diff --git a/apps/vectorcraft/src/main.rs b/apps/vectorcraft/src/main.rs
index 8d35e65d..30e29492 100644
--- a/apps/vectorcraft/src/main.rs
+++ b/apps/vectorcraft/src/main.rs
@@ -128,6 +128,10 @@ fn app_icon() -> egui::IconData {
     eframe::icon_data::from_png_bytes(png).unwrap_or_default()
 }
 
+/// Windows and Linux: no OS title bar; the app bar is the title bar (`vectorcraft_ui_egui::titlebar`).
+/// macOS keeps its traffic lights over the integrated title strip.
+const CUSTOM_TITLEBAR: bool = !cfg!(target_os = "macos");
+
 fn main() -> eframe::Result {
     let mut control_port: Option<u16> = std::env::var("VECTORCRAFT_CONTROL_PORT").ok().and_then(|p| p.parse().ok());
     let mut files = Vec::new();
@@ -148,6 +152,7 @@ fn main() -> eframe::Result {
             .with_inner_size([1440.0, 900.0])
             .with_min_inner_size([800.0, 500.0])
             .with_drag_and_drop(true)
+            .with_decorations(!CUSTOM_TITLEBAR)
             .with_fullsize_content_view(true)
             .with_titlebar_shown(false)
             .with_title_shown(false)
@@ -165,6 +170,7 @@ fn main() -> eframe::Result {
             let swatches = prefs_path().and_then(|p| Some(p.parent()?.join("Swatches").to_string_lossy().to_string()));
             app.session.swatch_libraries.set_user_dir(swatches);
             app.integrated_titlebar = cfg!(target_os = "macos");
+            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);
diff --git a/crates/ui-egui/src/chrome.rs b/crates/ui-egui/src/chrome.rs
index c7a411fe..010ff5d3 100644
--- a/crates/ui-egui/src/chrome.rs
+++ b/crates/ui-egui/src/chrome.rs
@@ -8,12 +8,20 @@ use crate::panels::stroke as stroke_panel;
 use crate::state::{ZOOM_STOPS, zoom_label};
 use crate::theme::{self, Tokens};
 use crate::widgets::{self, paint_chip};
-use crate::{VectorcraftApp, icons, menus};
+use crate::{VectorcraftApp, icons, menus, titlebar};
 
+/// 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.
 pub fn app_bar(app: &mut VectorcraftApp, ui: &mut Ui) {
     let t = Tokens::get(ui.ctx());
+    let custom = app.custom_titlebar;
     let left = if app.integrated_titlebar { 78 } else { 8 };
-    egui::Panel::top("app_bar").exact_size(44.0).frame(egui::Frame::NONE.fill(t.app_bar).inner_margin(egui::Margin { left, right: 14, top: 0, bottom: 0 }).stroke(Stroke::new(1.0, t.border))).show(ui, |ui| {
+    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(44.0).frame(frame.stroke(Stroke::new(1.0, t.border))).show(ui, |ui| {
+        if custom {
+            titlebar::drag_area(ui, ui.max_rect());
+        }
         ui.horizontal_centered(|ui| {
             // Brand mark (our own artwork, matches the app icon).
             let (r, _) = ui.allocate_exact_size(vec2(22.0, 22.0), Sense::hover());
@@ -23,19 +31,31 @@ pub fn app_bar(app: &mut VectorcraftApp, ui: &mut Ui) {
                 app.ui.dialog = Some(crate::state::Dialog::new("newDocument", json!({"preset": "Letter", "width": "612 pt", "height": "792 pt", "units": "Points", "artboards": 1, "colorMode": "RGB", "name": "Untitled-1"})));
             }
             ui.add_space(2.0);
-            if app.native_menu {
+            let menus_end = if app.native_menu {
                 let full = ui.max_rect();
                 ui.painter().text(full.center(), egui::Align2::CENTER_CENTER, "VectorCraft", egui::FontId::proportional(13.5), t.text);
+                ui.cursor().min.x
             } else {
-                menus::menu_bar(app, ui);
-            }
+                menus::menu_bar(app, ui)
+            };
+            // The right-side group fills the space after the menus from the right; when it runs
+            // short, Discord goes first (it is also under Help), then the search box becomes an
+            // icon, then the workspace switcher narrows.
