From 691d9692e69fee60ffb4fb736babdbfde4a580b7 Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Thu, 17 Sep 2026 20:58:02 -0700
Subject: [PATCH] fix(pty): stop detached OMP tools on immediate terminal close
 (#20642)

* test(omp): add opt-in owned PTY closure probe

* fix(pty): sweep detached tools on immediate unrecognized shell close

* test(omp): create close probe evidence root in fresh worktrees

* test(pty): account for asynchronous immediate descendant cleanup

* test(pty): reject inconclusive descendant cleanup probes
---
 .../daemon-audit-eligibility-event.test.ts    |   1 +
 ...emon-authenticated-client-activity.test.ts |   1 +
 .../daemon/daemon-endpoint-ownership.test.ts  |   1 +
 src/main/daemon/daemon-health.test.ts         |   1 +
 src/main/daemon/daemon-idle-shutdown.test.ts  |   1 +
 ...aemon-preflight-client-replacement.test.ts |   1 +
 ...-pty-adapter-cold-restore-reanchor.test.ts |   1 +
 ...emon-pty-adapter-cold-restore-seed.test.ts |   1 +
 ...on-pty-adapter-concurrent-recovery.test.ts |   1 +
 ...daemon-pty-adapter-daemon-recovery.test.ts |   1 +
 ...on-pty-adapter-history-checkpoints.test.ts |   1 +
 ...aemon-pty-adapter-history-recovery.test.ts |   1 +
 ...emon-pty-adapter-inventory-respawn.test.ts |   1 +
 ...pty-adapter-protocol-compatibility.test.ts |   1 +
 ...aemon-pty-adapter-session-adoption.test.ts |   1 +
 src/main/daemon/daemon-pty-adapter.test.ts    |   1 +
 .../daemon-pty-router-history-handoff.test.ts |   1 +
 .../daemon-pty-upgrade-adoption.test.ts       |   1 +
 ...emon-reattach-checkpoint-isolation.test.ts |   1 +
 .../daemon-restore-scrollback-depth.test.ts   |   1 +
 .../daemon-self-retirement-respawn.test.ts    |   1 +
 ...on-server-async-spawn-cancellation.test.ts |   1 +
 .../daemon/daemon-server-attach-only.test.ts  |   1 +
 ...daemon-server-attachment-lifecycle.test.ts |   1 +
 .../daemon-server-error-handling.test.ts      |   1 +
 .../daemon-server-kill-attribution.test.ts    |   1 +
 src/main/daemon/daemon-server.test.ts         |   1 +
 .../daemon-session-scrollback-window.test.ts  |   1 +
 ...n-final-checkpoint-caller-deadline.test.ts |   1 +
 ...emon-stream-droppability-lifecycle.test.ts |   1 +
 ...aemon-transport-attachment-release.test.ts |   1 +
 ...6814-daemon-failure-classification.test.ts |   1 +
 src/main/daemon/mock-descendant-sweep.ts      |   8 +
 src/main/daemon/reattach-snapshot.test.ts     |   1 +
 .../slow-daemon-session-verification.test.ts  |   1 +
 .../terminal-host-agent-session.test.ts       |   1 +
 .../daemon/terminal-host-attach-only.test.ts  |   1 +
 .../terminal-host-process-inspection.test.ts  |   1 +
 .../terminal-host-readiness-reporting.test.ts |   1 +
 ...terminal-host-session-reaping-leak.test.ts |  16 +-
 src/main/daemon/terminal-host-startup.test.ts |   1 +
 .../daemon/terminal-host-wsl-context.test.ts  |   1 +
 .../daemon/terminal-session-teardown.test.ts  |  74 +++---
 src/main/daemon/terminal-session-teardown.ts  |  26 +-
 .../pty-listener-teardown-and-orphans.test.ts |  19 +-
 .../local-pty-provider-shutdown.test.ts       |   9 +-
 src/main/providers/local-pty-termination.ts   |  15 +-
 ...escendant-termination-job-coverage.test.ts |   3 +-
 ...session-host-authority.integration.test.ts |   1 +
 tests/tools/omp-close-lifecycle.md            |  98 ++++++++
 tests/tools/omp-close-lifecycle.test.mjs      | 224 ++++++++++++++++++
 51 files changed, 459 insertions(+), 74 deletions(-)
 create mode 100644 src/main/daemon/mock-descendant-sweep.ts
 create mode 100644 tests/tools/omp-close-lifecycle.md
 create mode 100644 tests/tools/omp-close-lifecycle.test.mjs

