diff --git a/docs/UI_DESIGN.md b/docs/UI_DESIGN.md
index ee92f94..206678b 100644
--- a/docs/UI_DESIGN.md
+++ b/docs/UI_DESIGN.md
@@ -48,7 +48,15 @@ Login uses `Screen`.
   collapse to nothing under reduce-motion. Per-game and lobby in-memory caches
   (`lib/gamecache.ts`, `lib/lobbycache.ts`) render a re-opened game or the lobby instantly
   and refresh in the background, removing the blank-loading flash and the lobby's "draw-in"
-  on lobby ↔ game navigation.
+  on lobby ↔ game navigation. The caches are kept fresh **across** screens, so the instant render
+  is already current and not a stale frame the background refresh then corrects. The single global
+  stream handler (`lib/app.svelte.ts`) is the one place that runs for every live event regardless of
+  the mounted screen, so it owns cross-screen freshness: it upserts the affected game's `GameView`
+  into the lobby snapshot (`patchLobbyGame`) on every game event — opponent move, game-over,
+  opponent-joined, and a match/started game (which it also adds) — and advances a not-currently-viewed
+  game's own cache from the move/over delta (`advanceCached`, skipping the game in view, whose mounted
+  board owns its cache). The game board additionally mirrors the player's **own** move and its own
+  `load()` into the lobby snapshot — the two updates no live event carries.
 - **Telegram integration** (`lib/telegram.ts`): inside the Mini App the colour
   scheme is forced from `Telegram.WebApp.colorScheme` (over the OS `prefers-color-scheme`,
   which leaks into the Telegram Desktop webview and otherwise fights it) and the Settings
diff --git a/ui/src/game/Game.svelte b/ui/src/game/Game.svelte
index 4e1de95..e4c928d 100644
--- a/ui/src/game/Game.svelte
+++ b/ui/src/game/Game.svelte
@@ -20,6 +20,7 @@
   import { alphabetLetters, hasAlphabet } from '../lib/alphabet';
   import { shareOrDownloadGcg } from '../lib/share';
   import { getCachedGame, setCachedGame, type CachedGame } from '../lib/gamecache';
+  import { patchLobbyGame } from '../lib/lobbycache';
   import { applyGameOver, applyMoveDelta, type DeltaResult } from '../lib/gamedelta';
   import { telegramClosingConfirmation, telegramHaptic } from '../lib/telegram';
   import {
@@ -138,6 +139,9 @@
       view = st;
       moves = hist.moves;
       setCachedGame(id, st, hist.moves);
+      // Mirror the fresh status into the lobby snapshot so returning there shows it without a
+      // stale flash before the lobby's own background refresh lands.
+      patchLobbyGame(st.game);
       selected = null;
       await applyDraft(st);
       recompute();
@@ -559,6 +563,7 @@
     view = { game: r.game, seat: r.move.player, rack: r.rack, bagLen: r.bagLen, hintsRemaining: view?.hintsRemaining ?? 0 };
     moves = [...moves, r.move];
     setCachedGame(id, view, moves);
+    patchLobbyGame(r.game);
     rackIds = r.rack.map((_, i) => i);
     placement = newPlacement(r.rack);
     selected = null;
diff --git a/ui/src/lib/app.svelte.ts b/ui/src/lib/app.svelte.ts
index df11a9c..60ca96c 100644
--- a/ui/src/lib/app.svelte.ts
+++ b/ui/src/lib/app.svelte.ts
@@ -25,8 +25,9 @@ import { parseStartParam } from './deeplink';
 import { clearSession, loadPrefs, loadSession, saveSession, savePrefs } from './session';
 import { connection, reportOffline, reportOnline, resetConnection } from './connection.svelte';
 import { isConnectionCode } from './retry';
-import { clearGameCache, setCachedGame } from './gamecache';
-import { clearLobby } from './lobbycache';
+import { clearGameCache, getCachedGame, setCachedGame } from './gamecache';
+import { advanceCached } from './gamedelta';
+import { clearLobby, patchLobbyGame } from './lobbycache';
 import type { BoardLabelMode } from './boardlabels';
 
 export interface Toast {
@@ -144,6 +145,16 @@ export function handleError(err: unknown): void {
   showToast(t(code ? errorKey(code) : 'error.generic'), 'error');
 }
 
+/**
+ * viewingGame reports whether the game board for the given game id is the current route. That screen
+ * maintains its own cache from live events, so the global stream handler must not also advance it (a
+ * double application). The chat / dictionary sub-screens leave the board unmounted, so they do not
+ * count as viewing — there the global handler keeps the cache warm for the return to the board.
