sl0p: CSS-style 1/2/4-value shorthand for inner padding

`padding` now accepts:
  padding 1          -> all four sides
  padding 1 2        -> up/down = 1, left/right = 2
  padding 1 2 3 4    -> up=1 down=2 left=3 right=4

NOTE the 4-value order is UP DOWN LEFT RIGHT as requested, deliberately NOT
CSS's clockwise top-right-bottom-left. Documented on PanePadding and at the
parser, since the similarity to CSS invites the wrong assumption.

3 or 5 values are rejected with a message naming the accepted forms, rather
than being silently reinterpreted. Negative values clamp to 0.

ASPECT: only the 1-value form is aspect-corrected (left/right multiplied by
gap_aspect) so `padding 1` looks square on a non-square cell grid. The 2- and
4-value forms are literal: specifying axes separately means the caller is
already controlling horizontal size, and silently doubling it would surprise.

Style now carries a PanePadding {top,bottom,left,right} instead of an x/y
pair, which also collapses the reconfigure plumbing back to a single field
rather than growing another parameter per side.

to_kdl always emits the explicit 4-value form: emitting the 1-value form
would re-apply gap_aspect on the next read and silently double the padding
on every config round-trip.

Baselines held: zellij-utils 435/5, zellij-server 1421/30.

14 files changed, 171 insertions, 77 deletions

diff --git a/sl0ppij/zellij-client/src/web_client/server_listener.rs b/sl0ppij/zellij-client/src/web_client/server_listener.rs
index 8f80f4a..398c973 100644
--- a/sl0ppij/zellij-client/src/web_client/server_listener.rs
+++ b/sl0ppij/zellij-client/src/web_client/server_listener.rs
@@ -86,8 +86,7 @@ pub fn zellij_server_listener(
                             pane_title_alignment: config.ui.pane_frames.title_alignment,
                             pane_gap_x: config.ui.pane_frames.resolved_gap().0,
                             pane_gap_y: config.ui.pane_frames.resolved_gap().1,
-                            pane_padding_x: config.ui.pane_frames.resolved_padding().0,
-                            pane_padding_y: config.ui.pane_frames.resolved_padding().1,
+                            pane_padding: config.ui.pane_frames.resolved_padding(),
                         },
                     };
 
diff --git a/sl0ppij/zellij-server/src/lib.rs b/sl0ppij/zellij-server/src/lib.rs
index a80bda2..fe5b3b1 100644
--- a/sl0ppij/zellij-server/src/lib.rs
+++ b/sl0ppij/zellij-server/src/lib.rs
@@ -462,8 +462,7 @@ impl SessionMetaData {
                     pane_title_alignment: new_config.ui.pane_frames.title_alignment,
                     pane_gap_x: new_config.ui.pane_frames.resolved_gap().0,
                     pane_gap_y: new_config.ui.pane_frames.resolved_gap().1,
-                    pane_padding_x: new_config.ui.pane_frames.resolved_padding().0,
-                    pane_padding_y: new_config.ui.pane_frames.resolved_padding().1,
+                    pane_padding: new_config.ui.pane_frames.resolved_padding(),
                     stacked_resize: new_config.options.stacked_resize.unwrap_or(true),
                     stacked_pane_list: new_config.options.stacked_pane_list.unwrap_or(true),
                     default_editor: new_config.options.scrollback_editor.clone(),
@@ -1008,8 +1007,7 @@ pub fn start_server_impl(
                         pane_title_alignment: config.ui.pane_frames.title_alignment,
                         pane_gap_x: config.ui.pane_frames.resolved_gap().0,
                         pane_gap_y: config.ui.pane_frames.resolved_gap().1,
-                        pane_padding_x: config.ui.pane_frames.resolved_padding().0,
-                        pane_padding_y: config.ui.pane_frames.resolved_padding().1,
+                        pane_padding: config.ui.pane_frames.resolved_padding(),
                     },
                 };
 