             let full = ui.max_rect();
-            let right = egui::Rect::from_min_max(egui::pos2(full.right() - 440.0, full.top()), full.right_bottom());
+            let right_edge = if custom { full.right() - titlebar::WIDTH - 10.0 } else { full.right() };
+            let right = egui::Rect::from_min_max(egui::pos2(menus_end + 8.0, full.top()), egui::pos2(right_edge, full.bottom()));
+            let room = right.width();
+            let ws = ui.painter().layout_no_wrap(app.ui.workspace.clone(), egui::FontId::proportional(12.0), t.text);
+            let ws_w = (ws.size().x + 36.0).clamp(112.0, 190.0);
+            let gap = ui.spacing().item_spacing.x;
+            let with_search = ws_w + 8.0 + gap + 200.0;
+            let search_full = room >= with_search;
+            let discord = room >= with_search + 10.0 + gap + crate::community::discord_width(ui, false);
+            let ws_w = if search_full { ws_w } else { ws_w.min(room - 8.0 - gap - 24.0).max(64.0) };
             let mut rui = ui.new_child(egui::UiBuilder::new().max_rect(right).layout(egui::Layout::right_to_left(egui::Align::Center)));
             let ui = &mut rui;
             // Workspace switcher: shows the current workspace, opens Window → Workspace.
-            let ws = ui.painter().layout_no_wrap(app.ui.workspace.clone(), egui::FontId::proportional(12.0), t.text);
-            let (wr, wresp) = ui.allocate_exact_size(vec2((ws.size().x + 36.0).clamp(112.0, 190.0), 24.0), Sense::click());
+            let (wr, wresp) = ui.allocate_exact_size(vec2(ws_w, 24.0), Sense::click());
             ui.painter().rect_filled(wr, CornerRadius::same(4), if wresp.hovered() { t.hover } else { t.panel });
             ui.painter().with_clip_rect(wr.shrink2(vec2(4.0, 0.0))).galley(wr.left_center() + vec2(10.0, -ws.size().y / 2.0), ws, t.text);
             icons::paint(ui, "chevron-down", egui::Rect::from_center_size(wr.right_center() - vec2(12.0, 0.0), vec2(12.0, 12.0)), t.text_dim);
@@ -43,19 +63,29 @@ pub fn app_bar(app: &mut VectorcraftApp, ui: &mut Ui) {
             egui::Popup::menu(&wresp).show(|ui| crate::workspaces::popup(app, ui));
             ui.add_space(8.0);
             // Search box → command palette.
-            let (r, resp) = ui.allocate_exact_size(vec2(200.0, 24.0), Sense::click());
-            ui.painter().rect_filled(r, CornerRadius::same(12), t.input);
-            ui.painter().rect_stroke(r, CornerRadius::same(12), Stroke::new(1.0, if resp.hovered() { t.input_border } else { t.divider }), StrokeKind::Inside);
-            icons::paint(ui, "search", egui::Rect::from_center_size(r.left_center() + vec2(14.0, 0.0), vec2(13.0, 13.0)), t.text_dim);
-            ui.painter().text(r.left_center() + vec2(26.0, 0.0), egui::Align2::LEFT_CENTER, "Search commands and tools", egui::FontId::proportional(11.5), t.text_dim);
-            if resp.clicked() {
+            let open_palette = if search_full {
+                let (r, resp) = ui.allocate_exact_size(vec2(200.0, 24.0), Sense::click());
+                ui.painter().rect_filled(r, CornerRadius::same(12), t.input);
+                ui.painter().rect_stroke(r, CornerRadius::same(12), Stroke::new(1.0, if resp.hovered() { t.input_border } else { t.divider }), StrokeKind::Inside);
+                icons::paint(ui, "search", egui::Rect::from_center_size(r.left_center() + vec2(14.0, 0.0), vec2(13.0, 13.0)), t.text_dim);
+                ui.painter().text(r.left_center() + vec2(26.0, 0.0), egui::Align2::LEFT_CENTER, "Search commands and tools", egui::FontId::proportional(11.5), t.text_dim);
+                resp.clicked()
+            } else {
+                widgets::icon_button(ui, "search", "Search commands and tools", false, 24.0).clicked()
+            };
+            if open_palette {
                 app.ui.palette_open = true;
                 app.ui.palette_query.clear();
             }
-            ui.add_space(10.0);
-            crate::community::discord_button(app, ui, false);
+            if discord {
+                ui.add_space(10.0);
+                crate::community::discord_button(app, ui, false);
+            }
         });
     });
+    if custom {
+        titlebar::caption_buttons(app, ui, bar.response.rect);
+    }
 }
 
 /// A Control bar chip that opens something: `draw` paints the chip, a chevron follows it.
diff --git a/crates/ui-egui/src/community.rs b/crates/ui-egui/src/community.rs
index 0beb7a1f..16ac8ea5 100644
--- a/crates/ui-egui/src/community.rs
+++ b/crates/ui-egui/src/community.rs
@@ -10,12 +10,23 @@ use crate::{VectorcraftApp, icons};
 /// Discord's brand colour (a colour, not a logo).
 const DISCORD: Color32 = Color32::from_rgb(0x58, 0x65, 0xF2);
 
-/// A Discord pill button: compact for the header, large for About / Home.
