feat(ui): explicit offline state inside an online game (+ offline word check)

When an online game loses the connection the game screen now says so and freezes
instead of silently greying out: a "connection lost" banner appears and the rack,
the move controls, the add-friend/block controls and the chat/dictionary entry all
disable (a started move stays a draft, committed by the player on reconnect). It is
driven off the net-state machine (netState.offline), so it also covers the
Telegram/VK mini-apps, where a lost connection was previously mute in-game.

If the player is already in the dictionary when the drop happens, the word check
falls back to the game's pinned on-device dictionary (exact when that dawg is
cached; "unavailable offline" otherwise) and the network-only complaint + external
look-up hide. Chat, when already open, keeps its existing read-only degrade
(send/nudge disable). New pure helper localWordCheck is unit-tested; the in-game
gating gets an e2e.

ui/src/game/CheckScreen.svelte

@@ -2,6 +2,8 @@
   import { onMount } from 'svelte';
   import { gateway } from '../lib/gateway';
   import { gameSource, isLocalGameId } from '../lib/gamesource';
+  import { connection } from '../lib/connection.svelte';
+  import { localWordCheck } from '../lib/dict/check';
   import { handleError, showToast } from '../lib/app.svelte';
   import { t } from '../lib/i18n/index.svelte';
   import { alphabetLetters } from '../lib/alphabet';
@@ -14,8 +16,12 @@
   let { id }: { id: string } = $props();
 
   let variant = $state<Variant>('scrabble_en');
+  let dictVersion = $state('');
   let word = $state('');
   let result = $state<{ word: string; legal: boolean } | null>(null);
+  // unavailable is set when an offline check cannot run because the game's pinned dictionary is not
+  // on the device (not cached/bundled); the panel then shows a neutral "offline" note.
+  let unavailable = $state(false);
   let cooling = $state(false);
   const checked = new Map<string, boolean>();
 
@@ -26,6 +32,7 @@
       // network.
       const st = await gameSource(id).gameState(id, true);
       variant = st.game.variant;
+      dictVersion = st.game.dictVersion;
     } catch (e) {
       handleError(e);
     }
@@ -33,6 +40,7 @@
 
   function onInput(e: Event) {
     word = sanitizeCheckWord((e.target as HTMLInputElement).value, alphabetLetters(variant));
+    unavailable = false;
   }
   // Disabled while cooling, for an already-checked word, or an out-of-range length.
   function canCheck(): boolean {
@@ -43,7 +51,22 @@
     const w = word.trim().toUpperCase();
     cooling = true;
     setTimeout(() => (cooling = false), 5000);
+    unavailable = false;
     try {
+      // Offline in an online game the network check_word would fail, so fall back to the game's own
+      // pinned dictionary read on-device: exact when that dawg is cached/bundled, otherwise the check
+      // is unavailable. A local game already resolves checkWord on-device, so it keeps that path.
+      if (!isLocalGameId(id) && !connection.online) {
+        const legal = await localWordCheck(variant, dictVersion, w);
+        if (legal === null) {
+          result = null;
+          unavailable = true;
+          return;
+        }
+        checked.set(w, legal);
+        result = { word: w, legal };
+        return;
+      }
       const r = await gameSource(id).checkWord(id, w, variant);
       checked.set(w, r.legal);
       result = { word: w, legal: r.legal };
@@ -73,7 +96,9 @@
     />
     <button onclick={runCheck} disabled={!canCheck()}>{t('game.check')}</button>
   </div>
-  {#if result}
+  {#if unavailable}
+    <p class="verdict">{t('game.checkOffline')}</p>
+  {:else if result}
     <p class="verdict" class:ok={result.legal} class:bad={!result.legal}>
       {result.legal
         ? t('game.wordLegal', { word: result.word })
@@ -82,10 +107,10 @@
     <div class="actions">
       <!-- Complaints go to the admin over the network; a local (offline) game has no backend to
            receive them, so the control is dropped there. -->
-      {#if !isLocalGameId(id)}
+      {#if !isLocalGameId(id) && connection.online}
         <button class="complain" onclick={complain}>{t('game.complain')}</button>
       {/if}
-      {#if result.legal}
+      {#if result.legal && connection.online}
         <a
           class="lookup"
           href={dictionaryLookupUrl(result.word, variant)}

ui/src/game/Game.svelte

@@ -15,6 +15,7 @@
   import { app, handleError, showToast, markChatRead, seedChatUnread } from '../lib/app.svelte';
   import { connection } from '../lib/connection.svelte';
   import { offlineMode } from '../lib/offline.svelte';
+  import { netState } from '../lib/netstate.svelte';
   import { maybeShowInterstitial } from '../lib/ads';
   import { GatewayError } from '../lib/client';
   import { t, type MessageKey } from '../lib/i18n/index.svelte';
@@ -63,6 +64,10 @@
   // disabled while disconnected or in offline mode (which also stops the "something went wrong"
   // toasts a blocked call would otherwise raise).
   const netReady = $derived(isLocalGameId(id) || (connection.online && !offlineMode.active));
+  // offlineInGame marks an online game that has lost the connection (confirmed offline, on any
+  // platform including Telegram/VK): the play area shows an explicit "connection lost" banner and
+  // the tray/actions freeze. It follows netState (not offlineMode, which is inert in the mini-apps).
+  const offlineInGame = $derived(!isLocalGameId(id) && netState.offline);
   // Unsubscribes from a local game's robot-reply events (offline only; null for a network game).
   let localUnsub: (() => void) | null = null;
 