diff --git a/src/main/daemon/daemon-audit-eligibility-event.test.ts b/src/main/daemon/daemon-audit-eligibility-event.test.ts
index 13d3e0f39ed..0b2c480118f 100644
--- a/src/main/daemon/daemon-audit-eligibility-event.test.ts
+++ b/src/main/daemon/daemon-audit-eligibility-event.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-authenticated-client-activity.test.ts b/src/main/daemon/daemon-authenticated-client-activity.test.ts
index 6579ced7a47..bc1e63ab8e2 100644
--- a/src/main/daemon/daemon-authenticated-client-activity.test.ts
+++ b/src/main/daemon/daemon-authenticated-client-activity.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { readFileSync, mkdtempSync, rmSync } from 'node:fs'
 import { connect, type Socket } from 'node:net'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-endpoint-ownership.test.ts b/src/main/daemon/daemon-endpoint-ownership.test.ts
index cf6af2e0956..7aff5fb32ee 100644
--- a/src/main/daemon/daemon-endpoint-ownership.test.ts
+++ b/src/main/daemon/daemon-endpoint-ownership.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import {
   existsSync,
diff --git a/src/main/daemon/daemon-health.test.ts b/src/main/daemon/daemon-health.test.ts
index 7d0d64271fa..c1b98c06397 100644
--- a/src/main/daemon/daemon-health.test.ts
+++ b/src/main/daemon/daemon-health.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { spawn } from 'node:child_process'
diff --git a/src/main/daemon/daemon-idle-shutdown.test.ts b/src/main/daemon/daemon-idle-shutdown.test.ts
index 05f4b3aa39f..1500718e98f 100644
--- a/src/main/daemon/daemon-idle-shutdown.test.ts
+++ b/src/main/daemon/daemon-idle-shutdown.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { EventEmitter } from 'node:events'
 import { connect, type Socket } from 'node:net'
 import { existsSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
diff --git a/src/main/daemon/daemon-preflight-client-replacement.test.ts b/src/main/daemon/daemon-preflight-client-replacement.test.ts
index 7fbb46ebfd5..726c00a89ed 100644
--- a/src/main/daemon/daemon-preflight-client-replacement.test.ts
+++ b/src/main/daemon/daemon-preflight-client-replacement.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { connect, type Socket } from 'node:net'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-pty-adapter-cold-restore-reanchor.test.ts b/src/main/daemon/daemon-pty-adapter-cold-restore-reanchor.test.ts
index fd3a7dca13c..b1b3d9a4259 100644
--- a/src/main/daemon/daemon-pty-adapter-cold-restore-reanchor.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-cold-restore-reanchor.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Re-anchoring after a cold restore: aliveness probing, sticky restore cache, persistence. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-pty-adapter-cold-restore-seed.test.ts b/src/main/daemon/daemon-pty-adapter-cold-restore-seed.test.ts
index 71e56014a42..4b6c5e74b52 100644
--- a/src/main/daemon/daemon-pty-adapter-cold-restore-seed.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-cold-restore-seed.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Cold-restore seed transfer and the payload shapes handed back to the renderer. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { hostname } from 'node:os'
diff --git a/src/main/daemon/daemon-pty-adapter-concurrent-recovery.test.ts b/src/main/daemon/daemon-pty-adapter-concurrent-recovery.test.ts
index 12805c0b3ee..66a3320ac81 100644
--- a/src/main/daemon/daemon-pty-adapter-concurrent-recovery.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-concurrent-recovery.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-pty-adapter-daemon-recovery.test.ts b/src/main/daemon/daemon-pty-adapter-daemon-recovery.test.ts
index b53d75b2032..b6bb872c50b 100644
--- a/src/main/daemon/daemon-pty-adapter-daemon-recovery.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-daemon-recovery.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Dead-endpoint write handling and daemon respawn after the daemon dies. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { existsSync, rmSync } from 'node:fs'
diff --git a/src/main/daemon/daemon-pty-adapter-history-checkpoints.test.ts b/src/main/daemon/daemon-pty-adapter-history-checkpoints.test.ts
index 3bdd53034d6..b0a5612c582 100644
--- a/src/main/daemon/daemon-pty-adapter-history-checkpoints.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-history-checkpoints.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Periodic/final history checkpointing: scheduling, work caps, cooldown and shutdown writes. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-pty-adapter-history-recovery.test.ts b/src/main/daemon/daemon-pty-adapter-history-recovery.test.ts
index 4703f11300b..9e2914a6a56 100644
--- a/src/main/daemon/daemon-pty-adapter-history-recovery.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-history-recovery.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* History recovery / quarantine / reconcile regressions for DaemonPtyAdapter. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-pty-adapter-inventory-respawn.test.ts b/src/main/daemon/daemon-pty-adapter-inventory-respawn.test.ts
index f53e2c4c410..bccb0cbd19c 100644
--- a/src/main/daemon/daemon-pty-adapter-inventory-respawn.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-inventory-respawn.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Inventory after the terminal host dies: worktree removal must not hard-fail. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { DaemonPtyAdapter } from './daemon-pty-adapter'
diff --git a/src/main/daemon/daemon-pty-adapter-protocol-compatibility.test.ts b/src/main/daemon/daemon-pty-adapter-protocol-compatibility.test.ts
index a2f2cbf3497..8132f2de4e2 100644
--- a/src/main/daemon/daemon-pty-adapter-protocol-compatibility.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-protocol-compatibility.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* DaemonPtyAdapter behaviour that varies with the negotiated daemon protocol version. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { rmSync } from 'node:fs'
diff --git a/src/main/daemon/daemon-pty-adapter-session-adoption.test.ts b/src/main/daemon/daemon-pty-adapter-session-adoption.test.ts
index cd6acc2352f..a603c21f037 100644
--- a/src/main/daemon/daemon-pty-adapter-session-adoption.test.ts
+++ b/src/main/daemon/daemon-pty-adapter-session-adoption.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Adopting daemon sessions that already exist: reattach, attach-only, inventory, tombstones, startup reconcile. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-pty-adapter.test.ts b/src/main/daemon/daemon-pty-adapter.test.ts
index 379d6a23b8f..410caddbe21 100644
--- a/src/main/daemon/daemon-pty-adapter.test.ts
+++ b/src/main/daemon/daemon-pty-adapter.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /* Core IPtyProvider surface of DaemonPtyAdapter: spawn, io, sizing, teardown. */
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { rmSync } from 'node:fs'
diff --git a/src/main/daemon/daemon-pty-router-history-handoff.test.ts b/src/main/daemon/daemon-pty-router-history-handoff.test.ts
index e57375467ef..0a7eead083a 100644
--- a/src/main/daemon/daemon-pty-router-history-handoff.test.ts
+++ b/src/main/daemon/daemon-pty-router-history-handoff.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-pty-upgrade-adoption.test.ts b/src/main/daemon/daemon-pty-upgrade-adoption.test.ts
index 99c2a792e1e..7a92aecf150 100644
--- a/src/main/daemon/daemon-pty-upgrade-adoption.test.ts
+++ b/src/main/daemon/daemon-pty-upgrade-adoption.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-reattach-checkpoint-isolation.test.ts b/src/main/daemon/daemon-reattach-checkpoint-isolation.test.ts
index b2c0bf59cbc..d716cb9372d 100644
--- a/src/main/daemon/daemon-reattach-checkpoint-isolation.test.ts
+++ b/src/main/daemon/daemon-reattach-checkpoint-isolation.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-restore-scrollback-depth.test.ts b/src/main/daemon/daemon-restore-scrollback-depth.test.ts
index b2c2c7c5028..dead1a7b64f 100644
--- a/src/main/daemon/daemon-restore-scrollback-depth.test.ts
+++ b/src/main/daemon/daemon-restore-scrollback-depth.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-self-retirement-respawn.test.ts b/src/main/daemon/daemon-self-retirement-respawn.test.ts
index 7d70d02e70a..7adaa3050fe 100644
