[tomsem]

The manual section you reference concerns issues with 'networked drives', in contrast to file syncing tool 'like DropBox' (OneDrive in this case). I'm not doing 'simultaneous access' scenario here, which calibre does not support. I use calibre on a single computer.

It's just to back up the files in a convenient way, and at some point local copy gets removed, which makes disk storage go further. And as such, sometimes the file I want has to be downloaded. There's no risk of file or database corruption associated with this. The filenames calibre uses are compatible with what can be stored in OneDrive.

I mostly work with recently added books, which have not yet been 'archived' and stubbed out (or whatever the term is). So it isn't that much of an inconvenience.

A more relevant error might be something like 'file is not present in local file system, needs to be downloaded from cloud'. But timeout error will do, I don't expect calibre to explicitly integrate with cloud services, or to support multi-user scenarios.

Sure: it would be nice if calibre would wait patiently for the file to download. I can, for example, select a file with Finder that is not locally stored, and tell it to open in calibre viewer, without explicitly downloading it first. And there's no error.

I did a little experiment and downloaded only the .opf, and not the content file. I was able to do everything without any errors.

So perhaps a fix would be for calibre to wait longer for .opf file to open. They're very small of course and as long as there's an internet connection, they will download very quickly.