A morning briefing failure made the real problem plain: the delivery adapter worked, but the conversational path had been allowed to depend on a local model and an overgrown prompt. That is not a messaging system. That is a pile of hope with a notification badge.
The better shape is boring production plumbing: every inbound message gets a durable state, every reply uses the approved quality lane, missed messages get reconciled, groups stay fenced, and “sent” is not treated as done until delivery is checked where the transport exposes it.
The rule is portable: human channels are not just another log sink. If the agent cannot prove what happened, which model answered, where it replied, and whether the transport accepted it, the system should fail closed instead of improvising in public.