[FO4] PSA: Fallout 4 CK 1.11.137 and Navmeshes in Mods

[Arthmoor]

Heads up to anyone who has an existing mod that was created prior to the November 10 2025 CK update (version 1.11.137). If you have navmeshes in your mod you need to take care when updating said mod.

As background, users on Nexus reported that they were getting game freezes with the most recent UFO4P updates when approaching the Electrical Hobbyists Club building. Last night I identified the cause. The 1.11.137 version of the CK scrambled the "Cover Triangle Mappings" data on every single navmesh that the UFO4P had edited up to this point. This was discovered after running a delta patch between the 2.1.9 and 2.2.0 files, then reverting every navmesh back to what 2.1.9 had in it, since 2.2.0 had no intentional navmesh edits.

After loading the game from the place I had my test save, the freeze when approaching the Electrical Hobbyists Club went away, and 2 Nexus users have since confirmed the same. One of those users also reports that they have a mod with navmesh data that got saved in the 1.11.137 CK and has since thrown errors at him too.

The one thing I am not sure of at this point is if NEW navmeshes in a file that never had them will suffer the same problem if saved in the 1.11.137 version. So that's something to keep in mind.

Obviously for us on the UFO4P this is going to mean we have to suspend any navmesh editing and keep an eye on this in future updates. I would strongly suggest anyone planning to make updates to their mods keep a backup that was previously worked on in an older CK so that you can recover your navmesh data if needed.

[BlackPete]

Out of curiosity, does this apply to mods that may carry over edits from another mod? There are mods that use the UFO4P as a master. They may make an edit to a cell that contains a navmesh edit that is carried over by the patch. Not sure if that makes any sense. I don't have any mods that make edits to navmeshes except the patch, so there probably won't be any problems for me.

Edited December 2 by BlackPete

[Arthmoor]

It will apply to any mod saved in the 1.11.137 CK that contains navmesh edits. Which is generally something you have to do if you're updating navmeshes in a mod so that the NAVI record is properly updated. It doesn't matter whether they're pulling navmesh data from UFO4P or not, they'd have to resave their own mod for that data to incorporate properly and that's where the issue comes from.

[emiral]

I just did a test ... I copied a plugin where I had new navmesh in an interior cell. I opened the copy in both NG and AE CK, and finalized navmesh in a different interior cell than the new navmesh in my original plugin. In both cases, the cover triangles were updated in the new navmesh, even though I didn't touch that cell in the CK. So, this doesn't appear to be new behaviour. Are you sure it's what lead to the CTDs or whatever the players were experiencing?

Edited December 2 by emiral