Tried the following putting a \vbox before the \blank. There is probably better solution for this.

\setuplayout[grid=both]
\showgrid
\starttext
\endgraf\vbox to \lineheight{}\blank[samepage, -halfline]
HalfLine
\blank[halfline]
Text
\page
Text
\endgraf\vbox to \lineheight{}\blank[samepage, -halfline]
HalfLine
\blank[halfline]
Text
\stoptext

De : Marcus Vinicius Mesquita
Envoyé le :vendredi 30 septembre 2016 23:08
À : mailing list for ConTeXt users
Objet :Re: [NTG-context] \blank[force, halfline] at top page issue

Try

\blank[force,halfline,depth]