diff --git a/test/routes/system-routes-settings-admin-only.test.ts b/test/routes/system-routes-settings-admin-only.test.ts
new file mode 100644
index 00000000..44505cd3
--- /dev/null
+++ b/test/routes/system-routes-settings-admin-only.test.ts
@@ -0,0 +1,241 @@
+/**
+ * @fileoverview Multi-user mode: server-wide settings writes are admin-only.
+ *
+ * `~/.codeman/settings.json` is ONE file for the whole server (feature switches, the
+ * plan-usage collection switch, run mode, respawn presets, the tunnel). Before this,
+ * any signed-in NON-ADMIN could rewrite it through PUT /api/settings, although
+ * docs/multi-user-plan.md makes settings writes admin-only. Pinned here:
+ *  - a non-admin PUT /api/settings is 403 FORBIDDEN before anything is parsed (an
+ *    invalid body is still 403, not 400), written, toggled or started (watchers, the
+ *    tunnel, the tmux history limit);
+ *  - the same gate on the other server-wide writes: PUT /api/execution/model-config,
+ *    PUT /api/config and PUT /api/cases/order;
+ *  - an admin, and single-user mode, write as before; GET /api/settings stays readable.
+ *
+ * Uses app.inject(), so no real HTTP port is needed. Port: N/A.
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { createRouteTestHarness, type RouteTestHarness } from './_route-test-utils.js';
+import { registerSystemRoutes } from '../../src/web/routes/system-routes.js';
+import { registerCaseRoutes } from '../../src/web/routes/case-routes.js';
+
+const { STORED, subagentWatcher, imageWatcher, workflowRunWatcher } = vi.hoisted(() => {
+  const makeWatcher = (running: boolean) => {
+    let isOn = running;
+    return {
+      isRunning: vi.fn(() => isOn),
+      start: vi.fn(() => {
+        isOn = true;
+      }),
+      stop: vi.fn(() => {
+        isOn = false;
+      }),
+      getStats: vi.fn(() => ({})),
+      watchSession: vi.fn(),
+      getRecentRunSummaries: vi.fn(() => []),
+      __reset: () => {
+        isOn = running;
+      },
+    };
+  };
+  return {
+    // The persisted settings.json these tests start from.
+    STORED: { subagentTrackingEnabled: false, imageWatcherEnabled: true, cliManagementEnabled: false },
+    subagentWatcher: makeWatcher(false),
+    imageWatcher: makeWatcher(true),
+    workflowRunWatcher: makeWatcher(false),
+  };
+});
+
+vi.mock('node:fs/promises', () => ({
+  default: {
+    readFile: vi.fn(async () => JSON.stringify(STORED)),
+    writeFile: vi.fn(async () => undefined),
+  },
+}));
+
+vi.mock('node:fs', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('node:fs')>();
+  return { ...actual, existsSync: vi.fn(() => true), mkdirSync: vi.fn(), readdirSync: vi.fn(() => []) };
+});
+
+vi.mock('../../src/subagent-watcher.js', () => ({ subagentWatcher }));
+vi.mock('../../src/image-watcher.js', () => ({ imageWatcher }));
+vi.mock('../../src/workflow-run-watcher.js', () => ({ workflowRunWatcher }));
+
+import fs from 'node:fs/promises';
+const writeFile = vi.mocked(fs.writeFile);
+
+const NON_ADMIN = { username: 'bob', role: 'user' } as const;
+const ADMIN = { username: 'root', role: 'admin' } as const;
+
+function makeTunnelManager() {
+  return {
+    start: vi.fn(),
+    stop: vi.fn(),
+    isRunning: vi.fn(() => false),
+    getUrl: vi.fn(() => null),
+    getStatus: vi.fn(() => ({ running: false })),
+  };
+}
+
+/** A body that would touch everything PUT /api/settings can act on. */
+const EVERYTHING = {
+  tunnelEnabled: true,
+  subagentTrackingEnabled: true,
+  imageWatcherEnabled: false,
+  showUltracodeAgents: true,
+  tmuxHistoryLimit: 50000,
+  cliManagementEnabled: true,
+  runMode: 'shell',
+};
+
+describe('server-wide settings writes are admin-only in multi-user mode', () => {
+  const savedMultiUser = process.env.CODEMAN_MULTIUSER;
+  let harness: RouteTestHarness | undefined;
+  let tunnel: ReturnType<typeof makeTunnelManager>;
+
+  async function as(user: typeof NON_ADMIN | typeof ADMIN | null, register = registerSystemRoutes) {
+    if (user) process.env.CODEMAN_MULTIUSER = '1';
+    else delete process.env.CODEMAN_MULTIUSER;
+    harness = await createRouteTestHarness(register, user ? { authUser: user } : undefined);
+    tunnel = makeTunnelManager();
+    (harness.ctx as unknown as { tunnelManager: unknown }).tunnelManager = tunnel;
+    return harness;
+  }
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    for (const w of [subagentWatcher, imageWatcher, workflowRunWatcher]) w.__reset();
+  });
+
+  afterEach(async () => {
+    await harness?.app.close();
+    harness = undefined;
