diff --git a/scripts/e2e/parallels-npm-update-smoke.sh b/scripts/e2e/parallels-npm-update-smoke.sh
index 9f47c75cf07..b1f549af1bc 100755
--- a/scripts/e2e/parallels-npm-update-smoke.sh
+++ b/scripts/e2e/parallels-npm-update-smoke.sh
@@ -67,6 +67,7 @@ die() {
 cleanup() {
   if [[ -n "${SERVER_PID:-}" ]]; then
     kill "$SERVER_PID" >/dev/null 2>&1 || true
+    wait "$SERVER_PID" 2>/dev/null || true
   fi
   rm -rf "$MAIN_TGZ_DIR"
 }
@@ -662,7 +663,7 @@ start_timeout_guard() {
       sleep 2
       kill -9 "$pid" >/dev/null 2>&1 || true
     fi
-  ) &
+  ) >&2 &
   printf '%s\n' "$!"
 }
 
@@ -670,6 +671,7 @@ stop_timeout_guard() {
   local pid="${1:-}"
   [[ -n "$pid" ]] || return 0
   kill "$pid" >/dev/null 2>&1 || true
+  wait "$pid" 2>/dev/null || true
 }
 
 extract_log_progress() {
diff --git a/test/scripts/parallels-npm-update-smoke.test.ts b/test/scripts/parallels-npm-update-smoke.test.ts
new file mode 100644
index 00000000000..c0d483a2085
--- /dev/null
+++ b/test/scripts/parallels-npm-update-smoke.test.ts
@@ -0,0 +1,14 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+const SCRIPT_PATH = "scripts/e2e/parallels-npm-update-smoke.sh";
+
+describe("parallels npm update smoke", () => {
+  it("does not leave guard/server children attached to the wrapper", () => {
+    const script = readFileSync(SCRIPT_PATH, "utf8");
+
+    expect(script).toContain('wait "$SERVER_PID" 2>/dev/null || true');
+    expect(script).toContain(") >&2 &");
+    expect(script).toContain('wait "$pid" 2>/dev/null || true');
+  });
+});