FA-82440 / Chess move legality / Member archive

Queenside castling through a piece on b1 · case 05

White castles long with a knight still on b1.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input: {"board", "side": "w" or "b", "wing": "K" or "Q", "rights": subset of "KQkq"}. Standard castling is legal when the right is held, the king is on e1/e8 and the matching own rook on h- or a-file, the squares between them are empty (f,g or b,c,d), and none of the king's squares e, f, g (kingside) or e, d, c (queenside) is attacked by the opponent.

Why this case matters

Move validators gate every move in engines, servers and arbiters; accepting an illegal move or rejecting a legal one corrupts the game record.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
queenside b-file blocked	`true`	`false`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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