diff --git a/locales/ar-SA/opencadstudio.ftl b/locales/ar-SA/opencadstudio.ftl
index 54486f961..e135b89d3 100644
--- a/locales/ar-SA/opencadstudio.ftl
+++ b/locales/ar-SA/opencadstudio.ftl
@@ -1625,6 +1625,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/bg-BG/opencadstudio.ftl b/locales/bg-BG/opencadstudio.ftl
index 80e2c2fb4..ce46a93f6 100644
--- a/locales/bg-BG/opencadstudio.ftl
+++ b/locales/bg-BG/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/cs-CZ/opencadstudio.ftl b/locales/cs-CZ/opencadstudio.ftl
index f33b4c5b7..85a433500 100644
--- a/locales/cs-CZ/opencadstudio.ftl
+++ b/locales/cs-CZ/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/de-DE/opencadstudio.ftl b/locales/de-DE/opencadstudio.ftl
index 49488dc70..5bf936ee4 100644
--- a/locales/de-DE/opencadstudio.ftl
+++ b/locales/de-DE/opencadstudio.ftl
@@ -1613,6 +1613,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/el-GR/opencadstudio.ftl b/locales/el-GR/opencadstudio.ftl
index 2271ec48d..acf6e2b58 100644
--- a/locales/el-GR/opencadstudio.ftl
+++ b/locales/el-GR/opencadstudio.ftl
@@ -1614,6 +1614,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/en-US/opencadstudio.ftl b/locales/en-US/opencadstudio.ftl
index fc6f231cd..236b34ea8 100644
--- a/locales/en-US/opencadstudio.ftl
+++ b/locales/en-US/opencadstudio.ftl
@@ -1613,6 +1613,8 @@ common =
     .window-selection-color = Window selection color
     .crossing-selection-color = Crossing selection color
     .selection-highlight-color = Selection highlight color
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = Grip Settings
     .grip-size = Grip size
     .unselected-grip-color = Unselected grip color
diff --git a/locales/es-ES/opencadstudio.ftl b/locales/es-ES/opencadstudio.ftl
index 70d2c59a0..842c132a1 100644
--- a/locales/es-ES/opencadstudio.ftl
+++ b/locales/es-ES/opencadstudio.ftl
@@ -1613,6 +1613,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/fi-FI/opencadstudio.ftl b/locales/fi-FI/opencadstudio.ftl
index e4a72c32f..419dfaa62 100644
--- a/locales/fi-FI/opencadstudio.ftl
+++ b/locales/fi-FI/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/fr-FR/opencadstudio.ftl b/locales/fr-FR/opencadstudio.ftl
index 02d85d828..738a361e4 100644
--- a/locales/fr-FR/opencadstudio.ftl
+++ b/locales/fr-FR/opencadstudio.ftl
@@ -1613,6 +1613,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/hi-IN/opencadstudio.ftl b/locales/hi-IN/opencadstudio.ftl
index 58492873c..ad0634ff0 100644
--- a/locales/hi-IN/opencadstudio.ftl
+++ b/locales/hi-IN/opencadstudio.ftl
@@ -1601,6 +1601,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/hu-HU/opencadstudio.ftl b/locales/hu-HU/opencadstudio.ftl
index 0a3492b63..2d788cda8 100644
--- a/locales/hu-HU/opencadstudio.ftl
+++ b/locales/hu-HU/opencadstudio.ftl
@@ -1618,6 +1618,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/it-IT/opencadstudio.ftl b/locales/it-IT/opencadstudio.ftl
index 228cd874d..73f7fc2a1 100644
--- a/locales/it-IT/opencadstudio.ftl
+++ b/locales/it-IT/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/ja-JP/opencadstudio.ftl b/locales/ja-JP/opencadstudio.ftl
index be823af57..8c496cfa7 100644
--- a/locales/ja-JP/opencadstudio.ftl
+++ b/locales/ja-JP/opencadstudio.ftl
@@ -1603,6 +1603,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/ko-KR/opencadstudio.ftl b/locales/ko-KR/opencadstudio.ftl
index ec8f98f83..5828cb7cd 100644
--- a/locales/ko-KR/opencadstudio.ftl
+++ b/locales/ko-KR/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/lo-LA/opencadstudio.ftl b/locales/lo-LA/opencadstudio.ftl