+ */
+function viewingGame(gameId: string): boolean {
+  return router.route.name === 'game' && router.route.params.id === gameId;
+}
+
 function openStream(): void {
   closeStream();
   app.streamAlive = true;
@@ -168,15 +179,36 @@ function openStream(): void {
         showToast(t('chat.nudge'), 'info');
       } else if (e.kind === 'your_turn') {
         showToast(t('game.yourTurn'), 'info');
+      } else if (e.kind === 'opponent_moved' || e.kind === 'game_over') {
+        // Keep both caches fresh from any screen, so neither the lobby nor the game flashes a stale
+        // frame on the next navigation. The lobby snapshot is patched from the event's own GameView
+        // (independent of whether this device has the game cached). The per-game cache is advanced
+        // only for a game not currently in view — the mounted game board owns its own cache (see
+        // game/Game.svelte), so skipping it avoids a double apply.
+        if (e.game) patchLobbyGame(e.game);
+        if (!viewingGame(e.gameId)) {
+          const c = advanceCached(getCachedGame(e.gameId), e);
+          if (c) setCachedGame(e.gameId, c.view, c.moves);
+        }
+      } else if (e.kind === 'opponent_joined') {
+        // The opponent took an open game's empty seat: mirror the new status into the lobby snapshot
+        // from any screen. A mounted game board adopts the change in place itself (game/Game.svelte).
+        if (e.state) patchLobbyGame(e.state.game);
       } else if (e.kind === 'match_found') {
-        // Seed the cache from the event's initial state so the game renders instantly on arrival,
-        // then navigate.
-        if (e.state) setCachedGame(e.state.game.id, e.state, []);
+        // Seed both caches from the event's initial state so the game renders instantly on arrival
+        // and the new game is already in the lobby on a later return, then navigate.
+        if (e.state) {
+          setCachedGame(e.state.game.id, e.state, []);
+          patchLobbyGame(e.state.game);
+        }
         navigate(`/game/${e.gameId}`);
       } else if (e.kind === 'notify') {
-        // A started invited game seeds its cache so opening it is instant; the lobby badge stays
-        // on the authoritative refresh.
-        if (e.sub === 'game_started' && e.state) setCachedGame(e.state.game.id, e.state, []);
+        // A started invited game seeds its cache so opening it is instant and lands in the lobby
+        // snapshot from any screen; the lobby badge stays on the authoritative refresh.
+        if (e.sub === 'game_started' && e.state) {
+          setCachedGame(e.state.game.id, e.state, []);
+          patchLobbyGame(e.state.game);
+        }
         void refreshNotifications();
       }
     },
diff --git a/ui/src/lib/gamedelta.test.ts b/ui/src/lib/gamedelta.test.ts
index 5e09f7f..c61c1cc 100644
--- a/ui/src/lib/gamedelta.test.ts
+++ b/ui/src/lib/gamedelta.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vitest';
-import { applyGameOver, applyMoveDelta, seedInitialState, type MoveDelta } from './gamedelta';
+import { advanceCached, applyGameOver, applyMoveDelta, seedInitialState, type MoveDelta } from './gamedelta';
 import type { CachedGame } from './gamecache';
-import type { GameView, MoveRecord, StateView } from './model';
+import type { GameView, MoveRecord, PushEvent, StateView } from './model';
 
 function gameView(moveCount: number, over = false): GameView {
   return {
