                  value={preferences.language}
+                  onChange={(event) =>
+                    onPreferencesChange({
+                      ...preferences,
+                      language: event.target.value as PanelLanguage,
+                    })
+                  }
+                >
+                  <option value="en">{text.common.english}</option>
+                  <option value="ru">{text.common.russian}</option>
+                </select>
+              </label>
+              <label className="field-group">
+                {text.common.theme}
+                <select
+                  value={preferences.theme}
+                  onChange={(event) =>
+                    onPreferencesChange({
+                      ...preferences,
+                      theme: event.target.value as PanelTheme,
+                    })
+                  }
+                >
+                  <option value="light">{getThemeLabel(preferences.language, 'light')}</option>
+                  <option value="dark">{getThemeLabel(preferences.language, 'dark')}</option>
+                  <option value="system">{getThemeLabel(preferences.language, 'system')}</option>
+                </select>
+              </label>
+            </div>
+          </article>
 
-        <article className="panel-card">
-          <div className="card-header">
-            <h2>Services</h2>
-            <button
-              type="button"
-              className="button-secondary"
-              onClick={() =>
-                setDraft((current) => ({
-                  ...current,
-                  services: [...current.services, createServiceDraft(current.services)],
-                }))
-              }
-            >
-              Add service
-            </button>
-          </div>
-          <div className="service-editor-list">
-            {draft.services.map((service, index) => (
-              <section key={service.id} className="service-editor-row">
-                <div className="service-editor-header">
-                  <div>
-                    <strong>Service {index + 1}</strong>
-                    <p>{service.id}</p>
-                  </div>
-                  <button
-                    type="button"
-                    className="button-secondary button-small"
-                    onClick={() =>
-                      setDraft((current) => ({
-                        ...current,
-                        services: current.services.filter((entry) => entry.id !== service.id),
-                      }))
-                    }
-                  >
-                    Remove
-                  </button>
-                </div>
-                <div className="service-editor-grid">
-                  <label className="field-group">
-                    Name
-                    <input
-                      value={service.name}
-                      onChange={(event) =>
-                        updateService(service.id, (current) => ({ ...current, name: event.target.value }))
-                      }
-                    />
-                  </label>
-                  <label className="field-group">
-                    Port
-                    <input
-                      inputMode="numeric"
-                      value={String(service.port)}
-                      onChange={(event) =>
-                        updateService(service.id, (current) => ({
-                          ...current,
-                          port: Number(event.target.value),
-                        }))
-                      }
-                    />
-                  </label>
-                  <label className="field-group">
-                    Command
-                    <select
-                      value={service.command}
-                      onChange={(event) =>
-                        updateService(service.id, (current) => {
-                          const command = event.target.value as ProxyServiceRecord['command'];
-                          return {
-                            ...current,
-                            command,
-                            protocol: getProtocolForCommand(command),
-                            assignable: command === 'admin' ? false : current.assignable,
-                          };
-                        })
-                      }
+          <article className="panel-card">
+            <div className="card-header">
+              <h2>{text.settings.title}</h2>
+              <button
+                type="button"
