In your mission folder, create or edit description.ext :
-beclient Without this, BattleEye rejects the HC, triggering a Steam Auth cascade failure. The HC needs to tell Steam which game it is. By default, it might not pass the correct AppID. Force it. arma 3 headless client steam authentication failed hot
If you see this red text scrolling in your HC console or server RPT logs, your HC is being rejected by the Steam backend. It cannot connect, and your server will lag. In your mission folder, create or edit description
class Header gameType = "Coop"; playerCount = 1; ; class Params class headlessClients title = "Headless Client"; values[] = 0,1; default = 1; ; ; Force it
For server automation, combine a persistent Steam login with Task Scheduler and the -steamport parameter. Avoid -noSteam . Always validate files via SteamCMD.