Formulas including \hbox break in some cases.

[ssolbUR]

Biber rewrites Formulas in titles in some cases, especially when it is called with --decodecharsset=null and you have something like \macro<space>{X} where X is a single letter. This is rewritten to \macro X. This is OK in most cases (like \frac or \text) but creates invalid TeX code when \macro is \box, because \hbox requires braces.

A fix is to avoid the space: \macro{X} is not rewritten.

My assumption from reading the man page was that title = "{ ..... }" are never rewritten if called with --decodecharsset=null, but the reverse seems to be true. I don't know if this the intended behaviour or a bug.

MWE:

\documentclass{article}
\usepackage{biblatex}
% this yields an error:
%
% pdflatex mwe && biber --decodecharsset=null mwe && pdflatex mwe
%
% 
% This is OK:
% 
% pdflatex mwe && biber mwe && pdflatex mwe
%
%
\begin{filecontents*}[overwrite]{\jobname.bib}
@article{one,
  title = "{$\hbox {N}^3$}",
  author = "One, Eins",
  year = 2025,
  journal = "Heft",
}
\end{filecontents*}
\addbibresource{\jobname.bib}
\begin{document}
Eins: \cite{one}.
\printbibliography
\end{document}

[plk]

This is inevitable I'm afraid - there is no way to cover all cases of TeX encoding/decoding. In general, just use UTF8 directly in the .bib file and use a UTF-8 TeX engine.

[ssolbUR]

Thank you for the reply! However, this wasn't quite my question. I always was under the impression that bibtex entries with just "..." or just {...} can be changed but entries with "{...}" should be unchanged. That biber changes even this entries seems to be a feature. However, the manpage states that "The virtual set name "null" may be specified which effectively turns off macro decoding." which doesn't seem to be the case here. With --decodecharsset=null the title is changed, without --decodecharsset=... the title is unchanged. Maybe I misunderstood the meaning of decodecharsset? I'd also like understand the logic behind changing \foo {x} to \foo x but not changing \foo{x} (without the space beween the macro and the brace.)

[plk]

This will be fixed in the DEV version shortly. However, it's not recommended to use macros in TITLE, especially if protected as then bibers decoding to UTF8 will be blocked and you'll lose the benefits of full UTF8 sorting for TITLEs.