I've copied the following example from the ConTeXt archive:

\defineoverlay[frames][\positionoverlay{frames}]

\setupbackgrounds[text][background=frames]


\startMPpositiongraphic{frame}

if unknown context_apos : input mp-apos.mpiv ; fi ;

\MPgetposboxes{\MPvar{self}}{\MPanchorid}

if nofposboxes = 1 :

draw posboxes[1] ;

fi ;

\stopMPpositiongraphic


\startpositionoverlay{frames}

\setMPpositiongraphic{one}{frame}

\setMPpositiongraphic{two}{frame}

\stoppositionoverlay


\starttext

This \hpos{one}{word} should be \hpos{two}{framed}.

\stoptext

Frames are misplaced, so I don't know if that's a bug or something else has
been updated/changed/deprecated. Thank you in advance.

Jairo