# What changed in sphinx-substitution-extensions

> 4 changes in sphinx-substitution-extensions 2026 from its official release notes, upgrade guides and advisories: 1 new APIs and options. Each one cited. Sources checked 2026-10-18. HTML: https://unstale.sh/pypi/sphinx-substitution-extensions/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## sphinx-substitution-extensions 2026

### New APIs and options

- MyST substitutions can now be defined in document frontmatter. (2026.08.05) — [release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases/tag/2026.10.09), [release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases/tag/2026.08.05)

### Fixes and other changes

- Files consumed by the include directive remain tracked by Sphinx. (2026.10.09) — [release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases/tag/2026.10.09)
- Slash-prefixed include paths are again resolved relative to Sphinx's source directory. (2026.10.09) — [release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases/tag/2026.10.09)
- Restores the include-read event and composes listener changes with substitutions for parsed and literal content, while preserving nested includes' substitution settings. (2026.10.09) — [release notes](https://github.com/adamtheturtle/sphinx-substitution-extensions/releases/tag/2026.10.09)