diff --git a/gateway/run.py b/gateway/run.py
index 23be3793d7..596edf2edd 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -2800,6 +2800,23 @@ class GatewayRunner:
 
             self._finalize_shutdown_agents(active_agents)
 
+            # Also shut down memory providers on idle cached agents.
+            # _finalize_shutdown_agents only handles agents that were
+            # mid-turn at drain time; the _agent_cache may still hold
+            # idle agents whose MemoryProviders never received
+            # on_session_end().
+            _cache_lock = getattr(self, "_agent_cache_lock", None)
+            _cache = getattr(self, "_agent_cache", None)
+            if _cache_lock is not None and _cache is not None:
+                with _cache_lock:
+                    _idle_agents = list(_cache.values())
+                    _cache.clear()
+                for _entry in _idle_agents:
+                    _agent = (
+                        _entry[0] if isinstance(_entry, tuple) else _entry
+                    )
+                    self._cleanup_agent_resources(_agent)
+
             for platform, adapter in list(self.adapters.items()):
                 try:
                     await adapter.cancel_background_tasks()
diff --git a/tests/gateway/test_shutdown_cache_cleanup.py b/tests/gateway/test_shutdown_cache_cleanup.py
new file mode 100644
index 0000000000..82970d20c5
--- /dev/null
+++ b/tests/gateway/test_shutdown_cache_cleanup.py
@@ -0,0 +1,210 @@
+"""Regression tests for gateway shutdown cleaning up cached agent memory providers (issue #11205).
+
+When the gateway shuts down, ``stop()`` called ``_finalize_shutdown_agents()``
+which only drained agents in ``_running_agents``.  Idle agents sitting in
+``_agent_cache`` (LRU cache) were never cleaned up, so their
+``MemoryProvider.on_session_end()`` hooks never fired.
+
+The fix adds an explicit sweep of ``_agent_cache`` after
+``_finalize_shutdown_agents`` in the ``_stop_impl`` coroutine.
+"""
+
+import asyncio
+import threading
+from collections import OrderedDict
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+# Import the module (not the class) to reach stop() and helpers
+import gateway.run as gw_mod
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+class _FakeGateway:
+    """Minimal stand-in with just enough state for ``stop()`` to run."""
+
+    def __init__(self):
+        self._running = True
+        self._draining = False
+        self._restart_requested = False
+        self._restart_detached = False
+        self._restart_via_service = False
+        self._stop_task = None
+        self._exit_cleanly = False
+        self._exit_with_failure = False
+        self._exit_reason = None
+        self._exit_code = None
+        self._restart_drain_timeout = 0.01
+        self._running_agents = {}
+        self._running_agents_ts = {}
+        self._agent_cache = OrderedDict()
+        self._agent_cache_lock = threading.Lock()
+        self.adapters = {}
+        self._background_tasks = set()
+        self._failed_platforms = []
+        self._shutdown_event = asyncio.Event()
+        self._pending_messages = {}
+        self._pending_approvals = {}
+        self._busy_ack_ts = {}
+
+    def _running_agent_count(self):
+        return len(self._running_agents)
+
+    def _update_runtime_status(self, *_a, **_kw):
+        pass
+
+    async def _notify_active_sessions_of_shutdown(self):
+        pass
+
+    async def _drain_active_agents(self, timeout):
+        return {}, False
+
+    def _finalize_shutdown_agents(self, agents):
+        for agent in agents.values():
+            self._cleanup_agent_resources(agent)
+
+    def _cleanup_agent_resources(self, agent):
+        if agent is None:
+            return
+        try:
+            if hasattr(agent, "shutdown_memory_provider"):
+                agent.shutdown_memory_provider()
+        except Exception:
+            pass
+        try:
+            if hasattr(agent, "close"):
+                agent.close()
+        except Exception:
+            pass
+
+    def _evict_cached_agent(self, key):
+        pass
+
+
+def _make_mock_agent():
+    a = MagicMock()
+    a.shutdown_memory_provider = MagicMock()
+    a.close = MagicMock()
+    return a
+
+
+# ---------------------------------------------------------------------------
+# Tests
+# ---------------------------------------------------------------------------
+
+class TestCachedAgentCleanupOnShutdown:
+    """Verify that ``stop()`` calls ``_cleanup_agent_resources`` on idle
+    cached agents, triggering ``shutdown_memory_provider()`` (which calls
+    ``on_session_end``)."""
