Why do players avoid trading cannons too early in xiangqi?
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
Because an early cannon is close to its peak value, with the board still full of potential screens and the piece still able to reach almost anywhere. Trading it away in the opening gives up all of that future usefulness for a simple one-for-one swap, when the same piece kept a little longer could have created a real threat first.
What you actually lose by trading early
Not material, since the trade is even, but tempo and potential. A cannon that never got to threaten anything did no work at all for its sixteen or so opening moves, and its replacement on the board, usually nothing in particular, does not make up for it.
When trading a cannon early is actually fine
If the trade removes an opposing Central Cannon before it creates a threat, or opens a file you specifically want, the early trade is a plan rather than a waste. The distinction is whether the trade serves a purpose or simply happens because a cannon was available to swap.
Related questions
Is it ever correct to offer a cannon trade on move one or two?
Rarely as a first choice, though answering an opponent's central cannon with your own is a standard and sound reply.
Does the same caution apply to horses?
Less so; horses generally want to develop and engage quickly rather than sit in reserve.
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