Agents that never play the game built a Hearthstone AI that climbed the live ladder to a 1.60 average placement
AutoTavern coordinates specialised LLM research agents through a shared typed research memory and five verification gates, and in 20 days they built TavernGym, a full-content reproduction of Hearthstone Battlegrounds, plus 23 versions of TavernAgent. The agent plays ranked games on the live ladder by itself, with its rating rising from 6,000 to about 15,000; on the public leaderboard's measure its last 20 records average a placement of 1.60 with 80% first places, against 2.34 and 59% for the server's ten highest-rated players together. Asked to make the same decisions directly, frontier LLMs answer at most 63% of play tasks, while TavernAgent answers 91%.