diff --git a/crates/doc/src/lib.rs b/crates/doc/src/lib.rs
index 82d0dd527f..92dd20c42d 100644
--- a/crates/doc/src/lib.rs
+++ b/crates/doc/src/lib.rs
@@ -543,6 +543,14 @@ impl LayerContent {
             LayerContent::Smart(_) => "Smart Object",
         }
     }
+
+    /// English indefinite article for this layer kind ("an" for Adjustment, "a" for all others).
+    pub fn article(&self) -> &'static str {
+        match self {
+            LayerContent::Adjustment(_) => "an",
+            _ => "a",
+        }
+    }
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -1224,6 +1232,14 @@ mod tests {
         d.layer_mut(bg).unwrap().surface_mut().unwrap().write_pixel(0, 0, &[0.0, 0.0, 0.0, 1.0]);
         assert_eq!(snap.layers[0].surface().unwrap().pixel(0, 0), vec![1.0; 4]);
     }
+
+    #[test]
+    fn layer_content_article_and_kind_name() {
+        assert_eq!(LayerContent::Adjustment(Adjustment::Invert).article(), "an");
+        assert_eq!(LayerContent::Adjustment(Adjustment::Invert).kind_name(), "Adjustment");
+        assert_eq!(LayerContent::Raster(Surface::new(PixelFormat::RGBA8)).article(), "a");
+        assert_eq!(LayerContent::Group(Group { children: Vec::new(), expanded: true, artboard: None }).article(), "a");
+    }
 }
 
 #[cfg(test)]
diff --git a/crates/engine/src/adjust_cmds.rs b/crates/engine/src/adjust_cmds.rs
index a9483ee62c..a42704d211 100644
--- a/crates/engine/src/adjust_cmds.rs
+++ b/crates/engine/src/adjust_cmds.rs
@@ -204,7 +204,7 @@ fn has_pixels(s: &Session) -> std::result::Result<(), String> {
     }
     let d = s.active().ok_or("no document open")?;
     let l = d.active_layer.and_then(|id| d.doc.layer(id)).ok_or("no active layer")?;
-    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is a {} layer, not a pixel layer", l.content.kind_name())) }
+    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name())) }
 }
 
 fn has_doc(s: &Session) -> std::result::Result<(), String> {
diff --git a/crates/engine/src/channel_cmds.rs b/crates/engine/src/channel_cmds.rs
index a9c30e9715..7e056d1071 100644
--- a/crates/engine/src/channel_cmds.rs
+++ b/crates/engine/src/channel_cmds.rs
@@ -1649,6 +1649,6 @@ fn has_apply_target(s: &Session) -> std::result::Result<(), String> {
     if matches!(l.content, LayerContent::Raster(_)) {
         Ok(())
     } else {
-        Err(format!("Apply Image needs a pixel layer (active layer is a {} layer)", l.content.kind_name()))
+        Err(format!("Apply Image needs a pixel layer (active layer is {} {} layer)", l.content.article(), l.content.kind_name()))
     }
 }
diff --git a/crates/engine/src/commands.rs b/crates/engine/src/commands.rs
index 91d723f0fc..4dde5d6282 100644
--- a/crates/engine/src/commands.rs
+++ b/crates/engine/src/commands.rs
@@ -39,7 +39,7 @@ fn has_layer(s: &Session) -> std::result::Result<(), String> {
 }
 fn has_pixel_layer(s: &Session) -> std::result::Result<(), String> {
     let l = crate::active_layer_of(s)?;
-    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is a {} layer, not a pixel layer", l.content.kind_name())) }
+    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name())) }
 }
 /// A pixel layer, or a targeted alpha channel / Quick Mask (adjustments and fills apply to it).
 fn has_pixel_or_channel(s: &Session) -> std::result::Result<(), String> {
@@ -57,7 +57,7 @@ pub(crate) fn has_paintable(s: &Session) -> std::result::Result<(), String> {
     if matches!(l.content, LayerContent::Raster(_)) || l.mask.is_some() {
         Ok(())
     } else {
-        Err(format!("active layer is a {} layer without a mask", l.content.kind_name()))
+        Err(format!("active layer is {} {} layer without a mask", l.content.article(), l.content.kind_name()))
     }
 }
 
