Captain Kagi reads: "When an enemy ship acquires a target lock, it must lock onto your ship if able."

So how does this interaction work with U-Boats?

Let's say that you have a Decimator directly in front of a U-Boat and the U-Boat has a focus token. Now let's say that Captain Kagi is directly behind the U-Boat.

When the U-Boat spends the focus to activate their torpedoes, and the intended target is the Decimator directly in front of them, does the target lock go on the Decimator or Captain Kagi?

R4 Agromech specifies that the target lock goes on the defender, but based on the Dark Curse ruling that I read, spending your focus token to activate a secondary weapon occurs before declaring a defender? But, if there's no defender yet, how can R4 Agromech acquire the target lock? I'm a bit muddled on the timing.

Your input is appreciated.

Honestly, for as tricky as that scenario is, I think that the target lock would still be placed onto Captain Kagi - the only time that wouldn't trigger is if Kagi is out of range of the lock attempt, all other scenarios are handled simply by acquiring a target lock under any scenario.

I assume that R4 Agromech works as follows:

1: Spend focus, triggering R4 Agromech

2: Declare defender and Acquire TL on Defender happen at the same timing step; you can choose which order to do them, so you choose the one that makes R4 Agro work.

Accordingly, as with FCS, Kagi's ability doesn't fire here; R4 Agromech specifies a target for the lock to go on, which means it's not able to go on Kagi, so it goes on the defender as normal.

Equally, there's an argument that says that the R4 Agromech/Deadeye combo doesn't actually work, because of exactly this timing issue, so... Evidently the FAQ covers this one.

If a ship equipped with R4 Agromech is attacking with a secondary weapon that requires the ship to spend a focus token (such as a Blaster Turret), that ship may acquire a target lock on the defender and spend it during that attack.

There's a clear precedent in the interaction between Fire Control System and Captain Kagi. If a game effect requires you to pick up a lock against a particular ship, as both Fire Control System and R4 Agromech do, then Kagi's ability doesn't override the requirement.

It may be worth adding that, for instance, if the Jumpmaster in question also had a Weapons Engineer on board, the second lock would have to be on Kagi if he was in range.

Rules reference, page 4, "Attack":

"The attacker may measure range to any number of enemy ships and check which enemy ships are inside his firing arc. Then the attacker chooses one of his weapons to attack with. Then he chooses one enemy ship to be the target and pays any costs required for the attack."

Followed by

"After a valid weapon and target are chosen and any indicated costs are paid, the target is considered to be the defender."

So in the example mentionned, the Jumpaster measures to the Decimator, pays the cost using deadeye (focus) and from that point, the Decimator is the defender. The aggromech allows you to take the target lock on the defender only, so Kagi's ability cannot come into play. See Kagi's FAQ entry for a similar example with Fire Control System.

What's a U-Boat and how does it play into this question?

What's a U-Boat and how does it play into this question?

A "U-Boat" is a Jumpmaster 5000, in this case loaded out with Deadeye, R4 Agromech, and at least one Torpedo.