Council of Four is an open-source Magic: The Gathering rules engine and simulation harness focused on answering the question deckbuilders actually ask: how does this deck perform over many games?
The public Council of Four engine parses card text into typed Go definitions, applies Commander rules, and records a rich event stream from every game. This private companion corpus expands that engine across thousands of supported cards.
A single goldfish can mislead. Repeated deterministic simulations expose recurring mana pressure, cards stranded in hand, commander reliance, and the turns where a deck succeeds or falls behind.
This first web app runs on your machine. The Go backend fetches public decklists, runs games in memory, and serves the results directly to your browser.
The project optimizes for batch throughput: pay setup costs once, then use concurrency and shared immutable card definitions to play hundreds of independent games quickly.