diff --git a/apps/vectorcraft/src/main.rs b/apps/vectorcraft/src/main.rs
index 915daadd..0ce3d74f 100644
--- a/apps/vectorcraft/src/main.rs
+++ b/apps/vectorcraft/src/main.rs
@@ -400,6 +400,32 @@ fn adapter_summary(info: &eframe::wgpu::AdapterInfo) -> String {
 /// macOS keeps its traffic lights over the integrated title strip.
 const CUSTOM_TITLEBAR: bool = !cfg!(target_os = "macos");
 
+/// Whether this start draws its own title bar: Windows and Linux do, unless Preferences ›
+/// User Interface › System Title Bar asks for the system's. Read from the saved preferences
+/// before the window opens; a missing or unreadable value keeps the default.
+fn custom_titlebar(saved: Option<&vectorcraft_ui_egui::UiState>) -> bool {
+    CUSTOM_TITLEBAR && !saved.map(|ui| ui.engine_prefs.get("systemTitleBar").and_then(serde_json::Value::as_bool).unwrap_or(false)).unwrap_or(false)
+}
+
+fn native_options(custom_titlebar: bool) -> eframe::NativeOptions {
+    eframe::NativeOptions {
+        viewport: egui::ViewportBuilder::default()
+            .with_title("VectorCraft")
+            .with_inner_size(window::DEFAULT_SIZE)
+            .with_min_inner_size(window::MIN_SIZE)
+            .with_drag_and_drop(true)
+            .with_decorations(!custom_titlebar)
+            .with_fullsize_content_view(true)
+            .with_titlebar_shown(false)
+            .with_title_shown(false)
+            .with_icon(app_icon())
+            .with_app_id("ai.storyteller.vectorcraft"),
+        #[cfg(feature = "windows7")]
+        renderer: eframe::Renderer::Glow,
+        ..Default::default()
+    }
+}
+
 fn main() -> std::process::ExitCode {
     // First, so every start-up warning is recorded (`logging`).
     let logger = logging::install();
@@ -486,22 +512,8 @@ fn main() -> std::process::ExitCode {
     }
     #[cfg(feature = "wgpu")]
     let startup = std::sync::Arc::new(gpu::Startup::default());
-    let options = eframe::NativeOptions {
-        viewport: egui::ViewportBuilder::default()
-            .with_title("VectorCraft")
-            .with_inner_size(window::DEFAULT_SIZE)
-            .with_min_inner_size(window::MIN_SIZE)
-            .with_drag_and_drop(true)
-            .with_decorations(!CUSTOM_TITLEBAR)
-            .with_fullsize_content_view(true)
-            .with_titlebar_shown(false)
-            .with_title_shown(false)
-            .with_icon(app_icon())
-            .with_app_id("ai.storyteller.vectorcraft"),
-        #[cfg(feature = "windows7")]
-        renderer: eframe::Renderer::Glow,
-        ..Default::default()
-    };
+    let custom_titlebar = custom_titlebar(saved.as_ref());
+    let options = native_options(custom_titlebar);
     #[cfg(feature = "wgpu")]
     let options = {
         let mut options = options;
@@ -575,7 +587,7 @@ fn main() -> std::process::ExitCode {
                 {
                     app.graphics_adapter = Some("OpenGL (Windows 7 compatibility)".into());
                 }
-                app.custom_titlebar = CUSTOM_TITLEBAR;
+                app.custom_titlebar = custom_titlebar;
                 if let Some(port) = control_port {
                     let rx = control_server::start(port, cc.egui_ctx.clone());
                     app = app.with_control(rx).with_automation_roots(roots.clone());
@@ -618,6 +630,27 @@ fn main() -> std::process::ExitCode {
 mod tests {
     use super::*;
 
+    fn ui_state_with_prefs(prefs: serde_json::Value) -> vectorcraft_ui_egui::UiState {
+        let mut ui = vectorcraft_ui_egui::UiState::default();
+        ui.engine_prefs = prefs;
+        ui
+    }
+
+    #[test]
+    fn the_system_title_bar_preference_keeps_the_window_decorations() {
+        // Preferences › User Interface › System Title Bar gives the window back its system
+        // decorations on Windows and Linux; macOS always has them.
