What is perpetual chase in xiangqi?
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
長捉 is repeatedly threatening to capture the same piece so the opponent must keep moving it, producing a repetition. As with perpetual check, the chaser is required to vary and loses if they refuse. It is the subtler half of the repetition laws and the part where rule codes differ most.
What counts as a chase
Broadly: a repeated threat to capture a specific piece where the threat is real and the target must keep running. What does not count is the harder question, and the official casebook exists to settle it. Common distinctions include whether the chased piece is protected, and whether the chasing piece could actually take it profitably.
Why it is hard to adjudicate
Because a position can involve checking, chasing and ordinary repetition at once, and the two sides may be doing different things. This is why the WXF publishes a 110-diagram casebook of worked examples, and why our engine is regression-tested against it rather than against a summary of the rule.
Related questions
Is chasing a soldier a perpetual chase?
Generally the rules treat chasing a soldier differently from chasing a major piece. The casebook is the authority on which cases count.
What if I chase and my opponent checks?
Mixed cases are exactly what the casebook covers, and the answer depends on the specific combination.
.