fix(mcp): preserve loop during probes

tests/tools/test_mcp_stability.py

@@ -57,6 +57,32 @@ class TestMCPLoopExceptionHandler:
         finally:
             mcp_mod._stop_mcp_loop()
 
+    def test_probe_cleanup_does_not_stop_loop_with_registered_servers(self):
+        """Probe cleanup must not kill the shared loop used by live MCP tools."""
+        import tools.mcp_tool as mcp_mod
+
+        with mcp_mod._lock:
+            mcp_mod._servers.clear()
+            mcp_mod._server_connecting.clear()
+        try:
+            mcp_mod._ensure_mcp_loop()
+            with mcp_mod._lock:
+                loop = mcp_mod._mcp_loop
+                mcp_mod._servers["live"] = MagicMock(session=object())
+
+            assert mcp_mod._stop_mcp_loop_if_idle() is False
+
+            with mcp_mod._lock:
+                assert mcp_mod._mcp_loop is loop
+                assert mcp_mod._mcp_thread is not None
+            assert loop is not None
+            assert loop.is_running()
+        finally:
+            with mcp_mod._lock:
+                mcp_mod._servers.clear()
+                mcp_mod._server_connecting.clear()
+            mcp_mod._stop_mcp_loop()
+
 
 # ---------------------------------------------------------------------------
 # Fix 2: stdio PID tracking