+                className="button-secondary"
+                onClick={() =>
+                  setDraft((current) => ({
+                    ...current,
+                    services: [...current.services, createServiceDraft(current.services)],
+                  }))
+                }
+              >
+                {text.common.addService}
+              </button>
+            </div>
+            <div className="service-editor-list">
+              {draft.services.map((service, index) => (
+                <section key={service.id} className="service-editor-row">
+                  <div className="service-editor-header">
+                    <div>
+                      <strong>
+                        {text.settings.serviceLabel} {index + 1}
+                      </strong>
+                      <p>{service.id}</p>
+                    </div>
+                    <button
+                      type="button"
+                      className="button-secondary button-small"
+                      onClick={() => setRemoveServiceId(service.id)}
                     >
-                      <option value="socks">socks</option>
-                      <option value="proxy">proxy</option>
-                      <option value="admin">admin</option>
-                    </select>
-                  </label>
+                      {text.common.remove}
+                    </button>
+                  </div>
+                  <div className="service-editor-grid">
+                    <label className="field-group">
+                      {text.settings.name}
+                      <input
+                        value={service.name}
+                        onChange={(event) =>
+                          updateService(service.id, (current) => ({ ...current, name: event.target.value }))
+                        }
+                      />
+                    </label>
+                    <label className="field-group">
+                      {text.settings.port}
+                      <input
+                        inputMode="numeric"
+                        value={String(service.port)}
+                        onChange={(event) =>
+                          updateService(service.id, (current) => ({
+                            ...current,
+                            port: Number(event.target.value),
+                          }))
+                        }
+                      />
+                    </label>
                   <label className="field-group">
-                    Protocol
-                    <input value={service.protocol} readOnly />
-                  </label>
-                  <label className="field-group field-span-2">
-                    Description
-                    <input
-                      value={service.description}
-                      onChange={(event) =>
-                        updateService(service.id, (current) => ({
-                          ...current,
-                          description: event.target.value,
-                        }))
-                      }
-                    />
-                  </label>
-                </div>
-                <div className="toggle-row">
-                  <label className="toggle-check">
-                    <input
-                      type="checkbox"
-                      checked={service.enabled}
-                      onChange={(event) =>
-                        updateService(service.id, (current) => ({
-                          ...current,
-                          enabled: event.target.checked,
-                        }))
-                      }
-                    />
-                    Enabled
-                  </label>
-                  <label className="toggle-check">
-                    <input
-                      type="checkbox"
-                      checked={service.assignable}
-                      disabled={service.command === 'admin'}
-                      onChange={(event) =>
-                        updateService(service.id, (current) => ({
-                          ...current,
-                          assignable: current.command === 'admin' ? false : event.target.checked,
-                        }))
-                      }
-                    />
-                    Assignable to users
-                  </label>
-                </div>
-              </section>
-            ))}
-          </div>
-          {error ? <p className="form-error">{error}</p> : null}
-          <div className="system-actions">