-pub fn discord_button(app: &mut VectorcraftApp, ui: &mut Ui, large: bool) -> egui::Response {
+/// The Discord button's label, height and width.
+fn discord_layout(ui: &Ui, large: bool) -> (std::sync::Arc<egui::Galley>, f32, f32) {
     let (h, font, label) = if large { (36.0, theme::semibold(14.0), "Join our Discord") } else { (24.0, theme::semibold(12.0), "Discord") };
     let galley = ui.painter().layout_no_wrap(label.to_string(), font, Color32::WHITE);
+    let w = galley.size().x + h * 0.55 + h * 0.9;
+    (galley, h, w)
+}
+
+/// The Discord button's width (the app bar drops it when space runs out).
+pub fn discord_width(ui: &Ui, large: bool) -> f32 {
+    discord_layout(ui, large).2
+}
+
+/// A Discord pill button: compact for the header, large for About / Home.
+pub fn discord_button(app: &mut VectorcraftApp, ui: &mut Ui, large: bool) -> egui::Response {
+    let (galley, h, w) = discord_layout(ui, large);
     let icon = h * 0.55;
-    let w = galley.size().x + icon + h * 0.9;
     let (r, resp) = ui.allocate_exact_size(vec2(w, h), Sense::click());
     let fill = if resp.hovered() { DISCORD.gamma_multiply(0.85) } else { DISCORD };
     ui.painter().rect_filled(r, CornerRadius::same((h / 2.0) as u8), fill);
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 673c65bd..dfbcd2e8 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -26,6 +26,7 @@ pub mod shortcut_editor;
 pub mod shortcuts;
 pub mod state;
 pub mod theme;
+pub mod titlebar;
 pub mod toolbar;
 pub mod unsaved;
 pub mod widgets;
@@ -146,6 +147,9 @@ pub struct VectorcraftApp {
     pub(crate) clipboard_in: Option<String>,
     /// A URL to open through egui next frame (when the host has no `open_url` service).
     pending_url: Option<String>,
+    /// 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,
 }
 
 impl VectorcraftApp {
@@ -184,6 +188,7 @@ impl VectorcraftApp {
             last_time: 0.0,
             canvas_rect: None,
             hover_doc: None,
+            custom_titlebar: false,
         }
     }
 
@@ -520,6 +525,9 @@ impl VectorcraftApp {
         panels::library_panel::show_window(self, &ctx);
         dialogs::show(self, &ctx);
         palette::show(self, &ctx);
+        if self.custom_titlebar {
+            titlebar::resize_zones(ui);
+        }
         self.perf.frame_ms = now_ms() - t0;
         let _ = json!(null);
     }
diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index 6802cfe3..cb01b4f6 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -1396,23 +1396,28 @@ pub fn menu_tree() -> Vec<(&'static str, Vec<Item>)> {
 }
 
 /// Render the menu bar.
-pub fn menu_bar(app: &mut VectorcraftApp, ui: &mut egui::Ui) {
+/// The in-window menu bar. Returns where its titles end (x): the bar itself takes the full width.
+pub fn menu_bar(app: &mut VectorcraftApp, ui: &mut egui::Ui) -> f32 {
     let t = Tokens::get(ui.ctx());
     let mut clicked: Option<(String, Value)> = None;
     let tree = menu_tree();
-    egui::MenuBar::new().ui(ui, |ui| {
-        for (i, (title, items)) in tree.iter().enumerate() {
-            let text = if i == 0 {
-                egui::RichText::new(*title).font(theme::semibold(13.0)).color(t.text)
-            } else {
-                egui::RichText::new(*title).size(13.0).color(t.text)
-            };
-            ui.menu_button(text, |ui| menu_body(app, ui, items, &mut clicked));
-        }
-    });
+    let end = egui::MenuBar::new()
+        .ui(ui, |ui| {
+            for (i, (title, items)) in tree.iter().enumerate() {
+                let text = if i == 0 {
+                    egui::RichText::new(*title).font(theme::semibold(13.0)).color(t.text)
+                } else {
+                    egui::RichText::new(*title).size(13.0).color(t.text)
+                };
+                ui.menu_button(text, |ui| menu_body(app, ui, items, &mut clicked));
+            }
+            ui.cursor().min.x
+        })
+        .inner;
     if let Some((id, p)) = clicked {
         invoke(app, &id, p);
     }
+    end
 }
 
 /// A top-level menu's popup: as wide as its widest item (label plus shortcut), at least 230 pt.