+        assert_eq!(super::custom_titlebar(None), super::CUSTOM_TITLEBAR, "no preferences: the default");
+        let off = ui_state_with_prefs(serde_json::json!({"systemTitleBar": false}));
+        assert_eq!(super::custom_titlebar(Some(&off)), super::CUSTOM_TITLEBAR);
+        let on = ui_state_with_prefs(serde_json::json!({"systemTitleBar": true}));
+        assert!(!super::custom_titlebar(Some(&on)));
+        assert_eq!(super::native_options(false).viewport.decorations, Some(true));
+        if super::CUSTOM_TITLEBAR {
+            assert_eq!(super::native_options(true).viewport.decorations, Some(false));
+        }
+    }
+
     /// The file extensions the macOS bundle declares: its document types and its own exported type.
     fn plist_extensions(plist: &str) -> Vec<&str> {
         ["<key>CFBundleTypeExtensions</key>", "<key>public.filename-extension</key>"]
diff --git a/crates/engine/src/cmd/prefscmds.rs b/crates/engine/src/cmd/prefscmds.rs
index d1562c5e..0c764faa 100644
--- a/crates/engine/src/cmd/prefscmds.rs
+++ b/crates/engine/src/cmd/prefscmds.rs
@@ -282,6 +282,7 @@ pub const PREF_SPECS: &[PrefSpec] = &[
     p!("scaleCursorWithUi", "User Interface", "UI Scaling", "Scale Cursor Proportional to UI", bool),
     // `auto` or a language code the shell registers (`zh-hant`); the shell shows it as a dropdown.
     p!("interfaceLanguage", "User Interface", "Language", "Language", text),
+    p!("systemTitleBar", "User Interface", "", "System Title Bar", bool),
     // Performance
     p!("gpuPerformance", "Performance", "GPU Performance", "GPU Performance", bool),
     p!("animatedZoom", "Performance", "GPU Performance", "Animated Zoom", bool),
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index ec72f1ee..8a964610 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -512,6 +512,10 @@ pub struct Prefs {
     /// UI language: `auto` (follow the system locale) or a language code such as `en`, `zh-hant`.
     /// The list of languages belongs to the shell (`ui-egui` i18n); an unknown code reads as `auto`.
     pub interface_language: String,
+    /// Windows and Linux: use the system's title bar and window buttons instead of the app bar
+    /// acting as the title bar (tiling window managers, desktops that draw their own decorations).
+    /// Read when the app starts. macOS always uses the system's.
+    pub system_title_bar: bool,
     // Performance
     pub gpu_performance: bool,
     pub animated_zoom: bool,
@@ -726,6 +730,7 @@ impl Default for Prefs {
             ui_scaling: 1.0,
             scale_cursor_with_ui: false,
             interface_language: s("auto"),
+            system_title_bar: false,
             gpu_performance: true,
             animated_zoom: true,
             gpu_preference: s("automatic"),
diff --git a/crates/ui-egui/src/brand.rs b/crates/ui-egui/src/brand.rs
index 1d88dfb2..0a528569 100644
--- a/crates/ui-egui/src/brand.rs
+++ b/crates/ui-egui/src/brand.rs
@@ -36,6 +36,12 @@ pub fn paint_mark(ui: &Ui, r: Rect) {
     ui.painter().image(texture(ui.ctx()).id(), r, uv, Color32::WHITE);
 }
 
+/// The mark's texture id (tests: find the painted marks among the shapes).
+#[cfg(test)]
+pub fn texture_id(ctx: &Context) -> egui::TextureId {
+    texture(ctx).id()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -55,6 +61,9 @@ mod tests {
         let ctx = Context::default();
         crate::theme::install_fonts(&ctx);
         let mut app = VectorcraftApp::new(vectorcraft_engine::Session::new(), Default::default());
+        // The system title bar hides the in-app mark (the OS draws its own icon), so paint the
+        // app-drawn bar here.
