Today, I was pondering a feature idea for AFO. That idea is loosely related to iCloud Drive. But ever since AFO’s release a few years back, I got dozens of support requests from folks who ran into issues while attempting to use iCloud Drive as means of synchronizing their vaults between their devices.
Usually, my one-word answer to these questions is “Don’t.", accompanied by a link to a FAQ entry that I wrote a while back: “Can I use iCloud Sync with Obsidian and Actions for Obsidian?"(Spoiler: Yes, but it’ll be painful.)
So I had a pretty good mental model of iCloud Drive’s behavior built up already, but as I was thinking about that aforementioned feature idea, I figured that Claude Opus 4.1’s “research mode” might speed up the process a bit, so I tasked it to dive deep into researching how iCloud Drive synchronization works, particularly focusing on iOS behavior and specific scenarios with Obsidian vaults and the “Keep Downloaded” feature.
So here’s that deep dive, because sharing is caring.