@@ -1196,8 +1194,7 @@ pub fn start_server_impl(
                         pane_title_alignment: config.ui.pane_frames.title_alignment,
                         pane_gap_x: config.ui.pane_frames.resolved_gap().0,
                         pane_gap_y: config.ui.pane_frames.resolved_gap().1,
-                        pane_padding_x: config.ui.pane_frames.resolved_padding().0,
-                        pane_padding_y: config.ui.pane_frames.resolved_padding().1,
+                        pane_padding: config.ui.pane_frames.resolved_padding(),
                     },
                 };
 
diff --git a/sl0ppij/zellij-server/src/panes/floating_panes/mod.rs b/sl0ppij/zellij-server/src/panes/floating_panes/mod.rs
index 8252612..3e5e80f 100644
--- a/sl0ppij/zellij-server/src/panes/floating_panes/mod.rs
+++ b/sl0ppij/zellij-server/src/panes/floating_panes/mod.rs
@@ -1725,16 +1725,14 @@ impl FloatingPanes {
         title_alignment: zellij_utils::data::PaneTitleAlignment,
         gap_x: usize,
         gap_y: usize,
-        padding_x: usize,
-        padding_y: usize,
+        padding: zellij_utils::data::PanePadding,
     ) {
         self.style.pane_title_alignment = title_alignment;
         self.style.pane_gap_x = gap_x;
         self.style.pane_gap_y = gap_y;
-        self.style.pane_padding_x = padding_x;
-        self.style.pane_padding_y = padding_y;
+        self.style.pane_padding = padding;
         for pane in self.panes.values_mut() {
-            pane.update_frame_layout(title_alignment, gap_x, gap_y, padding_x, padding_y);
+            pane.update_frame_layout(title_alignment, gap_x, gap_y, padding);
         }
         // Unlike the tiled panes, `set_pane_frame_style` only re-runs the
         // content-offset sweep for a fullscreen floating pane, so gap/padding
diff --git a/sl0ppij/zellij-server/src/panes/plugin_pane.rs b/sl0ppij/zellij-server/src/panes/plugin_pane.rs
index 4f4e138..6c1e870 100644
--- a/sl0ppij/zellij-server/src/panes/plugin_pane.rs
+++ b/sl0ppij/zellij-server/src/panes/plugin_pane.rs
@@ -773,10 +773,10 @@ impl Pane for PluginPane {
             Offset::default()
         } else {
             Offset {
-                top: self.gap_offset.top.saturating_add(self.style.pane_padding_y),
-                bottom: self.gap_offset.bottom.saturating_add(self.style.pane_padding_y),
-                left: self.gap_offset.left.saturating_add(self.style.pane_padding_x),
-                right: self.gap_offset.right.saturating_add(self.style.pane_padding_x),
+                top: self.gap_offset.top.saturating_add(self.style.pane_padding.top),
+                bottom: self.gap_offset.bottom.saturating_add(self.style.pane_padding.bottom),
+                left: self.gap_offset.left.saturating_add(self.style.pane_padding.left),
+                right: self.gap_offset.right.saturating_add(self.style.pane_padding.right),
             }
         };
         self.content_offset =
@@ -915,14 +915,12 @@ impl Pane for PluginPane {
         title_alignment: zellij_utils::data::PaneTitleAlignment,
         gap_x: usize,
         gap_y: usize,
-        padding_x: usize,
-        padding_y: usize,
+        padding: zellij_utils::data::PanePadding,
     ) {
         self.style.pane_title_alignment = title_alignment;
         self.style.pane_gap_x = gap_x;
         self.style.pane_gap_y = gap_y;
-        self.style.pane_padding_x = padding_x;
-        self.style.pane_padding_y = padding_y;
+        self.style.pane_padding = padding;
         self.frame.clear();
     }
     fn set_should_be_suppressed(&mut self, should_be_suppressed: bool) {
diff --git a/sl0ppij/zellij-server/src/panes/terminal_pane.rs b/sl0ppij/zellij-server/src/panes/terminal_pane.rs
index 8c44d7b..7fb7817 100644
--- a/sl0ppij/zellij-server/src/panes/terminal_pane.rs
+++ b/sl0ppij/zellij-server/src/panes/terminal_pane.rs