--- a/src/main/daemon/daemon-self-retirement-respawn.test.ts
+++ b/src/main/daemon/daemon-self-retirement-respawn.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { existsSync, mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-server-async-spawn-cancellation.test.ts b/src/main/daemon/daemon-server-async-spawn-cancellation.test.ts
index 57585dc9318..7c42e88c93d 100644
--- a/src/main/daemon/daemon-server-async-spawn-cancellation.test.ts
+++ b/src/main/daemon/daemon-server-async-spawn-cancellation.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
diff --git a/src/main/daemon/daemon-server-attach-only.test.ts b/src/main/daemon/daemon-server-attach-only.test.ts
index 60e9ee83495..8b4099368a8 100644
--- a/src/main/daemon/daemon-server-attach-only.test.ts
+++ b/src/main/daemon/daemon-server-attach-only.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-server-attachment-lifecycle.test.ts b/src/main/daemon/daemon-server-attachment-lifecycle.test.ts
index 2f4d1b734ac..61243f56920 100644
--- a/src/main/daemon/daemon-server-attachment-lifecycle.test.ts
+++ b/src/main/daemon/daemon-server-attachment-lifecycle.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import type { Socket } from 'node:net'
 import { mkdtempSync, rmSync } from 'node:fs'
diff --git a/src/main/daemon/daemon-server-error-handling.test.ts b/src/main/daemon/daemon-server-error-handling.test.ts
index 7ab9d1ffa95..adca3e19834 100644
--- a/src/main/daemon/daemon-server-error-handling.test.ts
+++ b/src/main/daemon/daemon-server-error-handling.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { chmodSync, linkSync, mkdtempSync, readFileSync, rmSync, unlinkSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-server-kill-attribution.test.ts b/src/main/daemon/daemon-server-kill-attribution.test.ts
index b2f506f42ed..d5c0bcf8bd2 100644
--- a/src/main/daemon/daemon-server-kill-attribution.test.ts
+++ b/src/main/daemon/daemon-server-kill-attribution.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-server.test.ts b/src/main/daemon/daemon-server.test.ts
index 27727aa2b3d..ef89b3ef3b0 100644
--- a/src/main/daemon/daemon-server.test.ts
+++ b/src/main/daemon/daemon-server.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { connect, type Server, type Socket } from 'node:net'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-session-scrollback-window.test.ts b/src/main/daemon/daemon-session-scrollback-window.test.ts
index b2dfb5118c9..d78ace1a038 100644
--- a/src/main/daemon/daemon-session-scrollback-window.test.ts
+++ b/src/main/daemon/daemon-session-scrollback-window.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /**
  * OOM regression: a daemon owning 100+ terminals retained ~5000 rows of grid per session with no
  * bound, grew to ~1.9 GB, and was killed under system memory pressure — losing every session it
diff --git a/src/main/daemon/daemon-shutdown-final-checkpoint-caller-deadline.test.ts b/src/main/daemon/daemon-shutdown-final-checkpoint-caller-deadline.test.ts
index 64ae0f77ba0..f134a8c8f8c 100644
--- a/src/main/daemon/daemon-shutdown-final-checkpoint-caller-deadline.test.ts
+++ b/src/main/daemon/daemon-shutdown-final-checkpoint-caller-deadline.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/daemon-stream-droppability-lifecycle.test.ts b/src/main/daemon/daemon-stream-droppability-lifecycle.test.ts
index fda1fe25b98..e65e8ab18ba 100644
--- a/src/main/daemon/daemon-stream-droppability-lifecycle.test.ts
+++ b/src/main/daemon/daemon-stream-droppability-lifecycle.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { randomUUID } from 'node:crypto'
 import type { Socket } from 'node:net'
diff --git a/src/main/daemon/daemon-transport-attachment-release.test.ts b/src/main/daemon/daemon-transport-attachment-release.test.ts
index 7b7c5e4fee6..511b9bf944e 100644
--- a/src/main/daemon/daemon-transport-attachment-release.test.ts
+++ b/src/main/daemon/daemon-transport-attachment-release.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 /**
  * Attachment-leak regression: an attachment that outlives its transport leaves the session looking
  * viewed forever — producer pause/resume and any attachment-gated behavior then act on a client that
diff --git a/src/main/daemon/issue-6814-daemon-failure-classification.test.ts b/src/main/daemon/issue-6814-daemon-failure-classification.test.ts
index 35b84245a83..a7504a5e2a3 100644
--- a/src/main/daemon/issue-6814-daemon-failure-classification.test.ts
+++ b/src/main/daemon/issue-6814-daemon-failure-classification.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 // Regression coverage for issue #6814 (terminal lockup after upgrade).
 //
 // Drives the real DaemonServer + checkDaemonHealth client over a real unix
diff --git a/src/main/daemon/mock-descendant-sweep.ts b/src/main/daemon/mock-descendant-sweep.ts
new file mode 100644
index 00000000000..e8baa228c10
--- /dev/null
+++ b/src/main/daemon/mock-descendant-sweep.ts
@@ -0,0 +1,8 @@
+import { vi } from 'vitest'
+
+// Mock subprocess PIDs must never reach the host process table or signal real descendants.
+vi.mock('../pty-descendant-termination', () => ({
+  killWithDescendantSweep: async (_pid: number, killRoot: () => void): Promise<void> => {
+    killRoot()
+  }
+}))
diff --git a/src/main/daemon/reattach-snapshot.test.ts b/src/main/daemon/reattach-snapshot.test.ts
index 9bbf7a103d6..c707521223e 100644
--- a/src/main/daemon/reattach-snapshot.test.ts
+++ b/src/main/daemon/reattach-snapshot.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import { TerminalHost } from './terminal-host'
 import { HeadlessEmulator } from './headless-emulator'
diff --git a/src/main/daemon/slow-daemon-session-verification.test.ts b/src/main/daemon/slow-daemon-session-verification.test.ts
index 082f1949a5f..9668f1de26d 100644
--- a/src/main/daemon/slow-daemon-session-verification.test.ts
+++ b/src/main/daemon/slow-daemon-session-verification.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { connect, createServer, type Server, type Socket } from 'node:net'
 import { tmpdir } from 'node:os'
diff --git a/src/main/daemon/terminal-host-agent-session.test.ts b/src/main/daemon/terminal-host-agent-session.test.ts
index 1cf929fb93f..41b2f0c53e3 100644
--- a/src/main/daemon/terminal-host-agent-session.test.ts
+++ b/src/main/daemon/terminal-host-agent-session.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import type { SubprocessHandle } from './session-subprocess-handle'
 import { TerminalHost } from './terminal-host'
diff --git a/src/main/daemon/terminal-host-attach-only.test.ts b/src/main/daemon/terminal-host-attach-only.test.ts
index 97284451233..f33630536ee 100644
--- a/src/main/daemon/terminal-host-attach-only.test.ts
+++ b/src/main/daemon/terminal-host-attach-only.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi, type Mock } from 'vitest'
 import type { SubprocessHandle } from './session-subprocess-handle'
 import { TerminalHost, type TerminalHostOptions } from './terminal-host'
diff --git a/src/main/daemon/terminal-host-process-inspection.test.ts b/src/main/daemon/terminal-host-process-inspection.test.ts
index 50858a89ae1..eca0207dade 100644
--- a/src/main/daemon/terminal-host-process-inspection.test.ts
+++ b/src/main/daemon/terminal-host-process-inspection.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { describe, expect, it, vi } from 'vitest'
 import type { SubprocessHandle } from './session-subprocess-handle'
 import { TerminalHost } from './terminal-host'
diff --git a/src/main/daemon/terminal-host-readiness-reporting.test.ts b/src/main/daemon/terminal-host-readiness-reporting.test.ts
index 677bcae258a..6e636e766e1 100644
--- a/src/main/daemon/terminal-host-readiness-reporting.test.ts
+++ b/src/main/daemon/terminal-host-readiness-reporting.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import type { SubprocessHandle } from './session-subprocess-handle'
 import { TerminalHost } from './terminal-host'
diff --git a/src/main/daemon/terminal-host-session-reaping-leak.test.ts b/src/main/daemon/terminal-host-session-reaping-leak.test.ts
index c937607a33a..4d0c53e1a77 100644
--- a/src/main/daemon/terminal-host-session-reaping-leak.test.ts
+++ b/src/main/daemon/terminal-host-session-reaping-leak.test.ts
@@ -130,13 +130,21 @@ describe('TerminalHost dead-session reaping (leak regression)', () => {
     })
     lastSubprocess.forceKill = vi.fn()
 
