diff --git a/Cargo.lock b/Cargo.lock
index 0b45984f9..08ca88a21 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3082,6 +3082,7 @@ dependencies = [
  "rfd",
  "serde_json",
  "winresource",
+ "zbus",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index b3c0caa17..db854caa7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -91,6 +91,9 @@ eframe = { version = "0.36", default-features = false }
 egui_kittest = "0.36"
 rfd = "0.17"
 muda = { version = "0.21", default-features = false } # native menu bar (macOS: objc2/AppKit, pure Rust; no GTK)
+# Linux: the desktop's dark/light setting from the XDG settings portal (Settings ▸ Interface ▸
+# Appearance Mode ▸ Auto). Pure Rust; the version accesskit already brings in, pinned to it.
+zbus = "=5.19.0"
 web-time = "1"
 
 # web (apps/lightcraft-web)
diff --git a/apps/lightcraft-web/src/web.rs b/apps/lightcraft-web/src/web.rs
index ba6da7254..b635442d7 100644
--- a/apps/lightcraft-web/src/web.rs
+++ b/apps/lightcraft-web/src/web.rs
@@ -233,6 +233,8 @@ fn services(originals: Originals, backend: Option<Backend>, files: Files, frozen
             w.open_with_url_and_target(url, "_blank").map(|_| ()).map_err(|_| "the browser blocked the new tab".to_string())
         })),
         pick_folder: None,
+        // the browser reports prefers-color-scheme to egui
+        system_theme: None,
     }
 }
 
diff --git a/apps/lightcraft/Cargo.toml b/apps/lightcraft/Cargo.toml
index 5873dce7e..345e090d1 100644
--- a/apps/lightcraft/Cargo.toml
+++ b/apps/lightcraft/Cargo.toml
@@ -37,5 +37,8 @@ winresource = "0.1"
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 rfd = { workspace = true }
 
+[target.'cfg(target_os = "linux")'.dependencies]
+zbus = { workspace = true }
+
 [target.'cfg(target_os = "macos")'.dependencies]
 muda = { workspace = true }
diff --git a/apps/lightcraft/src/appearance.rs b/apps/lightcraft/src/appearance.rs
new file mode 100644
index 000000000..74333a301
--- /dev/null
+++ b/apps/lightcraft/src/appearance.rs
@@ -0,0 +1,198 @@
+//! The desktop's dark/light setting for Settings ▸ Interface ▸ Appearance Mode ▸ Auto, on Linux
+//! desktops whose windowing layer reports no theme to egui (many Wayland compositors).
+//!
+//! The XDG settings portal is read once, then its `SettingChanged` signal is followed on a worker
+//! thread that wakes the UI only when the value changes. Nothing is polled. `gsettings` is a
+//! one-shot fallback at start-up, run by absolute path, only when the portal gives no answer.
+//! Elsewhere egui's own report (`Context::system_theme`) is used.
+
+#[cfg(target_os = "linux")]
+const PORTAL_NAMESPACE: &str = "org.freedesktop.appearance";
+#[cfg(target_os = "linux")]
+const PORTAL_KEY: &str = "color-scheme";
+
+#[cfg(target_os = "linux")]
+fn portal_proxy() -> Option<zbus::blocking::Proxy<'static>> {
+    let conn = zbus::blocking::connection::Builder::session().ok()?.method_timeout(std::time::Duration::from_secs(2)).build().ok()?;
+    zbus::blocking::Proxy::new(&conn, "org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop", "org.freedesktop.portal.Settings").ok()
+}
+
+#[cfg(target_os = "linux")]
+fn portal_theme(proxy: &zbus::blocking::Proxy<'_>) -> Option<egui::Theme> {
+    let value: zbus::zvariant::OwnedValue = proxy.call("Read", &(PORTAL_NAMESPACE, PORTAL_KEY)).ok()?;
+    decode(portal_code(value)?)
+}
+
+/// The `u32` inside a portal value. `Settings.Read` answers a variant, and some portals nest
+/// another variant inside it.
+#[cfg(target_os = "linux")]
+fn portal_code(value: zbus::zvariant::OwnedValue) -> Option<u32> {
+    let mut value: zbus::zvariant::Value<'_> = value.into();
+    for _ in 0..4 {
+        match value {
+            zbus::zvariant::Value::Value(inner) => value = *inner,
+            other => return u32::try_from(other).ok(),
+        }
+    }
+    None
+}
+
+/// The portal's `color-scheme`: 0 = no preference, 1 = prefer dark, 2 = prefer light.
+#[cfg(target_os = "linux")]
+fn decode(code: u32) -> Option<egui::Theme> {
+    match code {
+        1 => Some(egui::Theme::Dark),
+        2 => Some(egui::Theme::Light),
+        _ => None,
+    }
+}
+
+/// One-shot fallback for desktops without the settings portal. It runs once at start-up, by
+/// absolute path, and is never repeated.
+#[cfg(target_os = "linux")]
+fn gtk_theme() -> Option<egui::Theme> {
+    let exe = ["/usr/bin/gsettings", "/bin/gsettings", "/usr/local/bin/gsettings"].into_iter().find(|p| std::path::Path::new(p).is_file())?;
+    let output = std::process::Command::new(exe).args(["get", "org.gnome.desktop.interface", "color-scheme"]).output().ok()?;
+    if !output.status.success() {
+        return None;
+    }
+    parse_gtk_scheme(std::str::from_utf8(&output.stdout).ok()?)
+}
+
+#[cfg(target_os = "linux")]
+fn parse_gtk_scheme(s: &str) -> Option<egui::Theme> {
+    match s.trim().trim_matches('\'') {
+        "prefer-dark" => Some(egui::Theme::Dark),
+        "prefer-light" => Some(egui::Theme::Light),
+        _ => None,
+    }
+}
+
+#[cfg(target_os = "linux")]
+fn code_of(theme: Option<egui::Theme>) -> u8 {
+    match theme {
+        Some(egui::Theme::Dark) => 1,
+        Some(egui::Theme::Light) => 2,
+        None => 0,
+    }
+}
+
+/// Wake the first frame after a slow initial Read as well as subsequent real changes.
+#[cfg(target_os = "linux")]
+fn publish(value: &std::sync::atomic::AtomicU8, wake: &std::sync::OnceLock<egui::Context>, code: u8) {
+    if value.swap(code, std::sync::atomic::Ordering::Relaxed) != code
+        && let Some(ctx) = wake.get()
+    {
+        ctx.request_repaint();
+    }
+}
+
+/// The host's system-appearance service (Linux), or `None` where egui's report is enough.
+pub fn service() -> Option<lightcraft_ui_egui::SystemThemeFn> {
+    #[cfg(target_os = "linux")]
+    {
+        use std::sync::{
+            Arc, OnceLock,
+            atomic::{AtomicU8, Ordering},
+        };
+        let value = Arc::new(AtomicU8::new(0));
+        let wake: Arc<OnceLock<egui::Context>> = Arc::new(OnceLock::new());
+        let (worker_value, worker_wake) = (Arc::clone(&value), Arc::clone(&wake));
+        let (ready, wait) = std::sync::mpsc::channel();
+        if std::thread::Builder::new()
+            .name("appearance-portal".into())
+            .spawn(move || {
+                let proxy = portal_proxy();
+                // Subscribe before Read so a change during startup is queued rather than lost.
+                let signals = proxy.as_ref().and_then(|proxy| proxy.receive_signal("SettingChanged").ok());
+                let initial = proxy.as_ref().and_then(portal_theme).or_else(gtk_theme);
+                publish(&worker_value, &worker_wake, code_of(initial));
+                let _ = ready.send(());
+                let Some(signals) = signals else { return };
+                // Blocks until the portal sends a signal: no polling.
+                for message in signals {
+                    let Ok((namespace, key, changed)) = message.body().deserialize::<(String, String, zbus::zvariant::OwnedValue)>() else {
+                        continue;
+                    };
+                    if namespace != PORTAL_NAMESPACE || key != PORTAL_KEY {
+                        continue;
+                    }
+                    let code = code_of(portal_code(changed).and_then(decode));
+                    publish(&worker_value, &worker_wake, code);
+                }
+            })
+            .is_err()
+        {
+            return None;
+        }
+        // The first frame shows the right theme when the portal answers quickly; a slow one
+        // only delays the switch (the worker wakes the UI when the value changes).
+        let _ = wait.recv_timeout(std::time::Duration::from_millis(250));
+        Some(Box::new(move |ctx| {
+            let _ = wake.set(ctx.clone());
+            decode(u32::from(value.load(Ordering::Relaxed)))
+        }))
+    }
+    #[cfg(not(target_os = "linux"))]
+    {
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn delayed_initial_read_repaints_only_on_change() {
+        use std::sync::{
+            Arc, OnceLock,
+            atomic::{AtomicU8, AtomicUsize, Ordering},
+        };
+        let ctx = egui::Context::default();
+        let settle = |ctx: &egui::Context| {
+            for _ in 0..8 {
+                let mut output = ctx.run_ui(egui::RawInput::default(), |_| {});
+                output.textures_delta.clear();
+            }
+        };
+        settle(&ctx);
+        let calls = Arc::new(AtomicUsize::new(0));
+        let observed = Arc::clone(&calls);
+        ctx.set_request_repaint_callback(move |_| {
+            observed.fetch_add(1, Ordering::Relaxed);
+        });
+        let wake = OnceLock::new();
+        assert!(wake.set(ctx.clone()).is_ok());
+        let value = AtomicU8::new(0);
+        super::publish(&value, &wake, 2);
+        assert_eq!(value.load(Ordering::Relaxed), 2);
+        let after_change = calls.load(Ordering::Relaxed);
+        assert!(after_change > 0);
+        settle(&ctx);
+        let after_settle = calls.load(Ordering::Relaxed);
+        super::publish(&value, &wake, 2);
+        assert_eq!(calls.load(Ordering::Relaxed), after_settle);
+    }
+
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn portal_values_and_gsettings_output_decode() {
+        assert_eq!(super::decode(0), None);
+        assert_eq!(super::decode(1), Some(egui::Theme::Dark));
+        assert_eq!(super::decode(2), Some(egui::Theme::Light));
+        assert_eq!(super::decode(9), None);
+        let nested = zbus::zvariant::Value::Value(Box::new(zbus::zvariant::Value::Value(Box::new(zbus::zvariant::Value::U32(2)))));
+        assert_eq!(super::portal_code(zbus::zvariant::OwnedValue::try_from(nested).unwrap()), Some(2));
+        let plain = zbus::zvariant::OwnedValue::from(1u32);
+        assert_eq!(super::portal_code(plain), Some(1));
+        let wrong = zbus::zvariant::OwnedValue::try_from(zbus::zvariant::Value::from("dark")).unwrap();
+        assert_eq!(super::portal_code(wrong), None);
+        assert_eq!(super::parse_gtk_scheme("'prefer-light'\n"), Some(egui::Theme::Light));
+        assert_eq!(super::parse_gtk_scheme("'prefer-dark'\n"), Some(egui::Theme::Dark));
+        assert_eq!(super::parse_gtk_scheme("'default'\n"), None);
+        assert_eq!(super::parse_gtk_scheme(""), None);
+        for theme in [None, Some(egui::Theme::Dark), Some(egui::Theme::Light)] {
+            assert_eq!(super::decode(u32::from(super::code_of(theme))), theme);
+        }
+    }
+}
diff --git a/apps/lightcraft/src/main.rs b/apps/lightcraft/src/main.rs
index 42435e39b..49cde2da2 100644
--- a/apps/lightcraft/src/main.rs
+++ b/apps/lightcraft/src/main.rs
@@ -23,6 +23,7 @@
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 
 mod alloc_release;
+mod appearance;
 mod control_server;
 mod dialog_filter;
 mod editors;
@@ -579,6 +580,7 @@ fn services(cc: &eframe::CreationContext<'_>, log_file: Option<&std::path::Path>
         // the library is a folder on disk: backed up with the user's other files
         backup_library: None,
         restore_library: None,
+        system_theme: appearance::service(),
     }
 }
 