index 786bbc3e1..9cbd0f602 100644
--- a/locales/lo-LA/opencadstudio.ftl
+++ b/locales/lo-LA/opencadstudio.ftl
@@ -1618,6 +1618,8 @@ common =
     .window-selection-color = ສີການເລືອກແບບ Window
     .crossing-selection-color = ສີການເລືອກແບບ Crossing
     .selection-highlight-color = ສີການເນັ້ນການເລືອກ
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = ການຕັ້ງຄ່າຈຸດກຣິບ
     .grip-size = ຂະໜາດຈຸດກຣິບ
     .unselected-grip-color = ສີຈຸດກຣິບທີ່ບໍ່ໄດ້ເລືອກ
diff --git a/locales/nl-NL/opencadstudio.ftl b/locales/nl-NL/opencadstudio.ftl
index 308cba371..0e833a32c 100644
--- a/locales/nl-NL/opencadstudio.ftl
+++ b/locales/nl-NL/opencadstudio.ftl
@@ -1611,6 +1611,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/pl-PL/opencadstudio.ftl b/locales/pl-PL/opencadstudio.ftl
index d0bc3dc97..a8c680f87 100644
--- a/locales/pl-PL/opencadstudio.ftl
+++ b/locales/pl-PL/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/pt-BR/opencadstudio.ftl b/locales/pt-BR/opencadstudio.ftl
index 6ca88dd6a..ee9061395 100644
--- a/locales/pt-BR/opencadstudio.ftl
+++ b/locales/pt-BR/opencadstudio.ftl
@@ -1613,6 +1613,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/ru-RU/opencadstudio.ftl b/locales/ru-RU/opencadstudio.ftl
index 10a5f642d..f432c23e7 100644
--- a/locales/ru-RU/opencadstudio.ftl
+++ b/locales/ru-RU/opencadstudio.ftl
@@ -1616,6 +1616,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/tr-TR/opencadstudio.ftl b/locales/tr-TR/opencadstudio.ftl
index 189759229..d9fd70437 100644
--- a/locales/tr-TR/opencadstudio.ftl
+++ b/locales/tr-TR/opencadstudio.ftl
@@ -1599,6 +1599,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/zh-CN/opencadstudio.ftl b/locales/zh-CN/opencadstudio.ftl
index 9751345d2..5c90421f8 100644
--- a/locales/zh-CN/opencadstudio.ftl
+++ b/locales/zh-CN/opencadstudio.ftl
@@ -1600,6 +1600,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/locales/zh-TW/opencadstudio.ftl b/locales/zh-TW/opencadstudio.ftl
index 8febd85e8..2e7b7164b 100644
--- a/locales/zh-TW/opencadstudio.ftl
+++ b/locales/zh-TW/opencadstudio.ftl
@@ -1612,6 +1612,8 @@ common =
     .window-selection-color = { common.selection }: { common.window }: { common.color }
     .crossing-selection-color = { common.selection }: { common.crossing }: { common.color }
     .selection-highlight-color = { common.selection }: { common.highlight }: { common.color }
+    .selection-highlight-opacity = Selection highlight opacity
+    .selection-highlight-extra-width = Selection highlight extra width
     .grip-settings = { common.grips }: { properties.settings }
     .grip-size = { common.grips }: { common.size }
     .unselected-grip-color = { common.grips }: { common.unselected }: { common.color }
diff --git a/src/app/config.rs b/src/app/config.rs
index 408fa6679..3f8b8f534 100644
--- a/src/app/config.rs
+++ b/src/app/config.rs
@@ -357,6 +357,11 @@ pub struct ModelSpaceThemeConfig {
     pub selection_crossing_color: u8,
     /// SELECTIONEFFECTCOLOR: ACI index for selected entities highlight (0 = Theme Primary, 1..=255 = ACI).
     pub selection_highlight_color: u8,
+    /// Selection highlight opacity in percent (10–100); below 100 the
+    /// object's own colour shows through.
+    pub selection_highlight_opacity: u8,
+    /// Extra screen pixels the selection highlight is drawn wider (0–6).
+    pub selection_highlight_widen: u8,
     /// SELECTIONEFFECT: whether selected objects glow with solid highlight (true) or dash (false).
     pub selection_effect: bool,
     /// SELECTIONPREVIEW bitmask: 1 = idle, 2 = during a command, 3 = both.