+    let releaseSweep = (): void => {}
+    killWithDescendantSweepMock.mockImplementationOnce(
+      () =>
+        new Promise<void>((resolve) => {
+          releaseSweep = resolve
+        })
+    )
     const killed = host.kill('session-1', { immediate: true })
 
-    // Immediate teardown skips the graceful kill and force-kills the child directly. On POSIX
-    // that reaches the child pgroup, so no Windows taskkill /T /F descendant sweep is needed.
+    expect(killWithDescendantSweepMock).toHaveBeenCalledTimes(1)
     expect(lastSubprocess.kill).not.toHaveBeenCalled()
-    expect(lastSubprocess.forceKill).toHaveBeenCalled()
-    expect(killWithDescendantSweepMock).not.toHaveBeenCalled()
+    expect(lastSubprocess.forceKill).not.toHaveBeenCalled()
+    expect(emulatorDispose).not.toHaveBeenCalled()
+    releaseSweep()
+    await vi.waitFor(() => expect(lastSubprocess.forceKill).toHaveBeenCalledTimes(1))
     expect(emulatorDispose).not.toHaveBeenCalled()
     expect(host.listSessions()).toHaveLength(1)
     lastSubprocess._onExitCb?.(137)
diff --git a/src/main/daemon/terminal-host-startup.test.ts b/src/main/daemon/terminal-host-startup.test.ts
index e7b7c7b4c09..c6817b1e758 100644
--- a/src/main/daemon/terminal-host-startup.test.ts
+++ b/src/main/daemon/terminal-host-startup.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { TerminalHost } from './terminal-host'
 import type { SubprocessHandle } from './session-subprocess-handle'
diff --git a/src/main/daemon/terminal-host-wsl-context.test.ts b/src/main/daemon/terminal-host-wsl-context.test.ts
index 3958e370684..de0523b7ff1 100644
--- a/src/main/daemon/terminal-host-wsl-context.test.ts
+++ b/src/main/daemon/terminal-host-wsl-context.test.ts
@@ -1,3 +1,4 @@
+import './mock-descendant-sweep'
 import { afterEach, describe, expect, it, vi } from 'vitest'
 import type * as WslModule from '../wsl'
 
diff --git a/src/main/daemon/terminal-session-teardown.test.ts b/src/main/daemon/terminal-session-teardown.test.ts
index 95010efd106..aeb9c7e31d2 100644
--- a/src/main/daemon/terminal-session-teardown.test.ts
+++ b/src/main/daemon/terminal-session-teardown.test.ts
@@ -61,50 +61,60 @@ describe('TerminalSessionTeardown plain-shell teardown', () => {
     expect(() => killRoot()).not.toThrow()
   })
 
-  it('win32 immediate kill claims termination before awaiting the sweep', async () => {
-    // Why: createOrAttach rejects a doomed plain shell only via isTerminating, so the claim
-    // must land before the taskkill await or an attach can bind a pane to a dying session.
-    setPlatform('win32')
-    const session = createPlainShellSession()
-    const beginTermination = session.beginTermination as unknown as ReturnType<typeof vi.fn>
-    let claimedBeforeSweep = false
-    killWithDescendantSweepMock.mockImplementation(async () => {
-      claimedBeforeSweep = beginTermination.mock.calls.length === 1
-    })
-    const teardown = new TerminalSessionTeardown(new Map([['s1', session]]))
+  it.each(['win32', 'linux', 'darwin'] as const)(
+    '%s immediate kill claims termination before awaiting the sweep',
+    async (platform) => {
+      // Why: createOrAttach rejects a doomed plain shell only via isTerminating, so the claim
+      // must land before the taskkill await or an attach can bind a pane to a dying session.
+      setPlatform(platform)
+      const session = createPlainShellSession()
+      const beginTermination = session.beginTermination as unknown as ReturnType<typeof vi.fn>
+      let claimedBeforeSweep = false
+      killWithDescendantSweepMock.mockImplementation(async () => {
+        claimedBeforeSweep = beginTermination.mock.calls.length === 1
+      })
+      const teardown = new TerminalSessionTeardown(new Map([['s1', session]]))
 
-    await teardown.killSession('s1', session, true)
+      await teardown.killSession('s1', session, true)
 
-    expect(claimedBeforeSweep).toBe(true)
-  })
+      expect(claimedBeforeSweep).toBe(true)
+    }
+  )
 