diff --git a/crates/engine/src/cutout_cmds.rs b/crates/engine/src/cutout_cmds.rs
index f6bf4cc71e..762830ee83 100644
--- a/crates/engine/src/cutout_cmds.rs
+++ b/crates/engine/src/cutout_cmds.rs
@@ -21,7 +21,7 @@ const REFINE: RefineParams = RefineParams { radius: 2.0, smart_radius: true, smo
 /// Remove Background needs an unlocked pixel layer.
 fn check(doc: &Document, l: &Layer) -> std::result::Result<(), String> {
     if !matches!(l.content, LayerContent::Raster(_)) {
-        return Err(format!("the layer is a {} layer, not a pixel layer", l.content.kind_name()));
+        return Err(format!("the layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name()));
     }
     let locks = doc.effective_locks(l.id);
     if locks.pixels || locks.all {
diff --git a/crates/engine/src/distort_cmds.rs b/crates/engine/src/distort_cmds.rs
index 786702cbbc..77cfdd88a0 100644
--- a/crates/engine/src/distort_cmds.rs
+++ b/crates/engine/src/distort_cmds.rs
@@ -201,7 +201,7 @@ fn pixel_layer(s: &Session) -> std::result::Result<(), String> {
     match &d.doc.layer(id).ok_or("no active layer")?.content {
         LayerContent::Raster(_) => Ok(()),
         LayerContent::Smart(sm) if sm.cache.is_some() => Ok(()),
-        other => Err(format!("needs a pixel layer or smart object (active layer is a {} layer)", other.kind_name())),
+        other => Err(format!("needs a pixel layer or smart object (active layer is {} {} layer)", other.article(), other.kind_name())),
     }
 }
 
diff --git a/crates/engine/src/edit_menu_cmds.rs b/crates/engine/src/edit_menu_cmds.rs
index c545824ab5..994b84d6a7 100644
--- a/crates/engine/src/edit_menu_cmds.rs
+++ b/crates/engine/src/edit_menu_cmds.rs
@@ -112,7 +112,7 @@ fn pixel_layer(s: &Session) -> std::result::Result<LayerId, String> {
     let id = d.active_layer.ok_or("no active layer")?;
     let l = d.doc.layer(id).ok_or("no active layer")?;
     if !matches!(l.content, LayerContent::Raster(_)) {
-        return Err(format!("active layer is a {} layer, not a pixel layer", l.content.kind_name()));
+        return Err(format!("active layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name()));
     }
     let locks = d.doc.effective_locks(id);
     if locks.all || locks.pixels {
diff --git a/crates/engine/src/eraser_cmds.rs b/crates/engine/src/eraser_cmds.rs
index c83135b432..1694d74c41 100644
--- a/crates/engine/src/eraser_cmds.rs
+++ b/crates/engine/src/eraser_cmds.rs
@@ -47,7 +47,7 @@ fn enum_param<T: serde::de::DeserializeOwned>(p: &Value, cmd: &str, k: &str, def
 fn has_pixel_layer(s: &Session) -> std::result::Result<(), String> {
     let d = s.active().ok_or("no document open")?;
     let l = d.active_layer.and_then(|id| d.doc.layer(id)).ok_or("no active layer")?;
-    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is a {} layer, not a pixel layer", l.content.kind_name())) }
+    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name())) }
 }
 
