A participant who drops out mid-tournament doesn't break the history: the points and matches already played are never touched, only how what's left pending gets resolved changes — and that depends on the format.
League and mini-league
The schedule is already set: every pending match for the withdrawn participant is awarded to the opponent by no-show (W.O.). Matches already played stay as they are and keep counting toward the standings.
Knockout
Their pending match is awarded to the opponent, who advances to the next round. In two-legged knockout ties the walkover decides the whole tie — the withdrawn participant doesn't advance even if the aggregate score favored them.
Swiss and McMahon
The withdrawn participant stops being paired in subsequent rounds, with the option to skip a specific round instead of withdrawing them entirely. Their initial McMahon score can be corrected by hand if needed.
Mexicano
Their pending match in the current round is awarded to the opponent, even if the withdrawn participant was their court partner. They don't get paired again in subsequent rounds.
Ladder
Their pending challenges are canceled and no one can challenge them until they're reactivated.
Manual pairing
From that same panel, before generating a Swiss or McMahon round, specific pairs can be fixed by hand — late arrivals, an ad-hoc pairing between the top players — and the engine respects them as is, automatically pairing everyone else without checking whether they've already played each other.
Reactivation
A withdrawn participant can be reactivated at any time. If the next phase is already seeded, the reactivation doesn't add them back to the bracket — it just stops them from being excluded from new rounds going forward.