diff --git a/frontends/rioterm/src/layout/compute_tests.rs b/frontends/rioterm/src/layout/compute_tests.rs
index 266737bf..fae0f90f 100644
--- a/frontends/rioterm/src/layout/compute_tests.rs
+++ b/frontends/rioterm/src/layout/compute_tests.rs
@@ -261,6 +261,28 @@ fn test_compute_margin_exceeds_size() {
     assert_eq!(rows, MIN_LINES);
 }
 
+#[test]
+fn test_context_dimension_update_scale_refreshes_scaled_font_size() {
+    let dims = TextDimensions {
+        width: 8.0,
+        height: 16.0,
+        scale: 1.0,
+    };
+    let cell = cell_for(dims);
+    let mut context =
+        ContextDimension::build(800.0, 600.0, dims, cell, 1.0, 14.0, Margin::all(10.0));
+
+    context.update_scale(2.0);
+
+    assert_eq!(context.dimension.scale, 2.0);
+    assert_eq!(context.scaled_font_size, 28.0);
+    // Width/height-derived layout is recomputed separately after the new
+    // cell metrics are installed, so update_scale itself must not clobber
+    // the current row/column counts.
+    assert_eq!(context.columns, 97);
+    assert_eq!(context.lines, 36);
+}
+
 #[test]
 fn test_context_dimension_build() {
     let dims = TextDimensions {
diff --git a/frontends/rioterm/src/layout/mod.rs b/frontends/rioterm/src/layout/mod.rs
index 0e36e287..4edd878e 100644
--- a/frontends/rioterm/src/layout/mod.rs
+++ b/frontends/rioterm/src/layout/mod.rs
@@ -1673,6 +1673,15 @@ impl ContextDimension {
         // recomputed metrics do.
     }
 
+    /// Update only the stored scale factor. Caller must follow with
+    /// `compute_cell_metrics` + `update_dimensions` so width/height
+    /// and canonical cell stride are recomputed for the new DPI.
+    #[inline]
+    pub fn update_scale(&mut self, scale: f32) {
+        self.dimension.scale = scale;
+        self.scaled_font_size = self.font_size * scale;
+    }
+
     /// Re-baseline the font size — both current and "original".
     /// Called from `update_config` so a config edit becomes the new
     /// reset target. Per-panel zoom (`change_font_size`) uses
diff --git a/frontends/rioterm/src/screen/mod.rs b/frontends/rioterm/src/screen/mod.rs
index 070bf03c..5ef264c6 100644
--- a/frontends/rioterm/src/screen/mod.rs
+++ b/frontends/rioterm/src/screen/mod.rs
@@ -601,16 +601,37 @@ impl Screen<'_> {
     ) -> &mut Self {
         self.sugarloaf.rescale(new_scale);
         self.sugarloaf.resize(new_size.width, new_size.height);
-        self.mark_dirty();
-        self.resize_all_contexts();
-        self.context_manager
-            .current_grid_mut()
-            .update_dimensions(&mut self.sugarloaf);
+
+        for context_grid in self.context_manager.contexts_mut() {
+            let old_scale = context_grid.current().dimension.dimension.scale.max(1.0);
+            let scaled_margin = context_grid.scaled_margin;
+            let unscaled_margin = Margin::new(
+                scaled_margin.top / old_scale,
+                scaled_margin.right / old_scale,
+                scaled_margin.bottom / old_scale,
+                scaled_margin.left / old_scale,
+            );
+
+            context_grid.update_scaled_margin(Margin::new(
+                unscaled_margin.top * new_scale,
+                unscaled_margin.right * new_scale,
+                unscaled_margin.bottom * new_scale,
+                unscaled_margin.left * new_scale,
+            ));
+
+            for context in context_grid.contexts_mut().values_mut() {
+                context.context_mut().dimension.update_scale(new_scale);
+            }
+
+            context_grid.update_dimensions(&mut self.sugarloaf);
+        }
+
         let width = new_size.width as f32;
         let height = new_size.height as f32;
 
         self.context_manager
             .resize_all_grids(width, height, &mut self.sugarloaf);
+        self.mark_dirty();
 
         self
     }