@@ -386,6 +391,8 @@ impl Default for ModelSpaceThemeConfig {
             selection_window_color: 0,
             selection_crossing_color: 0,
             selection_highlight_color: 0,
+            selection_highlight_opacity: 100,
+            selection_highlight_widen: 0,
             selection_effect: true,
             selection_preview: 3,
             grip_size: 5,
@@ -437,15 +444,13 @@ impl ModelSpaceThemeConfig {
 
     /// Resolve active selection highlight overlay color as [f32; 4].
     pub fn resolve_selection_color(&self) -> [f32; 4] {
-        if self.selection_highlight_color == 0 {
-            crate::scene::model::wire_model::WireModel::SELECTED
-        } else if let Some((r, g, b)) =
-            codec::types::aci_table::aci_to_rgb(self.selection_highlight_color)
-        {
-            [r as f32 / 255.0, g as f32 / 255.0, b as f32 / 255.0, 1.0]
-        } else {
-            crate::scene::model::wire_model::WireModel::SELECTED
-        }
+        let mut color = codec::types::aci_table::aci_to_rgb(self.selection_highlight_color)
+            .filter(|_| self.selection_highlight_color != 0)
+            .map_or(crate::scene::model::wire_model::WireModel::SELECTED, |(r, g, b)| {
+                [r as f32 / 255.0, g as f32 / 255.0, b as f32 / 255.0, 1.0]
+            });
+        color[3] = f32::from(self.selection_highlight_opacity.clamp(10, 100)) / 100.0;
+        color
     }
 }
 
diff --git a/src/app/mod.rs b/src/app/mod.rs
index 163dabb90..f81649499 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -2674,6 +2674,8 @@ pub enum Message {
     SelectionAreaToggled(bool),
     /// Change Selection Area opacity percentage (0–100, SELECTIONAREAOPACITY).
     SelectionOpacityChanged(u8),
+    SelectionHighlightOpacityChanged(u8),
+    SelectionHighlightWidenChanged(u8),
     /// Change Window selection color ACI index (0 = Theme Primary, 1..=255 = ACI).
     SelectionWindowColorChanged(u8),
     /// Change Crossing selection color ACI index (0 = Theme Success, 1..=255 = ACI).
diff --git a/src/app/update/file.rs b/src/app/update/file.rs
index 5a8ba9737..fecfbb10f 100644
--- a/src/app/update/file.rs
+++ b/src/app/update/file.rs
@@ -1278,6 +1278,9 @@ impl OpenCADStudio {
             return;
         }
         tab.scene.model_lineweight_scale = self.lineweight_display_scale as f32 / 100.0;
+        tab.scene.selection_color = self.model_space.resolve_selection_color();
+        tab.scene.selection_effect = self.model_space.selection_effect;
+        tab.scene.selection_widen = f32::from(self.model_space.selection_highlight_widen.min(6));
         if bg.is_none() && paper_bg.is_none() {
             return;
         }
@@ -1551,6 +1554,7 @@ impl OpenCADStudio {
         let paper_bg = self.model_space.resolve_paper_bg();
         let sel_color = self.model_space.resolve_selection_color();
         let sel_effect = self.model_space.selection_effect;
+        let sel_widen = f32::from(self.model_space.selection_highlight_widen.min(6));
         self.default_bg_color = Some(model_bg);
         self.default_paper_bg_color = Some(paper_bg);
 
@@ -1563,10 +1567,14 @@ impl OpenCADStudio {
             tab.scene.paper_bg_color = paper_bg;
             tab.scene.selection_color = sel_color;
             tab.scene.selection_effect = sel_effect;
+            let old_sel_widen = std::mem::replace(&mut tab.scene.selection_widen, sel_widen);
             tab.bg_color = Some(model_bg);
             tab.paper_bg_color = Some(paper_bg);
 
-            if old_sel_color != sel_color || old_sel_effect != sel_effect {
+            if old_sel_color != sel_color
+                || old_sel_effect != sel_effect
+                || old_sel_widen != sel_widen
+            {
                 tab.scene.selection_generation = tab.scene.selection_generation.wrapping_add(1);
             }
 
diff --git a/src/app/update/mod.rs b/src/app/update/mod.rs
index ed713554c..b0e36bbe5 100644
--- a/src/app/update/mod.rs
+++ b/src/app/update/mod.rs
@@ -9175,6 +9175,20 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::SelectionHighlightOpacityChanged(opacity) => {
+                self.model_space.selection_highlight_opacity = opacity.clamp(10, 100);
+                self.sync_model_space_theme(false);
+                self.persist_settings_if_changed();
+                Task::none()
+            }
+
+            Message::SelectionHighlightWidenChanged(widen) => {
+                self.model_space.selection_highlight_widen = widen.min(6);
+                self.sync_model_space_theme(false);
+                self.persist_settings_if_changed();
+                Task::none()
+            }
+
             Message::GripSizeChanged(size) => {
                 self.model_space.grip_size = size.clamp(1, 25);
                 self.sync_model_space_theme(false);
diff --git a/src/locale_catalog.rs b/src/locale_catalog.rs
index e367c7b5c..33b411619 100644
--- a/src/locale_catalog.rs
+++ b/src/locale_catalog.rs
@@ -5183,6 +5183,10 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "Window selection color" => Some(("common", "window-selection-color")),
         "Crossing selection color" => Some(("common", "crossing-selection-color")),
         "Selection highlight color" => Some(("common", "selection-highlight-color")),
+        "Selection highlight opacity" => Some(("common", "selection-highlight-opacity")),
+        "Selection highlight extra width" => {
+            Some(("common", "selection-highlight-extra-width"))
+        }
         "Grip Settings" => Some(("common", "grip-settings")),
         "Grip size" => Some(("common", "grip-size")),
         "Unselected grip color" => Some(("common", "unselected-grip-color")),
diff --git a/src/scene/mod.rs b/src/scene/mod.rs
index 5a070a2d8..d90117db5 100644
--- a/src/scene/mod.rs
+++ b/src/scene/mod.rs
@@ -2204,6 +2204,8 @@ pub struct Scene {
     pub selection_color: [f32; 4],
     /// Whether selection visual effect (glow/highlight) is enabled (SELECTIONEFFECT).
