How are resources recovered during a long rest that was interrupted?

Question

A DM can choose (deliberately or randomly) to interrupt the players long rests with a random encounter. See for example this question: Our DM keeps interrupting our long rests

Now rules as written say that less than 1 hour of interruption, even strenuous fighting, doesn't invalidate the long rest. The players can fight the monsters that attacked them during their rest, go back to sleep, and still get the benefits of the long rest.

But how does that apply to resources like spell slots that were spent during the rest? Imagine the interruption happens one hour before the end of the long rest, the barbarian uses one of his rages, the casters use up spell slots, and so on, do they get all of that back one hour later? Or do they only recover the resources they had spent before starting the long rest?

Answer 1

Resources are regained at the end of a long rest.

The barbarian's rage class feature states:

you must finish a long rest before you can rage again.

Spellcaster's spell slot section states:

You regain all expended spell slots when you finish a long rest.

For hit points and hit die:

At the end of a long rest, a character regains all lost hit points. The character also regains spent Hit Dice...

So it doesn't matter what is spent during the rest as long as the PCs get to finish that rest. This also means that any resources spent before the rest started remain spent during the rest and ensuing combat, until the long rest is completed.

It's also worth noting that it's not intended for the PCs to be able to gain the benefits of a short rest during a long rest, as per this unofficial guidance by rules designer Jeremy Crawford on Twitter:

Q: can a PC benefit from short rests during a long rest? A PC (fighter) is abusing second wind to save hit dies.

A: The intent is that you can't take a short rest and a long rest at the same time.

Obviously a DM can rule whichever way they want but the designers didn't intend for a long rest to include a short rest.

Answer 2

Spent resources are recovered at the end of a long rest, not during it, so these resources are recovered by continuing the rest as normal. No difference is made between slots and other resources spent before the start of the rest and those spent after. See section Long Rest, on page 186 of Player's Handbook.

Answer 3

There are several issues...

1. All benefits of a long rest occur at completion
2. some activity during a long rest is allowed - up to 2 hours of light activity, or a single fight.
3. a long rest includes a short rest.

At least to date, I've not yet encountered any rule which provides benefits of a long rest before the end.

Much argument is made of the minimum durations - 8 hours for the rest, 2 hours of allowed light work (4 for an elf) with the rest being sleep or total inactivity...

If the rest, at interruption, is under 8 hours, but over 1 hour, it should count as a short rest.

So, for HP, spend some Hit Dice if you have any left, as the fight ends the short rest. Likewise, the fighter should have his second wind and action surge, and the Warlock his spells; the cleric and wizard might recover one slot if they haven't already used those benefits.

Answer 4

The rules are not entirely clear about this, which is why this is a good question. And indeed this came up in the game I was running yesterday, with an encounter about 6 hours into a long rest. My ruling was that at the end of the long rest, everything that had been spent before the long rest began was recovered, and also since the remaining part of the long rest was longer than a short rest, everything that was spent during the interruption that recovers on a short rest also was regained. However, those things that were expended during the interruption that only recover after a long rest were not regained, as the characters did not spend the time to make a long rest after the interruption.

So, for example, one character of 4th level, who had 40 maximum hitpoints, was at 31 current at the start of the long rest, and had used all of his recovery hitdice. During the interruption, he took a further 21 points of damage, leaving him at 10 current hp. After resuming and finishing the remaining 2 hours of the long rest, he regained the 9 hp he was down at the start of the rest, making 19 current hp. He also, due to completing the long rest, regained 2 of his recovery hitdice, and due to the short rest completed after the interruption he could apply those to the 21 hp he had taken from the fight during the interruption, which healed him up to full. So, starting the new day, he was at full maximum hp, but out of recovery hitdice until he completed another long rest.