Sparring
Sparring between PCs is not uncommon on Dominium Fuego, as it offers a chance to explore your PC's capabilities in a lower-stakes environment and get a better grip on combat mechanics.
All sparring is considered 'canon' unless both players agree otherwise before the spar begins. If there are other PCs around watching, make sure they understand if the spar is not-canon, as they may wish you to go to another room so they may continue roleplaying.
Generally, it is preferable to make spars "canon," meaning they actually happen in the game. If you take Consequences, they stick around as usual. You cannot use sparring to build up FPs under the Concession/Take-Out rules for Cashing In unless you go into a PRS or GM-run scene with those Consequences.
As always, any sparring is considered PvP. Take-out conditions and Consequences for a 'canon' spar are usually very minor. You are not allowed to kill or seriously injure a PC in a canon spar unless both players are very clear with each other before and during the fight, and both players are okay with those possible outcomes. It is equally wrong to take a serious Consequence and then have your PC get mad at the other PC as it is to inflict a serious Take-Out condition and do the same.
Remember that sparring is a tool for having fun, exploring PC capability, and learning the combat mechanics better, not one for dominating other PCs, hurting other PCs, or making them/their players feel bad about their combat abilities.