smithy-lang · joewyz · May 14, 2026
diff --git a/...nt-streams/src/main/java/software/amazon/smithy/java/aws/events/AwsEventShapeDecoder.java b/...nt-streams/src/main/java/software/amazon/smithy/java/aws/events/AwsEventShapeDecoder.java
@@ -170,7 +170,8 @@ static class EventStreamDeserializer extends SpecificShapeDeserializer {
         public <T> void readStruct(Schema schema, T builder, ShapeDeserializer.StructMemberConsumer<T> consumer) {
             var payloadWritten = false;
             for (Schema member : schema.members()) {
-                if (member.hasTrait(TraitKey.EVENT_HEADER_TRAIT)) {
+                if (member.hasTrait(TraitKey.EVENT_HEADER_TRAIT)
+                        && headersDeserializer.headers.containsKey(member.memberName())) {
                     consumer.accept(builder, member, headersDeserializer);
                 } else if (member.hasTrait(TraitKey.EVENT_PAYLOAD_TRAIT)) {
                     consumer.accept(builder, member, codecDeserializer);

diff --git a/...n/src/it/java/software/amazon/smithy/java/client/aws/restjson/RestJson1ProtocolTests.java b/...n/src/it/java/software/amazon/smithy/java/client/aws/restjson/RestJson1ProtocolTests.java
@@ -11,6 +11,7 @@
 import java.nio.charset.StandardCharsets;
 import software.amazon.smithy.java.io.ByteBufferUtils;
 import software.amazon.smithy.java.io.datastream.DataStream;
+import software.amazon.smithy.java.protocoltests.harness.EventStreamClientTests;
 import software.amazon.smithy.java.protocoltests.harness.HttpClientRequestTests;
 import software.amazon.smithy.java.protocoltests.harness.HttpClientResponseTests;
 import software.amazon.smithy.java.protocoltests.harness.ProtocolTest;
@@ -26,6 +27,40 @@
         skipOperations = {
                 // We dont ignore defaults on input shapes
                 "aws.protocoltests.restjson#OperationWithDefaults",
+        },
+        skipTests = {
+                // Need to add exception type to header
+                "ClientErrorInput",
+                "DuplexClientErrorInput",
+                // Currently we are using JSON codec for plain text payload, need to correct it.
+                "StringPayloadOutput",
+                "DuplexStringPayloadOutput",
+                // eventstream:1.0.1 made ByteValue.encodeValue() and
+                // ShortValue.encodeValue() no-ops, producing malformed frames.
+                "ByteHeaderInput",
+                "DuplexByteHeaderInput",
+                "ShortHeaderInput",
+                "DuplexShortHeaderInput",
+                // Blob test params use inconsistent encoding conventions —
+                // headers use base64, payloads use raw strings.
+                "BlobPayloadInput",
+                "DuplexBlobPayloadInput",
+                "BlobPayloadOutput",
+                "DuplexBlobPayloadOutput",
+                "BlobHeaderInput",
+                "DuplexBlobHeaderInput",
+                "BlobHeaderOutput",
+                "DuplexBlobHeaderOutput",
+                "MultipleHeaderInput",
+                "DuplexMultipleHeaderInput",
+                "MultipleHeaderOutput",
+                "DuplexMultipleHeaderOutput",
+                // Decoder returns modeled error events instead of throwing
+                "ClientErrorOutput",
+                "DuplexClientErrorOutput",
+                // Client doesn't validate missing @required initial response members
+                "MissingRequiredInitialResponseOutput",
+                "DuplexMissingRequiredInitialResponseOutput"
         })
 public class RestJson1ProtocolTests {
     private static final String EMPTY_BODY = "";
@@ -57,4 +92,9 @@ public void requestTest(DataStream expected, DataStream actual) {
     public void responseTest(Runnable test) {
         test.run();
     }
+
+    @EventStreamClientTests
+    public void eventStreamClientTest(Runnable test) {
+        test.run();
+    }
 }
diff --git a/protocol-test-harness/build.gradle.kts b/protocol-test-harness/build.gradle.kts
@@ -19,6 +19,7 @@ dependencies {
     implementation(project(":client:client-http"))
     implementation(project(":codecs:json-codec", configuration = "shadow"))
     implementation(libs.assertj.core)
+    implementation(project(":aws:aws-event-streams"))
 
     api(platform(libs.junit.bom))
     api(libs.junit.jupiter.api)

diff --git a/...t-harness/src/main/java/software/amazon/smithy/java/protocoltests/harness/Assertions.java b/...t-harness/src/main/java/software/amazon/smithy/java/protocoltests/harness/Assertions.java
@@ -5,18 +5,35 @@
 
 package software.amazon.smithy.java.protocoltests.harness;
 
