diff --git a/runtime/src/main/java/org/capnproto/TwoPartyVatNetwork.java b/runtime/src/main/java/org/capnproto/TwoPartyVatNetwork.java
index 9e5d0af..d9f67d8 100644
--- a/runtime/src/main/java/org/capnproto/TwoPartyVatNetwork.java
+++ b/runtime/src/main/java/org/capnproto/TwoPartyVatNetwork.java
@@ -12,7 +12,6 @@ public class TwoPartyVatNetwork
         void incoming(IncomingRpcMessage message, RpcTwoPartyProtocol.Side side);
     }
 
-    private static BuilderArena.AllocationStrategy allocationStrategy = BuilderArena.SUGGESTED_ALLOCATION_STRATEGY;
     private CompletableFuture<java.lang.Void> previousWrite = CompletableFuture.completedFuture(null);
     private final CompletableFuture<java.lang.Void> peerDisconnected = new CompletableFuture<>();
     private final AsynchronousSocketChannel channel;
@@ -68,22 +67,30 @@ public class TwoPartyVatNetwork
 
     @Override
     public CompletableFuture<IncomingRpcMessage> receiveIncomingMessage() {
-        return Serialize.readAsync(channel)
+        var message = Serialize.readAsync(channel)
                 .thenApply(reader -> (IncomingRpcMessage) new IncomingMessage(reader))
                 .whenComplete((msg, exc) -> {
                     if (exc != null) {
                         this.peerDisconnected.complete(null);
                     }
-                })
-                .whenComplete((msg, exc) -> {
-                    if (this.tap != null && msg != null) {
-                        this.tap.incoming(
-                                msg,
-                                this.getSide() == RpcTwoPartyProtocol.Side.CLIENT
-                                        ? RpcTwoPartyProtocol.Side.SERVER
-                                        : RpcTwoPartyProtocol.Side.CLIENT);
-                    }
                 });
+
+        // send to message tap
+        if (this.tap != null) {
+            message = message.whenComplete((msg, exc) -> {
+                if (this.tap == null || msg == null) {
+                    return;
+                }
+
+                var side = this.getSide() == RpcTwoPartyProtocol.Side.CLIENT
+                        ? RpcTwoPartyProtocol.Side.SERVER
+                        : RpcTwoPartyProtocol.Side.CLIENT;
+
+                this.tap.incoming(msg, side);
+            });
+        }
+
+        return message;
     }
 
     @Override
@@ -114,11 +121,13 @@ public class TwoPartyVatNetwork
 
     final class OutgoingMessage implements OutgoingRpcMessage {
 
-        final MessageBuilder message;
-        List<Integer> fds = List.of();
+        private final MessageBuilder message;
+        private List<Integer> fds = List.of();
 
         OutgoingMessage(int firstSegmentWordSize) {
-            this.message = new MessageBuilder(firstSegmentWordSize, allocationStrategy);
+            this.message = new MessageBuilder(firstSegmentWordSize == 0
+                    ? BuilderArena.SUGGESTED_FIRST_SEGMENT_WORDS
+                    : firstSegmentWordSize);
         }
 
         @Override
@@ -148,8 +157,8 @@ public class TwoPartyVatNetwork
 
     final class IncomingMessage implements IncomingRpcMessage {
 
-        final MessageReader message;
-        final List<Integer> fds;
+        private final MessageReader message;
+        private final List<Integer> fds;
 
         IncomingMessage(MessageReader message) {
             this(message, List.of());
@@ -162,12 +171,12 @@ public class TwoPartyVatNetwork
 
         @Override
         public AnyPointer.Reader getBody() {
-            return message.getRoot(AnyPointer.factory);
+            return this.message.getRoot(AnyPointer.factory);
         }
 
         @Override
         public List<Integer> getAttachedFds() {
-            return fds;
+            return this.fds;
         }
     }
 }