What is it? Patch Notes?

I had the same issue few months ago when I was replaying the game and was wondering what was that about and if I should roll back to the 2.6.6.0. I am trying to remember what my conclusion was. I think I found confirmation this is nothing coming from the devs(Beamdog) and I thought it was related to the recenet release they had of portrait packs. The P at the end even make sense(to be short for portrait). I assumed GOG needed to change/add something for these packs to be correctly added if you own them. I had no issues with any of the mods I used for BG1 and 2

Thanks - makes sense. There were two reasons for asking: Steam doesn't have this patch (which could mean that it's a GOG-only patch indeed), and I wondered about mod compatibility (which you say isn't an issue).

Yea I assumed its the mods you are worried because I also was. I used some of the well known mods - the Tweaks Anthology, EEUITweaks, Talents of Faerun, Klatu Tweaks and even SCS for BG1(plus one old portraits mod) - they all worked. Have fun!