+    if (savedMultiUser === undefined) delete process.env.CODEMAN_MULTIUSER;
+    else process.env.CODEMAN_MULTIUSER = savedMultiUser;
+  });
+
+  describe('PUT /api/settings', () => {
+    it('refuses a non-admin with 403 FORBIDDEN, and nothing is written, toggled or started', async () => {
+      const { app, ctx } = await as(NON_ADMIN);
+      const res = await app.inject({ method: 'PUT', url: '/api/settings', payload: EVERYTHING });
+
+      expect(res.statusCode).toBe(403);
+      const body = JSON.parse(res.body);
+      expect(body.success).toBe(false);
+      expect(body.errorCode).toBe('FORBIDDEN');
+      expect(writeFile).not.toHaveBeenCalled();
+      for (const w of [subagentWatcher, imageWatcher, workflowRunWatcher]) {
+        expect(w.start).not.toHaveBeenCalled();
+        expect(w.stop).not.toHaveBeenCalled();
+      }
+      expect(tunnel.start).not.toHaveBeenCalled();
+      expect(ctx.mux.setHistoryLimit).not.toHaveBeenCalled();
+    });
+
+    it('refuses a non-admin before the body is even parsed (an invalid body is 403, not 400)', async () => {
+      const { app } = await as(NON_ADMIN);
+      const res = await app.inject({ method: 'PUT', url: '/api/settings', payload: { notASetting: 1 } });
+      expect(res.statusCode).toBe(403);
+      expect(JSON.parse(res.body).errorCode).toBe('FORBIDDEN');
+      expect(writeFile).not.toHaveBeenCalled();
+    });
+
+    it('still lets a non-admin READ the settings', async () => {
+      const { app } = await as(NON_ADMIN);
+      const res = await app.inject({ method: 'GET', url: '/api/settings' });
+      expect(res.statusCode).toBe(200);
+      expect(JSON.parse(res.body)).toEqual(STORED);
+    });
+
+    for (const [label, user] of [
+      ['an admin in multi-user mode', ADMIN],
+      ['single-user mode', null],
+    ] as const) {
+      it(`writes, reconciles watchers and starts the tunnel for ${label}`, async () => {
+        const { app, ctx } = await as(user);
+        // Single-user mode with no CODEMAN_PASSWORD needs the COD-55 tunnel acknowledgement
+        // (multi-user mode counts as authenticated); that guard is not what this file tests.
+        const payload = user ? EVERYTHING : { ...EVERYTHING, acknowledgeUnauthTunnel: true };
+        const res = await app.inject({ method: 'PUT', url: '/api/settings', payload });
+
+        expect(res.statusCode).toBe(200);
+        expect(writeFile).toHaveBeenCalledTimes(1);
+        const written = JSON.parse(String(writeFile.mock.calls[0][1]));
+        expect(written).toMatchObject({ ...STORED, ...EVERYTHING });
+        expect(subagentWatcher.start).toHaveBeenCalledTimes(1);
+        expect(imageWatcher.stop).toHaveBeenCalledTimes(1);
+        expect(workflowRunWatcher.start).toHaveBeenCalledTimes(1);
+        expect(tunnel.start).toHaveBeenCalledTimes(1);
+        expect(ctx.mux.setHistoryLimit).toHaveBeenCalledTimes(1);
+      });
+    }
+  });
+
+  describe('PUT /api/execution/model-config', () => {
+    const config = { defaultModel: 'opus', agentTypeOverrides: { explore: 'sonnet' } };
+
+    it('refuses a non-admin with 403 FORBIDDEN and writes nothing', async () => {
+      const { app } = await as(NON_ADMIN);
+      const res = await app.inject({ method: 'PUT', url: '/api/execution/model-config', payload: config });
+      expect(res.statusCode).toBe(403);
+      expect(JSON.parse(res.body).errorCode).toBe('FORBIDDEN');
+      expect(writeFile).not.toHaveBeenCalled();
+    });
+
+    it('writes it for an admin', async () => {
+      const { app } = await as(ADMIN);
+      const res = await app.inject({ method: 'PUT', url: '/api/execution/model-config', payload: config });
+      expect(res.statusCode).toBe(200);
+      expect(JSON.parse(String(writeFile.mock.calls[0][1])).modelConfig).toEqual(config);
+    });
+
+    it('stays readable by a non-admin', async () => {
+      const { app } = await as(NON_ADMIN);
+      const res = await app.inject({ method: 'GET', url: '/api/execution/model-config' });
+      expect(res.statusCode).toBe(200);
+    });
+  });
+
+  describe('PUT /api/config', () => {
+    it('refuses a non-admin with 403 FORBIDDEN and changes nothing', async () => {
+      const { app, ctx } = await as(NON_ADMIN);
+      const res = await app.inject({ method: 'PUT', url: '/api/config', payload: { maxConcurrentSessions: 50 } });
+      expect(res.statusCode).toBe(403);
+      expect(JSON.parse(res.body).errorCode).toBe('FORBIDDEN');
+      expect(ctx.store.setConfig).not.toHaveBeenCalled();
+    });
+
+    it('updates it for an admin', async () => {