-  it('win32 sweep ownsRoot guard requires the live session to still own the id', async () => {
-    setPlatform('win32')
-    const session = createPlainShellSession()
-    const sessions = new Map([['s1', session]])
-    const teardown = new TerminalSessionTeardown(sessions)
+  it.each(['win32', 'linux', 'darwin'] as const)(
+    '%s sweep ownsRoot guard requires the live session to still own the id',
+    async (platform) => {
+      setPlatform(platform)
+      const session = createPlainShellSession()
+      const sessions = new Map([['s1', session]])
+      const teardown = new TerminalSessionTeardown(sessions)
 
-    await teardown.killSession('s1', session, true)
-    const ownsRoot = (killWithDescendantSweepMock.mock.calls[0][2] as { ownsRoot: () => boolean })
-      .ownsRoot
-    expect(ownsRoot()).toBe(true)
+      await teardown.killSession('s1', session, true)
+      const ownsRoot = (killWithDescendantSweepMock.mock.calls[0][2] as { ownsRoot: () => boolean })
+        .ownsRoot
+      expect(ownsRoot()).toBe(true)
 
-    // A natural exit or reap must stop us from taskkilling a recycled PID.
-    ;(session as unknown as { isAlive: boolean }).isAlive = false
-    expect(ownsRoot()).toBe(false)
-    sessions.delete('s1')
-    ;(session as unknown as { isAlive: boolean }).isAlive = true
-    expect(ownsRoot()).toBe(false)
-  })
+      // A natural exit or reap must stop us from taskkilling a recycled PID.
+      ;(session as unknown as { isAlive: boolean }).isAlive = false
+      expect(ownsRoot()).toBe(false)
+      sessions.delete('s1')
+      ;(session as unknown as { isAlive: boolean }).isAlive = true
+      expect(ownsRoot()).toBe(false)
+    }
+  )
 
-  it('non-win32 immediate kill skips the tree kill (pgroup force-kill suffices)', async () => {
+  it('POSIX immediate close sweeps detached OMP tools before killing their parent', async () => {
     setPlatform('linux')
     const session = createPlainShellSession()
     const teardown = new TerminalSessionTeardown(new Map([['s1', session]]))
 
     await teardown.killSession('s1', session, true)
 
-    expect(killWithDescendantSweepMock).not.toHaveBeenCalled()
+    expect(killWithDescendantSweepMock).toHaveBeenCalledWith(
+      session.pid,
+      expect.any(Function),
+      expect.objectContaining({ ownsRoot: expect.any(Function) })
+    )
     expect(session.forceKillAndWaitForExit).toHaveBeenCalled()
   })
 
diff --git a/src/main/daemon/terminal-session-teardown.ts b/src/main/daemon/terminal-session-teardown.ts
index 017f841a5e0..d35bfc4d64c 100644
--- a/src/main/daemon/terminal-session-teardown.ts
+++ b/src/main/daemon/terminal-session-teardown.ts
@@ -80,27 +80,13 @@ export class TerminalSessionTeardown {
     return operation
   }
 
-  /**
-   * Immediate teardown of a non-agent shell. On Windows, closing the ConPTY does not
-   * reap orphaned children (node-pty `useConptyDll` skips the console-process reap), so a
-   * live `pnpm i`/`node` survives shell exit, keeps the ConPTY console non-empty, and holds
-   * the worktree cwd — failing destructive worktree removal with "Failed to physically stop
-   * every PTY". Tree-kill only when the OS identity probe returns `own`; `unknown`/`foreign`/
-   * `absent` skip taskkill and rely on root close alone. Mirrors the agent path
-   * (#10004/#10100). POSIX shells already reach their child pgroup on forceKill, so they
-   * stay on the plain force-kill path.
-   */
+  /** Immediate close must reach detached tools even when startup did not identify an agent. */
   private async forceKillPlainShellSession(sessionId: string, session: Session): Promise<void> {
-    if (process.platform === 'win32') {
-      // Why: forceKillAndWaitForExit claims termination synchronously; awaiting the sweep
-      // ahead of it would leave attach open on a doomed session for the taskkill's duration.
-      session.beginTermination()
-      await killWithDescendantSweep(session.pid, () => {}, {
-        // Why: the descendant tree is only ours while this Session still owns the live root PID.
-        ownsRoot: () => this.sessions.get(sessionId) === session && session.isAlive,
-        terminateOwnedTree: () => session.terminateOwnedTree()
-      })
-    }
+    session.beginTermination()
+    await killWithDescendantSweep(session.pid, () => {}, {
+      ownsRoot: () => this.sessions.get(sessionId) === session && session.isAlive,
+      terminateOwnedTree: () => session.terminateOwnedTree()
+    })
     await session.forceKillAndWaitForExit()
   }
 
diff --git a/src/main/ipc/pty-listener-teardown-and-orphans.test.ts b/src/main/ipc/pty-listener-teardown-and-orphans.test.ts
index ae749f8dbe0..7e4178f35d3 100644
--- a/src/main/ipc/pty-listener-teardown-and-orphans.test.ts
+++ b/src/main/ipc/pty-listener-teardown-and-orphans.test.ts
@@ -1,6 +1,7 @@
 import { describe, expect, it, vi } from 'vitest'
 import {
   existsSyncMock,
+  loginPreflightExecFileMock,
   spawnMock,
   openCodeClearPtyMock,
   piClearPtyMock
@@ -162,9 +163,25 @@ describe('registerPtyHandlers', () => {
       rows: 24
     })) as { id: string }
 
+    let finishSnapshot: (() => void) | undefined
+    loginPreflightExecFileMock.mockImplementationOnce(
+      (
+        _file: string,
+        _args: string[],
+        _options: unknown,
+        callback: (error: Error | null, stdout: string) => void
+      ) => {
+        finishSnapshot = () => callback(null, '')
+      }
+    )
     const killPromise = handlers.get('pty:kill')!(null, { id: spawnResult.id }) as Promise<void>
 
-    expect(killSpy).toHaveBeenCalledTimes(1)
+    await vi.waitFor(() => expect(finishSnapshot).toBeTypeOf('function'))
+    expect(killSpy).not.toHaveBeenCalled()
+    expect(onDataDisposable.dispose).not.toHaveBeenCalled()
+    expect(onExitDisposable.dispose).not.toHaveBeenCalled()
+    finishSnapshot?.()
+    await vi.waitFor(() => expect(killSpy).toHaveBeenCalledTimes(1))
     expect(onDataDisposable.dispose).not.toHaveBeenCalled()
     expect(onExitDisposable.dispose).not.toHaveBeenCalled()
 
diff --git a/src/main/providers/local-pty-provider-shutdown.test.ts b/src/main/providers/local-pty-provider-shutdown.test.ts
index cb7595800c1..cccede7186b 100644
--- a/src/main/providers/local-pty-provider-shutdown.test.ts
+++ b/src/main/providers/local-pty-provider-shutdown.test.ts
@@ -513,13 +513,16 @@ describe('LocalPtyProvider', () => {
       expect(killWithDescendantSweepMock).not.toHaveBeenCalled()
     })
 
