Updated Creation Kit not Compatible with Old Fallout 4

[Kharos]

A heads-up to all mod authors: As I just found out the "Fallout 4 Next Gen" update to the creation kit breaks compatibility of the created mods with the previous Fallout 4 version. Not sure about the technical reason for that, my guess is that they made a breaking change to the .ba2 format, but it could also be caused by papyrus changes. The patch notes do not mention anything like that...

TL/DR: If you want to continue supporting the old version with your mods, make sure that you block updates to the creation kit.

In case you forgot to do that like me, the following reddit thread was useful: https://www.reddit.com/r/fo4/comments/1cdfe3j/how_do_you_rollback_the_update_to_fo4s_creation/

 

[Slorm]

2 hours ago, Kharos said:

A heads-up to all mod authors: As I just found out the "Fallout 4 Next Gen" update to the creation kit breaks compatibility of the created mods with the previous Fallout 4 version. Not sure about the technical reason for that, my guess is that they made a breaking change to the .ba2 format, but it could also be caused by papyrus changes. The patch notes do not mention anything like that...

TL/DR: If you want to continue supporting the old version with your mods, make sure that you block updates to the creation kit.

In case you forgot to do that like me, the following reddit thread was useful: https://www.reddit.com/r/fo4/comments/1cdfe3j/how_do_you_rollback_the_update_to_fo4s_creation/

 

 

Yes it looks like there's a new BA2 format, I just spotted this on Nexus https://www.nexusmods.com/fallout4/mods/81640

[OldTimer91]

Question for a brave sole that updated.

 

Archive Tool

Has the old version of \Steam\steamapps\Common\Fallout 4\Tools\Archive2\Archive2.exe been updated?

If so does it unpack the old versions still? If so then unpacking and repacking to the new format should be an straight forward fix.

 

File Header

Has the header number been updated?

[EgoBallistic]

The plugin file header format is still 1.0 and plugins made in the new CK will work in FO4 .163.  The issue is with BA2s created by the CK.

 

The stupid part is that the only change to BA2s is the header version number.  They are otherwise byte for byte identical to the previous version.