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+---
+status: open
+opened: 2026-09-29
+located-in:
+  - hq 02-DECISIONS/0138 (reach: internal | public | both)
+  - mesh-controller internal/catalogue/filtering.go (Reaches)
+fixed-by:
+amended-design:
+---
+
+# 150 — A machine's own network is not a reach
+
+## What was observed
+
+Preparing ace's modules. ace sits on a home network (192.168.1.0/24) behind a router, and several of
+its services are reached **from that network by devices that will never be mesh machines**:
+
+- mosquitto `1883` — an IoT light switch (`sonoff-office-light-switch`) and home-assistant;
+- unifi `8080`/`3478 udp`/`10001 udp` — the access points' inform, STUN and discovery;
+- plex `32400` — LAN streaming clients (three connected at survey time);
+- home-assistant `8123`, and the resolver on the LAN address.
+
+ADR 0138 gives an endpoint's reach as `internal` (the private overlay), `public` (anywhere) or `both`.
+None of them says *this machine's own network*. The predecessor could: its unifi manifest opened
+inform/STUN/discovery `from: 192.168.0.0/16, 10.0.0.0/8, 172.16.0.0/12`.
+
+## Consequence
+
+The only reach that includes a LAN device is `public`. While ace is adopted that is harmless — its
+own firewall stays and admits the LAN — and behind NAT "anywhere" happens to mean the LAN. But:
+
+- it states the wrong thing: an operator reading `reach: public` on an IoT broker believes it is on
+  the internet, and a router port-forward added later for something else makes it so;
+- at `converge ace`, the mesh's filter is the sum of what it listens on (ADR 0045). An endpoint left
+  `internal` cuts every LAN device off at the flip; one set `public` opens it to the internet on any
+  machine with a public address.
+
+## What would be right (for diagnosis)
+
+A reach — or a source — that means the networks the machine is directly attached to (its uplink's
+subnets, as the machine reports them), so a LAN-only service is declared as exactly that and the
+filter can admit it without admitting the internet.