What is the 110-diagram repetition casebook?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws for movement, checkmate and both repetition rulings: a side that forces a repetition by perpetual check or perpetual chase loses rather than drawing. The chase half has not been validated against the official casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it before publishing.
Direct answer
It is the official collection of worked repetition positions used to decide how perpetual check and perpetual chase cases are ruled. The repetition laws cannot be stated compactly enough to cover every position, so the casebook supplies adjudicated examples. It exists only as a scanned manual, which is why so few programs implement chase: there is nothing machine-readable to test against, including for us.
Why a casebook rather than a rule
Because the interesting cases are combinations. One side checks while the other chases; a chased piece is protected; two pieces are chased alternately. A short rule cannot resolve these without ambiguity, so the federation published decided examples instead — the same approach a legal system takes for the same reason.
Why it matters here
Most descriptions of xiangqi online either omit the repetition rules or state a simplified version that is wrong in the cases that actually arise. Testing an engine against the casebook is the difference between implementing the rule and implementing a summary of it.
Related questions
Do online servers follow it?
Many implement a simplified repetition rule. This site enforces both halves: a perpetual checker loses, and so does a perpetual chaser. The chase half has not been validated against the casebook, so we do not claim correctness on its hardest cases.
Do I need to know all 110?
No. Knowing that perpetual check loses, and that chasing is also adjudicated, covers everything a club player meets.
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