feat(offline): offline lobby lists + creates local vs_ai games

In offline mode the lobby now shows only the device-local games and its
New-vs-AI entry creates one through the in-browser engine — the visible
payoff of the offline mode.

- LocalSource.list() reconstructs a lobby GameView per stored local game by
  replay, exposed through the lazy gamesource proxy; unit-tested via an
  in-memory store.
- Lobby.load() branches on offlineMode: lists local games and skips every
  gateway call (no online games/invitations/incoming); the Stats tab is
  disabled offline.
- NewGame offline: find() creates a device-local vs_ai game via
  LocalSource.create using the profile's advertised dict version + a local
  seed; the friends flow and the random-opponent option are hidden, and the
  variant picker / Start are enabled offline (were gated on connection).
- id.ts: newLocalGameId + randomSeed (tested).

Docs: ARCHITECTURE + FUNCTIONAL(+ru) offline-mode section.

Deferred to fast-follow: the Settings Friends/Profile/Feedback affordance
gating, the flip-to-offline readiness wait, the offline mock e2e (needs
mock-dawg support), and the local-hint UI. The offline flow is verified on
the test contour — the mock e2e cannot enter offline mode (the toggle is
gated to an installed PWA).

docs/ARCHITECTURE.md

@@ -1248,8 +1248,12 @@ and the Connect stream and runtime API POSTs are never precached nor intercepted
 never served stale. This satisfies Chromium's installability requirement (a registered SW, needed
 for install on Android) and powers the opt-in **offline mode** (in progress): a deliberate, device-scoped Settings
 toggle — distinct from the transient gateway-reachability signal — that tints the header blue with
-an *Offline* chip and confines play to on-device `vs_ai` games. To have data ready before the
+an *Offline* chip and confines play to on-device `vs_ai` games. The **offline lobby lists only those
-switch, the **Profile advertises the current dictionary version per variant** (`dict_versions`,
+device-local games** (reconstructed by replaying the IndexedDB move journal) and its New-vs-AI entry
+creates one through the in-browser engine — the same game screen then drives it, the robot replying
+locally; online-only affordances (the Stats tab, the friend/random options in New Game) are disabled
+or hidden. To have data ready before the switch, the **Profile advertises the current dictionary
+version per variant** (`dict_versions`,
 filled from the registry on the existing cold-start profile request — no extra round-trip), and an
 eligible installed PWA (standalone web + confirmed email) **background-preloads** those dictionaries
 — on lobby entry and on a variant-preference change — through the same three-tier loader, retried

docs/FUNCTIONAL.md

@@ -256,6 +256,18 @@ the same occasional move against its plan that fades out by the endgame), and ch
 add-friend are off. AI games are **practice** — they never count toward a player's
 statistics.
 
+### Offline mode
+An installed web PWA signed in with a confirmed email can switch to a deliberate **offline mode**
+(Settings → Play mode). Offline, the app never touches the network: the header turns blue with an
+*Offline* chip, the lobby lists only the games stored on the device, and online-only surfaces are
+disabled or hidden (the Stats tab; the *with friends* and *random opponent* options in New Game).
+Only **vs_ai** games are playable — New Game creates a device-local game against the robot, which
+plays entirely in the browser with no backend. Local games are kept on the device, visible only in
+offline mode, and never sync to the account. So a game can be created and played with no connection,
+the app quietly preloads the dictionaries for the player's enabled variants while still online, and
+(once installed) launches from a precached shell even with no network. The mode is device-scoped and
+sticky across launches.
+
 ### Social: friends, block, chat, nudge
 Become friends in two ways: redeem a **one-time code** the other player issues (six
 digits, valid for twelve hours), or send a **request to someone you have played

docs/FUNCTIONAL_ru.md

@@ -261,6 +261,18 @@ e-mail) либо ввод фразы. Активные игры форфейтя
 паузы), сохраняет ту же силу (по-прежнему играет на победу лишь примерно в 40% партий, с теми же
 редкими ходами вопреки плану, затухающими к эндшпилю), а чат, nudge и «добавить в друзья» выключены. Партии с ИИ — это **тренировка**: они не идут в статистику игрока.
 