@@ -1463,6 +1468,7 @@
     // a local (offline) game, whose seats are account-less: vs_ai, and hotseat's synthetic seat ids.
     if (view?.game.vsAi || isLocalGameId(id)) return false;
     return (
+      netReady &&
       !!s.accountId &&
       !app.profile?.isGuest &&
       s.accountId !== app.session?.userId &&
@@ -1476,7 +1482,7 @@
   // An already-blocked opponent hides it (both controls go, and the name is struck).
   function canBlock(s: { accountId: string; seat: number }): boolean {
     if (view?.game.vsAi || isLocalGameId(id)) return false;
-    return !!s.accountId && !app.profile?.isGuest && s.accountId !== app.session?.userId && !seatBlocked(s);
+    return netReady && !!s.accountId && !app.profile?.isGuest && s.accountId !== app.session?.userId && !seatBlocked(s);
   }
 </script>
 
@@ -1490,6 +1496,9 @@
   selfInset={landscape}
 >
   {#if view}
+    {#if offlineInGame}
+      <div class="offline-banner" role="status">{t('game.offlineBanner')}</div>
+    {/if}
     {#if landscape}
       <div class="game-land">
         <div class="leftpane">
@@ -1607,7 +1616,7 @@
            — so drop the entry only when a local game is finished; an active local game keeps it for
            the Dictionary. An online game always keeps it (chat outlives the game). -->
       {#if !(gameOver && (view.game.vsAi || view.game.hotseat))}
-        <button class="hicon" onclick={() => navigate(`/game/${id}/chat`)} aria-label={t('game.chat')}>
+        <button class="hicon" disabled={!netReady} onclick={() => navigate(`/game/${id}/chat`)} aria-label={t('game.chat')}>
           {#key chatBlink}<span class="chat-ico" class:blink={chatBlink > 0 && !app.reduceMotion}>💬</span>{/key}
         </button>
       {/if}
@@ -1694,6 +1703,7 @@
           draggingId={reorderDragId}
           dropIndex={reorderTo}
           confirm={!gameOver && placement.pending.length > 0 && !recallOverRack ? confirmBtn : undefined}
+          frozen={!netReady}
           ondown={onRackDown}
         />
       {/if}
@@ -2178,6 +2188,17 @@
     color: var(--text-muted);
     padding: 40px;
   }
+  /* An online game that lost the connection: a slim, non-blocking strip at the top of the play area.
+     A solid token background (not color-mix) keeps it visible on the old-WebView floor. */
+  .offline-banner {
+    padding: 7px var(--pad);
+    text-align: center;
+    font-size: 0.85rem;
+    line-height: 1.25;
+    color: var(--text);
+    background: var(--surface-2);
+    border-bottom: 1px solid var(--border);
+  }
   .ghost {
     position: fixed;
     width: 40px;

ui/src/game/Rack.svelte

@@ -13,6 +13,7 @@
     shuffling = false,
     draggingId = null,
     dropIndex = null,
+    frozen = false,
     confirm,
     ondown,
   }: {
@@ -26,6 +27,10 @@
     // the drag ghost stands in) and dropIndex is the slot where a gap opens.
     draggingId?: number | null;
     dropIndex?: number | null;
+    /** frozen disables tile interaction (offline in an online game): tiles cannot be picked up to
+     *  compose or reorder a move until the connection returns. The confirm control is gated
+     *  separately by the parent. */
+    frozen?: boolean;
     /** The confirm-move control, rendered as the fixed 7th slot of the rack while a play is staged
      *  (the parent owns the button and its enablement; the rack only positions it). */
     confirm?: Snippet;
@@ -65,6 +70,7 @@
       class:selected={selected === slot.index}
       class:shift={dropIndex != null && i >= dropIndex}
       data-rack-index={slot.index}
+      disabled={frozen}
       animate:hop={shuffling}
       onpointerdown={(e) => ondown(e, slot.index)}
     >
@@ -114,6 +120,10 @@
     outline: 3px solid var(--accent);
     outline-offset: -3px;
   }
+  /* Frozen (offline in an online game): the tray is inert until the connection returns. */
+  .tile:disabled {
+    opacity: 0.5;
+  }
   /* While reordering, tiles at/after the drop slot slide right to open a gap there (one
      tile width plus the rack gap), so the drop position is visible. */
   .rack.reordering .tile {

