any one can see what silly error I am making here? I do not think it is worth posting question on this. But I have been starring at this for 20 minutes and do not see my error

\documentclass[crop,tikz]{standalone}
\usepackage{amsmath}
\usepackage{forest}
\useforestlibrary{edges}
\begin{document}

\begin{forest}
[
  {\begin{align*}
      x&=1
  \end{align*}}
]
\end{forest}
\end{document}

Compiling gives  (/usr/local/texlive/2022/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))
! Missing \endgroup inserted.
<inserted text>
\endgroup
l.13 \end{forest}

if I remove align environment and change it with normal math  {$x=1$} then the error goes away.

@mickep yes!!

\documentclass[crop,tikz]{standalone}
\usepackage{amsmath}

\usepackage{forest}
\useforestlibrary{edges}
\begin{document}

\begin{forest}
[
  {$\begin{aligned}
      x &= 1
  \end{aligned}$}
]
\end{forest}
\end{document}

\starttext

$[0,1\mathclose[ \cong
  [a,b\mathclose[ \hskip5ex
  \mathopen]0,1] \cong
  \mathopen]a,b] \hskip5ex
  \mathopen]0,1\mathclose[ \cong
  \mathopen]a,b\mathclose[$

\stoptext