+        app.custom_titlebar = true;
         let mut frame = || {
             let mut out = ctx.run_ui(egui::RawInput::default(), |ui| crate::chrome::app_bar(&mut app, ui));
             let uploads = out.textures_delta.set.values().flat_map(|d| d.iter()).filter(|d| d.image.size() == [128, 128]).count();
diff --git a/crates/ui-egui/src/chrome.rs b/crates/ui-egui/src/chrome.rs
index be7d3f3c..653f24fb 100644
--- a/crates/ui-egui/src/chrome.rs
+++ b/crates/ui-egui/src/chrome.rs
@@ -18,9 +18,12 @@ pub const APP_BAR_HEIGHT: f32 = 44.0;
 /// The application bar: brand mark, Home, menus, then Discord, search and the workspace switcher
 /// at the right. With [`VectorcraftApp::custom_titlebar`] it is also the window's title bar
 /// ([`titlebar`]): the caption buttons take the right end and the rest of the bar drags the window.
+/// With the system title bar (Windows and Linux, `system_title_bar`) the OS draws its own icon and
+/// title, so the in-app bar shows Home, menus and workspace controls only: no brand mark.
 pub fn app_bar(app: &mut VectorcraftApp, ui: &mut Ui) {
     let t = Tokens::get(ui.ctx());
     let custom = app.custom_titlebar;
+    let system = system_title_bar(app);
     let left = app.titlebar_inset.clamp(8.0, f32::from(i8::MAX)) as i8;
     let frame = egui::Frame::NONE.fill(t.app_bar).inner_margin(egui::Margin { left, right: if custom { 0 } else { 14 }, top: 0, bottom: 0 });
     let bar = egui::Panel::top("app_bar").exact_size(APP_BAR_HEIGHT).frame(frame.stroke(Stroke::new(1.0, t.border))).show(ui, |ui| {
@@ -28,10 +31,12 @@ pub fn app_bar(app: &mut VectorcraftApp, ui: &mut Ui) {
             titlebar::drag_area(ui, ui.max_rect());
         }
         ui.horizontal_centered(|ui| {
-            // Brand mark: the app icon.
-            let (r, _) = ui.allocate_exact_size(vec2(22.0, 22.0), Sense::hover());
-            crate::brand::paint_mark(ui, r);
-            ui.add_space(4.0);
+            // With the system title bar the OS draws its own icon: no in-app brand mark.
+            if !system {
+                let (r, _) = ui.allocate_exact_size(vec2(22.0, 22.0), Sense::hover());
+                crate::brand::paint_mark(ui, r);
+                ui.add_space(4.0);
+            }
             let on_home = menus::home_showing(app);
             if widgets::icon_button(ui, "house", tl!("Home"), on_home, 24.0).clicked() {
                 app.run("app.home", json!({})).ok();
@@ -109,6 +114,35 @@ pub fn app_bar(app: &mut VectorcraftApp, ui: &mut Ui) {
     }
 }
 
+/// Whether the window shows the system's title bar instead of the app drawing its own: Windows
+/// and Linux with Preferences › User Interface › System Title Bar. macOS always has system
+/// decorations, but keeps the in-app brand mark, so it never counts as system mode here; nor
+/// does the web build (the browser tab has no document title), nor an embedder that never
+/// turned the preference on.
+pub fn system_title_bar(app: &VectorcraftApp) -> bool {
+    !app.custom_titlebar && app.session.prefs.system_title_bar && !cfg!(any(target_os = "macos", target_arch = "wasm32"))
+}
+
+/// The OS window title: the active document's name suffixed with the app name (a `*` prefix
+/// marks unsaved changes, like the `*` in the document tabs), or just the app name with no
+/// document open.
