Not currently surfaced in the X-ray Coach. This is a whole-game pipeline label, computed across an entire game rather than for a single position, so it is not part of the per-position tactic set the X-ray Coach receives.
How Koga decides
Definition Throwing away a winning position
- An unforced error is not a tactical pattern on the board — it is a judgement about the move that was actually played. We flag it when a player who was already clearly winning makes a move that hands that advantage away, even though nothing forced them to.
- We only consider it when the position before the move was already a solid advantage — roughly a pawn and a half ahead or more. If the game was level or unclear, a mistake there is judged by its tactical content instead.
Condition Most good moves kept the win
- Before calling it an unforced error we check that the win was easy to hold: among the engine's top five choices in that position, at least three of them keep the player comfortably ahead — clearly better than the move that was actually played.
- When many reasonable moves all preserved the advantage, choosing the one that loses it is a self-inflicted slip rather than a forced concession. If instead only one or two moves held the win — the position was already delicate — we do not call it unforced, and the position is judged on its tactics instead.
Split Unforced error vs. missed opportunity
- Both labels start from the same situation: a clearly winning position where most moves held the advantage but the move played did not.
- If the player is still winning afterwards — they merely let some of the lead slip — we call it a missed opportunity.
- If the advantage is gone after the move — the position is no longer winning — we call it an unforced error.
Test positions (the examples that guard against regressions)