diff --git a/run_agent.py b/run_agent.py
index bcacec3909b69..34b5e22133b5f 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -3601,6 +3601,14 @@ class AIAgent:
         except Exception:
             pass
 
+        try:
+            codex_session = getattr(self, "_codex_session", None)
+            if codex_session is not None:
+                self._codex_session = None
+                codex_session.close()
+        except Exception:
+            pass
+
         # 6. Free conversation history.  Mirrors _release_evicted_agent_soft's
         # soft-eviction clear — close() is the hard teardown for true session
         # boundaries (/new, /reset, session expiry), so the message list won't
diff --git a/tests/run_agent/test_codex_app_server_lifecycle.py b/tests/run_agent/test_codex_app_server_lifecycle.py
new file mode 100644
index 0000000000000..49ed592642938
--- /dev/null
+++ b/tests/run_agent/test_codex_app_server_lifecycle.py
@@ -0,0 +1,33 @@
+import threading
+
+from run_agent import AIAgent
+
+
+class _FakeCodexSession:
+    def __init__(self):
+        self.close_calls = 0
+
+    def close(self):
+        self.close_calls += 1
+
+
+def test_agent_close_releases_codex_app_server_session(monkeypatch):
+    agent = AIAgent.__new__(AIAgent)
+    agent.session_id = "test-codex-lifecycle"
+    agent.client = None
+    agent._active_children_lock = threading.Lock()
+    agent._active_children = set()
+    agent._end_session_on_close = False
+    agent._session_messages = ["retained"]
+    codex_session = _FakeCodexSession()
+    agent._codex_session = codex_session
+
+    monkeypatch.setattr("run_agent.cleanup_vm", lambda _task_id: None)
+    monkeypatch.setattr("run_agent.cleanup_browser", lambda _task_id: None)
+
+    agent.close()
+    agent.close()
+
+    assert codex_session.close_calls == 1
+    assert agent._codex_session is None
+    assert agent._session_messages == []