diff --git a/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithProduceResult.java b/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithProduceResult.java
index a5ab3bbc68..dd6b47f852 100644
--- a/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithProduceResult.java
+++ b/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithProduceResult.java
@@ -14,10 +14,13 @@
  */
 package io.aklivity.zilla.runtime.binding.grpc.kafka.internal.config;
 
+import static io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcType.BASE64;
+
 import java.util.List;
 import java.util.function.Supplier;
 
 import org.agrona.DirectBuffer;
+import org.agrona.ExpandableDirectByteBuffer;
 import org.agrona.concurrent.UnsafeBuffer;
 
 import io.aklivity.zilla.runtime.binding.grpc.kafka.config.GrpcKafkaCorrelationConfig;
@@ -31,9 +34,17 @@
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.KafkaOffsetType;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.OctetsFW;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.String16FW;
+import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcMetadataFW;
+import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcType;
 
 public class GrpcKafkaWithProduceResult
 {
+    public static final String META_PREFIX = "meta:";
+    public static final String BIN_SUFFIX = "-bin";
+
+    private static final int META_PREFIX_LENGTH = META_PREFIX.length();
+    private static final int BIN_SUFFIX_LENGTH = BIN_SUFFIX.length();
+
     private static final KafkaOffsetFW KAFKA_OFFSET_HISTORICAL =
         new KafkaOffsetFW.Builder()
             .wrap(new UnsafeBuffer(new byte[32]), 0, 32)
@@ -50,10 +61,13 @@ public class GrpcKafkaWithProduceResult
     private final GrpcKafkaWithProduceHash hash;
     private final String16FW service;
     private final String16FW method;
+    private final Array32FW<GrpcMetadataFW> metadata;
+    private final ExpandableDirectByteBuffer nameBuffer;
 
     GrpcKafkaWithProduceResult(
         String16FW service,
         String16FW method,
+        Array32FW<GrpcMetadataFW> metadata,
         String16FW topic,
         KafkaAckMode acks,
         Supplier<DirectBuffer> keyRef,
@@ -64,6 +78,7 @@ public class GrpcKafkaWithProduceResult
     {
         this.service = service;
         this.method = method;
+        this.metadata = metadata;
         this.overrides = overrides;
         this.replyTo = replyTo;
         this.correlation = correlation;
@@ -71,6 +86,8 @@ public class GrpcKafkaWithProduceResult
         this.acks = acks;
         this.keyRef = keyRef;
         this.hash = hash;
+        this.nameBuffer = new ExpandableDirectByteBuffer();
+        this.nameBuffer.putStringWithoutLengthAscii(0, META_PREFIX);
 
         hash.updateHash(correlation.service.value());
         hash.updateHash(service.value());
@@ -140,6 +157,27 @@ public void headers(
         builder.item(this::method);
         builder.item(this::replyTo);
         builder.item(this::correlationId);
+        metadata.forEach(m -> builder.item(i -> metadata(i, m)));
+    }
+
+    private void metadata(
+        KafkaHeaderFW.Builder builder,
+        GrpcMetadataFW metadata)
+    {
+        GrpcType type = metadata.type().get();
+        DirectBuffer name = metadata.name().value();
+        int nameLen = META_PREFIX_LENGTH + metadata.nameLen();
+        nameBuffer.putBytes(META_PREFIX_LENGTH, name, 0, name.capacity());
+        if (type == BASE64)
+        {
+            nameBuffer.putStringWithoutLengthAscii(nameLen, BIN_SUFFIX);
+            nameLen += BIN_SUFFIX_LENGTH;
+        }
+        builder
+            .nameLen(nameLen)
+            .name(nameBuffer, 0, nameLen)
+            .valueLen(metadata.valueLen())
+            .value(metadata.value().value(), 0, metadata.valueLen());
     }
 
     private void service(
diff --git a/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithResolver.java b/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithResolver.java
index dd84c6acf1..156cc954db 100644
--- a/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithResolver.java
+++ b/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/config/GrpcKafkaWithResolver.java
@@ -169,7 +169,7 @@ public GrpcKafkaWithProduceResult resolveProduce(
 
         String16FW replyTo = new String16FW(produce.replyTo);
 
-        return new GrpcKafkaWithProduceResult(service, method, topic, acks, keyRef, overrides, replyTo,
+        return new GrpcKafkaWithProduceResult(service, method, metadata, topic, acks, keyRef, overrides, replyTo,
             options.correlation, hash);
     }
 
diff --git a/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/stream/GrpcKafkaProxyFactory.java b/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/stream/GrpcKafkaProxyFactory.java
index 5aa5fccb09..eb44a9cea2 100644
--- a/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/stream/GrpcKafkaProxyFactory.java
+++ b/runtime/binding-grpc-kafka/src/main/java/io/aklivity/zilla/runtime/binding/grpc/kafka/internal/stream/GrpcKafkaProxyFactory.java
@@ -16,8 +16,11 @@
 
 import static io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.KafkaCapabilities.FETCH_ONLY;
 import static io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.KafkaCapabilities.PRODUCE_ONLY;
+import static io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcType.BASE64;
+import static io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcType.TEXT;
 import static java.time.Instant.now;
 
+import java.util.Arrays;
 import java.util.function.LongUnaryOperator;
 
 import org.agrona.DirectBuffer;
@@ -46,7 +49,9 @@
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcAbortExFW;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcBeginExFW;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcDataExFW;
+import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcMetadataFW;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcResetExFW;
+import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.GrpcType;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.KafkaBeginExFW;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.KafkaDataExFW;
 import io.aklivity.zilla.runtime.binding.grpc.kafka.internal.types.stream.KafkaMergedBeginExFW;
@@ -64,6 +69,10 @@ public final class GrpcKafkaProxyFactory implements GrpcKafkaStreamFactory
 {
     private static final String GRPC_TYPE_NAME = "grpc";
     private static final String KAFKA_TYPE_NAME = "kafka";
+    private static final byte[] META_PREFIX = "meta:".getBytes();
+    private static final byte[] BIN_SUFFIX = "-bin".getBytes();
+    private static final int META_PREFIX_LENGTH = META_PREFIX.length;
+    private static final int BIN_SUFFIX_LENGTH = BIN_SUFFIX.length;
 
     private static final int DATA_FLAG_INIT = 0x02;
     private static final int DATA_FLAG_FIN = 0x01;
@@ -73,6 +82,13 @@ public final class GrpcKafkaProxyFactory implements GrpcKafkaStreamFactory
     private static final String16FW HEADER_VALUE_GRPC_OK = new String16FW("0");
     private static final String16FW HEADER_VALUE_GRPC_ABORTED = new String16FW("10");
     private static final String16FW HEADER_VALUE_GRPC_INTERNAL_ERROR = new String16FW("13");
+    private static final Array32FW<KafkaHeaderFW> EMPTY_HEADERS =
+        new Array32FW.Builder<>(new KafkaHeaderFW.Builder(), new KafkaHeaderFW())
+            .wrap(new UnsafeBuffer(new byte[8]), 0, 8)
+            .build();
+
+    private final byte[] headerPrefix = new byte[META_PREFIX_LENGTH];
+    private final byte[] headerSuffix = new byte[BIN_SUFFIX_LENGTH];
 
     private final Varuint32FW.Builder lenRW =
         new Varuint32FW.Builder().wrap(new UnsafeBuffer(new byte[1024 * 8]), 0, 1024 * 8);;
@@ -106,16 +122,21 @@ public final class GrpcKafkaProxyFactory implements GrpcKafkaStreamFactory
     private final KafkaBeginExFW kafkaBeginExRO = new KafkaBeginExFW();
     private final KafkaDataExFW kafkaDataExRO = new KafkaDataExFW();
 
+    private final GrpcBeginExFW.Builder grpcBeginExRW = new GrpcBeginExFW.Builder();
     private final GrpcDataExFW.Builder grpcDataExRW = new GrpcDataExFW.Builder();
     private final GrpcResetExFW.Builder grpcResetExRW = new GrpcResetExFW.Builder();
     private final GrpcAbortExFW.Builder grpcAbortExRW = new GrpcAbortExFW.Builder();
+    private final Array32FW.Builder<GrpcMetadataFW.Builder, GrpcMetadataFW> grpcMetadataRW =
+        new Array32FW.Builder<>(new GrpcMetadataFW.Builder(), new GrpcMetadataFW());
 
     private final KafkaBeginExFW.Builder kafkaBeginExRW = new KafkaBeginExFW.Builder();
     private final KafkaDataExFW.Builder kafkaDataExRW = new KafkaDataExFW.Builder();
     private final GrpcKafkaIdHelper messageFieldHelper = new GrpcKafkaIdHelper();
 
     private final MutableDirectBuffer writeBuffer;
+    private final MutableDirectBuffer progressBuffer;
     private final MutableDirectBuffer extBuffer;
+    private final MutableDirectBuffer metaBuffer;
     private final BindingHandler streamFactory;
     private final LongUnaryOperator supplyInitialId;
     private final LongUnaryOperator supplyReplyId;
@@ -130,7 +151,9 @@ public GrpcKafkaProxyFactory(
         EngineContext context)
     {
         this.writeBuffer = context.writeBuffer();
+        this.progressBuffer = new UnsafeBuffer(new byte[context.writeBuffer().capacity()]);
         this.extBuffer = new UnsafeBuffer(new byte[context.writeBuffer().capacity()]);
+        this.metaBuffer = new UnsafeBuffer(new byte[context.writeBuffer().capacity()]);
         this.streamFactory = context.streamFactory();
         this.supplyInitialId = context::supplyInitialId;
         this.supplyReplyId = context::supplyReplyId;
@@ -525,13 +548,19 @@ protected void onKafkaAbort(
             long traceId,
             long authorization)
         {
+            if (!GrpcKafkaState.replyOpening(state))
+            {
+                doGrpcBegin(traceId, authorization, 0L, emptyRO);
+            }
+
             cleanup(traceId, authorization);
         }
 
