There is no chess engine here. Your opponent is Jev, a general-purpose model from TypeSafe AI that was not built to play chess.

What Jev is

Jev is a "System One" model: you hand it a situation and a multiple-choice question, and it answers in one shot with a probability for each option. It does not search, look ahead, calculate variations, or use an opening book or endgame tablebase. Stockfish examines millions of positions per move; Jev examines one.

What happens on each move

1. The current position is described to Jev: the FEN, a board diagram, both sides' pieces, the material count, the moves so far, and which of its pieces are under attack.
2. Every legal move becomes one answer option, each labelled with plain facts worked out from the rules: whether the piece can be captured where it lands, whether the exchange wins or loses material, whether it gives check or mate, whether it leaves something else hanging.
3. Jev gets a short list of priorities (take mate, don't lose material, deal with threats, then general principles) and picks one option. That pick is played.

The bars under "Jev's read" are the probabilities it gave its top five options, and "Told" is exactly what it was told about the move it chose.

What the facts are, and are not

The facts come from ordinary rules code, not an engine. They say what is true on the board right now ("this square is attacked by a pawn"), never which move is best, and they look no further than the exchange on a single square. Deciding is left entirely to Jev.

What to expect

• It can only choose from the list of legal moves, so it never plays an illegal one. En passant and underpromotion included.
• It plays sensible-looking chess and avoids the most obvious blunders, but it misses anything that needs two moves of foresight: forks, pins, mating nets, slow plans.
• It has no memory between moves. Each move is a fresh question.
• In Jev v Jev, both sides are the same model with the same information.

Your data

Each position and the move list are sent to TypeSafe's API so Jev can answer. Nothing else is sent, there are no accounts, and your game is saved only in this browser.

Board by chessground (lichess). Pieces by Colin M.L. Burnett (cburnett), CC BY-SA 3.0. Rules by chess.js. Not affiliated with TypeSafe AI.