diff --git a/crates/openpencil-shell-native/src/widget_host/input.rs b/crates/openpencil-shell-native/src/widget_host/input.rs
index 325aac89c..27bc1e082 100644
--- a/crates/openpencil-shell-native/src/widget_host/input.rs
+++ b/crates/openpencil-shell-native/src/widget_host/input.rs
@@ -378,6 +378,19 @@ impl WidgetHostNative {
             // only effect, nothing more to do.
             return false;
         }
+        // Defensive source-validity check — symmetric with the
+        // cursor_move and paint guards. `reorder_before/after`
+        // already silently no-ops on a missing source, but bailing
+        // here keeps the rest of this method (drop_target_at +
+        // dispatch) from running pointlessly on a dead drag.
+        if self
+            .document
+            .active_page()
+            .map(|p| p.find(d.source).is_none())
+            .unwrap_or(true)
+        {
+            return false;
+        }
         use openpencil_shell_core::widgets::{DropPosition, LayerPanel, TOP_BAR_HEIGHT};
         let layer_rect = openpencil_shell_core::Rect {
             origin: openpencil_shell_core::Point2D::new(0.0, TOP_BAR_HEIGHT),
diff --git a/crates/openpencil-shell-web/src/widget_host.rs b/crates/openpencil-shell-web/src/widget_host.rs
index 4184befd8..8bfa44b60 100644
--- a/crates/openpencil-shell-web/src/widget_host.rs
+++ b/crates/openpencil-shell-web/src/widget_host.rs
@@ -465,6 +465,16 @@ impl WidgetHost {
         if !d.active {
             return false;
         }
+        // Defensive source-validity check (mirrors native) — bail
+        // if the dragged node disappeared between move and release.
+        if self
+            .document
+            .active_page()
+            .map(|p| p.find(d.source).is_none())
+            .unwrap_or(true)
+        {
+            return false;
+        }
         use openpencil_shell_core::widgets::{DropPosition, LayerPanel};
         let layer_rect = self.layer_panel_rect(viewport_h);
         let panel = LayerPanel::from_document(&self.document);