@@ -98,3 +98,46 @@ describe('applyGameOver', () => {
     expect(res.cache?.view.game.moveCount).toBe(10);
   });
 });
+
+function movedEvent(moveCount: number, player: number, bagLen = 45): PushEvent {
+  return { kind: 'opponent_moved', gameId: 'g1', move: move(player), game: gameView(moveCount), bagLen };
+}
+
+function gameOverEvent(moveCount: number): PushEvent {
+  return { kind: 'game_over', gameId: 'g1', result: 'win', scoreLine: '10:0', game: gameView(moveCount, true) };
+}
+
+describe('advanceCached', () => {
+  it("advances the cache from an opponent's move for a game not on screen", () => {
+    const res = advanceCached(cache(3, 0), movedEvent(4, 1, 42));
+    expect(res?.view.game.moveCount).toBe(4);
+    expect(res?.view.bagLen).toBe(42);
+    expect(res?.moves).toHaveLength(1);
+  });
+
+  it('returns undefined on a gap, so the cache is left for the next open to cold-load', () => {
+    expect(advanceCached(cache(3, 0), movedEvent(6, 1))).toBeUndefined();
+  });
+
+  it('returns undefined for an already-applied move (idempotent re-delivery / own echo)', () => {
+    expect(advanceCached(cache(4, 0), movedEvent(4, 1))).toBeUndefined();
+  });
+
+  it('settles a game_over event when the cached board is current', () => {
+    const res = advanceCached(cache(10, 0), gameOverEvent(10));
+    expect(res?.view.game.status).toBe('finished');
+  });
+
+  it('returns undefined for game_over when the cached board is behind the final count', () => {
+    expect(advanceCached(cache(9, 0), gameOverEvent(10))).toBeUndefined();
+  });
+
+  it('returns undefined when nothing is cached for the game', () => {
+    expect(advanceCached(undefined, movedEvent(1, 1))).toBeUndefined();
+  });
+
+  it('ignores event kinds that do not advance a game board', () => {
+    const yourTurn: PushEvent = { kind: 'your_turn', gameId: 'g1', deadlineUnix: 0, moveCount: 4 };
+    expect(advanceCached(cache(3, 0), yourTurn)).toBeUndefined();
+  });
+});
diff --git a/ui/src/lib/gamedelta.ts b/ui/src/lib/gamedelta.ts
index 9e7b46c..9466c2f 100644
--- a/ui/src/lib/gamedelta.ts
+++ b/ui/src/lib/gamedelta.ts
@@ -4,7 +4,7 @@
 // `refetch` — which keeps the gap / own-move / idempotency logic unit-testable in isolation.
 
 import type { CachedGame } from './gamecache';
-import type { GameView, MoveRecord, StateView } from './model';
+import type { GameView, MoveRecord, PushEvent, StateView } from './model';
 
 /** The fields an opponent_moved delta carries that advance a cached game. */
 export interface MoveDelta {
@@ -67,3 +67,20 @@ export function applyGameOver(cached: CachedGame | undefined, game: GameView | u
   const view: StateView = { ...cached.view, game };
   return { cache: { view, moves: cached.moves }, refetch: false };
 }
+
+/**
+ * advanceCached applies a live game event to a cached game off-screen, for the global stream handler
+ * to keep a game the player is not currently viewing warm: opening it from the lobby then renders the
+ * opponent's move (or the final result) with no stale-board flash. It returns the advanced cache, or
+ * undefined when nothing changes — no cache, an idempotent re-delivery, an unrelated event kind, or a
+ * gap / missing payload that the next open cold-loads (off-screen there is no game screen to honour a
+ * refetch, so a fall-back simply leaves the cache for load() to repair). The mounted game screen owns
+ * its own cache, so the caller skips the game currently in view to avoid applying a delta twice.