diff --git a/crates/ui-egui/locales/de.json b/crates/ui-egui/locales/de.json
index c9a788bd2..c1854810c 100644
--- a/crates/ui-egui/locales/de.json
+++ b/crates/ui-egui/locales/de.json
@@ -2030,6 +2030,19 @@
   "Not saved": "Nicht gespeichert",
   "A folder is being synchronized": "Ein Ordner wird gerade synchronisiert",
   "Wait for the import to finish": "Warten Sie, bis der Import abgeschlossen ist",
+  "Appearance": "Erscheinungsbild",
+  "Appearance Mode": "Erscheinungsmodus",
+  "Sync with System": "Mit System synchronisieren",
+  "Light Mode": "Heller Modus",
+  "Dark Mode": "Dunkler Modus",
+  "Next Appearance Mode": "Nächster Erscheinungsmodus",
+  "Light Theme": "Helles Design",
+  "Dark Theme": "Dunkles Design",
+  "In Use": "In Verwendung",
+  "Charcoal": "Anthrazit",
+  "Midnight": "Mitternacht",
+  "Silver": "Silber",
+  "Paper": "Papier",
   "Show less": "Weniger anzeigen",
   "Quit while tasks are running?": "Beenden, während Aufgaben laufen?",
   "Exporting contact sheet": "Kontaktabzug wird exportiert",
@@ -2080,5 +2093,8 @@
   "Move to Folder": "In Ordner verschieben",
   "Move to Folder…": "In Ordner verschieben…",
   "Move Selected Photos Here": "Ausgewählte Fotos hierher verschieben",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "Verschiebt die Dateien samt XMP-Filialdateien in diesen Ordner; nichts wird überschrieben"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "Verschiebt die Dateien samt XMP-Filialdateien in diesen Ordner; nichts wird überschrieben",
+  "Appearance Settings…": "Erscheinungsbild-Einstellungen…",
+  "Add to favorites": "Zu Favoriten hinzufügen",
+  "Remove from favorites": "Aus Favoriten entfernen"
 }
diff --git a/crates/ui-egui/locales/es.json b/crates/ui-egui/locales/es.json
index fd9c74647..792ca4d02 100644
--- a/crates/ui-egui/locales/es.json
+++ b/crates/ui-egui/locales/es.json
@@ -1875,6 +1875,19 @@
   "Not saved": "Sin guardar",
   "A folder is being synchronized": "Se está sincronizando una carpeta",
   "Wait for the import to finish": "Espera a que termine la importación",
+  "Appearance": "Apariencia",
+  "Appearance Mode": "Modo de apariencia",
+  "Sync with System": "Sincronizar con el sistema",
+  "Light Mode": "Modo claro",
+  "Dark Mode": "Modo oscuro",
+  "Next Appearance Mode": "Siguiente modo de apariencia",
+  "Light Theme": "Tema claro",
+  "Dark Theme": "Tema oscuro",
+  "In Use": "En uso",
+  "Charcoal": "Carbón",
+  "Midnight": "Medianoche",
+  "Silver": "Plata",
+  "Paper": "Papel",
   "Show less": "Mostrar menos",
   "Quit while tasks are running?": "¿Salir con tareas en curso?",
   "Exporting contact sheet": "Exportando hoja de contactos",
@@ -1922,5 +1935,8 @@
   "Move to Folder": "Mover a carpeta",
   "Move to Folder…": "Mover a carpeta…",
   "Move Selected Photos Here": "Mover aquí las fotos seleccionadas",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "Mueve los archivos y sus archivos XMP auxiliares a esta carpeta; nunca sobrescribe"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "Mueve los archivos y sus archivos XMP auxiliares a esta carpeta; nunca sobrescribe",
+  "Appearance Settings…": "Ajustes de apariencia…",
+  "Add to favorites": "Añadir a favoritos",
+  "Remove from favorites": "Quitar de favoritos"
 }
diff --git a/crates/ui-egui/locales/fr.json b/crates/ui-egui/locales/fr.json
index 014c340eb..2055d4385 100644
--- a/crates/ui-egui/locales/fr.json
+++ b/crates/ui-egui/locales/fr.json
@@ -1922,5 +1922,8 @@
   "Move to Folder": "Déplacer vers un dossier",
   "Move to Folder…": "Déplacer vers un dossier…",
   "Move Selected Photos Here": "Déplacer ici les photos sélectionnées",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "Déplace les fichiers et leurs fichiers annexes XMP dans ce dossier ; n'écrase jamais rien"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "Déplace les fichiers et leurs fichiers annexes XMP dans ce dossier ; n'écrase jamais rien",
+  "Appearance Settings…": "Réglages d’apparence…",
+  "Add to favorites": "Ajouter aux favoris",
+  "Remove from favorites": "Retirer des favoris"
 }
diff --git a/crates/ui-egui/locales/ja.json b/crates/ui-egui/locales/ja.json
index 39206b6e0..f38a87708 100644
--- a/crates/ui-egui/locales/ja.json
+++ b/crates/ui-egui/locales/ja.json
@@ -1877,6 +1877,19 @@
   "Not saved": "保存されていません",
   "A folder is being synchronized": "フォルダを同期中です",
   "Wait for the import to finish": "読み込みが終わるまでお待ちください",
+  "Appearance": "外観",
+  "Appearance Mode": "外観モード",
+  "Sync with System": "システムと同期",
+  "Light Mode": "ライトモード",
+  "Dark Mode": "ダークモード",
+  "Next Appearance Mode": "次の外観モード",
+  "Light Theme": "ライトテーマ",
+  "Dark Theme": "ダークテーマ",
+  "In Use": "使用中",
+  "Charcoal": "チャコール",
+  "Midnight": "ミッドナイト",
+  "Silver": "シルバー",
+  "Paper": "ペーパー",
   "Show less": "表示を減らす",
   "Quit while tasks are running?": "タスクの実行中に終了しますか？",
   "Exporting contact sheet": "コンタクトシートを書き出し中",
@@ -1924,5 +1937,8 @@
   "Move to Folder": "フォルダへ移動",
   "Move to Folder…": "フォルダへ移動…",
   "Move Selected Photos Here": "選択した写真をここへ移動",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "ファイルと XMP サイドカーをこのフォルダへ移動します。上書きはしません"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "ファイルと XMP サイドカーをこのフォルダへ移動します。上書きはしません",
+  "Appearance Settings…": "外観設定…",
+  "Add to favorites": "お気に入りに追加",
+  "Remove from favorites": "お気に入りから削除"
 }
diff --git a/crates/ui-egui/locales/pt-br.json b/crates/ui-egui/locales/pt-br.json
index f27bd0e36..5ab30b05f 100644
--- a/crates/ui-egui/locales/pt-br.json
+++ b/crates/ui-egui/locales/pt-br.json
@@ -1875,6 +1875,19 @@
   "Not saved": "Não salvo",
   "A folder is being synchronized": "Uma pasta está sendo sincronizada",
   "Wait for the import to finish": "Aguarde a importação terminar",
+  "Appearance": "Aparência",
+  "Appearance Mode": "Modo de aparência",
+  "Sync with System": "Sincronizar com o sistema",
+  "Light Mode": "Modo claro",
+  "Dark Mode": "Modo escuro",
+  "Next Appearance Mode": "Próximo modo de aparência",
+  "Light Theme": "Tema claro",
+  "Dark Theme": "Tema escuro",
+  "In Use": "Em uso",
+  "Charcoal": "Carvão",
+  "Midnight": "Meia-noite",
+  "Silver": "Prata",
+  "Paper": "Papel",
   "Show less": "Mostrar menos",
   "Quit while tasks are running?": "Sair com tarefas em andamento?",
   "Exporting contact sheet": "Exportando folha de contato",
@@ -1922,5 +1935,8 @@
   "Move to Folder": "Mover para pasta",
   "Move to Folder…": "Mover para pasta…",
   "Move Selected Photos Here": "Mover as fotos selecionadas para cá",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "Move os arquivos e seus arquivos XMP auxiliares para esta pasta; nunca sobrescreve"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "Move os arquivos e seus arquivos XMP auxiliares para esta pasta; nunca sobrescreve",
+  "Appearance Settings…": "Configurações de aparência…",
+  "Add to favorites": "Adicionar aos favoritos",
+  "Remove from favorites": "Remover dos favoritos"
 }
diff --git a/crates/ui-egui/locales/ru.json b/crates/ui-egui/locales/ru.json
index 2177adbeb..d777309c9 100644
--- a/crates/ui-egui/locales/ru.json
+++ b/crates/ui-egui/locales/ru.json
@@ -1588,6 +1588,19 @@
   "Not saved": "Не сохранено",
   "A folder is being synchronized": "Идёт синхронизация папки",
   "Wait for the import to finish": "Дождитесь окончания импорта",
+  "Appearance": "Оформление",
+  "Appearance Mode": "Режим оформления",
+  "Sync with System": "Как в системе",
+  "Light Mode": "Светлый режим",
+  "Dark Mode": "Тёмный режим",
+  "Next Appearance Mode": "Следующий режим оформления",
+  "Light Theme": "Светлая тема",
+  "Dark Theme": "Тёмная тема",
+  "In Use": "Используется",
+  "Charcoal": "Графит",
+  "Midnight": "Полночь",
+  "Silver": "Серебро",
+  "Paper": "Бумага",
   "Show less": "Свернуть",
   "Quit while tasks are running?": "Выйти, пока выполняются задачи?",
   "Exporting contact sheet": "Экспорт контрольного листа",
@@ -1636,5 +1649,8 @@
   "Move to Folder": "Переместить в папку",
   "Move to Folder…": "Переместить в папку…",
   "Move Selected Photos Here": "Переместить выбранные фото сюда",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "Перемещает файлы и их XMP-файлы в эту папку; ничего не перезаписывает"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "Перемещает файлы и их XMP-файлы в эту папку; ничего не перезаписывает",
+  "Appearance Settings…": "Настройки оформления…",
+  "Add to favorites": "Добавить в избранное",
+  "Remove from favorites": "Удалить из избранного"
 }
diff --git a/crates/ui-egui/locales/uk.json b/crates/ui-egui/locales/uk.json
index c1e559e42..7d6237d27 100644
--- a/crates/ui-egui/locales/uk.json
+++ b/crates/ui-egui/locales/uk.json
@@ -2116,5 +2116,8 @@
   "Move to Folder": "Перемістити до теки",
   "Move to Folder…": "Перемістити до теки…",
   "Move Selected Photos Here": "Перемістити вибрані фото сюди",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "Переміщує файли та їхні XMP-файли до цієї теки; нічого не перезаписує"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "Переміщує файли та їхні XMP-файли до цієї теки; нічого не перезаписує",
+  "Appearance Settings…": "Налаштування вигляду…",
+  "Add to favorites": "Додати до вибраного",
+  "Remove from favorites": "Видалити з вибраного"
 }
diff --git a/crates/ui-egui/locales/zh-hans.json b/crates/ui-egui/locales/zh-hans.json
index c28b4eee5..4226c22a1 100644
--- a/crates/ui-egui/locales/zh-hans.json
+++ b/crates/ui-egui/locales/zh-hans.json
@@ -1875,6 +1875,19 @@
   "Not saved": "未保存",
   "A folder is being synchronized": "正在同步文件夹",
   "Wait for the import to finish": "请等待导入完成",
+  "Appearance": "外观",
+  "Appearance Mode": "外观模式",
+  "Sync with System": "与系统同步",
+  "Light Mode": "浅色模式",
+  "Dark Mode": "深色模式",
+  "Next Appearance Mode": "下一个外观模式",
+  "Light Theme": "浅色主题",
+  "Dark Theme": "深色主题",
+  "In Use": "使用中",
+  "Charcoal": "炭灰",
+  "Midnight": "午夜",
+  "Silver": "银色",
+  "Paper": "纸白",
   "Show less": "收起",
   "Quit while tasks are running?": "要在任务运行时退出吗？",
   "Exporting contact sheet": "正在导出联系表",
@@ -1922,5 +1935,8 @@
   "Move to Folder": "移动到文件夹",
   "Move to Folder…": "移动到文件夹…",
   "Move Selected Photos Here": "将所选照片移到此处",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "将文件及其 XMP 附属文件移到此文件夹；绝不覆盖"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "将文件及其 XMP 附属文件移到此文件夹；绝不覆盖",
+  "Appearance Settings…": "外观设置…",
+  "Add to favorites": "添加到收藏",
+  "Remove from favorites": "从收藏中移除"
 }
diff --git a/crates/ui-egui/locales/zh-hant.json b/crates/ui-egui/locales/zh-hant.json
index fba96a088..717c1449c 100644
--- a/crates/ui-egui/locales/zh-hant.json
+++ b/crates/ui-egui/locales/zh-hant.json
@@ -1875,6 +1875,19 @@
   "Not saved": "未儲存",
   "A folder is being synchronized": "正在同步資料夾",
   "Wait for the import to finish": "請等待匯入完成",
+  "Appearance": "外觀",
+  "Appearance Mode": "外觀模式",
+  "Sync with System": "與系統同步",
+  "Light Mode": "淺色模式",
+  "Dark Mode": "深色模式",
+  "Next Appearance Mode": "下一個外觀模式",
+  "Light Theme": "淺色主題",
+  "Dark Theme": "深色主題",
+  "In Use": "使用中",
+  "Charcoal": "炭灰",
+  "Midnight": "午夜",
+  "Silver": "銀色",
+  "Paper": "紙白",
   "Show less": "收合",
   "Quit while tasks are running?": "要在工作執行時結束嗎？",
   "Exporting contact sheet": "正在匯出聯絡表",
@@ -1922,5 +1935,8 @@
   "Move to Folder": "移至資料夾",
   "Move to Folder…": "移至資料夾…",
   "Move Selected Photos Here": "將所選照片移至此處",
-  "Moves the files and their XMP sidecars into this folder; never overwrites": "將檔案及其 XMP 附屬檔案移至此資料夾；絕不覆寫"
+  "Moves the files and their XMP sidecars into this folder; never overwrites": "將檔案及其 XMP 附屬檔案移至此資料夾；絕不覆寫",
+  "Appearance Settings…": "外觀設定…",
+  "Add to favorites": "加入最愛",
+  "Remove from favorites": "從最愛移除"
 }
diff --git a/crates/ui-egui/src/headless.rs b/crates/ui-egui/src/headless.rs
index 7e30d3ca9..a317069e0 100644
--- a/crates/ui-egui/src/headless.rs
+++ b/crates/ui-egui/src/headless.rs
@@ -3238,10 +3238,21 @@ mod tests {
         assert_eq!(h.app.ui.settings.startup_view, crate::state::StartupView::Detail);
         // Interface: filmstrip names off, grid badges always
         h.request("ui.clickWidget", json!({"id": "button:settingsTab-interface"}), t);
+        // Appearance cards (one row per theme, with its favorite star) sit above these controls;
+        // scroll the compact settings viewport past them.
+        h.request("ui.hoverWidget", json!({"id": "radio:theme-charcoal"}), t);
+        h.request("ui.scroll", json!({"dy": -700.0}), t);
+        for _ in 0..4 {
+            h.step();
+        }
         h.request("ui.clickWidget", json!({"id": "check:settings.filmNames"}), t);
         assert!(!h.app.ui.settings.film_names);
         h.request("ui.clickWidget", json!({"id": "button:settingsGridBadges-1"}), t);
         assert_eq!(h.app.ui.settings.grid_badges, crate::state::GridBadges::Always);
+        h.request("ui.scroll", json!({"dy": 700.0}), t);
+        for _ in 0..4 {
+            h.step();
+        }
         // Performance: the thumbnail cache size goes to the library preferences
         h.request("ui.clickWidget", json!({"id": "button:settingsTab-performance"}), t);
         h.request("ui.clickWidget", json!({"id": "button:settingsCache-0"}), t);
diff --git a/crates/ui-egui/src/icons.rs b/crates/ui-egui/src/icons.rs
index 0cf998e0f..3441f109e 100644
--- a/crates/ui-egui/src/icons.rs
+++ b/crates/ui-egui/src/icons.rs
@@ -83,6 +83,12 @@ pub enum Icon {
     Chat,
     /// Face boxes on/off: four corner brackets round a small face.
     FaceBox,
+    /// Appearance Mode ▸ Auto (follow the system): a monitor on its stand.
+    Monitor,
+    /// Appearance Mode ▸ Light: a sun (a disc with eight rays).
+    Sun,
+    /// Appearance Mode ▸ Dark: a crescent moon.
+    Moon,
 }
 