 fn active_pixel_layer(s: &Session, cmd: &str) -> Result<LayerId> {
diff --git a/crates/engine/src/extra_cmds.rs b/crates/engine/src/extra_cmds.rs
index 9972bf4624..643cb50fae 100644
--- a/crates/engine/src/extra_cmds.rs
+++ b/crates/engine/src/extra_cmds.rs
@@ -29,7 +29,7 @@ fn has_layer(s: &Session) -> std::result::Result<(), String> {
 fn has_pixels(s: &Session) -> std::result::Result<(), String> {
     match active_layer(s)?.content {
         LayerContent::Raster(_) => Ok(()),
-        ref c => Err(format!("active layer is a {} layer, not a pixel layer", c.kind_name())),
+        ref c => Err(format!("active layer is {} {} layer, not a pixel layer", c.article(), c.kind_name())),
     }
 }
 
diff --git a/crates/engine/src/filters.rs b/crates/engine/src/filters.rs
index e24b67c9df..af99de42fe 100644
--- a/crates/engine/src/filters.rs
+++ b/crates/engine/src/filters.rs
@@ -195,7 +195,7 @@ pub(crate) fn has_filterable_layer(s: &Session) -> std::result::Result<(), Strin
     match &l.content {
         LayerContent::Raster(_) => Ok(()),
         LayerContent::Smart(sm) if sm.cache.is_some() => Ok(()),
-        other => Err(format!("filters need a pixel layer (active layer is a {} layer)", other.kind_name())),
+        other => Err(format!("filters need a pixel layer (active layer is {} {} layer)", other.article(), other.kind_name())),
     }
 }
 
diff --git a/crates/engine/src/layer_menu_cmds.rs b/crates/engine/src/layer_menu_cmds.rs
index f16442a23a..4039ea2664 100644
--- a/crates/engine/src/layer_menu_cmds.rs
+++ b/crates/engine/src/layer_menu_cmds.rs
@@ -38,7 +38,7 @@ fn has_layer(s: &Session) -> Enabled {
 
 fn has_raster(s: &Session) -> Enabled {
     let l = active_layer(s)?;
-    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is a {} layer, not a pixel layer", l.content.kind_name())) }
+    if matches!(l.content, LayerContent::Raster(_)) { Ok(()) } else { Err(format!("active layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name())) }
 }
 
 fn has_raster_with_mask(s: &Session) -> Enabled {
diff --git a/crates/engine/src/lens_cmds.rs b/crates/engine/src/lens_cmds.rs
index 17ee60e2c6..d4b3f54c95 100644
--- a/crates/engine/src/lens_cmds.rs
+++ b/crates/engine/src/lens_cmds.rs
@@ -262,7 +262,7 @@ fn filterable(s: &Session) -> std::result::Result<(), String> {
     match &d.doc.layer(id).ok_or("no active layer")?.content {
         LayerContent::Raster(_) => Ok(()),
         LayerContent::Smart(sm) if sm.cache.is_some() => Ok(()),
-        other => Err(format!("filters need a pixel layer (active layer is a {} layer)", other.kind_name())),
+        other => Err(format!("filters need a pixel layer (active layer is {} {} layer)", other.article(), other.kind_name())),
     }
 }
 
diff --git a/crates/engine/src/plugin_cmds.rs b/crates/engine/src/plugin_cmds.rs
index 40946acdb5..5c7d2dd71a 100644
--- a/crates/engine/src/plugin_cmds.rs
+++ b/crates/engine/src/plugin_cmds.rs
@@ -93,7 +93,7 @@ fn run(s: &mut Session, p: &Value) -> Result<Value> {
                 };
                 crate::smart_cmds::add_smart_filter(doc, layer, sf, selection.as_ref())
             }
-            other => Err(EngineError::Other(format!("plug-in filters need a pixel layer (active layer is a {} layer)", other.kind_name()))),
+            other => Err(EngineError::Other(format!("plug-in filters need a pixel layer (active layer is {} {} layer)", other.article(), other.kind_name()))),
         }
     })?;
     Ok(json!({"layer": layer.0, "plugin": id}))
diff --git a/crates/engine/src/retouch_cmds.rs b/crates/engine/src/retouch_cmds.rs
index abcc76ded3..3eed2901af 100644
--- a/crates/engine/src/retouch_cmds.rs
+++ b/crates/engine/src/retouch_cmds.rs
@@ -42,7 +42,7 @@ fn has_pixel_layer(s: &Session) -> std::result::Result<(), String> {
     if matches!(l.content, LayerContent::Raster(_)) || l.mask.is_some() {
         Ok(())
     } else {
-        Err(format!("active layer is a {} layer, not a pixel layer", l.content.kind_name()))
+        Err(format!("active layer is {} {} layer, not a pixel layer", l.content.article(), l.content.kind_name()))
     }
 }
 
