diff --git a/test/helpers.ts b/test/helpers.ts
index 49c3a685..90d6898b 100644
--- a/test/helpers.ts
+++ b/test/helpers.ts
@@ -1,5 +1,5 @@
 import { spawnSync } from 'node:child_process';
-import { readFileSync } from 'node:fs';
+import { readdirSync, readFileSync } from 'node:fs';
 import {
   mkdir,
   mkdtemp,
@@ -13,6 +13,7 @@ import { join } from 'node:path';
 import process from 'node:process';
 
 import type { SessionRecord as ProtocolSessionRecord } from '../src/protocol/schemas.js';
+import { parseProcStat } from '../src/host/programGroup.js';
 import type { SemanticSnapshot } from '../src/renderer/types.js';
 import { hasErrorCode } from '../src/util/hasErrorCode.js';
 
@@ -359,10 +360,108 @@ export function killGroupIfAlive(group: number): void {
   }
 }
 
-// init reaps the killed processes a moment after they die.
+const GONE_CODES = ['ENOENT', 'ESRCH'];
+
+function isGone(error: unknown): boolean {
+  return GONE_CODES.some((code) => hasErrorCode(error, code));
+}
+
+// Whether /proc shows the processes of every user. hidepid leaves other
+// users out, and an unreadable mountinfo counts as hiding them.
+function procShowsEveryUser(): boolean {
+  let mountinfo: string;
+  try {
+    mountinfo = readFileSync('/proc/self/mountinfo', 'utf8');
+  } catch {
+    return false;
+  }
+  let shows = false;
+  for (const line of mountinfo.split('\n')) {
+    const fields = line.split(' ');
+    const separator = fields.indexOf('-');
+    if (fields[4] === '/proc' && fields[separator + 1] === 'proc') {
+      shows = !/(^|,)hidepid=(2|4|invisible|ptraceable)(,|$)/.test(
+        fields[separator + 3] ?? '',
+      );
+    }
+  }
+  return shows;
+}
+
+// Whether a scan of /proc shows a thread of the group that is not a zombie,
+// or null when a read is refused or the scan shows no member at all, as a
+// /proc of another pid namespace does, so the scan proves nothing.
+function scanFindsLiveThread(group: number): boolean | null {
+  let seen = false;
+  try {
+    for (const entry of readdirSync('/proc')) {
+      if (!/^\d+$/.test(entry)) {
+        continue;
+      }
+      let tasks: string[];
+      try {
+        if (
+          parseProcStat(readFileSync(`/proc/${entry}/stat`, 'utf8')).pgid !==
+          group
+        ) {
+          continue;
+        }
+        seen = true;
+        tasks = readdirSync(`/proc/${entry}/task`);
+      } catch (error) {
+        if (isGone(error)) {
+          continue;
+        }
+        throw error;
+      }
+      for (const task of tasks) {
+        let state: string;
+        try {
+          state = parseProcStat(
+            readFileSync(`/proc/${entry}/task/${task}/stat`, 'utf8'),
+          ).state;
+        } catch (error) {
+          if (isGone(error)) {
+            continue;
+          }
+          throw error;
+        }
+        if (state !== 'Z' && state !== 'X') {
+          return true;
+        }
+      }
+    }
+  } catch (error) {
+    if (
+      ['EACCES', 'EPERM', 'ENOENT'].some((code) => hasErrorCode(error, code))
+    ) {
+      return null;
+    }
+    throw error;
+  }
+  return seen ? false : null;
+}
+
+// A killed process stays a zombie until its parent reaps it. An orphan's
+// parent is init, which can take seconds to reap on a loaded machine, so on
+// Linux a group whose threads are all zombies counts as ended. A process can
+// fork and end between the /proc listing and its own read, so two scans must
+// agree. Where /proc cannot show the whole group, the probe decides alone.
+function groupHasLiveThread(group: number): boolean {
+  if (!isGroupAlive(group)) {
+    return false;
+  }
+  if (process.platform !== 'linux' || !procShowsEveryUser()) {
+    return true;
+  }
+  return (
+    scanFindsLiveThread(group) !== false || scanFindsLiveThread(group) !== false
+  );
+}
+
 export async function groupEnds(group: number): Promise<boolean> {
-  const deadline = Date.now() + 2_000;
-  while (isGroupAlive(group)) {
+  const deadline = Date.now() + 5_000;
+  while (groupHasLiveThread(group)) {
     if (Date.now() > deadline) {
       return false;
     }
diff --git a/test/integration/lifecycle.test.ts b/test/integration/lifecycle.test.ts
index d7ad5e77..33789fb7 100644
--- a/test/integration/lifecycle.test.ts
+++ b/test/integration/lifecycle.test.ts
@@ -23,6 +23,7 @@ import { parseProcStat } from '../../src/host/programGroup.js';
 import { probeLibghosttyVt } from '../../src/renderer/readiness.js';
 import { SessionRecordSchema } from '../../src/protocol/schemas.js';
 import { writeManifest } from '../../src/storage/manifests.js';
+import { hasErrorCode } from '../../src/util/hasErrorCode.js';
 import {
   manifestPath,
   programRecordPath,
@@ -1849,7 +1850,7 @@ describe('lifecycle integration', { timeout: 60_000 }, () => {
     ];
 