+      const { app, ctx } = await as(ADMIN);
+      const res = await app.inject({ method: 'PUT', url: '/api/config', payload: { maxConcurrentSessions: 10 } });
+      expect(res.statusCode).toBe(200);
+      expect(ctx.store.setConfig).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  describe('PUT /api/cases/order (the one global caseOrder in settings.json)', () => {
+    it('refuses a non-admin with 403 FORBIDDEN and writes nothing', async () => {
+      const { app, ctx } = await as(NON_ADMIN, registerCaseRoutes);
+      const res = await app.inject({ method: 'PUT', url: '/api/cases/order', payload: { order: ['b', 'a'] } });
+      expect(res.statusCode).toBe(403);
+      expect(JSON.parse(res.body).errorCode).toBe('FORBIDDEN');
+      expect(writeFile).not.toHaveBeenCalled();
+      expect(ctx.broadcast).not.toHaveBeenCalled();
+    });
+
+    for (const [label, user] of [
+      ['an admin in multi-user mode', ADMIN],
+      ['single-user mode', null],
+    ] as const) {
+      it(`writes it for ${label}`, async () => {
+        const { app } = await as(user, registerCaseRoutes);
+        const res = await app.inject({ method: 'PUT', url: '/api/cases/order', payload: { order: ['b', 'a'] } });
+        expect(res.statusCode).toBe(200);
+        expect(JSON.parse(String(writeFile.mock.calls[0][1])).caseOrder).toEqual(['b', 'a']);
+      });
+    }
+  });
+});
diff --git a/test/settings-admin-only-multiuser.test.ts b/test/settings-admin-only-multiuser.test.ts
new file mode 100644
index 00000000..fcfebae8
--- /dev/null
+++ b/test/settings-admin-only-multiuser.test.ts
@@ -0,0 +1,143 @@
+/**
+ * @fileoverview Multi-user mode, end to end: a non-admin cannot change the server-wide
+ * settings.json (live server, ephemeral port, real multi-user auth, real file on disk).
+ *
+ * The route tests (test/routes/system-routes-settings-admin-only.test.ts) pin each
+ * gate with a mocked filesystem. This one runs the real auth middleware and reads the
+ * real file back, so "settings.json is unchanged" is asserted on bytes:
+ *  - PUT /api/settings, PUT /api/execution/model-config and PUT /api/cases/order are
+ *    403 FORBIDDEN for a non-admin, and the file is byte-identical afterwards;
+ *  - GET /api/settings stays readable by the non-admin;
+ *  - a non-admin's quick-start does not record its case as `lastUsedCase` (a key every
+ *    user can read through GET /api/settings), while an admin's still does;
+ *  - an admin's PUT /api/settings still writes.
+ */
+
+import { afterAll, beforeAll, describe, expect, it, vi } from 'vitest';
+import fs from 'node:fs/promises';
+import { dirname } from 'node:path';
+import { WebServer } from '../src/web/server.js';
+import { TmuxManager } from '../src/tmux-manager.js';
+import { createUser, invalidateUsersCache } from '../src/user-store.js';
+import { SETTINGS_PATH } from '../src/web/route-helpers.js';
+
+vi.spyOn(TmuxManager, 'isTmuxAvailable').mockReturnValue(true);
+
+const basic = (u: string, p: string) => 'Basic ' + Buffer.from(`${u}:${p}`).toString('base64');
+const bob = { Authorization: basic('bob', 'bobpass1234') };
+const root = { Authorization: basic('root', 'rootpass123') };
+
+let server: WebServer;
+const saved: Record<string, string | undefined> = {};
+const url = (p: string) => `http://localhost:${server.boundPort}${p}`;
+
+const INITIAL = {
+  autoNameSessions: false,
+  cliManagementEnabled: false,
+  lastUsedCase: 'rootcase',
+  caseOrder: ['rootcase'],
+  modelConfig: { defaultModel: 'sonnet' },
+};
+const readSettingsBytes = () => fs.readFile(SETTINGS_PATH, 'utf-8');
+
+async function send(method: string, path: string, headers: Record<string, string>, body?: unknown) {
+  const res = await fetch(url(path), {
+    method,
+    headers: { ...headers, ...(body === undefined ? {} : { 'Content-Type': 'application/json' }) },
+    body: body === undefined ? undefined : JSON.stringify(body),
+  });
+  return { status: res.status, body: (await res.json()) as Record<string, any> };
+}
+
+/** The quick-start write of lastUsedCase is fire-and-forget: poll for it briefly. */
+async function settleSettings(predicate: (s: Record<string, unknown>) => boolean): Promise<Record<string, unknown>> {
+  let last: Record<string, unknown> = {};
+  for (let i = 0; i < 40; i++) {
+    last = JSON.parse(await readSettingsBytes());
+    if (predicate(last)) return last;
+    await new Promise((r) => setTimeout(r, 25));
+  }
+  return last;
+}
+
+beforeAll(async () => {
+  for (const k of ['CODEMAN_MULTIUSER', 'CODEMAN_PASSWORD', 'CODEMAN_USERNAME']) saved[k] = process.env[k];