-            <button
-              type="button"
-              className="button-secondary"
-              onClick={() => {
-                setDraft(cloneSystemSettings(snapshot.system));
-                setError('');
-              }}
-            >
-              Reset
-            </button>
-            <button type="submit" disabled={isSaving}>
-              {isSaving ? 'Saving...' : 'Save system'}
-            </button>
-          </div>
-        </article>
+                      {text.settings.serviceType}
+                      <select
+                        value={service.command}
+                        onChange={(event) =>
+                          updateService(service.id, (current) => {
+                            const command = event.target.value as ProxyServiceRecord['command'];
+                            return {
+                              ...current,
+                              command,
+                              protocol: getProtocolForCommand(command),
+                              assignable: command === 'admin' ? false : current.assignable,
+                            };
+                          })
+                        }
+                      >
+                        <option value="socks">{text.settings.typeSocks}</option>
+                        <option value="proxy">{text.settings.typeProxy}</option>
+                        <option value="admin">{text.settings.typeAdmin}</option>
+                      </select>
+                    </label>
+                    <label className="field-group field-span-2">
+                      {text.settings.description}
+                      <input
+                        value={service.description}
+                        onChange={(event) =>
+                          updateService(service.id, (current) => ({
+                            ...current,
+                            description: event.target.value,
+                          }))
+                        }
+                      />
+                    </label>
+                  </div>
+                  <div className="toggle-row">
+                    <label className="toggle-check">
+                      <input
+                        type="checkbox"
+                        checked={service.enabled}
+                        onChange={(event) =>
+                          updateService(service.id, (current) => ({
+                            ...current,
+                            enabled: event.target.checked,
+                          }))
+                        }
+                      />
+                      {text.common.enabled}
+                    </label>
+                    <label className="toggle-check">
+                      <input
+                        type="checkbox"
+                        checked={service.assignable}
+                        disabled={service.command === 'admin'}
+                        onChange={(event) =>
+                          updateService(service.id, (current) => ({
+                            ...current,
+                            assignable: current.command === 'admin' ? false : event.target.checked,
+                          }))
+                        }
+                      />
+                      {text.common.assignable}
+                    </label>
+                  </div>
+                </section>
+              ))}
+            </div>
+            {error ? <p className="form-error">{error}</p> : null}
+            <div className="system-actions">
+              <button
+                type="button"
+                className="button-secondary"
+                onClick={() => {
+                  setDraft(cloneSystemSettings(snapshot.system));
+                  setError('');
+                }}
+              >
+                {text.common.reset}
+              </button>
+              <button type="submit" disabled={isSaving}>
+                {isSaving ? `${text.common.save}...` : text.common.saveSettings}
+              </button>
+            </div>
+          </article>
 
-        <article className="panel-card wide-card">
-          <div className="card-header">
-            <h2>Generated config</h2>
-          </div>
-          <pre>{snapshot.system.previewConfig}</pre>
-        </article>
-      </section>
-    </form>
+          <article className="panel-card wide-card">
+            <div className="card-header">
+              <h2>{text.settings.generatedConfig}</h2>
+            </div>