     async function readEnvelopeOnceWritten(path: string): Promise<unknown> {
-      const deadline = Date.now() + 15_000;
+      const deadline = Date.now() + 30_000;
       while (Date.now() < deadline) {
         await sleep(100);
         try {
@@ -1889,11 +1890,12 @@ describe('lifecycle integration', { timeout: 60_000 }, () => {
     // the whole destroy. The hold matches the host's argv only, so the inner
     // CLI, which inherits it, runs at full speed. A held host never answers
     // create, which gives up after about 5 s and sends it SIGTERM. On a slow
-    // runner that came before the inner destroy, so create is killed once the
-    // program runs, and the destroy kills the held host.
+    // runner that came before the inner destroy, so create is killed once it
+    // has written the manifest, which the host still reads after its creator
+    // died, and the destroy kills the held host.
     it('destroy --force before the host names the program prints its result', async () => {
       const out = join(testHome, 'early-destroy.json');
-      const started = `${out}.started`;
+      const sessions = join(testHome, 'sessions');
       const create = spawn(
         process.execPath,
         [
@@ -1905,7 +1907,7 @@ describe('lifecycle integration', { timeout: 60_000 }, () => {
           '--',
           '/bin/sh',
           '-c',
-          ': > "$0.started"; "$@" destroy "$AGENT_TTY_SESSION_ID" --force --json > "$0"',
+          '"$@" destroy "$AGENT_TTY_SESSION_ID" --force --json > "$0"',
           out,
           ...cli,
         ],
@@ -1923,22 +1925,32 @@ describe('lifecycle integration', { timeout: 60_000 }, () => {
           stdio: 'ignore',
         },
       );
+      let sessionId: string | undefined;
       try {
         const deadline = Date.now() + 20_000;
-        while (!existsSync(started)) {
+        while (
+          sessionId === undefined ||
+          !existsSync(manifestPath(sessionDir(testHome, sessionId)))
+        ) {
           expect(Date.now()).toBeLessThan(deadline);
-          await sleep(50);
+          await sleep(20);
+          // create makes the sessions folder only after it starts.
+          [sessionId] = await readdir(sessions).catch((error: unknown) => {
+            if (hasErrorCode(error, 'ENOENT')) {
+              return [];
+            }
+            throw error;
+          });
         }
       } finally {
         create.kill('SIGKILL');
       }
-      const [sessionId] = await readdir(join(testHome, 'sessions'));
 
       expect(await readEnvelopeOnceWritten(out)).toMatchObject({
         ok: true,
         result: { sessionId, destroyed: true },
       });
-      expect(inspectSession(testHome, sessionId as string)).toMatchObject({
+      expect(inspectSession(testHome, sessionId)).toMatchObject({
         status: 'destroyed',
         childPid: null,
       });