why would my OneDrive suddenly be processing over 40,000 changes?

I have the same issue today. No obvious reason why it has to reprocess over a quarter million files.. Argh - a lot of CPU consumption for no apparent reason. This has not happened often, but even 3 or 4 times in a couple years raises a red flag regarding the durability of the Onedrive cloud system.

I am also having this issue...trying to process > 500,000 files. Nothing has changed on my MacBook Air, so what has changed with Microsoft that is triggering this issue?

I have the same issue, it's been "processing changes" for days now.

I suspect, and this is just a hunch, and I have zero proof, that since MS is pushing AI tools down everyone's throats, this "reindexing" is some kind of AI-analysis during which all files are being "touched" and, as a result, changed (on a metadata level), so now OneDrive has to sync all those changes.

I cannot think of any other reason, maybe except for MS going full vibe coding mode and their codebase have been poisoned by poor quality AI slop.

It's a sad state, I really used to trust MS with this kind of stuff and am a - for now happily - paying customer, but if goes further this route I will have to move my files elsewhere.

This worked for me and is a really simple fix. Thanks.

Adding info that might help someone in the future get to the bottom of what is causing this:

I use "Obsidian.md" for note taking. I use a third party plugin with the program that syncs my "Vault" directly with OneDrive. There is a built in feature in this plugin that warns you when a sync attempt would replace/remove/edit >50% of all files, the goal of the feature being to avoid syncing an accidental deletion of many files at once. For reference, the saving situation includes a local (non-OneDrive) "Vault" folder that updates in real time as you edit while the sync plugin creates a separate folder in your OneDrive that updates when you manually ask to sync your local files to the cloud files.

When I attempted to sync my Obsidian files to OneDrive after both instances of OneDrive trying to process 40,000+ files, Obsidian warned me that 100% of the files I was trying to sync were different than the ones already saved in OneDrive. Now, my files were unchanged (to my eye) when I did allow the sync and I did not have any problems, but such a warning suggests that when OneDrive is "processing" the 40,000+ changes, it actually is processing ""changes.""

I do not know much at all about technology and have no clue what that could mean on the technical side, but because this thread is full of other comments about this I thought it would be smart to add in info that could help the smarter people figure out what's going on.

Edit: In terms of what worked for me when I encountered this problem twice, I had to unlink and relink my desktop from OneDrive and allow it to go through the motions of syncing all files after I relinked the account.