The `kaobook`'s `thmtools` was conflict with the latest latex-kernel and need to be patched?

[Explorer-cc]

Description

See the issue and post here, now the kaobook would get the thmtools with slibing option.

Minimal Working Example

I made some exploration of the case, now I have three examples:

MWE1

\documentclass{kaobook}
\usepackage{kaotheorems}

\begin{document}

Hello!

\begin{proposition}
This is a proposition.
\end{proposition}

\end{document}

Expected behavior:

Compile smoothly.

Actual behavior:

It raised an error message:

! LaTeX Error: Command \c@proposition already defined.
               Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.33 \makeatother
                 
? 

MWE2

Here below is a simpler version to show the issues:

\documentclass{book}
\let\openbox\relax
\RequirePackage{amsmath} % Improved mathematics
\RequirePackage{amsthm} % Mathematical environments
\RequirePackage{thmtools} % Theorem styles
\makeatletter
    % Theorem styles
    \declaretheoremstyle[
    	spaceabove=.6\thm@preskip,
    	spacebelow=.1\thm@postskip,
    	bodyfont=\normalfont\itshape,
    	headpunct={},
    ]{kaoplain}
    \theoremstyle{kaoplain}
    \declaretheorem[
    	name=Theorem,
    	refname={theorem,theorems},
    	Refname={Theorem,Theorems},
    	numberwithin=section,
    ]{theorem}
    \declaretheorem[
    	name=Proposition,
    	refname={proposition,propositions},
    	Refname={Proposition,Propositions},
    	sibling=theorem,%<---------------------
    ]{proposition}
\makeatother

\begin{document}

Hello!

\begin{proposition}
This is a proposition.
\end{proposition}

\end{document}

gives the same error.

MWE3

The mbert's workaround works:

\documentclass{book}
\let\openbox\relax
\RequirePackage{amsmath} % Improved mathematics
\RequirePackage{amsthm} % Mathematical environments
\RequirePackage{thmtools} % Theorem styles
\makeatletter
\renewcommand\thmt@autorefsetup{%
  \@xa\def\csname\thmt@envname autorefname\@xa\endcsname\@xa{\thmt@thmname}%
}
\makeatother
\makeatletter
    % Theorem styles
    \declaretheoremstyle[
    	spaceabove=.6\thm@preskip,
    	spacebelow=.1\thm@postskip,
    	bodyfont=\normalfont\itshape,
    	headpunct={},
    ]{kaoplain}
    \theoremstyle{kaoplain}
    \declaretheorem[
    	name=Theorem,
    	refname={theorem,theorems},
    	Refname={Theorem,Theorems},
    	numberwithin=section,
    ]{theorem}
    \declaretheorem[
    	name=Proposition,
    	refname={proposition,propositions},
    	Refname={Proposition,Propositions},
    	sibling=theorem,%<-
    ]{proposition}
\makeatother

\begin{document}

Hello!

\begin{proposition}
This is a proposition.
\end{proposition}

\end{document}

But that not work with simply the kaotheorems package.

\documentclass{kaobook}
\usepackage{kaotheorems}
\makeatletter
\renewcommand\thmt@autorefsetup{%
  \@xa\def\csname\thmt@envname autorefname\@xa\endcsname\@xa{\thmt@thmname}%
}
\makeatother
\begin{document}

Hello!

\begin{proposition}
This is a proposition.
\end{proposition}

\end{document}

still gives:

! LaTeX Error: Command \c@proposition already defined.
               Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.336     \declaretheorem
                         [
? 

Should this be fixed from thmtools side? Or from the kaobook side?

[Explorer-cc]

But that not work with simply the kaotheorems package.

\documentclass{kaobook}
\usepackage{kaotheorems}
\makeatletter
\renewcommand\thmt@autorefsetup{%
  \@xa\def\csname\thmt@envname autorefname\@xa\endcsname\@xa{\thmt@thmname}%
}
\makeatother
\begin{document}

Hello!

\begin{proposition}
This is a proposition.
\end{proposition}

\end{document}

still gives:

! LaTeX Error: Command \c@proposition already defined.
               Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.336     \declaretheorem
                         [
? 

Thanks to Ulrike Fischer's help, the package hooks would work as a quick-fix:

% Source - https://tex.stackexchange.com/a/764883
% Posted by Ulrike Fischer
% Retrieved 2026-07-23, License - CC BY-SA 4.0

\providecommand\extrasenglish{} % unrelated varioref bug ...
\documentclass{kaobook}
\makeatletter
\AddToHook{package/thmtools/after}{%
\renewcommand\thmt@autorefsetup{%
  \@xa\def\csname\thmt@envname autorefname\@xa\endcsname\@xa{\thmt@thmname}%
}}
\makeatother
\usepackage{kaotheorems}
\begin{document}

Hello!

\begin{proposition}
This is a proposition.
\end{proposition}

\end{document}