It's unfortunate but understandable that the stuff which is most different from other programming environments grabs attention and the basic stuff is hardly mentioned.
> break it irreversibly
Nope. "Cuis-Smalltalk records any action occurring in the environment: the code you edit in the System Browser, the code you execute in a Workspace. Therefore, in the event of a Cuis-Smalltalk crash you can restore unsaved changes when you launch the same Cuis-Smalltalk image again."
https://drcuis.github.io/TheCuisBook/The-Change-Log.html
> bespoke and unreproducible
So there have been all manner of ways to save code changes as plain text in files (or other formats in databases).
https://drcuis.github.io/TheCuisBook/The-Change-Set.html
https://drcuis.github.io/TheCuisBook/The-Package.html