+  process.env.CODEMAN_MULTIUSER = '1';
+  delete process.env.CODEMAN_PASSWORD;
+  delete process.env.CODEMAN_USERNAME;
+  invalidateUsersCache();
+  await createUser({ username: 'root', role: 'admin', password: 'rootpass123' });
+  await createUser({ username: 'bob', role: 'user', password: 'bobpass1234' });
+
+  await fs.mkdir(dirname(SETTINGS_PATH), { recursive: true });
+  await fs.writeFile(SETTINGS_PATH, JSON.stringify(INITIAL, null, 2));
+
+  server = new WebServer(0, false, true);
+  await server.start();
+});
+
+afterAll(async () => {
+  await server?.stop();
+  for (const [k, v] of Object.entries(saved)) {
+    if (v === undefined) delete process.env[k];
+    else process.env[k] = v;
+  }
+  invalidateUsersCache();
+});
+
+describe('a non-admin and the server-wide settings.json', () => {
+  it('cannot write it through any settings route, and the file stays byte-identical', async () => {
+    const before = await readSettingsBytes();
+    for (const [path, body] of [
+      ['/api/settings', { autoNameSessions: true, cliManagementEnabled: true, runMode: 'shell' }],
+      ['/api/execution/model-config', { defaultModel: 'opus' }],
+      ['/api/cases/order', { order: ['bobcase'] }],
+    ] as const) {
+      const res = await send('PUT', path, bob, body);
+      expect(res.status, path).toBe(403);
+      expect(res.body.success, path).toBe(false);
+      expect(res.body.errorCode, path).toBe('FORBIDDEN');
+    }
+    expect(await readSettingsBytes()).toBe(before);
+  });
+
+  it('can still read it', async () => {
+    const res = await send('GET', '/api/settings', bob);
+    expect(res.status).toBe(200);
+    expect(res.body.data.autoNameSessions).toBe(false);
+  });
+
+  it("does not get its quick-start case recorded as everyone's lastUsedCase; an admin's still is", async () => {
+    const mine = await send('POST', '/api/quick-start', bob, { caseName: 'bobproj' });
+    expect(mine.status).toBe(200);
+    expect(mine.body.success).toBe(true);
+    // Give a (wrong) fire-and-forget write every chance to land before checking.
+    await new Promise((r) => setTimeout(r, 200));
+    expect(JSON.parse(await readSettingsBytes()).lastUsedCase).toBe('rootcase');
+
+    const theirs = await send('POST', '/api/quick-start', root, { caseName: 'rootproj2' });
+    expect(theirs.status).toBe(200);
+    expect((await settleSettings((s) => s.lastUsedCase === 'rootproj2')).lastUsedCase).toBe('rootproj2');
+  });
+
+  it('does not get its Ralph loop case recorded as lastUsedCase either; an admin still does', async () => {
+    const mine = await send('POST', '/api/ralph-loop/start', bob, { caseName: 'bobralph', taskDescription: 'x' });
+    expect(mine.status).toBe(200);
+    expect(mine.body.success).toBe(true);
+    await new Promise((r) => setTimeout(r, 200));
+    expect(JSON.parse(await readSettingsBytes()).lastUsedCase).toBe('rootproj2');
+
+    const theirs = await send('POST', '/api/ralph-loop/start', root, { caseName: 'rootralph', taskDescription: 'x' });
+    expect(theirs.status).toBe(200);
+    expect((await settleSettings((s) => s.lastUsedCase === 'rootralph')).lastUsedCase).toBe('rootralph');
+  });
+});
+
+describe('an admin and the server-wide settings.json', () => {
+  it('still writes it', async () => {
+    const res = await send('PUT', '/api/settings', root, { autoNameSessions: true });
+    expect(res.status).toBe(200);
+    expect(res.body.success).toBe(true);
+    expect(JSON.parse(await readSettingsBytes()).autoNameSessions).toBe(true);
+  });
+});
diff --git a/test/settings-admin-only-ui.test.ts b/test/settings-admin-only-ui.test.ts
new file mode 100644
index 00000000..525e4b1a
--- /dev/null
+++ b/test/settings-admin-only-ui.test.ts
@@ -0,0 +1,400 @@
+/**
+ * @fileoverview Multi-user mode: a NON-ADMIN's browser and the admin-only settings writes.
+ *
+ * In multi-user mode PUT /api/settings (and PUT /api/execution/model-config,
+ * PUT /api/cases/order) answer 403 FORBIDDEN for a non-admin (system-routes.ts,
+ * case-routes.ts), because settings.json is one file for the whole server. The page
+ * must not break on that:
+ *  - App Settings Save/Apply keeps saving the per-device keys to localStorage exactly
+ *    as before, sends no settings PUT and no model-config PUT, keeps every SYNCED key
+ *    at the server's value, and shows ONE "only an admin" toast, only when the user
+ *    really changed a synced setting (an untouched synced key that no admin ever
+ *    stored must not read as a change: that is what the form baseline is for).
