Tailscale System Extension Issue on macOS 26 (Tahoe)

On this page I will explain how I fixed Tailscale 1.90.6 Standalone version giving the OSSystemExtensionErrorDomain Error 4 after upgrading to macOS 26.1 (Tahoe).

Situation

After updating to macOS 26.1 (Tahoe), the installed Tailscale standalone version stopped working. Attempting to start Tailscale resulted in the following error:

macOS returned an error when initializing the Tailscale system extension. This is oftentimes caused by system restrictions, or security software interfering with Tailscale. Restarting your Mac might address the issue. If this error persists, contact support for help.

The operation couldn’t be completed. (OSSystemExtensionErrorDomain error 4.)

The version of Tailscale Standalone that was installed at the time was 1.90.6.

What I tried

First thing I tried was checking if there were any permissions pending in the system settings. There weren’t any.

Idecided to reinstall Tailscale, following the official Tailscale documentation for removing Tailscale Standalone from macOS, before reinstalling. According to their guide, you need to forcefully remove the following files/folders, on top of removing the application to fully uninstall Tailscale, using the sudo rm -rf command.

~/Library/Application Scripts/*.io.tailscale.ipn.macsys #
~/Library/Application Scripts/io.tailscale.ipn.macsys
~/Library/Application Scripts/io.tailscale.ipn.macsys.login-item-helper
~/Library/Application Scripts/io.tailscale.ipn.macsys.share-extension
~/Library/Caches/io.tailscale.ipn.macsys
~/Library/Containers/io.tailscale.ipn.macsys
~/Library/Containers/io.tailscale.ipn.macsys.login-item-helper
~/Library/Containers/io.tailscale.ipn.macsys.share-extension
~/Library/Containers/Tailscale
~/Library/Group Containers/*.io.tailscale.ipn.macsys
~/Library/HTTPStorages/io.tailscale.ipn.macsys
~/Library/Preferences/io.tailscale.ipn.macsys.plist
/Library/Tailscale

In my case however, that did not completly work for two reasons. First, not all files/folders were found on my device in the first place. And seccond, my terminal had not enough permissions (even with sudo) to remove certain files. I had to give the Terminal application Full Disk Access in Settings > Privacy and Securty > Full Disk Access for it to be able to delete everything.

Note: I also used \ before a space, since macOS wont recognize it otherwise without " brackets at the begin and end.

In the end, I ran the following command to completly remove everything from Tailscale that was still on my Mac.

sudo rm -rf \
~/Library/Application\ Scripts/io.tailscale.ipn.macsys \
~/Library/Application\ Scripts/io.tailscale.ipn.macsys.login-item-helper \
~/Library/Application\ Scripts/io.tailscale.ipn.macsys.share-extension \
~/Library/Caches/io.tailscale.ipn.macsys \
~/Library/Containers/io.tailscale.ipn.macsys.login-item-helper \
~/Library/Containers/io.tailscale.ipn.macsys.share-extension \
~/Library/Containers/Tailscale \
~/Library/HTTPStorages/io.tailscale.ipn.macsys \
~/Library/Preferences/io.tailscale.ipn.macsys.plist \
/Library/Tailscale

After that, I rebooted my Mac and installed Tailscale Standalone with the official .pkg file.

But even all that, did not solve my problem. The error was still there and Tailscale still refused to work.

Then I decided to further look into the permissions that Tailscale had on my Mac. More specifically, what permissions it had regarding extensions.

I found out, that in Settings > General > Login Items & Extensions > Networkextensions, there were two identical entries listed as Tailscale Network Extension and one entry called Unknown. All of witch gave the following error when I tried to enable them.

Unable to enable Tailscale Network Extension: Opperation couldn't be completed. (OSSystemExtensionErrorDomain error 4.)

I double-checked this in the terminal with systemextensionsctl list and got this:

enabled    active    teamID       bundleID (version)               name                        [state]
*          W5XXXXXXZB io.tailscale.ipn.macsys.network-extension (1.90.3/101.90.3) Tailscale Network Extension [activated disabled]
*          W5XXXXXXZB io.tailscale.ipn.macsys.network-extension (1.90.6/101.90.6) Tailscale Network Extension [activated disabled]

This indicated that a dead duplicate was causing the issue. I removed the duplicate by running the following command:

sudo systemextensionsctl uninstall io.tailscale.ipn.macsys.network-extension 1.90.3

This also resulted in the Unknown extention disappearing. After that, I restarted my mac reinstalled Tailscale one last time, and it worked flawless.

I’m uncertain whether that last reinstall was necessary, but I did it as a preventive measure anyway, and now it works. I’m not complaining.