diff --git a/crates/ui-egui/src/panels/comments.rs b/crates/ui-egui/src/panels/comments.rs
index edf0e8b84..5acb71402 100644
--- a/crates/ui-egui/src/panels/comments.rs
+++ b/crates/ui-egui/src/panels/comments.rs
@@ -130,29 +130,34 @@ fn comment_card(app: &mut SlideApp, ui: &mut Ui, slide: usize, index: usize, c:
             for r in &c.replies {
                 ui.label(egui::RichText::new(format!("↳ {}: {}", r.author, r.text)).color(t.text_dim));
             }
+            // The buttons are laid out first, from the right, so the reply field takes exactly the
+            // width they leave. A fixed allowance overflowed the card and widened the pane every
+            // frame until it stuck at its widest (#1431).
             ui.horizontal(|ui| {
-                let id = ui.scope_id().with(("reply", slide, index));
-                let mut txt: String = ui.data_mut(|d| d.get_temp(id).unwrap_or_default());
-                let r = ui.add(egui::TextEdit::singleline(&mut txt).hint_text("Reply…").desired_width(ui.available_width() - 70.0));
-                if r.lost_focus() && ui.input(|i| i.key_pressed(egui::Key::Enter)) && !txt.trim().is_empty() {
-                    focus_comment(app, slide, index);
-                    run(app, "comment.reply", json!({"index": index, "text": txt}));
-                    txt.clear();
-                }
-                ui.data_mut(|d| d.insert_temp(id, txt));
-                if ui.small_button(if c.resolved { "Reopen" } else { "Resolve" }).clicked() {
-                    focus_comment(app, slide, index);
-                    run(app, "comment.resolve", json!({"index": index, "resolved": !c.resolved}));
-                }
-                if ui.small_button("🗑").clicked() {
-                    let _ = app.run("slide.go", json!({"index": slide}));
-                    let _ = app.run("comment.delete", json!({"index": index}));
-                    match app.ui.comment_focus {
-                        Some((fs, fi)) if fs == slide && fi == index => app.ui.comment_focus = None,
-                        Some((fs, fi)) if fs == slide && fi > index => app.ui.comment_focus = Some((fs, fi - 1)),
-                        _ => {}
+                ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+                    if ui.small_button("🗑").clicked() {
+                        let _ = app.run("slide.go", json!({"index": slide}));
+                        let _ = app.run("comment.delete", json!({"index": index}));
+                        match app.ui.comment_focus {
+                            Some((fs, fi)) if fs == slide && fi == index => app.ui.comment_focus = None,
+                            Some((fs, fi)) if fs == slide && fi > index => app.ui.comment_focus = Some((fs, fi - 1)),
+                            _ => {}
+                        }
                     }
-                }
+                    if ui.small_button(if c.resolved { "Reopen" } else { "Resolve" }).clicked() {
+                        focus_comment(app, slide, index);
+                        run(app, "comment.resolve", json!({"index": index, "resolved": !c.resolved}));
+                    }
+                    let id = ui.scope_id().with(("reply", slide, index));
+                    let mut txt: String = ui.data_mut(|d| d.get_temp(id).unwrap_or_default());
+                    let r = ui.add(egui::TextEdit::singleline(&mut txt).hint_text("Reply…").desired_width(ui.available_width()));
+                    if r.lost_focus() && ui.input(|i| i.key_pressed(egui::Key::Enter)) && !txt.trim().is_empty() {
+                        focus_comment(app, slide, index);
+                        run(app, "comment.reply", json!({"index": index, "text": txt}));
+                        txt.clear();
+                    }
+                    ui.data_mut(|d| d.insert_temp(id, txt));
+                });
             });
         });
     if focused {
diff --git a/crates/ui-egui/src/tests.rs b/crates/ui-egui/src/tests.rs
index 29fa755fd..5221544a1 100644
--- a/crates/ui-egui/src/tests.rs
+++ b/crates/ui-egui/src/tests.rs
@@ -2361,3 +2361,47 @@ fn overdue_visible_logic_does_not_reanchor_a_later_hidden_show() {
     let _ = ctx.run_logic(&raw_at(12.0, true, false), |ctx| app.tick_hidden_show(ctx, visible_anchor + std::time::Duration::from_secs(3)));
     assert_eq!(app.show.as_ref().unwrap().state.slide, 1, "time from the full visible frame is preserved through the logic-only pass");
 }
+
+/// #1431: a comment card's reply row was wider than the pane, so the Comments pane grew every
+/// frame until it stuck at its widest and dragging its edge did nothing.
+#[test]
+fn comments_pane_keeps_its_width_and_resizes() {
+    let mut h = egui_kittest::Harness::builder().with_size(egui::vec2(1200.0, 800.0)).build_ui_state(
+        |ui, app: &mut SlideApp| {
+            app.logic(ui.ctx());
+            app.ui(ui);
+        },
+        SlideApp::new(Session::with_new(), Services::default()),
+    );
+    h.run_steps(3);
+    h.state_mut().run("comment.add", json!({"text": "Check the figures on this slide"})).unwrap();
+    h.state_mut().run("comment.add", json!({"text": "Resolved one"})).unwrap();
+    h.state_mut().run("comment.resolve", json!({"index": 1, "resolved": true})).unwrap();
+    h.state_mut().run("view.pane", json!({"pane": "comments"})).unwrap();
+    h.run_steps(30);
+    let width = h.state().ui.pane_width;
+    assert!(width < 320.0, "the pane keeps its default width, not {width}");
+    // The cards stay compact: the second one starts near the top, not below a stretched first.
+    let second = h.get_by_label("Resolved one").rect();
+    assert!(second.top() < 450.0, "the second comment sits near the top, at {second:?}");
+
+    // Drag the pane's left edge: right narrows it, left widens it.
+    let drag = |h: &mut egui_kittest::Harness<'_, SlideApp>, dx: f32| {
+        let start = egui::pos2(1200.0 - h.state().ui.pane_width - 1.0, 500.0);
+        let end = start + egui::vec2(dx, 0.0);
+        h.event(egui::Event::PointerMoved(start));
+        h.run_steps(1);
+        h.event(egui::Event::PointerButton { pos: start, button: egui::PointerButton::Primary, pressed: true, modifiers: egui::Modifiers::NONE });
+        for i in 1..=6 {
+            h.event(egui::Event::PointerMoved(start + (end - start) * (i as f32 / 6.0)));
+            h.run_steps(1);
+        }
+        h.event(egui::Event::PointerButton { pos: end, button: egui::PointerButton::Primary, pressed: false, modifiers: egui::Modifiers::NONE });
+        h.run_steps(10);
+        h.state().ui.pane_width
+    };
+    let narrow = drag(&mut h, 50.0);
+    assert!(narrow < width - 40.0, "dragging right narrows the pane: {width} -> {narrow}");
+    let wide = drag(&mut h, -150.0);
+    assert!(wide > narrow + 140.0, "dragging left widens the pane: {narrow} -> {wide}");
+}