diff --git a/crates/ui-egui/src/theme.rs b/crates/ui-egui/src/theme.rs
index bfef706c..14d7b398 100644
--- a/crates/ui-egui/src/theme.rs
+++ b/crates/ui-egui/src/theme.rs
@@ -78,6 +78,9 @@ pub struct Tokens {
     pub flyout_active: Color32,
     /// Hint-bar / tab-bar heights etc. scale with this base font size.
     pub font_size: f32,
+    /// Window Close button (custom title bar) when hovered, and its glyph there.
+    pub caption_close: Color32,
+    pub caption_close_text: Color32,
 }
 
 impl Tokens {
@@ -116,6 +119,8 @@ impl Tokens {
             anchor_selected: hex(0x3d82ff),
             flyout_active: hex(0x54b2f7),
             font_size: 13.0,
+            caption_close: hex(0xc42b1c),
+            caption_close_text: Color32::WHITE,
         };
         match b {
             Brightness::Dark => base,
diff --git a/crates/ui-egui/src/titlebar.rs b/crates/ui-egui/src/titlebar.rs
new file mode 100644
index 00000000..9209b30a
--- /dev/null
+++ b/crates/ui-egui/src/titlebar.rs
@@ -0,0 +1,364 @@
+//! The window's own title bar on Windows and Linux, where the window has no OS decorations
+//! ([`VectorcraftApp::custom_titlebar`]): empty space in the app bar drags the window and a
+//! double-click there maximizes it, caption buttons at the far right minimize, maximize/restore and
+//! close, and thin invisible zones along the window's edges resize it.
+
+use egui::{CursorIcon, Id, LayerId, Order, PointerButton, Rect, ResizeDirection, Sense, Stroke, Ui, ViewportCommand, pos2, vec2};
+use serde_json::json;
+
+use crate::VectorcraftApp;
+use crate::theme::Tokens;
+
+/// One caption button: as wide as the native Windows ones.
+pub const BUTTON_WIDTH: f32 = 46.0;
+/// The three caption buttons together.
+pub const WIDTH: f32 = 3.0 * BUTTON_WIDTH;
+/// Resize zone thickness along an edge, and the side of a corner zone.
+const EDGE: f32 = 5.0;
+const CORNER: f32 = 12.0;
+
+#[derive(Clone, Copy, PartialEq, Debug)]
+enum Caption {
+    Minimize,
+    Maximize,
+    Close,
+}
+
+/// Left to right.
+const CAPTIONS: [Caption; 3] = [Caption::Minimize, Caption::Maximize, Caption::Close];
+
+/// Caption button ids (stable, so tests and agents can find them).
+fn caption_id(c: Caption) -> Id {
+    Id::new(("titlebar-caption", c as u8))
+}
+
+fn maximized(ctx: &egui::Context) -> bool {
+    ctx.input(|i| i.viewport().maximized.unwrap_or(false))
+}
+
+fn toggle_maximize(ctx: &egui::Context) {
+    ctx.send_viewport_cmd(ViewportCommand::Maximized(!maximized(ctx)));
+}
+
+/// The bar's background: a press-and-drag on empty space moves the window, a double-click toggles
+/// maximize. Call it before laying out the bar so its widgets, registered later, take the clicks.
+pub fn drag_area(ui: &Ui, rect: Rect) {
+    let ctx = ui.ctx();
+    let resp = ui.interact(rect, Id::new("titlebar-drag"), Sense::click_and_drag());
+    // egui hands a drag that starts on a click-only widget (a menu title) to the drag-sensing
+    // background below it, so remember whether the press itself landed on bare background.
