Steam Play compatibility tools on Linux defined in should be able to map save file directories used by Steam Cloud.
Currently, the Steam client for Linux seems to only remap Win* paths (e.g. WinAppDataLocal) to a fixed location in $STEAM_COMPAT_DATA_PATH/pfx when doing Steam Cloud sync operations. There are no mappings for Mac* paths (e.g. MacAppSupport) for compatibility tools that will run the macOS version of the game, and some compatibility tools that may use other non-Wine methods for achieving native Linux compatibility (or ones that may start up a more hardened container that doesn't allow access to the global home directory) would see it more beneficial to map these paths to a different directory, either within the compatdata folder or in another folder.
For example:
a tool that sandboxes games may want to direct LinuxHome to $STEAM_COMPAT_DATA_PATH/home/ to avoid exposing the full contents of the user's home directory to the container (without needing to know the name of the game's save directory beforehand)
a tool that runs macOS versions of games may want to remap MacAppSupport in save directories to point to $STEAM_COMPAT_DATA_PATH/Users/steamuser/Library/Application Support/
a tool that runs a natively compiled Linux engine build of a specific game may want to direct WinAppDataLocal to XDG_DATA_HOME if %localappdata%/GameName maps directly to $XDG_DATA_HOME/GameName
Use case / Current issue
When using a custom Steam Play compatibility tool with a from_oslist value of "macos" to run the macOS build of a game that uses MacAppSupport as it's savegame directory, Steam Cloud sync currently always fails and reports being "out of sync".
From cloud_log.txt:
[2026-01-03 11:46:08] [AppID 1671210] Starting sync (down,)
[2026-01-03 11:46:08] [AppID 1671210] Skipping rule 0 because it does not run on our platform
[2026-01-03 11:46:08] [AppID 1671210] Unable to resolve path with root MacAppSupport (7)
...
[2026-01-03 11:46:08] [AppID 1671210] YldWriteCacheDirectoryToFile - saved to '/home/emma/.local/share/Steam/userdata/SNIP/1671210/remotecache.vdf'
[2026-01-03 11:46:08] [AppID 1671210] Currently already synced to global change number '25', should be nothing to download
[2026-01-03 11:46:08] [AppID 1671210] Skipping download of file com.tobyfox.deltarune/config_0.ini to our platform, failed to resolve path
...
[2026-01-03 11:46:08] [AppID 1671210] Skipping download of file com.tobyfox.deltarune/filech4_0 to our platform, failed to resolve path
[2026-01-03 11:46:08] ...
[2026-01-03 11:46:08] [AppID 1671210] Download complete in build list
[2026-01-03 11:46:08] [AppID 1671210] Successfully synced to ChangeNumber 0
The original save files are never downloaded anywhere accessible from the compatibility tool so Steam Cloud saves are not able to function in-game.
Feature Request
Steam Play compatibility tools on Linux defined in should be able to map save file directories used by Steam Cloud.
Currently, the Steam client for Linux seems to only remap Win* paths (e.g. WinAppDataLocal) to a fixed location in
$STEAM_COMPAT_DATA_PATH/pfxwhen doing Steam Cloud sync operations. There are no mappings for Mac* paths (e.g. MacAppSupport) for compatibility tools that will run the macOS version of the game, and some compatibility tools that may use other non-Wine methods for achieving native Linux compatibility (or ones that may start up a more hardened container that doesn't allow access to the global home directory) would see it more beneficial to map these paths to a different directory, either within the compatdata folder or in another folder.For example:
$STEAM_COMPAT_DATA_PATH/home/to avoid exposing the full contents of the user's home directory to the container (without needing to know the name of the game's save directory beforehand)$STEAM_COMPAT_DATA_PATH/Users/steamuser/Library/Application Support/%localappdata%/GameNamemaps directly to$XDG_DATA_HOME/GameNameUse case / Current issue
When using a custom Steam Play compatibility tool with a
from_oslistvalue of "macos" to run the macOS build of a game that usesMacAppSupportas it's savegame directory, Steam Cloud sync currently always fails and reports being "out of sync".From
cloud_log.txt:The original save files are never downloaded anywhere accessible from the compatibility tool so Steam Cloud saves are not able to function in-game.