Events

All events fire synchronously on the target player's owner thread. All three cover only the vanilla advancement layer; category-entry unlock, activation, and claim currently publish no public events

Event	Timing	Cancellable	Mutable fields	Cancellation/effect	Runtime path
AdvancementGrantEvent	After the Codex advancement is resolved and is not yet complete, before the codex criterion is awarded	Yes	None	Cancellation leaves progress untouched and returns CANCELLED	Central AdvancementService.grant: the public operation, built-in triggers, and external trigger grant paths
AdvancementRevokeEvent	After completion is confirmed, before the criterion is revoked	Yes	None	Cancellation keeps the completion state	Central AdvancementService.revoke
AdvancementCompletedEvent	When Bukkit's PlayerAdvancementDoneEvent confirms a registrar-managed advancement completed	No	None	Post notification, cannot be rolled back	API grant, configured triggers, external AdvancementTrigger, or any other path that truly completes the registered advancement

The completed event is published by the advancement-completion listener, and its scope is not limited to public grant implementations. It only covers definitions known to the Codex registrar; it is not a global listener for every vanilla advancement. For grant/revoke, the player, the caller-supplied id, and the resolved namespaced key are all read-only