diff --git a/stelloauth/rootfs/usr/local/bin/addon-supervisor b/stelloauth/rootfs/usr/local/bin/addon-supervisor
index b0c1782..4ce318f 100755
--- a/stelloauth/rootfs/usr/local/bin/addon-supervisor
+++ b/stelloauth/rootfs/usr/local/bin/addon-supervisor
@@ -172,6 +172,21 @@ def wait_until_ready(
     raise ReadinessError(f"{name} did not become ready")
 
 
+def process_group_alive(
+    pgid: int,
+    killpg: Callable[[int, int], None] = os.killpg,
+) -> bool:
+    try:
+        killpg(pgid, 0)
+    except ProcessLookupError:
+        return False
+    except PermissionError:
+        return True
+    except OSError:
+        return True
+    return True
+
+
 class ProcessManager:
     def __init__(
         self,
@@ -179,6 +194,7 @@ class ProcessManager:
         *,
         popen: Callable[..., subprocess.Popen] = subprocess.Popen,
         killpg: Callable[[int, int], None] = os.killpg,
+        group_alive: Callable[[int], bool] = process_group_alive,
         cloak_probe: Callable[[], None] = probe_cloak,
         stelloauth_probe: Callable[[], None] = probe_stelloauth,
         monotonic: Callable[[], float] = time.monotonic,
@@ -188,12 +204,15 @@ class ProcessManager:
         self.environment = environment
         self._popen = popen
         self._killpg = killpg
+        self._group_alive = group_alive
         self._cloak_probe = cloak_probe
         self._stelloauth_probe = stelloauth_probe
         self._monotonic = monotonic
         self._sleep = sleep
         self._profile_path = profile_path
         self._children: list[tuple[str, subprocess.Popen]] = []
+        self._groups: list[int] = []
+        self._dead_groups: set[int] = set()
         self._stopping = False
         self._term_sent = False
         self._shutdown_deadline: float | None = None
@@ -221,11 +240,9 @@ class ProcessManager:
             start_new_session=True,
         )
         self._children.append((name, process))
+        self._groups.append(process.pid)
         if self._stopping:
-            try:
-                self._killpg(process.pid, signal.SIGTERM)
-            except OSError:
-                pass
+            self._signal_groups(signal.SIGTERM, [process.pid])
         return process
 
     def _first_exited_child(self) -> tuple[str, int] | None:
@@ -238,12 +255,30 @@ class ProcessManager:
     def _startup_stopping(self) -> bool:
         return self._stopping or self._first_exited_child() is not None
 
-    def _signal_running(self, sent_signal: int) -> None:
-        for _name, process in self._children:
-            if process.poll() is not None:
+    def _live_groups(self) -> list[int]:
+        live_groups = []
+        for pgid in self._groups:
+            if pgid in self._dead_groups:
+                continue
+            if self._group_alive(pgid):
+                live_groups.append(pgid)
+            else:
+                self._dead_groups.add(pgid)
+        return live_groups
+
+    def _signal_groups(
+        self, sent_signal: int, groups: list[int] | None = None
+    ) -> None:
+        for pgid in self._live_groups() if groups is None else groups:
+            if pgid in self._dead_groups:
+                continue
+            if groups is not None and not self._group_alive(pgid):
+                self._dead_groups.add(pgid)
                 continue
             try:
-                self._killpg(process.pid, sent_signal)
+                self._killpg(pgid, sent_signal)
+            except ProcessLookupError:
+                self._dead_groups.add(pgid)
             except OSError:
                 pass
 
@@ -251,7 +286,7 @@ class ProcessManager:
         if self._shutdown_deadline is None:
             self._shutdown_deadline = self._monotonic() + 10.0
         if not self._term_sent:
-            self._signal_running(signal.SIGTERM)
+            self._signal_groups(signal.SIGTERM)
             self._term_sent = True
 
     def _reap_all(self) -> None:
@@ -267,16 +302,15 @@ class ProcessManager:
         logging.info("Stopping child processes")
         self._begin_shutdown()
         assert self._shutdown_deadline is not None
-        while (
-            any(process.poll() is None for _name, process in self._children)
-            and self._monotonic() < self._shutdown_deadline
-        ):
+        live_groups = self._live_groups()
+        while live_groups and self._monotonic() < self._shutdown_deadline:
             remaining = self._shutdown_deadline - self._monotonic()
             self._sleep(min(0.25, max(0.0, remaining)))
+            live_groups = self._live_groups()
 
