diff --git a/frontend/src/Graph.svelte b/frontend/src/Graph.svelte
index 6307128..b8b2da9 100644
--- a/frontend/src/Graph.svelte
+++ b/frontend/src/Graph.svelte
@@ -20,7 +20,7 @@
   // when we update nodes and edges
   let [nodes, edges] = createNodesAndEdges(tasks);
   function hack() {
-    [nodes, edges] = createNodesAndEdges(tasks);
+    [nodes, edges] = createNodesAndEdges(tasks, nodes, edges);
     runSimulation();
   }
   $: {
@@ -103,8 +103,6 @@
   }
 </style>
 
-{@debug tasks}
-
 <div bind:this={container} bind:clientHeight bind:clientWidth>
   <svg bind:this={svgElement}>
     <g>
diff --git a/frontend/src/graph-types.ts b/frontend/src/graph-types.ts
index 0391c8b..08f2d82 100644
--- a/frontend/src/graph-types.ts
+++ b/frontend/src/graph-types.ts
@@ -8,21 +8,37 @@ export type TaskId = {
     task: TaskDescriptor;
 } & SimulationNodeDatum;
 
+function toMapById(nodes: TaskId[]): Map<string, TaskId> {
+    let nodeMap = new Map<string, TaskId>();
+    for (let task of nodes) {
+        if (task.id in nodeMap)
+            throw 'duplicate IDs';
+        nodeMap.set(task.id, task);
+    }
+    return nodeMap;
+}
+
 function createNodes(tasks: TasksFile, old?: TaskId[]): TaskId[] {
-    return tasks.tasks.map((t) => {
+    let m = (old == undefined) ? new Map<string, TaskId>() : toMapById(old);
+
+    let res = tasks.tasks.map((t) => {
         return { id: t.id, task: t };
     });
+
+    for (let t of res) {
+        if (m.has(t.id)) {
+            Object.assign(t, m.get(t.id))
+        }
+    }
+
+    return res;
 }
 
-export function createNodesAndEdges(tasks: TasksFile, oldNodes?, oldEdges?): [TaskId[], SimulationLinkDatum<TaskId>[]] {
+export function createNodesAndEdges(tasks: TasksFile, oldNodes?: TaskId[], oldEdges?: SimulationLinkDatum<TaskId>[]): [TaskId[], SimulationLinkDatum<TaskId>[]] {
     let nodes = createNodes(tasks, oldNodes);
 
     // create mapping from ID to node
-    let nodeMap = new Map<string, TaskId>();
-    for (let task of nodes) {
-        if (task.id in nodeMap) throw 'duplicate IDs';
-        nodeMap.set(task.id, task);
-    }
+    let nodeMap = toMapById(nodes);
 
     let links: SimulationLinkDatum<TaskId>[] = [];
     for (const task of tasks.tasks) {