@@ -991,10 +991,10 @@ impl Pane for TerminalPane {
             Offset::default()
         } else {
             Offset {
-                top: self.gap_offset.top.saturating_add(self.style.pane_padding_y),
-                bottom: self.gap_offset.bottom.saturating_add(self.style.pane_padding_y),
-                left: self.gap_offset.left.saturating_add(self.style.pane_padding_x),
-                right: self.gap_offset.right.saturating_add(self.style.pane_padding_x),
+                top: self.gap_offset.top.saturating_add(self.style.pane_padding.top),
+                bottom: self.gap_offset.bottom.saturating_add(self.style.pane_padding.bottom),
+                left: self.gap_offset.left.saturating_add(self.style.pane_padding.left),
+                right: self.gap_offset.right.saturating_add(self.style.pane_padding.right),
             }
         };
         self.content_offset =
@@ -1269,14 +1269,12 @@ impl Pane for TerminalPane {
         title_alignment: zellij_utils::data::PaneTitleAlignment,
         gap_x: usize,
         gap_y: usize,
-        padding_x: usize,
-        padding_y: usize,
+        padding: zellij_utils::data::PanePadding,
     ) {
         self.style.pane_title_alignment = title_alignment;
         self.style.pane_gap_x = gap_x;
         self.style.pane_gap_y = gap_y;
-        self.style.pane_padding_x = padding_x;
-        self.style.pane_padding_y = padding_y;
+        self.style.pane_padding = padding;
         self.frame.clear();
     }
     fn drain_fake_cursors(&mut self) -> Option<HashSet<(usize, usize)>> {
diff --git a/sl0ppij/zellij-server/src/panes/tiled_panes/mod.rs b/sl0ppij/zellij-server/src/panes/tiled_panes/mod.rs
index 835c8e7..4d8f0a4 100644
--- a/sl0ppij/zellij-server/src/panes/tiled_panes/mod.rs
+++ b/sl0ppij/zellij-server/src/panes/tiled_panes/mod.rs
@@ -3156,16 +3156,14 @@ impl TiledPanes {
         title_alignment: zellij_utils::data::PaneTitleAlignment,
         gap_x: usize,
         gap_y: usize,
-        padding_x: usize,
-        padding_y: usize,
+        padding: zellij_utils::data::PanePadding,
     ) {
         self.style.pane_title_alignment = title_alignment;
         self.style.pane_gap_x = gap_x;
         self.style.pane_gap_y = gap_y;
-        self.style.pane_padding_x = padding_x;
-        self.style.pane_padding_y = padding_y;
+        self.style.pane_padding = padding;
         for pane in self.panes.values_mut() {
-            pane.update_frame_layout(title_alignment, gap_x, gap_y, padding_x, padding_y);
+            pane.update_frame_layout(title_alignment, gap_x, gap_y, padding);
         }
     }
     pub fn stack_panes(
diff --git a/sl0ppij/zellij-server/src/screen.rs b/sl0ppij/zellij-server/src/screen.rs
index c3c06ca..438fee2 100644
--- a/sl0ppij/zellij-server/src/screen.rs
+++ b/sl0ppij/zellij-server/src/screen.rs
@@ -43,7 +43,7 @@ use zellij_utils::data::{
     CommandOrPlugin, Direction, EventType, FloatingPaneCoordinates, GetFocusedPaneInfoResponse,
     HostTerminalThemeMode, KeyWithModifier, LayoutInfo, LayoutWithError, ListPanesResponse,
     ListTabsResponse, NewPanePlacement, PaneContents, PaneInfo, PaneListEntry, PaneManifest,
-    PaneRenderReport, PaneScrollbackResponse, PaneTitleAlignment, PluginPermission,
+    PaneRenderReport, PanePadding, PaneScrollbackResponse, PaneTitleAlignment, PluginPermission,
     RegexHighlight, Resize,
     ResizeStrategy, SessionInfo, Styling, TabInfo, ThemeHue, WebSharing,
 };
@@ -779,8 +779,7 @@ pub enum ScreenInstruction {
         pane_title_alignment: PaneTitleAlignment,
         pane_gap_x: usize,
         pane_gap_y: usize,
-        pane_padding_x: usize,
-        pane_padding_y: usize,
+        pane_padding: PanePadding,
         stacked_resize: bool,
         stacked_pane_list: bool,
         default_editor: Option<PathBuf>,
@@ -6270,8 +6269,7 @@ impl Screen {
