diff --git a/frontend/src/features/analysis/ui/GraphView.vue b/frontend/src/features/analysis/ui/GraphView.vue
index 331b32c..713f09e 100644
--- a/frontend/src/features/analysis/ui/GraphView.vue
+++ b/frontend/src/features/analysis/ui/GraphView.vue
@@ -238,6 +238,14 @@ async function renderGraph(): Promise<void> {
   )
   parentMap.value = computedParentMap
 
+  // Guard against dangling edges (source/target not in the node set). Both
+  // backends can emit them in edge cases — e.g. ON_PAGE edges whose page_no
+  // doesn't match any returned Page node, or DERIVED_FROM edges crossing
+  // document boundaries in Neo4j. Cytoscape-dagre auto-creates a skeleton
+  // graphlib entry for the missing endpoint with undefined data, then crashes
+  // in its ordering phase when it tries to set `.order` on that entry.
+  const nodeIds = new Set(payload.value.nodes.map((n) => n.id))
+
   const elements = [
     ...payload.value.nodes.map((n) => ({
       data: {
@@ -256,14 +264,16 @@ async function renderGraph(): Promise<void> {
         raw: n,
       },
     })),
-    ...payload.value.edges.map((e) => ({
-      data: {
-        id: e.id,
-        source: e.source,
-        target: e.target,
-        type: e.type,
-      },
-    })),
+    ...payload.value.edges
+      .filter((e) => nodeIds.has(e.source) && nodeIds.has(e.target))
+      .map((e) => ({
+        data: {
+          id: e.id,
+          source: e.source,
+          target: e.target,
+          type: e.type,
+        },
+      })),
   ]
 
   cy.value = cytoscape({