diff --git a/App.tsx b/App.tsx
index 92176989..3b7dc402 100644
--- a/App.tsx
+++ b/App.tsx
@@ -46,7 +46,7 @@ import LoginScreen from './src/screens/LoginScreen';
 import MailTab from './src/screens/MailTab';
 import FilesScreen from './src/screens/FilesScreen';
 import CalendarScreen from './src/screens/CalendarScreen';
-import ContactsScreen from './src/screens/ContactsScreen';
+import ContactsTab from './src/screens/ContactsTab';
 import ContactDetailScreen from './src/screens/ContactDetailScreen';
 import ContactFormScreen from './src/screens/ContactFormScreen';
 import GroupDetailScreen from './src/screens/GroupDetailScreen';
@@ -325,7 +325,7 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
       />
       <Tab.Screen
         name="Contacts"
-        component={ContactsScreen}
+        component={ContactsTab}
         options={{
           title: tabLabels.contacts,
           tabBarIcon: ({ color, size }) => <BookUser size={size} color={color} />,
diff --git a/src/components/contacts/ContactListRow.tsx b/src/components/contacts/ContactListRow.tsx
index b1e7853e..72e878d9 100644
--- a/src/components/contacts/ContactListRow.tsx
+++ b/src/components/contacts/ContactListRow.tsx
@@ -19,6 +19,8 @@ interface ContactListRowProps {
   onPress?: () => void;
   onLongPress?: () => void;
   selected?: boolean;
+  /** The contact open in the detail pane of a split view. */
+  active?: boolean;
   selectionMode?: boolean;
   secondaryText?: string;
 }
@@ -28,6 +30,7 @@ export default function ContactListRow({
   onPress,
   onLongPress,
   selected,
+  active = false,
   selectionMode,
   secondaryText,
 }: ContactListRowProps) {
@@ -52,6 +55,7 @@ export default function ContactListRow({
       style={({ pressed }) => [
         styles.row,
         pressed && styles.rowPressed,
+        active && styles.rowActive,
         selected && styles.rowSelected,
       ]}
     >
@@ -95,6 +99,13 @@ function makeStyles(c: ThemePalette) {
   },
   rowPressed: { backgroundColor: c.surfaceHover },
   rowSelected: { backgroundColor: c.primaryBg },
+  // Same as the open message in the mail list (webmail bg-selection + bar).
+  rowActive: {
+    backgroundColor: c.selection,
+    borderLeftWidth: 2,
+    borderLeftColor: c.primary,
+    paddingLeft: spacing.lg - 2,
+  },
   checkbox: {
     width: 22,
     height: 22,
diff --git a/src/navigation/pane.tsx b/src/navigation/pane.tsx
new file mode 100644
index 00000000..5ff21676
--- /dev/null
+++ b/src/navigation/pane.tsx
@@ -0,0 +1,62 @@
+import React from 'react';
+import { NavigationProvider, type NavigationProp, type ParamListBase } from '@react-navigation/native';
+
+/** True inside the detail pane of a split view. */
+const PaneContext = React.createContext(false);
+
+/** A screen in a split view's detail pane has no back button. */
+export function useInPane(): boolean {
+  return React.useContext(PaneContext);
+}
+
+/** Routes a pane shows itself instead of pushing them on the stack. */
+export type PaneTarget = { name: string; params?: object };
+
+/**
+ * Runs a stack screen inside a split view's detail pane. The screen's own
+ * `useNavigation()` / `useRoute()` get the pane: `goBack` closes it, the
+ * routes `onOpen` accepts open in it, everything else goes to the stack.
+ */
+export function PaneScreen({
+  navigation,
+  name,
+  params,
+  onOpen,
+  onClose,
+  children,
+}: {
+  navigation: NavigationProp<ParamListBase>;
+  name: string;
+  params: object;
+  /** Return true when the pane shows this route itself. */
+  onOpen: (target: PaneTarget) => boolean;
+  onClose: () => void;
+  children: React.ReactNode;
+}) {
+  const route = React.useMemo(() => ({ key: `pane-${name}`, name, params }), [name, params]);
+  const paneNavigation = React.useMemo(() => {
+    const open = (method: 'navigate' | 'push' | 'replace') => (...args: unknown[]) => {
+      const [target, targetParams] = args as [string, object | undefined];
+      if (typeof target === 'string' && onOpen({ name: target, params: targetParams })) return;
+      // `push` and `replace` only exist on a stack; from a tab they become a
+      // navigate, which reaches the root stack all the same.