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.stream.Collectors;
+import software.amazon.eventstream.HeaderValue;
+import software.amazon.eventstream.MessageDecoder;
+import software.amazon.smithy.java.core.error.ModeledException;
 import software.amazon.smithy.java.http.api.HttpMessage;
 import software.amazon.smithy.java.http.api.HttpRequest;
 import software.amazon.smithy.java.io.uri.SmithyUri;
+import software.amazon.smithy.model.node.Node;
+import software.amazon.smithy.model.node.ObjectNode;
+import software.amazon.smithy.model.node.StringNode;
 import software.amazon.smithy.protocoltests.traits.HttpRequestTestCase;
+import software.amazon.smithy.protocoltests.traits.TestFailureExpectation;
+import software.amazon.smithy.protocoltests.traits.eventstream.Event;
+import software.amazon.smithy.protocoltests.traits.eventstream.EventHeaderValue;
+import software.amazon.smithy.protocoltests.traits.eventstream.EventStreamTestCase;
 
 /**
  * Provides a number of testing utilities for validating protocol test results.
@@ -52,7 +69,7 @@ static void assertUriEquals(HttpRequestTestCase testCase, SmithyUri uri) {
     }
 
     private static void assertQueryParamsEquals(List<String> expectedParams, String actualQuery) {
-        var expectedSet = paserQueryParamsList(expectedParams);
+        var expectedSet = parseQueryParamsList(expectedParams);
         var actualSet = parseQueryParamsString(actualQuery);
         assertEquals(expectedSet, actualSet, "Query parameters mismatch");
     }
@@ -67,7 +84,7 @@ private static Set<String> parseQueryParamsString(String query) {
         return result;
     }
 