         pane_title_alignment: PaneTitleAlignment,
         pane_gap_x: usize,
         pane_gap_y: usize,
-        pane_padding_x: usize,
-        pane_padding_y: usize,
+        pane_padding: PanePadding,
         stacked_resize: bool,
         stacked_pane_list: bool,
         default_editor: Option<PathBuf>,
@@ -6331,7 +6329,7 @@ impl Screen {
             tab.update_copy_options(&self.copy_options);
             // must precede set_pane_frames: gap/padding are baked into
             // content_offset by the sweep that set_pane_frames triggers
-            tab.update_frame_layout(pane_title_alignment, pane_gap_x, pane_gap_y, pane_padding_x, pane_padding_y);
+            tab.update_frame_layout(pane_title_alignment, pane_gap_x, pane_gap_y, pane_padding);
             tab.set_pane_frames(pane_frame_style);
             tab.update_arrow_fonts(should_support_arrow_fonts);
             tab.update_advanced_mouse_actions(advanced_mouse_actions);
@@ -10850,8 +10848,7 @@ pub(crate) fn screen_thread_main(
                 pane_title_alignment,
                 pane_gap_x,
                 pane_gap_y,
-                pane_padding_x,
-                pane_padding_y,
+                pane_padding,
                 stacked_resize,
                 stacked_pane_list,
                 default_editor,
@@ -10882,8 +10879,7 @@ pub(crate) fn screen_thread_main(
                         pane_title_alignment,
                         pane_gap_x,
                         pane_gap_y,
-                        pane_padding_x,
-                        pane_padding_y,
+                        pane_padding,
                         stacked_resize,
                         stacked_pane_list,
                         default_editor,
diff --git a/sl0ppij/zellij-server/src/tab/mod.rs b/sl0ppij/zellij-server/src/tab/mod.rs
index c9047d6..ec08842 100644
--- a/sl0ppij/zellij-server/src/tab/mod.rs
+++ b/sl0ppij/zellij-server/src/tab/mod.rs
@@ -751,8 +751,7 @@ pub trait Pane {
         _title_alignment: zellij_utils::data::PaneTitleAlignment,
         _gap_x: usize,
         _gap_y: usize,
-        _padding_x: usize,
-        _padding_y: usize,
+        _padding: zellij_utils::data::PanePadding,
     ) {
     }
     fn set_should_be_suppressed(&mut self, _should_be_suppressed: bool) {}
@@ -7420,20 +7419,18 @@ impl Tab {
         title_alignment: zellij_utils::data::PaneTitleAlignment,
         gap_x: usize,
         gap_y: usize,
-        padding_x: usize,
-        padding_y: usize,
+        padding: zellij_utils::data::PanePadding,
     ) {
         self.style.pane_title_alignment = title_alignment;
         self.style.pane_gap_x = gap_x;
         self.style.pane_gap_y = gap_y;
-        self.style.pane_padding_x = padding_x;
-        self.style.pane_padding_y = padding_y;
+        self.style.pane_padding = padding;
         self.floating_panes
-            .update_pane_frame_layout(title_alignment, gap_x, gap_y, padding_x, padding_y);
+            .update_pane_frame_layout(title_alignment, gap_x, gap_y, padding);
         self.tiled_panes
-            .update_pane_frame_layout(title_alignment, gap_x, gap_y, padding_x, padding_y);
+            .update_pane_frame_layout(title_alignment, gap_x, gap_y, padding);
         for (_, pane) in self.suppressed_panes.values_mut() {
-            pane.update_frame_layout(title_alignment, gap_x, gap_y, padding_x, padding_y);
+            pane.update_frame_layout(title_alignment, gap_x, gap_y, padding);
         }
     }
     pub fn update_arrow_fonts(&mut self, should_support_arrow_fonts: bool) {
diff --git a/sl0ppij/zellij-utils/src/data.rs b/sl0ppij/zellij-utils/src/data.rs
index aa455b3..218db21 100644
--- a/sl0ppij/zellij-utils/src/data.rs
+++ b/sl0ppij/zellij-utils/src/data.rs
@@ -1413,6 +1413,32 @@ impl std::str::FromStr for PaneTitleAlignment {
     }
 }
 
