smithy-lang · mtdowling · Mar 4, 2026
diff --git a/...-streams/src/main/java/software/amazon/smithy/java/aws/events/AwsEventDecoderFactory.java b/...-streams/src/main/java/software/amazon/smithy/java/aws/events/AwsEventDecoderFactory.java
@@ -7,8 +7,7 @@
 
 import java.util.Objects;
 import java.util.function.Supplier;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
+import software.amazon.smithy.java.core.schema.ApiOperation;
 import software.amazon.smithy.java.core.schema.Schema;
 import software.amazon.smithy.java.core.schema.SerializableStruct;
 import software.amazon.smithy.java.core.schema.ShapeBuilder;
@@ -60,8 +59,9 @@ private AwsEventDecoderFactory(
      * @param <IE>        The output event type
      * @return A new event decoder factory
      */
+    @SuppressWarnings("unchecked")
     public static <IE extends SerializableStruct> AwsEventDecoderFactory<IE, ?> forInputStream(
-            InputEventStreamingApiOperation<?, ?, IE> operation,
+            ApiOperation<?, ?> operation,
             Codec codec,
             FrameTransformer<AwsEventFrame> transformer
     ) {
@@ -70,7 +70,7 @@ private AwsEventDecoderFactory(
                 operation::inputBuilder,
                 operation.inputStreamMember(),
                 codec,
-                operation.inputEventBuilderSupplier(),
+                (Supplier<ShapeBuilder<IE>>) (Supplier<?>) operation.inputEventBuilderSupplier(),
                 transformer);
     }
 
@@ -83,8 +83,9 @@ private AwsEventDecoderFactory(
      * @param <OE>        The output event type
      * @return A new event decoder factory
      */
+    @SuppressWarnings("unchecked")
     public static <OE extends SerializableStruct> AwsEventDecoderFactory<OE, ?> forOutputStream(
-            OutputEventStreamingApiOperation<?, ?, OE> operation,
+            ApiOperation<?, ?> operation,
             Codec codec,
             FrameTransformer<AwsEventFrame> transformer
     ) {
@@ -93,7 +94,7 @@ private AwsEventDecoderFactory(
                 operation::outputBuilder,
                 operation.outputStreamMember(),
                 codec,
-                operation.outputEventBuilderSupplier(),
+                (Supplier<ShapeBuilder<OE>>) (Supplier<?>) operation.outputEventBuilderSupplier(),
                 transformer);
     }
 

diff --git a/...-streams/src/main/java/software/amazon/smithy/java/aws/events/AwsEventEncoderFactory.java b/...-streams/src/main/java/software/amazon/smithy/java/aws/events/AwsEventEncoderFactory.java
@@ -7,8 +7,7 @@
 
 import java.util.Objects;
 import java.util.function.Function;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
+import software.amazon.smithy.java.core.schema.ApiOperation;
 import software.amazon.smithy.java.core.schema.Schema;
 import software.amazon.smithy.java.core.serde.Codec;
 import software.amazon.smithy.java.core.serde.event.EventEncoder;
@@ -54,7 +53,7 @@ private AwsEventEncoderFactory(
      * @return A new event encoder factory
      */
     public static AwsEventEncoderFactory forInputStream(
-            InputEventStreamingApiOperation<?, ?, ?> operation,
+            ApiOperation<?, ?> operation,
             Codec codec,
             String payloadMediaType,
             FrameTransformer<AwsEventFrame> transformer,
@@ -78,7 +77,7 @@ public static AwsEventEncoderFactory forInputStream(
      * @return A new event encoder factory
      */
     public static AwsEventEncoderFactory forOutputStream(
-            OutputEventStreamingApiOperation<?, ?, ?> operation,
+            ApiOperation<?, ?> operation,
             Codec codec,
             String payloadMediaType,
             FrameTransformer<AwsEventFrame> transformer,

diff --git a/...treams/src/test/java/software/amazon/smithy/java/aws/events/AwsEventShapeDecoderTest.java b/...treams/src/test/java/software/amazon/smithy/java/aws/events/AwsEventShapeDecoderTest.java
@@ -9,6 +9,7 @@
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 
 import java.nio.charset.StandardCharsets;
+import java.util.function.Supplier;
 import org.junit.jupiter.api.Test;
 import software.amazon.eventstream.Message;
 import software.amazon.smithy.java.aws.events.model.BodyAndHeaderEvent;
@@ -143,10 +144,11 @@ public void testDecodeStringMember() {
         assertEquals(expected, actual);
     }
 
