Steam and mods

Overview

The vast majority of mod changes have to be made by altering the hex code of the game executable file 'XComGame.exe' directly. As a consequence, every time a patch to the game is released, or Steam 'verifies' the game files, any mods installed will be removed and vanilla files restored, and eventually you will find it necessary to reapply all your desired mods.

Retaining Control

Here is how to take control of Steam updates:

Ensure X-Com is *unable* to phone home to acquire certain updates (intended to prevent cheating on multiplayer) that will overwrite part of the mod. There are two ways to do this, and both may prove necessary:

1. Offline Mode. Easier to accomplish. This prevents Steam from connecting to the Internet, but you won't be able to chat, play multi-player, or update other games until you switch back to 'on-line'. See this page for the official Steam instructions for going into 'offline' mode for your computer.
   1. Start Steam.
   2. Steam Menu (top left) > Go Offline > Restart in offline mode.
2. Modifying hosts file -- prevents XCom from calling out. More complicated, but lets you use Steam's online functions such as multi-player.
   1. Start Menu > Right click on Notepad, select "Run as Administrator"
   2. File > Open >  %systemroot%\system32\drivers\etc\hosts -- The hosts file has no '.' suffix, so make sure you don't add '.txt' or anything else. Also, %systemroot% on my system is C:\Windows, but it may vary.
   3. Add these three lines to the file:
      • # Prevent XCOM Phone Home
      • 127.0.0.1 prod.xcom.firaxis.com
      • 127.0.0.1 65.118.245.165
   4. Save the file.

Restoring to Vanilla

Eventually you will need to patch your game and re-apply your mods, sometimes because you will desire to apply different mods or apply them in a different order. Here is how to restore your game to the latest version of vanilla:

1. Take Steam back 'online'.
2. Wait while the game is repatched (progress is indicated on the filename in the Steam Library).
3. Once patched, right-click, select game 'Properties', and 'Verify cache'.
4. Once verified, while still 'online', play the game to the Main Menu at least TWICE.

   The first time played, the game will install any files the verification process determined needed updating.

   Take the opportunity to check/reset the game configuration options, particularly 'video'.

   The second 'play' enables final game 'sync' to the Steam servers.

5. Finally, take Steam 'offline', and mod again.

References

Basic Guide to installing mods