Negotiation takes place early on the turn, before rolling for movement. Combat, of course, happens afterwards.
Betrayal in combat (as well as playing other cardS) takes place before you start rolling dice, right when the combat starts.
Are you sure about that?
In 8.4 it says that after a successful betrayal combat immediately ensues.
We always interpreted that to mean that the combat happens right after a successful negotiation in a space with more than one enemy unit. And that this combat happened before the next negotiation roll. We certainly weren't waiting until the combat phase.
But yes, the rules are poorly written, so another opinion is appreciated.