Does True Strike end before it is useful?

Question

True Strike has a duration of "concentration, up to 1 round". But it says "On your next turn, you gain advantage on your first attack roll against a target, provided this spell hasn't ended."

But True Strike has to have ended, because a round has elapsed. How is that not true?

Answer 1

The way I've interpreted this is that the spell itself, the casting of it, takes the duration of one round, your current action. The effect itself does not take place until your next turn as stated in the spell text proper. Once your next turn begins the spell is active, so to speak, and for the duration of that round you gain the advantage listed.

Furthermore if concentration is lost between casting and actual use, you'd resolve it as you would normally for checking on a break in concentration.

TRUE STRIKE
Divination cantrip
Casting Time: 1 action
Range: 30 feet
Components: S
Duration: Concentration, up to 1 round

You extend your hand and point a finger at a target in range. Your magic grants you a brief insight into the target's defenses. On your next turn, you gain advantage on your first attack roll against the target, provided that this spell hasn't ended.

So cast spell, wait for next turn, spell effect is active for that turn, profit.

Furthermore I'd treat an attack on that turn that a PC might be able to make as a bonus action as the "next turn" attack with advantage, aka the first attack roll against the target mentioned in the spell proper. But the text is pretty clear that it starts working on your next turn, so that would likely be up to the DM.

Answer 2

The designer's intent of how the spell is meant to be used seems pretty clear to me. The maximum duration of 1 round includes your following turn.

As an example:

1. You cast True Strike and begin concentrating on it.
2. Your current turn ends.
3. Combat proceeds in standard initiative order. If you take damage during this period you must make Constitution saving throws to maintain your concentration.
4. Your next turn comes up. Assuming your concentration hasn't been broken, the first attack you take on this turn has advantage.
5. At the end of your turn, True Strike has exceeded its maximum duration and the spell ends.

Answer 3

A spell's duration begins after completing its casting time. True Strike has a casting time of 1 Action and a duration of Concentration, up to 1 Round.

Page 203 of the PHB:

A spell's duration is the length of time the spell persists. A duration can be expressed in rounds, minutes, hours, or even years. Some spells specify that their effects last until the spells are dispelled or destroyed.

...

Concentration Some spells require you to maintain concentration in order to keep their magic active. If you lose concentration, such a spell ends. If a spell must be maintained with concentration, that fact appears in its Duration entry, and the spell specifies how long you can concentrate on it.

So after using your action to cast True Strike, the Concentration must be held until your next turn where you can use your attack with advantage or else the spell ends. The concentration doesn't end after the same round that the spell is cast because the duration of the spell, one full round, hasn't elapsed after casting the spell that turn.