+/// Inner padding between a pane's frame and its content, per side.
+///
+/// Configured CSS-shorthand style, but note the 4-value order is
+/// **up down left right** (as requested), NOT the CSS clockwise
+/// top-right-bottom-left. See the KDL parser for the accepted forms.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default, Serialize, Deserialize)]
+pub struct PanePadding {
+    pub top: usize,
+    pub bottom: usize,
+    pub left: usize,
+    pub right: usize,
+}
+
+impl PanePadding {
+    pub fn uniform(n: usize) -> Self {
+        Self { top: n, bottom: n, left: n, right: n }
+    }
+    /// vertical (up/down) and horizontal (left/right)
+    pub fn axes(v: usize, h: usize) -> Self {
+        Self { top: v, bottom: v, left: h, right: h }
+    }
+    pub fn is_zero(&self) -> bool {
+        self.top == 0 && self.bottom == 0 && self.left == 0 && self.right == 0
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default, Serialize, Deserialize)]
 pub struct Style {
     pub colors: Styling,
@@ -1436,11 +1462,9 @@ pub struct Style {
     /// an equal distance. See FrameConfig::gap_aspect.
     pub pane_gap_x: usize,
     pub pane_gap_y: usize,
-    /// INNER padding: cells between a pane's frame and its content. Purely
-    /// cosmetic breathing room inside the pane; does not move the frame.
-    /// Also aspect-corrected.
-    pub pane_padding_x: usize,
-    pub pane_padding_y: usize,
+    /// INNER padding: cells between a pane's frame and its content, per side.
+    /// Purely cosmetic breathing room inside the pane; does not move the frame.
+    pub pane_padding: PanePadding,
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Deserialize, Serialize)]
diff --git a/sl0ppij/zellij-utils/src/input/config.rs b/sl0ppij/zellij-utils/src/input/config.rs
index be08adb..db86de5 100644
--- a/sl0ppij/zellij-utils/src/input/config.rs
+++ b/sl0ppij/zellij-utils/src/input/config.rs
@@ -1393,6 +1393,51 @@ mod config_test {
     }
 
