How do I know if a combination is sound before playing it?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws and is regression-tested against the official 110-diagram repetition casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it against the engine before publishing.
Direct answer
Calculate all the way to a position you can actually judge, against the opponent's best defence, not their easiest mistake. A combination is only as sound as its final position, and "I am up material" is not a complete evaluation if your own palace is left exposed at the end of the line.
Play the position out against yourself
After finding a combination, switch sides mentally and look for the opponent's most stubborn reply at every branch, not the first one that comes to mind. A combination that only works against a passive defence is not sound, it is optimistic.
Judge the final position, not just the material
At the end of the calculated line, ask three things: is my own general safe, are my pieces coordinated or scattered, and can the opponent's remaining material create a problem of its own. A combination that wins a piece but leaves your palace open has not necessarily won the game.
Related questions
What if I cannot calculate to a clear end?
Then it is speculative rather than sound. That is not automatically wrong, but know which one you are playing.
Should I trust a combination that feels obviously right?
Verify it anyway. Feeling right and calculating out correctly are not the same thing.
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