assertTrue(ex2.getMessage().contains("Already closed"));
    }

    @Test
    @DisplayName("ensureOpen opens SMB2 via UNC path and marks open")
    void ensureOpen_smb2_opens() throws Exception {
        // Arrange
        SmbPipeHandleImpl handle = newHandleWithBasicStubs(0, "\\\\pipe\\\\foo");
        when(pipe.ensureTreeConnected()).thenReturn(tree);