+ */
+export function advanceCached(cached: CachedGame | undefined, e: PushEvent): CachedGame | undefined {
+  if (e.kind === 'opponent_moved') {
+    return applyMoveDelta(cached, { move: e.move, game: e.game, bagLen: e.bagLen }).cache;
+  }
+  if (e.kind === 'game_over') return applyGameOver(cached, e.game).cache;
+  return undefined;
+}
diff --git a/ui/src/lib/lobbycache.test.ts b/ui/src/lib/lobbycache.test.ts
new file mode 100644
index 0000000..d7d0035
--- /dev/null
+++ b/ui/src/lib/lobbycache.test.ts
@@ -0,0 +1,61 @@
+import { beforeEach, describe, expect, it } from 'vitest';
+import { clearLobby, getLobby, patchLobbyGame, setLobby } from './lobbycache';
+import type { AccountRef, GameView } from './model';
+
+function gameView(id: string, status: GameView['status'] = 'active', toMove = 0): GameView {
+  return {
+    id,
+    variant: 'scrabble_en',
+    dictVersion: 'v1',
+    status,
+    players: 2,
+    toMove,
+    turnTimeoutSecs: 300,
+    multipleWordsPerTurn: true,
+    moveCount: 0,
+    endReason: '',
+    lastActivityUnix: 0,
+    seats: [],
+  };
+}
+
+beforeEach(() => clearLobby());
+
+describe('patchLobbyGame', () => {
+  it('replaces the matching game by id and leaves the others untouched', () => {
+    setLobby({ games: [gameView('a', 'active', 0), gameView('b', 'active', 0)], invitations: [], incoming: [] });
+    // The player's own move flipped game "a" to the opponent's turn.
+    patchLobbyGame(gameView('a', 'active', 1));
+    const snap = getLobby();
+    expect(snap?.games.map((g) => g.id)).toEqual(['a', 'b']);
+    expect(snap?.games.find((g) => g.id === 'a')?.toMove).toBe(1);
+    expect(snap?.games.find((g) => g.id === 'b')?.toMove).toBe(0);
+  });
+
+  it('preserves invitations and incoming when patching a game', () => {
+    const incoming: AccountRef[] = [{ accountId: 'u9', displayName: 'Nine' }];
+    setLobby({ games: [gameView('a')], invitations: [], incoming });
+    patchLobbyGame(gameView('a', 'finished'));
+    expect(getLobby()?.incoming).toEqual(incoming);
+    expect(getLobby()?.games[0].status).toBe('finished');
+  });
+
+  it('adds the game when it is not yet in the cached lobby (a game started elsewhere)', () => {
+    setLobby({ games: [gameView('a')], invitations: [], incoming: [] });
+    patchLobbyGame(gameView('z', 'active'));
+    // Order is irrelevant — the lobby re-groups and re-sorts on render — so assert membership.
+    expect(getLobby()?.games.map((g) => g.id).sort()).toEqual(['a', 'z']);
+  });
+
+  it('is a no-op when there is no cached lobby yet', () => {
+    patchLobbyGame(gameView('a'));
+    expect(getLobby()).toBeNull();
+  });
+
+  it('does not mutate the previous snapshot array', () => {
+    const games = [gameView('a', 'active', 0)];
+    setLobby({ games, invitations: [], incoming: [] });
+    patchLobbyGame(gameView('a', 'active', 1));
+    expect(games[0].toMove).toBe(0); // the original array/object is left intact
+  });
+});
diff --git a/ui/src/lib/lobbycache.ts b/ui/src/lib/lobbycache.ts
index 5184bf8..51bbd41 100644
--- a/ui/src/lib/lobbycache.ts
+++ b/ui/src/lib/lobbycache.ts
@@ -24,6 +24,24 @@ export function setLobby(s: LobbySnapshot): void {
   snapshot = s;
 }
 
+/**
+ * patchLobbyGame upserts the given game into the cached lobby — replacing the matching entry, or
+ * prepending it when absent — so a game-state change seen while the lobby is unmounted (the player's
+ * own move, or any live game event the global stream handler applies from another screen) is already
+ * reflected the next time the lobby renders from the snapshot, instead of showing the stale status
+ * until the background refresh lands. Prepending a freshly started game likewise lets it appear at
+ * once. It is a no-op only when there is no snapshot yet (the lobby cold-loads on its first mount).
+ * The lobby re-groups and re-sorts on render, so the insert position carries no meaning.
+ */
+export function patchLobbyGame(g: GameView): void {
+  if (!snapshot) return;
+  const i = snapshot.games.findIndex((x) => x.id === g.id);
+  const games = snapshot.games.slice();
+  if (i === -1) games.unshift(g);
+  else games[i] = g;
+  snapshot = { ...snapshot, games };
+}
+
 /** clearLobby drops the cached lobby (called on logout). */
 export function clearLobby(): void {
   snapshot = null;