diff --git a/crates/engine/src/smart_cmds.rs b/crates/engine/src/smart_cmds.rs
index 73bfe3a4e6..94b7b5589e 100644
--- a/crates/engine/src/smart_cmds.rs
+++ b/crates/engine/src/smart_cmds.rs
@@ -890,7 +890,7 @@ fn active_smart(s: &Session) -> std::result::Result<&SmartObject, String> {
     let id = d.active_layer.ok_or("no active layer")?;
     match &d.doc.layer(id).ok_or("no active layer")?.content {
         LayerContent::Smart(sm) => Ok(sm),
-        other => Err(format!("the active layer is a {} layer, not a smart object", other.kind_name())),
+        other => Err(format!("the active layer is {} {} layer, not a smart object", other.article(), other.kind_name())),
     }
 }
 fn has_smart(s: &Session) -> std::result::Result<(), String> {
diff --git a/crates/engine/src/smartselect_cmds.rs b/crates/engine/src/smartselect_cmds.rs
index 3a9b0dcafa..21c9822bd4 100644
--- a/crates/engine/src/smartselect_cmds.rs
+++ b/crates/engine/src/smartselect_cmds.rs
@@ -190,7 +190,7 @@ fn refine_edge(s: &mut Session, p: &Value) -> Result<Value> {
             let src_layer = d.doc.layer(id).ok_or(EngineError::NoLayer(id))?;
             let src = src_layer
                 .surface()
-                .ok_or_else(|| EngineError::Other(format!("the active layer is a {} layer without pixels", src_layer.content.kind_name())))?;
+                .ok_or_else(|| EngineError::Other(format!("the active layer is {} {} layer without pixels", src_layer.content.article(), src_layer.content.kind_name())))?;
             let name = d.doc.copy_name(&src_layer.name);
             let empty = Region { bbox: Rect::EMPTY, mask: Vec::new() };
             let reg = region.as_ref().unwrap_or(&empty);
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 1a616eb0e7..5116cbd173 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -1086,3 +1086,22 @@ fn move_document_reorders_tabs_and_keeps_the_active_one() {
     }
     assert_eq!(names(&s), first);
 }
+
+#[test]
+fn adjustment_layer_disabled_diagnostics_use_grammatical_article() {
+    let mut s = session_with_doc();
+    s.execute("layer.newAdjustmentLayer.curves", json!({})).unwrap();
+
+    let err_blur = s.execute("filter.blur.gaussianBlur", json!({"radius": 2})).unwrap_err().to_string();
+    assert!(err_blur.contains("an Adjustment layer"), "expected 'an Adjustment layer', got: {err_blur}");
+    assert!(!err_blur.contains("a Adjustment layer"), "found 'a Adjustment layer': {err_blur}");
+
+    let err_equalize = s.execute("image.adjustments.equalize", json!({})).unwrap_err().to_string();
+    assert!(err_equalize.contains("an Adjustment layer"), "expected 'an Adjustment layer', got: {err_equalize}");
+    assert!(!err_equalize.contains("a Adjustment layer"), "found 'a Adjustment layer': {err_equalize}");
+
+    let err_clear = s.execute("edit.clear", json!({})).unwrap_err().to_string();
+    assert!(err_clear.contains("an Adjustment layer"), "expected 'an Adjustment layer', got: {err_clear}");
+    assert!(!err_clear.contains("a Adjustment layer"), "found 'a Adjustment layer': {err_clear}");
+}
+
diff --git a/crates/engine/src/trap_cmds.rs b/crates/engine/src/trap_cmds.rs
index ca63e6cb7d..8934082374 100644