+
+    @pytest.mark.asyncio
+    async def test_cached_agent_memory_provider_shut_down(self):
+        """A cached agent's shutdown_memory_provider is called during gateway stop."""
+        gw = _FakeGateway()
+        agent = _make_mock_agent()
+        gw._agent_cache["session-1"] = (agent, "sig-123")
+
+        # Call the real stop() from GatewayRunner
+        await gw_mod.GatewayRunner.stop(gw)
+
+        agent.shutdown_memory_provider.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_cache_cleared_after_shutdown(self):
+        """The _agent_cache dict is cleared after stop."""
+        gw = _FakeGateway()
+        agent = _make_mock_agent()
+        gw._agent_cache["s1"] = (agent, "sig1")
+
+        await gw_mod.GatewayRunner.stop(gw)
+
+        assert len(gw._agent_cache) == 0
+
+    @pytest.mark.asyncio
+    async def test_no_cached_agents_no_error(self):
+        """stop() works fine when _agent_cache is empty."""
+        gw = _FakeGateway()
+
+        await gw_mod.GatewayRunner.stop(gw)  # Should not raise
+
+        assert len(gw._agent_cache) == 0
+
+    @pytest.mark.asyncio
+    async def test_multiple_cached_agents_all_cleaned(self):
+        """All cached agents get cleaned up."""
+        gw = _FakeGateway()
+        agents = []
+        for i in range(5):
+            a = _make_mock_agent()
+            agents.append(a)
+            gw._agent_cache[f"s{i}"] = (a, f"sig{i}")
+
+        await gw_mod.GatewayRunner.stop(gw)
+
+        for a in agents:
+            a.shutdown_memory_provider.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_cleanup_survives_agent_exception(self):
+        """An exception from one agent's shutdown doesn't prevent others."""
+        gw = _FakeGateway()
+
+        bad = _make_mock_agent()
+        bad.shutdown_memory_provider.side_effect = RuntimeError("boom")
+        bad.close.side_effect = RuntimeError("boom")
+
+        good = _make_mock_agent()
+
+        gw._agent_cache["bad"] = (bad, "sig-bad")
+        gw._agent_cache["good"] = (good, "sig-good")
+
+        await gw_mod.GatewayRunner.stop(gw)
+
+        # The good agent should still be cleaned up
+        good.shutdown_memory_provider.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_plain_agent_not_tuple(self):
+        """Cache entries that aren't tuples (just bare agents) are also cleaned."""
+        gw = _FakeGateway()
+        agent = _make_mock_agent()
+        gw._agent_cache["s1"] = agent  # Not a tuple
+
+        await gw_mod.GatewayRunner.stop(gw)
+
+        agent.shutdown_memory_provider.assert_called_once()
+        assert len(gw._agent_cache) == 0
+
+    @pytest.mark.asyncio
+    async def test_none_entry_skipped(self):
+        """A None cache entry doesn't cause errors."""
+        gw = _FakeGateway()
+        gw._agent_cache["s1"] = None
+
+        await gw_mod.GatewayRunner.stop(gw)
+
+        assert len(gw._agent_cache) == 0
+
+
+class TestRunningAgentsNotDoubleCleaned:
+    """Verify behavior when agents appear in both _running_agents and _agent_cache."""
+
+    @pytest.mark.asyncio
+    async def test_running_and_cached_agent_cleaned_at_least_once(self):
+        """An agent in both _running_agents and _agent_cache gets
+        shutdown_memory_provider called at least once."""
+        gw = _FakeGateway()
+        shared = _make_mock_agent()
+
+        gw._running_agents["s1"] = shared
+        gw._agent_cache["s1"] = (shared, "sig1")
+
+        await gw_mod.GatewayRunner.stop(gw)
+
+        # Called at least once — either from _finalize_shutdown_agents
+        # or from the cache sweep (or both)
+        assert shared.shutdown_memory_provider.call_count >= 1