A weird scenario happened during a tournament this weekend:

- Tie Defender moves and does a boost action

- (other stuff happens here)

- Lambda moves and does a coordinate action on the tie defender, trying to perform a boost.

I realized this and blurt out that a ship cannot do the same action twice during the same round, which we both knew was true. What I could not figure out, however, was what happened next. Was it a failed action? Was the Lambda now forced to still perform a coordinate action on that defender? Fortunately, this was not at a critical time of the game; we were not even within firing range, but it did cause some confusion.

Any ideas?

Rules Reference page 8

"Coordinate ()

Pilots can coordinate to assist their allies. When a ship performs the action, it coordinates. A COORDINATING ship is a ship that is attempting to coordinate by performing the following steps:

Measure range from the coordinating ship to any friendly ships.

Choose another friendly ship at range 1-2.

The chosen ship performs one action.

Additionally:

While a ship coordinates, the coordinate fails if no friendly ship can be chosen.

If the chosen ship attempts to perform an action but that action fails, the coordinate does not fail.

If an ability instructs a ship to coordinate, this is different than performing a action. A ship that coordinates without performing the action can still perform the action this round."

So the Coordinate from the Lambda succeeded (picked the Defender). The Defender has to choose an action it hasn't already done, so in your example it has to either pick another action to perform or choose not to use the coordinated action (resulting in a wasted action on the behalf of the Lambda).

@Hiemfire got it exactly: The Coordinate from the Lambda succeeds. Then the Defender gets to choose an action to perform (or may choose to not perform an action).

When in doubt, Lock a Rock.

Yeah. The coordinate was successful. The defender just needed to pick another action.

... like locking a rock 😜

It's worth noting that when a ship like the Lambda coordinates, it doesn't have to declare the target of the coordinate, or the action the target will perform. You can measure to all nearby ships, then choose one ship in range, then that ship performs an action. Someone being confused, wanting the Defender to perform the same action twice, doesn't invalidate any step of that chain.