-    it('non-win32 immediate shutdown of a plain shell skips the tree kill', async () => {
-      // beforeEach pins platform to linux; POSIX force-kill already reaches the child pgroup.
+    it('POSIX immediate shutdown sweeps detached OMP tools without startup recognition', async () => {
       const { id } = await provider.spawn({ cols: 80, rows: 24 })
 
       await provider.shutdown(id, { immediate: true })
 
-      expect(killWithDescendantSweepMock).not.toHaveBeenCalled()
+      expect(killWithDescendantSweepMock).toHaveBeenCalledWith(
+        mockProc.pid,
+        expect.any(Function),
+        expect.objectContaining({ ownsRoot: expect.any(Function) })
+      )
     })
   })
 
diff --git a/src/main/providers/local-pty-termination.ts b/src/main/providers/local-pty-termination.ts
index 470d5b600ab..7a19e9d7326 100644
--- a/src/main/providers/local-pty-termination.ts
+++ b/src/main/providers/local-pty-termination.ts
@@ -175,19 +175,8 @@ async function shutdownTrackedPty(
     operation.rootSignalled = true
     requestTrackedPtyShutdown(id, proc, operation.immediate)
   }
-  if (ptyAgentSessionIds.has(id)) {
-    // Why: POSIX needs a pre-kill descendant snapshot; Windows tree-kills only when the
-    // identity probe returns `own` so agent/MCP orphans cannot hold the worktree cwd
-    // (#10004). `unknown`/`foreign`/`absent` skip taskkill and rely on root close alone.
-    await killWithDescendantSweep(proc.pid, signalRoot, {
-      ownsRoot: () => ptyProcesses.get(id) === proc,
-      terminateOwnedTree: () => terminatePtyJob(proc)
-    })
-  } else if (process.platform === 'win32' && operation.immediate) {
-    // Why: a plain shell's ConPTY teardown doesn't reap orphaned children (useConptyDll
-    // skips the console reap), so a live `pnpm i`/`node` keeps the ConPTY console alive and
-    // holds the worktree cwd. Tree kill runs only when the OS identity probe returns `own`;
-    // otherwise root close alone, and detached children may block physical stop (#10004).
+  if (ptyAgentSessionIds.has(id) || operation.immediate) {
+    // Typed agents also detach tool process groups; immediate close must snapshot before root exit.
     await killWithDescendantSweep(proc.pid, signalRoot, {
       ownsRoot: () => ptyProcesses.get(id) === proc,
       terminateOwnedTree: () => terminatePtyJob(proc)
diff --git a/src/main/pty-descendant-termination-job-coverage.test.ts b/src/main/pty-descendant-termination-job-coverage.test.ts
index 21e14012caa..738d16ab16f 100644
--- a/src/main/pty-descendant-termination-job-coverage.test.ts
+++ b/src/main/pty-descendant-termination-job-coverage.test.ts
@@ -16,7 +16,8 @@ import { describe, expect, it } from 'vitest'
  */
 const SRC_DIR = join(__dirname, '..')
 const CALL = 'killWithDescendantSweep('
-const EXPECTED_MINIMUM_SITES = 5
+// Local immediate and recognized-agent shutdown share one guarded call site.
+const EXPECTED_MINIMUM_SITES = 4
 