+pub fn window_title(app: &VectorcraftApp) -> String {
+    app.session
+        .active()
+        .map(|d| format!("{}{} \u{2014} VectorCraft", if d.is_dirty() { "*" } else { "" }, d.title()))
+        .unwrap_or_else(|| "VectorCraft".into())
+}
+
+/// Keep the OS window title (and the taskbar / Alt-Tab entry) on the active file. Sends
+/// `ViewportCommand::Title` only when the title changed since the last frame.
+pub fn sync_window_title(app: &mut VectorcraftApp, ctx: &egui::Context) {
+    let want = window_title(app);
+    if app.last_window_title != want {
+        app.last_window_title = want.clone();
+        ctx.send_viewport_cmd(egui::ViewportCommand::Title(want));
+    }
+}
+
 /// An anchor button: icon, tooltip, command and the convert command's `to`.
 type AnchorButton<'a> = (&'a str, &'a str, &'a str, Option<&'a str>);
 
@@ -965,4 +999,81 @@ mod tests {
         let off = hint(&mut app);
         assert!(off.contains(" to zoom into an area") && !off.contains("Hold"), "{off}");
     }
+
+    fn title_test_app(custom_titlebar: bool) -> crate::VectorcraftApp {
+        let mut app = crate::VectorcraftApp::new(Session::new(), Default::default());
+        app.custom_titlebar = custom_titlebar;
+        // The preference that makes the shell launch without its own title bar.
+        app.run("prefs.set", json!({"key": "systemTitleBar", "value": !custom_titlebar})).unwrap();
+        app
+    }
+
+    #[test]
+    fn without_the_preference_the_mark_stays() {
+        // The default (e.g. the web build): no custom bar, no preference.
+        let app = crate::VectorcraftApp::new(Session::new(), Default::default());
+        assert!(!super::system_title_bar(&app));
+    }
+
+    #[test]
+    fn window_title_with_no_document_is_the_app_name() {
+        assert_eq!(super::window_title(&title_test_app(true)), "VectorCraft");
+    }
+
+    #[test]
+    fn window_title_follows_the_active_file() {
+        let mut app = title_test_app(true);
+        app.run("file.new", json!({"width": 100, "height": 100, "name": "foo.svg"})).unwrap();
+        assert_eq!(super::window_title(&app), "foo.svg \u{2014} VectorCraft");
+        // Unsaved changes gain a `*` prefix, like the `*` in the document tabs.
+        app.run("shape.rectangle", json!({"x": 0, "y": 0, "width": 10, "height": 10})).unwrap();
+        assert_eq!(super::window_title(&app), "*foo.svg \u{2014} VectorCraft");
+    }
+
+    #[test]
+    fn system_mode_hides_the_mark() {
+        for custom in [true, false] {
+            let mut app = title_test_app(custom);
+            app.run("file.new", json!({"width": 100, "height": 100, "name": "foo.svg"})).unwrap();
+            let ctx = egui::Context::default();
+            crate::theme::install_fonts(&ctx);
+            let mut out = ctx.run_ui(egui::RawInput::default(), |ui| super::app_bar(&mut app, ui));
+            let uploads = out.textures_delta.set.values().flat_map(|d| d.iter()).filter(|d| d.image.size() == [128, 128]).count();
+            out.textures_delta.clear();
+            let marks: Vec<egui::Rect> = out
+                .shapes
+                .iter()
+                .filter_map(|c| match &c.shape {
+                    egui::Shape::Mesh(m) if m.texture_id == crate::brand::texture_id(&ctx) => Some(m.calc_bounds()),
+                    _ => None,
+                })
+                .collect();
+            let system = super::system_title_bar(&app);
+            assert_eq!(system, !custom && !cfg!(target_os = "macos"));
+            assert_eq!(marks.is_empty(), system, "mark in system mode (custom={custom})");
+            assert_eq!(uploads, if system { 0 } else { 1 }, "mark texture in system mode (custom={custom})");
+        }
+    }
+
+    #[test]
+    fn sync_window_title_sends_only_on_change() {
+        let mut app = title_test_app(true);
+        let ctx = egui::Context::default();
+        crate::theme::install_fonts(&ctx);
+        super::sync_window_title(&mut app, &ctx);
+        assert_eq!(app.last_window_title, "VectorCraft");
+        let mut out = ctx.run_ui(egui::RawInput::default(), |_| {});
+        out.textures_delta.clear();
+        let cmds = out.viewport_output.remove(&egui::ViewportId::ROOT).map(|v| v.commands).unwrap_or_default();
+        assert!(cmds.iter().any(|c| matches!(c, egui::ViewportCommand::Title(t) if t == "VectorCraft")), "{cmds:?}");
+        // Same document state again: the cached title stops a repeat command.
