The first move out of book is not automatically the leak
Leaving theory is a moment, not a diagnosis. The useful fork is the board you keep choosing later, when you already had a usual move.
Chessigma looks for a move that scored worse than what you normally play from the same position. Book exit is a label. The habit is the repeat.
Book is someone else’s tree
Your opponents will take you out of a course on move six. That is not a leak until you keep answering with the same worse move.
Train the FEN you actually reach. A named opening report is only a way to find that FEN.
Engine book is a different product
Stockfish will tell you the best exit. Your history tells you which exit you already take. Chessigma is the second question.
Frequently asked questions
Should I memorise more theory?
Only if the leak is actually in the first ten moves you repeat. Many club leaks are on move fifteen of a position you already know.
What if I have no usual move?
Then there is no fork yet. Play more games in that structure before you buy a repertoire.
Chessigma imports public Chess.com and Lichess history and reports repeated choices — not engine grades. Import your games · Methodology