I've got a Mac OS 26 guest running on Mac OS 26 host. The guest has Sharing > Share Custom Mac Folders With Macos enabled. When an app in the guest accesses a text file via "My Shared Files", it appears that the guest caches the contents of that file and doesn't invalidate the cache when it gets changed on the host -- that is, the guest doesn't see changes to the text file until the guest restarts. If the guest accesses host files using Network and shared network folders, then the guest sees the most recent version of the host files, as expected. Is this a bug?
I'm experiencing the same problem using a macOS 15 host and a macOS 26 guest under Parallels Desktop 26. When I modify a file on the host side the guest sees that the file size has changed but the contents have not. If the file size grows on the host the guest sees the old bytes followed by random garbage.
Just did a few more experiments. I opened Terminal windows in both the guest and host and used the command line to echo strings into a text file. When I alter the contents of a file on the guest side (macOS 26) the host sees the new contents. When I alter the contents on the host side (macOS 15) the guest sees the new metadata (file length) but not new contents. If the file expands on the host the guest sees that the file is longer but the contents are stale and padded out with zeros. Parallels Version 26.3.0 (57392) on an Apple Studio running Sequoia 15.7.4, guest is Tahoe 26.3.1. I'm trying to open a ticket with support but since I don't do social media this is not easy.
Guest OS appears to cache file contents from shared folders and does not invalidate cache when host files are updated, causing sync inconsistency.
I only test on the macOS guest intermittently so it hasn't been a priority. I'll take another shot at it today. I really, really don't want to open a Facebook account just to get support (and X is entirely out of the question).
I just encountered a similar caching issue with a Windows 11 guest via the UNC path \\Mac. I'm weighing the cost of submitting a bug report versus living with it, sigh.
I am in communication with Parallels support to open a ticket on this. Using my macOS 15 host I can reproduce with a macOS 14 or 26 guest but not with a macOS 13 guest. @johnrellis I'm not seeing this happen on my Windows 11 guest. If you can provide me with steps to reproduce I'll report it to Parallels. I've already compromised myself by creating an account on Twitter (ugh) so I might as well use it. (Facebook wouldn't let me create an account for mysterious reasons it would not disclose.)
@MartinFox, I failed to produce a simple test case for a Windows 11 guest, and the symptoms are fleeting, happening perhaps once every several days. So until I can narrow it down, best not to include that in the bug process for Mac OS guests. Thanks much for working this process.