+    @SuppressWarnings("unchecked")
     static AwsEventShapeDecoder<?, ?> createDecoder() {
         return new AwsEventShapeDecoder<>(InitialEventType.INITIAL_RESPONSE,
                 () -> TestOperation.instance().outputBuilder(), // output builder
-                TestOperation.instance().outputEventBuilderSupplier(),
+                (Supplier) TestOperation.instance().outputEventBuilderSupplier(),
                 TestOperation.instance().outputStreamMember(),
                 createJsonCodec());
     }

diff --git a/...ent-streams/src/test/java/software/amazon/smithy/java/aws/events/model/TestOperation.java b/...ent-streams/src/test/java/software/amazon/smithy/java/aws/events/model/TestOperation.java
@@ -7,19 +7,18 @@
 
 import java.util.List;
 import java.util.function.Supplier;
+import software.amazon.smithy.java.core.schema.ApiOperation;
 import software.amazon.smithy.java.core.schema.ApiService;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
 import software.amazon.smithy.java.core.schema.Schema;
+import software.amazon.smithy.java.core.schema.SerializableStruct;
 import software.amazon.smithy.java.core.schema.ShapeBuilder;
 import software.amazon.smithy.java.core.serde.TypeRegistry;
 import software.amazon.smithy.model.shapes.ShapeId;
 import software.amazon.smithy.utils.SmithyGenerated;
 
 @SmithyGenerated
 public final class TestOperation
-        implements InputEventStreamingApiOperation<TestOperationInput, TestOperationOutput, TestEventStream>,
-        OutputEventStreamingApiOperation<TestOperationInput, TestOperationOutput, TestEventStream> {
+        implements ApiOperation<TestOperationInput, TestOperationOutput> {
 
     private static final TestOperation $INSTANCE = new TestOperation();
 
@@ -51,7 +50,7 @@ public ShapeBuilder<TestOperationInput> inputBuilder() {
     }
 
     @Override
-    public Supplier<ShapeBuilder<TestEventStream>> inputEventBuilderSupplier() {
+    public Supplier<ShapeBuilder<? extends SerializableStruct>> inputEventBuilderSupplier() {
         return () -> TestEventStream.builder();
     }
 
@@ -61,7 +60,7 @@ public ShapeBuilder<TestOperationOutput> outputBuilder() {
     }
 
     @Override
-    public Supplier<ShapeBuilder<TestEventStream>> outputEventBuilderSupplier() {
+    public Supplier<ShapeBuilder<? extends SerializableStruct>> outputEventBuilderSupplier() {
         return () -> TestEventStream.builder();
     }
 

diff --git a/...src/main/java/software/amazon/smithy/java/aws/client/restjson/RestJsonClientProtocol.java b/...src/main/java/software/amazon/smithy/java/aws/client/restjson/RestJsonClientProtocol.java
@@ -19,8 +19,6 @@
 import software.amazon.smithy.java.client.http.binding.HttpBindingErrorFactory;
 import software.amazon.smithy.java.context.Context;
 import software.amazon.smithy.java.core.schema.ApiOperation;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
 import software.amazon.smithy.java.core.schema.SerializableStruct;
 import software.amazon.smithy.java.core.schema.TraitKey;
 import software.amazon.smithy.java.core.serde.Codec;
@@ -79,8 +77,8 @@ public <I extends SerializableStruct, O extends SerializableStruct> HttpRequest
                 .omitEmptyPayload(omitEmptyPayload())
                 .allowEmptyStructPayload(hasStructPayload(input));
 
-        if (operation instanceof InputEventStreamingApiOperation<?, ?, ?> i) {
-            serializer.eventEncoderFactory(getEventEncoderFactory(i));
+        if (operation.inputEventBuilderSupplier() != null) {
+            serializer.eventEncoderFactory(getEventEncoderFactory(operation));
         }
 
         return serializer.serializeRequest();
@@ -107,23 +105,19 @@ protected boolean omitEmptyPayload() {
     }
 
     @Override
-    protected EventEncoderFactory<AwsEventFrame> getEventEncoderFactory(
-            InputEventStreamingApiOperation<?, ?, ?> inputOperation
-    ) {
+    protected EventEncoderFactory<AwsEventFrame> getEventEncoderFactory(ApiOperation<?, ?> operation) {
         // TODO: this is where you'd plumb through Sigv4 support, another frame transformer?
         return AwsEventEncoderFactory.forInputStream(
-                inputOperation,
+                operation,
                 payloadCodec(),
                 payloadMediaType(),
                 FrameTransformer.identity(),
                 (e) -> new EventStreamingException("InternalServerException", "Internal Server Error"));
     }
 
