We used to play AD&D for 15 years and now want to "upgrade" to 5e.
Do bonus actions need to be announced at the beginning of the round, like normal action announcements, when the DM starts asking the PCs what the want to do in the given round?
The relevance of this question is that some spells can be cast as a bonus action and the player can still have an action (e.g. make an attack) in the same round. So if the player (a cleric) only announced at the beginning of the round to the DM that he/she only wants to make a melee attack, but during the round he/she realizes that one of the party members has got heavily injured, can he/she besides the melee attack cast a Healing word as a bonus action even if not announced to the DM before?
Best Answer
No actions need to be announced at the beginning of the round.
Nowhere in the default rules for combat in 5e is it stated that creatures have to announce their actions at the beginning of the round, or for that matter even at the beginning of their turn.
Yes, there is the optional Speed Factor variant rule on pages 270-271 of the DMG (which might actually be more akin to AD&D rules, I really wouldn't know), which says an action must be chosen at the beginning of the round but it appears you're not using that.
Given the ever-changing nature of combat, (bonus) actions are announced "as they happen", in a sense, which is how the general rules are moulded to work.
Players take their turn when their initiative order comes up and that's when they decide what they're going to do (with the exception of things like reactions, which can happen on someone else's turn). With any luck the players are strategising and already thinking about what they're going to do before their turn comes up to hopefully help speed up the combat process. They could even announce their intentions before their turn (i.e. I'm going to attack the monster) but those actions aren't set in stone and it's perfectly acceptable to decide to do something else if the circumstance has changed by the time their turn comes around.