ADR 0104: a provision may be answered by an adapter to the predecessor; issue 093 located; connectivity says how the proxy hands over

03-DESIGN/01-to-be/08-connectivity.md

@@ -9,6 +9,7 @@ code:
   - mesh-host internal/apply (the service that reflects a rule set)
 updated: 2026-09-22
 decisions:
+  - 02-DECISIONS/0104-a-provision-may-be-answered-by-an-adapter-to-the-predecessor.md
   - 02-DECISIONS/0103-what-an-adopted-node-holds-and-what-its-guard-refuses.md
   - 02-DECISIONS/0100-a-node-in-use-is-adopted-before-it-is-converged.md
   - 02-DECISIONS/0099-a-step-that-runs-once-names-what-it-reads.md
@@ -535,6 +536,19 @@ undeclared one does not — then the module is removed and the port closes with
 rule. *A rule set that is written but never loaded passes every check that reads the file, which
 is why the check reads packets.*
 
+### While a predecessor still serves the same thing
+
+*2026-09-22, [ADR 0104](../../02-DECISIONS/0104-a-provision-may-be-answered-by-an-adapter-to-the-predecessor.md).*
+The mesh's proxy owns the two public ports and derives its routes from what modules contributed, so
+it cannot stand beside a predecessor's proxy and cannot serve the predecessor's names. During a
+migration a provision of this shape — one provider, a scarce machine-wide resource — may instead be
+answered by an **adapter**: a module that provides `route` and writes each contribution into the
+predecessor's own configuration, pointing at the machine port the contributing module publishes.
+The predecessor's proxy goes on serving every name and renewing every certificate; the mesh's proxy
+is taken last, when every route is one the mesh contributed. The adapter is refused on a converged
+node, and removed when the predecessor's proxy retires. *How it is checked:* the adoption bed takes
+a module behind the adapter and asserts the name answers and the predecessor's own names still do.
+
 ### On an adopted node
 
 *2026-09-22, [ADR 0100](../../02-DECISIONS/0100-a-node-in-use-is-adopted-before-it-is-converged.md).* **The firewall found on the machine stays in force**, and the mesh