diff --git a/components/email/email-list.tsx b/components/email/email-list.tsx
index 394384fc0..42914a057 100644
--- a/components/email/email-list.tsx
+++ b/components/email/email-list.tsx
@@ -683,6 +683,15 @@ export function EmailList({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [selectedEmailId]);
 
+  // Keep the moving end of a Shift+Arrow range on screen (#992).
+  const selectionFocusKey = useEmailStore((state) => state.selectionFocus?.focus ?? null);
+  useEffect(() => {
+    if (!selectionFocusKey) return;
+    const index = threadGroups.findIndex((thread) => thread.emails.some((e) => emailKeyFor(e) === selectionFocusKey));
+    if (index >= 0) virtualizer.scrollToIndex(index, { align: 'auto' });
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [selectionFocusKey]);
+
   // Re-measure all items when density or preview settings change
   useEffect(() => {
     virtualizer.measure();
diff --git a/components/mail/mail-app.tsx b/components/mail/mail-app.tsx
index 170d9c29a..2672d322e 100644
--- a/components/mail/mail-app.tsx
+++ b/components/mail/mail-app.tsx
@@ -1007,6 +1007,12 @@ export function MailApp({ linkSegments: routeSegments }: MailAppProps = {}) {
     onDeselectAll: () => {
       clearSelection();
     },
+    // Shift + ↓/↑ (and Shift + j/k): grow or shrink the ticked range from the
+    // open message without opening each row on the way. (#992)
+    onExtendSelection: (direction: 1 | -1) => {
+      if (isScheduledView) return;
+      useEmailStore.getState().extendSelection(direction);
+    },
     // `x` under Mountain View: put the focused conversation in or out of the
     // selection. Only reachable there, where `x` is handed over from thread
     // expansion.
diff --git a/hooks/__tests__/use-keyboard-shortcuts.test.ts b/hooks/__tests__/use-keyboard-shortcuts.test.ts
index 7074abc79..9d20d9e0b 100644
--- a/hooks/__tests__/use-keyboard-shortcuts.test.ts
+++ b/hooks/__tests__/use-keyboard-shortcuts.test.ts
@@ -41,3 +41,52 @@ describe('useKeyboardShortcuts: x toggles thread expansion', () => {
     expect(onToggleThreadExpansion).not.toHaveBeenCalled();
   });
 });
+
+// #992: Shift + arrow (or j/k) extends the selection instead of moving to the
+// next message; plain arrows still move.
+describe('useKeyboardShortcuts: Shift + arrow extends the selection', () => {
+  function press(key: string, code: string, shiftKey: boolean) {
+    document.dispatchEvent(new KeyboardEvent('keydown', { key, code, shiftKey, bubbles: true }));
+  }
+
+  it.each([
+    ['ArrowDown', 'ArrowDown', 1],
+    ['ArrowUp', 'ArrowUp', -1],
+    ['J', 'KeyJ', 1],
+    ['K', 'KeyK', -1],
+  ] as const)('Shift + %s (%s) extends by %i', (key, code, direction) => {
+    const onExtendSelection = vi.fn();
+    const onNextEmail = vi.fn();
+    const onPreviousEmail = vi.fn();
+    renderHook(() =>
+      useKeyboardShortcuts({
+        emails: [],
+        selectedEmailId: 'e1',
+        handlers: { onExtendSelection, onNextEmail, onPreviousEmail },
+      }),
+    );
+
+    press(key, code, true);
+
+    expect(onExtendSelection).toHaveBeenCalledWith(direction);
+    expect(onNextEmail).not.toHaveBeenCalled();
+    expect(onPreviousEmail).not.toHaveBeenCalled();
+  });
+
+  it('plain ArrowDown still moves to the next message', () => {
+    const onExtendSelection = vi.fn();
+    const onNextEmail = vi.fn();
+    renderHook(() =>
+      useKeyboardShortcuts({
+        emails: [],
+        selectedEmailId: 'e1',
+        handlers: { onExtendSelection, onNextEmail },
+      }),
+    );
+
+    press('ArrowDown', 'ArrowDown', false);
+
+    expect(onNextEmail).toHaveBeenCalledTimes(1);
+    expect(onExtendSelection).not.toHaveBeenCalled();
+  });
+});
diff --git a/hooks/use-keyboard-shortcuts.ts b/hooks/use-keyboard-shortcuts.ts
