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KAN › The bus · lesson 5 of 5

Forwarding across Macs

Two Macs, one squad. The squad's record has one home, and mail written on the other machine is carried into it without being lost or written twice.

Teaches from specs/kan/design/squad-bus.md, “Where the shared bus lives”, go/kan/cmd/kan/forward.go and specs/kan/design/transport.md, “Which transport carries the work”.

The rule

Where the bus lives was the Operator's choice, made on a decision card: the squad's KAN and its bus node run on m5. MacBook seats reach them through an SSH forward, so nothing is opened on the network. The card's own falsifier names when that would change: the bus moves to a Proxmox box if the bus stand on m5 touches port 6390, the Echo development Valkey, or slows a GA rehearsal.

A peer KAN's mail is carried in by kan forward. It “Ingests a peer KAN's squad mail into this KAN until interrupted (kan.31)”, as a durable consumer of the peer's origin topic, and each entry “is written here with kan.squad.ingest as --principal, which kan serve must name with --forwarder, and acknowledged on the bus only after it is.” An entry KAN refuses outright is parked on the topic's .dlq after --max-failures deliveries, three by default.

Delivery is still not authority. On every route, “Receipt, responsibility acknowledgment, completion and acceptance stay separate.”

Try it

A message from the other Mac

  1. Sent on the peer KAN
  2. Published by the peer's router
  3. Consumed by kan forward
  4. Ingested here
  5. Acknowledged on the bus
  6. Or parked

Sent on the peer KAN
A seat on the other machine sends a squad record to its own KAN.

In the EchoEdu delivery

The course author's session runs on a devbox, not on either Mac, and reaches the squad's KAN on m5 directly. Every message this course quotes, from the first checkpoint to the landing train, is in that one record, which is why each lesson can cite a KAN id that any seat can read back.

Check yourself

  1. Where does the squad's KAN run, and how does a MacBook seat reach it?
  2. When does kan forward acknowledge an entry on the bus, and why then?
  3. A forwarded READY arrived. Has anything been accepted?

Previous: Watching between turns · Up: The bus

Teaches ecd/kan at 0aebfbcb, 25 October 2026.