A room that somebody opened — a conference, a space, a P2P session, a match — appears in the conversation as a card. The card is not a screenshot of the room: it reads the room as you scroll past it, and it is the way in.
What a live card shows
The name of the room, who is in it and how many, and a badge saying it is happening now. Join opens it in a tab of its own so the conversation stays where it is, and Copy link hands the address to somebody else. A card never names a channel you could not have found on your own.
What an ended card shows
It goes grey, loses the way in, and becomes the record of what happened: how long the room ran and how many people were in it. In its place is the next plausible thing — the channel a conference happened in, or the game a match was played on. A match that somebody already took says so, because a full match is not a broken link: it stopped working by working.
A link that was closed
Revoking a link does not delete the card. It goes grey and says the address was closed, so a conversation that explained itself yesterday still explains itself today instead of leaving a bare address behind.
The P2P invite is one of these
A P2P request draws the same card, with the session's own address on it and Decline beside it. It has no link to copy: the token is the invitation, and it belongs to the two of you.