+### Офлайн-режим
+Установленный веб-PWA со входом по подтверждённой почте может переключиться в осознанный
+**офлайн-режим** (Настройки → Режим игры). В офлайне приложение не обращается к сети: шапка синеет с
+меткой *Офлайн*, лобби показывает только сохранённые на устройстве игры, а сетевые поверхности
+отключены или скрыты (вкладка Статистика; варианты «с другом» и «случайный соперник» в Новой игре).
+Играть можно только в **vs_ai** — Новая игра создаёт локальную игру против робота, который ходит
+целиком в браузере без бэкенда. Локальные игры хранятся на устройстве, видны только в офлайн-режиме и
+никогда не синхронизируются с аккаунтом. Чтобы игру можно было создать и сыграть без связи, приложение
+заранее, пока ещё онлайн, подгружает словари включённых игроком вариантов и (после установки)
+запускается из прекешированного шелла даже без сети. Режим привязан к устройству и сохраняется между
+запусками.
+
 ### Социальное: друзья, блок, чат, nudge
 Подружиться можно двумя способами: погасить **одноразовый код**, который выпускает
 другой игрок (шесть цифр, действует двенадцать часов), либо отправить **заявку

ui/src/lib/gamesource.ts

@@ -39,6 +39,7 @@ export const localSource = {
   draftGet: (_id) => load().then((s) => s.draftGet()),
   draftSave: (_id, _json) => load().then((s) => s.draftSave()),
   create: (opts) => load().then((s) => s.create(opts)),
+  list: () => load().then((s) => s.list()),
   // events must return the unsubscribe synchronously (the screen subscribes in onMount), so it wires
   // the real subscription once the engine loads and, until then, cancels a pending subscribe.
   events: (id, onEvent) => {
@@ -52,7 +53,7 @@ export const localSource = {
       unsub();
     };
   },
-} satisfies GameLoopSource & Pick<LocalSource, 'events' | 'create'>;
+} satisfies GameLoopSource & Pick<LocalSource, 'events' | 'create' | 'list'>;
 
 /**
  * gameSource returns the source that runs the game with the given id: the local engine for a local

ui/src/lib/localgame/id.test.ts

@@ -0,0 +1,24 @@
+import { describe, it, expect } from 'vitest';
+import { LOCAL_ID_PREFIX, isLocalGameId, newLocalGameId, randomSeed } from './id';
+
+describe('local game id helpers', () => {
+  it('recognises local ids by prefix', () => {
+    expect(isLocalGameId(LOCAL_ID_PREFIX + 'x')).toBe(true);
+    expect(isLocalGameId('deadbeef')).toBe(false);
+  });
+
+  it('mints unique local ids', () => {
+    const a = newLocalGameId();
+    const b = newLocalGameId();
+    expect(isLocalGameId(a)).toBe(true);
+    expect(a).not.toBe(b);
+  });
+
+  it('produces a bigint seed in the 32-bit range', () => {
+    for (let i = 0; i < 50; i++) {
+      const s = randomSeed();
+      expect(typeof s).toBe('bigint');
+      expect(s >= 0n && s <= 0xffffffffn).toBe(true);
+    }
+  });
+});

ui/src/lib/localgame/id.ts

@@ -10,3 +10,14 @@ export const LOCAL_ID_PREFIX = 'local:';
 export function isLocalGameId(id: string): boolean {
   return id.startsWith(LOCAL_ID_PREFIX);
 }
+
+/** newLocalGameId mints a fresh, device-unique local game id (time + random suffix — no crypto API,
+ *  so it also works on the older engines the SPA still supports). */
+export function newLocalGameId(): string {
+  return `${LOCAL_ID_PREFIX}${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
+}
+
+/** randomSeed returns a random 32-bit seed for a new local game's deterministic bag. */
+export function randomSeed(): bigint {
+  return BigInt(Math.floor(Math.random() * 0xffffffff));
+}