index 8c8579114..30e9de777 100644
--- a/hooks/use-keyboard-shortcuts.ts
+++ b/hooks/use-keyboard-shortcuts.ts
@@ -33,6 +33,8 @@ export interface KeyboardShortcutHandlers {
   // Selection
   onSelectAll?: () => void;
   onDeselectAll?: () => void;
+  /** Shift + ↓/j and Shift + ↑/k: grow or shrink the selection by one row. */
+  onExtendSelection?: (direction: 1 | -1) => void;
 
   // Thread actions
   onToggleThreadExpansion?: () => void;
@@ -174,13 +176,23 @@ export function useKeyboardShortcuts({
         case "j":
         case "arrowdown":
           event.preventDefault();
-          run("next-email", h.onNextEmail);
+          if (event.shiftKey && h.onExtendSelection) {
+            const extend = h.onExtendSelection;
+            run("extend-selection-down", () => extend(1));
+          } else {
+            run("next-email", h.onNextEmail);
+          }
           break;
 
         case "k":
         case "arrowup":
           event.preventDefault();
-          run("previous-email", h.onPreviousEmail);
+          if (event.shiftKey && h.onExtendSelection) {
+            const extend = h.onExtendSelection;
+            run("extend-selection-up", () => extend(-1));
+          } else {
+            run("previous-email", h.onPreviousEmail);
+          }
           break;
 
         case "enter":
@@ -396,6 +408,7 @@ export const KEYBOARD_SHORTCUTS = {
     { key: "?", description: "shortcuts.global.help" },
     { key: "Shift + G", description: "shortcuts.global.refresh" },
     { key: "Ctrl + A", description: "shortcuts.global.select_all" },
+    { key: "Shift + ↓ / ↑", description: "shortcuts.global.extend_selection" },
   ],
   threads: [
     { key: "x", description: "shortcuts.threads.expand_collapse", layout: "default" },
diff --git a/locales/ar/common.json b/locales/ar/common.json
index 0574e9019..b6333fac9 100644
--- a/locales/ar/common.json
+++ b/locales/ar/common.json
@@ -2625,7 +2625,8 @@
       "help": "إظهار الاختصارات",
       "refresh": "تحديث الرسائل",
       "select_all": "تحديد الكل",
-      "global_search": "البحث في كل شيء"
+      "global_search": "البحث في كل شيء",
+      "extend_selection": "توسيع التحديد لأسفل / لأعلى"
     },
     "threads": {
       "expand_collapse": "توسيع/طي المحادثة",
diff --git a/locales/ca/common.json b/locales/ca/common.json
index c37ce806e..166314246 100644
--- a/locales/ca/common.json
+++ b/locales/ca/common.json
@@ -2625,7 +2625,8 @@
       "help": "Mostra les dreceres",
       "refresh": "Actualitza els correus",
       "select_all": "Selecciona-ho tot",
-      "global_search": "Cerca-ho tot"
+      "global_search": "Cerca-ho tot",
+      "extend_selection": "Amplia la selecció cap avall / amunt"
     },
     "threads": {
       "expand_collapse": "Desplega/replega el fil",
diff --git a/locales/cs/common.json b/locales/cs/common.json
index b86d7b6c0..be1175d69 100644
--- a/locales/cs/common.json
+++ b/locales/cs/common.json
@@ -2625,7 +2625,8 @@
       "help": "Zobrazit zkratky",
       "refresh": "Obnovit zprávy",
       "select_all": "Vybrat vše",
-      "global_search": "Hledat ve všem"
+      "global_search": "Hledat ve všem",
+      "extend_selection": "Rozšířit výběr dolů / nahoru"
     },
     "threads": {
       "expand_collapse": "Rozbalit/sbalit vlákno",
diff --git a/locales/da/common.json b/locales/da/common.json
index d564cd684..5e47ee71b 100644
--- a/locales/da/common.json
+++ b/locales/da/common.json
@@ -2625,7 +2625,8 @@
       "help": "Vis genveje",
       "refresh": "Opdatér e-mails",
       "select_all": "Vælg alle",
-      "global_search": "Søg i alt"
+      "global_search": "Søg i alt",
+      "extend_selection": "Udvid markering ned / op"
     },
     "threads": {
       "expand_collapse": "Udvid/skjul tråd",
