Virtual Files performance issues: Slow sync, delayed status updates and Finder freezes on macOS

### ⚠️ Before submitting, please verify the following: ⚠️

- [x] This is a **bug**, not a question or a configuration issue.
- [x] This issue is **not** already reported on Github (I have searched for it).
- [x] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

After updating the Nextcloud Desktop Sync Client to version 34.0.1, I encountered additional problems with an already existing synchronization performance issue related to Virtual Files.

The synchronization performance problems did not initially start with version 34.0.1. They started several versions ago when I switched my existing synchronization setup to the Virtual Files system. Since then, synchronization has been noticeably slower.

After the update to version 34.0.1, the client required me to reinitialize my file system for Virtual Files because it claimed that both synchronization variants were active. This was not the case.

After reinitializing it, I had to initialize the file system again because changes from the Nextcloud server were not being synchronized to the local system.

This required files to be downloaded/synchronized again, and since then the already existing performance problem appears to have become even worse.

For example, I tried to synchronize a repository directory of only about 16.6 MB containing approximately 100 Markdown files. After about two hours, the synchronization was only around 25% complete.

Other directories show the same problem. Synchronizing only a few gigabytes of data can take several hours.

I have also experienced multiple cases where the macOS Finder became completely unresponsive for several minutes and crashing while files inside the Nextcloud Virtual Files directory were being updated.

In my case, these are Markdown files managed with Obsidian and stored in a Git repository. When changes from the Git repository are written back to the local Nextcloud virtual file system, Finder can become completely unresponsive for several minutes.

This has happened multiple times and appears to be related to file system activity while Nextcloud Virtual Files is processing or synchronizing the changed files.

The Virtual Files status indicators also appear to be heavily delayed. The status for “Keep offline” and the download/cloud icons sometimes do not update for 30 to 60 minutes after the actual state has changed.

The Nextcloud storage does not contain an unusually large number of files that would explain this behavior.

In summary, the synchronization performance issue has existed since switching to Virtual Files several client versions ago. The reinitialization and subsequent re-synchronization after updating to version 34.0.1 appear to have made the problem significantly more noticeable and possibly even slower.

### Steps to reproduce

1. Configure the Nextcloud Desktop Client to use Virtual Files on macOS.
2. Use a directory inside the Nextcloud Virtual Files location that contains a Git repository.
3. Modify Markdown files through Obsidian and/or update the local repository through Git, causing multiple files inside the Nextcloud-backed directory to be written or updated.
4. Let the Nextcloud Desktop Client detect and synchronize these local changes back to the server.
5. Observe the synchronization performance.
In my case, synchronizing this approximately 16.6 MB repository can take several hours. After about two hours, synchronization was only approximately 25% complete.
6. During this process, interact with the affected directory using macOS Finder.
I have experienced multiple cases where Finder became completely unresponsive for several minutes while Nextcloud Virtual Files was processing the changed files.
7. Check the Virtual Files status indicators in Finder.
The “Keep offline” state and download/cloud icons can remain outdated for approximately 30 to 60 minutes before reflecting the actual state.

Additional behavior observed after updating to Nextcloud Desktop Client 34.0.1:

8. After the update, the client reported that both synchronization variants were active, although this was not the case, and required the Virtual Files setup to be reinitialized.
9. After reinitialization, server-side changes were not properly synchronized to the local system, requiring another reinitialization.
10. The resulting re-download/re-synchronization made the already existing performance problems significantly more noticeable.

### Expected behavior

- Synchronization should complete within a reasonable amount of time.
- Writing or updating files inside a Nextcloud Virtual Files directory should not cause macOS Finder to become unresponsive, regardless of whether those changes originate from Obsidian, Git, or another local application.
- File system operations and Nextcloud synchronization should run without blocking Finder for several minutes.
- Server-side changes should be synchronized to the local file system without requiring the Virtual Files setup to be repeatedly reinitialized.
- The client should not incorrectly detect multiple synchronization variants when only one is configured.
- Virtual Files status indicators, including “Keep offline” and download/cloud icons, should update promptly when the state of a file or directory changes rather than remaining outdated for 30 to 60 minutes.

### Which files are affected by this bug

.git

### Operating system

macOS

### Which version of the operating system you are running.

MacOS Tahoe 26.5.2

### Installation method

Official Installer for macOS 13 and later

### Nextcloud Server version

33.0.6

### Nextcloud Desktop Client version

34.0.1

### Did this occur after an update or on a clean installation?

Minor version update (i.e. 33.0.0 → 33.0.1)

### Are you using the Nextcloud Server Encryption module?

No

### Are you using an external user-backend?

- [x] Default internal user-backend
- [ ] LDAP or Active Directory
- [ ] SSO - SAML
- [ ] Other

### Nextcloud Server logs

```shell

```

### Additional info

I generated and reviewed the local Nextcloud Desktop Client log.

I checked the error messages contained in the log, but none of them appear to be directly related to the synchronization issue described above.

The errors I found are associated with a different Nextcloud instance/account that is also configured in the same Desktop Client.

Therefore, as far as I can tell, the errors currently visible in the local client log do not explain the extremely slow synchronization or the Finder freezes described in this report.

No source file or failing test is named; the only affected path listed is .git. Start by reproducing the issue on macOS with Virtual Files, a Git repository containing Markdown files, and repeated local updates, then inspect the Desktop Client log while measuring sync delays, Finder responsiveness, and status-icon updates. Done means the reported workload syncs promptly without Finder freezes, stale indicators, or repeated Virtual Files reinitialization.

Written by the indexing model from the issue text.