 struct Pen<'a> {
@@ -178,6 +184,24 @@ fn paint_with(p: &Painter, rect: Rect, icon: Icon, color: Color32, turn: Option<
             pen.line(&[(4.0, 10.0), (16.0, 10.0)]);
             pen.line(&[(11.0, 5.0), (16.0, 10.0), (11.0, 15.0)]);
         }
+        Monitor => {
+            pen.rect(2.5, 3.5, 17.5, 13.5, 1.5);
+            pen.line(&[(10.0, 13.5), (10.0, 16.5)]);
+            pen.line(&[(6.5, 16.5), (13.5, 16.5)]);
+        }
+        Sun => {
+            pen.circle(10.0, 10.0, 3.2);
+            for i in 0..8 {
+                let a = (i as f32 * 45.0).to_radians();
+                let (c, s) = (a.cos(), a.sin());
+                pen.line(&[(10.0 + 5.4 * c, 10.0 + 5.4 * s), (10.0 + 7.4 * c, 10.0 + 7.4 * s)]);
+            }
+        }
+        Moon => {
+            // outer arc of the disc, then the inner arc of the bite, meeting at the horns
+            pen.arc(10.0, 10.0, 6.5, 2.9, 263.8);
+            pen.arc(13.4, 6.4, 5.0, 214.9, 51.8);
+        }
         Search => {
             pen.circle(8.5, 8.5, 5.0);
             pen.line(&[(12.2, 12.2), (16.5, 16.5)]);
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 299728743..57630067f 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -49,6 +49,8 @@ mod tests_compare;
 #[cfg(test)]
 mod tests_copy_paste_dialogs;
 #[cfg(test)]
+mod tests_appearance;
+#[cfg(test)]
 mod tests_crop_rotate;
 #[cfg(test)]
 mod tests_crop_tool;
@@ -147,6 +149,11 @@ pub type CheckEditorFn = Box<dyn Fn(&str) -> Result<(), String>>;
 /// storage); the work may finish asynchronously.
 pub type HostAction = Box<dyn FnMut(&mut Session) -> Result<Value, String>>;
 
+/// The system's dark/light appearance where egui doesn't report one (Linux desktops whose
+/// windowing layer says nothing, e.g. many Wayland compositors). The host answers from what it
+/// last heard and wakes the UI itself when that changes; it is never polled for changes.
+pub type SystemThemeFn = Box<dyn Fn(&egui::Context) -> Option<egui::Theme>>;
+
 /// Platform services injected by the host app (desktop or web).
 #[derive(Default)]
 pub struct Services {
@@ -203,6 +210,8 @@ pub struct Services {
     pub backup_library: Option<HostAction>,
     /// File ▸ Restore Library from Backup… (web only; keeps the current library).
     pub restore_library: Option<HostAction>,
+    /// The system appearance for Appearance Mode ▸ Auto, ahead of egui's own report.
+    pub system_theme: Option<SystemThemeFn>,
 }
 
 #[derive(Clone, Copy, Debug, Default)]
@@ -774,6 +783,20 @@ impl LightcraftApp {
         }
     }
 
+    /// The system's appearance: the host's answer first, then egui's (none: unknown).
+    pub fn system_theme(&self, ctx: &egui::Context) -> Option<egui::Theme> {
+        self.services.system_theme.as_ref().and_then(|read| read(ctx)).or_else(|| ctx.system_theme())
+    }
+
+    /// Restyle `ctx` when the theme the settings select (Appearance Mode, the dark and light
+    /// themes, the system's appearance in Auto) is not the one it shows. A no-op otherwise.
+    pub fn sync_theme(&mut self, ctx: &egui::Context) {
+        let wanted = self.ui.settings.theme(self.system_theme(ctx));
+        if theme::current(ctx) != Some(wanted) {
+            theme::apply_kind(ctx, wanted);
+        }
+    }
+
     /// Draw the UI into an offscreen context at the window's size; with `capture`, rasterize it
     /// on the CPU (photo textures come from the renderer's CPU copies).
     pub fn headless_screenshot(&mut self, main: &egui::Context, capture: bool) -> Option<egui::ColorImage> {
@@ -877,6 +900,7 @@ impl LightcraftApp {
         } else {
             self.fonts_ready = true;
         }
+        self.sync_theme(ctx);
         panels::notices::logic(self);
         // closing the window (or Quit) with changes only in memory: retry, else ask first
         if ctx.input(|i| i.viewport().close_requested()) && !panels::notices::may_close(self) {
diff --git a/crates/ui-egui/src/menubar.rs b/crates/ui-egui/src/menubar.rs
index 855babdf5..8a0cede2d 100644
--- a/crates/ui-egui/src/menubar.rs
+++ b/crates/ui-egui/src/menubar.rs
@@ -135,6 +135,7 @@ const LAYOUT: &[(&str, &[&str])] = &[
             "view.histogram",
             "view.navigator",
             "view.infoOverlay",
+            "@Appearance",
             "---",
             "view.fullScreenPreview",
             "view.lightsOut",
@@ -467,6 +468,29 @@ fn expanded(app: &LightcraftApp, name: &str) -> Option<Vec<MenuNode>> {
             v.push(item("dialog.labelNames", Value::Null, "Edit Label Names…", None, true, None));
             v
         }
+        "Appearance" => {
+            use crate::state::AppearanceMode;
+            use crate::theme::ThemeKind;
+            let s = &app.ui.settings;
+            let mut v: Vec<MenuNode> = [
+                ("auto", "Sync with System", AppearanceMode::Auto),
+                ("light", "Light Mode", AppearanceMode::Light),
+                ("dark", "Dark Mode", AppearanceMode::Dark),
+            ]
+            .into_iter()
+            .map(|(mode, label, m)| item("view.appearance", json!({"mode": mode}), label, None, true, Some(s.appearance_mode == m)))
+            .collect();
+            v.push(item("view.appearance", Value::Null, "Next Appearance Mode", None, true, None));
+            // the saved theme of each family is checked
+            for group in [[ThemeKind::Charcoal, ThemeKind::Midnight], [ThemeKind::Silver, ThemeKind::Paper]] {
+                v.push(MenuNode::Separator);
+                for k in group {
+                    let on = if k.is_dark() { s.dark_theme.kind() == k } else { s.light_theme.kind() == k };
+                    v.push(item("view.theme", json!({"theme": k.id()}), k.label(), None, true, Some(on)));
+                }
+            }
+            v
+        }
         "Grid Info" => ["filename", "exposure", "date"]
             .into_iter()
             .zip(["File Name", "Exposure (shutter · aperture · ISO)", "Capture Date"])
diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index ea027ef1c..8ce9f20be 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -145,6 +145,11 @@ pub const UI_COMMANDS: &[UiCommand] = &[
     ("view.secondWindow", "Second Window", Some("Cmd+F11"), "Window"),
     ("tool.keywordPainter", "Keyword Painter", None, ""),
     ("view.gridInfo", "Grid Info", None, ""),
+    // {mode?: auto | light | dark}: Appearance Mode (cycles Auto, Light, Dark when omitted; the
+    // top bar's appearance button). View ▸ Appearance lists the modes.
+    ("view.appearance", "Next Appearance Mode", None, ""),
+    // {theme: charcoal | midnight | silver | paper}: pick a theme and fix the mode to its family.
+    ("view.theme", "Theme", None, ""),
     ("dialog.allMetadata", "All Metadata…", None, "Photo"),
     ("dialog.faceModel", "Add Face Model…", None, ""),
     ("dialog.newSmartAlbum", "New Smart Album from Filter…", Some("Cmd+Alt+N"), "File"),
@@ -272,6 +277,41 @@ pub fn parse_rgb(v: &Value) -> Option<[u8; 3]> {
     Some([c(0)?, c(1)?, c(2)?])
 }
 