diff --git a/locales/de/common.json b/locales/de/common.json
index 3ef83bf87..c0876d03b 100644
--- a/locales/de/common.json
+++ b/locales/de/common.json
@@ -2625,7 +2625,8 @@
       "help": "Tastaturkürzel anzeigen",
       "refresh": "E-Mails aktualisieren",
       "select_all": "Alle auswählen",
-      "global_search": "Alles durchsuchen"
+      "global_search": "Alles durchsuchen",
+      "extend_selection": "Auswahl nach unten / oben erweitern"
     },
     "threads": {
       "expand_collapse": "Unterhaltung erweitern/einklappen",
diff --git a/locales/en/common.json b/locales/en/common.json
index bea47352e..68028cbff 100644
--- a/locales/en/common.json
+++ b/locales/en/common.json
@@ -2625,7 +2625,8 @@
       "help": "Show shortcuts",
       "refresh": "Refresh emails",
       "select_all": "Select all",
-      "global_search": "Search everything"
+      "global_search": "Search everything",
+      "extend_selection": "Extend selection down / up"
     },
     "threads": {
       "expand_collapse": "Expand/collapse thread",
diff --git a/locales/es/common.json b/locales/es/common.json
index 00af2bc88..9861f7bb3 100644
--- a/locales/es/common.json
+++ b/locales/es/common.json
@@ -2625,7 +2625,8 @@
       "help": "Mostrar atajos",
       "refresh": "Actualizar correos",
       "select_all": "Seleccionar todo",
-      "global_search": "Buscar en todo"
+      "global_search": "Buscar en todo",
+      "extend_selection": "Ampliar la selección hacia abajo / arriba"
     },
     "threads": {
       "expand_collapse": "Expandir/contraer conversación",
diff --git a/locales/fa/common.json b/locales/fa/common.json
index 8047731ff..15f3c42ce 100644
--- a/locales/fa/common.json
+++ b/locales/fa/common.json
@@ -2625,7 +2625,8 @@
       "help": "نمایش میانبرها",
       "refresh": "بازنشانی ایمیل‌ها",
       "select_all": "انتخاب همه",
-      "global_search": "جستجو در همه جا"
+      "global_search": "جستجو در همه جا",
+      "extend_selection": "گسترش انتخاب به پایین / بالا"
     },
     "threads": {
       "expand_collapse": "باز/بسته کردن رشته",
diff --git a/locales/fr/common.json b/locales/fr/common.json
index 6608cb9c3..7651271fe 100644
--- a/locales/fr/common.json
+++ b/locales/fr/common.json
@@ -2625,7 +2625,8 @@
       "help": "Afficher les raccourcis",
       "refresh": "Actualiser les emails",
       "select_all": "Tout sélectionner",
-      "global_search": "Tout rechercher"
+      "global_search": "Tout rechercher",
+      "extend_selection": "Étendre la sélection vers le bas / le haut"
     },
     "threads": {
       "expand_collapse": "Développer/réduire la conversation",
diff --git a/locales/he/common.json b/locales/he/common.json
index 852dd56b3..2a298f83c 100644
--- a/locales/he/common.json
+++ b/locales/he/common.json
@@ -2543,7 +2543,8 @@
       "help": "הצג קיצורי דרך",
       "refresh": "רענן מיילים",
       "select_all": "בחר הכל",
-      "global_search": "חיפוש בכל מקום"
+      "global_search": "חיפוש בכל מקום",
+      "extend_selection": "הרחבת הבחירה למטה / למעלה"
     },
     "threads": {
       "expand_collapse": "הרחב/כווץ את השרשור",
diff --git a/locales/hu/common.json b/locales/hu/common.json
index d680ae1b3..6edde12a6 100644
--- a/locales/hu/common.json
+++ b/locales/hu/common.json
@@ -2625,7 +2625,8 @@
       "help": "Parancsok mutatása",
       "refresh": "E-mailek frissítése",
       "select_all": "Összes kijelölése",
-      "global_search": "Keresés mindenben"
+      "global_search": "Keresés mindenben",
+      "extend_selection": "Kijelölés bővítése lefelé / felfelé"
     },
     "threads": {
       "expand_collapse": "Beszélgetés kibontása/összecsukása",
diff --git a/locales/it/common.json b/locales/it/common.json
index bb3de32e6..b19f0a543 100644
--- a/locales/it/common.json
+++ b/locales/it/common.json
@@ -2625,7 +2625,8 @@
