Work collaboratively on .tex documents; PDFs compile in real time.
Every edit is saved and versioned automatically with git in the background. History shows what changed, when, and by whom, and any earlier state can be restored. Restoring creates a new version, so that is likewise undoable.
Leave a comment on a passage, or propose an actual rewrite that someone else accepts or declines.
Full TeX Live, running in a sandbox with no network access. Citations run BibTeX or Biber on their own; cross-references are handled automatically for you.
Turn on git sync and your files will be synced with a git remote on every save.