+    if ctx.input(|i| i.pointer.any_pressed()) {
+        let bare = ctx.viewport(|v| v.hits.click.is_some_and(|w| w.id == resp.id));
+        ctx.data_mut(|d| d.insert_temp(resp.id, bare));
+    }
+    if resp.double_clicked() {
+        toggle_maximize(ctx);
+    } else if resp.drag_started_by(PointerButton::Primary) && ctx.data(|d| d.get_temp(resp.id).unwrap_or(false)) {
+        ctx.send_viewport_cmd(ViewportCommand::StartDrag);
+    }
+}
+
+/// Minimize, Maximize/Restore and Close at the right end of `bar` (the app bar's outer rect), full
+/// bar height down to its bottom border, flush with the window's edge so a maximized window's
+/// corner hits Close. Close runs `app.quit`, which asks about unsaved documents first.
+pub fn caption_buttons(app: &mut VectorcraftApp, ui: &mut Ui, bar: Rect) {
+    let t = Tokens::get(ui.ctx());
+    let max = maximized(ui.ctx());
+    let mut clicked = None;
+    for (i, c) in CAPTIONS.into_iter().enumerate() {
+        let r = Rect::from_min_size(pos2(bar.right() - WIDTH + i as f32 * BUTTON_WIDTH, bar.top()), vec2(BUTTON_WIDTH, bar.height() - 1.0));
+        let resp = ui.interact(r, caption_id(c), Sense::click());
+        let close = c == Caption::Close;
+        let fill = match (resp.is_pointer_button_down_on(), resp.hovered()) {
+            (true, _) if close => t.caption_close.gamma_multiply(0.8),
+            (_, true) if close => t.caption_close,
+            (true, _) => t.tool_active,
+            (_, true) => t.hover,
+            _ => egui::Color32::TRANSPARENT,
+        };
+        ui.painter().rect_filled(r, 0.0, fill);
+        let ink = if close && resp.hovered() { t.caption_close_text } else { t.icon };
+        paint_glyph(ui, c, max, r.center(), Stroke::new(1.0, ink));
+        let tip = match c {
+            Caption::Minimize => "Minimize",
+            Caption::Maximize if max => "Restore",
+            Caption::Maximize => "Maximize",
+            Caption::Close => "Close",
+        };
+        if resp.on_hover_text(tip).clicked() {
+            clicked = Some(c);
+        }
+    }
+    match clicked {
+        Some(Caption::Minimize) => ui.ctx().send_viewport_cmd(ViewportCommand::Minimized(true)),
+        Some(Caption::Maximize) => toggle_maximize(ui.ctx()),
+        Some(Caption::Close) => {
+            app.run("app.quit", json!({})).ok();
+        }
+        None => {}
+    }
+}
+
+/// The 10 pt line glyphs of the caption buttons.
+fn paint_glyph(ui: &Ui, c: Caption, maximized: bool, at: egui::Pos2, s: Stroke) {
+    let p = ui.painter();
+    let g = Rect::from_center_size(at, vec2(10.0, 10.0));
+    match c {
+        Caption::Minimize => {
+            p.line_segment([g.left_center(), g.right_center()], s);
+        }
+        // Restore: a front square with the corner of the one behind it.
+        Caption::Maximize if maximized => {
+            let front = Rect::from_min_max(g.min + vec2(0.0, 2.0), g.max - vec2(2.0, 0.0));
+            p.rect_stroke(front, 0.0, s, egui::StrokeKind::Middle);
+            p.line(vec![g.min + vec2(2.0, 2.0), g.min + vec2(2.0, 0.0), g.right_top(), g.max - vec2(0.0, 2.0), g.max - vec2(2.0, 2.0)], s);
+        }
+        Caption::Maximize => {
+            p.rect_stroke(g, 0.0, s, egui::StrokeKind::Middle);
+        }
+        Caption::Close => {
+            p.line_segment([g.left_top(), g.right_bottom()], s);
+            p.line_segment([g.right_top(), g.left_bottom()], s);
+        }
+    }
+}
+
+/// The edge and corner zones of a window with content rect `w`: (zone, direction, cursor). Corners
+/// come last so they win where they overlap the edges.