+ *  - The background writes (run mode, respawn presets, last used case, case order,
+ *    the respawn-preset migration on load, the tunnel toggles) are not sent.
+ *  - Admins and single-user mode send everything as before.
+ *  - Both toasts read in Chinese under zh-CN.
+ *
+ * The real modules run inside a JSDOM window (runScripts: 'outside-only') with the
+ * real index.html, so the form is the real App Settings form. Port: none.
+ */
+
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import vm from 'node:vm';
+import { JSDOM } from 'jsdom';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { SettingsUpdateSchema } from '../src/web/schemas.js';
+
+const PUBLIC = join(process.cwd(), 'src/web/public');
+const read = (name: string) => readFileSync(join(PUBLIC, name), 'utf8');
+const INDEX = read('index.html');
+const I18N = read('i18n.js');
+const SETTINGS_UI = read('settings-ui.js');
+const SESSION_UI = read('session-ui.js');
+const RESPAWN_UI = read('respawn-ui.js');
+const SCRIPTS = [read('constants.js'), read('app.js'), SETTINGS_UI];
+
+const DESKTOP_KEY = 'codeman-app-settings';
+const SAVE_TOAST = 'Saved on this device. Server-wide settings can only be changed by an admin.';
+const ADMIN_TOAST = 'Server-wide settings can only be changed by an admin';
+
+type Settings = Record<string, unknown>;
+type Who = 'non-admin' | 'admin' | 'single-user';
+const IDENTITY: Record<Who, Settings> = {
+  'non-admin': { username: 'bob', role: 'user', multiUser: true },
+  admin: { username: 'root', role: 'admin', multiUser: true },
+  'single-user': { username: 'admin', role: 'admin', multiUser: false },
+};
+
+/**
+ * Methods that run for real. Every other method is a no-op: openAppSettings() and
+ * saveAppSettings() fan out into panels (voice, webhook, tunnel, push, header) this
+ * file is not about.
+ */
+const REAL = new Set([
+  'openAppSettings',
+  'saveAppSettings',
+  'applyAppSettings',
+  'loadAppSettingsFromServer',
+  'loadAppSettingsFromStorage',
+  'saveAppSettingsToStorage',
+  'getSettingsStorageKey',
+  'getDefaultSettings',
+  'tabCliLogosEnabled',
+  'resolveTabArrangement',
+  'resolveTabStateOrder',
+  'resolveHeaderStatsStyle',
+  'resolveSessionSidebarFontSize',
+  'planUsageChipEnabled',
+  'planUsageCollectionFlip',
+  'loadModelConfigForSettings',
+  'saveModelConfigFromSettings',
+  '_modelConfigFromSettingsForm',
+  '_settingsReadOnly',
+  '_captureSettingsFormBaseline',
+  '_keepServerSyncedSettings',
+]);
+
+/** Methods the load/save paths call that other modules add to the prototype. */
+const ELSEWHERE = [
+  '_updateLocalEchoState',
+  'renderProjectInsightsPanel',
+  'updateSubagentWindowVisibility',
+  'showWelcome',
+  '_applyRunMode',
+];
+
+const windows: { close(): void }[] = [];
+afterEach(() => {
+  for (const win of windows.splice(0)) win.close();
+});
+
+const tick = () => new Promise((resolve) => setTimeout(resolve, 0));
+
+/**
+ * Boot index.html with constants.js, app.js and settings-ui.js, as `who`, with `stored` as
+ * this device's blob and `server` as GET /api/settings (merged in by the real loader, which
+ * is also what publishes the display-key list the non-admin save reads).