     #[test]
+    fn pane_padding_accepts_1_2_and_4_value_shorthand() {
+        let parse = |padding: &str| {
+            let contents = format!(
+                "ui {{\n pane_frames {{\n padding {}\n }}\n}}",
+                padding
+            );
+            Config::from_kdl(&contents, None).map(|c| c.ui.pane_frames.padding)
+        };
+
+        // 1 value: all sides, and left/right are aspect-corrected (x2 default)
+        // so that `padding 1` reads as square on a non-square cell grid
+        let p = parse("1").unwrap();
+        assert_eq!((p.top, p.bottom), (1, 1), "1-value: vertical");
+        assert_eq!((p.left, p.right), (2, 2), "1-value: horizontal is aspect-corrected");
+
+        // 2 values: up/down then left/right, taken LITERALLY (no aspect scaling -
+        // the caller is already controlling the horizontal size)
+        let p = parse("1 2").unwrap();
+        assert_eq!((p.top, p.bottom, p.left, p.right), (1, 1, 2, 2), "2-value");
+
+        // 4 values: up down left right (NOT css clockwise order)
+        let p = parse("1 2 3 4").unwrap();
+        assert_eq!((p.top, p.bottom, p.left, p.right), (1, 2, 3, 4), "4-value");
+
+        // 3 and 5 are rejected rather than silently reinterpreted
+        assert!(parse("1 2 3").is_err(), "3 values must be rejected");
+        assert!(parse("1 2 3 4 5").is_err(), "5 values must be rejected");
+
+        // negatives clamp to 0 instead of wrapping to a huge usize
+        let p = parse("-4").unwrap();
+        assert!(p.is_zero(), "negative padding must clamp to zero, got {:?}", p);
+    }
+
+    #[test]
+    fn pane_padding_aspect_is_configurable() {
+        let contents = "ui {\n pane_frames {\n gap_aspect 1\n padding 1\n }\n}";
+        let p = Config::from_kdl(contents, None).unwrap().ui.pane_frames.padding;
+        assert_eq!(
+            (p.top, p.left),
+            (1, 1),
+            "gap_aspect 1 disables horizontal correction"
+        );
+    }
+
+    #[test]
     fn can_define_ui_configuration_in_configfile() {
         let config_contents = r#"
             ui {
diff --git a/sl0ppij/zellij-utils/src/input/theme.rs b/sl0ppij/zellij-utils/src/input/theme.rs
index f4f2ec8..f1e0adf 100644
--- a/sl0ppij/zellij-utils/src/input/theme.rs
+++ b/sl0ppij/zellij-utils/src/input/theme.rs
@@ -30,8 +30,9 @@ pub struct FrameConfig {
     /// outer gap between panes, expressed in ROWS (see Style::pane_gap_y).
     /// Columns are scaled by `gap_aspect` so the gap looks square.
     pub gap: usize,
-    /// inner padding between a pane's frame and its content, in ROWS
-    pub padding: usize,
+    /// inner padding between a pane's frame and its content, per side.
+    /// Already resolved at parse time (including any aspect correction).
+    pub padding: crate::data::PanePadding,
     /// Columns per row. Terminal cells are roughly twice as tall as they are
     /// wide, so 1 row of gap needs ~2 columns to look like the same distance.
     /// 0 is treated as 1 (no correction).
@@ -49,7 +50,7 @@ impl Default for FrameConfig {
             hide_session_name: false,
             title_alignment: Default::default(),
             gap: 0,
-            padding: 0,
+            padding: Default::default(),
             gap_aspect: 2,
         }
     }
@@ -63,9 +64,8 @@ impl FrameConfig {
     pub fn resolved_gap(&self) -> (usize, usize) {
         (self.gap * self.aspect(), self.gap)
     }
-    /// (columns, rows) of inner padding
-    pub fn resolved_padding(&self) -> (usize, usize) {
-        (self.padding * self.aspect(), self.padding)
+    pub fn resolved_padding(&self) -> crate::data::PanePadding {
+        self.padding
     }
 }
 