--- a/crates/engine/src/trap_cmds.rs
+++ b/crates/engine/src/trap_cmds.rs
@@ -27,7 +27,7 @@ fn trap(s: &mut Session, p: &Value) -> Result<Value> {
         let bounds = doc.bounds();
         let l = doc.layer_mut(id).ok_or(EngineError::NoLayer(id))?;
         let LayerContent::Raster(surf) = &mut l.content else {
-            return Err(EngineError::BadParams { cmd: cmd.into(), msg: format!("Trap needs a pixel layer (active layer is a {})", l.content.kind_name()) });
+            return Err(EngineError::BadParams { cmd: cmd.into(), msg: format!("Trap needs a pixel layer (active layer is {} {})", l.content.article(), l.content.kind_name()) });
         };
         if bounds.is_empty() {
             return Ok(());
diff --git a/crates/engine/src/type_caret_cmds.rs b/crates/engine/src/type_caret_cmds.rs
index 73e047343e..451c992935 100644
--- a/crates/engine/src/type_caret_cmds.rs
+++ b/crates/engine/src/type_caret_cmds.rs
@@ -69,7 +69,7 @@ struct Frame {
 fn frame(doc: &Document, id: LayerId, cmd: &str) -> Result<Frame> {
     let layer = doc.layer(id).ok_or(EngineError::NoLayer(id))?;
     let LayerContent::Text(t) = &layer.content else {
-        return Err(bad(cmd, format!("layer {} is a {} layer, not a type layer", id.0, layer.content.kind_name())));
+        return Err(bad(cmd, format!("layer {} is {} {} layer, not a type layer", id.0, layer.content.article(), layer.content.kind_name())));
     };
     let text = t.text.clone();
     let transform = t.transform;
diff --git a/crates/engine/src/type_cmds.rs b/crates/engine/src/type_cmds.rs
index e845b0acf3..6689ef8e00 100644
--- a/crates/engine/src/type_cmds.rs
+++ b/crates/engine/src/type_cmds.rs
@@ -418,7 +418,7 @@ fn with_text_layer<R>(s: &mut Session, p: &Value, label: &str, f: impl FnOnce(&m
         let l = doc.layer_mut(id).ok_or(EngineError::NoLayer(id))?;
         let auto_named = is_auto_named(l);
         let LayerContent::Text(t) = &mut l.content else {
-            return Err(EngineError::Other(format!("layer {} is a {} layer, not a type layer", id.0, l.content.kind_name())));
+            return Err(EngineError::Other(format!("layer {} is {} {} layer, not a type layer", id.0, l.content.article(), l.content.kind_name())));
         };
         let before = t.cache.as_ref().map(|c| c.tile_bounds());
         let mut rename = None;
diff --git a/crates/engine/src/type_extra_cmds.rs b/crates/engine/src/type_extra_cmds.rs
index 654cffe903..78c463d461 100644
--- a/crates/engine/src/type_extra_cmds.rs
+++ b/crates/engine/src/type_extra_cmds.rs
@@ -72,7 +72,7 @@ fn with_text<R>(s: &mut Session, p: &Value, label: &str, f: impl FnOnce(&mut Tex
         let l = doc.layer_mut(id).ok_or(EngineError::NoLayer(id))?;
         let auto_named = is_auto_named(l);
         let LayerContent::Text(t) = &mut l.content else {
-            return Err(EngineError::Other(format!("layer {} is a {} layer, not a type layer", id.0, l.content.kind_name())));
+            return Err(EngineError::Other(format!("layer {} is {} {} layer, not a type layer", id.0, l.content.article(), l.content.kind_name())));
         };
         let r = f(t, &snapshot)?;
         refresh(&snapshot, t);