     pub selection_effect: bool,
+    /// Extra screen pixels the selection highlight is drawn wider.
+    pub selection_widen: f32,
     /// Whether entity transparency is honoured on screen. When false the
     /// wire shader forces every line opaque (a uniform toggle, no retessellate).
     pub transparency_display: bool,
@@ -2827,6 +2829,7 @@ impl Scene {
             constraint_hover_refs: Vec::new(),
             constraint_hover_wires: Vec::new(),
             selection_color: crate::scene::model::wire_model::WireModel::SELECTED,
+            selection_widen: 0.0,
             selection_effect: true,
             transparency_display: true,
             model_lineweight_scale: 1.0,
diff --git a/src/scene/pipeline/mod.rs b/src/scene/pipeline/mod.rs
index f669d3267..466877e15 100644
--- a/src/scene/pipeline/mod.rs
+++ b/src/scene/pipeline/mod.rs
@@ -182,6 +182,10 @@ pub struct Pipeline {
     uniform_buffer: wgpu::Buffer,
     frame_bgl: wgpu::BindGroupLayout,
     uniform_bind_group: wgpu::BindGroup,
+    /// The selection overlay's copy of the frame uniforms: transparency on,
+    /// so a translucent highlight colour shows, and lines widened.
+    selection_uniform_buffer: wgpu::Buffer,
+    selection_uniform_bind_group: wgpu::BindGroup,
     shadow_uniform_bind_group: wgpu::BindGroup,
     background_texture: wgpu::Texture,
     environment_texture: wgpu::Texture,
@@ -414,6 +418,37 @@ pub struct Pipeline {
     pub slot_id: u64,
 }
 
+/// The views and samplers the frame bind group carries beside its uniforms.
+struct FrameViews<'a> {
+    background: &'a wgpu::TextureView,
+    environment: &'a wgpu::TextureView,
+    background_sampler: &'a wgpu::Sampler,
+    shadow: &'a wgpu::TextureView,
+    shadow_sampler: &'a wgpu::Sampler,
+}
+
+fn frame_bind_group(
+    device: &wgpu::Device,
+    layout: &wgpu::BindGroupLayout,
+    uniforms: &wgpu::Buffer,
+    views: &FrameViews<'_>,
+) -> wgpu::BindGroup {
+    let entry = |binding, resource| wgpu::BindGroupEntry { binding, resource };
+    device.create_bind_group(&wgpu::BindGroupDescriptor {
+        label: Some("viewer.bind_group"),
+        layout,
+        entries: &[
+            entry(0, uniforms.as_entire_binding()),
+            entry(1, wgpu::BindingResource::TextureView(views.background)),
+            entry(2, wgpu::BindingResource::Sampler(views.background_sampler)),
+            entry(3, wgpu::BindingResource::TextureView(views.environment)),
+            entry(4, wgpu::BindingResource::Sampler(views.background_sampler)),
+            entry(5, wgpu::BindingResource::TextureView(views.shadow)),
+            entry(6, wgpu::BindingResource::Sampler(views.shadow_sampler)),
+        ],
+    })
+}
+
 impl Pipeline {
     pub fn new(device: &wgpu::Device, queue: &wgpu::Queue, format: wgpu::TextureFormat) -> Self {
         // ── Shared frame uniform buffer (view_proj etc.) ───────────────────
@@ -423,6 +458,12 @@ impl Pipeline {
             usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
             mapped_at_creation: false,
         });
+        let selection_uniform_buffer = device.create_buffer(&wgpu::BufferDescriptor {
+            label: Some("viewer.selection_uniform_buffer"),
+            size: std::mem::size_of::<Uniforms>() as u64,
+            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+            mapped_at_creation: false,
+        });
 
         // Bind group layout 0 — shared by wire and hatch pipelines.
