From 26ff760d7ce72110046bc044b166148dedc822dd Mon Sep 17 00:00:00 2001
From: George Fu <kuhe@users.noreply.github.com>
Date: Tue, 2 Sep 2025 15:19:00 -0400
Subject: [PATCH] fix: event stream serialization

---
 .../codegen/integration/EventStreamGenerator.java  |  2 +-
 .../integration/HttpRpcProtocolGenerator.java      | 14 +++++++++++++-
 .../codegen/protocols/cbor/SmithyRpcV2Cbor.java    |  6 +++++-
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/EventStreamGenerator.java b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/EventStreamGenerator.java
index 30b3a7ad548..3d115213acd 100644
--- a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/EventStreamGenerator.java
+++ b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/EventStreamGenerator.java
@@ -387,7 +387,7 @@ private void writeEventBody(
                     writer.write("body = input.$L;", payloadMemberName);
                 } else if (payloadShape instanceof StringShape) {
                     writer.write("body = context.utf8Decoder(input.$L);", payloadMemberName);
-                } else if (payloadShape instanceof BlobShape || payloadShape instanceof StringShape) {
+                } else if (payloadShape instanceof StructureShape || payloadShape instanceof UnionShape) {
                     Symbol symbol = getSymbol(context, payloadShape);
                     String serFunctionName = ProtocolGenerator.getSerFunctionShortName(symbol);
                     boolean mayElide = serdeElisionIndex.mayElide(payloadShape);
diff --git a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpRpcProtocolGenerator.java b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpRpcProtocolGenerator.java
index 68038e127d9..764e41ee3b6 100644
--- a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpRpcProtocolGenerator.java
+++ b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/HttpRpcProtocolGenerator.java
@@ -34,6 +34,7 @@
 import software.amazon.smithy.typescript.codegen.TypeScriptWriter;
 import software.amazon.smithy.typescript.codegen.knowledge.SerdeElisionIndex;
 import software.amazon.smithy.utils.OptionalUtils;
+import software.amazon.smithy.utils.SmithyInternalApi;
 import software.amazon.smithy.utils.SmithyUnstableApi;
 
 /**
@@ -107,7 +108,7 @@ public void generateSharedComponents(GenerationContext context) {
             getDocumentContentType(),
             () -> {
                 TypeScriptWriter writer = context.getWriter();
-                writer.write("body = context.utf8Decoder(body);");
+                serializeEventStreamBodyToBytes(writer);
             },
             serializingDocumentShapes
         );
@@ -606,6 +607,17 @@ protected String getErrorBodyLocation(GenerationContext context, String outputLo
         return outputLocation;
     }
 
+    /**
+     * Allows RPC protocols to designate how to convert the body into bytes.
+     *
+     * @deprecated superseded by schema-serde.
+     */
+    @Deprecated
+    @SmithyInternalApi
+    protected void serializeEventStreamBodyToBytes(TypeScriptWriter writer) {
+        writer.write("body = context.utf8Decoder(JSON.stringify(body));");
+    }
+
     /**
      * Writes the code needed to deserialize the output document of a response.
      *
diff --git a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/protocols/cbor/SmithyRpcV2Cbor.java b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/protocols/cbor/SmithyRpcV2Cbor.java
index ce9a10a9cd8..c647326a96a 100644
--- a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/protocols/cbor/SmithyRpcV2Cbor.java
+++ b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/protocols/cbor/SmithyRpcV2Cbor.java
@@ -67,7 +67,11 @@ public void generateSharedComponents(GenerationContext context) {
             service,
             getDocumentContentType(),
             () -> {
-                writer.write("body = context.utf8Decoder(body);");
+                writer.addImportSubmodule(
+                    "cbor", null,
+                    TypeScriptDependency.SMITHY_CORE, SmithyCoreSubmodules.CBOR
+                );
+                writer.write("body = cbor.encode(body);");
             },
             serializingDocumentShapes
         );