In Gmod 13 Beta you can mount CS:GO and Portal 2 now you can't, what's up with that?

So what’s happening with it then? Anybody got any ideas?

Due to Steam Pipe issues, Garry had to disable the mounting of them. Odds are once GMod moves to the new system the options will return.

Thanks, but what is Steam Pipe? is it the form of code used in source games?

It’s a new content delivery system for Steam games, i.e. controls how updates are sent out/installed etc.

Steam Pipe is the content form that CSGO and Portal 2 use afaik

I’m being told 2 different things what should I believe? (Google didn’t help).

Both things mentioned above are the same thing. Steam Pipe is a content delivery system that Valve has introduced recently that allows for delta updates to games on Steam, however the way the two content systems interact (HLDS update tool being the older version) causes some issues and incompatibilities that’s not seen to us, the end user. As a result Garry (for now) has disabled these until GMod moves to Steam Pipe.

I suspect its the same reason why I can’t mount L4D2.

Yes, but hopefully, as previously said, once Garry is on his own unique branch of Source, which he is to an extent, we will be able to mount them all once again.