         let frame_bgl = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
@@ -563,40 +604,17 @@ impl Pipeline {
             background_texture.create_view(&wgpu::TextureViewDescriptor::default());
         let environment_view =
             environment_texture.create_view(&wgpu::TextureViewDescriptor::default());
-        let uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
-            label: Some("viewer.bind_group"),
-            layout: &frame_bgl,
-            entries: &[
-                wgpu::BindGroupEntry {
-                    binding: 0,
-                    resource: uniform_buffer.as_entire_binding(),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 1,
-                    resource: wgpu::BindingResource::TextureView(&background_view),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 2,
-                    resource: wgpu::BindingResource::Sampler(&background_sampler),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 3,
-                    resource: wgpu::BindingResource::TextureView(&environment_view),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 4,
-                    resource: wgpu::BindingResource::Sampler(&background_sampler),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 5,
-                    resource: wgpu::BindingResource::TextureView(&shadow_fallback_view),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 6,
-                    resource: wgpu::BindingResource::Sampler(&shadow_sampler),
-                },
-            ],
-        });
+        let frame_views = FrameViews {
+            background: &background_view,
+            environment: &environment_view,
+            background_sampler: &background_sampler,
+            shadow: &shadow_fallback_view,
+            shadow_sampler: &shadow_sampler,
+        };
+        let uniform_bind_group =
+            frame_bind_group(device, &frame_bgl, &uniform_buffer, &frame_views);
+        let selection_uniform_bind_group =
+            frame_bind_group(device, &frame_bgl, &selection_uniform_buffer, &frame_views);
         let shadow_uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
             label: Some("shadow.frame_bind_group"),
             layout: &shadow_frame_bgl,
@@ -2390,6 +2408,8 @@ impl Pipeline {
             uniform_buffer,
             frame_bgl,
             uniform_bind_group,
+            selection_uniform_buffer,
+            selection_uniform_bind_group,
             shadow_uniform_bind_group,
             background_texture,
             environment_texture,
@@ -3926,40 +3946,18 @@ analytic={:.1} regular={:.1} blocks={:.1}",
         let environment_view = self
             .environment_texture
             .create_view(&wgpu::TextureViewDescriptor::default());
-        self.uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
-            label: Some("viewer.bind_group"),
-            layout: &self.frame_bgl,
-            entries: &[
-                wgpu::BindGroupEntry {
-                    binding: 0,
-                    resource: self.uniform_buffer.as_entire_binding(),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 1,
-                    resource: wgpu::BindingResource::TextureView(&background_view),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 2,
-                    resource: wgpu::BindingResource::Sampler(&self.background_sampler),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 3,
-                    resource: wgpu::BindingResource::TextureView(&environment_view),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 4,
-                    resource: wgpu::BindingResource::Sampler(&self.background_sampler),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 5,
-                    resource: wgpu::BindingResource::TextureView(self.shadow_view()),
-                },
-                wgpu::BindGroupEntry {
-                    binding: 6,
-                    resource: wgpu::BindingResource::Sampler(&self.shadow_sampler),
-                },
-            ],
-        });
+        let views = FrameViews {
+            background: &background_view,
+            environment: &environment_view,
+            background_sampler: &self.background_sampler,
+            shadow: self.shadow_view(),
+            shadow_sampler: &self.shadow_sampler,
+        };
+        let frame = frame_bind_group(device, &self.frame_bgl, &self.uniform_buffer, &views);
+        let selection =
+            frame_bind_group(device, &self.frame_bgl, &self.selection_uniform_buffer, &views);
+        self.uniform_bind_group = frame;
+        self.selection_uniform_bind_group = selection;
     }
 
     /// Allocate or drop the shadow target to match `shadow_enabled`.