+        super::sync_window_title(&mut app, &ctx);
+        let mut out = ctx.run_ui(egui::RawInput::default(), |_| {});
+        out.textures_delta.clear();
+        let cmds = out.viewport_output.remove(&egui::ViewportId::ROOT).map(|v| v.commands).unwrap_or_default();
+        assert!(!cmds.iter().any(|c| matches!(c, egui::ViewportCommand::Title(_))), "repeat Title: {cmds:?}");
+        app.run("file.new", json!({"width": 100, "height": 100, "name": "foo.svg"})).unwrap();
+        super::sync_window_title(&mut app, &ctx);
+        assert_eq!(app.last_window_title, "foo.svg \u{2014} VectorCraft");
+    }
 }
diff --git a/crates/ui-egui/src/i18n/cs.tsv b/crates/ui-egui/src/i18n/cs.tsv
index 06aa8084..065bda2a 100644
--- a/crates/ui-egui/src/i18n/cs.tsv
+++ b/crates/ui-egui/src/i18n/cs.tsv
@@ -673,3 +673,5 @@
 	Patchwork…	Patchwork…
 	Stained Glass…	Vitráž…
 	Texturizer…	Texturovač…
+	System Title Bar	Systémové záhlaví okna
+	Applies at next launch.	Projeví se při příštím spuštění.
diff --git a/crates/ui-egui/src/i18n/es.tsv b/crates/ui-egui/src/i18n/es.tsv
index f703db8b..f4927b5e 100644
--- a/crates/ui-egui/src/i18n/es.tsv
+++ b/crates/ui-egui/src/i18n/es.tsv
@@ -3975,3 +3975,5 @@ axis	Both	Ambos
 	Top Right	Arriba a la derecha
 	Bottom Right	Abajo a la derecha
 	Edge	Borde
+	System Title Bar	Barra de título del sistema
+	Applies at next launch.	Se aplicará en el próximo inicio.
diff --git a/crates/ui-egui/src/i18n/fr.tsv b/crates/ui-egui/src/i18n/fr.tsv
index 04728393..6dc963a7 100644
--- a/crates/ui-egui/src/i18n/fr.tsv
+++ b/crates/ui-egui/src/i18n/fr.tsv
@@ -3987,3 +3987,5 @@ axis	Both	Les deux
 	Bottom Right	En bas à droite
 effect	Soft	Doux
 	Edge	Bord
+	System Title Bar	Barre de titre du système
+	Applies at next launch.	Prend effet au prochain démarrage.
diff --git a/crates/ui-egui/src/i18n/it.tsv b/crates/ui-egui/src/i18n/it.tsv
index 975c1a03..bbb37c63 100644
--- a/crates/ui-egui/src/i18n/it.tsv
+++ b/crates/ui-egui/src/i18n/it.tsv
@@ -3977,3 +3977,5 @@ axis	Both	Entrambi
 effect	Soft	Morbido
 effect	Regular	Normale
 	Edge	Bordo
+	System Title Bar	Barra del titolo di sistema
+	Applies at next launch.	Si applica al prossimo avvio.
