


Install protontricks for for further installation of sneaky upgrade
reassigned the keys to match the settings from dishonored
Other manuals didn’t work for me, so I’ll write how I set up the sneaky upgrade setup
- go to desktop mode
- open discover
- type protontricks and install it
- download sneaky upgrade full herehttps://www.moddb.com/mods/thief-3-sneaky-upgrade/downloads/sneaky-upgrade-fat-edition
- put downloaded file into your game folder (where t3.ini located) Z:/home/deck/local/steam/steamapps/common/Thief Deadly Shadows\System
- run the installer and select thief deadly shadow in the window that appears
- In the same way we launch the configurator, selecting our thief deadly shadow in the window that appears
- Сonfigure everything as you wish and before exiting, click Apply and Close
- Return to game mode and launch game :) Enjoy
I noticed one thing that if you move in a straight line, the character moves very slowly, and if you add diagonal movements, then the speed increases significantly, which makes the game a little unpleasant. Unfortunately, I don’t remember whether this is correct or a steamdeck problem

Sneakypatch
Need to disable 'Audio Hardware Mixing' within options for in-game sound to work.
Menus are missing some buttons/textures but still navigable. (Sneaky Upgrade / Minimalist Patch)
To install Sneaky Upgrade:
- Install TDS via Steam
- Go to desktop mode and download the mod installer
- Add the installer exe to Steam as a non-Steam game
- Set the installer compatibility (within Steam) to your proton preference. I used experimental.
- Run the installer via Steam (using your proton compatibility version, and still in desktop mode)
- OK the error
- Point the installer to your TDS location. Usually something like Z:/home/deck/local/steam/steamapps/common/Thief Deadly Shadows
- Apply the mods as you see fit and apply all settings. I would NOT update the save location (meant for windows)
- Run configuration after install and set the config however you like.
- Go to the properties of the installer within Steam, change the target path to the actual TDS location (rough approximation of this path above) and to Thief3.exe, NOT T3.exe
- Change start in location to match the above path (as opposed to for the Sneaky Patch Installer)
- Run the game and test it, disable hardware audio.
I recommend copying a controller template of one of the user control profiles over to your 'non-steam' Sneaky Upgrade so you don't have to configure controls from scratch.

WINEDLLOVERRIDES="d3d8=n,b" %command%
Customised controls further for all keys.
Too dark with Wine's d3d8 implementation. Fixed by using the one from the Sneaky Upgrade mod.
Game crashes with Borderless from the Sneaky Upgrade mod.
The Sneaky Upgrade mod is not strictly needed, but makes the game much better. Just remember to adjust the launch parameters to use its d3d8 wrapper.
If you want to use Reshade use version 5.2.1. Newer versions crash on exit.