@@ -3995,7 +3993,11 @@ analytic={:.1} regular={:.1} blocks={:.1}",
         if self.shadow_full.is_none() {
             uniforms.shadow_params[0] = 0.0;
         }
+        let mut selection = uniforms;
+        selection.transparency_enable = 1.0;
+        uniforms.highlight_widen = 0.0;
         queue.write_buffer(&self.uniform_buffer, 0, bytemuck::bytes_of(&uniforms));
+        queue.write_buffer(&self.selection_uniform_buffer, 0, bytemuck::bytes_of(&selection));
     }
 
     pub fn upload_background_images(
@@ -5120,7 +5122,7 @@ analytic={:.1} regular={:.1} blocks={:.1}",
                     multiview_mask: None,
                 });
                 pass.set_viewport(raster.x, raster.y, raster.width, raster.height, 0.0, 1.0);
-                pass.set_bind_group(0, &self.uniform_bind_group, &[]);
+                pass.set_bind_group(0, &self.selection_uniform_bind_group, &[]);
                 pass.set_stencil_reference(stencil_ref);
                 if !self.gpu_selected_wires.is_empty() {
                     pass.set_pipeline(if occluded {
@@ -5160,7 +5162,7 @@ analytic={:.1} regular={:.1} blocks={:.1}",
                     } else {
                         &self.circle_xray_pipeline
                     });
-                    pass.set_bind_group(0, &self.uniform_bind_group, &[]);
+                    pass.set_bind_group(0, &self.selection_uniform_bind_group, &[]);
                     for cg in &self.gpu_selected_circles {
                         if cg.instance_count > 0 {
                             pass.set_vertex_buffer(0, cg.instance_buffer.slice(..));
@@ -5174,7 +5176,7 @@ analytic={:.1} regular={:.1} blocks={:.1}",
                     } else {
                         &self.ellipse_xray_pipeline
                     });
-                    pass.set_bind_group(0, &self.uniform_bind_group, &[]);
+                    pass.set_bind_group(0, &self.selection_uniform_bind_group, &[]);
                     for eg in &self.gpu_selected_ellipses {
                         if eg.instance_count > 0 {
                             pass.set_vertex_buffer(0, eg.instance_buffer.slice(..));
diff --git a/src/scene/pipeline/uniforms.rs b/src/scene/pipeline/uniforms.rs
index 06cb0cc1e..fe84756e9 100644
--- a/src/scene/pipeline/uniforms.rs
+++ b/src/scene/pipeline/uniforms.rs
@@ -39,7 +39,9 @@ pub struct Uniforms {
     // jitter.
     pub view_rot: glam::Mat4,
     pub eye_high: [f32; 3],
-    pub _pad_eh: f32,
+    /// Extra screen pixels added to every line width. Only the selection
+    /// overlay pass sees a non-zero value (`Pipeline::upload_uniforms`).
+    pub highlight_widen: f32,
     pub eye_low: [f32; 3],
     pub _pad_el: f32,
 
@@ -121,7 +123,7 @@ impl Uniforms {
             lineweight_scale: 1.0,
             view_rot: camera.view_proj_rte(bounds),
             eye_high,
-            _pad_eh: 0.0,
+            highlight_widen: 0.0,
             eye_low,
             _pad_el: 0.0,
             light_position_type: [[0.0; 4]; 4],
diff --git a/src/scene/view/render.rs b/src/scene/view/render.rs
index c42d93184..bf035050f 100644
--- a/src/scene/view/render.rs
+++ b/src/scene/view/render.rs
@@ -270,6 +270,8 @@ pub struct Primitive {
     pub(in crate::scene) selection_color: [f32; 4],
     /// Whether selection visual effect (glow/highlight) is enabled.
     pub(in crate::scene) selection_effect: bool,
+    /// Extra screen pixels the selection highlight is drawn wider.
+    pub(in crate::scene) selection_widen: f32,
     /// One input-to-render sample, carried only when PERF tracing is enabled.
     pub(in crate::scene) nav_perf: Option<NavPerfSample>,
 }
@@ -4298,6 +4300,7 @@ impl Scene {
             viewcube_text_color,
             selection_color: self.selection_color,
             selection_effect: self.selection_effect,
+            selection_widen: self.selection_widen,
             nav_perf: perf_nav,
         }
     }
@@ -4330,6 +4333,7 @@ impl Scene {
                 viewcube_text_color,
                 selection_color: self.selection_color,
                 selection_effect: self.selection_effect,
+                selection_widen: self.selection_widen,
                 nav_perf: None,
             };
         };
@@ -4392,6 +4396,7 @@ impl Scene {
             viewcube_text_color,
             selection_color: self.selection_color,
             selection_effect: self.selection_effect,
+            selection_widen: self.selection_widen,
             nav_perf: perf_nav,
         }
     }
@@ -4688,6 +4693,7 @@ impl Scene {
         uniforms.viewport_size = [visible_w, visible_h];
         uniforms.flat_shade = if flags.flat_shade { 1.0 } else { 0.0 };
         uniforms.transparency_enable = if self.transparency_display { 1.0 } else { 0.0 };
+        uniforms.highlight_widen = self.selection_widen;
         uniforms.viewport_background = display.background.base;
         uniforms.view_tone = [display.brightness, display.contrast, 0.0, 0.0];
         uniforms.background_top = display.background.colors[0];
diff --git a/src/shaders/block_wire.wgsl b/src/shaders/block_wire.wgsl
index 8399a2c2f..cca43637f 100644
--- a/src/shaders/block_wire.wgsl
+++ b/src/shaders/block_wire.wgsl
@@ -8,7 +8,7 @@ struct Uniforms {
     lineweight_scale: f32,
     view_rot: mat4x4<f32>,
     eye_high: vec3<f32>,
-    _pad_eh: f32,
+    highlight_widen: f32,
     eye_low: vec3<f32>,
     _pad_el: f32,
 }
@@ -63,7 +63,13 @@ struct VertexOut {
     @location(9) @interpolate(flat) cap_ends: vec3<f32>,
 }
 
+// The selection pass widens highlighted lines by `highlight_widen` pixels;
+// every other pass uploads zero.