+fn appearance_json(app: &LightcraftApp) -> Value {
+    let s = &app.ui.settings;
+    json!({"mode": s.appearance_mode, "darkTheme": s.dark_theme, "lightTheme": s.light_theme})
+}
+
+/// `view.appearance {mode?}`: set Appearance Mode, or step to the next one (Auto, Light, Dark).
+/// The theme follows on the next frame ([`LightcraftApp::sync_theme`]).
+fn appearance_command(app: &mut LightcraftApp, p: &Value) -> Result<Value, String> {
+    use crate::state::AppearanceMode;
+    let mode = match p.get("mode") {
+        None | Some(Value::Null) => app.ui.settings.appearance_mode.next(),
+        Some(v) => match v.as_str() {
+            Some("auto") => AppearanceMode::Auto,
+            Some("light") => AppearanceMode::Light,
+            Some("dark") => AppearanceMode::Dark,
+            _ => return Err(format!("view.appearance: unknown mode {v} (auto|light|dark)")),
+        },
+    };
+    app.ui.settings.appearance_mode = mode;
+    Ok(appearance_json(app))
+}
+
+/// `view.theme {theme}`: pick a theme; the mode becomes its family's (Dark or Light).
+fn theme_command(app: &mut LightcraftApp, p: &Value) -> Result<Value, String> {
+    let ids = crate::theme::ThemeKind::ALL.map(|k| k.id()).join("|");
+    let Some(id) = p.get("theme").and_then(Value::as_str) else {
+        return Err(format!("view.theme: `theme` is required ({ids})"));
+    };
+    let Some(kind) = crate::theme::ThemeKind::ALL.into_iter().find(|k| k.id() == id) else {
+        return Err(format!("view.theme: unknown theme `{id}` ({ids})"));
+    };
+    app.ui.settings.select_theme(kind);
+    Ok(appearance_json(app))
+}
+
 /// Handle UI commands; `None` means "not a UI command — send it to the engine".
 pub fn run_ui_command(app: &mut LightcraftApp, id: &str, p: &Value) -> Option<Result<Value, String>> {
     if matches!(id, "ui.dock" | "ui.dock.reset") {
@@ -335,6 +375,8 @@ pub fn run_ui_command(app: &mut LightcraftApp, id: &str, p: &Value) -> Option<Re
             app.ui.show_counts = p.get("show").and_then(Value::as_bool).unwrap_or(!app.ui.show_counts);
             Ok(json!({"show": app.ui.show_counts}))
         }
+        "view.appearance" => appearance_command(app, p),
+        "view.theme" => theme_command(app, p),
         "view.gridToggle" => {
             app.ui.view = if app.ui.view == ViewMode::PhotoGrid { ViewMode::SquareGrid } else { ViewMode::PhotoGrid };
             Ok(Value::Null)
diff --git a/crates/ui-egui/src/panels/dialogs.rs b/crates/ui-egui/src/panels/dialogs.rs
index 661224af2..26684fdec 100644
--- a/crates/ui-egui/src/panels/dialogs.rs
+++ b/crates/ui-egui/src/panels/dialogs.rs
@@ -171,8 +171,14 @@ pub const ABOUT_TABS: &[(&str, &str)] = &[("about", "About"), ("contributors", "
 /// Help ▸ What's New (docs/whats-new.md).
 pub const WHATS_NEW: &str = include_str!("../../../../docs/whats-new.md");
 
+/// The import review and Settings keep window ids of their own, so the size each is given
+/// doesn't carry over to the other dialogs.
 fn window_id(dialog: &Dialog) -> egui::Id {
-    egui::Id::new(if matches!(dialog, Dialog::Import { .. }) { "lightcraft-import-dialog" } else { "lightcraft-dialog" })
+    egui::Id::new(match dialog {
+        Dialog::Import { .. } => "lightcraft-import-dialog",
+        Dialog::Settings { .. } => "lightcraft-settings-dialog",
+        _ => "lightcraft-dialog",
+    })
 }
 
 /// Block the underlying panels from the first frame, before the window establishes its modal
diff --git a/crates/ui-egui/src/panels/settings.rs b/crates/ui-egui/src/panels/settings.rs
index 86da2cc47..7baf475ad 100644
--- a/crates/ui-egui/src/panels/settings.rs
+++ b/crates/ui-egui/src/panels/settings.rs
@@ -36,9 +36,8 @@ const LABEL_W: f32 = 150.0;
 /// The dialog body for `tab` (the tab bar switches `tab`).
 pub fn body(app: &mut LightcraftApp, ui: &mut egui::Ui, tab: &mut String) {
     let t = Tokens::get(ui.ctx());
-    ui.set_min_width(560.0);
-    ui.set_min_height(330.0);
-    ui.horizontal(|ui| {
+    ui.set_width((ui.ctx().content_rect().width() - 64.0).clamp(240.0, 560.0));
+    ui.horizontal_wrapped(|ui| {
         ui.spacing_mut().item_spacing.x = 4.0;
         for (id, label) in TABS {
             if crate::widgets::text_button(ui, &format!("settingsTab-{id}"), label, tab == id).clicked() {
@@ -632,6 +631,8 @@ fn display_tab(app: &mut LightcraftApp, ui: &mut egui::Ui, t: &Tokens) {
 }
 
 fn interface_tab(app: &mut LightcraftApp, ui: &mut egui::Ui, t: &Tokens) {
+    let system = app.system_theme(ui.ctx());
+    appearance(ui, t, &mut app.ui.settings, system);
     heading(ui, t, crate::i18n::tr("Filmstrip"));
     check(ui, "settings.filmNames", &mut app.ui.settings.film_names, "Show file names");
     check(ui, "settings.filmBadges", &mut app.ui.settings.film_badges, "Show ratings, flags and edit badges");
@@ -653,6 +654,229 @@ fn interface_tab(app: &mut LightcraftApp, ui: &mut egui::Ui, t: &Tokens) {
     });
 }
 
+/// Appearance Mode (`button:settingsAppearance-{0,1,2}`: Auto, Dark, Light) above the light and
+/// dark theme cards (`radio:theme-{id}`), each with a preview of the chosen theme. The card in
+/// use is outlined. Applied on the next frame ([`LightcraftApp::sync_theme`]).
+fn appearance(ui: &mut egui::Ui, t: &Tokens, s: &mut crate::state::AppSettings, system: Option<egui::Theme>) {
+    use crate::state::{AppearanceMode as M, DarkTheme, LightTheme};
+    heading(ui, t, crate::i18n::tr("Appearance"));
+    ui.label(RichText::new(crate::i18n::tr("Appearance Mode")).color(t.text_label));
+    ui.horizontal_wrapped(|ui| {
+        choices(ui, "settingsAppearance", &[(M::Auto, "Sync with System"), (M::Dark, "Dark Mode"), (M::Light, "Light Mode")], &mut s.appearance_mode);
+    });
+    ui.add_space(4.0);
+    let light_active = s.theme(system) == s.light_theme.kind();
+    let available = ui.available_width();
+    let mut cards = |ui: &mut egui::Ui, width: f32| {
+        ui.spacing_mut().item_spacing.x = 12.0;
+        let light: Vec<_> = LightTheme::ALL.iter().map(|l| (*l, l.kind())).collect();
+        theme_card(ui, t, "Light Theme", light_active, &light, &mut s.light_theme, &mut s.favorite_themes, width);
+        let dark: Vec<_> = DarkTheme::ALL.iter().map(|d| (*d, d.kind())).collect();
+        theme_card(ui, t, "Dark Theme", !light_active, &dark, &mut s.dark_theme, &mut s.favorite_themes, width);
+    };
+    if available < 440.0 {
+        ui.vertical(|ui| cards(ui, available));
+    } else {
+        ui.horizontal_top(|ui| cards(ui, ((available - 12.0) / 2.0).floor()));
+    }
+    ui.add_space(2.0);
+}
+
+/// One family's card: its title (and "Active" when it is the one shown), a preview of the
+/// selected theme and a radio button per theme.
+fn theme_card<V: PartialEq + Copy>(
+    ui: &mut egui::Ui,
+    t: &Tokens,
+    title: &str,
+    active: bool,
+    options: &[(V, crate::theme::ThemeKind)],
+    value: &mut V,
+    favorites: &mut Vec<String>,
+    width: f32,
+) {
+    egui::Frame::new()
+        .fill(t.inset)
+        .stroke(egui::Stroke::new(1.0, if active { t.accent } else { t.field_border }))
+        .corner_radius(6)
+        .inner_margin(8)
+        .show(ui, |ui| {
+            ui.vertical(|ui| {
+                let inner = (width - 18.0).clamp(120.0, 240.0);
+                ui.set_width(inner);
+                ui.horizontal(|ui| {
+                    ui.label(RichText::new(crate::i18n::tr(title)).font(t.semibold(12.0)).color(t.text));
+                    if active {
+                        ui.label(RichText::new(crate::i18n::tr("In Use")).size(11.0).color(t.accent));
+                    }
+                });
+                let shown = options.iter().find(|(v, _)| v == value).or(options.first()).map(|(_, k)| *k).unwrap_or_default();
+                theme_preview(ui, shown, inner);
+                for (v, kind) in options {
+                    let row = egui::Rect::from_min_size(ui.cursor().min, egui::vec2(ui.available_width(), 24.0));
+                    let hovered = ui.ctx().pointer_hover_pos().is_some_and(|p| row.contains(p));
+                    ui.horizontal(|ui| {
+                        let r = ui.radio_value(value, *v, crate::i18n::tr(kind.label()));
+                        register(ui.ctx(), format!("radio:theme-{}", kind.id()), r.rect);
+                        ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+                            let favorite = favorites.iter().any(|id| id == kind.id());
+                            let r = ui
+                                .add_visible(favorite || hovered, egui::Button::new("").min_size(egui::vec2(24.0, 24.0)).frame(false))
+                                .on_hover_text(crate::i18n::tr(if favorite { "Remove from favorites" } else { "Add to favorites" }));
+                            r.widget_info(|| {
+                                egui::WidgetInfo::labeled(
+                                    egui::WidgetType::Button,
+                                    true,
+                                    format!(
+                                        "{}: {}",
+                                        crate::i18n::tr(if favorite { "Remove from favorites" } else { "Add to favorites" }),
+                                        crate::i18n::tr(kind.label())
+                                    ),
+                                )
+                            });
+                            register(ui.ctx(), format!("button:themeFavorite-{}", kind.id()), r.rect);
+                            if favorite || hovered {
+                                crate::icons::paint(
+                                    ui.painter(),
+                                    r.rect.shrink(4.0),
+                                    if favorite { crate::icons::Icon::StarFilled } else { crate::icons::Icon::Star },
+                                    if favorite { t.accent } else { t.text_dim },
+                                );
+                            }
+                            if r.clicked() {
+                                if favorite {
+                                    favorites.retain(|id| id != kind.id());
+                                } else {
+                                    favorites.push(kind.id().into());
+                                }
+                            }
+                        });
+                    });
+                }
+            });
+        });
+}
+
+/// A small LightCraft window painted with `kind`'s tokens: the top bar with its search field, the
+/// photo with the filmstrip under it, the Edit panel (histogram and sliders), the tool strip and
+/// the bottom bar.
+fn theme_preview(ui: &mut egui::Ui, kind: crate::theme::ThemeKind, width: f32) {
+    use egui::{Color32, Rect, Stroke, StrokeKind, pos2, vec2};
+    let p = Tokens::for_kind(kind);
+    let (rect, _) = ui.allocate_exact_size(vec2(width, (width * 0.56).round().min(130.0)), egui::Sense::hover());
+    let painter = ui.painter_at(rect);
+    let bar = |y: f32, x: f32, w: f32, c: Color32| painter.rect_filled(Rect::from_min_size(pos2(x, y), vec2(w, 2.0)), 1.0, c);
+    painter.rect_filled(rect, 3.0, p.canvas);
+    // top bar: sidebar and back icons, the centred search field, icons on the right
+    let top = Rect::from_min_size(rect.min, vec2(rect.width(), 13.0));
+    painter.rect_filled(top, 0.0, p.chrome);
+    for x in [6.0, 14.0, 20.0] {
+        painter.rect_filled(Rect::from_min_size(top.min + vec2(x, 4.5), vec2(4.0, 4.0)), 1.0, p.icon);
+    }
+    let search = Rect::from_center_size(top.center(), vec2(rect.width() * 0.34, 8.0));
+    painter.rect(search, 2.0, p.field, Stroke::new(1.0, p.field_border), StrokeKind::Inside);
+    bar(search.center().y - 1.0, search.center().x - 9.0, 18.0, p.text_dim);
+    for i in 0..4 {
+        painter.rect_filled(Rect::from_min_size(pos2(top.right() - 10.0 - i as f32 * 9.0, top.top() + 4.5), vec2(4.0, 4.0)), 2.0, p.icon);
+    }
+    // bottom bar: view buttons, rating stars, a button
+    let bottom = Rect::from_min_max(pos2(rect.left(), rect.bottom() - 12.0), rect.max);
+    painter.rect_filled(bottom, 0.0, p.chrome);
+    for x in [6.0, 13.0, 20.0] {
+        painter.rect_filled(Rect::from_min_size(bottom.min + vec2(x, 4.0), vec2(4.0, 4.0)), 1.0, p.icon);
+    }
+    let stars_x = bottom.center().x - 30.0;
+    for i in 0..5 {
+        painter.circle_filled(pos2(stars_x + i as f32 * 5.0, bottom.center().y), 1.4, p.star);
+    }
+    let copy = Rect::from_min_size(pos2(stars_x + 28.0, bottom.top() + 2.5), vec2(30.0, 7.0));
+    painter.rect(copy, 3.0, p.button, Stroke::new(1.0, p.button_border), StrokeKind::Inside);
+    // tool strip on the right edge, the first tool (Edit) active
+    let strip = Rect::from_min_max(pos2(rect.right() - 12.0, top.bottom()), pos2(rect.right(), bottom.top()));
+    painter.rect_filled(strip, 0.0, p.chrome);
+    painter.line_segment([strip.left_top(), strip.left_bottom()], Stroke::new(1.0, p.divider));
+    for i in 0..5 {
+        let r = Rect::from_min_size(pos2(strip.left() + 3.0, strip.top() + 4.0 + i as f32 * 9.0), vec2(6.0, 6.0));
+        if i == 0 {
+            painter.rect_filled(r.expand(1.5), 1.5, p.tool_active);
+        }
+        painter.rect_stroke(r, 1.0, Stroke::new(1.0, if i == 0 { p.text } else { p.icon }), StrokeKind::Inside);
+    }
+    // Edit panel: histogram, then labelled sliders
+    let panel = Rect::from_min_max(pos2(strip.left() - (rect.width() * 0.27).round(), top.bottom()), pos2(strip.left(), bottom.top()));
+    painter.rect_filled(panel, 0.0, p.chrome);
+    painter.line_segment([panel.left_top(), panel.left_bottom()], Stroke::new(1.0, p.divider));
+    let hist = Rect::from_min_size(panel.min + vec2(4.0, 4.0), vec2(panel.width() - 8.0, 14.0));
+    painter.rect_filled(hist, 1.0, p.inset);
+    let curve = [0.2, 0.55, 0.9, 0.7, 0.5, 0.62, 0.4, 0.3, 0.18, 0.1];
+    let mut pts = vec![hist.left_bottom()];
+    for (i, h) in curve.iter().enumerate() {
+        pts.push(pos2(hist.left() + hist.width() * i as f32 / (curve.len() - 1) as f32, hist.bottom() - hist.height() * h));
+    }
+    pts.push(hist.right_bottom());
+    // the area under the curve, a column per stretch between two points
+    for pair in pts.windows(2) {
+        if let [a, b] = pair {
+            let r = Rect::from_min_max(pos2(a.x, a.y.max(b.y)), pos2(b.x, hist.bottom()));
+            painter.rect_filled(r, 0.0, p.track.gamma_multiply(0.5));
+        }
+    }
+    painter.add(egui::Shape::line(pts, Stroke::new(1.0, p.text_dim)));
+    let sliders = [0.55, 0.62, 0.35, 0.7, 0.6, 0.45];
+    let mut y = hist.bottom() + 7.0;
+    bar(y, panel.left() + 5.0, 14.0, p.text);
+    y += 6.0;
+    for v in sliders {
+        if y + 7.0 > panel.bottom() {
+            break;
+        }
+        bar(y, panel.left() + 5.0, 12.0, p.text_label);
+        bar(y, panel.right() - 10.0, 5.0, p.text_dim);
+        let track_y = y + 5.0;
+        painter.line_segment([pos2(panel.left() + 5.0, track_y), pos2(panel.right() - 5.0, track_y)], Stroke::new(1.0, p.track));
+        painter.circle_filled(pos2(panel.left() + 5.0 + (panel.width() - 10.0) * v, track_y), 1.8, p.thumb);
+        y += 10.0;
+    }
+    // the photo (its own colours: a photo looks the same in every theme) above the filmstrip
+    let film = Rect::from_min_max(pos2(rect.left(), bottom.top() - 18.0), pos2(panel.left(), bottom.top()));
+    let stage = Rect::from_min_max(pos2(rect.left(), top.bottom()), pos2(panel.left(), film.top()));
+    let photo = Rect::from_center_size(stage.center(), vec2(stage.width() * 0.62, stage.height() - 8.0));
+    painter.rect_filled(photo, 0.0, Color32::from_rgb(0x6f, 0x8f, 0xb4));
+    let horizon = photo.top() + photo.height() * 0.62;
+    painter.add(egui::Shape::convex_polygon(
+        vec![
+            pos2(photo.left(), horizon),
+            pos2(photo.left() + photo.width() * 0.3, photo.top() + photo.height() * 0.3),
+            pos2(photo.left() + photo.width() * 0.55, horizon),
+        ],
+        Color32::from_rgb(0x4a, 0x55, 0x66),
+        Stroke::NONE,
+    ));
+    painter.add(egui::Shape::convex_polygon(
+        vec![
+            pos2(photo.left() + photo.width() * 0.35, horizon),
+            pos2(photo.left() + photo.width() * 0.68, photo.top() + photo.height() * 0.2),
+            pos2(photo.right(), horizon),
+        ],
+        Color32::from_rgb(0x5a, 0x63, 0x72),
+        Stroke::NONE,
+    ));
+    painter.rect_filled(Rect::from_min_max(pos2(photo.left(), horizon), photo.max), 0.0, Color32::from_rgb(0x3d, 0x5a, 0x3a));
+    painter.line_segment([film.left_top(), film.right_top()], Stroke::new(1.0, p.divider));
+    for i in 0..5 {
+        let cell = Rect::from_min_size(pos2(film.left() + 4.0 + i as f32 * 17.0, film.top() + 3.0), vec2(15.0, 12.0));
+        if cell.right() > film.right() - 2.0 {
+            break;
+        }
+        let selected = i == 1;
+        painter.rect_filled(cell, 0.0, if selected { p.cell_selected } else { p.cell });
+        let thumb = cell.shrink(2.5);
+        painter.rect_filled(thumb, 0.0, Color32::from_rgb(0x6f + 8 * i as u8, 0x80, 0x8f));
+        if selected {
+            painter.rect_stroke(thumb, 0.0, Stroke::new(1.0, p.pick), StrokeKind::Outside);
+        }
+    }
+}
+
 // ------------------------------------------------------------------------------- Open Library…
 
