diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index e2b8c0cdc..56fcd0443 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -79,6 +79,8 @@ mod tests_home;
 #[cfg(test)]
 mod tests_labels;
 #[cfg(test)]
+mod tests_libmenus;
+#[cfg(test)]
 mod tests_nativemenu;
 #[cfg(test)]
 mod tests_nativeoptions;
diff --git a/crates/ui-egui/src/tests_libmenus.rs b/crates/ui-egui/src/tests_libmenus.rs
new file mode 100644
index 000000000..b1495a7d6
--- /dev/null
+++ b/crates/ui-egui/src/tests_libmenus.rs
@@ -0,0 +1,156 @@
+//! Swatch Libraries (#536): Window → Swatch Libraries and the Swatches panel's libraries menu open
+//! the library panel, clicked through the whole window as a user would.
+
+use egui::{Event, PointerButton, Pos2, Rect, pos2, vec2};
+use serde_json::json;
+use vectorcraft_engine::Session;
+
+use crate::VectorcraftApp;
+
+/// A short window, so the Window menu scrolls to reach its library submenus.
+const SW: f32 = 1100.0;
+const SH: f32 = 640.0;
+
+/// One headless frame of the whole window with `events` → the text painted, with its rect.
+fn frame(app: &mut VectorcraftApp, ctx: &egui::Context, events: Vec<Event>) -> Vec<(String, Rect)> {
+    let raw = egui::RawInput {
+        screen_rect: Some(Rect::from_min_size(Pos2::ZERO, vec2(SW, SH))),
+        events,
+        time: Some(ctx.input(|i| i.time) + 0.1),
+        ..Default::default()
+    };
+    let mut out = ctx.run_ui(raw, |ui| {
+        app.logic(ui.ctx());
+        app.ui(ui);
+    });
+    out.textures_delta.clear();
+    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 at(texts: &[(String, Rect)], label: &str) -> Pos2 {
+    texts
+        .iter()
+        .rev()
+        .find(|(t, _)| t.trim_start_matches(['✓', ' ']) == label)
+        .map(|(_, r)| r.center())
+        .unwrap_or_else(|| panic!("no `{label}` in {texts:?}"))
+}
+
+fn hover(app: &mut VectorcraftApp, ctx: &egui::Context, p: Pos2) -> Vec<(String, Rect)> {
+    frame(app, ctx, vec![Event::PointerMoved(p)]);
+    frame(app, ctx, vec![]);
+    frame(app, ctx, vec![])
+}
+
+fn click(app: &mut VectorcraftApp, ctx: &egui::Context, p: Pos2) -> Vec<(String, Rect)> {
+    let b = |pressed| Event::PointerButton { pos: p, button: PointerButton::Primary, pressed, modifiers: Default::default() };
+    frame(app, ctx, vec![Event::PointerMoved(p)]);
+    frame(app, ctx, vec![b(true)]);
+    frame(app, ctx, vec![b(false)]);
+    frame(app, ctx, vec![]);
+    frame(app, ctx, vec![])
+}
+
+fn app() -> (VectorcraftApp, egui::Context) {
+    let mut app = VectorcraftApp::new(Session::new(), Default::default());
+    app.run("file.new", json!({"width": 400, "height": 300})).unwrap();
+    let ctx = egui::Context::default();
+    for _ in 0..3 {
+        frame(&mut app, &ctx, vec![]);
+    }
+    (app, ctx)
+}
+
+#[test]
+fn window_swatch_libraries_opens_the_library_panel() {
+    let (mut app, ctx) = app();
+    let texts = frame(&mut app, &ctx, vec![]);
+    let texts = click(&mut app, &ctx, at(&texts, "Window"));
+    // Scroll the menu down to its library submenus.
+    let menu = at(&texts, "Actions");
+    let wheel = Event::MouseWheel {
+        unit: egui::MouseWheelUnit::Point,
+        delta: vec2(0.0, -2000.0),
+        modifiers: Default::default(),
+        phase: egui::TouchPhase::Move,
+    };
+    frame(&mut app, &ctx, vec![Event::PointerMoved(menu), wheel]);
+    for _ in 0..10 {
+        frame(&mut app, &ctx, vec![]);
+    }
+    let texts = frame(&mut app, &ctx, vec![]);
+    let texts = hover(&mut app, &ctx, at(&texts, "Swatch Libraries"));
+    let p = at(&texts, "Brights");
+    let texts = hover(&mut app, &ctx, pos2(p.x, p.y));
+    let texts = click(&mut app, &ctx, at(&texts, "Brights"));
+    assert_eq!(app.ui.library_panel.as_ref().map(|o| o.id.as_str()), Some("brights"));
+    assert!(texts.iter().any(|(t, _)| t == "Add to Swatches" || t == "Brights"), "{texts:?}");
+}
+
+#[test]
+fn every_swatch_library_shows() {
+    let (mut app, ctx) = app();
+    for l in vectorcraft_color::libraries::SWATCH_LIBRARIES.iter().chain(vectorcraft_color::libraries::GRADIENT_LIBRARIES) {
+        app.run("window.swatchLibrary", json!({"library": l.id})).unwrap();
+        frame(&mut app, &ctx, vec![]);
+        let texts = frame(&mut app, &ctx, vec![]);
+        assert!(!app.ui.status.contains("Internal error"), "{}: {}", l.id, app.ui.status);
+        assert!(texts.iter().any(|(t, _)| t == l.name), "{} shows: {texts:?}", l.id);
+        assert!(ctx.memory(|m| m.area_rect(egui::Id::new(("library-panel", "swatches")))).is_some());
+    }
+}
+
+/// Where the button whose tooltip is `tip` is in `area`: hovered along its bottom rows.
