diff --git a/src/App/App.tsx b/src/App/App.tsx
index 62c2e62..d45ac56 100644
--- a/src/App/App.tsx
+++ b/src/App/App.tsx
@@ -150,7 +150,7 @@ export function App() {
   }, [setTrace, setTime]);
 
   // raise input event, producing a new runtime configuration (or a runtime error)
-  function onRaise(inputEvent: string, param: any) {
+  const onRaise = (inputEvent: string, param: any) => {
     if (trace !== null && ast.inputEvents.some(e => e.event === inputEvent)) {
       const config = current(trace);
       if (config.kind === "bigstep") {
@@ -158,7 +158,7 @@ export function App() {
         produceNextConfig(simtime, {kind: "input", name: inputEvent, param}, config);
       }
     }
-  }
+  };
   // timer elapse events are triggered by a change of the simulated time (possibly as a scheduled JS event loop timeout)
   useEffect(() => {
     let timeout: NodeJS.Timeout | undefined;
@@ -219,6 +219,7 @@ export function App() {
         ...trace!.trace.slice(0, trace!.idx+1), // remove everything after current item
         newItem,
       ],
+      // idx: 0,
       idx: trace!.idx+1,
     }));
     scrollDownSidebar();
diff --git a/src/App/TextDialog.tsx b/src/App/TextDialog.tsx
index 627aa04..a478877 100644
--- a/src/App/TextDialog.tsx
+++ b/src/App/TextDialog.tsx
@@ -1,6 +1,6 @@
 import { Dispatch, ReactElement, SetStateAction, useState, KeyboardEvent, useEffect, useRef } from "react";
 
-import { parse as parseLabel } from "../statecharts/label_parser";
+import { cachedParseLabel } from "@/statecharts/parser";
 
 export function TextDialog(props: {setModal: Dispatch<SetStateAction<ReactElement|null>>, text: string, done: (newText: string|undefined) => void}) {
   const [text, setText] = useState(props.text);
@@ -22,7 +22,7 @@ export function TextDialog(props: {setModal: Dispatch<SetStateAction<ReactElemen
 
   let parseError = "";
   try {
-    parseLabel(text);
+    cachedParseLabel(text);
   } catch (e) {
     // @ts-ignore
     parseError = e.message;
diff --git a/src/statecharts/parser.ts b/src/statecharts/parser.ts
index 790c0d2..099272d 100644
--- a/src/statecharts/parser.ts
+++ b/src/statecharts/parser.ts
@@ -6,6 +6,7 @@ import { parse as parseLabel, SyntaxError } from "./label_parser";
 import { Connections } from "./detect_connections";
 import { HISTORY_RADIUS } from "../VisualEditor/parameters";
 import { VisualEditorState } from "@/VisualEditor/VisualEditor";
+import { memoize } from "@/App/util";
 
 export type TraceableError = {
   shapeUid: string;
@@ -13,6 +14,8 @@ export type TraceableError = {
   data?: any;
 }
 
+export const cachedParseLabel = memoize(parseLabel);
+
 function addEvent(events: EventTrigger[], e: EventTrigger, textUid: string) {
   const haveEvent = events.find(({event}) => event === e.event);
   if (haveEvent) {
@@ -229,7 +232,7 @@ export function parseStatechart(state: VisualEditorState, conns: Connections): [
   for (const text of textsSorted) {
     let parsed: ParsedText;
     try {
-      parsed = parseLabel(text.text); // may throw
+      parsed = cachedParseLabel(text.text); // may throw
       parsed.uid = text.uid;
     } catch (e) {
       if (e instanceof SyntaxError) {