\starttext
  \setupheadertexts[][\cldcontext{"Mode = " .. (tex.modes["1"] and "1" or tex.modes["2"] and "2" or "??")}] % Just for debugging

  \input knuth

  \page[right]
  \startmodeset
    [1]
    {%
      \setuplayout[page] foo
    }
    [2]
    {%
      \pagefigure[\jobname_.pdf][page=1]
    }
  \stopmodeset
\stoptext