 function collectTypeScriptFiles(dir: string): string[] {
   const found: string[] = []
diff --git a/src/main/runtime/remote-agent-session-host-authority.integration.test.ts b/src/main/runtime/remote-agent-session-host-authority.integration.test.ts
index 56d74744238..884a80a36fb 100644
--- a/src/main/runtime/remote-agent-session-host-authority.integration.test.ts
+++ b/src/main/runtime/remote-agent-session-host-authority.integration.test.ts
@@ -1,3 +1,4 @@
+import '../daemon/mock-descendant-sweep'
 import { mkdtempSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
diff --git a/tests/tools/omp-close-lifecycle.md b/tests/tools/omp-close-lifecycle.md
new file mode 100644
index 00000000000..03e2dd6fc31
--- /dev/null
+++ b/tests/tools/omp-close-lifecycle.md
@@ -0,0 +1,98 @@
+# OMP owned-PTY close probe (#9530)
+
+This opt-in probe launches an actual installed OMP binary in disposable local PTYs
+and calls Orca's production `shutdownLocalPty` and `killAllLocalPtys` functions,
+or daemon `Session`, native subprocess handle, and `TerminalSessionTeardown`.
+It sets the same agent-session ownership flag that `activateLocalPtySession` sets
+for `launchAgent` / recognized startup commands, then repeats without that flag
+to represent OMP typed into a shell. This isolates termination policy; it does not
+exercise Agent button delivery or terminal-tab/handle routing.
+
+```sh
+ORCA_BACKGROUND_LAUNCH=1 ORCA_OMP_PROBE_BINARY=/absolute/path/to/omp \
+  node node_modules/vitest/vitest.mjs run --config config/vitest.config.ts \
+  tests/tools/omp-close-lifecycle.test.mjs
+```
+
+The probe defaults to zsh on macOS and bash on other POSIX hosts. Set
+`ORCA_OMP_PROBE_SHELL` to the absolute path of either shell to override. Windows
+is skipped. It requires the existing node-pty native dependency for the current
+Node runtime. The normal unit suite skips the test unless a binary is supplied.
+
+Each case waits five seconds for OMP startup, captures the owned process tree,
+requests explicit close or local quit cleanup, and verifies those exact process
+IDs are absent using host `ps` after a six-second observation window. It records
+raw terminal output and before/after process rows in `.bench-fixtures/omp-close-*`.
+The fixture contains no prompt or model request. It disables the first-run setup
+wizard, startup splash and update checks in a temporary config; OMP's normal tools
+and extensions remain enabled. HOME, ZDOTDIR, XDG_CONFIG_HOME and OMP's agent home
+are disposable. Cleanup signals only owned identities with matching process start
+time and group, then removes the temporary home.
+
+## Observed on 2026-09-14
+
+At Orca base `93c370246388`, macOS arm64, installed `omp/18.1.18`:
+
+- Explicit local close with the agent flag: shell and foreground OMP exited.
+- Explicit local close without the flag: shell and foreground OMP exited.
+- Local quit cleanup with or without the flag: shell and foreground OMP exited.
+- Explicit close used the existing five-second force deadline for the shell.
+  Quit removes native exit tracking immediately, so the probe uses independent
+  host process evidence; an empty provider map is not its exit oracle.
+
+The same four outcomes were observed in an initial first-run setup-splash pass.
+The normal-idle transcript displayed the OMP prompt and reported no LSP servers.
+No stale foreground OMP was reproduced in these local termination-policy cases.
+
+## Detached external tool reproduction and correction
+
+Set `ORCA_OMP_PROBE_EXTERNAL_TOOL=1` to run `! /bin/sleep 120` in OMP before
+explicit immediate close. Add `ORCA_OMP_PROBE_BACKEND=daemon` to exercise the daemon
+backend. Each mode tests both recognized and typed launches; these modes do not
+run the local-quit cases. The probe makes no model requests. Both OMP/PI profiles
+are cleared, and XDG data/cache/state roots are isolated alongside configuration.
+
+On macOS, installed Orca `1.4.202-hourly.202609132311` and OMP `18.1.18`, an actual
+non-focus CLI-created terminal reproduced the detached-child leak: shell PID
+71632 and OMP PID 71667 exited after CLI close, but sleep PID 72125 (PGID 72125)
+remained after the grace window, reparented to PID 1. The owned survivor was
+cleaned using its captured PID/start-time/group identity. This is a detached-tool
+leak, not a reproduction of the reported foreground OMP surviving for days.
+
+With the correction, all four actual OMP/external-sleep cases (recognized/typed,
+local/daemon) left none of the captured shell, OMP or sleep PIDs present. This
+runs production backend code with real PTYs; it does not run a rebuilt installed
+app through the CLI. Reports/transcripts remain local under `.bench-fixtures/`.
+
+### Termination contract
+
+Immediate close now uses the existing descendant sweep for all local-provider
+and daemon shells, including agents typed after startup. This also terminates
+still-parented, intentionally detached jobs that previously survived POSIX close.
+The sweep captures descendants before root exit, checks current root ownership,
+and retains the existing identity-guarded delayed escalation. It adds a bounded
+process-table capture (one-second timeout) and, when descendants exist, the
+existing single two-second delayed recheck; there is no recurring polling.
+Daemon termination is claimed before awaiting capture, preventing reattachment.
+Physical root exit still gates session reaping. Snapshot failure falls back to
+root termination; children already reparented before capture are not covered.
+
+The execution host runs this policy. Paired runtimes using these backends receive
+the fix when their host updates; no wire fields or client-side remote PID signals
+are added. Direct SSH relay PTYs use separate `src/relay/pty-handler.ts` termination
+and are not fixed or runtime-validated by this change. Graceful plain-shell
+shutdown, disconnect and daemon/remote keep-alive policy are unchanged. The code
+uses no repository metadata and applies to folder workspaces as well as worktrees.
+Windows retains its existing guarded job/tree termination; this probe skips it.
+
+## Limits and next evidence
+
+Do not close #9530 from this probe. The original report did not identify Orca/OMP
+versions or the exact close action. A tab can disappear without this termination
+entry point running, which this probe does not cover. It also does not exercise
+full app quit lifecycle, background/floating/mobile handle resolution, a busy
+model turn, initialized eval workers or LSPs, Windows/WSL/Linux execution, or live SSH ownership. Daemon/remote keep-alive is intentional and remains unchanged.
+
+A failing reproduction needs the original surface/close action, provider mode,
+owning runtime, and process identities before and after. Signal-resistant fixture
+processes alone do not establish that current OMP has the reported leak.
diff --git a/tests/tools/omp-close-lifecycle.test.mjs b/tests/tools/omp-close-lifecycle.test.mjs
new file mode 100644
index 00000000000..47df8325c56
--- /dev/null
+++ b/tests/tools/omp-close-lifecycle.test.mjs
@@ -0,0 +1,224 @@
+import { it, expect } from 'vitest'
+import * as pty from 'node-pty'
+import { Session } from '../../src/main/daemon/session.ts'
+import { TerminalSessionTeardown } from '../../src/main/daemon/terminal-session-teardown.ts'
+import { createDaemonPtySubprocessHandle } from '../../src/main/daemon/pty-subprocess/subprocess-handle.ts'
+import { mkdtempSync, mkdirSync, writeFileSync, rmSync } from 'node:fs'
+import { join } from 'node:path'
+import { tmpdir } from 'node:os'
+import { runProcess } from '../../src/shared/child-process/run-process.ts'
+import {
+  captureDescendantSnapshot,
+  readProcessTable
