How to enlarge the boxed title frame of a tcolorbox environment?

Question

I created a tcolorbox environment to write summaries by adapting the code on page 15 of the manual. In this environment \newtcolorbox{resume}, the title is detached and placed in its own tcolorbox.

I would like to enlarge only the title frame withboxrule=10pt,colframe=black and I can't do it. I tried to adapt the code of this question tcolorbox, subtitle style, but I did not succeed.

The code is this:

\documentclass[a4paper, 11pt]{article}  
\usepackage{ae,lmodern}                 
\usepackage[french]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lipsum}  
\usepackage[most]{tcolorbox}

\tcbset{soustitre/.style={subtitle style={colback=gray!15!white,
fontupper={\sffamily\bfseries\large\selectfont\color{black!25!gray}}}}}

\tcbset{titre/.style={title style={boxrule=10pt,colframe=black
}}}

\newtcolorbox{resume}[2][]{colframe=gray!50,colback=white,
beforeafter skip=0pt,
lower separated=false,
leftrule=3mm,rightrule=3mm,toprule=2pt,bottomrule=2pt,
fonttitle=\sffamily\bfseries\large,
enhanced,
attach boxed title to top center={yshift=-2mm,xshift=-\linewidth/5},
title=#2,#1}

\begin{document}
\begin{resume}[soustitre,titre]{Title}
\tcbsubtitle{Subtitle\hfill }
\tcblower

\lipsum[1]
\end{resume}
\end{document}

The result is this:

How do I customize the boxrule width and its colframe color only for the title and not for the rest of the box?

Answer 1

The boxed title which is added by one of the attached boxed title... options uses the style set with boxed title style and not title style, so change the titre style to from title style=... to boxed title style=....

For more information see page 157 of the current (v. 4.11) tcolorbox manual.

The boxrule=10pt setting seems to be weird, however....

\documentclass[a4paper, 11pt]{article}  
\usepackage{ae,lmodern}                 
\usepackage[french]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lipsum}  
\usepackage[most]{tcolorbox}

\tcbset{soustitre/.style={subtitle style={colback=gray!15!white,
      fontupper={\sffamily\bfseries\large\selectfont\color{black!25!gray}}}}}

\tcbset{titre/.style={boxed title style={boxrule=10pt,colframe=black}}}

\newtcolorbox{resume}[2][]{
  colframe=gray!50,colback=white,
  beforeafter skip=0pt,
  lower separated=false,
  leftrule=3mm,rightrule=3mm,toprule=2pt,bottomrule=2pt,
  fonttitle=\sffamily\bfseries\large,
  enhanced,
  attach boxed title to top center={yshift=-2mm,xshift=-\linewidth/5},
  title=#2,
  #1
}

\begin{document}
\begin{resume}[soustitre,titre]{Title}
\tcbsubtitle{Subtitle\hfill }
\tcblower

\lipsum[1]
\end{resume}
\end{document}