MyST unusable with current Sphinx dev HEAD (future 8.3.0)

[jfbu]

What version of myst-parser are you using?

4.0.1

What version dependencies are you using?

Sphinx 8.3.0+/ead64dfda

What operating system are you using?

Mac

Describe the Bug

This index.md

---
myst:
  html_meta:
    keywords: Bug
---

# FOO documentation

leads to KeyError: 'writer' when attempting to exercise the Sphinx HTML builder.

I am opening this to be sure Sphinx upstream situation at sphinx-doc/sphinx#13713 is monitored prior to Sphinx 8.3.0 release.

Expected Behavior

No response

To Reproduce

No response