         @Override
         protected void onKafkaBegin(
             long traceId,
-            long authorization, OctetsFW extension)
+            long authorization,
+            OctetsFW extension)
         {
             if (!GrpcKafkaState.replyOpening(state))
             {
@@ -551,6 +580,25 @@ protected void onKafkaData(
             int length,
             OctetsFW extension)
         {
+            if (!GrpcKafkaState.replyOpening(state))
+            {
+                final ExtensionFW dataEx = extension.get(extensionRO::tryWrap);
+                final KafkaDataExFW kafkaDataEx =
+                    dataEx != null && dataEx.typeId() == kafkaTypeId ? extension.get(kafkaDataExRO::tryWrap) : null;
+
+                if (kafkaDataEx != null &&
+                    kafkaDataEx.merged() != null &&
+                    kafkaDataEx.merged().fetch() != null &&
+                    kafkaDataEx.merged().fetch().headers() != null)
+                {
+                    doGrpcBegin(traceId, authorization, 0L, kafkaDataEx.merged().fetch().headers());
+                }
+                else
+                {
+                    doGrpcBegin(traceId, authorization, 0L, EMPTY_HEADERS);
+                }
+            }
+
             doGrpcData(traceId, authorization, budgetId, reserved, flags, buffer, offset, length);
         }
 
@@ -605,6 +653,50 @@ private void doGrpcBegin(
                 traceId, authorization, affinity, extension);
         }
 
+        private void doGrpcBegin(
+            long traceId,
+            long authorization,
+            long affinity,
+            Array32FW<KafkaHeaderFW> headers)
+        {
+            state = GrpcKafkaState.openingReply(state);
+
+            Array32FW.Builder<GrpcMetadataFW.Builder, GrpcMetadataFW> builder =
+                grpcMetadataRW.wrap(metaBuffer, 0, metaBuffer.capacity());
+
+            headers.forEach(h ->
+            {
+                final OctetsFW name = h.name();
+                final DirectBuffer buffer = name.buffer();
+                final int offset = name.offset();
+                final int limit = name.limit();
+                buffer.getBytes(offset, headerPrefix);
+                buffer.getBytes(limit - BIN_SUFFIX.length, headerSuffix);
+                if (Arrays.equals(META_PREFIX, headerPrefix))
+                {
+                    final GrpcType type = Arrays.equals(BIN_SUFFIX, headerSuffix) ? BASE64 : TEXT;
+                    final int nameLen = type == BASE64
+                        ? h.nameLen() - META_PREFIX_LENGTH -  BIN_SUFFIX_LENGTH
+                        : h.nameLen() - META_PREFIX_LENGTH;
+                    builder.item(m -> m
+                        .type(t -> t.set(type))
+                        .nameLen(nameLen)
+                        .name(name.value(), META_PREFIX_LENGTH, nameLen)
+                        .valueLen(h.valueLen())
+                        .value(h.value()));
+                }
+            });
+
+            GrpcBeginExFW beginEx = grpcBeginExRW
+                .wrap(extBuffer, 0, extBuffer.capacity())
+                .typeId(grpcTypeId)
+                .metadata(builder.build())
+                .build();
+
+            doBegin(grpc, originId, routedId, replyId, replySeq, replyAck, replyMax,
+                traceId, authorization, affinity, beginEx);
+        }
+
         private void doGrpcData(
             long traceId,
             long authorization,
@@ -847,8 +939,6 @@ private void onKafkaBegin(
                 int lenSize = len.sizeof();
                 replyPad = result.fieldId().sizeof() + lenSize + partitions.sizeof();
             }
-
-            delegate.onKafkaBegin(traceId, authorization, extension);
         }
 
         private void onKafkaData(
@@ -879,7 +969,7 @@ private void onKafkaData(
                 final OctetsFW payload = data.payload();
                 final OctetsFW extension = data.extension();
 
-                final MutableDirectBuffer encodeBuffer = writeBuffer;
+                final MutableDirectBuffer encodeBuffer = progressBuffer;
                 final int encodeOffset = DataFW.FIELD_OFFSET_PAYLOAD;
                 final int payloadSize = payload.sizeof();
 
@@ -921,7 +1011,7 @@ private void onKafkaData(
                 }
 
                 int length = encodeProgress - encodeOffset;
-                delegate.onKafkaData(traceId, authorization, budgetId, reserved, flags,
+                delegate.onKafkaData(traceId, authorization, budgetId, reserved + length, flags,
                     encodeBuffer, encodeOffset, length, extension);
             }
         }
@@ -1139,7 +1229,7 @@ private void onGrpcData(
             assert acknowledge <= sequence;
             assert sequence >= initialSeq;
 
-            initialSeq = sequence;
+            initialSeq = sequence + reserved;
 
             assert initialAck <= initialSeq;
 
@@ -1272,17 +1362,23 @@ protected void onKafkaAbort(
             long traceId,
             long authorization)
         {
+            if (!GrpcKafkaState.replyOpening(state))
+            {
+                doGrpcBegin(traceId, authorization, 0L, emptyRO);
+            }
+
             cleanup(traceId, authorization);
         }
 
         @Override
         protected void onKafkaBegin(
             long traceId,
-            long authorization, OctetsFW extension)
+            long authorization,
+            OctetsFW extension)
         {
             if (!GrpcKafkaState.replyOpening(state))
             {
-                doGrpcBegin(traceId, authorization, 0L, emptyRO);
+                doGrpcBegin(traceId, authorization, 0L, extension);
             }
         }
 
@@ -1296,6 +1392,21 @@ protected void onKafkaData(
             OctetsFW payload,
             KafkaDataExFW kafkaDataEx)
         {
+            if (!GrpcKafkaState.replyOpening(state))
+            {
+                if (kafkaDataEx != null &&
+                    kafkaDataEx.merged() != null &&
+                    kafkaDataEx.merged().fetch() != null &&
+                    kafkaDataEx.merged().fetch().headers() != null)
+                {
+                    doGrpcBegin(traceId, authorization, 0L, kafkaDataEx.merged().fetch().headers());
+                }
+                else
+                {
+                    doGrpcBegin(traceId, authorization, 0L, EMPTY_HEADERS);
+                }
+            }
+
             if (GrpcKafkaState.replyClosing(state))
             {
                 replySeq += reserved;
@@ -1388,6 +1499,50 @@ private void doGrpcBegin(
                 traceId, authorization, affinity, extension);
         }
 
+        private void doGrpcBegin(
+            long traceId,
+            long authorization,
+            long affinity,
+            Array32FW<KafkaHeaderFW> headers)
+        {
+            state = GrpcKafkaState.openingReply(state);
+
+            Array32FW.Builder<GrpcMetadataFW.Builder, GrpcMetadataFW> builder =
+                grpcMetadataRW.wrap(metaBuffer, 0, metaBuffer.capacity());
+
+            headers.forEach(h ->
+            {
+                final OctetsFW name = h.name();
+                final DirectBuffer buffer = name.buffer();
+                final int offset = name.offset();
+                final int limit = name.limit();
+                buffer.getBytes(offset, headerPrefix);
+                buffer.getBytes(limit - BIN_SUFFIX.length, headerSuffix);
+                if (Arrays.equals(META_PREFIX, headerPrefix))
+                {
+                    final GrpcType type = Arrays.equals(BIN_SUFFIX, headerSuffix) ? BASE64 : TEXT;
+                    final int nameLen = type == BASE64
+                        ? h.nameLen() - META_PREFIX_LENGTH -  BIN_SUFFIX_LENGTH
+                        : h.nameLen() - META_PREFIX_LENGTH;
+                    builder.item(m -> m
+                        .type(t -> t.set(type))
+                        .nameLen(nameLen)
+                        .name(name.value(), META_PREFIX_LENGTH, nameLen)
+                        .valueLen(h.valueLen())
+                        .value(h.value()));
+                }
+            });
+
+            GrpcBeginExFW beginEx = grpcBeginExRW
+                .wrap(extBuffer, 0, extBuffer.capacity())
+                .typeId(grpcTypeId)
+                .metadata(builder.build())
+                .build();
+
+            doBegin(grpc, originId, routedId, replyId, replySeq, replyAck, replyMax,
+                traceId, authorization, affinity, beginEx);
+        }
+
         private void doGrpcData(
             long traceId,
             long authorization,
@@ -1623,8 +1778,6 @@ private void onKafkaBegin(
             final long sequence = begin.sequence();
             final long acknowledge = begin.acknowledge();
             final long traceId = begin.traceId();
-            final long authorization = begin.authorization();
-            final OctetsFW extension = begin.extension();
 
             assert acknowledge <= sequence;
             assert sequence >= replySeq;
@@ -1637,7 +1790,6 @@ private void onKafkaBegin(
             assert replyAck <= replySeq;
 
             doKafkaWindow(traceId);
-            delegate.onKafkaBegin(traceId, authorization, extension);
         }
 
         private void onKafkaEnd(
@@ -1910,8 +2062,6 @@ private void onKafkaBegin(
             final long sequence = begin.sequence();
             final long acknowledge = begin.acknowledge();
             final long traceId = begin.traceId();
-            final long authorization = begin.authorization();
-            final OctetsFW extension = begin.extension();
 
             assert acknowledge <= sequence;
             assert sequence >= replySeq;
@@ -1923,7 +2073,6 @@ private void onKafkaBegin(
 
             assert replyAck <= replySeq;
 
