If a lapsing ability triggers on a player's upkeep but is found during declare attackers, what is the correct course of action?

In this scenario, the key point is how lapsing abilities function within the game's rules. A lapsing ability is specifically designed to trigger at a certain time—in this case, the upkeep. If the ability is not addressed at that point and is only noticed during a later phase, such as declare attackers, it is considered missed.

When a player fails to acknowledge a lapsing ability that triggered during their upkeep, the official ruling is that the ability is ignored and no penalty is issued. This is because the opportunity to put the ability on the stack was during the upkeep, and since it wasn't done then, the game recognizes that the trigger simply didn't happen.

As a result, the current game state is maintained without retroactive implications when the trigger is identified later. This aligns with game balance and the orderly progression of play, ensuring that players are not penalized for oversight in a previous phase if it does not disrupt the integrity of the game state at the current point. Therefore, the correct course of action is to ignore the missed ability and continue with the game, reflecting the rules governing lapsing triggers.