Hello, I just wanted to share how I downgraded my game to preserve my mods for anyone else who needs the help.

I do not know much of anything about code, these are steps I had to get from ChatGPT, so I apologize that I won't be able to answer any specific questions if this doesn't work for you:

This is for PC/Steam and rolls the August 18 update (1.11.240) back to the previous executable (1.11.221).

1. Open the Steam Console
Press:
Windows Key + R
Paste:
steam://open/console
Press Enter.
Steam should open with a new Console tab.

2. Download the previous Fallout 4 executable
Paste this into the Steam Console:
download_depot 377160 377162 387388833281246371
Let it finish downloading.
Steam will tell you where it downloaded the files. It should be somewhere under:
Steam\steamapps\content\app_377160\depot_377162

3. Find your actual Fallout 4 installation
In Steam:
Fallout 4 → right-click → Manage → Browse local files
This opens the real Fallout 4 installation folder.
You should see your current Fallout4.exe there.

4. KEEP the new executable as a backup
Don't immediately delete it.
Rename the current updated executable to something obvious, such as:
Fallout4_NEW_VERSION.exe
That way, if something goes wrong, you haven't destroyed it.

5. Copy in the old executable
Go back to the depot folder Steam downloaded in Step 2.
Copy the downloaded Fallout4.exe.
Paste it into your actual Fallout 4 installation folder.
You should now have:
Fallout4.exe — the older working version
Fallout4_NEW_VERSION.exe — the updated version you backed up
That's the part that actually fixed my modded game.

6. STOP STEAM FROM DOING THIS AGAIN
Go to:
Steam\steamapps
Find:
appmanifest_377160.acf
377160 is Fallout 4's Steam App ID.
Right-click the file → Properties → check Read-only → Apply.
This prevents Steam from rewriting Fallout 4's app manifest and automatically updating the game again.

IMPORTANT: If Steam later gives you a disk-write/update error for Fallout 4, that is probably because you deliberately made this file read-only. Uncheck Read-only if you intentionally want to update the game again.

7. Do NOT launch Fallout 4 normally through Steam
If you're using F4SE, keep launching the game through:
f4se_loader.exe
or through your mod manager's F4SE launch option.
Don't casually hit the normal Play button in Steam when you're trying to preserve a specific modded version.

Extra precautions:
- Back up your saves before messing with game versions.
- Back up your working Fallout 4 folder if you have the disk space.
- Keep track of which Fallout 4 and F4SE versions your mods were built for.
- I didn't need to disable Steam Cloud just to swap this executable, but backing up important saves is still smart.
- Don't blindly use this exact depot command months from now for some completely different Fallout 4 update. This command is specifically for restoring the pre-August-18-2026 executable.

And, for the love of all that is holy, once you have a heavily modded Bethesda game working:
PROTECT THE WORKING VERSION FROM AUTOMATIC UPDATES.