diff --git a/docs/design/companion-process-manager.md b/docs/design/companion-process-manager.md
index 067c833b..b354a8fa 100644
--- a/docs/design/companion-process-manager.md
+++ b/docs/design/companion-process-manager.md
@@ -691,7 +691,7 @@ No per-companion logic in Arbiter.
 - [x] Add manager spawn/reap logic in Arbiter.
 - [x] Add manager shutdown handling in Arbiter.
 - [x] Wire Gunicorn reload to manager `reread` or restart.
-- [ ] Close Gunicorn-only fds in manager child.
+- [x] Close Gunicorn-only fds in manager child.
 - [ ] Close manager-only fds in companion child.
 - [ ] Add parent-death cleanup.
 - [ ] Add lifecycle logs.
diff --git a/gunicorn/arbiter.py b/gunicorn/arbiter.py
index afcda160..05fb3983 100644
--- a/gunicorn/arbiter.py
+++ b/gunicorn/arbiter.py
@@ -699,6 +699,7 @@ class Arbiter:
 
         # Process Child
         try:
+            self._close_gunicorn_fds()
             util._setproctitle("companion manager [%s]" % self.proc_name)
             manager.run()
             sys.exit(0)
@@ -708,6 +709,24 @@ class Arbiter:
             self.log.exception("Exception in companion manager process")
             sys.exit(-1)
 
+    def _close_gunicorn_fds(self):
+        """Close fds the manager inherited from the arbiter but never uses.
+
+        The companion manager serves no HTTP traffic and does not run the
+        arbiter's signal loop, so it drops the listening sockets, the arbiter's
+        wakeup pipe, and the worker heartbeat files. Closing them keeps the
+        manager (and the companions it forks) from pinning the arbiter's fds.
+        """
+        for listener in self.LISTENERS:
+            listener.close()
+        for pipe_fd in self.PIPE:
+            try:
+                os.close(pipe_fd)
+            except OSError:
+                pass
+        for worker in self.WORKERS.values():
+            worker.tmp.close()
+
     def reload_companion_manager(self):
         """Restart the companion manager so it picks up the new configuration.
 
diff --git a/tests/test_arbiter.py b/tests/test_arbiter.py
index 9d215c4a..523bbec5 100644
--- a/tests/test_arbiter.py
+++ b/tests/test_arbiter.py
@@ -205,6 +205,20 @@ def test_stop_companion_manager_clears_pid_when_already_gone():
     assert arbiter.companion_manager_pid == 0
 
 
+def test_close_gunicorn_fds_in_manager_child():
+    arbiter = gunicorn.arbiter.Arbiter(DummyApplication())
+    listener = mock.Mock()
+    worker = mock.Mock()
+    arbiter.LISTENERS = [listener]
+    arbiter.WORKERS = {1: worker}
+    arbiter.PIPE = [7, 8]
+    with mock.patch("os.close") as os_close:
+        arbiter._close_gunicorn_fds()
+    listener.close.assert_called_once_with()
+    worker.tmp.close.assert_called_once_with()
+    assert os_close.call_count == 2
+
+
 def test_reload_companion_manager_restarts_running():
     arbiter = gunicorn.arbiter.Arbiter(DummyApplication())
     arbiter.cfg.set("companion_workers", [{"name": "rq", "target": "pkg:run"}])