diff --git a/TASKS.md b/TASKS.md
index 675250c..3f59e34 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -425,3 +425,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T39b | 1 | FAIL | a long theme name pushed its badge past 280px; four-digit colors refused the theme |
 | T39b | 2 | PASS | |
 | T39c | 1 | FAIL | Windows caption buttons took their row's height; a long Windows title pushed the buttons past the bar |
+| T39c | 2 | FAIL | an untitled Windows bar lost its spacer; a centered title ran under the Linux buttons; caption buttons ignored the window's rem |
diff --git a/src/shell/chrome.rs b/src/shell/chrome.rs
index 624e6ee..392f570 100644
--- a/src/shell/chrome.rs
+++ b/src/shell/chrome.rs
@@ -172,6 +172,7 @@ fn caption_buttons(
         (Control::Maximize, maximize, WindowControlArea::Max),
         (Control::Close, IconName::X, WindowControlArea::Close),
     ];
+    let height = theme.caption_button_height(window.rem_size());
     div()
         .id(id)
         .flex()
@@ -190,7 +191,7 @@ fn caption_buttons(
                 .items_center()
                 .justify_center()
                 .w(theme.caption_button_width())
-                .h(theme.caption_button_height())
+                .h(height)
                 .debug_selector(move || format!("caption-{control:?}"))
                 .window_control_area(area)
                 .hover(|style| style.bg(hover))
@@ -363,6 +364,7 @@ impl RenderOnce for TitleBar {
                 .text_size(theme.text_size(TextSize::Sm))
                 .font_weight(FontWeight::MEDIUM)
                 .text_color(theme.colors.fg_muted)
+                .debug_selector(|| "titlebar-title".into())
                 .child(Ellipsis::new(title))
         });
         let centered = style != Platform::Windows;
@@ -379,33 +381,44 @@ impl RenderOnce for TitleBar {
             .bg(theme.colors.bg)
             .border_b_1()
             .border_color(theme.colors.border);
-        let bar = match (system, style) {
-            (true, _) if fullscreen => bar.pl_3().pr_2(),
-            (true, _) => bar.pl(inset).pr_2(),
-            (false, Platform::Mac) => bar.pl_3().pr_2().children(leading),
-            (false, Platform::Windows) => bar.pl_3(),
-            (false, Platform::Linux) => bar.pl_3().pr_2(),
-        };
-        let bar = bar.children(self.leading);
-        let bar = match (centered, title) {
-            (false, Some(title)) => bar.child(title.flex_1()),
-            (_, title) => bar.when_some(title, |bar, title| {
-                bar.child(
+        let bar = bar.when(!centered, |bar| bar.pl_3());
+        let start = div().flex().child(
+            div()
+                .flex()
+                .items_center()
+                .gap_2()
+                .when(centered, |start| match system && !fullscreen {
+                    true => start.pl(inset),
+                    false => start.pl_3(),
+                })
+                .children(leading)
+                .children(self.leading),
+        );
+        let end = div().flex().justify_end().child(
+            div()
+                .flex()
+                .items_center()
+                .gap_2()
+                .when(centered, |end| end.pr_2())
+                .children(self.actions)
+                .children(trailing.map(|controls| {
                     div()
-                        .absolute()
-                        .top_0()
-                        .bottom_0()
-                        .left(inset)
-                        .right(inset)
-                        .flex()
-                        .items_center()
-                        .justify_center()
-                        .child(title),
-                )
-            }),
+                        .flex_none()
+                        .debug_selector(|| "titlebar-controls".into())
+                        .child(controls)
+                })),
+        );
+        let middle = match title {
+            Some(title) if centered => title,
+            Some(title) => title.flex_1(),
+            None => div().flex_1(),
         };
-        bar.when(centered, |bar| bar.child(div().flex_1()))
-            .children(self.actions)
-            .children(trailing.map(|controls| div().flex_none().child(controls)))
+        match centered {
+            true => bar.child(start.flex_1()).child(middle).child(end.flex_1()),
+            false => bar
+                .child(start.flex_none())
+                .child(middle)
+                .child(end.flex_none()),
+        }
     }
 }
diff --git a/src/shell/tests.rs b/src/shell/tests.rs
index 5bb1338..75f0f51 100644
--- a/src/shell/tests.rs
+++ b/src/shell/tests.rs
@@ -190,3 +190,74 @@ fn caption_buttons_keep_their_height_in_a_wrapping_row(cx: &mut TestAppContext)
     assert!(combo.top() > row.top(), "the caps wrap below the buttons");
     assert!(combo.bottom() <= row.bottom(), "{combo:?} inside {row:?}");
 }
+
+struct Bar(Option<&'static str>, crate::theme::Platform);
+
+impl Render for Bar {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let bar = super::TitleBar::new("bar").platform(self.1);
+        div()
+            .w(px(280.0))
+            .flex()
+            .flex_col()
+            .child(
+                div()
+                    .debug_selector(|| "bar-box".into())
+                    .child(match self.0 {
+                        Some(title) => bar.title(title),
+                        None => bar,
+                    }),
+            )
+    }
+}
+
+/// A Windows bar with no title still keeps its buttons at its right end.
