diff --git a/packages/cli/tests/case-cleanup-time-fixture.mjs b/packages/cli/tests/case-cleanup-time-fixture.mjs
new file mode 100644
index 000000000..1bffa90da
--- /dev/null
+++ b/packages/cli/tests/case-cleanup-time-fixture.mjs
@@ -0,0 +1,27 @@
+// Invoked inside a private PID namespace. Check residual processes BEFORE its
+// init exits: namespace teardown would otherwise mask a missed descendant kill.
+import { readFileSync, writeFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { spawnSync } from 'node:child_process';
+import { instrumentCleanupTimer } from './case-inner-timing-fixture.mjs';
+import { blockingQuerySource, killRecordedPids, recordedPids, recordedLivePids } from './case-sudo-fixture.mjs';
+
+const [script,dir]=process.argv.slice(2),clock=join(dir,"clock '$;literal"),records=join(dir,'pids');
+try {
+  writeFileSync(clock,'',{mode:0o600});
+  const worker=join(dir,'blocked.mjs');
+  writeFileSync(worker,blockingQuerySource(records,'sleep')+'\nloadSystem();');
+  const source=instrumentCleanupTimer(readFileSync(script,'utf8'),clock);
+  const body=source.slice(source.indexOf('# row253-supervisor-begin'),source.indexOf('# row253-supervisor-end'));
+  const result=spawnSync('/bin/bash',['-c',body+'\nexec /bin/bash -c "$TESTER_SUPERVISOR" -- 2 /usr/bin/setsid /usr/bin/sleep "$@"','--',process.execPath,worker],{
+    encoding:'utf8',timeout:12000,killSignal:'SIGKILL',
+  });
+  // These PIDs belong to this namespace; never use them to signal host PIDs.
+  process.stdout.write(JSON.stringify({
+    status:result.status,signal:result.signal,error:result.error?.message,
+    stdout:result.stdout,stderr:result.stderr,pairs:recordedPids(records),
+    live:recordedLivePids(records),clock:readFileSync(clock,'utf8'),
+  }));
+} finally {
+  killRecordedPids(records);
+}
diff --git a/packages/cli/tests/case-cleanup-time.test.mjs b/packages/cli/tests/case-cleanup-time.test.mjs
new file mode 100644
index 000000000..e6fa10af5
--- /dev/null
+++ b/packages/cli/tests/case-cleanup-time.test.mjs
@@ -0,0 +1,69 @@
+// A delay in finish(), after timing2's end stamp, must fail independently of
+// the inner timer. One fixed process tree runs at a time, without host setup,
+// fake sudo, or a parent-side elapsed-time assertion.
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { mkdtempSync, readFileSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { spawnSync } from 'node:child_process';
+import { fileURLToPath } from 'node:url';
+import { instrumentCleanupTimer, removeInnerObservers, readProbeSeconds } from './case-inner-timing-fixture.mjs';
+
+const scripts=['case1-accept.sh','case2-unit.sh'];
+const read=name=>readFileSync(new URL(`../../../scripts/${name}`,import.meta.url),'utf8');
+// The namespace fixes /proc inventory size; it does not replace clean_session.
+// See org-cleanup-time-build.md for the standalone and loaded calibration. The
+// bound must reject 1s/2s delays and leave most of the 2s production headroom.
+// Constant delays below 0.5s can pass; this is not a bound on host-wide scan
+// cost. In particular, per-entry work needs a shipped scan-cost follow-up.
+const CLEANUP_LIMIT_SECONDS=0.5;
+const probe=fileURLToPath(new URL('./case-cleanup-time-fixture.mjs',import.meta.url));
+
+for(const name of scripts)test(`cleanup timing ${name}: observers preserve bytes and reject exit-anchor drift`,()=>{
+  const source=read(name),clock="/unused/clock '$;literal";
+  const copy=instrumentCleanupTimer(source,clock);
+  assert.equal(removeInnerObservers(copy,clock),source);
+  for(const marker of ['SO_PEERCRED','MOSAIC_TESTER_SOCKET_V1','MOSAIC_LEGACY_STATUS'])
+    assert.equal(copy.split(marker).length,source.split(marker).length,marker);
+  const exit='    exit "$rc"\n';
+  assert.throws(()=>instrumentCleanupTimer(source.replace(exit,''),clock),/anchor/);
+  assert.throws(()=>instrumentCleanupTimer(source.replace(exit,exit+exit),clock),/anchor/);
+});
+
+// Both shipped copies are executed: Case1 shares this supervisor across legacy
+// calls, queries and P10; Case2 uses its copy for config queries.
