Is there a parser/renderer reference spec?

I’d like to adapt some external tooling to work with Obsidian: specifically, I would like to add a reader to Pandoc that can parse Obsidian-flavored Markdown.

Is there a reference spec for Obsidian-flavored Markdown? Or a test suite? Or even a comprehensive list of all the ways Obsidian-flavored Markdown differs from CommonMark?

There is very little Obsidian-flavored Markdown. We us try to use common mark with some minor additions.

Not a reference spec bug, read this:
https://help.obsidian.md/How+to/Format+your+notes