     @Override
-    protected EventDecoderFactory<AwsEventFrame> getEventDecoderFactory(
-            OutputEventStreamingApiOperation<?, ?, ?> outputOperation
-    ) {
-        return AwsEventDecoderFactory.forOutputStream(outputOperation, payloadCodec(), f -> f);
+    protected EventDecoderFactory<AwsEventFrame> getEventDecoderFactory(ApiOperation<?, ?> operation) {
+        return AwsEventDecoderFactory.forOutputStream(operation, payloadCodec(), f -> f);
     }
 
     private <I extends SerializableStruct> boolean hasStructPayload(I input) {

diff --git a/...l/src/main/java/software/amazon/smithy/java/aws/client/restxml/RestXmlClientProtocol.java b/...l/src/main/java/software/amazon/smithy/java/aws/client/restxml/RestXmlClientProtocol.java
@@ -21,8 +21,6 @@
 import software.amazon.smithy.java.core.error.CallException;
 import software.amazon.smithy.java.core.error.ModeledException;
 import software.amazon.smithy.java.core.schema.ApiOperation;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
 import software.amazon.smithy.java.core.serde.Codec;
 import software.amazon.smithy.java.core.serde.TypeRegistry;
 import software.amazon.smithy.java.core.serde.document.Document;
@@ -81,23 +79,19 @@ protected HttpErrorDeserializer getErrorDeserializer(Context context) {
     }
 
     @Override
-    protected EventEncoderFactory<AwsEventFrame> getEventEncoderFactory(
-            InputEventStreamingApiOperation<?, ?, ?> inputOperation
-    ) {
+    protected EventEncoderFactory<AwsEventFrame> getEventEncoderFactory(ApiOperation<?, ?> operation) {
         // TODO: this is where you'd plumb through Sigv4 support, another frame transformer?
         return AwsEventEncoderFactory.forInputStream(
-                inputOperation,
+                operation,
                 payloadCodec(),
                 payloadMediaType(),
                 FrameTransformer.identity(),
                 (e) -> new EventStreamingException("InternalServerException", "Internal Server Error"));
     }
 
     @Override
-    protected EventDecoderFactory<AwsEventFrame> getEventDecoderFactory(
-            OutputEventStreamingApiOperation<?, ?, ?> outputOperation
-    ) {
-        return AwsEventDecoderFactory.forOutputStream(outputOperation, payloadCodec(), f -> f);
+    protected EventDecoderFactory<AwsEventFrame> getEventDecoderFactory(ApiOperation<?, ?> operation) {
+        return AwsEventDecoderFactory.forOutputStream(operation, payloadCodec(), f -> f);
     }
 
     private static final HttpErrorDeserializer.ErrorPayloadParser XML_ERROR_PAYLOAD_PARSER =

diff --git a/.../main/java/software/amazon/smithy/java/client/http/binding/HttpBindingClientProtocol.java b/.../main/java/software/amazon/smithy/java/client/http/binding/HttpBindingClientProtocol.java
@@ -11,8 +11,6 @@
 import software.amazon.smithy.java.context.Context;
 import software.amazon.smithy.java.core.error.CallException;
 import software.amazon.smithy.java.core.schema.ApiOperation;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
 import software.amazon.smithy.java.core.schema.SerializableStruct;
 import software.amazon.smithy.java.core.serde.Codec;
 import software.amazon.smithy.java.core.serde.TypeRegistry;
@@ -55,11 +53,11 @@ protected final HttpBinding httpBinding() {
         return httpBinding;
     }
 
-    protected EventEncoderFactory<F> getEventEncoderFactory(InputEventStreamingApiOperation<?, ?, ?> inputOperation) {
+    protected EventEncoderFactory<F> getEventEncoderFactory(ApiOperation<?, ?> operation) {
         throw new UnsupportedOperationException("This protocol does not support event streaming");
     }
 
-    protected EventDecoderFactory<F> getEventDecoderFactory(OutputEventStreamingApiOperation<?, ?, ?> outputOperation) {
+    protected EventDecoderFactory<F> getEventDecoderFactory(ApiOperation<?, ?> operation) {
         throw new UnsupportedOperationException("This protocol does not support event streaming");
     }
 
@@ -78,8 +76,8 @@ public <I extends SerializableStruct, O extends SerializableStruct> HttpRequest
                 .endpoint(endpoint)
                 .omitEmptyPayload(omitEmptyPayload());
 