+      const real = navigation as unknown as Record<string, ((...a: unknown[]) => void) | undefined>;
+      (real[method] ?? real.navigate)!(...args);
+    };
+    return {
+      ...navigation,
+      goBack: onClose,
+      navigate: open('navigate'),
+      push: open('push'),
+      replace: open('replace'),
+      canGoBack: () => true,
+    } as unknown as NavigationProp<ParamListBase>;
+  }, [navigation, onOpen, onClose]);
+  return (
+    <PaneContext.Provider value>
+      <NavigationProvider route={route} navigation={paneNavigation}>
+        {children}
+      </NavigationProvider>
+    </PaneContext.Provider>
+  );
+}
diff --git a/src/screens/ContactDetailScreen.tsx b/src/screens/ContactDetailScreen.tsx
index 6d9f7ce0..f72230e1 100644
--- a/src/screens/ContactDetailScreen.tsx
+++ b/src/screens/ContactDetailScreen.tsx
@@ -6,6 +6,7 @@ import {
 import * as FileSystem from 'expo-file-system/legacy';
 import * as Sharing from 'expo-sharing';
 import { SafeAreaView } from 'react-native-safe-area-context';
+import { useInPane } from '../navigation/pane';
 import { useNavigation, useRoute, type RouteProp } from '@react-navigation/native';
 import type { NativeStackNavigationProp } from '@react-navigation/native-stack';
 import {
@@ -132,6 +133,7 @@ export default function ContactDetailScreen() {
   const navigation = useNavigation<Nav>();
   const route = useRoute<Route>();
   const t = useLocaleStore((s) => s.t);
+  const inPane = useInPane();
   const { contactId } = route.params;
 
   const contact = useContactsStore((s) => s.contacts.find((c) => c.id === contactId));
@@ -360,16 +362,19 @@ export default function ContactDetailScreen() {
 
   return (
     <SafeAreaView style={styles.container} edges={['top']}>
-      <View style={styles.header}>
-        <Pressable
-          onPress={() => navigation.goBack()}
-          style={styles.headerBtn}
-          hitSlop={8}
-          accessibilityRole="button"
-          accessibilityLabel={t('common.back', 'Back')}
-        >
-          <ArrowLeft size={22} color={c.text} />
-        </Pressable>
+      <View style={[styles.header, inPane && styles.headerInPane]}>
+        {/* In a split view's pane the list is right next to it: no back. */}
+        {!inPane && (
+          <Pressable
+            onPress={() => navigation.goBack()}
+            style={styles.headerBtn}
+            hitSlop={8}
+            accessibilityRole="button"
+            accessibilityLabel={t('common.back', 'Back')}
+          >
+            <ArrowLeft size={22} color={c.text} />
+          </Pressable>
+        )}
         <Text style={styles.headerTitle} numberOfLines={1}>
           {isGroup(contact) ? t('contacts.group', 'Group') : t('contacts.contact', 'Contact')}
         </Text>
@@ -911,7 +916,8 @@ function makeStyles(c: ThemePalette) {
     container: { flex: 1, backgroundColor: c.background },
     scrollContent: { paddingBottom: spacing.xxxl * 2 },
 
-    header: {
+    headerInPane: { paddingLeft: spacing.lg },
+  header: {
       flexDirection: 'row',
       alignItems: 'center',
       paddingHorizontal: spacing.sm,
diff --git a/src/screens/ContactsScreen.tsx b/src/screens/ContactsScreen.tsx
index 58467fd3..0d0c3f86 100644
--- a/src/screens/ContactsScreen.tsx
