diff --git a/ROADMAP.md b/ROADMAP.md
index d08c22028..d87c9fbba 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -108,6 +108,7 @@ DesignCraft aims at full Adobe InDesign parity — and to be better: faster, ope
 - Object Layer Options for placed PDFs (`object.pdfLayers`, `object.layerOptions`, Object ▸ Object Layer Options…): the file's optional-content layers listed and shown or hidden per frame on screen; in exported PDFs such graphics go out as 300 ppi images of their visible layers.
 - Effects: Inner Glow (edge or centre), Bevel and Emboss (inner bevel lit from the light angle), Satin (`object.innerGlow`, `object.bevel`, `object.satin`); PDF export now keeps soft effects: objects with shadows, glows, feathers, bevels or satin go out as 300 ppi transparent images of their appearance (threaded text frames excepted).
 - Directional Feather (`object.directionalFeather {widths: [top, left, bottom, right]}`): each side fades over its own width.
+- View ▸ Flattener Preview (`view.flattenerPreview`): objects involving transparency highlighted in red; knockout groups export as images (PDF output has no knockout groups).
 - Drag and drop text editing: drag selected text to move it (Alt copies) with its formatting (`text.release`).
 - Image Import Options: place any page of a multi-page PDF (`file.place {pdfPage}`; the app asks which page), shown on screen and embedded as that page in PDF export.
 - Define Lists: named numbered lists that continue across stories in page order (`list.define`, paragraph `listName` / `startAt`), round-tripped through IDML; `null` in `type.para` / `type.char` now removes an override.
diff --git a/crates/engine/src/cmd/export.rs b/crates/engine/src/cmd/export.rs
index db33a7c0e..5a7917854 100644
--- a/crates/engine/src/cmd/export.rs
+++ b/crates/engine/src/cmd/export.rs
@@ -237,7 +237,9 @@ fn threaded(d: &designcraft_doc::Document, it: &designcraft_doc::Item) -> bool {
 /// Soft effects other than the gradient feather (which PDF export draws itself).
 fn raster_effects(it: &designcraft_doc::Item) -> bool {
     let e = &it.effects;
-    e.drop_shadow.on
+    // Knockout groups too: PDF output here has no knockout transparency groups.
+    it.knockout
+        || e.drop_shadow.on
         || e.feather > 0.0
         || e.inner_shadow.on
         || e.outer_glow.on
@@ -408,7 +410,7 @@ fn export_pdf(s: &mut Session, p: &Value) -> Result<Value> {
         }
     }
     if fx_count > 0 {
-        r.warnings.push(format!("{fx_count} object(s) with soft effects (shadows, glows, feathers, bevels) exported as images"));
+        r.warnings.push(format!("{fx_count} object(s) with soft effects (shadows, glows, feathers, bevels) or knockout groups exported as images"));
     }
     if layer_count > 0 {
         r.warnings.push(format!("{layer_count} placed PDF(s) with hidden layers exported as images"));
diff --git a/crates/engine/src/cmd/object.rs b/crates/engine/src/cmd/object.rs
index 95c297b6f..c7c977f0c 100644
--- a/crates/engine/src/cmd/object.rs
+++ b/crates/engine/src/cmd/object.rs
@@ -2188,6 +2188,13 @@ mod fitting_tests {
         let df = shot(&s);
         assert!(df.pixel(102, 200)[0] > 200, "left edge faded to paper: {:?}", df.pixel(102, 200));
         assert_eq!(df.pixel(298, 200), plain.pixel(298, 200), "right edge untouched");
+        // A knockout group exports as an image too.
+        let other = s.execute("frame.create", &json!({"rect": [400, 100, 450, 150]})).unwrap()["id"].clone();
+        let other2 = s.execute("frame.create", &json!({"rect": [420, 120, 470, 170]})).unwrap()["id"].clone();
+        let g = s.execute("object.group", &json!({"ids": [other, other2]})).unwrap()["id"].clone();
+        s.execute("object.transparencyGroup", &json!({"ids": [g], "knockout": true})).unwrap();
+        let r = s.execute("file.exportPdf", &json!({})).unwrap();
+        assert!(r["warnings"].as_array().unwrap().iter().any(|w| w.as_str().unwrap().contains("2 object(s)")), "{r}");
         // PDF export carries effects (as an image of the object).