+            <pre>{snapshot.system.previewConfig}</pre>
+          </article>
+        </section>
+      </form>
+
+      {removeTarget ? (
+        <div className="modal-backdrop" role="presentation" onClick={() => setRemoveServiceId(null)}>
+          <section
+            aria-labelledby="remove-service-title"
+            aria-modal="true"
+            className="modal-card confirm-card"
+            role="dialog"
+            onClick={(event) => event.stopPropagation()}
+          >
+            <div className="modal-header">
+              <h2 id="remove-service-title">{text.settings.serviceRemoveTitle}</h2>
+            </div>
+            <p className="confirm-copy">
+              <strong>{removeTarget.name}</strong>{' '}
+              {removeTargetUsers.length > 0 ? text.settings.removeWarningUsers : text.settings.removeWarningNone}
+            </p>
+            {removeTargetUsers.length > 0 ? (
+              <p className="confirm-copy">
+                {text.settings.removeWarningCount} {removeTargetUsers.join(', ')}
+              </p>
+            ) : null}
+            <div className="modal-actions">
+              <button type="button" className="button-secondary" onClick={() => setRemoveServiceId(null)}>
+                {text.common.cancel}
+              </button>
+              <button
+                type="button"
+                className="button-danger"
+                onClick={() => {
+                  setDraft((current) => ({
+                    ...current,
+                    services: current.services.filter((service) => service.id !== removeTarget.id),
+                  }));
+                  setRemoveServiceId(null);
+                }}
+              >
+                {text.common.remove}
+              </button>
+            </div>
+          </section>
+        </div>
+      ) : null}
+    </>
   );
 }
 
diff --git a/src/app.css b/src/app.css
index 774c2f2..37b6a0a 100644
--- a/src/app.css
+++ b/src/app.css
@@ -22,6 +22,23 @@
   --shadow: 0 1px 2px rgba(17, 24, 39, 0.04);
 }
 
+:root[data-theme='dark'] {
+  color-scheme: dark;
+  --page-bg: #111827;
+  --surface: #18212f;
+  --surface-muted: #1f2937;
+  --border: #334155;
+  --border-strong: #475569;
+  --text: #f8fafc;
+  --muted: #94a3b8;
+  --accent: #60a5fa;
+  --accent-muted: rgba(96, 165, 250, 0.15);
+  --success: #4ade80;
+  --warning: #fbbf24;
+  --danger: #f87171;
+  --shadow: 0 1px 2px rgba(2, 6, 23, 0.35);
+}
+
 * {
   box-sizing: border-box;
 }
@@ -372,13 +389,13 @@ button,
 .usage-bar {
   height: 8px;
   border-radius: 999px;
-  background: #eceff3;
+  background: color-mix(in srgb, var(--border) 70%, transparent);
   overflow: hidden;
 }
 
 .usage-bar div {
   height: 100%;
-  background: #94a3b8;
+  background: color-mix(in srgb, var(--accent) 55%, var(--muted));
 }
 
 .event-row,
@@ -608,8 +625,8 @@ pre {
   overflow: auto;
   border: 1px solid var(--border);
   border-radius: 10px;
-  background: #fbfbfc;
-  color: #1f2937;
+  background: color-mix(in srgb, var(--surface-muted) 80%, var(--surface));
+  color: var(--text);
   font: 13px/1.55 Consolas, "Courier New", monospace;
 }
 
diff --git a/src/lib/panelPreferences.ts b/src/lib/panelPreferences.ts
new file mode 100644
index 0000000..2b4e6f5
--- /dev/null
+++ b/src/lib/panelPreferences.ts
@@ -0,0 +1,74 @@
+export type PanelLanguage = 'en' | 'ru';
+export type PanelTheme = 'light' | 'dark' | 'system';
+
+export interface PanelPreferences {
+  language: PanelLanguage;
+  theme: PanelTheme;
+}
+
+const PREFERENCES_KEY = '3proxy-ui-panel-preferences';
+
+export const defaultPanelPreferences: PanelPreferences = {
+  language: 'en',
+  theme: 'system',
+};
+
+export function loadPanelPreferences(): PanelPreferences {
+  try {
+    const raw = window.localStorage.getItem(PREFERENCES_KEY);
+
+    if (!raw) {
+      return defaultPanelPreferences;
+    }
+
+    const parsed = JSON.parse(raw) as Partial<PanelPreferences>;
+
+    return {
+      language: parsed.language === 'ru' ? 'ru' : 'en',
+      theme: isPanelTheme(parsed.theme) ? parsed.theme : defaultPanelPreferences.theme,
+    };
+  } catch {
+    return defaultPanelPreferences;
+  }
+}
+
+export function savePanelPreferences(preferences: PanelPreferences): void {
+  window.localStorage.setItem(PREFERENCES_KEY, JSON.stringify(preferences));
+}
+
+export function applyPanelTheme(theme: PanelTheme): void {
+  document.documentElement.dataset.theme = resolvePanelTheme(theme);
+}
+
+export function observeSystemTheme(onChange: () => void): () => void {