ui/src/lib/dict/check.test.ts

@@ -0,0 +1,49 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { setAlphabet } from '../alphabet';
+
+// getDawg is the only side-effecting dependency; stub it so the test exercises localWordCheck's
+// own logic (load -> encode -> membership -> null handling) against a fake reader, not a real DAWG.
+vi.mock('./loader', () => ({ getDawg: vi.fn() }));
+import { getDawg } from './loader';
+import { localWordCheck } from './check';
+
+const mockedGetDawg = vi.mocked(getDawg);
+
+// A tiny cached alphabet so indexForLetter can encode the test words.
+setAlphabet('scrabble_en', [
+  { index: 0, letter: 'A', value: 1 },
+  { index: 1, letter: 'B', value: 3 },
+  { index: 2, letter: 'C', value: 3 },
+]);
+
+describe('localWordCheck', () => {
+  afterEach(() => vi.clearAllMocks());
+
+  it('returns true when the dawg contains the word', async () => {
+    mockedGetDawg.mockResolvedValue({ indexOf: () => 5 } as never);
+    expect(await localWordCheck('scrabble_en', 'v1', 'AB')).toBe(true);
+  });
+
+  it('returns false when the dawg does not contain the word', async () => {
+    mockedGetDawg.mockResolvedValue({ indexOf: () => -1 } as never);
+    expect(await localWordCheck('scrabble_en', 'v1', 'AB')).toBe(false);
+  });
+
+  it('returns null when the dawg is unavailable (offline and uncached)', async () => {
+    mockedGetDawg.mockResolvedValue(null);
+    expect(await localWordCheck('scrabble_en', 'v1', 'AB')).toBe(null);
+  });
+
+  it('encodes the word to alphabet indices for the membership test', async () => {
+    const indexOf = vi.fn(() => 0);
+    mockedGetDawg.mockResolvedValue({ indexOf } as never);
+    await localWordCheck('scrabble_en', 'v1', 'CAB');
+    expect(indexOf).toHaveBeenCalledWith([2, 0, 1]);
+  });
+
+  it('loads the dawg for the pinned (variant, version)', async () => {
+    mockedGetDawg.mockResolvedValue({ indexOf: () => 1 } as never);
+    await localWordCheck('scrabble_en', 'v1.3.0', 'AB');
+    expect(mockedGetDawg).toHaveBeenCalledWith('scrabble_en', 'v1.3.0');
+  });
+});

ui/src/lib/dict/check.ts

@@ -0,0 +1,26 @@
+// Offline word-check fallback for an online game. An online game's dictionary check normally goes to
+// the gateway (game.check_word); while disconnected that call fails, so the check falls back to the
+// game's own pinned dictionary read locally. Using the game's pinned (variant, version) means the
+// answer matches the server's — no divergence — as long as that dawg is available on-device; if it
+// is not cached/bundled offline, the check is simply unavailable (null). The membership test mirrors
+// the local engine's dictionaryHas (encode to alphabet indices, then Dawg.indexOf).
+
+import { getDawg } from './loader';
+import { indexForLetter } from '../alphabet';
+import type { Variant } from '../model';
+
+/**
+ * localWordCheck reports whether word is in the (variant, version) dictionary using the on-device
+ * dawg, or null when that dawg cannot be obtained (offline and neither cached nor bundled). word
+ * must already be sanitised to the variant's alphabet (as the check panel does).
+ */
+export async function localWordCheck(
+  variant: Variant,
+  version: string,
+  word: string,
+): Promise<boolean | null> {
+  const dawg = await getDawg(variant, version);
+  if (!dawg) return null;
+  const idx = Array.from(word, (ch) => indexForLetter(variant, ch));
+  return dawg.indexOf(idx) >= 0;
+}

ui/src/lib/i18n/en.ts

@@ -133,6 +133,8 @@ export const en = {
   'game.complaintSent': 'Thanks, sent for review.',
   'game.check': 'Check',
   'game.checkWait': 'Please wait a moment.',
+  'game.checkOffline': 'Word check is unavailable offline.',
+  'game.offlineBanner': 'Connection lost — your move will send once you’re back online.',
   'game.noHintOptions': 'No options with your letters.',
   'game.thinking': 'thinking…',
 

ui/src/lib/i18n/ru.ts

@@ -133,6 +133,8 @@ export const ru: Record<MessageKey, string> = {
   'game.complaintSent': 'Спасибо, отправлено на проверку.',
   'game.check': 'Проверить',
   'game.checkWait': 'Секунду, пожалуйста.',
+  'game.checkOffline': 'Проверка недоступна офлайн.',
+  'game.offlineBanner': 'Связь потеряна — ход отправится, когда вернётся сеть.',
   'game.noHintOptions': 'Нет вариантов с вашим набором.',
   'game.thinking': 'думает…',