+} from '../../src/main/pty-descendant-termination.ts'
+import {
+  createPtyPhysicalExit,
+  shutdownLocalPty,
+  killAllLocalPtys
+} from '../../src/main/providers/local-pty-termination.ts'
+import {
+  ptyProcesses,
+  ptyAgentSessionIds,
+  ptyPhysicalExits,
+  ptyExitDisposables,
+  clearPtyState
+} from '../../src/main/providers/local-pty-provider-state.ts'
+
+const binary = process.env.ORCA_OMP_PROBE_BINARY
+const externalTool = process.env.ORCA_OMP_PROBE_EXTERNAL_TOOL === '1'
+const daemonBackend = process.env.ORCA_OMP_PROBE_BACKEND === 'daemon'
+const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms))
+const quote = (value) => `'${value.replaceAll("'", "'\\''")}'`
+const ownedPidRows = async (pids) => {
+  const result = await runProcess({
+    program: 'ps',
+    args: ['-p', pids.join(','), '-o', 'pid=,ppid=,pgid=,stat=,comm='],
+    maxOutputBytes: 16000
+  })
+  expect(result.timedOut).toBe(false)
+  expect(result.signal).toBeNull()
+  expect(result.stderr.trim()).toBe('')
+  expect([0, 1]).toContain(result.code)
+  if (result.code === 1) {
+    expect(result.stdout.trim()).toBe('')
+  }
+  return result.stdout.trim()
+}
+it.skipIf(!binary || process.platform === 'win32')(
+  'observes actual OMP under production owned-PTY closure policy',
+  async () => {
+    const fixtures = join(process.cwd(), '.bench-fixtures')
+    mkdirSync(fixtures, { recursive: true })
+    const output = mkdtempSync(join(fixtures, 'omp-close-'))
+    const report = []
+    for (const launch of ['recognized', 'typed']) {
+      for (const close of externalTool || daemonBackend ? ['explicit'] : ['explicit', 'quit']) {
+        expect(ptyProcesses.size).toBe(0)
+        const home = mkdtempSync(join(tmpdir(), 'orca-omp-close-home-'))
+        const agentHome = join(home, 'agent')
+        mkdirSync(agentHome)
+        const config = join(home, 'probe.yml')
+        writeFileSync(
+          config,
+          'startup:\n  setupWizard: false\n  showSplash: false\n  checkUpdate: false\n'
+        )
+        const id = `${launch}-${close}`
+        let transcript = ''
+        let nativeExit = null
+        const shell =
+          process.env.ORCA_OMP_PROBE_SHELL ??
+          (process.platform === 'darwin' ? '/bin/zsh' : '/bin/bash')
+        const shellArgs = shell.endsWith('zsh') ? ['-f', '-i'] : ['--noprofile', '--norc', '-i']
+        const proc = pty.spawn(shell, shellArgs, {
+          name: 'xterm-256color',
+          cols: 120,
+          rows: 35,
+          cwd: home,
+          env: {
+            ...process.env,
+            HOME: home,
+            USERPROFILE: home,
+            ZDOTDIR: home,
+            XDG_CONFIG_HOME: join(home, 'config'),
+            XDG_DATA_HOME: join(home, 'data'),
+            XDG_CACHE_HOME: join(home, 'cache'),
+            XDG_STATE_HOME: join(home, 'state'),
+            OMP_CODING_AGENT_DIR: agentHome,
+            PI_CODING_AGENT_DIR: agentHome,
+            OMP_PROFILE: '',
+            PI_PROFILE: '',
+            PI_CONFIG_DIR: '.omp',
+            PI_CONFIG_FILES: '',
+            ORCA_BACKGROUND_LAUNCH: '1'
+          }
+        })
+        const daemonSession = daemonBackend
+          ? new Session({
+              sessionId: id,
+              cols: 120,
+              rows: 35,
+              shellReadySupported: false,
+              ...(launch === 'recognized' ? { launchAgent: 'omp' } : {}),
+              subprocess: createDaemonPtySubprocessHandle({
+                process: proc,
+                shellPath: shell,
+                spawnCwd: home,
+                env: process.env,
+                startupCommandDeliveredInShellArgs: false,
+                reportsChildExitStatus: true,
+                sessionId: id,
+                startupAgentRecognition: null
+              })
+            })
+          : null
+        proc.onData((data) => {
+          transcript = (transcript + data).slice(-131072)
+        })
+        if (!daemonSession) {
+          ptyProcesses.set(id, proc)
+          createPtyPhysicalExit(id)
+          if (launch === 'recognized') {
+            ptyAgentSessionIds.add(id)
+          }
+        }
+        ptyExitDisposables.set(
+          id,
+          proc.onExit((event) => {
+            nativeExit = event
+            ptyPhysicalExits.get(id)?.markExited()
+            clearPtyState(id)
+            rmSync(home, { recursive: true, force: true })
+          })
+        )
+        let snapshot
+        try {
+          proc.write(`${quote(binary)} --no-session --config ${quote(config)}\r`)
+          await delay(5000)
+          snapshot = await captureDescendantSnapshot(proc.pid)
+          expect(snapshot?.descendants.length).toBeGreaterThan(0)
+          if (externalTool) {
+            proc.write('! /bin/sleep 120\r')
+            for (let attempt = 0; attempt < 25; attempt++) {
+              await delay(200)
+              snapshot = await captureDescendantSnapshot(proc.pid)
+              if (snapshot?.descendants.length > 1) {
+                break
+              }
+            }
+            expect(snapshot?.descendants.length).toBeGreaterThan(1)
+          }
+          const pids = [proc.pid, ...snapshot.descendants.map((row) => row.pid)]
+          const before = await ownedPidRows(pids)
+          expect(before).toContain('omp')
+          if (externalTool) {
+            expect(before).toContain('sleep')
+          }
+          const started = Date.now()
+          let closeError = null
+          try {
+            if (daemonSession) {
+              await new TerminalSessionTeardown(new Map([[id, daemonSession]])).killSession(
+                id,
+                daemonSession,
+                true
+              )
+            } else if (close === 'explicit') {
+              await shutdownLocalPty(id, { immediate: externalTool })
+            } else {
+              killAllLocalPtys()
+            }
+          } catch (error) {
+            closeError = String(error)
+          }
+          await delay(6000)
+          const after = await ownedPidRows(pids)
+          report.push({
+            launch,
+            close,
+            externalTool,
+            backend: daemonBackend ? 'daemon' : 'local',
+            before,
+            after,
+            nativeExit,
+            tracked: daemonSession ? daemonSession.isAlive : ptyProcesses.has(id),
+            elapsedMs: Date.now() - started,
+            closeError,
+            home
+          })
+          writeFileSync(join(output, `${id}.txt`), transcript)
+          writeFileSync(join(output, 'report.json'), JSON.stringify(report, null, 2))
+          expect(closeError).toBeNull()
+          expect(after).toBe('')
+        } finally {
+          if (snapshot) {
+            const current = await readProcessTable()
+            const owned = [
+              ...snapshot.descendants,
+              ...(snapshot.root ? [{ ...snapshot.root, pgid: snapshot.rootPgid }] : [])
+            ]
+            for (const row of current.rows) {
+              if (
+                owned.some(
+                  (known) =>
+                    known.pid === row.pid &&
+                    known.startedAt === row.startedAt &&
+                    known.pgid === row.pgid
+                )
+              ) {
+                try {
+                  process.kill(row.pid, 'SIGKILL')
+                } catch {}
+              }
+            }
+          }
+          daemonSession?.dispose()
+          clearPtyState(id)
+          rmSync(home, { recursive: true, force: true })
+        }
+      }
+    }
+    writeFileSync(join(output, 'report.json'), JSON.stringify(report, null, 2))
+    console.log(output)
+  },
+  90000
+)