# tcolorbox problems with asymmetric page layout

Using tcolorbox for chapter headings I never had a problem, except when I changed to asymmetric layout. Usually tcolorbox's option spread sidewards works just fine in a chapter's heading (you can remove the asymmetric option from the code below and test).

But using asymmetric layout I seem to have to experiment to find some values that could be used to spread to the width. What is causing this behavior and why do I have to manually find some values?

tcolorbox default calculation:

manual calculation:

\documentclass[open=any]{scrbook}

\usepackage{scrlayer-scrpage}

\usepackage[skins]{tcolorbox}
\renewcommand\chapterlinesformat[3]{%
\begin{tcolorbox}[enhanced jigsaw,colframe=blue,colback=blue,sharp corners=all,
height=.275\paperheight,valign=bottom,coltext=white,move upwards*,
#2\raggedchapter#3%
\end{tcolorbox}
}

\begin{document}
\chapter{Let's do some chapters with even some very long titles to see the text width}
\chapter{Let's do some chapters with even some very long titles to see the text width}
\chapter{Let's do some chapters}
\chapter{Let's do some chapters}
\chapter{Let's do some chapters}
\end{document}


With the asymmetric option you have a oneside layout. So you should set toggle enlargement to none:

\documentclass[open=any]{scrbook}

\usepackage{scrlayer-scrpage}

\usepackage[skins]{tcolorbox}
\renewcommand\chapterlinesformat[3]{%
\begin{tcolorbox}[enhanced jigsaw,colframe=blue,colback=blue,sharp corners=all,
height=.275\paperheight,valign=bottom,coltext=white,move upwards*,