 /// `app.openLibrary {path?}`: close the current library and open (or create) the one at `path`,
diff --git a/crates/ui-egui/src/panels/topbar.rs b/crates/ui-egui/src/panels/topbar.rs
index 6462c87d6..a95805f83 100644
--- a/crates/ui-egui/src/panels/topbar.rs
+++ b/crates/ui-egui/src/panels/topbar.rs
@@ -53,7 +53,8 @@ pub fn show(app: &mut LightcraftApp, ui: &mut egui::Ui) {
             if app.integrated_titlebar {
                 window_handle(app, ui, full, left as f32, 12.0);
             }
-            let mut sw = 640.0f32.min(full.width() - 460.0).max(200.0);
+            // room for the filter icon and the six icons on the right
+            let mut sw = 640.0f32.min(full.width() - 540.0).max(200.0);
             if !app.native_menu {
                 // leave room for the in-window menus left of the (centred) search field
                 let menus_right = full.left() + 140.0 + crate::menubar::bar_width(ui) + 24.0;
@@ -187,6 +188,50 @@ pub fn show(app: &mut LightcraftApp, ui: &mut egui::Ui) {
                 }
                 x -= 40.0;
             }
+            // Appearance Mode: a click steps Auto → Light → Dark → Auto; the icon shows the mode
+            let (icon, mode) = appearance_icon(app.ui.settings.appearance_mode);
+            let r = Rect::from_center_size(pos2(x, full.center().y), vec2(28.0, 28.0));
+            let tip = format!("{}: {}", crate::i18n::tr("Appearance Mode"), crate::i18n::tr(mode));
+            let resp = ui.interact(r, egui::Id::new(("top", "appearance")), Sense::click()).on_hover_text(tip);
+            register(ui.ctx(), "icon:appearance", r);
+            paint(ui.painter(), r.shrink(5.0), icon, if resp.hovered() { t.text } else { t.icon });
+            if resp.clicked() {
+                let _ = app.run("view.appearance", json!({}));
+            }
+            resp.context_menu(|ui| {
+                let settings = ui.button(crate::i18n::tr("Appearance Settings…"));
+                register(ui.ctx(), "menu:appearanceSettings", settings.rect);
+                if settings.clicked() {
+                    let _ = app.run("app.settings", json!({"tab": "interface"}));
+                    ui.close();
+                }
+                let favorites = app.ui.settings.favorite_themes.clone();
+                for dark in [false, true] {
+                    let group: Vec<_> =
+                        crate::theme::ThemeKind::ALL.iter().filter(|k| k.is_dark() == dark && favorites.iter().any(|id| id == k.id())).collect();
+                    if !group.is_empty() {
+                        ui.separator();
+                    }
+                    for kind in group {
+                        let r = ui.selectable_label(app.ui.settings.theme(app.system_theme(ui.ctx())) == *kind, crate::i18n::tr(kind.label()));
+                        register(ui.ctx(), format!("menu:themeFavorite-{}", kind.id()), r.rect);
+                        if r.clicked() {
+                            let _ = app.run("view.theme", json!({"theme": kind.id()}));
+                            ui.close();
+                        }
+                    }
+                }
+            });
             let _ = Align2::CENTER_CENTER;
         });
 }
+
+/// The appearance button's icon and the mode's name for its tooltip.
+pub fn appearance_icon(mode: crate::state::AppearanceMode) -> (Icon, &'static str) {
+    use crate::state::AppearanceMode;
+    match mode {
+        AppearanceMode::Auto => (Icon::Monitor, "Sync with System"),
+        AppearanceMode::Light => (Icon::Sun, "Light Mode"),
+        AppearanceMode::Dark => (Icon::Moon, "Dark Mode"),
+    }
+}
diff --git a/crates/ui-egui/src/state.rs b/crates/ui-egui/src/state.rs
index f3e64e001..d1ca27aca 100644
--- a/crates/ui-egui/src/state.rs
+++ b/crates/ui-egui/src/state.rs
@@ -161,6 +161,67 @@ impl LightsOut {
 /// How many libraries File ▸ Open Recent Library remembers.
 pub const RECENT_LIBRARIES: usize = 8;
 