       "help": "Mostra scorciatoie",
       "refresh": "Aggiorna messaggi",
       "select_all": "Seleziona tutto",
-      "global_search": "Cerca ovunque"
+      "global_search": "Cerca ovunque",
+      "extend_selection": "Estendi la selezione in basso / in alto"
     },
     "threads": {
       "expand_collapse": "Espandi/comprimi conversazione",
diff --git a/locales/ja/common.json b/locales/ja/common.json
index c4b4c64c9..bdd2cca20 100644
--- a/locales/ja/common.json
+++ b/locales/ja/common.json
@@ -2625,7 +2625,8 @@
       "help": "ショートカットを表示",
       "refresh": "メールを更新",
       "select_all": "すべて選択",
-      "global_search": "すべてを検索"
+      "global_search": "すべてを検索",
+      "extend_selection": "選択範囲を下 / 上に広げる"
     },
     "threads": {
       "expand_collapse": "スレッドの展開/折りたたみ",
diff --git a/locales/ko/common.json b/locales/ko/common.json
index 1f9ae6c00..aa75e5e85 100644
--- a/locales/ko/common.json
+++ b/locales/ko/common.json
@@ -2625,7 +2625,8 @@
       "help": "단축키 보기",
       "refresh": "메일 새로고침",
       "select_all": "모두 선택",
-      "global_search": "전체 검색"
+      "global_search": "전체 검색",
+      "extend_selection": "선택 범위를 아래 / 위로 확장"
     },
     "threads": {
       "expand_collapse": "대화 펼치기/접기",
diff --git a/locales/lv/common.json b/locales/lv/common.json
index 3b7b61d26..e91ecde6f 100644
--- a/locales/lv/common.json
+++ b/locales/lv/common.json
@@ -2625,7 +2625,8 @@
       "help": "Rādīt īsinājumtaustiņus",
       "refresh": "Atsvaidzināt vēstules",
       "select_all": "Atlasīt visas",
-      "global_search": "Meklēt visā"
+      "global_search": "Meklēt visā",
+      "extend_selection": "Paplašināt atlasi uz leju / uz augšu"
     },
     "threads": {
       "expand_collapse": "Izvērst/sairt sarunu",
diff --git a/locales/mn/common.json b/locales/mn/common.json
index a783015d8..b4b7e0d85 100644
--- a/locales/mn/common.json
+++ b/locales/mn/common.json
@@ -2625,7 +2625,8 @@
       "help": "Товчлол харуулах",
       "refresh": "Имэйл сэргээх",
       "select_all": "Бүгдийг сонго",
-      "global_search": "Бүгдийг хайх"
+      "global_search": "Бүгдийг хайх",
+      "extend_selection": "Сонголтыг доош / дээш өргөтгөх"
     },
     "threads": {
       "expand_collapse": "Хэлхээсийг дэлгэх/хумих",
diff --git a/locales/nb/common.json b/locales/nb/common.json
index bb5328de9..6d35a0a9e 100644
--- a/locales/nb/common.json
+++ b/locales/nb/common.json
@@ -2625,7 +2625,8 @@
       "help": "Vis tastatursnarveier",
       "refresh": "Oppdater e-poster",
       "select_all": "Velg alle",
-      "global_search": "Søk i alt"
+      "global_search": "Søk i alt",
+      "extend_selection": "Utvid markeringen ned / opp"
     },
     "threads": {
       "expand_collapse": "Utvid eller fold sammen tråden",
diff --git a/locales/nl/common.json b/locales/nl/common.json
index db6b242d4..2845b20d2 100644
--- a/locales/nl/common.json
+++ b/locales/nl/common.json
@@ -2625,7 +2625,8 @@
       "help": "Sneltoetsen tonen",
       "refresh": "E-mails vernieuwen",
       "select_all": "Alles selecteren",
-      "global_search": "Alles doorzoeken"
+      "global_search": "Alles doorzoeken",
+      "extend_selection": "Selectie omlaag / omhoog uitbreiden"
     },
     "threads": {
       "expand_collapse": "Gesprek uitklappen/inklappen",
diff --git a/locales/pl/common.json b/locales/pl/common.json
index d14172b27..e957fce90 100644
--- a/locales/pl/common.json
+++ b/locales/pl/common.json
@@ -2625,7 +2625,8 @@
       "help": "Pokaż skróty",
       "refresh": "Odśwież wiadomości",
       "select_all": "Zaznacz wszystko",
-      "global_search": "Szukaj wszędzie"
+      "global_search": "Szukaj wszędzie",
+      "extend_selection": "Rozszerz zaznaczenie w dół / w górę"
     },
     "threads": {
       "expand_collapse": "Rozwiń/zwiń wątek",
