For power users or server hosts, you can force Steam to download Build 13500921 via Steam Console:
After updating to Build 13500921, you get a popup: "Unable to load steam_interfaces_009.vpk" . Cause: Corrupted Source Engine common files. Fix: Garrys Mod Build 13500921
In the context of Steam and Facepunch Studios, a "Build" or "Depot" number refers to a specific version of the game’s compiled files. is the unique identifier for the current stable public release of Garry’s Mod as of the latest major patches (2023–2024 era). For power users or server hosts, you can
Approximately 5 GB for the base game (significantly more with addons) 3. Development Context For power users or server hosts