diff --git a/tests/benchmarks/test_mcp_bench.py b/tests/benchmarks/test_mcp_bench.py
index 4e8330b..42e73ec 100644
--- a/tests/benchmarks/test_mcp_bench.py
+++ b/tests/benchmarks/test_mcp_bench.py
@@ -40,8 +40,9 @@ def _patch_mcp_config(monkeypatch, palace_path, tmp_path):
 
     import mempalace.mcp_server as mcp_mod
 
+    kg = KnowledgeGraph(db_path=str(tmp_path / "kg.sqlite3"))
     monkeypatch.setattr(mcp_mod, "_config", cfg)
-    monkeypatch.setattr(mcp_mod, "_kg", KnowledgeGraph(db_path=str(tmp_path / "kg.sqlite3")))
+    monkeypatch.setattr(mcp_mod, "_get_kg", lambda: kg)
 
 
 def _get_rss_mb():
diff --git a/tests/benchmarks/test_memory_profile.py b/tests/benchmarks/test_memory_profile.py
index b299b2d..047bfaa 100644
--- a/tests/benchmarks/test_memory_profile.py
+++ b/tests/benchmarks/test_memory_profile.py
@@ -84,8 +84,9 @@ class TestToolStatusMemoryProfile:
 
         cfg = MempalaceConfig(config_dir=str(tmp_path / "cfg"))
         monkeypatch.setattr(cfg, "_file_config", {"palace_path": palace_path})
+        kg = KnowledgeGraph(db_path=str(tmp_path / "kg.sqlite3"))
         monkeypatch.setattr(mcp_mod, "_config", cfg)
-        monkeypatch.setattr(mcp_mod, "_kg", KnowledgeGraph(db_path=str(tmp_path / "kg.sqlite3")))
+        monkeypatch.setattr(mcp_mod, "_get_kg", lambda: kg)
 
         from mempalace.mcp_server import tool_status
 
diff --git a/tests/test_mcp_server.py b/tests/test_mcp_server.py
index ec9562b..2ab2eb8 100644
--- a/tests/test_mcp_server.py
+++ b/tests/test_mcp_server.py
@@ -18,7 +18,7 @@ def _patch_mcp_server(monkeypatch, config, kg):
     from mempalace import mcp_server
 
     monkeypatch.setattr(mcp_server, "_config", config)
-    monkeypatch.setattr(mcp_server, "_kg", kg)
+    monkeypatch.setattr(mcp_server, "_get_kg", lambda: kg)
 
 
 def _get_collection(palace_path, create=False):