Where is documentation on Calc’s files in its temp directory ?
The files have name like
lu13705{4878E29E-97ED-4198-801A-CFC2741E1F89}.tmp
and
lu13705t9pgm.tmp
What kind of documentation do you expect on temporary files?
We create there any kind of data we need to store temporarily.
I’d like to read whatever exists. I anticipate there are technical docs that developers can refer to. I anticipate there are LO level docs, and Calc level docs.
.
Is there a reason you didn’t just point me to whatever documentation exists?
The reason is there is none. Your premise (“Where is” instead of “is there”; “I anticipate there are …”) is wrong.
The only documentation is the source code.
What gives? Why did you waste my time, or more importantly your time, when you’re first reply could have been the 6 words of your last line of your second reply?
I sincerely appreciate your kind care about how I spend my time. I don’t know what I’d do without it!
But seriously. Do not ever try to guide how others decide to provide answers. I am free to do whatever I decide to avoid XY problem. I may have reasons to believe that the questioner could get better answers, when they explain their actual goals. Or I may care not about the specific questioner’s needs, but may think that additional context may help other answerers; or otherwise help to improve this topic for some third parties reading this in, say, 10 years.
In this specific case: yes, I anticipated XY problem (and therefore, that I possibly could provide an answer, if details appear).
If you come to an open Ask site, and perceive improvement questions like mine as “waste of your time”: you are also free to fix your expectations.
…
but looking at the tag you added : recovery, you’d rather look for Saving Documents Automatically
https://wiki.documentfoundation.org/Videos/Preventing_data_disaster
Where is the recovery data and how do I use it? - #5 by WGroleau
…
.
https://wiki.documentfoundation.org/Videos/Preventing_data_disaster
.
“The reality of why data is lost could go on and on”
.
The list that proceeds that quote is long yet does not include warning to the user that anything the user saves to the temp directory will be permanently deleted when Calc is exited.
.
It is negligence, of course, that Calc defaults to the temp directory upon recovering a file, especially in light of the fact that Calc knows better than to put it’s own recovery data there. The foolishness of Calc defaulting to the temp directory is exacerbated by it often being an OS created ram-disk file system, which is effectively deleted on a power outage, crash-reboot, or normal power-down reboot.
bit of a strech with " its temp directory " of the OP.
feel free (and responsible) to improve the wiki.
like when ? 
On a true operating system (anything but Windows), I can read and write my own files, but not the files created by other users and system processes. I can read and write any file that is stored by any process on my behalf by LibreOffice and any other program started by me and storing temporary files. The program decides when a temporary file is no longer needed. If I decide to put any file in that directory, it remains there until I delete it or until the system shuts down.
For instance, I use to store sample files for this forum in /tmp/. If macros are involved, I store them in /tmp/test/ which is registered in my LibreOffice settings to allow macro execution. This way, I make sure that my home directory is not cluttered with hundreds of trivial office documents.
On a true operating system (anything but Windows), the /tmp directory evaporates when the system shuts down.