possible race-condition with python-doc

Bug report

Bug description:

While working on reproducible builds for openSUSE, I found that our python314 (and python311) doc sub-packages produce different html on 1-core-VMs and 4-core-VMs. This suggests that there is some race going on about what the correct content should be.

https://rb.zq1.de/other/python314-doc-compare.out has a diff

The interesting bit of it is

-<p class="audit-hook" id="audit_event_cpython_run_stdin_1">
+<p class="audit-hook" id="audit_event_cpython_run_stdin_2">

How to Reproduce

To test on openSUSE or Debian, use

osc checkout openSUSE:Factory/python314 && cd $_
for N in 1 14 ; do
    osc build -M=doc --noservice --clean --vm-type=kvm -j$N --release=1.1 --keep-pkg=RPMS.$N standard
    (cd RPMS.$N && unrpm python314-doc-3*.x86_64.rpm)
done
diff -ru RPMS.{1,14}/usr/

Environment Information

OS: openSUSE Tumbleweed 20250302
Sphinx-8.1.3

Sphinx extensions

Additional context

This bug was found while working on reproducible builds for openSUSE.

This was originally filed in https://github.com/sphinx-doc/sphinx/issues/13419 but apparently the Sphinx people think this is an issue in cpython.

CPython versions tested on:

3.11, 3.14, 3.13, 3.12

Operating systems tested on:

Linux

Linked PRs

• gh-136165

Start by running the documented openSUSE build loop with -j1 and -j14, then compare the extracted usr/ trees and the reported audit-hook IDs. Use the linked PR gh-136165 and the reproducible-build diff as context; done means repeated documentation builds produce identical HTML regardless of parallelism.