ui/src/lib/localgame/source.list.test.ts

@@ -0,0 +1,61 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import type { LocalGameRecord } from './serialize';
+
+// An in-memory stand-in for the IndexedDB store, so list() — which reads the *persisted* records,
+// not the source's in-memory cache — can be exercised in the node env (the real store is a
+// best-effort no-op without IndexedDB). Declared before the vi.mock factory that closes over it.
+const store = new Map<string, LocalGameRecord>();
+vi.mock('./store', () => ({
+  saveLocalGame: async (r: LocalGameRecord) => void store.set(r.id, r),
+  getLocalGame: async (id: string) => store.get(id) ?? null,
+  listLocalGames: async () => [...store.values()],
+  deleteLocalGame: async (id: string) => void store.delete(id),
+}));
+vi.mock('../dict', () => ({
+  getDawg: async () => {
+    const { Dawg } = await import('../dict/dawg');
+    const { readFileSync } = await import('node:fs');
+    return new Dawg(new Uint8Array(readFileSync(new URL('../dict/testdata/sample_en.dawg', import.meta.url))));
+  },
+}));
+
+import { LocalSource } from './source';
+import type { Seat } from './serialize';
+
+const seats: Seat[] = [
+  { kind: 'human', name: 'You' },
+  { kind: 'robot', name: 'Robot' },
+];
+const opts = (id: string, seed: bigint) => ({
+  id,
+  variant: 'scrabble_en' as const,
+  dictVersion: 'sample',
+  seed,
+  multipleWords: true,
+  seats,
+});
+
+beforeEach(() => store.clear());
+
+describe('LocalSource.list', () => {
+  it('is empty when no games are stored', async () => {
+    expect(await new LocalSource().list()).toEqual([]);
+  });
+
+  it('returns a lobby GameView for every stored local game', async () => {
+    const src = new LocalSource();
+    await src.create(opts('local:a', 1n));
+    await src.create(opts('local:b', 2n));
+    const list = await src.list();
+    expect(new Set(list.map((g) => g.id))).toEqual(new Set(['local:a', 'local:b']));
+    expect(list.every((g) => g.vsAi && g.status === 'active')).toBe(true);
+  });
+
+  it('reconstructs a game persisted by a previous session (not in the source cache)', async () => {
+    // Seed the store via one source, then list from a fresh source whose in-memory cache is empty.
+    await new LocalSource().create(opts('local:old', 7n));
+    const list = await new LocalSource().list();
+    expect(list.map((g) => g.id)).toEqual(['local:old']);
+    expect(list[0].variant).toBe('scrabble_en');
+  });
+});

ui/src/lib/localgame/source.ts

@@ -10,7 +10,7 @@
 
 import { LocalGame, type LocalMove } from './engine';
 import { serializeGame, replayGame, type LocalGameRecord, type Seat as LocalSeat } from './serialize';
-import { getLocalGame, saveLocalGame } from './store';
+import { getLocalGame, saveLocalGame, listLocalGames } from './store';
 import { RULESETS } from './ruleset';
 import { getDawg } from '../dict';
 import { LOCAL_ID_PREFIX, isLocalGameId } from './id';
@@ -131,6 +131,26 @@ export class LocalSource implements GameLoopSource {
     return this.stateView(entry);
   }
 
+  /**
+   * list returns a lobby GameView for every stored local game, most-recently-updated first, so the
+   * offline lobby renders them with the same card machinery as the online games. Each is
+   * reconstructed by replay; a record whose dictionary is unavailable (e.g. offline without its
+   * dawg) is skipped, since it cannot be rendered — never throws.
+   */
+  async list(): Promise<GameView[]> {
+    const records = await listLocalGames();
+    records.sort((a, b) => b.updatedAtUnix - a.updatedAtUnix);
+    const views: GameView[] = [];
+    for (const record of records) {
+      try {
+        views.push(this.gameView(await this.load(record.id)));
+      } catch {
+        /* a record that cannot be replayed (its dawg is not cached offline) is left out */
+      }
+    }
+    return views;
+  }
+
   async gameState(gameId: string): Promise<StateView> {
     return this.stateView(await this.load(gameId));
   }

ui/src/screens/Lobby.svelte

@@ -13,7 +13,8 @@
   import { badgeKind } from '../lib/unread';
   import { getLobby, setLobby } from '../lib/lobbycache';
   import { preloadGames } from '../lib/preload';
-  import { kickDictPreload } from '../lib/offline.svelte';
+  import { kickDictPreload, offlineMode } from '../lib/offline.svelte';
+  import { localSource } from '../lib/gamesource';
   import { gamePhase, groupGames, orderedSeats, scoreStanding, shouldBlink, type LobbyPhase } from '../lib/lobbysort';
   import type { AccountRef, GameView, Invitation } from '../lib/model';
   import { VARIANT_FLAG, VARIANT_RULES } from '../lib/variants';
@@ -34,6 +35,19 @@
   const settingsBadge = $derived(app.notifications + (app.feedbackReplyUnread ? 1 : 0));
 
   async function load() {
+    // Deliberate offline mode: never touch the network. The lobby shows only the device-local
+    // vs_ai games (reconstructed from the store) plus the New-vs-AI entry; there are no online
+    // games, invitations or incoming requests to fetch.
+    if (offlineMode.active) {
+      games = await localSource.list();
+      invitations = [];
+      incoming = [];
+      atGameLimit = false;
+      app.notifications = 0;
+      setLobby({ games, invitations, incoming, atGameLimit });
+      app.lobbyReady = true;
+      return;
+    }
     try {
       const list = await gateway.gamesList();
       games = list.games;
@@ -341,7 +355,7 @@
       <button class="tab" disabled={atGameLimit} onclick={() => navigate('/new')}>
         <span class="sq" data-coach="lobby-new">🎲</span><span class="lbl">{t('lobby.new')}</span>
       </button>
-      <button class="tab" onclick={() => navigate('/stats')}>
+      <button class="tab" disabled={offlineMode.active} onclick={() => navigate('/stats')}>
         <span class="sq" data-coach="lobby-stats">✏️</span><span class="lbl">{t('lobby.stats')}</span>
       </button>
       <button class="tab" onclick={() => navigate('/settings')}>