diff --git a/crates/ui-egui/src/i18n/ja.tsv b/crates/ui-egui/src/i18n/ja.tsv
index 93697179..40a9fe66 100644
--- a/crates/ui-egui/src/i18n/ja.tsv
+++ b/crates/ui-egui/src/i18n/ja.tsv
@@ -3970,3 +3970,5 @@ effect	Soft	ソフト
 effect	Horizontal	水平
 effect	Vertical	垂直
 	Edge	エッジ
+	System Title Bar	システムのタイトルバー
+	Applies at next launch.	次回の起動時に適用されます。
diff --git a/crates/ui-egui/src/i18n/pt-br.tsv b/crates/ui-egui/src/i18n/pt-br.tsv
index 6b1ef85a..182b9d5e 100644
--- a/crates/ui-egui/src/i18n/pt-br.tsv
+++ b/crates/ui-egui/src/i18n/pt-br.tsv
@@ -2733,3 +2733,5 @@
 	Patchwork…	Colcha de retalhos…
 	Stained Glass…	Vitral…
 	Texturizer…	Texturizador…
+	System Title Bar	Barra de título do sistema
+	Applies at next launch.	Aplica-se na próxima inicialização.
diff --git a/crates/ui-egui/src/i18n/ru.tsv b/crates/ui-egui/src/i18n/ru.tsv
index 83b26c87..3c04c962 100644
--- a/crates/ui-egui/src/i18n/ru.tsv
+++ b/crates/ui-egui/src/i18n/ru.tsv
@@ -3973,3 +3973,5 @@ axis	Both	Оба
 	Top Right	Сверху справа
 	Bottom Right	Снизу справа
 	Edge	Край
+	System Title Bar	Системная строка заголовка
+	Applies at next launch.	Применится при следующем запуске.
diff --git a/crates/ui-egui/src/i18n/uk.tsv b/crates/ui-egui/src/i18n/uk.tsv
index 5dab363e..34afec8f 100644
--- a/crates/ui-egui/src/i18n/uk.tsv
+++ b/crates/ui-egui/src/i18n/uk.tsv
@@ -3958,3 +3958,5 @@ axis	Both	Обидві
 	Top Right	Вгорі праворуч
 	Bottom Right	Знизу праворуч
 	Edge	Край
+	System Title Bar	Системний рядок заголовка
+	Applies at next launch.	Набуде чинності після перезапуску.
diff --git a/crates/ui-egui/src/i18n/zh-hans.tsv b/crates/ui-egui/src/i18n/zh-hans.tsv
index b4ec898e..1dd56e99 100644
--- a/crates/ui-egui/src/i18n/zh-hans.tsv
+++ b/crates/ui-egui/src/i18n/zh-hans.tsv
@@ -3606,3 +3606,5 @@ effect	Soft	柔和
 effect	Horizontal	水平
 effect	Vertical	垂直
 	Edge	边缘
+	System Title Bar	系统标题栏
+	Applies at next launch.	下次启动时生效。
diff --git a/crates/ui-egui/src/i18n/zh-hant.tsv b/crates/ui-egui/src/i18n/zh-hant.tsv
index 5101d723..70696085 100644
--- a/crates/ui-egui/src/i18n/zh-hant.tsv
+++ b/crates/ui-egui/src/i18n/zh-hant.tsv
@@ -3387,3 +3387,5 @@ axis	Both	兩者
 	Bottom Right	右下
 effect	Soft	柔和
 	Edge	邊緣
+	System Title Bar	系統標題列
+	Applies at next launch.	下次啟動時套用。
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 6a4c67e6..d82fbbde 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -353,6 +353,9 @@ pub struct VectorcraftApp {
     /// Windows and Linux: the window has no OS decorations, so the app bar is the title bar (drag,
     /// double-click to maximize, caption buttons) and invisible edge zones resize the window.
     pub custom_titlebar: bool,
+    /// Last window title sent to the OS (`ViewportCommand::Title`, see `chrome::sync_window_title`):
+    /// sent again only when it changes, so idle frames don't spam the backend.
