Sabotage

When another player plays an action card other than "Sabotage": Cancel that action card.

Action card

When another player plays an action card other than "Sabotage":

Cancel that action card.

4in the deck

–chance to draw

Nocomponent action

Source: Base game

ClarificationsSelect rulings confidence level

tirules.com

If a player has a second copy of an action card, they may play it if the first was cancelled by Sabotage.
If an action card is cancelled by Sabotage, no costs are paid.
A player playing an action card announces the following before Sabotage may be played:
- Any targeted planets, system, units, players, cards, outcomes, and/or other such objects.
- The value of any variable cost to be paid.
Any dice are rolled and any cards are drawn only after all other players has declined to play Sabotage.
If an action card instructs a player to research a technology, that player need not announce what technology they are researching until all other players has declined to play Sabotage.
If an action card is played that will have an effect later, such as a rider, that card may only be cancelled by Sabotage when it is originally played.
If the action card that was cancelled by Sabotage was to be used to perform a component action, the active player must perform a different action, or pass.

tirules.com

Other players must decide whether to play Sabotage, or otherwise cancel the action card, before the player playing Divert Funding announces which technology they are researching.

If Sabotage cancels an action card that the active player played as a component action for their second action of the turn, through an effect granting an additional action, the active player may end their turn without performing a second action and without passing.

Other players must decide whether to play Sabotage before the player playing Focused Research announces which technology they are researching.

The active player must announce which technology they are gaining before other players decide whether to cancel Plagiarize.

Other players must decide whether to cancel Reveal Prototype, before the player playing it announces which technology they are researching.

Sources