-            delegate.onKafkaBegin(traceId, authorization, extension);
             doKafkaWindow(traceId);
         }
 
diff --git a/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/config/KafkaGrpcBindingConfig.java b/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/config/KafkaGrpcBindingConfig.java
index 791c449c42..e063528b74 100644
--- a/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/config/KafkaGrpcBindingConfig.java
+++ b/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/config/KafkaGrpcBindingConfig.java
@@ -20,6 +20,8 @@
 import java.util.List;
 import java.util.Optional;
 
+import org.agrona.MutableDirectBuffer;
+
 import io.aklivity.zilla.runtime.binding.kafka.grpc.config.KafkaGrpcOptionsConfig;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.stream.KafkaGrpcFetchHeaderHelper;
 import io.aklivity.zilla.runtime.engine.config.BindingConfig;
@@ -35,7 +37,8 @@ public final class KafkaGrpcBindingConfig
     public final List<KafkaGrpcRouteConfig> routes;
 
     public KafkaGrpcBindingConfig(
-        BindingConfig binding)
+        BindingConfig binding,
+        MutableDirectBuffer metaBuffer)
     {
         this.id = binding.id;
         this.entryId = binding.entryId;
@@ -45,6 +48,6 @@ public KafkaGrpcBindingConfig(
                 .orElse(DEFAULT);
         this.routes = binding.routes.stream().map(r -> new KafkaGrpcRouteConfig(options, r))
             .collect(toList());
-        this.helper = new KafkaGrpcFetchHeaderHelper(options.correlation);
+        this.helper = new KafkaGrpcFetchHeaderHelper(options.correlation, metaBuffer);
     }
 }
diff --git a/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcFetchHeaderHelper.java b/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcFetchHeaderHelper.java
index b09f45ef6a..f517b8a995 100644
--- a/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcFetchHeaderHelper.java
+++ b/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcFetchHeaderHelper.java
@@ -14,25 +14,44 @@
  */
 package io.aklivity.zilla.runtime.binding.kafka.grpc.internal.stream;
 
+import static io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcType.BASE64;
+import static io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcType.TEXT;
+
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Consumer;
 
+import org.agrona.DirectBuffer;
+import org.agrona.MutableDirectBuffer;
+
 import io.aklivity.zilla.runtime.binding.kafka.grpc.config.KafkaGrpcCorrelationConfig;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.Array32FW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.KafkaHeaderFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.KafkaOffsetFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.OctetsFW;
+import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcMetadataFW;
+import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcType;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.KafkaDataExFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.KafkaMergedFetchDataExFW;
 
 public final class KafkaGrpcFetchHeaderHelper
 {
+    private static final byte[] META_PREFIX = "meta:".getBytes();
+    private static final byte[] BIN_SUFFIX = "-bin".getBytes();
+    private static final int META_PREFIX_LENGTH = META_PREFIX.length;
+    private static final int BIN_SUFFIX_LENGTH = BIN_SUFFIX.length;
+
     private final Map<OctetsFW, Consumer<OctetsFW>> visitors;
     private final OctetsFW serviceRO = new OctetsFW();
     private final OctetsFW methodRO = new OctetsFW();
     private final OctetsFW replyToRO = new OctetsFW();
     private final OctetsFW correlatedIdRO = new OctetsFW();
+    private final Array32FW.Builder<GrpcMetadataFW.Builder, GrpcMetadataFW> grpcMetadataRW =
+        new Array32FW.Builder<>(new GrpcMetadataFW.Builder(), new GrpcMetadataFW());
+    private final MutableDirectBuffer metaBuffer;
+    private final byte[] headerPrefix = new byte[META_PREFIX_LENGTH];
+    private final byte[] headerSuffix = new byte[BIN_SUFFIX_LENGTH];
 
     public int partitionId;
     public long partitionOffset;
@@ -41,10 +60,15 @@ public final class KafkaGrpcFetchHeaderHelper
     public OctetsFW method;
     public OctetsFW replyTo;
     public OctetsFW correlationId;
+    public Array32FW<GrpcMetadataFW> metadata;
+
+    private Array32FW.Builder<GrpcMetadataFW.Builder, GrpcMetadataFW> builder;
 
     public KafkaGrpcFetchHeaderHelper(
-        KafkaGrpcCorrelationConfig correlation)
+        KafkaGrpcCorrelationConfig correlation,
+        MutableDirectBuffer metaBuffer)
     {
+        this.metaBuffer = metaBuffer;
         Map<OctetsFW, Consumer<OctetsFW>> visitors = new HashMap<>();
         visitors.put(new OctetsFW().wrap(correlation.service.value(),
             0, correlation.service.length()), this::visitService);
@@ -65,6 +89,8 @@ public void visit(
         replyTo = null;
         correlationId = null;
 
+        builder = grpcMetadataRW.wrap(metaBuffer, 0, metaBuffer.capacity());
+
         if (dataEx != null)
         {
             final KafkaMergedFetchDataExFW kafkaMergedFetchDataEx = dataEx.merged().fetch();
@@ -76,6 +102,8 @@ public void visit(
 
             headers.forEach(this::dispatch);
         }
+
+        metadata = grpcMetadataRW.build();
     }
 
     public boolean resolved()
@@ -90,11 +118,30 @@ private boolean dispatch(
     {
         final OctetsFW name = header.name();
         final OctetsFW value = header.value();
+        final DirectBuffer buffer = name.buffer();
+        final int offset = name.offset();
+        final int limit = name.limit();
+        buffer.getBytes(offset, headerPrefix);
+        buffer.getBytes(limit - BIN_SUFFIX_LENGTH, headerSuffix);
+
         final Consumer<OctetsFW> visitor = visitors.get(name);
         if (visitor != null)
         {
             visitor.accept(value);
         }
+        else if (Arrays.equals(META_PREFIX, headerPrefix))
+        {
+            final GrpcType type = Arrays.equals(BIN_SUFFIX, headerSuffix) ? BASE64 : TEXT;
+            final int nameLen = type == BASE64
+                ? header.nameLen() - META_PREFIX_LENGTH -  BIN_SUFFIX_LENGTH
+                : header.nameLen() - META_PREFIX_LENGTH;
+            builder.item(m -> m
+                .type(t -> t.set(type))
+                .nameLen(nameLen)
+                .name(name.value(), META_PREFIX_LENGTH, nameLen)
+                .valueLen(header.valueLen())
+                .value(header.value()));
+        }
 
         return service != null &&
             method != null &&
diff --git a/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcRemoteServerFactory.java b/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcRemoteServerFactory.java
index 8a0b5114f6..2eb36c367a 100644
--- a/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcRemoteServerFactory.java
+++ b/runtime/binding-kafka-grpc/src/main/java/io/aklivity/zilla/runtime/binding/kafka/grpc/internal/stream/KafkaGrpcRemoteServerFactory.java
@@ -16,6 +16,7 @@
 
 import static io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.KafkaCapabilities.FETCH_ONLY;
 import static io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.KafkaCapabilities.PRODUCE_ONLY;
+import static io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcType.BASE64;
 import static io.aklivity.zilla.runtime.engine.budget.BudgetDebitor.NO_DEBITOR_INDEX;
 import static io.aklivity.zilla.runtime.engine.buffer.BufferPool.NO_SLOT;
 import static io.aklivity.zilla.runtime.engine.concurrent.Signaler.NO_CANCEL_ID;
@@ -33,6 +34,7 @@
 import java.util.function.LongUnaryOperator;
 
 import org.agrona.DirectBuffer;
+import org.agrona.ExpandableDirectByteBuffer;
 import org.agrona.MutableDirectBuffer;
 import org.agrona.collections.Long2ObjectHashMap;
 import org.agrona.collections.Object2ObjectHashMap;
@@ -41,7 +43,9 @@
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.KafkaGrpcConfiguration;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.config.KafkaGrpcBindingConfig;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.config.KafkaGrpcConditionResult;
+import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.Array32FW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.Flyweight;
+import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.KafkaHeaderFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.OctetsFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.String16FW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.queue.GrpcQueueMessageFW;
@@ -54,7 +58,9 @@
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcAbortExFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcBeginExFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcDataExFW;
+import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcMetadataFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcResetExFW;
+import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.GrpcType;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.KafkaBeginExFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.KafkaDataExFW;
 import io.aklivity.zilla.runtime.binding.kafka.grpc.internal.types.stream.KafkaFlushExFW;
@@ -72,6 +78,10 @@ public final class KafkaGrpcRemoteServerFactory implements KafkaGrpcStreamFactor
 {
     private static final String GRPC_TYPE_NAME = "grpc";
     private static final String KAFKA_TYPE_NAME = "kafka";
+    private static final String META_PREFIX = "meta:";
+    private static final String BIN_SUFFIX = "-bin";
+    private static final int META_PREFIX_LENGTH = META_PREFIX.length();
+    private static final int BIN_SUFFIX_LENGTH = BIN_SUFFIX.length();
 
     private static final int SIGNAL_INITIATE_KAFKA_STREAM = 1;
     private static final int GRPC_QUEUE_MESSAGE_PADDING = 3 * 256 + 33;
@@ -104,8 +114,10 @@ public final class KafkaGrpcRemoteServerFactory implements KafkaGrpcStreamFactor
     private final WindowFW.Builder windowRW = new WindowFW.Builder();
     private final ResetFW.Builder resetRW = new ResetFW.Builder();
 
