@Wasted_Youth said in #7:
> There are often several moves which will hold the advantage; required however is always "the best move for side x", and there ́s absolutely no doubt that in this case that ́s 26...Bd6.
Yes, the best move is required. Your phrase "hold the advantage" is key though. Holding the advantage is one thing, but clearly winning is quite another. And the latter, as I understand it, is what distinguishes what is allowed in puzzles and what is not.
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> There was a thread a few days ago showing an example of a puzzle which really did have two equally good winning moves, both of them leading to mate in 39 moves:
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lichess.org/forum/lichess-feedback/puzzle-hzyvj-is-wrong>
Yes, I remember that thread too. And the puzzle was removed. The problem here was that the search depth of the puzzle generator had been insufficient. If the puzzle generator had detected that the alternative move also won, it would not have selected the position for the puzzle base.
> It ́s interesting to put the second option there into the engine and watch the evaluation creep up with ever more depth of search. That doesn ́t happen here; even at depth 30 25...e5 remains greatly inferior to Bd6.
Yes. "Greatly inferior" is obvious. "No longer winning" is the question.