+/// Whether the interface uses the dark or the light theme (Settings ▸ Interface ▸ Appearance).
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum AppearanceMode {
+    /// Follow the operating system's dark/light setting (dark when it gives no answer).
+    Auto,
+    /// The dark theme, whatever the system says (the default: LightCraft's look so far).
+    #[default]
+    Dark,
+    Light,
+}
+
+impl AppearanceMode {
+    /// The header button's order: Auto, Light, Dark, then Auto again.
+    pub fn next(self) -> AppearanceMode {
+        match self {
+            AppearanceMode::Auto => AppearanceMode::Light,
+            AppearanceMode::Light => AppearanceMode::Dark,
+            AppearanceMode::Dark => AppearanceMode::Auto,
+        }
+    }
+}
+
+/// The theme the dark appearance uses.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum DarkTheme {
+    #[default]
+    Charcoal,
+    Midnight,
+}
+
+/// The theme the light appearance uses.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum LightTheme {
+    #[default]
+    Silver,
+    Paper,
+}
+
+impl DarkTheme {
+    pub const ALL: [DarkTheme; 2] = [DarkTheme::Charcoal, DarkTheme::Midnight];
+    pub fn kind(self) -> crate::theme::ThemeKind {
+        match self {
+            DarkTheme::Charcoal => crate::theme::ThemeKind::Charcoal,
+            DarkTheme::Midnight => crate::theme::ThemeKind::Midnight,
+        }
+    }
+}
+
+impl LightTheme {
+    pub const ALL: [LightTheme; 2] = [LightTheme::Silver, LightTheme::Paper];
+    pub fn kind(self) -> crate::theme::ThemeKind {
+        match self {
+            LightTheme::Silver => crate::theme::ThemeKind::Silver,
+            LightTheme::Paper => crate::theme::ThemeKind::Paper,
+        }
+    }
+}
+
 /// App-level preferences (Settings dialog). They belong to the app, not a library, and are
 /// saved with the UI state in the app's config folder (`ui.json`, key `settings`); library
 /// preferences (import defaults, XMP, cache size) live in the library's `prefs.json`.
@@ -200,6 +261,15 @@ pub struct AppSettings {
     pub grid_badges: GridBadges,
     /// Shortcuts the user changed (Help ▸ Keyboard Shortcuts): command id → shortcut, `""` = none.
     pub keymap: crate::shortcuts::Keymap,
+    /// Auto (follow the system), Dark or Light.
+    pub appearance_mode: AppearanceMode,
+    /// The theme of the dark appearance.
+    pub dark_theme: DarkTheme,
+    /// The theme of the light appearance.
+    pub light_theme: LightTheme,
+    /// Theme shortcuts in the appearance context menu.
+    #[serde(deserialize_with = "deserialize_favorite_themes")]
+    pub favorite_themes: Vec<String>,
     /// The monitor's ICC profile previews are shown through (`app.displayProfile`; "" = none:
     /// the display is treated as sRGB).
     pub display_profile: String,
@@ -223,6 +293,10 @@ impl Default for AppSettings {
             film_badges: true,
             grid_badges: GridBadges::Auto,
             keymap: Default::default(),
+            appearance_mode: AppearanceMode::Dark,
+            dark_theme: DarkTheme::Charcoal,
+            light_theme: LightTheme::Silver,
+            favorite_themes: Vec::new(),
             display_profile: String::new(),
         }
     }
@@ -306,6 +380,29 @@ pub const LOUPE_EDGE_STEP: usize = 64;
 pub const STANDARD_PREVIEW_EDGE: u32 = 2560;
 
 impl AppSettings {
+    /// The theme to show: the light theme in Light mode, or in Auto when `system` is light; the
+    /// dark theme otherwise (Auto with no answer from the system included).
+    pub fn theme(&self, system: Option<egui::Theme>) -> crate::theme::ThemeKind {
+        let light = match self.appearance_mode {
+            AppearanceMode::Light => true,
+            AppearanceMode::Dark => false,
+            AppearanceMode::Auto => system == Some(egui::Theme::Light),
+        };
+        if light { self.light_theme.kind() } else { self.dark_theme.kind() }
+    }
+
+    /// Pick `kind` and fix the mode to its family (the View ▸ Theme items).
+    pub fn select_theme(&mut self, kind: crate::theme::ThemeKind) {
+        use crate::theme::ThemeKind;
+        match kind {
+            ThemeKind::Charcoal => self.dark_theme = DarkTheme::Charcoal,
+            ThemeKind::Midnight => self.dark_theme = DarkTheme::Midnight,
+            ThemeKind::Silver => self.light_theme = LightTheme::Silver,
+            ThemeKind::Paper => self.light_theme = LightTheme::Paper,
+        }
+        self.appearance_mode = if kind.is_dark() { AppearanceMode::Dark } else { AppearanceMode::Light };
+    }
+
     /// Long edge (pixels) to render the loupe at when it is drawn `wanted_px` wide on screen:
     /// that size (rounded up to [`LOUPE_EDGE_STEP`], so resizing a window doesn't re-render at
     /// every pixel), never above the photo's own `native_long_edge`, the user's limit, the ceiling
@@ -1070,3 +1167,14 @@ impl UiState {
         self
     }
 }
+
+fn deserialize_favorite_themes<'de, D: serde::Deserializer<'de>>(d: D) -> Result<Vec<String>, D::Error> {
+    let values = Vec::<String>::deserialize(d)?;
+    let mut seen = std::collections::BTreeSet::new();
+    for id in &values {
+        if !crate::theme::ThemeKind::ALL.iter().any(|k| k.id() == id) || !seen.insert(id) {
+            return Err(serde::de::Error::custom("unknown or duplicate favorite theme"));
+        }
+    }
+    Ok(values)
+}
diff --git a/crates/ui-egui/src/tests_appearance.rs b/crates/ui-egui/src/tests_appearance.rs
new file mode 100644
index 000000000..947e6cf9f
--- /dev/null
+++ b/crates/ui-egui/src/tests_appearance.rs
@@ -0,0 +1,247 @@
+//! Appearance Mode: Auto (follow the system), Dark or Light, each with its own saved theme.
+
+use std::time::Duration;
+
+use serde_json::json;
+
+use crate::headless::Headless;
+use crate::state::{AppSettings, AppearanceMode, DarkTheme, LightTheme, UiState};
+use crate::theme::ThemeKind;
+use crate::{LightcraftApp, Services};
+
+const T: Duration = Duration::from_secs(20);
+
+fn app() -> LightcraftApp {
+    LightcraftApp::new(lightcraft_engine::Session::new(), Services { png: None, ..Default::default() })
+}
+
+/// One frame of logic on `ctx`: where the theme is applied.
+fn frame(app: &mut LightcraftApp, ctx: &egui::Context) {
+    let mut output = ctx.run_ui(egui::RawInput::default(), |ui| app.logic(ui.ctx()));
+    output.textures_delta.clear();
+}
+
+#[test]
+fn new_users_keep_the_dark_look_and_old_settings_load_unchanged() {
+    let s = AppSettings::default();
+    assert_eq!((s.appearance_mode, s.dark_theme, s.light_theme), (AppearanceMode::Dark, DarkTheme::Charcoal, LightTheme::Silver));
+    assert_eq!(s.theme(Some(egui::Theme::Light)), ThemeKind::Charcoal, "Auto is opt-in");
+    // a ui.json saved before appearance modes existed
+    let old: UiState = serde_json::from_str(r#"{"settings": {"gridBadges": "always", "confirmDelete": true}}"#).unwrap();
+    assert_eq!(old.settings.appearance_mode, AppearanceMode::Dark);
+    assert_eq!(old.settings.dark_theme, DarkTheme::Charcoal);
+    assert_eq!(old.settings.light_theme, LightTheme::Silver);
+    assert!(old.settings.confirm_delete);
+    // and the Charcoal tokens are the ones LightCraft always had
+    assert_eq!(crate::theme::Tokens::for_kind(ThemeKind::Charcoal).chrome, crate::theme::Tokens::default().chrome);
+}
+
+#[test]
+fn choices_validate_and_survive_a_restart() {
+    let mut a = app();
+    let ctx = egui::Context::default();
+    let set = |a: &mut LightcraftApp, p: serde_json::Value| {
+        let (req, _) = crate::control::ControlRequest::new("ui.set", p);
+        match crate::control::handle(a, &ctx, &req) {
+            crate::control::Outcome::Done(reply) => reply,
+            _ => panic!("expected a reply"),
+        }
+    };
+    let ok = set(&mut a, json!({"settings": {"appearanceMode": "auto", "darkTheme": "midnight", "lightTheme": "paper"}}));
+    assert_eq!(ok["ok"], true, "{ok}");
+    assert_eq!(a.ui.settings.appearance_mode, AppearanceMode::Auto);
+    for bad in [json!({"appearanceMode": "sepia"}), json!({"darkTheme": "paper"}), json!({"lightTheme": "midnight"}), json!({"appearanceMode": 3})] {
+        let reply = set(&mut a, json!({ "settings": bad }));
+        assert_eq!(reply["ok"], false, "{bad} accepted");
+    }
+    assert_eq!((a.ui.settings.dark_theme, a.ui.settings.light_theme), (DarkTheme::Midnight, LightTheme::Paper), "a rejected value changes nothing");
+    let saved = serde_json::to_string(&a.ui).unwrap();
+    assert!(saved.contains(r#""appearanceMode":"auto""#) && saved.contains(r#""darkTheme":"midnight""#) && saved.contains(r#""lightTheme":"paper""#));
+    let restarted: UiState = serde_json::from_str(&saved).unwrap();
+    assert_eq!(restarted.settings, a.ui.settings);
+}
+
+#[test]
+fn the_button_cycles_auto_light_dark_without_losing_theme_choices() {
+    let mut a = app();
+    let ctx = egui::Context::default();
+    a.services.system_theme = Some(Box::new(|_| Some(egui::Theme::Dark)));
+    a.run("view.theme", json!({"theme": "paper"})).unwrap();
+    a.run("view.theme", json!({"theme": "midnight"})).unwrap();
+    assert_eq!(a.ui.settings.appearance_mode, AppearanceMode::Dark, "a dark theme fixes the mode to Dark");
+    for (mode, shown) in
+        [(AppearanceMode::Auto, ThemeKind::Midnight), (AppearanceMode::Light, ThemeKind::Paper), (AppearanceMode::Dark, ThemeKind::Midnight)]
+    {
+        let r = a.run("view.appearance", json!({})).unwrap();
+        assert_eq!(a.ui.settings.appearance_mode, mode);
+        assert_eq!(r["darkTheme"], "midnight");
+        assert_eq!(r["lightTheme"], "paper");
+        frame(&mut a, &ctx);
+        assert_eq!(crate::theme::current(&ctx), Some(shown));
+        assert_eq!(crate::theme::Tokens::get(&ctx).chrome, crate::theme::Tokens::for_kind(shown).chrome);
+        let icon = match mode {
+            AppearanceMode::Auto => crate::icons::Icon::Monitor,
+            AppearanceMode::Light => crate::icons::Icon::Sun,
+            AppearanceMode::Dark => crate::icons::Icon::Moon,
+        };
+        assert_eq!(crate::panels::topbar::appearance_icon(mode).0, icon);
+    }
+    // a light theme from the menu fixes Light
+    a.run("view.theme", json!({"theme": "silver"})).unwrap();
+    assert_eq!(
+        (a.ui.settings.appearance_mode, a.ui.settings.light_theme, a.ui.settings.dark_theme),
+        (AppearanceMode::Light, LightTheme::Silver, DarkTheme::Midnight)
+    );
+    // bad parameters are errors, never a panic, and change nothing
+    for p in [json!({}), json!({"theme": 4}), json!({"theme": "neon"})] {
+        assert!(a.run("view.theme", p.clone()).is_err(), "{p}");
+    }
+    for p in [json!({"mode": "sepia"}), json!({"mode": 1}), json!({"mode": []})] {
+        assert!(a.run("view.appearance", p.clone()).is_err(), "{p}");
+    }
+    assert_eq!(a.ui.settings.appearance_mode, AppearanceMode::Light);
+    a.run("view.appearance", json!({"mode": "auto"})).unwrap();
+    assert_eq!(a.ui.settings.appearance_mode, AppearanceMode::Auto);
+}
+
+#[test]
+fn auto_follows_the_system_and_falls_back_to_dark() {
+    use std::sync::{Arc, Mutex};
+    let system = Arc::new(Mutex::new(Some(egui::Theme::Light)));
+    let mut a = app();
+    let reported = Arc::clone(&system);
+    a.services.system_theme = Some(Box::new(move |_| *reported.lock().unwrap()));
+    a.run("view.appearance", json!({"mode": "auto"})).unwrap();
+    let ctx = egui::Context::default();
+    frame(&mut a, &ctx);
+    assert_eq!(crate::theme::current(&ctx), Some(ThemeKind::Silver));
+    assert_eq!(ctx.theme(), egui::Theme::Light);
+    *system.lock().unwrap() = Some(egui::Theme::Dark);
+    frame(&mut a, &ctx);
+    assert_eq!(crate::theme::current(&ctx), Some(ThemeKind::Charcoal));
+    assert_eq!(ctx.theme(), egui::Theme::Dark);
+    // no answer from the host or from egui: dark
+    *system.lock().unwrap() = None;
+    frame(&mut a, &ctx);
+    assert_eq!(crate::theme::current(&ctx), Some(ThemeKind::Charcoal));
+    // without a host service, egui's report is used
+    let mut plain = app();
+    plain.ui.settings.appearance_mode = AppearanceMode::Auto;
+    let ctx = egui::Context::default();
+    let input = egui::RawInput { system_theme: Some(egui::Theme::Light), ..Default::default() };
+    let mut output = ctx.run_ui(input, |ui| {
+        assert_eq!(plain.system_theme(ui.ctx()), Some(egui::Theme::Light));
+        plain.logic(ui.ctx());
+    });
+    output.textures_delta.clear();
+    assert_eq!(crate::theme::current(&ctx), Some(ThemeKind::Silver));
+}
+
+#[test]
+fn view_menu_lists_modes_and_themes_with_checks() {
+    let mut a = app();
+    a.run("view.theme", json!({"theme": "paper"})).unwrap();
+    let menus = crate::menubar::menu_bar(&a);
+    let text = serde_json::to_string(&menus).unwrap();
+    for label in ["Appearance", "Sync with System", "Light Mode", "Dark Mode", "Next Appearance Mode", "Charcoal", "Midnight", "Silver", "Paper"] {
+        assert!(text.contains(&format!("\"{label}\"")), "{label} missing from the menus");
+    }
+    assert!(text.contains(r#""params":{"theme":"paper"}"#));
+}
+
+#[test]
+fn the_top_bar_button_and_settings_cards_drive_the_mode() {
+    let mut h = Headless::new(app(), [1400.0, 900.0], 1.0);
+    h.settle(Duration::from_secs(60));
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "icon:appearance"}), T)["ok"], true);
+    h.step();
+    assert_eq!(h.app.ui.settings.appearance_mode, AppearanceMode::Auto);
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "icon:appearance"}), T)["ok"], true);
+    h.step();
+    h.step();
+    assert_eq!(h.app.ui.settings.appearance_mode, AppearanceMode::Light);
+    assert_eq!(crate::theme::current(&h.view.ctx), Some(ThemeKind::Silver));
+    // Settings ▸ Interface: the mode buttons and the theme radios
+    h.app.ui.dialog = Some(crate::state::Dialog::Settings { tab: "interface".into() });
+    h.step();
+    h.step();
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "radio:theme-paper"}), T)["ok"], true);
+    h.step();
+    h.step();
+    assert_eq!(h.app.ui.settings.light_theme, LightTheme::Paper);
+    assert_eq!(crate::theme::current(&h.view.ctx), Some(ThemeKind::Paper));
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "button:settingsAppearance-1"}), T)["ok"], true);
+    h.step();
+    h.step();
+    assert_eq!(h.app.ui.settings.appearance_mode, AppearanceMode::Dark);
+    assert_eq!(crate::theme::current(&h.view.ctx), Some(ThemeKind::Charcoal));
+}
+
+#[test]
+fn interface_settings_fit_small_windows_and_stack_theme_choices() {
+    // Desktop windows have a 900×560 minimum; also stress a smaller headless viewport.
+    for size in [[900.0, 560.0], [640.0, 480.0]] {
+        let mut h = Headless::new(app(), size, 1.0);
+        h.app.ui.dialog = Some(crate::state::Dialog::Settings { tab: "interface".into() });
+        for _ in 0..4 {
+            h.step();
+        }
+        let window = h.app.widgets.iter().find(|(id, _)| id == "dialog:window").unwrap().1;
+        assert!(window.width() <= size[0], "{size:?}: {window:?}");
+        assert!(window.height() <= size[1], "{size:?}: {window:?}");
+        let silver = h.app.widgets.iter().find(|(id, _)| id == "radio:theme-silver").unwrap().1;
+        let mode = h.app.widgets.iter().find(|(id, _)| id == "button:settingsAppearance-0").unwrap().1;
+        assert!(silver.top() > mode.bottom() + 80.0, "theme choices must sit below their preview");
+        assert!(silver.right() <= window.right(), "theme choices stay inside the modal");
+    }
+}
+
+#[test]
+fn favorites_validate_roundtrip_and_stars_toggle_without_selecting() {
+    for bad in [json!(["paper", "paper"]), json!(["unknown"]), json!([3]), json!("paper")] {
+        assert!(serde_json::from_value::<AppSettings>(json!({"favoriteThemes": bad})).is_err());
+    }
+    let mut h = Headless::new(app(), [1400.0, 900.0], 1.0);
+    h.app.ui.dialog = Some(crate::state::Dialog::Settings { tab: "interface".into() });
+    for _ in 0..4 {
+        h.step();
+    }
+    assert_eq!(h.request("ui.hoverWidget", json!({"id": "radio:theme-paper"}), T)["ok"], true);
+    h.step();
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "button:themeFavorite-paper"}), T)["ok"], true);
+    h.step();
+    assert_eq!(h.app.ui.settings.favorite_themes, vec!["paper"]);
+    if let Some(path) = std::env::var_os("FAVORITES_SCREENSHOT_DIR") {
+        h.request("ui.scroll", json!({"dy": -90.0}), T);
+        for _ in 0..4 {
+            h.step();
+        }
+        let pixels = h.paint();
+        let image =
+            lightcraft_raster::Rgba8 { width: pixels.size[0], height: pixels.size[1], data: pixels.pixels.iter().map(|c| c.to_array()).collect() };
+        let png = lightcraft_codecs::encode_png(&lightcraft_codecs::EncodeImage::rgba8(&image), &lightcraft_codecs::EncodeMeta::default()).unwrap();
+        std::fs::create_dir_all(&path).unwrap();
+        std::fs::write(std::path::Path::new(&path).join("lightcraft-favorites.png"), png).unwrap();
+    }
+    assert_eq!(h.app.ui.settings.light_theme, LightTheme::Silver, "starring does not select");
+    let saved = serde_json::to_value(&h.app.ui.settings).unwrap();
+    assert_eq!(serde_json::from_value::<AppSettings>(saved).unwrap(), h.app.ui.settings);
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "button:themeFavorite-paper"}), T)["ok"], true);
+    h.step();
+    assert!(h.app.ui.settings.favorite_themes.is_empty());
+    h.app.ui.dialog = None;
+    h.app.ui.settings.favorite_themes = vec!["midnight".into(), "paper".into()];
+    h.step();
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "icon:appearance", "button": "right"}), T)["ok"], true);
+    h.step();
+    h.step();
+    let light = h.app.widgets.iter().find(|(id, _)| id == "menu:themeFavorite-paper").unwrap().1;
+    let dark = h.app.widgets.iter().find(|(id, _)| id == "menu:themeFavorite-midnight").unwrap().1;
+    assert!(light.top() < dark.top(), "light favorites precede dark favorites");
+    assert_eq!(h.request("ui.clickWidget", json!({"id": "menu:themeFavorite-paper"}), T)["ok"], true);
+    h.step();
+    h.step();
+    assert_eq!(h.app.ui.settings.appearance_mode, AppearanceMode::Light);
+    assert_eq!(h.app.ui.settings.light_theme, LightTheme::Paper);
+    assert_eq!(h.app.ui.settings.dark_theme, DarkTheme::Charcoal);
+}
diff --git a/crates/ui-egui/src/theme.rs b/crates/ui-egui/src/theme.rs
index 620871c36..f383f3337 100644
--- a/crates/ui-egui/src/theme.rs
+++ b/crates/ui-egui/src/theme.rs
@@ -1,5 +1,9 @@
 //! Design tokens (colours, sizes, fonts). Values measured from black-box observation of the
 //! reference app's dark theme (see plan/lightroom/10-observed-ui.md); everything is our own code.
+//!
+//! Themes come in two families, picked by the Appearance Mode setting (Settings ▸ Interface):
+//! - dark: **Charcoal** (the default, the observed dark look) and **Midnight** (near black);
+//! - light: **Silver** (light grey chrome) and **Paper** (near white).
 