+    private final GrpcBeginExFW grpcBeginExRO = new GrpcBeginExFW();
     private final GrpcDataExFW grpcDataExRO = new GrpcDataExFW();
     private final GrpcAbortExFW abortExRO = new GrpcAbortExFW();
+    private final Array32FW<GrpcMetadataFW> metadataRO = new Array32FW<>(new GrpcMetadataFW());
 
     private final ExtensionFW extensionRO = new ExtensionFW();
     private final KafkaDataExFW kafkaDataExRO = new KafkaDataExFW();
@@ -126,6 +138,8 @@ public final class KafkaGrpcRemoteServerFactory implements KafkaGrpcStreamFactor
     private final BufferPool bufferPool;
     private final MutableDirectBuffer writeBuffer;
     private final MutableDirectBuffer extBuffer;
+    private final MutableDirectBuffer metaBuffer;
+    private final ExpandableDirectByteBuffer nameBuffer;
     private final BindingHandler streamFactory;
     private final LongUnaryOperator supplyInitialId;
     private final LongUnaryOperator supplyReplyId;
@@ -150,6 +164,7 @@ public KafkaGrpcRemoteServerFactory(
         this.bufferPool = context.bufferPool();
         this.writeBuffer = context.writeBuffer();
         this.extBuffer = new UnsafeBuffer(new byte[context.writeBuffer().capacity()]);
+        this.metaBuffer = new UnsafeBuffer(new byte[context.writeBuffer().capacity()]);
         this.streamFactory = context.streamFactory();
         this.supplyInitialId = context::supplyInitialId;
         this.supplyReplyId = context::supplyReplyId;
@@ -164,6 +179,8 @@ public KafkaGrpcRemoteServerFactory(
         this.grpcTypeId = context.supplyTypeId(GRPC_TYPE_NAME);
         this.kafkaTypeId = context.supplyTypeId(KAFKA_TYPE_NAME);
         this.groupIdFormat = config.groupIdFormat();
+        this.nameBuffer = new ExpandableDirectByteBuffer();
+        this.nameBuffer.putStringWithoutLengthAscii(0, META_PREFIX);
     }
 
     @Override
@@ -182,7 +199,7 @@ public int routedTypeId()
     public void attach(
         BindingConfig binding)
     {
-        KafkaGrpcBindingConfig newBinding = new KafkaGrpcBindingConfig(binding);
+        KafkaGrpcBindingConfig newBinding = new KafkaGrpcBindingConfig(binding, metaBuffer);
         bindings.put(binding.id, newBinding);
 
         if (activate.test(binding.id))
@@ -415,6 +432,8 @@ private void onKafkaData(
                 deferred = kafkaDataEx.merged().fetch().deferred();
             }
 
+            Array32FW<GrpcMetadataFW> metadata = helper.metadata;
+
             if ((flags & DATA_FLAG_INIT) != 0x00 && payload != null)
             {
                 if (helper.resolved())
@@ -428,11 +447,11 @@ private void onKafkaData(
                             .set(helper.correlationId)
                             .build();
                         lastCorrelationId = newCorrelationId;
-                        grpcClient = newGrpcClient(traceId, authorization, helper.service, helper.method,
+                        grpcClient = newGrpcClient(traceId, authorization, helper.service, helper.method, metadata,
                             helper.replyTo, newCorrelationId);
                     }
 
-                    flushGrpcClientData(grpcClient, traceId, authorization, helper.service, helper.method,
+                    flushGrpcClientData(grpcClient, traceId, authorization, helper.service, helper.method, metadata,
                         helper.partitionId, helper.partitionOffset, deferred, flags, reserved, payload);
                 }
                 else if (helper.correlationId != null)
@@ -450,7 +469,7 @@ else if (helper.correlationId != null)
                 }
                 else
                 {
-                    flushGrpcClientData(grpcClient, traceId, authorization, null, null,
+                    flushGrpcClientData(grpcClient, traceId, authorization, helper.service, helper.method, metadata,
                         helper.partitionId, helper.partitionOffset, deferred, flags, reserved, payload);
                 }
             }
@@ -463,13 +482,14 @@ private GrpcClient newGrpcClient(
             long authorization,
             OctetsFW service,
             OctetsFW method,
+            Array32FW<GrpcMetadataFW> metadata,
             OctetsFW replyTo,
             OctetsFW correlationId)
         {
             final GrpcClient grpcClient = new GrpcClient(originId, entryId, routedId, correlationId, replyTo, this);
             grpcClients.put(correlationId, grpcClient);
 
-            grpcClient.doGrpcBegin(traceId, authorization, 0L, service, method);
+            grpcClient.doGrpcBegin(traceId, authorization, 0L, service, method, metadata);
 
             return grpcClient;
         }
@@ -491,6 +511,7 @@ private void flushGrpcMessagesIfBuffered(
                 final OctetsFW messageCorrelationId = queueMessage.correlationId();
                 final OctetsFW service = queueMessage.service();
                 final OctetsFW method = queueMessage.method();
+                final OctetsFW metadata = queueMessage.metadata();
                 final long messageTraceId = queueMessage.traceId();
                 final long messageAuthorization = queueMessage.authorization();
                 final int partitionId = queueMessage.partitionId();
@@ -507,9 +528,10 @@ private void flushGrpcMessagesIfBuffered(
 
                 if (correlationId.equals(messageCorrelationId))
                 {
+                    Array32FW<GrpcMetadataFW> meta = metadataRO.wrap(metadata.buffer(), metadata.offset(), metadata.limit());
                     GrpcClient grpcClient = grpcClients.get(messageCorrelationId);
                     grpcClient = grpcClient != null ? grpcClient :
-                        newGrpcClient(traceId, authorization, service, method, helper.replyTo, messageCorrelationId);
+                        newGrpcClient(traceId, authorization, service, method, meta, helper.replyTo, messageCorrelationId);
 
                     final int progress = grpcClient.onKafkaData(messageTraceId, messageAuthorization,
                         partitionId, partitionOffset, deferred, flags, payload);
@@ -527,7 +549,7 @@ else if (progress > 0)
                     {
                         final int remainingPayload = queuedMessageSize - progress;
                         queueGrpcMessage(traceId, authorization, partitionId, partitionOffset, messageCorrelationId,
-                            service, method, deferred, flags, reserved, payload, remainingPayload);
+                            service, method, meta, deferred, flags, reserved, payload, remainingPayload);
                         final int remainingMessageOffset = grpcQueueSlotOffset - progressOffset;
                         grpcQueueBuffer.putBytes(oldProgressOffset, grpcQueueBuffer, progressOffset, remainingMessageOffset);
                         grpcQueueSlotOffset -= queuedMessageSize;
@@ -551,6 +573,7 @@ private void flushGrpcClientData(
             long authorization,
             OctetsFW service,
             OctetsFW method,
+            Array32FW<GrpcMetadataFW> metadata,
             int partitionId,
             long partitionOffset,
             int deferred,
@@ -574,7 +597,7 @@ private void flushGrpcClientData(
             {
                 flags = progress == 0 ? flags : DATA_FLAG_CON;
                 queueGrpcMessage(traceId, authorization, partitionId, partitionOffset,
-                    grpcClient.correlationId, service, method, deferred, flags, reserved, payload, remaining);
+                    grpcClient.correlationId, service, method, metadata, deferred, flags, reserved, payload, remaining);
             }
         }
 
@@ -586,6 +609,7 @@ private void queueGrpcMessage(
             OctetsFW correlationId,
             OctetsFW service,
             OctetsFW method,
+            Array32FW<GrpcMetadataFW> metadata,
             int deferred,
             int flags,
             int reserved,
@@ -603,6 +627,7 @@ private void queueGrpcMessage(
                 .correlationId(correlationId)
                 .service(service)
                 .method(method)
+                .metadata(metadata.buffer(), metadata.offset(), metadata.sizeof())
                 .traceId(traceId)
                 .authorization(authorization)
                 .partitionId(partitionId)
@@ -1330,14 +1355,12 @@ private final class GrpcClient
         private BudgetDebitor initialDeb;
         private long initialDebIndex = NO_DEBITOR_INDEX;
 
-
         private int state;
 
         private long replySeq;
         private long replyAck;
         private int replyMax;
 
-
         private GrpcClient(
             long originId,
             long routedId,
@@ -1408,6 +1431,7 @@ private void onGrpcBegin(
             final long traceId = begin.traceId();
             final long authorization = begin.authorization();
             final long affinity = begin.affinity();
+            final OctetsFW extension = begin.extension();
 
             assert acknowledge <= sequence;
             assert sequence >= replySeq;
@@ -1419,6 +1443,8 @@ private void onGrpcBegin(
 
             assert replyAck <= replySeq;
 
+            extension.get(grpcBeginExRO::tryWrap);
+
             correlater.doKafkaBegin(traceId, authorization, affinity);
         }
 
