Why does chasing a protected piece not count as 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
Because perpetual chase is defined around a genuine, profitable threat, not the mere appearance of one. If the piece being approached is defended well enough that capturing it would simply lose material back, there is nothing to gain from the capture, so repeatedly threatening it is not treated as forcing the opponent to do anything under the rule.
The logic behind this distinction
The whole justification for making the chaser vary is that they are the one choosing to force a repetition for their own benefit. If the supposed capture is not actually beneficial, the chaser has no real threat and no real choice being forced onto the other side, so the rule has nothing to bite on.
Why this is one of the harder cases to judge
Whether a piece is "adequately defended" can itself be a close call, depending on what would happen after the exchange and any pieces that follow it. This is exactly the kind of borderline situation the official 110-diagram casebook works through with specific, decided positions.
Related questions
Does this mean any defended piece can be approached forever safely?
In terms of the repetition rule, broadly yes, though the position might still be bad for other reasons unrelated to perpetual chase.
Who decides whether a piece counts as adequately defended here?
The arbiter, guided by the casebook, in a formal dispute; online platforms apply their own, often simplified, version of the same logic.
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