 use std::sync::Arc;
 
@@ -75,6 +79,44 @@ pub struct Tokens {
     pub film_h: f32,
 }
 
+/// An interface theme. Each belongs to the dark or the light family.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
+pub enum ThemeKind {
+    #[default]
+    Charcoal,
+    Midnight,
+    Silver,
+    Paper,
+}
+
+impl ThemeKind {
+    pub const ALL: [ThemeKind; 4] = [ThemeKind::Charcoal, ThemeKind::Midnight, ThemeKind::Silver, ThemeKind::Paper];
+
+    pub fn is_dark(self) -> bool {
+        matches!(self, ThemeKind::Charcoal | ThemeKind::Midnight)
+    }
+
+    /// The theme's id (settings value and command suffix).
+    pub fn id(self) -> &'static str {
+        match self {
+            ThemeKind::Charcoal => "charcoal",
+            ThemeKind::Midnight => "midnight",
+            ThemeKind::Silver => "silver",
+            ThemeKind::Paper => "paper",
+        }
+    }
+
+    /// The English display name.
+    pub fn label(self) -> &'static str {
+        match self {
+            ThemeKind::Charcoal => "Charcoal",
+            ThemeKind::Midnight => "Midnight",
+            ThemeKind::Silver => "Silver",
+            ThemeKind::Paper => "Paper",
+        }
+    }
+}
+
 impl Default for Tokens {
     fn default() -> Self {
         Tokens {
@@ -118,6 +160,92 @@ impl Default for Tokens {
 }
 
 impl Tokens {
+    /// The tokens of `kind`. Metrics are shared; only colours change.
+    pub fn for_kind(kind: ThemeKind) -> Tokens {
+        let rgb = |v: u32| Color32::from_rgb((v >> 16) as u8, (v >> 8) as u8, v as u8);
+        let base = Tokens::default();
+        match kind {
+            ThemeKind::Charcoal => base,
+            ThemeKind::Midnight => Tokens {
+                chrome: rgb(0x1e1e1e),
+                canvas: rgb(0x121212),
+                grid_bg: rgb(0x080808),
+                cell: rgb(0x121212),
+                cell_selected: rgb(0x262626),
+                divider: rgb(0x0e0e0e),
+                inset: rgb(0x181818),
+                field: rgb(0x161616),
+                field_border: rgb(0x333333),
+                button: rgb(0x191919),
+                button_border: rgb(0x404040),
+                hover: rgb(0x2e2e2e),
+                pressed: rgb(0x343434),
+                tool_active: rgb(0x343434),
+                ..base
+            },
+            ThemeKind::Silver => Tokens {
+                chrome: rgb(0xe6e6e6),
+                canvas: rgb(0xcfcfcf),
+                grid_bg: rgb(0xd9d9d9),
+                cell: rgb(0xcbcbcb),
+                cell_selected: rgb(0xb4b4b4),
+                divider: rgb(0xc4c4c4),
+                inset: rgb(0xdcdcdc),
+                field: rgb(0xf6f6f6),
+                field_border: rgb(0xb8b8b8),
+                button: rgb(0xf2f2f2),
+                button_border: rgb(0xb0b0b0),
+                hover: rgb(0xd2d2d2),
+                pressed: rgb(0xc4c4c4),
+                tool_active: rgb(0xcacaca),
+                text: rgb(0x1c1c1c),
+                text_label: rgb(0x383838),
+                text_dim: rgb(0x6a6a6a),
+                text_disabled: rgb(0xa2a2a2),
+                icon: rgb(0x555555),
+                track: rgb(0xa8a8a8),
+                thumb: rgb(0x5e5e5e),
+                thumb_hover: rgb(0x262626),
+                accent: rgb(0x0a62d0),
+                star: rgb(0x3a3a3a),
+                pick: rgb(0x2a2a2a),
+                reject: rgb(0xc83434),
+                caution: rgb(0xb0761a),
+                ..base
+            },
+            ThemeKind::Paper => Tokens {
+                chrome: rgb(0xfafafa),
+                canvas: rgb(0xececec),
+                grid_bg: rgb(0xf2f2f2),
+                cell: rgb(0xe8e8e8),
+                cell_selected: rgb(0xd2d2d2),
+                divider: rgb(0xe0e0e0),
+                inset: rgb(0xf0f0f0),
+                field: rgb(0xffffff),
+                field_border: rgb(0xcccccc),
+                button: rgb(0xffffff),
+                button_border: rgb(0xc6c6c6),
+                hover: rgb(0xebebeb),
+                pressed: rgb(0xdedede),
+                tool_active: rgb(0xe2e2e2),
+                text: rgb(0x161616),
+                text_label: rgb(0x343434),
+                text_dim: rgb(0x707070),
+                text_disabled: rgb(0xababab),
+                icon: rgb(0x585858),
+                track: rgb(0xbdbdbd),
+                thumb: rgb(0x606060),
+                thumb_hover: rgb(0x202020),
+                accent: rgb(0x0a62d0),
+                star: rgb(0x3a3a3a),
+                pick: rgb(0x2a2a2a),
+                reject: rgb(0xc83434),
+                caution: rgb(0xb0761a),
+                ..base
+            },
+        }
+    }
+
     pub fn get(ctx: &egui::Context) -> Tokens {
         ctx.data(|d| d.get_temp::<Tokens>(egui::Id::NULL)).unwrap_or_default()
     }
@@ -215,15 +343,32 @@ fn craft_font_name(f: &lightcraft_engine::CraftFont) -> String {
     format!("craft-fonts {} {}", f.family, f.style)
 }
 
