diff --git a/crates/ui-egui/src/comments.rs b/crates/ui-egui/src/comments.rs
index 20ea284e..fe75ba96 100644
--- a/crates/ui-egui/src/comments.rs
+++ b/crates/ui-egui/src/comments.rs
@@ -275,6 +275,13 @@ impl CommentPrefs {
         }
     }
 
+    /// The tool's opacity, 10–100 % (an invisible comment can't be found again).
+    pub fn set_opacity(&mut self, tool: CommentTool, o: f64) {
+        if let Some((_, s)) = self.styles.iter_mut().find(|(t, _)| *t == tool) {
+            s.opacity = if o.is_finite() { o.clamp(0.1, 1.0) } else { 1.0 };
+        }
+    }
+
     pub fn set_style(&mut self, tool: CommentTool, style: Style) {
         if let Some((_, s)) = self.styles.iter_mut().find(|(t, _)| *t == tool) {
             *s = style;
@@ -1253,7 +1260,7 @@ pub fn swatch_grid(ui: &mut egui::Ui, current: Option<Rgb>) -> Option<Rgb> {
     picked
 }
 
-/// The comment tools' extra quick-bar controls: pin, colour and thickness.
+/// The comment tools' extra quick-bar controls: pin, colour, opacity and thickness.
 pub(crate) fn quick_bar_controls(ui: &mut egui::Ui, tool: CommentTool, prefs: &mut CommentPrefs) {
     let style = prefs.style(tool);
     if icons::button(ui, "pin", 32.0, prefs.pinned, if prefs.pinned { "Keep tool selected: on" } else { "Keep tool selected" }).clicked() {
@@ -1269,6 +1276,15 @@ pub(crate) fn quick_bar_controls(ui: &mut egui::Ui, tool: CommentTool, prefs: &m
             ui.close();
         }
     });
+    let resp = icons::button(ui, "blend", 32.0, false, "Opacity");
+    egui::Popup::menu(&resp).align(egui::RectAlign::RIGHT_START).close_behavior(egui::PopupCloseBehavior::CloseOnClickOutside).show(|ui| {
+        ui.set_min_width(180.0);
+        let mut percent = (style.opacity * 100.0).round();
+        ui.label(egui::RichText::new("Opacity").font(theme::semibold(12.0)));
+        if ui.add(egui::Slider::new(&mut percent, 10.0..=100.0).step_by(5.0).suffix(" %")).changed() {
+            prefs.set_opacity(tool, percent / 100.0);
+        }
+    });
     if tool.has_width() {
         let resp = icons::button(ui, "sliders-horizontal", 32.0, false, "Line thickness");
         egui::Popup::menu(&resp).align(egui::RectAlign::RIGHT_START).close_behavior(egui::PopupCloseBehavior::CloseOnClickOutside).show(|ui| {
diff --git a/crates/ui-egui/tests/comments.rs b/crates/ui-egui/tests/comments.rs
index 499f7840..f58216f5 100644
--- a/crates/ui-egui/tests/comments.rs
+++ b/crates/ui-egui/tests/comments.rs
@@ -568,3 +568,33 @@ fn the_squiggly_tool_marks_selected_text() {
     assert!(printcraft_ui_egui::comments::GROUPS[1].contains(&printcraft_ui_egui::comments::CommentTool::Squiggly));
     assert_eq!(printcraft_ui_egui::comments::tool_for(&c[0]), Some(printcraft_ui_egui::comments::CommentTool::Squiggly));
 }
+
+#[test]
+fn the_opacity_set_for_a_tool_goes_into_its_new_comments() {
+    use printcraft_ui_egui::comments::CommentTool;
+    let mut h = harness(|app| app.comment_prefs.set_opacity(CommentTool::StrikeOut, 0.5));
+    // Clamped: an invisible comment can't be found again.
+    h.state_mut().comment_prefs.set_opacity(CommentTool::Underline, 0.0);
+    assert!((h.state().comment_prefs.style(CommentTool::Underline).opacity - 0.1).abs() < 1e-9);
+    h.state_mut().views[0].select_text(0, 4, 8);
+    assert!(h.state_mut().execute("comment.strikeout"));
+    h.run_steps(2);
+    let c = comments(&h);
+    assert_eq!(c.len(), 1, "{c:?}");
+    // The new comment carries /CA 0.5 (read back from the document's bytes).
+    let bytes = h.state().session.get(h.state().views[0].id).unwrap().bytes.as_ref().clone();
+    let doc = printcraft_cos::Document::open(std::sync::Arc::new(bytes)).unwrap();
+    let opacities: Vec<f64> = doc
+        .object_numbers()
+        .into_iter()
+        .filter_map(|n| doc.try_get(n).ok())
+        .filter_map(|o| o.as_dict().cloned())
+        .filter(|d| d.name(b"Subtype") == Some(b"StrikeOut"))
+        .filter_map(|d| d.get(b"CA").and_then(|v| v.as_f64()))
+        .collect();
+    assert_eq!(opacities, [0.5]);
+    // The quick bar offers the control.
+    h.state_mut().set_option("quick", "strikeout").unwrap();
+    h.run_steps(2);
+    h.get_by_label("Opacity");
+}
diff --git a/parity/acrobat-features.toml b/parity/acrobat-features.toml
index 9cf0b43e..d4875498 100644
--- a/parity/acrobat-features.toml
+++ b/parity/acrobat-features.toml
@@ -3767,11 +3767,11 @@ title = "Comment properties bar"
 area = "E"
 tier = "P1"
 milestone = "M5"
-status = "partial"
+status = "shipped"
 commands = ["comment.note"]
 tools = ["comment_edit"]
-evidence = ["crates/annot/src/tests.rs::restyle_and_resize_redraw_the_appearance"]
-notes = "quick-bar colour swatches and line thickness per tool, colour from the context menu; no opacity control in the UI yet"
+evidence = ["crates/annot/src/tests.rs::restyle_and_resize_redraw_the_appearance", "crates/ui-egui/tests/comments.rs::the_opacity_set_for_a_tool_goes_into_its_new_comments"]
+notes = "quick-bar colour swatches, opacity (10–100 %) and line thickness per tool; colour from the context menu"
 
 [[feature]]
 id = "comment.lock-comment"