-        if (operation instanceof InputEventStreamingApiOperation<?, ?, ?> i) {
-            serializer.eventEncoderFactory(getEventEncoderFactory(i));
+        if (operation.inputEventBuilderSupplier() != null) {
+            serializer.eventEncoderFactory(getEventEncoderFactory(operation));
         }
 
         return serializer.serializeRequest();
@@ -106,8 +104,8 @@ public <I extends SerializableStruct, O extends SerializableStruct> O deserializ
                 .outputShapeBuilder(outputBuilder)
                 .response(response);
 
-        if (operation instanceof OutputEventStreamingApiOperation<?, ?, ?> o) {
-            deser.eventDecoderFactory(getEventDecoderFactory(o));
+        if (operation.outputEventBuilderSupplier() != null) {
+            deser.eventDecoderFactory(getEventDecoderFactory(operation));
         }
 
         deser.deserialize();

diff --git a/...-rpcv2-cbor/src/main/java/software/amazon/smithy/java/client/rpcv2/RpcV2CborProtocol.java b/...-rpcv2-cbor/src/main/java/software/amazon/smithy/java/client/rpcv2/RpcV2CborProtocol.java
@@ -22,8 +22,6 @@
 import software.amazon.smithy.java.client.http.HttpErrorDeserializer;
 import software.amazon.smithy.java.context.Context;
 import software.amazon.smithy.java.core.schema.ApiOperation;
-import software.amazon.smithy.java.core.schema.InputEventStreamingApiOperation;
-import software.amazon.smithy.java.core.schema.OutputEventStreamingApiOperation;
 import software.amazon.smithy.java.core.schema.SerializableStruct;
 import software.amazon.smithy.java.core.schema.Unit;
 import software.amazon.smithy.java.core.serde.Codec;
@@ -82,9 +80,9 @@ public <I extends SerializableStruct, O extends SerializableStruct> HttpRequest
             // Top-level Unit types do not get serialized
             builder.headers(HttpHeaders.of(headersForEmptyBody()))
                     .body(DataStream.ofEmpty());
-        } else if (operation instanceof InputEventStreamingApiOperation<?, ?, ?> i) {
+        } else if (operation.inputEventBuilderSupplier() != null) {
             // Event streaming
-            var encoderFactory = getEventEncoderFactory(i);
+            var encoderFactory = getEventEncoderFactory(operation);
             var body = RpcEventStreamsUtil.bodyForEventStreaming(encoderFactory, input);
             builder.headers(HttpHeaders.of(headersForEventStreaming()))
                     .body(body);
@@ -108,8 +106,8 @@ public <I extends SerializableStruct, O extends SerializableStruct> O deserializ
             throw errorDeserializer.createError(context, operation, typeRegistry, response);
         }
 
-        if (operation instanceof OutputEventStreamingApiOperation<I, O, ?> o) {
-            var eventDecoderFactory = getEventDecoderFactory(o);
+        if (operation.outputEventBuilderSupplier() != null) {
+            var eventDecoderFactory = getEventDecoderFactory(operation);
             return RpcEventStreamsUtil.deserializeResponse(eventDecoderFactory, bodyDataStream(response));
         }
 
@@ -154,22 +152,17 @@ private Map<String, List<String>> headersForEventStreaming() {
                 CONTENT_TYPE);
     }
 
-    private EventEncoderFactory<AwsEventFrame> getEventEncoderFactory(
-            InputEventStreamingApiOperation<?, ?, ?> inputOperation
-    ) {
-
+    private EventEncoderFactory<AwsEventFrame> getEventEncoderFactory(ApiOperation<?, ?> operation) {
         // TODO: this is where you'd plumb through Sigv4 support, another frame transformer?
-        return AwsEventEncoderFactory.forInputStream(inputOperation,
+        return AwsEventEncoderFactory.forInputStream(operation,
                 payloadCodec(),
                 PAYLOAD_MEDIA_TYPE,
                 FrameTransformer.identity(),
                 (e) -> new EventStreamingException("InternalServerException", "Internal Server Error"));
     }
 
-    private EventDecoderFactory<AwsEventFrame> getEventDecoderFactory(
-            OutputEventStreamingApiOperation<?, ?, ?> outputOperation
-    ) {
-        return AwsEventDecoderFactory.forOutputStream(outputOperation, payloadCodec(), f -> f);
+    private EventDecoderFactory<AwsEventFrame> getEventDecoderFactory(ApiOperation<?, ?> operation) {
+        return AwsEventDecoderFactory.forOutputStream(operation, payloadCodec(), f -> f);
     }
 
     private static ShapeId extractErrorType(Document document, String namespace) {