@@ -1460,7 +1486,12 @@ private void onGrpcData(
                         .timestamp(now().toEpochMilli())
                         .partition(p -> p.partitionId(-1).partitionOffset(-1))
                         .key(k -> server.condition.key(correlationId, k))
-                        .headers(h -> server.condition.headers(correlationId, h))))
+                        .headers(h ->
+                        {
+                            server.condition.headers(correlationId, h);
+                            Array32FW<GrpcMetadataFW> metadata = grpcBeginExRO.metadata();
+                            metadata.forEach(md -> h.item(i -> metadata(i, md)));
+                        })))
                     .build();
             }
 
@@ -1683,18 +1714,39 @@ private void cleanupBudgetIfNecessary()
             }
         }
 
+        private void metadata(
+            KafkaHeaderFW.Builder builder,
+            GrpcMetadataFW metadata)
+        {
+            GrpcType type = metadata.type().get();
+            DirectBuffer name = metadata.name().value();
+            int nameLen = META_PREFIX_LENGTH + metadata.nameLen();
+            nameBuffer.putBytes(META_PREFIX_LENGTH, name, 0, name.capacity());
+            if (type == BASE64)
+            {
+                nameBuffer.putStringWithoutLengthAscii(nameLen, BIN_SUFFIX);
+                nameLen += BIN_SUFFIX_LENGTH;
+            }
+            builder
+                .nameLen(nameLen)
+                .name(nameBuffer, 0, nameLen)
+                .valueLen(metadata.valueLen())
+                .value(metadata.value().value(), 0, metadata.valueLen());
+        }
+
         private void doGrpcBegin(
             long traceId,
             long authorization,
             long affinity,
             OctetsFW service,
-            OctetsFW method)
+            OctetsFW method,
+            Array32FW<GrpcMetadataFW> metadata)
         {
             state = KafkaGrpcState.openingInitial(state);
 
             grpc = newGrpcStream(this::onGrpcMessage, originId, routedId, initialId, initialSeq, initialAck, initialMax,
                 traceId, authorization, affinity, server.condition.scheme(), server.condition.authority(),
-                service, method);
+                service, method, metadata);
         }
 
         private void doGrpcData(
@@ -2019,7 +2071,8 @@ private MessageConsumer newGrpcStream(
         String16FW scheme,
         String16FW authority,
         OctetsFW service,
-        OctetsFW method)
+        OctetsFW method,
+        Array32FW<GrpcMetadataFW> metadata)
     {
         final GrpcBeginExFW grpcBeginEx =
             grpcBeginExRW.wrap(extBuffer, 0, extBuffer.capacity())
@@ -2028,6 +2081,7 @@ private MessageConsumer newGrpcStream(
                 .authority(authority)
                 .service(service.buffer(), service.offset(), service.sizeof())
                 .method(method.buffer(), method.offset(), method.sizeof())
+                .metadata(metadata)
                 .build();
 
         final BeginFW begin = beginRW.wrap(writeBuffer, 0, writeBuffer.capacity())
diff --git a/runtime/binding-kafka-grpc/src/main/zilla/internal.idl b/runtime/binding-kafka-grpc/src/main/zilla/internal.idl
index dd32862ae4..bf25b87389 100644
--- a/runtime/binding-kafka-grpc/src/main/zilla/internal.idl
+++ b/runtime/binding-kafka-grpc/src/main/zilla/internal.idl
@@ -24,6 +24,8 @@ scope internal
             octets[serviceLength] service = null;
             int32 methodLength;
             octets[methodLength] method = null;
+            int32 metadataLength;
+            octets[metadataLength] metadata = null;
             int64 traceId;
             int64 authorization;
             int32 partitionId;
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.read.abort.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.read.abort.unary.rpc/client.rpt
index 6ed757bbad..87c007d8b6 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.read.abort.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.read.abort.unary.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.write.abort.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.write.abort.unary.rpc/client.rpt
index e6263d2148..4b87c4bedd 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.write.abort.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/client.sent.write.abort.unary.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reject.request.body.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reject.request.body.unary.rpc/client.rpt
index 78c0060785..fe2e93d712 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reject.request.body.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reject.request.body.unary.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                             .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/client.rpt
index e24b17835e..409450f6d0 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -32,6 +33,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .bytes(32767, grpc_kafka:messageId()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/server.rpt
index b67d93cef2..7972b740e6 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/reliable.unary.rpc/server.rpt
@@ -32,6 +32,12 @@ read zilla:data.empty
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .metadataBase64("customProperty", "dGVzdA==")
+                            .build()}
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .bytes(32767, grpc_kafka:messageId()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/client.rpt
index be3fe6ff52..8397925f18 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -31,6 +32,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .bytes(32767, grpc_kafka:messageId()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/server.rpt
index c788bae4f8..395d491021 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/fetch/unreliable.unary.rpc/server.rpt
@@ -31,6 +31,12 @@ read zilla:data.empty
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .metadataBase64("customProperty", "dGVzdA==")
+                            .build()}
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .bytes(32767, grpc_kafka:messageId()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/client.rpt
index ea5baa610b..5a58bcbf4c 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -33,11 +34,17 @@ write ${grpc:protobuf()
             .build()}
 write flush
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .build()}
 
 read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
 
+read notify DATA_RECEIVED
+
 read zilla:reset.ext ${grpc:resetEx()
                             .typeId(zilla:id("grpc"))
                             .status("13")
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/server.rpt
index 5419111648..bf5f00379d 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc.write.abort/server.rpt
@@ -33,6 +33,10 @@ read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .build()}
 
 write ${grpc:protobuf()
             .string(1, "Hello World1")
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/client.rpt
index 3a5aa74d54..b37d938ff7 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -23,7 +24,7 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoBidiStream")
-                              .metadata("custom", "test")
+                              .metadataBase64("custom", "dGVzdA==")
                               .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                               .build()}
 connected
@@ -38,6 +39,12 @@ write ${grpc:protobuf()
             .build()}
 write flush
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/server.rpt
index 72d1d3cdf5..90355cddda 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/bidi.stream.rpc/server.rpt
@@ -24,7 +24,7 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoBidiStream")
-                           .metadata("custom", "test")
+                           .metadataBase64("custom", "dGVzdA==")
                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                            .build()}
 connected
@@ -37,6 +37,12 @@ read ${grpc:protobuf()
            .string(1, "Hello World2")
            .build()}
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .metadataBase64("customProperty", "dGVzdA==")
+                            .build()}
+
 write ${grpc:protobuf()
             .string(1, "Hello World1")
             .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc.write.abort/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc.write.abort/client.rpt
index 4494bb5b59..8146acfe15 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc.write.abort/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc.write.abort/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/client.rpt
index 4e05a7c568..a959a8b036 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -23,7 +24,7 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoClientStream")
-                              .metadata("custom", "test")
+                              .metadataBase64("custom", "dGVzdA==")
                               .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                               .build()}
 connected
@@ -40,6 +41,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/server.rpt
index 22048338e9..b19e659496 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/client.stream.rpc/server.rpt
@@ -24,7 +24,7 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoClientStream")
-                           .metadata("custom", "test")
+                           .metadataBase64("custom", "dGVzdA==")
                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                            .build()}
 connected
@@ -39,6 +39,12 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .metadataBase64("customProperty", "dGVzdA==")
+                            .build()}
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc.read.aborted/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc.read.aborted/client.rpt
index 6341916260..6a65a247fb 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc.read.aborted/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc.read.aborted/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/client.rpt
index a570d1a3b2..473b43f5c9 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -23,7 +24,7 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoServerStream")
-                              .metadata("custom", "test")
+                              .metadataBase64("custom", "dGVzdA==")
                               .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                               .build()}
 
@@ -36,6 +37,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/server.rpt
index 8758f82dee..108abbabd5 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/server.stream.rpc/server.rpt
@@ -24,7 +24,7 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoServerStream")
-                           .metadata("custom", "test")
+                           .metadataBase64("custom", "dGVzdA==")
                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                            .build()}
 connected
@@ -35,6 +35,12 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .metadataBase64("customProperty", "dGVzdA==")
+                            .build()}
+
 write ${grpc:protobuf()
             .string(1, "Hello World1")
             .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.error/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.error/client.rpt
index dfc9f9f631..5b6c8329bd 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.error/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.error/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/client.rpt
index f8d64c29be..a71806eda3 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/client.rpt
@@ -18,6 +18,7 @@ property string100k ${core:randomString(102400)}
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -42,6 +43,11 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .build()}
+
 read zilla:data.ext ${grpc:dataEx()
                               .typeId(zilla:id("grpc"))
                               .deferred(94217)
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/server.rpt
index b91f68a5a2..0c4d775cc0 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.message.value.100k/server.rpt
@@ -39,6 +39,13 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .build()}
+
+write flush
+
 write zilla:data.ext ${grpc:dataEx()
                               .typeId(zilla:id("grpc"))
                               .deferred(94217)
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.rejected/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.rejected/client.rpt
index 5efc8097d0..ce806ae3ca 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.rejected/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.rejected/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.sent.write.abort/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.sent.write.abort/client.rpt
index e1cdc161c4..8bd042680f 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.sent.write.abort/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc.sent.write.abort/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/client.rpt
index 47922b4509..5cfe61ef71 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/client.rpt
@@ -16,6 +16,7 @@
 connect "zilla://streams/grpc0"
     option zilla:window 8192
     option zilla:transmission "half-duplex"
+    option zilla:update "proactive"
 
