diff --git a/internal/runmgr/exec_tool_artifact_test.go b/internal/runmgr/exec_tool_artifact_test.go
index e6256f9..10c011e 100644
--- a/internal/runmgr/exec_tool_artifact_test.go
+++ b/internal/runmgr/exec_tool_artifact_test.go
@@ -77,9 +77,11 @@ func TestRunPythonRegisterArtifactBackfill(t *testing.T) {
 	if err := tools.RegisterInterpreterTools(c.mgr.registry); err != nil {
 		t.Fatal(err)
 	}
+	// 夹具必须是结构合法的最小 docx：登记口会做 OPC 结构自检，
+	// 伪 zip（PK 魔数+垃圾字节）现在会被拒绝而非登记。
 	py := c.ExecuteTool(core.ToolCallRequest{
 		CallID: "py1", Name: "run_python",
-		Arguments: json.RawMessage(`{"script":"open('note.docx','wb').write(b'PK\\x03\\x04hello')\n"}`),
+		Arguments: json.RawMessage(`{"script":"import zipfile\nwith zipfile.ZipFile('note.docx','w') as z:\n    z.writestr('[Content_Types].xml','<?xml version=\"1.0\"?><Types/>')\n    z.writestr('word/document.xml','<?xml version=\"1.0\"?><doc/>')\n"}`),
 	})
 	if py.Status != "ok" || !strings.Contains(py.Output, "exit=0") {
 		t.Fatalf("run_python: %s %s", py.Status, py.Output)