+fn zones(w: Rect) -> [(Rect, ResizeDirection, CursorIcon); 8] {
+    use ResizeDirection::*;
+    let (e, c) = (EDGE, CORNER);
+    [
+        (Rect::from_min_max(w.left_top(), pos2(w.right(), w.top() + e)), North, CursorIcon::ResizeVertical),
+        (Rect::from_min_max(pos2(w.left(), w.bottom() - e), w.right_bottom()), South, CursorIcon::ResizeVertical),
+        (Rect::from_min_max(w.left_top(), pos2(w.left() + e, w.bottom())), West, CursorIcon::ResizeHorizontal),
+        (Rect::from_min_max(pos2(w.right() - e, w.top()), w.right_bottom()), East, CursorIcon::ResizeHorizontal),
+        (Rect::from_min_size(w.left_top(), vec2(c, c)), NorthWest, CursorIcon::ResizeNwSe),
+        (Rect::from_min_size(w.right_top() - vec2(c, 0.0), vec2(c, c)), NorthEast, CursorIcon::ResizeNeSw),
+        (Rect::from_min_size(w.left_bottom() - vec2(0.0, c), vec2(c, c)), SouthWest, CursorIcon::ResizeNeSw),
+        (Rect::from_min_size(w.right_bottom() - vec2(c, c), vec2(c, c)), SouthEast, CursorIcon::ResizeNwSe),
+    ]
+}
+
+/// Invisible resize zones along the window's edges, above everything else; a press in one starts
+/// an OS resize in that direction. None while the window is maximized or fullscreen.
+pub fn resize_zones(ui: &mut Ui) {
+    let ctx = ui.ctx().clone();
+    if maximized(&ctx) || ctx.input(|i| i.viewport().fullscreen.unwrap_or(false)) {
+        return;
+    }
+    let w = ctx.content_rect();
+    let layer = LayerId::new(Order::Foreground, Id::new("titlebar-resize"));
+    let zui = ui.new_child(egui::UiBuilder::new().layer_id(layer).max_rect(w));
+    for (i, (r, dir, cursor)) in zones(w).into_iter().enumerate() {
+        let resp = zui.interact(r, Id::new(("titlebar-resize", i)), Sense::drag()).on_hover_cursor(cursor);
+        if resp.drag_started_by(PointerButton::Primary) {
+            ctx.send_viewport_cmd(ViewportCommand::BeginResize(dir));
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use egui::{Event, Pos2, RawInput, ViewportId};
+    use vectorcraft_engine::Session;
+
+    /// A headless window `width` pt wide showing the app bar (as the title bar) and the resize zones.
+    struct Win {
+        ctx: egui::Context,
+        app: VectorcraftApp,
+        width: f32,
+        time: f64,
+        maximized: bool,
+    }
+
+    impl Win {
+        fn new(width: f32) -> Self {
+            let ctx = egui::Context::default();
+            crate::theme::install_fonts(&ctx);
+            crate::theme::apply(&ctx, Default::default());
+            let mut app = VectorcraftApp::new(Session::new(), Default::default());
+            app.custom_titlebar = true;
+            Self { ctx, app, width, time: 0.0, maximized: false }
+        }
+
+        fn frame(&mut self, events: Vec<Event>) -> egui::FullOutput {
+            self.time += 0.05;
+            let mut input = RawInput {
+                screen_rect: Some(Rect::from_min_size(Pos2::ZERO, vec2(self.width, 600.0))),
+                time: Some(self.time),
+                events,
+                ..Default::default()
+            };
+            if let Some(v) = input.viewports.get_mut(&ViewportId::ROOT) {
+                v.maximized = Some(self.maximized);
+            }
+            let app = &mut self.app;
+            let mut out = self.ctx.run_ui(input, |ui| {
+                crate::chrome::app_bar(app, ui);
+                resize_zones(ui);
+            });
+            out.textures_delta.clear();
+            out
+        }
+    }
+
+    fn texts(out: &egui::FullOutput) -> Vec<(String, Rect)> {
+        fn walk(s: &egui::Shape, v: &mut Vec<(String, Rect)>) {
+            match s {
+                egui::Shape::Text(t) => v.push((t.galley.text().to_string(), Rect::from_min_size(t.pos, t.galley.size()))),
+                egui::Shape::Vec(s) => s.iter().for_each(|s| walk(s, v)),
+                _ => {}
+            }
+        }
+        let mut v = vec![];
+        out.shapes.iter().for_each(|c| walk(&c.shape, &mut v));
+        v
+    }
+
+    fn button(p: Pos2, pressed: bool) -> Event {
+        Event::PointerButton { pos: p, button: egui::PointerButton::Primary, pressed, modifiers: Default::default() }
+    }
+
+    impl Win {
+        /// Frames for a pointer gesture: move to `path[0]`, press, move along `path`, release. The
+        /// viewport commands the frames sent.