+    pub(crate) last_window_title: String,
     /// The graphics adapter the window renders with ("name (backend)"), as the host reports it:
     /// shown in Help › About and `ui.inspect` for GPU bug reports. `None` when unknown.
     pub graphics_adapter: Option<String>,
@@ -462,6 +465,7 @@ impl VectorcraftApp {
             canvas_rect: None,
             hover_doc: None,
             custom_titlebar: false,
+            last_window_title: String::new(),
             graphics_adapter: None,
             place: Default::default(),
             system_paste: false,
@@ -958,6 +962,9 @@ impl VectorcraftApp {
         }
         shortcut_editor::sync(&self.ui);
         prefs_dialog::apply_runtime(self, ctx);
+        // The OS title bar (and the taskbar / Alt-Tab entry) follows the active file; with the
+        // system title bar this is where the document name lives, as the in-app mark is hidden.
+        crate::chrome::sync_window_title(self, ctx);
         self.drain_control(ctx);
         if !self.synthetic.is_empty() {
             ctx.request_repaint();
diff --git a/crates/ui-egui/src/prefs_dialog.rs b/crates/ui-egui/src/prefs_dialog.rs
index da7595de..72b649a5 100644
--- a/crates/ui-egui/src/prefs_dialog.rs
+++ b/crates/ui-egui/src/prefs_dialog.rs
@@ -261,6 +261,11 @@ fn category_fields(ui: &mut egui::Ui, d: &mut Dialog, cat: &str) {
             PrefKind::Bool if sp.key == "animatedZoom" => {
                 ui.add_enabled_ui(d.bool("gpuPerformance"), |ui| bool_row(ui, d, sp.key, sp.label));
             }
+            PrefKind::Bool if sp.key == "systemTitleBar" && cfg!(all(not(target_arch = "wasm32"), not(target_os = "macos"))) => {
+                bool_row(ui, d, sp.key, sp.label);
+                // The window's decorations are chosen once, when the app starts.
+                ui.label(egui::RichText::new(tl!("Applies at next launch.")).color(t.text_dim).size(11.0));
+            }
             PrefKind::Bool => bool_row(ui, d, sp.key, sp.label),
             PrefKind::Num { min, max, unit } => {
                 labeled(ui, sp.label, |ui| {
@@ -530,6 +535,37 @@ mod tests {
         assert_eq!(saved["engine_prefs"]["gpuPreference"], json!("highPerformance"));
     }
 
+    /// User Interface › System Title Bar: shown with its next-launch note, applied by OK and
+    /// saved with the UI state under the key the desktop app reads before the window opens.
+    #[test]
+    fn system_title_bar_preference_shows_and_persists() {
+        fn texts(s: &egui::Shape, out: &mut Vec<String>) {
+            match s {
+                egui::Shape::Text(t) => out.push(t.galley.text().to_string()),
+                egui::Shape::Vec(v) => v.iter().for_each(|s| texts(s, out)),
+                _ => {}
+            }
+        }
+        let mut a = app();
+        open(&mut a, Some("User Interface"));
+        let ctx = egui::Context::default();
+        crate::theme::install_fonts(&ctx);
+        // The window sizes itself on the first frame and draws on the second.
+        let mut out = ctx.run_ui(egui::RawInput::default(), |ui| show(&mut a, ui.ctx()));
+        out.textures_delta.clear();
+        let mut out = ctx.run_ui(egui::RawInput::default(), |ui| show(&mut a, ui.ctx()));
+        out.textures_delta.clear();
+        let mut shown = vec![];
+        out.shapes.iter().for_each(|c| texts(&c.shape, &mut shown));
+        assert!(shown.iter().any(|t| t == "System Title Bar"), "{shown:?}");
+        assert!(shown.iter().any(|t| t == "Applies at next launch."), "{shown:?}");
+        a.ui.dialog.as_mut().unwrap().fields.insert("systemTitleBar".into(), json!(true));
+        confirm(&mut a).unwrap();
+        assert!(a.session.prefs.system_title_bar);
+        let saved: Value = serde_json::from_slice(&serde_json::to_vec(&a.ui).unwrap()).unwrap();
+        assert_eq!(saved["engine_prefs"]["systemTitleBar"], json!(true));
+    }
+
     /// Units › Numbers Without Units Are Points (#394): the preference reaches the fields when it
     /// changes, and its checkbox is dimmed unless a unit is Picas.
     #[test]