diff --git a/locales/pt/common.json b/locales/pt/common.json
index 784fd0456..6d92d4602 100644
--- a/locales/pt/common.json
+++ b/locales/pt/common.json
@@ -2625,7 +2625,8 @@
       "help": "Mostrar atalhos",
       "refresh": "Atualizar e-mails",
       "select_all": "Selecionar todos",
-      "global_search": "Pesquisar em tudo"
+      "global_search": "Pesquisar em tudo",
+      "extend_selection": "Expandir a seleção para baixo / cima"
     },
     "threads": {
       "expand_collapse": "Expandir/recolher conversa",
diff --git a/locales/ro/common.json b/locales/ro/common.json
index 6890d530c..f0cf6b503 100644
--- a/locales/ro/common.json
+++ b/locales/ro/common.json
@@ -2625,7 +2625,8 @@
       "help": "Afișați comenzile rapide",
       "refresh": "Reîmprospătați e-mailurile",
       "select_all": "Selectează tot",
-      "global_search": "Caută în tot"
+      "global_search": "Caută în tot",
+      "extend_selection": "Extinde selecția în jos / în sus"
     },
     "threads": {
       "expand_collapse": "Extindeți/reduceți firul de discuție",
diff --git a/locales/ru/common.json b/locales/ru/common.json
index 5df224fe4..2c4b9c474 100644
--- a/locales/ru/common.json
+++ b/locales/ru/common.json
@@ -2625,7 +2625,8 @@
       "help": "Показать сочетания клавиш",
       "refresh": "Обновить письма",
       "select_all": "Выбрать все",
-      "global_search": "Искать везде"
+      "global_search": "Искать везде",
+      "extend_selection": "Расширить выделение вниз / вверх"
     },
     "threads": {
       "expand_collapse": "Развернуть/свернуть цепочку",
diff --git a/locales/sk/common.json b/locales/sk/common.json
index b8ad26c65..216b75f86 100644
--- a/locales/sk/common.json
+++ b/locales/sk/common.json
@@ -2625,7 +2625,8 @@
       "help": "Zobraziť skratky",
       "refresh": "Obnoviť e-maily",
       "select_all": "Vybrať všetko",
-      "global_search": "Hľadať všade"
+      "global_search": "Hľadať všade",
+      "extend_selection": "Rozšíriť výber nadol / nahor"
     },
     "threads": {
       "expand_collapse": "Rozbaliť/zbaliť vlákno",
diff --git a/locales/tr/common.json b/locales/tr/common.json
index c76a6fb32..b40d8206f 100644
--- a/locales/tr/common.json
+++ b/locales/tr/common.json
@@ -2625,7 +2625,8 @@
       "help": "Kısayolları göster",
       "refresh": "E-postaları yenile",
       "select_all": "Tümünü seç",
-      "global_search": "Her yerde ara"
+      "global_search": "Her yerde ara",
+      "extend_selection": "Seçimi aşağı / yukarı genişlet"
     },
     "threads": {
       "expand_collapse": "İleti dizisini genişlet/daralt",
diff --git a/locales/uk/common.json b/locales/uk/common.json
index 3b507e5f2..580e25b0f 100644
--- a/locales/uk/common.json
+++ b/locales/uk/common.json
@@ -2625,7 +2625,8 @@
       "help": "Показати ярлики",
       "refresh": "Оновити електронні листи",
       "select_all": "Вибрати все",
-      "global_search": "Шукати скрізь"
+      "global_search": "Шукати скрізь",
+      "extend_selection": "Розширити виділення вниз / вгору"
     },
     "threads": {
       "expand_collapse": "Розгорнути/згорнути ланцюжок",
diff --git a/locales/zh-TW/common.json b/locales/zh-TW/common.json
index 7ec086cf6..593b9cfec 100644
--- a/locales/zh-TW/common.json
+++ b/locales/zh-TW/common.json
@@ -2625,7 +2625,8 @@
       "help": "顯示快速鍵",
       "refresh": "重新整理郵件",
       "select_all": "全部選取",
-      "global_search": "全域搜尋"
+      "global_search": "全域搜尋",
+      "extend_selection": "向下 / 向上擴展選取"
     },
     "threads": {
       "expand_collapse": "展開／收合對話串",
diff --git a/locales/zh/common.json b/locales/zh/common.json
index a735101ef..b8b0ab9c1 100644
--- a/locales/zh/common.json
+++ b/locales/zh/common.json
@@ -2625,7 +2625,8 @@
       "help": "显示快捷方式",
       "refresh": "刷新邮件",
       "select_all": "全选",
