PDF output using `cite-method: biblatex` may generate nested optional argument when citing in a theorem title

Start with the minimal Quarto .qmd example and index.bib, render it with PDF and cite-method: biblatex, and inspect the generated .tex around the theorem title. Trace how the citation becomes the theorem's optional argument; done means the resulting PDF compiles without nested optional arguments.

Bug description

Take this minimal example:

---
title: "Test"
format:
  pdf:
    cite-method: biblatex
bibliography: index.bib
---

:::{#thm-test}

## Test [@something, sec. 1]

Test.
:::

When using cite-method: biblatex in a PDF output, such citation in the title of a theorem results in the following .tex code:

\begin{theorem}[Test
\autocite[sec.~1]{something}]\protect\hypertarget{thm-test}{}\label{thm-test}

Test.

\end{theorem}

Which contains nested optional arguments. It is known that TeX does not handle nested square brackets well (e.g. see this LaTeX Stack Exchange post), thus above causes an error when compiling.

Perhaps such nested optional arguments should be handled more carefully? e.g. adding a pair of braces around the optional argument?

Your environment

• IDE: VSCode
• OS: Windows 11

Quarto check output

Quarto 1.7.26
[>] Checking environment information...
      Quarto cache location: C:\Users\sun123zxy\AppData\Local\quarto
[>] Checking versions of quarto binary dependencies...       
      Pandoc version 3.6.3: OK
      Dart Sass version 1.85.1: OK
      Deno version 1.46.3: OK
      Typst version 0.13.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.7.26
      Path: C:\Program Files\Quarto\bin
      CodePage: 936

[>] Checking tools....................OK

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\Users\sun123zxy\AppData\Roaming\TinyTeX\bin\windows\
      Version: 2025

[>] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: C:\Program Files\Google\Chrome\Application\chrome.exe
      Source: Windows Registry

[>] Checking basic markdown render....OK

[>] Checking Python 3 installation....OK
      Version: 3.12.4 (Conda)
      Path: C:/Users/sun123zxy/.conda/envs/main/python.exe
      Jupyter: 5.7.2
      Kernels: python3

[>] Checking Jupyter engine render....OK

[>] Checking R installation...........(None)

      Unable to locate an installed version of R.
      Install R from https://cloud.r-project.org/