-        if any(process.poll() is None for _name, process in self._children):
+        if live_groups:
             logging.info("Forcing child processes to stop")
-            self._signal_running(signal.SIGKILL)
+            self._signal_groups(signal.SIGKILL, live_groups)
         self._reap_all()
         logging.info("Child processes stopped")
 
diff --git a/tests/test_supervisor.py b/tests/test_supervisor.py
index 3ed7699..3c51fad 100644
--- a/tests/test_supervisor.py
+++ b/tests/test_supervisor.py
@@ -407,6 +407,8 @@ def manager_harness(
         FakeProcess(1001, ignores_term=ignores_term[0]),
         FakeProcess(1002, ignores_term=ignores_term[1]),
     ]
+    groups = {process.pid: True for process in processes}
+    group_checks: list[int] = []
     spawned: list[FakeProcess] = []
 
     def popen(command, *, env, start_new_session):
@@ -419,7 +421,13 @@ def manager_harness(
         events.append(("signal", pid, sent_signal))
         process = next(item for item in processes if item.pid == pid)
         if sent_signal == signal.SIGKILL or not process.ignores_term:
-            process.returncode = -sent_signal
+            groups[pid] = False
+            if process.returncode is None:
+                process.returncode = -sent_signal
+
+    def group_alive(pid: int) -> bool:
+        group_checks.append(pid)
+        return groups[pid]
 
     def default_cloak_probe() -> None:
         events.append("probe cloak")
@@ -433,6 +441,7 @@ def manager_harness(
         environment,
         popen=popen,
         killpg=killpg,
+        group_alive=group_alive,
         cloak_probe=cloak_probe or default_cloak_probe,
         stelloauth_probe=stelloauth_probe or default_stelloauth_probe,
         monotonic=clock.monotonic,
@@ -444,12 +453,32 @@ def manager_harness(
         clock=clock,
         events=events,
         processes=processes,
+        groups=groups,
+        group_checks=group_checks,
         spawned=spawned,
         profile_path=profile_path,
         environment=environment,
     )
 
 
+@pytest.mark.parametrize(
+    "exception,expected",
+    [(None, True), (ProcessLookupError(), False), (PermissionError(), True)],
+)
+def test_process_group_liveness_uses_signal_zero(
+    supervisor, exception: OSError | None, expected: bool
+) -> None:
+    calls = []
+
+    def killpg(pgid: int, sent_signal: int) -> None:
+        calls.append((pgid, sent_signal))
+        if exception is not None:
+            raise exception
+
+    assert supervisor.process_group_alive(4242, killpg) is expected
+    assert calls == [(4242, 0)]
+
+
 def test_lifecycle_startup_order_and_profiles(supervisor, tmp_path: Path, monkeypatch) -> None:
     harness = manager_harness(supervisor, tmp_path)
     harness.profile_path.mkdir()
@@ -551,6 +580,121 @@ def test_child_exit_stops_sibling_and_returns_failure(
     assert [process.wait_calls for process in harness.processes] == [[None], [None]]
 
