diff --git a/apps/app/src/components/generative-ui/__tests__/export-utils.test.ts b/apps/app/src/components/generative-ui/__tests__/export-utils.test.ts
index 8853eee..196430d 100644
--- a/apps/app/src/components/generative-ui/__tests__/export-utils.test.ts
+++ b/apps/app/src/components/generative-ui/__tests__/export-utils.test.ts
@@ -88,6 +88,33 @@ describe("assembleStandaloneHtmlFromActivity", () => {
     expect(doc).toContain('document.title = "<\\/script>";');
   });
 
+  it("keeps js pieces separate when they omit trailing semicolons", async () => {
+    const doc = assembleStandaloneHtmlFromActivity({
+      jsFunctions: "let count = 0",
+      jsExpressions: [
+        "window.exportFirst = count + 1",
+        "(function () { window.exportSecond = 2 })()",
+        "[3].forEach(function (n) { window.exportThird = n })",
+      ],
+    });
+    const script = doc.slice(
+      doc.lastIndexOf("<script>") + "<script>".length,
+      doc.lastIndexOf("</script>")
+    );
+    const globals = window as unknown as Record<string, unknown>;
+    try {
+      expect(() => new Function(script)()).not.toThrow();
+      await Promise.resolve();
+      expect(globals.exportFirst).toBe(1);
+      expect(globals.exportSecond).toBe(2);
+      expect(globals.exportThird).toBe(3);
+    } finally {
+      delete globals.exportFirst;
+      delete globals.exportSecond;
+      delete globals.exportThird;
+    }
+  });
+
   it("neutralizes closing style sequences embedded in generated css", () => {
     const doc = assembleStandaloneHtmlFromActivity(
       {
diff --git a/apps/app/src/components/generative-ui/export-utils.ts b/apps/app/src/components/generative-ui/export-utils.ts
index 106eec4..fd80fac 100644
--- a/apps/app/src/components/generative-ui/export-utils.ts
+++ b/apps/app/src/components/generative-ui/export-utils.ts
@@ -25,6 +25,13 @@ export interface StandaloneActivityContent {
 
 const WEBSANDBOX_STUB = `window.Websandbox = { connection: { remote: { sendPrompt: async () => {}, openLink: async ({ url }) => { if (/^https:/.test(url)) window.open(url, "_blank", "noopener,noreferrer"); } } } };`;
 
+// The live sandbox runs jsFunctions and each jsExpression as separate scripts,
+// so generated code often omits trailing semicolons. Joined into one script,
+// automatic semicolon insertion would merge the pieces: "let n = 0" followed
+// by "(function () {...})()" parses as a call on 0. An explicit separator keeps
+// each piece a separate statement.
+const STATEMENT_SEPARATOR = "\n;\n";
+
 function escapeScriptClose(js: string): string {
   return js.replace(/<\/script/gi, "<\\/script");
 }
@@ -56,7 +63,7 @@ export function assembleStandaloneHtmlFromActivity(
     ...(expressions.length > 0
       ? [
           `(async () => {
-${expressions.map(escapeScriptClose).join("\n")}
+${expressions.map(escapeScriptClose).join(STATEMENT_SEPARATOR)}
 })();`,
         ]
       : []),
@@ -64,7 +71,7 @@ ${expressions.map(escapeScriptClose).join("\n")}
   const generatedScript =
     scriptParts.length > 0
       ? `<script>
-${scriptParts.join("\n")}
+${scriptParts.join(STATEMENT_SEPARATOR)}
   </script>`
       : "";
   return `<!DOCTYPE html>