When attacking while invisible, when exactly does invisibility break?

Question

When using spells such as Invisibility and Mislead, and features or abilities such as the One with Shadows invocation and Misty Escape, you may become invisible and remain invisible until certain time limits or actions are taken, such as attacking or casting a spell.

Invisibility (Spell - PHB pg.254)

A creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target’s person. The spell ends for a target that attacks or casts a spell.

Misty Escape (PHB pg. 109)

...you can vanish in a puff of mist in response to harm. When you take damage, you can use your reaction to turn invisible and teleport up to 60 feet to an unoccupied space you can see. You remain invisible until the start of your next turn or until you attack or cast a spell.

I know some features allow you to remain invisible while attacking, like Greater Invisibility , but for those that do not, when exactly do you lose the invisibility trait? Is it different depending on whether or not you cast a spell, make a melee attack, or make a ranged weapon attack?

For instance, do you lose invisibility as soon as you nock an arrow, or when you let it fly, as simply placing it on your bow, or even drawing back the string is not attacking, per se.

Or perhaps you've cocked back a closed fist or heavy mace, do you lose your invisibility as soon as you begin to bring back the weapon, or when the steel connects with the target?

Also, if you were to cast Find Familiar, which has a casting time of 1 hour, are you invisible the entire time you are preparing the ritual up until the point the spell is finally cast, or are you immediately revealed as soon as you begin to prepare the ritual spell?

Answer 1

I can find no Sage Advice regarding the matter, but the rules about unseen attackers starts with this:

Combatants often try to escape their foes' notice by hiding, casting the invisibility spell ...(PHB 195)

This seems to suggest what I believe every table uses: If you are invisible, you attack someone who cannot see you with advantage, even if doing so breaks the invisibility.

Regarding nocking an arrow or swinging back for a punch: this would be a Ready action and not Attack or Cast a Spell, and thus would not end the spell invisibility.

If you cast a spell with a longer casting time

you must spend your action each turn casting the spell (PHB 202)

thus you reveal yourself on the first turn as you have taken a Cast a Spell action.

Answer 2

It seems like this question boils down to determining what constitutes casting a spell or making an attack.

Casting a spell (PHB, p. 202):

Certain spells (including spells cast as rituals) require more time to cast: minutes or even hours. When you cast a spell with a casting time longer than a single action or reaction, you must spend your action each turn casting the spell, and you must maintain your concentration while you do so (see “Concentration” below).

Note the emphasized text: as soon as you start taking the Cast a Spell action, you are casting a spell. If that were not the case (for example, if you were only "casting" find familiar at the end of the hour), then the rules would read something like "In order to cast a spell with a casting time longer than a singe action ...".

Also note the concentration requirement — invisibility requires concentration, so even without the above interpreation, you would need to drop concentration to cast a multi-action spell like find familiar or find steed. This is also true of greater invisibility, which doesn't otherwise end when you cast a spell.

As for an invisible character casting a single-action spell while another character has taken the Ready action to (for example) fire an arrow at them once they become visible: this seems to fall under the rules for adjudicating the timing of reactions (DMG, p. 252):

If a reaction has no timing specified, or the timing is unclear, the reaction occurs after its trigger finishes, as in the Ready action.

So any reaction to an invisible spellcaster becoming visible as a result of casting a spell would occur after the spell takes effect.

Making an attack

We have the general rule about what constitutes an attack (PHB p.193):

If there’s ever any question whether something you’re doing counts as an attack, the rule is simple: if you’re making an attack roll, you’re making an attack.

For the purpose of this discussion, we can re-formulate that as when you make an attack roll, you're making an attack. The most significant game-mechanical implication of this with regard to invisibility is that an invisible attacker becomes visible even if the attack misses.

Preparing an attack, however that may be represented in game mechanics (loading a crossbow bolt, taking the Ready action, etc.), isn't making an attack roll, and thus wouldn't cause invisibility to end.

However, considering the actual actions of the characters, it's not well-defined when the attack roll happens in the course of combat, or exactly what it represents. A pair of fighters dueling with swords will, in the course of a six-second combat round, exchange several plays, remedies, counter-remedies, and other motions; they may represented by one or more "attacks" in the game-mechanical sense, but there will be many more weapon swings involved than attacks rolled. So the motion of a weapon (or limb) towards an opponent doesn't necessarily coincide with the exact moment that the die-rolling part of the attack happens.

Nevertheless, the distinction seems largely cosmetic for most purposes. Consider what's being narrated to a sword-wielding hero being struck by an invisible assassin.

If invisibility drops only as the damaging part of the attack starts:

You feel a sudden blow to your sword, swiping it aside, and then see a cloaked figure appear before you, stabbing towards your exposed chest with a shortsword.

Or if it drops just before any hostile action starts:

A cloaked figure appears before you, wielding a shortsword; they swat your blade aside before you can react and step inside your guard, stabbing towards your exposed chest.

The difference is an interesting narrative detail, but not one that's relevant for any game-mechanical interactions.

Answer 3

Wording of the effect is important to determine when it is applied, and when it drops.

D&D 5e is very careful with wording of spells and effects. In particular, differentiations between things like when you attack and on hit.

For example:

Extra Attack is a feature that states when you take the attack action on your turn, you may make up to X number of extra attacks.

Whereas Smite is a feature that states when you hit with an attack you can expend a spell slot to deal damage.

For invisibility, it's no different. If invisibility is lost like the spell effect description, PHB pg. 254:

The spell ends for a target that attacks or casts a spell.

...then it is lost the moment you use your action to attack or cast a spell.

If it's triggered by an event, such as Misty Escape, you become invisible as soon as the trigger occurs. In this case, it's upon taking damage.

As for when you're standing there with an arrow knocked, until you take the attack action, you remain invisible. Consider that a Dragonborn ALWAYS has a weapon at the ready, and if the mere threat of a weapon was enough to breach invisibility than certain classes, races and weapons would prevent people from ever using the spell.