GRAIN ROT Save File - Location & Backup
GRAIN ROT save file: Steam Cloud manages saves; local path follows Steam userdata/SteamID/4450620. Backup before updates.
Where saves live
Saves are handled by Steam, both through Steam Cloud and a local file. The local pattern is typically Steam/userdata/<SteamID>/4450620/remote/ - confirm the exact subfolder in-game, because Valve's layout can vary slightly by title.
Known issues already fixed
Patch 1.02 fixed offline save loading, and patch 1.03 fixed a save bug that caused black-void loads and key-binding saves to misbehave. Those fixes mean modern saves are far more stable than at launch.
Backup first
Before any update, back up the userdata directory or rely on Steam Cloud. Verify your save loaded correctly after each patch, since the early post-launch bugs show saves are worth protecting.