tikzposter and hyperref error

When you use the tikzposter LaTeX class and also the hyperref package with colorlinks=true, and you encounter a compilation error similar to ! LaTeX Error: Loading a class or package in a group, then the following snippet in your preamble may resolve the issue:

\makeatletter
\patchcmd{%
    \Hy@AtBeginDocumentHook%
}{%
    \RequirePackage {color}%
}{}{}{%
    \PackageWarning{patch}{patch failed!}%
}
\makeatother

The core problem is that the tikzposter class puts all of the main content inside one big tikzpicture environment. More specifically, it starts a \begin{tikzpicture} in \AtBeginDocument but never closes it there.

On the other hand , if hyperref is configured with colorlinks=true, it tries to load the color package through its own \AtBeginDocument, that package ends up being loaded inside the still-open tikzpicture environment. That’s what triggers the error about loading a class or package “in a group.”

The fix we used basically prevents hyperref from trying to load color during its custom \AtBeginDocument to resolve the conflict. The color package is likely already loaded by other packages before hyperref, so it’s fine not loading it in \AtBeginDocument.