 
+def test_exited_leader_with_live_descendants_still_gets_group_sigterm(
+    supervisor, tmp_path: Path, monkeypatch
+) -> None:
+    harness = manager_harness(supervisor, tmp_path)
+    triggered = False
+
+    def sleep(delay: float) -> None:
+        nonlocal triggered
+        harness.clock.sleep(delay)
+        if not triggered:
+            triggered = True
+            harness.processes[0].returncode = 7
+            assert harness.groups[1001] is True
+
+    harness.manager._sleep = sleep
+    monkeypatch.setattr(supervisor.signal, "signal", lambda *_args: None)
+
+    assert harness.manager.run() == 7
+    assert ("signal", 1001, signal.SIGTERM) in harness.events
+    assert ("signal", 1002, signal.SIGTERM) in harness.events
+    assert [process.wait_calls for process in harness.processes] == [[None], [None]]
+
+
+def test_group_disappearance_ends_shared_wait_without_sigkill(
+    supervisor, tmp_path: Path, monkeypatch
+) -> None:
+    harness = manager_harness(supervisor, tmp_path, ignores_term=(True, True))
+    triggered = False
+
+    def sleep(delay: float) -> None:
+        nonlocal triggered
+        if not triggered:
+            triggered = True
+            harness.manager._handle_signal(signal.SIGTERM, None)
+        harness.clock.sleep(delay)
+        if harness.clock.now >= 0.5:
+            harness.groups[1001] = False
+            harness.groups[1002] = False
+
+    harness.manager._sleep = sleep
+    monkeypatch.setattr(supervisor.signal, "signal", lambda *_args: None)
+
+    assert harness.manager.run() == 0
+    assert harness.clock.now == pytest.approx(0.5)
+    assert all(event[2] != signal.SIGKILL for event in harness.events if event[0] == "signal")
+    assert [process.wait_calls for process in harness.processes] == [[None], [None]]
+
+
+def test_dead_group_is_not_rechecked_or_signalled_after_possible_pgid_reuse(
+    supervisor, tmp_path: Path, monkeypatch
+) -> None:
+    harness = manager_harness(supervisor, tmp_path)
+    calls = []
+
+    def group_alive(pgid: int) -> bool:
+        calls.append(pgid)
+        if pgid == 1001:
+            return len([item for item in calls if item == 1001]) > 1
+        return harness.groups[pgid]
+
+    harness.manager._group_alive = group_alive
+    triggered = False
+
+    def sleep(delay: float) -> None:
+        nonlocal triggered
+        harness.clock.sleep(delay)
+        if not triggered:
+            triggered = True
+            harness.processes[0].returncode = 7
+
+    harness.manager._sleep = sleep
+    monkeypatch.setattr(supervisor.signal, "signal", lambda *_args: None)
+
+    assert harness.manager.run() == 7
+    assert calls.count(1001) == 1
+    assert not any(
+        event[0] == "signal" and event[1] == 1001 for event in harness.events
+    )
+    assert [process.wait_calls for process in harness.processes] == [[None], [None]]
+
+
+def test_group_disappearing_at_deadline_is_rechecked_before_sigkill(
+    supervisor, tmp_path: Path, monkeypatch
+) -> None:
+    harness = manager_harness(supervisor, tmp_path, ignores_term=(True, True))
+    deadline_checks = {1001: 0, 1002: 0}
+
+    def group_alive(pgid: int) -> bool:
+        if harness.clock.now < 10.0:
+            return True
+        deadline_checks[pgid] += 1
+        return deadline_checks[pgid] == 1
+
+    harness.manager._group_alive = group_alive
+    triggered = False
+
+    def sleep(delay: float) -> None:
+        nonlocal triggered
+        if not triggered:
+            triggered = True
+            harness.manager._handle_signal(signal.SIGTERM, None)
+        harness.clock.sleep(delay)
+
+    harness.manager._sleep = sleep
+    monkeypatch.setattr(supervisor.signal, "signal", lambda *_args: None)
+
+    assert harness.manager.run() == 0
+    assert deadline_checks == {1001: 2, 1002: 2}
+    assert not any(
+        event[0] == "signal" and event[2] == signal.SIGKILL
+        for event in harness.events
+    )
+    assert [process.wait_calls for process in harness.processes] == [[None], [None]]
+
+
 @pytest.mark.parametrize("incoming_signal", [signal.SIGTERM, signal.SIGINT])
 def test_signal_shutdown_forwards_sigterm_and_returns_zero(
     supervisor, tmp_path: Path, monkeypatch, incoming_signal: int