Carry each contribution, composed, and the consumer's address in its plan entry, and let a process read another module's state, so route-proxy serves routes from the seat's plans alone (issue 774, research 072 row 34)

go/process/state.go

@@ -43,9 +43,28 @@ func (s State) bucket() string { return s.Module + "_" + s.Name }
 // (js.KeyValue) is what asks $JS.API.STREAM.INFO.KV_<bucket>, so it is what withRefusal watches: a bucket
 // not granted is refused there, promptly, as nats.ErrPermissionViolation.
 func (c *Conn) State(name string) State {
-	bucket := c.account.Module + "_" + name
-	return State{Module: c.account.Module, Name: name, closed: func() bool { return c.nc.IsClosed() }, kv: func(ctx context.Context) (jetstream.KeyValue, error) {
-		if err := c.refusedUnannounced(name); err != nil {
+	return c.bound(c.account.Module, name, func() error { return c.refusedUnannounced(name) })
+}
+
+// Read is another module's state this connection's module reads, named as its manifest's `reads` names it
+// (`<module>.<state>`, novox/hq ADR 0495): bound like State to the bucket <module>_<state>, so Get, Keys and Watch
+// work as far as the account's read grant goes, and a write is refused by the bus (issue 774: route-proxy follows
+// the seat mesh-provisioner's plans). A name that is not `<module>.<state>` fails at the call that needed it.
+func (c *Conn) Read(read string) State {
+	module, name, ok := strings.Cut(read, ".")
+	return c.bound(module, name, func() error {
+		if !ok || module == "" || name == "" || strings.Contains(name, ".") {
+			return fmt.Errorf("%q is not a state another module keeps, <module>.<state>", read)
+		}
+		return nil
+	})
+}
+
+// bound is module's state name on this connection, checked by refused before every bind.
+func (c *Conn) bound(module, name string, refused func() error) State {
+	bucket := module + "_" + name
+	return State{Module: module, Name: name, closed: func() bool { return c.nc.IsClosed() }, kv: func(ctx context.Context) (jetstream.KeyValue, error) {
+		if err := refused(); err != nil {
 			return nil, err
 		}
 		js, err := jetstream.New(c.nc)