Different Results from Overleaf and VSCode?

Question

My question is mostly trying to troubleshoot why I get different results in VSCode vs Overleaf. When I paste this code into Overleaf vs VSCode/LaTeX Workshop I get different results. The code comes from a previous answer about updating headers based on levels of page content.

In Overleaf pages 3-4 of the results have a "Level 3" header, as they should because the Level 3 paragraph runs from page 3 to page 4.

In VSCode the page 4 header does not carry forward the "Level 3" from the paragraph spanning pages, and instead uses the highest from page 4 which is "Level 2" header.

Overleaf: This is pdfTeX, Version 3.141592653-2.6-1.40.23 (TeX Live 2021)

VSCode: This is pdfTeX, Version 3.141592653-2.6-1.40.23 (TeX Live 2022/dev)

MWE

\documentclass{article}
\usepackage{afterpage}
\usepackage{lipsum}
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhf{}
\newcounter{pagelevel}
\newcounter{currentlevel}
\usepackage{atbegshi}
\usepackage{zref-user}
\usepackage{zref-abspage}
\newcounter{clscnt}
\makeatletter
% When we ship out the page, check if the paragraph spans the break.
\AtBeginShipout{%
    \ifnum\zref@extract{markingenv-begin-\theclscnt}{abspage}
            =\zref@extract{markingenv-end-\theclscnt}{abspage}
        \setcounter{pagelevel}{0}%
    \else
        \setcounter{pagelevel}{\thecurrentlevel}%
    \fi
}
\makeatother
\newcommand{\marking}[2]{%
    \stepcounter{clscnt}%
    \zlabel{markingenv-begin-\theclscnt}%
    (#1 --- \thepagelevel)
    \ifnum #1 > \thepagelevel%
        \setcounter{pagelevel}{#1}%
        \chead{Level \thepagelevel}%
    \fi%
    \setcounter{currentlevel}{#1}
    #2
    \zlabel{markingenv-end-\theclscnt}%
}
\newcommand{\VI}[1]{\marking{3}{(V) #1}}
\newcommand{\IMP}[1]{\marking{2}{(I) #1}}
\newcommand{\TRI}[1]{\marking{1}{(U) #1}}
\begin{document}
\TRI{\lipsum[1]\par}
\TRI{\lipsum[2]\par}
\TRI{\lipsum[3]\par}
\IMP{\lipsum[4]\par}
\TRI{\lipsum[5]\par}
\TRI{\lipsum[6]\par}
\TRI{\lipsum[7]\par}
\TRI{\lipsum[8]\par}
\IMP{\lipsum[9]\par}
\TRI{\lipsum[10]\par}
\TRI{\lipsum[11]\par}
\TRI{\lipsum[12]\par}
\TRI{\lipsum[13]\par}
\TRI{\lipsum[14]\par}
\TRI{\lipsum[15]\par}
\VI{\lipsum[16]\par}
\IMP{\lipsum[17]\par}
\TRI{\lipsum[18]\par}
\TRI{\lipsum[19]\par}
\TRI{\lipsum[20]\par}
\TRI{\lipsum[21]\par}
\TRI{\lipsum[22]\par}
\TRI{\lipsum[23]\par}
\TRI{\lipsum[24]\par}
\TRI{\lipsum[25]\par}
\TRI{\lipsum[26]\par}
\TRI{\lipsum[27]\par}
\TRI{\lipsum[28]\par}
\TRI{\lipsum[29]\par}
\end{document}

Overleaf Results

VSCode Results

Answer 1

This is a matter of label update. Your code requires knowledge of the page so it will not work properly with only one run. So if you look into the log information, you will find it tells you

LaTeX Warning: Label(s) may have changed. Rerun to get cross-references right.

So you need to compile it the second time and then the results of the VS Code and Overleaf are the same. Overleaf did it cleverly by using latexmk, which is also a convenient way for you to do with VS Code if you do not want to carefully choose how many times to run LaTeX, BibTeX or Biber. Using latexmk is also very convenient with LaTeX-Workshop extension in VS Code. (Remeber to add the -pdf option).