-    private static Set<String> paserQueryParamsList(List<String> params) {
+    private static Set<String> parseQueryParamsList(List<String> params) {
         Set<String> result = new HashSet<>();
         for (String paramPair : params) {
             var pair = paramPair.split("=", 2);
@@ -106,4 +123,123 @@ private static String convertHeaderToString(String key, List<String> values) {
             return value;
         }).collect(Collectors.joining(", "));
     }
+
+    static void assertEventHeaderEquals(String key, EventHeaderValue<?> expected, HeaderValue actual) {
+        switch (expected.getType()) {
+            case BOOLEAN -> assertEquals(expected.asBoolean(), actual.getBoolean(), key);
+            case BYTE -> assertEquals(expected.asByte(), actual.getByte(), key);
+            case SHORT -> assertEquals(expected.asShort(), actual.getShort(), key);
+            case INTEGER -> assertEquals(expected.asInteger(), actual.getInteger(), key);
+            case LONG -> assertEquals(expected.asLong(), actual.getLong(), key);
+            case STRING -> assertEquals(expected.asString(), actual.getString(), key);
+            case BLOB -> assertArrayEquals(expected.asBlob(), actual.getByteArray(), key);
+            case TIMESTAMP -> assertEquals(expected.asTimestamp(), actual.getTimestamp(), key);
+        }
+    }
+
+    static void assertEventStreamRequestEquals(HttpRequest request, Event event) {
+        var bodyBytes = request.body().asByteBuffer();
+        var decoder = new MessageDecoder();
+        decoder.feed(bodyBytes.duplicate());
+        var messages = decoder.getDecodedMessages();
+        var message = messages.getFirst();
+        var actualHeaders = message.getHeaders();
+        for (var entry : event.getHeaders().entrySet()) {
+            var key = entry.getKey();
+            var expected = entry.getValue();
+            var actual = actualHeaders.get(key);
+            assertThat(actual).as("Missing header: " + key).isNotNull();
+            Assertions.assertEventHeaderEquals(key, expected, actual);
+        }
+        for (var header : event.getForbidHeaders()) {
+            assertFalse(actualHeaders.containsKey(header));
+        }
+        for (var header : event.getRequireHeaders()) {
+            assertTrue(actualHeaders.containsKey(header));
+        }
+        event.getBody().ifPresent(expectedBody -> {
+            assertEventStreamBodyEquals(expectedBody,
+                    new String(message.getPayload(), StandardCharsets.UTF_8),
+                    event.getBodyMediaType().orElse(null));
+        });
+    }
+
+    static void assertInitialRequestEquals(EventStreamTestCase testCase, HttpRequest request) {
+        if (testCase.getInitialRequest().isPresent()) {
+            var initialRequest = testCase.getInitialRequest().get();
+            assertEquals(initialRequest.expectStringMember("uri").getValue(), request.uri().getPath());
+            assertEquals(initialRequest.expectStringMember("method").getValue(), request.method());
+            initialRequest.getStringMember("resolvedHost").ifPresent(host -> {
+                assertEquals(host.getValue(), request.uri().getHost());
+            });
+            var actualQueryParams = request.uri().getQuery();
+            if (actualQueryParams != null) {
+                assertInitialRequestQueryMatches(initialRequest, actualQueryParams);
+            }
+            assertInitialRequestHeaderMatches(initialRequest, request);
+            initialRequest.getStringMember("body").ifPresent(bodyNode -> {
+                assertEventStreamBodyEquals(bodyNode.getValue(),
+                        new StringBuildingSubscriber(request.body()).getResult(),
+                        initialRequest.getStringMember("bodyMediaType").map(StringNode::getValue).orElse(null));
+            });
+        }
+    }
+
+    private static void assertInitialRequestQueryMatches(ObjectNode initialRequest, String actualQuery) {
+        initialRequest.getArrayMember("queryParams").ifPresent(params -> {
+            assertQueryParamsEquals(params.getElementsAs(StringNode::getValue), actualQuery);
+        });
+        var queryParamSet = parseQueryParamsString(actualQuery);
+        initialRequest.getArrayMember("forbidQueryParams").ifPresent(params -> {
+            for (var param : params.getElementsAs(StringNode::getValue)) {
+                assertFalse(queryParamSet.contains(param));
+            }
+        });
+
+        initialRequest.getArrayMember("requireQueryParams").ifPresent(params -> {
+            for (var param : params.getElementsAs(StringNode::getValue)) {
+                assertTrue(queryParamSet.contains(param));
+            }
+        });
+    }
+
+    private static void assertInitialRequestHeaderMatches(ObjectNode initialRequest, HttpRequest actualRequest) {
+        var actualHeaders = actualRequest.headers().map();
+        initialRequest.getObjectMember("headers").ifPresent(headersNode -> {
+            Map<String, String> headers = new HashMap<>();
+            headersNode.getStringMap().forEach((k, v) -> headers.put(k, v.expectStringNode().getValue()));
+            assertHeadersEqual(actualRequest, headers);
+        });
+
+        initialRequest.getArrayMember("forbidHeaders").ifPresent(headers -> {
+            for (var header : headers.getElementsAs(StringNode::getValue)) {
+                assertFalse(actualHeaders.containsKey(header));
+            }
+        });
+
+        initialRequest.getArrayMember("requireHeaders").ifPresent(headers -> {
+            for (var header : headers.getElementsAs(StringNode::getValue)) {
+                assertTrue(actualHeaders.containsKey(header));
+            }
+        });
+    }
+
+    private static void assertEventStreamBodyEquals(String expectedBody, String actualBody, String bodyType) {
+        if ("application/json".equals(bodyType)) {
+            Node.assertEquals(Node.parse(expectedBody), Node.parse(actualBody));
+        } else {
+            assertEquals(expectedBody, actualBody);
+        }
+    }
+
+    static void assertExpectationEquals(EventStreamTestCase testCase, Throwable e) {
+        testCase.getExpectation()
+                .getFailure()
+                .flatMap(TestFailureExpectation::getErrorId)
+                .ifPresent(errorId -> {
+                    assertInstanceOf(ModeledException.class, e);
+                    assertEquals(errorId.getName(),
+                            ((ModeledException) e).schema().id().getName());
+                });
+    }
 }
diff --git a/...c/main/java/software/amazon/smithy/java/protocoltests/harness/EventStreamClientTests.java b/...c/main/java/software/amazon/smithy/java/protocoltests/harness/EventStreamClientTests.java
@@ -0,0 +1,23 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.java.protocoltests.harness;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import org.junit.jupiter.api.TestTemplate;
+import org.junit.jupiter.api.Timeout;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.platform.commons.annotation.Testable;
+
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+@TestTemplate
+@Testable
+@Timeout(5)
+@ExtendWith(EventStreamClientTestsProtocolTestProvider.class)
+public @interface EventStreamClientTests {}