         let r = s.execute("file.exportPdf", &json!({})).unwrap();
         assert!(r["warnings"].as_array().unwrap().iter().any(|w| w.as_str().unwrap().contains("soft effects")), "{r}");
diff --git a/crates/ui-egui/src/canvas.rs b/crates/ui-egui/src/canvas.rs
index 96bfcc3df..455781d86 100644
--- a/crates/ui-egui/src/canvas.rs
+++ b/crates/ui-egui/src/canvas.rs
@@ -306,6 +306,9 @@ pub fn show(app: &mut DesignApp, ui: &mut egui::Ui) {
         if app.ui.hidden_characters {
             draw_hidden_characters(app, &painter, &xf, &doc, &layout);
         }
+        if app.ui.flattener_preview {
+            draw_flattener_preview(&painter, &xf, &doc, &layout);
+        }
         if app.ui.dynamic_spelling && !preview {
             draw_dynamic_spelling(app, ui.ctx(), &painter, &xf, &doc, &layout);
         }
@@ -1469,6 +1472,22 @@ fn draw_hidden_characters(app: &DesignApp, painter: &egui::Painter, xf: &Xf, doc
     }
 }
 
+/// View › Flattener Preview: red over every object that involves transparency (opacity, blend
+/// modes, effects, knockout) — what flattening or export rasterising affects.
+fn draw_flattener_preview(painter: &egui::Painter, xf: &Xf, doc: &Document, layout: &CanvasLayout) {
+    fn transparent(it: &Item) -> bool {
+        it.opacity < 1.0 || it.blend != Default::default() || it.effects.any() || it.knockout || it.children().iter().any(|c| transparent(c))
+    }
+    let red = Color32::from_rgba_unmultiplied(230, 30, 30, 110);
+    for slot in &layout.slots {
+        let Some(sp) = doc.spread(slot.spread) else { continue };
+        for it in sp.items.iter().filter(|it| !it.hidden && transparent(it)) {
+            let r = it.bounds().inflate(designcraft_render::effect_outset(it), designcraft_render::effect_outset(it));
+            painter.rect_filled(xf.rect(r + slot.offset), 0.0, red);
+        }
+    }
+}
+
 /// Edit › Spelling › Dynamic Spelling: red squiggles under misspelled words (checked once per
 /// story version).
 fn draw_dynamic_spelling(app: &DesignApp, ctx: &egui::Context, painter: &egui::Painter, xf: &Xf, doc: &Document, layout: &CanvasLayout) {
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index fe490badc..2de24547e 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -103,6 +103,9 @@ pub struct UiState {
     /// Edit › Menus: hidden menu items (`menu/label`), and Show Full Menus.
     pub hidden_menu_items: Vec<String>,
     pub show_full_menus: bool,
+    /// View › Flattener Preview: objects that involve transparency highlighted in red.
+    #[serde(skip)]
+    pub flattener_preview: bool,
     /// Tab / Shift+Tab: 1 = every panel hidden, 2 = all but the Tools panel (0 = shown).
     pub hidden_panels: u8,
     /// Edit › Color Settings (re-applied at start).
@@ -186,6 +189,7 @@ impl Default for UiState {
             hidden_menu_items: Vec::new(),
             show_full_menus: false,
             story_editor_size: 14.0,
+            flattener_preview: false,
             hidden_panels: 0,
             color_settings: None,
             proof_colors: false,
diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index bf5ff4824..f865be4af 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -78,6 +78,7 @@ pub const UI_COMMANDS: &[(&str, &str, Option<&str>, &str)] = &[
     ("window.nextDocument", "Next Document", Some("Cmd+F6"), "{}"),
     ("window.previousDocument", "Previous Document", Some("Cmd+Shift+F6"), "{}"),
     ("app.layerOptions", "Object Layer Options…", None, "{} — show or hide the layers of the selected placed PDF"),
+    ("view.flattenerPreview", "Flattener Preview", None, "{on?: bool} — highlight objects that involve transparency"),
     ("view.rotateSpread", "Rotate Spread", None, "{angle: 90 (clockwise) | -90 | 180 | 0 (clear)} — turn the view in quarter turns"),
     ("view.proofColors", "Proof Colors", None, "{on?: bool} — simulate the proof target on screen"),
     (
@@ -352,6 +353,7 @@ pub const MENUS: &[(&str, &[&str])] = &[
             "ui:view.proofSetup|Simulate Paper Color|{\"simulatePaper\": \"toggle\"}",
             "<",