-      "global_search": "全局搜索"
+      "global_search": "全局搜索",
+      "extend_selection": "向下 / 向上扩展选择"
     },
     "threads": {
       "expand_collapse": "展开/折叠会话",
diff --git a/stores/__tests__/email-selection.test.ts b/stores/__tests__/email-selection.test.ts
index d46f0ff95..b5dbc7695 100644
--- a/stores/__tests__/email-selection.test.ts
+++ b/stores/__tests__/email-selection.test.ts
@@ -146,6 +146,69 @@ describe('email-store selection', () => {
     });
   });
 
+  // #992: Shift+Arrow grows the selection from the open message one row at a
+  // time and shrinks it again when the direction reverses.
+  describe('extendSelection', () => {
+    const keys = () => [...useEmailStore.getState().selectedEmailKeys].sort();
+
+    beforeEach(() => {
+      // Opening a message makes it the anchor, as selectEmail does.
+      useEmailStore.setState({ lastSelectedEmailKey: 'b', selectionFocus: null });
+    });
+
+    it('selects the open message and the next one on the first press', () => {
+      useEmailStore.getState().extendSelection(1);
+      expect(keys()).toEqual(['b', 'c']);
+    });
+
+    it('keeps growing in the same direction', () => {
+      useEmailStore.getState().extendSelection(1);
+      useEmailStore.getState().extendSelection(1);
+      expect(keys()).toEqual(['b', 'c', 'd']);
+    });
+
+    it('shrinks back when the direction reverses', () => {
+      useEmailStore.getState().extendSelection(1);
+      useEmailStore.getState().extendSelection(1);
+      useEmailStore.getState().extendSelection(-1);
+      expect(keys()).toEqual(['b', 'c']);
+    });
+
+    it('crosses the anchor and grows the other way', () => {
+      useEmailStore.getState().extendSelection(1);
+      useEmailStore.getState().extendSelection(-1);
+      useEmailStore.getState().extendSelection(-1);
+      expect(keys()).toEqual(['a', 'b']);
+    });
+
+    it('stops at the end of the list', () => {
+      for (let i = 0; i < 10; i++) useEmailStore.getState().extendSelection(1);
+      expect(keys()).toEqual(['b', 'c', 'd', 'e']);
+    });
+
+    it('continues a shift-click range', () => {
+      useEmailStore.getState().selectRangeEmails({ id: 'd' });
+      useEmailStore.getState().extendSelection(-1);
+      expect(keys()).toEqual(['b', 'c']);
+    });
+
+    it('walks list rows, taking a whole thread with its row', () => {
+      useEmailStore.setState({
+        emails: ['t2', 'x', 't1', 'y'].map((id) => makeEmail(id, id.startsWith('t') ? 'thread-t' : `thread-${id}`)),
+        listRows: [
+          { key: 'x', members: ['x'] },
+          { key: 't2', members: ['t2', 't1'] },
+          { key: 'y', members: ['y'] },
+        ],
+        lastSelectedEmailKey: 'x',
+      });
+      useEmailStore.getState().extendSelection(1);
+      expect(keys()).toEqual(['t1', 't2', 'x']);
+      useEmailStore.getState().extendSelection(-1);
+      expect(keys()).toEqual(['x']);
+    });
+  });
+
   describe('selectAllEmails', () => {
     it('should select all emails', () => {
       useEmailStore.getState().selectAllEmails();
diff --git a/stores/email-store.ts b/stores/email-store.ts
index 14049f158..e508ca6b3 100644
--- a/stores/email-store.ts
+++ b/stores/email-store.ts
@@ -283,7 +283,17 @@ interface EmailStore {
   /** Take the email, not its id: the id alone collides across accounts. */
   toggleEmailSelection: (email: SelectableEmail) => void;
   selectRangeEmails: (target: SelectableEmail) => void;
+  /**
+   * Shift+Arrow (and Shift+J/K): grow or shrink the selection by one row,
+   * from the open or last ticked message, like a desktop mail client. (#992)
+   */
+  extendSelection: (direction: 1 | -1) => void;
   lastSelectedEmailKey: string | null;
+  /**
+   * The moving end of a keyboard range and the anchor it was taken from.