+ */
+async function boot(who: Who, stored: Settings, server: Settings) {
+  const dom = new JSDOM(INDEX, { url: 'http://localhost/', runScripts: 'outside-only' });
+  const win = dom.window as unknown as Window &
+    typeof globalThis & { eval(src: string): void; __App: any; __codemanUser: Settings; fetch: unknown };
+  windows.push(win);
+  if (win.document.readyState !== 'complete') await new Promise((resolve) => win.addEventListener('load', resolve));
+  win.setInterval = (() => 0) as unknown as typeof win.setInterval;
+  win.localStorage.setItem(DESKTOP_KEY, JSON.stringify(stored));
+  const fetchCalls: { url: string; method: string; body?: string }[] = [];
+  win.fetch = vi.fn(async (url: string, opts: { method?: string; body?: string } = {}) => {
+    fetchCalls.push({ url, method: opts.method || 'GET', body: opts.body });
+    const data = url === '/api/execution/model-config' ? { defaultModel: 'sonnet', showRecommendations: true } : {};
+    return { ok: true, status: 200, json: async () => ({ success: true, data }) };
+  });
+  win.eval(
+    [
+      `var MobileDetection = {
+         getDeviceType: () => 'desktop',
+         isHandheldDevice: () => false,
+         isMobile: () => false,
+         isTouchDevice: () => false,
+       };
+       var KeyboardHandler = {}, SwipeHandler = {}, DeepgramProvider = {}, NotificationManager = function () {};
+       var KeyboardAccessoryBar = { setMode() {} };
+       var VoiceInput = { _getDeepgramConfig: () => ({}), _saveDeepgramConfig() {}, refreshClaudeStatus: () => Promise.resolve() };
+       var FocusTrap = function () { this.activate = () => {}; this.deactivate = () => {}; };
+       var DEFAULT_VOICE_KEYTERMS = '';`,
+      ...SCRIPTS,
+      'window.__App = CodemanApp;',
+    ].join('\n')
+  );
+  win.__codemanUser = IDENTITY[who];
+  const target = Object.create(win.__App.prototype);
+  target.sessions = new Map();
+  target.sessionOrder = [];
+  target._apiPut = vi.fn(async () => ({ ok: true }));
+  target.showToast = vi.fn();
+  target.closeAppSettings = vi.fn();
+  const noop = () => undefined;
+  for (const name of ELSEWHERE) target[name] = noop;
+  const app = new Proxy(target, {
+    get(t, key, receiver) {
+      const value = Reflect.get(t, key, receiver);
+      const stubbed =
+        typeof key === 'string' && typeof value === 'function' && !Object.hasOwn(t, key) && !REAL.has(key);
+      return stubbed ? noop : value;
+    },
+  }) as any;
+  await app.loadAppSettingsFromServer(Promise.resolve(server));
+  const doc = win.document;
+  const box = (id: string) => doc.getElementById(id) as HTMLInputElement;
+  const storedBlob = () => JSON.parse(win.localStorage.getItem(DESKTOP_KEY) || '{}') as Settings;
+  const toasts = () => (target.showToast.mock.calls as unknown[][]).map((c) => c[0]);
+  const puts = () => fetchCalls.filter((c) => c.method === 'PUT');
+  return { win, doc, app, target, box, storedBlob, toasts, puts };
+}
+
+// What the server already holds for this instance: an admin has saved App Settings before.
+const SERVER: Settings = { autoNameSessions: false, workspaceHooksEnabled: true, claudeMode: 'auto' };
+
+describe('a non-admin in multi-user mode saving App Settings', () => {
+  it('keeps the per-device keys, sends no PUT, keeps the synced key at the server value, and toasts once', async () => {
+    const { app, target, box, storedBlob, toasts, puts } = await boot('non-admin', { ...SERVER }, SERVER);
+    await open_(app);
+    box('appSettingsTabTwoRows').checked = true; // per-device (displayKeys)
+    box('appSettingsAutoNameSessions').checked = true; // synced, server-wide
+    await app.saveAppSettings();
+
+    expect(target._apiPut).not.toHaveBeenCalled();
+    expect(puts()).toEqual([]);
+    expect(storedBlob().tabTwoRows).toBe(true);
+    expect(storedBlob().autoNameSessions).toBe(false);
+    expect(toasts()).toEqual([SAVE_TOAST]);
+  });
+
+  it('says "Settings saved" (no admin toast) when only per-device keys changed', async () => {
+    const { app, target, box, storedBlob, toasts, puts } = await boot('non-admin', { ...SERVER }, SERVER);
+    await open_(app);
+    box('appSettingsTabTwoRows').checked = true;
+    await app.saveAppSettings();
+
+    expect(target._apiPut).not.toHaveBeenCalled();
+    expect(puts()).toEqual([]);
+    expect(storedBlob().tabTwoRows).toBe(true);
+    expect(toasts()).toEqual(['Settings saved']);
+  });
+
+  it('does not read untouched synced keys no admin ever stored as a change', async () => {
+    // A fresh instance: the server holds nothing, so the blob has no synced keys while the
+    // form shows their defaults. Comparing against the blob would toast on every save.
+    const { app, box, storedBlob, toasts, puts } = await boot('non-admin', {}, {});
+    await open_(app);
+    box('appSettingsTabTwoRows').checked = true;
+    await app.saveAppSettings();
+    expect(toasts()).toEqual(['Settings saved']);
+    expect(puts()).toEqual([]);
+    // The synced keys the form read stay absent (the server default), never the form's copy.
+    expect('autoNameSessions' in storedBlob()).toBe(false);
+    expect('claudeMode' in storedBlob()).toBe(false);
+    expect(storedBlob().tabTwoRows).toBe(true);
+
+    // And a real change there still gets the one admin toast.
