redefine \hyper@natlinkbreak to avoid problems with natbib, see https://tug.org/pipermail/tex-live/2026-March/052345.html

[samcarter]

Test document:

\begin{filecontents}{refs.bib}
@article{vaswani2017attention,
  title={Attention is all you need},
  author={Vaswani, Ashish and Shazeer, Noam and Parmar, Niki and Uszkoreit, Jakob and Jones, Llion and Gomez, Aidan N and Kaiser, {\L}ukasz and Polosukhin, Illia},
  journal={Advances in neural information processing systems},
  volume={30},
  year={2017}
}
\end{filecontents}

\documentclass{beamer}
\usepackage[authoryear,round]{natbib}

\begin{document}

\begin{frame}
Observed \citep{vaswani2017attention} (Missing comma)

Observed \citet{vaswani2017attention} (Missing parentheses around year)
\end{frame}

\begin{frame}[fragile]{References}
\bibliographystyle{plainnat}
\bibliography{refs.bib}
\end{frame}

\end{document}

[samcarter]

@u-fischer Do you think this would be a good idea?

[samcarter]

typo, see latex3/hyperref@dd9019d#commitcomment-180895630

[u-fischer]

Yes it is a typo, but actually I think this reveals a problem in beamer. beamer does define \hyper@natlinkstart and \hyper@natlinkend to add the link commands (which hyperref doesn't do due to implicit), but it doesn't redefine the break command.

\def\hyper@natlinkbreak#1#2{%
  \hyper@linkend#1\hyper@linkstart{cite}{cite.#2}%
}

[samcarter]

@u-fischer Thanks a lot for having a look -- great to have a hyperref expert!

I'll add the break command.