+        fn gesture(&mut self, path: &[Pos2]) -> Vec<ViewportCommand> {
+            let mut events = vec![vec![Event::PointerMoved(path[0])], vec![button(path[0], true)]];
+            events.extend(path[1..].iter().map(|p| vec![Event::PointerMoved(*p)]));
+            events.push(vec![button(*path.last().unwrap_or(&path[0]), false)]);
+            events.into_iter().flat_map(|e| self.frame(e).viewport_output.remove(&ViewportId::ROOT).map(|v| v.commands).unwrap_or_default()).collect()
+        }
+
+        fn click(&mut self, p: Pos2) -> Vec<ViewportCommand> {
+            self.gesture(&[p])
+        }
+
+        fn caption(&self, c: Caption) -> Rect {
+            self.ctx.read_response(caption_id(c)).map(|r| r.rect).unwrap_or(Rect::NOTHING)
+        }
+
+        /// The bar's clickable widgets other than its background and the caption buttons.
+        fn bar_widgets(&self) -> Vec<Rect> {
+            let skip: Vec<Id> = std::iter::once(Id::new("titlebar-drag")).chain(CAPTIONS.map(caption_id)).collect();
+            self.ctx.viewport(|v| {
+                v.prev_pass
+                    .widgets
+                    .layers()
+                    .filter(|(l, _)| l.order != Order::Foreground)
+                    .flat_map(|(_, ws)| ws.iter())
+                    .filter(|w| w.sense.senses_click() && w.rect.top() < 44.0 && !skip.contains(&w.id))
+                    .map(|w| w.rect)
+                    .collect()
+            })
+        }
+    }
+
+    #[test]
+    fn caption_buttons_take_the_right_end_and_nothing_overlaps_down_to_800_pt() {
+        for width in [800.0, 1100.0, 1440.0] {
+            let mut w = Win::new(width);
+            w.frame(vec![]);
+            let out = w.frame(vec![]);
+            let [min, max, close] = CAPTIONS.map(|c| w.caption(c));
+            assert_eq!((close.right(), close.top()), (width, 0.0), "Close sits in the window's corner at {width}");
+            assert!(close.height() >= 42.0 && [min, max, close].iter().all(|r| r.width() == BUTTON_WIDTH));
+            assert_eq!((min.right(), max.right()), (max.left(), close.left()));
+            let widgets = w.bar_widgets();
+            assert!(widgets.len() >= 12, "home, nine menus, workspace switcher, search: {widgets:?}");
+            for (i, a) in widgets.iter().enumerate() {
+                assert!(a.right() <= min.left() - 8.0, "{a:?} runs into the caption buttons at {width}");
+                for b in &widgets[i + 1..] {
+                    assert!(!a.shrink(0.5).intersects(b.shrink(0.5)), "{a:?} overlaps {b:?} at {width}");
+                }
+            }
+            // Wide windows show the whole group; narrow ones drop Discord and shorten the search.
+            let texts: Vec<String> = texts(&out).into_iter().map(|(t, _)| t).collect();
+            let has = |s: &str| texts.iter().any(|t| t == s);
+            assert_eq!((has("Discord"), has("Search commands and tools")), (width > 1000.0, width > 1000.0), "{width}: {texts:?}");
+        }
+    }
+
+    #[test]
+    fn close_runs_the_quit_flow_instead_of_closing_the_window() {
+        let mut w = Win::new(1000.0);
+        w.app.run("file.new", serde_json::json!({"width": 100, "height": 100})).unwrap();
+        w.app.run("shape.rectangle", serde_json::json!({"x": 0, "y": 0, "width": 10, "height": 10})).unwrap();
+        w.frame(vec![]);
+        let close = w.caption(Caption::Close).center();
+        let cmds = w.click(close);
+        assert!(!cmds.iter().any(|c| matches!(c, ViewportCommand::Close)), "{cmds:?}");
+        let dialog = w.app.ui.dialog.as_ref().map(|d| d.kind.clone());
+        assert_eq!(dialog.as_deref(), Some(crate::unsaved::KIND), "a modified document asks first");
+        assert_ne!(w.app.ui.status, "quit");
+        // Nothing to save: the host is told to quit.