ui/src/screens/NewGame.svelte

@@ -4,6 +4,9 @@
   import { gateway } from '../lib/gateway';
   import { app, handleError, showToast } from '../lib/app.svelte';
   import { connection } from '../lib/connection.svelte';
+  import { offlineMode } from '../lib/offline.svelte';
+  import { localSource } from '../lib/gamesource';
+  import { newLocalGameId, randomSeed } from '../lib/localgame/id';
   import { navigate } from '../lib/router.svelte';
   import { t, type MessageKey } from '../lib/i18n/index.svelte';
   import type { AccountRef, Variant } from '../lib/model';
@@ -54,6 +57,30 @@
     if (starting) return;
     starting = true;
     try {
+      // Offline mode: create a device-local vs_ai game instead of enqueuing on the backend. The
+      // dictionary version comes from the profile (advertised for exactly this), and the bag is
+      // seeded locally; the same game screen then drives it through the local source.
+      if (offlineMode.active) {
+        const version = app.profile?.dictVersions?.[v];
+        if (!version) {
+          handleError(new Error('dict_unavailable'));
+          return;
+        }
+        const id = newLocalGameId();
+        await localSource.create({
+          id,
+          variant: v,
+          dictVersion: version,
+          seed: randomSeed(),
+          multipleWords: multipleWordsForRequest(v, multipleWords),
+          seats: [
+            { kind: 'human', name: app.profile?.displayName ?? 'You' },
+            { kind: 'robot', name: 'Robot' },
+          ],
+        });
+        navigate(`/game/${id}`);
+        return;
+      }
       const r = await gateway.lobbyEnqueue(v, multipleWordsForRequest(v, multipleWords), opponent === 'ai');
       if (r.game) navigate(`/game/${r.game.id}`);
     } catch (e) {
@@ -117,7 +144,9 @@
 
 <Screen title={t('new.title')} back="/">
   <div class="page">
-      {#if !guest}
+      <!-- Offline mode offers only a local vs_ai game: the friends flow needs the network, so the
+           auto/friends selector is hidden and the auto (vs_ai) flow shows on its own. -->
+      {#if !guest && !offlineMode.active}
         <div class="seg modes">
           <button class="opt" class:active={mode === 'auto'} onclick={() => (mode = 'auto')}>{t('new.auto')}</button>
           <button class="opt" class:active={mode === 'friends'} onclick={() => (mode = 'friends')}>{t('new.withFriends')}</button>
@@ -125,17 +154,19 @@
       {/if}
 
       {#if mode === 'auto'}
-        <div class="seg modes">
+        {#if !offlineMode.active}
-          <button class="opt" class:active={opponent === 'ai'} onclick={() => (opponent = 'ai')}>🤖 {t('new.opponentAI')}</button>
+          <div class="seg modes">
-          <button class="opt" class:active={opponent === 'random'} onclick={() => (opponent = 'random')}>👤 {t('new.opponentRandom')}</button>
+            <button class="opt" class:active={opponent === 'ai'} onclick={() => (opponent = 'ai')}>🤖 {t('new.opponentAI')}</button>
-        </div>
+            <button class="opt" class:active={opponent === 'random'} onclick={() => (opponent = 'random')}>👤 {t('new.opponentRandom')}</button>
+          </div>
+        {/if}
         <div class="variants">
           {#each variants as v (v.id)}
             <button
               class="variant"
               class:selected={selectedAuto === v.id}
               onclick={() => (selectedAuto = v.id)}
-              disabled={!connection.online}
+              disabled={!connection.online && !offlineMode.active}
             >
               <span class="vmain">
                 <span class="vname">{t(v.label)}</span>
@@ -160,7 +191,7 @@
         {#if opponent === 'random'}<p class="searchhint">{t('new.searchHint')}</p>{/if}
         <button
           class="invite"
-          disabled={!selectedAuto || !connection.online || starting}
+          disabled={!selectedAuto || (!connection.online && !offlineMode.active) || starting}
           onclick={() => selectedAuto && find(selectedAuto)}
         >{t('new.start')}</button>
       {:else if friends.length === 0}