When you're invited to a campaign or accepted into one, a chat thread with the brand opens automatically: one thread per campaign, so conversations never mix.
You chat with the brand as a whole, not individual employees: anyone on the brand's team can reply, and you always see the brand's identity.
Invites and applications appear inside the thread as a card with Accept and Decline buttons. Accepting a campaign invite accepts the deal and unlocks the chat in one step: the card here and your Deals tab do the same thing.
Chats support images, files, voice notes, video attachments (up to 5 minutes / 200 MB), replies, and reactions. Note: sent messages can't be deleted, so write accordingly.