Is a creature's reach linked to the reach of its attacks?

Question

This is an issue I've seen coming up with the addition of the Eldritch Claw Tattoo in Tasha's Cauldron of Everything, though there seem like there were possible cases of it before.

As far as I can tell, every character starts with a reach of 5 feet. If they are wielding a weapon with the Reach property this explicitly increases the reach of both their attacks, and their reach for the purposes of being able to perform an opportunity attack reaction, by five feet:

This weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for opportunity attacks with it.

However, an Eldritch Claw Tattoo's Eldritch Maul effect doesn't mention opportunity attacks in the same way, it only mentions the range of your attacks:

As a bonus action, you can empower the tattoo for 1 minute. For the duration, each of your melee attacks with a weapon or an unarmed strike can reach a target up to 15 feet away from you, as inky tendrils launch toward the target.

There is a similar case for the playable Bugbear race from Volo's Guide to Monsters, which has the long-limbed trait:

Long-Limbed. When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.

In both cases it sounds like the additional reach only applies when you actually attack; it's unclear whether your reach is also increased for triggering an attack of opportunity or not.

I think the tricky point is that the reach that determines whether you can make an opportunity attack, occurs before you're actually making any kind of attack roll (i.e- it determines whether you can use your reaction or not), whereas the latter two quotes suggest your reach is only increased when actually attacking (about to make the attack roll). As far as I can tell (though I may have missed it) the rules don't state that your reach is based on your melee attack reach, it just happens to be convention that some effects that increase one, also increase the other.

This feels like it might be a bit of a weak distinction, but it also feels very strange that a temporary increase in range should render a character unwilling to strike at an enemy that they would have attacked just a moment before.

So my question is, is there anything in RAW that makes clear that Eldritch Maul, Long-limbed and so-on should also apply to reach for the purposes of triggering an opportunity attack, or am I correct in thinking these may be separate?

Answer 1

"Reach" is specifically defined as your melee attack range

Reach is defined in the section on melee attacks:

Used in hand-to-hand combat, a melee attack allows you to attack a foe within your reach. [...]

Most creatures have a 5-foot reach and can thus attack targets within 5 feet of them when making a melee attack. Certain creatures (typically those larger than Medium) have melee attacks with a greater reach than 5 feet, as noted in their descriptions.

So whenever the game mentions "reach", it is specifically referring to the range of your melee attacks, unless otherwise noted. With this in mind, the rules for opportunity attacks say:

You can make an opportunity attack when a hostile creature that you can see moves out of your reach. To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves your reach.

This means that an opportunity attack is triggered right before an enemy leaves your reach, which is the range of your melee attacks. Anything that extends the reach of your attacks also extends the distance at which enemies provoke opportunity attacks, because these both refer to the same reach.

(It's not explicitly stated, but we can reasonably infer that if you have multiple reaches, e.g. if you are dual wielding weapons with different reaches, then the reach used to determine when an opportunity attack is triggered is the reach of the weapon with which you are making the opportunity attack. With normal attacks on your turn, you can't use the reach of one weapon when attacking with a different weapon, and there's no reason opportunity attacks should be any different in this regard.)

We can read the specific features mentioned to see how they affect opportunity attacks. Let's start with the bugbear's Long-Limbed racial feature:

When you make a melee attack on your turn, your reach for it is 5 feet greater than normal.

Since you generally do not make opportunity attacks on your own turn, this feature usually does not extend your reach for the purposes of triggering an opportunity attack. In the unlikely case that an enemy provokes an opportunity attack on your turn via something like a readied move, then your reach for that attack, and thus the range at which the opportunity attack is triggered, is extended by 5 feet.

Next, let's look at the Eldritch Claw tattoo's Eldritch Maul ability:

As a bonus action, you can empower the tattoo for 1 minute. For the duration, each of your melee attacks with a weapon or an unarmed strike can reach a target up to 15 feet away from you, as inky tendrils launch toward the target. [...]

This pretty clearly extends the reach of all your melee weapon attacks to a minimum of 15 feet, similar to how the Barkskin spell raises your AC to 16 but no further. Hence, 15 feet also becomes the range at which enemies provoke opportunity attacks when moving away from you (unless your reach was already greater than that).

What about that extra bit in the weapon property?

At some point in the past, the description for the reach weapon property was modified by an erratum to add the clause about the extending reach applying to opportunity attacks. In this answer, I have essentially arrived at the same conclusion without referring to this clause at all, suggesting that it is in fact redundant. However, I had to carefully read and cross-reference 2 different sections of the PHB in order to conclude what the erratum simply states outright, and this is not something that is practical to do on the fly in the middle of a session. In fact, it's notable that the full text added in the erratum includes the parenthetical "see chapter 9", suggesting that the erratum was intended more as a clarification and reference to existing rules than an actual change to the rules. Hence, I don't think there's much we can read into the lack of such a clause in other abilities, especially those printed in source books other than the PHB.