No. The mediator owns how the peers collaborate.

Room maps member names to receiver callbacks. It validates the sender and broadcasts to everyone else. Unlike a facade’s simpler external entry point, the mediator defines peer interaction rules. The sample is synchronous, local, and not durable; receiver failures can produce partial delivery.

What the function promises: Member names are unique; unknown senders raise. No real messages leave the process.

class Room:
    def __init__(self):
        self.receivers = {}
    def join(self, name, receiver):
        if name in self.receivers:
            raise ValueError("Duplicate member")
        self.receivers[name] = receiver
    def send(self, sender, text):
        if sender not in self.receivers:
            raise ValueError("Unknown sender")
        for name, receiver in tuple(self.receivers.items()):
            if name != sender:
                receiver((sender, text))

room, ana, bo = Room(), [], []
room.join("Ana", ana.append)
room.join("Bo", bo.append)
room.send("Ana", "hello")
assert ana == [] and bo == [("Ana", "hello")]

Work and storage: O(recipients) notification work plus listener costs.

When to recognize it: A mediator reduces tangled peer references. It should not absorb every unrelated feature just because messages pass through it.

Check before applying it: A mediator does not automatically provide reliable distributed delivery.

Durable membership and message history, authorization, IDs, deduplication, and routing ownership. The high-level chat lesson adds those boundaries.