diff --git a/settings/hyprland.nix b/settings/hyprland.nix
index da7c6ab..df0f350 100644
--- a/settings/hyprland.nix
+++ b/settings/hyprland.nix
@@ -3,6 +3,7 @@
 let
   isMacbook = config.networking.hostName == "FredOS-Macbook";
   isGaming  = !isMacbook;
+  ui = import ./ui.nix;   # shared corner-rounding knob
 
 in
 {
@@ -114,7 +115,8 @@ in
             };
 
             decoration = {
-              rounding = 8;
+              # tracks Theme.radius via settings/ui.nix
+              rounding = ui.radius;
               blur = {
                 enabled = true;
                 size = 1;
diff --git a/settings/quickshell.nix b/settings/quickshell.nix
index 151ab21..9ba2299 100644
--- a/settings/quickshell.nix
+++ b/settings/quickshell.nix
@@ -4,6 +4,7 @@
 { config, pkgs, lib, ... }:
 let
   isMacbook = config.networking.hostName == "FredOS-Macbook";
+  ui = import ./ui.nix;   # shared corner-rounding knob
 in
 {
   config = lib.mkIf (lib.elem config.networking.hostName [ "FredOS-Gaming" "FredOS-Macbook" ]) {
@@ -180,9 +181,19 @@ in
                 // here, not in ~15 places. Wide enough for the stacked HH/mm
                 // clock, which is what sets the floor.
                 readonly property int barWidth: 46
-                readonly property int radius: 32       // cards, panels, dropdowns
-                readonly property int radiusSmall: 24  // workspace dots, pill buttons
-                readonly property int radiusTiny: 16   // hover rows, action chips
+                // ── Rounding. ONE knob: settings/ui.nix `radius`. Everything
+                // below derives from it, and hyprland's window rounding reads
+                // the same value, so changing that one number rescales the
+                // roundness of the entire desktop.
+                readonly property int radius: ${toString ui.radius}   // panels, dropdowns, screen cutout
+                // Concentric, NOT a factor: a card inside a panel needs the
+                // panel's radius MINUS the gap between them. Give it the same
+                // radius as its container and the inner corner is over-round
+                // for its size — the card reads as inflated/balloon-like,
+                // invisible at r=8 and obvious by r=32.
+                readonly property int radiusCard: radius - panelGap
+                readonly property int radiusSmall: Math.round(radius * 0.75) // pill buttons, workspace dots
+                readonly property int radiusTiny: Math.round(radius * 0.5)   // hover rows, action chips
                 readonly property int cardPad: 8       // card inner padding (inset = 2×)
                 readonly property int panelGap: 8      // gap between panel border and cards (all dropdowns/menus/toast)
 
@@ -311,7 +322,7 @@ in
                             anchors.horizontalCenter: parent.horizontalCenter
                             width: 280
                             height: 44
-                            radius: Theme.radius
+                            radius: Theme.radiusCard
                             color: Theme.cardBg
                             border.width: Theme.borderWidth
                             border.color: pam.active ? Theme.base0D
@@ -744,7 +755,7 @@ in
                 component Card: Rectangle {
                     default property alias cardData: _cardCol.data
                     property alias cardSpacing: _cardCol.spacing
-                    radius: Theme.radius
+                    radius: Theme.radiusCard
                     color: Theme.cardBg
                     implicitHeight: _cardCol.height + 2 * Theme.cardPad
                     Column {
@@ -1110,7 +1121,7 @@ in
                             Rectangle {
                                 width: parent.width
                                 height: launcherList.contentHeight + 2 * Theme.cardPad
-                                radius: Theme.radius
+                                radius: Theme.radiusCard
                                 color: Theme.cardBg
                                 visible: launcherList.count > 0
 
@@ -1173,7 +1184,7 @@ in
                             Rectangle {
                                 width: parent.width
                                 height: 36
-                                radius: Theme.radius
+                                radius: Theme.radiusCard
                                 color: Theme.cardBg
 
                                 SIcon {
@@ -2201,7 +2212,7 @@ in
                         anchors.centerIn: parent
                         width: 48
                         height: sessionCol.height + 8
-                        radius: Theme.radius
+                        radius: Theme.radiusCard
                         color: Theme.cardBg
 
                         // Sliding selection pill — same tech as the power
@@ -2209,7 +2220,7 @@ in
                         Rectangle {
                             width: 40
                             height: 40
-                            radius: Theme.radius
+                            radius: Theme.radiusCard
                             color: Theme.base02
                             border.width: 1
                             border.color: Theme.base03
@@ -2984,7 +2995,7 @@ in
                             Rectangle {
                                 width: parent.width
                                 height: weatherRow.height + 16
-                                radius: Theme.radius
+                                radius: Theme.radiusCard
                                 color: Theme.cardBg
                                 visible: calPopup.weatherDays.length > 0
 
@@ -3046,7 +3057,7 @@ in
                                     property var pwNode: calPopup.streamFor(modelData)
                                     width: parent.width
                                     height: mediaCol.height + 16
-                                    radius: Theme.radius
+                                    radius: Theme.radiusCard
                                     color: Theme.cardBg
 
                                     PwObjectTracker { objects: mediaCard.pwNode ? [mediaCard.pwNode] : [] }
@@ -3497,7 +3508,7 @@ in
                             anchors.margins: Theme.panelGap
                             width: 320 - 2 * Theme.panelGap
                             height: Math.max(toastPreview.visible ? 48 : 0, toastCol.height) + 16
-                            radius: Theme.radius
+                            radius: Theme.radiusCard
                             color: Theme.cardBg
 
                             property string previewSource: bar.notifPreviewSource(toastItem.currentNotif)
diff --git a/settings/ui.nix b/settings/ui.nix
new file mode 100644
index 0000000..c05bd47
--- /dev/null
+++ b/settings/ui.nix
@@ -0,0 +1,16 @@
+# settings/ui.nix — shared UI metrics.
+#
+# Single source of truth for corner rounding. Both the quickshell shell
+# (settings/quickshell.nix -> Theme.qml) and hyprland's window decoration
+# (settings/hyprland.nix) read `radius` from here, and every other rounding
+# value is derived from it, so this one number rescales the roundness of the
+# whole desktop — panels, cards, pills, hover rows and window corners.
+#
+# Derived values live next to their consumers:
+#   Theme.radiusCard  = radius - panelGap  (concentric nesting, see Theme.qml)
+#   Theme.radiusSmall = radius * 0.75
+#   Theme.radiusTiny  = radius * 0.5
+#   hyprland decoration.rounding = radius
+{
+  radius = 24;
+}