+#[gpui::test]
+fn an_untitled_windows_bar_keeps_its_buttons_at_the_end(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| Bar(None, crate::theme::Platform::Windows));
+    settle(cx);
+    let close = cx.debug_bounds("caption-Close").expect("a close button");
+    assert_eq!(close.right(), px(280.0));
+}
+
+/// A long centered title ends before the Linux round buttons.
+#[gpui::test]
+fn a_long_centered_title_ends_before_the_buttons(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let long = "Ely — Projects at a narrow width, and more besides";
+    let (_, cx) = cx.add_window_view(|_, _| Bar(Some(long), crate::theme::Platform::Linux));
+    settle(cx);
+    let title = cx.debug_bounds("titlebar-title").expect("the title");
+    let controls = cx.debug_bounds("titlebar-controls").expect("the buttons");
+    assert!(
+        title.right() <= controls.left(),
+        "{title:?} before {controls:?}"
+    );
+}
+
+/// At half the rem size the caption buttons shrink with the bar and stay inside it.
+#[gpui::test]
+fn caption_buttons_follow_the_windows_rem(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| Bar(None, crate::theme::Platform::Windows));
+    cx.update(|window, _| window.set_rem_size(px(8.0)));
+    settle(cx);
+    let bar = cx.debug_bounds("bar-box").expect("the bar");
+    let close = cx.debug_bounds("caption-Close").expect("a close button");
+    assert!(
+        close.top() >= bar.top() && close.bottom() <= bar.bottom(),
+        "{close:?} inside {bar:?}"
+    );
+}
+
+/// A short title sits at the bar's center, whatever stands at either end.
+#[gpui::test]
+fn a_short_title_sits_at_the_center(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| Bar(Some("Notes"), crate::theme::Platform::Linux));
+    settle(cx);
+    let title = cx.debug_bounds("titlebar-title").expect("the title");
+    let middle = title.left() + title.size.width / 2.0;
+    assert!((middle - px(140.0)).abs() < px(1.0), "{title:?} centered");
+}
diff --git a/src/theme/tokens.rs b/src/theme/tokens.rs
index fdbab9d..cb2cede 100644
--- a/src/theme/tokens.rs
+++ b/src/theme/tokens.rs
@@ -230,9 +230,9 @@ impl Theme {
         px_to_rems(46.0)
     }
 
-    /// A Windows caption button's height: the title bar's, less its bottom hairline.
-    pub fn caption_button_height(&self) -> Pixels {
-        self.titlebar_height().to_pixels(self.base_rem()) - px(1.0)
+    /// A Windows caption button's height at a window's rem: the title bar's, less its hairline.
+    pub fn caption_button_height(&self, rem: Pixels) -> Pixels {
+        self.titlebar_height().to_pixels(rem) - px(1.0)
     }
 
     /// Resize margin of a client-drawn window.