+    await open_(app);
+    box('appSettingsAutoNameSessions').checked = true;
+    await app.saveAppSettings();
+    expect(toasts()).toEqual(['Settings saved', SAVE_TOAST]);
+    expect('autoNameSessions' in storedBlob()).toBe(false);
+  });
+
+  it('does not send the model config either, and folds a change to it into the same one toast', async () => {
+    const { app, doc, toasts, puts } = await boot('non-admin', { ...SERVER }, SERVER);
+    await open_(app);
+    (doc.getElementById('appSettingsDefaultModel') as HTMLSelectElement).value = 'opus';
+    await app.saveAppSettings();
+    expect(puts()).toEqual([]);
+    expect(toasts()).toEqual([SAVE_TOAST]);
+  });
+
+  it('Apply behaves the same: nothing sent, the modal stays open', async () => {
+    const { app, target, box, toasts, puts } = await boot('non-admin', { ...SERVER }, SERVER);
+    await open_(app);
+    box('appSettingsAutoNameSessions').checked = true;
+    await app.applyAppSettings();
+    expect(target._apiPut).not.toHaveBeenCalled();
+    expect(puts()).toEqual([]);
+    expect(target.closeAppSettings).not.toHaveBeenCalled();
+    expect(toasts()).toEqual([SAVE_TOAST]);
+  });
+});
+
+describe('an admin, and single-user mode, saving App Settings', () => {
+  for (const who of ['admin', 'single-user'] as const) {
+    it(`${who}: sends the settings PUT and the model config as before`, async () => {
+      const { app, target, box, storedBlob, toasts, puts } = await boot(who, { ...SERVER }, SERVER);
+      await open_(app);
+      box('appSettingsAutoNameSessions').checked = true;
+      await app.saveAppSettings();
+
+      expect(target._apiPut).toHaveBeenCalledTimes(1);
+      const [path, body] = target._apiPut.mock.calls[0] as [string, Settings];
+      expect(path).toBe('/api/settings');
+      expect(body.autoNameSessions).toBe(true);
+      expect(SettingsUpdateSchema.safeParse(body).error?.issues ?? []).toEqual([]);
+      expect(puts().map((p) => p.url)).toEqual(['/api/execution/model-config']);
+      expect(storedBlob().autoNameSessions).toBe(true);
+      expect(toasts()).toEqual(['Settings saved']);
+    });
+  }
+});
+
+/** Open App Settings and let its async model-config read land, as a user would. */
+async function open_(app: { openAppSettings(): void }) {
+  app.openAppSettings();
+  await tick();
+  await tick();
+}
+
+// ─── Background writes (vm harness: settings-ui.js + session-ui.js + respawn-ui.js) ───
+
+function loadBackground(who: Who) {
+  const storage = new Map<string, string>();
+  const elements: Record<string, any> = {
+    quickStartCase: { value: 'mine' },
+    welcomeTunnelBtn: { classList: { contains: () => false }, disabled: false },
+    runModeMenu: { classList: { remove: () => {} } },
+    runBtn: { className: '', nextElementSibling: { className: '' } },
+    runBtnLabel: { textContent: '' },
+  };
+  const CodemanApp = function CodemanApp(this: any) {};
+  const fetchMock = vi.fn(async () => ({ ok: true, status: 200, json: async () => ({ success: true, data: {} }) }));
+  const confirmMock = vi.fn(() => true);
+  const context = vm.createContext({
+    CodemanApp,
+    VoiceInput: {},
+    window: { __codemanUser: IDENTITY[who] },
+    localStorage: {
+      getItem: (key: string) => storage.get(key) ?? null,
+      setItem: (key: string, value: string) => storage.set(key, value),
+    },
+    document: { getElementById: (id: string) => elements[id] ?? null },
+    fetch: fetchMock,
+    confirm: confirmMock,
+    console,
+  });
+  vm.runInContext(SETTINGS_UI, context, { filename: 'settings-ui.js' });
+  vm.runInContext(SESSION_UI, context, { filename: 'session-ui.js' });
+  vm.runInContext(RESPAWN_UI, context, { filename: 'respawn-ui.js' });
+  const app = new (CodemanApp as any)();
+  app.loadAppSettingsFromStorage = () => ({});
+  app.saveAppSettingsToStorage = () => {};
+  app._apiPut = vi.fn(() => Promise.resolve({ ok: true }));
+  app.showToast = vi.fn();
+  app.loadQuickStartCases = vi.fn(async () => {});
+  app.renderCaseManageList = vi.fn();
+  app.closeTunnelPanel = vi.fn();
+  app._showTunnelConnecting = vi.fn();
+  app._pollTunnelStatus = vi.fn();
+  app._dismissTunnelConnecting = vi.fn();
+  app._updateWelcomeTunnelBtn = vi.fn();
+  app._updateTunnelIndicator = vi.fn();
+  return { app, fetchMock, confirmMock, storage };
+}
+
+const settingsPuts = (b: ReturnType<typeof loadBackground>) => [
+  ...b.app._apiPut.mock.calls.filter((c: unknown[]) => c[0] === '/api/settings'),
