Hi,
when will Patch 3 be available on GOG Galaxy?

Just Downloaded Offline Installer, GOG can't make those until Galaxy is patched.

Big problem with the new patch, if you're short on drive space. It claims to require 135GB of space to install, despite only being a few GB in size.

FYI the Packs with numbers, are split archives, each a 4GB chunk, but it's one huge pak as far as games concened.
So the "Big Problem" is unfortunately an inevitable consequence of patching the huge VirtualTextures.pak (71.9 GB).
It must be extracted, patched, then repacked, the entire pak is much larger when loose files.

It's pretty much the universal patching method now, and this games massive.

Forgot to add, old method, would download entire pak again even for a single file change.
For Downloading this is far better, just need to remember to leave room to patch the biggest texture Pak,
Rule of thumb Double the biggest pack, here that rule says approx 144 GB, so can be used as a good guide.

if you don't have space then you don't meet the min require to install/ run the game

Actually...
I've checked bg3.exe file and it's on 4.1.1.3732833 version, so looks like Patch 3!

Ah... that's my current issue. Only 120gb free - with BG3 already taking 155gb. Guess I'll try moving some files around.

**That Fixed my issue** Updating now.

Thanks for the info.

Wrong.

It demands this space ADDITIONALLY to the already installed game.

It doesnt actually need this space. You can install the full version just fine after uninstalling the previous one.

This bug has been in past installers, too.

Its a fault on Larians side though, not of GoG.

Your'e also wrong it does need this space (for install).
I explained in my previous posts, the space is the size of the biggest game Pak (72GB), which is compressed.
Installer extracts the content, and it roughly double size as loose files.
Updates get applied, then the loose files get repacked, and the extra space is returned, when loose files get deleted.

The reason some patches, don't need this much space is simply because this massive Pak wasn't being patched.
This reduces downloads sixe to only the new files, instead of replacing every full pak, even for a single file update.

Steam patches like this
Every PC games patched like this now,

This is dumb.

Thats definitely not true, most PC games are much smaller, so even if they use the strategy you described they would still not have such a massive demand in regards to disk space.

I know that, it makes no difference to the process, only the Pak size is different, and I never claimed otherwise
Most games are much smaller than BG3, so their pak archives are also much smaller, duh!
That is stating the bleeding obvious, and basically on PC, it's Steam that sets the standard (whether we GOG users like it, or not).

Regardless of size of game, if the Assets are packed in an archive, this is how Steam patches them.
If you have Steam, you can see this in action on the Downloads page.
With any patch you are shown the download total, and the installed totals.
Install will ALWAYS be bigger, because it's patching each archive that needs updating.

Also obviously, most older games don't get patched anymore, and if they do it's mostly the management files for Steam/GOG that change, not the old game, so you will not see the patching process in action then.

GOG is no different in the underlying Pak patching principle, though in practice it's not exactly the same.
Steam uses "Steam\SteamApps\DepotCache" folder for all games.
With GOG you see a "!Temp" folder, created in each games folder while patching, which gets deleted once the patching is done.

I mod virtually all my games, and pay very close attention to what Steam, and GOG are doing in my file system, where when, & Why.
I know so much about it, because I watch it, and this entire process is why asset BG3 mods come in Paks.
All UE4/5 games, Unity games, EA, Ubifoft, CDPR, BGS, Capcom, whatever the game engine being used, and virtually the entire gaming industry now uses some form of Packed Archive, for storing game assets.