+        w.app.ui.dialog = None;
+        w.app.session.doc_mut().unwrap().mark_saved();
+        w.click(close);
+        assert_eq!(w.app.ui.status, "quit");
+    }
+
+    #[test]
+    fn minimize_and_maximize_follow_the_window_state() {
+        let mut w = Win::new(1000.0);
+        w.frame(vec![]);
+        let (min, max) = (w.caption(Caption::Minimize).center(), w.caption(Caption::Maximize).center());
+        assert!(w.click(min).contains(&ViewportCommand::Minimized(true)));
+        assert!(w.click(max).contains(&ViewportCommand::Maximized(true)));
+        w.maximized = true;
+        assert!(w.click(max).contains(&ViewportCommand::Maximized(false)), "Restore");
+    }
+
+    #[test]
+    fn empty_bar_space_drags_and_double_click_maximizes() {
+        let mut w = Win::new(1440.0);
+        w.frame(vec![]);
+        let empty = pos2(700.0, 22.0);
+        assert!(w.bar_widgets().iter().all(|r| !r.contains(empty)), "the probe point must be empty bar space");
+        let cmds = w.gesture(&[empty, empty + vec2(12.0, 4.0), empty + vec2(30.0, 8.0)]);
+        assert_eq!(cmds.iter().filter(|c| matches!(c, ViewportCommand::StartDrag)).count(), 1, "{cmds:?}");
+        // Double-click toggles maximize.
+        let mut cmds = w.click(empty);
+        cmds.extend(w.click(empty));
+        assert!(cmds.contains(&ViewportCommand::Maximized(true)), "{cmds:?}");
+        w.maximized = true;
+        w.time += 1.0;
+        let mut cmds = w.click(empty);
+        cmds.extend(w.click(empty));
+        assert!(cmds.contains(&ViewportCommand::Maximized(false)), "{cmds:?}");
+        // Widgets keep their clicks: dragging from a menu title doesn't move the window.
+        let file = texts(&w.frame(vec![])).into_iter().find(|(t, _)| t == "File").map(|(_, r)| r.center());
+        let file = file.expect("the File menu title");
+        let cmds = w.gesture(&[file, file + vec2(12.0, 4.0), file + vec2(30.0, 8.0)]);
+        assert!(!cmds.iter().any(|c| matches!(c, ViewportCommand::StartDrag)), "{cmds:?}");
+    }
+
+    #[test]
+    fn edge_zones_resize_unless_maximized() {
+        use ResizeDirection::*;
+        let mut w = Win::new(1000.0);
+        w.frame(vec![]);
+        for (p, dir) in [
+            (pos2(1.0, 300.0), West),
+            (pos2(998.0, 300.0), East),
+            (pos2(500.0, 1.0), North),
+            (pos2(500.0, 598.0), South),
+            (pos2(2.0, 2.0), NorthWest),
+            (pos2(997.0, 3.0), NorthEast),
+            (pos2(3.0, 597.0), SouthWest),
+            (pos2(998.0, 598.0), SouthEast),
+        ] {
+            let cmds = w.gesture(&[p, p + vec2(6.0, 6.0)]);
+            assert_eq!(cmds, vec![ViewportCommand::BeginResize(dir)], "at {p:?}");
+        }
+        let out = w.frame(vec![Event::PointerMoved(pos2(1.0, 300.0))]);
+        assert_eq!(out.platform_output.cursor_icon, CursorIcon::ResizeHorizontal);
+        // Maximized: no zones, and the window's top-right corner is Close.
+        w.maximized = true;
+        let cmds = w.gesture(&[pos2(1.0, 300.0), pos2(8.0, 300.0)]);
+        assert!(!cmds.iter().any(|c| matches!(c, ViewportCommand::BeginResize(_))), "{cmds:?}");
+        assert!(w.click(pos2(999.5, 0.5)).is_empty());
+        assert_eq!(w.app.ui.status, "quit");
+    }
+}
diff --git a/docs/control-protocol.md b/docs/control-protocol.md
index 5c616691..a0278e51 100644
--- a/docs/control-protocol.md
+++ b/docs/control-protocol.md
@@ -94,3 +94,9 @@ folder, `selectedOnly` with `names`); `ui.dialog.confirm` runs `swatch.library.s
 Tile Edge Color: Object → Pattern → Tile Edge Color… (`ui.tileEdgeColor`) opens the `tileEdgeColor` dialog (field
 `color`: `#rrggbb` or a preset name such as "Light Blue"); `ui.dialog.confirm` sets the preference
 `patternTileEdgeColor` (`prefs.set`), the colour pattern editing mode draws the tile edge and the swatch bounds in.
+
+Window title bar: on Windows and Linux the window has no OS decorations and the app bar is the title bar. Its
+caption buttons (Minimize, Maximize/Restore, Close) sit at the bar's right end, 46 pt each; they are window chrome,
+not commands, so drive them with `ui.click` if needed. Close runs `app.quit` (the same `saveChanges` questions for
+modified documents), and empty bar space and the 5 pt window edges move and resize the window. macOS and the web
+build are unchanged.