Does perpetual check require the same piece every time?
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
No. The rule looks at whether one side is checking repeatedly without genuine variation, not at which piece is doing the checking. Alternating between two different pieces to give check, if it produces the same recurring position with no real progress, is still perpetual check under the repetition laws.
What actually counts as varying
A change that alters the resulting position meaningfully, forcing the general somewhere genuinely new, gaining material, or creating a fresh threat, counts as variation. Simply switching which piece happens to deliver an equivalent check does not, since the underlying position keeps recurring regardless.
Why this closes an obvious loophole
If swapping checking pieces reset the count, perpetual check would be trivially easy to disguise. Judging the rule by the resulting position rather than the mechanism keeps the spirit of the law intact: the checking side must actually be making progress, not just varying cosmetically.
Related questions
Who decides whether a change counts as real variation?
The arbiter in formal play, using the repetition casebook as a reference for borderline cases.
Does this apply to perpetual chase the same way?
Yes, the same principle: the position and the threat matter, not the specific piece or exact move sequence used to create it.
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