+fn button_with_tip(app: &mut VectorcraftApp, ctx: &egui::Context, area: Rect, tip: &str) -> Pos2 {
+    for dy in [22.0, 18.0, 26.0, 30.0, 14.0] {
+        for i in 0..12 {
+            let p = pos2(area.left() + 12.0 + 6.0 * i as f32, area.bottom() - dy);
+            frame(app, ctx, vec![Event::PointerMoved(p)]);
+            for _ in 0..8 {
+                if frame(app, ctx, vec![]).iter().any(|(t, _)| t == tip) {
+                    return p;
+                }
+            }
+        }
+    }
+    panic!("no button `{tip}` in {area:?}");
+}
+
+#[test]
+fn the_swatches_panel_library_button_opens_a_library() {
+    let (mut app, ctx) = app();
+    app.run("window.panel", json!({"panel": "swatches"})).unwrap();
+    for _ in 0..3 {
+        frame(&mut app, &ctx, vec![]);
+    }
+    let area = ctx.memory(|m| m.area_rect(egui::Id::new("icon-panel"))).expect("the Swatches flyout");
+    let p = button_with_tip(&mut app, &ctx, area, "Swatch Libraries Menu");
+    let texts = click(&mut app, &ctx, p);
+    let texts = click(&mut app, &ctx, at(&texts, "Pastels"));
+    assert_eq!(app.ui.library_panel.as_ref().map(|o| o.id.as_str()), Some("pastels"), "{}", app.ui.status);
+    assert!(ctx.memory(|m| m.area_rect(egui::Id::new(("library-panel", "swatches")))).is_some());
+    assert!(texts.iter().any(|(t, _)| t == "Pastels"), "{texts:?}");
+}
+
+#[test]
+fn a_library_shows_without_a_document() {
+    let mut app = VectorcraftApp::new(Session::new(), Default::default());
+    let ctx = egui::Context::default();
+    for _ in 0..3 {
+        frame(&mut app, &ctx, vec![]);
+    }
+    app.run("window.swatchLibrary", json!({"library": "pastels"})).unwrap();
+    frame(&mut app, &ctx, vec![]);
+    let texts = frame(&mut app, &ctx, vec![]);
+    assert!(!app.ui.status.contains("Internal error"), "{}", app.ui.status);
+    assert!(texts.iter().any(|(t, _)| t == "Pastels"), "{texts:?}");
+}
diff --git a/crates/ui-egui/src/tests_nativemenu.rs b/crates/ui-egui/src/tests_nativemenu.rs
index 9ffe28142..0993e7b44 100644
--- a/crates/ui-egui/src/tests_nativemenu.rs
+++ b/crates/ui-egui/src/tests_nativemenu.rs
@@ -420,3 +420,24 @@ fn the_app_bar_hides_its_menus_with_the_mac_menu_bar() {
         assert_eq!(n(&native) + 1, n(&in_window), "{title}");
     }
 }
+
+/// Window › Swatch Libraries › a library, chosen in the Mac menu bar, opens the library panel (#536).
+#[test]
+fn a_swatch_library_chosen_in_the_mac_menu_opens_the_library_panel() {
+    let mut m = Mac::new(true);
+    let brights = m
+        .fake
+        .last()
+        .items()
+        .into_iter()
+        .find(|it| it.command == Some("window.swatchLibrary") && it.params["library"] == "brights")
+        .cloned()
+        .unwrap();
+    m.fake.report(native_menu::Event::Click(brights));
+    m.frame(vec![]);
+    let out = m.frame(vec![]);
+    assert_eq!(m.app.ui.library_panel.as_ref().map(|o| o.id.as_str()), Some("brights"), "{}", m.app.ui.status);
+    let texts: Vec<String> =
+        out.shapes.iter().filter_map(|s| if let egui::Shape::Text(t) = &s.shape { Some(t.galley.text().to_string()) } else { None }).collect();
+    assert!(texts.iter().any(|t| t == "Brights"), "{texts:?}");
+}