 write zilla:begin.ext ${grpc:beginEx()
                               .typeId(zilla:id("grpc"))
@@ -23,7 +24,7 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoUnary")
-                              .metadata("custom", "test")
+                              .metadataBase64("custom", "dGVzdA==")
                               .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                               .build()}
 connected
@@ -35,6 +36,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/server.rpt
index 310ef438f8..aa3ab812e6 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/grpc/produce/unary.rpc/server.rpt
@@ -24,7 +24,7 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoUnary")
-                           .metadata("custom", "test")
+                           .metadataBase64("custom", "dGVzdA==")
                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                            .build()}
 connected
@@ -35,6 +35,12 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                            .typeId(zilla:id("grpc"))
+                            .metadata("custom", "value")
+                            .metadataBase64("customProperty", "dGVzdA==")
+                            .build()}
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/client.rpt
index 28d30e4817..bb6d038f00 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/client.rpt
@@ -51,6 +51,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                               .progress(0, 2)
                               .progress(1, 1)
                               .key("test")
+                              .header("meta:custom", "value")
+                              .header("meta:customProperty-bin", "dGVzdA==")
                               .build()
                            .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/server.rpt
index 8d6b0bee95..32e2767c5e 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/reliable.unary.rpc/server.rpt
@@ -54,6 +54,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/client.rpt
index 06175c7086..c6df09dca7 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/client.rpt
@@ -51,6 +51,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                               .progress(0, 2)
                               .progress(1, 1)
                               .key("test")
+                              .header("meta:custom", "value")
+                              .header("meta:customProperty-bin", "dGVzdA==")
                               .build()
                            .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/server.rpt
index 766dc240c3..85feb51170 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/fetch/unreliable.unary.rpc/server.rpt
@@ -53,6 +53,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/client.rpt
index 13097e848b..b2f902879e 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoBidiStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                                     .header("meta:custom", "test")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -60,6 +62,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoBidiStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -97,12 +101,15 @@ read zilla:data.ext ${kafka:matchDataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
                                 .build()
                             .build()}
 read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
 
+read notify DATA_RECEIVED
+
 read aborted
 write abort
 
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/server.rpt
index bd89e7610f..211298efee 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc.write.abort/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoBidiStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -61,6 +63,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoBidiStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -92,6 +96,7 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -99,6 +104,8 @@ write ${grpc:protobuf()
             .build()}
 write flush
 
+write await DATA_RECEIVED
+
 write abort
 
 read aborted
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/client.rpt
index 089e230868..37eddfa123 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoBidiStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                                     .header("meta:custom-bin", "dGVzdA==")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -60,6 +62,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoBidiStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                                     .header("meta:custom-bin", "dGVzdA==")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -81,6 +85,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoBidiStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                                .header("meta:custom-bin", "dGVzdA==")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -116,6 +122,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/server.rpt
index 96ed317970..ea7d670785 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/bidi.stream.rpc/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoBidiStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -61,6 +63,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoBidiStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -79,6 +83,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoBidiStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-14f43bae85c2ce394c9bd81ff6fa9d77")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -111,6 +117,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/client.rpt
index b6e9f89a71..0ea4b44a7f 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoClientStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                                     .header("meta:custom", "test")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -62,6 +64,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoClientStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/server.rpt
index 1fa1fa669c..42f1e09858 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc.write.abort/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoClientStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -63,6 +65,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoClientStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/client.rpt
index 2e86e4dec6..5589c0ccce 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoClientStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                                     .header("meta:custom-bin", "dGVzdA==")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -60,6 +62,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoClientStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                                     .header("meta:custom-bin", "dGVzdA==")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -79,6 +83,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoClientStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                                .header("meta:custom-bin", "dGVzdA==")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -115,6 +121,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/server.rpt
index f0299d0558..be8c806b97 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/client.stream.rpc/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoClientStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -61,6 +63,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoClientStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -79,6 +83,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoClientStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-97e816c79fb6624b7d221026cc36107c")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -111,6 +117,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/client.rpt
index 4a76d9f5f5..c390354af6 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/client.rpt
@@ -42,6 +42,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoServerStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-08085616660359db13a42b81ed633c5d")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/server.rpt
index c0f1cf9d6c..2170e7c34d 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc.read.aborted/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoServerStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-08085616660359db13a42b81ed633c5d")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/client.rpt
index 2b1dbe4598..0ea7a40b70 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoServerStream")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-08085616660359db13a42b81ed633c5d")
+                                     .header("meta:custom-bin", "dGVzdA==")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -60,6 +62,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoServerStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-08085616660359db13a42b81ed633c5d")
+                                .header("meta:custom-bin", "dGVzdA==")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -96,6 +100,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                               .progress(0, 2)
                               .progress(1, 1)
                               .key("test")
+                              .header("meta:custom", "value")
+                              .header("meta:customProperty-bin", "dGVzdA==")
                               .build()
                            .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/server.rpt
index 18f5e83aad..d31d73bdf3 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/server.stream.rpc/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoServerStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-08085616660359db13a42b81ed633c5d")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -61,6 +63,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoServerStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-08085616660359db13a42b81ed633c5d")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -93,6 +97,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/client.rpt
index 2e72214717..814ab190e1 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoUnary")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                     .header("meta:custom", "test")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -60,6 +62,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -97,6 +101,7 @@ read zilla:data.ext ${kafka:matchDataEx()
                               .progress(1, 1)
                               .key("test")
                               .header("zilla:status", "9")
+                              .header("meta:custom", "value")
                               .build()
                            .build()}
 read zilla:data.null
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/server.rpt
index ee7639472e..d38e6b81b5 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.error/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 
@@ -62,6 +64,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -95,6 +99,7 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(1, 1)
                                 .key("test")
                                 .header("zilla:status", "9")
+                                .header("meta:custom", "value")
                                 .build()
                             .build()}
 
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/client.rpt
index 6aa0fee10e..2758f74348 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/client.rpt
@@ -43,6 +43,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoUnary")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                     .header("meta:custom", "test")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -62,6 +64,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -99,6 +103,7 @@ read zilla:data.ext ${kafka:matchDataEx()
                               .progress(0, 2)
                               .progress(1, 1)
                               .key("test")
+                              .header("meta:custom", "value")
                               .build()
                            .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/server.rpt
index 4417660509..d1c7cbf242 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.message.value.100k/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 
@@ -62,6 +64,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -95,6 +99,7 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/client.rpt
index 6c84ae591b..f71481de68 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/server.rpt
index d76aa21ab0..d6d4fff808 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc.sent.write.abort/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/client.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/client.rpt
index 18487e21af..2357a488d1 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/client.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/client.rpt
@@ -41,6 +41,8 @@ write zilla:data.ext ${kafka:dataEx()
                                      .header("zilla:method", "EchoUnary")
                                      .header("zilla:reply-to", "responses")
                                      .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                     .header("meta:custom-bin", "dGVzdA==")
+                                     .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                      .build()
                                  .build()}
 write ${grpc:protobuf()
@@ -60,6 +62,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                                .header("meta:custom-bin", "dGVzdA==")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 
@@ -96,6 +100,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                               .progress(0, 2)
                               .progress(1, 1)
                               .key("test")
+                              .header("meta:custom", "value")
+                              .header("meta:customProperty-bin", "dGVzdA==")
                               .build()
                            .build()}
 read ${grpc:protobuf()
diff --git a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/server.rpt b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/server.rpt
index 7040d097a8..404987e85b 100644
--- a/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/server.rpt
+++ b/specs/binding-grpc-kafka.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/kafka/streams/kafka/produce/unary.rpc/server.rpt
@@ -43,6 +43,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 
@@ -62,6 +64,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-479f2c3fb58bc3f04bbe15440a657670")
+                               .header("meta:custom-bin", "dGVzdA==")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read zilla:data.null
@@ -94,6 +98,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .progress(0, 2)
                                 .progress(1, 1)
                                 .key("test")
+                                .header("meta:custom", "value")
+                                .header("meta:customProperty-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-grpc.spec/src/main/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctions.java b/specs/binding-grpc.spec/src/main/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctions.java
index f31186e95b..bffa60a0b2 100644
--- a/specs/binding-grpc.spec/src/main/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctions.java
+++ b/specs/binding-grpc.spec/src/main/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctions.java
@@ -92,13 +92,9 @@ public static GrpcDataExBuilder dataEx()
     public static final class GrpcBeginExBuilder
     {
         private final GrpcBeginExFW.Builder beginExRW;
-        private final OctetsFW.Builder nameBuilder;
-        private final OctetsFW.Builder valueBuilder;
 
         private GrpcBeginExBuilder()
         {
-            nameBuilder = new OctetsFW.Builder().wrap(new UnsafeBuffer(new byte[1024 * 8]), 0, 1024 * 8);
-            valueBuilder = new OctetsFW.Builder().wrap(new UnsafeBuffer(new byte[1024 * 8]), 0, 1024 * 8);
             MutableDirectBuffer writeBuffer = new UnsafeBuffer(new byte[1024 * 8]);
             this.beginExRW = new GrpcBeginExFW.Builder().wrap(writeBuffer, 0, writeBuffer.capacity());
         }
@@ -145,16 +141,28 @@ public GrpcBeginExBuilder metadata(
             return metadata("TEXT", name, value);
         }
 