+  if (typeof window.matchMedia !== 'function') {
+    return () => undefined;
+  }
+
+  const media = window.matchMedia('(prefers-color-scheme: dark)');
+  const listener = () => onChange();
+
+  if (typeof media.addEventListener === 'function') {
+    media.addEventListener('change', listener);
+    return () => media.removeEventListener('change', listener);
+  }
+
+  media.addListener(listener);
+  return () => media.removeListener(listener);
+}
+
+function resolvePanelTheme(theme: PanelTheme): 'light' | 'dark' {
+  if (theme === 'light' || theme === 'dark') {
+    return theme;
+  }
+
+  if (typeof window.matchMedia === 'function') {
+    return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+  }
+
+  return 'light';
+}
+
+function isPanelTheme(value: unknown): value is PanelTheme {
+  return value === 'light' || value === 'dark' || value === 'system';
+}
diff --git a/src/lib/panelText.ts b/src/lib/panelText.ts
new file mode 100644
index 0000000..71f8669
--- /dev/null
+++ b/src/lib/panelText.ts
@@ -0,0 +1,269 @@
+import type { ServiceCommand } from '../shared/contracts';
+import type { PanelLanguage, PanelTheme } from './panelPreferences';
+
+const text = {
+  en: {
+    tabs: {
+      dashboard: 'Dashboard',
+      users: 'Users',
+      settings: 'Settings',
+    },
+    auth: {
+      title: '3proxy UI',
+      subtitle: 'Sign in to the control panel.',
+      login: 'Login',
+      password: 'Password',
+      open: 'Open panel',
+      opening: 'Opening...',
+    },
+    common: {
+      close: 'Close',
+      cancel: 'Cancel',
+      reset: 'Reset',
+      save: 'Save',
+      saveSettings: 'Save settings',
+      signOut: 'Sign out',
+      addService: 'Add service',
+      remove: 'Remove',
+      delete: 'Delete',
+      deleteUser: 'Delete user',
+      copy: 'Copy',
+      copied: 'Copied',
+      createUser: 'Create user',
+      create: 'Create',
+      endpoint: 'Endpoint',
+      protocol: 'Protocol',
+      status: 'Status',
+      version: 'Version',
+      users: 'Users',
+      enabled: 'Enabled',
+      assignable: 'Assignable to users',
+      unavailable: 'Unavailable',
+      unknownService: 'Unknown service',
+      serviceMissing: 'service missing',
+      optional: 'Optional',
+      activeUsers: 'Active users',
+      total: 'Total',
+      connections: 'Connections',
+      process: 'Process',
+      uptime: 'Uptime',
+      lastEvent: 'Last event',
+      settingsSaved: 'Settings updated from panel',
+      left: 'left',
+      unlimited: 'Unlimited',
+      exceeded: 'Exceeded',
+      panelPreferences: 'Panel preferences',
+      language: 'Panel language',
+      theme: 'Panel style',
+      english: 'English',
+      russian: 'Russian',
+      light: 'Light',
+      dark: 'Dark',
+      system: 'System',
+    },
+    dashboard: {
+      service: 'Service',
+      traffic: 'Traffic',
+      dailyUsage: 'Daily usage',
+      attention: 'Attention',
+      start: 'Start',
+      restart: 'Restart',
+    },
+    users: {
+      title: 'Users',
+      accountsInProfile: 'accounts in current profile',
+      newUser: 'New user',
+      live: 'live',
+      nearQuota: 'near quota',
+      exceeded: 'exceeded',
+      enableServiceHint: 'Enable an assignable service in Settings before creating new users.',
+      user: 'User',
+      endpoint: 'Endpoint',
+      used: 'Used',
+      remaining: 'Remaining',
+      share: 'Share',
+      proxy: 'Proxy',
+      actions: 'Actions',
+      addUser: 'Add user',
+      username: 'Username',
+      password: 'Password',
+      service: 'Service',
+      quotaMb: 'Quota (MB)',
+      pause: 'Pause',
+      resume: 'Resume',
+      deleteTitle: 'Delete user',
+      deletePrompt: 'Remove profile',
+      deletePromptSuffix: '? This action will delete the user entry from the current panel state.',
+      cancel: 'Cancel',
+      deleteAction: 'Delete user',
+    },
+    settings: {
+      title: 'Services',
+      generatedConfig: 'Generated config',
+      serviceLabel: 'Service',
+      serviceType: 'Type',
+      typeSocks: 'SOCKS5 proxy',
+      typeProxy: 'HTTP proxy',
+      typeAdmin: 'Admin interface',
+      name: 'Name',
+      port: 'Port',
+      description: 'Description',
+      serviceRemoveTitle: 'Delete service',
+      removeWarningNone: 'Delete this service from the panel configuration?',
+      removeWarningUsers: 'Delete this service and remove all linked users?',
+      removeWarningCount: 'Linked users to be removed:',
+    },
+    status: {
+      live: 'live',
+      warn: 'warn',