+++ b/src/screens/ContactsScreen.tsx
@@ -101,7 +101,14 @@ function categoryTitle(
   }
 }
 
-export default function ContactsScreen() {
+interface ContactsScreenProps {
+  /** Split view: open the contact in the detail pane instead of the stack. */
+  onOpenContact?: (contact: ContactCard) => void;
+  /** The contact open in the detail pane. */
+  activeContactId?: string | null;
+}
+
+export default function ContactsScreen({ onOpenContact, activeContactId = null }: ContactsScreenProps = {}) {
   const c = useColors();
   const styles = React.useMemo(() => makeStyles(c), [c]);
   const navigation = useNavigation<Nav>();
@@ -210,7 +217,9 @@ export default function ContactsScreen() {
       toggleSelect(c.id);
       return;
     }
-    if (isGroup(c)) {
+    if (onOpenContact) {
+      onOpenContact(c);
+    } else if (isGroup(c)) {
       navigation.navigate('GroupDetail', { groupId: c.id });
     } else {
       navigation.navigate('ContactDetail', { contactId: c.id });
@@ -541,6 +550,7 @@ export default function ContactsScreen() {
             onPress={() => handleRowPress(item)}
             onLongPress={() => handleLongPress(item)}
             selected={selection.has(item.id)}
+            active={item.id === activeContactId}
             selectionMode={selectionMode}
           />
         )}
diff --git a/src/screens/ContactsTab.tsx b/src/screens/ContactsTab.tsx
new file mode 100644
index 00000000..1b1a6956
--- /dev/null
+++ b/src/screens/ContactsTab.tsx
@@ -0,0 +1,97 @@
+import React from 'react';
+import { StyleSheet, Text, View, useWindowDimensions } from 'react-native';
+import { useNavigation, type NavigationProp, type ParamListBase } from '@react-navigation/native';
+import { BookUser } from 'lucide-react-native';
+
+import ContactsScreen from './ContactsScreen';
+import ContactDetailScreen from './ContactDetailScreen';
+import GroupDetailScreen from './GroupDetailScreen';
+import type { ContactCard } from '../api/types';
+import { isGroup } from '../lib/contact-utils';
+import { listPaneWidth, useLayout } from '../lib/use-layout';
+import { PaneScreen, type PaneTarget } from '../navigation/pane';
+import { useLocaleStore } from '../stores/locale-store';
+import { useColors } from '../theme/colors';
+import { spacing, typography, type ThemePalette } from '../theme/tokens';
+
+type Open =
+  | { name: 'ContactDetail'; params: { contactId: string } }
+  | { name: 'GroupDetail'; params: { groupId: string } };
+
+function openFor(contact: ContactCard): Open {
+  return isGroup(contact)
+    ? { name: 'GroupDetail', params: { groupId: contact.id } }
+    : { name: 'ContactDetail', params: { contactId: contact.id } };
+}
+
+/**
+ * The Contacts tab: the list on a phone; list and contact side by side on a
+ * wide window, where the contact (or group) opens in the right pane.
+ */
+export default function ContactsTab() {
+  const c = useColors();
+  const styles = React.useMemo(() => makeStyles(c), [c]);
+  const t = useLocaleStore((s) => s.t);
+  const navigation = useNavigation<NavigationProp<ParamListBase>>();
+  const { isSplit } = useLayout();
+  const { width } = useWindowDimensions();
+  const [open, setOpen] = React.useState<Open | null>(null);
+
+  // Narrowed with a contact open: hand it to the stack.