+   * Only valid while the anchor is still lastSelectedEmailKey.
+   */
+  selectionFocus: { anchor: string; focus: string } | null;
   /**
    * The message list's rows in screen order, each with the keys a click on it
    * selects. Shift-click ranges walk these, so a thread is in a range only
@@ -2140,6 +2150,7 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
   selectedEmailKeys: new Set(),
   retainedInViewIds: new Set(),
   lastSelectedEmailKey: null,
+  selectionFocus: null,
   listRows: null,
   hasMoreEmails: false,
   totalEmails: 0,
@@ -2411,7 +2422,7 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
         for (let i = Math.min(anchorRow, targetRow); i <= Math.max(anchorRow, targetRow); i++) {
           for (const key of listRows[i].members) newSelection.add(key);
         }
-        set({ selectedEmailKeys: newSelection });
+        set({ selectedEmailKeys: newSelection, selectionFocus: { anchor: anchorKey, focus: targetKeyForRows } });
         return;
       }
     }
@@ -2425,7 +2436,48 @@ export const useEmailStore = create<EmailStore>((set, get) => ({
     for (let i = start; i <= end; i++) {
       newSelection.add(emailKeyFor(emails[i]));
     }
-    set({ selectedEmailKeys: newSelection });
+    set({ selectedEmailKeys: newSelection, selectionFocus: { anchor: anchorKey, focus: targetKey } });
+  },
+
+  extendSelection: (direction) => {
+    const { emails, listRows, lastSelectedEmailKey, selectedEmail, selectedEmailKeys, selectionFocus } = get();
+    // Walk the rows on screen, as shift-click does; without them, the emails.
+    const rows: ListRow[] = listRows && listRows.length > 0
+      ? listRows
+      : emails.map((e) => ({ key: emailKeyFor(e), members: [emailKeyFor(e)] }));
+    if (rows.length === 0) return;
+    const membersOf = (from: number, to: number) => {
+      const keys: string[] = [];
+      for (let i = Math.min(from, to); i <= Math.max(from, to); i++) keys.push(...rows[i].members);
+      return keys;
+    };
+
+    const anchorKey = lastSelectedEmailKey ?? (selectedEmail ? emailKeyFor(selectedEmail) : null);
+    const anchor = anchorKey ? findListRow(rows, anchorKey) : -1;
+    if (!anchorKey || anchor === -1) {
+      // Nothing to extend from: start with the row at the end the key points from.
+      const start = rows[direction > 0 ? 0 : rows.length - 1];
+      set({
+        selectedEmailKeys: new Set([...selectedEmailKeys, ...start.members]),
+        lastSelectedEmailKey: start.key,
+        selectionFocus: { anchor: start.key, focus: start.key },
+      });
+      return;
+    }
+
+    // Continue the range this anchor already has, or begin one at the anchor.
+    const previous = selectionFocus && selectionFocus.anchor === anchorKey && selectedEmailKeys.size > 0
+      ? findListRow(rows, selectionFocus.focus)
+      : -1;
+    const focus = previous === -1 ? anchor : previous;
+    const nextFocus = Math.max(0, Math.min(rows.length - 1, focus + direction));
+
+    const newSelection = new Set(selectedEmailKeys);
+    if (previous !== -1) {
+      for (const key of membersOf(anchor, previous)) newSelection.delete(key);
+    }
+    for (const key of membersOf(anchor, nextFocus)) newSelection.add(key);
+    set({ selectedEmailKeys: newSelection, selectionFocus: { anchor: anchorKey, focus: rows[nextFocus].key } });
   },
 
   selectAllEmails: () => {