channels resource): a record that says which client a Slack channel belongs to, or that it is one of your own. Routing is the code that reads those records.
A message in a channel becomes an event, the event is routed to one copy of a worker, and that copy takes a turn.
The rule, in order
The questions are asked in that order, and the first yes decides. No model is consulted. Which client a turn is about is therefore fixed by which copy runs it, never by anything in the message.
A mapping is a decision
A channel is mapped to a client, or marked internal. Both are explicit records. A channel with no mapping at all routes nowhere, and is not treated as internal. Moving a channel that is already mapped to one client onto another has to be confirmed, so a re-point is always something you asked for twice. Direct messages are never mapped. A DM routes by who is in it, through that person’s binding to a client. That is one route to the answer rather than two, so there is nothing to disagree.Dispatch
Once the copy is chosen, the message is signed and sent to that copy’s sandbox, which has its own key. The reply comes back as a stream of pieces (text, a progress step, a request to send a message) and is posted to Slack by the platform, never by the copy. A copy never holds a Slack token. A message that arrives while that copy is busy is queued and handled next. A run of messages from one sender is folded into one turn; messages from two senders are two turns.Worth knowing. Routines, webhooks, and a task’s log changing start turns the same way: the platform decides which copy, then dispatches. A routine for Acme fires on Acme’s copy, and a webhook aimed at an Acme channel is refused if that channel is ever re-mapped to someone else.