+  const openRef = React.useRef(open);
+  openRef.current = open;
+  React.useEffect(() => {
+    if (isSplit || !openRef.current) return;
+    navigation.navigate(openRef.current.name, openRef.current.params);
+    setOpen(null);
+  }, [isSplit, navigation]);
+
+  const onOpen = React.useCallback((target: PaneTarget) => {
+    if (target.name === 'ContactDetail' || target.name === 'GroupDetail') {
+      setOpen(target as Open);
+      return true;
+    }
+    return false;
+  }, []);
+  const onClose = React.useCallback(() => setOpen(null), []);
+
+  if (!isSplit) return <ContactsScreen />;
+
+  const activeId = open ? ('contactId' in open.params ? open.params.contactId : open.params.groupId) : null;
+  return (
+    <View style={styles.row}>
+      <View style={[styles.listPane, { width: listPaneWidth(width) }]}>
+        <ContactsScreen onOpenContact={(contact) => setOpen(openFor(contact))} activeContactId={activeId} />
+      </View>
+      <View style={styles.detailPane}>
+        {open ? (
+          <PaneScreen
+            key={activeId ?? undefined}
+            navigation={navigation}
+            name={open.name}
+            params={open.params}
+            onOpen={onOpen}
+            onClose={onClose}
+          >
+            {open.name === 'ContactDetail' ? <ContactDetailScreen /> : <GroupDetailScreen />}
+          </PaneScreen>
+        ) : (
+          <View style={styles.empty}>
+            <BookUser size={40} color={c.textMuted} strokeWidth={1.5} />
+            <Text style={styles.emptyText}>{t('contacts.detail.no_contact_selected', 'Select a contact to view details')}</Text>
+          </View>
+        )}
+      </View>
+    </View>
+  );
+}
+
+function makeStyles(c: ThemePalette) {
+  return StyleSheet.create({
+    row: { flex: 1, flexDirection: 'row', backgroundColor: c.background },
+    listPane: { borderRightWidth: 1, borderRightColor: c.border },
+    detailPane: { flex: 1 },
+    empty: { flex: 1, alignItems: 'center', justifyContent: 'center', gap: spacing.md, padding: spacing.xl },
+    emptyText: { ...typography.body, color: c.textMuted, textAlign: 'center' },
+  });
+}
diff --git a/src/screens/GroupDetailScreen.tsx b/src/screens/GroupDetailScreen.tsx
index f0e36b83..8a5c410b 100644
--- a/src/screens/GroupDetailScreen.tsx
+++ b/src/screens/GroupDetailScreen.tsx
@@ -3,6 +3,7 @@ import {
   View, Text, StyleSheet, Pressable, FlatList, Alert,
 } from 'react-native';
 import { SafeAreaView } from 'react-native-safe-area-context';
+import { useInPane } from '../navigation/pane';
 import { useNavigation, useRoute, type RouteProp } from '@react-navigation/native';
 import type { NativeStackNavigationProp } from '@react-navigation/native-stack';
 import {
@@ -35,6 +36,7 @@ export default function GroupDetailScreen() {
   const navigation = useNavigation<Nav>();
   const route = useRoute<Route>();
   const t = useLocaleStore((s) => s.t);
+  const inPane = useInPane();
   const { groupId } = route.params;
 
   const allContacts = useContactsStore((s) => s.contacts);
@@ -132,16 +134,19 @@ export default function GroupDetailScreen() {
 
   return (
     <SafeAreaView style={styles.container} edges={['top']}>
-      <View style={styles.header}>
-        <Pressable
-          onPress={() => navigation.goBack()}
-          style={styles.headerBtn}
-          hitSlop={8}
-          accessibilityRole="button"
-          accessibilityLabel={t('common.back', 'Back')}
-        >
-          <ArrowLeft size={22} color={c.text} />
-        </Pressable>
+      <View style={[styles.header, inPane && styles.headerInPane]}>
+        {/* In a split view's pane the list is right next to it: no back. */}
+        {!inPane && (
+          <Pressable
+            onPress={() => navigation.goBack()}
+            style={styles.headerBtn}
+            hitSlop={8}
+            accessibilityRole="button"
+            accessibilityLabel={t('common.back', 'Back')}
+          >
+            <ArrowLeft size={22} color={c.text} />
+          </Pressable>
+        )}
         <Text style={styles.headerTitle} numberOfLines={1}>{name}</Text>
         <View style={styles.headerActions}>
           <Pressable
@@ -263,6 +268,7 @@ export default function GroupDetailScreen() {
 function makeStyles(c: ThemePalette) {
   return StyleSheet.create({
   container: { flex: 1, backgroundColor: c.background },
+  headerInPane: { paddingLeft: spacing.lg },
   header: {
     flexDirection: 'row',
     alignItems: 'center',