+  ...b.fetchMock.mock.calls.filter((c: unknown[]) => c[0] === '/api/settings' || c[0] === '/api/cases/order'),
+];
+
+describe('background writes', () => {
+  it('a non-admin sends none of them, and the device keeps its own copy', async () => {
+    const b = loadBackground('non-admin');
+    b.app.setRunMode('codex');
+    expect(b.storage.get('codeman_runMode')).toBe('codex');
+    b.app.saveRespawnPresets([{ id: 'p', name: 'mine' }]);
+    expect(JSON.parse(b.storage.get('codeman-respawn-presets')!)).toEqual([{ id: 'p', name: 'mine' }]);
+    await b.app.saveLastUsedCase('mine');
+    await b.app.toggleTunnelFromWelcome();
+    await b.app._tunnelPanelToggle(true);
+    expect(settingsPuts(b)).toEqual([]);
+    expect(b.app.showToast.mock.calls.map((c: unknown[]) => c[0])).toEqual([ADMIN_TOAST, ADMIN_TOAST]);
+  });
+
+  it('a non-admin case reorder is not sent: one toast, and the list goes back to the server order', async () => {
+    const b = loadBackground('non-admin');
+    await b.app.saveCaseOrder(['b', 'a']);
+    expect(settingsPuts(b)).toEqual([]);
+    expect(b.app.showToast.mock.calls.map((c: unknown[]) => c[0])).toEqual([ADMIN_TOAST]);
+    expect(b.app.loadQuickStartCases).toHaveBeenCalledWith('mine');
+    expect(b.app.renderCaseManageList).toHaveBeenCalled();
+  });
+
+  it('a non-admin never runs the respawn-preset migration PUT on page load', async () => {
+    const b = loadBackground('non-admin');
+    b.storage.set('codeman-respawn-presets', JSON.stringify([{ id: 'p' }]));
+    await b.app.loadAppSettingsFromServer(Promise.resolve({ autoNameSessions: false }));
+    expect(settingsPuts(b)).toEqual([]);
+  });
+
+  it('a 403 FORBIDDEN on a tunnel enable is the admin-only answer, not the no-password prompt', async () => {
+    const b = loadBackground('admin');
+    const refused = await b.app._handleTunnelEnableRefusal({
+      ok: false,
+      status: 403,
+      json: async () => ({ success: false, error: 'You do not have permission', errorCode: 'FORBIDDEN' }),
+    });
+    expect(refused).toBe(true);
+    expect(b.confirmMock).not.toHaveBeenCalled();
+    expect(b.fetchMock).not.toHaveBeenCalled();
+    expect(b.app.showToast.mock.calls.map((c: unknown[]) => c[0])).toEqual([ADMIN_TOAST]);
+  });
+
+  for (const who of ['admin', 'single-user'] as const) {
+    it(`${who}: every background write is still sent`, async () => {
+      const b = loadBackground(who);
+      b.app.setRunMode('codex');
+      b.app.saveRespawnPresets([{ id: 'p' }]);
+      await b.app.saveLastUsedCase('mine');
+      await b.app.saveCaseOrder(['b', 'a']);
+      expect(b.app._apiPut.mock.calls.map((c: unknown[]) => c[0])).toEqual(['/api/settings', '/api/settings']);
+      expect(b.fetchMock.mock.calls.map((c: unknown[]) => c[0])).toEqual(['/api/settings', '/api/cases/order']);
+      b.storage.set('codeman-respawn-presets', JSON.stringify([{ id: 'p' }]));
+      b.app._apiPut.mockClear();
+      await b.app.loadAppSettingsFromServer(Promise.resolve({}));
+      expect(b.app._apiPut).toHaveBeenCalledWith('/api/settings', { respawnPresets: [{ id: 'p' }] });
+    });
+  }
+});
+
+// ─── zh-CN ───
+
+describe('the admin-only toasts in zh-CN', () => {
+  type Api = { t(s: string): string; configure(o: Record<string, string>): void };
+  function translator(language: string) {
+    const dom = new JSDOM('<!doctype html><html><body></body></html>', {
+      runScripts: 'outside-only',
+      url: 'http://localhost/',
+    });
+    windows.push(dom.window);
+    vm.runInContext(I18N, dom.getInternalVMContext(), { filename: 'i18n.js' });
+    const api = (dom.window as unknown as { CodemanI18n: Api }).CodemanI18n;
+    api.configure({ language });
+    return api;
+  }
+
+  it('finds both toasts in the code that shows them', () => {
+    expect(SETTINGS_UI).toContain(`this.showToast('${SAVE_TOAST}', 'warning')`);
+    expect(SETTINGS_UI).toContain(`this.showToast('${ADMIN_TOAST}', 'warning')`);
+    expect(SESSION_UI).toContain(`this.showToast('${ADMIN_TOAST}', 'warning')`);
+  });
+
+  it('translates both, and leaves English as it is', () => {
+    const zh = translator('zh-CN');
+    const en = translator('en');
+    for (const text of [SAVE_TOAST, ADMIN_TOAST]) {
+      const t = zh.t(text);
+      expect(t, text).not.toBe(text);
+      expect(/[A-Za-z]/.test(t), t).toBe(false);
+      expect(en.t(text)).toBe(text);
+    }
+  });
+});