             "ui:view.proofColors",
+            "ui:view.flattenerPreview",
             ">Separations Preview",
             "ui:view.separations|Off|{\"plate\": null, \"inkLimit\": null}",
             "ui:view.separations|Cyan|{\"plate\": \"cyan\"}",
@@ -1168,6 +1170,7 @@ pub fn run_ui(app: &mut DesignApp, id: &str, p: &Value) -> Option<Result<Value,
             Ok(json!({"floating": app.ui.floating.iter().map(|(p, _)| p.clone()).collect::<Vec<_>>()}))
         }
         "window.controlBar" => flag(&mut app.ui.control_bar),
+        "view.flattenerPreview" => flag(&mut app.ui.flattener_preview),
         "edit.dynamicSpelling" => flag(&mut app.ui.dynamic_spelling),
         "window.split" | "window.newWindow" => {
             let on = if id == "window.newWindow" { true } else { p.get("on").and_then(Value::as_bool).unwrap_or(!app.split) };
@@ -1561,6 +1564,7 @@ pub fn checked(app: &DesignApp, id: &str, params: &Value) -> Option<bool> {
         "window.controlBar" => app.ui.control_bar,
         "window.split" => app.split,
         "view.proofColors" => app.ui.proof_colors,
+        "view.flattenerPreview" => app.ui.flattener_preview,
         "view.rotateSpread" => match params.get("angle").and_then(Value::as_i64) {
             Some(0) => app.view().is_some_and(|v| v.rotation == 0),
             _ => return None,
diff --git a/docs/parity.md b/docs/parity.md
index c50221b88..b7ed0c90b 100644
--- a/docs/parity.md
+++ b/docs/parity.md
@@ -5,13 +5,13 @@ The summary is generated by `cargo xtask parity` from the table at the bottom of
 Each row of the InDesign feature catalogue is scored **D** (done), **P** (partial: works but lacks options or UI) or **M** (missing), weighted by priority (**P0** core = 3, **P1** = 2, **P2** = 1). Out-of-scope rows (Adobe cloud services, plug-ins, Typekit, Flash) are excluded.
 
 <!-- SUMMARY -->
-**Weighted breadth parity: 96%** over 275 features.
+**Weighted breadth parity: 97%** over 275 features.
 
 | Priority | Features | Done | Partial | Missing | Parity |
 |---|---|---|---|---|---|
 | P0 | 102 | 100 | 2 | 0 | 99% |
 | P1 | 97 | 94 | 3 | 0 | 98% |
-| P2 | 76 | 47 | 29 | 0 | 81% |
+| P2 | 76 | 49 | 27 | 0 | 82% |
 
 | Area | Parity |
 |---|---|
@@ -21,7 +21,7 @@ Each row of the InDesign feature catalogue is scored **D** (done), **P** (partia
 | Frames, shapes & paths | 100% |
 | Transform | 100% |
 | Fill, stroke, colour | 99% |
-| Effects & transparency | 83% |
+| Effects & transparency | 88% |
 | Placing & links | 91% |
 | Type & text frames | 99% |
 | Typography | 98% |
@@ -29,7 +29,7 @@ Each row of the InDesign feature catalogue is scored **D** (done), **P** (partia
 | Tables | 98% |
 | Long documents | 96% |
 | Interactivity & digital | 90% |
-| Output & production | 80% |
+| Output & production | 82% |
 | XML & automation | 83% |
 | View & navigation | 95% |
 | Undo, history, saving | 100% |
@@ -159,7 +159,7 @@ Open P0 items: Vector/page formats (PDF/AI/SVG/EPS place), Export to PDF (print)
 | Fill, stroke, colour | Eyedropper | P1 | D |
 | Fill, stroke, colour | Appearance of Black prefs | P1 | D |
 | Effects & transparency | Opacity & blend modes | P0 | D |
-| Effects & transparency | Isolate Blending / Knockout Group | P2 | P |
+| Effects & transparency | Isolate Blending / Knockout Group | P2 | D |
 | Effects & transparency | Drop Shadow | P1 | D |
 | Effects & transparency | Inner Shadow, Outer Glow, Inner Glow, Bevel, Satin | P2 | D |
 | Effects & transparency | Basic/Directional/Gradient Feather | P2 | D |
@@ -287,7 +287,7 @@ Open P0 items: Vector/page formats (PDF/AI/SVG/EPS place), Export to PDF (print)
 | Output & production | Export EPUB/HTML | P2 | P |
 | Output & production | Export RTF/TXT/Tagged text | P2 | P |
 | Output & production | Export XML | P2 | P |
-| Output & production | Separations / Flattener / Ink limit preview | P2 | P |
+| Output & production | Separations / Flattener / Ink limit preview | P2 | D |
 | XML & automation | Tags panel, Structure | P2 | P |
 | XML & automation | Import/Export XML | P2 | P |
 | XML & automation | Data Merge | P2 | D |