+      fail: 'fail',
+      idle: 'idle',
+      paused: 'paused',
+      enabled: 'enabled',
+      disabled: 'disabled',
+    },
+  },
+  ru: {
+    tabs: {
+      dashboard: 'Панель',
+      users: 'Пользователи',
+      settings: 'Настройки',
+    },
+    auth: {
+      title: '3proxy UI',
+      subtitle: 'Войдите в панель управления.',
+      login: 'Логин',
+      password: 'Пароль',
+      open: 'Открыть панель',
+      opening: 'Открываем...',
+    },
+    common: {
+      close: 'Закрыть',
+      cancel: 'Отмена',
+      reset: 'Сбросить',
+      save: 'Сохранить',
+      saveSettings: 'Сохранить настройки',
+      signOut: 'Выйти',
+      addService: 'Добавить сервис',
+      remove: 'Удалить',
+      delete: 'Удалить',
+      deleteUser: 'Удалить пользователя',
+      copy: 'Копировать',
+      copied: 'Скопировано',
+      createUser: 'Создать пользователя',
+      create: 'Создать',
+      endpoint: 'Точка входа',
+      protocol: 'Протокол',
+      status: 'Статус',
+      version: 'Версия',
+      users: 'Пользователи',
+      enabled: 'Включен',
+      assignable: 'Можно назначать пользователям',
+      unavailable: 'Недоступно',
+      unknownService: 'Неизвестный сервис',
+      serviceMissing: 'сервис отсутствует',
+      optional: 'Необязательно',
+      activeUsers: 'Активные пользователи',
+      total: 'Всего',
+      connections: 'Соединения',
+      process: 'Процесс',
+      uptime: 'Время работы',
+      lastEvent: 'Последнее событие',
+      settingsSaved: 'Настройки обновлены из панели',
+      left: 'осталось',
+      unlimited: 'Без лимита',
+      exceeded: 'Превышено',
+      panelPreferences: 'Параметры панели',
+      language: 'Язык панели',
+      theme: 'Стиль панели',
+      english: 'Английский',
+      russian: 'Русский',
+      light: 'Светлый',
+      dark: 'Темный',
+      system: 'Системный',
+    },
+    dashboard: {
+      service: 'Сервис',
+      traffic: 'Трафик',
+      dailyUsage: 'Дневное использование',
+      attention: 'Внимание',
+      start: 'Запустить',
+      restart: 'Перезапустить',
+    },
+    users: {
+      title: 'Пользователи',
+      accountsInProfile: 'аккаунтов в текущем профиле',
+      newUser: 'Новый пользователь',
+      live: 'в работе',
+      nearQuota: 'близко к лимиту',
+      exceeded: 'превышено',
+      enableServiceHint: 'Сначала включите назначаемый сервис во вкладке Настройки.',
+      user: 'Пользователь',
+      endpoint: 'Точка входа',
+      used: 'Использовано',
+      remaining: 'Остаток',
+      share: 'Доля',
+      proxy: 'Прокси',
+      actions: 'Действия',
+      addUser: 'Добавить пользователя',
+      username: 'Имя пользователя',
+      password: 'Пароль',
+      service: 'Сервис',
+      quotaMb: 'Лимит (МБ)',
+      pause: 'Пауза',
+      resume: 'Возобновить',
+      deleteTitle: 'Удаление пользователя',
+      deletePrompt: 'Удалить профиль',
+      deletePromptSuffix: '? Это действие удалит пользователя из текущего состояния панели.',
+      cancel: 'Отмена',
+      deleteAction: 'Удалить пользователя',
+    },
+    settings: {
+      title: 'Сервисы',
+      generatedConfig: 'Сгенерированный конфиг',
+      serviceLabel: 'Сервис',
+      serviceType: 'Тип',
+      typeSocks: 'SOCKS5 прокси',
+      typeProxy: 'HTTP прокси',
+      typeAdmin: 'Админ-интерфейс',
+      name: 'Название',
+      port: 'Порт',
+      description: 'Описание',
+      serviceRemoveTitle: 'Удаление сервиса',
+      removeWarningNone: 'Удалить этот сервис из конфигурации панели?',
+      removeWarningUsers: 'Удалить этот сервис и всех связанных с ним пользователей?',
+      removeWarningCount: 'Будут удалены пользователи:',
+    },
+    status: {
+      live: 'в работе',
+      warn: 'предупреждение',
+      fail: 'ошибка',
+      idle: 'ожидание',
+      paused: 'пауза',
+      enabled: 'включен',
+      disabled: 'выключен',
+    },
+  },
+} as const;
+
+export function getPanelText(language: PanelLanguage) {
+  return text[language];
+}
+
+export function getThemeLabel(language: PanelLanguage, theme: PanelTheme): string {
+  const t = getPanelText(language);
+  return theme === 'light' ? t.common.light : theme === 'dark' ? t.common.dark : t.common.system;
+}
+
+export function getServiceTypeLabel(language: PanelLanguage, command: ServiceCommand): string {
+  const t = getPanelText(language);
+  if (command === 'socks') {
+    return t.settings.typeSocks;
+  }
+
+  if (command === 'proxy') {
+    return t.settings.typeProxy;
+  }
+
+  return t.settings.typeAdmin;
+}