diff --git a/src/python/PythonPycParser.test.ts b/src/python/PythonPycParser.test.ts
index 26a81f15db..2c37f97a28 100644
--- a/src/python/PythonPycParser.test.ts
+++ b/src/python/PythonPycParser.test.ts
@@ -1265,11 +1265,10 @@ it("keeps one descendant list when many wrappers share a container", () => {
     marshalCode("py311", { constsObject: Buffer.concat(pieces) }),
   ]);
   const before = process.memoryUsage().heapUsed;
-  const started = Date.now();
   const report = parseWith(bytes, { max_objects: 65_536 });
   const retained = process.memoryUsage().heapUsed - before;
-  // 1,800 children and 14,000 wrappers: 49,612 reads, previously ~181 MiB.
-  expect(Date.now() - started).toBeLessThan(5000);
+  // 1,800 children and 14,000 wrappers: 49,612 reads. A copied list per wrapper
+  // previously retained ~181 MiB; retention, not host speed, shows the sharing.
   expect(retained).toBeLessThan(64 * 1024 * 1024);
   expect(report.coverage.objects).toBe(49_612);
   expect(report.code_objects).toHaveLength(children + 1);
diff --git a/tests/boundary/process/nativeUiVerifierLane.test.ts b/tests/boundary/process/nativeUiVerifierLane.test.ts
index 5ddf216c58..01b219762e 100644
--- a/tests/boundary/process/nativeUiVerifierLane.test.ts
+++ b/tests/boundary/process/nativeUiVerifierLane.test.ts
@@ -10,8 +10,9 @@ import { systemProcessOwnershipHost } from "../../../src/process/ProcessOwnershi
 import { liveProcesses } from "../../../src/process/ProcessOwnershipProcessTree.js";
 import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
 
-// Stands in for /usr/bin/open: starts a detached app that inherits its environment.
-// Each stand-in records itself and leaves when the test releases it, or expires.
+// Stands in for /usr/bin/open -W: starts a detached app that inherits its
+// environment and exits once that app exits. Each stand-in records itself and
+// leaves when the test releases it, or expires.
 const standInPrelude = `
 import { appendFileSync, existsSync, readFileSync } from "node:fs";
 const config = JSON.parse(readFileSync(new URL("./config.json", import.meta.url), "utf8"));
@@ -32,7 +33,7 @@ const coordinates = args[args.indexOf("--stdout") + 1];
 spawn(process.execPath, [new URL("./fixture.mjs", import.meta.url).pathname], {
   detached: true,
   stdio: ["ignore", openSync(coordinates, "a"), "ignore"],
-}).unref();
+}).once("exit", () => process.exit(0));
 `;
 
 const fixtureSource = `