diff --git a/sl0ppij/zellij-utils/src/kdl/mod.rs b/sl0ppij/zellij-utils/src/kdl/mod.rs
index c2500eb..b567019 100644
--- a/sl0ppij/zellij-utils/src/kdl/mod.rs
+++ b/sl0ppij/zellij-utils/src/kdl/mod.rs
@@ -3,7 +3,7 @@ use crate::data::{
     BareKey, Direction, FloatingPaneCoordinates, InputMode, KeyWithModifier, LayoutInfo,
     LayoutMetadata, MultiplayerColors, Palette, PaletteColor, PaneId, PaneInfo, PaneManifest,
     PermissionType, Resize, SessionInfo, StyleDeclaration, Styling, TabInfo, WebSharing,
-    DEFAULT_STYLES,
+    DEFAULT_STYLES, PanePadding,
 };
 use crate::envs::EnvironmentVariables;
 use crate::home::{find_default_config_dir, get_layout_dir};
@@ -5548,16 +5548,53 @@ impl UiConfig {
             };
             // negative values are meaningless here and would wrap on `as usize`,
             // so clamp at 0 rather than silently producing a gigantic inset
-            let gap = kdl_children_property_first_arg_as_i64!(pane_frames, "gap")
-                .unwrap_or(0)
-                .max(0) as usize;
-            let padding = kdl_children_property_first_arg_as_i64!(pane_frames, "padding")
-                .unwrap_or(0)
-                .max(0) as usize;
             // default 2: terminal cells are ~2x taller than wide
             let gap_aspect = kdl_children_property_first_arg_as_i64!(pane_frames, "gap_aspect")
                 .unwrap_or(2)
                 .max(1) as usize;
+            let gap = kdl_children_property_first_arg_as_i64!(pane_frames, "gap")
+                .unwrap_or(0)
+                .max(0) as usize;
+            // `padding` accepts CSS-style shorthand, but note the 4-value order
+            // is UP DOWN LEFT RIGHT (not CSS's clockwise top-right-bottom-left):
+            //   padding 1          -> all four sides
+            //   padding 1 2        -> up/down = 1, left/right = 2
+            //   padding 1 2 3 4    -> up=1 down=2 left=3 right=4
+            //
+            // ASPECT: the single-value form is aspect-corrected (left/right are
+            // multiplied by gap_aspect) so `padding 1` looks square. The 2- and
+            // 4-value forms are taken literally, because specifying axes
+            // separately means you are already controlling the horizontal size
+            // and silently doubling it would be surprising.
+            let padding = match pane_frames.children().and_then(|c| c.get("padding")) {
+                Some(node) => {
+                    let values: Vec<i64> = kdl_entries_as_i64!(node).flatten().collect();
+                    let clamp = |v: i64| v.max(0) as usize;
+                    match values.len() {
+                        0 => Default::default(),
+                        1 => PanePadding::axes(clamp(values[0]), clamp(values[0]) * gap_aspect),
+                        2 => PanePadding::axes(clamp(values[0]), clamp(values[1])),
+                        4 => PanePadding {
+                            top: clamp(values[0]),
+                            bottom: clamp(values[1]),
+                            left: clamp(values[2]),
+                            right: clamp(values[3]),
+                        },
+                        n => {
+                            return Err(ConfigError::new_kdl_error(
+                                format!(
+                                    "padding takes 1, 2 or 4 values (got {}): \
+`padding <all>`, `padding <up/down> <left/right>`, or `padding <up> <down> <left> <right>`",
+                                    n
+                                ),
+                                node.span().offset(),
+                                node.span().len(),
+                            ))
+                        },
+                    }
+                },
+                None => Default::default(),
+            };
             let frame_config = FrameConfig {
                 rounded_corners,
                 hide_session_name,
@@ -5607,10 +5644,19 @@ impl UiConfig {
             gap.push(KdlValue::Base10(self.pane_frames.gap as i64));
             frame_config_children.nodes_mut().push(gap);
         }
-        if self.pane_frames.padding > 0 {
+        if !self.pane_frames.padding.is_zero() {
             has_ui_config = true;
+            // always the explicit 4-value form: the 1-value form would be
+            // re-multiplied by gap_aspect when read back
             let mut padding = KdlNode::new("padding");
-            padding.push(KdlValue::Base10(self.pane_frames.padding as i64));
+            for v in [
+                self.pane_frames.padding.top,
+                self.pane_frames.padding.bottom,
+                self.pane_frames.padding.left,
+                self.pane_frames.padding.right,
+            ] {
+                padding.push(KdlValue::Base10(v as i64));
+            }
             frame_config_children.nodes_mut().push(padding);
         }
         if self.pane_frames.gap_aspect != 2 {
diff --git a/sl0ppij/zellij-utils/src/plugin_api/event.rs b/sl0ppij/zellij-utils/src/plugin_api/event.rs
index 87af043..7bb1c7a 100644
--- a/sl0ppij/zellij-utils/src/plugin_api/event.rs
+++ b/sl0ppij/zellij-utils/src/plugin_api/event.rs
@@ -2495,8 +2495,7 @@ fn serialize_mode_update_event_with_non_default_values() {
             pane_title_alignment: Default::default(),
             pane_gap_x: Default::default(),
             pane_gap_y: Default::default(),
-            pane_padding_x: Default::default(),
-            pane_padding_y: Default::default(),
+            pane_padding: Default::default(),
         },
         capabilities: PluginCapabilities { arrow_fonts: false },
         session_name: Some("my awesome test session".to_owned()),
diff --git a/sl0ppij/zellij-utils/src/plugin_api/style.rs b/sl0ppij/zellij-utils/src/plugin_api/style.rs
index 266ab7f..527f984 100644
--- a/sl0ppij/zellij-utils/src/plugin_api/style.rs
+++ b/sl0ppij/zellij-utils/src/plugin_api/style.rs
@@ -28,8 +28,7 @@ impl TryFrom<ProtobufStyle> for Style {
             pane_title_alignment: Default::default(),
             pane_gap_x: Default::default(),
             pane_gap_y: Default::default(),
-            pane_padding_x: Default::default(),
-            pane_padding_y: Default::default(),
+            pane_padding: Default::default(),
         })
     }
 }