 fn resolve_hw(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
+    return resolve_hw_base(taper_ratio, world_hw, px_hw) + u.highlight_widen * 0.5;
+}
+
+fn resolve_hw_base(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
     if taper_ratio > 0.0 {
         return max((taper_ratio * world_hw) / u.world_per_pixel, 0.5);
     }
diff --git a/src/shaders/block_wire_storage.wgsl b/src/shaders/block_wire_storage.wgsl
index ebb5a7ea6..e79268b23 100644
--- a/src/shaders/block_wire_storage.wgsl
+++ b/src/shaders/block_wire_storage.wgsl
@@ -27,7 +27,7 @@ struct Uniforms {
     lineweight_scale: f32,
     view_rot: mat4x4<f32>,
     eye_high: vec3<f32>,
-    _pad_eh: f32,
+    highlight_widen: f32,
     eye_low: vec3<f32>,
     _pad_el: f32,
 }
@@ -87,7 +87,13 @@ struct VertexOut {
     @location(9) @interpolate(flat) cap_ends: vec3<f32>,
 }
 
+// The selection pass widens highlighted lines by `highlight_widen` pixels;
+// every other pass uploads zero.
 fn resolve_hw(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
+    return resolve_hw_base(taper_ratio, world_hw, px_hw) + u.highlight_widen * 0.5;
+}
+
+fn resolve_hw_base(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
     if taper_ratio > 0.0 {
         return max((taper_ratio * world_hw) / u.world_per_pixel, 0.5);
     }
diff --git a/src/shaders/circle.wgsl b/src/shaders/circle.wgsl
index ef6bbf99d..c923c112f 100644
--- a/src/shaders/circle.wgsl
+++ b/src/shaders/circle.wgsl
@@ -20,7 +20,7 @@ struct Uniforms {
     // Relative-to-eye (double-single)
     view_rot:            mat4x4<f32>,
     eye_high:            vec3<f32>,
-    _pad_eh:             f32,
+    highlight_widen:             f32,
     eye_low:             vec3<f32>,
     _pad_el:             f32,
 }
@@ -56,7 +56,13 @@ struct VertexOut {
     @location(10) @interpolate(flat) is_world:     f32,
 }
 
+// The selection pass widens highlighted lines by `highlight_widen` pixels;
+// every other pass uploads zero.
 fn resolve_px_hw(px_hw: f32) -> f32 {
+    return resolve_px_hw_base(px_hw) + u.highlight_widen * 0.5;
+}
+
+fn resolve_px_hw_base(px_hw: f32) -> f32 {
     var display_hw = max(px_hw * u.lineweight_scale, 0.5);
     if u.lineweight_scale < 0.0 {
         let scale = -u.lineweight_scale;
diff --git a/src/shaders/ellipse.wgsl b/src/shaders/ellipse.wgsl
index 2fbe20ab5..ee6bc13e4 100644
--- a/src/shaders/ellipse.wgsl
+++ b/src/shaders/ellipse.wgsl
@@ -15,7 +15,7 @@ struct Uniforms {
     // Relative-to-eye (double-single)
     view_rot:            mat4x4<f32>,
     eye_high:            vec3<f32>,
-    _pad_eh:             f32,
+    highlight_widen:             f32,
     eye_low:             vec3<f32>,
     _pad_el:             f32,
 }
@@ -50,7 +50,13 @@ struct VertexOut {
     @location(9) @interpolate(flat) end_param:   f32,
 }
 
+// The selection pass widens highlighted lines by `highlight_widen` pixels;
+// every other pass uploads zero.
