diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 2cbf0510f..f549aec2b 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -209,9 +209,31 @@ pub struct Perf {
     last: f64,
 }
 
+/// Which parts of the app's own window chrome are drawn. Everything is on by default; a host
+/// that embeds the sheet in its own window (and owns files itself) can turn off the title bar
+/// and the File tab, whose Backstage view then never opens. Not persisted: it describes the
+/// host, not a user preference.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Chrome {
+    /// The title bar: AutoSave, Home, Save, Undo/Redo, the file name, Comments, Share, Search and
+    /// the theme switch.
+    pub title_bar: bool,
+    /// The ribbon's File tab and the Backstage view it opens (also reached by keyboard and
+    /// commands such as `ui.backstage`).
+    pub file_tab: bool,
+}
+
+impl Default for Chrome {
+    fn default() -> Self {
+        Chrome { title_bar: true, file_tab: true }
+    }
+}
+
 pub struct SheetApp {
     pub session: Session,
     pub ui: UiState,
+    /// The window chrome to draw (see [`Chrome`]).
+    pub chrome: Chrome,
     pub views: HashMap<(u64, usize), SheetView>,
     pub editor: Option<editor::EditState>,
     pub text_box_editor: Option<text_box::EditState>,
@@ -270,6 +292,7 @@ impl SheetApp {
         SheetApp {
             session,
             ui: UiState::default(),
+            chrome: Chrome::default(),
             views: HashMap::new(),
             editor: None,
             text_box_editor: None,
@@ -752,6 +775,9 @@ impl SheetApp {
     /// Opens the File tab's Backstage view on `page`, committing a cell still being edited first
     /// (File actions work on the whole workbook). A draft that can't be committed keeps the sheet.
     pub fn open_backstage(&mut self, page: backstage::Page) {
+        if !self.chrome.file_tab {
+            return;
+        }
         if !self.commit_edit(0, 0, false, false) {
             return;
         }
@@ -1115,10 +1141,16 @@ impl SheetApp {
         // The language the widgets translate with this frame (see `i18n::current`).
         i18n::set_current(&ctx, self.ui.language);
         let t = theme::Tokens::get(&ctx);
+        // A host can turn the File tab off while Backstage is already open: close it.
+        if !self.chrome.file_tab {
+            self.backstage = None;
+        }
         if self.backstage.is_none() {
             self.ribbon_keys(&ctx);
         }
-        ribbon::title_bar(self, ui);
+        if self.chrome.title_bar {
+            ribbon::title_bar(self, ui);
+        }
         if self.backstage.is_some() {
             // File tab: the Backstage view replaces everything below the title bar.
             backstage::show(self, ui);
diff --git a/crates/ui-egui/src/ribbon.rs b/crates/ui-egui/src/ribbon.rs
index 662c87ef1..a0ab5a339 100644
--- a/crates/ui-egui/src/ribbon.rs
+++ b/crates/ui-egui/src/ribbon.rs
@@ -176,7 +176,9 @@ pub fn show(app: &mut SheetApp, ui: &mut Ui) {
                 ui.horizontal(|ui| {
                     ui.spacing_mut().item_spacing.x = 2.0;
                     ui.add_space(8.0);
-                    file_menu(app, ui);
+                    if app.chrome.file_tab {
+                        file_menu(app, ui);
+                    }
                     let mut tabs: Vec<&str> = TABS.to_vec();
                     let ctx_tabs = contextual_tabs(app);
                     tabs.extend(ctx_tabs.iter());
diff --git a/crates/ui-egui/tests/host_chrome.rs b/crates/ui-egui/tests/host_chrome.rs
new file mode 100644
index 000000000..627e24025
--- /dev/null
+++ b/crates/ui-egui/tests/host_chrome.rs
@@ -0,0 +1,65 @@
+//! A host that embeds the sheet in its own window can turn off the app's title bar and File tab.
+
+use egui_kittest::kittest::Queryable as _;
+use gridcraft_engine::Session;
+use gridcraft_ui_egui::{Chrome, Services, SheetApp, backstage::Page};
+
+fn harness(chrome: Chrome) -> egui_kittest::Harness<'static, SheetApp> {
+    let mut session = Session::new();
+    session.new_workbook();
+    let mut app = SheetApp::new(session, Services::default());
+    app.chrome = chrome;
+    let mut h = egui_kittest::Harness::builder().with_size(egui::vec2(1200.0, 800.0)).build_ui_state(
+        |ui, app: &mut SheetApp| {
+            let ctx = ui.ctx().clone();
+            app.logic(&ctx);
+            app.ui(ui);
+        },
+        app,
+    );
+    h.run_steps(4);
+    h
+}
+
+#[test]
+fn the_title_bar_and_file_tab_are_drawn_by_default() {
+    let h = harness(Chrome::default());
+    assert!(h.query_by_label("AutoSave").is_some(), "the title bar is drawn");
+    assert!(h.query_by_label("File").is_some(), "the File tab is drawn");
+}
+
+#[test]
+fn a_host_can_leave_out_the_title_bar_and_the_file_tab() {
+    let full = harness(Chrome::default());
+    let h = harness(Chrome { title_bar: false, file_tab: false });
+    assert!(h.query_by_label("AutoSave").is_none(), "no title bar");
+    assert!(h.query_by_label("File").is_none(), "no File tab");
+    // The ribbon tabs are painted text, so measure the move with the first ribbon control.
+    let (with_bar, without) = (full.get_by_label("Paste").rect(), h.get_by_label("Paste").rect());
+    let moved = with_bar.min.y - without.min.y;
+    assert!((25.0..=40.0).contains(&moved), "the ribbon moves up by the title bar's height (28 on macOS, 38 elsewhere), moved {moved}");
+    assert_eq!(with_bar.min.x, without.min.x, "the ribbon's groups keep their place across");
+}
+
+#[test]
+fn without_the_file_tab_the_backstage_view_never_opens() {
+    let mut h = harness(Chrome { title_bar: true, file_tab: false });
+    h.state_mut().open_backstage(Page::Home);
+    h.run_steps(3);
+    assert!(h.state().backstage.is_none(), "opening Backstage directly is ignored");
+    h.state_mut().open_backstage(Page::Print);
+    h.run_steps(3);
+    assert!(h.state().backstage.is_none(), "so is every page, Print and Save As included");
+    assert!(h.query_by_label("AutoSave").is_some(), "the title bar can stay on its own");
+}
+
+#[test]
+fn turning_the_file_tab_off_closes_an_open_backstage() {
+    let mut h = harness(Chrome::default());
+    h.state_mut().open_backstage(Page::Home);
+    h.run_steps(3);
+    assert!(h.state().backstage.is_some(), "Backstage opens with the File tab on");
+    h.state_mut().chrome.file_tab = false;
+    h.run_steps(3);
+    assert!(h.state().backstage.is_none(), "and closes when the host turns the File tab off");
+}