diff --git a/src/runtime/communication.rs b/src/runtime/communication.rs
index ae4c9985bebf731f91caeaf5bec0a4158c378339..e7db616c1ac626a4471c7c0ba5a446b86ad02755 100644
--- a/src/runtime/communication.rs
+++ b/src/runtime/communication.rs
@@ -37,6 +37,9 @@ struct CyclicDrainInner<'a, K: Eq + Hash, V> {
     swap: &'a mut HashMap<K, V>,
     output: &'a mut HashMap<K, V>,
 }
+trait PayloadMsgSender {
+    fn send(&mut self, port_info: &PortInfo, putter: &PortId, msg: SendPayloadMsg);
+}
 
 ////////////////
 impl Connector {
@@ -122,8 +125,8 @@ impl Connector {
             }
         }
     }
-
-    // TODO make cu immutable
+    // private function. mutates state but returns with round
+    // result ASAP (allows for convenient error return with ?)
     fn connected_sync(
         cu: &mut ConnectorUnphased,
         comm: &mut ConnectorCommunication,
@@ -131,13 +134,14 @@ impl Connector {
     ) -> Result<Option<RoundOk>, SyncError> {
         use SyncError as Se;
         let mut deadline = timeout.map(|to| Instant::now() + to);
-        // 1. run all proto components to Nonsync blockers
         log!(
             cu.logger,
             "~~~ SYNC called with timeout {:?}; starting round {}",
             &timeout,
             comm.round_index
         );
+
+        // 1. run all proto components to Nonsync blockers
         let mut branching_proto_components =
             HashMap::<ProtoComponentId, BranchingProtoComponent>::default();
         let mut unrun_components: Vec<(ProtoComponentId, ProtoComponent)> =
@@ -262,7 +266,6 @@ impl Connector {
             branching_proto_components.len()
         );
         for (&proto_component_id, proto_component) in branching_proto_components.iter_mut() {
-            let ConnectorUnphased { port_info, proto_description, .. } = cu;
             let BranchingProtoComponent { ports, branches } = proto_component;
             let mut swap = HashMap::default();
             let mut blocked = HashMap::default();
@@ -515,7 +518,6 @@ impl BranchingNative {
         &mut self,
         cu: &mut ConnectorUnphased,
         solution_storage: &mut SolutionStorage,
-        // payloads_to_get: &mut Vec<(PortId, CommMsgContents)>,
         getter: PortId,
         send_payload_msg: SendPayloadMsg,
     ) {
@@ -617,7 +619,7 @@ impl BranchingProtoComponent {
         cd: CyclicDrainer<Predicate, ProtoComponentBranch>,
         cu: &mut ConnectorUnphased,
         solution_storage: &mut SolutionStorage,
-        payloads_to_get: &mut Vec<(PortId, SendPayloadMsg)>,
+        payload_msg_sender: &mut impl PayloadMsgSender,
         proto_component_id: ProtoComponentId,
         ports: &HashSet<PortId>,
     ) {
@@ -683,9 +685,8 @@ impl BranchingProtoComponent {
                         } else {
                             // keep in "unblocked"
                             log!(cu.logger, "Proto component {:?} putting payload {:?} on port {:?} (using var {:?})", proto_component_id, &payload, putter, var);
-                            let getter = *cu.port_info.peers.get(&putter).unwrap();
                             let msg = SendPayloadMsg { predicate: predicate.clone(), payload };
-    payloads_to_get.push((getter, msg));
+                            payload_msg_sender.send(&cu.port_info, &putter, msg);
                             drainer.add_input(predicate, branch);
                         }
                     }
@@ -697,7 +698,7 @@ impl BranchingProtoComponent {
         cu: &mut ConnectorUnphased,
         solution_storage: &mut SolutionStorage,
         proto_component_id: ProtoComponentId,
-        payloads_to_get: &mut Vec<(PortId, SendPayloadMsg)>,
+        payload_msg_sender: &mut impl PayloadMsgSender,
         getter: PortId,
         send_payload_msg: SendPayloadMsg,
     ) {
@@ -756,7 +757,7 @@ impl BranchingProtoComponent {
             cd,
             cu,
             solution_storage,
-            payloads_to_get,
+            payload_msg_sender,
             proto_component_id,
             ports,
         );
@@ -806,7 +807,7 @@ impl SolutionStorage {
         self.old_local.clear();
         self.new_local.clear();
     }
-    pub(crate) fn reset(&mut self, subtree_ids: impl Iterator<Item = Route>) {
+    fn reset(&mut self, subtree_ids: impl Iterator<Item = Route>) {
         self.subtree_id_to_index.clear();
         self.subtree_solutions.clear();
         self.old_local.clear();
@@ -880,12 +881,18 @@ impl SolutionStorage {
         }
     }
 }
+impl PayloadMsgSender for Vec<(PortId, SendPayloadMsg)> {
+    fn send(&mut self, port_info: &PortInfo, putter: &PortId, msg: SendPayloadMsg) {
+        let getter = *port_info.peers.get(putter).unwrap();
+        self.push((getter, msg));
+    }
+}
 impl SyncProtoContext<'_> {
-    pub fn is_firing(&mut self, port: PortId) -> Option<bool> {
+    pub(crate) fn is_firing(&mut self, port: PortId) -> Option<bool> {
         let var = self.port_info.firing_var_for(port);
         self.predicate.query(var)
     }
-    pub fn read_msg(&mut self, port: PortId) -> Option<&Payload> {
+    pub(crate) fn read_msg(&mut self, port: PortId) -> Option<&Payload> {
         self.inbox.get(&port)
     }
 }