-        public GrpcBeginExBuilder metadata(
+        public GrpcBeginExBuilder metadataBase64(
+            String name,
+            String value)
+        {
+            return metadata("BASE64", name, value);
+        }
+
+        private GrpcBeginExBuilder metadata(
             String type,
             String name,
             String value)
         {
+            DirectBuffer nameBuffer = new UnsafeBuffer(name.getBytes());
+            OctetsFW nameOctets = new OctetsFW().wrap(nameBuffer, 0, nameBuffer.capacity());
+            DirectBuffer valueBuffer = new UnsafeBuffer(value.getBytes());
+            OctetsFW valueOctets = new OctetsFW().wrap(valueBuffer, 0, valueBuffer.capacity());
+
             beginExRW.metadataItem(b -> b.type(t -> t.set(GrpcType.valueOf(type)))
                 .nameLen(name.length())
-                .name(nameBuilder.set(name.getBytes()).build())
+                .name(nameOctets)
                 .valueLen(value.length())
-                .value(valueBuilder.set(value.getBytes()).build()));
+                .value(valueOctets));
             return this;
         }
 
@@ -172,10 +180,6 @@ public static final class GrpcBeginExMatcherBuilder
         private final DirectBuffer bufferRO = new UnsafeBuffer();
 
         private final GrpcBeginExFW beginExRO = new GrpcBeginExFW();
-        private final OctetsFW.Builder nameBuilder =
-            new OctetsFW.Builder().wrap(new UnsafeBuffer(new byte[1024 * 8]), 0, 1024 * 8);
-        private final OctetsFW.Builder valueBuilder =
-            new OctetsFW.Builder().wrap(new UnsafeBuffer(new byte[1024 * 8]), 0, 1024 * 8);
 
         private final Map<OctetsFW, MetadataValue> metadata = new LinkedHashMap<>();
 
@@ -227,19 +231,29 @@ public GrpcBeginExMatcherBuilder metadata(
             return metadata("TEXT", name, value);
         }
 
-        public GrpcBeginExMatcherBuilder metadata(
+        public GrpcBeginExMatcherBuilder metadataBase64(
+            String name,
+            String value)
+        {
+            return metadata("BASE64", name, value);
+        }
+
+        private GrpcBeginExMatcherBuilder metadata(
             String type,
             String name,
             String value)
         {
-            metadata.put(nameBuilder.set(name.getBytes()).build(),
-                new MetadataValue(GrpcType.valueOf(type), valueBuilder.set(value.getBytes()).build()::equals));
+            DirectBuffer nameBuffer = new UnsafeBuffer(name.getBytes());
+            OctetsFW nameOctets = new OctetsFW().wrap(nameBuffer, 0, nameBuffer.capacity());
+            DirectBuffer valueBuffer = new UnsafeBuffer(value.getBytes());
+            OctetsFW valueOctets = new OctetsFW().wrap(valueBuffer, 0, valueBuffer.capacity());
+            metadata.put(nameOctets, new MetadataValue(GrpcType.valueOf(type), valueOctets::equals));
             return this;
         }
 
         public BytesMatcher build()
         {
-            return method != null ? this::match : buf -> null;
+            return this::match;
         }
 
         private GrpcBeginExFW match(
@@ -280,25 +294,25 @@ private boolean matchMetadata(
         private boolean matchMethod(
             GrpcBeginExFW beginEx)
         {
-            return method.equals(beginEx.method().asString());
+            return method == null || method.equals(beginEx.method().asString());
         }
 
         private boolean matchScheme(
             GrpcBeginExFW beginEx)
         {
-            return scheme.equals(beginEx.scheme().asString());
+            return scheme == null || scheme.equals(beginEx.scheme().asString());
         }
 
         private boolean matchAuthority(
             GrpcBeginExFW beginEx)
         {
-            return authority.equals(beginEx.authority().asString());
+            return authority == null || authority.equals(beginEx.authority().asString());
         }
 
         private boolean matchService(
             GrpcBeginExFW beginEx)
         {
-            return service.equals(beginEx.service().asString());
+            return service == null || service.equals(beginEx.service().asString());
         }
 
         private boolean matchTypeId(
diff --git a/specs/binding-grpc.spec/src/main/resources/META-INF/zilla/grpc.idl b/specs/binding-grpc.spec/src/main/resources/META-INF/zilla/grpc.idl
index 9d6ce62d4d..9f7471c7eb 100644
--- a/specs/binding-grpc.spec/src/main/resources/META-INF/zilla/grpc.idl
+++ b/specs/binding-grpc.spec/src/main/resources/META-INF/zilla/grpc.idl
@@ -33,10 +33,10 @@ scope grpc
 
         struct GrpcBeginEx extends core::stream::Extension
         {
-            string16 scheme;
-            string16 authority;
-            string16 service;
-            string16 method;
+            string16 scheme = null;
+            string16 authority = null;
+            string16 service = null;
+            string16 method = null;
             GrpcMetadata[] metadata;
         }
 
diff --git a/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/client.rpt b/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/client.rpt
index 48a87dcdd5..d4c4b41bd3 100644
--- a/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/client.rpt
+++ b/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/client.rpt
@@ -23,7 +23,7 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoUnary")
-                              .metadata("BASE64", "custom", "dGVzdA==")
+                              .metadataBase64("custom", "dGVzdA==")
                               .build()}
 connected
 
diff --git a/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/server.rpt b/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/server.rpt
index a6d0681938..7f23d80391 100644
--- a/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/server.rpt
+++ b/specs/binding-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/grpc/streams/application/unary.rpc/binary.metadata/server.rpt
@@ -24,7 +24,7 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoUnary")
-                           .metadata("BASE64", "custom", "dGVzdA==")
+                           .metadataBase64("custom", "dGVzdA==")
                            .build()}
 connected
 
diff --git a/specs/binding-grpc.spec/src/test/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctionsTest.java b/specs/binding-grpc.spec/src/test/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctionsTest.java
index 5295818147..909475f72e 100644
--- a/specs/binding-grpc.spec/src/test/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctionsTest.java
+++ b/specs/binding-grpc.spec/src/test/java/io/aklivity/zilla/specs/binding/grpc/internal/GrpcFunctionsTest.java
@@ -92,6 +92,23 @@ public void shouldGenerateBeginExtension()
         assertTrue(beginEx.metadata().sizeof() > 0);
     }
 
+    @Test
+    public void shouldGenerateBeginExtensionWithMetadata()
+    {
+        byte[] build = GrpcFunctions.beginEx()
+            .typeId(0x01)
+            .metadata("custom", "test")
+            .build();
+        DirectBuffer buffer = new UnsafeBuffer(build);
+        GrpcBeginExFW beginEx = new GrpcBeginExFW().wrap(buffer, 0, buffer.capacity());
+        beginEx.metadata().forEach(h ->
+        {
+            assertTrue(nameBuilder.set("custom".getBytes()).build().equals(h.name()));
+            assertTrue(valueBuilder.set("test".getBytes()).build().equals(h.value()));
+        });
+        assertTrue(beginEx.metadata().sizeof() > 0);
+    }
+
     @Test
     public void shouldMatchBeginExtension() throws Exception
     {
@@ -122,6 +139,28 @@ public void shouldMatchBeginExtension() throws Exception
         assertNotNull(matcher.match(byteBuf));
     }
 
+    @Test
+    public void shouldMatchBeginExtensionWithMetadata() throws Exception
+    {
+        String value = "value";
+        String custom = "custom";
+        BytesMatcher matcher = GrpcFunctions.matchBeginEx()
+            .typeId(0x01)
+            .metadata(custom, value)
+            .build();
+
+        ByteBuffer byteBuf = ByteBuffer.allocate(1024);
+
+        new GrpcBeginExFW.Builder().wrap(new UnsafeBuffer(byteBuf), 0, byteBuf.capacity())
+            .typeId(0x01)
+            .metadataItem(h -> h.type(t -> t.set(TEXT).build()).nameLen(custom.length())
+                .name(nameBuilder.set(custom.getBytes()).build())
+                .valueLen(value.length()).value(valueBuilder.set(value.getBytes()).build()))
+            .build();
+
+        assertNotNull(matcher.match(byteBuf));
+    }
+
     @Test
     public void shouldGenerateResetExtension()
     {
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/client.rpt
index 5c68875bef..1526309cd2 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/client.rpt
@@ -23,8 +23,8 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoBidiStream")
-                              .metadata("custom", "test")
                               .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                              .metadataBase64("custom", "dGVzdA==")
                               .build()}
 connected
 
@@ -38,6 +38,12 @@ write ${grpc:protobuf()
             .build()}
 write flush
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/server.rpt
index 3edecf506f..d5c3d17ad7 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/bidi.stream.rpc/server.rpt
@@ -24,6 +24,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoBidiStream")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                           .metadataBase64("custom", "dGVzdA==")
                            .build()}
 connected
 
@@ -35,6 +37,13 @@ read ${grpc:protobuf()
            .string(1, "Hello World2")
            .build()}
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .metadataBase64("customProperty", "dGVzdA==")
+                              .build()}
+write flush
+
 write ${grpc:protobuf()
             .string(1, "Hello World1")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/client.rpt
index 625553053f..6ede234069 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/client.rpt
@@ -23,6 +23,7 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoUnary")
+                              .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                               .metadata("custom", "test")
                               .build()}
 connected
@@ -34,6 +35,11 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .build()}
+
 read ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/server.rpt
index 7ac5cde045..999c25ded6 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.sent.write.abort/server.rpt
@@ -24,6 +24,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoUnary")
+                           .metadata("custom", "test")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                            .build()}
 connected
 