+fn theme_id() -> egui::Id {
+    egui::Id::new("lightcraft-theme")
+}
+
+/// The theme `ctx` is styled with (none before the first [`apply_kind`]).
+pub fn current(ctx: &egui::Context) -> Option<ThemeKind> {
+    ctx.data(|d| d.get_temp::<ThemeKind>(theme_id()))
+}
+
+/// Style `ctx` with the default theme.
 pub fn apply(ctx: &egui::Context) {
-    // Cmd+= / Cmd+- / Cmd+0 (Ctrl on Windows and Linux) are View ▸ Zoom In / Zoom Out / Zoom to Fit
-    // for the photo. egui would take the same keys at the end of every frame for its browser-style
-    // interface zoom (issue #566); on macOS the native menu bar got them first, elsewhere the whole
-    // UI scaled.
+    apply_kind(ctx, ThemeKind::default());
+}
+
+/// Style `ctx` with `kind`. The visuals go to both of egui's styles, so egui following the
+/// system's dark/light setting on its own never swaps in its stock look.
+pub fn apply_kind(ctx: &egui::Context, kind: ThemeKind) {
+    // Keep photo zoom shortcuts from resizing egui itself.
     ctx.options_mut(|o| o.zoom_with_keyboard = false);
-    let t = Tokens::default();
-    ctx.data_mut(|d| d.insert_temp(egui::Id::NULL, t));
-    let mut v = Visuals::dark();
+    let t = Tokens::for_kind(kind);
+    ctx.data_mut(|d| {
+        d.insert_temp(egui::Id::NULL, t);
+        d.insert_temp(theme_id(), kind);
+    });
+    let dark = kind.is_dark();
+    let mut v = if dark { Visuals::dark() } else { Visuals::light() };
     v.panel_fill = t.chrome;
     v.window_fill = t.chrome;
     v.extreme_bg_color = t.field;
@@ -234,8 +379,9 @@ pub fn apply(ctx: &egui::Context) {
     v.selection.bg_fill = t.accent.gamma_multiply(0.6);
     v.selection.stroke = Stroke::new(1.0, t.accent);
     v.override_text_color = Some(t.text_label);
-    v.popup_shadow = egui::epaint::Shadow { offset: [0, 4], blur: 16, spread: 0, color: Color32::from_black_alpha(140) };
-    v.window_shadow = egui::epaint::Shadow { offset: [0, 8], blur: 30, spread: 0, color: Color32::from_black_alpha(160) };
+    let (popup, window) = if dark { (140, 160) } else { (50, 60) };
+    v.popup_shadow = egui::epaint::Shadow { offset: [0, 4], blur: 16, spread: 0, color: Color32::from_black_alpha(popup) };
+    v.window_shadow = egui::epaint::Shadow { offset: [0, 8], blur: 30, spread: 0, color: Color32::from_black_alpha(window) };
     let w = &mut v.widgets;
     craft_ui::theme::WidgetPalette { noninteractive: t.chrome, inactive: t.button, hovered: t.hover, active: t.pressed, open: t.hover }.apply_to(
         w,
@@ -244,8 +390,10 @@ pub fn apply(ctx: &egui::Context) {
     );
     w.noninteractive.bg_stroke = Stroke::new(1.0, t.divider);
     w.inactive.bg_stroke = Stroke::new(1.0, t.button_border);
-    ctx.set_visuals(v);
-    ctx.global_style_mut(|s| {
+    ctx.set_visuals_of(egui::Theme::Dark, v.clone());
+    ctx.set_visuals_of(egui::Theme::Light, v);
+    ctx.set_theme(if dark { egui::Theme::Dark } else { egui::Theme::Light });
+    ctx.all_styles_mut(|s| {
         s.spacing.item_spacing = egui::vec2(6.0, 4.0);
         s.spacing.button_padding = egui::vec2(8.0, 3.0);
         s.spacing.interact_size.y = 22.0;
diff --git a/docs/control-protocol.md b/docs/control-protocol.md
index d6c0c3d17..964aa042e 100644
--- a/docs/control-protocol.md
+++ b/docs/control-protocol.md
@@ -87,6 +87,12 @@ scrolling pans in both axes and respects the operating system's scrolling direct
 These gestures work in Detail (including editing tools and full-screen preview), Compare and Reference
 views, and only apply over their image areas. Panning stops at the image edges.
 
+The interface theme is `view.appearance {mode?: "auto" | "light" | "dark"}` (no mode: the next one,
+Auto → Light → Dark → Auto, like the top bar's `icon:appearance` button) and `view.theme {theme:
+"charcoal" | "midnight" | "silver" | "paper"}`, which picks a theme and fixes the mode to its family.
+Both reply `{mode, darkTheme, lightTheme}`; the same values are `settings.appearanceMode`,
+`settings.darkTheme` and `settings.lightTheme` in `ui.set`. Auto follows the system (on Linux the
+XDG desktop portal, watched for changes rather than polled) and is dark when the system says nothing.
 Mask brushing uses the UI command `tool.brush` through `engine.execute`. With `{}` it activates
 painting on the current mask. `{"new": true}` creates a separate brush mask; `{"op": "add"}` or
 `{"op": "subtract"}` appends a brush component to the selected mask. Creating either starts in
diff --git a/docs/parity-checklist.md b/docs/parity-checklist.md
index 7c345055d..ee6a5e1b2 100644
--- a/docs/parity-checklist.md
+++ b/docs/parity-checklist.md
@@ -424,7 +424,7 @@ differences and missing bindings are in [ui-parity.md](ui-parity.md#shortcuts).
 | LR-PREF-GENERAL | General settings | P0 | ✅ | `cmd:app.settings`, `cmd:app.openLibrary`, `crates/ui-egui/src/panels/settings.rs`, `crates/ui-egui/src/panels/notices.rs` | General / Import / Performance / Display / Interface tabs; app settings in ui.json (written atomically, saved when the library changes and every few seconds), library settings in prefs.json; a damaged settings file is kept as `.corrupt-<time>` and reported, an unreadable one is not overwritten that session (`library.info` → `settingsWarnings`); quitting with unsaved changes retries, then asks |
 | LR-PREF-LOCALSTORAGE | Storage & cache | P1 | ✅ | `cmd:library.preferences`, `cmd:library.clearPreviews`, `cmd:library.compact` | thumbnail cache size + clear in Settings → Performance; library location + Open Library… in General |
 | LR-PREF-ACCOUNT | Account | OOS | 🚫 | | |
-| LR-PREF-INTERFACE | Interface options | P1 | ✅ | `cmd:app.settings` | filmstrip names/badges, grid badges (auto/always/never), square-grid names, navigator, info overlay |
+| LR-PREF-INTERFACE | Interface options | P1 | ✅ | `cmd:app.settings`, `cmd:view.appearance`, `cmd:view.theme` | Appearance Mode (Sync with System / Dark / Light; the top bar button cycles Auto, Light, Dark) with separate dark (Charcoal, Midnight) and light (Silver, Paper) themes previewed in cards; hover stars persist favorite themes, the appearance button context menu opens Interface settings and lists light favorites before dark favorites; filmstrip names/badges, grid badges (auto/always/never), square-grid names, navigator, info overlay |
 | LR-PREF-DISPLAY | Monitor (display) colour management | P1 | 🟡 | `cmd:app.displayProfile`, `crates/codecs/src/display.rs`, `crates/engine/src/display.rs`, `crates/ui-egui/src/panels/settings.rs`, `docs/display-profiles.md` | Settings ▸ Display: a monitor ICC profile (matrix/TRC exactly, LUT-based through the CMS) chosen by hand; the loupe, Before, Compare, hover previews and the second window render into the display's primaries (its full gamut, CPU and GPU), thumbnails and stand-ins are converted from sRGB; histogram, preview caches and exports stay sRGB; soft proofing's display gamut warning uses the display's gamut. Missing: picking up the profile the OS assigns (X11 `_ICC_PROFILE`, colord, ColorSync, WCS), per-monitor profiles |
 | LR-PREF-PERFORMANCE | GPU / performance | P1 | ✅ | `cmd:app.gpu`, `cmd:app.memoryBudget`, `cmd:app.settings` | GPU on/off (a crash while the GPU device or its kernels are built, issue #250, turns it off for the next launch), preview size (Automatic = the whole-frame loupe render at canvas size, up to 2560 px; or a 1600–5120 px size for it; zoomed views add a window at up to 100 %, issue #323), memory budget (a quarter of it is the idle per-view stage caches' share; the open photo's views are counted and reported, and cut only past four times that, the before side's and the zoom window's first — a Before/After at 1:1 on a 2800 px canvas holds about 1 GB of GPU stages, plus the one 288 MB copy of the original, which `ui.inspect` reports as `sharedSourceBytes`), thumbnail cache size in Settings |
 | LR-PREF-PEOPLE | Face recognition | P2 | 🟡 | `cmd:faces.enable`, `cmd:faces.models.list`, `cmd:faces.models.inspect`, `cmd:faces.models.install`, `cmd:faces.models.download`, `cmd:faces.models.downloads`, `cmd:faces.models.downloadCancel`, `cmd:faces.models.remove`, `cmd:faces.models.select`, `cmd:dialog.faceModel`, `crates/faces/src/lib.rs`, `crates/ui-egui/src/panels/faces.rs` | Settings ▸ Faces: an off-by-default toggle and the face model list. Models are opt-in and never bundled, the 232 KB YuNet detector included. Press Download (terms first; then a pinned address, size and SHA-256 checked, fetched over pure-Rust https with `lightcraft-fetch`), or add any `.onnx` by picking or dropping it: it is recognised by hash or described from its shape, shows its licence terms and training-data note, runs a self-test, and installs only after an "I accept" box; an installed model is chosen and recognition switched on at once (the newest wins, each model keeps its own embedding cache). Non-commercial models are add-by-file only, never offered for download. Suggestions of names run on the shared pure-Rust CPU interpreter (`crates/faces/src/net.rs`, `crates/faces/src/runtime.rs`; bounded im2col/GEMM, checked ONNX shapes/operators; no external inference runtime; 40 public crops agree within 2.1e-6, one-thread SFace 34–36 ms / AuraFace 233–252 ms, see docs/faces.md) in a background worker and are never applied automatically. Thresholds are starting points calibrated on busts, not yet on live faces; the Recognise faces switch is off until a recognition model is chosen and installed (`faces.enable {enabled: true}` refuses otherwise; removing the last recogniser switches it off), issue #678 |
diff --git a/docs/whats-new.md b/docs/whats-new.md
index 95b298ba0..7c8475552 100644
--- a/docs/whats-new.md
+++ b/docs/whats-new.md
@@ -40,6 +40,14 @@
   buttons stay visible. Long lists in dialogs (What's New, All Metadata, Keyboard Shortcuts) get shorter to fit.
   Dialogs that fit look as before.
 
+### Appearance
+- Settings ▸ Interface ▸ Appearance Mode: Sync with System, Dark Mode or Light Mode, above a light
+  and a dark theme card, each previewing its theme (dark: Charcoal, the look so far, or Midnight;
+  light: Silver or Paper). New and existing installs stay dark; following the system is opt-in.
+- The top bar's appearance button cycles Auto, Light, Dark (a monitor, sun or moon), and View ▸
+  Appearance lists the modes and themes. On Linux, Auto follows the desktop portal's colour scheme
+  as it changes, without polling.
+
 ### Activity stack
 - Long-running tasks show in one place, top left under the top bar, as in Lightroom Classic (issue #345): imports and
   folder scans, exports (and the contact sheet PDF), Synchronize Folder, Build / Smart Previews, Lightroom catalog import, Photo Merge, model downloads, the face scan,