% https://tex.stackexchange.com/a/162895
\NewDocumentEnvironment{balign*} {}
  {
    \begingroup
    \allowdisplaybreaks
    \start@align\@ne\st@rredtrue\m@ne
  }
  {
    \endalign
    \endgroup
  }

\NewDocumentEnvironment{balign} {}
  {
    \begingroup
    \allowdisplaybreaks
    \align
  }
  {
    \endalign
    \endgroup
  }

\NewDocumentEnvironment{hfuzzpar} {m}
  {
    \begingroup
    \hfuzz=#1
  }
  {
    \par
    \endgroup
  }