 fn resolve_hw(px_hw: f32) -> f32 {
+    return resolve_hw_base(px_hw) + u.highlight_widen * 0.5;
+}
+
+fn resolve_hw_base(px_hw: f32) -> f32 {
     var display_hw = max(px_hw * u.lineweight_scale, 0.5);
     if u.lineweight_scale < 0.0 {
         let scale = -u.lineweight_scale;
diff --git a/src/shaders/wire.wgsl b/src/shaders/wire.wgsl
index 4d312896f..40c0d5730 100644
--- a/src/shaders/wire.wgsl
+++ b/src/shaders/wire.wgsl
@@ -37,7 +37,7 @@ struct Uniforms {
     // jitter on pan / zoom / rotate.
     view_rot:         mat4x4<f32>,
     eye_high:         vec3<f32>,
-    _pad_eh:          f32,
+    highlight_widen:          f32,
     eye_low:          vec3<f32>,
     _pad_el:          f32,
 }
@@ -98,7 +98,13 @@ struct VertexOut {
 // Half-width of one segment end: a tapered band's own end width wins, then a
 // constant world-unit band, then the screen-pixel lineweight (LWDISPLAY off
 // collapses to a hairline).
+// The selection pass widens highlighted lines by `highlight_widen` pixels;
+// every other pass uploads zero.
 fn resolve_hw(taper: f32, world_hw: f32, px_hw: f32) -> f32 {
+    return resolve_hw_base(taper, world_hw, px_hw) + u.highlight_widen * 0.5;
+}
+
+fn resolve_hw_base(taper: f32, world_hw: f32, px_hw: f32) -> f32 {
     if taper >= 0.0 { return max(taper / u.world_per_pixel, 0.5); }
     if world_hw > 0.0 { return max(world_hw / u.world_per_pixel, 0.5); }
     if world_hw < 0.0 { return max(-world_hw, 0.5); }
diff --git a/src/shaders/wire_indexed.wgsl b/src/shaders/wire_indexed.wgsl
index 162fdbcd2..e7b7722fe 100644
--- a/src/shaders/wire_indexed.wgsl
+++ b/src/shaders/wire_indexed.wgsl
@@ -15,7 +15,7 @@ struct Uniforms {
     lineweight_scale: f32,
     view_rot:         mat4x4<f32>,
     eye_high:         vec3<f32>,
-    _pad_eh:          f32,
+    highlight_widen:          f32,
     eye_low:          vec3<f32>,
     _pad_el:          f32,
 }
@@ -79,7 +79,13 @@ struct VertexOut {
 // Half-width of one segment end: a tapered band's own end width wins, then a
 // constant world-unit band, then the screen-pixel lineweight (LWDISPLAY off
 // collapses to a hairline).
+// The selection pass widens highlighted lines by `highlight_widen` pixels;
+// every other pass uploads zero.
 fn resolve_hw(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
+    return resolve_hw_base(taper_ratio, world_hw, px_hw) + u.highlight_widen * 0.5;
+}
+
+fn resolve_hw_base(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
     if taper_ratio > 0.0 {
         return max((taper_ratio * world_hw) / u.world_per_pixel, 0.5);
     }
diff --git a/src/ui/window/options.rs b/src/ui/window/options.rs
index 87318baba..a28174dea 100644
--- a/src/ui/window/options.rs
+++ b/src/ui/window/options.rs
@@ -1120,6 +1120,38 @@ pub fn view_window<'a>(
         ]
         .spacing(10)
         .align_y(iced::Center),
+        Space::new().height(10),
+        row![
+            text(crate::t!("Selection highlight opacity")).size(12).width(140),
+            slider(
+                10..=100,
+                model_space.selection_highlight_opacity.clamp(10, 100),
+                Message::SelectionHighlightOpacityChanged,
+            )
+            .step(5)
+            .width(Fill),
+            text(format!("{}%", model_space.selection_highlight_opacity.clamp(10, 100)))
+                .size(11)
+                .width(44),
+        ]
+        .spacing(10)
+        .align_y(iced::Center),
+        Space::new().height(10),
+        row![
+            text(crate::t!("Selection highlight extra width")).size(12).width(140),
+            slider(
+                0..=6,
+                model_space.selection_highlight_widen.min(6),
+                Message::SelectionHighlightWidenChanged,
+            )
+            .step(1)
+            .width(Fill),
+            text(format!("{} px", model_space.selection_highlight_widen.min(6)))
+                .size(11)
+                .width(44),
+        ]
+        .spacing(10)
+        .align_y(iced::Center),
         Space::new().height(24),
         text(crate::t!("Preview")).size(15),
         Space::new().height(10),