+for(const name of scripts)test(`cleanup timing ${name}: inner timeout kills descendants within the cleanup budget`,t=>{
+  const dir=mkdtempSync(join(tmpdir(),'cl-'));
+  t.after(()=>rmSync(dir,{recursive:true,force:true}));
+  // No skip/fallback: this Linux test requires unprivileged user/PID/mount
+  // namespaces. --kill-child also removes our namespace if the probe times out.
+  const outer=spawnSync('/usr/bin/unshare',[
+    '--user','--map-root-user','--pid','--fork','--kill-child=KILL','--mount-proc',
+    process.execPath,probe,fileURLToPath(new URL(`../../../scripts/${name}`,import.meta.url)),dir,
+  ],{
+    encoding:'utf8',timeout:15000,killSignal:'SIGKILL',
+  });
+  const prerequisite='requires /usr/bin/unshare and unprivileged user/PID/mount namespaces (check kernel/AppArmor/container seccomp)';
+  assert.equal(outer.error,undefined,`${prerequisite}: ${outer.error?.message}`);
+  assert.equal(outer.status,0,`${prerequisite}; probe output:\n${outer.stdout}${outer.stderr}`);
+  assert.equal(outer.stderr,'');
+  const result=JSON.parse(outer.stdout);
+  assert.equal(result.error,undefined,result.error);
+  assert.equal(result.signal,null,result.stderr);
+  assert.equal(result.status,81,result.stderr);
+  assert.equal(result.stdout,'');
+  assert.equal(result.stderr,'');
+  const pairs=result.pairs;
+  assert.equal(pairs.length,2,'the session leader and its live descendant both started');
+  assert.equal(pairs[0][0],pairs[0][1],'the command leads its kernel session');
+  assert.notEqual(pairs[1][0],pairs[0][0]);
+  assert.equal(pairs[1][1],pairs[0][1],'the descendant belongs to the supervised session');
+  assert.deepEqual(result.live,[],'cleanup must kill the whole process tree before namespace teardown');
+  // A positive centisecond pair relies on clean_session's current mandatory
+  // 0.01s retry sleep. Revisit this measurement if shipped cleanup removes it;
+  // keep the shared inner-timer parser strict in the meantime.
+  const seconds=readProbeSeconds(result.clock);
+  t.diagnostic(`${name}: cleanup ${seconds}s; limit ${CLEANUP_LIMIT_SECONDS}s`);
+  assert.ok(seconds<CLEANUP_LIMIT_SECONDS,`${name}: cleanup ${seconds}s must be < ${CLEANUP_LIMIT_SECONDS}s`);
+});
diff --git a/packages/cli/tests/case-inner-timing-fixture.mjs b/packages/cli/tests/case-inner-timing-fixture.mjs
index a7a28c447..688d1a876 100644
--- a/packages/cli/tests/case-inner-timing-fixture.mjs
+++ b/packages/cli/tests/case-inner-timing-fixture.mjs
@@ -33,3 +33,18 @@ export function removeInnerObservers(source,clock) {
   for(const block of Object.values(innerObservers(clock))){unique(source,block);source=source.replace(block,'');}
   return source;
 }
+
+// Reuse the timing2 finish-entry stamp, moving only the other observation.
+// The end is in the supervisor, after clean_session and both waits, immediately
+// before exit. Parent scheduling and process start-up never enter this pair.
+export function instrumentCleanupTimer(source,clock) {
+  const blocks=innerObservers(clock);
+  let observed=instrumentInnerTimer(source,clock);
+  const from=unique(observed,BEGIN),to=unique(observed,END);
+  let supervisor=observed.slice(from,to);
+  const exit='    exit "$rc"\n';
+  unique(supervisor,exit);
+  supervisor=supervisor.replace(blocks.begin,'').replace(blocks.end,blocks.begin);
+  supervisor=supervisor.replace(exit,blocks.end+exit);
+  return observed.slice(0,from)+supervisor+observed.slice(to);
+}