@@ -32,6 +34,12 @@ read ${grpc:protobuf()
             .build()}
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .build()}
+write flush
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/client.rpt
index 113e5a2b48..61319aa562 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/client.rpt
@@ -23,6 +23,8 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoClientStream")
+                              .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                              .metadataBase64("custom", "dGVzdA==")
                               .build()}
 connected
 
@@ -38,6 +40,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/server.rpt
index 80ecbd27bb..e45f74cbbc 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/client.stream.rpc/server.rpt
@@ -24,6 +24,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoClientStream")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                           .metadataBase64("custom", "dGVzdA==")
                            .build()}
 connected
 
@@ -37,6 +39,13 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .metadataBase64("customProperty", "dGVzdA==")
+                              .build()}
+write flush
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/client.rpt
index 6ad4a356e1..ba2d5bf73e 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/client.rpt
@@ -32,6 +32,8 @@ write zilla:begin.ext ${grpc:beginEx()
                             .authority("localhost:8080")
                             .service("example.EchoService")
                             .method("EchoUnary")
+                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                            .metadataBase64("custom", "dGVzdA==")
                             .build()}
 connected
 
@@ -42,6 +44,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/server.rpt
index 175a5e3c7b..0bd20d226d 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/retry.on.unavailable.server/server.rpt
@@ -27,6 +27,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoUnary")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                           .metadataBase64("custom", "dGVzdA==")
                            .build()}
 connected
 
@@ -36,6 +38,13 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .metadataBase64("customProperty", "dGVzdA==")
+                              .build()}
+write flush
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/client.rpt
index 79c8b6aa9c..75592c73f0 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/client.rpt
@@ -23,6 +23,8 @@ write zilla:begin.ext ${grpc:beginEx()
                               .authority("localhost:8080")
                               .service("example.EchoService")
                               .method("EchoServerStream")
+                              .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                              .metadataBase64("custom", "dGVzdA==")
                               .build()}
 
 connected
@@ -34,6 +36,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World1")
            .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/server.rpt
index 420481872a..cbc435aff7 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/server.stream.rpc/server.rpt
@@ -24,6 +24,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoServerStream")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                           .metadataBase64("custom", "dGVzdA==")
                            .build()}
 connected
 
@@ -33,6 +35,13 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .metadataBase64("customProperty", "dGVzdA==")
+                              .build()}
+write flush
+
 write ${grpc:protobuf()
             .string(1, "Hello World1")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/client.rpt
index 3698254892..88ed425829 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/client.rpt
@@ -23,6 +23,8 @@ write zilla:begin.ext ${grpc:beginEx()
                             .authority("localhost:8080")
                             .service("example.EchoService")
                             .method("EchoUnary")
+                            .metadata("custom", "test")
+                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                             .build()}
 connected
 
@@ -37,6 +39,11 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .build()}
+
 read zilla:data.ext ${grpc:dataEx()
                               .typeId(zilla:id("grpc"))
                               .deferred(94217)
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/server.rpt
index b280d3bdd1..77fc7f0f2b 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc.message.value.100k/server.rpt
@@ -26,6 +26,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoUnary")
+                           .metadata("custom", "test")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                            .build()}
 connected
 
@@ -39,6 +41,12 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .build()}
+write flush
+
 write zilla:data.ext ${grpc:dataEx()
                               .typeId(zilla:id("grpc"))
                               .deferred(94217)
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/client.rpt
index 667e3f0070..fe37ab077a 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/client.rpt
@@ -23,6 +23,8 @@ write zilla:begin.ext ${grpc:beginEx()
                             .authority("localhost:8080")
                             .service("example.EchoService")
                             .method("EchoUnary")
+                            .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                            .metadataBase64("custom", "dGVzdA==")
                             .build()}
 connected
 
@@ -33,6 +35,12 @@ write flush
 
 write close
 
+read zilla:begin.ext ${grpc:matchBeginEx()
+                           .typeId(zilla:id("grpc"))
+                           .metadata("custom", "value")
+                           .metadataBase64("customProperty", "dGVzdA==")
+                           .build()}
+
 read ${grpc:protobuf()
            .string(1, "Hello World")
            .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/server.rpt
index 035e65267e..08ceffd283 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/grpc/unary.rpc/server.rpt
@@ -24,6 +24,8 @@ read zilla:begin.ext ${grpc:matchBeginEx()
                            .authority("localhost:8080")
                            .service("example.EchoService")
                            .method("EchoUnary")
+                           .metadata("idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                           .metadataBase64("custom", "dGVzdA==")
                            .build()}
 connected
 
@@ -33,6 +35,13 @@ read ${grpc:protobuf()
 
 read closed
 
+write zilla:begin.ext ${grpc:beginEx()
+                              .typeId(zilla:id("grpc"))
+                              .metadata("custom", "value")
+                              .metadataBase64("customProperty", "dGVzdA==")
+                              .build()}
+write flush
+
 write ${grpc:protobuf()
             .string(1, "Hello World")
             .build()}
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/client.rpt
index a5d878ef13..703de00865 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/client.rpt
@@ -47,6 +47,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoBidiStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                               .header("meta:custom-bin", "dGVzdA==")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -138,6 +140,8 @@ write zilla:data.ext ${kafka:dataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 write ${grpc:protobuf()
@@ -152,6 +156,8 @@ write zilla:data.ext ${kafka:dataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/server.rpt
index 4f1fed4136..bb68140864 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/bidi.stream.rpc/server.rpt
@@ -50,6 +50,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoBidiStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                                .header("meta:custom-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -141,6 +143,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 
@@ -155,6 +159,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/client.rpt
index 8299007a8e..6bb128e5d5 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/client.rpt
@@ -47,6 +47,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -113,6 +115,7 @@ write zilla:data.ext ${kafka:dataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
                                .build()
                            .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/server.rpt
index 5d45201cdc..03b0286bb4 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.sent.write.abort/server.rpt
@@ -50,6 +50,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -113,6 +115,7 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
                                .build()
                            .build()}
 
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/client.rpt
index 40600f7621..bb02da2dc3 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/client.rpt
@@ -47,6 +47,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoClientStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                               .header("meta:custom-bin", "dGVzdA==")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -139,6 +141,8 @@ write zilla:data.ext ${kafka:dataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/server.rpt
index 9555157a3c..5bd8e7aab8 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/client.stream.rpc/server.rpt
@@ -50,6 +50,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoClientStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                                .header("meta:custom-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -142,6 +144,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/client.rpt
index af55281d58..4fdbd83f01 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/client.rpt
@@ -47,6 +47,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoServerStream")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                               .header("meta:custom-bin", "dGVzdA==")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -110,6 +112,8 @@ write zilla:data.ext ${kafka:dataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 write ${grpc:protobuf()
@@ -124,6 +128,8 @@ write zilla:data.ext ${kafka:dataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/server.rpt
index 13130ecdb4..6b7afef49c 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/server.stream.rpc/server.rpt
@@ -50,6 +50,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoServerStream")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                                .header("meta:custom-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -111,6 +113,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 
@@ -125,6 +129,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .deferred(0)
                                .partition(-1, -1)
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/client.rpt
index 6ebe12df95..d3fe1402ea 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/client.rpt
@@ -48,6 +48,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "test")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -113,6 +115,7 @@ write zilla:data.ext ${kafka:dataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
                                .build()
                            .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/server.rpt
index 43a83ee736..c40e88821b 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc.message.value.100k/server.rpt
@@ -53,6 +53,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                                .header("meta:custom", "test")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -118,6 +120,7 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
                                .build()
                            .build()}
 
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/client.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/client.rpt
index 710f3a4cf7..9708ea0c01 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/client.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/client.rpt
@@ -47,6 +47,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .header("zilla:method", "EchoUnary")
                                .header("zilla:reply-to", "responses")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                               .header("meta:custom-bin", "dGVzdA==")
                                .build()
                            .build()}
 read ${grpc:protobuf()
@@ -112,6 +114,8 @@ write zilla:data.ext ${kafka:dataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}
 write ${grpc:protobuf()
diff --git a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/server.rpt b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/server.rpt
index 19af1d1734..b8d38ad0b2 100644
--- a/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/server.rpt
+++ b/specs/binding-kafka-grpc.spec/src/main/scripts/io/aklivity/zilla/specs/binding/kafka/grpc/streams/kafka/unary.rpc/server.rpt
@@ -50,6 +50,8 @@ write zilla:data.ext ${kafka:dataEx()
                                 .header("zilla:method", "EchoUnary")
                                 .header("zilla:reply-to", "responses")
                                 .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                                .header("meta:idempotency-key", "59410e57-3e0f-4b61-9328-f645a7968ac8")
+                                .header("meta:custom-bin", "dGVzdA==")
                                 .build()
                             .build()}
 write ${grpc:protobuf()
@@ -115,6 +117,8 @@ read zilla:data.ext ${kafka:matchDataEx()
                                .partition(-1, -1)
                                .key("59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
                                .header("zilla:correlation-id", "59410e57-3e0f-4b61-9328-f645a7968ac8-d41d8cd98f00b204e9800998ecf8427e")
+                               .header("meta:custom", "value")
+                               .header("meta:customProperty-bin", "dGVzdA==")
                                .build()
                            .build()}