diff --git a/crates/engine/src/vector_cmds.rs b/crates/engine/src/vector_cmds.rs
index a7e4f41c72..11ec80a436 100644
--- a/crates/engine/src/vector_cmds.rs
+++ b/crates/engine/src/vector_cmds.rs
@@ -503,7 +503,7 @@ fn shape_info(s: &Session, id: LayerId) -> Result<Value> {
     let d = s.active().ok_or(EngineError::NoDocument)?;
     let l = d.doc.layer(id).ok_or(EngineError::NoLayer(id))?;
     let LayerContent::Shape(sh) = &l.content else {
-        return Err(EngineError::Other(format!("layer {} is a {} layer, not a shape layer", id.0, l.content.kind_name())));
+        return Err(EngineError::Other(format!("layer {} is {} {} layer, not a shape layer", id.0, l.content.article(), l.content.kind_name())));
     };
     let bounds = sh.cache.as_ref().map(|c| c.content_bounds()).filter(|r| !r.is_empty()).map(|r| json!([r.x0, r.y0, r.width(), r.height()]));
     Ok(json!({
@@ -523,7 +523,7 @@ pub(crate) fn with_shape<R>(s: &mut Session, id: LayerId, label: &str, f: impl F
         let snapshot = doc.clone();
         let l = doc.layer_mut(id).ok_or(EngineError::NoLayer(id))?;
         if !matches!(l.content, LayerContent::Shape(_)) {
-            return Err(EngineError::Other(format!("layer {} is a {} layer, not a shape layer", id.0, l.content.kind_name())));
+            return Err(EngineError::Other(format!("layer {} is {} {} layer, not a shape layer", id.0, l.content.article(), l.content.kind_name())));
         }
         let LayerContent::Shape(mut sh) = std::mem::replace(&mut l.content, LayerContent::Fill(Fill::Solid(Color::BLACK))) else {
             return Err(EngineError::Other(format!("layer {} is not a shape layer", id.0)));
diff --git a/crates/engine/src/vp_cmds.rs b/crates/engine/src/vp_cmds.rs
index ec30a1f990..0c8cdbbec0 100644
--- a/crates/engine/src/vp_cmds.rs
+++ b/crates/engine/src/vp_cmds.rs
@@ -69,7 +69,7 @@ fn has_layer(s: &Session) -> std::result::Result<(), String> {
     let d = s.active().ok_or("no document open")?;
     match d.active_layer.and_then(|id| d.doc.layer(id)).map(|l| &l.content) {
         Some(LayerContent::Raster(_)) => Ok(()),
-        Some(other) => Err(format!("Vanishing Point needs a pixel layer (active layer is a {} layer)", other.kind_name())),
+        Some(other) => Err(format!("Vanishing Point needs a pixel layer (active layer is {} {} layer)", other.article(), other.kind_name())),
         None => Err("no active layer".into()),
     }
 }
diff --git a/crates/ui-egui/src/distort_ui.rs b/crates/ui-egui/src/distort_ui.rs
index c2ad3124a7..42b2329d6b 100644
--- a/crates/ui-egui/src/distort_ui.rs
+++ b/crates/ui-egui/src/distort_ui.rs
@@ -51,7 +51,7 @@ pub(crate) fn active_pixels(app: &PhotocraftApp) -> Result<(LayerId, Surface, bo
     match &l.content {
         LayerContent::Raster(s) => Ok((id, s.clone(), false)),
         LayerContent::Smart(sm) => sm.cache.clone().map(|c| (id, c, true)).ok_or_else(|| "the smart object has no pixels".to_string()),
-        other => Err(format!("needs a pixel layer or smart object (active layer is a {} layer)", other.kind_name())),
+        other => Err(format!("needs a pixel layer or smart object (active layer is {} {} layer)", other.article(), other.kind_name())),
     }
 }